JPS5935000B2 - Radiographic image conversion panel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radiation image conversion panel using a stimulable phosphor.

More particularly, the present invention relates to a radiation conversion panel with improved physical properties having a phosphor layer whose binder is a mixture of methylene chloride soluble polyester-urethane resin and cellulose acetate.

Conventionally, a so-called photographic method has been used to obtain radiation images as images, using a photographic film having an emulsion layer made of a silver salt photosensitive material, but in recent years silver salts have been used due to problems such as the depletion of iron resources. A method of converting a radiation image without using a silver salt has become desirable.As one method of converting a radiation image without using a silver salt, US Pat.
No. 142, No. 55-12143, No. 55-12144
The methods described in the following publications are attracting attention:

This radiation image conversion method uses stimulable phosphors (phosphors that emit light when excited with electromagnetic waves selected from visible light and infrared rays after being irradiated with radiation).

Here, radiation refers to electromagnetic waves or particle beams such as X-rays, α-rays, β-rays, γ-rays, high-energy neutron beams, electron beams, and vacuum ultraviolet rays.

), the radiation transmitted through the subject is absorbed by the stimulable phosphor of the panel, and the corresponding hindlimb panel is exposed to electromagnetic waves selected from visible light and infrared light (hereinafter referred to as "excitation light"). The radiation image accumulated in the stimulable phosphor is extracted in time series as stimulated luminescence, and this is electrically processed to form an image.

The radiation image conversion panel used in the above-mentioned radiation image conversion method basically consists of a support and a phosphor layer provided on one side of the support.

The phosphor layer is a stimulable phosphor dispersed in a binder.
Generally, a protective film is provided on the surface of the phosphor layer (opposite to the support side) to physically or chemically protect the phosphor layer.

In some cases, an undercoat layer is provided between the phosphor layer and the support for the purpose of adhering the phosphor layer and support more closely. It is manufactured by the manufacturing method described below.

First, a suitable amount of a binder and a stimulable phosphor are mixed together, and a suitable amount of a solvent is added thereto to prepare a coating solution with an optimum viscosity.

Next, the obtained coating liquid is applied onto a support using a doctor blade, roll coater, knife coater, etc., and dried to form a phosphor layer.

In addition, in the case of a panel having a structure that has an undercoat layer between the support and the phosphor layer, the undercoat layer is provided on the support in advance, and a coating liquid is applied on top of it and dried to form the phosphor layer. .

After the phosphor layer is formed, a protective film is generally provided on the phosphor layer to protect the phosphor layer.

In this specification, when the term "support" is used, unless otherwise specified, the above-mentioned undercoat layer and the light-reflecting layer described later are applied on the support in advance, and in the resulting panel, the support and the phosphor layer are applied. This term also includes those provided with a layer (intermediate layer) located between the two.

The radiation image conversion panel is used by being incorporated into an imaging device in the process of recording a radiation image, and is also used by being incorporated into a reading device in the process of reproducing a radiation image.

For this reason, radiation image conversion panels are practically required to have resistance to bending.

That is, the panel must be such that the phosphor layer does not crack or peel off from the support when bent.

From this point of view, the phosphor layer of the radiation image storage panel is required to have flexibility and adhesion to the support.

However, if the phosphor layer is too soft and has too high a degree of flexibility, the phosphor layer is likely to be locally damaged by pressure or other factors.

Therefore, the radiation image conversion panel has high resistance to bending, and the phosphor layer does not crack or peel from the support when bent, and at the same time, the phosphor layer is less likely to be damaged. It is clear from the above that in order to obtain this, the panel's phosphor layer must have an appropriate degree of flexibility, neither too high nor too low, and the degree of adhesion of the phosphor layer to the support must be increased. It is.

Furthermore, when the radiation image conversion panel is incorporated into a reading device and used in the radiation image reproduction process, it is irradiated with excitation light, and the panel is used repeatedly.

For this reason, radiation image conversion panels are practically required to have light resistance to excitation light.

That is, the panel needs to be such that its sensitivity does not decrease or its resistance to bending decreases when exposed to excitation light for a long period of time.

From this point of view, the binder used in the phosphor layer of a radiation image storage panel becomes yellowish due to excitation light, which absorbs the excitation light and/or the generation of stimulable phosphor, reducing the sensitivity of the panel. It must be a binder that does not deteriorate the flexibility of the phosphor layer and its adhesion to the support by causing further curing by excitation light. Generally, cellulose derivatives such as nitrocellulose and cellulose acetate, polyalkyl methacrylates such as polymethyl methacrylate, polyurethane resins, etc. are used.

Among the above binders, panels using cellulose derivatives or polyalkyl methacrylate as the binder for the phosphor layer generally have a low flexibility of the phosphor layer, and a low degree of adhesion of the phosphor layer to the support, resulting in excessive bending. On the other hand, panels using polyurethane resin as the binder for the phosphor layer, which uses the cellulose derivative or polyurethane resin as the binder, The flexibility of the phosphor layer is significantly higher than that of panels that use alkyl methacrylate as the binding agent for the phosphor layer. It is easy to handle, and there are also difficulties in its handling, such as the tendency for nicks to occur during handling.

In addition, although this panel has a sufficiently high flexibility of the phosphor layer, the affinity of the polyurethane resin to the support is generally poor, so the degree of adhesion of the phosphor layer to the support is low, and the phosphor layer resists bending. easily peels off from the support.

Further, all of the conventional radiation image conversion panels described above have low light resistance to excitation light.

That is, all of the above-mentioned binders tend to yellow due to excitation light, and therefore, when the panel is exposed to excitation light for a long time, the sensitivity of the panel decreases significantly.

As mentioned above, conventional radiation image storage panels have low resistance to bending and also have low light resistance to excitation light.

Therefore, a radiation image storage panel that has higher resistance to bending than conventional radiation image storage panels and also has higher light resistance to excitation light is desired. The flexibility of the phosphor layer of the panel using methacrylate as a binder is between the flexibility of the phosphor layer of the panel using the polyurethane resin as the binder, and the degree of fixation of the phosphor layer to the support is between the flexibility of the phosphor layer of the panel using methacrylate as the binder. The light resistance of the binder constituting the phosphor layer to excitation light is higher than that of the phosphor layer of the panel, and the light resistance of the binder constituting the phosphor layer to excitation light is higher than each of the above binders, and the binder does not yellow or harden due to excitation light. A radiation image conversion panel is desired.

The present invention was made under the above-mentioned circumstances,
The phosphor layer has appropriate flexibility and a high degree of adhesion to the support, and therefore has high resistance to bending, and the phosphor layer does not crack or peel off from the support when bent. The purpose of the present invention is to provide a radiation image conversion panel that does not require water replenishment.0 In addition, the present invention has high light resistance to excitation light, and therefore sensitivity decreases when exposed to excitation light for a long time. It is an object of the present invention to provide a radiation image conversion panel in which the phosphor layer is not easily damaged and the resistance to bending does not deteriorate. The purpose is to provide panels.

In order to achieve the above object, the present inventors have conducted research to find a binder to be used in the phosphor layer.

As a result, it was discovered that the above object could be achieved when a mixture of a methylene chloride-soluble polyester-urethane resin consisting of a specific polyester and cellulose acetate was used as a binder for the phosphor layer, and the present invention was completed. It's arrived.

The radiation image storage panel of the present invention is a radiation image storage panel comprising a support and a phosphor layer provided on the support and comprising a stimulable phosphor dispersed in a binder. A methylene chloride-soluble polyester consisting of a polyester represented by the general formula (where l is an integer of 2 to 4, m is an integer of 2 to 4, and n is an integer of 1 to 100).
It is characterized by being composed of a mixture of urethane resin and cellulose acetate with an acetylation degree of 49 or higher.

*Gu The present invention will be explained in detail below.

The polyester constituting the methylene chloride-soluble polyester-urethane resin, which is one component of the binder mixture used in the radiation image storage panel of the present invention, has the general formula as described above (where l is an integer from 2 to 4, m is an integer from 2 to 4 and n is an integer from 1 to 100)
It is expressed as

That is, it has hydroxyl groups at both ends, the glycol component is ethylene glycol, 1,3-butanediol, or 1,4-butanediol, and the dibasic acid component is succinic acid, glucuric acid, or adipic acid. can be,
It is a polyester having a degree of polymerization n of 1 to 100.

The optimum polymerization degree of this polyester varies depending on the type of glycol component (and dibasic acid component), but it is generally preferable to have a polymerization degree such that the molecular weight of the polyester is 1000 to 4500. Polyester-urethane resins are obtained by reacting the above polyesters with diisocyanates.

This methylene chloride-soluble polyester-urethane resin has a repeating unit represented by the general formula (where l is an integer of 2 to 4, n is an integer of 1 to 100, and R represents a divalent atomic group residue). .

The divalent atomic group residue represented by R above is, for example, +CH2
+p (where p is an integer from 2 to 8), etc.

The methylene chloride soluble polyester-urethane resin preferably has a molecular weight of 2,000 to 50,000.

The diisocyanates used in the production of the methylene chloride-soluble polyester-urethane resin include general formulas such as ethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, etc. is an integer from 2 to 8) Polymethylene diisocyanate, p-phenylene diisocyanate, tolylene diisocyanate,
p,p'-diphenylmethane diisocyanate, 1,5
- Aromatic diisocyanates typified by naphthylene diisocyanate, m-xylylene diisocyanate, etc. 0 However, the diisocyanates used in the present invention are not limited to the above, and any diisocyanate may be used. Of the above diisocyanates, tolylene diisocyanate, tetramethylene diisocyanate and m-xylylene diisocyanate are relatively stable in handling, and can be produced using these diisocyanates. It is preferable to use these diisocyanates because the polyester-urethane resins prepared above have particularly good compatibility with cellulose acetate.

On the other hand, cellulose acetate, which is the other component of the binder mixture used in the radiation image storage panel of the present invention, has an acetylation degree of 49% or higher, preferably 58% or higher.

This cellulose acetate is well compatible with the methylene chloride soluble polyester-urethane resin.

As described below, the methylene chloride soluble polyester-urethane resin and the cellulose acetate are
They are mixed in the form of a solution during the process of preparing a coating solution for forming a phosphor layer.

By changing the mixing ratio of the two, the flexibility of the phosphor layer of the resulting panel can be changed.

Therefore, by appropriately selecting the mixing ratio of the two, it is possible to obtain a radiation image conversion panel in which the phosphor layer has the desired flexibility.

This is one of the advantages of the invention.

However, in order to obtain particularly desirable physical properties, the methylene chloride soluble polyester-urethane resin of the present invention and cellulose acetate should be mixed in a ratio of 9.5:0.5 to 3, especially 9.
:1 to 4:6 (weight ratio).

The radiation image storage panel of the present invention is manufactured as follows.

First, a stimulable phosphor is dispersed in a suitable organic solvent to prepare a phosphor dispersion.

Examples of organic solvents include methanol, ethanol, n-
Alcohols such as 0/-nol and n-butanol, chlorinated hydrocarbons such as methylene chloride and ethylene chloride, ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone, esters such as methyl acetate, ethyl acetate and butyl acetate, dioxane and Ethers such as monoethyl ether S and monomethyl ether of ethylene glycol and mixtures thereof are used.

Further, as the stimulable phosphor, for example, the above-mentioned U.S. Patent No. 3,
SrS:Ce described in 859,527
, Sm, SrS:Eu, Sm, La2O2S:Eu,
Sm and (Zn, Cd)S:Mn,
ZnS:Cu, P described in 84740 specification
b, Ba(1xA1203:Eu (however, X is 0.8≦
X≦10) and MIl() xs i02:
A (However, Mll is Mg, Ca.

Sr, Zn, Cd or Ba, A is Ce, T
b.

Eu, Tm, Pb, Tl, Bi or Mn, and X is 0.5≦X≦2.5), JP-A-55-12143
(Bal-x y , Mgx, Cay) FX: aE described in the patent application No. 53-84742
u2t (where X is at least one of Cl and Br
and x':F6 and y are O< x + y≦0.
6 and Xy\0, and a is 10-6≦a≦5×10-
2), Japanese Patent Application Laid-Open No. 12144/1982 (Patent Application No. 12144/1983)
LnOX described in 84743):
xA (where Ln is at least one of La, Y, Gct and Lu, X is at least one of CI and Br, A is at least one of Ce and Tb,
X is O< x < 0.1), Japanese Patent Application Laid-Open No. 55-12
No. 145 (Japanese Patent Application No. 53-84744) (Bat x, MIlx) FX:yA (where Mll is at least one of Mg, Ca, Sr, Zn, and Cd, and X is CIJ , Br and ■, A is Eu, Tb.

Ce, Tm, Dy, Pr, Ho, Nd, Yb and Er
At least one of X is 0≦X≦0.6. y is O
≦y≦0, 2), etc. are used.

However, the stimulable phosphor used in the radiation image conversion panel of the present invention is not limited to the above-mentioned phosphors, and may be any phosphor that exhibits stimulated luminescence when irradiated with radiation and then irradiated with excitation light. Needless to say, any phosphor may be used.

From a practical standpoint, the stimulable phosphor has a wavelength of 500 to 800 nm.
The phosphor is preferably a phosphor that exhibits stimulated luminescence in the range of 300 to 600 nm when excited by the excitation light.

Next, a methylene chloride-soluble polyester-urethane resin solution and a cellulose acetate solution prepared in advance were added to the above phosphor dispersion, and the mixture was milled using a ball mill, impeller mill, etc.
Mix thoroughly using a roll mill or the like to prepare a coating solution.

As the solvent for the methylene chloride-soluble polyester-urethane resin solution, methylene chloride or a mixture of methylene chloride and the solvent used for preparing the phosphor dispersion is used.

A mixture of methylene chloride and alcohol is used as the solvent for the cellulose acetate solution.

The mixing ratio of the binder (i.e., the total amount of methylene chloride-soluble polyester-urethane resin and cellulose acetate) and the stimulable phosphor in the coating solution varies depending on the characteristics of the intended panel, the type of stimulable phosphor, etc. Generally, the mixing ratio of the binder and the stimulable phosphor is 1:1 to 1:2.
0, preferably from 1:5 to 1:
selected from 15 weight ratio ranges.

The coating solution also contains a dispersant for improving the dispersibility of the stimulable phosphor particles in the coating solution, and a bonding agent between the binder and the stimulable phosphor particles in the phosphor layer of the resulting intensifying screen. Additives such as plasticizers may be added to improve strength.

As the dispersant, phthalic acid, stearic acid, caproic acid, lipophilic surfactant, etc. are used.

Examples of the plasticizer include phosphoric acid esters such as triphenyl phosphate, tricresyl phosphate, and diphenyl phosphate; Acid esters, polyesters of polyethylene glycol and aliphatic dibasic acids, such as polyesters of triethylene glycol and acyhinic acid, and polyesters of diethylene glycol and succinic acid, are used.

In addition, Japanese Patent Application Laid-Open No. 146447/1982
No. 631), the sharpness of a radiation image storage panel can be improved by dispersing white powder in the phosphor layer of the panel.

Also, Japanese Patent Application Publication No. 55-163500 (Japanese Patent Application No. 54-71
As disclosed in Japanese Patent No. 604), the sharpness of a radiation image conversion panel can be improved by dispersing a coloring agent that absorbs at the wavelength of excitation light in the phosphor layer of the panel to color the phosphor layer. can be improved.

In the present invention, a white powder or colorant is further added to the coating solution and dispersed, and this is used to form a phosphor layer in which the white powder or colorant is dispersed as described below. The sharpness of the resulting radiation image conversion panel can be improved.

When preparing a coating solution for a colored phosphor layer, it is also possible to attach (adhere or adsorb) a colorant to the surface of the stimulable phosphor in advance, and then use this to prepare a coating solution as described above. good.

Next, the coating solution is uniformly applied onto the support using a doctor blade, roll coater, knife coater, etc. to form a coating film.

Supports include general paper, baryta paper, resin coated paper, pigment paper containing pigments such as titanium dioxide,
Processed paper such as paper sized with polyvinyl alcohol, sheets made of polyester such as polyethylene, polypropylene, polyethylene terephthalate, or other polymer materials, metal sheets such as aluminum foil, aluminum alloy foil, etc. are used.

The binder used in the present invention generally has a good affinity for any support, but has a particularly high affinity for polyethylene terephthalate.

From this point of view, it is particularly preferable to use a polyethylene terephthalate sheet as the support.

The surface of the support to which the coating liquid is applied may be treated by applying gelatin or the like in advance.

In addition, when the support used is one that transmits excitation light, the obtained radiation image conversion panel can be irradiated with excitation light from the surface of the support opposite to the surface on the phosphor layer side. It becomes possible.

In addition, the above-mentioned Japanese Patent Application Laid-open No. 163500/1983 (Japanese Patent Application No. 1984-
71604), the sharpness of the resulting radiation image storage panel can be improved by using a support colored with a colorant.

The radiation image conversion panel of the present invention has an undercoat layer between the phosphor layer and the support for more closely adhering both.
No. 6-11393 (Japanese Patent Application No. 1987-87801)
An intermediate layer such as a light-reflecting layer for improving sensitivity as disclosed in .

When producing a radiation image storage panel having such an intermediate layer, a support as described above on which an intermediate layer such as an undercoat layer or a light reflecting layer is previously provided is used as the support.

In this case, it goes without saying that the coating liquid is applied onto the intermediate layer.

The subbing layer is applied by applying a conventional adhesive onto the support.

The above-mentioned Japanese Patent Application Publication No. 163500/1983 (Patent Application No. 716/1982
As disclosed in No. 04), the sharpness of the resulting radiation image conversion panel can be improved by providing an undercoat layer colored with a colorant that absorbs at the wavelength of excitation light.

The light-reflecting layer is formed by vapor deposition of a metal such as aluminum, laminate of a metal foil such as aluminum foil, or white powder such as titanium dioxide, aluminum oxide, barium sulfate, etc. with a suitable binder (the binder used in the present invention may also be used). ) is provided on the support by coating a coating liquid formed by dispersing the material in the substrate.

The light absorption layer is made by applying a coating solution on a support, which is made by dispersing carbon black or a coloring agent that absorbs the light emitted from the stimulable phosphor in a suitable binder (which may be the binder used in the present invention). It is applied by coating.

After the coating film is formed, the coating film is gradually heated and dried to form a phosphor layer on the support.

The thickness of the phosphor layer varies depending on the characteristics of the intended radiation image conversion panel, the type of stimulable phosphor, the mixing ratio of the binder and the stimulable phosphor, etc., but is generally 20 μm to 1 mm.
Preferably it is 100 to 500μ.

In the radiation image conversion panel of the present invention, a protective film for physically or chemically protecting the phosphor layer is generally provided on the surface of the phosphor layer (the surface opposite to the support side).

This protective film is prepared by dissolving cellulose derivatives such as cellulose acetate and nitrocellulose, polymethyl methacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, vinyl acetate, vinyl chloride-vinyl acetate copolymer, etc., in an appropriate solvent to form a coating on the surface of the phosphor layer. Alternatively, the phosphor can be provided by applying a thin film of polyethylene terephthalate, polyethylene, vinylidene chloride, nylon, etc. to the surface of the phosphor with a suitable adhesive.

The thickness of the protective film is preferably about 3 to 20 μm. This protective film must be able to transmit the light emitted from the stimulable phosphor contained in the phosphor layer, and if the excitation light is irradiated from the protective film side (generally, the irradiation of excitation light is It goes without saying that the protective film must be transparent to the excitation light.

In addition, the above-mentioned Japanese Patent Application Laid-Open No. 163500/1983 (Japanese Patent Application No. 1984-
71604), the sharpness of the resulting radiation conversion panel can be improved by providing a protective film colored with a colorant that absorbs the wavelength of excitation light.

Table 1 below shows the physical characteristics of the radiation image storage panel of the present invention in comparison with conventional radiation image storage panels.

That is, Table 1 below compares the bending hardness measurement results, crack test and phosphor layer peeling test results, and light resistance test results against excitation light of the radiation image conversion panel of the present invention with the conventional radiation image conversion panel. This is shown below.

Measurement of bending hardness, crack test, phosphor layer peeling test, and light resistance test to excitation light were conducted as follows.

(1) Measurement of bending hardness...Width 8mm, length 10
A panel test piece of 0 plates was bent, both ends were joined to form an arc, and the bending hardness was determined by reading the change in the arc when the upper part of the arc was loaded with a tension gauge.

The higher the bending hardness, the harder the panel is and the lower the flexibility.

(2) Crack test: Observe the extent of cracks in the phosphor layer when a 50 mm wide panel is wrapped around a 15 mm diameter glass tube with the phosphor layer facing outside. did.

Naturally, the more cracks occur, the less flexible the panel is, meaning that it has less resistance to bending.

(3) Phosphor layer peeling test: The phosphor layer of a panel test piece with a width of 80 mm and a length of 150 mm was cut in the shape of a substrate at 7-diameter intervals using a razor blade.

Next, place a 50 mm x 50 tnm on the cut phosphor layer.
The adhesive sheet was fixed, and then the adhesive sheet was peeled from the test piece by forcefully pulling the edge of the adhesive sheet while holding the test piece.

The area where the phosphor layer was peeled off from the support and the support was exposed was determined, and the ratio (a) of this area to the cut-off area of the phosphor layer was determined.

0 (4 ) Light resistance test against excitation light: A 20 W white fluorescent lamp was installed at a distance of 10 cIrL from the panel, and the panel was irradiated with light at an illuminance of about 15,000 lux.

Before irradiating the panel with light and after irradiating the panel with light for 100 hours, the amount of photostimulated light on the panel was measured, and the ratio of the amount of emitted light after irradiation to the amount of emitted light before irradiation was determined.

The smaller this ratio is, the more easily yellowing occurs in the binder due to excitation light, which means that the binder has lower light resistance to excitation light.

The amount of stimulated luminescence was measured by irradiating the panel with X-rays of 80 kVp, exciting the panel with He-Ne laser light, and measuring the brightness of the produced stimulated luminescence.

In addition, a test similar to the crack test in (2) above was conducted on the panel after 100 hours of light irradiation.

If the result of this crack test is worse than the crack test result in (2) above, it means that the binder has been further hardened by the excitation light, and it means that the binder has low light resistance to the excitation light. do.

The radiation image conversion panel of the present invention and the conventional radiation image conversion panel used in the above measurements and tests were both
A polyethylene terephthalate sheet with a thickness of 80μ is used as a support, and a phosphor layer with a thickness of about 300μ is provided.

That is, the only difference between the panels of the present invention and conventional panels is the binder.

Furthermore, regarding the panels of the present invention, several types of panels having different mixing ratios of polyester-urethane resin and cellulose acetate were measured, tested, and tested.

As is clear from the bending hardness measurement results in Table 1 above, the flexibility of the radiation image conversion panel of the present invention is generally the same as that of the conventional radiation image conversion panel (conventional product A) using polyurethane resin as a binder. and conventional radiation image conversion panels using nitrocellulose, cellulose acetate and polymethyl methacrylate as binders (conventional products B, C and D, respectively)
) is in the middle of flexibility.

That is, in general, the panel of the present invention has an appropriate flexibility that is neither too high as in conventional product A nor too low as in conventional products B, C, and D.

Furthermore, as is clear from the crack test and phosphor layer peeling test results in Table 1 above, the panel of the present invention has appropriate flexibility, so cracks do not occur in the phosphor layer when bent. Moreover, since the degree of adhesion of the phosphor layer to the support is extremely high, the phosphor layer does not peel off from the support due to forced tension.

On the other hand, conventional product A has sufficiently high flexibility so that cracks do not occur in the phosphor layer when bent, but the degree of adhesion of the phosphor layer to the support is lower than that of the panel of the present invention. The phosphor layer peels off from the support due to the low and forced tension.

In addition, conventional products B, C, and D have low flexibility, so the phosphor layer easily cracks when bent, and the degree of adhesion of the phosphor layer to the support is also low, and the phosphor layer is damaged by forced tension. It will peel off from the support.

As is clear from the results of this crack test and phosphor layer peeling test, the panel of the present invention has higher resistance to bending than conventional products A-D, and has higher resistance to bending than conventional products B-D.
If cracks occur in the phosphor layer, or if the conventional product A
- The phosphor layer does not peel off from the support as in D. Furthermore, as is clear from the light resistance test results against excitation light in Table 1 above, the panel of the present invention does not peel off from the support when irradiated with excitation light. The decrease in sensitivity after being exposed to excitation light for a long time is less than that of conventional products A-D, and the excellent bending resistance of the panel of the present invention remains unchanged even after being exposed to excitation light for a long time. has been done.

Based on the test results, especially the data on the decrease in sensitivity, it can be said that the panel of the present invention has higher light resistance to excitation light than the conventional products A-D.

That is, the binder used in the panel of the present invention has higher light resistance to excitation light than the binders used in conventional products A to D, and has higher light resistance than the binders used in conventional products A to D. Therefore, there is less yellowing due to excitation light.

Furthermore, the binder used in the panel of the present invention is completely cured at the time of panel manufacture, and as in the case of the binder of conventional product B, for example, the excitation light causes further curing, which changes (deteriorates) the resistance to bending. Never.

Furthermore, since the panel of the present invention generally has a lower flexibility of the phosphor layer than the conventional product A, compared to the conventional product A,
The phosphor layer is less likely to be damaged, and the handleability is also excellent, with no nicks occurring during handling.

As explained above, the present invention provides a radiation conversion panel with improved physical properties such as resistance to bending and light resistance to excitation light, and its industrial utility value is extremely large.

Next, the present invention will be explained by examples.

In addition, the bending hardness measurement, crack test, phosphor layer peeling test, and light resistance test to excitation light in each of the following examples were conducted in the same manner as described above.

Example 1 Divalent europium-activated barium fluoride phosphor (BaF
Br:Eu2t) 300 parts by weight to methyl ethyl ketone 4
A phosphor dispersion liquid was prepared by dispersing it in 9 parts by weight.

Separately, a methylene chloride-soluble polyester with an average molecular weight of 6,970 was synthesized using a double-terminated dihydroxy polyester consisting of adipic acid and ethylene glycol and having an average molecular weight of 2,125 and having a repeating unit expressed by the formula %, and tolylene diisocyanate. A polyester-urethane resin solution was prepared by dissolving 20 parts by weight of polyester-urethane resin in 77 parts by weight of methylene chloride, and 5 parts by weight of cellulose acetate with a vinegar ratio of 61.5 parts and an average degree of polymerization of 260 was dissolved in 46 parts by weight of methylene chloride. A cellulose acetate solution was prepared by dissolving the cellulose acetate in a mixture of 5 parts by weight and 4 parts by weight of methanol.

Next, the polyester-urethane resin solution and cellulose acetate solution were added to the phosphor dispersion, and 2.5 parts by weight of tricresyl phosphate was added and thoroughly mixed using a propeller mixer, so that the phosphor was uniformly dispersed. A coating solution was prepared.

As is clear from the above, the composition of the obtained coating liquid was as follows.

BaFBr:Eu” 300 parts by weight Polyester-urethane resin 20 Cellulose acetate
5 Tricresyl phosphate
2.5 Methylene chloride 123
Methanol 4 Methyl ethyl ketone 49 Next, the above coating solution was uniformly applied using a doctor blade onto a 180 μm thick polyethylene terephthalate (support) placed on a horizontally held glass plate.

After application, the coating was dried in a drying casing.

During this drying, the temperature inside the drying casing is increased from 25℃ to 100℃.
This was done by gradually increasing the temperature to .

In this way, a phosphor layer with a thickness of 300 μm was provided on the support.

Next, polymethyl methacrylate 3 was applied to the surface of the phosphor layer.
A solution prepared by dissolving 0 part by weight of triol in 170 parts by weight was applied, and the coating film was dried in a drying casing.

This drying is performed by increasing the temperature inside the drying casing from 25℃ to 110℃.
This was done by gradually increasing the temperature to .

In this way, a 10 μm thick protective film was provided on the phosphor layer.

The bending hardness of the radiation image conversion panel obtained as described above was measured, and the panel was also subjected to a crack test, a phosphor layer peeling test, and a light resistance test to excitation light.

The results are shown below. Bending hardness 2.
8 X 10 dyne-ffl*・Crack test
Phosphor layer peeling test without cracking
0% light resistance test Emission light amount ratio 90% crack test
No cracks were generated.On the other hand, for comparison, polyurethane resin, nitrocellulose, and polymethyl methacrylate, which are conventionally used as binders for radiation image storage panels, were used in the same manner as above except that these binders were used. Three types of radiation image conversion panels were manufactured.

The composition of each coating liquid used in the production and the thickness of the phosphor layer and transparent protective film of each panel obtained were as shown in Table 2 below.

Next, the bending hardness of each comparative example panel obtained was measured, and a crack test and a phosphor layer peeling test were conducted using each of these comparative example panels.

The results are shown in Table 3 below.

As can be seen from the comparison of the above crack test and phosphor peel test results, the panels of the present invention are more resistant to bending than panels using conventional binders (Comparative Examples A-C).

In addition, the panel of the present invention has higher bending hardness (lower flexibility) than the panel using polyurethane resin as a binder (comparative example A), so unlike the panel using polyurethane resin as a binder, the phosphor layer is There is no scratching, and no nicks occur during handling, improving ease of handling.

Furthermore, as is clear from the light resistance test results to excitation light, the panels of the present invention have higher light resistance to excitation light than the panels of Comparative Examples A to C using conventional binders.

Example 2 Same polyester-urethane resin as Example 1 and Example 1
A coating solution having the following composition was prepared in the same manner as in Example 1, using the same mixture of cellulose acetate as the binder.

BaFBr: Eu2+ phosphor 300 parts by weight Polyester-urethane resin 12.5 // Cellulose acetate 12.5 // Tricresyl phosphate
2.5 Methylene chloride
123 Methanol 4
〃Methyl ethyl ketone 49//Next, using this coating solution, a 300μ thick film was coated on a 180μ thick polyethylene terephthalate sheet (support) in the same manner as in Example 1.
A phosphor layer with a thickness of 8* was provided, and a protective film with a thickness of 10 μm was provided on the 8* phosphor layer in the same manner as in Example 1.

On the other hand, for comparison, a coating liquid having the following composition was prepared using cellulose acetate (degree of acetylation: 55%, average degree of polymerization: 260), which has been conventionally used as a binder for radiation image storage panels, as a binder.

BaFBr: Eu2+ phosphor 300 parts by weight Cellulose acetate 25 Triphenyl phosphate 2.5 Methyl chloride
158 Methanol
18 Using the above coating solution, apply 180 mL in the same manner as above.
300 μm on μ-thick polyethylene terephthalate sheet
A radiation image storage panel was manufactured in which a phosphor layer with a thickness of 10 μm and a protective film with a thickness of 10 μm were provided in this order.

Next, the bending hardness of the radiation image conversion panel of the present invention and the comparative radiation image conversion panel obtained as described above was measured,
Furthermore, using these panels, a crack test, a phosphor layer peeling test, and a light resistance test against excitation light were conducted.

The results are shown in Table 4 below. As is clear from Table 4 above, the panel of the present invention has a higher degree of flexibility than the panel of the comparative example, and also has a higher degree of fixation of the phosphor layer to the support. The panels of the invention are more resistant to bending than the comparative panels.

Furthermore, the panel of the present invention has higher light resistance to excitation light than the panel of the comparative example.

Example 3 A coating solution having the following composition was prepared in the same manner as in Example 1, using as a binder a mixture of the same polyester-urethane resin as in Example 1 and the same cellulose acetate as in Example 1.

BaFBr: Eu2+ phosphor 300 parts by weight Polyester-urethane resin 10 parts by weight Cellulose acetate 15 Tricresyl phosphate
2.5 Methylene chloride
123 Methanol 4
Methyl ethyl ketone 497 Next, using this coating solution, a 300 μ thick phosphor layer was formed on a 180 μ thick polyethylene terephthalate sheet in the same manner as in Example 1, and a 10 μ thick phosphor layer was formed on this phosphor layer in the same manner as in Example 1. A protective film was provided.

The bending hardness of the radiation image conversion panel obtained as described above was measured, and the panel was also subjected to a crack test, a phosphor layer peeling test, and a light resistance test to excitation light.

The results are shown below. Bending hardness 3.
9 X 10 dyme-crjY crack test
Phosphor layer peeling test with no cracks O light fastness test Emission light intensity ratio 92 crack test No cracks This panel is similar to the polyester layer of the panel of Example 1.
The mixing ratio of urethane resin and cellulose acetate was changed (
Although the amount of cellulose acetate was increased, as is clear from the above measurement and test results, the physical properties of the panel do not change much even if the mixing ratio of both changes.

Like the panel of Example 1, the panel of this example also has high resistance to bending and high light resistance to excitation light.

Claims (1)

[Claims] 1. A radiation image conversion panel comprising a support and a phosphor layer provided on the support and comprising a stimulable phosphor dispersed in a binder, wherein the binder is generally Methylene chloride-soluble polyester consisting of a polyester represented by the formula (where l is an integer of 2 to 4, m is an integer of 2 to 4, and n is an integer of 1 to 100)
A radiation image conversion panel comprising a mixture of urethane resin and cellulose acetate having a degree of acetylation of 49 degrees or more. 2. The radiation image storage panel according to claim 1, wherein the methylene chloride-soluble polyester-urethane resin has a molecular weight of 2,000 to 50,000, and the cellulose acetate has a degree of acetylation of 58 fb or more.