JP2005077878A - Packaging material for sheetlike recording material and package - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive packaging material excellent in humidity control performance and widely usable as a packaging material for charging various sheetlike recording materials. <P>SOLUTION: The packaging material for a sheetlike recording material is made of base paper comprising pulp, 20-80 mass% of which is mechanical pulp. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a packaging material for a sheet-shaped recording material and a packaging body. In particular, the present invention relates to a packaging material that can be used as a contact ball for a sheet-shaped recording material such as a heat-developable photosensitive material or a heat-sensitive recording material, and a package using the packaging material.

  Sheet-shaped recording materials are widely used in various fields as sheets for recording images. Usually, a sheet-like recording material is loaded in a state where a predetermined number of sheets are stacked in a packaging material such as a contact ball. For example, a photothermographic material, which is one of sheet-like recording materials, is loaded on a contact ball 1 as shown in FIG. 2A so that the laminated state can be maintained. The photothermographic material loaded in the contact ball in this manner is further sealed with the light-proof moisture-proof bag 12 or the like and distributed as a package.

  When performing image recording on the photothermographic material, an image recording apparatus is generally used. As shown in FIG. 6, in the image recording apparatus 13, an unexposed photothermographic material is set in advance in a light-shielded cassette 14 in the image recording apparatus, and heat is generated when image recording becomes necessary. The developing photosensitive material is unloaded one by one from the cassette and exposed and developed. It is necessary to securely set a large number of photothermographic materials unexposed in the cassette. For this reason, usually, the photothermographic material is set by loading the cassette 14 in the state of being kept in the light-proof and moisture-proof bag 12 and removing the light-proof and moisture-proof bag while keeping the light-shielded state. At this time, the photothermographic material is set in the cassette while being loaded on the contact ball.

  As described above, the photothermographic material is loaded in a state of being in direct contact with the contact ball, distributed, and used. Therefore, the contact ball greatly affects the environment where the photothermographic material is placed. Since the contact ball loaded with the photothermographic material is sealed in the light-proof and moisture-proof bag, the moisture absorption and moisture release properties of the contact ball greatly influence the humidity environment in the light-proof and moisture-proof bag. For example, when the contact ball releases moisture in the light-proof moisture-proof bag, the humidity in the bag increases and the performance of the photothermographic material decreases. In addition, if the hygroscopicity of the contact ball is low, the moisture that has entered the light-shielding moisture-proof bag is absorbed by the photothermographic material, and the performance of the photothermographic material is similarly reduced.

  Such a problem also exists in sheet-like recording materials (for example, heat-sensitive recording materials) other than the photothermographic material. Further, not only a so-called dry type sheet-like recording material that develops without using a developer but also a so-called wet type sheet-like recording material that develops using a developer has the same problem. Therefore, it is required to devise so that the sheet-shaped recording material loaded in the contact ball does not absorb moisture and deteriorate the performance.

  In order to meet such a demand, it has been proposed to provide a humidity control member on a contact ball loaded with a heat-sensitive recording material to adjust the humidity in the light-proof moisture-proof bag within an appropriate range (Japanese Patent Laid-Open No. 9-101596). Publication: Patent Document 1). However, in this method, there is a problem that a step of providing a humidity control member on the contact ball is required when producing a package, and that the production and attachment of the humidity control member are costly.

In addition, it has also been proposed that the moisture content of a contact ball loaded with a sheet-shaped recording material is 10% or less and hermetically packaged (Japanese Patent Laid-Open No. 9-5936: Patent Document 2). However, in this method, there is a problem that a step of reducing the moisture content of the contact ball to 10% or less is required before sealing, and that the cost for humidity control is high.
Japanese Patent Application Laid-Open No. 9-101596, Claims Japanese Patent Application Laid-Open No. 9-5936, Claims

  Accordingly, an object of the present invention is to provide a packaging material that can be widely used as a packaging material for loading various types of sheet-shaped recording materials, has excellent humidity control and can be provided at low cost. Another object of the present invention is to provide a package having excellent humidity control.

As a result of intensive studies, the present inventor has found that if a base paper characterized in that 20 to 80% by mass of the pulp contained in the base paper is a mechanical pulp, a packaging material for the above purpose can be obtained, The present invention has been reached as follows.
(1) A packaging material for a sheet-like recording material composed of a base paper, wherein 20 to 80% by mass of the pulp contained in the base paper is mechanical pulp.
(2) The packaging material for sheet-shaped recording material according to (1), wherein the basis weight is 250 to 400 g / m ² .
(3) The packaging material for sheet-shaped recording material according to (1) or (2), wherein the basis weight is 270 to 360 g / m ² .
(4) A contact ball made of the packaging material according to any one of (1) to (3).
(5) A package in which the packaging material according to any one of (1) to (3) is loaded with a sheet-like recording material.
(6) A package in which the photothermographic material is loaded on the packaging material according to any one of (1) to (3).
(7) A package in which the packaging material according to any one of (1) to (3) is loaded with a heat-sensitive recording material.
(8) The package according to any one of (5) to (7), wherein the packaging material has a form of a hitting ball.
(9) The package according to any one of (5) to (8), wherein the sheet-shaped recording material is accommodated in a state where at least a part of the sheet-shaped recording material is in contact with the packaging material.

  The packaging material for sheet-shaped recording material of the present invention has the advantage that it is excellent in humidity control and can be manufactured at low cost. For this reason, even if the sheet-shaped recording material is stored for a long period of time or stored under a high temperature condition, the sheet-shaped recording material can be maintained with high performance. The packaging material for sheet-like recording materials of the present invention can be widely used for loading sheet-like recording materials such as heat-developable photosensitive materials and heat-sensitive recording materials.

BEST MODE FOR CARRYING OUT THE INVENTION

  Below, the packaging material for sheet-like recording materials and package of this invention are demonstrated in detail. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

  The base paper constituting the packaging material for sheet-like recording material of the present invention is characterized in that 20 to 80% by mass of the pulp contained in the base paper is mechanical pulp. The mechanical pulp is preferably 30 to 70% by mass of the pulp contained in the base paper, and more preferably 40 to 60% by mass.

  Although there are various types of mechanical pulp, any type of mechanical pulp can be used for the base paper constituting the packaging material for sheet-like recording material of the present invention. For example, GP (groundwood pulp), RGP (refiner groundwood pulp), TMP (thermomechanical pulp), etc. can be used. The method for producing these mechanical pulps is not particularly limited. For example, the grinding conditions by the grinder in the GP manufacturing process, the shape of the disk used in the RGP manufacturing process, the operating conditions, etc. are not particularly limited.

  The packaging material for sheet-like recording material of the present invention comprising the base paper, characterized in that 20 to 80% by mass of the pulp contained in the base paper is mechanical pulp, has a function of high moisture absorption and desorption ability. For this reason, when the environmental humidity in which the sheet-like recording material is placed is high, the packaging material of the present invention absorbs moisture and can adjust the environmental humidity within an appropriate range. In addition, since the function of adjusting the environmental humidity is persistent, the performance of the loaded sheet-shaped recording material can be maintained at a high level even when stored for a long period of time.

  If the packaging material for sheet-shaped recording materials of this invention is used, it can moderately adjust humidity, without using a humidity control member together. However, in order to further enhance the humidity control function, a humidity control member as described in JP-A-9-101596 may be used. Although the shape of the humidity control member is not particularly limited, for example, it can be used in the mode described in FIG. 1 of JP-A-9-101596.

  Among the base papers constituting the packaging material for sheet-like recording material of the present invention, the type of pulp other than mechanical pulp is not particularly limited. Usually, NBKP or LBKP is used. Preferred is LBKP. Moreover, you may use combining several pulp. For example, you may manufacture the base paper used for this invention by mix | blending NBKP and LBKP with a mechanical pulp.

The basis weight of the base paper used in the present invention is preferably 250~400g / m ^2, and more preferably 270~360g / m ^2. Further, the moisture content (JIS-P-8127) of the base paper of the present invention is preferably 7% or less, and more preferably 1 to 4%. The amount of moisture can be appropriately adjusted by a method such as drying.

  The base paper satisfying the conditions of the present invention can be used as it is as a packaging material. That is, even if it uses it as a packaging material for sheet-like recording materials with a base paper, the effect made into the objective of this invention can be acquired. However, the base paper may be subjected to a surface treatment in order to fully exhibit the effects of the present invention.

  There are various surface treatment methods, for example, a method of coating polyvinyl alcohol. In particular, when a photothermographic material or a heat-sensitive recording material is stored as a sheet-like recording material, a packaging material coated with polyvinyl alcohol can be preferably used. As another surface treatment method, a method of coating with an ultraviolet curable resin is also preferable. Specifically, an ultraviolet curable resin described in JP-B-4-13697 can be used. The thickness of the coating layer made of an ultraviolet curable resin is preferably 0.05 μm to 15 μm, and more preferably 0.1 μm to 5 μm.

  Next, the structure of the packaging material of the present invention will be described.

  The packaging material of the present invention has the characteristics that dust generation is low and that it is difficult to generate cracks. For this reason, the packaging material of the present invention can be widely used as a material involved in the packaging of the sheet-like recording material. For example, it may have a structure in direct contact with the sheet-shaped recording material, or may have a structure in which the sheet-shaped recording material may be in direct contact with the sheet-shaped recording material. It may have a structure that does not contact the material. Preferred is a structure in which at least a part of the packaging material is in contact with at least a part of the sheet-like recording material. Even if the packaging material of the present invention is stored in contact with the recording surface of a dry type sheet-shaped recording material for a long period of time, the effect on the photographic properties of the sheet-shaped recording material is small compared to conventional packaging materials. Specifically, it is possible to suppress a change in sensitivity of the sheet-shaped recording material and to reduce the chance of white spot failure (white spot failure) or the like in the recorded image. Therefore, the packaging material of the present invention can be effectively used in a packaging form in which the recording surface of a sheet-shaped recording material, particularly a dry type sheet-shaped recording material, is in direct contact.

  The packaging material of this invention should just be comprised with the base paper which satisfy | fills the conditions of this invention. For example, the paper material may be used for a portion in contact with the sheet-shaped recording material, and a material other than the paper material may be used for other portions. Preferred is an embodiment in which at least a portion that may come into contact with the sheet-like recording material is constituted by the base paper of the present invention. In consideration of the ease of processing and environmental problems in the case of waste, it is particularly preferable to use a packaging material composed entirely of the paper material.

  The packaging material of the present invention is not limited to the one having a structure covering the entire sheet-like recording material, but a case-like object having an opening for loading and discharging like a hitting ball, or a part of the sheet-like recording material It may have a structure (for example, a plate shape, an L shape) in contact with. A structure that can be easily inserted into an exposure apparatus or a developing machine and does not cause a problem in distribution is preferable.

  A typical structure (a hitting ball) of the packaging material of the present invention will be described with reference to FIG.

  The base paper of the present invention is first processed by punching into the shape shown in FIG. In FIG. 1, the bottom surface 2, the connecting portion 3, and the top surface 4 are integrated, and a contact ball (packaging material) 1 can be obtained by bending the ruled line 5 inward approximately 90 degrees. In the figure, 6a and 6b indicate flaps, and 7a and 7b indicate notches. A laminated body 11 in which sheet-like recording materials 10 having a predetermined size are laminated is loaded on the contact ball 1 as shown in FIG. The bottom surface 2 of the contact ball 1 has substantially the same size as the sheet-shaped recording material 10, and the notches 7 a and 7 b formed on the bottom surface 2 are formed by the sheet-shaped recording material 10 loaded on the bottom surface 2. Fully covered. The laminated body 11 of the sheet-like recording material is loaded in a state where the bottom surface, two side surfaces, and a part of the top surface are in contact with the contact ball 1.

The width W ₄ of the top surface 4 of the contact ball 1 is preferably 50.5% or more of the width W ₂ of the bottom surface 2, more preferably 51.5% or more, and 53% or more. Further preferred. The upper limit is set so as not to hinder the discharge of the sheet-like recording material 10. For example, when using a device that sucks the laminated sheet-shaped recording material with a sheet-shaped recording material single-wafer suction disk (hereinafter simply referred to as a suction disk) during exposure and then transports it to the exposure unit, The top surface needs to be open to the extent that it does not interfere. The upper limit of the width W ₄ of the top surface 4 of the contact ball 1 varies depending on the size of the sheet-like recording material 10, but is preferably 70% or less of the width W ₂ of the bottom surface 2, for example, 60% or less. More preferred.

  FIG. 3 shows another typical structure (a hit ball) of the packaging material of the present invention.

3 is different from the hitting ball of FIG. 1 in that there is no flap and the positional relationship between the notches 7a and 7b and the top surface 4 is different. By folding the ruled line 5 in FIG. 3A inward by approximately 90 degrees, the contact ball (packaging material) 1 can be obtained. FIG. 3B is a view showing a state in which the laminated body 11 in which the sheet-like recording material 10 is laminated is loaded on the ball 1. The laminate 11 of sheet-shaped recording material is loaded with its bottom surface, one side surface, and a part of the top surface in contact with the contact ball 1. The relationship between the width W ₄ of the top surface 4 of the contact ball 1 and the width W _{2 of the} bottom surface 2 is the same as that of the packaging material of FIG.

  The packaging material of FIG. 3 has the advantage that, unlike the packaging material of FIG.

  In addition to FIG. 1 and FIG. 3, the structure of the packaging material of the present invention can be modified as appropriate according to the purpose.

  It is preferable that the process of producing a contact ball loaded with a laminate of sheet-like recording material is automated. For example, a sheet-like recording material and a packaging material can be supplied to a sheet-layer stacking supply apparatus described in Japanese Patent Application Laid-Open No. 2001-72015, and a contact ball loaded with the sheet-like recording material stack can be automatically produced. . At this time, the packaging material supplied to the sheet body stacking and feeding apparatus is a planar material having the shape of a developed view as illustrated in FIG. 1, but this is along the folding line in the sheet body stacking and feeding apparatus. It is generally difficult to bend quickly. For this reason, it is preferable to fold the packaging material in advance along the folding line in advance to put a crease, return it to a flat shape again, and then supply it to the sheet stack supply device. And it is preferable that the process (temporary folding process) which attaches such a crease is also automated, For example, the sheet | seat body protective cover supply apparatus described in Unexamined-Japanese-Patent No. 2001-72013 can be used preferably.

  The packaging material of the present invention can be preferably used for such a temporary folding step. That is, it is possible to form a hitting ball having sufficient strength even if it is temporarily folded once and then returned to the flat shape again and then folded back along the folding line. Further, even if such temporary folding is performed, since dust generation is suppressed, the sheet-shaped recording material is not damaged. For this reason, the packaging material of the present invention is suitable for automation of assembly and storage.

The entire contact ball loaded with a laminate of sheet-like recording material is usually sealed in a moisture-proof bag having a high light-shielding property, preferably a completely light-shielding moisture-proof bag. The light-proof and moisture-proof bag is prepared by continuously joining both ends of a roll-shaped long film having moisture resistance by heat sealing (center seal) or the like and processing it into a cylindrical shape. The moisture permeability of the material used for the light-shielding moisture-proof bag is preferably 5 g / m ² · 24 hr or less, and preferably 1 g / m ² · 24 hr or less. Then, a contact ball loaded with a laminate of sheet-like recording material is inserted into a cylindrical light-proof and moisture-proof bag, deaerated, and heat-sealed (cross-sealed) at position 15 in FIG. Seal. Thereafter, as shown in FIG. 4, both ends are folded and fixed with a label 17. At this time, the heat seal (center seal) 16 that is performed when the moisture-proof sheet-like film is processed into a cylindrical body is usually disposed at the center of the top surface. The heat seal portion is thicker than other portions of the light-proof and moisture-proof bag, and the load tends to concentrate on the contact ball by external pressure. For this reason, as described above, if the width W ₄ of the top surface of the contact ball is set to 50.5% or more of the width W ₂ of the bottom surface, the load applied through the heat seal portion is recorded in sheet form via the top surface of the contact ball. Since it is dispersed in the material, the sheet-like recording material can be protected.

  4 is housed in an individual packaging box 18 as shown in FIG. 5, for example, and after a label 19 is pasted, a plurality of individual packaging boxes 18 are further attached to an outer packaging box. 20, the flap is closed, sealed with a hot melt adhesive, and a tape 21 is applied. Thereby, it can be set as the package which can be put in a distribution | circulation stage. The individual packaging box and the outer packaging box are usually formed of cardboard, but may be formed of other materials. Moreover, it is preferable to automate these series of boxes and packaging.

  When recording an image on a sheet-like recording material, an image recording apparatus is generally used. When image recording is performed using a typical image recording apparatus, a sheet-like recording material protected by a contact ball is loaded into the cassette 14 of the image recording apparatus 13 while being kept in a light-proof moisture-proof bag. Next, after cutting one end of the light-proof and moisture-proof bag, the cassette is closed as shown in FIG. 5 to form a light-shielded state, and the light-proof and moisture-proof bag is pulled out and only the light and moisture-proof bag is taken out of the cassette (FIG. 6).

  In this way, the sheet-like recording material is sucked one by one by the suction disk from the contact ball loaded in the cassette of the image recording apparatus and carried out to the exposure unit. The suction disk hits a portion corresponding to a notch formed in the contact ball. When all the unexposed sheet-shaped recording material in the cassette has been carried out, it can be sensed that all the sheet-shaped recording material has been used because air flows into the suction disk from the notch.

  Thus, the packaging material of the present invention has an appropriate strength in a series of steps of loading a sheet-shaped recording material, packaging with a light-proof and moisture-proof bag, transporting, loading into an image recording apparatus, and adsorption with a suction disk, It must be able to retain its structure. Since the paper material used for the packaging material of the present invention has a high hinge strength, it can sufficiently meet such a demand.

  The packaging material of the present invention can be used to load a sheet-like recording material. The sheet-like recording material to be loaded is in the form of a sheet, and the type thereof is not particularly limited as long as image recording can be performed by some recording method. Further, the shape of the sheet is not particularly limited, and may be any of a square, a rectangle, and a circle, and the thickness thereof is not limited. As a typical sheet-like recording material, a recording material having a standard size such as half-cut, B4, large angle, and six-cut can be exemplified.

  Further, the sheet-like recording material may be capable of recording only on one side, or may be recorded on both sides. The sheet-like recording material that can be preferably loaded into the packaging material of the present invention is a sheet-like recording material for X-ray photography. If a sheet-like recording material that can be preferably loaded from another viewpoint is described, it is a so-called dry-type sheet-like recording material that is developed without using a developer. For example, a photothermographic material or a heat sensitive recording material can be exemplified. The dry type sheet-shaped recording material is more strongly affected by the packaging material due to its characteristics. However, if it is loaded into the packaging material of the present invention, the influence on photographic properties due to packaging and subsequent transportation can be sufficiently suppressed. Specifically, it is possible to suppress a change in sensitivity of the sheet-shaped recording material and avoid a problem that white spot failure (white spot failure) occurs in the recorded image.

  Next, a heat-developable image recording material that is a typical sheet-like recording material that can be loaded into the packaging material of the present invention will be described.

  The heat-developable image recording material has a constitution containing at least one non-photosensitive organic silver salt, a reducing agent for silver ions and a binder on one surface of the support. The organic silver salt and the binder are contained in the image forming layer, and the image forming layer preferably further contains an organic silver salt reducing agent for silver ions. The heat-developable image recording material preferably has a photosensitive layer containing a photosensitive silver halide and a binder. Most preferably, the image forming layer contains a photosensitive silver halide and functions as a photosensitive layer. In such a heat-developable image recording material, an image-forming layer, particularly preferably a photosensitive image-forming layer, can be applied with an aqueous coating using a coating solution in which 30% by mass of a solvent that is preferable from an environmental viewpoint is water. And a polymer having an equilibrium water content of 2% by mass or less at 25 ° C. and a relative humidity of 60%, which is preferable for obtaining good photographic performance, is preferred. In the following description, a photothermographic material containing photosensitive silver halide in the image forming layer will be described as an example. The photothermographic material is preferably a mono-sheet type (a type capable of forming an image on the photothermographic material without using another sheet such as an image receiving material). This is particularly effective in a photothermographic material for red to infrared exposure.

  The photothermographic material has a photosensitive layer containing a photosensitive silver halide (catalytic activity amount of photocatalyst) and a reducing agent, and a non-photosensitive layer. The photosensitive layer preferably further contains a binder (generally a synthetic polymer), an organic silver salt (a reducible silver source) and a reducing agent. Furthermore, it is preferable to contain a hydrazine compound (super high contrast agent) and a color tone adjusting agent (controlling the color tone of silver). A plurality of photosensitive layers may be provided in the photothermographic material. For example, a high-sensitivity photosensitive layer and a low-sensitivity photosensitive layer can be provided in the photothermographic material for the purpose of adjusting gradation. The order of arrangement of the high-sensitivity photosensitive layer and the low-sensitivity photosensitive layer may be such that the low-sensitivity photosensitive layer is disposed below (support side) or the high-sensitivity photosensitive layer is disposed below. The non-photosensitive layer may be provided as another functional layer such as a surface protective layer in addition to a layer containing a dye, that is, a filter layer or an antihalation layer.

  Supports for photothermographic materials include paper, polyethylene-coated paper, polypropylene-coated paper, parchment, cloth, metal (eg, aluminum, copper, magnesium, zinc) sheets or thin films, glass, metal (eg, Glass and plastic films coated with chromium alloy, steel, silver, gold, platinum). Preferably, it is a transparent plastic film, and examples of plastic used for the support include polyalkyl methacrylate (eg, polymethyl methacrylate), polyester (eg, polyethylene terephthalate: PET), polyvinyl acetal, polyamide (eg, nylon) and Cellulose esters (eg, cellulose nitrate, cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate) are included. Especially as a support body, the thing of thickness of 90-190 micrometers is preferable, More preferably, it is 150-185 micrometers.

  The support may be coated with a polymer. Examples of the polymer include polyvinylidene chloride, acrylic acid-based polymers (eg, polyacrylonitrile, methyl acrylate), unsaturated dicarboxylic acid (eg, itaconic acid, acrylic acid) polymers, carboxymethyl cellulose, and polyacrylamide. Copolymers may be used. Instead of coating with a polymer, an undercoat layer containing the polymer may be provided.

Examples of the organic silver salt used in the photothermographic material include silver salts of fatty acids (eg, gallic acid, oxalic acid, behenic acid, stearic acid, palmitic acid, lauric acid), carboxyalkylthiourea (eg, 1- (3 -Carboxypropyl) thiourea, 1- (3-carboxypropyl) -3,3-dimethylthiourea) silver salt, polymer reaction product of aldehyde (eg formaldehyde, acetaldehyde, butyraldehyde) and hydroxy-substituted aromatic carboxylic acid Silver complexes of products, silver salts of aromatic carboxylic acids (eg salicylic acid, benzoic acid, 3,5-dihydroxybenzoic acid, 5,5-thiodisalicylic acid), thioenes (eg 3- (2-carboxyethyl) -4-hydroxymethyl-4-thiazoline-2-thioene, 3-carboxymethyl-4-thiazoli 2-thioene) silver salt or silver complex, nitrogen acid (eg, imidazole, pyrazole, urazole, 1,2,4-thiazole, 1H-tetrazole, 3-amino-5-benzylthio-1,2,4-triazole , Benzotriazole) silver salts or silver complexes, silver salts of saccharin, silver salts of 5-chlorosalicylaldoxime and silver salts of mercaptides. Silver behenate is most preferred. The organic silver salt is preferably used at a silver amount of 0.05 to 3 g / m ² , and more preferably 0.3 to ² g / m ² .

The photothermographic material contains a reducing agent for the organic silver salt. The reducing agent for the organic silver salt may be any substance (preferably an organic substance) that reduces silver ions to metallic silver. Such a reducing agent is described in paragraph Nos. 0043 to 0045 of JP-A No. 11-65021 and page 7, line 34 to page 18, line 12 of European Patent Publication No. 0803764. Among them, bisphenol reducing agents (for example, 1,1-bis (2-hydroxy-3,5-dimethylphenyl) -3,5,5-trimethylhexane) are particularly preferable. The addition amount of the reducing agent is preferably from 0.01~5.0g / m ^2, more preferably from 0.1 to 3.0 g / m ^2, with respect to silver 1mol of the surface having the image forming layer Is preferably contained in an amount of 5-50% mol, more preferably 10-40 mol%. The reducing agent is preferably contained in the image forming layer.

  The reducing agent may be contained in the coating solution by any method such as a solution form, an emulsified dispersion form, or a solid fine particle dispersion form, and may be contained in the photothermographic material. Well-known emulsifying dispersion methods include dissolving oil using an oil such as dibutyl phthalate, tricresyl phosphate, glyceryl triacetate or diethyl phthalate, or an auxiliary solvent such as ethyl acetate or cyclohexanone, and mechanically emulsifying the dispersion. The method of producing is mentioned. In addition, as a solid fine particle dispersion method, a reducing agent powder is dispersed in an appropriate solvent such as water by a ball mill, a colloid mill, a vibration ball mill, a sand mill, a jet mill, a roller mill, or an ultrasonic wave to create a solid dispersion. A method is mentioned. In this case, a protective colloid (for example, polyvinyl alcohol) or a surfactant (for example, an anionic surfactant such as sodium triisopropylnaphthalenesulfonate (a mixture of three isopropyl groups having different substitution positions)) may be used. Good. The aqueous dispersion can contain a preservative (eg, benzoisothiazolinone sodium salt).

  The photosensitive silver halide used in the photothermographic material is not particularly limited as a halogen composition, and silver chloride, silver chlorobromide, silver bromide, silver iodobromide, and silver iodochlorobromide can be used. The distribution of the halogen composition in the grains may be uniform, the halogen composition may be changed stepwise, or may be continuously changed. Further, silver halide grains having a core / shell structure can be preferably used. A preferable structure is a 2- to 5-fold structure, and more preferably 2- to 4-fold core / shell particles can be used. A technique of localizing silver bromide on the surface of silver chloride or silver chlorobromide grains can also be preferably used. Methods for forming photosensitive silver halide are well known in the art, for example using the methods described in Research Disclosure No. 17029 of June 1978 and US Pat. No. 3,700,458. Specifically, a method is used in which a photosensitive silver halide is prepared by adding a silver supply compound and a halogen supply compound to gelatin or another polymer solution, and then mixed with an organic silver salt.

  The grain size of the photosensitive silver halide is preferably small in order to keep the cloudiness after image formation low, specifically 0.20 μm or less, more preferably 0.01 to 0.15 μm, and still more preferably 0.02. ˜0.12 μm is preferable. As used herein, the grain size refers to the volume of silver halide grains when the silver halide grains are cubic or octahedral so-called normal crystals, and other than normal crystals such as spherical grains and rod-like grains. This refers to the diameter when an equivalent sphere is considered. When the silver halide grain is a tabular grain, it means the diameter when converted into a circular image having the same area as the projected area of the main surface.

  Examples of the shape of the silver halide grains include cubes, octahedrons, tabular grains, spherical grains, rod-like grains, and potato-like grains, with cubic grains being particularly preferred. Grains with rounded corners of silver halide grains can also be preferably used. The surface index (Miller index) on the outer surface of the photosensitive silver halide grain is not particularly limited, but the ratio of the {100} plane, which has high spectral sensitizing efficiency when adsorbed by the spectral sensitizing dye, is high. preferable. The ratio is preferably 50% or more, more preferably 65% or more, and still more preferably 80% or more. The ratio of the Miller index {100} plane is T.Tani; J.Imaging Sci., 29, 165 (1985) using the adsorption dependence of {111} plane and {100} plane in the adsorption of sensitizing dyes. It can be determined by the method described.

The photosensitive silver halide grains contain a metal or metal complex of Group 8 to Group 10 of the Periodic Table (showing Groups 1 to 18). As the central metal of the group 8 to group 10 metal or metal complex of the periodic table, rhodium, rhenium, ruthenium, osmium and iridium are preferable. One kind of these metal complexes may be used, or two or more kinds of complexes of the same metal and different metals may be used in combination. The preferred content is in the range of 1 × 10 ⁻⁹ mol to 1 × 10 ⁻³ mol with respect to 1 mol of silver. These metal complexes are described in JP-A No. 11-65021, paragraph numbers 0018 to 0024.

Among them, it is preferable to contain an iridium compound in the silver halide grains. Examples of the iridium compound include hexachloroiridium, hexaammineiridium, trioxalatoiridium, hexacyanoiridium, pentachloronitrosyliridium, and the like. These iridium compounds are used by dissolving in water or an appropriate solvent, and are generally used in order to stabilize a solution of the iridium compound, that is, an aqueous hydrogen halide solution (for example, hydrochloric acid, odorous acid, hydrofluoric acid). Or a method of adding an alkali halide (for example, KCl, NaCl, KBr, NaBr, etc.) can be used. Instead of using water-soluble iridium, it is also possible to add another silver halide grain previously doped with iridium and dissolve it at the time of silver halide preparation. The addition amount of these iridium compounds is preferably in the range of 1 × 10 ⁻⁸ mol to 1 × 10 ⁻³ mol per mol of silver halide, and more preferably in the range of 1 × 10 ⁻⁷ mol to 5 × 10 ⁻⁴ mol.

Japanese Patent Application Laid-Open No. 11-84574 discloses a metal atom (for example, [Fe (CN) ₆ ] ⁴⁻ ), a desalting method, and a chemical sensitization method that can be contained in silver halide grains used in a photothermographic material. Nos. 0046 to 0050 and paragraph numbers 0025 to 0031 of JP-A-11-65021. The photosensitive silver halide emulsion in the photothermographic material may be of one type or two or more types (for example, those having different average grain sizes, those having different halogen compositions, those having different crystal habits, conditions for chemical sensitization) May be used in combination. The gradation can be adjusted by using a plurality of types of photosensitive silver halides having different sensitivities. As technologies relating to these, Japanese Patent Application Laid-Open Nos. 57-119341, 53-106125, 47-3929, 48-55730, 46-5187, 50-73627, 57-150841 etc. are mentioned. The sensitivity difference is preferably 0.2 log E or more for each emulsion.

The addition amount of the photosensitive silver halide is preferably 0.03 to 0.6 g / m ² , expressed as an applied silver amount per 1 m ^{2 of the} photothermographic material, and is preferably 0.05 to 0.4 g / m ^{2. 2} is most preferable, 0.1 to 0.4 g / m ² is most preferable, and 0.01 to 0.5 mol of photosensitive silver halide is preferable with respect to 1 mol of the organic silver salt. 0.02-0.3 mol is more preferable, and 0.03-0.25 mol is particularly preferable. Regarding the mixing method and mixing conditions of the separately prepared photosensitive silver halide and organic silver salt, the silver halide grains and organic silver salt that were prepared respectively were mixed with a high-speed stirrer, ball mill, sand mill, colloid mill, vibration mill, homogenizer. However, there is no particular limitation, but there is no particular limitation. However, there is no particular limitation, for example, or a method of preparing an organic silver salt by mixing photosensitive silver halide that has been prepared at any timing during the preparation of the organic silver salt.

  The preferred addition time of the silver halide to the image forming layer coating solution is from 180 minutes before application, preferably from 60 minutes to 10 seconds before application, but there is no particular limitation. Specific mixing methods include mixing in a tank in which the average residence time calculated from the addition flow rate and the amount of liquid delivered to the coater is the desired time, and by N. Harnby, MFEdwards, AWNienow, Takahashi There is a method of using a static mixer or the like described in Chapter 8 of the translation of Koji "Liquid Mixing Technology" (published by Nikkan Kogyo Shimbun, 1989).

  When the organic silver salt-containing layer is formed using a coating solution in which 30% by mass or more of the solvent is water and dried, the binder of the organic silver salt-containing layer is further added to the aqueous solvent (aqueous solvent). It is preferably made of a latex of a polymer that is soluble or dispersible and that has an equilibrium water content of 2% by mass or less, particularly at 25 ° C. and a relative humidity of 60%. The most preferable form is one prepared so that the ionic conductivity is 2.5 mS / cm or less, and as such a preparation method, there is a method of performing purification treatment using a separation functional membrane after polymer synthesis. The aqueous solvent in which the polymer is soluble or dispersible here is a mixture of water or water and 70% by mass or less of a water-miscible organic solvent. Examples of the water-miscible organic solvent include alcohols such as methyl alcohol, ethyl alcohol and propyl alcohol, cellosolves such as methyl cellosolve, ethyl cellosolve and butyl cellosolve, ethyl acetate and dimethylformamide. In the case of a system in which the polymer is not dissolved thermodynamically and exists in a so-called dispersed state, the term aqueous solvent is used here.

  The “equilibrium moisture content at 25 ° C. and 60% relative humidity” means the mass W1 of the polymer in a humidity-controlled equilibrium in an atmosphere of 25 ° C. and 60% relative humidity and the mass W0 of the polymer in an absolutely dry state at 25 ° C. Can be expressed as follows.

W1-W0
――――――――― × 100 (mass%)
W0
For the definition and measurement method of moisture content, for example, Polymer Engineering Course 14, Polymer Material Testing Method (Edited by Society of Polymer Sciences, Jinshokan) can be referred to. The equilibrium moisture content at 25 ° C. and 60% relative humidity of the binder polymer is preferably 2% by mass or less, more preferably 0.01 to 1.5% by mass, and still more preferably 0.02 to 1% by mass. desirable.

  Particularly preferred are polymers that are dispersible in aqueous solvents. Examples of the dispersed state include latex in which fine particles of solid polymer are dispersed and polymer molecules dispersed in a molecular state or forming micelles, and all are preferable. As preferred embodiments, hydrophobic polymers such as acrylic resins, polyester resins, rubber resins (for example, SBR resins), polyurethane resins, vinyl chloride resins, vinyl acetate resins, vinylidene chloride resins, and polyolefin resins can be preferably used. The polymer may be a linear polymer, a branched polymer, or a crosslinked polymer. The polymer may be a so-called homopolymer obtained by polymerizing a single monomer, or a copolymer obtained by polymerizing two or more monomers. In the case of a copolymer, it may be a random copolymer or a block copolymer. The molecular weight of the polymer is 5,000 to 1,000,000, preferably 10,000 to 200,000 in terms of number average molecular weight. When the molecular weight is too small, the mechanical strength of the emulsion layer is insufficient, and when the molecular weight is too large, the film formability is poor, which is not preferable.

The “aqueous solvent” refers to a dispersion medium in which 30% by mass or more of the composition is water. The dispersion state may be any emulsified dispersion, micellar dispersion, or a polymer having a hydrophilic part in the molecule dispersed in the molecular state. Among these, latex is particularly preferable. . Specific examples of preferable polymer latex include the following. Below, it represents using a raw material monomer, the numerical value in a parenthesis is the mass%, and molecular weight is a number average molecular weight.
P-1; -MMA (70) -EA (27) -MAA (3)-latex (molecular weight 37000) P-2; -MMA (70) -2EHA (20) -St (5) -AA (5) -Latex (molecular weight 40000) P-3; -St (50) -Bu (47) -MAA (3)-Latex (molecular weight 45000) P-4; -St (68) -Bu (29) -AA ( 3) -Latex (molecular weight 60000) P-5; -St (70) -Bu (27) -IA (3) -Latex (molecular weight 120000) P-6; -St (75) -Bu (24)- Latex of AA (1)-(molecular weight 108000) P-7; -St (60) -Bu (35) -DVB (3) -MAA (2)-Latex (molecular weight 150000) P-8; -St (70 ) -Bu (25) -DVB (2) -AA (3)-latex (molecular weight 280000) P-9; -VC (50) -MMA (20) -EA (20) -AN (5) -AA ( 5)-Latex (molecular weight 80000) P-10; -VDC (85) -MMA (5) -EA (5) -MAA (5)-Latex (molecular weight 67000) P-11; -Et (90)- Latex of MAA (10)-(Molecular weight 12000) P-12; -St (70) -2EHA (27) -AA (3) Latex (Molecular weight 130000) P-13; -MMA (63) -EA (35) -Latex of AA (2) (molecular weight 33000) The abbreviations of the above structures represent the following monomers. MMA; methyl methacrylate, EA; ethyl acrylate, MAA; methacrylic acid, 2EHA; 2 ethyl hexyl acrylate, St; styrene, Bu; butadiene, AA; acrylic acid, DVB; divinylbenzene, VC; vinyl chloride, AN; acrylonitrile, VDC; Vinylidene chloride, Et; Ethylene, IA; Itaconic acid.

  The polymer latex described above is also commercially available, and the following polymers can be used. Examples of acrylic resins include polyester resins such as Ceviane A-4635, 46583, 4601 (manufactured by Daicel Chemical Industries, Ltd.), Nipol Lx811, 814, 821, 820, 857 (manufactured by Nippon Zeon Co., Ltd.). Examples include polyurethane resins such as FINITEX ES650, 611, 675, and 850 (manufactured by Dainippon Ink Chemical Co., Ltd.), WD-size, WMS (manufactured by Eastman Chemical), and HYDRAN AP10, 20, Examples of rubber-based resins such as 30, 40 (manufactured by Dainippon Ink Chemical Co., Ltd.) include LACSTAR 7310K, 3307B, 4700H, 7132C (manufactured by Dainippon Ink Chemical Co., Ltd.), Nipol Lx416, 410, 438C. , 2507 (made by Nippon Zeon Co., Ltd.) Examples of vinyl resins include G351 and G576 (manufactured by Nippon Zeon Co., Ltd.). Examples of vinylidene chloride resins include L502 and L513 (manufactured by Asahi Kasei Kogyo Co., Ltd.). Examples of olefin resins include: Chemipearl S120, SA100 (made by Mitsui Petrochemical Co., Ltd.) and the like can be mentioned. These polymer latexes may be used alone or in combination of two or more as required.

  As the polymer latex, a latex of a styrene-butadiene copolymer is particularly preferable. The mass ratio of the styrene monomer unit to the butadiene monomer unit in the styrene-butadiene copolymer is preferably 40:60 to 95: 5. The proportion of the styrene monomer unit and the butadiene monomer unit in the copolymer is preferably 60 to 99% by mass. The preferred molecular weight range is the same as described above. Preferred latexes of styrene-butadiene copolymer include the aforementioned P-3 to P-8, commercially available LACSTAR-3307B, 7132C, Nipol Lx416, and the like.

If necessary, a hydrophilic polymer such as gelatin, polyvinyl alcohol, methylcellulose, or hydroxypropylcellulose may be added to the organic silver salt-containing layer of the photothermographic material. The amount of these hydrophilic polymers added is preferably 30% by mass or less, more preferably 20% by mass or less, based on the total binder of the organic silver salt-containing layer. The organic silver salt-containing layer (that is, the image forming layer) is preferably formed using a polymer latex. The amount of the binder in the organic silver salt-containing layer is preferably such that the total binder / organic silver salt mass ratio is 1/10 to 10/1, more preferably 1/5 to 4/1. In addition, such an organic silver salt-containing layer is usually a photosensitive layer (emulsion layer) containing a photosensitive silver halide which is a photosensitive silver salt. The mass ratio of silver is preferably 400-5, more preferably 200-10. The total binder amount of the image forming layer of the photothermographic material is preferably 0.2 to 30 g / m ² , more preferably 1 to 15 g / m ² . A crosslinking agent for crosslinking, a surfactant for improving coating properties, and the like may be added to the image forming layer.

  The solvent for the organic silver salt-containing layer coating solution of the photothermographic material (here, for simplicity, the solvent and the dispersion medium are collectively referred to as a solvent) is an aqueous solvent containing 30% by mass or more of water. As a component other than water, any water-miscible organic solvent such as methyl alcohol, ethyl alcohol, isopropyl alcohol, methyl cellosolve, ethyl cellosolve, dimethylformamide, and ethyl acetate may be used. The water content of the solvent of the coating solution is preferably 50% by mass or more, more preferably 70% by mass or more. Examples of preferred solvent compositions include water, water / methyl alcohol = 90/10, water / methyl alcohol = 70/30, water / methyl alcohol / dimethylformamide = 80/15/5, water / methyl alcohol / Ethyl cellosolve = 85/10/5, water / methyl alcohol / isopropyl alcohol = 85/10/5, etc. (numerical values are mass%).

  As a sensitizing dye that can be applied to a photothermographic material, it can spectrally sensitize silver halide grains in a desired wavelength region when adsorbed on silver halide grains, and has a spectral sensitivity suitable for the spectral characteristics of the exposure light source. Sensitizing dyes can be advantageously selected. Regarding the sensitizing dye and the addition method, paragraphs 0103 to 0109 of JP-A No. 11-65021, compounds represented by the general formula (II) of JP-A No. 10-186572, and EP-A-0803764 It is described on page 19, line 38 to page 20, line 35. In the present invention, the time when the sensitizing dye is added to the silver halide emulsion is preferably the time from the desalting step to the coating, and more preferably the time from the desalting to the start of chemical ripening.

  Antifoggants, stabilizers and stabilizer precursors that can be used in the photothermographic material Paragraph No. 0070 of JP-A-10-62899, page 20, lines 57 to 21 of European Patent Publication No. 0803764 Patents described in the seventh line are listed. Further, the antifoggant preferably used in the photothermographic material is an organic halide, and examples thereof include those disclosed in Japanese Patent Application Laid-Open No. 11-65021, paragraphs 0111 to 0112. . In particular, an organic polyhalogen compound represented by general formula (II) in JP-A-10-339934 (specifically, tribromomethylnaphthylsulfone, tribromomethylphenylsulfone, tribromomethyl (4- (2,4,4 6-trimethylphenylsulfonyl) phenyl) sulfone and the like are preferred.

Examples of the method for incorporating the antifoggant into the photothermographic material include the methods described in the method for containing a reducing agent, and the organic polyhalogen compound is also preferably added as a solid fine particle dispersion. Examples of other antifoggants include mercury (II) salts described in paragraph No. 0113 of JP-A No. 11-65021 and benzoic acids described in paragraph No. 0114 of the same publication. An azolium salt may be used in the photothermographic material for the purpose of fog prevention. As the azolium salt, a compound represented by the general formula (XI) described in JP-A-59-193447, a compound described in JP-B-55-12581, a general formula described in JP-A-60-153039 ( And a compound represented by II). The azolium salt may be added to any part of the photothermographic material, but the addition layer is preferably added to the layer having the photosensitive layer, and more preferably to the organic silver salt-containing layer. The azolium salt may be added at any step in the coating solution preparation. When added to the organic silver salt-containing layer, any step from the preparation of the organic silver salt to the preparation of the coating solution may be used. To immediately before coating. The azolium salt may be added by any method such as powder, solution, fine particle dispersion. Moreover, you may add as a solution mixed with other additives, such as a sensitizing dye, a reducing agent, and a color toning agent. The azolium salt may be added in any amount, but is preferably 1 × 10 ⁻⁶ mol to 2 mol, more preferably 1 × 10 ⁻³ mol to 0.5 mol, per 1 mol of silver.

  In order to suppress or promote development and control development, to improve spectral sensitization efficiency, to improve storage stability before and after development, a mercapto compound, a disulfide compound, and a thione compound can be contained. Paragraph Nos. 0067 to 0069 of JP-A-62899, compounds represented by general formula (I) of JP-A No. 10-186572, and specific examples thereof include paragraph Nos. 0033 to 0052 and No. 20 of European Patent Publication No. 0803764. It is described in pages 36 to 56 on the page. Of these, mercapto-substituted heteroaromatic compounds are preferred.

  It is preferable to add a color toner to the photothermographic material. The color toning agent is described in paragraph Nos. 0054 to 0055 of JP-A No. 10-62899 and lines 21 to 23 to 48 of European Patent Publication No. 0803764, and in particular, phthalazinone, phthalazinone derivatives or metal salts. Or derivatives of 4- (1-naphthyl) phthalazinone, 6-chlorophthalazinone, 5,7-dimethoxyphthalazinone and 2,3-dihydro-1,4-phthalazinedione; phthalazinone and phthalic acid derivatives (eg , Phthalic acid, 4-methylphthalic acid, 4-nitrophthalic acid and tetrachlorophthalic anhydride); phthalazines (phthalazine, phthalazine derivatives or metal salts, or 4- (1-naphthyl) phthalazine, 6-isopropylphthalate) Razine, 6-t-Butylfuratazine, 6-Chlorophthala , Derivatives of 5,7-dimethoxyphthalazine and 2,3-dihydrophthalazine); phthalazines and phthalic acid derivatives (eg, phthalic acid, 4-methylphthalic acid, 4-nitrophthalic acid, tetrachlorophthalic anhydride, etc.) ), And a combination of phthalazines and phthalic acid derivatives is particularly preferable.

  Regarding the plasticizer and the lubricant that can be used in the photosensitive layer of the photothermographic material, paragraph No. 0117 of JP-A No. 11-65021, and for the ultra-high contrast agent for forming an ultra-high contrast image, paragraph number of the same publication. Japanese Patent Application Laid-Open No. 11-65021, paragraph Nos. 11 to 65021 for the compounds of the general formulas (III) to (V) (specific compounds: 21 to 24) described in Japanese Patent Application No. 11-91652 0102.

The photothermographic material can be provided with a surface protective layer for the purpose of preventing adhesion of the image forming layer. The surface protective layer is described in paragraph numbers 0119 to 0120 of JP-A No. 11-65021. Gelatin is preferred as the binder for the surface protective layer, but polyvinyl alcohol (PVA) is also preferred. As PVA, PVA-105 of a completely saponified product [polyvinyl alcohol (PVA) content 94.0% by mass or more, saponification degree 98.5 ± 0.5 mol%, sodium acetate content 1.5% by mass or less, volatile content 5.0% by mass or less, viscosity (4% by mass, 20 ° C.) 5.6 ± 0.4 mPa · s], partially saponified product PVA-205 [PVA content 94.0% by mass, saponification degree 88.0 ± 1.5 mol%, sodium acetate content 1.0 mass%, volatile matter 5.0 mass%, viscosity (4 mass%, 20 ° C) 5.0 ± 0.4 mPa · s], MP-102 of modified polyvinyl alcohol , MP-202, MP-203, R-1130, R-2105 (above, product names manufactured by Kuraray Co., Ltd.), and the like. Preferably 0.3 to 4.0 g / m ² of polyvinyl alcohol coating amount as (per support 1 m ²⁾ is the protective layer (per one layer), 0.3 to 2.0 g / m ² is more preferable.

The preparation temperature of the image forming layer coating solution is preferably 30 to 65 ° C, more preferably 35 ° C or more and less than 60 ° C, and more preferably 35 to 55 ° C. Moreover, it is preferable that the temperature of the image forming layer coating liquid immediately after the addition of the polymer latex is maintained at 30 to 65 ° C. Moreover, it is preferable that the reducing agent and the organic silver salt are mixed before adding the polymer latex. The organic silver salt-containing fluid or the thermal image forming layer coating solution is preferably a so-called thixotropic fluid. Thixotropy refers to the property that the viscosity decreases as the shear rate increases. Although any apparatus may be used for the viscosity measurement, an RFS fluid spectrometer manufactured by Rheometrics Far East Co., Ltd. is preferably used and measured at 25 ° C. Here, the organic silver salt-containing fluid or the thermal image forming layer coating solution has a viscosity at a shear rate of 0.1 S ⁻¹ of preferably 400 to 100,000 mPa · s, more preferably 500 to 20,000 mPa · s. Moreover, in shear rate 1000S- ¹ , 1-200 mPa * s is preferable, More preferably, it is 5-80 mPa * s.

  Various systems that exhibit thixotropic properties are known, and are described in “Lectures / Rheology” edited by Polymer Publishing Co., “Polymer Latex” (published by Polymer Publishing Co., Ltd.) co-authored by Muroi and Morino. In order for the fluid to exhibit thixotropy, it is necessary to contain a large amount of solid fine particles. In order to enhance the thixotropy, it is effective to contain a thickening linear polymer, increase the aspect ratio in the anisotropic shape of the contained solid fine particles, increase the alkali viscosity, and use a surfactant.

  The photothermographic emulsion is composed of one or more layers on a support. One layer composition must contain organic silver salts, silver halides, developers and binders, and optional additional materials such as toning agents, coating aids and other aids. The two-layer construction must contain an organic silver salt and silver halide in the first emulsion layer (usually the layer adjacent to the support) and some other components in the second or both layers. Don't be. However, a two-layer configuration comprising a single emulsion layer containing all components and a protective topcoat is also conceivable. The construction of a multicolor photosensitive photothermographic material may include a combination of these two layers for each color, and all within a single layer as described in US Pat. No. 4,708,928. May be included. In the case of multi-dye multicolor photosensitive photothermographic materials, each emulsion layer is generally functional or non-functional between each photosensitive layer as described in U.S. Pat. No. 4,460,681. By using functional barrier layers, they are kept separate from each other.

Various dyes and pigments can be used for the photosensitive layer from the viewpoints of improving the color tone, preventing interference fringes during laser exposure, and preventing irradiation. These are described in detail in International Publication WO98 / 36322. Preferred dyes and pigments used in the photosensitive layer include anthraquinone dyes, azomethine dyes, indoaniline dyes, azo dyes, anthraquinone-based indanthrone pigments (such as CI Pigment Blue 60), phthalocyanine pigments (such as copper phthalocyanine such as CI Pigment Blue 15), CI Pigment Blue 16 and the like), dyed lake pigment type triarylcarbonyl pigments, indigo, and inorganic pigments (ultraviolet, cobalt blue, etc.). As a method for adding these dyes and pigments, any method such as a solution, an emulsion, a solid fine particle dispersion, or a state mordanted in a polymer mordant may be used. The amount of these compounds to be used is determined by the target absorption amount, but generally it is preferably used in the range of 1 μg to 1 g per 1 m ^{2 of the} photothermographic material.

  The antihalation layer can be provided on the side far from the light source with respect to the photosensitive layer. The antihalation layer is described in paragraph numbers 0123 to 0124 of JP-A No. 11-65021. It is preferable to add a decoloring dye and a base precursor to the non-photosensitive layer of the photothermographic material so that the non-photosensitive layer functions as a filter layer or an antihalation layer. The photothermographic material generally has a non-photosensitive layer in addition to the photosensitive layer. The non-photosensitive layer includes (1) a protective layer provided on the photosensitive layer (on the side farther from the support), and (2) a plurality of photosensitive layers or between the photosensitive layer and the protective layer. (3) an undercoat layer provided between the photosensitive layer and the support, and (4) a back layer provided on the opposite side of the photosensitive layer. The filter layer is provided in the photothermographic material as the layer (1) or (2). The antihalation layer is provided in the photothermographic material as the layer (3) or (4).

  The decolorizing dye and the base precursor are preferably added to the same non-photosensitive layer. However, it may be added separately to two adjacent non-photosensitive layers. A barrier layer may be provided between the two non-photosensitive layers. As a method of adding the decoloring dye to the non-photosensitive layer, a method of adding a solution, an emulsion, a solid fine particle dispersion, or a polymer impregnated product to the coating solution for the non-photosensitive layer can be employed. Moreover, you may add dye to a non-photosensitive layer using a polymer mordant. These addition methods are the same as the method of adding a dye to a normal photothermographic material. Regarding the latex used in the polymer impregnation, US Pat. No. 4,199,363, West German Patent Publications 25141274, 2541230, European Patent Publication No. 0291104 and Japanese Patent Publication No. 53-41091 are disclosed. There is a description. An emulsification method in which a dye is added to a solution in which a polymer is dissolved is described in International Publication WO88 / 00723.

The amount of decoloring dye added is determined by the use of the dye. In general, the optical density (absorbance) measured at the target wavelength is used in an amount exceeding 0.1. The optical density is preferably 0.2-2. The amount of the dye for obtaining such an optical density is generally 0.001 to 1 g / m ² approximately, particularly preferably about 0.01~0.2g / m ^2. If the dye is decolored in this way, the optical density can be reduced to 0.1 or less. Two or more kinds of decoloring dyes may be used in combination in a heat decoloring type recording material or a photothermographic material. Similarly, two or more kinds of base precursors may be used in combination. The photothermographic material is preferably a so-called single-sided photosensitive material having a photosensitive layer containing at least one silver halide emulsion on one side of the support and a back layer on the other side.

In the photothermographic material, it is preferable to add a matting agent for improving transportability, and the matting agent is described in paragraph numbers 0126 to 0127 of JP-A No. 11-65021. The matting agent is preferably 1 to 400 mg / m ² , more preferably 5 to 300 mg / m ² in terms of the coating amount per 1 m ^{2 of the} photothermographic material. The emulsion surface may have any matte degree as long as no stardust failure occurs, but the Beck smoothness is preferably 30 seconds or more and 2000 seconds or less, and particularly preferably 40 seconds or more and 1500 seconds or less. As the matting degree of the back layer, the Beck smoothness is preferably 1200 seconds or less and 10 seconds or more, preferably 800 seconds or less and 20 seconds or more, and more preferably 500 seconds or less and 40 seconds or more. The matting agent is preferably contained in the outermost surface layer of the photothermographic material, the layer functioning as the outermost surface layer, or a layer close to the outer surface, and is preferably contained in a layer acting as a so-called protective layer. preferable. Back layers that can be applied to the photothermographic material are described in paragraph Nos. 0128 to 0130 of JP-A No. 11-65021.

  A hardener may be used for each layer such as the photosensitive layer, the protective layer, and the back layer. Examples of hardeners include each method described on pages 77 to 87 of "THE THEORY OF THE PHOTOGRAPHIC PROCESS FOURTH EDITION" (Macmillan Publishing Co., Inc., published in 1977) by THJames. Polyvalent metal ions, polyisocyanates such as US Pat. No. 4,281,060, JP-A-6-208193, epoxy compounds such as US Pat. No. 4,791,042, Vinyl sulfone compounds such as Japanese Utility Model Laid-Open No. 62-89048 are preferably used.

  The hardening agent is added as a solution, and the addition time of this solution into the protective layer coating solution is from 180 minutes before to immediately before application, preferably from 60 minutes to 10 seconds before application. There are no particular restrictions. Specific mixing methods include mixing in a tank in which the average residence time calculated from the addition flow rate and the amount of liquid delivered to the coater is the desired time, and by N. Harnby, MFEdwards, AWNienow, Takahashi There is a method of using a static mixer described in Chapter 8 of "Liquid Mixing Technology" (published by Nikkan Kogyo Shimbun, 1989).

  For surfactants, paragraph number 0132 of JP-A-11-65021, for solvent, paragraph number 0133 of the same, for support, paragraph number 0134 of the same publication, for antistatic or conductive layer, paragraph number of the same publication. A method for obtaining a color image is described in paragraph number 0136 of the same publication. The transparent support may be colored with a blue dye (for example, dye-1 described in Examples of JP-A-8-240877) or may be uncolored. The undercoating technique of the support is described in JP-A Nos. 11-84574 and 10-186565. Further, techniques such as JP-A-56-143430, JP-A-56-143431, JP-A-58-62646, JP-A-56-120519 can be applied to the antistatic layer or the undercoat.

  The photothermographic material is preferably a mono-sheet type (a type capable of forming an image on the photothermographic material without using another sheet such as an image receiving material). An antioxidant, a stabilizer, a plasticizer, an ultraviolet absorber, or a coating aid may be further added to the photothermographic material. Various additives are added to either the photosensitive layer or the non-photosensitive layer. For these, reference can be made to International Publication WO98 / 36322, European Patent Publication No. 803764, JP-A-10-186567, 10-18568, and the like.

  It is preferable that the photosensitive layer further contains a super-high contrast agent, and the super-high contrast agent may be further included in the non-photosensitive layer. When the photothermographic material is used in the field of photographic printing, it is important to reproduce a continuous tone image or a line image using halftone dots. The reproducibility of a dot image or a line image can be improved by using a super-high contrast agent. As the ultra-high contrast agent, a hydrazine compound, a quaternary ammonium compound or an acrylonitrile compound (described in US Pat. No. 5,545,515) is used. Hydrazine compounds are particularly preferred ultrahigh contrast agents.

The hydrazine compound includes hydrazine (H ₂ N—NH ₂ ) and a compound in which at least one of its hydrogen atoms is substituted. In the substituent, an aliphatic group, an aromatic group or a heterocyclic group is directly bonded to the nitrogen atom of hydrazine, or an aliphatic group, an aromatic group or a heterocyclic group is bonded to the nitrogen atom of hydrazine through a linking group. . Examples of the linking group include —CO—, —CS—, —SO ₂ —, —POR— (R is an aliphatic group, aromatic group or heterocyclic group), —CNH—, and combinations thereof. As for the hydrazine compound, U.S. Pat. Nos. 5,464,738, 5,496,695, 5,512,411, 5,536,622, JP-B-6- 77138, 6-93082, JP-A-6-230497, 6-289520, 6-313951, 7-5610, 7-77783, and 7-104426. There is.

  The hydrazine compound can be dissolved in a suitable organic solvent and added to the coating solution for the photosensitive layer. Examples of the organic solvent include alcohol (eg, methanol, ethanol, propanol, fluorinated alcohol), ketone (eg, acetone, methyl ethyl ketone), dimethylformamide, dimethyl sulfoxide and methyl cellosolve. Moreover, you may emulsify the solution which melt | dissolved the hydrazine compound in the oil-based (auxiliary) solvent in the coating liquid. Examples of oily (co-) solvents include dibutyl phthalate, tricresyl phosphate, glyceryl triacetate, diethyl phthalate, ethyl acetate and cyclohexanone. Furthermore, you may add the solid dispersion of a hydrazine compound to a coating liquid. The dispersion of the hydrazine compound can be carried out using a known disperser such as a ball mill, a colloid mill, a manton goring, a microfluidizer or an ultrasonic disperser.

The addition amount of the super-high contrast agent is preferably 1 × 10 ⁻⁶ to 1 × 10 ⁻² mol, preferably 1 × 10 ⁻⁵ to 5 × 10 ⁻³ mol, relative to 1 mol of silver halide. Is more preferably 2 × 10 ⁻⁵ to 5 × 10 ⁻³ mol. In addition to the ultrahigh contrast agent, a high contrast accelerator may be used. Examples of the contrast accelerator include amine compounds (described in US Pat. No. 5,545,505), hydroxamic acid (described in US Pat. No. 5,545,507), acrylonitriles (US Pat. , 545,507) and hydrazine compounds (described in US Pat. No. 5,558,983).

  The photothermographic material may be applied by any method. Specifically, various types including extrusion coating, slide coating, curtain coating, dip coating, knife coating, flow coating, or extrusion coating using a hopper of the type described in US Pat. No. 2,681,294. Coating operation is used, and extrusion coating or slide coating described in pages 399 to 536 of "LIQUID FILM COATING" (CHAPMAN & HALL, 1997) by Stephen F. Kistler and Petert M. Schweizer is preferably used. Preferably slide coating is used. An example of the shape of a slide coater used for slide coating is shown in FIG. 11b. 1 If desired, two or more layers may be simultaneously coated by the method described on pages 399 to 536 of the same document, the method described in US Pat. No. 2,761,791 and British Patent No. 837,095. can do.

  Techniques that can be used for the photothermographic material include European Patent Publication No. 80376, Japanese Patent No. 883022, International Publication No. WO98 / 36322, Japanese Patent Laid-Open Nos. 56-62648, 58-62644. JP-A-9-281737, JP-A-9-297367, JP-A-9-304869, JP-A-9-31405, JP-A-9-329865, JP-A-10-10669, JP-A-10-62899, No. 10-69023, No. 10-186568, No. 10-90823, No. 10-171663, No. 10-186565, No. 10-186567, No. 10-186669, No. 10 to No. 10 -186572, 10-197974, 10-197982, 10-197 No. 83, No. 10-197985 to No. 10-197987, No. 10-207001, No. 10-207004, No. 10-221807, No. 10-282601, No. 10-288823. Gazette, 10-288824 gazette, 10-307365 gazette, 10-312038 gazette, 10-339934 gazette, 11-7100 gazette, 11-15105 gazette, 11-24200 gazette. Gazette, 11-24201 gazette, 11-30832 gazette, 11-84574 gazette, 11-65021 gazette, 11-125880 gazette, 11-129629 gazette, 11-133536 gazette. ~ 11-133539, 11-133542, 11-133543 It may also be mentioned.

  The photothermographic material may be developed by any method, but is usually developed by raising the temperature of the photothermographic material exposed imagewise. The preferred development temperature is 80 to 250 ° C, more preferably 100 to 140 ° C. The development time is preferably 1 to 180 seconds, more preferably 10 to 90 seconds, and particularly preferably 10 to 40 seconds. A plate heater method is preferred as the heat development method. The heat development method by the plate heater method is preferably a method described in Japanese Patent Application No. 9-229684 and Japanese Patent Application Laid-Open No. 11-133572, and a means for heating the photothermographic material on which a latent image is formed in a heat developing unit. A heat developing device that obtains a visible image by contacting the plate, wherein the heating means comprises a plate heater, and a plurality of pressing rollers are arranged to face each other along one surface of the plate heater, In the heat developing apparatus, the heat development photosensitive material is passed between a roller and the plate heater to perform heat development. It is preferable to divide the plate heater into 2 to 6 stages and lower the temperature about 1 to 10 ° C. at the tip. Such a method is also described in JP-A No. 54-30032, which can exclude moisture and organic solvents contained in the photothermographic material out of the system, and can be rapidly exposed to photothermographic material. Changes in the shape of the support of the photothermographic material due to heating of the material can also be suppressed.

The photothermographic material may be exposed by any method, but a laser beam is preferred as the exposure light source. As the laser light, a gas laser (Ar ⁺ , He—Ne), a YAG laser, a dye laser, a semiconductor laser, and the like are preferable. A semiconductor laser and a second harmonic generation element can also be used. Red to infrared emission gas or semiconductor laser is preferable. As the laser light, a single mode laser can be used, but the technique described in paragraph No. 0140 of JP-A-11-65021 can be used. The laser output is preferably 1 mW or more, more preferably 10 mW or more, and even more preferably 40 mW or more. At that time, a plurality of lasers may be combined. The diameter of the laser beam can be about 30 to 200 μm in terms of the 1 / e ² spot size of the Gaussian beam. As a laser imager provided with an exposure part and a heat development part, Fuji Medical Dry Laser Imager FM-DPL can be mentioned.

  The photothermographic material forms a black and white image by a silver image and is used as a photothermographic material for medical diagnosis, a photothermographic material for industrial photography, a photothermographic material for printing, and a photothermographic material for COM. It is preferable. In these uses, on the basis of the black and white image formed, a duplicate image is formed on a reproduction film MI-Dup manufactured by Fuji Photo Film Co., Ltd. for medical diagnosis, or Fuji Photo Film Co., Ltd. is used for printing. It goes without saying that it can be used as a mask for forming an image on the return film DO-175, PDO-100 or offset printing plate.

  Hereinafter, a heat-sensitive recording material that is one of sheet-like recording materials that can be preferably loaded into the packaging material of the present invention will be described.

  The heat-sensitive recording material has a heat-sensitive recording layer and a protective layer in this order on a support, and further includes other layers as necessary.

  When an intermediate layer is provided on the heat-sensitive recording layer or as the other layer on the heat-sensitive recording layer, the protective layer is formed on the intermediate layer. The protective layer is formed by coating a protective layer coating liquid, and the protective layer coating liquid contains at least a pigment and a binder, and further improves head matching and obtains a good coated surface. Preferably, it contains an emulsion of silicone oil (hereinafter sometimes simply referred to as “silicone oil”) dispersed to an average particle size of 0.15 μm or less, and if necessary, contains other components. .

  The silicone oil is preferably dispersed so that the average particle size is 0.15 μm or less, the average particle size is preferably 0.10 μm or less, and the average particle size is more preferably 0.08 μm or less. When the average particle diameter exceeds 0.15 μm, the emulsion of silicone oil is broken by strong stirring or ultrasonic irradiation to form huge oil droplets, which tends to cause coating failure due to repelling. In this specification, the average particle diameter of the silicone oil indicates a value measured by an N4 type submicron particle analyzer manufactured by COULTER.

  In order to disperse the average particle size of the silicone oil to 0.15 μm or less, for example, in the presence of a dispersion aid such as polyvinyl alcohol and various surfactants, preferably a nonionic surfactant and an alkylbenzene sulfonate, It can disperse | distribute to the average particle diameter mentioned above with known dispersers, such as a homogenizer, a dissolver, a colloid mill, and an ultrasonic emulsifier.

  As the silicone oil, ordinary poly (dimethylsiloxane) can be used, but ether-modified silicone oil, carboxy-modified silicone oil, amino-modified silicone oil, carbinol-modified silicone oil, phenol-modified silicone oil, and mercapto-modified silicone. Oil is preferable, and ether-modified silicone oil, carboxy-modified silicone oil, and amino-modified silicone oil are more preferable. These may be used alone or in combination of two or more. These modified silicone oils may be modified at the side chain or at the terminal.

  The viscosity of the silicone oil is preferably 400 to 100,000 mPa · s, more preferably 1000 to 50000 mPa · s. If the viscosity is less than 400 mPa · s, the surface of the protective layer may become sticky and leave a fingerprint mark when touched with the finger. On the other hand, when the viscosity exceeds 100,000 mPa · s, it may be difficult to emulsify and disperse the average particle diameter to 0.15 μm or less.

  The addition amount of the silicone oil is preferably 1 to 15% by mass and more preferably 2 to 10% by mass with respect to the total coating amount of the protective layer. If the amount added is less than 1% by mass, the effect of imparting slipperiness to the head may not be obtained. On the other hand, even if the addition amount exceeds 15% by mass, not only the effect can be obtained, but also the head contamination may be caused.

  The pigment used for the heat-sensitive recording material is usually used for the purpose of making recording with a thermal head suitable, that is, for the purpose of suppressing the occurrence of sticking or abnormal noise, but organic and / or inorganic pigments should be used. Is preferred.

  As the pigment used in the protective layer, its average particle diameter, specifically, 50% volume average particle diameter measured by a laser diffraction method (measured by a laser diffraction particle size distribution measuring apparatus LA700 (manufactured by Horiba, Ltd.), The average particle diameter of the pigment particles corresponding to 50% volume in the pigment (hereinafter sometimes simply referred to as “average particle diameter”) is preferably 0.20 to 1.00 μm. From the viewpoint of preventing the occurrence of sticking or abnormal noise between the head and the heat-sensitive recording material during recording, it is more preferable that the 50% volume average particle size is in the range of 0.20 to 0.50 μm. . If the 50% volume average particle diameter exceeds 1.00 μm, the effect of reducing wear on the thermal head is small, which is not preferable. If it is less than 0.20 μm, the effect of adding a pigment, that is, in the thermal head and the protective layer, is not preferable. The effect of preventing adhesion between the binder and the binder decreases, and as a result, the thermal head and the protective layer of the heat-sensitive recording material adhere to each other at the time of printing.

  The pigment contained in the protective layer is not particularly limited, and examples thereof include known organic and inorganic pigments. In particular, calcium carbonate, titanium oxide, kaolin, aluminum hydroxide, amorphous Preferred are inorganic pigments such as porous silica and zinc oxide, and organic pigments such as urea formalin resin and epoxy resin. Of these, kaolin, aluminum hydroxide, and amorphous silica are more preferable. These pigments may be used alone or in combination of two or more. Among these, an inorganic pigment whose surface is coated with at least one selected from the group consisting of higher fatty acids, higher fatty acid metal salts, higher alcohols, and higher fatty acid amides is particularly preferable. Examples of the higher fatty acid include stearic acid, palmitic acid, myristic acid, lauric acid and the like.

  These pigments include, for example, sodium hexametaphosphate, partially saponified or fully saponified modified polyvinyl alcohol, polyacrylic acid copolymer, various surfactants and the like, preferably partially saponified or completely saponified and modified. In the presence of polyvinyl alcohol and polyacrylic acid copolymer ammonium salt, it is preferably used after being dispersed to the above average particle diameter by a known disperser such as a dissolver, a sand mill, or a ball mill. That is, the pigment is preferably used after being dispersed until the 50% volume average particle size of the pigment is in the range of 0.20 to 1.00 μm.

  From the viewpoint of improving the transparency of the protective layer, the binder is preferably fully saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, silica-modified polyvinyl alcohol or the like.

  The protective layer may contain a known hardener, metal soap, and the like. In order to form a protective layer uniformly on the thermosensitive recording layer or the intermediate layer, it is preferable to add a surfactant to the protective layer forming coating solution. Examples of the surfactant include sulfosuccinic acid-based alkali metal salts and fluorine-containing surfactants. Specifically, di- (2-ethylhexyl) sulfosuccinic acid, di- (n-hexyl) sulfosulfate Examples thereof include sodium salts such as acids and ammonium salts.

  Further, a wax, a surfactant, metal oxide fine particles, an inorganic electrolyte, a polymer electrolyte, and the like may be added to the protective layer for the purpose of reducing wear of the recording head, and for the purpose of preventing electrification of the heat-sensitive recording material.

  The wax has a melting point in the range of 40 to 100 ° C., and its 50% volume average particle size is preferably 0.7 μm or less, and more preferably 0.4 μm or less. When the average particle size exceeds 0.7 μm, the transparency of the protective layer tends to be reduced, and image blurring tends to occur. When the melting point is less than 40 ° C., the surface of the protective layer may become sticky, and when it exceeds 100 ° C., sticking tends to occur.

  Examples of the wax having a melting point of 40 to 100 ° C. include paraffin wax; petroleum wax such as microcrystalline wax; synthetic wax such as polyethylene wax; plant wax such as candelilla wax, carnauba wax and rice wax; lanolin and the like Animal waxes; mineral waxes such as montan waxes. Among these, paraffin wax having a melting point of 55 to 75 ° C. is particularly preferable. The amount of the wax used is preferably 0.5 to 40% by mass, more preferably 1 to 20% by mass, based on the entire protective layer. These waxes may be used in combination with 12-hydroxystearic acid derivatives, higher fatty acid amides and the like.

  Examples of the method for dispersing the wax to the 50% volume average particle diameter include a method in which the wax is dispersed with a known wet disperser such as a dynomill or a sand mill in the presence of an appropriate protective colloid or a surfactant. From the viewpoint of microparticulation, once the wax is melted by heating, it is emulsified at a temperature equal to or higher than this melting point by means such as high-speed stirring and ultrasonic dispersion in a solvent in which the wax is insoluble or hardly soluble. Examples thereof include a method and a method in which a wax is dissolved in a suitable solvent and then emulsified in a solvent in which the wax is insoluble or hardly soluble. At this time, an appropriate surfactant or protective colloid may be used in combination.

The protective layer may have a single layer structure or a laminated structure of two or more layers. Dry coating amount of the protective layer is preferably 0.2~7g / m ^2, more preferably 1 to 4 g / m ^2.

  The heat-sensitive recording layer contains at least a coloring component, and further contains other components as necessary.

The heat-sensitive recording layer can be used in any composition as long as it has excellent transparency when untreated and has a property of being colored by heating. As such a heat-sensitive recording layer, a so-called two-component heat-sensitive recording layer containing a substantially colorless coloring component A and a substantially colorless coloring component B that reacts with the coloring component A and develops color is used. The coloring component A or the coloring component B is preferably encapsulated in a microcapsule. Examples of the combination of the two components constituting the two-component type heat-sensitive recording layer include the following (a) to (su).
(A) A combination of an electron-donating dye precursor and an electron-accepting compound.
(A) A combination of a photodegradable diazo compound and a coupler.
(C) A combination of an organic metal salt such as silver behenate or silver stearate and a reducing agent such as protocatechinic acid, spiroindane or hydroquinone.
(D) A combination of a long-chain aliphatic salt such as ferric stearate or ferric myristate and a phenol such as gallic acid or ammonium salicylate.
(E) Organic acid heavy metal salts such as nickel, cobalt, lead, copper, iron, mercury, silver, etc., such as acetic acid, stearic acid, palmitic acid, etc., and alkaline earths such as calcium sulfide, strontium sulfide, potassium sulfide, etc. A combination of a metal sulfide or a combination of the organic acid heavy metal salt and an organic chelating agent such as s-diphenylcarbazide or diphenylcarbazone.
(F) A combination of a (heavy) metal sulfate such as silver sulfide, lead sulfide, mercury sulfide, or sodium sulfide and a sulfur compound such as Na-tetrathionate, sodium thiosulfate, or thiourea.
(G) A combination of an aliphatic ferric salt such as ferric stearate and an aromatic polyhydroxy compound such as 3,4-dihydroxytetraphenylmethane.
(H) A combination of an organic noble metal salt such as silver oxalate or mercury oxalate and an organic polyhydroxy compound such as polyhydroxy alcohol, glycerin or glycol.
(G) A combination of an aliphatic ferric salt such as ferric pelargonate or ferric laurate and a thiocesylcarbamide or isothiocecilcarbamide derivative.
(Co) A combination of a lead salt of an organic acid such as lead caproate, lead pelargonate or lead behenate and a thiourea derivative such as ethylenethiourea or N-dodecylthiourea.
(Sa) A combination of a higher fatty acid heavy metal salt such as ferric stearate and copper stearate and zinc dialkyldithiocarbamate.
(B) A substance that forms an oxazine dye such as a combination of resorcin and a nitroso compound.
(Su) A combination of a formazan compound and a reducing agent and / or a metal salt.

  Among these, (a) a combination of an electron donating dye precursor and an electron accepting compound, (b) a combination of a photodegradable diazo compound and a coupler, or (c) a combination of an organometallic salt and a reducing agent. It is preferable to use, and it is more preferable to use a combination of the above (a) or (b).

  Further, the heat-sensitive recording material can obtain an image having excellent transparency by constituting the heat-sensitive recording layer so as to lower the haze value calculated from (diffuse transmittance / total light transmittance) × 100 (%). Can do. The haze value is an index representing the transparency of the material, and is generally calculated from the total light transmission amount, diffuse transmission light amount, and parallel transmission light amount using a haze meter. As a method for reducing the haze value, for example, the 50% volume average particle size of both the coloring components A and B contained in the heat-sensitive recording layer is 1.0 μm or less, preferably 0.6 μm or less, and a binder. In a range of 30 to 60% by mass of the total solid content of the heat-sensitive recording layer, either one of the color forming components A and B is microencapsulated, and the other is coated and dried so as to constitute a substantially continuous layer. Examples thereof include a method for use as an emulsion. It is also effective to make the refractive index of the component used for the thermosensitive recording layer as close to a constant value as possible.

  Next, the composition combinations (a, i, c) preferably used for the heat-sensitive recording layer will be described in detail below. First, (a) a combination of an electron donating dye precursor and an electron accepting compound will be described. The electron donating dye precursor preferably used for the heat sensitive recording material is not particularly limited as long as it is substantially colorless, but donates electrons or accepts protons such as acids. In particular, it has a partial skeleton such as lactone, lactam, sultone, spiropyran, ester, amide, etc., and when these contact with an electron-accepting compound, these partial skeletons are ring-opened or It is preferably a colorless compound that cleaves.

  Examples of the electron-donating dye precursor include triphenylmethane phthalide compounds, fluoran compounds, phenothiazine compounds, indolyl phthalide compounds, leucooramine compounds, rhodamine lactam compounds, triphenylmethane compounds. Examples thereof include compounds, triazene compounds, spiropyran compounds, fluorene compounds, pyridine compounds, pyrazine compounds.

  Specific examples of the phthalides include U.S. Reissue Patent No. 23,024, U.S. Pat. Nos. 3,491,111, 3,491,112, and 3,491. Examples thereof include compounds described in Nos. 116 and 3,509,174. Specific examples of the fluorans include U.S. Pat. Nos. 3,624,107, 3,627,787, 3,641,011, and 3,462,828. No. 3,681,390, No. 3,920,510, No. 3,959,571 and the like. Specific examples of the spiropyrans include compounds described in US Pat. No. 3,971,808. Examples of the pyridine-based and pyrazine-based compounds include compounds described in US Pat. Nos. 3,775,424, 3,853,869, 4,246,318, and the like. Is mentioned. Specific examples of the fluorene compound include compounds described in Japanese Patent Application No. 61-240989. Among these, black-colored 2-arylamino-3- [H, halogen, alkyl, or alkoxy-6-substituted aminofluorane] is particularly preferable.

  Specifically, for example, 2-anilino-3-methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6-N-cyclohexyl-N-methylaminofluorane, 2-p-chloroanilino-3- Methyl-6-dibutylaminofluorane, 2-anilino-3-methyl-6-dioctylaminofluorane, 2-anilino-3-chloro-6-diethylaminofluorane, 2-anilino-3-methyl-6-N- Ethyl-N-isoamylaminofluorane, 2-anilino-3-methyl-6-N-ethyl-N-dodecylaminofluorane, 2-anilino-3-methoxy-6-dibutylaminofluorane, 2-o-chloroanilino -6-dibutylaminofluorane, 2-p-chloroanilino-3-ethyl-6-N-ethyl-N-isoamylaminophen Oran, 2-o-chloroanilino-6-p-butylanilinofluorane, 2-anilino-3-pentadecyl-6-diethylaminofluorane, 2-anilino-3-ethyl-6-dibutylaminofluorane, 2-o -Toluidino-3-methyl-6-diisopropylaminofluorane, 2-anilino-3-methyl-6-N-isobutyl-N-ethylaminofluorane, 2-anilino-3-methyl-6-N-ethyl-N -Tetrahydrofurfurylaminofluorane, 2-anilino-3-chloro-6-N-ethyl-N-isoamylaminofluorane, 2-anilino-3-methyl-6-N-methyl-N-γ-ethoxypropylamino Fluorane, 2-anilino-3-methyl-6-N-ethyl-N-γ-ethoxypropylaminofluorane, 2-anilino 3-methyl -6-N-ethyl--N-.gamma. propoxypropyl aminofluoran like.

  Examples of the electron-accepting compound that interacts with the electron-donating dye precursor include acidic substances such as phenol compounds, organic acids or metal salts thereof, and oxybenzoic acid esters. For example, JP-A-61-291183. Can be mentioned. Specifically, 2,2-bis (4′-hydroxyphenyl) propane (generic name: bisphenol A), 2,2-bis (4′-hydroxyphenyl) pentane, 2,2-bis (4′-hydroxy) -3 ', 5'-dichlorophenyl) propane, 1,1-bis (4'-hydroxyphenyl) cyclohexane, 2,2-bis (4'-hydroxyphenyl) hexane, 1,1-bis (4'-hydroxyphenyl) ) Propane, 1,1-bis (4′-hydroxyphenyl) butane, 1,1-bis (4′-hydroxyphenyl) pentane, 1,1-bis (4′-hydroxyphenyl) hexane, 1,1-bis (4′-hydroxyphenyl) heptane, 1,1-bis (4′-hydroxyphenyl) octane, 1,1-bis (4′-hydroxyphenyl) -2-methyl-pentane, 1, -Bis (4'-hydroxyphenyl) -2-ethyl-hexane, 1,1-bis (4'-hydroxyphenyl) dodecane, 1,4-bis (p-hydroxyphenylcumyl) benzene, 1,3-bis Bisphenols such as (p-hydroxyphenylcumyl) benzene, bis (p-hydroxyphenyl) sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, bis (p-hydroxyphenyl) acetic acid benzyl ester; A salicylic acid derivative such as -di-α-methylbenzylsalicylic acid, 3,5-di-tert-butylsalicylic acid, 3-α-α-dimethylbenzylsalicylic acid, 4- (β-p-methoxyphenoxyethoxy) salicylic acid; Polyvalent metal salts (especially zinc and aluminum are preferred); benzyl ester of p-hydroxybenzoate Teroxy, oxybenzoic acid esters such as p-hydroxybenzoic acid-2-ethylhexyl ester and β-resorcinic acid- (2-phenoxyethyl) ester; p-phenylphenol, 3,5-diphenylphenol, cumylphenol, 4 And phenols such as -hydroxy-4'-isopropoxy-diphenylsulfone and 4-hydroxy-4'-phenoxy-diphenylsulfone. Among these, bisphenols are particularly preferable from the viewpoint of obtaining good color development characteristics. Moreover, said electron-accepting compound may be used individually by 1 type, and may use 2 or more types together.

  Next, (a) a combination of a photodegradable diazo compound and a coupler will be described. The photodegradable diazo compound is a compound that reacts with a coupler as a coupling component, which will be described later, to develop a desired color, decomposes when receiving light in a specific wavelength region before the reaction, and is no longer coupled. It is a photodegradable diazo compound that does not have a coloring ability even in the presence of a component. The hue in this color developing system is determined by a diazo dye formed by the reaction of a diazo compound and a coupler. Accordingly, the color hue can be easily changed by changing the chemical structure of the diazo compound or coupler, and an arbitrary color hue can be obtained depending on the combination.

  Examples of the photodegradable diazo compound that is preferably used in the heat-sensitive recording material include aromatic diazo compounds, and specifically include aromatic diazonium salts, diazosulfonate compounds, diazoamino compounds, and the like. Examples of the aromatic diazonium salt include, but are not limited to, compounds represented by the following general formula. In addition, the aromatic diazonium salt is preferably used since it has excellent photofixability, little generation of colored stain after fixing, and a stable color developing portion.

Ar-N ₂ ⁺ X ^-
In the above formula, Ar represents a substituted or unsubstituted aromatic hydrocarbon ring group, N ₂ ⁺ represents a diazonium group, and X ⁻ represents an acid anion.

  Many diazo sulfonate compounds are known in recent years, and are obtained by treating each diazonium salt with a sulfite, and can be suitably used for heat-sensitive recording materials.

  The diazoamino compound can be obtained by coupling a diazo group with dicyandiamide, sarcosine, methyltaurine, N-ethylanthranic acid-5-sulfonic acid, monoethanolamine, diethanolamine, guanidine, etc. It can be suitably used for a recording material. Details of these diazo compounds are described in detail, for example, in JP-A-2-136286.

  On the other hand, examples of couplers that undergo a coupling reaction with the above-mentioned diazo compound include those described in JP-A-62-146678, including resorcin, in addition to 2-hydroxy-3-naphthoic acid anilide. It is done.

  In the thermosensitive recording layer, when using a combination of a diazo compound and a coupler, these coupling reactions can be further promoted by performing them in a basic atmosphere. Basic substances may be added. Examples of the basic substance include water-insoluble or hardly soluble basic substances and substances that generate alkali by heating, such as inorganic or organic ammonium salts, organic amines, amides, urea, thiourea or derivatives thereof, Nitrogenous compounds such as thiazoles, pyrroles, pyrimidines, piperazines, guanidines, indoles, imidazoles, imidazolines, triazoles, morpholines, piperidines, amidines, forimazines or pyridines. . Specific examples thereof include those described in JP-A No. 61-291183.

  Next, (c) a combination of an organic metal salt and a reducing agent will be described. Specific examples of the organic metal salts include silver salts of long chain aliphatic carboxylic acids such as silver laurate, silver myristate, silver palmitate, silver stearate, silver arachidate or silver behenate; benzotriazole silver Silver salts of organic compounds having an imino group such as salts, benzimidazole silver salts, carbazole silver salts or phthalazinone silver salts; silver salts of sulfur-containing compounds such as s-alkylthioglycolates; aromas such as silver benzoate and silver phthalate A silver salt of an aromatic carboxylic acid; a silver salt of a sulfonic acid such as silver ethanesulfonate; a silver salt of a sulfinic acid such as silver o-toluenesulfinate; a silver salt of a phosphoric acid such as silver silver phenylphosphate; a silver barbiturate; Examples include silver saccharinate, silver salt of salicyl asdoxime, or any mixture thereof. Of these, long-chain aliphatic carboxylic acid silver salts are preferable, and silver behenate is more preferable. Further, behenic acid may be used together with silver behenate.

  The reducing agent can be appropriately used based on the description in JP-A-53-1020, page 227, lower left column, line 14 to page 229, upper right column, line 11. Among them, mono, bis, tris or tetrakisphenols, mono or bisnaphthols, di or polyhydroxynaphthalenes, di or polyhydroxybenzenes, hydroxy monoethers, ascorbic acids, 3-pyrazolidones, pyrazolines, pyrazolones It is preferable to use reducing sugars, phenylenediamines, hydroxylamines, reductones, hydroxamic acids, hydrazides, amide oximes, N-hydroxyureas and the like. Of the above, aromatic organic reducing agents such as polyphenols, sulfonamidophenols or naphthols are particularly preferred.

  In order to ensure sufficient transparency of the heat-sensitive recording material, (a) a combination of an electron-donating dye precursor and an electron-accepting compound, or (a) a photodegradable diazo compound and a coupler, It is preferable to use a combination of Further, it is preferable to use one of the color forming component A and the color forming component B in a microencapsulated form, and it is more preferable to use the electron donating dye precursor or the photodegradable diazo compound in a microencapsulated form. preferable.

  Below, the manufacturing method of a microcapsule is explained in full detail. There are an interfacial polymerization method, an internal polymerization method, an external polymerization method and the like in the production of microcapsules, and any method can be adopted. As described above, the heat-sensitive recording material is preferably microencapsulated with an electron-donating dye precursor or a photodegradable diazo compound, and in particular, an electron-donating dye precursor or a photodegradable diazo that becomes the core of the capsule. An oil phase prepared by dissolving or dispersing a compound in a hydrophobic organic solvent is mixed in an aqueous phase in which a water-soluble polymer is dissolved, emulsified and dispersed by means such as a homogenizer, and then heated to heat the oil droplets. It is preferable to employ an interfacial polymerization method in which a polymer forming reaction is caused at the interface to form a microcapsule wall of the polymer substance.

  The reactant that forms the polymer substance is added inside the oil droplet and / or outside the oil droplet. Specific examples of the polymer substance include polyurethane, polyurea, polyamide, polyester, polycarbonate, urea-formaldehyde resin, melamine resin, polystyrene, styrene methacrylate copolymer, styrene-acrylate copolymer, and the like. Among these, polyurethane, polyurea, polyamide, polyester, and polycarbonate are preferable, and polyurethane and polyurea are particularly preferable.

  For example, when polyurea is used as a capsule wall material, polyisocyanates such as diisocyanate, triisocyanate, tetraisocyanate, and polyisocyanate prepolymer, polyamines such as diamine, triamine, and tetraamine, two or more amino acids A microcapsule wall can be easily formed by reacting a prepolymer having a group, piperazine or a derivative thereof, or a polyol with the interfacial polymerization method in the aqueous phase.

  In addition, for example, a composite wall made of polyurea and polyamide or a composite wall made of polyurethane and polyamide is made of, for example, polyisocyanate and a second substance (for example, acid chloride, polyamine, or polyol) that forms a capsule wall by reacting with it. It can be prepared by mixing in a water-soluble polymer aqueous solution (aqueous phase) or an oily medium to be encapsulated (oil phase), emulsifying and dispersing them, and then heating. Details of the method for producing the composite wall comprising polyurea and polyamide are described in JP-A-58-66948.

  As the polyisocyanate compound, a compound having a trifunctional or higher isocyanate group is preferable, but a bifunctional isocyanate compound may be used in combination. Specifically, diisocyanates such as xylene diisocyanate and hydrogenated products thereof, hexamethylene diisocyanate, tolylene diisocyanate and hydrogenated products thereof, isophorone diisocyanate and the like, and dimers thereof. Alternatively, in addition to a trimer (burette or isocyanurate), a polyfunctional adduct of a polyol such as trimethylolpropane and a bifunctional isocyanate such as xylylene diisocyanate, a polyol such as trimethylolpropane and a xylylene Examples thereof include a compound in which a high molecular weight compound such as polyether having active hydrogen such as polyethylene oxide is introduced into an adduct with a bifunctional isocyanate such as range isocyanate, and a formalin condensate of benzene isocyanate. The compounds described in JP-A-62-212190, JP-A-4-26189, JP-A-5-317694, JP-A-10-114153 and the like are preferable.

  The polyisocyanate is preferably added so that the average particle size of the microcapsules is 0.3 to 12 μm and the thickness of the capsule wall is 0.01 to 0.3 μm. The dispersed particle size is generally about 0.2 to 10 μm.

  Specific examples of polyols and / or polyamines that react with the polyisocyanate and are added to the water phase and / or the oil phase as one of the components of the microcapsule wall include propylene glycol, glycerin, trimethylolpropane, Examples include ethanolamine, sorbitol, hexamethylenediamine, and the like. When a polyol is added, a polyurethane wall is formed. In the above reaction, it is preferable to keep the reaction temperature high or to add an appropriate polymerization catalyst from the viewpoint of increasing the reaction rate. Polyisocyanates, polyols, reaction catalysts, polyamines for forming a part of the wall agent, etc. are well known in the book (Polyurethane Handbook, Nikkan Kogyo Shimbun (1987) edited by Keiji Iwata).

  In addition, a metal-containing dye, a charge control agent such as nigrosine, or any other additive can be added to the microcapsule wall as necessary. These additives can be included in the wall of the capsule at the time of wall formation or at any time. Further, a monomer such as a vinyl monomer may be graft-polymerized in order to adjust the chargeability of the capsule wall surface as necessary.

  Furthermore, it is preferable to use a plasticizer suitable for the polymer used as the wall material in order to make the wall of the microcapsule excellent in material permeability even under a lower temperature and rich in color development. The plasticizer preferably has a melting point of 50 ° C. or higher, and more preferably has a melting point of 120 ° C. or lower. Among these, those that are solid at room temperature can be suitably selected and used. For example, when the wall material is made of polyurea or polyurethane, a hydroxy compound, a carbamic acid ester compound, an aromatic alkoxy compound, an organic sulfonamide compound, an aliphatic amide compound, an arylamide compound, or the like is preferably used.

  In the preparation of the oil phase, the hydrophobic organic solvent used when the electron donating dye precursor or the photodegradable diazo compound is dissolved to form the core of the microcapsule is an organic solvent having a boiling point of 100 to 300 ° C. A solvent is preferred. Specifically, in addition to esters, dimethylnaphthalene, diethylnaphthalene, diisopropylnaphthalene, dimethylbiphenyl, diisopropylbiphenyl, diisobutylbiphenyl, 1-methyl-1-dimethylphenyl-2-phenylmethane, 1-ethyl-1-dimethylphenyl -1-phenylmethane, 1-propyl-1-dimethylphenyl-1-phenylmethane, triallylmethane (eg, tritoluylmethane, toluyldiphenylmethane), terphenyl compound (eg, terphenyl), alkyl compound, alkylated diphenyl ether (For example, propyl diphenyl ether), hydrogenated terphenyl (for example, hexahydroterphenyl), diphenyl ether, and the like. Among these, it is particularly preferable to use esters from the viewpoint of emulsion stability of the emulsion dispersion.

  Examples of the esters include phosphate esters such as triphenyl phosphate, tricresyl phosphate, butyl phosphate, octyl phosphate, cresyl phenyl phosphate; dibutyl phthalate, 2-ethylhexyl phthalate, ethyl phthalate, Phthalic acid esters such as octyl phthalate and butyl benzyl phthalate; Dioctyl tetrahydrophthalate; Benzoic acid esters such as ethyl benzoate, propyl benzoate, butyl benzoate, isopentyl benzoate and benzyl benzoate; Ethyl abietic acid, abietic acid Abietic acid esters such as benzyl; dioctyl adipate; isodecyl succinate; dioctyl azelate; oxalic acid esters such as dibutyl oxalate and dipentyl oxalate; diethyl malonate; dimethyl maleate, diethyl maleate, di maleate Maleic acid esters such as chill; Tributyl citrate; Sorbic acid esters such as methyl sorbate, ethyl sorbate, and butyl sorbate; Sebacic acid esters such as dibutyl sebacate and dioctyl sebacate; Formic acid monoesters and diesters, butyric acid monoester And ethylene glycol esters such as diester, lauric acid monoester and diester, palmitic acid monoester and diester, stearic acid monoester and diester, oleic acid monoester and diester; triacetin; diethyl carbonate; diphenyl carbonate; ethylene carbonate; propylene carbonate And boric acid esters such as tributyl borate and tripentyl borate.

  Among these, in particular, when tricresyl phosphate is used alone or in combination, the stability of the emulsion is most favorable, which is preferable. It is also possible to use the above oils in combination with other oils.

  When the electron-donating dye precursor to be encapsulated or the photodegradable diazo compound has poor solubility in the hydrophobic organic solvent, a low-boiling solvent having high solubility can be supplementarily used together. Preferred examples of such a low boiling point solvent include ethyl acetate, isopropyl acetate, butyl acetate, and methylene chloride.

When the electron donating dye precursor or the photodegradable diazo compound is used in the heat sensitive recording layer of the heat sensitive recording material, the content of the electron donating dye precursor is preferably 0.1 to 5.0 g / m ^2. 1.0 to 3.5 g / m ² is more preferable. Moreover, 0.02-5.0 g / m < ² > is preferable and, as for content of a photodegradable diazo compound, 0.10-4.0 g / m < ² > is more preferable from the point of coloring density.

When the content of the electron donating dye precursor is less than 0.1 g / m ² or the content of the photodegradable diazo compound is less than 0.02 g / m ² , a sufficient color density can be obtained. When the content of both exceeds 5.0 g / m ² , the transparency of the thermosensitive recording layer may be lowered.

  On the other hand, an aqueous solution in which a water-soluble polymer is dissolved as a protective colloid is used for the aqueous phase to be used, and after the oil phase is added thereto, emulsification and dispersion are performed by means such as a homogenizer. It acts as a dispersion medium that makes the aqueous solution emulsified and dispersed stable. Here, in order to more uniformly emulsify and disperse and stabilize, a surfactant may be added to at least one of the oil phase and the aqueous phase. A known emulsifying surfactant can be used as the surfactant. 0.1-5% is preferable with respect to the mass of an oil phase, and, as for the addition amount of surfactant, 0.5-2% is more preferable.

  As the surfactant to be contained in the aqueous phase, an anionic or nonionic surfactant that does not cause precipitation or aggregation by acting with the protective colloid can be suitably selected and used. Preferable surfactants include, for example, sodium alkylbenzene sulfonate, sodium alkyl sulfate, dioctyl sodium sulfosuccinate, polyalkylene glycol (for example, polyoxyethylene nonyl phenyl ether) and the like.

  For emulsification, means used for normal fine particle emulsification such as high-speed stirring, ultrasonic dispersion, etc., for example, a homogenizer, a manton gory, an ultra-phase, an oil phase containing the above components and an aqueous phase containing a protective colloid and a surfactant. It can be easily carried out using a known emulsifying device such as a sonic disperser, a dissolver, a teddy mill or the like. After emulsification, the emulsion is preferably heated to 30 to 70 ° C. in order to promote the capsule wall formation reaction. Further, during the reaction, in order to prevent aggregation between the capsules, it is preferable to add water to reduce the collision probability between the capsules or perform sufficient stirring.

  Further, a dispersion for preventing aggregation may be added again during the reaction. Generation of carbon dioxide gas is observed as the polymerization reaction proceeds, and the end of the generation can be regarded as an approximate end point of the capsule wall formation reaction. Usually, the target microcapsule can be obtained by reacting for several hours.

  When an electron donating dye precursor or a photodegradable diazo compound is encapsulated as a core substance, the electron accepting compound or coupler to be used is, for example, a water-soluble polymer and an organic base, other color forming aids, etc. At the same time, it can be used as a solid dispersion by means of a sand mill or the like. However, after previously dissolving in a high-boiling organic solvent that is hardly soluble or insoluble in water, this is used as a protective colloid with a surfactant and / or a water-soluble polymer. It is more preferable to use as an emulsified dispersion mixed with the aqueous polymer solution (aqueous phase) contained and emulsified with a homogenizer or the like. In this case, a low boiling point solvent can be used as a dissolution aid, if necessary. Further, the coupler and the organic base can be emulsified and dispersed separately, or mixed and then dissolved in a high boiling point organic solvent to be emulsified and dispersed. A preferable emulsified and dispersed particle size is 1 μm or less.

  The high boiling point organic solvent used in this case can be appropriately selected from, for example, high boiling point oils described in JP-A-2-141279. Among them, the use of esters is preferable from the viewpoint of the emulsion stability of the emulsified dispersion, and tricresyl phosphate is particularly preferable. The above oils can be used together with other oils.

  The water-soluble polymer contained as the protective colloid can be appropriately selected from known anionic polymers, nonionic polymers, and amphoteric polymers, and has a solubility in water at the temperature to be emulsified. A water-soluble polymer of 5% or more is preferable, and specific examples thereof include polyvinyl alcohol or a modified product thereof, polyacrylic acid amide or a derivative thereof, ethylene-vinyl acetate copolymer, styrene-maleic anhydride copolymer, ethylene -Maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, polyvinylpyrrolidone, ethylene-acrylic acid copolymer, vinyl acetate-acrylic acid copolymer, cellulose derivatives such as carboxymethylcellulose, methylcellulose, casein, gelatin, Starch derivatives, arabic gum, sodium alginate Etc. The. Among these, polyvinyl alcohol, gelatin, and cellulose derivatives are particularly preferable.

  Moreover, 0.02-0.6 are preferable and, as for the mixing ratio (oil phase mass / aqueous phase mass) with respect to the water phase of an oil phase, 0.1-0.4 are more preferable. If the mixing ratio is less than 0.02, the aqueous phase is too dilute and lacks suitability for production. On the other hand, if the mixing ratio is greater than 0.6, the viscosity of the liquid increases, This is not preferable because it causes inconvenience in handling and a decrease in coating solution stability.

  When an electron accepting compound is used in the heat-sensitive recording material, the electron accepting compound is preferably 0.5 to 30 parts by weight, and 1.0 to 10 parts by weight with respect to 1 part by weight of the electron donating dye precursor. Is more preferable. Further, when a coupler is used in the heat-sensitive recording material, the amount of the coupler is preferably 0.1 to 30 parts by mass with respect to 1 part by mass of the diazo compound.

  The thermal recording layer coating liquid can be prepared, for example, by mixing the microcapsule liquid prepared as described above and an emulsified dispersion. Here, the water-soluble polymer used as a protective colloid in the preparation of the microcapsule liquid and the water-soluble polymer used as a protective colloid in the preparation of the emulsified dispersion are used as a binder in the thermosensitive recording layer. Function. In addition to these protective colloids, a binder may be added and mixed to prepare a thermal recording layer coating solution. The binder to be added is generally a water-soluble binder, such as polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, epichlorohydrin-modified polyamide, ethylene-maleic anhydride copolymer, styrene-maleic anhydride copolymer. Examples of the polymer include isobutylene-maleic salicylic acid copolymer, polyacrylic acid, polyacrylic acid amide, methylol-modified polyacrylamide, starch derivative, casein, and gelatin. Further, for the purpose of imparting water resistance to these binders, a water-proofing agent may be added, or a hydrophobic polymer emulsion, specifically, a styrene-butadiene rubber latex, an acrylic resin emulsion, or the like may be added.

  When applying the thermal recording layer coating solution on the support, known coating means used for aqueous or organic solvent coating solutions are used. In this case, the thermal recording layer coating solution is applied safely and uniformly. In addition, in order to maintain the strength of the coating film, in the thermosensitive recording material, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, starches, gelatin, polyvinyl alcohol, carboxy-modified polyvinyl alcohol, polyacrylamide, polystyrene or a copolymer thereof, polyester Or a copolymer thereof, polyethylene or a copolymer thereof, an epoxy resin, an acrylate resin or a copolymer thereof, a methacrylate resin or a copolymer thereof, a polyurethane resin, a polyamide resin, a polyvinyl butyral resin, or the like. it can.

  Hereinafter, other components that can be used in the thermosensitive recording layer will be described. The other components are not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include known thermofusible substances, ultraviolet absorbers and antioxidants.

  The heat-fusible substance can be contained in the heat-sensitive recording layer for the purpose of improving thermal response. Examples of the heat-fusible substance include aromatic ethers, thioethers, esters, aliphatic amides, ureidos and the like. Examples of these are disclosed in JP-A Nos. 58-57989, 58-87094, 61-58789, 62-109682, 62-132673, 63-151478, and 63-235961. It is described in Japanese Laid-Open Patent Publication Nos. 2-184289 and 2-215585.

  Preferred examples of the UV absorber include benzophenone UV absorbers, benzotriazole UV absorbers, salicylic acid UV absorbers, cyanoacrylate UV absorbers, and oxalic acid anilide UV absorbers. Examples of these are disclosed in JP-A-47-10537, 58-111942, 58-21284, 59-19945, 59-46646, 59-109555, 63-53544, JP-A 36-10466, 42-26187, 48-30492, 48-31255, 48-41572, 48-54965, 50-10726, U.S. Pat. 719,086, 3,707,375, 3,754,919, and 4,220,711.

  Preferable examples of the antioxidant include hindered amine antioxidants, hindered phenol antioxidants, aniline antioxidants, and quinoline antioxidants. Examples of these are described in JP-A Nos. 59-155090, 60-107383, 60-107384, 61-137770, 61-139481, 61-160287, and the like. Yes.

As the coating amount of the other components, preferably about ^{0.05~1.0g / m 2, 0.1~0.4g / m} 2 is more preferable. The other components may be added inside the microcapsule or may be added outside the microcapsule.

The heat-sensitive recording layer suppresses density unevenness caused by a slight difference in thermal conduction of the thermal head, etc., and obtains a high-quality image, so that the amount of energy necessary for obtaining a saturated transmission density (D _T-max ), That is, a heat-sensitive recording layer having a wide dynamic range is preferable. The heat-sensitive recording material has a heat-sensitive recording layer as described above, and has a characteristic capable of obtaining a transmission density D _T 3.0 with a heat energy amount in the range of 90 to 150 mJ / mm ^2. Is preferred.

The heat-sensitive recording layer is preferably applied so that the dry coating amount after application and drying is 1 to 25 g / m ² , and the thickness of the layer is 1 to 25 μm.

  As the heat-sensitive recording material, it is preferable to use a transparent support in order to obtain a transparent heat-sensitive recording material. Examples of the transparent support include polyester films such as polyethylene terephthalate and polybutylene terephthalate, cellulose triacetate films, and synthetic polymer films such as polyolefin films such as polypropylene and polyethylene, which are used alone or in combination. be able to. The thickness of the synthetic polymer film is preferably 25 to 250 μm, and more preferably 50 to 200 μm.

  The synthetic polymer film may be colored in an arbitrary hue. As a method of coloring a polymer film, a method of forming a film by kneading a dye into a resin before forming a resin film, preparing a coating solution in which a dye is dissolved in an appropriate solvent, and preparing this as a colorless transparent resin Examples of the coating method include a known coating method on the film, for example, a gravure coating method, a roller coating method, a wire coating method, and the like. Among them, a polyester resin such as polyethylene terephthalate or polyethylene naphthalate kneaded with a blue dye is preferably formed into a film and subjected to heat treatment, stretching treatment, and antistatic treatment.

  In particular, when a transparent heat-sensitive recording material is observed from the support side on a Schaukasten, illusion may occur due to Sherkasten light transmitted through a transparent non-image portion, resulting in an unsightly image. In order to avoid this, as the transparent support, A (x = 0.8055, y = 0.3005), B (x = 0.820, on the chromaticity coordinates defined by the method described in JIS-Z8701. y = 0.2970), C (x = 0.2885, y = 0.015), D (x = 0.2870, y = 0.04040) is colored blue in a rectangular region formed by four points It is particularly preferable to use a synthetic polymer film prepared.

  In the thermosensitive recording material, an intermediate layer, an undercoat layer, an ultraviolet filter layer, an antireflection layer, and the like can be provided as other layers on the support.

  The intermediate layer is preferably formed on the thermosensitive recording layer. The intermediate layer is provided for prevention of mixing of layers and blocking of gases (oxygen or the like) harmful to image storability. The binder to be used is not particularly limited, and polyvinyl alcohol, gelatin, polyvinyl pyrrolidone, cellulose derivatives and the like can be used depending on the system. Various surfactants may be added for imparting coating suitability. In order to further improve the gas barrier property, inorganic fine particles such as mica may be added in an amount of 2 to 20% by mass, more preferably 5 to 10% by mass with respect to the binder.

  In the thermosensitive recording material, for the purpose of preventing the thermosensitive recording layer from being peeled off from the support, an undercoat layer is provided on the support before applying a thermosensitive recording layer containing microcapsules or the like or an antireflection layer. be able to. As the undercoat layer, an acrylate copolymer, polyvinylidene chloride, SBR, aqueous polyester, or the like can be used, and the thickness of the layer is preferably 0.05 to 0.5 μm.

  When applying a heat-sensitive recording layer on the undercoat layer, the undercoat layer may swell due to moisture contained in the heat-sensitive recording layer coating solution, and the image recorded on the heat-sensitive recording layer may deteriorate. Is preferably hardened using dialdehydes such as glutaraldehyde, 2,3-dihydroxy-1,4-dioxane, and hardeners such as boric acid. The amount of these hardeners can be appropriately added in accordance with the desired degree of curing in the range of 0.2 to 3.0% by mass depending on the mass of the undercoat material.

  An ultraviolet filter layer may be provided on the back side of the support opposite to the coated surface of the thermosensitive recording layer for the purpose of preventing image fading. The ultraviolet filter layer contains an ultraviolet absorber such as benzotriazole, benzophenone, or hindered amine.

  An antireflection layer containing fine particles having an average particle diameter of 1 to 20 μm, preferably 1 to 10 μm may be provided on the back side of the support opposite to the coated surface of the thermosensitive recording layer. By applying this antireflection layer, the gloss measured at an incident light angle of 20 ° is preferably 50% or less, and more preferably 30% or less. The fine particles contained in the light reflection preventing layer include fine particles such as starch obtained from barley, wheat, corn, rice, beans, cellulose fiber, polystyrene resin, epoxy resin, polyurethane resin, urea formalin resin, poly ( (Meth) acrylate resin, polymethyl (meth) acrylate resin, copolymer resin such as vinyl chloride or vinyl acetate, fine particles of synthetic polymer such as polyolefin, calcium carbonate, titanium oxide, kaolin, smectite clay, aluminum hydroxide, silica, Examples include inorganic fine particles such as zinc oxide. These may be used alone or in combination of two or more. Further, from the viewpoint of improving the transparency of the heat-sensitive recording material, it is preferably a particulate material having a refractive index of 1.45 to 1.75.

  The heat-sensitive recording material can be suitably produced by the production method described below, but is not limited thereto, and can be produced by other production methods. The heat-sensitive recording material contains an emulsion of silicone oil dispersed in an average particle size of 0.15 μm or less in the coating solution for the protective layer, and thus has a good coating surface with excellent head matching and no coating failure. In particular, it is suitably used in fields that require high image quality, such as medical recording media.

  Hereinafter, a method for producing the heat-sensitive recording material will be described. A method for producing a heat-sensitive recording material comprises forming a heat-sensitive recording layer by applying a heat-sensitive recording layer-forming coating solution on a support, and forming a protective layer-forming coating containing at least a pigment and a binder on the heat-sensitive recording layer. A liquid is applied to form a protective layer, and other layers are formed as necessary. Here, the heat-sensitive recording layer and the protective layer may be formed simultaneously. In that case, the heat-sensitive recording layer-forming coating solution and the protective layer-forming coating solution are simultaneously coated on the support in a multilayer manner. The thermosensitive recording layer and the protective layer can be simultaneously formed thereon.

  The method for producing a heat-sensitive recording material passes through a pump or a filter at the time of liquid feeding because the protective layer forming coating liquid preferably contains an emulsion of silicone oil dispersed in an average particle size of 0.15 μm or less. The emulsion is not broken by the shear at the time or the ultrasonic defoaming machine, so that huge oil droplets are not formed to cause repelling coating failure, and the production stability is excellent.

  As the support used here, the support described above which is used for the heat-sensitive recording material can be used. Further, as the heat-sensitive recording layer forming coating solution, the above-mentioned heat-sensitive recording layer coating solution can be used. Further, the protective layer-forming coating solution is also used for the protective layer containing the pigment and binder described above. A coating solution can be used. Examples of the other layers include other layers such as the intermediate layer and the undercoat layer described above. In the method for producing a heat-sensitive recording material, in order to sequentially form an undercoat layer, a heat-sensitive recording layer, an intermediate layer, a protective layer, etc. on a support, a blade coating method, an air knife coating method, a gravure coating method, a roll coating coating method, Known coating methods such as spray coating, dip coating, and bar coating are used. According to the above manufacturing method, the above-described heat-sensitive recording material can be manufactured.

  JP, 2000-355164, A can be referred to for a desirable mode of a heat sensitive recording material.

  The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

<Example 1>
(Production of moisture-proof light-shielding bag)
Film A was obtained by stretching a mixture having the composition shown in the following table to a thickness of 40 μm.

  Using this film A, a moisture-proof light-shielding bag sheet was produced by laminating in the following order, and this was heat-sealed to obtain a moisture-proof light-shielding bag.

(Production of package)
Paper of GP / LBKP = 70/30 valve was made by a 6-layer circular mesh method. A modified starch was spray-coated between the layers in the bonding layer. Alkyl clam dimer and cationized starch (Arakawa Chemical Co., Ltd.) are used as internal additives, polyacrylamide emulsion (Arakawa Chemical Co., Ltd.) is used as an internal paper strength enhancer, and polyvinyl ayuule (Kuraray Co., Ltd.) is used as a surface tension enhancer. Was used. The obtained paper had a basis weight of 395 g / m ² .

  Using this base paper, an individual packaging box 24 as shown in FIG. 7 (a) is prepared, and this is conditioned at 23 ° C. and a relative humidity of 50% for 24 hours, and then sheet-like recording material (thermal recording material) 23 101 pieces of Fuji dry image recording film DI-AT manufactured by a certain Fuji Photo Film Co., Ltd. were placed. This was further placed in the moisture-proof light-shielding bag, air deaerated so as to reduce the pressure, and both sides were heat-sealed as shown in FIG.

After that, as shown in FIG. 8 (a) in a room of US Federal Standard 209d class 10,000, it is packed in a zippered cosmetic box 26 (the zipper is indicated by reference numeral 27), and further, as shown in FIG. 8 (b). The original sealing property securing and opening tape (or label) 28 and the quality label 29 were attached. The zippered decorative box 26 is made of E cardboard (the front and back liners are made of unbleached kraft pulp, paperboard with a basis weight of 210 g / m ² , and the core E flute is made of semicraft pulp with a basis weight of 180 g / m. ² ). Further, as shown in FIG. 8 (c), this decorative box 26 with zipper (5 boxes) is packed in an outer box 30, and as shown in FIG. 8 (d), the flap of the outer box is sealed with a hot melt adhesive. The product name, expiration date, serial number, and product abbreviation were displayed to make a package of heat-sensitive recording material. A series of operations was performed at 23 ° C. and a relative humidity of 45%.

<Example 2>
A package of heat-sensitive recording material was obtained in the same manner as in Example 1 except that the pulp of GP / LBKP = 30/70 was used.

<Comparative Example 1>
A package of a heat-sensitive recording material was obtained in the same manner as in Example 1 except that NBKP / LBKP = 50/50 pulp was used.

<Test Example 1>
The following tests were conducted on the sheet-like recording materials (heat-sensitive recording materials) of the respective packages produced in Example 1, Example 2, and Comparative Example 1.

(Temperature dependency test)
Using a Fuji Medical Dry Imager DRYPIX 3000, printing was performed on each sheet-like recording material at 25 ° C. and 45% relative humidity with thermal energy at which the color density (OD) was 1.2. Printing was performed under the conditions of 25 ° C. and a relative humidity of 70% and under the conditions of 25 ° C. and a relative humidity of 20%, and each OD was measured. The temperature dependence was evaluated by setting ΔOD (1) as a value obtained by subtracting the OD at 25 ° C. and 20% relative humidity from the OD at 25 ° C. and 70% relative humidity. In addition, OD (optical density) was calculated | required by measuring an image part using the Macbeth transmission densitometer TD-904 (visual filter).

(Aging stability test)
Each package was left at 50 ° C. for 3 days. Thereafter, using a Fuji Medical Dry Imager DRYPIX 3000, each sheet-shaped recording material was printed at 25 ° C. and a relative humidity of 45%. The thermal energy applied at this time was such that the OD was 1.2 when printed on a sheet-like recording material before standing for 3 days at 25 ° C. and 45% relative humidity. The OD was measured for the 100th sheet-shaped recording material in contact with the cartridge. The stability over time is defined as ΔOD (2) obtained by subtracting the OD of the sheet-like recording material after standing at 50 ° C. for 3 days from the OD (1.2) of the sheet-like recording material before standing for 3 days. Evaluated.

(result)
Each evaluation result is shown in the following table.

<Example 3>
(Preparation of hitting ball)
As a material for the batting ball, a paper having a basis weight of 320 g / m ² (the pulp composition used is GP: LBKP = 60: 40, a neutral paper using an alkyl ketene dimer as a sizing agent, and a cation-modified starch as a fixing agent, JIS P The paper pH measured by -8133 was 7.0 ± 0.5). This material was dried while adjusting the time in a drying room at about 45 ° C., so that the water content measured by JIS-P-8127 was 4.5% by mass. The obtained material was punched to prepare a sheet having the shape shown in FIG. The sheet was bent approximately 90 degrees inward at the position of each fold line 5 in FIG. 2 to produce a contact ball.

(Production of package)
A photothermographic material (sample 108 of the publication) produced by the method described in Example 2 of JP-A No. 2003-149766 was cut into a size of 35.4 cm × 43.0 cm. 100 cut photothermographic materials were stacked and loaded into the contact balls produced above as shown in FIG. At this time, the emulsion surface was loaded so that it faced the bottom surface of the contact ball.

  A contact ball loaded with 100 photothermographic materials was placed in the light shielding bag produced above, degassed, and heat sealed at both ends as shown in FIG. 2B to obtain a package.

(Measurement of air content in the light shielding bag)
The mass and volume of the obtained package were measured, and the mass in water was further measured. From these measurement results, the air amount V in the light shielding bag was determined according to the Archimedes method. The air content L in the light-shielding bag obtained by the following formula was calculated from the number n of the sheet-like recording materials loaded and the area A (unit: cm ² ) per sheet-like recording material. .

V
L = ――――――― × 10 ⁵
n x A

<Comparative example 2>
A package of a photothermographic material was obtained in exactly the same manner as in Example 3 except that NBKP / LBKP = 50/50 pulp was used.

<Test Example 2>
The following tests were conducted on the sheet-like recording materials (thermophotosensitive materials) of the respective packages prepared in Example 3 and Comparative Example 2.

(Image formation)
One end of the light shielding bag of the obtained package was cut and loaded into a cassette (magazine box) 14 of an image forming apparatus (FM-DPL, manufactured by Fuji Photo Film Co., Ltd.) 13 as shown in FIG. Thereafter, the light shielding bag was taken out of the cassette by pulling out the end portion of the light shielding bag on the cut side. The photothermographic material was unloaded one by one from the packaging material containing the photothermographic material loaded in the cassette, and the image was formed through exposure and development.

(Photographic evaluation)
After producing the package, it was stored in a room at 20 ± 3 ° C. and a relative humidity of 65 ± 5% for one year. Thereafter, the image formation was performed. However, development processing was performed without performing exposure. The density after development (fogging density: Dmin) was measured using a densitometer (Macbeth TD904).
Moreover, the density | concentration when the developing process was similarly performed without performing exposure using the package produced without using a contact ball was set to A.
The photographic properties of the photothermographic material were evaluated according to the following five levels according to the value of B-A.
5 B-A is ± 0.02 or less.
4 B-A is larger than ± 0.02 and not larger than ± 0.04.
3 B-A is larger than ± 0.04 and not larger than ± 0.06.
2 B-A is larger than ± 0.06 and not larger than ± 0.08.
1 B-A is greater than ± 0.10.

(result)
The results were as shown in the following table.

  As is apparent from the table, the package satisfying the conditions of the present invention (Example 3) had good photographic properties of the photothermographic material. Moreover, the package satisfying the conditions of the present invention was sufficiently smooth to carry out the photothermographic material by the suction disk of the image recording apparatus.

It is a perspective view which shows the expanded view of the one aspect | mode of the packaging material (contact ball) of this invention. It is a perspective view which shows the state which accommodated the packaging material loaded with the sheet-like recording material in the light-proof moisture-proof bag. FIG. 5 is a development view of another aspect of the packaging material (a hit ball) of the present invention and a perspective view showing a state in which the sheet-like recording material is loaded into the packaging material. It is a perspective view which shows the state which affixed the label on the light-proof moisture-proof bag which accommodated the packaging material with which the sheet-like recording material was loaded. It is a perspective view which shows the process of accommodating a light-shielding moisture-proof bag in an individual packaging box, and also accommodating in an exterior box. It is a schematic diagram showing a state in which a packaging material loaded with a sheet-like recording material is loaded in a cassette of the image recording apparatus while being put in a light-proof moisture-proof bag. It is a perspective view which shows the state which accommodated the packaging material loaded with the sheet-like recording material in the light-proof moisture-proof bag. It is a perspective view which shows the process of accommodating a light-shielding moisture-proof bag in an individual packaging box, and also accommodating in an exterior box.

1 Application ball (packaging material)
2 bottom surface 3 connecting portion 4 top surface 5 fold line 6a, 6b flap 7a, 7b notch 10 sheet-like recording material 11 laminate of sheet-like recording material 12 light-shielding moisture-proof bag 13 image recording device 14 cassette 15 heat seal 16 heat seal 17 label 18 Individual packaging box 19 Label 20 Outer packaging box 21 Tape 23 Sheet-like recording material 24 Individual packaging box 26 Cosmetic box with zipper 27 Shipper 28 Tape 29 Quality label 30 Outer packaging box

Claims (3)

A packaging material for a sheet-like recording material comprising a base paper, wherein 20 to 80% by mass of the pulp contained in the base paper is mechanical pulp. A package in which the photothermographic material or the heat-sensitive recording material is loaded on the sheet-shaped recording material packaging material according to claim 1. The package according to claim 2, wherein the sheet-shaped recording material is stored in a state where at least a part of the sheet-shaped recording material is in contact with the packaging material.

Images