BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The present invention relates to a method of conveying a stimulable phosphor sheet.
Description of Prior Arts
[0002] For obtaining a radiation image, there has been conventionally employed a radiography
utilizing a combination of a radiographic film having a sensitive silver salt material
layer and an intensifying screen.
[0003] As a method replacing the above-mentioned conventional radiography, a radiation
image recording and reproducing method utilizing a stimulable phosphor as described,
for instance, in U.S. Patent No. 4,239,698, has been developed and paid much attention.
The method involves steps of causing a stimulable phosphor to absorb a radiation having
passed through an object or having radiated from an object; sequentially exciting
(or scanning) the phosphor with an electromagnetic wave such as visible light or
infrared rays (stimulating rays) to release the radiation energy stored in the phosphor
as light emission (stimulated emission); photoelectrically detecting the emitted light
to obtain electric signals; and reproducing the radiation image of the object as a
visible image, numerals, symbols, etc. from the electric signals.
[0004] In the radiation image recording and reproducing method, a radiation image is obtainable
with a sufficient amount of information by applying a radiation to the object at
a considerably smaller dose, as compared with the conventional radiography. Accordingly,
the radiation image recording and reproducing method is of great value, especially
when the method is used for medical diagnosis.
[0005] In performing the radiation image recording an reproducing method, a stimulable phosphor
is generally employed in the form of a stimulable phosphor sheet (also referred to
as a radiation image storage panel, and generally in the form of a sheet of rectangle,
square, etc.) which comprises a support and a phosphor layer provided thereon. The
phosphor layer comprises a stimulable phosphor and a binder. Further, a protective
film made of a transparent plastic film is provided on a surface of the phosphor layer
to protect the phosphor layer from physical and chemical deterioration.
[0006] The stimulable phosphor sheet does not serve to finally record image information,
but only stores the information temporarily to provide the image or the like or an
independently prepared final recording medium as described above. Accordingly, the
stimulable phosphor sheet can be repeatedly used and such repeated use brings about
economical advantage.
[0007] The repeated use of the stimulable phosphor sheet is particularly advantageous, for
instance, in the case that a radiation image information recording and reading device
employing the stimulable phosphor sheet is mounted on a traveling station such as
a radiographic apparatus-carryig car to conduct mass radiographic examination in
various places. More in detail, it is inconvenient to carry a great number of stimulable
phosphor sheets on a traveling station, and there is a limitation on the number of
sheets capable of being carried on a car such as a radiographic apparatus-carrying
car. Accordingly, it is pratically useful that the stimulable phosphor sheets are
mounted on a radiographic car under such conditions that the stimulable phosphor sheets
are repeatedly used; radiation image information of an object is recorded on each
stimulable phosphor sheet and read out to obtain image information as a signal; and
the obtained signal is transferred to a recording medium having a great recording
capacity such as a magnetic tape so as to repeatedly use the stimulable phosphor sheet
in cycle. This means that radiation images of a number of objects can be obtained
by the use of a small number of stimulable phosphor sheets. Further, the combination
of the repeated uses of the stimulable phosphor sheets with a continuous radiographic
process enables to perform rapid radiography in the mass radiographic examinations.
This combination is of great value in practical use.
[0008] In the case of performing repeated uses of the stimulable phosphor sheets in cycle,
after the radiation energy stored in the stimulable phosphor sheet is read out and
aimed image information is obtained, the remaining energy in the sheet is released
and erased in a manner as disclosed, for instance, in Japanese Patent Provisional
Publications No 56(1981)-11392 and 56(1981)-12599. By employing such manner, the
stimulable phosphor sheet can be efficiently and repeatedly used in cycle.
[0009] Thus, the radiation image information recording and reading device, in one aspect,
is desirably mounted on a traveling station such as a radiographic apparatus-carrying
car in the form of a united built-in device which comprises an image recording means
for exposing a stimulable phosphor sheet to a radiation having passed through an
object so as to record and store a radiation image in the stimulable phosphor sheet,
a read-out means for reading out the radiation image stored in the stimulable phosphor
sheet, an erasure means for releasing and eras ing radiation energy remaining in
the stimulable phosphor sheet for the next use of the stimulable phosphor sheet, and
a conveyance means for moving the stimulable phosphor sheet in cycle to each of the
above-mentioned means. The radiation image information recording and reading device
having the above-mentioned constitution have various advantages not only in mounting
in the traveling station such as a radiographic apparatus-carrying car but also in
setting in hospitals, so that the above device is convenient in practical use.
[0010] The radiation image information recording and reading device utilizing the above-mentioned
system of repeatedly and cyclically using the stimulable phosphor sheet is disclosed
in Japanese Patent Application No. 58(1983)-66730 filed in the present applicant (assignee).
In the device, the stimulable phosphor sheet is occasionally conveyed vertically
or almost vertically for the purpose of making the device compact.
[0011] If a stimulable phosphor sheet has physical deterioration such as a scratch on a
surface thereof (a phosphor layer-side surface of the sheet), the quality of image
or the accuracy of image information provided by the phosphor sheet tends to decrease
markedly. For this reason, it is necessary to select the means for conveying a stimulable
phosphor sheet with such a careful consideration that the surface of the stimulable
phosphor sheet is not damaged. From this viewpoint, as a means for conveying a stimulable
phosphor sheet, a belt conveyor made of a soft sheet-material is generally employed.
However, while the belt conveyor is suitable for conveying the stimulable phosphor
sheet horizontally, it is unsuitable for conveying the stimulable phosphor sheet
in the direction other than the horizontal direction. More in detail, in the process
for conveying a stimulable phosphor sheet vertically or almost vertically using a
belt conveyor, it is necessary to arrange a pair of belt conveyors in such a manner
that the belt conveyors are in face to face contact with each other so as to convey
the stimulable phosphor sheet is sandwiched between that pair of belt conveyors.
However, said conveying device is complicated in structure, and it is difficult to
make the device compact. Further, there are other problems such that the surface
of the stimulable phosphor sheet tends to suffer scratches when the rate of one belt
conveyor is made different from that of the other, even if the difference therebetween
is very small.
SUMMARY OF THE INVENTION
[0012] The present invention provides a method suitable for conveying a stimulable phosphor
sheet, particularly suitable for conveying a stimulable phosphor sheet in the vertical
or almost vertical direction which is highly required in the radiation image information
recording and reading device in which the stimulable phosphor sheet is repeatedly
used in cycle.
[0013] The method of conveying a stimulable phosphor sheet of the present invention comprises
applying a driving force to a surface of the stimulable phosphor sheet by means of
a driving member, keeping both side edges of said phosphor sheet by means of a guiding
member to move the stimulable phosphor sheet in a given direction.
[0014] The above-mentioned method of conveying a stimulable phosphor sheet is effectively
performed by utilizing a device comprising a guiding member for keeping both sides
of said stimulable phosphor sheet and two or more driving members arranged along the
conveying direction for applying a driving force to a surface of said phosphor sheet,
the distance between two driving members adjoining each other along the conveying
direction being smaller than the length of said stimulable phosphor sheet measured
in the conveying direction.
[0015] The stimulable phosphor sheet comprises, in one aspect, a support, a phosphor layer
containing a stimulable phosphor and a binder, and a protective film superposed
in this order, which is characterized in that at least both sides of the phosphor
layer along the direction to be conveyed are retracted from the corresponding side
edges of the support, and both of said sides of the phosphor layer and support, are
protected by a polymer coating layer of a polymer film.
[0016] The stimulable phosphor sheet comprises, in another aspect, comprises a support,
a phosphor layer containing a stimulable phosphor and a binder, and a protective
film superimposed in this order, which is characterized in that at least both sides
of the phosphor layer along the direction to be conveyed are retracted from the corresponding
side edges of the support, and both of said retracted sides of the phosphor layer
are protected by a solid material fixedly placed in the area formed by the retraction
of the side of phosphor layer.
[0017] The stimulable phosphor sheet, in a further aspect, comprises a substrate, a support,
a phosphor layer containing a stimulable phosphor and a binder, and a protective
film superimposed in this order, which is characterized in that at least both sides
of the phosphor layer and support along the direction to be conveyed are retracted
from the corresponding side edges of the substrate, and both of said sides of the
sheet are protected by a polymer coating layer or a polymer film.
[0018] The stimulable phosphor sheet, in a still further aspect, comprises a substrate,
a support, a phosphor layer containing a stimulable phosphor and a binder, and a protective
film superposed in this order, which is characterized in that at least both sides
of the phosphor layer and support along the direction to be conveyed are retracted
from the corresponding side edges of the substrate, and both of said retracted sides
of the phosphor layer and support are protected by a solid material fixedly placed
in the area formed by the retraction of the side of phosphor layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019]
Fig. 1 is a schematic view illustrating the constitution of a conventional stimulable
phosphor sheet, and
Fig. 2 is a schematic view illustrating the constitution of the device preferably
employed in the method of conveying a stimulable phosphor sheet according to the present
invention.
Fig. 3-(1) is a schematic view illustrating the constitution of another device preferably
employed in the conveying method. Fig. 3-(2) is a side view of the device of Fig.
3-(1) seen along the indicated arrow A.
Figs. 4a 4b and 4c are schematic view illustrating the constitutions of embodiments
of the stimulable phosphor sheet.
Figs. 6a and 6b are schematic views illustrating the constitution of embodiment of
the stimulable phosphor sheet.
Figs. 7a and 7b are schematic view illustrating the constitutions of embodiments of
the stimulable phosphor sheet.
Figs. 8a 8b and 8b are schematic view illustrating the constitutions of embodiments
of the stimulable phos phor sheet.
DETAILED DESCRIPTION OF THE INVENTION
[0020] The present invention will be described more in detail hereinafter referring to the
accompanying drawings.
[0021] The general constitution of the conventional stimulable phosphor sheet which is
an object of the conveyance in the present invention is well known. The stimulable
phosphor sheet is generally employed, as described above, in the form of a sheet comprising
a support and a phosphor layer provided thereon which comprises a stimulable phosphor
and a binder. On the surface of the phosphor layer is provided a protective film of
a transparent plastic material, because the phosphor layer is easily affected by physical
shocks.
[0022] Fig. 1 schematically illustrates the constitution of the conventional stimulable
phosphor sheet.
[0023] In Fig. 1, the stimulable phosphor sheet comprises a support 11, a phosphor layer
12 and a protective film 13. Examples of the support material include plastic films
such as films of cellulose acetate and polyethylene terephthalate, metal sheets such
as aluminum foil, ordinary papers, baryta paper, and resin-coated papers. On the surface
of the support, (phosphor layer-side surface of the support) may be provided other
functional layers such as an adhesive layer, a light-reflecting layer and a light-absorbing
layer.
[0024] The phosphor layer essentially comprises stimulable phosphor particles dispersed
in a binder. A great number of stimulable phosphors are known. The stimulable phosphor
employed in the invention can be selected from the known stimulable phosphors. Examples
of the known stimulable phosphor include a divalent europium activated alkaline earth
metal fluorohalide phosphor (M
IIFX:Eu²⁺, 6in which M
II is at least one alkaline earth metal selected form the group consisting of Mg, Ca
and Ba; and X is at least one halogen selected from the group consisting of Cℓ, Br
and I); an europium and samarium activated strontium sulfide phosphor (SrS:Eu:Sm);
an europium and samarium activated lanthanum oxysulfide phosphor (La₂O₂S:Eu,Sm); an
europium activated barium aluminate phosphor (BaO·Aℓ₂O₃:Eu); an europium activated
alkaline earth metal silicate phosphor (M²⁺O·SiO₂:Eu, in which M²⁺ is at least one
alkaline earth metal selected from the group consisting of Mg, Ca and Ba); a cerium
activated rare earth oxyhalide phosphor (LnOX:Ce, in which Ln is at least one rate
earth element selected from the group consisting of La, Y, Gd and Lu; and X is at
least one halogen selected from the group consisting of Cℓ, Br and I) and the like.
[0025] A transparent protective film is then provided on the surface of the phosphor layer
to physically and chemically protect the phosphor layer. Examples of the material
employable for the preparation of the transparent protective film include cellulose
acetate, polymethyl methacrylate, polyethylene terephthalate and polyethylene. The
transparent protective film generally has a thickness within the range of approx.
0.1 - 20 µm.
[0026] The stimulable phosphor sheet can be colored with an appropriate colorant as described
in U.S. Patent No. 4,394,581 and U.S. Patent Application No. 326,642. Further, white
powder may be dispersed in the phosphor layer as described in U.S. Patent Application
No. 326,642. Further, white powder way be dispersed in the phosphor layer as described
in U.S. Patent No 4,350,893.
[0027] Figs. 2 and 3 [(1) and (2)] are schematic views of the conveying device which are
preferably employed in the method of conveying a stimulable phosphor sheet according
to the present invention. The method of conveying a stimulable phosphor sheet of
the invention is described hereinafter, by referring to an embodiment employing the
conveying devices shown in Figs. 2 and 3.
[0028] The conveying device preferably employed in the method of conveying a stimulable
phosphor sheet according to the invention is a device basically comprising guiding
members 22 and 23 (22a, 23a, 22b, 23b, ...)[32 and 33 (32a, 33a, 32b, 33b, ...)[ for
keeping both sides of a stimulable phosphor sheet 21[31], and two or more driving
members 24 (24a, 24b, 24c, ...)[34 (34a, 34b, 34c, ...)] arranged along the conveying
direction (direction along the indicated arrow) for providing a driving force on both
surfaces of the stimulable phosphor sheet 21[31], in which the distance between said
two driving members which adjoin each other along the conveying direction (e.g., 24b
and 24c)[e.g., 34b and 34c] is smaller than the length of the stimulable phosphor
sheet measured in the conveying direction.
[0029] The guiding members of the device keep the stimulable phosphor sheet at the both
sides thereof. The guiding members prevent the sheet from bending in the vertical
direction against the surface plane of the sheet (namely, flexure) and from moving
laterally. The guiding member is, for instance, U-shaped in the section. Accordingly,
the guiding member is not necessarily in contact with the stimulable phosphor sheet
to keep it. As is evident from Figs. 2 and 3, between the two driving members 24[34],
the surface of the sheet on which the radiation image is stored and recorded is kept
being from contact with members of the device, since the stimulable phosphor sheet
21 is kept by the guiding members 22 and 23[32 and 33] at both sides of the sheet
which do not participate in storing and recording the radiation image. Accordingly,
the surface of the sheet is hardly damaged. The shape of the guiding member is not
restricted to one as shown in Figs. 2 and 3, and any shape can be optionally used,
as far as the guiding member has the above-described functions. Further, there is
no specific limitation on the material of the guiding member. The guiding member is
not necessarily employed in the form of individually separated member as shown in
Figs. 2 and 3, and a united guiding member, for instance, a member in which one guiding
member 22[32] is combined with another guiding member 23[33] on the back surface-side
of the stimulable phosphor sheet 21[31] (support side-surface of the sheet) in Figs.
2 and 3, can be employed with appropriate selection of the driving members as described
hereinafter.
[0030] The driving members of the conveying device
apply a driving force to the surface(s) of the stimulable phosphor sheet, and
make it possible to convey (i.e., move) the stimulable phosphor sheet in a given direction.
The driving members comprises at least two members, and the distance (ℓ) between the
two driving members which are adjacent to each other along the conveying direction
is smaller than the length (m) of the stimulable phosphor sheet in the conveying direction.
Two or more driving members having the above-described constitution can convey the
stimulable phosphor sheet with little error.
[0031] Representative examples of the driving member for providing a driving force on the
surfaces of the stimulable phosphor sheet are a driving member comprising a pair
of rollers as shown in Figs. 2 and 3. The length of the roller is preferably as almost
the same as width of the stimulable phosphor sheet (length measured in the lateral
direction, but the length of the roller is not restricted to the above-mentioned length.
The roller may comprise a plurality of short rollers. The driving member may not
consist a pair of rollers, and for example, a driving member comprising a driving
roller and a fixed supporting member which is associated with the roller is employable.
Further, other driving members than the above-mentioned rollers can be employed in
the invention.
[0032] The surface of the driving member, especially the surface thereof which are to be
in contact with the surface of the stimulable phosphor sheet, are preferably formed
by a soft and elastic material such as rubber. By employing a driving member having
a surface of such material, the surface of the stimulable phosphor sheet can be protected
from physical shock so as not to be damaged.
[0033] The driving force is generally supplied to the driving members 24 (24a, 24b, 24c,
...)[24 (34a, 34b, 34c, ...)] from a means 26[37] such as a motor through a driving
power-transmitting means 25[36] such as a chain and a belt. This driving force is
then supplied to the stimulable phosphor sheet 21[31] under rotation via surfaces
thereof.
[0034] The guiding member and driving members are supported by an appropriate means such
as a fixing means or a supporting means so as to fulfill each function in the area.
[0035] In the method of conveying a stimulable phosphor sheet according to the present invention,
the stimulable phosphor sheet can be easily and reliably conveyed in direactions
other that horizontal direction, particularly in the vertical or almost vertical direction,
(upward and/or downward conveying), without damaging the surfaces of the sheet. The
vertical or almost vertical conveyance giving no damage to the surface of stimulable
phosphor sheet has been hardly attained in the conventional method using a belt conveyor.
The method of conveying the stimulable phosphor sheet of the invention can be effectively
used not only in the conveyance of a stimulable phosphor sheet in the vertical or
almost vertical direction but also in the conveyance with alteration of the direction
(e.g. L-turn and U-turn). Further, the method of the invention can be effectively
employed in the conveyance of a stimulable phosphor sheet in the horizontal direction.
A belt conveyor is conventionally used in the conveyance thereof in such direction.
Furthermore, the method of the pre sent invention can be employed in combination
with a conventional method using a belt conveyor in conveying the stimulable phosphor
sheet in a radiation image information recording and reading device.
[0036] The device illustrated in the Fig. 3 is further provided with a guiding means 35
(35a, 35b, 35c, ...) for guiding the front end of the stimulable phosphor sheet. The
guiding means 35 is arranged in the vicinity of the driving means 24, for instance,
just in front of the driving means 34. The guiding means 35 serves to smoothly engage
the coming stimulable phosphor sheet with the driving means. Although the stimulable
phosphor sheet essentially comprising a support and a phosphor layer is considerably
rigid, flexure may occasionally happen on most of the conventional stimulable phosphor
sheet used in a relatively thin plate having a width of approx. 30 - 60 cm at the
front end. If flexure takes place at the front end of the stimulable phosphor sheet,
the front end sometimes suffers damage, or in the worst case, the conveying action
is stopped by unsuitable engagement between the sheet and the driving means. The guiding
means 35 for guiding the front end of the stimulable phosphor sheet is very effective
to enable smooth engagement between the stimulable phosphor sheet and the driving
means.
[0037] There is no specific limitation on the shape, size, and location of the front end-guiding
means, as far as it serves to enable the smooth engagement. Otherwise, the front end-guiding
means can be in the form of a roller arranged in the vicinity of the driving means.
The front end-guiding means can be arranged merely on one side of the conveyor. The
front end-guiding means is generally made of plastic material and metal.
[0038] As described above, the method of the invention is suitable for conveying a stimulable
phosphor sheet in the vertical or almost vertical direction. Accordingly, from the
viewpoint of making the device compact, the method of the invention can be preferably
and practically employed in the radiation image information recording and reading
device in which the stimulable phosphor sheet is required to be conveyed in such direction
so as to be repeatedly used in cycle.
[0039] Both sides of the stimulable phosphor sheet to be employed in the conveying method
of the invention are preferably formed or processed to have enhanced protection against
the physical (mechanical) shock given to these sides by the side-guiding means in
the course of the conveying stage, as well as enhance protection against chemical
deterioration.
[0040] For instance, at least both sides of the phosphor layer along the direction to be
conveyed are retracted from the corresponding side edges of the support, as illustrated
in Fig. 4a in which the support, phosphor layer and protective layer are indicated
by 41, 42 and 43, respectively. Alternatively, at least both sides of the phosphor
layer and support are protected by a polymer coating layer, as illustrated in Fig.
4b in which the support, phosphor layer, protective layer and polymer coating layer
are indicated by 41, 42, 43 and 44, respectively. Alternatively, at least both sides
of the phosphor layer and support are protected by a polymer film, as illustrated
in Fig. 4c in which the support, phosphor layer, protective layer and polymer film
are indicated by 41, 42, 43 and 45, respectively. The polymer film 45 is fixed to
the side by an adhesive layer 46.
[0041] In other aspects, at least both sides of the phosphor layer along the direction
to be conveyed are retracted from the corresponding side edges of the support, and
both of said sides of the phosphor layer and support are protected by a polymer coating
layer, as illustrated in Fig. 5a in which the support, phosphor layer, protective
layer and polymer coating layer are indicated by 51, 52, 53 and 54, respectively.
The side edges on the bottom surface of the support can be chamferred, as illustrated
in Fig. 5b.
[0042] In other aspects, at least both sides of the phosphor layer along the direction
to be conveyed are retracted from the corresponding side edges of the support, and
both of said sides of the phosphor layer and support are protected by a polymer film,
as illustrated in Fig. 6a in which the support, phosphor layer, protective layer and
polymer film are indicated by 61, 62, 63 and 65, respectively. The polymer film 65
is fixed to the side by an adhesive layer 64. The side edges on the bottom surface
of the support can be chamferred, as illustrated in Fig. 6b.
[0043] In another aspect, at least both sides of the phosphor layer along the direction
to be conveyed are retraced from the corresponding side edges of the support, and
both of said retracted sides of the phosphor layer are protected by a solid material
fixedly placed in the area formed by the retraction of the phosphor layer, as illustrated
in Fig. 7a in which the support, phosphor layer, protective layer and solid material
are indicated by 71, 72, 73 and 74, respectively. The side edges on the bottom surface
of the support can be chamferred, as illustrated in Fig. 7b.
[0044] In another aspect, a stimulable phosphor sheet may comprise a substrate, a support,
a phosphor layer and a protective film superposed in this order, in which at lest
both sides of the phosphor layer and support along the direction to be conveyed are
retracted from the corresponding side edges of the substrate, and both of said sides
of the sheet are protected by a polymer coating layer. This embodiment is illustrated
in Fig. 8a, in which the substrate, support, phosphor layer, protective layer and
polymer coating layer are indicated by 81, 82, 83, 84, and 85, respectively. The protection
can be made by means of an adhesive layer 86 and a polymer film 87, as illustrated
in Fig. 8b. The protection can be made by means of a solid material 88, as illustrated
in Fig. 8c.
[0045] There is no specific limitation on the material of the substrate. For instance, the
substrate can be produced from any material employable for the production of the
support.
[0046] The above-described protections can be given to the front and/or rear ends of the
stimulable phosphor sheets, to protect the phosphor layer against physical shocks,
as well as to keep the phosphor layer from chemical deterioration. The front and/or
rear ends can be chamferred on the bottom surface.
[0047] In the above-described embodiments, the sides of the protruded support or substrate
can effectively keep the phosphor layer from physical shock, friction, and the like
applied to the sides of the stimulable phosphor sheet.
[0048] The polymer coating layer can be provided to the side of the stimulable phosphor
sheet, for instance, by applying a solution of a film-forming polymer in a solvent
to the side and then drying to remove the solvent, or applying reactive material(s)
to form a polymer material to the side and causing the reaction to form in-situ the
polymer coating film. There is no specific limitation on the film-forming polymer
employed in the above process. For instance, a polyurethane-acrylic resin and a mixture
of an acrylic resin and vinyl chloride-vinyl acetate copolymer 9 which is disclosed
in Japanese Patent Provisional Publication 58(1983)-68746)-can be used.
[0049] The polymer film can be produced from the same material as that employed for the
production of the protective material. For instance, cellulose acetate, polymethyl
methacrylate, polyethylene terephthalate, and polyethylene can be mentioned. The polymer
film employed for this purpose may be transparent or not. The film can be fixed to
the side, for instance, by an adhesive or other sticky material.
[0050] There is no specific limitation on the solid material to be arranged adjacent to
the side of the phosphor layer. For instance, a solid polymer material and a metal
can be employed. The solid polymer material can be that mentioned hereinbefore as
the material for production of the surface protective film or a polymer film for protection
of the side. The solid material can be provided adjacent to the side of the phosphor
layer by placing it. Otherwise, a polymer material solution can be introduced in the
area and the solid polymer can be formed in-situ after removal of the solvent. Otherwise,
a solid polymer material can be formed in-situ by a reaction of reactive compound(s).
The solid material can be fixed to the side of the phosphor layer and/or the upper
surface of the support or substrate.