JPH02182493A - Support for lithographic printing plates - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a support for a lithographic printing plate, and particularly to a support for a lithographic printing plate having a printed image forming layer on a support in which both sides of a base paper are coated with a resin. It is related to.

[Prior Art] A lithographic printing plate generally has a structure in which a printed image forming layer is provided on a support such as a metal plate such as aluminum or zinc, a plastic film such as polyethylene terephthalate or polyvinyl chloride, or paper.

Among these supports, metal plates and plastic films have been used as supports for lithographic printing plates because they have excellent mechanical strength, etc., good dimensional stability, and long printing durability. However, these plates are expensive and have the drawback of poor bendability, especially when it comes to plastic films.

On the other hand, paper is inferior to the above-mentioned supports in terms of mechanical strength, dimensional stability, etc., but because it is inexpensive, it is used as a support for lithographic printing plates that can last for a small number of sheets.

In addition to being used as a paper base in printing and plate-making, there are many other materials that are used as blueprint materials and plate preparation materials.

Paper-based printing plates are mainly used as lithographic (offset) printing plates, which take advantage of the characteristics that paper is cheap, light, and has a certain amount of strength.

In recent years, paper coated on both sides of a paper base as a support for planographic printing plates has superior mechanical strength and printing durability compared to ordinary paper bases, and has fewer problems such as expansion and contraction, wrinkles, and tearing during plate making and printing processes. .

It is known that so-called polyethylene-coated papers, in which the paper substrate is coated with a polyethylene resin, are used in some printing plates and can be used in a variety of printing plates. Polyethylene-coated paper is as inexpensive as a normal paper support, and has better mechanical strength and water resistance than a normal paper support, resulting in improved printing durability.

The polyethylene resin layer of a conventional lithographic printing plate material using polyethylene coated paper as a support has a density of 0.925.
The strength of low-density polyethylene resin-coated paper is not very strong, and the wet strength of the base paper is also low, although it is less than that of a paper support that uses low-density polyethylene resin of less than g/cm Due to the presence of moisture, the printing plate installed in the master cylinder of the offset printing press receives a strong force in the direction of rotation due to the pressure of the foam roller and blanket roller due to the rotation of the printing press, causing the printing plate to elongate, resulting in printing problems. This causes misalignment.

This tendency becomes even more pronounced when the printing plate is hung horizontally, which is a drawback.

[Problems to be Solved by the Invention] The present invention overcomes the disadvantage of large plate elongation of the conventional method, and provides a support for a lithographic printing plate that is inexpensive and has improved printing durability, especially plate elongation during printing. This was done to provide the body.

[Means for Solving the Problem] As a result of extensive research into improving plate elongation during printing, the present inventors have developed a planographic printing plate support in which both sides of a base paper are coated with polyethylene resin. It was discovered that plate elongation during printing can be improved by containing polyamide polyamine epichlorohydrin resin, dialkyl ketene dimer and/or dialkyl ketone in the base paper, and based on this knowledge, the present invention was made. The polyamide polyamine epichlorohydrin resin according to the present invention, dialkyl ketene dimer and/or
Mana is obtained by containing a dialkyl ketone.

In the present invention, since the dialkyl ketene dimer and/or dialkyl ketone according to the present invention is used as a sizing agent, it can prevent moisture penetration but cannot obtain wet strength. As a reinforcing agent, the polyamide polyamine epichlorohydrin resin according to the invention is required.

In the present invention, the method for incorporating the polyamide polyamine epichlorohydrin resin, dialkyl ketene dimer, and dialkyl ketone according to the present invention into the base paper is to add the polyamide polyamine epichlorohydrin resin, dialkyl ketene dimer, and dialkyl ketone according to the present invention directly into the pulp slurry, or to add the polyamide polyamine epichlorohydrin resin according to the present invention on both sides of the base paper. The polyamide polyamine epichlorohydrin resin, dialkyl ketene dimer, and dialkyl ketone may be impregnated or applied by a size press method, a tab size method, or the like.

The amount of the polyamide polyamine epichlorohydrin resin, dialkyl ketene dimer, and dialkyl ketone added to the base paper in the present invention is preferably in the range of 0.1 to 2% by weight relative to the valve.0 The polyamide polyamine epichlorohydrin resin according to the present invention, When the added amount of dialkyl ketene dimer and dialkyl ketone is less than 0.1% by weight, the effect is hardly obtained.
Even if it is added in an amount of 2% by weight or more, the effect is almost the same, and it is wasteful when economical efficiency is considered. Furthermore, if it is added in excess, the physical properties of the base paper will change significantly, which will not only reduce the handling properties as a printing plate, but also reduce the sizing properties, resulting in increased plate elongation during printing, which is counterproductive.

Furthermore, the base paper used in the present invention may contain various sizing agents. Sizing agents include fatty acid metal salts and/or alkenyl or alkyl succinic anhydrides, epoxidized higher fatty acid amides described in JP-A-54-147211, and organic fluorocarbons described in JP-A-56-109343. Examples include compounds.

More preferred sizing agents include aluminum chloride,
Examples include higher fatty acid metal salts that are fixed to the valve with water-soluble aluminum salts such as aluminum sulfate and polyaluminum chloride. The content of higher fatty acid metal salts in base paper is
0.5 to 3% by weight, based on the bulb, is preferred.

The base paper used in the present invention may contain various water-soluble polymer compounds. Examples of water-soluble polymer compounds include polyacrylamide, starch, starch derivatives,
Natural polymer compounds other than starch, polyvinyl alcohol,
The polyacrylamide which may contain at least one type of gelatin may be cationic, anionic or amphoteric.

The starch may be any starch that is commonly used in the papermaking field, and particularly preferred for internal addition are cationized starch,
Phosphate starch, oxidized starch for tub size, etc. The natural high-molecular polysaccharide may be any one commonly used in the paper manufacturing field, such as guar gum and its modified products, alginic acid and its derivatives, and the like. Polyvinyl alcohol may be completely saponified, partially saponified, carboxy-modified, cation-modified, or any other type of modified polyvinyl alcohol; gelatin may be treated with alkali, acid-treated, or various modified gelatin;
As for the method of containing it, it may be added to the valve slurry before paper making, it may be included in the tab size after paper making, or the aqueous solution may be applied using various coaters. .

The base paper used in the present invention may further contain various water-soluble inorganic salts. As water-soluble inorganic salts, inorganic salts containing sodium, calcium, lithium, magnesium, and barium are preferable, such as sodium chloride. , sodium sulfate, trisodium phosphate, calcium chloride,
Lithium chloride, magnesium chloride, magnesium sulfate,
Examples include barium chloride.

The content of these water-soluble inorganic salts in the base paper is from 0.1 to
5g/■2 is preferable; if it is less than O, Ig/+", the antistatic properties of the base paper will not be sufficient and various problems will occur in operability*
If the amount is more than 5 g/s, the strength of the base paper decreases, which is not preferable.

There are no particular restrictions on the method of incorporating these water-soluble inorganic salts into the base paper, but it is common to add them to the tab size liquid.

In addition to the above-mentioned base paper used in the present invention, fixing agents such as aluminum sulfate and aluminum chloride, melamine resin,
Paper strength agents such as urea resin and epoxidized polyamide resin,
Fillers such as calcium carbonate, kaolin, talc, clay, etc.
Additives such as organic conductive agents, optical brighteners, dyes, pigments, and antioxidants are blended.

The base paper constituting the support according to the present invention may be any paper that is generally used for photographic paper; for example, it may be any pulp paper made from natural valve, synthetic valve, or a mixture thereof. However, natural valve paper containing wood valves as a main component, such as softwood valves, hardwood valves, and mixed softwood and hardwood valves, is advantageously used.

There is no particular restriction on the thickness of the base paper used in the present invention, but it is preferable to use paper with good smoothness, such as by compressing the paper by applying pressure in a calendar after making the paper, and its basis weight is 3.
0 to 300 g/m2 is preferred.

In the present invention, it is preferable to blend high-density polyethylene into the polyethylene resin, and it is even more preferable to blend 30% by weight or more of high-density polyethylene into the polyethylene resin. It has strong mechanical strength and is highly effective in preventing the plate itself from elongating due to a decrease in the strength of the inner paper due to moisture permeation from the resin to the inner paper during offset printing.

In addition, the high-density polyethylene contained in the polyethylene resin layer is effective even if it is blended on at least one side of the polyethylene resin layer, and it is especially effective when high-density polyethylene is blended on the one side on which the printed image is formed. ,
More preferably, high-density polyethylene is blended on both sides of the polyethylene resin layer, which is very effective.

Further, in the polyethylene resin for coating the base paper in the present invention, an antihalation agent such as carbon black, an antistatic agent, an antioxidant, etc. may be contained in the resin layer on the side having the printed image forming layer. Further, the surface of the resin layer may be roughened for the purpose of improving grain, and the resin layer opposite to the side having the printed image forming layer may contain additives such as an antistatic agent. Alternatively, the surface may be roughened like the surface.

The lithographic printing support according to the present invention is produced by a so-called extrusion coating method in which heated and molten resin is cast onto a running base paper, and both sides of the support are coated with the resin.
Before coating the base paper with resin, the base paper is subjected to corona discharge treatment.
It is preferable to perform an activation treatment such as flame treatment.

Various back coat layers can be applied to the back surface of the support for the lithographic printing plate according to the present invention in order to prevent static electricity, prevent curling, provide writability, and the like.

Further, the back coat layer may contain an appropriate combination of an inorganic antistatic agent, an organic antistatic agent, a hydrophilic binder, a latex, a hardening agent, a chemical agent, a surfactant, and the like.

The lithographic printing plate in the present invention includes various types, but among them, a printing plate in which a silver image is used as an ink receptor is preferred, and a typical lithographic printing plate in which a silver image is used as an ink receptor is Examples include lithographic printing plates that apply the silver complex diffusion transfer method. Lithographic printing plates using the silver complex diffusion transfer method are coated with heavy metals (e.g. gold, silver, copper, platinum, palladium, zinc, etc.) or their sulfides on the support, subbing layer, silver halide emulsion layer, etc. It is obtained by depositing silver image-wise from a silver halide emulsion layer onto a printing plate support provided with silver precipitation nuclei by a silver complex salt diffusion transfer process.

[Examples] Hereinafter, the present invention will be explained in detail with reference to Examples, but the content of the present invention is not limited to the Examples.

Example A mixed sample of 50 parts by weight of hardwood bleached kraft valve and 50 parts by weight of softwood bleached kraft valve was beaten into Canadian Standard Freeness 31C1wl, and the dialkyl ketene dimer emulsion and polyamide polyamine epichlorohydrin face fat listed in Table 1 were prepared as follows. By adding a predetermined amount to the internal addition formulation, a base paper with a basis weight of 135 g/ra2 was made.

Internal addition compounding valve (LBKP/NBKP) 100 guar gum
0.6 (Numbers in the formulation indicate parts by weight.) Next, as a comparative example, the sizing agents were changed to soap, rosin, and sulfuric acid, and a predetermined amount was added to the internal additive formulation, and base paper was prepared in the same manner. I made a paper.

Table 2 Table 1 The numbers in this table indicate parts by weight of solid content.

(Margin below) The numbers in this table indicate parts by weight of solid content.

The obtained wet paper was wet pressed and then dried with a drum dryer at 110°C. This paper was impregnated with 20 g/rrf of tab size liquid of the following formulation and dried in a hot air constant temperature dryer at 110°C (the amounts in the formulation indicate parts by weight).

<Table 3> Carboxy-modified polyvinyl alcohol 4 Salt
3.3 Add water
100 impregnated, dry paper has a linear pressure of 90 K
After supercalendering at g/cm, both sides were treated with corona discharge.Then, the front and back sides of the base paper were
Low density polyethylene (density 0, 920 g/c+n
3, MI=5) and high-density polyethylene (density 0.96
0 g/Cm3, MI=5> was blended in a predetermined amount and coated to a thickness of 20 μm using a melt extrusion coating machine at a resin temperature of 330°C. The contents of high density polyethylene in these resin formulations are shown in Tables 3 and 4.

The original paper number is the same as Table 1.

*HDPE is high-density polyethylene, and LDPE is low-density polyethylene.

Next, as a comparative example, Table 4 shows samples prepared by changing the sizing agents to soap, rosin, and sulfuric acid.

<Table 4> The original paper number is the same as Table 1 and Table 2.

*HDPE is high density polyethylene, LDPE is low density polyethylene.

Next, the back surface was subjected to a corona discharge treatment, and then an aqueous gelatin solution containing silica powder was applied. After the surface was further subjected to corona discharge treatment, the next layer was coated as a primary coating to obtain a lithographic printing plate material.

■Carbon black, fine silica powder with an average particle size of 7 microns, and a formalin-containing gelatin layer.

■Formalin-containing gelatin-silver halide emulsion layer.

■Palladium sulfide sol layer dispersed in a trace amount of methyl vinyl ether/maleic anhydride copolymer.

The obtained lithographic printing plate material was heated at a temperature of 50°C and a humidity of 80%.
The gelatin layer and emulsion layer were stored under these conditions for 2 days to promote hardening of the gelatin layer and emulsion layer.

After imagewise exposing the lithographic printing plate material obtained as described above, a silver complex salt diffusion transfer development treatment is performed to form a silver image to obtain a lithographic printing plate.The lithographic printing plate is mounted on an offset printing machine, and the plate surface is 0 which was printed after being treated with a fat treatment solution.
The plate elongation was evaluated by measuring the distance between the images on the first sheet of printing and the 10,000th sheet, and evaluating the plate elongation as a percentage of the length of the entire plate. The evaluation results are shown in Table 5.

(Margin below)

Claims (2)

[Claims] (1) A lithographic printing plate support comprising a base paper coated on both sides with polyethylene resin, wherein the base paper contains a polyamide polyamine epichlorohydrin resin and a dialkyl ketene dimer and/or dialkyl ketone. Support for. (2) The support for a lithographic printing plate according to claim 1, wherein at least one of the polyethylene resin layers contains high-density polyethylene.