JP2011154251A - Processing method for photosensitive letterpress printing original plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photosensitive letterpress printing original plate which solves the problem of photo curing shortage on the surface of a printing plate, and which has an excellent printing durability and printing quality. <P>SOLUTION: To a photosensitive letterpress printing original plate on which at least (A) a supporting body, (B) a photosensitive resin layer and (C) a heat-sensitive mask layer are laminated sequentially, ultraviolet rays are radiated, in which the quantity of light ratio (UV-C/UV-A) of the illuminance at 250 nm and the illuminance at 350 nm after the development of the (B) photosensitive resin layer is equal to or more than 0.1 and equal to or less than 1.0. Thereby, a printing plate in which the surface Shore D hardness of the plate is equal to or more than 45 degrees and equal to or less than 85 degrees is obtained. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention is a method for producing a relief printing plate by computer plate making technology. More specifically, a photosensitive relief printing original plate excellent in printing quality is obtained by irradiating an actinic ray to a photosensitive layer after water development. It relates to a method of manufacturing.

  Currently, in the field of letterpress and flexographic printing, computer plate making technology (CTP technology), also known as digital image forming technology, has become very common. In CTP technology, a photographic mask (also referred to as a photomask or negative film) conventionally used to cover a non-polymerized area of a photosensitive printing plate replaces a mask formed and integrated in the printing plate. It has been. There are several possible methods for obtaining such an integrated mask, but there are two techniques already in practical use. That is, a mask is printed with an inkjet printer on a photosensitive printing plate, or a layer (IR ablation layer or substantially opaque to actinic radiation (that is, substantially free of actinic radiation) on a photosensitive layer. A thermal mask layer) and forming an image on such a mask with an IR laser. Such a heat-sensitive mask layer usually contains carbon black as an IR absorbing material. The photosensitive printing original plate which has this thermal mask layer is disclosed by patent document 1 or patent document 2, for example. By irradiating with an IR laser, the black layer is lost at that portion, and the underlying photosensitive layer is exposed. The laser device is directly connected to the layout computer system. Using this technique, the image is generally formed directly on the plate and irradiated with actinic light in the next step.

  An important step in a method for producing a printing plate using a photosensitive printing original plate having a thermal mask layer is to form an image by irradiating an IR laser, and then irradiate the photosensitive resin layer through the image with actinic radiation. This is a step of forming a latent image. The irradiation with actinic radiation is characterized in that a sharp relief image can be obtained due to the exposure obstruction effect in the presence of oxygen by performing it without using the decompression function provided in the exposure apparatus.

  However, since the CTP technique is generally exposed in an atmosphere that does not deoxygenate in the air or the like, the photosensitive resin layer near the printing plate surface is subject to photopolymerization inhibition. For this reason, there is a problem that cracks peculiar to printing plates whose hardness is classified from high hardness to medium hardness are liable to occur at the solid portion of the printing plate surface during printing, and the deterioration of printing performance is remarkable.

On the other hand, a printing plate precursor having a barrier layer provided between a photosensitive layer and a thermal mask layer has been proposed (Patent Document 3). By providing a barrier layer having an oxygen blocking ability, inhibition of photopolymerization of the photosensitive resin layer is suppressed. However, there is a problem that wrinkles enter the mask layer after ablation depending on the material of the barrier layer.
Patent Document 4 proposes a method for producing a water-developable printing plate for letterpress printing using a solid plate of a photosensitive resin composition comprising a hydrophilic resin containing conjugated diene as a main component. Under the condition of a low oxygen concentration atmosphere, ultraviolet light having a wavelength of 200 to 300 nm and light having a maximum energy intensity at 300 to 400 nm are irradiated. Since the printing plate of Patent Document 4 is a soft plate classified as a flexographic plate, cracks peculiar to printing plates whose surface hardness is classified from high hardness to medium hardness do not occur, but the plate surface when irradiated with an arbitrary amount of ultraviolet light The bad odor generated from the was also a problem.

Japanese National Patent Publication No. 10-509254 JP-A-9-171247 JP 7-509789 Japanese Patent No. 3933675

It is an object of the present invention to provide a photosensitive relief printing original plate that eliminates insufficient photocuring on the printing plate surface and is excellent in printing durability and printing quality.

As a result of earnestly researching and studying the photosensitive printing plate to solve the above-mentioned problems, the present inventors finally completed the present invention. That is, the present invention relates to (B) the photosensitive resin for the photosensitive letterpress printing original plate in which (A) a support, (B) a photosensitive resin layer, and (C) a thermal mask layer are sequentially laminated. After the development of the layer, ultraviolet light having an illuminance ratio at 250 nm to 350 nm (UV-C / UV-A) of 0.1 to 1.0 is irradiated, and the surface hardness of the plate is Shore D 45 ° to 85 ° A printing plate manufacturing method for obtaining the following printing plate.

  The photosensitive letterpress printing original plate of the present invention is excellent in printing durability and printing quality, and exhibits an effect that no bad odor is generated from the plate surface during exposure.

  Hereinafter, the photosensitive relief printing original plate of the present invention will be described in detail.

  The relief printing original plate of the present invention has a structure in which at least (A) a support, (B) a photosensitive resin layer, and (C) a thermal mask layer are sequentially laminated.

  The support (A) suitable for the photosensitive printing original plate of the present invention is preferably a flexible material having excellent dimensional stability, for example, a plate made of a metal such as steel, aluminum, copper, nickel, Examples thereof include a film made of a resin such as polyethylene terephthalate (PET), polyethylene naphthalate, polybutylene terephthalate, or polycarbonate. These have sufficiently high viscoelasticity that can be used as a support material excellent in dimensional stability. Of these, polyethylene terephthalate film is preferably used as a support material having excellent dimensional stability and excellent flexibility. The thickness of the support used here is preferably from 50 to 350 μm, preferably from 100 to 250 μm from the viewpoint of mechanical properties, shape stabilization, or handleability during printing plate making. If necessary, a conventionally known adhesive layer may be provided in order to improve the adhesion between the support and the photosensitive resin layer.

  The photosensitive resin layer (B) used for the photosensitive printing original plate of the present invention preferably contains a known soluble synthetic polymer compound, a photopolymerizable unsaturated compound and a photopolymerization initiator. Furthermore, additives such as plasticizers, thermal polymerization inhibitors, dyes, pigments, ultraviolet absorbers, fragrances or antioxidants may be included.

  In the present invention, as the soluble synthetic polymer compound (B) constituting the photosensitive resin layer, a known soluble synthetic polymer compound can be used. For example, polyether amide (for example, JP-A No. 55-79437), polyether ester amide (for example, JP-A No. 58-117537), ammonium salt type tertiary nitrogen atom-containing polyamide (for example, JP-A No. 53- 36555), an addition polymer of an amide compound having one or more amide bonds and an organic diisocyanate compound (for example, JP-A-58-140737), an addition polymer of a diamine having no amide bond and an organic diisocyanate compound ( For example, Japanese Patent Laid-Open No. 4-97154, etc.), among them, tertiary nitrogen atom-containing polyamides and ammonium salt type tertiary nitrogen atom-containing polyamides are preferred.

  In the present invention, (B) a compound suitably used as the photopolymerizable unsaturated compound constituting the photosensitive resin layer includes ring-opening addition of polyglycidyl ether of polyhydric alcohol, methacrylic acid and acrylic acid. Examples of the polyhydric alcohol include dipentaerythritol, pentaerythritol, trimethylolpropane, glycerin, ethylene glycol, diethylene glycol, triethylene glycol, and ethylene oxide adducts of phthalic acid. Methylolpropane is preferred.

  Furthermore, in the present invention, examples of (B) the photoinitiator constituting the photosensitive resin layer include benzophenones, benzoins, acetophenones, benzyls, benzoin alkyl ethers, benzyl alkyl ketals, anthraquinones, thioxanthones. And the like. Specifically, benzophenone, chlorobenzophenone, benzoin, acetophenone, benzyl, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzyl dimethyl ketal, benzyl diethyl ketal, benzyl diisopropyl ketal, anthraquinone, 2-ethylanthraquinone Examples include 2-methylanthraquinone, 2-allyl anthraquinone, 2-chloroanthraquinone, thioxanthone, and 2-chlorothioxanthone.

  The heat-sensitive mask layer (C) used in the original plate of the present invention is composed of carbon black, which is a material having a function of absorbing an IR laser and converting it into heat, and a function of blocking ultraviolet light, and a dispersion binder thereof. It is preferable. Further, as an optional component other than these, a pigment dispersant, a filler, a surfactant, a coating aid, or the like can be contained within a range that does not impair the effects of the present invention.

  In the present invention, it is preferable to use a butyral resin and a polar group-containing polyamide in combination as a dispersing binder constituting the thermal mask layer (C). The butyral resin can improve the dispersibility of the carbon black and can contribute to high light-shielding properties. However, when the butyral resin is used alone, the coating of the thermal mask layer becomes brittle and the scratch resistance is poor. Therefore, in the present invention, it is preferable to use a polar group-containing polyamide in order to overcome this scratch resistance. The polar group-containing polyamide is excellent in the dispersibility of carbon black due to the effect of containing a polar group, and even if a part of the butyral resin is replaced, the dispersibility is not lowered. In addition, since both the butyral resin and the polar group-containing polyamide are dissolved in alcohol and water, when they are used together as a dispersion binder, a heat-sensitive mask layer excellent in handling during film formation and developability in a solvent and water can be easily formed. be able to. Since the heat-sensitive mask layer made of butyral resin and polar group-containing polyamide is easily dispersed in water, it can be suitably used particularly as a heat-sensitive mask layer of a water-developable plate.

  In the present invention, (C) the polar group-containing polyamide used as the dispersion binder constituting the heat-sensitive mask layer is preferably a copolymer polyamide having a polar group. The polyamide used may be appropriately selected from conventionally known cationic polyamides, nonionic polyamides, and anionic polyamides, such as tertiary amine group-containing polyamides, quaternary ammonium base-containing polyamides, ether group-containing polyamides, and sulfonic acids. Examples thereof include group-containing polyamide.

  (C) The weight ratio of the butyral resin and the polar group-containing polyamide in the dispersion binder constituting the heat-sensitive mask layer is preferably 20 to 80:20 to 80. If the weight ratio between the two is not within the above range, the dispersibility of the carbon black and the scratch resistance of the heat-sensitive mask layer may not be achieved in a well-balanced manner.

  (C) It is preferable that the weight ratio of the carbon black and the dispersion binder in the heat-sensitive mask layer is 25 to 50:20 to 75. If the weight ratio between the two is not within the above range, the light shielding property by carbon black may not be achieved with a thin layer.

(C) The thermal mask layer preferably has an optical density of 2.0 or more with respect to actinic radiation, more preferably an optical density of 2.0 to 3.0, and particularly preferably 2.2 to 2. The optical density is 5. The optical density is generally represented by D and is defined by the following equation.
D = log ₁₀ (100 / T) = log ₁₀ (I ₀ / I)
(T represents transmittance%, I ₀ represents incident light intensity when measuring transmittance, and I represents transmitted light intensity)

  (C) The layer thickness of the thermal mask layer is preferably 0.5 to 2.5 μm, more preferably 1.0 to 2.0 μm. If it is more than the said minimum, a high coating technique is not required but an optical density more than fixed can be obtained. Moreover, if it is below the said upper limit, high energy is not required for evaporation of a thermal mask layer, and it is advantageous in cost.

  (C) It is preferable to protect the printing original plate by providing a peelable flexible cover film on the thermal mask layer. Suitable examples of the peelable flexible cover film include a polyethylene terephthalate film, a polyethylene naphthalate film, and a polybutylene terephthalate film. However, such a protective film is not absolutely necessary.

The method for producing the relief printing original plate of the present invention is not particularly limited, but is generally produced as follows.
First, components such as a dispersion binder other than carbon black of the thermal mask layer are dissolved in an appropriate solvent, and carbon black is dispersed therein to prepare a dispersion. Next, a dispersion liquid is apply | coated on the support body (for example, PET film) for thermal mask layers, a solvent is evaporated, and one laminated body is created. Further, separately from this, a photosensitive resin layer is formed on the support by coating, and the other laminate is prepared. The two laminated bodies thus obtained are laminated so that the photosensitive resin layer is adjacent to the thermal mask layer under pressure and / or heating. The heat-sensitive mask layer support functions as a protective film on the surface of the printing original plate after completion.

  As a method for producing a printing plate from the printing original plate of the present invention, when a protective film is present, the protective film is first removed from the photosensitive printing plate. Thereafter, image information is drawn on the heat-sensitive mask layer with an IR laser to form a mask on the photosensitive resin layer. Examples of suitable IR lasers include ND / YAG laser (wavelength 1064 nm) or diode laser (wavelength example, 830 nm). Laser systems suitable for computer plate making technology are commercially available, and for example, CDI Spark (Esco Graphics) can be used. This laser system includes a rotating cylindrical drum that holds a printing original, an IR laser irradiation device, and a layout computer, and image information is directly transferred from the layout computer to the laser device.

  After the image information is written on the heat-sensitive mask layer, the photosensitive printing original plate is irradiated with actinic rays through the mask. This can be done with the plate attached to the laser cylinder, but removing the plate from the laser device and irradiating with a conventional flat irradiation unit is advantageous in that it can cope with non-standard plate sizes. It is general. As the actinic ray, ultraviolet rays having a wavelength of 150 to 500 nm, particularly 310 to 400 nm can be used. As the light source, a low-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a metal halide lamp, a xenon lamp, a zirconium lamp, a carbon arc lamp, an ultraviolet fluorescent lamp, or the like can be used. Thereafter, the irradiated plate is eluted with an uncured photopolymerizable layer by a brush type developing machine or a spray type developing device, and an image can be formed on the support.

  After development, in order to remove the developer and photosensitive resin remaining on the plate surface, the substrate is washed with rinsing water and then dried with a hot air dryer or the like. The drying conditions are, for example, 60 to 70 ° C. for 5 to 240 minutes.

After drying, as a post-treatment, the developed photosensitive resin is completely cured by irradiating ultraviolet rays (UV-A) of 310 to 400 nm. In this case, it is desirable that the irradiation amount is equal to or more than the irradiation amount through the mask layer. More preferably the amount of energy 600 mJ / cm ² or more 1000 mJ / cm ² or less is good. Even if the irradiation exceeds 1000 mJ / cm ² , the curing does not proceed any further and the work is wasted.

  Further, the present invention is characterized by irradiating 200 to 300 nm ultraviolet rays (UV-C) as the post-treatment. The order of UV-A and UV-C irradiation in the post-treatment is not a problem, and either of them may be irradiated first or simultaneously.

  The post-treatment ultraviolet irradiation in the present invention needs to have a UV-C / UV-A ratio of 0.1 to 1.0, particularly preferably 0.2 to 0.8. If the ratio is less than 0.1, the crack resistance of the plate surface is poor, and if it exceeds 1, the odor generated from the plate surface during exposure is strong, and the burden on the operator is large.

  The ultraviolet light source of 310 to 400 nm used in the post-treatment can be an ultraviolet fluorescent lamp or the like used in the previous main exposure. Moreover, what has wavelength distribution in a germicidal line (254 nm) as a 200-300 nm ultraviolet light source is desirable. Such a light source is available as a germicidal lamp (GL) from each lamp manufacturer.

  The ultraviolet irradiation in the post-treatment in the present invention is performed on a photosensitive letterpress printing original plate in which the surface hardness of the printing plate after photocuring is from 45 degrees to 85 degrees Shore D (JIS K6253). If the Shore D is less than 45 degrees, cracks are unlikely to occur on the printing plate during printing, but there is a problem that the printing plate is soft and fine images such as letters are crushed. On the other hand, if the shore exceeds D85 degrees, the solid image portion is poorly crushed before cracking occurs, and there is a problem in print quality.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited by these Examples. Moreover, the evaluation method in an Example is based on the method described below.

Reference Example 1 <Creation of thermal mask layer>

Preparation of Dispersion Binder As a dispersion binder, a butyral resin and a tertiary amine group-containing polyamide were prepared. As the butyral resin, BM-5 manufactured by Sekisui Chemical Co., Ltd. was used. As the tertiary amine group-containing polyamide and the ether group-containing polyamide, those synthesized as follows were used.

Synthesis of tertiary amine group-containing polyamide Autoclaving 50 parts by weight of ε-caprolactam, 40 parts by weight of N, N, -di (γ-aminopropyl) piperazine adipate, 10 parts by weight of 3-bisaminomethylcyclohexane adipate and 100 parts by weight of water The solution was charged into the interior, purged with nitrogen, sealed and gradually heated. From the time when the internal pressure reached 10 kg / m ³ , water was distilled off until the pressure could not be maintained, returned to normal pressure in about 2 hours, and then reacted at normal pressure for 1 hour. The maximum polymerization reaction temperature was 255 ° C. As a result, a tertiary amine group-containing polyamide having a melting point of 137 ° C. and a specific viscosity of 1.96 was obtained.

Synthesis of ether group-containing polyamide equimolar salt of α, ω-diaminopolyoxyethylene obtained by adding acrylonitrile to both ends of polyethylene glycol having a number average molecular weight of 600 and reducing this with hydrogen: 60 parts by weight , Ε-caprolactam: 20 parts by weight and an equimolar salt of hexamethylenediamine and adipic acid: 20 parts by weight were melt polymerized to obtain a relative viscosity (viscosity obtained by dissolving 1 g of polymer in 100 ml of water chloral and measuring at 25 ° C.) Of 2.50 was obtained.

Preparation of thermal mask layer coating liquid 27 parts of butyral resin and 39 parts of tertiary amine group-containing polyamide were dissolved in a solvent, and carbon black was dispersed therein to prepare a dispersion liquid, which was used as a thermal mask layer coating liquid. The solvent used was a mixed solution of methanol and ethanol in a weight ratio of 70:30.

Preparation of heat-sensitive mask layer A heat-sensitive mask layer coating solution is applied to a PET film support (Toyobo Co., Ltd., E5000, thickness 100 μm) subjected to release treatment on both sides so that the layer thickness becomes 1.5 μm Coating was performed using an appropriately selected bar coater, and drying was performed at 120 ° C. for 5 minutes to form a thermal mask layer.

Example 1
A. Preparation of original plate Photosensitive resin letterpress printing original plate (printite) composed of a PET film support (E5002 manufactured by Toyobo Co., Ltd.) having a thickness of 100 μm, a photosensitive resin layer, a polyvinyl alcohol layer and a chemically matted PET protective film. JF95C (manufactured by Toyobo Co., Ltd.) was peeled off, and the lower polyvinyl alcohol layer was removed from the photosensitive resin layer using a conventional adhesive tape. The heat-sensitive mask layer produced in Reference Example 1 was overlaid on the exposed photosensitive resin layer. Using a heat press machine, lamination was performed at 100 ° C. and 100 kg weight / cm ² to obtain a plate comprising a PET support, a photosensitive resin layer, a thermal mask layer, and a chemically matted PET protective film (cover film).

B. Preparation of plate After removing the protective film from the photosensitive letterpress printing original plate, (C) heat sensitivity under conditions of laser output 8 W and drum rotation speed 850 rpm with an external drum type IR laser plate setter (Esco Graphics CDI Spark 2530) Draw on the mask layer. The drawn original plate was exposed to UV with a 20 W chemical lamp for 5 minutes (750 mJ / cm ² ), then washed with a brush-type washer / dryer integrated device (JEOL Seiki, JOWA 2 SD) for 2 minutes and 30 seconds, 60 Drying was performed at 10 ° C. for 10 minutes. Subsequent post-treatment conditions were as follows and evaluated.

C. Post-processing of printing plate 310 to 400 nm UV lamp (indicated as UV-A) is an exposure machine (Tomihiro Sangyo, Tomiflex A-2, 16 illuminants of 20 W chemical lamps (Mitsubishi OSRAM FL20S BL360) with an illuminance of 2 .5 mW / cm ² ) for 5 minutes. The 200 to 300 nm UV lamp (indicated as UV-C) uses an exposure machine (GM GL GL irradiator with illuminance of 3.2 mW / cm ² ) with 21 40 W germicidal lamps (Panasonic GL40) lined up. For 3 minutes. The respective illuminances are measured using the light receiving parts UV-25 and UV-35 using Oak Seisakusho UV-M02. Assuming that the illuminance is illuminance at 350 nm, the light amount and the light amount ratio were 0.77. The Shore D hardness of the photosensitive resin plate at this time was 55 degrees.

D. Evaluation of printability If the surface of the plate is weak, fine cracks will occur as printing proceeds. The occurrence of cracks was evaluated by a printing durability acceleration test described below. The operating environment of the printing press was 20 to 25 ° C. and humidity 30 to 40% RH. The printing press was placed on the plate cylinder using a convex rotary printing press (Sanjo Machine P-20) in a state where printing pressure was applied to all images. The shape of the printing plate image was a star mark type with a diameter of 16 mm including a white image. The printing pressure was usually applied to a printed material of 150 to 250 μm, and the load was excessively applied by pushing 450 μm. The printing speed at this time was 20 to 30 m / min. The ink used was UV ink (T & K TOKA Best Cure UV Color Indigo B), and the ink density was adjusted to 0.6 to 2.0 with a reflection densitometer (Dainippon Screen Manufacturing DM-800). Mirror-coated tack paper (Lintec gloss PW 8K) was used as printing paper. Printing was performed up to 8000 shots, and ranking was based on the number of shots where cracks occurred. The evaluation of the occurrence of cracks was determined by visually observing the presence of crack marks appearing on the printed matter with a loupe. This plate did not crack and the printing durability was A rank. In addition, the white image was not buried and no bad odor was generated.

Example 2
A printing original plate was prepared in the same manner as in Example 1, and using the same exposure machine, UV-A was irradiated for 4 minutes and UV-C was irradiated for 45 seconds. The light quantity ratio was 0.25. As a result of the evaluation, the printing durability was 8000 shots, and no cracking occurred. There were no buried white images and no bad smell.

Example 3
B. Plate preparation and C.I. In the post-treatment of the printing plate, instead of the 20 W chemical lamp, an exposure machine (A & V A-2, illumination intensity 8.0 mW / cm ² ) in which 14 W high-intensity lamps (Phillips TLK40W ACTINIC BL) were arranged was used.
UV-A was irradiated for 90 seconds and UV-C was irradiated for 45 seconds. The light quantity ratio was 0.20. As a result of the evaluation, the printing durability was 8000 shots, and no cracking occurred. There was no odor.

Example 4
Using the same exposure machine as in Example 3, UV-A was irradiated for 120 seconds and UV-C was irradiated for 5 minutes. The light quantity ratio was 1.00. As a result of the evaluation, the printing durability was 8000 shots, and no cracking occurred. A slight odor was felt.

Comparative Example 1
The same procedure as in Example 1 was performed except that UV-C irradiation was omitted. As for printing durability, cracking occurred after 3000 shots, and the printing performance was not satisfactory.

Example 5
The same procedure as in Example 1 was performed except that UV-C irradiation was performed for 25 seconds. The light quantity ratio was 0.10. As a result of evaluation, the printing durability was cracked after 5000 shots, and an improvement was seen compared to Comparative Example 1, but the evaluation tank was B rank.

Comparative Example 2
The same procedure as in Example 1 was performed except that UV-C irradiation was performed for 5 minutes and 30 seconds. The light quantity ratio was 1.40. As a result of the evaluation, although the printing durability was 8000 shots and no cracks were generated, a bad odor was generated during post-processing and the workability was impaired.

Example 6
A. used in Example 1. Instead of making the original plate, a 125 μm thick PET film support (E5002 manufactured by Toyobo Co., Ltd.), a photosensitive resin layer, a polyvinyl alcohol layer, and a photosensitive resin relief printing original plate (printer) A plate was obtained using Ito KF95GC (Toyobo Co., Ltd.). Using the same exposure machine, UV-A was irradiated for 5 minutes and UV-C was irradiated for 45 seconds. The light quantity ratio was 0.20. The Shore D hardness of the photosensitive resin plate at this time was 67 degrees. As a result of the evaluation, the printing durability was 8000 shots, and no cracking occurred. There was no odor.

Comparative Example 3
The same procedure as in Example 6 was performed except that UV-C irradiation was omitted. The printing durability was cracked after 6000 shots, and the evaluation rank was B rank. There was no odor.

Comparative Example 4
A. used in Example 1. Instead of making the original plate, a 125 μm thick PET film support (E5002 manufactured by Toyobo Co., Ltd.), a photosensitive resin layer, a polyvinyl alcohol layer, and a photosensitive resin relief printing original plate (printer) A plate was obtained using Ito SF95GB (manufactured by Toyobo). Using the same exposure machine, UV-A was 5 minutes and UV-C was not irradiated. The Shore D hardness of the photosensitive resin plate at this time was 40 degrees. As a result of the evaluation, the printing durability was 8000 shots with no cracking and no bad odor. However, a fine image is crushed in the white image, and the printing performance is not satisfactory.

耐刷性
Ａ；8,000ショットで割れなし
Ｂ；4,000〜8,000ショットでヒビ割れ発生
Ｃ；3,000ショット以下でヒビ割れ
臭気
×；強い悪臭あり
△；微かに悪臭あり
○；悪臭なし

Printing durability A: No cracking after 8,000 shots B: Cracking occurred between 4,000 and 8,000 shots C: Cracking under 3,000 shots Odor
×: Strong odor △; Slightly odor ○; No odor

  The photosensitive letterpress printing original plate of the present invention is excellent in printing durability, does not impair fine print quality, and does not generate a bad odor. .

Claims (1)

  (A) A support, (B) a photosensitive resin layer, and (C) a thermosensitive mask layer are sequentially laminated to a photosensitive letterpress printing original plate at 250 nm after development of the (B) photosensitive resin layer. Printing plate whose surface hardness is 45 ° to 85 ° Shore D is irradiated with ultraviolet rays with a light intensity ratio (UV-C / UV-A) between 0.1 and 1.0 at 350 nm. A method for producing a printing plate.