JPS6322305B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lithographic printing plate that does not require the use of dampening water in printing operations, and a method for manufacturing the same.

In particular, the present invention relates to a novel lithographic printing plate that does not require dampening water and has an ink-repellent layer made of a linear silicone compound having substantially no crosslinked structure.

As is well known, traditional lithographic printing is
Unlike intaglio or letterpress printing, which selectively receives ink based on the unevenness of the surface of the printing plate used, printing is performed using an almost flat plate, so it is more effective than other printing methods. It is an excellent printing method in many respects, such as not only making it possible to express finer details, but also allowing plate making to be done in a short time, and the price of the plate material being low.

However, it is common knowledge in planographic printing that the biggest problem in planographic printing is caused by the dampening water that is essential during printing. For this reason, attempts have been made for a long time to perform offset printing using a lithographic plate without using dampening water, but all of these have been accompanied by various difficulties and have never been used in actual production.

Recently announced, Special Publication No. 44-23042, Special Publication No. 46
16044 and Japanese Patent Publication No. 47-2361, which do not use water and use silicone rubber as an ink-repellent material, are considered to be more substantial.

The planographic plate that does not use dampening water disclosed in the above-mentioned patent consists of an ink-repellent silicone rubber layer constituting a non-printing area and an ink-philic printing area, and has various effects during printing. It must be firmly attached to the plate so that it can withstand the force of However, this is very difficult to implement because the properties of silicone rubber that prevent ink from adhering to the surface also prevent adhesion to the image material. For this reason, various attempts have been made, but
It is hard to say that it is sufficient in terms of performance or workability. For example, Japanese Patent Publication No. 44-23042 attempts to improve adhesive strength by inserting a metal foil layer between the photosensitive layer constituting the image area and the silicone rubber layer constituting the non-image area. In the case of such a product, it takes a long time to produce the original plate, and it is difficult to produce it at a price that can be put to practical use. Further, the development after exposure and the subsequent etching of the metal foil during use unnecessarily complicate the operation.

The adhesion between the above-mentioned silicone rubber layer, which is the non-image area, and the image area to the plate is one of the important factors that affects the printing durability of the plate, but the thickness of the silicone rubber layer also affects the durability. This is an important factor related to printing force.

In such a system in which the silicone rubber layer is located above the photosensitive layer, there is a general tendency that the printing durability increases as the thickness of the silicone rubber layer increases. However, as the silicone rubber layer becomes thicker, the reproducibility of the plate with negative or positive film decreases, and since silicone rubber has a crosslinked structure, it is insoluble in solvents like general crosslinked polymers. Therefore, it is difficult to completely remove these silicone rubbers from the image area during development.

Furthermore, uncrosslinked silicone rubber stock solutions of the room temperature curing type which are generally well known for coating silicone rubber are difficult to handle because they are immediately crosslinked and insolubilized by moisture in the air. On the other hand, heat-curing silicone rubber is easy to handle, but it takes a long time to heat-cure after applying the silicone rubber stock solution, and the photosensitive layer may change due to heating, resulting in quality and process problems. There is a problem.

The ink repellency of silicone compounds is most excellent in silicone compounds with a linear non-crosslinked structure (hereinafter referred to as "silicone compounds") typified by silicone oil, followed by silicone rubber and then silicone resin. It is rather difficult to use silicone resin as an ink repellent component.
However, silicone compounds do not have shape retention properties when used alone, so they have not been able to be used until now despite their excellent ink repellency.

For example, the specification of JP-A-47-32906 discloses a dry lithography method using silicone oil (linear silicone compound), but in the example of the applied patent, the silicone oil is manufactured by Shin-Etsu Chemical Co., Ltd.
We use KF96H (dimethylpolysiloxane with methyl at both ends), a non-adhesive substance (ink repellent substance) mixed with silicone alkyd varnish, and ultrafine powder silica.

As shown in this known example, until now, the only way to impart shape retention to silicone oil and form a layer that is fixed on the printing plate is to mix silicone oil with other substances, and the ink repellency of silicone oil It has been thought that there is no choice but to sacrifice the

We made use of the excellent ink repellency of silicone compounds to provide shape retention, and as a result of intensive studies aimed at solving various problems with systems using silicone rubber, we found that a planographic printing plate using silicone rubber They have discovered a lithographic plate that uses a silicone compound as an ink-repellent material and does not use dampening water, and a method for producing the same, which solves almost all of the drawbacks.

That is, the present invention provides: (1) a flexible substrate, and a flexible substrate coated on at least a portion of the substrate surface, which has a peel adhesive strength of 50 g/10 mm or less when dry and is represented by the following general formula (A). (2) a flexible lithographic printing plate which does not require dampening water, comprising a linear silicone compound layer having substantially no crosslinked structure, the silicone compound layer repelling ink; The following general formula (A) coats a photosensitive layer on a photosensitive substrate and does not substantially provide a crosslinked structure on the photosensitive layer.
A linear silicone compound shown by is coated after exposure, and then a selected portion of the photosensitive layer and the overlapping silicone compound layer are removed together, and the remaining silicone compound layer is used as a non-image area. The present invention relates to a method for producing a lithographic printing plate that does not require dampening water.

(Here, n is an integer of 0 or more, R is a monovalent alkyl group having 1 to 7 carbon atoms, an aryl group, an aralkyl group, a halogenated alkyl group, or a cyanoalkyl group, and R may be the same or different. You can leave it there.

X represents a hydroxyl group, an alkoxy group, an acetoxy group, or a halogen. ) The content of the present invention will be explained in detail with reference to the drawings.

FIGS. 1 and 2 show the respective cross-sectional structures of a positive planographic printing plate precursor using a photoinsolubilizable photosensitive layer and a printing plate obtained using the same.

A photosensitive layer 2 and a silicone compound layer 3 are present on the surface of the flexible substrate 1 . In FIG. 2, 2a indicates the exposed portion of the photosensitive layer.

In the lithographic printing plate precursor, a photosensitive layer 2, preferably in the form of a solution, is applied onto the surface of a flexible substrate 1 and dried. Coating methods include commonly used methods such as a bar coater, a method using a doctor blade, a roll coater, a curtain flow coater,
A method using a gravure coater or the like can be adopted.

The thickness of the photosensitive layer is arbitrary, but around 10 μm is sufficient. However, defects such as uneven coating and pinholes are undesirable because they degrade the quality of printed matter.

A silicone compound layer functioning as an ink-repellent layer is formed on the photosensitive layer by the same coating method, and this silicone compound may be applied before or after exposure.

It is sufficient that the thickness of the silicone compound layer is several microns or less.

Here, as the silicone compound, if a compound having a hydroxyl group, an acetoxy group, an alkoxy group, or a halogen at at least one terminal is used, the adhesive force between the photosensitive layer and the photosensitive layer is improved, and for example, it can be used in the development process or printing process after exposure. , the silicone compound becomes difficult to peel off.

Flexible substrates used in the present invention include many flexible thin plates commonly used in lithography, such as metal plates such as aluminum plates, zinc plates, and copper plates, and plastic films such as polyester, polypropylene, and polyamide. , metal-deposited organic films, natural paper, synthetic paper, etc. can be used depending on the purpose. Moreover, it is also possible to use a material that has been surface-treated.

To form an image or non-image part of the plate,
A photosensitive layer using a known photosensitive substance is used.
The components of such a photosensitive layer have a boiling point of 100°C.
The above describes unsaturated monomers or oligomers thereof that are nonvolatile at room temperature, such as ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, glycidyl ( A series of acrylic esters and methacrylic esters such as meth)acrylate, 1-chloro-2-hydroxyethyl (meth)acrylate, and dimethylaminoethyl (meth)acrylate. Acrylamide derivatives such as methylenebisacrylamide, N-methylolacrylamide, methoxymethylacrylamide. Allyl alcohol esters such as triallyl cyanurate, triallylphosphate, and diallyl phthalate, and oligomers thereof, as well as styrene derivatives, cinnamic acid derivatives, and the like can also be used.

Photo-insolubilizable diazo resins or azide resins can also be used. Examples of these photo-insolubilized diazo resins include condensates of formaldehyde and diazo amines such as paradiazodiphenylamine, paradiazomonoethylaniline, and paradiazobenzylethylaniline.

Examples of the photo-insolubilizable azide resin include azidophthalate ester of polyvinyl alcohol, azidobenzoate ester, ester of styrene-maleic anhydride copolymer and aromatic azido alcohol, such as β-(4-azidophenoxy)ethanol, etc. can be given.

The photo-solubilized photosensitive material is a layer in which the surface of an aluminum substrate is treated with a heteromultiple acid or isomultiple acid such as phosphotungstic acid, phosphomolybdic acid, vanadium tungstic acid, etc., and then the above-mentioned diazo resin photosensitive solution is applied. is also possible.

In addition, the special public interest rates are 37-18015, 37-3627, 37-1954.
Orthoquinone diazides such as those shown in No. 45-9610 can also be used.

If necessary, a photosensitizer,
A thermal polymerization inhibitor, a filler to provide shape retention at room temperature, and some additives can be added.

As such photosensitizers, benzophenone derivatives, benzoin derivatives, anthraquinone derivatives, aldehydes, ketones, sulfur compounds, halogen compounds, or dyes such as methylene blue and riboflavin can be used.

As thermal polymerization inhibitors, hydroquinone derivatives,
Phenol derivatives, nitro-substituted benzenes, tertiary amines, and phenothiazine derivatives are used.

Such fillers or additives include colloidal silica, calcium carbonate, magnesium carbonate, fine powder of inorganic substances such as iron oxide, polyvinyl acetate, poly(meth)acrylate,
Vinyl polymers such as polyethylene, polypropylene, polyvinyl chloride, and polyvinylidene chloride with a molecular weight of several thousand, resol phenol systems before curing,
Examples include urea-based, melamine-based, epoxy-based, and unsaturated polyester-based resins.

In order to obtain the lithographic printing plate of the present invention, for example, (1) a positive film is placed on the lithographic printing plate precursor and exposed to light by a conventional method. By this operation, the exposed areas are cured and the unexposed areas remain uncured.

(2) Next, the silicone compound layer is simultaneously removed by washing out the unexposed areas of the photosensitive layer with a solvent such as water through the silicone compound layer, thereby obtaining a lithographic printing plate having the cross-sectional structure shown in FIG. .

Although the mechanism by which the linear silicone compound is fixed to the non-image area of the printing plate by the method described above is not clear, the hydroxyl group, alkoxy group, halogen, It is thought that a reactive group such as an acetoxy group is fixed by reacting or ionically bonding with the material constituting the printing plate on the surface.

As the silicone compound constituting the ink-repellent layer of the lithographic printing plate of the present invention, a polysiloxane represented by the above formula (A) is used. The silicone compound can be used in the form of a low viscosity liquid, a grease or a sticky substance. Preferably the viscosity measured at 25°C is approximately 80
Those having a molecular weight equivalent to centipoise or more are preferable.

In addition, n in the above formula (A) is an integer of 0 or more,
R may be the same or different. R like this
It may be a monovalent alkyl group having 1 to 7 carbon atoms, an aryl group, an aralkyl group, a halogenated alkyl group, or a cyanoalkyl group,
It must not be an active group that gives a crosslinked structure under the conditions of original plate production or plate making, such as a vinyl group or a group having condensation activity. The most preferred of such silicone compounds is that the majority of R
is a polysiloxane in which is a methyl group.

In the above general formula (A), the terminal group X of the silicone compound is a hydroxyl group, an alkoxy group, an acetoxy group,
and halogen.

Depending on the purpose, fillers such as dyes and pigments and silica, and condensation catalysts may be added to these silicone compounds. Moreover, the above-mentioned silicone compounds can be used not only alone but also in combination of two or more.

When the silicone compound described above is applied to the printing plate of the present invention, the silicone compound forms the non-image area of the plate surface and must exhibit excellent ink repellency.

The ink repellency of this silicone compound varies greatly depending on the type of ink used in printing. For example, when using an ink that is highly transferable from one ink roller to another, that is, a so-called soft ink, the ink tends to adhere to the surface of the silicone compound, resulting in scumming.

Although the physical property value representing the transferability specific to this ink is not yet clear, the tack value is generally used.

An ink with a low tack value has excellent transferability, and in this case, a silicone compound with high non-adhesion (ink repellency) must be used. On the other hand, inks with high tack values have poor transferability, so
Silicone compounds with relatively low adhesion can be used.

The ink repellency of the surface of the silicone compound used as the non-image area is correlated with the peel adhesion strength when cellophane adhesive tape is pressed onto the non-image area of the plate, rather than the critical surface tension of the plate. It was found that this is a preferable evaluation method.

When using a commercially available offset ink, the silicone compound surface that forms the non-image area of the printing plate in the present invention has a peel adhesion strength of 50 g/10
mm or less, preferably 40 g/10 mm or less, particularly preferably 20 g/10 mm or less. It goes without saying that silicone compounds outside the above range can also be used depending on the transferability of the ink used for printing.

Japanese Industrial Standards (JIS Z 1522) describes a method for testing the normal adhesive strength between cellophane adhesive tape and stainless steel plate.

JIS standard cellophane adhesive tape has a normal adhesive strength of 150g/10mm or more using this test method.

The peel adhesion strength of the cellophane adhesive tape to the silicone compound surface can be measured by a measuring method similar to the test method of JIS Z 1522.

Create a plate with only the non-printing area, and then
A test piece was cut out from a plate 10 mm long and 250 mm long.

Align one end with the test piece in the center of this test piece and
“Nichiban Cellotape” (JIS
Standard product) was crimped with a rubber roller weighing 2 kg, and 20
After more than a minute has passed, fold the free part of the tape back to 180° and peel it off about 25mm from the edge of the test piece, then place the tape in the upper grip of the tensile tester and the test piece in the lower grip for 300±20mm. The average load of 10 pieces was determined when they were continuously peeled off at a speed of /min. Peel adhesion strength is expressed as an average load.

The lithographic printing plate blank constructed as described above is baked and developed by the following method.
A dry lithographic printing plate can be obtained. That is,
A negative or positive film is vacuum-adhered to a printing plate original plate using an ordinary lithographic vacuum printing frame, and ultraviolet light from a mercury lamp, a chemical lamp, etc. is irradiated through the film to perform printing.

Next, by completely removing the silicone compound and the photosensitive layer in the portions of the printing plate corresponding to the image areas in a developing step, a lithographic printing plate that functions in a dry manner can be obtained. In the present invention, since a substantially linear silicone compound is used instead of silicone rubber, the development process is further simplified.

That is, when developing with a developer that does not dissolve the silicone compound but can dissolve the photosensitive layer,
The silicone compound used in the present invention has excellent permeability to the developer, and the photosensitive layer in the image area can be easily eluted by simply immersing the printing plate in the developer. can also be removed. Of course, the outline of the image area (the area where the silicone has been removed) becomes clearer than that of silicone rubber.

The dry lithographic printing plate thus obtained can be directly mounted on a conventional offset printing machine and printed without using dampening water.

The feature of the lithographic printing plate that does not use dampening water obtained by the present invention is that the thickness of the ink-repellent layer can be made significantly thinner than when silicone rubber is used. The point is that you can get printed matter. This is also related to the fact that, since the silicone compound does not have a crosslinked structure, there is no need to physically tear off the silicone compound from the image area and remove it, unlike when silicone rubber is used. This can be easily confirmed by comparing the image area of a lithographic plate using silicone rubber with the image area of a lithographic plate obtained by the method of the present invention using a silicone compound having substantially no cross-linked structure using a microscope. This is understandable.

The second feature is that the thickness of the silicone compound layer that acts as a non-image area is thin and strongly embedded in the surface of the photosensitive layer, so it does not suffer from scratches like when silicone rubber is used. The reason is that it is difficult to attach. This property can be said to be an excellent feature that not only facilitates plate-making work and handling of the plate after plate-making, but also significantly improves printing durability.

Next, typical examples for explaining the present invention are shown below.

Example 1 A photosensitive layer made of a condensate of paradiazodiphenylamine and formaldehyde was provided on a grained aluminum plate, and exposed to light from an ultra-high pressure mercury lamp (Oak Manufacturing Co., Ltd. Jet Light 3KW) through a positive film for 1 minute.

On the exposed printing plate (1000 cm ² ), dimethylpolysiloxane (1% by weight) and dibutyltin diacetate (0.01% by weight) having a methoxy group at both ends and having a viscosity of 1 million centipoise (25°C) were applied as silicone compounds.
% by weight) in n-heptane was applied and dried at 40°C for 1 hour.

Next, when the printing plate was immersed in water, the photosensitive layer in the unexposed areas was eluted, and at the same time, the silicone compound layer was also peeled off, exposing the bare surface of the aluminum plate. On the other hand, a lithographic printing plate was obtained in which the photosensitive layer and silicone layer remained in the exposed portion of the plate surface.

Using this printing plate, offset printing was performed using "DryOcolor" ink manufactured by Dainippon Ink and Chemicals Co., Ltd. as the printing ink, and more than 1000 good prints were obtained.

Example 2 A photosensitive layer with a thickness of about 10 μm having the following composition was formed on a grained aluminum plate.

Condensation product of naphthoquinonediazide sulfone chloride and phenol novolac resin A n-heptane solution (0.5 wt. %) and dried to obtain a lithographic printing plate blank.

Negative film is vacuum-adhered onto the printing plate master plate,
Chemical lamp passed through negative film (Mitsubishi Electric)
FL-205-BL-360) light was irradiated for 3 minutes.

Isopar E (manufactured by Etsuo Chemical)/Ethanol =
When the plate surface was immersed in a developer with a 50/50 composition and rubbed lightly, the photosensitive layer in the exposed areas eluted and at the same time the silicone layer also peeled off, exposing the bare surface of the aluminum plate. On the other hand, a lithographic printing plate was obtained in which the photosensitive layer and silicone layer remained in the unexposed portions of the plate surface.

Using this printing plate, printing was carried out using an offset printing machine using "Dryocolor" ink manufactured by Dainippon Ink and Chemicals Co., Ltd. as the printing ink, and more than 1000 good prints were obtained.

Comparative Example 1 A lithographic printing plate was prepared in the same manner as in Example 2, except that dimethylpolysiloxane (100 centipoise, 25° C.) having methyl groups at both ends was used as the silicone compound.

When offset printing was carried out in the same manner as in Example 2 using this printing plate, the non-image areas became smeared after about 10 sheets of printing, and no good printed matter could be obtained.

[Brief explanation of the drawing]

FIGS. 1 and 2 show enlarged cross-sectional views of a printing plate blank and a printing plate of the present invention, respectively.

Claims (1)

[Scope of Claims] 1. A flexible substrate, and a substance having a peel adhesive strength of 50 g/10 mm or less when dried, which is coated on at least a portion of the substrate surface and is represented by the following general formula (A). 1. A lithographic printing plate which does not require dampening water, comprising a linear silicone compound layer having no crosslinked structure, the silicone compound layer repelling ink. (where n is an integer of 0 or more, R is a monovalent alkyl group having 1 to 7 carbon atoms, an aryl group, an aralkyl group,
It is a halogenated alkyl group or a cyanoalkyl group, and R may be the same or different. X represents a hydroxyl group, an alkoxy group, an acetoxy group, or a halogen. ) 2 A photosensitive layer is coated on a flexible substrate, a linear silicone compound represented by the following general formula (A) that does not substantially provide a crosslinked structure is coated on the photosensitive layer after exposure, and then 2. The method for producing a lithographic printing plate according to claim 1, wherein a selected portion of the photosensitive layer and the silicone compound layer overlying the photosensitive layer are removed together, and the remaining silicone compound layer is used as a non-image area. (Here, n is a base number of 0 or more, R is a monovalent alkyl group having 1 to 7 carbon atoms, an aryl group, an aralkyl group,
It is a halogenated alkyl group or a cyanoalkyl group, and R may be the same or different. X represents a hydroxyl group, an alkoxy group, an acetoxy group, or a halogen. )