JP2952970B2 - Lithographic printing plate - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a lithographic printing plate having a low specific gravity, rich in whiteness, and having a hydrophilic resin layer. More specifically, it relates to a lithographic printing plate used as a PS plate.

[Prior Art] A lithographic printing plate generally comprises a hydrophilic non-image portion and a lipophilic image portion. Among them, the PS plate, known as a PS plate, polishes or anodizes the surface of a support metal plate (aluminum plate or zinc plate) to impart hydrophilicity, and makes this a hydrophilic non-image portion. It is manufactured by exposing and developing a photosensitive resin to form an lipophilic image area. In addition, as a printing plate for trial printing or a small number of printing plates for office use, a hydrophilic resin layer (hydrophilic non-image) is provided on water-resistant paper, synthetic paper, plastic film or metal foil as a support. Lipophilic image portion (for example, a toner image by an electrophotographic method, a drawn image by a ballpoint pen or oil-based ink, a printed image by a typewriter, a printed image by thermal recording, etc.) and provided for printing. ing. A lithographic printing plate having such a conventional hydrophilic resin layer has insufficient hydrophilicity and water resistance, has poor coating strength, and has good adhesion to a support (particularly under high humidity). But it was weak. In Japanese Patent Publication No. 2-11440, PVM / MA is used as a hydrophilic resin in an organic solvent.
After once forming a water-insoluble aggregate (copolymer of lower alkyl vinyl ether and maleic anhydride) of the copolymer,
There has been proposed a method of imparting hydrophilicity by treating with an aqueous alkali solution. Although this method improves the printing durability, it involves two steps of production, so that the number of steps is increased, and furthermore, it is necessary to treat with an alkaline aqueous solution, which is disadvantageous in that it is complicated.

In the case of using a plastic film as a support,
Due to lack of cushioning property, there was a defect that the adhesion between the lithographic printing plate and the transfer medium was insufficient during printing.

[Problems to be Solved by the Invention] Accordingly, an object of the present invention is to eliminate these conventional disadvantages, to provide excellent hydrophilicity, water resistance, excellent coating film strength, excellent adhesion to a support, and manufacturing. To provide a lithographic printing plate which is easy to use, has a low specific gravity, and is excellent in cushioning property and whiteness.

[Means for Solving the Problems] As a result of intensive studies, the present inventors have found that a white polyester film having a low specific gravity and a high cushioning property is used as a support, and a specific hydrophilic resin layer is provided on the hydrophilic resin layer. As a result, the inventors have found that the above-mentioned disadvantages can be solved, and completed the present invention.

That is, the present invention provides a lithographic printing plate in which a hydrophilic resin layer and a lipophilic image portion are laminated in this order on a support,
The hydrophilic resin layer is a porous layer, and the support is at 150 ° C.
A lithographic printing plate characterized by being a polyester film having a heat shrinkage of less than 2% and a specific gravity of 0.95 or less.

The present invention is a laminate in which a hydrophilic resin layer composed of a porous layer and a lipophilic image portion are laminated on a support in this order.

The porous layer referred to in the present invention has a layer structure having a large number of voids inside and on the surface of the layer. It is particularly preferable that the void is a so-called through-hole which leads to the outside in the porous layer from the viewpoint of hydrophilicity.

In the present invention, the peak pore size in the pore size distribution curve of the pores of the porous layer is 0.06 to 2.0 μm, preferably 0.08 to 1.0 μm.
m, more preferably 0.1 to 0.5 μm. When the peak pore size of the pore size distribution curve is less than 0.06 μm, the hydrophilicity is insufficient, and the peak pore size in the pore size distribution curve is 2.0 μm.
If it exceeds m, the surface smoothness will be reduced, and there will be a drawback that uneven coating of the lipophilic image area will occur.

Further, the pore area ratio is preferably in the range of 20 to 85%, preferably 30 to 75%, more preferably 35 to 65%. When the pore area ratio is less than 20%, the hydrophilicity tends to decrease. When it exceeds 85%, it is easy to take a form in which holes are partially connected, and bleeding and sharpness tend to decrease.

The pores, when observed from the surface of the porous layer, are independent of each other, and have a roundness r (= b / a, a: major axis diameter of the hole, b: minor axis diameter of the hole) of 1 to 1. A value of 5 is particularly preferred because of good hydrophilicity. This roundness is an average value of 1000 or more measurement points and is usually determined by an image analyzer.

Further, it is desirable that the expansion of the pore size distribution in the pore size distribution curve is smaller, that is, it is desirable to have a sharp pore size distribution, and 50% or more, preferably 60% or more, more preferably 70% or more of the number of pores has a peak pore size of ± 30%. It is desirable to be within.

Next, the center line average roughness of the porous layer surface in the present invention is
0.5 μm or less, preferably 0.3 μm or less, more preferably
When the thickness is 0.1 μm or less, hydrophilicity is good, and pinhole-shaped coating of the lipophilic image layer is less likely to occur.

In the present invention, in order to further enhance the hydrophilicity, those having a surface undulation are preferable. For this purpose, the porous layer preferably satisfies the following conditions. That is, the surface of the porous layer is at least 0.2 μm in height, preferably 0.3 μm.
m, more preferably 0.4 μm or more swell 5/40
It is preferable that it has a size of at least 7 μm, preferably at least 7/40 μm, more preferably at least 10/40 μm. Height is 0.2
If the number of undulations of μm or more is less than 5/40 μm or more, the water absorption speed is low, the printing speed is low, and the workability is reduced.

Furthermore, the waviness index of the porous layer surface is 0.035 to 0.3 μm,
Preferably 0.045 to 0.2 μm, more preferably 0.055 to 0.1
3 μm. If the swell index is less than 0.035 μm,
It is not preferable because of poor hydrophilicity. The swell index is 0.3
If it exceeds μm, pinhole-shaped coating in the lipophilic image area is undesirably increased.

The porous layer of the present invention is obtained by mixing a water-dispersible polymer and a specific colloidal silica in a specific range, and applying the mixture.
It is obtained by drying. Here, the water-dispersible polymer may be an aqueous dispersion of various polymers, and specific examples include an acrylic polymer,
Aqueous dispersions such as ester-based polymers, urethane-based polymers, olefin-based polymers, vinylidene chloride-based polymers, epoxy-based polymers, amide-based polymers, and modified products and copolymers thereof can be used. Use of an acrylic polymer or urethane polymer is preferred because the pore size distribution is sharp and the pore area is large, and an acrylic polymer is particularly preferred in view of the mechanical stability of the coating film and the strength of the coating film.

The polymer used in the present invention is preferably dispersed in water and has a particle shape. When it does not have a particle shape, it cannot be made porous with a polymer dissolved in a water-soluble polymer or an organic solvent. The particles are preferably dispersed in primary particles, but need not necessarily be dispersed in primary particles, and may include secondary particles.

The acrylic polymer suitable as the porous layer-forming polymer of the present invention is at least 40 mol% or more of an acrylic monomer and / or a methacrylic monomer and their ester-forming monomers, acrylic monomers having various functional groups such as acrylic acid and methacrylic acid. Acid, alkyl acrylate, alkyl methacrylate (the alkyl group is a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group,
Ethylhexyl, lauryl, stearyl, cyclohexyl, phenyl, benzyl, etc.), and 2-
Hydroxy-containing monomers such as hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, acrylamide, methacrylamide, N-methylacrylamide, N-methylmethacrylamide, N-methylolacrylamide, N- Amide group-containing monomers such as methylol methacrylamide, N, N-dimethylolacrylamide, N-methoxymethyl methacrylamide, N-phenylacrylamide, N, N-
Amino group-containing monomers such as diethylaminoethyl methacrylate and N, N-diethylaminoethyl acrylate; epoxy group-containing monomers such as glycidyl acrylate and glycidyl methacrylate; salts of acrylic acid and methacrylic acid (sodium salt, potassium salt, ammonium salt, etc.) These can be used in combination with other monomers. Examples of the other monomer include an epoxy group-containing monomer such as acrylic glycidyl ether and a sulfonic acid group such as styrene sulfonic acid, vinyl sulfonic acid and salts thereof (sodium salt, potassium salt, ammonium salt, etc.) or a salt thereof. Monomers, monomers containing carboxyl groups or salts thereof, such as crotonic acid, itaconic acid, maleic acid, fumaric acid, and salts thereof, monomers containing acid anhydrides, such as maleic anhydride and itaconic anhydride, vinyl isocyanate , Allyl isocyanate, styrene, vinyl methyl ether, vinyl ethyl ether, vinyl trisalkoxysilane, alkyl maleic acid monoester, alkyl fumaric acid monoester, acrylonitrile, methacrylonitrile, alkyl itaconic acid monoes Le, vinyl chloride, vinyl acetate, vinylidene chloride and the like.

The above-mentioned monomers are copolymerized using one kind or two or more kinds.

As the colloidal silica to be mixed with 20 to 90 parts by weight of the water dispersion of the above water-dispersible polymer, known colloidal silica can be used. The shape can be appropriately selected from a spherical shape and an irregular shape. Among them, the following silica is suitable for causing undulation in the porous layer.
For example, a porous membrane having a long chain structure in which spherical colloidal silica is connected in a bead shape and a product in which the linked silica is branched can be used to obtain a porous film having a waviness structure on the surface. The colloidal silica is obtained by interposing primary particles of spherical silica with metal ions having a valence of 2 or more.
It is one in which particles are connected, and at least three, preferably five or more, more preferably seven or more are connected, and further includes one in which beads connected in a bead shape are branched.

Further, the particles may be composite or mixed particles of colloidal silica and other inorganic particles, for example, alumina, ceria, titania, or the like, or may be connected by interposing these. The metal ion to be interposed is preferably a divalent or higher valent metal ion, for example, Ca ²⁺ , Zn ²⁺ , Mg ²⁺ , Ba ²⁺ , Al ³⁺ , Ti ⁴⁺
And so on. In particular, when Ca ²⁺ is used, it is suitable for producing colloidal silica linked and branched in a bead shape. The primary particle size of colloidal silica is 5 nm to 100 nm,
When the thickness is preferably 7 nm to 50 nm, more preferably 8 nm to 30 nm, it is preferable in terms of increasing the pore forming property and the pore area ratio.
Further, the undulation of the porous layer is manifested when the silica particles are connected and branched in a rosary, and the larger the number of primary particles of the connected silica is, the more preferable, but usually 3 or more.
It is desirable that the number be less than 100, preferably 5 or more and less than 50, and more preferably 7 or more and less than 30. If the number is two or less, undulation is insufficiently expressed, and if the number is 100 or more, beads linked and / or branched in a bead form tend to be thickened and water dispersibility tends to be poor. The content of the beads in the porous coating film of the beads linked and / or branched is 3 to 80% by weight, preferably 10 to 70% by weight, and more preferably 20 to 60% by weight. 3% by weight content
If it is less than 4, there is no porosity formation and no undulation is exhibited, so that the hydrophilicity tends to decrease. When it is contained in excess of 80% by weight, the hydrophilicity decreases because the porous formability decreases, the pore diameter decreases, and the pore area ratio decreases.
Since the strength of the coating film is inferior, defects such as easy generation of dust at the time of cutting are likely to occur. When it is desired that the surface undulation is small, it is preferable to use colloidal silica that is a spherical single particle that is not connected in a bead shape.

Porosity changes depending on the ratio of the average particle size of the water-dispersible polymer and the colloidal silica, and the average particle size of the colloidal silica needs to be smaller than the average particle size of the water-dispersible polymer. Can not. In the case of the colloidal silica connected in a bead shape, the length of the connected particles observed in an electron microscope in the minor axis direction is defined as the particle diameter, and the average value of 100 measured lengths is defined as the average particle diameter.

The average particle diameter ratio of the water-dispersible polymer / colloidal silica is 2/1 to 1000/1, preferably 5/1 to 500/1, and more preferably 10/1 to 200/1. It is particularly preferable in view of the formability of the polymer.

In particular an average particle size ratio in relation to an average particle size of colloidal silica and (a ₁₎ and the average particle size of the water-dispersible polymer (a ₂₎ is in the above range, and complete one surface water-dispersible polymer particles when the minimum number of particles of colloidal silica necessary to coating was _{α (α = 2π (a 1} + a 2) 2/3 1/2 · a 1 2) , the per average particles of the water-dispersible polymer, 0.3 α
When the compounding ratio is in the range of from 10 to 10α, preferably in the range of from 0.5α to 6α, and more preferably in the range of from 0.7α to 3α, the effect of the present invention is more remarkably exhibited.

Known additives in the porous layer of the present invention within a range not impairing the effects of the present invention, for example, inorganic or organic fine particles, plasticizers, lubricants, surfactants, antistatic agents, crosslinking agents, crosslinking catalysts , A heat-resistant agent, a weather-resistant agent, and the like may be added. In particular, the addition of an antistatic agent is preferable in terms of eliminating the effects of static electricity in the manufacturing process and preventing double feeding when producing a cut sheet-like material, and the addition of a crosslinking agent or a crosslinking catalyst is preferred for coating a porous layer. It is more preferable because toughness, water resistance, chemical resistance and heat resistance are improved.

The method of application is a known method, for example, gravure coat,
Any method such as reverse coating, bar coating, kiss coating, and die coating can be used.

Although the thickness of the porous layer is not particularly limited, it is usually 0.1 to 50 μm.
m, preferably 0.5-30 μm, more preferably 1-20 μm
m is good. If the thickness is too thin, the hydrophilicity is insufficient, and if it is too thick, the strength of the coating film tends to be insufficient.

The polyester film as the support of the present invention has a thickness of 150
The heat shrinkage at 0 ° C. is less than 2%, and the specific gravity is 0.95 or less, preferably 0.90 or less, more preferably 0.80 or less. This is because a soft feeling and flexibility are not imparted to a film larger than 0.95. The flexibility is a necessary item for obtaining a clear printing surface even when the contact pressure between the lithographic printing plate and the transfer medium during printing is reduced. Of course, the feel when touching the hand is also an important factor. For this reason, it is desired that the cushion rate is 10% or more.

The thermal dimensional stability is also important because the film does not deform even in a process to which heat is applied such as thermal transfer, printing, and drying. In particular, the heat shrinkage at 150 ° C. is often important.

The polyester referred to in the present invention is a polymer obtained by condensation polymerization of a diol and a dicarboxylic acid, and examples of the dicarboxylic acid include terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, adipic acid, sebacic acid, and the like. The diol is represented by ethylene glycol, trimethylene glycol, tetramethylene glycol, cyclohexane dimethanol and the like. Specifically, for example, polyethylene terephthalate, polytetramethylene terephthalate, polyethylene-p-oxybenzoate, poly-1,4-cyclohexylene dimethylene terephthalate,
And polyethylene-2,6-naphthalenedicarboxylate. In the case of the present invention, polyethylene terephthalate and polyethylene naphthalate are particularly preferred.

Of course, these polyesters may be homopolyesters or copolyesters, and examples of the copolymerization component include diol components such as diethylene glycol, neopentyl glycol, and polyalkylene glycol, adipic acid, sebacic acid, and phthalic acid. And dicarboxylic acid components such as isophthalic acid, 2,6-naphthalenedicarboxylic acid and 5-sodium sulfoisophthalic acid.

Further, various known additives such as an antioxidant and an antistatic agent may be added to the polyester. Polyethylene terephthalate is preferred as the polyester used in the present invention. The polyethylene terephthalate film is excellent in water resistance, durability, chemical resistance and the like.

Incompatible polymers include poly-3-methylbutene-1,
Poly-4-methylpentene-1, polyvinyl-t-butane, 1,4-trans-poly-2,3-dimethylbutadiene,
Polyvinylcyclohexane, polystyrene, polymethylstyrene, polydimethylstyrene, polyfluorostyrene, poly-2-methyl-4-fluorostyrene, polyvinyl-t-butyl ether, cellulose triacetate, cellulose tripropionate, polyvinyl fluoride, polychlorotrifluoro It is a polymer with a melting point of 200 ° C or higher selected from ethylene and the like. In the case of the present invention, poly-4-methylpentene-1, cellulose triacetate, and modified products thereof are particularly preferable in terms of price, heat stability, dispersibility with polyester, and the like. Of course, the melting point of the incompatible polymer must be 200 ° C. or higher, preferably 210 ° C. or higher, and more preferably 220 ° C. or higher.
If the temperature is lower than 00 ° C., the dispersed shape of the incompatible polymer in the polyester film does not take a spherical shape, often takes a flat, layered shape, and a highly cushioning polyester film cannot be obtained. . Further, the melting point of the incompatible polymer is preferably 300 ° C. or lower, preferably 280 ° C. or lower, more preferably 260 ° C. or lower. This is because the incompatible polymer does not dissolve unless the temperature is lower than the melt extrusion temperature of the polyester.

The addition amount of the incompatible polymer is preferably 3 to
The content is 30% by weight, more preferably 5 to 20% by weight. When the amount is less than 3% by weight, not only is it difficult to obtain a specific gravity of the polyester film of the present invention of 0.95 or less, but also it is difficult to obtain a white polyester film having a whiteness of 80% or more,
Further, it is difficult to obtain a polyester film having a high cushioning rate of 10% or more and excellent in cushioning property. Conversely, when the amount of the immiscible polymer is 30
When the amount exceeds 10% by weight, not only the mechanical properties of the polyester film of the present invention are inferior, but also the thermal dimensional stability is inferior, and the heat shrinkage at 150 ° C. is as large as 5% or more. Because it is.

Next, the low specific gravity agent is a compound having an effect of reducing specific gravity by adding to polyester, and the effect is recognized only for a specific compound.

For example, polyalkylene glycols such as polyethylene glycol, methoxypolyethylene glycol, polytetramethylene glycol, and polypropylene glycol, ethylene oxide / propylene oxide copolymers, and sodium dodecylbenzene sulfonate;
Representative examples thereof include sodium alkylsulfonate, glycerin monostearate, and tetrabutylphosphonium paraaminobenzenesulfonate. In the case of the present invention, polyethylene glycol is particularly preferred. The specific gravity of the polyester film is reduced to 0.
It can be reduced by more than 1g / cc. further,
The addition of the low specific gravity agent has the effect of improving the whiteness of the polyester film, smoothing the surface, improving the wall opening resistance, and greatly improving the stretchability of the polyester. The amount of the low specific gravity agent added in the present invention is preferably 0.1 to 5% by weight, and more preferably 0.5 to 3% by weight. When the addition amount is less than 0.1% by weight, the specific gravity of the polyester film does not become low, the film does not become a soft film, and the specific gravity of the polyester film is 0.95 or less, preferably 0.90 or less, more preferably 0.85% or less.
This is because it is difficult to be below. Conversely, if the amount of the additive exceeds 5% by weight, not only the effect of reducing the specific gravity is not recognized, but also
This is because the whiteness of the film decreases and the b value becomes a large positive value.

Next, it is preferable that the immiscible polymer has a nearly spherical shape in the polyester film, that is, the shape factor is in the range of 1 to 4. Even if an incompatible polymer is added to the polyester film, the film properties obtained by the shape of the incompatible polymer, especially the correlation between the specific gravity of the film and the cushion rate, thermal dimensional stability, surface roughness, whiteness, etc. A big difference arises. In other words, when the shape of the immiscible polymer is close to spherical, not only can the specific gravity be reduced compared to the case where the incompatible polymer is dispersed in layers,
A film having high whiteness and a high cushioning ratio and good thermal dimensional stability can be obtained. It is predicted that the dispersion in a shape close to a spherical shape strongly depends on the viscosity, compatibility parameter, melting point, type of low specific gravity agent, addition amount, etc. of the incompatible polymer added to the polyester. It is very difficult. The shape close to a spherical shape means that the ratio of the major axis to the minor axis of the incompatible polymer dispersed in the film is 1
To 4, preferably 1 to 2.

Of course, if the thermal dimensional stability of the obtained film is not low, it cannot be used in a process in which a lithographic printing plate is subjected to heat in the process of producing it. That is, the heat shrinkage in both longitudinal and width directions at 150 ° C. must be less than 2%, preferably less than 1%. For this purpose, the polyester film needs to be heat-treated at 200 ° C. or more, preferably 220 ° C. or more, and may be subjected to a relaxation treatment.

The whiteness of the polyester film is preferably 80% or more, more preferably 90% or more. Further, the color tone b value obtained by the color difference meter is -3 or less, preferably -4 or less, and-.
It is good to be 20 or more. As the b value is smaller, the apparent whiteness of the film is improved, giving a high-quality image.

The color tone changes depending on the addition of the above-mentioned incompatible polymer or low specific gravity agent, but if necessary, a fluorescent whitening agent may be added. As optical brighteners, trade name "Ubitek" OB,
MD (Ciba-Geigy), "OB-1" (Eastman) and the like.

In the polyester film of the present invention, fine particles such as calcium carbonate, amorphous zeolite particles, anatase type titanium dioxide, calcium phosphate, silica, kaolin, talc and clay may be used in combination. The amount of these additives is preferably 0.005 to 25 parts by weight based on 100 parts by weight of the polyester composition. In addition to the fine particles, fine particles precipitated by the reaction between the catalyst residue and the phosphorus compound in the polyester polycondensation reaction system can be used in combination. As the precipitated fine particles, for example, those composed of calcium, lithium and phosphorus compounds, or those composed of calcium, magnesium and phosphorus compounds, and the like, the content of these particles in the polyester is based on 100 parts by weight of the polyester It is preferably 0.05 to 1.0 part by weight.

Next, a method for producing the film of the present invention will be described.
It is not limited to such an example.

Mix 4-methylpentene-1 polymer as an incompatible polymer, polyethylene glycol as a low specific gravity agent, and polyethylene terephthalate, and mix them thoroughly.
It is fed to the extruder A which has been dried and heated to a temperature of 270-300 ° C. If necessary, polyethylene terephthalate containing an inorganic additive such as TiO ₂ , SiO ₂ , CaCO ₃ is supplied to the extruder B by a conventional method, and the extruder B is placed in the three-layer die of the T die.
It may be laminated to three layers of B / A / B so that the polymer of the layer comes to both surface layers.

The melted sheet is tightly cooled and solidified by electrostatic force on a drum cooled to a drum surface temperature of 10 to 60 ° C., and the unstretched film is guided to a group of rolls heated to 80 to 120 ° C.
The film is longitudinally stretched 2.0 to 5.0 times in the longitudinal direction, and cooled with a group of rolls at 20 to 30 ° C.

Subsequently, the longitudinally stretched film is guided to a tenter while gripping both ends of the film with clips, and is horizontally stretched in a direction perpendicular to the longitudinal direction in an atmosphere heated to 90 to 140 ° C.

The stretching ratio is 2 to 5 times each in the vertical and horizontal directions, and the area ratio (longitudinal stretching ratio × lateral stretching ratio) is preferably 6 to 20 times. If the area magnification is less than 6 times, the whiteness of the obtained film becomes poor, and if it exceeds 20 times, the film tends to be broken at the time of stretching and the film forming property tends to be poor.

In order to impart the planarity and the dimensional stability of the biaxially stretched film in this manner, the film is heat-set at 150 to 230 ° C. in a tenter, uniformly cooled, cooled to room temperature, and wound up. Get the film.

When the film has been subjected to a surface treatment by a known method, that is, a film subjected to a corona discharge treatment (in air, nitrogen, carbon dioxide gas or the like) or an easy adhesion treatment, adhesion to the porous layer, water resistance It can be more preferably used because the solvent resistance and the like are improved. A variety of well-known methods can be used for the easy-adhesion treatment.Acrylic-based, urethane-based, polyester-based or the like or a blend of these in the film manufacturing process, or those coated with various easy-adhesives such as those grafted, Alternatively, a film obtained by applying the above-mentioned various adhesives to a film after uniaxial or biaxial stretching can be suitably used.

The thickness of this film is not particularly limited, but is usually 1 μm.
It is desirably not less than 1 mm and preferably not less than 10 μm and not more than 800 μm, more preferably not less than 30 μm and not more than 600 μm. The center line average roughness of this film is 0.001-0.3μ
m, preferably 0.005 to 0.2 μm, more preferably 0.01 to
Preferably, it is 0.1 μm.

By imparting an antistatic property to at least one surface of a laminate obtained by laminating a hydrophilic resin layer composed of a porous layer on the support of the present invention, or eliminating the influence of static electricity in the production process, or a cut sheet-like material Double feed during production can be prevented. The antistatic treatment may be performed on either the porous layer or the other surface of the film provided with the porous layer. The antistatic treatment preferably has a surface resistivity of 10 ⁸ to 10 ¹² Ω / □, and these may be mixed with a known antistatic agent in the porous layer within a range that does not impair the effects of the present invention. Can be obtained by coating on a surface on which a porous layer is not provided. In particular, when the treated layer containing 5 to 40% by weight of sulfonated polystyrene is used as the undercoat layer, the adhesion to the porous layer is also excellent, which is more preferable.

In the present invention, a hydrophilic resin layer comprising the porous layer is formed on the support, and thereafter, a lipophilic image area is formed by a usual method to obtain a target lithographic printing plate.

Examples of the method for forming the lipophilic image area include a method of forming a toner image by an electrophotographic method, a method of forming a drawn image with a ballpoint pen or oil-based ink and a print image by a typewriter, and a method of photoengraving using a photosensitive resin (process). : Coating, exposure, and development). In the case of the photoengraving method, both negative type and positive type photosensitive resins can be used as the photosensitive resin. Negative types include those obtained by mixing a diazo resin and an alkali-soluble hydrophobic resin, those using p-diazoquinone, and a photopolymerizable photopolymer type obtained by mixing a vinyl monomer and a photopolymerization initiator in an alkali-soluble hydrophobic resin. And a dimerized photopolymer having a photocrosslinkable side chain. A generally known outer type photosensitive resin can also be used. As the positive type photosensitive resin, a combination of orthonaphthoquinone azide and a phenol resin can be used.

In this way, the support of the present invention has a cushioning property at a low specific gravity, and a lithographic printing plate having a hydrophilic resin layer composed of a porous layer can be obtained. The printing ink may be applied to the lipophilic image area by applying water.

[Effects of the Invention] In the present invention, since a porous hydrophilic resin layer and a lipophilic image area are laminated in this order on a specific support, the hydrophilic resin layer has excellent hydrophilicity, water resistance, and excellent coating film strength. An inexpensive lithographic printing plate having excellent adhesion to the body, easy production, low specific gravity, excellent cushioning properties and whiteness was obtained.

Therefore, the planographic printing plate of the present invention can be used not only as a normal PS plate, but also as a small number printing plate for office use, a printing plate for trial printing, and the like.

[Measurement of Physical Properties and Method of Evaluating Effect] Methods of evaluating physical properties and effects of the present invention are as follows.

(1) Surface roughness According to JIS B0601-1976, cutoff 0.25mm, measuring length 4
The center line average roughness Ra and the maximum roughness Rt were determined in mm (μ
m).

(2) Equivalent sphere equivalent diameter of voids A cross section cut in the machine direction or its vertical direction in the film forming process is taken at a magnification of 1000 to 5000 times with a scanning electron microscope, and at least the specified thickness range Ten
The distribution of the diameter of a circle corresponding to the area of the void was obtained by applying an image analyzer of zero or more voids. The volume average diameter of this distribution is defined as the average sphere equivalent diameter of the voids.

(3) Specific gravity A carbon tetrachloride-n-heptane-based density gradient tube
The value at ° C was used.

(4) Overlay the optical density OD film to a thickness around 150 μm,
It is measured with an optical densitometer (TR927 manufactured by Macbeth). The thickness and the optical density were plotted, and the optical density corresponding to the thickness of 150 μm was defined as the optical density converted to the thickness of 150 μm.

(5) Whiteness Based on JIS-L-1015, UV-260 manufactured by Shimadzu Corporation
, The reflectance at a wavelength of 450 nm is B (%), the wavelength is 550
Assuming that the reflectance at nm is G (%), the whiteness (%) was determined by the following equation.

Whiteness (%) = 4B-3G (6) Color Tone The surface color of the film was measured using a color difference meter manufactured by Nippon Denshoku Industries Co., Ltd.
The measurement was carried out at 80 and judged by the obtained L value, a value and b value.

(7) Stretchability When a film was continuously formed for 24 hours, a film having no film tear was evaluated as “good”, and a film having two or more film breaks was evaluated as “breakable”.

(8) Slit chips When the film of the present invention is cut with a single-blade razor for 24 hours,
The case where white powder was adhered to the leather was defined as "generated".

(9) Cushion ratio (%) Standard gauge 90930 is used for dial gauge No.2109-10 manufactured by Mitoyo Seisakusho Co., Ltd.
Use No.7001DGS-M to apply load to dial gauge holding part
Each film thickness when 50g and 500g are applied
It is obtained from d ₅₀ and d ₅₀₀ by the following equation.

(10) Shape factor The shape of the incompatible polymer in the cross section of the film is subjected to an image analyzer in the same manner as when the average diameter of the voids is determined, and is expressed as a ratio of 100 average major axis / minor axis.

(11) Pore size distribution curve Mark the pores in the electron micrograph taken at 10,000 times, and perform image processing using a QUant: met-720 type image analyzer (manufactured by Image Analyzing Computer) to determine each pore size. The area between the minimum pore diameter and the maximum pore diameter when converted to a perfect circle was divided in units of 10 μm, and the number of holes in each division was measured. From this measured value, a pore size distribution curve was drawn with the vertical axis being the number of pores per unit area and the horizontal axis being the pore size, and the pore size at the peak was determined.

(12) Pore area ratio The area occupied by pores per unit area was calculated from the above pore diameter distribution curve by the following equation.

ai: Average pore diameter in each division when the pore diameter in the measurement area is divided in units of 10 μm ni: Number of holes in each division when the pore diameter in the measurement area is divided in units of 10 μm A: Measurement area ( 13) Center line average roughness Measured at a cutoff of 0.25 mm according to JIS B 0601-1976.

(14) Height of undulation, number of undulations, undulation index Using a scanning electron microscope ESM-3200 (manufactured by Elionix Inc.) equipped with a cross-section measuring device PMS-1, the surface irregularities observed at a magnification of 3000 times were measured. 0 above the surface roughness curve.
When the valleys adjacent to the peaks of 2 μm or more were connected by a straight line, the number of the peaks in the measurement length of 40 μm was measured, and the number of undulations having a undulation height of 0.2 μm or more was determined.

The center line average roughness (Ra ₁₀ ) at a cut-off of ₁₀ μm and the center line average roughness (Ra ₁ ) at a cut-off of 1 μm were obtained from the surface roughness curve, and the undulation index was calculated by the following equation.

The undulation index (μm) = Ra ₁₀ −Ra ₁ The number of undulations and the undulation index were average values of 50 measurement points.

(15) Hydrophilicity Printing was carried out using a fountain solution with a lithographic printing press, 1000 copies were printed, and judged according to the following criteria.

：: No abnormality in printed matter and printing plate.

X: The printed matter has background stains.

(16) Clarity and bleeding of the printed surface The surface of the printed surface printed by the above method was visually observed, and the presence or absence of a transfer defect (a portion where ink was not transferred) was determined based on the following criteria. In addition, the blur of the ink was determined by observing the boundary between the printed portion and the non-printed portion with a 100-fold optical microscope, and the presence or absence of the blur at the boundary surface was determined based on the following criteria.

転 写 No transfer bleeding or bleeding was observed.

○ There is no transfer bleeding, but the surface gloss is slightly reduced, and slight bleeding is observed.

Δ 1 to 5 transfer bleeds, which can be visually judged, are present in 10 cm ^2, and the boundaries are not clear.

× There are countless spots in the transfer, and bleeding is large.

(17) Coating Strength The surface of the porous layer was subjected to a cross cut of 1 mm square, and a 90 ° peel test was performed using a cellophane adhesive tape manufactured by Nichiban Co., Ltd., and the evaluation was made based on the residual ratio of the porous layer.

Residual rate 80% or more: [○] Residual rate less than 80%: [×] (18) Average particle diameter Particle diameter by laser light scattering method using a COULTER N4 submicron particle analyzer (manufactured by Nikkaki Co., Ltd.) Was determined as an average value of 10 measurements. When measurement was not possible by this method, it was determined from a 200,000 magnification electron micrograph.

(19) Average number of particles The average number of particles contained in 1 ml of an aqueous dispersion of V wt% was obtained from the following equation based on the average particle diameter a obtained as described above and the particle specific gravity ρ obtained by the density gradient method.

[Examples] Next, embodiments of the present invention will be described based on examples.

Example 1 Polyethylene terephthalate (intrinsic viscosity [η] = 0.6
5) 88% by weight, 10% by weight of poly-4-methylpentene-1 (TPX-d820, Mitsui Petrochemicals Co., Ltd.), and 2% by weight of 4000% molecular weight polyethylene glycol were mixed into extruder A. Supply and melt at 285 ° C by the usual method
It was introduced into the central layer of the layer composite die.

On the other hand, a raw material obtained by adding 10% by weight of calcium carbonate (average particle diameter: 0.8 μm) and 0.01% by weight of an optical brightener “OB-1” to 90% by weight of the above polyethylene terephthalate was supplied to an extruder B, and the mixture was subjected to a conventional method. Melted at 285 ° C, laminated on both surface layers of T-die three-layer composite die,
On a cooling drum kept at 25 ° C., it was tightly cooled and solidified by an electrostatic charge method. Then, cast the sheet in the longitudinal direction according to the usual method.
Using a roll group heated to 98 ° C, stretched 3.5 times, 25
Cooled to ° C. Furthermore, the stretched film was guided to a tenter and stretched 3.2 times in the width direction in an atmosphere heated to 125 ° C.
The film was thermally solidified at 225 ° C. to obtain a film having a thickness of 250 μm. The thickness of the film is 12.5 μm for the surface layer and 220 μm for the center layer.
m (film support (I)).

After the surface of the stretched film was subjected to a discharge treatment in air, the following coating agent was applied and dried at 130 ° C. for 2 minutes to obtain a surface porous film.

[Coating Material Composition] 70 parts by weight (solid content weight ratio) of an acrylic polymer emulsion (methyl methacrylate / ethyl acrylate / acrylic acid (60/35/5 wt%) copolymer) having an average particle diameter of 0.2 μm and a branched beaded colloid Silica (Snowtex
30 parts by weight (solid content weight ratio) of UP (manufactured by Nissan Chemical Industries, Ltd., average particle diameter 0.015 μm) were mixed and diluted with water to obtain a 30% by weight coating material.

Next, a positive photosensitive liquid was applied thereon and dried to obtain a positive PS plate. A positive image was applied to the PS plate, exposed and baked, and then developed to produce a lithographic printing plate. Using this lithographic printing plate, printing was performed using a fountain solution on a lithographic printing press.

Table 1 summarizes the characteristics of the lithographic printing plate. As is evident from Table 1, the support is a low-density polyester film having excellent heat stability, high cushioning properties and high whiteness. Further, the hydrophilic resin layer composed of a porous layer, the peak pore diameter in the pore diameter distribution curve, the pore area ratio, the center line average roughness is within the range of the present invention, as a lithographic printing plate, hydrophilicity, sharpness, bleeding In each case, excellent characteristics were exhibited, no abnormality was observed in the plate, and good printed matter was obtained.

Examples 2 to 3 A lithographic printing plate was obtained in the same manner as in Example 1 except that the amount of the low specific gravity polyethylene glycol (PEG) used in Example 1 was changed to 0.8 and 0.2 in the order of Examples 2 and 3. Was.

Table 1 shows the properties of the obtained lithographic printing plate. It can be seen that a support having a low specific gravity and excellent thermal dimensional stability can be obtained by the addition amount of the low specific gravity agent polyethylene glycol.

Example 4 A lithographic printing plate was obtained in the same manner as in Example 1, except that spherical colloidal silica having an average particle size of 0.015 μm was used in place of the branched beaded colloidal silica in the coating composition of Example 1.

 Table 1 shows the characteristics of the obtained lithographic printing plate.

Examples 5 to 7, Comparative Examples 1 to 3 In the coating composition of Example 1, the average particle diameter of the acrylic polymer emulsion and the branched beaded colloidal silica,
A lithographic printing plate having the characteristics shown in Table 1 was obtained in the same manner as in Example 1 except that the solid content was changed as follows.

All of those having the porous layer formed thereon exhibited good characteristics.

Comparative Example 4 The same evaluation was performed using only the film support (I) of Example 1. However, since the porous layer was not formed, the applicability of the photosensitive material was poor, and the hydrophilicity was poor. Could not be used.

Example 8 A lithographic printing plate was prepared in the same manner as in Example 1 except that a negative photosensitive solution was used instead of the positive photosensitive solution. Using this lithographic printing plate, printing was performed using a fountain solution on a lithographic printing press. Excellent characteristics were exhibited as in Example 1.

Example 9 A support having a hydrophilic resin layer composed of a porous layer obtained in Example 1 was set in an electrophotographic copying machine, a desired original image was copied on the hydrophilic layer, heat-fixed, and A lipophilic image was obtained. Even when offset printing was performed using this printing plate in the same manner, no abnormality was observed in the plate, and a good printed matter was obtained.

Continuation of the front page (56) References JP-A-3-173692 (JP, A) JP-A-2-225088 (JP, A) JP-A-4-49093 (JP, A) JP-A-62-218969 (JP) , A) JP-A-58-181692 (JP, A) JP-A-63-147690 (JP, A) Japanese Utility Model Showa 50-85301 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB Name) B41N 1/14

Claims (9)

(57) [Claims] 1. A lithographic printing plate having a hydrophilic resin layer and a new oily image portion laminated in this order on a support, wherein the hydrophilic resin layer is a porous layer, and the support is at 150 ° C. A lithographic printing plate comprising a polyester film having a heat shrinkage of less than 2% and a specific gravity of 0.95 or less. 2. The lithographic printing plate according to claim 1, wherein an incompatible polymer is dispersed and mixed in the polyester film, and the shape factor of the incompatible polymer in the film is from 1 to 4. . 3. The incompatible polymer is a methylbutene polymer,
The lithographic printing plate according to claim 2, wherein the lithographic printing plate is a polymer having a melting point of 200C or more selected from a methylpentene polymer, a styrene-based polymer, a fluorine-based polymer, cellulose acetate, and a cellulose propionate polymer. 4. The lithographic printing plate according to claim 1, wherein the color tone b value of the polyester film determined by a color difference meter is -3 or less. 5. The lithographic printing plate according to claim 1, wherein the polyester film is obtained by adding a low specific gravity agent to polyester. 6. A polyalkylene glycol as the low specific gravity agent,
Ethylene oxide / propylene oxide copolymer,
The lithographic printing plate according to claim 5, wherein the lithographic printing plate is selected from an alkyl benzene sulfonate, an alkyl sulfonate and a modified product thereof. 7. The lithographic printing plate according to claim 1, wherein a peak pore size in a pore size distribution curve of the porous layer is 0.06 to 2.0 μm. 8. The lithographic printing plate according to claim 1, wherein the pore area ratio of the porous layer is from 20 to 85%. 9. The lithographic printing plate according to claim 1, wherein a center line average roughness of the porous layer is 0.5 μm or less.