JPH07149072A - Lithographic printing block - Google Patents

Abstract

PURPOSE:To improve bending properties and strength after bending, by a method wherein a polyester film whose light transmission rate, bending angle and film strength after the bending of the specific film express respectively specific values is used. CONSTITUTION:A direct drawing type where a hydrophilic layer is provided on a substrate as an image receptive layer or an electrophotographic type where an photconductive layer is provided on a conductive substrate as the image receptive layer are mentioned as a lithographic printing block which are used in a light printing field, in the lithographic printing block like this, it is decided that a polyester film wherein a light transmission rate is exceeding 50%, a film bending angle is 30-90 degrees and film strength after bending is at least 8kg/mm<2> is used. A polyester which is constituted so that a fine cave to be made by orientating at least monoaxially a polymer mixture into which thermoplastic resin not compatible with the polyester is mixed and has an apparent specific gravity of 1.05-1.3 is used.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a lithographic printing plate such as a PS plate, an LBP plate and a pink plate.

[0002]

2. Description of the Related Art At present, as a lithographic printing plate used in the field of light printing, a direct drawing type (LBP plate) having a hydrophilic layer as an image receiving layer on a support, an image receiving layer on a conductive support. Examples thereof include an electrophotographic type (pink plate) provided with a photoconductive layer and a PS plate provided with a diazo photosensitive layer as an image receiving layer on a support. So far as the basis for these editions,
Aluminum plates, papers, plastic films and the like are known. However, the aluminum plate is expensive and has a difficulty in handling. Although paper is inexpensive, it has a problem in durability.
On the other hand, even in plastic films that have solved these drawbacks, the flexibility and the strength of the film after folding are insufficient, so that the durability and printability when the plate is wrapped around the plate cylinder become poor. Had.

[0003]

SUMMARY OF THE INVENTION The present invention relates to a lithographic printing plate using a plastic film as a base material, which has good foldability and strength after bending by optimizing the drawbacks of the previous term.

[0004]

Means for Solving the Problems That is, the gist of the present invention as means for solving these is that the light transmittance is 5
When the bending angle of the film is 0% or less, the bending angle of the film is 30 degrees or more and 90 degrees or less, and the film strength after bending is 8 kg / mm ²
The present invention relates to a lithographic printing plate characterized by using the polyester film described above. The polyester in the present invention means an aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid or naphthalenedicarboxylic acid or an ester thereof and ethylene glycol, diethylene glycol, 1,4-
It is a polyester produced by polycondensing glycols such as butanediol and neopentyl glycol. These polyesters may be obtained by directly reacting an aromatic dicarboxylic acid with a glycol, and then transesterifying an alkyl ester of an aromatic dicarboxylic acid with a glycol, followed by polycondensation, or a diglycol ester of an aromatic dicarboxylic acid. Is produced by a method such as polycondensation. Typical examples of such polyesters include polyethylene terephthalate, polyethylene butylene terephthalate or polyethylene-2,6-naphthalate. This polyester may be a homopolymer or a copolymer of a third component. In any case, in the present invention, the ethylene terephthalate unit, the butylene terephthalate unit or the ethylene-2,6-naphthalate unit is 70 mol%.
Or more, preferably 80 mol% or more, more preferably 90 mol% or more.
A polyester having a mol% or more is preferable.

The polyester-incompatible thermoplastic resin used in the present invention must be one that is incompatible with the above-mentioned polyester. Specifically, polystyrene resin, polyolefin resin, polyacrylic resin,
Examples thereof include polycarbonate resin, polysulfone resin, cellulose resin, polyamide resin and the like. In particular, polystyrene resins, polyolefin resins such as polymethylpentene and polypropylene are preferable. The polymer mixture obtained by mixing the polyester of the present invention and the incompatible thermoplastic resin to the polyester is obtained, for example, by mixing chips of each resin, melt-kneading in an extruder, and then extruding and solidifying. Method, a method in which both resins are previously kneaded by a kneader, and further melt-extruded by an extruder to solidify, or an incompatible thermoplastic resin is added to the polyester in the polyester polymerization step, and the mixture is stirred and dispersed. It can also be obtained by a method in which chips are melt-extruded and solidified. The polymer obtained by solidifying (unstretched sheet) is usually in a non-oriented state or a weakly oriented state. Further, the thermoplastic resin incompatible with the polyester is present in the polyester in a form dispersed in various shapes such as a spherical shape, an elliptic spherical shape, or a thread shape.

Important points in the present invention are that the light transmittance is 50% or less, the bending angle of the film is 30 degrees or more and 90 degrees or less, and the film strength after bending is 8 kg.
/ Mm ² or more, the void-containing polyester film. For that purpose, in the thickness direction of the film, from the surface to the X layer having a low void content, and then to the Y layer having a low
It is preferred to form layers, and most Z layers.
For that purpose, each of the three independent extruders is charged with different raw materials, extruded, laminated after stretching, preferably before stretching, and the laminated unstretched sheet is stretched in the longitudinal and transverse directions to obtain a void content. The lower the film is, the closer it is to the surface. Therefore, the raw material is X, Y, and the layer forming Z has an amount of the cavity developing agent contained in the polyester of Z.
It becomes possible by setting>Y> X. Further, by increasing the shear stress at the time of melt extrusion, the void developing agent in the X layer is finely dispersed, so that the effect of lowering the void expressing rate is increased. However, in order to have a distribution in the cavity expression amount in order to have the bending amount and the bending resistance which are the gist of the present invention, it is difficult to control under the extrusion conditions, and as described above, it is possible to control the cavity expressing agent. This is a good thing to do. However, as long as the bending property and the bending resistance are within the scope of the present invention, the method is not limited to the above-mentioned method. For example, a method of mixing an elastomer such as polyester and polyolefin or a copolyester, and a third component such as a plasticizer may be used. You may use the method of adding, the method of controlling by drawing conditions and the heat processing conditions after drawing, or these methods may be combined. If necessary, the polymer mixture may contain inorganic particles in order to improve the hiding property and the drawing property. Examples of the inorganic particles therefor include, but are not particularly limited to, titanium dioxide, silicon dioxide, calcium carbonate, barium sulfate, aluminum oxide, kaolin, and talc.

It is possible to add a colorant, a light-proofing agent, a fluorescent agent, an antistatic agent, etc. to the polymer mixture depending on the application. The polymer mixture thus obtained is further stretched between rolls having different speeds (roll stretch), stretched by gripping and expanding with a clip (tenter stretch), and stretched by expanding by air pressure (inflation stretch). At least one axis is subjected to orientation treatment by, for example,
At this time, peeling occurs at the interface between the insoluble thermoplastic resin and the polyester dispersed in the polyester, and a large number of voids are generated in the polymer mixture.

The film used in the printing plate of the present invention preferably has an apparent specific gravity of 1.05 or more and less than 1.3.
If it is less than 1.05, external deformation tends to occur during printing.
If it is 1.3 or more, the bending property becomes poor, and the adhesion between the plate holding part and the plate body part deteriorates, so that sufficient durability cannot be obtained. The apparent specific gravity is calculated from the following formula. Apparent specific gravity = W × 5
× 5 × t × 10000 (the weight of a 5 cm × 5 cm sample is W and the thickness is t)

On the other hand, a PS plate which uses an aluminum plate as a method of imparting a dampening water suitability (hydrophilicity) to a non-image area by utilizing the repulsion of ink by dampening water is gummed in a PS plate, but natural raw materials such as gum arabic I am worried about the stability of the quality because it is used. Therefore, the present invention is characterized by utilizing a water-insoluble hydrophilic compound formed by a reaction between zinc oxide and an etchant, as a method for imparting a dampening water suitability. Commercially available etchants are roughly classified into a cyan type and a non-cyan type, but a non-cyan type is preferred for the lithographic printing plate of the present invention from the viewpoint of improving dampening water suitability.

The dampening water suitability-imparting layer comprises a pigment and a binder component, and the pigment is preferably zinc oxide which is excellent in reactivity with a commercially available etchant. As the binder, PVA, C
Examples include water-soluble resins such as MC, hydroxyethyl cellulose, casein, gelatin and water-soluble polyurethane, and emulsion resins such as polymers or copolymers of vinyl acetate, vinyl chloride, acrylic acid ester, styrene, butadiene, ethylene and the like. Is generally used because of its excellent hydrophilicity and coating strength. PVA
Epoxy resin, isocyanate resin,
Although melamine resin and the like can be mentioned, melamine resin is generally widely used.

However, since the PS plate is coated with a photosensitive solution containing ethyl cellosolve and dried and is required to have higher printing durability, higher water resistance and coating strength are required, and a melamine resin as a cross-linking agent for PVA is required. It is not enough to do so alone, and it is better to use a catalyst such as an organic amine salt together.
As a preferred embodiment, the binder used in the dampening water suitability-imparting layer is PVA, a melamine resin, and an organic amine salt in an amount of 2 to 10%, preferably 4 based on the solid content of the binder.
By blending up to 8%, the characteristics are further improved. When the content of the organic amine salt is 2% or less based on the solid content of the binder, the degree of crosslinking is low, and the solvent resistance, water resistance and coating strength tend to be low, and when it exceeds 10%, it is suitable for dampening water. Is less likely to occur, and scumming tends to occur.

However, when a dampening water suitability-imparting layer is provided by directly coating a coating solution for a dampening water suitability-imparting layer, which comprises the above pigment and a binder, when the dampening water suitability-imparting layer is provided, PVA is used as the binder. Since it is mainly composed of, the adhesive force on the support which is a polyester film becomes insufficient. In order to solve this difficulty, a copolyester resin contained as a branched glycol component and an undercoat layer composed of a resin composition containing a block type isocyanate group-containing resin as a main component are provided on the undercoat layer. It is preferable to provide a water suitability imparting layer. The method of applying the undercoat layer to the support is as follows: offline coating applied to the support (white polyester film) after biaxial stretching or dry coating on a uniaxially oriented film, followed by stretching and heat setting. Any of the in-line coating methods obtained by the above may be used.

Further, after the fountain solution suitability-imparting layer is formed, the surface thereof is subjected to corona discharge treatment, flame plasma treatment, electron beam treatment, etc., and then the photosensitive layer is provided, so that other properties are not deteriorated. It is also possible to impart hydrophilicity. The printing plate of the present invention is not limited to these methods, and by using a white polyester film obtained by the following method, a paper, an aluminum plate, a plastic film or the like was used as a substrate. A lithographic printing plate such as a PS plate, a laser beam plate-making (LBP plate), and a pink plate which have excellent bending property and strength after bending can be obtained.

Film strength after bending is 8 kg / mm
^{2. In} order to obtain a white polyester film having a bending angle of 30 degrees or more and 90 degrees or less, the void content (X) contained between the surface of the film and 1/20 of the total thickness is 5 volume. % Or less, 1/20 to 1/4 of the total thickness
The void content (Y) included in the thickness of 5 to 25% by volume, and the void content (Z) included in the thickness of 1/4 to 1/2 of the total thickness is 10% to 25% by volume. It is preferable that the volume ratio is not less than 30% by volume and the difference between Z and Y is not less than 5% by volume and not more than 20% by volume. As shown in the examples, the void content can be controlled by at least selecting the raw material composition of each layer and laminating two or more layers by a method such as a coextrusion method. If the bending angle is less than 30 degrees or more than 90 degrees, the adhesion will be poor when the sheet is bent and brought into close contact with a roll, such as a printing plate such as a lithographic plate, an intaglio plate, and a relief plate. If the film strength after bending is less than 8 kg / mm ^2, preferably less than 10 kg / mm ² , the durability after bending and use is poor. Since the film of the present invention is strong, the initial elastic modulus is preferably 300 kg / mm ² or more. If it is less than this, the film becomes weak.

The condition for the orientation treatment of the polymer mixture is an important point for obtaining a strong film. Therefore, the conditions for achieving the object of the present invention include, for example, the most commonly used sequential biaxial stretching step, in which a continuous sheet of the polymer mixture is roll-stretched in the longitudinal direction and then in the width direction. In the case of the sequential biaxial stretching method in which the tenter stretching is performed, it is as follows. In roll stretching (longitudinal stretching), in order to develop a large number of cavities, the temperature is the second-order transition temperature of polyester + 30 ° C. or less, and the magnification is 2.0 to
The temperature is set to 5.0 and the temperature is set to 80 to 150 ° C. and the magnification is set to 2.8 to 5 times in order to stably form a film without breaking in tenter stretching (transverse stretching). Further, in the present invention, it is desirable to carry out the heat treatment condition after stretching by the method described below. After the stretching, the heat treatment must be performed at 200 ° C. or higher, preferably 220 ° C. or higher, more preferably 230 ° C. or higher. Further, at this time, heat fixation must be performed while relaxing by 3 to 8%. If it is less than 200 ° C or less than 3%, a void-containing film having a heat shrinkage rate at 150 ° C of less than 2%, preferably less than 1.7%, and more preferably less than 1.5% cannot be obtained. The lithographic printing plate thus obtained was excellent in bending property and strength after bending.

[0016]

In the present invention, the polyester is used
This is because the heat resistance and mechanical strength of the void-containing polyester film are satisfied. In the present invention, preferably, a polyester is mixed with a thermoplastic resin incompatible with the polyester to obtain a polymer mixture by dispersing fine particles of a thermoplastic resin incompatible with the polyester in the polyester. This is to form a nucleus of a cavity generated by the next alignment treatment. In the present invention, the polymer mixture is oriented at least uniaxially in order to improve mechanical strength and preferably to generate a large number of fine voids in the polymer mixture. By forming cavities, the film can be made lighter in weight, workability is improved, and price per area is reduced. In addition, the inclusion of voids increases flexibility and enables clear printing when printing or transferring. Further, by containing a cavity, light hiding property and whiteness can be obtained. Further, a large number of protrusions derived from the thermoplastic resin which is incompatible with the polyester are formed on the surface of the film, which enables writing with a pencil or a ballpoint pen. Furthermore, the bending angle of the film is 30 degrees or more 90
The reason for setting the degree to be less than or equal to the degree is to improve suitability when used by bending. Further, the reason why the film strength after bending is 8 kg / mm ² is to improve the durability after bending.

Examples Next, examples and comparative examples of the present invention will be shown. The measurement / evaluation methods used in the present invention are shown below. 1) Intrinsic viscosity of polyester Polyester was dissolved in a mixed solvent of phenol (6 parts by weight) and tetrachloroethane (4 parts by weight) and measured at 30 ° C. 2) Melt Flow Index of Polystyrene Resin Measured at 200 ° C. under a load of 5 kg according to JIS-K7210. 3) Melt flow index of polypropylene resin The measurement was performed according to JIS-K6758-1981.

4) Porosity of X, Y, and Z Layers of Cavity-Containing Film After taking a photograph with a scanning electron microscope in the vicinity of the surface layer of the cross section of the film, a diagram in which the cavities in each region were traced on a tracing film and painted Image processing was performed with an image analyzer, and the void ratio was calculated as an area ratio, and this value was displayed as volume% as it was. -Scanning electron microscope used S-510 scanning electron microscope manufactured by Hitachi Ltd.-Image analysis processor used Luzex IID (Nireco Corporation)

5) Bending angle A film having a width of 15 mm and a length of 40 mm was bent so that a crease was formed in the width direction. A thermal tilt tester (HG-100, manufactured by Toyo Seiki Co., Ltd.) was used for bending, and the temperature was 1.
A load of 5 kgf / mm ² was applied for 1 minute. Then, the load was released, and the film was left in an environment of 25 ° C. and RH of 65% for 5 minutes, and the angle formed by the film on two sides was determined.

6) Film Strength after Bending A film having a width of 15 mm and a length of 100 mm is folded in half under the condition of 5), the film is flattened, and a chuck is used between Shimadzu Corporation Autograph (HG-3000). The strength at the time of breaking by pulling at a length of 40 mm and a pulling speed of 200 mm / min was obtained.

7) Initial elastic modulus It was measured by ASTM D-882-81 (method A). 8) Heat shrinkage The film has a width of 10 mm and a length of 250 mm and is 200 m
Mark at m intervals and fix under a constant tension of 5 g, and mark intervals A
Measure Subsequently, the distance B between the marks after being placed in an oven in an atmosphere of 150 ° C. for 30 minutes under no tension was determined, and the heat shrinkage rate was defined by the following formula: (A−B) / A × 100 (%)

9) Light transmittance According to JIS-K6714, Poic integrating sphere type H.264. T.
The light transmittance of the film was measured using an R meter (manufactured by Nippon Seimitsu Optical Co., Ltd.). The smaller this value is, the higher the hiding property is.

10) Surface Peel Strength Using cellophane tape (18 mm width, made by Nichiban), the surface peel strength was evaluated by a cellophane tape peel test. The peeling angle was in the direction of about 150 degrees while keeping the void-containing film flat. The area of the peeled void-containing film was differentiated as follows. Class 5 ... Peeled off entirely Class 4 ... Almost peeled off Class 3 ... Around half peeled off Class 2 ... Almost peeled off Class 1 ... No peeled off at all

11) Adhesion between the plate and the plate cylinder The adhesion to the plate cylinder when the plate was mounted on the plate cylinder of a TEXEL AR01 type offset printing machine manufactured by Shinanomensi Co., Ltd. was determined as follows. ○: The plate is completely attached from the gripper to the plate cylinder. △: A slight gap is observed between the plate and the plate cylinder from the gripper to the plate cylinder. X: A gap is recognized between the plate and the plate cylinder from the gripper to the plate cylinder.

12) Vividness of printed matter 20,000 sheets of four colors were printed using a TEXEL AR01 type offset printing machine manufactured by Shinanomenshi Co., Ltd. and judged as follows. O: There was no color shift and printing was possible to the end. ×: The plate was torn in the middle of the grip and printing was stopped.

Example 1 Polyethylene terephthalate resin having an intrinsic viscosity of 0.62 was used as a raw material for the X layer, and polyethylene terephthalate resin was used as a raw material for the Y layer in 85% by weight of a melt flow index of 2.0 g / 10 min. % By weight, 5% by weight of titanium dioxide having an average particle size of 0.3 μm,
As a raw material for the Z layer, a polyethylene terephthalate resin was added to 80% by weight to obtain a melt flow index of 2.0 g /
10 minutes General-purpose polystyrene 15% by weight, average particle size 0.3
5 wt% of titanium dioxide of μm was melt-extruded at 290 ° C. from a T-die by separate twin-screw extruders, electrostatically adhered and solidified on a cooling rotary roll, and each layer was X / Y / Z / Y. An unstretched sheet of the polymer mixture with / X = 5/20/50/20/5 μm was obtained. Subsequently, the unstretched sheet was longitudinally stretched 3.5 times at 83 ° C. by a roll stretching machine, then horizontally stretched 3.5 times at 140 ° C. by a tenter, and then heat-treated at 235 ° C. while being relaxed by 4%. A polyester film containing voids was obtained. Thickness is X / Y / Z / Y / X = 5/20/50/20/5 μm
Met. The obtained film characteristics are as shown in Table 1.

A resin having a block type isocyanate group on this film (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd .: Elastron c
0.5 parts of at32 (5% solution), 4 parts of copolyester resin (MDI16 (30% solution) manufactured by Toyobo Co., Ltd.) containing branched glycol as a constituent, colloidal silica (manufactured by Nissan Chemical Co., Ltd .: Snowdex OL (2
0% solution)), 0.3 parts of water, 45 parts of water, and 44.2 parts of isopropyl alcohol.
5) and dried at 160 ° C. for 1 minute to form an undercoat layer having an average coating amount of 0.2 g / m ² .

Next, zinc oxide (manufactured by Sakai Chemical Co., Ltd .:
SAZEX # 2000) 12 parts, 32% of 15% aqueous solution of PVA (Nippon Gosei Co., Ltd .: Gozenol NL-05)
Part, melamine resin (Sumitomo Chemical Co., Ltd .: Sumitec Resin M
3) 2 parts of 80% solution, organic amine salt (Sumitomo Chemical Co., Ltd .:
Accelerator ACX) 1 part of a 35% solution (6% based on the solid content of the binder), 34 parts of water, and 20 parts of isopropylene alcohol, a wire bar (# 10).
Coating and drying at 160 ° C for 1 minute, average coating amount 7g /
A lithographic printing plate precursor having a dampening water suitability-imparting layer of m ² was prepared. Next, H. F. GERERATOR
Using HFSS-201, 250 ~ 3 with 1mm spacing
The dampening water suitability-imparting layer was corona-treated under the condition of 00w. Then, a commercially available positive plate photosensitive solution was applied onto this and dried to prepare a PS plate having an average coating amount of 3 g / m ² . A positive image film was applied to this PS plate, exposed and baked, and developed to prepare a lithographic printing plate. Then, the surface of the planographic printing plate was treated with an etchant (PP Clean H, manufactured by Niken Chemical Co., Ltd.), and then applied to a TEXELAR01 type offset printing machine manufactured by Shinano Kenshi Co., Ltd. to actually print 10,000 sheets of coated paper. The evaluation results are shown in Table 1.

Examples 2 to 5 and Comparative Examples 1 to 4 Example 1 except that the raw materials were changed as shown in Table 1.
A lithographic printing plate was obtained in the same manner as described above.

Example 6 A polyester resin elastomer obtained by copolymerizing dimethyl terephthalate as a dicarboxylic acid component as a raw material, butanediol and polytetramethylene glycol as a glycol component in a molar ratio of 85:15 and anatase type titanium dioxide are shown in Table 1. A lithographic printing plate was obtained in exactly the same manner as in Example 1 except that polyethylene terephthalate was mixed in.

Example 7 A carbon black-containing acrylic resin was applied onto the film of Example 1 to form a conductive intermediate layer. Further on this, photoconductive zinc oxide (Sakai Chemical Co., Ltd., # 4000), acrylic resin LR333 (Mitsubishi Rayon Co., Ltd.) and Acrylic 44-179 (Dainippon Ink and Chemicals, Inc.) 63/7.
The mixture was mixed at a ratio of / 3, 0.1 part of rose bengal (sensitizer) and 90 parts of toluene were added, and the mixture was dried at 160 ° C. for 1 minute to form a photoconductive layer having a solid content thickness of 13 μm. Further, on the surface opposite to the support, potassium titanate whiskers (manufactured by Otsuka Chemical Co., Ltd., TISTAT-PHS), copolyester resin (manufactured by Toyobo Co., Ltd., MD16), water, isopropyl alcohol of 30/30/33/8. Apply the mixture in a ratio with a wire bar (# 10) and apply 1 at 160 ° C.
After minute drying, a back coat layer having a solid content of 0.3 μm was formed. In this way, a wet lithographic printing plate was prepared. The lithographic printing plate of the present invention, compared to a plate using an aluminum plate or paper,
Not only is it easy to handle, it has good flexibility and cushioning properties, but it also has good bendability and the strength of the film after bending, so that it is easy to attach to the plate cylinder. Therefore, a large number of sheets of color can be printed, which is extremely effective as a lithographic printing plate.

[0032]

INDUSTRIAL APPLICABILITY It can be seen that the present invention is very effective as a lithographic printing plate since the easiness of folding and the strength of that portion are high in terms of bendability.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

Claims (3)

[Claims] 1. A polyester film having a light transmittance of 50% or less, a film bending angle of 30 ° or more and 90 ° or less, and a film strength after bending of 8 kg / mm ² or more is used. Planographic printing plate. 2. A polyester containing fine cavities formed by orienting at least uniaxially a polymer mixture in which a thermoplastic resin incompatible with the polyester is mixed, and an apparent specific gravity of 1.05 or more. The lithographic printing plate according to claim 1, which is less than 1.3. 3. The lithographic printing plate as claimed in claim 1, wherein a surface layer made of polyester is provided on at least one surface of the central layer containing a large number of cavities inside.