JPH0364319B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a master plate for lithographic printing, and more particularly to a master plate for direct drawing type lithographic printing.

Lithographic printing plates are usually produced by creating a lipophilic image on a support such as an aluminum plate that has been treated to be hydrophilic. The image area is required to have lipophilicity and water repellency, and the non-image area is required to have properties such as hydrophilicity, water retention and ink repulsion.

And, due to the difference in creating a hydrophilic image area,
Original plates for direct-drawing lithographic printing, original plates for electrophotographic lithography, original plates for photolithographic printing (so-called PS plates)
and so on.

Conventionally, the hydrophilic layer of a direct plate lithographic printing plate has been formed by saponifying cellulose acetate film or cellulose acetate coated on a suitable support with an alkali to make it hydrophilic. Also known is a lithographic printing original plate having a layer containing an ethylene-vinyl alcohol copolymer as a main component as a hydrophilic layer.

However, printing using these lithographic printing plates required strict control of the amounts of water and ink supplied, making it impossible to perform stable printing, and the printing durability was only about 500 to 1000 copies.

The present invention is intended to eliminate the above-mentioned drawbacks, and it is an object of the present invention to provide a master plate for lithographic printing that can be easily and stably printed even by non-experts and has a printing durability of 5,000 to 10,000 copies. purpose.

That is, the lithographic printing original plate of the present invention has a porous recording layer and a hydrophilic slipping layer on a support, and the image area after image formation is durable, and the non-image area is free from scumming. Features.

As shown in FIG. 1, a lithographic printing original plate 1 of the present invention
The support 2 is made of plastic, metal, or strong paper, and on its surface is a porous recording layer 3 made of a pigment/resin, and further thereon a hydrophilic slipping layer 4 made of solid lubricant particles/hydrophilic resin. A two-layer structure is provided. Since the most practical method for forming this layer is to apply a coating liquid, the coating film will be described in detail below.

First, a method for forming a coating film of a porous recording layer will be described below.

The basic composition of the coating liquid consists of particles, a resin that uniformly disperses and binds the particles, and an organic solvent that dissolves the resin. As specific examples of particles, any inorganic or organic pigment can be used. For example, titanium oxide, calcium carbonate, zinc oxide, silicon oxide, barium sulfate, lead carbonate, alumina, clay, etc. can be used. On the other hand, as for the resin, binder resins used in paints and inks, such as polyester-based, phenyl-based, alkyd-based, acrylic-based, epoxy-based, polyurethane-based, modified cellulose-based resins, and mixtures thereof, can be used. Kneading and dispersion for preparing a coating liquid is performed by a well-known method. This coating is applied to a durable support such as plastic, metal or tough paper and dried to form a porous recording layer. Note that a well-known coating method may be applied for coating. As a result of extensive research, the following requirements were clarified in order for this coating film to have good recording properties.

First, the composition ratio of pigment/resin is determined by recording properties (related to the porosity of the coating film), coating film strength, adhesion to the support,
It has a remarkable effect on abrasion resistance, but in order to satisfy all conditions, the pigment/resin composition ratio must be in the range of 1/3 to 4/1 by weight.

However, depending on the pigment material type, pigment particle size, and shape, the above-mentioned full range may not be applicable.
The common range for all material compositions is 1/3
~4/1. Next, regarding the particle size and particle size distribution of the pigment, consider the porosity and surface roughness, and determine the particle size.
A particle size distribution as narrow as possible in the range 0.5-5μ gives good results. Also, the thickness of the coating film is 10
~30μ is appropriate.

In addition, in order to improve the strength and solvent resistance of the coating film, it is more preferable to use a crosslinked binder resin. For example, well-known techniques can be applied as appropriate, such as selecting a resin containing a polyester resin having a polyol group or a polyurethane resin, and creating a binder resin composition with an isocyanate group-containing compound or resin added as a crosslinking agent.

Incidentally, when the adhesion between the support and the porous recording layer to be provided is weak, it is natural to provide an undercoat layer in advance to improve the adhesion before coating the porous recording layer.

Next, a method for forming a coating film of the hydrophilic slipping layer will be described below. The basic composition of the coating liquid consists of solid lubricant particles (preferably hydrophilic), a hydrophilic binder resin that uniformly disperses and binds the particles, and an organic solvent that dissolves the resin. As specific examples of solid lubricant particles, fine powders of boron nitride, sulfur, mica, talc, aluminum stearate, calcium stearate, titanium sulfide, molybdenum sulfide, polyethylene, polyacetal, polytetrafluoroethylene, etc. are suitable. On the other hand, hydrophilic resins contain hydrophilic functional groups (e.g., -OH, -SO ₃ H, -COOH, -CO, -
NH ₂ ) and must be water-insoluble, such as modified cellulose, polyamide,
Polyester resins, acrylic resins, epoxy resins, polyurethane resins, and mixtures thereof can be used. Kneading and dispersion for preparing a coating liquid is performed by a well-known method. This coating liquid is applied onto the above-mentioned porous recording layer and dried to form a hydrophilic slipping layer. Note that a well-known coating method may be applied for coating. As a result of studies in order to obtain lubricity and hydrophilic properties that should allow this hydrophilic lubricity layer to pass through the image forming material and water and prevent background smearing, the following requirements were further clarified. First, the composition ratio of solid lubricant particles/resin has a large effect on the image forming material's permeability, coating strength, adhesion to the porous recording layer, and abrasion resistance, but in order to satisfy all conditions, The composition ratio of solid lubricant/resin is 2/1 to 20/1 by weight.
must be within the range.

Next, regarding the particle size, if it is too small, the permeability of the image forming material will be reduced, and if it is too large, the surface roughness will become too large and the scumming prevention effect will be reduced. Therefore, the optimum particle size range is determined.
Must be between 0.5 and 10μ. Next, regarding the thickness of the coating film, we considered that if it is too thin, it will not be able to sufficiently cover the surface of the underlying porous recording layer, and if it is too thick, the permeability of the image forming material will decrease. The optimum film thickness range should be between 2 and 10 microns.

Lipophilic image forming methods that can be applied to the lithographic printing original plate of the present invention include printing with a typewriter, handwriting with oil-based ink, transfer using a thermal transfer recording method, or electrophotographic method.

Here, an example of the method for forming an image on a lithographic printing original plate of the present invention will be explained in detail with reference to the drawings.
As shown in the figure, the hydrophilic slipping layer 4 of the lithographic printing original plate 1
The ink ribbon 5 is brought close to the surface of the ink, and the ink is transferred and permeated into the hydrophilic lubricating layer 4 and the porous recording layer 3 using a transfer means by pressing the head 6 of a wire dot impact printer or a typewriter. A penetration image 7 is formed. This penetration image 7
Since the ink permeates into the hydrophilic slipping layer 4 and the porous recording layer 3 at the same time as the transfer, there is no need for any subsequent fixing means, and the ink can withstand harsh use over a long period of time.

When a lithographic printing original plate with an image formed in this way is attached to an actual offset printing machine and printed, the hydrophilic slipping layer contains solid lubricant particles, so it is resistant to mechanical abrasion, and the image can be printed. Since the part is a penetration image, it has excellent printing durability, and
The non-image area has the ability to allow dampening water to penetrate and retain the dampening water in a sufficiently stable manner up to the hydrophilic slipping layer and the porous recording layer below it, making it possible to adjust the amount of water and ink supplied. It is easy to obtain a large quantity of stable printed matter of good quality without background smudges.

Examples of the present invention will be shown below.

Example 1 On a polyester film (thickness 100μ), 2 parts of powdered silica (manufactured by Mizusawa Chemical Co., Ltd./average particle size 2μ), (same weight ratio below), polyurethane resin (manufactured by Nippon Polyurethane Co., Ltd., polyester polyol/ A mixed solution consisting of 4 parts of isocyanate, 8 parts of methyl ethyl ketone, and 2 parts of toluene was stirred for about 20 minutes using a screw-type disperser, and the uniformly dispersed coating solution was applied using a roll coater, and dried to form a porous coating. A recording layer was formed. The film thickness was 20μ. On top of this, a mixed solution consisting of 7 parts of powdered talc (average particle size 3μ), 1 part of polyurethane resin, 8 parts of methyl ethyl ketone, and 2 parts of toluene was added in a screw-type stirring disperser to approx.
The coating solution was uniformly dispersed by stirring for 10 minutes, and then applied using a roll coater, and dried to form a hydrophilic slipping layer with a thickness of 4 μm. This was used as a master plate for planographic printing.

Next, this lithographic printing original plate was mounted on a wire dot printer, and impact printing was performed to form a clear penetration image on the hydrophilic slipping layer using a commercially available carbon ribbon made of nylon cloth, thereby forming a printing plate. Even when the printing plate was rubbed with a finger immediately after the image was printed, the ink in the image area did not disappear or run.

When this printing plate was printed on an offset printing machine (Rotaprint Offsetter), 8,000 copies of clean prints with no background smudges were obtained.

Example 2 8 parts of calcium carbonate powder (manufactured by Shiraishi Calcium Co., Ltd.), 1 part of polyester resin (manufactured by Toyobo Co., Ltd.), 0.2 parts of nitrocellulose (manufactured by Teisel), 15 parts of methyl ethyl ketone, and toluene were added to high-quality paper (110 kg).
A coating solution obtained by kneading a mixed solution of 15 parts in a ball mill for about 4 hours was applied using a roll coater and dried to form a porous recording layer. Furthermore, on top of that
2 parts of boron nitride powder (manufactured by Denki Kagaku Co., Ltd.), epoxy resin (Epicoat 828/manufactured by Yuka Ciel Epoxy Co., Ltd.)
Epicure H-2 series) 1 part, mercapto-based silane coupling agent KBM803 (manufactured by Shin-Etsu Chemical Co., Ltd.) 0.1 part,
A mixed solution consisting of 15 parts of isopropyl alcohol and 3 parts of toluene was stirred for about 1 hour using a screw-type stirrer disperser, and the uniformly dispersed coating liquid was applied using a gravure coater and dried by heating to form a hydrophilic film with a thickness of 3 μm. Formed a sexual layer. This was cut to a predetermined size to obtain a master plate for lithographic printing.

Next, this lithographic printing original plate was printed using a thermal transfer ribbon on which an ink layer of carnauba wax and carbon wax (weight ratio 4/1) was formed on 20μ glassine paper to a thickness of 3.5μ, using a thermal recording method. When the image was transferred and recorded using a heat-sensitive recording head, a clear penetration image was formed. Although no heat fixing was performed immediately after recording, the ink did not disappear or run even when the recorded surface was strongly rubbed with a finger.

When this printing plate was printed on an offset printing machine (Rotaprint Offsetter), 5,000 copies of clean prints with no background smudges were obtained.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is a diagram showing the configuration of a lithographic printing original plate of the invention, and FIG. 2 is an explanatory diagram showing an example of a method for recording an image on the lithographic printing original plate. 1...Original plate for lithographic printing, 2...Support, 3...
Porous recording layer, 4... Hydrophilic slipping layer, 5... Ink ribbon, 6... Head, 7... Penetration image.

Claims (1)

[Claims] 1 Consisting of an inorganic or organic pigment with a particle size of 0.5 to 5μ and a resin that uniformly disperses and binds the pigment on a support, with a pigment/resin composition ratio of 1/3 to 1/3 by weight.
After providing a porous recording layer of 4/1 with a thickness of 10 to 30μ, solid lubricant particles with a particle size of 0.5 to 10μ are uniformly dispersed and bound on the porous recording layer. A lithographic plate comprising a hydrophilic slipping layer made of a hydrophilic resin and having a particle/resin composition ratio of 2/1 to 20/1 in terms of weight ratio, with a thickness of 2 to 10 μm. Original plate for printing.