JP2002019290A - Heat sensitive recording body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat sensitive recording body employing a thermoplastic resin film, which has good transparency and enough drape for the inserting properties to a transmitted light image film light box, restorability of curling habit and good image dimensional accuracy. SOLUTION: This heat sensitive recording body consists of a thermoplastic resin film support made of a crystalline thermoplastic resin having a glass transition point of 0 deg.C or lower and having the haze of the thermoplastic resin film of 20% or less and its Clark stiffness of 25 to 500 and an at least one heat sensitive recording layer including a leuco dye and a developer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording medium which has sufficient rigidity for use in an OHP film or a transmitted light film, and has excellent transparency, flexibility, and dimensional accuracy of a recorded image. It is.

[0002]

2. Description of the Related Art A heat-sensitive recording material is known which uses a colorless or pale-colored leuco dye and a color developer to contact a color-forming substance by heat to obtain a recorded image. A body using a film or synthetic paper as a body, and a two-color type heat-sensitive recording body depending on the use have been proposed. Such a thermosensitive recording medium is inexpensive and has a simple apparatus, and is therefore used not only as a recording medium for facsimile machines and various computers but also in a wide range of fields.

On the other hand, in the medical field, X-ray imaging devices,
Inspection machines such as an ultrasonic imaging apparatus and an X-ray CT are used. At this time, the obtained image information is recorded using various image recording devices. However, since all of the image recording apparatuses use an optical system, a fixing / developing process is required, and the apparatus tends to be large. On the other hand, the thermal recording method using a thermal head does not require development, is easy to handle, and is inexpensive, and is therefore expected in the medical field. Further, it can be used as an OHP sheet and a plate making negative sheet by further increasing the transparency.

A heat-sensitive recording medium using a transparent thermoplastic resin film as a support is already known, and a polyethylene terephthalate film has been mainly used conventionally.
For example, Examples 1-4 of JP-A-7-266697
And JP-A-11-208117 discloses that a 75 μm thick polyethylene terephthalate film is used as a transparent support. However, polyethylene terephthalate is expensive and has a glass transition temperature of 70 ° C., so it is difficult to return to a lithographic form once it has a curl because it is inflexible at room temperature that is usually used. There was a drawback that it was not suitable for storage in a warehouse. As an example of using a polypropylene film which is less expensive than a polyethylene terephthalate film and has a low glass transition temperature and a flexibility at room temperature, Japanese Patent Application Laid-Open No. 3-140288 discloses a film having a thickness of 60 μm.
It is disclosed to use m of polypropylene fill.

However, according to these inventions, the rigidity of the support and the manufacturing method are not specified, and when the OHP film is transferred to an OHP or inserted into a light box in an OHP film or a medical transmitted light film such as an X-ray image. It has been found that the printer cannot be reproduced because of lack of rigidity, and cannot reproduce a printer output image of which definition is advanced due to contraction deformation due to stretching orientation. Further, polyethylene terephthalate, which has been conventionally mainly used, has a glass transition point of 70 ° C. and has no flexibility at room temperature. Therefore, when stored in a roll at room temperature, there is an advantage that the curl is hard to stick, but once the curl is attached, it does not easily return to flat, and the image created by the curl due to the curl There was a drawback that it was difficult to recognize.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a film having a good transparency and sufficient insertion into a film light box for a transmitted light image, capable of recovering curl, and having an image size. An object of the present invention is to provide a thermosensitive recording medium using a highly accurate thermoplastic resin film.

[0007]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve these problems, and as a result, by forming a heat-sensitive recording layer using a specific thermoplastic resin film as a support. The present inventors have found that a heat-sensitive recording medium having the characteristics of the present invention can be provided, and have completed the present invention. That is, the present invention uses a thermoplastic resin film comprising a crystalline thermoplastic resin having a glass transition point of 0 ° C. or less, a haze of 20% or less, and a Clark stiffness of 25 to 500 as a support, and a leuco dye and a color developing agent. Transparent thermosensitive recording characterized by having at least one thermosensitive recording layer containing an agent and having sufficient rigidity for use in an OHP film or a transmitted light film, and having good transparency, flexibility, and dimensional accuracy of a recorded image. It provides the body.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the thermal transfer recording paper of the present invention will be described in more detail. (1) Support The thermoplastic resin used for the transparent thermoplastic resin film as the support of the present invention preferably has flexibility at room temperature. That is, those having a glass transition point of room temperature or lower are preferable, and those having a glass transition point of 0 ° C. or lower are more preferable. Examples of such a thermoplastic resin include a propylene-based resin, polyethylene, polyoxymethylene, and ethylene-vinyl acetate copolymer, and a propylene-based resin is suitable from the viewpoint of transparency, cost, and thermal stability.

[0009] The propylene resin is a propylene homopolymer, polypropylene having isotactic or syndiotactic and various degrees of stereoregularity, or propylene as a main component, and ethylene, butene-1 , Hexene-1, heptene-
A copolymer with an α-olefin such as 1,4-methylpentene-1 is used. The copolymer may be a binary, ternary, or quaternary system, and may be a random copolymer or a block copolymer, but a random copolymer is a film having better transparency. Is obtained. These propylene resins are used alone or in combination of two or more.

[0010] A nucleating agent can be used in the thermoplastic resin film. By using a nucleating agent, the crystal size is reduced, and the transparency and Clark rigidity are improved. Specific examples of the nucleating agent include benzylidene sorbitol,
Carboxylic acid-based, inorganic phosphate-based, inorganic substances, and the like, more specific examples of which are 1,3,2,4-dibenzylidene sorbitol, 1,3,2,4-di- (p-methylbenzylidene) ) Sorbitol, 1,3-o-methylbenzylidene, 2,4-p-methylbenzylidene, aluminum pt-butylbenzoate, sodium bis (4-t-butylphenyl) phosphate, 2,2′-phosphate Examples include sodium ethylidene-bis (4,6-di-t-butylphenyl), aluminum oxide, kaolin clay, and talc. The amount of the nucleating agent added varies depending on the effect, but is generally 0.001 to 1% by weight.

If necessary, stabilizers, light stabilizers, lubricants, antiblocking agents, neutralizing agents, antistatic agents, and coloring agents may be added. As a stabilizer, a sterically hindered phenol-based, phosphorus-based, amine-based, sulfur-based or the like stabilizer is used.
001 to 1% by weight, as a light stabilizer 0.001 to 1% by weight of a sterically hindered amine, a benzotriazole-based or benzophenone-based light stabilizer, and as a lubricant, higher fatty acid, fatty acid amide, metal soap, fatty alcohol 0.001 to 1% by weight of a lubricant such as an anti-blocking agent, 0.001 to 5% by weight of an anti-blocking agent such as an inorganic fine powder or an organic fine powder, and a neutralizing agent such as a carboxylate. 0.001 to 1% by weight of an agent, 0.001 to 2% by weight of a cationic, anionic, nonionic or amphoteric antistatic agent as an antistatic agent, and a dye, organic pigment or inorganic pigment as a coloring agent 0.00 colorant
You may mix | blend 1 to 1 weight%. The thermoplastic resin film may be a single layer, a two-layer structure having a base layer and a surface layer, or a three-layer structure having a surface layer on the front and back surfaces of the base layer. It may have a multilayer structure in which another resin film layer exists between layers.

[Formation of Resin Film] The method of forming the thermoplastic resin film is not particularly limited, and various known methods can be used. Specific examples thereof include a single layer or a single layer connected to a screw type extruder. Cast molding that extrudes molten resin into a sheet using a multi-layer T-die or I-die,
Examples include inflation molding in which a molten resin is extruded into a tube shape using a circular die and expanded by the internal air pressure, calender molding in which the kneaded material is rolled with a plurality of hot rolls and processed into a sheet shape, and roll molding. However, when a propylene-based resin is used, cast molding and inflation molding are generally used.

In the case of using the cast molding, various known methods can be used for cooling the molten resin. Specific examples include a cooling roll method, a polishing method, a twin belt method, a cooling water tank method and the like. A general method is a cooling roll method, in which a molten resin is brought into close contact with a metal cooling roll using an air knife, a vacuum suction device, a touch roll, or the like. In addition, when it is desired to obtain a surface smoothness that cannot be obtained by the cooling roll method, and to further increase the cooling efficiency, a combination of the cooling roll method and a water film or a water spray, a polishing method, a twin belt method, a cooling water tank method, and the like are used. used.

In the case of using inflation molding, various known cooling methods can be used.
Specific examples include an air-cooled ring system and a water-cooled ring system, and the water-cooled ring system has higher cooling efficiency than the air-cooled ring system. When the thermoplastic resin film is a non-stretched film, the crystallinity of the film changes depending on the cooling rate, so that the transparency and the Clark stiffness are affected by the cooling rate. When the cooling rate is high (rapid cooling), the degree of crystallinity decreases and a film having high transparency is obtained. When the cooling rate is low (gradual cooling), the degree of crystallinity increases and a film having high Clark stiffness is obtained. In order to obtain a target film with both transparency and Clarke stiffness, it is necessary to optimize the cooling method and cooling rate, and it is also effective to use a nucleating agent in combination.

[Stretching] The thermoplastic resin film used for the support may be a stretched one. Stretching can be performed by any of various methods commonly used, and by stretching, it is possible to improve the Clark stiffness, haze, and thickness uniformity. The stretching temperature can be performed within a known temperature range suitable for a thermoplastic resin having a glass transition point or higher and a melting point of a crystal part or lower. Specifically, it is preferable to set the temperature at 5 to 70C lower than the melting point of the thermoplastic resin. The stretching speed is 20 to 350 m
/ Min. As a stretching method, when stretching a cast molded film, longitudinal stretching using a peripheral speed difference between roll groups, transverse stretching using a tenter oven, rolling, simultaneous biaxial stretching using a combination of a tenter oven and a linear motor, and the like. Can be mentioned. As a method for stretching an inflation film, simultaneous biaxial stretching by a tubular method can be used.

The stretching ratio is not particularly limited, and is appropriately determined in consideration of the characteristics of the thermoplastic resin used. For example, when a propylene homopolymer or a copolymer thereof is used as a thermoplastic resin, when it is stretched in one direction, about 1.2
To 12 times, preferably 2 to 10 times, and in the case of biaxial stretching, 1.5 to 60 times, preferably 4 to 50 times in area magnification.
It is twice. When using other thermoplastic resins, when stretching in one direction, 1.2 to 10 times, preferably 2 to 5 times
And in the case of biaxial stretching, 1.5 to 20 in area magnification.
Times, preferably 4 to 12 times.

[Heat Treatment] The dimensional change of the thermoplastic resin film of the present invention before and after the temperature is measured at a temperature in the range of room temperature to 150 ° C. by thermomechanical analysis is 2.5% or less, preferably 1% or less. In addition to the above-mentioned molding so as to be 0.5% or less, the dimensional change rate can be reduced by high-temperature setting in a heat setting zone or heat treatment after molding. Heating temperature is 5
The temperature ranges from 0 ° C to 250 ° C, preferably from 70 ° C to 190 ° C. If the temperature is lower than 50 ° C., the effect of the heat treatment is insufficient.
If it exceeds 50 ° C., the film may be deformed or uneven. Furthermore, when the thermoplastic resin is a propylene-based resin, the heating temperature is preferably 70 to 190 ° C, more preferably or 80 to 170 ° C, and further preferably 90 to 190 ° C.
１５155 ° C. When the temperature is lower than 70 ° C., the effect of the heat treatment is insufficient or a long time is required to obtain a sufficient effect, so that the efficiency in industrial production is hardly increased.

The heating time can be variously selected from the range of preferably from 2 seconds to 30 days, more preferably from 4 seconds to 7 days, further preferably from 4 seconds to 2 days.
If it is longer than 30 days, the film is likely to deteriorate, and if it is less than 2 seconds, the processing effect may be insufficient. Examples of the method of the heat treatment include a heat treatment in a high-temperature heat setting zone after stretching by a tenter oven, a treatment in an oven in a sheet or wound roll state, a heating with high-temperature air, steam, or another heat medium. . In the case where the edge of the film is not constrained so as to be gradually shrunk with heating, and when the edge of the film is fixed, the distance between two opposite ends or two sets of two opposite ends of the film is determined by the heat shrinkage of the film. And a state where at least two opposite ends of the film are fixed and the film does not follow shrinkage of the film. Specific examples include heating in a wound roll state in a ventilation oven, heating in a state where a single sheet or a plurality of sheets are stacked, and a method of heating by contacting at least one high-temperature roll.

The thermoplastic resin film needs to have a certain degree of rigidity when used for radiographs and OHP films, and has a Clark stiffness of preferably 20 to 20%.
500, more preferably 40 to 400, and still more preferably 60 to 300. When the Clark stiffness is 20 or less, it is difficult to insert into a light box or transfer to an OHP or the like. On the other hand, if the Clarke stiffness is 500 or more, it is difficult to confirm the image even if a flexible raw material is used and an image sheet having a strong curl is placed on a light box or an OHP because of curling. The thickness of the thermoplastic resin film is preferably 100 to 300 μm, more preferably 1 to 300 μm.
It is 100 to 250 μm, more preferably 100 to 200 μm, and the Clark stiffness aimed at by the present invention cannot be obtained with a thermoplastic resin film of 100 μm or less. Also, 300 μm
The above films are not suitable because of high cost.

[Thermal Recording Layer] The thermal recording layer is not particularly limited, and known leuco dyes and developers can be used. It is desirable that the haze of the heat-sensitive recording medium after the heat-sensitive recording layer is provided on the thermoplastic resin film is 40% or less. If the haze of the thermosensitive recording medium is 40% or less, image recognition with transmitted light such as an X-ray photograph or OHP can be clearly performed. If the haze is 40% or more, even if transmitted light is applied, the contrast is not clear and a clear image cannot be obtained.

Various colorless or pale-color leuco dyes used in the heat-sensitive recording layer of the present invention are known.
For example, 3,3-bis (p-dimethylaminophenyl)
-6-dimethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3- (1,2-dimethylindol-3-yl) phthalide, 3- (P-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3,3-bis (1,2-dimethylindole-3
-Yl) -6-dimethylaminophthalide, 3,3-bis (9-ethylcarbazol-3-yl) -6-dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl)- 6-dimethylaminophthalide,

3-p-dimethylaminophenyl-3-
Triallylmethane dyes such as (1-methylpyrrol-3-yl) -6-dimethylaminophthalide, 4,4′-bis-dimethylaminobenzhydryl benzyl ether,
N-halophenyl-leuco auramine, N-2,4,5
-Diphenylmethane dyes such as trichlorophenylleuco auramine, benzoyl leucomethylene blue, p-
Thiazine dyes such as nitrobenzoyl leucomethylene blue, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-
Spiro dyes such as dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho- (6'-methoxybenzo) spiropyran, 3-propyl-spiro-dibenzopyran, rhodamine-βanilinolactam, rhodamine (p- Lactam dyes such as nitroanilino) lactam and rhodamine- (o-chloroanilino) lactam;

3-dimethylamino-7-methoxyfluoran, 3-diethylamino-6-methoxyfluoran,
3-diethylamino-7-methoxyfluoran, 3-diethylamino-7-chlorofluoran, 3-diethylamino-6-methyl-7-chlorofluoran, 3-diethylamino-6,7-dimethylfluoran, 3- (N -Ethyl-p-toluidino) -7 methylfluorane, 3-diethylamino-7-N-acetyl-N-methylaminofluoran, 3-diethylamino-7-N-methylaminofluoran, 3-diethylamino-7-dimene Ziraminofluoran, 3-diethylamino-7-N-metal-
N-benzylaminofluoran, 3-diethylamino-
7-N-chloroethyl-N-methylaminofluoran,

3-diethylamino-7-N-diethylaminofluoran, 3- (N-ethyl-p-toluidino)
-6-methyl-7-phenylaminofluoran, 3-
(N-cyclopentyl-N-ethylamino) -6-methyl-7-anilinofluoran, 3- (N-ethyl-p-
Toluidino) -6-methyl-7- (p-toluidino) fluoran, 3-diethylamino-6-methyl-7-phenylaminofluoran, 3-diethylamino-7- (2
-Carbomethoxyphenylamino) fluoran, 3-
(N-ethyl-N-isoamylamino) -6-methyl-
7-phenylaminofluoran, 3-piperidino-6
Methyl-7-phenylaminofluoran, 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-
Phenylaminofluoran, 3-piperidino-6-methyl-7-phenylsiminofluoran,

3-Diethylamino-6-methyl-7-xylidinofluoran, 3-diethylamino-7- (o-
Chlorophenylamino) fluoran, 3-dibutylamino-7- (o-chlorophenylamino) fluoran, 3
-Pyrrolidino-6-methyl-7-p-butylphenylaminofluoran, 3-N-methyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluoran, 3-N-methyl-N-tetrahydro Flufurinoamino-6-methyl-7anilinofluoran, 3-di (n-
One or more fluoran dyes such as butyl) amino-6-methyl-7-anilinofluoran and the like are appropriately selected and used.

As the color developer which reacts with these leuco dyes to develop color, various known ones can be used. For example, activated clay, acid clay, attapulgite, bentonite, colloidal silica, inorganic acidic substances such as aluminum silicate, 4-tert-butylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol,
4-hydroxyacetophenol, 4-tert-octylcatechol, 2,2′-dihydroxydiphenol, 2,2′-methylenebis (4-methyl-6-ter
t-isobutylphenol), 4,4′-isopropylidenebis (2-tert-butylphenol),
4'-sec-butylidene diphenol, 4-phenylphenol, 4,4 'isopropylidene bis (2-te
rt-butylphenol), 4,4′-isopropylidenediphenol (bisphenol A), 2,2′-methylenebis (4-chlorophenol), hydroquinone,

Phenolic compounds such as 4,4'-cyclohexylidene diphenol, benzyl 4-hydroxybenzoate, dimethyl 4-hydroxyphthalate, hydroquinone monobenzyl ether, novolak type phenolic resins, phenolic polymers, benzoic acid, p -Tert-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, 3-
sec-butyl-4-hydroxybenzoic acid, 3-cyclohexyl-4-hydroxybenzoic acid, 3,5-dimethyl-4-hydroxybenzoic acid, salicylic acid, 3-isopropylsalicylic acid, 3-tert-butylsalicylic acid, 3
-Benzylsalicylic acid, 3- (α-methylbenzyl) salicylic acid, 3-chloro-5- (α-methylbenzyl) salicylic acid, 3,5-di-tert-butylsalicylic acid,

Aromatic carboxylic acids such as 3-phenyl-5- (α, α-dimethylbenzyl) salicylic acid and 3,5-di-α-methylbenzylsalicylic acid, and phenolic compounds and aromatic carboxylic acids, for example, zinc , Magnesium, aluminum, calcium, titanium, manganese,
One or more salts, such as salts with polyvalent metals such as tin and nickel, are appropriately selected and used. The developer is preferably used in an amount of 1 to 20 parts by weight, preferably 1 to 5 parts by weight, based on 1 part by weight of the dye. The preparation of a coating solution containing these substances is generally carried out by pulverizing the color former and the developer together or separately to 2 μm or less with a stirring / pulverizer such as a ball mill, an attritor or a sand mill using water as a dispersion medium. In addition, the transparency of the heat-sensitive recording material is further improved.

In the heat-sensitive recording layer, in addition to the leuco dye and the developer, for example, starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, acetoacetyl group-modified polyvinyl Alcohol, diisobutylene / maleic anhydride copolymer salt, styrene / maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, styrene-butadiene copolymer, vinyl acetate -Ethylene-vinyl chloride copolymer, ethylene-vinyl chloride copolymer, vinyl chloride resin, urea resin, melamine resin, amide resin,
It is preferable to contain a binder such as an amino resin in an amount of 2 to 40% by weight, preferably about 5 to 25% by weight of the total solid. Further, various auxiliaries can be added to the coating liquid, for example, dispersants such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, alginates, metal salts of fatty acids, and the like. Benzophenone-based and triazole-based ultraviolet absorbers, other defoamers, fluorescent dyes, coloring dyes, coloring pigments, conductive substances, and the like can be appropriately added.

If necessary, lubricants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, etc., kaolin, clay, talc, calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, particulate anhydrous Silica, inorganic pigments such as activated clay, and stearic acid amides, methylene bisamide stearic acid, amide oleic acid, amide palmitic acid, fatty acid amides such as oleic acid amide, coconut fatty acid amide, 1,2-diphenoxyethane,
1,2-bis (3-methylphenoxine) ethane, 1,
Ethers such as 2-bis (4-methylphenoxine) ethane, phenyl 1-hydroxy-2-naphthoate, dibenzyl terephthalate, dibenzyl oxalate, bis (p-chlorobenzyl) oxalate
Esters, esters such as benzyl p-benzyloxybenzoate, aromatic compounds such as p-benzylbiphenyl and m-terphenyl, and various known heat-fusible substances can also be added as a sensitizer.

Various pigments can be used in the heat-sensitive coating solution as long as the object of the present invention is not impaired.
Inorganic pigments such as kaolin, clay, calcium carbonate, calcined clay, calcined kaolin, diatomaceous earth, fine anhydrous silica, activated clay, and organic pigments such as styrene microballs, nylon powder, polyethylene powder, urea, formalin resin filler, raw starch particles, etc. However, in the heat-sensitive recording material of the present invention, in order to form a recorded image using the color tone and background of the support surface, avoid the compounding of a pigment that makes the heat-sensitive recording layer concealability too high. For example, when a pigment is blended in the heat-sensitive recording layer, it is desirable to blend the pigment in an amount of 30% by weight or less, preferably 20% by weight or less based on the total solid content of the heat-sensitive recording layer.

In the heat-sensitive recording medium of the present invention, the coating liquid for forming the heat-sensitive recording layer is applied onto a support by a conventionally well-known and commonly used coating method such as air knife coating, blade coating, bar coating, or gravure coating. Dried. The coating amount of the heat-sensitive recording layer coating solution is generally about 1 to 30 g / m <2> by dry weight, preferably 3 to 30 g / m <2>.
It is adjusted in the range of about 20 g / m2. By providing an overcoat layer on the heat-sensitive recording layer of the heat-sensitive recording medium for the purpose of protecting the heat-sensitive recording layer, storage stability can be further improved. Various known techniques in the field of heat-sensitive recording material production, such as providing an antistatic layer and a protective layer on the back surface of the support, can also be used as needed.

[Haze] The haze of the thermoplastic resin film and the heat-sensitive recording medium in the present invention is measured according to JIS-K-7105, and the heat-sensitivity after the heat-sensitive recording layer is provided on the haze of the support. If the haze of the recording medium is 40% or less, the image formed on the thermosensitive recording medium can be clearly recognized when transmitted light is used. In order to reduce the haze of the heat-sensitive recording medium to 40% or less, the haze of the support is preferably 20% or less, more preferably 15% or less, depending on the coating amount of the heat-sensitive recording layer. More preferably, it is 10% or less.

[Clark rigidity] The Clark rigidity in the present invention is measured according to JIS-P-8143, and the Clark rigidity of the support is preferably 25 to 500, more preferably 30 to 400, and further preferably 40 to 400. 300. The thermoplastic resin film as a support has different Clark stiffness in the MD (machine direction) direction and the TD (traverse direction) direction depending on the molding method. However, in order to achieve the object of the present invention, MD, T
D is desirably within this range, and if the Clark stiffness of the support is less than 25, it is difficult to insert it into a light box or transfer it to an OHP or the like. Further, if the Clark stiffness exceeds 500, even if a flexible thermoplastic resin material is used, even if an image sheet having a strong curl is placed on a light box or an OHP, the image sheet is curled, making it difficult to confirm the image. is there.

[Heating Dimensional Change Rate] The heating dimensional change rate before and after the temperature is measured from room temperature to 150 ° C. by a thermomechanical analyzer of the support in the present invention is preferably −.
2.5% to 2.5%, more preferably -2.0 to 1.5
%, More preferably -2.0 to 1.0%. If the dimensional change rate by the thermomechanical analyzer is out of this range, the support contracts and expands due to the heat of the thermal head, and the desired image accuracy cannot be obtained. Thermomechanical analysis can be measured using a commercially available thermomechanical analyzer. A typical example of the apparatus, principle, features, and applications is the Japan Analytical Instruments Manufacturers Association, edited and published by “1997 Analytical Instruments Overview,” Chapter IV, 9
2 pages (September 1, 1997), Bernhard
Wanderlich, Thermal Analysis
sis "Chapter 6, pages 311 to 332, A
Cademic Press, Inc. It is shown in literature such as 1990.

As a specific example of a TMA measuring device used for thermomechanical analysis, "T" manufactured by Seiko Instruments Inc.
MA120C "and" TMA "manufactured by PerkinElmer.
7 "," TMA-50 "manufactured by Shimadzu Corporation," TM-9200 "manufactured by Vacuum Engineering Co., Ltd., and the like. T of the present invention
As an example of the dimensional change rate measurement before and after the temperature rise and fall measurement by MA, using a TMA device, for example, “TMA120C” manufactured by Seiko Instruments Inc., in the tension mode, the size of the measurement portion of the film test piece to be measured. Is 4 mm in width and 10 mm in length (excluding the size of the portion fixed to the upper and lower clamps), and the load applied to the test piece is 16
g / mm ^2, and both the rate of temperature rise and
The measurement temperature range is 25 ° C./50° C. as a starting point, the temperature is raised to 150 ° C., and then the temperature is measured by lowering the temperature to room temperature. The length of the measurement portion of the test piece before the measurement is L0, and the length of the test piece after the measurement is L1, which is calculated from the following equation. Heating dimensional change rate = [(L0−L1) / L0] × 1
00 [%]

[0037]

EXAMPLES The present invention will be more specifically described below with reference to Production Examples, Examples, Comparative Examples and Test Examples. The materials, usage amounts, ratios, operations, and the like shown below can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the following specific examples. In addition,% described below is% by weight unless otherwise specified. The materials used are summarized in Table 1.

[0038]

[Table 1]

<Production Example a> A method for producing the support a used in the examples will be specifically described. 230 of thermoplastic resin A
After kneading with an extruder set at 250 ° C., the mixture was extruded from a T-die connected to an extruder set at 250 ° C., and cooled with a roll type cooling device having a touch roll mechanism with a cooling roll temperature of 10 ° C. and a thickness of 120 μm. , Haze 4%, Clark stiffness (MD) 37, Clark stiffness (TD) 30, heating dimensional change (MD)-0.45%, heating dimensional change (TD)-
A 0.07% unstretched film was obtained.

<Production Example b> A method for producing the support b used in the examples will be specifically described. 230 of thermoplastic resin C
After kneading with an extruder set at 250 ° C., the mixture was extruded from a T-die connected to an extruder set at 250 ° C., cooled with a twin-belt type cooling device, and was 200 μm thick, 3% haze, and Clark stiffness (MD). 58, Clark stiffness (TD) 63,
A non-stretched film having a heated dimensional change (MD) of -0.82% and a heated dimensional change (TD) of -0.92% was obtained.

<Production Example c> A method for producing the support c used in the examples will be specifically described. 230 of thermoplastic resin B
After kneading with an extruder set at 250 ° C., the mixture was extruded from a T-die connected to an extruder set at 250 ° C., cooled with a twin-belt type cooling device to a thickness of 300 μm, a haze of 15%,
Clark stiffness (MD) 212, Clark stiffness (TD) 1
96, a non-stretched film having a heated dimensional change (MD) of -0.73% and a heated dimensional change (TD) of -0.73% were obtained.

<Production Example d> The production method of the support d used in the examples will be specifically described. 230 of thermoplastic resin C
After kneading with an extruder set to 230 ° C., the mixture was extruded from a circular die connected to an extruder set to 230 ° C., expanded to a blow ratio of 1.8 times, and cooled by a water-cooled ring-type cooling device having a water temperature of 15 ° C. Thickness 110 μm, haze 5%, Clark stiffness (MD) 90, Clark stiffness (TD) 42, heating dimensional change (MD) 0.39%, heating dimensional change (TD) 0.
A 27% unstretched film was obtained.

<Production Example e> The production method of the support e used in the examples will be specifically described. 250 parts of thermoplastic resin A
After kneading with an extruder set at ℃, extruded from the T-die connected to the extruder set at 230 ℃, cooled with a roll cooling device having a touch roll mechanism with a cooling roll temperature of 60 ℃, and unstretched sheet I got 150 ° C
, And stretched 5.0 times in the machine direction by a machine for stretching composed of rolls having different peripheral speeds to obtain a uniaxially stretched film having a thickness of 150 μm. This uniaxially stretched film is further
Heated at 5 ° C. and heat-treated by a heat set roll composed of roll groups having different week speeds, thickness 150 μm, haze 8%, Clark rigidity (MD) 125, Clark rigidity (TD) 7
6. A uniaxially stretched film having a heated dimensional change (MD) of 0.83% and a heated dimensional change (TD) of -0.09% was obtained.

<Production Example f> A method for producing the support f used in the examples will be specifically described. 250 parts of thermoplastic resin B
After kneading with an extruder set at 0 ° C, the mixture was extruded from a T-die connected to an extruder set at 230 ° C, and cooled with a cooling roll type cooling device having a touch roll mechanism with a cooling roll temperature of 50 ° C. A stretched sheet was obtained. This sheet 1
It was reheated to 55 ° C and stretched 5 times in the machine direction. Next, the film was heated again to about 160 ° C. using a tenter oven and stretched 8.0 times in the transverse direction, and then heat-treated in a heat set zone adjusted to 162 ° C. to have a thickness of 110 μm, a haze of 6%, and a Clark stiffness (MD ) 68, Clark stiffness (TD) 22
9. A biaxially stretched film having a heated dimensional change (MD) of 1.44% and a heated dimensional change (TD) of 0.84% was obtained.

<Production Example g> The production method of the support g used in the examples will be specifically described. 250 parts of thermoplastic resin B
After kneading with an extruder set at 0 ° C, the mixture was extruded from a T-die connected to an extruder set at 230 ° C, and cooled with a cooling roll type cooling device having a touch roll mechanism with a cooling roll temperature of 50 ° C. A stretched sheet was obtained. This sheet 1
It was reheated to 55 ° C and stretched 5 times in the machine direction. After the thermoplastic resin C was kneaded with an extruder set at 250 ° C., it was extruded into a sheet and laminated on both sides of the 5-fold stretched film adjusted as described above to obtain a laminated film having a three-layer structure. Next, the three-layer laminated film was cooled to 60 ° C., heated again to about 160 ° C. using a tenter oven, stretched 8.5 times in the horizontal direction, and then heat-treated in a heat set zone adjusted to 165 ° C. Was done. After cooling to 60 ° C., the ears were slit and the thickness was 130 μm, haze 8%, Clark stiffness (MD) 76, Clark stiffness (TD) 232, rate of change in heating dimension (MD) 0.77%, heating dimension Change rate (TD)
A stretched film having a three-layer structure of 0.66% was obtained. (B / A
/ B = 20/90/20 μm)

<Production Example h> The production method of the support h used in the comparative example will be specifically described. 230 of thermoplastic resin A
After kneading with an extruder set at 250 ° C., the mixture was extruded from a T-die connected to an extruder set at 250 ° C., and cooled with a cooling roll type cooling device having an air knife mechanism with a cooling roll temperature of 80 ° C. 130 μm, haze 25%, Clark stiffness (MD) 52, Clark stiffness (TD) 34, heating dimensional change (MD) −0.41%, heating dimensional change (T
D) A -0.11% unstretched film was obtained.

<Production Example i> A method for producing a support i used in a comparative example will be specifically described. 230 of thermoplastic resin B
After kneading with an extruder set at 250 ° C., the mixture was extruded from a T-die connected to an extruder set at 250 ° C., and cooled with a cooling roll type cooling device having a touch roll mechanism with a cooling roll temperature of 10 ° C. 400 μm, haze 19%, Clark stiffness (MD) 659, Clark stiffness (TD) 581,
A non-stretched film having a heated dimensional change (MD) of 0.32% and a heated dimensional change (TD) of -0.05% was obtained.

<Production Example j> A method for producing a support j used in a comparative example will be specifically described. 230 of thermoplastic resin A
After kneading with an extruder set at 250 ° C., the mixture was extruded from a T-die connected to an extruder set at 250 ° C., and cooled with a cooling roll type cooling device having a touch roll mechanism with a cooling roll temperature of 10 ° C. 80 μm, haze 10%, Clark stiffness (MD) 16, Clark stiffness (TD) 16, heating dimensional change (MD) −0.23%, heating dimensional change (T
D) An unstretched film of -0.04% was obtained.

<Production Example k> The production method of the support k used in the comparative example will be specifically described. 250 parts of thermoplastic resin A
After kneading with an extruder set at ℃, extruded from the T-die connected to the extruder set at 230 ℃, cooled with a cooling roll cooling device with an air knife mechanism with a cooling roll temperature of 60 ℃, no stretching I got a sheet. 15 this sheet
It is heated to a temperature of 5 ° C., stretched 5.0 times in the longitudinal direction by a longitudinal stretching machine composed of roll groups having different peripheral speeds, and has a thickness of 90 μm, a haze of 5%, a Clark rigidity (MD) of 27, and a Clark rigidity (T
D) A uniaxially stretched film having a heating dimension change rate (MD) of 2.66% and a heating dimension change rate (TD) of -0.08% was obtained.

<Production Example 1> The support 1 used in the comparative example will be specifically described. Thickness 60 μm, haze 2%, Clark stiffness (MD) 11, Clark stiffness (TD) 37,
Polypropylene-based biaxially stretched film having a heating dimension change rate (MD) of 1.57% and a heating dimension change rate (TD) of -0.09% (trade name: Pyrene OP, P22, manufactured by Toyobo Co., Ltd.
61 "was used.

[0051]

Examples 1 to 7 and Comparative Examples 1 to 5 The supports obtained in the above Production Examples a to l were treated according to the following procedures,
Various kinds of heat-sensitive recording materials were manufactured. (Adjustment of thermosensitive layer) [Preparation of solution A] 3- (N-ethyl-N-isoamylamino) -6-methyl-7-phenylamino fluoran 20 parts Dibenzyl terephthalate 20 parts Methyl cellulose 5% aqueous solution 20 parts Water 40 parts The product is sand-milled with an average particle size of 0.5 μm
And crushed.

[Preparation of Solution B] A composition comprising 30 parts of 4,4′-isopropylidene diphenol, 40 parts of a 5% aqueous solution of methylcellulose, 40 parts of water and a sand mill has an average particle diameter of 0.5 μm.
And crushed. A coating liquid for a recording layer is prepared by mixing and stirring a composition comprising 100 parts of liquid A, 100 parts of liquid B, 45 parts of styrene / butadiene having a solid concentration of 50%, 1 part of a 10% aqueous solution of dioctylsulfosuccinate, and 75 parts of water. I got

(Preparation of Thermosensitive Recording Material) This coating solution was applied to the thermoplastic resin film obtained in each of the production examples so that the coating amount after drying was 5 g / m ² , and dried and solidified. A thermosensitive recording medium was obtained. Table 2 shows the evaluation results of the obtained thermosensitive recording medium support and the thermosensitive recording medium in the following test examples. <Test Example> (Haze) Good if the haze evaluated according to JIS-K-7105 is 30% or less (（) 30 to 35% or less, slightly good (○) 35 to 40% If there is any defect (△), 40% or more was evaluated in four steps of defective (×).

(Image Dimension Accuracy) A reference point is formed at the center of the thermal recording medium at a distance of about 100 mm in each of the MD and TD directions, and a thermal printer (manufactured by Sony Corporation).
After a solid image was recorded on the mark line under the trade name “UP-980”), the distance between the mark points was measured to measure the dimensional change rate in each of the MD direction and the TD direction. Good if the dimensional change rate is within ± 0.2% in both the MD and TD directions (Ｄ) Slightly good if within ± 0.3% (○) Somewhat poor if within ± 0.5% Δ) The others were evaluated on a four-point scale of poor (x).

(Plug-in property) A 200 mm-square thermosensitive recording medium was set on a vertical wall with a light box (Light Box 8W, AAA, trade name, manufactured by Fuji Photo Film Co., Ltd.), and the insertion test was performed by hand. The test was performed 10 times, good (◎), failed 1 time, slightly good (○), failed 2-5 times or more, slightly poor (△), and failed 5 times or more, poor (×).

(Recovery of curl) MD 300 mm, TD2
A thermosensitive recording medium of 00 mm is wound around a 50.8 mm diameter paper tube in the MD direction, and placed in an oven maintained at a temperature of 60 ± 3 ° C.
After holding for 8 hours, it was taken out and left at room temperature for 30 minutes to promote the curl. Remove the heat-sensitive recording medium with a curl from the paper tube, put it between glass plates and leave it at room temperature for 3 hours. Immediately after taking out from the glass plate, place it on a flat table and observe the curl state. Good (◎) The maximum lifting height up to four sides of the heat-sensitive recording material is 3 cm or less (◎) Somewhat good with a maximum curl height of 6 cm or less (○) Somewhat poor but not cylindrical (△) Bad cylindrical (X) was evaluated in four stages.

[0057]

[Table 2]

[0058]

As described above, according to the present invention, it is possible to obtain a thermosensitive recording medium having sufficient rigidity for use in an OHP film or a medical transmitted light film, and having good transparency, flexibility and dimensional accuracy of a recorded image. be able to.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akimitsu Asazuma 4-3, Kanda Surugadai, Chiyoda-ku, Tokyo Oji Oil Chemicals Co., Ltd. F term (reference) 2H026 AA07 BB02 BB21 EE05 EE08 FF01

Claims (4)

[Claims] 1. A crystalline thermoplastic resin having a glass transition point of 0 ° C. or less, a haze of 20% or less, and a Clark stiffness of 2% or less.
A thermoplastic resin film of 5 to 500 as a support,
A heat-sensitive recording material comprising at least one heat-sensitive recording layer containing a leuco dye and a developer. 2. The thermosensitive recording medium according to claim 1, wherein the crystalline thermoplastic resin is a propylene-based resin. 3. The dimensional change rate of the thermoplastic resin film before and after the temperature is measured at room temperature to 150 ° C. by a thermomechanical analyzer within a range of −2.5% to 2.5%. The heat-sensitive recording material according to claim 1. 4. A thermoplastic resin film having a thickness of 100 to 100.
The thermosensitive recording medium according to any one of claims 1 to 3, which has a thickness of 300 µm.