JPH041900B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a lithographic printing plate that does not require dampening water, and relates to a lithographic printing plate that does not require dampening water and has a particularly selected photosensitive layer and a silicone rubber layer coated on a support. In planographic printing using the conventional offset method, the composition of the dampening water, the supply amount, etc., and the balance of the ink have a large effect on the printing results, so very advanced techniques are required for supplying the dampening water. For this reason, the offset printing industry has long awaited the emergence of a lithographic printing plate that does not require dampening water. In recent years, many proposals have been made regarding lithographic printing plates that do not require dampening water to meet this requirement. For example, JP-A-55-59466 and JP-A-55-110249 disclose a lithographic printing plate that does not require dampening water and uses a novolak resin naphthoquinone-1,2-diazide-5-sulfonic acid ester as a photosensitive layer. Disclosed. This printing plate is made by rubbing the surface with a brush, cloth, etc. impregnated with a solvent that penetrates the silicone rubber layer and dissolves the portion that has changed into a carboxylic acid compound in the exposed area, dissolving the photosensitive layer in the exposed area and Developing is done by peeling off the silicone device. However, the developing speed is not sufficient and varies, and the developing speed is particularly low when stored in a dry atmosphere. As a result of intensive studies by the present inventors to solve the above-mentioned problems, the photosensitive layer has a number average molecular weight (n) of 650 or less and a dispersity [weight average molecular weight (
When a novolak type phenolic resin orthonaphthoquinone-1,2-diazide-5-sulfonic acid ester or 4-sulfonic acid ester with a ratio of w) and n (w/n) of 3 or less is used, the development speed is high. Furthermore, the present inventors have discovered that there is no variation in the development speed, and that the development speed hardly changes even when stored in a dry atmosphere, leading to the present invention. This invention relates to a lithographic printing plate that does not require dampening water and has a photosensitive layer and a silicone rubber layer coated in this order. The reason for the lack of variation has not yet been elucidated, but it is thought to be explained as follows: That is, the development speed of the printing plate with the photosensitive layer made of orthonaphthoquinonediazide sulfonic acid ester of the conventional novolac resin is not sufficient, and The reason why the speed fluctuates is that the ketene compound generated by exposure not only reacts with moisture present in the photosensitive layer to generate a carboxylic acid compound, but also reacts with the residual hydroxyl group derived from the novolac resin to form an ester bond. This is thought to be because cross-linking occurs in some areas and the ratio of carboxylic acid compounds to ester bonds varies depending on the moisture content present in the photosensitive layer at the time of exposure.Of course, when stored in a dry atmosphere, , it goes without saying that the formation ratio of ester bonds increases and the development speed becomes slower.Naphthoquinone-1,2-diazide-5-, a novolak type phenolic resin with n of 650 or less and a dispersity of 3 or less, used in the present invention. When a sulfonic acid ester or 4-sulfonic acid ester is used as a photosensitive layer, even if a cross-linked structure is formed by ester bonds, the molecular weight and degree of dispersion are small, so the molecular weight does not become large and is resistant to alcohol, etc. of the developing solvent. This is presumed to be because the solubility does not decrease so much.The structure of the present invention will be described in detail below.The photosensitive layer is composed of n, which is obtained by condensing phenol or cresol with formaldehyde.
Orthonaphthoquinone-1,2-diazide-5-sulfonic acid ester or -4- of novolac type phenolic resin having a dispersity of 650 or less and a dispersity of 3 or less
Sulfonic acid esters are used. Photosensitive resins synthesized from novolac type phenolic resins where n is greater than 650 and dispersion degree is greater than 3 are not suitable for the structure of the present invention because when a crosslinking reaction occurs, the solubility in a developing solvent such as ethanol is extremely reduced. is not suitable. Such a novolac type phenolic resin with n of 650 or less and dispersity of 3 or less can be obtained by appropriately controlling the type and amount of catalyst, the charging ratio of phenol or cresol to formaldehyde, reaction temperature and time, etc. be able to. Alternatively, it can also be obtained by fractionation. Moreover, those having an esterification rate (quantified from IR spectrum) of 35 to 100% are used. When the esterification rate is less than 35%, a difference in solubility in a developing solvent between exposed and unexposed areas is unlikely to appear. The thickness of the photosensitive layer is preferably 0.5 to 5μ. If it is too thin, it will cause pinholes, and if it is too thick, cracks will easily occur, and it will also be disadvantageous from an economic standpoint. Necessary additives such as pigments, dyes, resins, plasticizers, etc. can be added to the photosensitive layer as long as their performance is not impaired. The thickness of the silicone rubber layer used as the ink repellent layer used in the present invention is 0.5 to 100 microns, preferably 1 to 50 microns. A useful silicone rubber is a silicone rubber whose main component is a linear organic polysiloxane having the following repeating units and a molecular weight of several thousand to several hundred thousand. (R is an alkyl group or phenyl group having 1 to 10 carbon atoms, and 60% or more of R is preferably a methyl group.) This linear organic polysiloxane is usually one having a terminal hydroxyl group, and an acetoxy In the presence of a cross-linking agent such as silane, ketoxime silane, or alkoxysilane, and in the coexistence of a catalyst such as an organotin compound,
It is cross-linked by heat treatment and used as a silicone rubber layer. If necessary, a known silicone primer or silicone coupling agent layer may be provided between the layers for adhesion between the silicone rubber layer and the photosensitive layer or between the photosensitive layer and the support. It is also effective to add a silicone primer or a silane coupling agent. As the support, paper, plastic film or sheet, natural or artificial rubber sheet, metal plate, etc. are used. These supports can be further provided with a coating layer or a laminating layer for prevention of halation and other purposes and used as a support. The silicone rubber layer forming the surface of the dampening water-free lithographic printing plate constructed as described above can also be laminated with a protective film to prevent scratches and dust from forming. Useful protective films include polyethylene, polypropylene, polyvinyl chloride, polyvinyl alcohol, polyethylene terephthalate, and the like. The lithographic printing plate that does not require dampening water according to the present invention is produced, for example, as follows. First, a photosensitive material solution is applied onto the support using a normal coater such as a reverse roll coater, air knife coater, Meyer bar coater, etc., or a rotary coating device such as a Whaler, and after drying, a similar solution is applied on the photosensitive layer. Apply an adhesive layer as necessary using a standard method, dry it, and then apply a silicone rubber solution in the same way, usually at 100-120℃.
The silicone rubber layer is formed by heat treatment for several minutes at a temperature of . Furthermore, if necessary, a protective film is laminated on this silicone rubber layer using a laminator or the like. The thus-manufactured lithographic printing plate of the present invention, which does not require dampening water, is exposed to ultraviolet light by vacuum-adhering a negative film having a predetermined pattern, for example. As a light source that generates ultraviolet rays, a mercury lamp, a carbon arc lamp, a xenon lamp, a metal halide lamp, a fluorescent lamp, etc. can be used. Next, when the surface is rubbed with a developing pad such as a cloth or brush impregnated with a developing solution, the photosensitive layer in the exposed area is dissolved and the upper silicone rubber layer is easily peeled off to expose the support. As a developer, it penetrates the silicone rubber layer,
A material that dissolves only the exposed photosensitive layer is used. Such developers include methanol,
Alcohols such as ethanol are preferred, but in order to more easily penetrate into the photosensitive layer, aliphatic hydrocarbons such as hexane and heptane, which can swell the silicone layer, aromatic hydrocarbons such as toluene and xylene, etc. It is also preferable to use a mixture of these. EXAMPLES The present invention will be explained in more detail by way of Examples below, but the embodiments of the present invention are not limited thereto. Example 1 n= on chemical conversion treated aluminum plate (manufactured by Sumitomo Light Metals)
434, 7% by weight of naphthoquinone-1,2-diazide-5-sulfonic acid ester (esterification rate 74%) of phenolic novolac resin with w/n = 2.1
3.5 at 100℃ after spin-coating dioxane solution with wheller
It was dried for a minute to form a 2.4μ photosensitive layer. On top of this, 0.5% by weight of γ-aminopropyltriethoxysilane (manufactured by UCC, A-1100)
After spin-coating the solution (manufactured by Etsuso) with wheal, 120℃,
Dry for 30 seconds. A 7% Isopar solution of a silicone composition having the following composition was spin-coated on top of this with a wheal, and then heated at 120°C for 3.5 minutes. (a) Polydimethylsiloxane (molecular weight approximately 80,000, terminal OH group) 100 Part (b) Ethyltriacetoxysilane 5 parts (c) Dibutyltin acetate 0.2 parts The thickness of the obtained silicone rubber layer was 2.3μ.The printing original plate obtained as above was heated at 23°C x 60°C.
After storing for 7 days in a desiccator on %RH and silica gel, a metal halide lamp (manufactured by Iwasaki Electric) was passed through a negative film with a line width of 100 μ to 15 mm in vacuum contact.
2000) and exposed for 60 seconds from a distance of 1 m. Next, the plate surface was immersed in the ethanol developer for 1 minute, and then rubbed with a pad (manufactured by Kawashima Textile Co., Ltd., Long Run Carpet) under a load of 10 g/cm ² , the exposed area was removed and the chemically treated aluminum surface was exposed. An image faithful to the negative film was obtained.At this time, the number of times of rubbing until the support surface was exposed was determined as the development speed.The results are listed in Table 1 along with the following three comparative examples.Comparative Example 1 The photosensitive layer of Example 1 was n=818, w/n=
After storage under the same conditions, exposure and development was carried out by replacing the phenol novolac resin in No. 5.6 with naphthoquinone-1,2-diazide-5-sulfonic acid ester (esterification rate: 58%). Comparative Example 2 The photosensitive layer of Example 1 was n=608, w/n=
After storage under the same conditions, the sample was exposed and developed in place of naphthoquinone-1,2-diazide-5-sulfonic acid ester (esterification rate: 64%) of the phenol novolak resin in No. 3.8. Comparative Example 3 The photosensitive layer of Example 1 was n=713, w/n=
After storing under the same conditions in place of naphthoquinone-1,2-diazide-5-sulfonic acid ester (esterification rate 63%) of the phenol novolac resin in 2.5,
Exposure and development.

[Table] From the data in Table 1, it can be seen that the developing speed in Example 1 is very fast, whereas it is slow in Comparative Examples 1, 2, and 3. In particular, when stored in a silica gel desiccator, the difference becomes even more pronounced.
In Example 1, the developing speed was almost unchanged, whereas in Comparative Examples 1, 2, and 3, it was approximately twice as slow. Example 2 A 0.25 mm thick Shore A rubber with a hardness of 70 was placed on a 0.25 mm thick polyethylene terephthalate film.
On a support provided with a nitrile rubber layer of n=
A printing original plate having a naphthoquinone 1,2-diazido-5-sulfonic acid ester (esterification rate 61%) of a phenol novolac resin having 620, w/n = 2.6 as a photosensitive layer was obtained in the same manner as in Example 1, evaluated. Development speed: 8 times at 23℃ x 60%RH x 7 days storage.
It was stored 9 times at 23°C in a silica gel desiccator for 7 days. Example 3 The photosensitive layer of Example 1 was prepared with n=403, w/n=
1.7 of the phenol novolak resin was produced and evaluated by replacing it with naphthoquinone 1,2-diazide-5-sulfonic acid ester (esterification rate: 66%). Development speed: 4 times at 23℃ x 60%RH x 7 days storage.
It was stored 6 times at 23°C in a silica gel desiccator for 7 days.

Claims (1)

[Scope of Claims] 1. In a lithographic printing plate that does not require dampening water and is prepared by coating a photosensitive layer made of an orthonaphthoquinonediazide compound and a silicone rubber layer in this order on a support, the number average molecular weight (n ) is 650 or less and the dispersity [ratio of weight average molecular weight (w) to n (w/n)] is 3 or less. Water-free lithographic printing plate.