JPH0356680B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a substrate for a lithographic printing plate having excellent printability and printing durability.

[Conventional technology]

Generally, metals such as aluminum and stainless steel sheets are used as substrates for lithographic printing plates.

However, base materials for lithographic printing plates made of a single metal are heavy, have poor workability, and are expensive.

Therefore, a printing plate structure was proposed in which an aluminum sheet (foil) was laminated on one side of a thermoplastic resin sheet (Japanese Patent Publication No. 41362/1983).

[Problems to be solved by the invention] However, the base material of the single-sided metal foil laminated sheet curls, and the printing plate using this sheet has poor printing durability and printing suitability, making it unsuitable as a printing base material. .

Therefore, in order to suppress the curling of this single-sided metal foil laminated sheet, a base material for lithographic printing plates was proposed using a sheet made of a mixture of polyolefin resin and inorganic filler as a thermoplastic resin sheet. .

However, such substrates for lithographic printing plates also have poor printing durability, especially in multi-printing (e.g. multicolor printing) where tens of thousands of sheets or more are printed, and their uses are limited. There is a problem that

The present inventors completed the present invention as a result of intensive research to provide a base material for a lithographic printing plate that combines a thermoplastic resin sheet and a metal foil and does not have the above-mentioned problems.

[Means for solving problems]

That is, the present invention provides a sheet having a thickness of 30 to 400 μm obtained by forming a modified polyolefin composite material consisting of 100 parts by weight of a modified polyolefin resin partially or wholly graft-modified with an organic silane compound and 5 to 150 parts by weight of mica. Thickness 5~ on both sides of the sheet
This invention relates to a base material for a lithographic printing plate, which is made of a laminated layer of 100μ metal foil.

In the present invention, a modified polyolefin composite material consisting of 100 parts by weight of a modified polyolefin resin partially or wholly graft-modified with an organic silane compound and 5 to 150 parts by weight of mica is used as a resin sheet to be laminated with metal foil. thickness 30
By using a sheet of ~400μ, curling of the lithographic printing plate substrate does not occur, and printing durability and printability can be improved.

The polyolefin resins used to obtain the modified polyolefin resins include crystalline homopolymers of propylene, propylene and ethylene, or other α-olefins (for example, butene-olefins).
1. Pentene, hexene, heptene, octene
Polypropylene resins such as crystalline random or block copolymers with 1) and crystalline terpolymers of propylene, ethylene, and other α-olefins, and ethylene homopolymers with a density of 0.93 g/cm ³ or more Examples include copolymers of ethylene and α-olefin, and polypropylene resins are preferred. The melt flow rate index (MFR) of the polyolefin resin is preferably 0.1 to 100 g/10 minutes.

The organic silane compounds include vinyltriethoxysilane, methacryloyloxytrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, methacryloyloxycyclohexyltrimethoxysilane, γ-methacryloyloxypropyltriacetyloxysilane, methacryloyloxytriethoxysilane, Examples include γ-methacryloyloxypropyltriethoxysilane. These organic silane compounds are 1
Only the seeds may be used or two or more types may be mixed.

The modified polyolefin resin used in the present invention is obtained by grafting at least a portion of the polyolefin resin and an organic silane compound, preferably in the presence of an organic peroxide.

The above-mentioned organic peroxide is preferably one having a half-life temperature of about 160 to 260°C, such as tert-butyl peroxyisopropyl carbonate, di-tert-butyl Diperoxyphthalate, tert-butylperoxyacetate, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-butylperoxy) Hexine-3, tert-butyl peroxylaurate,
Tertiary butyl peroxymale acid, tertiary butyl peroxybenzoate, methyl ethyl ketone peroxide, dicumyl peroxide,
Examples include cyclohexanone peroxide, tert-butylcumyl peroxide, 2,5-dimethylhexane 2,5-dihydroperoxide, and the like. These organic peroxides may be used alone or in combination of two or more.

The modified polyolefin resin preferably contains 0.01 to 5 parts by weight, especially 0.05 to 3 parts by weight of an organic silane compound and 0.01 to 5 parts by weight, especially 0.05 parts by weight of an organic peroxide, per 100 parts by weight of a polyolefin resin, especially a polypropylene resin. -2 parts by weight, and heating the resulting mixture to a temperature of 160 to 270°C, particularly 180 to 270°C, for grafting. The simplest heat treatment operation is to melt and heat the mixture in an extruder at the above temperature for about 1 to 10 minutes. Especially as a modified polyolefin resin, MFR
The polypropylene resin was graft-modified as described above so that the MFR was 5 to 200 g/10 minutes, and then cross-linked with water (including steam).
~80 g/10 min modified polypropylene is preferred.
The water crosslinking (including water vapor crosslinking) is performed at 25 to 120°C in an atmosphere containing water vapor (or in the air).
This is suitably achieved by contacting the modified polypropylene resin with water vapor for at least 24 hours, particularly for at least 24 hours. In the present invention, the modified polyolefin resin is used alone, or more preferably, a modified polyolefin resin and an unmodified polyolefin resin (preferably MFR of 0.1 to 10 g/10 min) are used as a mixture. When used as a mixture, it is preferable to mix the modified polyolefin resin in a proportion of 5 to 150 parts by weight based on 100 parts by weight of the unmodified polyolefin resin. The modified polyolefin resin obtained by grafting a part or all of it with an organic silane compound has an MFR of 0.3 to 0.3 in terms of sheet formability and physical properties.
Preferably it is 80 g/10 minutes, particularly 0.3 to 10 g/10 minutes.

In the present invention, mica is used as an inorganic filler. Examples of mica include muscovite, phlogopite, biotite, and synthetic mica containing fluorine. A portion of the mica may be replaced with another scaly filler. Mica has an average diameter (weighted average flake diameter) of 10 to 280μ, and an average aspect ratio (weighted average aspect ratio) of 15 to 70, especially
It is preferable that the amount of particles having a diameter of 600 μm or more is 2% by weight or less. Mica may be surface treated with a surface treatment agent known per se, such as aminosilane. The amount of mica to be blended is 5 to 150 parts by weight, preferably 10 to 150 parts by weight, particularly preferably 20 to 100 parts by weight, based on 100 parts by weight of the modified polyolefin resin, which is partially or entirely graft-modified with a silane compound. If the amount of mica blended is less than 5 parts by weight, the effect of improving the printing durability of the base material for lithographic printing plates will be small;
If the amount exceeds 150 parts by weight, printing durability will decrease.

The base material for a lithographic printing plate of the present invention may be, for example, the above-mentioned modified polyolefin resin, or a modified polyolefin composite material obtained by heating and mixing a modified polyolefin resin, an unmodified polyolefin resin, and mica (when the polyolefin resin and mica are mixed, the polyolefin resin may be graft-modified with a silane compound), with a thickness of 10 to 400μ,
Preferably on both sides of a sheet of 100-280μ thick, preferably 5-100μ, directly or via an adhesive.
Obtained by laminating 10-50μ metal foils. The laminated base material has a thickness of 100 to 500 μ and 1
0.6 kg or less per m ² is preferred.

As the metal foil, aluminum foil is preferably used on both sides. In particular, hard aluminum foil with an elongation rate of 3% or less is preferably used.

The adhesive described above may be of a solution type, an emulsion type, or a hot melt type, and includes, for example, epoxy resin, chlorinated polypropylene, polyurethane, modified polyolefin resin, ethylene-vinyl acetate copolymer, ionomer resin, epoxidized 1,2-
Examples include polybutadiene.

In the present invention, a photosensitive resin layer is provided on at least one side of metal foil laminated on both sides of a sheet (resin sheet) obtained by forming the composite material into a sheet, and the sheet is used as a lithographic printing plate (printing plate).

When laminating these metal foils, after laminating them, the surface is polished (sanded) and other treatments are applied, and a photosensitive resin is applied to create a lithographic printing plate (printing plate), or the surface of the metal foil is polished. (sand) sharpening,
In some cases, a lithographic printing plate is made by applying a photosensitive resin after being laminated after pretreatment such as anodizing or various hydrophilic treatments, or by pretreatment after (sand) graining. You can make a lithographic printing plate by applying a photosensitive resin and then laminating the plates, or you can do pre-treatment after sanding, apply a photosensitive resin, cut it to an appropriate size, and then laminate it after the plate-making process. Either method can be used to make a lithographic printing plate.

The method for laminating metal foil on both sides of a resin sheet is to first apply adhesive to one side of the metal foil or resin sheet, and then apply the three layers of metal foil/adhesive/resin sheet.
Examples include a two-stage roll method in which the metal foil is passed through a pressure roller so as to form a layer, and then another metal foil is similarly laminated on the resin sheet surface of the three-layer sheet, or a one-stage roll method in which each of the layers is laminated at once.

The lithographic printing plate base material of the present invention is less prone to curling and has substantially the same performance as a single metal base material, and is also lightweight and has excellent workability.

〔Example〕

In the following description, parts indicate parts by weight.

Example 1 0.5 part of γ-methacryloyloxypropyltrimethoxysilane and 0.25 part of t-butyl peroxybenzoate were added to 100 parts of crystalline polypropylene homopolymer of MFR 9.0 g/10 min, and then extruded at a resin temperature of 220°C. Modified polypropylene (MFR100) immediately after modification obtained by thermal decomposition in the machine
Modified polypropylene (MFR50
14 parts of pellets (2 mmφ x 3 mm) of
Crystalline polypropylene homopolymer (MFR0.5
56 parts of pellets (2 mmφ x 3 mm) (added to 0.1 phr of BHT, 0.1 phr of Irganox 1010, and 0.2 phr of calcium stearate) and mica [Suzolite mica manufactured by Kuraray Co., Ltd.] ,
Phlogopite 325HK, average diameter 20μ, average aspect ratio 20
~30 parts of 1% by weight or less of 1% by weight or larger than 25,100 μm were uniformly mixed at 200° C. using an FCM manufactured by Kobe Steel to obtain a composite material.

This material was molded at a molding temperature of 200°C by Mitsubishi Heavy Industries, Ltd.
It is made into a sheet using a manufactured sheet molding machine (NRM),
A sheet with a thickness of 240 μm and a width of 1 m was obtained. This sheet has a tensile strength of 3.96Kg/mm ² (MD) and 3.82Kg/mm ²
(TD), elongation was 10% (MD), 4% (TD), and tensile modulus was 310 Kg/mm ² (MD) and 291 Kg/mm ² (TD).

Using urethane adhesive on both sides of this sheet, 30μ thick aluminum foil (elongation rate 2.0%,
(hard 1N30H) is laminated by roll method (adhesive 5
g/ ^m2 ...front side, 10g/ ^m2 ...back side), thickness approximately 300μ
A double-sided aluminum foil laminated sheet of (approx. 0.45
kg/ ^m2 ). No curling was observed in this sheet.

This laminated sheet (cut to 560mm x 670mm, approx. 0.45mm
Kg/m ² ) was evaluated as a substrate for lithographic printing plates by the following method.

Evaluation method: After graining the front (mirror side) aluminum surface of the laminated sheet using an abrasive with an appropriate grain size (surface grain size: approx. 1.5μ) and making it hydrophilic, a commercially available photosensitive resin was applied. A lithographic printing plate was created.

This lithographic printing plate was subjected to a printing durability test using an offset printing machine under the following conditions.

1 Plate making () Exposure: Ultra-high pressure mercury lamp 2kw () Development: Sakura PS plate automatic developing machine 860A, developer Sakura SDP-1 2 Printing machine test method () Printing machine: 480K offset printing machine manufactured by Ryobi Co., Ltd. Ink: Process Four colors: red, yellow, blue, and black () Printing speed: 10,000 rpm Printing durability was evaluated based on changes in dot area and dot density in shadow areas and highlight areas of the printed matter, as well as changes in reflection density in gray scale areas.

From the start of printing to the printing of 50,000 sheets, no development such as thinning of halftone dots or deterioration of ink receptivity in printed areas was observed, and good printability was maintained.

In addition, during printing, the defect rate due to breakage at the gripping portion when the printing plate was attached to the printing roll was 0% (tested on 5 sheets).

Example 2 The same procedure was carried out except that the blending ratio of each component was changed to 14 parts of modified polypropylene (MFR50g/10min), 36 parts of crystalline polypropylene homopolymer (MFR0.5g/10min), and 50 parts of mica (325HK). A composite material was obtained in the same manner as in Example 1.

Using this composite material, approximately
A 0.5 Kg/m ² laminated sheet (substrate for lithographic printing plate) was obtained. This composite sheet has a tensile strength of 4.18
Kg/mm ² (MD), 3.94Kg/mm ² (TD), elongation 5%
(MD), 3% (TD), tensile modulus is 425Kg/mm ²
(MD) and 418Kg/mm ² (TD). No curling was observed in this laminated sheet. Then, a lithographic printing plate was obtained in the same manner.

When a printing durability test was conducted on this lithographic printing plate in the same manner as in Example 1, it was found that
Until 50,000 sheets were printed, no development such as thinning of halftone dots or decrease in ink adhesion in the image area was observed, and good printability was maintained.

The defect rate due to breakage at the gripping portion during printing was 0% (tested on 5 sheets).

Comparative Example 1 Using crystalline polypropylene homopolymer as a composite material, the thickness obtained by forming it into a sheet
A 30 μm thick aluminum foil was laminated on one side of a 270 μm sheet using a urethane adhesive as an adhesive by a roll method to obtain a single-sided aluminum foil laminated sheet with a thickness of about 300 μm.

This laminated sheet curled significantly and was unsuitable as a printing substrate, so the printing durability test was discontinued.

Comparative Example 2 Using crystalline polypropylene homopolymer as a composite material, the thickness obtained by forming it into a sheet
In the same manner as in Example 1, on both sides of a 240μ sheet,
Using urethane adhesive as adhesive, the thickness
Laminate 30μ aluminum foil using a roll method to obtain a double-sided aluminum foil laminated sheet with a thickness of approximately 300μ.
A lithographic printing plate was then obtained.

When a printing durability test was conducted on this lithographic printing plate, local thinning of halftone dots was observed from the beginning of printing, and there was a problem in printing durability.

Examples 3, 4, 5 As the mica, 325S (manufactured by Kuraray Co., Ltd., average diameter 40μ, average aspect ratio 30, 210μ or more is 1% by weight or less) in place of 325HK (Susolite mica)
(Example 3), 325K-1 [Aminosilane surface treatment grade of 325S manufactured by Kuraray Co., Ltd.] (Example 4), or
The same procedure as in Example 1 was carried out except that 350K-1 (manufactured by Kuraray Co., Ltd., 325HK, aminosilane surface treated grade) (Example 5) was used. Good results equivalent to those of Example 1 were obtained in all cases.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to obtain a base material for a lithographic printing plate that is lightweight, easy to handle, and provides a lithographic printing plate having excellent printability and printing durability.

Claims (1)

[Claims] 1 A sheet having a thickness of 30 to 100% obtained by sheeting a modified polyolefin composite material consisting of 100 parts by weight of a modified polyolefin resin partially or wholly graft-modified with an organic silane compound and 5 to 150 parts by weight of mica.
Thickness 5-100μ on both sides of 400μ sheet, elongation rate 3
% or less of aluminum foil is laminated.