Recording media

Description

Field of the Invention

[0001] This invention relates to a recording medium comprising as a recording component, a material which is obtained by physical denaturation of a thermally coagulatable proteinaceous compound.

Background of the Invention

[0002] In the field ofthermographic orthermosensitive recording process, many thermal recording media are known which provide relief images by insolubilizing a recording layer by the application of a heat pattern, and removing the soluble areas of the recording layer. These media, and processes using them, are disclosed in U.S. Patent 4,115,613 (corresponding to Japanese Patent Publication No. 10870/79 and 36075/80 and Japanese Patent Application (OPI) No. 15817/80) and U.S. Patent 4288509 (corresponding to Japanese Patent Application (OPI) No. 15818/80 (the term "OPI" as used herein refers to a "published unexamined Japanese Patent Application").

[0003] Another known thermosensitive recording medium comprising a chemically modified, thermally coagulatable proteinaceous compound is disclosed in EP-A-0034502 published on 19-8-81 and belonging to the prior art according to Article 54 (3) on (4) for the designated states, BE, CH, DE, FR, GB and LI, said EP-A-0034052 corresponding to Japanese Patent Application (OPI) Nos. 15395/81 and 110931/80 and Japanese Patent Application No. 172643/80).

[0004] In the foregoing references, the recording media are characterized by the use of thermally coagulatable proteinaceous compounds or of a chemically modified thermally coagulatable proteinaceous compounds, without any denaturation.

[0005] The preparation of recording layers comprising a thermally coagulatable proteinaceous compound is disclosed in U.S. Patent 4115613 at column 5, lines 25 to 33 which states that drying is carried out under conditions in which the granular state is not destroyed i.e. denaturation does not take place and with particular attention to temperature. In general, the coating layer is dried using (e.g.) warm air at a temperature of lower than 70°C, more generally at about 30°C to about 60°C.

[0006] Also, in chemical modification, a certain condition must be maintained, as described in EP-A-0034052. More specifically, the Preparation Examples of this European Patent Application indicate that the temperature was maintained between 0°C to 40°C during the chemical modification reaction. In this temperature range, the thermally coagulatable proteinaceous compound is not denatured.

[0007] Accordingly, in the manufacture of the above described recording media, the drying procedure must be controlled at a comparatively low temperature such that denaturation does not take place. Consequently, in such case, a lengthy drying chamber and an over-sized dehumidifier are inevitably required.

[0008] Further, the properties of the resulting recording medium can be adversely affected by the temperature and/or humidity of atmosphere. Accordingly, in order to obtain a high quality image using such recording media, the temperature and humidity of the atmosphere must be strictly controlled.

[0009] With regard to the term "denaturation" Collier's Ency/copedia, Vol. 16, p.397 (1958), teaches that: "Proteins are extremely difficult substances to handle, because they are readilly altered into "denatured" proteins. This change is accompanied by an alteration in solubility. Thus, a "native" protein, which is soluble in water or dilute salt solution, becomes insoluble in these solvents when denatured. The change may be produced by mild heat, acid or alkali, ultraviolet light, alcohol, high pressure, and even by simply remaining standing in solution".

[0010] The term "chemically modification" is utilized by G.E. Means and R. E. Feeny, Chemical Modifications of Proteins, p.10, lines 11 to 19 (1970), Holden-Day, Inc., in the sense that: "Chemical modification of proteins often entails the use of distinctly harsh conditions. Extremes of pH, for example, may be desirable to maintain a reagent or amino acid side chain in reactive state, but can have undesirable effects on protein structure. In some cases harsh conditions result from the use of agents (e.g. urea, guanidine hydrochloride) to unfold the protein, or to otherwise increase the accessibility and reactivity of its various side chains. Ideally removal of perturbing agent (and the modifying reagent) results in reversion of the protein to its original conformation".

[0011] With respect to proteinaceous compounds therefore, the terms "denaturation" and "chemical modification" represent quite different concepts.

[0012] As described above, in known thermosensitive recording media which contain a thermally coagulatable proteinaceous compound and/or a chemically modified, thermally coagulatable pro- , teinaceous compound, the image_recording is carried out using a thermal coagulation property of the proteinaceous compound, i.e. a thermal denaturation property. Accordingly, no denaturation should take place during the preparation of recording medium.

Summary of the Invention

[0013] The inventors have now found that, in a recording medium comprising a recording layer containing as a recording component a material which is obtained by physical denaturation of a thermally coagulatable proteinaceous compound, the recording layer becomes non-removable from a support upon application of energy, e.g. light and heat.

[0014] In accordance with the present invention, there is provided a recording medium comprising a support having provided thereon a recording layer, characterized in that said recording layer contains at least one material which is obtained by physical denaturation of a thermally coagulatable proteinaceous compound.

[0015] In accordance with the present invention, a recording medium can be prepared at a low cost on an industrial scale, and the properties of this recording medium are not adversely affected by the temperature and/or humidity of atmosphere, so that a high-quality image stable over a long period of time of, e.g. several years, can be obtained with good reproducibility.

Detailed Description of the Invention

[0016] In the preparation of the material which is obtained by physical denaturation of a thermally coagulatable proteinaceous compound, at least one physical means of heat, pressure, freezing, sound waves and surface forces may be applied, as taught for example in Chemical Review, vol. 34, p.163-165.

[0017] In the preparation of the material which is obtained by physical denaturation of a theramally coagulatable proteinaceous compound, physical denaturation by thermal means (hereinafter called thermal denaturation) may be employed in combination with chemical denaturation, other physical denaturation and/or biological denaturation.

[0018] Where chemical denaturation is used in combination with thermal denaturation at least one chemical denaturation agent selected from the following groups may be used:-

(a) acrylic amidine derivatives such as guan- dine, aminoguanidine, acetamidine, car- bomoylguanidine, or biguanide; salts of these derivatives such as hydrochloride carbonates, hydrobromides, hydroiodides or thiocyanates; and heterocyclic amidine derivatives such as imidazole or 3-aminotriazole;

(b) thiourea and its derivatives, such as thiourea, methylthiourea, or 1,3-diethylthiourea;

(c) carbamates such a urethane, N-methylurethane, or n-butyl or carbamate;

(d) amino acids such as glycine, glycylglycine, N-acetyl-D,L-alanine or N-acetyl-D,L-leucine;

(e) organic and inorganic salts, such as ammonium formate, ammonium chloride, potassium iodide, sodium salicylate, or sodium thioglycolate;

(f) organic acids, such as acetic acid, lactic acid or citric acid;

(g) amides and imides, such as formamide, acetamide, glycolamide, N,N-dimethylacetamide, or e-caprolactam;

(h) urea derivatives, such as urea, methylurea, ethylurea or semicarbazide;

(i) amines and salts thereof such as ethylamine hydrochloride, triethylamine hydrochloride, triethanolamine, propanolamine, tetramethylammonium chloride, or hydroxylamine;

(j) alcohols such as methanol, ethanol, or butanol;

(k) ethers or acetals such as dioxane, furfaral or diethyl acetal;

(I) ketones such as acetone, methyl ethyl ketone, diacetone alcohol, phorone, cyclohexanone, or acetohenone;

(m) polyhydric alcohol derivatives such as ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, ethylene glycol monoacetate, or ethylene glycol ester;

(n) phenol dereivatives such as catechol, phloroglucinol, or pyrogallol;

(o) sulfonic acid derivatives such as benzenesulfonic acid, or p-toluenesulfonic acid; and

(p) thiazole derivatives such as 2-mercaptobenzothiazole, acetamidothiazole, or benzothiazole.

[0019] Where biological denaturation is used in combination with thermal denaturation, at least one biological means of application of microorganisms and enzymes may be employed, as taught for example in Chemical Review, vol 34, p. 165-166.

[0020] Chemical denaturation, physical denaturation and/or biological denaturation as described above may be applied as a first stage and followed by thermal denaturation.

[0021] In the preparation of the material, certain additives (such as surfactants, water-soluble polymers, dyes, antiseptic or mold-proofing agents) may be present in the material in order to facilitate subsequent procedures.

[0022] In the preparation of the recording medium of this invention, at least one material which is obtained by physical denaturation of a thermally coagulatable proteinaceous compound may be emulsified and dispersed in a dispersing medium, such as a water, and coated on a support, followed by drying to form a recording layer.

[0023] It is also possible to form a recording layer by coating a mixture of a material which is obtained by physical denaturatiuon of thermally coagulatable proteinaceous compound and (a) a thermally coagulatable proteinaceous compound and/or (b) a chemically modified, thermally coagulatable proteinaceous compound described in the foregoing references. In the mixture, the material which is obtained by physical denaturation of a theramlly coagulatable proteinaceous compound can be present in an amount of at least 1 weight percent, and more preferably, at least 30 weight percent of the total weight.

[0024] Examples ofthermally coagulatable proteinaceous compounds which can be used as starting product to prepare the material which is obtained by physical denaturation include isolated proteins, such as albumin, hemoglobin, globulin, prolamin an glutelin; egg white and dry egg white, each containing albumin as a major ingredient; blood powder contaning hemoglobin as a major ingredient; soybean protein containing globulin as a major ingredient, such as dry soybean milk and concentrated soybean powder; wheat gluten containing prolamin and glutelin as major ingredients, such as active wheat protein; and corn protein containing prolamin as a major ingredient, such as sein.

[0025] The recording layer of the recording medium of this invention may contain at least one heat- sensitizer as disclosed in U.S. Patent 4 115 613. The recording layer of the recording medium of this invention may further contain fine particles of substances capable of absorbing light and converting it to heat, such as carbon black and graphite, as disclosed in U.S. Patent 4 115 613, or colouring materials, such as yellow, orange and red dye-pigments as disclosed in U.S. Patent 4 288 509.

[0026] Further, when the recording layer on the recording medium of this invention comprises a material which is obtained by physical denaturation of a light-sensitive, chemically modified, thermally coagulatable proteinaceous compound, it may contain a light-sensitizer.

[0027] Support which can be used for the recording layer include polymer film (e.g. of polyesters, cellulose triacetate, polystyrene, or polycarbonates) matted film such as polyester film whose surface is matted, sythetic paper, glass, and metal sheet (e.g. of aluminium or copper). A subbing layer may be provided on the support to improve the adhesiveness of the support to the recording layer.

[0028] Recording using the recording medium of this invention is effected by the application of light and/or heat. One or more light sources, such as a carbon arc lamp, a metal halide lamp, and argon ion laser, a YAG laser, a xenon flash lamp, and a photographic flood lamp, can be used for "imagewise" exposure.

[0029] Methods of recording by the application of heat can be classified as external heating methods and internal heating methods. In accordance with external heating methods, selective heating is achieved by bringing the recording layer into direct contact with heat or a heat pattern, or by receiving heat generated and accumulated by light-exposure in heat-absorbing areas of an original in accordance with a reflective light-exposure method. The recording layer is then non-removable from the support after such heating. Internal heating methods are mainly applied to a recording layer containing therein a light-heat conversion substance as disclosed in U.S Patent 4 115 613. In accordance with such internal heating methods, electromagnetic radiation rays are selectively applied onto the recording layer e.g. by exposing it to light through a mask. The recording layer is thereafter non-removable from the support, due to the heat generated by the light-heat conversion substance.

[0030] In forming a recorded image on the recording layer on which heat and/or light has been applied as described above, unchanged areas are removed and changed areas form images. Usually, on removing unchanged areas of the recording layer by applying thereto a solvent (such as water, dilute aqueous solution of an acid, dilute aqueous solution of an alkali, or an aqueous solution of neutral salt) at room temperature by a method such as shower development, spray development, dip development, or wipe development, the changed areas i.e. the non-removable areas corresponding to the heat and/or light pattern) are obtained as recorded images.

[0031] The following Preparation Examples and Examples are given to illustrate this invention in greater detail.

Preparation Example 1

[0032] 10 g of egg albumin (a product of Calibiochem-Behring Corp., La Jolla, California, distributed by Hoechst Japan Ltd) was dissolved in 90 g of water, and the solution was heated for 10 minutes to 70°C to obtain a white turbid solution. The thus obtained turbid solution contained thermally denatured egg albumin.

Preparation Example 2

[0033] 5 g of dry egg white (a product of Sigma Chemical Co., Saint Louis, Missouri, U.S.A.) was dissolved in 45 g of water, and the solution was added dropwise to 50 g of water at 90°C under stirring. The hot water was kept at 90°C or higher until the completion of the dropwise addition, to obtain a white turbid suspension. The thus obtained white turbid suspension contained thermally denatured egg white.

Preparation Example 3

[0034] 100 g of egg albumin powder (a product of E. Merk Aktiengesellschaft, Darmstadt, West Germany) was dissolved in 900 g of water, and the solution was heated for 3 hours at 125°C in an autoclave to obtain a white, soft cake. The thus obtained white, soft cake which comprised egg albumin denatured by heat and pressure was dispersed using an agitator and/or ultrasonic dispersion means to obtain a white turbid suspension.

Preparation Example 4

[0035] 30 g of a 10 percent egg white aqueous solution was added dropwise to 30 g of ethanol at 70°C over 2 minutes with stirring. The resulting white suspension contained thermally and chemically denatured egg white.

Preparation Example 5

[0036] 5 g of dry egg white (a product of Sigma Chemical Co.) was dissolved in 92 g of water, and 3 g of a 25 percent urea aqueous solution was added thereto, followed by heating of the resulting solution at 85°C for 3 minutes. The thus obtaind suspension contained chemically and thermally denatured egg white.

Preparation Example 6

[0037] 10 g of soybean protein (soybean acetone powder; a product of Sigma Chemical Co.) was dissolved in 95 g of water, and the dispersion was heated at 89°C for 30 minutes. A film, formed on the liquid surface, was dried and pulverized by means of mortar, to obtain a fine powder of thermally denatured soybean protein.

Preparation Example 7

[0038] 5 g of dry egg white (a product of Sigma Chemical Co.) was dissolved in 95 g of water, and 5 g of a red pigment (Sumitone Red, a product of Sumitomo Chemical Co,. Ltd) was dispersed therein by applying thereto ultrasonic waves. Then, a shearing force was applied to the dispersion by means of a roller to cause pressure denaturation? Thus, there was obtained water- insoluble, non-sticky film. 100 g of water was added to 100 g of the thus obtained film, and emulsified and dispersed by means of a mortar to obtain a red dispersion. The thus obtained dispersion contained physically denatured egg white.

Example 1

[0039] 20 g of water and 2 g of carbon black (Coloidex No. 3; a product of Columbian Carbon Japan Ltd.) were added to 50 g of the turbid solution obtained in Preparation Example 1, and the mixture was subjected to ultrasonic dispersion to obtain a black coating mixture. The coating mixture was located in a 100µm thick polyester film by use of a wire bar and dried in 80°C hot air to form a black recording layer having an optical density of 3.8. Thus, a recording medium was formulated.

[0040] The thus obtained recording layer was brought into intimate contact with a lith film original having a 150 line half tone pattern, exposed by use of a xenon flash light source (XENOFAX FX-150), made by Riso Kagaku Kogyo Co.; exposure time: 5 x 10-³sec.) and then developed by applying therein a shower of water having a pressure of 2.0 kg/cm to obtain a distinct positive image.

[0041] The above described recording process was carried out in various environments with temperature ranging from 0°C to 40°C and relative humidity ranging from 10% to 80%. In each case, a distinct image was obtained.

[0042] The thus prepared recording medium was packed in an open paper bag lined with plastic film. The paper bag was then placed in an incubator having a temperature of 40°C and a relative humidity of 80% for 72 hours. Thereafter, the recording medium was processed by the above described process to obtain thereby a distinct image.

Example 2

[0043] 5 g of water and 0.5 g of a red pigment (Lake Red 4R; a product of Tokyo Ink Manufacturing Co. Ltd) were added to 11 g of the turbid suspension obtained in Preparation Example 2, and the mixture was subjected to ultrasonic dispersion to obtain a red coating mixture. The thus obtained coating mixture was coated on a 100llm thick polyester film by use of a wire bar and dried in 110°C hot air to form a red recording layer having an optical density of 2.5 with a green filter.

[0044] The thus obtained recording layer was brought into intimate contact with a reflection original having a black line pattern, exposed by use of a xenon flash light source (exposure time: 5 x 10-³sec.) and then developed in the same manner as in Example 1 to obtain distinct positive image.

[0045] The above described recording process was carried out in various environments with temperature ranging from 0°C to 40°C and relative humidity ranging from 10% to 80%. In each case, a distinct image was obtained.

Example 3

[0046] 35 g of water and 2 g of carbon black (No. 999, a product of Columbian Carbon Japan Ltd.) were added to 50 g of the turbid suspension obtained in Preparation Example 3, and the mixture was subjected to ultrasonic dispersion to obtain a black coating mixture. The coating mixture was coated in a 130pm thick synthetic white paper (FPG-130; a product of Ooji Yuka Co. Ltd) by use of a wire bar and dried in 70°C hot air to form a black recording layer having an optical density of 2.0.

[0047] The thus obtained recording paper was treated in the same manner as in Example 1. Thus, the same results as in Example 1 were obtained.

Example 4

[0048] Instead of the turbid solution, the white suspension or turbid solution obtained in Preparation Example 4 or 5 was used for the preparation of coating mixture. The resulting recording layer was treated in the same manner as in Example 1, 2 or 3 to obtain the same results.

Example 5

[0049] 5 g of water was added to 5 g of the fine powder of thermally denatured soybean protein obtained in Preparation Example 6, and emulsified and dispersed by ultrasonic dispersion to obtain a white supension.

[0050] The thus obtained suspension was used for the preparation of coating mixture in Example 1, 2 or 3 to obtain the same results.

Example 6

[0051] The red dispersion mixture obtained in Preparation Example 7 was coated on a 100um thick polymer film and dried in about 100°C hot air to a red recording layer. When the exposure and spray development were effected in the same manner as in Example 2, there was obtained a distinct red positive image.

Comparative Example

[0052] This Comparative Example is referred to Example 5 of U.S. Patent 4 115 613.

[0053] 10 g of powdery egg albumin was added to 30 g of distilled water, and the mixture was allowed to stand overnight to swell the egg albumin sufficiently. The albumin was then dis-. solved with stirring at 20°C to 30°C. The solution was then filtered using a filter paper to remove a very small amount of insoluble materials and a 25% aqueous solution of albumin was obtained.

[0054] 2 g of carbon black was wet well with 5 g of ethyl alcohol, and 17 g of distilled water was added thereto. The mixture was dispersed ultrasonically to produce 20 g of a dispersion containing 10% carbon black.

[0055] To 5 g of the aqueous solution of albumin prepared as above, 3.5 g of the above described carbon black dispersion was added dropwise, while exposing the solution to ultrasonic waves, to prepare a black coating solution. The resulting coating solution was applied to a polyester film and dried with warm air at 30°C for 10 minutes to produce a black recording layer. Thus, a recording medium was formulated.

[0056] The recording medium was treated in the same manner as in Example 1. As the result, the treated recording layer gave a distinct image in an atmosphere of 20°C to 25°C and 50%RH to 60%RH.

[0057] Further, the recording medium was treated in an atmosphere of 20°C and 15%RH (such as a room condition in the winter season). As the result, the recording layer did not give as distinct an image as that obtained in the atmosphere of 20°C and 50%RH because the sensitivity of the recording layer decreased.

[0058] Still further, the recording medium was treated in an atmosphere of 30°C and 80%RH (such as a room condition in rainy weather of the summer season). As the result, the recording layer did not give an image because the recording layer became non-removable in the non-image areas.

[0059] Even further, the recording medium was packed in an open paper bag lined with plastic film. The paper bag was placed in an incubator having a temperature of 40°C and a relative humidity of 80%. A critical term for obtaining a distinct image was 24 hours.

Claims

1. A recording medium comprising a support having provided thereon a recording layer, characterized in that said recording layer contains at least one material which is obtained by physical denaturation of a thermally coagulatable proteinaceous compound.

2. A recording medium as claimed in claim 1, characterized in that said material has been prepared by thermal denaturation.

3. A recording medium as claimed in claim 1, characterized in that said material has been prepared by thermal denaturation in combination with at least one other denaturation.

. 4. A recording medium as claimed in claim 1, characterized in that said material has been prepared by thermal denaturation following at least one denaturation selected from physical denaturation, chemical denaturation and biological denaturation.

5. A recording medium as claimed in any one of Claims 1 to 4, characterized in that said material is a denatured globular protein.

6. A recording medium as claimed in any one of Claims 1 to 4, characterized in that said material is . denatured albumin.

Ansprüche

1. Aufzeichnungsmedium, umfassend einen Träger mit einer darauf vogesehenen Aufzeichnungsshicht, dadurch gekennzeichnet, daß die Aufzeichnungsshicht mindestens ein Material enthält, das durch physikalische Denaturierung einer thermisch koagulierbaren, proteinhaltigen Verbindung erhalten wird.

2. Aufzeichnungsmedium nach Anspruch 1, dadurch gekennzeichnet, daß das Material durch thermische Denaturierung hergestellt worden ist.

3. Aufzeichnungsmedium nach Anspruch 1, dadurch gekennzeichnet, daß das Material durch thermische Denaturierung in Kombination mit mindestens einer anderen Denaturierung hergestellt worden ist.

4. Aufzeichnungsmedium nach Anspruch 1, dadurch gekennzeichnet, daß das Material durch thermische Denaturierung, anschließend an mindestens eine Denaturierung, gewählt aus physikalischer Denaturierung, chemischer Denaturierung und biologischer Denaturierung, hergestellt worden ist.

5. Aufzeichnungsmedium nach mindestens einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß das Material ein denaturiertes Globularprotein ist.

6. Aufzeichnungsmedium nach mindestens einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß das Material denaturiertes Albumin ist.

Revendications

1. Un milieu d'enregistrement comprenant un support muni d'une couche d'enregistrement, caractérisé en ce que ladite couch d'enregistrement contient au moins une substance qui est obtenue par dénaturation physique d'un composé portéique coagulable thermiquement.

2. Milieu d'enregistrement selon la revendication 1, caractérisé en ce que ladite substance a été préparée par dénaturation thermique.

3. Milieu d'enregistrement selon la revendication 1, caractérisé en ce que ladite substance a été préparée par une dénaturation thermique associée à au moins une autre dénaturation.

4. Milieu d'enregistrement selon la revendication 1, caractérisé en ce que ladite substance a été préparée par une dénaturation thermique suivie d'au moins une dénaturation choisie parmi la dénaturation physique, la dénaturation chimique et la dénaturation biologique.

5. Milieu d'enregistrement selon l'une quelconque des revendications 1 à 4, caractérisé en ce que ladite substance est une protéine globulaire dénaturée.

6. Milieu d'enregistrement selon l'une quelconque des revendications 1 à 4, caractérisé en ce que ladite substance est de l'albumin dénaturée.