JP2002248859A - Transparent heat sensitive recording material and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat sensitive recording material, in which no coating defect such as streaks, unevenness or the like develops, which has a high transparency and, at the same time, in which no problem such as void and sticking develops and which is excellent in head matching properties, and its manufacturing method. SOLUTION: The transparent heat sensitive recording material is produced by providing a heat sensitive recording layer mainly made of a leuco dye, a developer and a binder resin on a support and, in addition, by providing a protective layer containing the resin on the heat sensitive recording layer. At this time, a protective layer coating liquid including a pigment dispersed with a circulating type horizontal sand mill is ultrasonically treated with an ultrasonic defoaming machine within the liquid temperature of 5 to 40 deg.C at an ultrasonic sound pressure value (Px) represented by formula (1): Px= Vm×10<-((> S<v+α)/20)> of 2×10<10> to 12×10<10> ×Pa, where Px (in μPa) is the sound pressure value, Vm (in V) is a voltage value, Sv (in dB) is a wave-receiving sensitivity value and α (in dB) is a correction value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent thermosensitive recording medium utilizing a color development reaction between an electron-donating color-forming compound and an electron-accepting compound, and more particularly to a film for a medical video printer, a CAD. The present invention relates to a transparent thermosensitive recording material used for an image forming film sheet for use as an image forming sheet for an overhead projector, and a method for producing the same.

[0002]

2. Description of the Related Art Various heat-sensitive recording materials utilizing a heat-sensitive coloring process have been proposed. This heat-sensitive recording material is generally produced by applying a coating solution in which a colorless or light-colored leuco dye and a developer are dissolved or dispersed on a base material such as paper, synthetic paper, or a plastic film.

[0003] Thermal recording materials have conventionally been used as various recording materials for electronic computers, facsimile machines, ticket vending machines, label printers, recorders, etc., and do not require frequent processing such as development and fixing. The market is rapidly expanding due to its advantages such as being able to record in a short time using a compact device with a simple structure, generating less noise, and being inexpensive.

In recent years, particularly in the medical field, the problem of waste liquid treatment caused by the wet process of silver halide X-ray film and the flow of digitization of images have led to simple applications for ultrasonic diagnostics and X-ray images. There is a need for a transparent dry film system that can output to a computer. In such a flow, there is a demand for a heat-sensitive recording film that is transparent and has excellent image contrast because of the simplicity of the heat-sensitive process.

[0005] This transparency is related to the smoothness of the coated surface (coating film surface), and it is well known that the smoother the surface, the higher the transparency due to the scattering of light and the refractive index.

[0006]

However, in general, a coating liquid for a protective layer containing a pigment and a resin as main components has poor dispersion stability of the pigment itself, and uniform particle diameter due to secondary aggregation and the like. It is known that when coated with a coating liquid, the smoothness of the surface is impaired because the coating liquid is easily broken, and large irregularities are caused, thereby lowering the transparency.

[0007] In this case, the printability becomes poor due to poor head matching due to the inability to form appropriate irregularities, and poor adhesion between the thermal head and the surface due to irregularities due to the aggregation of particles. There was a problem. Particularly when used for outputting medical images or the like for the purpose of image diagnosis, image defects are fatal in diagnosis.
Furthermore, streaks due to bubbles and the like that are minutely present in the coating liquid,
There has also been a problem that coating defects such as unevenness and roughness of the coating surface cause poor transparency.

Therefore, in order to suppress the secondary aggregation of the pigment,
A technique such as addition of a dispersion stabilizer is disclosed in JP-A-04-325287.
Although proposed in the gazette, it was not always sufficient.

Japanese Patent Application Laid-Open No. 07-76168 proposes a heat-sensitive recording material having excellent transparency, which has a specified surface roughness, but is insufficient from the viewpoint of head matching.

Further, styrene-organic pigment is used as an organic pigment in the protective layer.
A methacrylic acid copolymer is disclosed in
Japanese Patent Application Laid-Open No. 5988/1990 and Japanese Patent Application Laid-Open No. 05-278334 each propose a product containing cross-linked polystyrene, but none of them was sufficient in terms of achieving both transparency and head matching.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has no coating defects such as streaks and unevenness, has high transparency, and has excellent head matching properties free from white spots and sticking. It is an object to provide a recording material and a method for manufacturing the recording material.

[0012]

The transparent heat-sensitive recording material and the method for producing the same according to the present invention comprise a leuco dye on a support, and a binder as a developer and a binder for coloring the leuco dye by heating. Providing a heat-sensitive recording layer mainly containing an agent resin,
Further, in the transparent thermosensitive recording material having a protective layer containing a resin thereon and a method for producing the same, the protective layer coating solution containing the pigment dispersed in a circulating horizontal sand mill is subjected to a liquid temperature of 5 to 40 ° C.
The ultrasonic treatment is carried out at an ultrasonic sound pressure value (Px) represented by the following formula (1) within a range of 2 × 10 ^{10 to} 12 × 10 ¹⁰ μPa by an ultrasonic defoaming machine. Px = Vm × 10 ^{-((Sv + α) / 20)} (1) Px (μPa): Sound pressure value, Vm (V): Voltage value, Sv (dB): Receiving sensitivity value of sensor element, α ( dB): Correction value In the transparent thermosensitive recording material and the method for producing the same according to the present invention, the average particle diameter (D50) of the pigment in the protective layer coating solution is 1 μm.
m or less.

Further, in the transparent heat-sensitive recording material and the method for producing the same according to the present invention, the pigment in the protective layer coating liquid may be any one or more of melamine-formaldehyde copolymer, kaolin and calcium carbonate. There is a feature.

In the transparent thermosensitive recording material and the method for producing the same according to the present invention, the developer is an organic phosphoric acid compound represented by the following structural formula, and the binder resin has a hydroxyl group in the molecule. It is characterized by the following.

[0015]

Embedded image (R1 represents a linear alkyl group having 12 to 24 carbon atoms.) The transparent thermosensitive recording material and the method for producing the same according to the present invention are further characterized by further providing a back layer having antistatic ability.

The transparent thermosensitive recording material according to the present invention and the method for producing the same are characterized in that the support is a polyethylene terephthalate film.

Further, the transparent thermosensitive recording material and the method for producing the same according to the present invention are characterized in that at least one of the support, the thermosensitive recording layer and the protective layer is tinted.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the transparent thermosensitive recording material according to the present invention and a method for producing the same will be described below.

The transparent heat-sensitive recording material according to the present invention and the method for producing the same (hereinafter, this may be simply referred to as the present invention) include a leuco dye, a developer capable of heating and developing the leuco dye on a support, and In a transparent heat-sensitive recording material comprising a heat-sensitive recording layer having a binder resin as a main component as a main component and a protective layer containing a resin provided thereon, and a method for producing the same, the protection comprising a dispersed pigment is provided. Layer coating liquid temperature
Ultrasonic treatment is performed at an ultrasonic sound pressure value (Px) represented by the following formula (1) within the range of 5 to 40 ° C. and 2 × 10 ^{10 to} 12 × 10 ¹⁰ μPa. Px = Vm × 10 ^{-((Sv + α) / 20)} (1) Px (μPa): Sound pressure value, Vm (V): Voltage value, Sv (dB): Receiving sensitivity value of sensor element, α ( dB): Correction value At this time, preferably, the pigment is dispersed using a circulation type horizontal sand mill, and ultrasonic treatment is performed using an ultrasonic defoaming machine.

Here, the ultrasonic wave is a sound wave having a frequency of 15 to 16 kHz or more, and is used in many applications in engineering.

By treating the coating liquid for the protective layer with an ultrasonic defoamer, the energy of the ultrasonic vibration acts on the pigment particles in the coating liquid for the protective layer, which greatly contributes to the quality of the transparency, resulting in a strong shock wave. What is present in the solution in a soft agglomerated manner is loosened, and the pigment particles are independently and uniformly present. In addition, by defoaming by the ultrasonic treatment, fine bubbles in the coating liquid for the protective layer gather and become large bubbles to be removed.

Thus, when the coating liquid for the protective layer is applied, the surface of the protective layer in which the pigment particles are finely and uniformly distributed is formed without unevenness and coating defects caused by bubbles and the like, and the transparency is high. A transparent thermosensitive recording material is obtained.

In this case, since the sand mill is generally operated by filling the vessel with 60 to 90% of the medium, the initial power is large, and particularly in the case of the vertical type, the medium is pressed downward by the weight of the medium, and is particularly large. Due to this load, a change in liquid properties such as aggregation due to a rise in the liquid temperature is apt to occur, which is disadvantageous for transparency. However, the horizontal sand mill is superior in dispersion efficiency to the vertical sand mill, and the particle size distribution at the time of dispersion is likely to be sharp, so that the pigment particles dispersed in the horizontal sand mill have a uniform and stable particle size distribution, Transparency is improved by the manifestation of the sonication effect.

At this time, the intensity of the ultrasonic wave represented by the equation (1)
The ultrasonic sound pressure value indicating 2 × 10^TenBelow μPa, the supersonic
The above effects cannot be obtained because the wave energy is weak. Also,
12 × 10 ^TenAbove μ, the ultrasonic energy is too strong
When the protective layer coating liquid foams or heat energy increases,
Liquid changes and may cause thickening or aggregation.
And impairs the liquid stability of the coating solution.

Further, since the protective layer coating liquid contains a large amount of resin, when the liquid temperature becomes 5 ° C. or lower, the liquid property changes to thickening, gelation, etc., which may adversely affect coating properties. High in nature. Further, even at a high temperature of 40 ° C. or more, the pigment particles 2
Subsequent aggregation is likely to occur, and a uniform particle film surface is not obtained, but the surface is roughened and transparency is reduced.

As the pigment for the protective layer, the smaller the particle size, the easier it is to form a fine surface, and the surface of the protective layer becomes smooth and excellent in transparency. At this time, it is preferable to use a pigment having an average particle size (D50) of 1 μm or less, since the effect of ultrasonic treatment is remarkably exhibited.

The pigment used in the protective layer in the present invention includes phosphate fiber, potassium titanate, acicular magnesium hydroxide, whisker, talc, mica, glass flake, calcium carbonate, plate-like carbon, aluminum hydroxide, plate-like. Inorganic fillers such as aluminum hydroxide, silica, clay, kaolin, talc, calcined clay, hydrotalcite, cross-linked polystyrene resin, urea
Organic fillers such as formalin resin, silicone resin, cross-linked polymethyl methacrylate resin, and melamine-formaldehyde resin are exemplified.

More preferably, the pigment in the coating liquid for the protective layer is highly transparent when it is one or a mixture of two or more of melamine / formaldehyde copolymer, kaolin and calcium carbonate. The present invention provides a transparent heat-sensitive recording material which is free from white streaks and has excellent head matching properties.

Further, in order to improve the head matching property, various lubricants, oils and the like can be added to the protective layer coating solution. Specific examples include stearic acid amide,
Palmitic acid amide, oleic acid amide, lauric acid amide, ethylene bis stearoamide, methylene bis stearoamide, methylol stearoamide,
Examples include paraffin wax, polyethylene, carnauba wax, oxidized paraffin, zinc stearate, and aluminum stearate. As the oil, a general silicone oil or the like can be used.

The resin used for the protective layer in the present invention includes, in addition to a water-soluble resin, an aqueous emulsion, a hydrophobic resin, an ultraviolet ray and an electron beam curable resin. Specific examples of the resin include poly (meth) acrylate resin,
Polyvinyl butyral resin, polyvinyl acetoacetal resin, ethyl cellulose, methyl cellulose, cellulose acetate, hydroxyethyl cellulose, cellulose acetate propionate, polyurethane resin, polyester resin, polyvinyl acetate resin, styrene acrylate resin, polyolefin resin, polystyrene resin Resins, polyvinyl chloride resins, polyether resins, polyamide resins, polycarbonate resins, polyethylene resins, polypropylene resins, polyacrylamide resins, and the like.

From the viewpoint of transparency, it is preferable to use a resin having a refractive index ratio of 0.8 to 1.2 with respect to the transparent support as the protective layer resin in the present invention.

[0032] If necessary, a crosslinking agent may be added. As the crosslinking agent used together with such a resin, a conventionally known compound can be used. The developer used in the present invention is an electron-accepting compound, and various conventionally known electron-accepting developers can be used. More preferably, in the present invention, JP-A-5-12436 is used.
It is an electron-accepting developer containing a long-chain alkyl group represented by No. 0 or the like in the molecule. For example, an organic phosphoric acid compound, an aliphatic carboxylic acid compound or a phenol compound having an aliphatic group having 12 or more carbon atoms, a metal salt of mercaptoacetic acid having an aliphatic group having 10 to 18 carbon atoms, or a metal salt of 5 to 8 carbon atoms Alkyl esters of caffeic acid having an alkyl group of
Acid phosphates having the above aliphatic groups and the like. The aliphatic group includes a linear or branched alkyl group and alkenyl group, and may have a substituent such as a halogen, an alkoxy group, and an ester.

Specific examples of the color developer will be described below.

(A) Organophosphate Compound As the organophosphate compound, a compound represented by the following structural formula is preferably used.

[0035]

Embedded image (R1 represents a linear alkyl group having 12 to 24 carbon atoms) Specific examples of the organic phosphoric acid compound represented by the above structural formula include, for example, dodecylphosphonic acid, tetradecylphosphonic acid, hexadecylphosphonic acid, Octadecylphosphonic acid, eicosylphosphonic acid, docosylphosphonic acid, tetracosylphosphonic acid, hexacosylphosphonic acid, octacosylphosphonic acid and the like.

As the organic phosphoric acid compound, α-hydroxyalkylphosphonic acid represented by the following structural formula is also preferably used.

[0037]

Embedded image (However, R ₂ is an aliphatic group having 11 to 29 carbon atoms.) Specific examples of the α-hydroxyalkylphosphonic acid represented by the above structural formula include α-hydroxydodecylphosphonic acid and α-hydroxytetraacid. Decylphosphonic acid, α-hydroxyhexadecylphosphonic acid, α-hydroxyoctadecylphosphonic acid, α-hydroxyeicosylphosphonic acid, α-hydroxydocosylphosphonic acid, α-hydroxytetracosylphosphonic acid, and the like.

As the organic phosphoric acid compound, an acidic organic phosphoric acid ester represented by the following structural formula is also used.

[0039]

Embedded image (In the formula, R ₃ represents an aliphatic group having 16 or more carbon atoms, and R ₄ represents a hydrogen atom or an aliphatic group having 1 or more carbon atoms.) The acidic organic phosphorus represented by the above structural formula (3) Specific examples of the acid ester include dihexadecyl phosphate, dioctadecyl phosphate, dieicosyl phosphate, didocosyl phosphate, monohexadecyl phosphate, monooctadecyl phosphate, monoeicosyl phosphate, monodocosyl phosphate, methylhexadecyl Examples include phosphate, methyl octadecyl phosphate, methyl eicosyl phosphate, methyl docosyl phosphate, amyl hexadecyl phosphate, octyl hexadecyl phosphate, lauryl hexadecyl phosphate, and the like. (B) Aliphatic carboxylic acid compounds α-hydroxy fatty acids represented by the following structural formula are preferably used.

[0040]

Embedded image (However, R ₅ represents an aliphatic group having 12 or more carbon atoms.) Specific examples of the α-hydroxyaliphatic carboxylic acid compound represented by the above structural formula include α-hydroxydecanoic acid and α-hydroxydecanoic acid.
Hydroxytetradecanoic acid, α-hydroxyhexadecanoic acid, α-hydroxyoctadecanoic acid, α-hydroxypentadecanoic acid, α-hydroxyeicosanoic acid, α-hydroxydocosanoic acid, α-hydroxytetracosanoic acid, α-hydroxyhexacosanoic acid, α-hydroxyoctacosanoic acid and the like.

As the aliphatic carboxylic acid compound, an aliphatic carboxylic acid compound having an aliphatic group having 12 or more carbon atoms substituted by a halogen element and having a halogen element at least in the α-position or β-position carbon is also used. It is preferably used.

Specific examples of such compounds include, for example, 2-bromohexadecanoic acid, 2-bromoheptadecanoic acid, 2-bromooctadecanoic acid, 2-bromoeicosanoic acid,
2-bromodocosanoic acid, 2-bromotetracosanoic acid, 3-bromooctadecanoic acid, 3-bromoeicosanoic acid, 2,3-dibromooctadecanoic acid, 2-fluorododecanoic acid, 2-fluorotetradecanoic acid, 2-fluorohexadecanoic acid , 2-fluorooctadecanoic acid, 2-fluoroeicosanoic acid, 2-fluorodocosanoic acid, 2-iodohexadecanoic acid, 2-iodooctadecanoic acid, 3-iodohexadecanoic acid, 3-iodooctadecanoic acid, perfluorooctadecanoic acid, etc. Is mentioned.

The aliphatic carboxylic acid compound is an aliphatic carboxylic acid compound having an oxo group in the carbon and having an aliphatic group having 12 or more carbon atoms, wherein at least the carbon at the α-position, the β-position or the γ-position is an oxo group. Are also preferably used.

Specific examples of such compounds include, for example, 2-oxododecanoic acid, 2-oxotetradecanoic acid,
Oxohexadecanoic acid, 2-oxooctadecanoic acid, 2-oxoeicosanoic acid, 2-oxotetracosanoic acid, 3-oxododecanoic acid, 3-oxotetradecanoic acid, 3-oxohexadecanoic acid, 3-oxooctadecanoic acid, 3- Oxoeicosanoic acid, 3-oxotetracosanoic acid, 4-oxohexadecanoic acid, 4-oxooctadecanoic acid, 4-oxodokosanoic acid, and the like.

As the aliphatic carboxylic acid compound, a dibasic acid represented by the following structural formula is also preferably used.

[0046]

Embedded image (However, R ₆ represents an aliphatic group having 12 or more carbon atoms, X represents an oxygen atom or a sulfur atom, and n represents 1 or 2.) Specific examples of the dibasic acid represented by the above structural formula Is, for example, dodecylmalic acid, tetradecylmalic acid, hexadecylmalic acid, octadecylmalic acid, eicosylmalic acid, docosylmalic acid, tetracosylmalic acid, dodecylthiomalic acid, tetradecylthiomalic acid, hexadecylthio Malic acid, octadecylthiomalic acid, eicosylthiomalic acid, docosylthiomalic acid, tetracosylthiomalic acid, dodecyldithiomalic acid, tetradecyldithiomalic acid, eicosyldithiomalic acid, docosyldithiomalic acid, tetra Cosyl dithiomalic acid and the like.

As the aliphatic carboxylic acid compound, a dibasic acid represented by the following structural formula (6) is also preferably used.

[0048]

Embedded image (However, R7, R8, and R9 represent hydrogen or an aliphatic group, at least one of which is an aliphatic group having 12 or more carbon atoms.) Specific examples of the dibasic acid represented by the above structural formula include: For example, dodecyl butane diacid, tridecyl butane diacid, tetradecyl butane diacid, pentadecyl butane diacid, octadecyl butane diacid, eicosyl butane diacid, docosyl butane diacid, 2,3-dihexadecyl butane diacid Acid, 2,3-dioctadecyl butane diacid, 2-methyl-3-dodecyl butane diacid, 2-methyl-3-tetradecyl butane diacid, 2-methyl-3-
Hexadecyl butane diacid, 2-ethyl-3-dodecyl butane diacid, 2-propyl-3-dodecyl butane diacid, 2-octyl-
3-hexadecylbutanedioic acid, 2-tetradecyl-3-octadecylbutanedioic acid and the like can be mentioned.

As the aliphatic carboxylic acid compound, a dibasic acid represented by the following structural formula is also preferably used.

[0050]

Embedded image (However, R10 and R11 represent hydrogen or an aliphatic group, at least one of which is an aliphatic group having 12 or more carbon atoms.) Specific examples of the dibasic acid represented by the above structural formula include, for example, , Dodecylmalonic acid, tetradecylmalonic acid, hexadecylmalonic acid, octadecylmalonic acid, eicosylmalonic acid, docosylmalonic acid, tetracosylmalonic acid, didodecylmalonic acid, ditetradecylmalonic acid, dihexadecylmalonic acid, dioctadecyl Malonic acid, dieicosylmalonic acid, didocosylmalonic acid, methyloctadecylmalonic acid, methyldocosylmalonic acid, methyltetracosylmalonic acid, ethyloctadecylmalonic acid, ethyleicosylmalonic acid, ethyldocosylmalonic acid, ethyltetracossi Lumaronic acid and the like.

As the aliphatic carboxylic acid compound, a dibasic acid represented by the following structural formula is also preferably used.

[0052]

Embedded image (However, R ₁₂ represents an aliphatic group having 12 or more carbon atoms, and n is 0
Or 1 and m represents 1, 2 or 3, and when n is 0, m
Is 2 or 3, and when n is 1, m represents 1 or 2.) Specific examples of the dibasic acid represented by the above structural formula include, for example, 2-dodecyl-pentanedioic acid, 2-hexadecyl -Pentanedioic acid, 2-octadecylpentanedioic acid, 2-eicosyl-
Pentanedioic acid, 2-docosyl-pentanedioic acid, 2-dodecyl-
Hexane diacid, 2-pentadecyl-hexane diacid, 2-octadecyl-hexane diacid, 2-eicosyl-hexane diacid,
2-docosyl-hexanedioic acid and the like.

As the aliphatic carboxylic acid compound, a tribasic acid such as citric acid acylated with a long-chain fatty acid is also preferably used. Specific examples thereof include, for example, the following structural formulas.

[0054]

Embedded image

[0055]

Embedded image

[0056]

Embedded image (C) Phenol compound A compound represented by the following structural formula is preferably used.

[0057]

Embedded image (However, Y represents -S-, -O-, -CONH- or -COO-, and R13
Represents an aliphatic group having 12 or more carbon atoms, and n is 1, 2 or 3. Specific examples of the phenol compound represented by the above structural formula include, for example, p- (dotesylthio) phenol, p- (tetradecylthio) phenol, p- (hexadecylthio) phenol, p- (octadecylthio) phenol, p- (octadecylthio) phenol -(Eicosylthio) phenol, p- (docosylthio) phenol, p-
(Tetracosylthio) phenol, p- (dodecyloxy) phenol, p- (tetradecyloxy) phenol, p- (hexadecyloxy) phenol, p- (octadecyloxy) phenol, p- (eicosyloxy) phenol, p-
(Docosyloxy) phenol, p- (tetracosyloxy)
Phenol, p-dodecylcarbamoylphenol, p-tetradecylcarbamoylphenol, p-hexadecylcarbamoylphenol, p-octadecylcarbamoylphenol, p-eicosylcarbamoylphenol, p-docosylcarbamoylphenol, p-tetracosylcarbamoylphenol, gallic Hexadecyl acid, octadecyl gallate, eicosyl gallate, docosyl gallate, tetracosyl gallate and the like.

As the phenol compound, an alkyl caffeic acid ester represented by the following structural formula can also be used.

[0059]

Embedded image (However, R14 is an alkyl group having 5 to 8 carbon atoms.) Specific examples of the caffeic acid alkyl ester represented by the above structural formula include caffeic acid-n-pentyl, caffeic acid-n-hexyl, and caffeic acid. Acid-n-octyl and the like. (C) Metal salt of mercaptoacetic acid A metal salt of alkyl or alkenyl mercaptoacetic acid represented by the following structural formula can be preferably used.

[0060]

Embedded image (However, R15 represents an aliphatic group having 10 to 18 carbon atoms, and M represents tin, magnesium, zinc or copper.) Specific examples of the metal mercaptoacetate represented by the above structural formula include, for example, decyl Tin mercaptoacetate, tin dodecylmercaptoacetate, tin tetradecylmercaptoacetate, tin hexadecylmercaptoacetate, tin octadecylmercaptoacetate, magnesium decylmercaptoacetate, magnesium dodecylmercaptoacetate,
Magnesium tetradecylmercaptoacetate, magnesium hexadecylmercaptoacetate, magnesium octadecylmercaptoacetate, zinc decylmercaptoacetate, zinc dodecylmercaptoacetate, zinc tetradecylmercaptoacetate, zinc hexadecylmercaptoacetate, zinc octadecylmercaptoacetate Salts, copper decyl mercapto acetate, copper dodecyl mercapto acetate, copper tetradecyl mercapto acetate, copper hexadecyl mercapto acetate, copper octadecyl mercapto acetate, and the like.

In the present invention, the color developer is not limited to the compounds described above, and various other electron-accepting compounds can be used.

In the heat-sensitive recording medium of the present invention, the developer is used in an amount of 1 to 20 parts by mass, preferably 2 to 10 parts by mass, per 1 part by mass of the color former (leuco dye). The developers can be used alone or in combination of two or more. The color former (leuco dye) used in the present invention is a compound having an electron donating property, and is used alone or as a mixture of two or more, but is itself a colorless or pale color dye precursor, and is not particularly limited. Conventionally known ones, for example, triphenylmethanephthalide type, triallylmethane type, fluoran type, phenothiian type, thioferoran type, xanthene type, indophthalyl type, spiropyran type, azaphthalide type, chromenopyrazole type, methine type, Leuco compounds such as rhodamine anilinolactams, rhodamine lactams, quinazolines, diazaxanthenes and bislactones are preferably used. Examples of such compounds include, for example, those shown below. 2-anilino-3-methyl-6-diethylaminofluoran, 2-anilino-3-methyl
-6- (di-n-butylamino) fluoran, 2-anilino-3-methyl-6- (Nn-propyl-N-methylamino) fluoran, 2-
Anilino-3-methyl-6- (N-isopropyl-N-methylamino) fluoran, 2-anilino-3-methyl-6- (N-isobutyl-N-methylamino) fluoran, 2-anilino-3-methyl -
6- (Nn-amyl-N-methylamino) fluoran, 2-anilino-3-methyl-6- (N-sec-butyl-N-ethylamino) fluoran, 2-anilino-3-methyl-6- (Nn -Amyl-N-ethylamino) fluoran, 2-anilino-3-methyl-6- (N-iso-amyl-N-ethylamino) fluoran, 2-anilino-3-methyl-
6- (Nn-propyl-N-isopropylamino) fluoran, 2
-Anilino-3-methyl-6- (N-cyclohexyl-N-methylamino) fluoran, 2-anilino-3-methyl-6- (N-ethyl-p
-Toluidino) fluoran, 2-anilino-3-methyl-6- (N-
Methyl-p-toluidino) fluoran, 2- (m-trichloromethylanilino) -3-methyl-6-diethylaminofluoran, 2- (m-trifluoromethylanilino) -3-methyl-6-diethylaminofluoran , 2- (m-trifluoromethylanilino) -3-methyl-6- (N-cyclohexyl-N-methylamino) fluoran, 2- (2,4-dimethylanilino) -3-methyl-6-diethylamino Fluoran, 2- (N-ethyl-p-toluidino) -3-
Methyl-6- (N-ethylanilino) fluoran, 2- (N-methyl
-p-Toluidino) -3-methyl-6- (N-propyl-p-toluidino) fluoran, 2-anilino-6- (Nn-hexyl-N-ethylamino) fluoran, 2- (o-chloroanilino) -6 -Diethylaminofluoran, 2- (o-bromoanilino) -6-diethylaminofluoran, 2- (o-chloroanilino) -6-dibutylaminofluoran, 2- (o-fluoroanilino) -6-dibutylaminofluoran, 2 -(m-trifluoromethylanilino) -6-diethylaminofluoran, 2- (p-acetylanilino) -6- (Nn-amyl-Nn-butylamino) fluoran, 2
-Benzylamino-6- (N-ethyl-p-toluidino) fluoran, 2-benzylamino-6- (N-methyl-2,4-dimethylanilino) fluoran, 2-benzylamino-6- (N-ethyl -2,4-
Dimethylanilino) fluoran, 2-dibenzylamino-6-
(N-methyl-p-toluidino) fluoran, 2-dibenzylamino-6- (N-ethyl-p-toluidino) fluoran, 2- (di-p-
Methylbenzylamino) -6- (N-ethyl-p-toluidino) fluoran, 2- (α-phenylethylamino) -6- (N-ethyl-
(p-toluidino) fluoran, 2-methylamino-6- (N-methylanilino) fluoran, 2-methylamino-6- (N-ethylanilino) fluoran, 2-methylamino-6- (N-propylanilino) fluoran, 2-ethylamino-6- (N-methyl-p-
Toluidino) fluoran, 2-methylamino-6- (N-methyl-
(2,4-dimethylanilino) fluoran, 2-ethylamino-6-
(N-methyl-2,4-dimethylanilino) fluoran, 2-dimethylamino-6- (N-methylanilino) fluoran, 2-dimethylamino-6- (N-ethylanilino) fluoran, 2-diethylamino-6- ( N-methyl-p-toluidino) fluoran, 2-
Diethylamino-6- (N-ethyl-p-toluidino) fluoran, 2-dipropylamino-6- (N-methylanilino) fluoran, 2-dipropylamino-6- (N-ethylanilino) fluoran, 2-amino-6 -(N-methylanilino) fluoran, 2
-Amino-6- (N-ethylanilino) fluoran, 2-amino-6
-(N-propylanilino) fluoran, 2-amino-6- (N-methyl-p-toluidino) fluoran, 2-amino-6- (N-ethyl
-p-Toluidino) fluoran, 2-amino-6- (N-propyl-p
-Toluidino) fluoran, 2-amino-6- (N-methyl-p-ethylanilino) fluoran, 2-amino-6- (N-ethyl-p-ethylanilino) fluoran, 2-amino-6- (N-propyl- p-
Ethylanilino) fluoran, 2-amino-6- (N-methyl-2,
4-dimethylanilino) fluoran, 2-amino-6- (N-ethyl-2,4-dimethylanilino) fluoran, 2-amino-6- (N-
Propyl-2,4-dimethylanilino) fluoran, 2-amino
-6- (N-methyl-p-chloroanilino) fluoran, 2-amino
-6- (N-ethyl-p-chloroanilino) fluoran, 2-amino
-6- (N-propyl-p-chloroanilino) fluoran, 2,3-dimethyl-6-dimethylaminofluoran, 3-methyl-6- (N-
Ethyl-p-toluidino) fluoran, 2-chloro-6-diethylaminofluoran, 2-bromo-6-diethylaminofluoran, 2-chloro-6-dipropylaminofluoran, 3-
Chlor-6-cyclohexylaminofluoran, 3-bromo-
6-cyclohexylaminofluoran, 2-chloro-6- (N-ethyl-N-isoamylamino) fluoran, 2-chloro-3-methyl-6-diethylaminofluoran, 2-anilino-3-chloro-6-diethylamino Fluoran, 2- (o-chloroanilino) -3-chloro-6-cyclohexylaminofluoran, 2-
(m-Trifluoromethylanilino) -3-chloro-6-diethylaminofluoran, 2- (2,3-dichloroanilino) -3-chloro-
6-diethylaminofluoran, 1,2-benzo-6-diethylaminofluoran, 1,2-benzo-6- (N-ethyl-N-isoamylamino) fluoran, 1,2-benzo-6-dibutylaminofluoran , 1,2-benzo-6- (N-ethyl-N-cyclohexylamino) fluoran, 1,2-benzo-6- (N-ethyl-toluidino) fluoran, and others.

Specific examples of other color formers preferably used in the present invention are as follows. 2-anilino-3
-Methyl-6- (N-2-ethoxypropyl-N-ethylamino) fluoran, 2- (p-chloroanilino) -6- (Nn-octylamino) fluoran, 2- (p-chloroanilino) -6- (Nn -Partimylamino) fluoran, 2- (p-chloroanilino) -6- (di-
(n-octylamino) fluoran, 2-benzoylamino-6-
(N-ethyl-p-toluidino) fluoran, 2- (o-methoxybenzoylamino) -6- (N-ethyl-p-toluidino) fluoran, 2-dibenzylamino-4-methyl-6-diethylaminofluoran, 2-dibenzylamino-4-methoxy-6- (N-methyl-p-toluidino) fluoran, 2-dibenzylamino-4-
Methyl-6- (N-ethyl-p-toluidino) fluoran, 2- (α-
Phenylethylamino) -4-methyl-6-diethylaminofluoran, 2- (p-toluidino) -3- (t-butyl) -6- (N-methyl-p-toluidino) fluoran, 2- (o-methoxy (Carbonylanilino) -6-diethylaminofluoran, 2-acetylamino-6- (N-methyl-p-toluidino) fluoran, 3-diethylamino-6- (m-trifluoromethylanilino) fluoran, 4-methoxy- 6- (N-ethyl-p-toluidino) fluoran, 2-ethoxyethylamino-3-chloro-6-dibutylaminofluoran, 2-dibenzylamino-4-chloro-6- (N-ethyl-p-toluidino ) Fluoran, 2- (α-phenylethylamino) -4-chloro-6-diethylaminofluoran, 2- (N-
(Benzyl-p-trifluoromethylanilino) -4-chloro-6-diethylaminofluoran, 2-anilino-3-methyl-6-pyrrolidinofluoran, 2-anilino-3-chloro-6-pyrrolidinofluoran , 2-anilino-3-methyl-6- (N-ethyl-N-tetrahydrofurfurylamino) fluoran, 2-mesidino-
4 ', 5'-benzo-6-diethylaminofluoran, 2- (m-trifluoromethylanilino) -3-methyl-6-pyrrolidinofluoran, 2- (α-naphthylamino) -3,4- Benzo-4'-bromo-6
-(N-benzyl-N-cyclohexylamino) fluoran, 2-
Piperidino-6-diethylaminofluoran, 2- (Nn-propyl-p-trifluoromethylanilino) -6-morpholinofluoran, 2- (di-Np-chlorophenyl-methylamino) -6
-Pyrrolidinofluoran, 2- (Nn-propyl-m-trifluoromethylanilino) -6-morpholinofluoran, 1,2-benzo-6- (N-ethyl-Nn-octylamino) fluoran, 1 ,
2-benzo-6-diallylaminofluoran, 1,2-benzo-6-
(N-ethoxyethyl-N-ethylamino) fluoran, benzolecomethylene blue, 2- [3,6-bis (diethylamino)]-6- (o-chloroanilino) xanthylbenzoate lactam, 2- [3,6-bis (Diethylamino)]-9- (o-chloroanilino) xanthylbenzoic acid lactam, 3,3-bis (p-dimethylaminophenyl) phthalide, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide , (Also known as crystal violet lactone) 3,3-bis (p-dimethylaminophenyl) -6-diethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-bis (p
-Dibutylaminophenyl) phthalide, 3- (2-methoxy-4-
Dimethylaminophenyl) -3- (2-hydroxy-4,5-dichlorophenyl) phthalide, 3- (2-hydroxy-4-dimethylaminophenyl) -3- (2-methoxy-5-chlorophenyl) phthalide, 3- (2-hydroxy-4-dimethoxyaminophenyl)-
3- (2-methoxy-5-chlorophenyl) phthalide, 3- (2-hydroxy-4-dimethylaminophenyl) -3- (2-methoxy-5-
(Nitrophenyl) phthalide, 3- (2-hydroxy-4-diethylaminophenyl) -3- (2-methoxy-5-methylphenyl)
Phthalide, 3,6-bis (dimethylamino) fluorenespiro
(9,3 ')-6'-dimethylaminophthalide, 6'-chloro-8'-methoxy-benzoindolino-spiropyran, 6'-bromo-2'
-Methoxy-benzoindolino-spiropyran and the like.

In the heat-sensitive recording medium of the present invention, the color former can be used alone or as a mixture of two or more, like the color developer. Next, as the binder resin (binder resin) in the thermosensitive coloring layer (thermosensitive recording layer) used in the present invention, various known resins can be used, and examples thereof include polyacrylamide, maleic acid copolymer, and polyacrylamide. Acid ester, polymethacrylic acid ester, vinyl chloride / vinyl acetate copolymer, styrene copolymer, polyester, polyurethane, polyvinyl butyral, ethyl cellulose,
Polyvinyl acetal, polyvinyl acetoacetal,
Examples include polycarbonate, epoxy resin, and polyamide. Here, as in the case of the protective layer, it is preferable from the viewpoint of transparency that the ratio of the refractive index of the resin to the refractive index of the support is between 0.8 and 1.2.

The content of the binder resin in the heat-sensitive coloring layer is preferably not less than 15% by mass of the total solid content of the heat-sensitive coloring layer from the viewpoint of transparency. A more preferred range is the range of 25 to 40% by mass. The specific examples of the leuco dye, the color developer, and the binder resin which are the main components in the heat-sensitive coloring layer of the heat-sensitive recording material of the present invention have been described above, but are not limited thereto. In addition, known fillers, pigments, surfactants, and heat-fusible substances can be added as necessary.

Among the resins used for the protective layer of the present invention, organic solvents (toluene, methyl ethyl ketone, alcohols, etc.)
When used on a heat-sensitive coloring layer, the leuco dye and the color developer generally dissolve and come into contact with each other to develop a color immediately after coating. In order to prevent this color formation, insoluble or slightly soluble leuco dye in the solvent used,
And / or a developer is selectively used. A leuco dye and / or a developer is coated with a microcapsule so that the dye and the developer are hardly contacted. It is desirable to take a method such as making it difficult for the colorant to contact.

Among them, it is preferable to use an organic phosphoric acid compound represented by the structural formula (1) as a color developer in terms of fog due to a solvent, color sensitivity, and color density.
When this compound is used as a color developer, those having a hydroxyl group among the resins used in the above-mentioned heat-sensitive recording layer are preferable from the viewpoint of color development and storage. Specific examples include polyvinyl butyral and polyvinyl acetoacetal.

The heat-sensitive recording layer of the present invention is prepared by uniformly dispersing or dissolving or microencapsulating a color former and a developer together with a binder resin in water or an organic solvent, and coating and drying this on a support. However, the coating method is not particularly limited. Dye and developer are dispersed in the recording layer coating solution,
Alternatively, when a microencapsulated liquid is used, the particle size of the dye, the developer or the microcapsules containing these greatly affects the surface roughness of the protective layer, transparency, and, consequently, dot reproducibility during printing. The diameter is preferably 1 μm or less. The thickness of the recording layer depends on the composition of the recording layer and the use of the thermosensitive recording medium, but is about 1 to 50 μm, preferably 3 to 20 μm.
It is about. In addition, the recording layer coating solution, if necessary,
Various additives such as a surfactant can be added for the purpose of improving coating properties or recording characteristics.

In the case of using a synthetic paper or a plastic film as the support (substrate) in the heat-sensitive recording material of the present invention, the possibility of dust adhesion due to electrification or the like becomes extremely high, which causes printing failure. In addition, transportability may be reduced due to static electricity. In order to prevent these inconveniences, it is preferable to provide a back layer to perform antistatic. Examples of the antistatic material include known materials such as an electron conduction type and an ion conduction type, and the surface resistance is preferably 1 × 10 ¹⁰ ohm / m ² or less, which is effective for dust adhesion. In the present invention, curl adjustment,
It is also possible to provide a back layer for adjusting the transportability, and a back layer containing a matting agent in a silver salt film-like, and also using various known materials such as the above-described materials for the protective layer and the recording layer. You can do it. The particle size of the matting agent is preferably about 0.3 to 1 μm, and the thickness of the back layer is preferably in the range of 0.1 to 1 μm. Examples of the transparent support used in the present invention include polyester films such as polyethylene terephthalate and polybutylene terephthalate;
A cellulose derivative film such as cellulose triacetate, a polyolefin film such as polypropylene or polyethylene, a polyethylene naphthalate, a polystyrene film, or a transparent film in which these are laminated are preferable.
Since the transparency of the support also affects the transparency of the entire sheet, it is preferable to use a support having a Haze degree of 10% or less in the present invention. Among them, in the present invention, a polyethylene terephthalate film is most preferable from the viewpoint of including other qualities such as cost and heat resistance of the support. In the present invention, from the viewpoint of transmission image diagnosis in medical applications, strong light emission in
From the standpoint of preventing dazzling by blocking light at 590 to 630 nm and improving diagnostic performance, it is also preferable to make the transparent thermosensitive recording material of the present invention bluish. As a bluing method, it is possible to bluish the support itself as a base, or to bluish one part by mass of the coating layer, and a bluing density level is in a range of 0.15 to 0.25 in transmission density. , The color is CIE-
A * =-4 to -12 b * =-5 to -15 (measurement conditions; d-0, 10
Colors in the range enclosed by a degree field of view and calculated by measuring absorbance at every 10 nm with a light source D65) are preferable. The coating method of the protective layer is not particularly limited, and can be applied by a conventionally known method. The preferred thickness of the protective layer is 0.1 to 20 μm, more preferably 0.1 to 20 μm.
5 to 10 μm. If the protective layer thickness is too thin, the function as a protective layer such as storage stability and head matching of the recording medium is insufficient, and if too thick, the thermal sensitivity of the recording medium decreases,
It is disadvantageous in terms of cost. The recording method of the transparent thermosensitive recording medium of the present invention is a hot pen, a thermal head,
There is no particular limitation, such as laser heating.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments. For particle size, use a laser diffraction particle size analyzer (HORIB
A LA-700). Example 1 The following composition was pulverized and dispersed in a ball mill to a particle size of 0.35 μm to prepare a developer dispersion [solution A]. [Solution A] Octadecylphosphonic acid 3 parts by mass 10% polyvinyl acetoacetal resin methyl ethyl ketone solution 8 parts by mass (manufactured by Sekisui Chemical, KS-3Z) Methyl ethyl ketone 11 parts by mass Next, [Solution B] prepared with the following composition was sufficiently added. The mixture was stirred to produce a recording layer coating liquid. [Solution B] Developer dispersion [Solution A] 120 parts by mass 2-anilino-3-methyl-6-diethylaminofluoran 5 parts by mass 15% polyvinyl butyral resin methyl ethyl ketone solution 16 parts by mass (manufactured by Denki Kagaku Kogyo Co., Ltd., Denka Co., Ltd.) Butyral # 3000-2) 30% solution of urethane modified polyester resin in toluene 50 parts by mass (Toyobo Co., Ltd., Byron UR-3200) Methyl ethyl ketone 6 parts by mass Toluene 6 parts by mass The recording layer coating solution [B] Liquid]
After coating with a wire bar on a μm polyester film (Emblet S-100 manufactured by Unitika), it was dried to form a 17 μm thick thermosensitive recording layer. Next, the following composition was dispersed in a circulating horizontal sand mill for 48 hours to prepare a pigment dispersion liquid [liquid C] for a protective layer. [Liquid C] Melamine-formaldehyde copolymer 30 parts by mass (Nippon Shokubai, Eposter S, average particle size 0.3 μm) 10% polyvinyl acetoacetal resin methyl ethyl ketone solution 30 parts by mass (Sekisui Chemical Co., Ltd., KS-1) Methyl ethyl ketone 140 Parts by mass Next, the following composition was dispersed in a ball mill, and a filler dispersion
[Liquid D] was prepared. [D liquid] Zinc stearate 30 parts by mass 12.5% silicon-modified polyvinyl butyral methyl ethyl ketone solution 24 parts by mass (manufactured by Dainichi Seika Co., Ltd., dialomer SP-2002) Methyl ethyl ketone 146 parts by mass Further, the following composition was sufficiently stirred, Coating solution for protective layer [E
Liquid] was prepared. [E solution] [C solution] 100 parts by mass [D solution] 6 parts by mass 15% polyvinyl acetoacetal resin methyl ethyl ketone solution 57 parts by mass (manufactured by Sekisui Chemical, KS-1) 28 parts by mass of methyl ethyl ketone The layer coating solution [Solution E] was subjected to ultrasonic treatment for 3 hours at a liquid temperature of 20 ° C. in an ultrasonic defoamer at an ultrasonic sound pressure of 10 × 10 ¹⁰ μPa, and then the previously obtained heat-sensitive coloring layer was obtained. On the (thermosensitive recording layer), a protective layer having a thickness of 3.0 μm was provided by coating with a wire bar and dried, and aging was performed at 40 ° C. for 48 hours to obtain a transparent thermosensitive recording material of the present invention.

At this time, the frequency of the ultrasonic defoamer was 28 kHz.
z, the ultrasonic sound pressure value was measured by using an ultrasonic meter type 1501 manufactured by Kaijo Co., Ltd., the voltage value Vm was measured, and the reception sensitivity value Sv of the sensor element was -201.2 dB. ,
The correction value α is -17.5 dB from the frequency characteristic diagram. (Example 2) Except for changing the ultrasonic sound pressure value of the ultrasonic defoaming machine of the coating liquid [E liquid] for the protective layer of Example 1 to 3 × 10 ¹⁰ μPa.
In the same manner as in Example 1, a transparent thermosensitive recording material of Example 2 was obtained. (Example 3) The temperature of the protective layer coating solution [E solution] of Example 1 was set to 35.
Example 3 was carried out in the same manner as in Example 1 except that the temperature was changed to
Was obtained. (Example 4) Except that the melamine-formaldehyde copolymer of the pigment dispersion liquid [liquid C] for the protective layer of Example 1 was changed to kaolin (ASP-170 from Tsuchiya Kaolin, average particle size 0.4 µm). A transparent thermosensitive recording material of Example 4 was obtained in the same manner as in Example 1. (Example 5) Except that the melamine-formaldehyde copolymer of the pigment dispersion liquid for protective layer [liquid C] of Example 1 was changed to calcium carbonate (BR-15, manufactured by Shiraishi Kogyo, average particle size 0.55 µm). A transparent thermosensitive recording material of Example 5 was obtained in the same manner as in Example 1. (Example 6) 30 parts by weight of the melamine-formaldehyde copolymer of the pigment dispersion liquid [liquid C] for the protective layer of Example 1 was mixed with 30 parts by weight of the melamine-formaldehyde copolymer and kaolin (Tsuchiya Kaolin, ASP-170, Average particle size 0.4μm) 1
A transparent thermosensitive recording material of Example 6 was obtained in the same manner as in Example 1 except that the amount was changed to 5 parts by mass. (Example 7) 30 parts by mass of the melamine-formaldehyde copolymer of the pigment dispersion liquid [liquid C] for the protective layer of Example 1 was combined with 10 parts by mass of the melamine-formaldehyde copolymer and kaolin (ASP-170, manufactured by Tsuchiya Kaolin, Inc.). (Average particle size 0.4 μm)
10 parts by mass and calcium carbonate (BR-1 manufactured by Shiraishi Kogyo)
5, an average particle size of 0.55 μm) A transparent thermosensitive recording material of Example 7 was obtained in the same manner as in Example 1 except that the amount was changed to 10 parts by mass. (Comparative Example 1) A transparent heat-sensitive recording material of Comparative Example 1 was obtained in the same manner as in Example 1, except that the coating liquid [E liquid] for the protective layer of Example 1 was applied without ultrasonic treatment. . (Comparative Example 2) The same procedure as in Example 1 was carried out except that the ultrasonic sound pressure value of the ultrasonic defoaming machine for the coating liquid [E liquid] for the protective layer in Example 1 was changed to 0.5 × 10 ¹⁰ μPa. A transparent heat-sensitive recording material of Comparative Example 2 was obtained. (Comparative Example 3) Except that the ultrasonic sound pressure value of the ultrasonic defoaming machine for the coating liquid [E liquid] for the protective layer of Example 1 was changed to 15 × 10 ¹⁰ μPa.
In the same manner as in Example 1, a transparent thermosensitive recording material of Comparative Example 3 was obtained. (Comparative Example 4) The temperature of the protective layer coating solution [E solution] of Example 1 was set to 45.
Comparative Example 4 in the same manner as in Example 1 except that the temperature was changed to
Was obtained. (Comparative Example 5) The melamine-formaldehyde copolymer of the pigment dispersion liquid [liquid C] for the protective layer of Example 1 had an average particle size of 1.2 μm.
A transparent heat-sensitive recording material of Comparative Example 5 was obtained in the same manner as in Example 1 except that the melamine-formaldehyde copolymer (Nippon Shokubai Co., Ltd., Eposter S12) was used. (Comparative Example 6) Except that the melamine-formaldehyde copolymer of the pigment dispersion liquid for protective layer [liquid C] of Example 1 was changed to talc (manufactured by Fuji Talc, LMS-300, average particle size 1.3 µm). In the same manner as in Example 1, a transparent thermosensitive recording material of Comparative Example 6 was obtained. (Comparative Example 7) The transparent thermosensitive recording material of Comparative Example 7 was produced in the same manner as in Example 1 except that the pigment dispersion for the protective layer [Liquid C] of Example 1 was prepared by dispersing it with a circulation type vertical sand mill. I got

The transparent thermosensitive recording material produced as described above was evaluated as follows. (Transparency) The transparency was measured by a direct-reading haze meter manufactured by Suga Test Instruments in accordance with JIS7105. (White drop) The white drop is a Sony video printer UP-
At 930, the transmission density (X-Rite
309; Visual filter) was applied at an energy of 0.5, each sample was printed, and the print sample was mounted on a Schaukasten, and the number of white spots of 0.1 mm ² or more was counted. (Sticking) Sticking was performed by using a Sony video printer UP-930 at the energy at which the transmission density (X-Rite 309; Visual filter) of the material of Example 1 was 1.5, and a transparent heat-sensitive recording material during printing. And the sticking sound of the thermal head were evaluated on the following four levels.

◎: No sticking sound ○: Little sticking sound △: Sticky sound ×: Loud sticking sound (coating defect (streak, unevenness)) The coating defect was visually judged on the following three levels. ：: no coating defect Δ: slight coating defect ×: coating defect Table 1 shows the evaluation results of the respective transparent thermosensitive recording materials.

[0073]

[Table 1]

According to the present invention, a protective layer coating solution containing a pigment dispersed in a circulating horizontal sand mill is treated with an ultrasonic defoamer at a liquid temperature of 5 to 40 ° C. by the following formula (1). By performing ultrasonic treatment at an expressed ultrasonic sound pressure value (Px) of 2 × 10 ^{10 to} 12 × 10 ¹⁰ μPa, the pigment is excellent in stability, transparent, excellent in head matching, And a transparent thermosensitive recording material free from coating defects such as streaks, and a method for producing the same.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B41M 5/18 E 101E 108 (72) Inventor Hiroyuki Iwase 1-3-6 Nakamagome, Ota-ku, Tokyo Stock F-term in Ricoh Company (reference) 2H026 AA07 BB02 BB24 DD07 DD32 DD48 DD55 EE05 FF01 FF11 FF17 GG10 HH03 4D075 BB13X DB48 DC27 EC11

Claims (14)

[Claims] 1. A thermosensitive recording layer comprising a leuco dye, a developer for causing the leuco dye to heat and form a binder resin as a main component, and a protective layer containing a resin on the leuco dye. In the transparent heat-sensitive recording material provided, a protective layer coating liquid containing a pigment dispersed in a circulating horizontal sand mill is applied at a liquid temperature of 5 to 4.
The ultrasonic treatment is carried out at an ultrasonic sound pressure value (Px) of 2 × 10 ^{10 to} 12 × 10 ¹⁰ μPa expressed by the following formula (1) by an ultrasonic defoaming machine within a range of 0 ° C. Transparent thermal recording material. Px = Vm × 10 ^{-((Sv + α) / 20)} (1) Px (μPa): Sound pressure value, Vm (V): Voltage value, Sv (dB): Receiving sensitivity value of sensor element, α ( dB): Correction value 2. An average particle size (D5) of a pigment in the protective layer coating solution.
2. The transparent thermosensitive recording material according to claim 1, wherein (0) is 1 μm or less. 3. The method according to claim 1, wherein the pigment in the coating liquid for the protective layer is at least one of melamine-formaldehyde copolymer, kaolin and calcium carbonate. Transparent thermal recording material. 4. The method according to claim 1, wherein the developer is an organic phosphoric acid compound represented by the following structural formula, and the binder resin has a hydroxyl group in a molecule. 6. The transparent heat-sensitive recording material according to item 1. Embedded image (R1 represents a linear alkyl group having 12 to 24 carbon atoms) 5. The transparent heat-sensitive recording material according to claim 1, further comprising a back layer having an antistatic ability. 6. The transparent thermosensitive recording material according to claim 1, wherein said support is a polyethylene terephthalate film. 7. The transparent heat-sensitive material according to claim 1, wherein at least one of the support, the heat-sensitive recording layer, and the protective layer is tinted. Recording material. 8. A heat-sensitive recording layer comprising a leuco dye, a developer for causing the leuco dye to heat and a binder resin as a main component, and a protective layer containing a resin thereon. In the method for producing a transparent thermosensitive recording material provided above, a protective layer coating solution containing a pigment dispersed in a circulating horizontal sand mill is coated with an ultrasonic defoaming machine at a liquid temperature of 5 to 40 ° C. using the following formula (1). The ultrasonic sound pressure value (Px) expressed by is 2 × 10 ^{10 to} 12 × 10
^A method for producing a transparent thermosensitive recording material, which comprises performing ultrasonic treatment at ¹⁰ μPa. Px = Vm × 10 ^{-((Sv + α) / 20)} (1) Px (μPa): Sound pressure value, Vm (V): Voltage value, Sv (dB): Receiving sensitivity value of sensor element, α ( dB): Correction value 9. An average particle diameter (D5) of the pigment in the protective layer coating liquid.
9. The method for producing a transparent thermosensitive recording material according to claim 8, wherein (0) is 1 μm or less. 10. The method according to claim 8, wherein the pigment in the coating liquid for the protective layer is at least one of melamine-formaldehyde copolymer, kaolin and calcium carbonate. A method for producing a transparent thermosensitive recording material. 11. The method according to claim 8, wherein the developer is an organic phosphoric acid compound represented by the following structural formula, and the binder resin has a hydroxyl group in a molecule. 13. The method for producing a transparent thermosensitive recording material according to the above item. Embedded image (R1 represents a linear alkyl group having 12 to 24 carbon atoms) 12. The method according to claim 8, further comprising a back layer having an antistatic function.
13. The method for producing a transparent thermosensitive recording material according to the above item. 13. The method according to claim 8, wherein the support is a polyethylene terephthalate film.
The method for producing a transparent thermosensitive recording material according to the above. 14. The transparent heat-sensitive material according to claim 8, wherein at least one of the support, the heat-sensitive recording layer, and the protective layer has a bluish tint. Manufacturing method of recording material.