JP2003167330A - Heat sensitive composition, original plate for planographic printing plate and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat sensitive composition forming a latent image upon irradiation with light, capable of forming a high resolution image only upon development without requiring a preheating step and free of lowering of developability due to storage at high temperature and high humidity, to provide an original plate of a planographic printing plate using the heat sensitive composition, capable of direct plate making from digital signals of a computer or the like and exhibiting high printing resistance and to provide an image forming method for the original plate. <P>SOLUTION: The heat sensitive composition contains thermoplastic resin particles containing 60-85 mass% styrene or styrene derivative and 15-40 mass% acrylic acid or methacrylic acid as essential constituent monomers, a material which absorbs light and generates heat, and water, wherein the average particle diameter of the thermoplastic resin particles is 2 to <5 nm. The original plate of a planographic printing plate has a dry coating film of the composition on the hydrophilic surface of a support. In the image forming method, a latent image is formed in the original plate by irradiation with laser light and development is carried out with an alkaline developing solution. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive composition, a lithographic printing plate precursor used in the field of offset printing, and an image forming method.
P) A heat-sensitive composition for a lithographic printing plate precursor used as a plate, a lithographic printing plate precursor, and an image forming method.

[0002]

2. Description of the Related Art A PS plate has long been used as a lithographic printing plate precursor used in the field of offset printing. The PS plate is one in which a thermosensitive resin layer is formed on a substrate having a surface that has been subjected to a hydrophilic treatment, and an image is formed by a photolithography technique such as exposure and development through a silver salt mask film.

On the other hand, with the recent development of computer image processing technology and laser technology, a computer-to-plate (CTP) system for drawing digitized image information on a lithographic printing plate using a laser has been proposed, and has been spotlighted. Taking a bath. The lithographic printing plate precursor (CTP plate) used in the CTP system uses a photosensitive type using a silver salt or a high-sensitivity photopolymer sensitizer sensitive to visible light or ultraviolet light, and an infrared absorber (IR absorber). , And a heat-sensitive type using a sensitizer which is sensitive to heat generated by absorbing near-infrared light or infrared light. Since the photosensitive type has high sensitivity, a low output laser can be used, but the storage stability is poor, and further work in a dark room is required, which is problematic in handling and workability.
On the other hand, the thermal type has lower sensitivity than the photosensitive type,
Recently, a compact and high-power near-infrared laser has been developed. It is insensitive to visible light and ultraviolet light, and is excellent in workability in a bright room (bright place). It has become popular.

An example of such a CTP plate is Japanese Patent Laid-Open No. 7-2.
Japanese Patent No. 0629 discloses a CTP plate in which a photosensitive layer made of a resole resin, a novolac resin, a latent Bronsted acid, and an infrared absorber is formed on a support. This is because the infrared absorber in the laser irradiation part absorbs the laser to generate heat, and the heat decomposes the Bronsted acid to generate an acid, and the acid serves as a catalyst to cause a cross-linking reaction to generate an alkaline developer. It is a system that becomes insoluble in and forms images. The plate obtained by this system has excellent printing durability, but requires a certain amount of energy for the crosslinking reaction,
The ability to form an image is poor only with the heat generated by laser irradiation. That is, because of the low sensitivity, it was necessary to perform development by heating (preheating) and applying energy before the development to strongly crosslink the latent image.

On the other hand, as a thermosensitive CTP plate, in particular, a CTP plate of a type in which resin particles are contained in the thermosensitive layer and which does not require a preheating step is under development. This utilizes the phenomenon that resin fine particles are melted and fused by heat, and the thermosensitive layer consisting of the resin fine particles and the IR absorber is irradiated with light, and the heat generated by the IR absorber in the irradiated portion causes thermoplasticity. After the resin particles are fused to form an image latent image, the unexposed portion is removed by development to form an image. Since the latent image portion has reduced solubility in a developing solution due to light irradiation, an image can be formed only by washing with a developing solution.

For example, Japanese Patent Laid-Open No. 9-171249,
Japanese Patent Application Laid-Open No. 11-268225 discloses a method for making a lithographic printing plate precursor using a hydrophobic resin fine particle and an image forming material composed of a hydrophilic binder or an alkali-soluble resin. However, the image forming layer of the printing plate produced by these production methods contains an alkali-soluble resin or a hydrophilic binder as a binder resin, and if this ratio is high, even the image area is removed during development. However, there are problems that image defects occur and that the developability deteriorates when the obtained lithographic printing plate precursor is stored for a long time under high temperature and high humidity.

On the other hand, Japanese Patent Laid-Open No. 9-127683 discloses a lithographic printing plate precursor in which a self-water-dispersible thermoplastic resin fine particle layer capable of being lipophilic by heat is formed on a substrate having a hydrophilic surface. Further, in JP-A No. 11-348446, a heat-sensitive material containing a substance having a hydrophilic surface, which absorbs light to generate heat, anionic self-water-dispersible resin particles and a fluorine-based surfactant, is disclosed. A lithographic printing plate precursor having a functional composition layer is disclosed. Since the resin fine particles are alkali-soluble or hydrophilic, it is not necessary to use a binder resin having alkali-solubility and a printing plate excellent in developability and resolution can be obtained. However, for such an original plate, there is a strong demand for an original plate having more excellent heat and heat storage stability, and even when the original plate is stored particularly under high humidity, the progress of particle fusion in the heat-sensitive composition layer. Therefore, there is a strong demand for an original plate that is free from the problem of deterioration in developability. That is, a heat-sensitive C type resin fine particle fusion system excellent in developability, printing durability, etc., and excellent in storage stability under high temperature and high humidity.
At present, there is a strong demand for the TP version.

[0008]

The problem to be solved by the present invention is to form a latent image by irradiation of light, and to form a high resolution image only by development without the need for a preheating step, and A heat-sensitive composition that does not deteriorate in developability by storage under high temperature and high humidity, and a lithographic plate that uses the heat-sensitive composition and can be directly plate-made from a digital signal of a computer or the like and exhibits high printing durability. An object is to provide a printing plate precursor and an image forming method thereof.

[0009]

That is, in order to solve the above problems, the present invention provides 60 to 85% by mass of styrene or a styrene derivative and 15 to 40% by mass of acrylic acid or methacrylic acid as essential constituent monomers. Contains thermoplastic resin particles, a substance that absorbs light to generate heat, and water,
Provided is a thermosensitive composition in which the thermoplastic resin particles have an average particle diameter of 2 nm or more and less than 5 nm.

In order to solve the above-mentioned problems, the present invention provides a support surface having a hydrophilic surface with 60 to 85% by mass of styrene or a styrene derivative as an essential constituent monomer and 15 or 15% of acrylic acid or methacrylic acid. To 40% by mass of thermoplastic resin particles, a substance that absorbs light to generate heat, and water, and a thermosensitive composition having an average particle diameter of the thermoplastic resin particles of 2 nm or more and less than 5 nm is dried. Provided is a lithographic printing plate precursor having a coating film.

In order to solve the above-mentioned problems, the present invention provides a support having a hydrophilic surface with 60 to 85% by mass of styrene or a styrene derivative as an essential constituent monomer and 15 or 15% of acrylic acid or methacrylic acid. To 40% by mass of the thermoplastic resin particles, a substance that absorbs light to generate heat, and water, and the thermoplastic resin particles have an average particle size of 2 nm or more and less than 5 nm. An image forming method is provided in which a lithographic printing plate precursor having a photosensitive layer is irradiated with a laser beam to form an image latent image, and then the latent image is developed using an alkaline developer having a pH of 9 to 13.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The heat-sensitive composition of the present invention contains thermoplastic resin particles, a substance that absorbs light to generate heat, and water, and a coating film made of this material absorbs light. A substance that generates heat by receiving light is converted to light energy by being irradiated with light, and the heat generated at that time causes the thermoplastic resin particles to melt and fuse. The planographic printing plate precursor of the invention has a dry coating film of the heat-sensitive composition of the invention on the surface of a support having a hydrophilic surface. Then, by irradiating the coating film with light, the generated heat fuses the thermoplastic resin particles to form an image latent image, and then the unexposed portion is removed with a developer to form an image. . Since the latent image portion has a reduced solubility in a developing solution, an image can be formed only by washing the unexposed area with the developing solution.

The thermoplastic resin particles used in the present invention contain styrene or a styrene derivative as an essential constituent monomer.
~ 85 mass%, acrylic acid or methacrylic acid 15 to 4
It is a resin particle containing 0% by mass (hereinafter, abbreviated as thermoplastic resin particle used in the present invention). Examples of the styrene derivative include 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-methoxystyrene and 4-methylstyrene.
Phenylstyrene, 4-chlorostyrene, 3,4-dichlorostyrene, 4-ethylstyrene, 2,4-dimethylstyrene, 4-n-butylstyrene, 4-tert-butylstyrene, 4-n-hexylstyrene, 4- Examples thereof include n-octyl styrene, 4-n-nonyl styrene, 4-n-decyl styrene, 4-hydroxy styrene, 4-acetoxy styrene, 4-chloromethyl styrene and pn-dodecyl styrene.

The average particle diameter of the thermoplastic resin particles used in the present invention is 2 nm or more and less than 5 nm. 2nm or more and 5nm
The particle size of less than means that the peak of the particle size distribution obtained by a particle size measuring device by a light scattering method is in the range of 2 nm or more and less than 5 nm. The smaller the particle size of the thermoplastic resin particles, the larger the surface area of the particles, so that the particles can be fused with lower thermal energy, and the sensitivity becomes high.
Further, the smaller the particle size of the particles, the better the film-forming property,
In order to obtain a smooth coating film having excellent film strength, it is preferable that the particle size is small within the above range. However, if the average particle size is less than 2 nm, it becomes difficult to measure the particle size itself, and the molecular weight of the thermoplastic resin forming the particles becomes small, and the image area of the printing plate after image formation is weak, resulting in poor printing durability. There is a tendency. On the other hand, when the average particle size is 5 nm or more, the sensitivity and printing durability tend to be lowered.

Generally, when the particle size is reduced to increase the sensitivity, the storage stability tends to decrease. When a high acid value resin having a large amount of carboxyl groups and the like is used for the purpose of improving storage stability, particularly heat and heat storage stability, the solubility of the particles in the developing solution becomes too high, and the solubility of the exposed portion does not sufficiently decrease. , Brings about a decrease in sensitivity.

In the present invention, an average particle size of 2 nm or more and less than 5 nm, which is made of a thermoplastic resin containing 60 to 85% by mass of styrene or a styrene derivative and 15 to 40% by mass of acrylic acid or methacrylic acid as essential constituent monomers. It was found that by using thermoplastic resin particles, a heat-sensitive composition having an excellent balance between sensitivity and storage stability can be obtained. That is, in order to increase the hydrophobicity of the particles and further reduce the solubility in a developing solution, the content of styrene or a styrene derivative is set to 60 to 85% by mass, and in order to improve the wet heat storage stability, acrylic acid is used. Alternatively, the content of methacrylic acid is set to 15 to 40% by mass. By using the thermoplastic resin particles having a particle diameter of 2 nm or more and less than 5 nm, which contains the above-mentioned monomer as an essential component, it is possible to obtain a heat-sensitive composition having an excellent balance between sensitivity and storage stability.

15 to 40 acrylic acid or methacrylic acid
The amount of carboxyl groups in 100 g of the thermoplastic resin contained by mass% is in the range of 208 to 555 mmol when acrylic acid is used and 174 to 465 mmol when methacrylic acid is used. Among them, the amount of carboxyl group is 250 ~
It is preferable to set the content rate of acrylic acid or methacrylic acid to be 450 mmol. In particular, when acrylic acid is used, it is possible to obtain a thermoplastic resin having a high carboxyl group content with a smaller content, so that a constituent monomer other than styrene or a styrene derivative can be used as the third component, and the development width can be increased. It is more preferable because the (latitude) becomes wider.

In order to fuse the thermoplastic resin particles with lower thermal energy, the glass transition temperature (Tg) of the thermoplastic resin is preferably in the range of 20 to 150 ° C. If the Tg exceeds 150 ° C, relatively high heat energy is required for fusion of the particles, while if it is less than 20 ° C, fusion of the particles proceeds during storage at room temperature, resulting in deterioration of developability. There is a tendency. Among them, it is more preferable that Tg is in the range of 60 to 150 ° C., since the heat-sensitive composition may be heated and dried in order to obtain a dry coating film after being applied to the support, and when it is stored for a long time, The range of 90 to 150 ° C. is particularly preferable, in which there is no risk of fusion of the plastic resin.

The heat-sensitive composition of the present invention comprises the thermoplastic resin particles used in the present invention, a substance that absorbs light to generate heat,
And water, the thermoplastic resin particles, a substance that absorbs light to generate heat is dispersed in water, and the dispersion of the thermoplastic resin particles in water absorbs light and absorbs heat. Can be obtained by a method of adding a substance that generates heat, a method of adding a thermoplastic resin particle to a dispersion in which a substance that absorbs light and generates heat is dispersed in water, but the former method is simple. Yes preferred. As a method for obtaining a dispersion in which thermoplastic resin particles used in the present invention are dispersed in water, for example, a pulverization method of pulverizing a lumpy thermoplastic resin, a thermoplastic resin solution is mixed with water in an emulsifier to form a resin. Examples thereof include an emulsification method for emulsification, a phase inversion emulsification method, and an emulsion polymerization method. Among them, the phase inversion emulsification method in which a thermoplastic resin solution is neutralized with a basic compound and dispersed in water to obtain an aqueous dispersion of a resin is that an emulsifier is not used and that the average particle size is 2 nm or more and less than 5 nm. It is preferable because an aqueous dispersion can be easily obtained.

A thermoplastic resin containing 60 to 85% by mass of styrene or a styrene derivative and 15 to 40% by mass of acrylic acid or methacrylic acid as essential constituent monomers used in the present invention (hereinafter, used in the present invention. (Abbreviated as thermoplastic resin) is, for example, styrene or a styrene derivative of 60-
85% by mass, acrylic acid or methacrylic acid 15 to 40
It can be obtained by copolymerizing a monomer mixture containing mass%. As the polymerization method at this time, various methods such as bulk polymerization and solution polymerization can be used. Among them, simple solution polymerization is preferable, and the solvent used is preferably an organic solvent.

Examples of the organic solvent include aromatic hydrocarbons such as benzene, toluene and xylene; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; esters such as ethyl acetate and butyl acetate; methanol and ethanol. And alcohols such as isopropyl alcohol. These organic solvents may be used as a mixture of two or more kinds.
Further, for example, when an aqueous dispersion of thermoplastic resin particles used in the present invention is obtained by a phase inversion emulsification method, phase inversion emulsification is easy, a solvent having an affinity for water, and a low amount that can be easily removed after phase inversion emulsification. Preference is given to using organic solvents having a boiling point. Such solvents include acetone, methyl ethyl ketone,
Examples thereof include ethyl acetate, methanol and ethanol.

As the polymerization initiator used in the solution polymerization, known radical polymerization initiators may be used.
Azo-based polymerization initiators such as 2-azobisisobutyronitrile and 2,2-azobis (2,4-dimethylvaleronitrile); benzoyl peroxide, lauryl peroxide, tert-butylperoxy 2-ethylhexanoate, etc. And a peroxide-based polymerization initiator of

If necessary, styrene or a styrene derivative is contained in an amount of 60 to 85% by mass, acrylic acid or methacrylic acid is contained in an amount of 15 to 40% by mass, and Tg is in a range not exceeding 20 to 150 ° C. Other monomers for copolymerization may be copolymerized.

The molecular weight of the thermoplastic resin used in the present invention is preferably in the range of 5,000 to 200,000 in terms of mass average molecular weight (generally referred to as weight average molecular weight), and 8,000 to 100,000. Is more preferable. When the mass average molecular weight is less than 5,000, the image area of the printing plate obtained by image formation is weak and the printing durability tends to be poor. On the other hand, if it exceeds 200,000, it tends to be difficult to form particles.

Next, a method for obtaining an aqueous dispersion of thermoplastic resin particles used in the present invention will be described by taking the phase inversion emulsification method as an example. Examples of the basic compound used when neutralizing the thermoplastic resin used in the present invention with a basic compound include:
Amines such as triethylamine, tributylamine, triethanolamine and dimethylethanolamine; ammonia and the like can be mentioned. Ammonia is particularly preferable because it does not impair the ink receptivity of the image area on the printing plate after image formation and the printing durability of the printing plate. The basic compound is added in an amount such that the thermoplastic resin particles used in the present invention have an average particle size of 2 nm or more and less than 5 nm. Generally, it is preferable to add a basic compound corresponding to 0.8 to 1.2 equivalents of the carboxyl group.

Next, water is slowly added to the organic solvent solution of the thermoplastic resin neutralized with the basic compound with stirring to carry out phase inversion emulsification. Alternatively, a method of adding an organic solvent solution of a thermoplastic resin neutralized to water, a method of adding water containing a basic compound to an organic solvent solution of a thermoplastic resin, an organic solvent solution of a thermoplastic resin to water containing a basic compound May be added. The stirring device used at this time is
A normal stirring device such as a homomixer, or a disperser such as an emulsifying disperser which gives a shearing force can be used. The aqueous dispersion of thermoplastic resin particles used in the present invention may contain an organic solvent. The resulting dispersion is a colloidal dispersion exhibiting the Tyndall phenomenon.

In the present invention, in order to improve the image forming property. A substance that absorbs light and generates heat is used. The substance that absorbs light and generates heat used in the present invention is light,
Particularly, from red to near infrared, pigments and dyes having an absorption wavelength in the wavelength range of infrared laser light can be used, for example, carbon black, phthalocyanine, naphthalocyanine, cyanine and other pigments and dyes, polymethine pigments and dyes, squarylium. Examples include red absorbers such as dyes, near infrared absorbers, and infrared absorbers. These may be used alone or in combination of two or more. Especially 760 nm-3000
It is more preferable to use a substance having a maximum absorption wavelength (λmax) in the near-infrared to infrared region of nm since the obtained lithographic printing plate precursor can be handled in a bright room. The amount of the substance added is adjusted so that the absorbance of the heat-sensitive composition in the wavelength range of the laser beam is approximately 0.5 to 3, but specifically, it is in the range of 0.5 to 70% by mass. The range of 1 to 50 mass% is more preferable. When the amount is less than 0.5% by mass, heat is less generated, so that an image is not sufficiently formed, and when the amount is more than 70% by mass, the lithographic printing plate precursor surface is easily scratched or stains on non-image areas are not generated. It tends to occur.

The heat-sensitive composition of the present invention contains the above-mentioned thermoplastic resin particles, a substance which absorbs light to generate heat, and water. Examples of the disperser used when preparing the heat-sensitive composition of the present invention include an ultrasonic disperser, a sand mill,
Attritor, bar mill, super mill, ball mill, impeller, disperser, KD mill, colloid mill, dynatron, three roll mill, pressure kneader,
Paint conditioner etc. are mentioned. At this time, an organic solvent may be used in combination, and in that case, it is preferable to use an organic solvent having a low boiling point which can be uniformly dissolved in water, and specifically, methanol, ethanol, n-propyl alcohol, isopropyl. Alcohol, n-butanol, s
Examples thereof include alcohols such as ec-butanol and tert-butanol; ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate.

The heat-sensitive composition of the present invention has an average particle size of 2n.
Since it contains thermoplastic resin particles of m or more and less than 5 nm,
It is characterized in that it can be coated without using a surfactant that may reduce storage stability and a smooth and good coated surface can be obtained. Therefore, no special auxiliary agent is required in normal use, but for example, natural water-soluble polymer or synthetic water-soluble polymer for adjusting viscosity; leveling agent; methanol, ethanol, isopropyl alcohol, acetone, methyl ethyl ketone , Water-soluble organic solvents such as ethyl acetate, ethylene glycol, propylene glycol; vinyl alcohol, acrylamide, methylol acrylamide, methylol methacrylamide, acrylic acid, methacrylic acid, hydroxyethyl acrylate or hydroxyethyl methacrylate homopolymer and If necessary, hydrophilic binders such as copolymers, maleic anhydride / methyl vinyl ether copolymers, natural polymers such as gelatin and polysaccharides may be added. On the other hand, when the purpose is not long-term storage, a surfactant may be appropriately used, but the amount is preferably small.

The heat-sensitive composition of the present invention is preferably prepared so that the non-volatile component is 1 to 50% by mass, and then coated on a support having a hydrophilic surface and then dried to form a hydrophilic surface. The lithographic printing plate precursor according to the invention can be obtained by forming a heat-sensitive layer having a thickness of preferably about 0.5 to 10 μm.

Examples of the support include those usually used as a support for a lithographic printing plate precursor.
Metal plates of aluminum, zinc, stainless steel, iron, etc .; plastic films of polyethylene glycol terephthalate (PET), polycarbonate, polyvinyl acetal, polyethylene, etc., vacuum applied to paper or plastic film melt-coated with synthetic resin or coated with synthetic resin liquid Examples thereof include a composite support coated with a metal by a method such as vapor deposition or laminating. These are used as a support having a hydrophilic surface after subjecting the surface to hydrophilic treatment, if necessary. Among these, it is particularly preferable to use an aluminum plate or a composite support obtained by coating a plastic film with aluminum. The surface of the aluminum support is preferably subjected to surface treatment such as graining or anodic oxidation for the purpose of enhancing water retention and improving adhesion with the heat-sensitive layer.

As the coating method, for example, a spin coating method using a spin coater, a dip coating method, a roll coating method,
A curtain coating method, a blade coating method, an air knife coating method, a spray coating method, a bar coater coating method and the like can be mentioned. The method for drying the heat-sensitive composition after coating on the support is not particularly limited, but drying at room temperature is convenient and preferable. 30 for faster drying
It can also be dried using a warm air dryer, an infrared dryer or the like at ˜150 ° C. for 10 seconds to 10 minutes.

Next, the image forming method of the present invention will be described. The image forming method using the lithographic printing plate precursor of the present invention is a method of irradiating a laser beam directly on the original plate based on image information to form an image latent image, and then developing with a developing solution. The image information is preferably digitized image information from a computer or the like. The laser used for forming an image latent image has an oscillation wavelength of 50.
A laser of 0 nm to 3000 nm can be mentioned. Particularly, it is more preferable to use a laser having a maximum intensity in the near infrared to infrared region of 760 nm to 3000 nm because the lithographic printing plate precursor can be handled in a bright room. Examples of such a laser include a semiconductor laser and a YAG laser. These lasers are used in correspondence with the absorption wavelength of a substance that absorbs light to be used and generates heat.

After the image latent image is formed, the unexposed portion is dissolved and removed with an alkaline developing solution for development. The alkaline developer is preferably an aqueous solution of an alkaline substance. As the alkaline substance, for example, sodium silicate, potassium silicate, potassium hydroxide, sodium hydroxide, lithium hydroxide, sodium, potassium or ammonium salt of secondary or tertiary phosphate, sodium metasilicate, sodium carbonate, ammonia. Inorganic alkaline compounds such as monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoisopropylamine, diisopropylamine, n-butylamine, di-n-butylamine, monoethanolamine, diethanolamine, triethanolamine, ethylene Examples thereof include organic alkaline compounds such as imine and ethylenediamine.

The content of the alkaline substance in the developer is
The range of 0.005 to 10 mass% is preferable, and 0.05 to
The range of 5% by mass is particularly preferable. These developers include
If necessary, organic solvents; water-soluble sulfites such as potassium sulfite and sodium sulfite; hydroxyaromatic compounds such as alkali-soluble pyrazolone compounds and alkali-soluble thiol compounds; water softeners such as polyphosphates and aminopolycarboxylic acids; Various surfactants such as sodium isopropyl naphthalene sulfonate and sodium n-butyl naphthalene sulfonate, and various antifoaming agents can also be used.

As the alkaline developer, a commercially available developer for negative PS plate or positive PS plate may be used. Since the lithographic printing plate precursor according to the invention has a high solubility in an alkaline developing solution, it can be used in commercially available PS plates.
It is preferable to adjust the pH to 9 to 13, which is thinner than H13.5 to 14.0, and develop.

The lithographic printing plate precursor according to the invention is irradiated with laser light to form an image latent image and then developed by immersing it in an alkaline developing solution. The temperature of the developing solution at this time is 15 to 4
The range of 0 ° C. is preferable, and the immersion time is preferably in the range of 1 second to 2 minutes. If necessary, the surface can be lightly rubbed during development.

After the development, it is washed with water, and if necessary, an aqueous desensitizing agent is applied. Examples of the water-based desensitizing agent include aqueous solutions of water-soluble natural polymers such as gum arabic, dextrin, and carboxymethylcellulose, and water-soluble synthetic polymers such as polyvinyl alcohol, polyvinylpyrrolidone, and polyacrylic acid. An acid, a surfactant or the like can be added depending on the type. After applying the desensitizing agent, the planographic printing plate precursor is dried to complete the printing plate.

These steps may of course be carried out step by step, but in practice it is preferable to carry out them continuously using an image exposure machine or an automatic developing machine. For example, the lithographic printing plate precursor of the present invention is mounted on an image exposing machine using a laser such as a YAG laser or an infrared semiconductor laser, and digital information from a computer is directly written on the printing plate precursor to write an image latent image. Form an image. After that, development is performed using an automatic developing machine to obtain a printing plate.

The lithographic printing plate precursor according to the present invention is characterized in that it can be worked under normal room light by being formulated so as to be sensitive mainly to light in the infrared region. Further, in the conventional lithographic printing plate precursor, a preheating step was required before the development after the image latent image was formed, but the lithographic printing plate precursor of the present invention also has a feature that the step is not required.

[0041]

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the scope of these examples. The measurement of the non-volatile component, the measurement of the average particle size, the measurement of the mass average molecular weight, the measurement of the glass transition temperature (Tg), and the storage stability test were performed by the following methods.

[Measurement of non-volatile components] About 1 g of the sample
Dry for 1 hour in a dryer at ℃, from the mass measurement before and after drying,
The non-volatile components were expressed by mass%. [Measurement of Average Particle Size] The particle size at the peak of the particle size distribution obtained by measurement with a laser Doppler particle size distribution analyzer Microtrac UPA-150 was taken as the average particle size. [Measurement of mass average molecular weight] Measured by gel / permeation / chromatography (GPC), and expressed as a polystyrene-equivalent molecular weight.

[Measurement of glass transition temperature (Tg)] It was measured using a differential scanning calorimeter (DSC). [Storage stability test] The lithographic printing plate precursor was allowed to stand for 15 hours in a thermo-hygrostat at a temperature of 60 ° C and a humidity of 75%, and the storage stability was examined by comparing the developability before and after storage.

Reference Example 1 (Preparation of Aqueous Dispersion (A) of Thermoplastic Resin Particles) In a four-necked flask having a capacity of 1 L equipped with a stirrer, a reflux device, a dry nitrogen introducing tube with a thermometer, and a dropping device. , 300 g of ethanol as a solvent was charged, and the temperature was raised to 70 ° C. with stirring, then 230 g of styrene, 70 g of acrylic acid,
2,2'-azobis (2-methylbutyronitrile) 12
g mixture was added dropwise over 2 hours. 1 more after dropping
By continuing the stirring for 6 hours, the non-volatile component was reduced to 50.
An ethanol solution of a thermoplastic resin having 0%, a mass average molecular weight of 15,000 and a Tg of 110 ° C. was obtained.

To a beaker having a capacity of 500 mL, 100 g of the obtained thermoplastic resin ethanol solution and 10 g of 25% ammonia water were added, and a total amount of 200 g of water was added dropwise with stirring to carry out phase inversion emulsification to obtain a dry solid content. An aqueous dispersion (A) containing ethanol of 17% and thermoplastic resin particles having an average particle diameter of 3.3 nm was obtained.

Reference Example 2 (Preparation of Aqueous Dispersion of Thermoplastic Resin Particles (B)) In a four-necked flask having a capacity of 1 L equipped with a stirrer, a reflux device, a dry nitrogen introducing tube with a thermometer, and a dropping device. Then, 300 g of methyl ethyl ketone was charged as a solvent, the temperature was raised to 80 ° C. with stirring, and then a mixture of 200 g of styrene, 100 g of methacrylic acid and 12 g of 2,2′-azobis (2-methylbutyronitrile) was added dropwise over 2 hours. . After the dropping, stirring is continued for another 16 hours to obtain 50.0% of non-volatile components, mass average molecular weight of 16,000 and Tg.
A methyl ethyl ketone solution of a thermoplastic resin at 124 ° C. was obtained.

In a beaker having a capacity of 500 mL, 100 g of a solution of the obtained thermoplastic resin in methyl ethyl ketone, 25%
Ammonia water 10g was added, and the total amount was 300g with stirring.
The water was added dropwise to obtain an aqueous dispersion containing methyl ethyl ketone. Methyl ethyl ketone was distilled off under reduced pressure with an evaporator to obtain an aqueous dispersion (B) of thermoplastic resin particles having a dry solid content of 20% and an average particle size of 4.1 nm.

Reference Example 3 (Preparation of Aqueous Dispersion of Thermoplastic Resin Particles (C)) In a four-necked flask having a capacity of 1 L, equipped with a stirrer, a reflux device, a dry nitrogen introducing tube with a thermometer, and a dropping device. After charging 300 g of methyl ethyl ketone as a solvent and heating to 80 ° C. with stirring, a mixture of 230 g of styrene, 70 g of acrylic acid and 12 g of 2,2′-azobis (2-methylbutyronitrile) was added dropwise over 2 hours. . After dropping
By continuing stirring for another 16 hours, 50.0% of non-volatile components, mass average molecular weight of 16,000, Tg11
A solution of the thermoplastic resin in methyl ethyl ketone at 2 ° C. was obtained.

In a 500 mL beaker, 100 g of a solution of the obtained thermoplastic resin in methyl ethyl ketone, 25%
Ammonia water 10g was added, and the total amount was 300g with stirring.
Water was added dropwise to obtain an aqueous dispersion containing methyl ethyl ketone. Methyl ethyl ketone was distilled off under reduced pressure with an evaporator to obtain an aqueous dispersion (C) of thermoplastic resin particles having a dry solid content of 20% and an average particle diameter of 3.6 nm.

Reference Example 4 (Preparation of Aqueous Dispersion of Thermoplastic Resin Particles (D)) In a four-necked flask with a capacity of 1 L equipped with a stirrer, a reflux device, a dry nitrogen introducing tube with a thermometer, and a dropping device. After charging 400 g of methyl ethyl ketone as a solvent and heating to 80 ° C. with stirring, 80 g of styrene, 238.9 g of methyl methacrylate, 24.5 g of methacrylic acid, 56.6 g of butyl acrylate, Perbutyl O (NOF CORPORATION)
The polymerization initiator) was added dropwise over 8 hours. After the dropping, after stirring for 8 hours, 0.5 g of perbutyl O was added, and the stirring was continued for further 8 hours, whereby the nonvolatile component was 49.5%, the acid value was 39.1, and the mass average molecular weight was 20,
000 thermoplastic resin solutions in methyl ethyl ketone were obtained.

To a beaker having a capacity of 500 mL, 100 g of a methyl ethyl ketone solution of the obtained thermoplastic resin and 2.71 g of triethylamine were added, and water was added dropwise with stirring. The prepolymer solution gradually thickened, but was about 150
The viscosity was remarkably reduced around the point where g of water was dropped, and the phase inversion was completed. After adding an additional 150 g of water, the resulting dispersion is heated to 30 ° C. to remove methyl ethyl ketone and excess water under reduced pressure to give the nonvolatile component 3
An aqueous dispersion (D) of thermoplastic resin particles having a mean particle size of 7.7% and an average particle size of 120 nm was obtained.

<Example 1> 20 g of the aqueous dispersion (A) of the thermoplastic resin particles obtained in Reference Example 1 was mixed with the infrared absorbent "YKR".
-3070 "(manufactured by Yamamoto Kasei Co., Ltd.), 6 g of water, and 180 g of 1 mm zirconia beads were added, the mixture was stirred for 1 hour with a paint conditioner, and the zirconia beads were removed by filtration to obtain a heat-sensitive dispersion of the infrared absorbent. A sex composition (A ′) was obtained.

The surface of an A2 size aluminum plate having a thickness of 0.3 mm was polished with a nylon brush using an aqueous suspension of pumice, the surface was grained, and then 20%.
Anodize at a current density of 2 A / dm ² in sulfuric acid electrolyte,
After forming an oxide film of 2.7 g / m ² , it was washed with water and dried to obtain a support. After applying the heat-sensitive composition (A ') to this support using a No. 8 bar coater, 6
It was dried at 0 ° C. for 4 minutes to obtain a lithographic printing plate precursor having a film thickness of 2 μm.

Using this lithographic printing plate precursor, an exposure machine trend setter 3244 equipped with a near infrared semiconductor laser
A laser beam was irradiated at F (manufactured by Creo) to form an image latent image. Then, the positive PS plate developer "PD-
1 "(manufactured by Kodak Polychrome Graphics) 1:
25 at 30 ° C. using a 99 water diluted solution (pH 12.3)
The plate was soaked for 2 seconds for development, washed with water, and then dried to obtain a printing plate having an image on a computer formed on the plate. Also, in the storage stability test of the lithographic printing plate precursor, no change was observed in the developability.

Example 2 20 g of the aqueous dispersion (B) of the thermoplastic resin particles obtained in Reference Example 2 was mixed with the infrared absorber "IR".
T "(Showa Denko KK) 0.3 g, ethanol 6 g, water 3
g, and 180 g of 1 mm zirconia beads were added,
After stirring with a paint conditioner for 1 hour, the zirconia beads were removed by filtration to obtain a heat-sensitive composition (B ') in which the infrared absorber was dispersed. This heat-sensitive composition (B ′) was applied to a support whose surface was hydrophilized in the same manner as in Example 1 using a No. 8 bar coater, and then dried at 60 ° C. for 4 minutes to give a film thickness. A lithographic printing plate precursor of 2 μm was obtained. Using this lithographic printing plate precursor, a printing plate was obtained in the same manner as in Example 1. Also, in the storage stability test of the lithographic printing plate precursor, no change was observed in the developability.

<Example 3> 20 g of the aqueous dispersion (C) of the thermoplastic resin particles obtained in Reference Example 3 was used as an infrared absorber.
-Methylbenzenesulfonic acid 2- (2- (2-chloro-
3-((1,3-dihydro-1,1,3-trimethyl-
2H-benz (e) indole-2-ylidene) ethylidene) -1-cyclohexen-1-yl) ethenyl)-
0.3 g of 1,1,3-trimethyl-1H-benz (e) indolium, 6 g of ethanol, 3 g of water, and 1
180 g of mm zirconia beads was added, and the mixture was stirred with a paint conditioner for 1 hour. Then, the zirconia beads were removed by filtration to obtain a heat-sensitive composition (C ′) in which the infrared absorber was dispersed.

The heat-sensitive composition (C ') was applied to a support whose surface was hydrophilized in the same manner as in Example 1 by using a No. 8 bar coater, and then dried at 60 ° C for 4 minutes. Thus, a lithographic printing plate precursor having a film thickness of 2 μm was obtained. Using this lithographic printing plate precursor, a printing plate was obtained in the same manner as in Example 1. Also, in the storage stability test of the lithographic printing plate precursor, no change was observed in the developability.

<Comparative Example 1> A dispersion of carbon black "Carbon Black CWA" in which 36.0 g of the aqueous dispersion (D) of thermoplastic resin particles obtained in Reference Example 4 was grafted with an acrylic acid resin while stirring. (Manufactured by Ciba Geigy) 3
0.0 g, distilled water 75.0 g, methanol 30.0 g, and fluorine surfactant Megafac F-470 (manufactured by Dainippon Ink and Chemicals, Inc.) 0.02 g were added in this order, and further, at room temperature for 10 minutes. The mixture was stirred to give a heat-sensitive composition (D ').

Positive PS plate HP with matting agent removed in advance
On top of (Kodak Polychrome Graphics)
The heat-sensitive composition (D ′) was applied using a No. 9 bar coater and dried at 50 ° C. for 3 minutes to obtain a lithographic printing plate precursor.
The coating amount was 1.4 g / m ² . Using this lithographic printing plate precursor, a printing plate was obtained in the same manner as in Example 1. In the storage stability test of the lithographic printing plate precursor, the unexposed portion of the lithographic printing plate precursor after storage did not elute with the developing solution, and images could not be formed.

(Printing Test) The printing plates obtained in Examples 1 to 3 were mounted on a printing machine (TOHAMA N-600 rotary press), and a printing test was carried out. The printing conditions are as follows: printing speed: 120,000 copies / hour, printing paper: Zhuetsu Pulp newspaper newspaper, ink: MKHS-EZ (newspaper ink), fountain solution: FST
An accelerated printing durability test was performed on 20,000 sheets at -212 2% and a printing pressure of 0.25. As a result, Examples 1 to 1 after the print test
No abnormality was found in the printing plate obtained in No. 3.

[0061]

EFFECTS OF THE INVENTION The heat-sensitive composition of the present invention can be coated without using a surfactant which may reduce storage stability, so that it has good film-forming properties and a smooth coating film excellent in film strength. When used as a coating film for lithographic printing plate precursor,
Since it can be fused with lower heat energy, it has high sensitivity. Further, the lithographic printing plate precursor of the present invention forms a latent image by irradiation with light, and by using the heat-sensitive composition of the present invention, after laser writing, a high resolution is obtained only by development without requiring a preheating step. Image can be formed, developability does not decrease due to storage under high temperature and high humidity, sensitivity, storage stability are excellent, and high printing durability is exhibited. Further, according to the image forming method of the present invention, a latent image can be formed by directly irradiating a laser with digitized image information from a computer or the like on the original plate, and development can be performed without the need for a preheating step. In the development, it is possible to work in a bright place without the need for a dark room, and since the sensitivity is high, a good image can be obtained, and a printing plate precursor having excellent printing durability can be obtained.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03F 7/00 503 G03F 7/00 503 (72) Inventor Naoto Saito 2-27 Haruji, Sakura City, Chiba Prefecture 8 (72) Inventor Yoshitomo Yonehara 1-1-1 Senari, Sakura City, Chiba Prefecture (72) Inventor Yasuyuki Suzuki 3-29-14 Higashi-Hatsutomi, Kamagaya City, Chiba Prefecture (72) Inventor Yasuhiko Kojima Akami, Konosu City, Saitama Prefecture Platform 1-14-3-403 (72) Inventor Eiji Hayakawa 15-1 Sumiyoshi-cho, Utsunomiya City, Tochigi Prefecture F-term (reference) 2H025 AA02 AA12 AB03 AC08 AD01 BJ03 BJ09 CB54 CC13 CC20 FA17 2H096 AA06 BA20 EA04 EA23 2H114 AA04 AA24 BA05 EA02 4F070 AA18 AA30 AC19 AC46 CA01 CA02 CB03 DA31 DA33 DC07 DC11 HB01 HB05 HB12 4J002 BC021 BC041 BG041 DA036 DE027 EG106 FD096 GP03 GT00

Claims (5)

[Claims] 1. A thermoplastic resin particle containing 60 to 85% by mass of styrene or a styrene derivative and 15 to 40% by mass of acrylic acid or methacrylic acid as essential constituent monomers.
A heat-sensitive composition comprising a substance that absorbs light to generate heat, and water, wherein the thermoplastic resin particles have an average particle size of 2 nm or more and less than 5 nm. 2. The heat-sensitive composition according to claim 1, wherein the Tg of the thermoplastic resin is in the range of 90 to 150 ° C. 3. A lithographic printing plate precursor having a dry coating film of the heat-sensitive composition according to claim 1 or 2 on the surface of a support having a hydrophilic surface. 4. An image is obtained by irradiating a lithographic printing plate precursor having a photosensitive layer comprising a dry coating film of the heat-sensitive composition according to claim 1 on the surface of a support having a hydrophilic surface with a laser beam. An image forming method, comprising: forming a latent image and then developing with an alkaline developer having a pH of 9 to 13. 5. The image forming method according to claim 4, wherein the irradiation of the laser light is based on digitized image information.