Noble gas discharge lamp

Abstract

 A noble gas discharge lamp of the present invention comprises an outer enclosure (1A) comprising a light emitting layer (2) formed therein, and a pair of outer electrodes (5, 6) having tape shapes comprising a metal, which are positioned to the entire length of the outside of the outer enclosure (1A) so as to separate one outer electrode (5) and the other outer electrode (6) at a certain distance, and to form a first opening portion (7) and a second opening portion (8); wherein a nonlinear portion (5A, 5B, 5C) is formed at one side portion (5b) of one outer electrode (5) forming the second opening portion (8), and other side portion (6b) being opposite to the nonlinear portion(5A, 5B, 5C), is formed linearly.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

[0001] The present invention relates to a noble gas discharge lamp. More particularly, the present invention relates to a noble gas discharge lamp comprising a light emitting layer comprising an aperture inside a glass bulb, and a pair of outer electrodes in the shape of a belt outside the glass bulb, in which the outer electrodes are improved in their structure so as to produce a stable travel of electric discharge.

[0002] This application is based on patent application No. Hei 09-094017 filed in Japan, the content of which is incorporated herein by reference.

Description of the Related Art

[0003] The applicants of the present invention previously proposed the noble gas discharge lamp shown in Figures 10 and 11. In Figures 10 and 11, reference number 1 indicates a hermetic outer enclosure in the shape of a straight tube, and is comprised of a glass bulb, for example. On the inside of the outer enclosure 1, a light emitting layer 2 is formed which is comprised of one or more kinds of fluorescent substances such as fluorescent rare earth substances and fluorescent halorine acid salt substances. In particular, an aperture 2a having a certain opening angle is formed to extend over the full length of the light emitting layer 2.

[0004] The outer enclosure 1 is sealed by adhering glass plates in the shape of a disc to the ends of the glass bulb. However, for example, the outer enclosure 1 can also be sealed by tapering and cutting the ends of the glass bulb, while heating.

[0005] Moreover, the internal part of the outer enclosure 1 is filled with one kind of noble gas such as xenon (Xe), krypton (Kr), neon (Ne), helium (He), and the like, or a mixture thereof in which a metallic vapor such as mercury is not contained. Among these noble gases, noble gas comprising xenon as a main component is preferable.

[0006] An outer laminate 3 is rolled closely into the outside of the outer enclosure 1. The outer laminate 3 may be composed of a light transmitting sheet 4, a pair of outer electrodes 5 and 6, terminals 51 and 61, and an adhesive layer 9.

[0007] The light transmitting sheet 4 has a length equal to a length of the outer enclosure 1, and a thickness in a range of 20 to 100 microns. This light transmitting sheet 4 have electrical insulating properties, and may be suitably comprised of polyethylene terephtalate (PET), however, polyester resin can be also used.

[0008] The above-mentioned pair of outer electrodes 5 and 6 are comprised of a metallic member having a light insulating property, the appearance thereof is tape shape, and it is adhered to one surface of the light transmitting sheet 4 so as to separate one outer electrode 5 from the other outer electrode 6 at a certain interval.

[0009] The terminals 51 and 61 are connected electrically to the ends of the outer electrodes 5 and 6. They are arranged at the edge of the light transmitting sheet 4 so that the ends thereof project from the edge of the light transmitting sheet 4. The thickness of the terminals 51 and 61 is preferably in a range of 0.1 to 0.5 mm.

[0010] The outer electrodes 5 and 6 and the terminals 51 and 61 are comprised of metals having differing corrosion potentials; for instance, aluminum foil in the shape of a tape is suitable for the outer electrodes 5 and 6. In addition to aluminum, nickel and other metals which have excellent electroconductivity and light insulating properties can comprise the outer electrodes 5 and 6. Regarding the terminals 51 and 61, copper in the shape of a strip is suitable. However, in addition to copper, metals such as silver, stainless steel, Cu-Ni alloy, and the like can comprise the terminals 51 and 61.

[0011] In particular, in the relationships of the widths between the outer electrodes 5 and 6 and the terminals 51 and 61, the width (w) of the outer electrodes 5 and 6, and the width (d) of the terminals 51 and 61 preferably satisfy the formula: 0.1 w ≦ d ≦ 0.5 w.

[0012] The adhesive layer 9 has sticky properties and/or adhesive properties, and is adhered to one surface of the light transmitting sheet 4. The adhesive layer 9 is suitably comprised of a silicon adhesive agent; however, acryl resin adhesive agents and the like can also be used.

[0013] Moreover, a plating layer (not shown in the Figures) is formed on the terminals 51 and 61. The plating layer is comprised of metals which are different from metals comprising the outer electrodes 5 and 6 and the terminals 51 and 61, and of which the corrosion potential difference is between the corrosion potential differences of the metals comprising the outer electrodes 5 and 6 and the terminals 51 and 61. For instance, in the case in which the outer electrodes 5 and 6 are comprised of aluminum foil and the terminals 51 and 61 are comprised of copper; nickel and lead-tin solder can be listed as metals suitable for comprising the plating layer.

[0014] The plating layer can be formed preferably by electroplating or electroless plating; however, the plating layer can also be formed by an immersion or a flame spray.

[0015] The thickness of the plating layer is preferably in a range of 5 to 30 microns, more preferably in a range of 10 to 20 microns. However, a plating layer having a thickness outside the range can also be used.

[0016] The aforementioned outer laminate 3 is formed onto the outside of the outer enclosure 1 so that the outer electrodes 5 and 6 are positioned between the outer enclosure 1 and the light transmitting sheet 4. One edge 4a of the light transmitting sheet 4 is laminated and adhered to the other edge 4b at the following second opening portion 8. Moreover, in a condition in which the outer laminate 3 is adhered to the outer enclosure 1, a first opening portion 7 is formed by the side portions of the outer electrodes 5 and 6, and the second opening portion 8 is formed by the other side portions of outer electrodes 5 and 6. The light from the light emitting layer 2 is emitted mainly from the first opening portion 7 via the aperture 2a.

[0017] The noble gas discharge lamp comprising the above-mentioned components can be produced by the following steps.

[0018] A water soluble fluorescent paint is made by mixing water soluble fluorescent substances having an emission spectrum in a blue range, a green range, and a red range, for example. Next, the light emitting layer 2 is formed by coating the water soluble fluorescent paint on the inside of the outer enclosure 1 comprised of a glass bulb, by drying and then firing.

[0019] The aperture 2a is formed by peeling off and by forcibly removing a part of the light emitting layer 2, while maintaining a certain opening angle, by using a scraper (not shown in the Figures). The obtained outer enclosure 1 is sealed and is filled with a certain amount of noble gas such as xenon and the like.

[0020] As shown in Figures 11 and 12, the outer laminate 3 is formed by positioning one pair of the outer electrodes 5 and 6 on the light transmitting sheet 4 so as to be disposed with a certain space therebetween, so that the terminals 51 and 61 project out from the edge of the outer electrodes 5 and 6, and by forming the adhesive layer 9 onto the upper surfaces of the light transmitting sheet 4 and the outer electrodes 5 and 6.

[0021] As shown in Figure 13, the unfolding of outer laminate 3 obtained by the above-mentioned steps is positioned on the stage 10. The outer enclosure 1 is positioned on the outer laminate 3 so that the outer enclosure 1 is positioned on the edge 4a of the light transmitting sheet 4, and the longitudinal axis of the outer enclosure 1 is parallel to the longitudinal axis of the outer electrodes 5 and 6. Rollers 11 and 11 are positioned so that the outer enclosure 1 is contacted with some pressure to the light transmitting sheet 4, while maintaining the above conditions.

[0022] While maintaining the above conditions, as shown in Figure 13, the stage 10 is moved in the direction M, and is then moved in the direction N. Because of these movements, the outer laminate 3 is wound around the outside of the outer enclosure 1, and one edge 4a is overlapped on the other edge 4b of the light transmitting sheet 4, as shown in Figure 10. Then, the noble gas discharge lamp is produced by adhering the edges 4a and 4b of the light transmitting sheet 4 with the adhesive layer 9.

[0023] According to the noble gas discharge lamp having the above-mentioned components, light emitted from the light emitting layer 2 is concentrated in the outer enclosure 1, and is emitted from the outside of the noble gas discharge lamp via the first opening portion 7 and the aperture 2a. Therefore, when the noble gas discharge lamp is used in an office automation device such as an illumination device, the intensity of illumination on a document being scanned can be increased. As a result, accurate scanning of documents can be improved.

[0024] Moreover, it is anticipated that the noble gas discharge lamp will have the following effects.

[0025] The plating layer is formed between the outer electrodes 5 and 6 and the terminals 51 and 61; therefore, even if the outer electrodes 5 and 6 and the terminals 51 and 61 which are comprised of metals having different corrosion potential from each other, are connected directly, generation of corrosion due to the contact of different kinds of metal can be prevented.

[0026] In particular, when the width (w) of the outer electrodes 5 and 6 and the width (d) of the terminals 51 and 61 are set to satisfy the following formula: 0.1 w ≦ d ≦ 0.5 w, corrosion due to contact of different kinds of metal can be effectively prevented, in company with the existence of the plating layer. Therefore, a stable travel of electric discharge of the noble gas discharge lamp can be maintained for long periods.

[0027] However, when the width (d) of the terminals 51 and 61 is less than 0.1 w, contact intensity to the outer electrodes 5 and 6 of the terminals 51 and 61 is decreased. In contrast, when the width (d) of the terminals 51 and 61 is more than 0.5 w, in winding the outer laminate 3 around the outside of the outer enclosure 1, the terminals 51 and 61 could not be wound around the outside of the outer enclosure 1 more easily . This process is extremely troublesome. Therefore, it is preferable that width (w) of the outer electrodes 5 and 6 and the width (d) of the terminals 51 and 61 satisfy the above-mentioned formula.

[0028] Moreover, the following effects can be obtained in the process for products. The adhesive layer 9 is formed on one surface of the light transmitting sheet 4; therefore, the outer laminate 3 can be adhered closely to the outside of the outer enclosure 1 by a simple step, that is, simply by rolling the outer enclosure 1 onto the outer laminate 3. In addition, the outer electrodes 5 and 6 are positioned previously so as to be disposed at a certain interval from each other on the light transmitting sheet 4; therefore, in adhering the outer laminate 3 to the outer enclosure 1, it is not necessary to adjust the positioning of the outer electrodes 5 and 6 to maintain a certain interval therebetween. Therefore, it can be anticipated that not only will the work efficiency be greatly improved, but automated production of the noble gas discharge lamp will also be possible. That is, production of the noble gas discharge lamp in large quantities may be anticipated.

[0029] As shown in Figure 14, the resulting noble gas discharge lamp is switched on to produce light by applying a high voltage of high frequency (for example, a frequency of 30 kHz and a voltage of 2500 V_o-p ) to the outer electrodes 5 and 6, from an inverter circuit 12, via the terminals 51 and 61.

[0030] For instance, the voltage applied to the outer electrodes 5 and 6 is approximately 2500 V_o-p in a noble gas discharge lamp which is 8 mm in external diameter and 360 mm in total length.

[0031] Moreover, this noble gas discharge lamp is different from lamps having one discharge along the longitudinal direction of the outer enclosure 1, such as a noble gas discharge lamp having a hot cathode or a cold cathode. More specifically, innumerable discharges occur between the outer electrodes 5 and 6 (discharges are generated approximately perpendicularly to the longitudinal direction of the outer enclosure 1); therefore, when such a light is turned on, light is emitted in a striped pattern in the above-mentioned noble gas discharge lamp. Electric discharges in a striped pattern cannot be confirmed under normal lighting conditions.

[0032] However, when the output electric power from the inverter circuit 12 is decreased 10 %, for example, by a change of voltage from a power source, the electric discharges in a striped pattern can be confirmed. Moreover, the electric discharging positions (points) are not stable and travel in the longitudinal direction of the outer enclosure 1, without interruption. The light emitting from aperture 2a is therefore intermittent.

[0033] In particular, in the case of employing the noble gas discharge lamp in an illumination device for the office equipment such as facsimile machines, image-scanners, and the like, the light intensities at the points in the longitudinal direction of the aperture 2a change continuously. Therefore, it is possible that the scan accuracy of the illuminated document is extremely degraded, and the quality of reproduction is also degraded.

Summary of the Invention

[0034] It is therefore an object of the present invention to provide a noble gas discharge lamp having a simple construction, which can produce a stable travel of electric discharge, and lamps improving light output.

[0035] According to an aspect of the present invention, the present invention provides a noble gas discharge lamp comprising: an outer enclosure comprising a light emitting layer formed therein, and a pair of outer electrodes in the shape of a tape comprising a metal, which are adhered to the total length of the outside of the outer enclosure so as to be separated at a certain interval, and to form a first opening portion and a second opening portion, wherein a nonlinear edge portion is formed at one side portion of one outer electrode forming the second opening portion, and other side portion being opposite to the nonlinear edge portion, is formed linearly.

[0036] Moreover, the nonlinear edge portion is formed at one side of one outer electrode, in which some projections project toward the opposite electrode.

[0037] In particular when facility of production and starting characteristics of the noble gas discharge lamps are taken into consideration, it is preferable that the projections project toward the opposite electrode along the outside of the outer enclosure.

[0038] Moreover, dents are formed among the projections of the nonlinear edge portion.

Brief Description of the Drawings

[0039] Figure 1 is a cross-sectional diagram showing the noble gas discharge lamp of the first embodiment of the present invention.

[0040] Figure 2 is a schematic view showing the outer enclosure and outer electrodes shown in Figure 1.

[0041] Figure 3 is a cross-sectional diagram showing the noble gas discharge lamp of the second embodiment of the present invention.

[0042] Figure 4 is a cross-sectional diagram showing the noble gas discharge lamp of the third embodiment of the present invention.

[0043] Figure 5 is a cross-sectional diagram showing the noble gas discharge lamp of the fourth embodiment of the present invention.

[0044] Figure 6 is a cross-sectional diagram showing the noble gas discharge lamp of the fifth embodiment of the present invention.

[0045] Figure 7 is a cross-sectional diagram showing the noble gas discharge lamp of the sixth embodiment of the present invention.

[0046] Figure 8 is a schematic view showing the outer enclosure and outer electrodes used in the seventh embodiment of the present invention.

[0047] Figure 9 is a schematic view showing the outer enclosure and outer electrodes used in the eighth embodiment of the present invention.

[0048] Figure 10 is a cross-sectional diagram showing a noble gas discharge lamp of background.

[0049] Figure 11 is a schematic view showing the outer laminate shown in Figure 10.

[0050] Figure 12 is a cross-sectional diagram taken along line X-X in Figure 11.

[0051] Figure 13 is a schematic view showing the process for producing the noble gas discharge lamp shown in Figure 10.

[0052] Figure 14 is a schematic view showing an electric circuit of a noble gas discharge lamp.

Description of the Preferred Embodiments

[0053] A detailed explanation will now be made of the noble gas discharge lamp of the present invention.

[0054] The first embodiment of the noble gas discharge lamp of the present invention is explained below with reference to Figures 1 and 2. The components in Figures 1 and 2 identical to those in Figures 10 to 13 are numbered with the same reference numbers as in Figures 10 to 13, and detailed explanations thereof will be omitted.

[0055] The characteristic components of the noble gas discharge lamp shown in Figures 1 and 2 are as follows:

The thickness of the outer enclosure 1A comprised of a glass bulb (tube) is set in a range of 0.2 to 0.7 mm, preferably in a range of 0.4 to 0.7 mm.

From among the side portions 5b and 6b of the outer electrodes 5 and 6 which form the second portion 8, a nonlinear portion 5A in which triangles are formed is formed at only side portion 5b.

The remaining side portions 5a, 6a, and 6b of the outer electrodes 5 and 6 are formed linearly.

[0056] The nonlinear portion 5A has a periodicity. More specifically, when the outer diameter of the outer enclosure 1A is 8 mm, it is preferable that the width of the outer electrode 5 including the nonlinear portion 5A be 8 mm, the pitch thereof be 4 mm, and the height thereof (the height of the triangle) be 1.5 mm. However, the sizes of the nonlinear portion 5A can be changed, depending on the situations of using the noble gas discharge lamp or the illumination device comprised of the noble gas discharge lamp.

[0057] Moreover, the interval between the apexes of the nonlinear portion 5A formed at the side portion 5b of the outer electrode 5 and the linear side portion 6b of the outer electrode 6 is fixed over the entire outer electrodes 5 and 6. The interval between the side portions 5a and 6a forming the first opening portion 7 is fixed over the entire outer electrodes 5 and 6.

[0058] The outer enclosure 1A is comprised of materials having a large dielectric constant, reliable hermetic sealing properties, and light transmitting properties. However, it is preferable to use a lead glass having a large dielectric constant, for example.

[0059] The thickness of the outer enclosure 1A is set in a range of 0.2 to 0.7 mm, preferably in a range of 0.4 to 0.7 mm. Excellent productivity and light properties can be obtained in this range.

[0060] However, when the thickness of the outer enclosure 1A is less than 0.4 mm, in particular less than 0.2 mm, the mechanical strength of the outer enclosure 1A is extremely decreased. Therefore, when the outer enclosures 1A are put into commercial production, the production rate of poor quality goods (broken glass, for example) increases. In contrast, when the thickness thereof is more than 0.7 mm, electric discharges in a striped pattern can be confirmed. Moreover, light emission from the aperture 2a becomes very intermittent. Therefore, it is preferable that the thickness of the outer enclosure 1A be in that range.

[0061] The internal part of the outer enclosure 1A is filled with one kind of noble gas, such as xenon (Xe), krypton (Kr), neon (Ne), helium (He), and the like, or a mixture thereof. The outer enclosure 1A is filled with the noble gas under the confining pressure being in a range of 83 to 200 Torr.

[0062] When the confining pressure is in this range, starting characteristics, and light output (illumination intensity on the illuminated document) can be improved, and the occurrence of intermittent illumination can be reduced. However, when the confining pressure is less than 83 Torr, light output is not sufficiently improved. In contrast, when the confining pressure is more than 200 Torr, not only are starting characteristics inferior, but the electric discharges in a striped pattern are confirmed, and the light emitted from the aperture 2a becomes intermittent. Therefore, it is preferable that the confining pressure of the noble gas be in that range.

[0063] The light emitting layer 2 may include one or more kinds of fluorescent substances, depending on the manner in which the noble gas discharge lamp is to be used.

[0064] Examples of the fluorescent substance comprising the light emitting layer 2 are fluorescent borates such as fluorescent europium activated yttrium·gallium borate, and the like; fluorescent phosphate such as fluorescent cerium·terbium activated lanthanum phosphate (LaPO₄ : Ce,Tb), fluorescent tin activated strontium·magnesium phosphate ((SrMg)₃(PO₄)₂ : Sn), fluorescent europium activated strontium boric phosphate (2SrO· (P₂O₇·B₂O₃) : Eu), and the like; fluorescent europium activated yttrium phosphovanadate (Y(PV)O₄ : Eu); fluorescent cerium·terbium activated magnesium aluminate (MgAl₁₁O₁₉ : Ce, Tb); fluorescent cerium·terbium activated yttrium· silicate (Y₂SiO₅ : Ce, Tb); fluorescent europium activated barium·magnesium aluminate (BaMg₂Al₁₆O₂₇ : Eu); fluorescent europium activated yttrium oxide (Y₂O₃ : Eu), and the like.

[0065] More specifically, for instance, in the case of a three-wavelength illumination system, the light emitting layer comprises a mixture of fluorescent substances, that is, fluorescent europium activated barium·magnesium aluminate having a blue emission spectrum; fluorescent cerium·terbium activated lanthanum phosphate having a green emission spectrum; and fluorescent europium activated yttrium·gallium borate having a red emission spectrum.

[0066] The coated amount of the fluorescent substances is set in a range of 5 to 30 mg/cm². In this range, the desired light output can be obtained. However, when the coated amount is less than 5 mg/cm², the light output decreases; therefore, the illumination intensity on the illuminated document is insufficient. In contrast, when the coated amount is more than 30 mg/cm², a light emitting layer 2 having uniform quality cannot be easily obtained. Therefore, the coated amount of the fluorescent substances is preferably in this range.

[0067] In addition, the first and second opening portions 7 and 8 are formed at the interval portions between the outer electrodes 5 and 6. The opening angle θ₁ of the first opening portion 7 is larger than the opening angle θ₂ of the second opening portion 8.

[0068] Among the angles satisfying the above conditions, it is preferable that the opening angle θ₁ of the first opening portion 7 be in the range of 60° to 90° and the opening angle θ₂ of the second opening portion 8 be approximately 55°. However, the opening angle θ₁ of the first opening portion 7 can be outside the range, depending on the situation of using the noble gas discharge lamp. It is preferable that the second opening portion 8 be narrow so as not to cause breaks in insulation; therefore, the distance between one outer electrode 5 and the other electrode 6 in the second opening portion 8 is preferably 2 mm or more.

[0069] Moreover, the opening angle of the aperture 2a is equivalent to the first angle θ₁ of the first opening portion 7, in the noble gas discharge lamp as shown in Figure 1.

[0070] In this embodiment, from among the side portions 5b and 6b of the outer electrodes 5 and 6 which form the second opening portion 8, the nonlinear portion 5A in which some projections project toward the opposite electrode, is formed at the side portion 5b. More specifically, as shown in Figure 2, the nonlinear portion 5A having a series of repeated triangles is formed at the side portion 5b of the outer electrode 5. The side portion 6b of the outer electrode 6 is formed linearly.

[0071] Therefore, when a high voltage of high frequency is applied to the outer electrodes 5 and 6, an electrical field is easily concentrated at the peaks of the triangles of the nonlinear portion 5A. Then, the electrical discharges easily occur between the nonlinear portion 5A and the linear side portion 6b. Therefore, when some electric power input to the outer electrodes 5 and 6 is decreased by fluctuating output electric power, the noble gas discharge lamp of this embodiment can be certainly lit.

[0072] In the case in which the nonlinear portions 5A and 5A are formed at the side portions 5b and 6b, when the peaks of triangles of the nonlinear portions 5A and 5A formed at the side portions 5b and 6b do not correspond to each other, it is difficult to produce stable travel of electric discharge. Therefore, it is necessary to position the outer electrodes 5 and 6 formed the nonlinear portions 5A and 5A with respect to each other so as to correspond the peaks of triangles of the nonlinear portions 5A and 5A. Therefore, the ease of production of the noble gas discharge lamp may be reduced. However, the side portion 6b being opposite to the nonlinear portion 5A (side portion 5b), is formed linearly in this embodiment. Therefore, the positioning of the side portion 6b and nonlinear portion 5A is not restricted, because the side portion 6b is formed linearly. As a result, assembly of the noble gas discharge lamp can be improved.

[0073] In addition, the thickness of the outer enclosure 1A is in a range of 0.2 to 0.7 mm. Therefore, in the case that the thickness of the outer enclosure 1A is at the top of this range, when a high voltage of high frequency is applied to the outer electrodes 5 and 6, intermittent illumination easily occurs, depending on the increase of voltage to the outer enclosure 1A caused by increase of resistive components. However, even if the outer enclosure 1A is at the top of that range, intermittent illumination can be effectively prevented by the thickness of the outer enclosure 1A being in that range, in company with the existence of the nonlinear portion 5A at only side portion 5b of the outer electrode 5. In addition, light output from the first opening portion 7 via the aperture 2a can be effectively improved.

[0074] Moreover, the nonlinear portion 5A having triangles is formed at the side portion 5b from among the side portions 5b and 6b of the outer electrodes 5 and 6 which form the second portion 8; however, the side portions 5a and 6a of the outer electrodes 5 and 6 forming the first opening portion 7 are formed linearly (this shape does not influence light emission). Therefore, even when the noble gas discharge lamp of this embodiment is used in an illumination device, illumination of a document can be approximately uniform without further measures being taken. As a result, the precision of scanning of an illuminated document can be improved by simple components.

[0075] In particular, when the confining pressure of noble gas is high, light output increases, but the starting characteristics of the noble gas discharge lamp are degraded. However, even if the confining pressure of the noble gas is set to 200 Torr, starting characteristics of a practical level can be obtained, by forming the nonlinear portion 5A in a series of repeated triangles at the side portion 5b of the outer electrode 5. Moreover, occurrence of intermittent illumination is effectively prevented, and the light output can be improved. Therefore, when the noble gas discharge lamp of this embodiment is used in an illumination device, stable travel of electric discharge can be obtained, and the illumination intensity on the illuminated document can be increased; therefore, the precision of scanning of an illuminated document can be improved.

[0076] When the coated amount of the fluorescent substance is in a range of 5 to 30 mg/cm²; the light output from the first opening portion 7 via the aperture 2a can be effectively improved by setting the thickness of the outer enclosure 1A to a range of 0.2 to 0.7 mm, in company with setting the confining pressure of noble gas in a range of 83 to 200 Torr.

[0077] In particular, the above-mentioned range of the coated amount of the fluorescent substances is 2 to 10 times as much as the amount of the fluorescent substances employed in ordinary fluorescent lamps for illumination. It is believed that the coated amount is not preferable for ordinary fluorescent lamps for illumination. However, the light output is effectively increased in the noble gas discharge lamp of the embodiment. A cause of this phenomena is not clear; however, it may be believed that this phenomena is characteristic of a noble gas discharge lamp in which innumerable discharges are formed between the outer electrodes 5 and 6 (approximately perpendicular to the longitudinal direction of the outer enclosure 1A); therefore, a striped pattern is produced.

[0078] When the thickness of the outer enclosure 1A is in that range, the shapes of the outer electrodes 5 and 6 are formed as described above, and the coated amount of the fluorescent substances and the confining pressure of the noble gas are preferably set in those ranges, in addition to set the opening angle θ₁ of the first opening portion 7 in a range of 60 to 90°, the light output emitted from the first opening portion 7 can be effectively increased.

[0079] Under these conditions, the leakage of light from the second portion 8 is prevented, and light output emitted from the first opening portion 7 can be more effectively increased by setting the size of the second portion 8, that is, the interval between the peak of the nonlinear portion 5A and the side portion 6b, to approximately 2 mm.

[0080] Figure 3 shows the second embodiment of the present invention, and the basic components of the noble gas discharge lamp shown in Figure 3 are the same as those of the noble gas discharge lamp shown in Figure 1.

[0081] However, they differ in the following point:

The opening angle θ₃ of the aperture 2a formed in the inside of the outer enclosure 1A at the position corresponding to the first opening portion 7, is larger than the opening angle θ₁ of the first opening portion 7.

[0082] The opening angle θ₃ of the aperture 2a is set in a range of 70° to 110° , for example; however, the angle θ₃ can be changed depending on the situation or the object of using the noble gas discharge lamp.

[0083] Moreover, it is preferable that the opening angle θ₁ of the first opening portion 7 and the opening angle θ₂ of the second opening portion 8 satisfy the relationship of θ₁ > θ₂ in this embodiment.

[0084] In this embodiment, in winding the outer laminate 3 onto the outside of the outer enclosure 1A, even if the center of the first opening portion 7 is a little off-center with respect to the center of the aperture 2a, a discrepancy of the optical axis of the light emitted from the first opening portion 7 can be mitigated. Therefore, it is possible to obtain full scanning accuracy when the noble gas discharge lamp of the second embodiment is used to an illumination device.

[0085] Figure 4 shows the third embodiment of the present invention, and the basic components of the noble gas discharge lamp shown in Figure 4 are the same as those of the noble gas discharge lamp shown in Figure 1.

[0086] However, they differ in the following point:

One edge 4a and the outer edge 4b of the light transmitting sheet 4 are laminated to each other on the outer electrode 5, and they are melted and adhered by ultrasonic waves.

[0087] In this embodiment, the laminated portions 4a and 4b are melted and adhered by ultrasonic waves on the outside of the outer electrode 5; therefore, an oscillation of ultrasonic waves applying the light emitting layer 2 positioning inside of the outer electrode 1A is relieved. In comparing the noble gas discharge lamps of the first and the second embodiments, the oscillation of ultrasonic waves applying the light emitting layer 2 positioning inside of the outer electrode 1A is relieved. As a result, a peeling off of the light emitting layer 2 from the outer enclosure 1A is substantially prevented, and light output can be improved.

[0088] Moreover, in the above embodiment, the laminated portions 4a and 4b of the light transmitting sheet 4 are melted and adhered by ultrasonic waves; however, adhesion by an adhesive agent, by heat, or simultaneous use of both may also be employed.

[0089] Figure 5 shows the fourth embodiment of the present invention, and the basic components of the noble gas discharge lamp shown in Figure 5 are the same as those of the noble gas discharge lamp shown in Figure 1.

[0090] However, they differ in the following point:

A pair of the outer electrodes 5 and 6 is adhered to the outside of the outer enclosure 1A by using the adhesive layer; then a light transmitting sheet 4A comprising PET resin and the like, for example, is wound and adhered on the outside of the outer enclosure 1A so as to cover the outer enclosures 5 and 6.

[0091] In this embodiment, the electrical insulating ability between the outer electrodes 5 and 6 can be improved by forming an insulating coating having light transmitting properties, which is comprised of silicon varnish, to the outside of the outer enclosure 1A, before winding the light transmitting sheet 4A onto the outside of the outer enclosure 1A.

[0092] Figure 6 shows the fifth embodiment of the present invention, and the basic components of the noble gas discharge lamp shown in Figure 6 are the same as those of the noble gas discharge lamp shown in Figure 1.

[0093] However, they differ in the following point:

After a pair of outer electrodes 5 and 6 are adhered to the outside of the outer enclosure 1A using the adhesive layer, a protective tube 13 comprising thermal shrinking resin, such as PET resin and the like, is covered thereon and shrunk with heat so that the outer electrodes 5 and 6 are covered with the protective tube 13.

[0094] Moreover, after the protective tube 13 is fit to the outside of the outer enclosure 1A, the protective tube 13 can be forcibly contacted to the outside of the outer enclosure 1A by heating them to approximately 150 to 200°C, and the protective tube 13 is made to shrink by heat.

[0095] Compared to the above-mentioned embodiments, manufacturing and working efficiency in this embodiment are not as good. However, because the adhesive layer is not used, erosion does not occur due to the reaction between the material comprising the terminals 51 and 61 and the adhesive composition comprising the adhesive layer. Therefore, stable travel conditions in the noble gas discharge lamp can be maintained for long periods. In addition, the joint portion is not formed in the protective tube 13; therefore, the peeling off of a laminated portion can be prevented as the peeling off of the light transmitting sheet 4 can be prevented in the third embodiment.

[0096] In particular, the insulating ability between the outer electrodes 5 and 6 can be improved more effectively by forming an insulating coating having light transmitting properties, which is comprised of silicon varnish, to the outside of the outer enclosure 1A, before covering the protective tube 13 over the outside of the outer enclosure 1A.

[0097] Figure 7 shows the sixth embodiment of the present invention, and the basic components of the noble gas discharge lamp shown in Figure 7 are the same as those of the noble gas discharge lamp shown in Figure 1.

[0098] However, they differ in the following point:

After fitting a protective tube 13 over the outside of the outer laminate 3, which is comprised of thermal shrinking resins, such as PET resin, and the like, the protective tube 13 is made to shrink with heat.

[0099] Moreover, after the protective tube 13 is fit over the outside of the outer laminate 3, the protective tube 13 can be contacted forcibly to the outside of the light transmitting sheet 4 by heating them to approximately 150°C to 200°C, and the protective tube 13 is made to shrink by heat.

[0100] In this embodiment, even if the noble gas discharge lamp is used under extreme conditions, or in situations requiring high safety standards, products having high quality can be produced by covering the outer laminate 3 with protective tube 13 having high heat-resistance and light transmitting properties.

[0101] In particular, the characteristic structure of this embodiment can be applied to the noble gas discharge lamps shown in Figures 3 to 6.

[0102] Moreover, the electrical insulating material such as the light transmitting sheet 4 and 4A and the protective tube 13, may be omitted in the aforementioned embodiments.

[0103] In the following, preferred embodiments of the nonlinear portion will be explained. As described above, the nonlinear portion is formed at one side portion forming the second opening 8, in which some projections project toward the opposite electrode. Among many possible kinds of the nonlinear portions, the nonlinear portions shown in Figures 8 and 9 are preferable.

[0104] Figure 8 shows the seventh embodiment of the present invention, and shows unfolding of outer enclosure 1A. The basic components of the noble gas discharge lamp shown in Figure 8 are the same as those of the noble gas discharge lamp shown in Figure 1.

[0105] However, they differ in the following points:

The nonlinear portion 5B is formed at only side portion 5b from among the side portions 5b and 6b forming the second opening portion 8. The nonlinear portion 5B is in a wave shape, such as a series of repeated semicircles.

The side portion 6b being opposite to the side portion 5b, that is, the nonlinear portion 5B, is formed linearly.

[0106] Moreover, the remaining side portions 5a, 6a, and 6b beside the side portion 5b are entirely formed linearly.

[0107] In this embodiment, when a high voltage of high frequency is applied to the outer electrodes 5 and 6, discharges occur between the nonlinear portion 5B (side portion 5b) and the side portion 6b linearly; however, the positioning of the outer electrodes 5 and 6 is not restricted, because the side portion 6b is formed linearly. Therefore, assembly of the noble gas discharge lamp can be improved.

[0108] Figure 9 shows the eighth embodiment of the present invention, and shows unfolding of outer enclosure 1A. The basic components of the noble gas discharge lamp shown in Figure 9 are the same as those of the noble gas discharge lamp shown in Figure 1.

[0109] However, they differ in the following points:

The nonlinear portion 5C is formed at only the side portion 5b from among side portions 5b and 6b (they form the second opening portion 8). The nonlinear portion 5C is in a series of repeated polygons, such as rectangles or trapezoids.

[0110] The side portion 6b, opposite to the nonlinear portion 5 C (side portion 5b), is formed linearly.

[0111] Moreover, the remaining side portions 5a, 6a, and 6b of the outer electrodes 5 and 6 beside the side portion 5b of the outer electrode 5 are formed linearly.

[0112] In particular, the outer electrodes 5 and 6 having the above-mentioned nonlinear portions 5B and 5C can be applied to the noble gas discharge lamps shown in Figures 1 to 7 in suitable combinations.

[0113] Moreover, the pitch and the height of the nonlinear portions can be modified, depending on the size of the noble gas discharge lamp.

Experimental Examples

[0114] The present invention will now be explained using Experimental Examples.

Experimental Example 1

[0115] The fluorescent water-soluble coating solution containing fluorescent cerium·terbium activated yttrium· silicate (Y₂SiO₅ : Ce, Tb) having an emission spectrum in yellow-green wavelengths was obtained.

[0116] Next, the light emitting layer 2 was formed by coating the obtained fluorescent water-soluble coating solution on the inside of the outer enclosure 1A comprised of lead glass, which was 8 mm in external diameter, 0.5 mm in thickness, and 360 mm in length. Moreover, the coated amount of the fluorescent water-soluble coating solution was 15 mg/cm².

[0117] Then, the aperture 2a having 75° in the opening angle θ₃ was obtained by forcibly peeling off a part of the obtained light emitting layer 2 using a scraper.

[0118] The outer enclosure 1A was sealed, and filled with xenon gas at a confining pressure being varied in a range of 70 to 230 Torr.

[0119] Then, the noble gas discharge lamps of this Experimental Example were produced by the same steps shown in Figures 13. Moreover, a pair of the outer electrodes 5 and 6 was comprised of aluminum foil in the shape of a tape 8 mm in width. As shown in Figure 2, the nonlinear portion 5A was formed at only one side portion 5b of the outer electrode 5 forming the second opening portion 8, in which triangles 4 mm in pitch and 1.5 mm in peak height were formed. The side portion 6b being opposite to the nonlinear portion 5A (side portion 5b) is formed linearly.

[0120] Next, the following measurement was carried out on the noble gas discharge lamps obtained in this Experimental Example.

(1) The electrical discharge occurring voltage (starting voltage)

[0121] The obtained noble gas discharge lamps were incorporated in an electric circuit as shown in Figure 14, and the output voltage (frequency fixed at 30 kHz, voltage 2500 V_o-p) of the inverter circuit 12 were gradually increased. Then, the voltages at which discharge occurred (starting voltages) were measured in which the intermittent illumination was not confirmed. The result of this measurement was shown in the following Table 1.

Table 1

Confining Pressure of Xenon Gas (Torr)	Starting Voltages (V)
70	1750
83	2000
90	2000
100	2000
110	2250
120	2250
150	2250
200	2250
210	2500
230	2500

[0122] As shown in Table 1, the following points were clear.

[0123] When the confining pressure of xenon gas is 200 Torr or less, even when the output voltage of the inverter circuit 12 was set to 90 % of a fixed voltage (2500 V_o-p), the intermittent illumination cannot be confirmed, and stable travel of electric discharge can be obtained after the lamps are lit. Compared with the conventional noble gas discharge lamp does not comprise the nonlinear portion 5A, the starting voltage in a range of 300 to 600 V can be decreased in the noble gas discharge lamps of this Experimental Example.

[0124] When the confining pressure is 83 Torr or greater in the conventional noble gas discharge lamp, the intermittent illumination can be confirmed. In addition, when the confining pressure reaches 100 Torr, the conventional noble gas discharge lamp cannot be used in practice without difficulty.

[0125] In the case of more than 200 Torr, specifically 210 Torr and 230 Torr, the lamps can be lit with a fixed voltage (2500 V_o-p); however, start-up is not assured when the input power was decreased.

[0126] Moreover, the following measurements were carried out for the noble gas discharge lamps obtained in this Experimental Example.

(1) Illumination intensity of the document

[0127] The obtained noble gas discharge lamps were incorporated in an electric circuit as shown in Figure 14, and the output voltage (frequency fixed at 30 kHz) of the inverter circuit 12 was set to 90 % of a fixed voltage (2500 V_o-p). In these conditions, the illumination intensities on the document were measured at a point 8 mm away from the outer enclosure 1A. The results were shown in the following Table 2.

(2) Occurrence of intermittent illumination

[0128] The obtained noble gas discharge lamps were incorporated in an electric circuit as shown in Figure 14, and the output voltage (frequency fixed at 30 kHz) of the inverter circuit 12 was set to 90 % of a fixed voltage (2500 V_o-p). In these conditions, the occurrence of intermittent illumination was evaluated at a point 8 mm away from the outer enclosure. The results were shown in the following Table 2.

[0129] In Table 2, ○ means that intermittent illumination did not occur, △ means that some intermittent illumination did occur, but the noble gas discharge lamp can be used in practice without difficulty, and X means that intermittent illumination did occur, and the noble gas discharge lamp cannot be used in practice without difficulty.

Table 2

Confining Pressure of Xenon Gas (Torr)	Illumination intensity on the document (Lx)	Occurrence of intermittent illumination
70	13000	○
83	15000	○
90	16000	○
100	16500	○
110	17000	○
120	17500	○
150	19000	○
200	19500	△
210	(20000)	X
230	(21000)	X

[0130] As shown in Table 2, the following points were clear.

[0131] When the confining pressure of xenon gas is 150 Torr or less, stable travel of electric discharge without occurrence of intermittent illumination can be obtained. When the confining pressure of xenon gas is 200 Torr, some intermittent illuminations did occur, but the noble gas discharge lamp can be used in practice without difficulty. However, in the case the pressure being more than 200 Torr, specifically 210 Torr and 230 Torr, the significant intermittent illumination occurs. Therefore, it is confirmed that it is difficult to use the noble gas discharge lamps in an illumination device because the scanning precision of an illuminated document is degraded.

[0132] Moreover, the illumination intensity on the illuminated document increases, depending on an increase of the confining pressure of xenon gas; however, a stable illumination intensity without occurrence of intermittent illumination can be obtained when the confining pressure of xenon gas is in a range of 200 Torr or less.

[0133] Therefore, it is clear from Table 2 that the confining pressure of noble gas is suitable in a range of 83 to 200 Torr.

Experimental Example 2

[0134] Noble gas discharge lamps were produced in the same way as in Experimental Example 1. However, the confining pressure of xenon gas was fixed at 120 Torr, and the thickness of the outer enclosure 1A was varied in a range of 0.18 to 0.8 mm as shown in the following Table 3.

[0135] Next, the following measurements were carried out for the noble gas discharge lamps obtained in this Experimental Example.

(1) Occurrence of intermittent illumination

[0136] The obtained noble gas discharge lamps were incorporated in an electric circuit as shown in Figure 14, and the output voltage (frequency fixed at 30 kHz) of the inverter circuit 12 was set to 90 % of a fixed voltage (2500 V_o-p). In these conditions, the occurrence of intermittent illumination was evaluated at a point 8 mm away from the outer enclosure. The results were shown in the following Table 3.

[0137] In Table 3, ○ means that intermittent illumination did not occur, △ means that some intermittent illumination did occur, but the noble gas discharge lamp can be used in practice, and X means that intermittent illumination did occur, and the noble gas discharge lamp cannot be used in practice without difficulty.

(2) Presence of damage in producing steps (Strength)

[0138] In production steps, the presence of damage in the outer enclosures of the obtained noble gas discharge lamps was evaluated.

[0139] In Table 3, ○ means that damage to the outer enclosure was not observed, and the strength of the outer enclosure is sufficient; △ means that some damage was observed in the outer enclosure, but the noble gas discharge lamps comprising the outer enclosures can be used in practice; and X means that serious damage to the outer enclosure was observed and the strength of the outer enclosure meant the produced lamps would be difficult to use.

Table 3

Thickness of the outer enclosure (mm)	Occurrence of intermittent illumination	Strength
0.18	○	X
0.2	○	△
0.25	○	△
0.4	○	○
0.5	○	○
0.6	○	○
0.7	△	○
0.8	X	○

[0140] As shown in Table 3, the following points were clear.

[0141] When the thickness of the outer enclosure 1A is in a range of 0.18 to 0.6 mm, the occurrence of intermittent illumination cannot be confirmed, even when the input to the outer electrodes 5 and 6 is low.

[0142] When the thickness is 0.7 mm, some intermittent illumination was confirmed; however, the noble gas discharge lamp can be used in practice without difficulty.

[0143] However, when the thickness is 0.8 mm, significant intermittent illumination was confirmed, and the effects obtained by forming the nonlinear portion 5A were decreased.

[0144] Moreover, when the thickness of the outer enclosure 1A is 0.4 mm or greater, damage cannot be confirmed in the production.

[0145] When the thickness is less than 0.4 mm, especially 0.25 mm and 0.2 mm, damage in the production was observed. In particular, when the thickness is 0.18 mm, damage such as cracks suddenly increases; therefore, it is confirmed that mechanical strength is low, and they are unsuitable for producing in large quantities.

[0146] Therefore, as shown in Table 3, the thickness of the outer enclosure is preferably in a range of 0.2 to 0.7 mm, more preferably in a range of 0.4 to 0.7 mm.

Claims

1. A noble gas discharge lamp comprising:

an outer enclosure (1A) comprising a light emitting layer (2) formed therein, and

a pair of outer electrodes (5, 6) having tape shapes comprising a metal, which are positioned to the entire length of the outside of the outer enclosure so as to separate one outer electrode (5) and the other outer electrode (6) at a certain distance, and to form a first opening portion (7) and a second opening portion (8);
wherein a nonlinear portion (5A, 5B, 5C) is formed at one side portion (5b) of one outer electrode (5) forming the second opening portion (8), and other side portion (6b) being opposite to the nonlinear portion (5A, 5B, 5C), is formed linearly.

2. A noble gas discharge lamp according to Claim 1, wherein light emitted from the light emitting layer (2) is mainly emitted from the first opening portion (7), and the side portions (5a, 6a) of a pair of the outer electrodes (5, 6) forming the first opening portion (7), are formed linearly.

3. A noble gas discharge lamp according to Claim 2, wherein an insulating material is coated on the outside of the outer enclosure (1A) so as to cover the outer electrodes (5, 6).

4. A noble gas discharge lamp according to Claim 3, wherein the insulating material is at least one material selected from the group consisting of a light transmitting sheet (4, 4A) and a protective tube (13) comprising thermal shrinking resin.

5. A noble gas discharge lamp according to Claim 1, the noble gas discharge lamp comprising the outer enclosure (1A) in a straight tube shape, and the outer laminate (3),

the outer laminate (3) comprising a light transmitting sheet (4, 4A), outer electrodes (5, 6), and an adhesive layer (9),

the light transmitting sheet (4, 4A) have the same length as the outer enclosure (1A),

a pair of outer electrodes (5, 6) having tape shapes comprised of a metal positioned on one surface of the light transmitting sheet (4) so as to separate one outer electrode (5) and the other outer electrode (6), and

the adhesive layer (9) formed on the surface of the light transmitting sheet (4, 4A) in which the outer electrodes (5, 6) are positioned,

   wherein the outer electrodes (5, 6) and the light transmitting layer (4, 4A) are formed on the outside of the outer enclosure (1A) in sequence.

6. A noble gas discharge lamp according to Claim 1, wherein the nonlinear portion (5A, 5B, 5C) is formed over the entire length of the outer electrode (5, 6).

7. A noble gas discharge lamp according to Claim 6, wherein the nonlinear portion (5A, 5B, 5C) is formed in a series of a repeated shape, the shape being at least one of a triangle, a polygon, and a wave shape.

8. A noble gas discharge lamp according to Claim 7, wherein the polygon is a trapezoid.

9. A noble gas discharge lamp according to Claim 7, wherein the wave shape is in a series of repeated semicircles.

10. A noble gas discharge lamp according to Claim 1, wherein an aperture (2a) is formed in the inside of the outer enclosure (1A) at a position corresponding to the first opening portion (7), in which the light emitting layer (2) is not formed.

11. A noble gas discharge lamp according to Claim 1, wherein the outer enclosure (1A) is filled with noble gas under a confining pressure in a range of 83 to 200 Torr.

12. A noble gas discharge lamp according to Claim 1, wherein the thickness of the outer enclosure (1A) is in a range of 0.2 to 0.7 mm.

13. A noble gas discharge lamp according to Claim 12, wherein the thickness of the outer enclosure (1A) is in a range of 0.4 to 0.7 mm.

Drawing