JPH0986061A - Lithographic printing plate support - Google Patents

Abstract

(57) Abstract: [PROBLEMS] To provide a lithographic printing plate support in which both sides of a base paper are coated with a resin, which has strength, little elongation, and sufficient printing durability. The purpose is to do. Another object of the present invention is to provide a lithographic printing plate support which is flat and has no unevenness in a printed image and which is economically excellent. The present invention is a lithographic printing plate support prepared by mixing and making glass fibers and natural pulp.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithographic printing plate support, and more particularly to a lithographic printing plate support having a printing image forming layer on a support having both sides of a base paper coated with a resin.

[0002]

2. Description of the Related 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 of aluminum, zinc or the like, a plastic film such as polyethylene terephthalate or polyvinyl chloride, or a paper. Among these supports, metal plates and plastic films have been used as lithographic printing plate supports because they are excellent in mechanical strength and the like, have good dimensional stability, and have a large number of printable sheets. However, these plates have the drawbacks of being expensive and of being inferior in bendability, especially for plastic films. On the other hand, paper is inferior in mechanical strength, dimensional stability, etc. to the above-mentioned support, but since it is inexpensive, it is used as a support for a lithographic printing plate which may have a small number of printed sheets. It is known that so-called resin-coated paper having both sides coated with a resin is used in some printing plates and can be used in various printing plates.

In recent years, automatic plate making and automatic printing systems for lithographic printing plate materials have been remarkably popular in the field of light printing. The characteristics required of these systems as a lithographic printing plate are that there is little change in morphology such as curl during the process, good transportability, easy cutting with an automatic cutter, etc. The holding type must be one in which the hook hole can be easily punched out, and it must have sufficient strength so that the hook hole is not broken or deformed during printing. Furthermore, the printing plate must have suitable flexibility in order to have good adhesion to the cylinder. In addition, it is important that deformation such as waviness or less expansion and contraction due to pretreatment or alcohol-based organic solvent used during printing, and that the lithographic printing plate can be firmly held. Further, smoothness of the surface is also required because image unevenness does not occur. In particular, in the case of a lithographic printing plate made by coating an emulsion, the above-mentioned characteristics are highly required in order to exert its high image accuracy, and image processing is performed to form an image as a plate material. In the process, deformation, expansion and contraction,
It must have the property of not causing pollution. From such requirements, conventionally, as a lithographic printing plate support,
A plastic film or plastic-coated paper, so-called resin-coated paper is used. Among them, the resin-coated paper is widely used because it has a certain degree of water resistance, stretch resistance, curling property, elasticity and flexibility, is easy to handle, is economical, and the like. The resin-coated paper is cheap like a normal paper support, and moreover has excellent mechanical strength and water resistance as compared with a normal paper support, so that the printing durability is improved. However, although less than the paper support due to the water present at the time of printing, the printing plate made of the resin-coated paper stretches, resulting in misregistration. This tendency becomes more remarkable when the printing plate is horizontally mounted. As a method of improving the printing durability of the printing plate with resin-coated paper, high-density polyethylene, high density such as polyethylene terephthalate, a method of coating a resin having high strength alone or mixed with a resin having excellent processability, Alternatively, a method of producing a base paper using high-strength pulp, a method of adding a paper strength agent in a large amount, and the like are conceivable, but none of these methods is satisfactory.

Japanese Unexamined Patent Publication (Kokai) No. 2-103184 discloses a lithographic printing plate support in which colloidal alumina is contained in a base paper to improve printing durability, particularly plate elongation during printing. Further, Japanese Patent Laid-Open No. 63-163358 discloses that
By containing guar gum in an amount of 0.2 or more by weight of pulp into the base paper, and by adding 20% by weight or more of Kraft softwood pulp to the entire pulp, it has an appropriate strength,
A lithographic printing plate support having low elongation and thereby having sufficient printing durability is disclosed. However, although these methods have some effects, they have not achieved sufficient printing durability.

In recent years, in the field of light printing, there has been an increasing demand for colorization. However, printing durability is required to be higher than that of a conventional lithographic printing plate support, and a conventional resin-coated paper type lithographic printing plate support is required. In the body, the printing plate undergoes stretching, resulting in misregistration. This tendency becomes more remarkable when the printing plate is horizontally mounted.

[0006]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention As a result of intensive studies by the present inventors in order to overcome the above-mentioned drawbacks, in a lithographic printing plate support in which both sides of a base paper are coated with a resin, natural pulp is contained in the base paper. By making a mixture of the and the glass fiber into a paper and preferably impregnating it with a polyacrylamide resin, it was possible to provide a support for a lithographic printing plate having strength and low elongation, and having sufficient printing durability. An object of the present invention is to provide such a lithographic printing plate support. Further, in the present invention, the surface is flat at the same time without causing unevenness in the printed image, the flexibility is appropriate, and the handling is easy,
It is also intended to provide an economically excellent support for a lithographic printing plate.

[0007]

DISCLOSURE OF THE INVENTION The inventors of the present invention have aimed to achieve the object of the present invention by making a mixture of natural pulp and glass fiber into paper and preferably impregnating it with a polyacrylamide resin in the formulation of the inside paper of resin-coated paper. Has been achieved.

The glass fiber in the present invention has a thickness of 6 to.
It is preferably 13 μm. If it is thinner than 6 μm, the printing plate tends to be stretched, resulting in misregistration of printing. This tendency tends to become more noticeable when the printing plate is laid horizontally. When it exceeds 13 μm, the elongation of the printing plate is obviously improved, but the surface quality of the lithographic printing plate support is deteriorated, and the unevenness of the printed image tends to occur.

The length of the glass fiber is preferably 6 to 13 mm. When the length is shorter than 6 mm, the strength effect tends to be reduced, and the hooking portion may be broken or the whole lithographic printing plate support may be stretched due to the tension, and the printing durability may not be obtained. If it is longer than 13 mm,
Although the effect of strength is clear, the surface quality of the lithographic printing plate support tends to deteriorate, and unevenness in the printed image tends to occur.

In the present invention, the compounding ratio of glass fiber is 5
10% by weight is desirable. When the compounding ratio is less than 5% by weight, the effect of strength tends to be reduced, and the lithographic printing plate support as a whole tends to be stretched due to breakage of hooks and tension, which tends to impair printing durability. It is in. 10
When the content is more than 10% by weight, the effect of strength is clear, but the surface quality of the lithographic printing plate support tends to deteriorate, and unevenness in the printed image tends to occur.

The polyacrylamide resin used in the present invention may be of anionic, cationic or amphoteric type. As a method of impregnating the polyacrylamide resin, a solution of the polyacrylamide resin according to the present invention dissolved in water may be impregnated or applied on both sides of the base paper by a size press method, a tab size method, or the like. The content of polyacrylamide in the base paper in the present invention is preferably 0.5 to 2.0% by weight based on the base paper. 0.5% by weight
When it is less than 1, the effect of improving the plate elongation during printing of the obtained lithographic printing plate support tends to be small.
When the content exceeds 0% by weight, the physical properties of the base paper change significantly and the handling property as a printing plate tends to deteriorate, and the rigidity of the printing plate improves and sufficient adhesion to the cylinder is obtained. Tend not to be able to.

Examples of the sizing agent used in the practice of the present invention include fatty acid metal salts, dialkyl ketene dimers, dialkyl ketones, alkenyl or alkyl succinic anhydrides, and epoxidized higher fatty acid amides described in JP-A-54-147211. JP-A-56-10934
The organic fluoro compounds described in JP-A-3 are mentioned. In order to effectively achieve the object of the present invention, examples of the sizing agent that can be advantageously used include alkyl ketene dimers (hereinafter referred to as AKD) described in JP-A-63-163358. The content of AKD in the base paper is preferably 0.1 to 2.0% by weight based on the pulp.

Further, it is preferable to add a cationic wet strength enhancer to the base paper according to the present invention. Examples of the cationic wet paper strength enhancer which is advantageously used in the present invention include polyamide polyamine epichlorohydrin resin described in JP-A-63-163358. The amount of the polyamide polyamine epichlorohydrin resin added to the base paper is preferably 0.1 to 2% by weight based on the pulp.

The chemicals for adding to the base paper used in the present invention may further contain various water-soluble polymer compounds. As the water-soluble polymer compound, at least one kind of polyacrylamide resin, starch, starch derivative, natural polymer compound other than starch, polyvinyl alcohol and gelatin may be contained. Preferably, guar gum and its modified products described in JP-A-63-163358 are more preferable.

The base paper used in the present invention may further contain various water-soluble inorganic salts. The water-soluble inorganic salt is preferably an inorganic salt containing sodium, calcium, lithium, magnesium, barium, for example, sodium chloride, sodium sulfate, sodium phosphate, calcium chloride, lithium chloride, magnesium chloride, magnesium sulfate, barium chloride, etc. Can be mentioned. The content of these water-soluble inorganic salts in the base paper is 0.1 to 0.5 g /
m ² is preferred. When the amount is less than 0.1 g / m ^2, the antistatic property of the base paper is not sufficient and various operability problems occur. 5 g / m
^If it is more than ^2, the strength of the base paper is lowered, which is not preferable. The method of incorporating these water-soluble inorganic salts into the base paper is not particularly limited, but a method of adding them to a size press solution or a tab size solution and impregnating them is common.

In the base paper used in the present invention, in addition to the above, fixing agents such as sulfuric acid bands and aluminum chloride, paper strength agents such as melamine resin, urea resin and epoxidized polyamide resin, calcium carbonate, kaolin and talc. ,clay,
Fillers such as titanium oxide, organic conductive agents, optical brighteners, dyes,
Additives such as pigments, antioxidants and antifoggants are blended.

The natural pulp constituting the support according to the present invention is not particularly limited as long as it does not practically affect the photographic emulsion and the added chemicals.

[0018] There is no particular limitation on the basis weight of the base paper used in the present invention, cost, flexibility, due to restrictions such as hook strength, but are papermaking in a conventional ^{100g / m 2 ~200g / m 2} , the printing plate As long as it has sufficient performance.

In the lithographic printing plate support of the present invention, a molten polyolefin resin is applied to both surfaces of a sheet-like substrate,
It can be produced by a so-called extrusion coating method, in which the polyolefin resin layer is cooled and solidified while being pressed onto a cooling roll. For the surface shape of the polyolefin resin, cooling rolls having different surface qualities are appropriately selected according to the target surface quality, and for example, surface states such as matte surface, silk grain, and fine grain surface are formed. In the present invention, the polyolefin forming the polyolefin resin coating layer can be arbitrarily selected from various conventionally used polyolefins. Examples of such polyolefins include α-olefin copolymers such as polyethylene and polypropylene, and mixtures of various copolymers thereof.
A particularly preferred polyolefin is polyethylene. As long as extrusion coating is possible, these polyolefins have a molecular weight in the range of 20,000 to 200,000. It is already known to add various additives such as white pigments, coloring pigments, fluorescent brightening agents, and antioxidants to the polyolefin resin used for forming the resin coating layer of the polyolefin resin-coated paper for photographic printing paper. Therefore, such various additives are naturally possible in the preparation of the polyolefin resin used in the present invention, and are preferable depending on the purpose.

[0020]

EXAMPLES The present invention will be described below in detail with reference to examples, but the contents of the present invention are not limited to the examples. Examples 1 to 10 Comparative Examples 1 to 2 A mixed sample of 50% by weight of hardwood bleached kraft pulp and 50% by weight of softwood bleached kraft pulp was beaten to 310 ml of Canadian Standard Freeness, and the pulp and glass fibers shown in Table 1 were used. Compounding ratio, glass fiber thickness,
The length was changed to give a pulp slurry. 0.3% by weight of alkyl ketene dimer, 1.0% by weight of polyamide polyamine epichlorohydrin resin, and 0. 0% of guar gum.
6% by weight was added, and a 135 g / m ² base paper was made with a Fourdrinier paper machine, and the size liquid shown in Table 1 was applied to this base paper. Low density polyethylene (density 0.92 g / cm ³ , MI = 5) was coated on the front and back surfaces of this base paper at a resin temperature of 330 ° C. using a melt extrusion coating machine to a thickness of 20 μm. Next, the back surface was subjected to corona discharge treatment, and then an aqueous gelatin solution containing silica powder was applied. Further, after corona discharge treatment on the surface, the following layers were sequentially applied to obtain a lithographic printing material. Carbon black, a fine silica powder having an average particle size of 7 μm and a gelatin layer containing formalin. Formalin-containing gelatin-silver halide emulsion layer. Palladium sulfide sol layer dispersed in a trace amount of methyl vinyl ether / maleic anhydride copolymer. The lithographic printing plate material obtained was stored for 2 days under the conditions of 50 ° C. and 80% RH to accelerate the hardening of the gelatin layer and the emulsion layer. After imagewise exposing the lithographic printing plate material obtained as described above, silver complex salt diffusion transfer development processing is performed to form a silver image to obtain a lithographic printing plate, and the lithographic printing plate is mounted on an offset printing machine, Was treated with a desensitizing resin treatment solution and printing was performed. Evaluation of plate elongation is 10000 at the start of printing and 10000.
The displacement distance of the image on the first sheet was measured, and the plate elongation was evaluated by% with respect to the length of the entire plate. If the elongation is 0.2% or more, there is a practical problem. Regarding the evaluation of surface quality, the image unevenness of the first sheet after the start of printing was visually evaluated. The best one is ◎, the best one is ○,
Those with no practical problems were evaluated as Δ, and those with practical problems as x. Table 1 shows the evaluation results.

[0021]

[Table 1]

[0022]

EFFECTS OF THE INVENTION As is clear from the examples, it can be seen that, in the lithographic printing plate support, when glass fiber and natural pulp are mixed and made into paper, the plate elongation is small and the surface quality is excellent. Preferably, the glass fiber has a thickness of 6 to 1
3 μm length 6 to 13 mm and 5 to 10% by weight, or
It is particularly preferable that the base paper is coated with a polyacrylamide resin, whereby the plate elongation is small and the surface quality is excellent.

Claims (3)

[Claims] 1. A lithographic printing plate support obtained by coating both sides of a stencil sheet with a resin, wherein the stencil sheet is made from a mixture of natural pulp and glass fibers. 2. The glass fiber has a thickness of 6 to 13 mm, and has a thickness of 6 to 13 mm.
It has a length of mm and the content is 5 to 10% by weight.
The support for lithographic printing plate described in 1. 3. The lithographic printing plate support according to claim 1, wherein the base paper is impregnated with a polyacrylic acid resin.