Patent Number: 060312378
Section: description

Examples embodying the present invention are given below, but those examples are by no means construed to restrict the invention. EXAMPLE 1 Composition of the Phosphor Sheet (layer) ______________________________________ Stimulable phosphor (BaFBr.sub.0.85 I.sub.0.15 :Eu.sup.2+ ) 200 g Binder: Polyurethane elastomer (Kuramiron U-8165 8.0 g (solid), product of Kuraray Co., Ltd.; Aromatic polyurethane having a repeating unit of dimethylphenylmethane diisocyanate; Vicat softening point: 69.degree. C.) Anti-yellowing agent: Epoxy resin (EP 1001 2.0 g (solid), product of Yuka Shell Epoxy Kabushiki Kaisha) Radical scavenger: Hindered amine compound 0.16 g (Mark LA-77, product of Adeka Argas Chemical CO., Ltd.) ______________________________________ The above composition was placed in tetrahydrofuran and dispersed by means of a propeller mixer to give a coating dispersion of a viscosity of 30 PS (at 25.degree. C.) in which the ratio of binder to phosphor was 1/20. The coating dispersion was coated on a polyethylene terephthalate temporary support (thickness: 150 .mu.m) having a silicon release coating. The coated layer was dried to give a stimulable phosphor sheet having a thickness of 150 .mu.m. Composition of the Undercoating Layer ______________________________________ Binder: Soft acryiic resin (solid) 90 g Nitrocellulose (solid) 30 g ______________________________________ The above composition was placed in methyl ethyl ketone and dispersed by means of a propeller mixer to give a coating dispersion for the undercoating layer of a viscosity in the range of 3 to 6 PS (at 25.degree. C.). The prepared coating dispersion was coated on a polyethylene terephthalate permanent support (thickness: 300 .mu.m) horizontally placed on a glass plate. The coated layer was dried to provide an undercoating layer (thickness: 15 .mu.m) on the permanent support. On the undercoating layer thus formed on the permanent support, the phosphor sheet was placed and then compressed by means of a calendar roll. The compression treatment was sequentially carried out under the conditions as follows: pressure: 500 kgw/cm.sup.2 ; temperature: 75.degree. C. (upper roller) and 25.degree. C. (lower roller); and moving speed: 0.3 m/min. The phosphor sheet was completely fixed on the support by the treatment. Composition of the Protective Film ______________________________________ Fluororesin: Fluoroolefin-vinyi ether copolymer 50 g (Lumiflon LF-504x (40 wt.% solution), product of Asahi Glass Co., Ltd.) Cross-linking agent: polyisocyanate (Olestar 9 g NP38-70s (70 wt. % solution), product of Mitsui Toatsu Chemicals, Inc.) Alcohol modified-silicone resin (X-22-2809 0.5 g (66 wt. % solution), product. of The Shin- Etsu. Chemical Co., Ltd.) Catalyst: dibutyltin dilaurate (KS1260, product of 3 mg Kyodo Chemical Co., Ltd.) ______________________________________ The above composition was dissolved in a mixed solvent of methyl ethyl ketone and cyclohexane (2:8, by volume) to prepare a coating solution of a viscosity in the range of 0.2 to 0.3 PS (at 25.degree. C.). The coating solution was applied on the phosphor layer using a doctor blade, and then heated at 120.degree. C. for 30 minutes to cure and dry the coated layer film. Thus, a protective film (thickness: 3 .mu.m) was formed on the phosphor layer. Composition of Edge Coating Film ______________________________________ Silicone polymer: Polyurethane having a repeating 70 g unit of polydimethylcyclohexane (Diaromer SP-3023 (15 wt. % methyl ethyl ketone-toluene mixed solution), product of Dainichiseika Color & Chemicals Mfg. Co., Ltd.) Cross-linking agent: polyisocynate (Crossnate 3 g D-70 (50 wt. % solution), product of Dainichiseika Color & Chemicals Mfg. Co., Ltd.) Anti-yellowing agent: Epoxy resin (EP 1001 0.6 g (solid), product of Yuka Shell Epoxy Kabushiki Kaisha) Alcohol modified-silicone (X-22-2809 0.2 g (66 wt. % solution), product of The Shin- Etsu Chemical Co., Ltd.) ______________________________________ The composition was dissolved in 15 g of methyl ethyl ketone to prepare a coating solution for edge coating film. The solution was coated on the edge (side surface) of the above-formed multi-layered body consisting of the support, the undercoating layer, the phosphor layer and the protective film. Thereafter, the coated solution was well dried to give a hard edge coating film (thickness: 25 .mu.m). Thus, a radiation image storage panel consisting of the support, the undercoating layer, the phosphor layer, the protective film and the edge coating film was produced. EXAMPLE 2 The procedures of Example 1 were repeated except that the radical scavenger of hindered amine compound (0.16 g of Mark LA-77) was replaced with a radical scavenger of hindered phenol compound (0.20 g of ADK SIAB A0-70, product of Adeka Argas Chemical Co., Ltd.), to produce a radiation image storage panel consisting of the support, the undercoating layer, the phosphor layer, the protective film and the edge coating film. EXAMPLE 3 The procedures of Example 1 were repeated except that the radical scavenger of hindered amine compound (0.16 g of Mark LA-77) was replaced with a radical scavenger of hindered amine compound (0.17 g of Sanol LS-765, product of Sankyo CO., Ltd.), to produce a radiation image storage panel consisting of the support, the undercoating layer, the phosphor layer, the protective film and the edge coating film. EXAMPLE 4 The procedures of Example 1 were repeated except that the phosphor sheet was prepared in the below-mentioned manner, to produce a radiation image storage panel consisting of the support, the undercoating layer, the phosphor layer, the protective film and the edge coating film. Composition of the Phosphor Sheet (layer) ______________________________________ Stimulable phosphor (BaFBr.sub.0.85 I.sub.0.15 :Eu.sup.2+) 200 g Binder 1: Polyurethane elastomer (P-22 (solid), 8.0 g product of Nippon Miractran Co., Ltd.; Aromatic polyurethane having a repeating unit of dimethylphenylmethane diisocyanate; Vicat softening point: 64.degree. C.) Anti-yellowing agent:.Epoxy resin (EP 1001 2.0 g (solid), product of Yuka Shell Epoxy Kablishiki Kaisha) Radical. scavenger: Hindered amine compound 0.16 g (Mark LA-77, product of Adeka Argas Chemical Co., Ltd.) ______________________________________ The composition was placed in tetrahydrofuran and dispersed by means of a propeller mixer to give a coating dispersion of a viscosity of 30 PS (at 25.degree. C.) in which the ratio of binder to phosphor was 1/20. The coating dispersion was coated on a polyethylene terephthalate temporary support (thickness: 150 .mu.m) having silicon release coating. The coated layer was dried to give a stimulable phosphor sheet having a thickness of 150 .mu.m. COMPARISON EXAMPLE 1 The procedures of Example 1 were repeated except that the radical scavenger was not employed, to produce a radiation image storage panel consisting of the support, the undercoating layer, the phosphor layer, the protective film and the edge coating film. COMPARISON EXAMPLE 2 The procedures of Example 2 were repeated except that the radical scavenger was not employed, to produce a radiation image storage panel consisting of the support, the undercoating layer, the phosphor layer, the protective film and the edge coating film. COMPARISON EXAMPLE 3 The procedures of Example 1 were repeated except that the radical scavenger was not employed and an aliphatic polyurethane (T5265H, product of Dainippon Ink & Chemicals, Inc.) was used as a polyurethane elastomer, to produce a radiation image storage panel consisting of the support, the undercoating layer, the phosphor layer, the protective film and the edge coating film. EVALUATION OF RADIATION IMAGE STORAGE PANEL With respect to each of the radiation image storage panels prepared in the above examples, durability against both repeated conveying and light was evaluated in the following manner. 1) Durability Against Repeated Conveying The radiation image storage panel was cut to prepare a rectangular sample piece (100 mm.times.250 mm). The sample piece was repeatedly transferred in a conveying-durability test machine (shown in U.S. Patent No. 5,641,968) until cracks occurred in the phosphor layer. The durability of the panel against repeated conveying was evaluated by the number of the repetition of the above transferring in the test machine. The results are shown in Table 1. 2) Durability Against Light (light-resistance) The phosphor layer of the radiation image storage panel was irradiated with the light from a sodium lump at an illuminance of 200,000 lux for 30 hours. Then, the sensitivity of the panel was measured and compared with that having received no irradiation. The reduction ratio of the sensitivity was calculated to evaluate the light-resistance. The results are shown in Table 1. TABLE 1 ______________________________________ repeated conveying light-resistance (repetition number) (reduction ratio) ______________________________________ Example 1 6000 times 1.5% Example 2 6000 times 2.2% Example 3 6000 times 2.50% Example 4 8000 times 1.8% Com. Example 1 6000 times 12.3% Com. Example 2 8000 times 13.5% Com. Example 3 4000 times 1.8% ______________________________________ From the results shown in Table 1, it has been confirmed that the radiation image storage panels of the invention exhibit excellent durability against not only repeated conveying but also light.