JPH042942B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a waterless lithographic printing plate, and particularly to a waterless lithographic printing plate with excellent fine halftone dot reproducibility.

[Prior art]

As a photosensitive compound for waterless planographic printing plates, 0-
Ester compounds of naphthoquinonediazide sulfonic acid and phenol novolak resin have excellent photosensitivity and storage stability, and several have been proposed in the past.

For example, JP-A No. 55-59466 discloses a waterless lithographic printing plate in which a silicone rubber layer is provided via an adhesive layer on a photo-solubilizable photosensitive layer made of a quinonediazide compound, which is lined with an aluminum plate. Disclosed. In addition, JP-A-56-80046 discloses that a partially esterified product of naphthoquinone-1,2-diazide-5-sulfonic acid chloride and a phenol novolac resin is crosslinked with a polyfunctional isocyanate on a photoreleasable photosensitive layer. A waterless lithographic printing plate provided with a silicone rubber layer is disclosed.

[Problem that the invention seeks to solve]

These conventional waterless planographic printing plates are
There are the following problems.

(1) In the case of a waterless planographic printing plate in which a silicone rubber layer is provided on a photo-solubilizable photosensitive layer, the image area is a planar intaglio plate in which the entire photosensitive layer is removed to expose the substrate. Therefore, the cell depth is the sum of the film thicknesses of the silicone rubber layer and the photosensitive layer, and if the cell depth is deep, it is difficult for ink to adhere to the minute halftone dots, resulting in so-called clear development. . For this reason, attempts have been made to reduce the thickness of the silicone rubber layer and the photosensitive layer, but if the thickness of the silicone rubber layer is made too thin, printing durability and ink repellency deteriorate. On the other hand, if the thickness of the photosensitive layer is made too thin, minute halftone dots will be difficult to reproduce due to effects such as halation from the substrate.

(2) In the case of a waterless lithographic printing plate with a silicone rubber layer provided on the photoreleasable photosensitive layer, only the silicone rubber layer is removed and the photosensitive layer becomes the image area, so the cell depth is virtually unchanged. In other words, it is only as thick as the silicone rubber layer, and is very advantageous against so-called see-through phenomena. However, when such a photoreleasable photosensitive layer crosslinked with polyfunctional isocyanate or the like is used, the photosensitive layer cannot fully absorb the impact force during printing, and cracks and cracks enter the photosensitive layer during printing. The silicone rubber layer is destroyed by cracks, etc., causing a decrease in printing durability. Therefore, attempts were made to reduce the thickness of the photosensitive layer, but although it was found to be effective in reducing cracks and cracks during printing, minute halftone dots were reproduced due to halation from the substrate, etc. become less likely to be

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to provide a pure lithographic printing plate with good fine halftone dot reproducibility even when the photosensitive layer is made thin.

[Means for solving problems]

The present invention provides a waterless lithographic printing plate comprising a support, a photosensitive layer containing a quinonediazide compound, and a silicone rubber layer, which are laminated in this order. The present invention relates to a waterless lithographic printing plate characterized by containing at least one selected from the group of agents.

The quinonediazide compound used in the photosensitive layer of the present invention is, for example, a normal positive PS plate, a Wipon plate,
Refers to quinonedias used in photoresists, etc. Specific compounds include, for example, benzoquinone-1,2-diazide-4- or -5-
Esters of sulfonic acid and polyhydroxyphenyl, esters of naphthoquinone-1,2-diazide-4- or -5-sulfonic acid and pyrogallolacetone resin, naphthoquinone-1,2-diazide-4- or -5-sulfone Esters of acids and phenol formaldehyde novolac resins or oak-modified novolac resins may be mentioned. Also,
Examples include a photoreleasable photosensitive layer in which quinone diazides are crosslinked with a polyfunctional compound, as proposed in JP-A-56-80046.

As the quinonediazide compound in the present invention,
Particularly preferred is a partially esterified product of naphthoquinone-1,2-diazide-5-sulfonic acid and phenol formaldehyde novolak resin. It is also possible to add other components such as polymers and plasticizers to the photosensitive layer for the purpose of improving coating film forming properties and adhesion.

The light absorbent to be added to the photosensitive layer should be from 300 nm in the ultraviolet/visible absorption spectrum.
It is preferable to have an absorption maximum between 450 nm and a maximum molecular extinction coefficient in the range of 100 to 50000·mol ⁻¹ , preferably 200 to 4000·mol ⁻¹ . Specifically, salicylic acid ester-based light absorbers, such as phenyl salicylate, p-
Benzophenone-based light absorbers such as tert-butylphenyl salicylate and p-octylphenyl salicylate, such as 2,4-di-hydroxybenzophenone, 2-hydroxy-4-acetoxybenzophenone, 2-hydroxy- 4-Methoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 4,4'-
benzotriazole-based light absorbers such as dimethylaminobenzophenone and 4,4'-diethylmaminobenzophenone; for example, 2(2'-hydroxy-
5′-methylphenyl)benzotriazole, 2
Examples include light absorbers such as (2'-hydroxy-3',5'-di-tort-butylphenyl)benzotriazole. Among these light absorbers, benzophenone light absorbers are particularly preferably used in terms of compatibility with the photosensitive layer.

Particularly preferably, an aminobenzophenone represented by the following general formula (wherein R ₁ , R ₂ , R ₃ , and R ₄ are each hydrogen or an alkyl group having 4 or less carbon atoms).

These light absorbers can be used alone or in combination of two or more, but the amount added to the photosensitive layer is usually preferably in the range of 1% by weight to 20% by weight. If it is less than 1% by weight, the effects of the present invention will not be exhibited, and if it exceeds 20% by weight, the compatibility with the photosensitive layer will be poor, and there is a high possibility that the light-absorbing agent will precipitate.

The composition for forming the above-mentioned photosensitive layer is a suitable organic solvent (for example, dioxane, tetrahydrofuran, cellosolve, cellosolve acetate, etc.).
It is prepared by dissolving it in

As mentioned above, the thickness of the photosensitive layer is preferably thin, but if it is too thin, pinholes are likely to occur, so the thickness is usually 0.1 to 20μ, more preferably 0.1 to 5μ.
is selected.

The silicone rubber layer used in the present invention usually has as a main component a linear organic polysiloxane having a molecular weight of several thousand to several hundred thousand and having the following repeating units.

Here, n is an integer of 2 or more, R is an alkyl group, alkenyl group, or phenyl group having 1 to 10 carbon atoms, and preferably 60% or more of R is a methyl group. Such a linear organic polysiloxane is sparsely crosslinked to form a silicone rubber.
Examples of crosslinking agents include acetoxysilane, ketoximylan, alkoxysilane, aminosilane, amidosilane, etc., which are used in so-called room temperature (low temperature) curing silicone rubber, and are usually linear organic polysiloxanes with hydroxyl groups at the ends. In combination, these silicone rubbers become deacetic acid type, oxime type, alcohol deal type, deamine type, and deamid type silicone rubber, respectively. Generally, a small amount of an organic tin compound or the like is further added as a catalyst to these silicone rubbers.

The thickness of the silicone rubber layer is about 0.5-100μ, about 0.5
~30μ is appropriate; if it is too thin, problems may occur in terms of printing durability and ink repulsion.
On the other hand, if it is too thick, it is not only economically disadvantageous, but also makes it difficult to remove the silicone rubber layer, which may lead to a decrease in image reproducibility.

In the waterless lithographic printing original plate of the present invention, adhesion between the photosensitive layer and the silicone rubber layer is important for basic plate performance such as image reproducibility and printing durability. Provide an adhesive layer,
Adhesive components may be added to each layer. In particular, for adhesion between the photosensitive layer and the silicone rubber layer, a known silicone primer, silane coupling agent, or titanate coupling agent layer may be provided between the layers, or a silicone primer, silane coupling agent, or titanate coupling agent layer may be provided between the silicone rubber layer or the photosensitive layer. It is effective to add a titanate coupling agent.

The support used in the present invention may be one that is flexible enough to be set in a normal lithographic printing machine and that can withstand the load applied during printing. Typical examples include metal plates such as aluminum, copper, zinc, and steel, plastic films or sheets such as polyethylene terephthalate, polystyrene, and polypropylene, chloroprene rubber, and NBR.
Examples include a support having rubber elasticity such as, a composite substrate of such a support having rubber elasticity and a plastic film or a metal plate, coated paper, and the like. It is also possible to coat these supports with other substances for antihalation and other purposes and dissolve them as a support.

In order to protect the silicone rubber layer forming the surface of the water or lithographic printing original plate constructed as described above, a thin protective film that is plain or textured can be laminated on the surface of the silicone rubber layer. .

〔Example〕

The present invention will be explained in more detail below with reference to Examples.

Example 1 A chemically treated aluminum plate (manufactured by Sumitomo Light Metals) was coated with phenol formaldehyde resol resin manufactured by Sumitomo Durez Co., Ltd. to a thickness of 1 micron, and cured at 200° C. for 3 minutes to obtain a substrate.

A photosensitive liquid having the composition shown below was applied thereon and dried at 100°C for 3 minutes to form a 1.5μ photosensitive layer.

(1) Ester of naphthoquinone-1,2-diazide-5-sulfonic acid (degree of esterification 40%) of phenol novolac resin (Sumitomo Durez: Sumilight Resin PR50622) 100 parts by weight (2) 4,4'- Diethylaminobenzophenone
5 parts by weight (3) Dioxane 525 parts by weight 0.2% by weight of γ-aminopropyltriethoxysilane (manufactured by UCC: A1100) on this photosensitive layer
After spin-coating the n-hexane solution of 110
℃ for 1 minute. Furthermore, a silicone rubber composition having the following composition was applied on top of this, and heated at 120℃ for 4 hours.
A 2.0μ silicone rubber layer was provided by heating and curing for a minute.

(1) Polydimethylpolysiloxane (molecular weight approx.
Less than 25,000 OH groups) 100 parts by weight (2) Ethyltriacetoxysilane 8 parts by weight (3) Dibutyltin diacetate 0.2 parts by weight (4) Hydrocarbon solvent "Isopar" E (manufactured by Exxon Chemical) 540 parts by weight Obtained A 10 micron thick polypropylene film ("Torefan" manufactured by Toray Industries, Inc.) was laminated on the silicone rubber layer to form a printing base plate.

A metal halide lamp (Idolfin 2000 manufactured by Iwasaki Electric Co., Ltd.) is passed through a negative film with a halftone image of 150 lines/inch that is vacuum-adhered to this printing original plate.
It was irradiated for 60 seconds from a distance of 1 m. When the plate surface is immersed in ethanol/"Isopar" E (20/80 weight ratio) and rubbed lightly with a developer pad, the exposed areas are removed along with the photosensitive layer, exposing the substrate. on the other hand,
The silicone rubber layer remained firmly in the unexposed areas, and an image that faithfully reproduced the negative film was obtained.

This printing plate was attached to an offset printing machine (Komori Sprint 2-color machine) and printed using Toyo Ink's "Aquares" ST monitor without using dampening water. Prints with extremely good images with 95% reproduction were obtained.

Comparative Examples 1 and 2 In Example 1, the photosensitive layer was made of phenol novolak resin (manufactured by Sumitomo Durez: Sumilite Resin).
PR50622) naphthoquinone-1,2-diazide
Ester of 5-sulfonic acid (degree of esterification 40%)
Printing original plates were produced in the same manner as in Example 1, except that the film thickness of the photosensitive layer was 1.5 μm (Comparative Example 1) and 3.0 μm (Comparative Example 2).

These printing original plates were exposed and developed in the same manner as in Example 1, and printed on an offset printing machine (Komori Sprint two-color machine).

In Comparative Example 1 in which the photosensitive layer had a thickness of 1.5 μm, the reproducibility of halftone dots was 3% to 90%, and the reproducibility of shadow areas was poor. On the other hand, in Comparative Example 2 in which the photosensitive layer had a film thickness of 3.0 μm, the reproduction was from 3% to 95%, but when the printed matter was looked closely, some of the halftone dots in the halite area were missing.

Example 2 The following primer composition was applied to an aluminum plate (manufactured by Sumitomo Light Metal Co., Ltd.) with a thickness of 0.3 mm, and heat treated at 200° C. for 2 minutes to form a 5.0 μm thick primer layer.

(1) Polyurethane resin (Samplen LQ-T1331,
Sanyo Chemical Industries, Ltd.) 100 parts by weight (2) Blocked isocyanate (Takenate B830,
(manufactured by Taseuchi Yakuhin Co., Ltd.) 20 parts by weight (3) Epoxy/phenol/urea resin (SJ9372,
(manufactured by Kansai Paint Co., Ltd.) 8 parts by weight (4) Dimethylformamide 725 parts by weight Subsequently, the following photosensitive composition was applied thereon using a bar coater, dried for 1 minute in hot air at 110°C, A photosensitive layer with a thickness of 1.5 μm was provided.

(1) Partial ester of naphthoquinone-1,2-diazide-5-sulfonic acid and phenol formaldehyde novolac resin (Sumilight Resin PR50622, manufactured by Sumitomo Durez) (degree of esterification 40%)
100 parts by weight (2) 4,4'-diphenylmethane diisocyanate
40 parts by weight (3) Dibutyltin diacetate 0.2 parts by weight (4) 4,4'-diethylaminobenzophenone
5 parts by weight (5) 800 parts by weight of tetrahydrofuran Next, a silicone rubber layer having the following composition was coated on the photosensitive layer using a bar coater, and heated at 115°C.
A silicone rubber layer with a thickness of 2.5 μm was provided by heating and curing for 3 minutes at a dew point of 30°C.

(1) Polydimethylsiloxane (molecular weight approximately 25,000,
(terminal OH group) 100 parts by weight (2) Vinyltri(methylethylketoxime)silane 8 parts by weight (3) Dibutyltin diacetate 0.1 part by weight (4) γ-Aminopropyltrimethoxysilane
0.5 parts by weight (5) 1400 parts by weight of “Isopar” E Add a layer of 10μ thick to the laminate obtained above.
A waterless lithographic printing original plate was obtained by laminating polypropylene film "Torefane" manufactured by Toray Industries, Inc. using a calendar roller.

A metal halide lamp (manufactured by Iwasaki Electric Co., Ltd., Idolfin 2000) was used on the printing original plate, and a UV meter (light measure type, manufactured by Oak Manufacturing Co., Ltd.) was used.
UV-402A) with an illuminance of 11 mW/cm ² for 6 full-surface exposures.
It was applied for seconds.

A negative film having a halftone dot image of 150 lines/inch was vacuum-adhered onto the printing original plate obtained as described above, and image exposure was carried out for 60 seconds from a distance of 1 m using the metal halide lamp described above. Next, the above "Trejuan" was peeled off and a pre-treatment liquid ("Isopar" H/butyl carbitol/ethyl cellosolve/monoethanolamine = 90/10/5/0.6
(weight ratio) to completely wet the exposed plate and process for 1 minute. Remove the pre-treatment liquid on the plate surface with a rubber squeegee, then apply developer solution (butyl carbitol/water/2-ethylbutyric acid/
When crystal violet (20/80/2/0.2 weight ratio) was poured and the plate surface was lightly rubbed with a developing pad, the imagewise exposed portions of the silicone rubber layer were removed and the surface of the photosensitive layer was exposed. On the other hand, the silicone rubber layer remained firmly in the exposed area, and an image that faithfully reproduced the negative film was obtained.

This printing plate was attached to an offset printing machine (Komori Sprint 2-color machine), and printed using Toyo Ink Co., Ltd.'s "Aquares" ST monitor without using dampening water, resulting in halftone dots of 3 with 150 lines/inch. Prints with very good images of between 95% and 95% were obtained. Even after printing 50,000 copies, no scumming or damage to the plate surface was observed, and printing could continue.

Comparative Examples 3 and 4 In Example 2, the photosensitive layer contains the light absorber 4,4'-
Contains no diethylaminobenzophenone;
Printing original plates were produced in the same manner as in Example 2, except that the photosensitive layer thickness was 1.5 μm (Comparative Example 3) and 30 μm (Comparative Example 4).

These printing original plates were exposed and developed in the same manner as in Example 2, and printed on an offset printing machine (Komori Sprint 2-color machine).

In Comparative Example 2 in which the photosensitive layer had a film thickness of 1.5 μm, the halftone dot reproducibility was 3% to 90%, and the reproducibility of shadow areas was poor. On the other hand, in Comparative Example 3 in which the photosensitive layer had a film thickness of 30μ, the reproduction was from 3% to 95%, but at the time of printing 20,000 copies, cracks appeared in the silicone rubber layer along with the cracks in the photosensitive layer. It caused stains.

〔Effect of the invention〕

According to the waterless lithographic printing plate of the present invention, the following effects are achieved.

(1) Good image reproducibility can be obtained even if the thickness of the photosensitive layer is made thinner than before.

(2) Since the thickness of the photosensitive layer can be made thinner, there will be no omission of minute halftone dots.

(3) Since the thickness of the photosensitive layer can be reduced, cracks and cracks in the photosensitive layer caused by impact during printing are reduced, and printing durability is improved.

Claims (1)

[Claims] 1. In a waterless lithographic printing plate formed by laminating a support, a photosensitive layer containing a quinonediazide compound, and a silicone rubber layer in this order, the photosensitive layer contains a group of salicylic acid ester-based, benzophenone-based, and benzotriazole-based light absorbers. A waterless lithographic printing plate characterized by containing at least one selected from the following.