JP2000275821A - Photosensitive lithographic printing plate material - Google Patents

Abstract

[PROBLEMS] To provide a lithographic printing plate having high sensitivity and excellent printability. A photosensitive composition comprising a polymer having a repeating unit represented by Chemical Formula 1, an azide compound, and a near-infrared absorbing dye. Embedded image Wherein R ₁ represents any substitutable group or atom;
p represents an integer of 1 to 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a negative photosensitive lithographic printing plate having sensitivity to light in the wavelength range of near infrared light.

[0002]

2. Description of the Related Art In recent years, semiconductor lasers have been increasing in output, longer life and lower cost, and have attracted attention as a preferable exposure light source. External semiconductor lasers having an output of 1 W or more have appeared on the market.

A so-called CTP for directly outputting digital data on a printing plate using the above-described semiconductor laser.
For use as a lithographic printing plate, see JP-A-7-20
No. 629, No. 271029, and No. 9-244226. Among these publications, a publication relating to a lithographic printing plate discloses a lithographic printing plate having a photosensitive layer basically containing a phenol resin, an infrared absorber, and an acid generator. Such a lithographic printing plate is exposed by, for example, a high-output semiconductor laser or the like, and utilizes the fact that the acid generated from a photoacid generator changes the solubility of a phenol resin in a developer due to crosslinking or the like.
In the negative type treatment, when using such a method, it is described in the above specification that the plate surface is subjected to heat treatment after exposure, and is required for promoting crosslinking of the phenol resin by a strong acid generated in the exposed part. In the process, the difference in solubility between the exposed and unexposed portions is not kept constant depending on the heating temperature. For example, if the heating is not performed sufficiently, the exposed portion may be dissolved to the exposed portion by a developer, or conversely, If the heating temperature is too high, there is a problem that the unexposed portion is partially insolubilized and the development is not sufficiently performed. Further, there is a problem in that the photosensitive layer naturally cures due to long-term storage property, particularly storage under high-temperature conditions, and that storage sensitivity decreases.

A photosensitive composition comprising a polymer having a polymerizable double bond in a side chain, an azide compound and a near-infrared absorbing dye is disclosed in JP-A-10-115914. When viewed as a lithographic printing plate, sensitivity and printing durability were not yet at a satisfactory level.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a photosensitive composition which has high sensitivity as a photosensitive material, has good storage stability, and can be used in a wide range of photosensitive wavelengths, so that a light source including various lasers can be used. The task is to give It is another object of the present invention to provide a lithographic printing plate which can be developed without particularly requiring heat treatment after exposure, and has excellent image quality and printing durability and good storage stability.

[0006]

The above objects are achieved by the present invention described below. That is, the gist of the present invention is a photosensitive composition comprising a polymer having a repeating unit represented by Chemical Formula 2, an azide compound, and a near-infrared absorbing dye.

[0007]

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In Chemical Formula 2, R ₁ represents any substitutable group or atom, and p represents an integer of 1 to 3.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A polymer having a repeating unit represented by the following chemical formula (2) is obtained by partially or completely saponified polyvinyl alcohol with hydroxybenzaldehyde alone or with another aldehyde as shown in a synthesis example described later. It can be easily synthesized by performing an acetalization reaction under a catalyst. Preferred examples of the polymer include various examples as shown in Chemical formula 3. Numerical values in the formula represent parts by weight.

[0010]

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In the above-mentioned various examples, there is no particular limitation on the molecular weight of the starting polyvinyl alcohol. However, when the one having a polymerization degree in the range of about 100 to 2,000 is used, the solubility is good. Which is preferable because the viscosity of the solution is in an appropriate range. Further, the saponification degree is preferably used when it is in the range of 60 to 100%.

In all of the above examples, the degree of acetalization to the starting polyvinyl alcohol is preferably at least 10%, more preferably at least 30%.

An azide compound can be cited as the second element constituting the light-sensitive material. Of these, particularly preferred examples include compounds represented by Chemical Formula 4.

[0014]

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As a third element constituting the photosensitive layer, there is a near infrared absorbing dye. Any dye may be used as long as it has absorption in the near infrared region, but the selection of the dye may greatly affect the sensitivity of the photosensitive material. Particularly preferred high output semiconductor laser having an oscillation wavelength in the near infrared region as a light source for applying light to a photosensitive material, especially lithographic printing plate material according to the present invention, the light energy is exposed to the printing plate surface several mW / cm ² The above light amount is preferable. Specifically, a 1 W class high-power semiconductor laser emitting at around 830 nm or a YAG laser emitting at 1064 nm can be mentioned as a preferred laser light source according to the present invention. Examples of dyes that exhibit absorption and sensitivity corresponding to such light sources include cyanine, merocyanine,
In addition to the porphyrin dyes, squarylium dyes, pyrylium dyes, dithiobenzylnickel complexes or carbon black, phthalocyanines and the like can be mentioned. Particularly preferred examples of the dye include the following chemical formulas.

[0016]

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[0017]

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[0018]

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Although the components constituting the photosensitive layer according to the present invention have been described, there is a preferable range for the proportion of each component in the photosensitive layer. The polymer 1
The preferred ratio of the azide compound is from 1 part by weight to 50 parts by weight, and more preferably from 1 part by weight to 20 parts by weight, per 100 parts by weight. The preferred ratio of the near-infrared absorbing dye is in the range of 0.1 to 20 parts by weight, and the more preferred range is in the range of 1 to 10 parts by weight.

The elements constituting the photosensitive layer may contain other elements in addition to the above-mentioned elements for various purposes. Various dyes for the purpose of enhancing the visibility of the image,
It is also preferable to add a pigment or to add inorganic fine particles or organic fine particles for the purpose of preventing blocking of the photosensitive layer. Further, another layer may be provided adjacent to the photosensitive layer for the purpose of protecting the photosensitive layer.

With respect to the thickness of the photosensitive layer itself, it is preferable to form the photosensitive layer on the support with a dry thickness in the range of 0.5 to 10 μm, and more preferably in the range of 1 to 5 μm. It is very preferable to greatly improve. The photosensitive layer is prepared by preparing a solution in which the above three components are mixed, coating the solution on a support using various known coating methods, and drying the solution. As the support, for example, a film or a polyethylene-coated paper may be used, but a more preferable support is an aluminum plate having a polished and anodized film.

In order to use the material having the photosensitive layer formed on the support as described above as a printing plate, the material is subjected to contact exposure or laser scanning exposure, and the exposed portion is crosslinked. Since the solubility in the alkaline developer decreases, pattern formation is performed by eluting the unexposed portions with the alkaline developer described below.

After the exposure, heat treatment is carried out in the prior art for the purpose of completing the crosslinking reaction and strengthening the resistance to an alkali developing solution, and the like. is not. In various systems disclosed in the prior art, when a heat treatment after exposure is required before development in a process of preparing a lithographic printing plate, it is necessary to strictly control heat treatment conditions. And
In particular, in the case of a large-size printing plate, it is extremely difficult and problematic to perform heating conditions uniformly over the entire plate surface. The fact that development can be performed immediately without the need for heat treatment after exposure as in the present invention is also a very advantageous point in terms of making a printing plate.

The alkaline developer is not particularly limited as long as it is a solution for dissolving the polymer according to the present invention, but is preferably an alkaline developer such as sodium hydroxide, potassium hydroxide, sodium silicate and sodium metasilicate. The aqueous developer in which the compound is dissolved is very preferable because it can satisfactorily selectively dissolve the unexposed portion and expose the lower support surface. After performing development processing using such an alkali developing solution, normal gumming is preferably performed using gum arabic or the like.

In order to dissolve the polymer according to the present invention more rapidly in the alkaline developer, various alcohols,
Addition of an organic compound such as amino alcohol is also performed. However, when an odor is generally accompanied, addition of such an organic compound is not always preferable. For the purpose of promoting the solubility of the polymer, it is preferable to add a polymer having solubility in an alkaline developer to the photosensitive composition. Preferred examples of the alkali-soluble polymer in this case include a polymer having a substituent such as a carboxy group or an acid anhydride in a side chain, such as a styrene / maleic anhydride polymer and a half-esterified product thereof. Alkyl vinyl ether / maleic anhydride polymers and their half-esterified products, or acrylic acid, various acrylic resins containing methacrylic acid as a copolymer component,
Examples include vinyl acetate-crotonic acid copolymer, carboxy-modified polyvinyl alcohol, and carboxy-modified cellulose.

When these various alkali-soluble resins are introduced into the photosensitive composition, they are preferably added in the range of 1% by weight to 200% by weight based on the polymer represented by the formula (2).

[0027]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples as well as the effects. Parts in Examples are parts by weight.

Synthesis Example (Synthesis Example of Chemical Formula 3, P-1) 120 g of polyvinyl alcohol (Kuraray PVA-203, saponification degree: 84 mol%) was dissolved in dimethylformamide (D
MF) suspended in 500 grams and 100 grams of benzene, and 4 grams of p-toluenesulfonic acid was added. At an internal temperature of 50 ° C., 122 g of m-hydroxybenzaldehyde was added in portions, and the mixture was stirred for 6 hours while refluxing benzene at reflux temperature while removing azeotropic water, and then cooled to room temperature. The whole was put into a large amount of ion-exchanged water, and the deposited precipitate was sufficiently washed with running water and dried by heating under reduced pressure. A small amount of the obtained polymer is sampled and deuterated D
As a result of structural analysis by proton NMR after dissolution in MSO, it was confirmed that about 80% of the hydroxyl groups of the original PVA were acetalized. Other polymers were synthesized in exactly the same manner.

Example 1 The polymer obtained in the above synthesis example was converted to DMF / dioxane (1 /
By heating and dissolving in the mixed solvent of 3), 100 g of a 10% by weight solution was prepared. As an azide compound, A-
10 g of the compound represented by No. 7 was added, and 3 g of the compound represented by S-1 in Chemical Formula 5 as a near infrared absorbing dye was added and dissolved. The obtained solution was applied on a grained anodized aluminum plate using a wire bar so that the amount of application was 2 g per square meter in a dry state, and then dried at 70 ° C. for 10 minutes using a dryer. After drying, a printing plate material was prepared.

In order to expose the printing plate material obtained as described above, a 1 W output semiconductor laser having an emission wavelength of 830 nm is used, the printing plate material is wound around a drum, pulse exposure is performed, and a resolution test pattern is obtained. Was printed. The exposure energy on the plate surface was 500 mJ / cm ² . The exposed printing plate material was immersed in a 6% aqueous sodium metasilicate solution for 10 seconds and developed to elute unexposed portions. When the image formed after washing and drying was observed with an optical microscope, a pattern of 10 μm in fine lines and 15 μm in dots was clearly reproduced, and non-image portions between fine lines formed at 20 μm intervals were also observed. It was confirmed that it was successfully eluted and removed.

The plate on which an image was formed as described above was coated with an aqueous solution of gum arabic and subjected to a printing test as a printing plate. Ryobi 3200 (Molton printing press) was used as the printing machine, the ink used was New Champion Boku H (Dainippon Ink), and the normal fountain solution was 1% Toho etch liquid for normal offset printing. . The ink inking property was better than at the beginning of printing, and the occurrence of background stain was not recognized throughout the printing in the non-image area. As for the printing durability, no problem occurred even when 200,000 copies were printed.

Example 2 In the same manner as in Example 1, a polymer represented by P-3 in Chemical Formula 3 was used as a polymer according to the present invention, and A-6 in Chemical Formula 4 was used as an azide compound. Chemical formula 5 as an infrared absorbing dye
A printing plate material was prepared in exactly the same manner except that the dye represented by S-3 was used. Laser exposure was performed in exactly the same manner as in Example 1. Further, as a result of performing a printing test under the same conditions as in Example 1, good results similar to those of Example 1 were obtained.

Example 3 The following experiment was conducted to evaluate the storage stability of a photosensitive lithographic printing plate. That is, the lithographic printing plate materials prepared in Examples 1 and 2 were stored for one month in a dryer heated to 50 ° C., and then subjected to the same laser exposure and printing test as in the examples. No difference was observed in development image quality and printability before and after heat storage.
No change was observed in developability and printability.

[0034]

According to the present invention, a lithographic printing plate having high sensitivity as a photosensitive material, a light wavelength range including various lasers can be used because the photosensitive wavelength range can be selected widely, and excellent image quality, excellent printing durability, and excellent storage stability. give.

Claims (1)

[Claims] 1. A photosensitive lithographic printing plate material comprising a polymer having a repeating unit represented by Chemical Formula 1, an azide compound and a near-infrared absorbing dye. Embedded image Wherein R ₁ represents any substitutable group or atom;
p represents an integer of 1 to 3.