Image formation methods

Abstract

To provide an image formation method that reduces the ejecta from the surface of a thermal recording material, allowing for the creation of high-contrast and uniform images.SOLUTION: A thermal recording material comprises, on a light-transmitting support, an image formation layer comprising an infrared absorbing dye, a non-photosensitive organic silver salt, and a reductant. When the thermal recording material is subjected to scanning exposure with infrared laser light, the overlap percentage of the exposure area in the sub-scan direction of the infrared laser light is 0.60-33%.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an image forming method that reduces ejecta generated from the surface of a thermal recording material and allows for the acquisition of high-contrast and uniform images. [Background technology]

[0002] For a long time, wet-process image formation methods using silver halide photosensitive materials have been commonly used as a high-quality image formation method for creating printing plates. However, wet-process image formation methods require the disposal of waste liquids such as developers and fixers, which has a significant environmental impact. Therefore, various dry-process image formation methods that do not require wet processing have been investigated. Currently, image formation systems such as inkjet recording, electrophotography, and dye thermal transfer methods are in practical use. However, these dry-process image formation methods make it difficult to obtain printing plates with excellent light shielding in the image area and excellent light transmission in the non-image area, in other words, high-contrast printing plates.

[0003] As a dry image forming method that can obtain high contrast equivalent to that of a wet image forming method using silver halide photosensitive material, there is a method of forming an image on a thermal recording material having a thermal recording layer on a support using a thermal head or infrared laser light. Among these, the thermal recording method using infrared laser light is superior from the viewpoint of high-density recording and high-quality recording. As thermal recording materials that can be drawn with infrared laser light, for example, Japanese Patent Application Publication No. 6-194781 (Patent Document 1) discloses a thermal recording material containing a thermally reducible silver source, a reducing agent for silver ions, a dye that absorbs laser light in the wavelength range of about 500 to 1100 nm, and a polymeric binder, and Japanese Patent Application Publication No. 10-29377 (Patent Document 2) discloses a thermal recording material having a thermal layer containing an organic silver salt, an organic silver salt developer, a merocyanine-based infrared absorbing dye having a specific structure, and a water-soluble binder. Furthermore, Japanese Patent Publication No. 2001-10229 (Patent Document 3) discloses an image-forming material having a thermal color image-forming layer containing a non-photosensitive organic silver salt, a reducing agent for silver ions, a binder, a color adjuster, and an absorber that absorbs radiation in the wavelength range of 750 to 1100 nm.

[0004] In the infrared laser-based thermal recording method, infrared laser light is used to scan and expose a thermal recording material, causing it to heat locally and develop color in the thermal recording layer for drawing. However, because infrared laser light is a high-energy beam, a problem arises in that components contained in the thermal recording material and by-products generated during the color development process of the thermal recording layer can volatilize or explode as ejected material from the surface of the thermal recording material, contaminating the surface of the thermal recording material and the infrared laser irradiation device.

[0005] Furthermore, because laser light generally has a small beam diameter, it is known that to prevent the image from becoming non-uniform due to image gaps (unexposed areas due to misalignment of the laser light irradiation position) and density unevenness (areas with poor color development due to insufficient laser light irradiation), the thermal recording material is exposed while overlapping the laser light in the sub-scanning direction. For example, Japanese Patent Application Publication No. 2000-2963 (Patent Document 4) discloses an image recording material in which at least one layer of the constituent layers contains a specific compound, and it is described that when exposing the image recording material, the scan lines are made invisible by exposing it so that the laser light overlaps. However, in a thermal recording method using infrared laser light, when scanning and exposing a thermal recording material while overlapping infrared laser light, the areas where scanning and exposing overlap in areas already image-recorded in the first scanning exposure absorb the infrared laser light more strongly, which can cause significant ejection from the surface of the thermal recording layer. Therefore, there has been a need for an image forming method that can obtain a high-contrast and uniform image while reducing such ejection.

[0006] On the other hand, regarding image formation methods for so-called thermally developed photosensitive recording materials containing a photosensitive silver halide, a non-photosensitive organic silver halide, and a reducing agent, International Publication No. 1995 / 31754 (Patent Document 5) discloses a method for creating a latent image by exposing a silver halide-containing black-and-white photothermal photographic element with radiation, which includes a step of emitting a second dose of radiation so as to overlap with the spot struck by the first dose of radiation, and states that this method can improve image quality. Furthermore, Japanese Patent Application Publication No. 4-51043 (Patent Document 6) discloses an image formation method in which a thermally developed photosensitive material having a binder, a photosensitive silver halide, a reducing agent, and / or a reducing agent precursor is exposed multiple times on a support, and then thermally developed, and states that it is preferable that the area ratio of the multiple exposure portions to the image formation area is 40% or more. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 6-194781 [Patent Document 2] Japanese Patent Application Publication No. 10-29377 [Patent Document 3] Japanese Patent Publication No. 2001-10229 [Patent Document 4] Japanese Patent Publication No. 2000-2963 [Patent Document 5] International Publication No. 1995 / 31754 pamphlet [Patent Document 6] Japanese Patent Application Publication No. 4-51043 [Overview of the project] [Problems that the invention aims to solve]

[0008] The object of the present invention is to provide an image forming method that reduces ejecta generated from the surface of a thermal recording material and allows for the acquisition of high-contrast and uniform images. [Means for solving the problem]

[0009] The above-mentioned problems are solved by the following invention. (1) An image forming method characterized in that, when scanning exposure is performed with infrared laser light on a thermal recording material having an image forming layer containing an infrared absorbing dye, a non-photosensitive organic silver salt, and a reducing agent on a light-transmitting support, the overlap rate of the exposure range in the sub-scanning direction of the infrared laser light is 0.60 to 33%. (2) The image forming method according to (1) above, characterized in that the irradiation amount X when scanning exposure of a thermal recording material with infrared laser light is expressed by the following formula. 1.03A ≤ X ≤ 1.55A (In the above formula, A represents the infrared laser irradiation dose at which the difference between the maximum ultraviolet light transmission density (Dmax) in the image area and the minimum ultraviolet light transmission density (Dmin) in the non-image area, Dmax-Dmin, is 3.0.) [Effects of the Invention]

[0010] The present invention can provide an image forming method capable of reducing ejected matter generated from the surface of a heat-sensitive recording material and obtaining a high-contrast and uniform image.

Brief Description of Drawings

[0011] [Figure 1] Schematic diagram showing an example of the image forming method of the present invention [Figure 2] Schematic diagram showing an example of overlap of exposure ranges in the sub-scanning direction of infrared laser light [Figure 3] Schematic diagram showing another example of the image forming method of the present invention

Embodiments for Carrying Out the Invention

[0012] Hereinafter, the details of the present invention will be described.

[0013] FIG. 1 is a schematic diagram showing an example of the image forming method of the present invention. In the image forming method of the present invention, the infrared laser light 22 is irradiated from an arbitrary position from the infrared laser light oscillator 21 to the image formation planned area 2 of the heat-sensitive recording material 1, and the heat-sensitive recording material 1 is scanned and exposed. The infrared laser light 22 moves while irradiating the infrared laser light 22 in the main scanning direction, and once the irradiation of the infrared laser light 22 is terminated at the end of the image formation planned area 2. Taking this as one cycle, in the subsequent cycle, the infrared laser light oscillator 21 moves in the sub-scanning direction, and the image 11 is formed by irradiating the infrared laser light 22 at an arbitrary position again. This is repeated until the entire area where image formation is planned in the image formation planned area 2 of the heat-sensitive recording material 1 is scanned and exposed. In FIG. 1, the image formation planned area 2 is shown by a broken line, but the broken line does not actually exist on the actual heat-sensitive recording material 1. When performing the scanning exposure, the infrared laser light oscillator 21 may move in the main scanning direction and the sub-scanning direction, or the heat-sensitive recording material 1 may move in the direction opposite to the main scanning direction and the direction opposite to the sub-scanning direction.

[0014] Figure 2 is a schematic diagram showing an example of the overlap of the exposure range in the sub-scanning direction of infrared laser light in the present invention. The scanning width 31 represents the width in the sub-scanning direction when scanning exposure with infrared laser light, and more specifically, it means the length of the exposure range in the sub-scanning direction of infrared laser light that can provide the energy necessary for the thermal recording material 1 to develop color. In the present invention, the specific numerical value of the scanning width 31 is not particularly limited. In a certain period, an image 35 is formed by continuously irradiating infrared laser light having a scanning width 31 in the main scanning direction. In the following period, an image 37 is formed by continuously irradiating infrared laser light having a scanning width 31 in the main scanning direction from an infrared laser light oscillator that has moved in the sub-scanning direction. At this time, infrared laser light having a scanning width 31 is irradiated so that image 35 and image 37 partially overlap. The ratio of the overlap width 33 of image 35 and image 37 to the scanning width 31 is the overlap rate of the exposure range in the sub-scanning direction in the present invention.

[0015] In the present invention, the overlap rate of the exposure range in the sub-scanning direction of the infrared laser light is 0.60 to 33%. If the overlap rate is less than 0.60%, image gaps occur and a uniform image cannot be obtained. If the overlap rate exceeds 33%, the generation of ejecta from the surface on the side having the image forming layer becomes significant. From the viewpoint of obtaining a high-contrast and uniform image while reducing the generation of ejecta from the surface of the thermal recording material, the overlap rate of the exposure range is more preferably 0.80 to 21%, and particularly preferably 1.0 to 12%.

[0016] The irradiation method of the infrared laser light is not particularly limited, and known irradiation methods such as the flatbed method, internal drum method, and external drum method can be used. Examples of infrared lasers include semiconductor lasers, carbon dioxide lasers, YAG lasers, and fiber lasers, but are not limited to these, and known infrared lasers can be used.

[0017] In Figure 1, mentioned above, for simplicity, a single infrared laser beam is shown being emitted from one infrared laser oscillator. However, in the present invention, the number of infrared laser oscillators and the number of infrared laser beams emitted simultaneously are not particularly limited. For example, infrared laser beams emitted from multiple infrared laser oscillators may be focused and emitted as a single infrared laser beam, or the focused infrared laser beam may be split and emitted as multiple infrared laser beams. Although not shown in Figure 1, the infrared laser oscillator 21 may have known optical components such as lenses and optical fibers.

[0018] The infrared laser oscillator 21 may be connected to a power supply and a control computer. As a device to which a power supply and a control computer are connected to the infrared laser oscillator 21, known devices such as thermal CTP setters used for plate making of flexographic printing plates and offset printing plates can be used. Examples of thermal CTP setters include the AURA series (manufactured by Guangzhou Amsky Technology Co., Ltd.), the Trendsetter® series (manufactured by Eastman Kodak Co.), and the Achieve® series (manufactured by Eastman Kodak Co.).

[0019] In this invention, the surface of the thermal recording material irradiated with infrared laser light is not limited, but it is preferable to irradiate the surface having an image forming layer in order to obtain a high-quality image. Furthermore, in this invention, any ultraviolet transmission density can be obtained by changing the energy and / or exposure time of the infrared laser light irradiated onto the thermal recording material. An example of a method for measuring ultraviolet light transmission density is the use of a transmission density meter, which will be described later.

[0020] In Figure 1 above, the image 11 formed by irradiating the image formation area 2 with infrared laser light 22 is not particularly limited and may be a solid fill image, a halftone image, or a fine line image. In the present invention, the inclusion of unintended non-image areas in the image formation area 2 is not considered an image defect, and a uniform image is considered to have been formed.

[0021] Although not shown in Figure 1 above, exposure apparatuses having an infrared laser oscillator generally have a holding mechanism for stably fixing the thermal recording material. The method for fixing the thermal recording material 1 in the holding mechanism is not particularly limited, and known methods can be used. Specifically, examples include fixing the ends of the thermal recording material with adhesive tape, fixing the thermal recording material by magnetic force using magnets, and fixing the thermal recording material by attracting it with air using intake slits or intake holes. Among the above, the method of fixing the thermal recording material by magnetic force and the method of fixing the thermal recording material by attracting it with air are preferred because they avoid contamination of the surface of the thermal recording material.

[0022] Figure 3 is a schematic diagram showing another example of the image forming method of the present invention. Similar to Figure 1, infrared laser light 22 is irradiated from an infrared laser light oscillator 21 onto the image formation area 2 of the thermal recording material 1. The thermal recording material 1 is held on a holding structure 41 having a plurality of intake slits (intake slits 42, intake slits 43), and the thermal recording material 1 is fixed by drawing in air through the intake slits to adsorb the thermal recording material.

[0023] Incidentally, if the surface of the holding structure 41 of the thermal recording material 1 is not flat, as shown in Figure 3, the image 11 formed on the thermal recording material 1 may become non-uniform. Specifically, when the thermal recording material 1 is laser-exposed in the state shown in Figure 3, the ultraviolet transmission density of the image 11 located directly above the intake slits 42 and 43 may increase or decrease compared to the surrounding area. This phenomenon is particularly noticeable when the image 11 is an image formed by halftones. If the ultraviolet transmission density of the image 11 becomes non-uniform, this non-uniformity will be reflected in the object to be exposed when the thermal recording material is used as a printing plate material. The mechanism of this phenomenon is unknown, but it is presumed to occur due to a combination of factors, such as heat dissipation due to air intake from the intake slits 42 and 43, differences in the amount of heat partially removed due to the thermal recording material being held in the air above the intake slits, and differences in the reflectivity of infrared laser light depending on the presence or absence of the intake slits. Furthermore, in this invention, in order to reduce ejecta generated from the surface of the thermal recording material, the overlap rate of the exposure area in the sub-scanning direction of the infrared laser light is limited to 0.60-33%. As a result, the amount of infrared laser irradiation on the surface of the thermal recording material is reduced, and the ultraviolet transmission density of the image is kept low overall, making density differences in the area directly above the intake slit more noticeable.

[0024] Even if the surface of the holding structure 41 is not flat due to minute irregularities, the above-mentioned problems may still occur. However, even in this case, the non-uniformity of the image formed on the thermal recording material can be improved by adjusting the amount of infrared laser irradiation on the surface of the thermal recording material to a certain range. Specifically, it is particularly preferable that the amount of infrared laser irradiation X during scanning exposure satisfies the following equation. 1.03A ≤ X ≤ 1.55A (In the above formula, A represents the infrared laser irradiation dose at which the difference between the maximum ultraviolet light transmission density (Dmax) in the image area and the minimum ultraviolet light transmission density (Dmin) in the non-image area, Dmax-Dmin, is 3.0.)

[0025] The amount of infrared laser irradiation on the surface of a thermal recording material is a value determined in relation to the output of the infrared laser oscillator, the infrared laser diameter on the surface of the thermal recording material, the irradiation speed in the main scanning direction, the overlap rate in the sub-scanning direction, etc. However, in this invention, the uniformity of the image can be improved by irradiating with infrared laser light within a certain range more than the infrared laser irradiation amount at which the Dmax-Dmin value is 3.0, that is, the infrared laser irradiation amount at which a high-contrast image is obtained as described later.

[0026] Since the uniformity of the image formed on the thermal recording material is excellent, it is more preferable that the infrared laser irradiation amount X satisfies the following equation. 1.10A ≤ X ≤ 1.45A

[0027] The method of exposure by gradually changing the amount of infrared laser irradiation on the surface of the thermal recording material is not particularly limited, and examples include changing the output of the oscillating laser, or keeping the laser output constant and accelerating or decelerating the laser movement speed in the main scanning direction. If the infrared laser irradiation method is an internal drum method or an external drum method, the drum rotation speed may be increased or decreased.

[0028] The thermal recording material used in the image forming method of the present invention is described in detail. In the present invention, the thermal recording material has a light-transmitting support. Examples of such light-transmitting supports include resin films such as polyethylene terephthalate, polyethylene naphthalate, cellulose nitrate, and polycarbonate, and inorganic materials such as glass. In the present invention, a light-transmitting support means a support with a total light transmittance of 60% or more, and more preferably 70% or more. Furthermore, it is preferable that the haze value of the light-transmitting support is 10% or less. The light-transmitting support may have known layers such as an easy-adhesion layer, a hard coat layer, and an antistatic layer. The thickness of the light-transmitting support in the present invention is not particularly defined, but it is preferably 50 to 300 μm from the viewpoint of handling.

[0029] The thermal recording material in this invention has an image-forming layer on a light-transmitting support. The image-forming layer may be on one side of the light-transmitting support or on both sides of the support. In this invention, the image-forming layer means a system in which a portion irradiated with infrared laser light changes color and a light-shielding image can be formed.

[0030] In the present invention, the image-forming layer of the thermal recording material contains an infrared-absorbing dye. The infrared-absorbing dye in the present invention means a known compound that absorbs infrared light. The infrared-absorbing dye is preferably a dye that has absorption in the wavelength region of 600 to 1500 nm, more preferably a dye that has an absorption maximum in the wavelength region of 650 to 1100 nm, and even more preferably a dye that has an absorption maximum in the wavelength region of 750 to 1100 nm. Furthermore, since the infrared-absorbing dye in the present invention provides a thermal recording material that can form high-contrast images suitable for the preparation of printing plates, it is preferable that the absorption in the wavelength region of 350 to 450 nm, where the emission peak in the ultraviolet region of high-pressure mercury lamps and chemical lamps exists, is as small as possible compared to the absorption in the wavelength region of 600 to 1500 nm mentioned above. Specifically, it is preferable that the ratio ε1 / ε2 of the absorbance ε1 at the absorption maximum in the 600-1500 nm wavelength range to the absorbance ε2 at the absorption maximum in the 350-450 nm wavelength range is 4.0 or higher, and it is even more preferable that the ratio ε(830) / ε(365) of the absorbance ε(830) at 830 nm to the absorbance ε(365) at 365 nm is 4.0 or higher. Examples of such infrared absorbing dyes include compounds having a polymethine skeleton such as squarylium, cyanine, merocyanine, and bis(aminoaryl)polymethine, and specifically, compounds represented by the following general formulas (1) to (3) are examples, but are not limited to these.

[0031] [ka]

[0032] In general formulas (1) to (3), R 1 ~R 10represents a substituent, and examples include hydrogen atoms, alkyl groups, aryl groups, alkoxy groups, acyl groups, ester groups, amide groups, halogen atoms, hydroxyl groups, thiol groups, thioether groups, sulfonyl groups, etc. These substituents may be the same or different, and may also be bonded to other substituents to form a ring structure. In general formulas (1) to (3), X - The negative charge represents an atom or group of atoms, and examples include halogen ions, oxo acids such as perchlorate ions, tetrafluoroborates, hexafluorophosphates, alkyls, and arylsulfonates. Specifically, examples include, but are not limited to, the following example compounds (1) to (7).

[0033] [ka]

[0034] [ka]

[0035] As an example of a method for measuring the absorbances ε1, ε2, ε(830), and ε(365) mentioned above, one can prepare a 2-butanone solution of an infrared absorbing dye and measure the absorption spectrum of the solution using a UV-2600 ultraviolet-visible spectrophotometer (manufactured by Shimadzu Corporation) with a quartz cell having a path length of 1 cm.

[0036] In this invention, a high-contrast image means that the difference between the maximum ultraviolet light transmission density (Dmax) of the image area and the minimum ultraviolet light transmission density (Dmin) of the non-image area, Dmax-Dmin, is 3.0 or greater, and more preferably 3.5 or greater. An example of a method for measuring ultraviolet light transmission density is to use the X-Rite® 361T manufactured by Videojet X-Rite Corporation as a transmission density meter and measure in ultraviolet light mode. When measuring ultraviolet light transmission density, it is preferable to measure a filled area of ​​a size suitable for the light-receiving part of the transmission density meter, rather than a part of the image area where the image area and non-image area are mixed in a narrow range, such as halftone dots or fine lines, in order to obtain a stable measurement value.

[0037] The content of the infrared absorbing dye is not particularly limited, but is preferably 0.01 to 25% by mass, and more preferably 0.02 to 15% by mass, relative to the total solid content of the image forming layer.

[0038] In the present invention, the image forming layer may contain an infrared absorbing dye alone, or it may contain two or more types of infrared absorbing dyes.

[0039] In the present invention, the image-forming layer of the thermal recording material contains a non-photosensitive organic silver salt. This organic silver salt is reduced by heating with a reducing agent, as described later, to form a silver image. Specifically, the organic silver salts include silver salts of organic acids such as gallic acid, oxalic acid, behenic acid, stearic acid, palmitic acid, and lauric acid, as described in Sections 17029(II) and 29963(XVI) of the Research Disclosure relating to thermally developed photosensitive materials; silver salts of carboxyalkylthioureas such as 1-(3-carboxypropyl)thiourea and 1-(3-carboxypropyl)-3,3-dimethylthiourea; aldehydes such as formaldehyde, acetaldehyde, and butyraldehyde, and aromatics such as salicylic acid, benzoic acid, 3,5-dihydroxybenzoic acid, and 5,5-thiodisalicylic acid. Examples include complexes of polymer reaction products with carboxylic acids and silver; silver salts or complexes of thions such as 3-(2-carboxyethyl)-4-hydroxymethyl-4-thiazoline-2-thion and 3-carboxymethyl-4-methyl-4-thiazoline-2-thion; silver salts or complexes of nitrogen-containing heterocyclic compounds selected from imidazole, pyrazole, urazole, 1,2,4-triazole, 1H-tetrazole, 3-amino-5-benzylthio-1,2,4-triazole and benzotriazole; silver salts of saccharin, 5-chlorosalicyldoxime, etc.; and silver salts of mercaptides. Of these, silver fatty acids with 10 or more carbon atoms are preferred, and silver stearate and silver behenate are particularly preferred.

[0040] In this invention, the content of the non-photosensitive organic silver salt contained in the image forming layer can be appropriately adjusted according to the ultraviolet light transmission density required for use as a printing plate material, and is approximately 0.2 to 3.0 g / m² in silver equivalent. 2 Preferably, 0.5 to 2.0 g / m 2 This is preferable.

[0041] In the present invention, it is preferable that the image-forming layer of the thermal recording material substantially does not contain photosensitive silver halide. "Substantially contained" here means that the amount of photosensitive silver halide contained in the image-forming layer is less than 1% by mass relative to the total solid content of the image-forming layer. This suppresses the increase in transmittance density in non-image areas during storage and normal use of the thermal recording material, resulting in a thermal recording material capable of forming high-contrast images.

[0042] The image-forming layer of the thermal recording material in the present invention contains a reducing agent. Examples of such reducing agents include polyhydroxybenzene compounds such as hydroquinone, catechol, 4-methylcatechol, 4-tert-butylcatechol, chlorohydroquinone, and pyrogallol; polyhydroxybenzoic acid compounds such as gallic acid, methyl gallate, propyl gallate, stearyl gallate, 2,5-dihydroxybenzoic acid, 3,4-dihydroxybenzoic acid, and ethyl 3,4-dihydroxybenzoate; aminophenol compounds such as 2-aminophenol, 3-aminophenol, and 4-aminophenol; 1-phenyl-3-pyrazolidone and its derivatives; hydroxylamines; polyhydroxyindanes described in Japanese Patent Application Publication No. 6-317870; and reducing agents having a specific structure with a dihydroxybenzene ring described in Japanese Patent Application Publication No. 2001-328357. Among the reducing agents mentioned above, polyhydroxybenzene compounds and polyhydroxybenzoic acid compounds are preferred from the viewpoint of obtaining high-contrast images.

[0043] The reducing agent content in the image forming layer can vary widely depending on the type of reducing agent and the type of organic silver salt, but it is preferably 0.1 to 3.0 moles per mole of organic silver salt, and more preferably 0.5 to 2.0 moles. Furthermore, two or more of the above-mentioned reducing agents may be used in combination for various purposes.

[0044] The image-forming layer of the thermal recording material in the present invention preferably contains so-called colorants known in the field of thermography or photothermography. Examples of colorants are known from the aforementioned Research Disclosures concerning thermally developed photosensitive materials, such as section 17029(V) and section 29963(XXII), and specifically include imides represented by phthalimide, mercapto compounds represented by 3-mercapto-1,2,4-triazole, phthalate derivatives represented by phthalazine, phthalazone, 4-methylphthalic acid, tetrachlorophthalic acid and their anhydrides, and benzoxazine derivatives represented by 1,3-benzoxazine-2,4-dione. Furthermore, two or more of the above-mentioned colorants may be used in combination for various purposes.

[0045] The image-forming layer of the thermal recording material in the present invention may contain various accelerators, stabilizers, and their precursors for purposes such as suppressing or promoting the formation of image silver, and improving the preservation of the thermal recording material before and after image formation. Specifically, these can be selected from benzotriazole, 5-methylbenzotriazole, 5-chlorobenzotriazole, 2-mercaptobenzotriazole, 2-mercaptobenzimidazole, 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, 4-hydroxy-6-methyl-1,3,3a,7-tetrazaindene, 1-phenyl-5-mercaptotetrazol, 2-amino-5-mercapto-1,3,4-thiadiazole, 3-mercapto-5-phenyl-1,2,4-triazole, 4-bentzamid-3-mercapto-5-phenyl-1,2,4-triazole, etc., which are known as photographic additives. Furthermore, two or more of the above-mentioned accelerators, stabilizers, and their precursors may be used in combination for various purposes.

[0046] The image-forming layer of the thermal recording material in the present invention preferably contains a binder component for the purpose of holding an infrared absorbing dye, a non-photosensitive organic silver salt, and a reducing agent. A thermoplastic resin is preferred as the binder component, and examples include cellulose derivatives such as hydroxyethylcellulose and hydroxypropylcellulose, acrylic resins, polyester resins, polyurethane resins, vinyl chloride resins, vinyl acetate resins, polyolefin resins, polyvinyl acetal resins represented by polyvinyl butyral resin, and polyvinyl alcohol resins. These binder components may be used dissolved in water or an organic solvent, or they may be latex in which hydrophobic polymer solids are dispersed as fine particles, or polymer molecules may be dispersed forming micelles. In the image-forming layer of the present invention, the above-mentioned binder components preferably form a light-transmitting film after drying. Furthermore, two or more mutually compatible resins may be used in combination as needed.

[0047] In addition to the infrared absorbing dye, non-photosensitive organic silver salt, reducing agent, and binder component described above, the image-forming layer of the thermal recording material in the present invention may also contain known additives such as ultraviolet absorbers, antioxidants, silane coupling agents, pigments, dyes, pH adjusters, surfactants, defoamers, thickeners, softeners, lubricants, antistatic agents, and antiblocking agents, depending on the purpose.

[0048] An example of a method for forming the image-forming layer of the thermal recording material in the present invention is to prepare an image-forming layer coating solution containing the above-mentioned infrared absorbing dye, a non-photosensitive organic silver salt, a reducing agent, a binder component, an additive capable of containing the image-forming layer, and a known solvent, and then to apply and dry the image-forming layer coating solution onto the above-mentioned light-transmitting support. The amount of the image-forming layer coating solution applied is 3.0 to 50.0 g / m² by dry mass. 2 Preferably, 5.0 to 40.0 g / m² 2 More preferably, 8.0-30.0 g / m 2 That is even more preferable.

[0049] As long as the above-described elements are provided, the configuration of the image forming layer of the heat-sensitive recording material in the present invention is not particularly limited. However, since a high-contrast image can be obtained by irradiating infrared laser light, the image forming layer is preferably formed on a light-transmissive support by a laminated structure including an infrared absorption layer containing an infrared absorption dye and a heat-sensitive recording layer containing a non-photosensitive organic silver salt and a reducing agent on the infrared absorption layer. Further, since the ejecta during infrared laser light irradiation can be effectively reduced, it is preferable to have a protective layer as the outermost layer on the image forming layer. Therefore, a particularly preferred embodiment of the heat-sensitive recording material in the present invention is to have at least an infrared absorption layer, a heat-sensitive recording layer, and a protective layer in this order from the side closer to the light-transmissive support on the light-transmissive support.

[0050] When the image forming layer has a heat-sensitive recording layer and an infrared absorption layer, the infrared absorption layer preferably contains a binder for the purpose of holding the infrared absorption dye. Examples of such a binder include the binders that the above-described image forming layer can contain. The content of the infrared absorption dye in the infrared absorption layer is not particularly limited, but is preferably 0.05 to 50% by mass, more preferably 0.1 to 20% by mass, based on the total solid content of the infrared absorption layer.

[0051] It is also a preferred embodiment that the infrared absorption layer contains a reducing agent in addition to the infrared absorption dye and the binder component. Examples of such a reducing agent include the reducing agents that the image forming layer contains. The reducing agents contained in the infrared absorption layer and the heat-sensitive recording layer may be the same, different, or may contain two or more types.

[0052] The infrared absorption layer is preferably formed by preparing an infrared absorption layer coating solution containing the above-described infrared absorption dye, binder component, reducing agent, additives that the image forming layer can contain, and a known solvent, and coating and drying the infrared absorption layer coating solution on the above-described light-transmissive support. The coating amount of the infrared absorption layer coating solution is preferably 0.01 to 8.0 g / m 2 in terms of dry mass, and more preferably 0.05 to 5.0 g / m 2 in terms of dry mass.

[0053] When the image-forming layer has a thermal recording layer, it is preferable that the thermal recording layer contains a binder for the purpose of holding a non-photosensitive organic silver salt and a reducing agent. Examples of such binders that can be preferably contained in the image-forming layer are listed. It is preferable that the binder component of the thermal recording layer does not contain free halide ions such as chloride ions and bromide ions. Halide ions react with the silver ions of the organic silver salt to form photosensitive silver halides, which can reduce the light resistance of the thermal recording material in this invention. Specifically, it is preferable that the content of halide ions is 100 ppm or less relative to the binder component.

[0054] In the present invention, when the image-forming layer has an infrared absorption layer and a thermal recording layer, it is preferable that the infrared absorption layer and the thermal recording layer are adjacent to each other. This makes image formation by irradiation with infrared laser light more efficient, and in particular, allows for the acquisition of high-contrast images. As a method for forming the thermal recording layer, it is preferable to prepare a thermal recording layer coating solution containing the aforementioned organic silver salt, reducing agent, colorant, binder component, and additives that can contain the image-forming layer, as well as a known solvent, and then apply and dry the thermal recording layer coating solution on the infrared absorption layer described above. Furthermore, the amount of the thermal recording layer coating solution applied is 2.0 to 30.0 g / m² by dry mass. 2 Preferably, 5.0 to 20.0 g / m² 2 More preferably, 7.0-15.0 g / m 2 That is even more preferable.

[0055] When a protective layer is provided as the outermost layer on the image-forming layer, it is preferable that the protective layer contains at least hydrophilic particles and a hydrophobic resin. This configuration effectively reduces ejecta when irradiated with infrared laser light.

[0056] In this invention, hydrophilic particles refer to particles whose surfaces are easily wetted by water. Specifically, this can include particles of inorganic materials that are easily wetted by water, such as metals like gold, silver, and copper; metal oxides like silica, alumina, and zirconia; layered silicates; or composites thereof; or particles of organic materials such as acrylic particles, styrene particles, and melamine particles whose surfaces are easily wetted by water; or particles of organic-inorganic composite materials whose surfaces are easily wetted by water. An example of a method for determining whether a particle is hydrophilic is to measure 10 mL of pure water into a glass beaker, add 0.1 g of the particles thereto, stir, and let stand for 10 minutes. If the particles remain floating on the water surface without separating, they are considered hydrophilic. Hydrophilic particles may be subjected to known surface treatments. Two or more types of hydrophilic particles may be used in combination.

[0057] Among the hydrophilic particles described above, hydrophilic inorganic particles are preferred because they are excellent at reducing ejecta generated from the surface of the thermal recording material when irradiated with infrared laser light.

[0058] The lower limit of the average particle diameter of hydrophilic particles is not particularly limited, but it is preferably 1 μm or larger because it can effectively reduce ejecta generated from the surface of the thermal recording material by irradiation with infrared laser light. The upper limit of the average particle diameter of hydrophilic particles is not particularly limited, but it is preferably 10 μm or smaller because it can obtain high-contrast images. As the average particle diameter, the volume-based calculated value obtained by laser diffraction / scattering particle size distribution measurement can be used. Specifically, a method using the MT3000II laser diffraction / scattering particle size distribution analyzer manufactured by Microtrac-Bell, Inc. can be exemplified.

[0059] The hydrophilic particles that can be contained in the protective layer of the present invention can be commercially available products. For example, as silica particles, commercially available products include the SeaHostar® KE series sold by Nippon Shokubai Co., Ltd., the SunSphere® series sold by AGC SI-TEC Inc., and the Silysia® series sold by Fuji Silysia Chemical Co., Ltd. As alumina particles, commercially available products include the fine alumina SA30 series, SA40 series, and SMM series sold by Nippon Light Metal Co., Ltd. As acrylic particles, commercially available products include the Chemisnow® MX series sold by Soken Chemical Co., Ltd. and the Techpolymer® AQS series sold by Sekisui Chemical Co., Ltd. As melamine particles, commercially available products include the OptoBeads® series sold by Nissan Chemical Corporation and the Epostor® series sold by Nippon Shokubai Co., Ltd. All of these can be preferably used.

[0060] The amount of hydrophilic particles that the protective layer can contain is not particularly limited, but it is preferably 0.8 to 40% by mass, and more preferably 1.2 to 30% by mass, relative to the total solid content of the protective layer.

[0061] The hydrophobic resin that the protective layer can contain is not particularly limited and may contain known hydrophobic resins such as acrylic resins, urethane resins, silicone resins, acrylic urethane resins, polyester resins, cellulose acetate resins, and epoxy resins. In this invention, a hydrophobic resin means a resin whose solubility in 100g of water at 25°C is less than 1g. Two or more hydrophobic resins may be used in combination.

[0062] The components and formation method of the protective layer are not particularly limited, but it is preferable to form the protective layer by applying a protective layer coating solution containing hydrophilic particles, a polyvalent isocyanate compound, and a polyol compound, as this provides a protective layer that can effectively reduce ejecta generated from the surface of the thermal recording material when irradiated with infrared laser light. Crosslinking of the polyvalent isocyanate compound and the polyol compound produces various urethane resins, which are hydrophobic resins. The polyvalent isocyanate compounds described above are preferably compounds having two or more isocyanate groups in their molecule. Examples include aliphatic polyvalent isocyanate compounds such as dimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, decanediisocyanate, and isophorone diisocyanate; aromatic polyvalent isocyanate compounds such as tolylene diisocyanate, 1,3-phenylene diisocyanate, 1,3-dimethylbenzol-2,6-diisocyanate, and naphthalene-1,4-diisocyanate; adduct compounds formed by the dimer or trimer of one or more of these polyvalent isocyanate compounds; and adduct compounds formed by the reaction of these polyvalent isocyanate compounds with divalent or trivalent polyols. Of these, hexamethylene diisocyanate and its adduct are preferred as aliphatic polyhydric isocyanate compounds, and tolylene diisocyanate and its adduct are preferred as aromatic polyhydric isocyanate compounds. These polyhydric isocyanate compounds may be used individually or in combination of two or more, depending on the purpose. Products that are commonly sold as isocyanate crosslinking agents can be used as such, and specific product names include the Barnock® series from DIC Corporation and the Coronate® series from Tosoh Corporation.

[0063] The amount of polyvalent isocyanate compound that the protective layer coating liquid in the present invention can contain is preferably 59 to 95% by mass relative to the total solid content of the protective layer coating liquid, more preferably 59 to 90% by mass, and even more preferably 59 to 80% by mass, because this provides excellent alcohol resistance to the surface of the thermal recording material.

[0064] Polyol compounds that can be contained in the protective layer coating liquid of the present invention include cellulose derivatives such as cellulose acetate, hydroxyethylcellulose, and hydroxypropylcellulose, as well as copolymers of polyhydric alcohols and various monomers, such as acrylic polyols, polyether polyols, polyester polyols, and polycarbonate polyols. These polymer compounds may be used individually or in combination of two or more, depending on the purpose. Among these, the use of acrylic polyols is even more preferable, and commercially available acrylic polyols include the Acrydic® series (manufactured by DIC Corporation) and the #6000 series (manufactured by Taisei Fine Chemical Co., Ltd.). Therefore, the protective layer in the present invention preferably contains an acrylic urethane resin obtained by the reaction of an acrylic polyol with a polyhydric isocyanate.

[0065] In the present invention, a method for forming a protective layer is to prepare a protective layer coating solution containing the hydrophilic particles, hydrophobic resin, an additive capable of containing an image-forming layer, and a known solvent, and then apply and dry the protective layer coating solution onto the thermal recording layer. The amount of the protective layer coating solution applied is 1.5 to 10 g / m² by dry mass. 2 Preferably, 2-8 g / m 2 This is preferable.

[0066] In the present invention, there are no particular limitations on the coating method for the infrared absorption layer coating liquid, the thermal recording layer coating liquid, and the protective layer coating liquid described above, and various coating methods such as those described in ED Cohen, EB Gutoff, “Modern Coating and Drying Technology”, WILEY-VCH, Inc. New York, 1992 can be selected. Furthermore, simultaneously coating multiple layers using a slide coating method with a slit-type die coater or a tandem coating method that repeats coating and drying processes by combining the same or different types of coater devices is particularly preferable in terms of improving productivity.

[0067] In the thermal recording material of the present invention, in addition to the infrared absorbing layer, thermal recording layer, and protective layer described above, an easy-adhesion layer or heat insulating layer may be provided between the light-transmitting support and the infrared absorbing layer, an intermediate layer may be provided between each of the infrared absorbing layer, thermal recording layer, and protective layer, an easy-peel layer may be provided on the protective layer, or an antistatic layer may be provided on the opposite side of the light-transmitting support having the infrared absorbing layer, thermal recording layer, and protective layer. However, as described above, from the viewpoint of obtaining a high-contrast image, it is preferable that the infrared absorbing layer and the thermal recording layer are adjacent to each other.

[0068] In the present invention, the thermal recording material preferably has a total light transmittance of 55% or more, more preferably 59% or more, and particularly preferably 64% or more, according to JIS K7361-1:1997. This reduces the amount of material ejected from the surface of the thermal recording material when irradiated with infrared laser light. As a specific method for measuring the total light transmittance, an example can be found in the method of measuring it using a haze meter HZ-V3 (manufactured by Suga Test Instruments Co., Ltd.) with a D65 light source.

[0069] The upper limit of the total light transmittance of the thermal recording material in the present invention is not particularly limited and can vary widely depending on the absorption of visible light wavelengths by the infrared absorbing dye contained in the image forming layer. However, it is preferable that it be 86% or less in order to obtain a high-contrast image.

[0070] The method for controlling the total light transmittance to 55% or more is not particularly limited, and examples include adjusting the amount of infrared absorbing dye in the image forming layer, adjusting the film thickness of the image forming layer, or incorporating dyes or pigments other than infrared absorbing dyes (such as carbon black) into the image forming layer.

[0071] The thermal recording material on which an image has been formed by the image forming method of the present invention can be suitably used as a light-shielding mask material, or so-called plate-making material, used when preparing printing plates such as flexographic printing plates and screen printing plates. However, it can also be used for other purposes, such as a photomask in photolithography. This description does not limit the present invention. [Examples]

[0072] The present invention will be described below using examples, but this description is not intended to limit the present invention. In the description, "%" refers to a mass basis.

[0073] <Preparation of thermal recording material 1> <Preparation and application of infrared absorbing layer coating solution> 81.0 g of 2-butanone and 24.0 g of methanol were mixed with 9.0 g of polyvinyl butyral (Butvar® B-79, manufactured by Eastman Chemical Japan Co., Ltd.) and 0.45 g of exemplary compound (5) (IRT, manufactured by Showa Denko K.K., ε(830) / ε(365)=6.2) as an infrared absorbing dye to prepare an infrared absorbing layer coating solution. This infrared absorbing layer coating solution was applied to a 100 μm thick polyethylene terephthalate base (total light transmittance 92%, haze value 4%) at a dry mass of 1.0 g / m². 2 The coating was applied using a wire bar, and dried at 60°C for 1 minute to form an infrared absorption layer.

[0074] <Preparation of silver behenate dispersion> 20.0 g of silver behenate crystals and 22.0 g of polyvinyl butyral (Butvar B-79) were added to 175 g of 2-butanone, and a silver behenate dispersion (average particle size 0.8 μm) was obtained using a bead mill (DYNO-MILL KD20B model, manufactured by Willy e. Bakkofen) packed with zirconia beads with a diameter of 0.65 mm.

[0075] <Preparation and application of thermal recording layer coating solution> 45.0 g of 2-butanone was mixed with 4.2 g of polyvinyl butyral (Butvar B-79), 91.2 g of the aforementioned silver behenate dispersion, 5.0 g of ethyl 3,4-dihydroxybenzoate, 0.1 g of tetrachlorophthalic anhydride, and 1.9 g of phthalazone to prepare the thermal recording layer coating solution. This thermal recording layer coating solution was then applied to the infrared absorption layer already obtained as described above at a silver equivalent value of 1.1 g / m². 2 The material was applied using a wire bar and dried at 80°C for 3 minutes to form a thermal recording layer.

[0076] <Preparation and application of protective coating solution> To 25.7g of toluene, 15.2g of Acrydic WBU-1218 (manufactured by DIC Corporation; acrylic polyol solution, solid content 30% by mass) and 0.35g of Seahostar KE-P250 (manufactured by Nippon Shokubai Co., Ltd.; hydrophilic silica particles, average particle size 2.5 μm) were added and stirred to make the mixture homogenized. Then, while stirring, 12g of Coronate 2715 (manufactured by Tosoh Corporation; polyisocyanate modified solution, solid content 90% by mass) was added to obtain a protective layer coating solution. This protective layer coating solution was applied to the above thermal recording layer with a dry mass of 4.5 g / m². 2 The material was applied using a wire bar, dried at 80°C for 3 minutes, and then heated at 40°C for 5 days to form a protective layer. In this way, thermal recording material 1 was obtained. The total light transmittance of thermal recording material 1, according to JIS K7361-1:1997, was 71.3%.

[0077] <Preparation of thermal recording material 2> A thermal recording material 2 was obtained in the same manner as the preparation of thermal recording material 1, except that the infrared absorbing dye in the infrared absorbing layer coating solution was changed to 0.45 g of example compound (1) (ε(830) / ε(365)=18.5). The total light transmittance of thermal recording material 2 was 85.1%.

[0078] <Preparation of thermal recording material 3> A thermal recording material 3 was obtained in the same manner as the preparation of thermal recording material 1, except that an infrared absorbing dye was not added to the infrared absorbing layer coating solution. The total light transmittance of thermal recording material 3 was 88.4%.

[0079] <Formation of a filled image> The surfaces of the thermal recording layers of the thermal recording materials 1 to 3 obtained in this manner were scanned and exposed with infrared laser light using a thermal CTP setter (AURA600E, manufactured by Guangzhou Amsky Technology Co., Ltd.) to obtain a 4000 dpi filled image (100 mm (width) × 100 mm (length)). The drum rotation speed of the thermal CTP setter was fixed at 300 rpm, and the laser output was set to 350 mW. The overlap rate of the exposure area in the sub-scanning direction of the infrared laser light was varied to 0.50%, 0.70%, 0.90%, 1.1%, 9.0%, 15%, 27%, and 39%, and filled images were obtained at each overlap rate. For thermal recording material 3, scanning exposure at an overlap rate of 1.1% did not produce color and a filled image was not obtained, so scanning exposure at other overlap rates was not performed.

[0080] <Evaluation of UV light transmission density> After obtaining the images as described above, the ultraviolet light transmission density of the image area and non-image area of ​​each of the thermal recording materials 1 to 3 was measured using the ultraviolet light mode of the X-Rite361T (manufactured by Videojet X-Rite Co., Ltd.) at each overlap rate, and the maximum ultraviolet light transmission density (Dmax) of the image area and the minimum ultraviolet light transmission density (Dmin) of the non-image area were obtained. The calculation results of Dmax-Dmin are shown in Table 1.

[0081] [Table 1]

[0082] <Image Uniformity Evaluation> After obtaining the images as described above, the image areas of each of the thermal recording materials 1 to 3 were observed under a microscope to check for image gaps and density variations. The results, judged according to the following criteria, are shown in Table 1. Note that thermal recording material 3 could not be evaluated because a solid image could not be obtained.

[0083] <Image Uniformity Standards> Excellent: There are no missing images, and the density of the image areas is uniform. Good: No image defects, but slight density variations are visible in the image area. Acceptable: There are no missing images, but density variations are clearly visible in the image area. Unacceptable: Missing images

[0084] <Evaluation of ejected material> After obtaining the images as described above, the areas surrounding the images were observed visually and under a microscope at each overlap rate of thermal recording materials 1 to 3 to check for contamination by ejected material around the image. The results, judged according to the following criteria, are shown in Table 1. Note that thermal recording material 3 could not be evaluated because a solid image could not be obtained.

[0085] <Ejecta standards> Excellent: No contamination from ejected material is observed. Good: Very small amounts of ejected material are visible around the image area (not visible to the naked eye, but visible under a microscope). Acceptable: Although some ejected material is visible around the image, there are no practical problems. Unusable: A large amount of ejected material has accumulated around the image area, making it unusable.

[0086] As is clear from the results in Table 1, the image forming method of the present invention reduces ejecta generated from the surface of the thermal recording material, and a high-contrast and uniform image can be obtained.

[0087] The surface of thermal recording material 1 having a thermal recording layer was scanned and exposed with infrared laser light using a thermal CTP setter (AURA600E, manufactured by Guangzhou Amsky Technology Co., Ltd.) to obtain a 4000 dpi filled image (100 mm (width) × 100 mm (length)). During this process, the drum rotation speed of the thermal CTP setter was fixed at 480 rpm, the overlap rate of the exposure area in the sub-scanning direction of the infrared laser light was fixed at 3.0%, and the laser output was stepped between 100 mW and 400 mW. In this way, the surface of the thermal recording material was exposed by stepwise varying the amount of infrared laser irradiation. When the ultraviolet light transmission density was evaluated in the same manner as in Example 1, the Dmax-Dmin value was 3.0 at a laser output of 350 mW. The amount of infrared laser irradiation on the surface of the thermal recording material in this state was defined as A.

[0088] <Evaluation of halftone uniformity> The surface of the thermal recording material 1 having a thermal recording layer was scanned and exposed with infrared laser light using a thermal CTP setter (AURA600E, manufactured by Guangzhou Amsky Technology Co., Ltd.) to obtain a 4000 dpi 50% halftone image (100 mm (width) × 100 mm (length)). In this process, the thermal recording material 1 was fixed on an intake slit on the drum, the laser output was fixed at 350 mW, and the exposure area overlap rate in the sub-scanning direction was fixed at 3.0%. Furthermore, halftone images were obtained by changing the drum rotation speed to 480 rpm, 453 rpm, 425 rpm, 400 rpm, 369 rpm, 343 rpm, 320 rpm, and 300 rpm. By reducing the drum rotation speed during exposure, the amount of infrared laser irradiation on the surface of the thermal recording material changed to 1.00A, 1.06A, 1.13A, 1.20A, 1.30A, 1.40A, 1.50A, and 1.60A.

[0089] Using the halftone image obtained as described above as the original artwork, a contact exposure was performed on a violet digital plate (VDPF175: a printing plate manufactured by Mitsubishi Paper Mills Ltd.) using a P-627-GA contact exposure printer (manufactured by SCREEN Corporation). The plate was then washed and developed with 30°C water to obtain a printing plate. The halftone image of the printing plate was visually observed to check whether the image density corresponding to the intake slit was visible. The results, judged according to the following criteria, are shown in Table 2.

[0090] <Standards for dot uniformity> Good: The image shading corresponding to the intake slit is not visible on the printed plate. Acceptable: Slight variations in image density corresponding to the intake slits are visible on the printed version, but this does not pose a practical problem. Unacceptable: The image shading corresponding to the intake slit is clearly visible on the printed plate, making it impractical.

[0091] [Table 2]

[0092] As is clear from the results in Table 2, the image forming method of the present invention can improve the uniformity of the image formed on the thermal recording material even when the surface of the holding structure for the thermal recording material is not flat. [Explanation of symbols]

[0093] 1. Thermal recording material 2 Image formation area 11 images 21. Infrared laser light oscillator 22 Infrared laser light 31, 32 Scanning width in the sub-scanning direction 33 overlap width Images 35 and 37 41 Retention structure 42, 43 Intake slits

Claims

[Claim 1] For a thermal recording material having an image-forming layer containing an infrared absorbing dye, a non-photosensitive organic silver salt, and a reducing agent on a light-transmitting support, the overlap rate of the exposure range in the sub-scanning direction of the infrared laser light during scanning exposure with infrared laser light is 0.60 to 9%. An image forming method characterized in that the irradiation amount X when scanning and exposing a thermal recording material with infrared laser light is expressed by the following formula. 1.03A≦X≦1.55A (In the above formula, A represents the infrared laser irradiation dose at which the difference between the maximum ultraviolet light transmission density (Dmax) in the image area and the minimum ultraviolet light transmission density (Dmin) in the non-image area, Dmax - Dmin, is 3.0.)

Images