JPH10166737A - Thermal recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent head matching (sticking) and adhesion of head refuse by adding an organic tiller to a recording layer or a protective layer. SOLUTION: An organic filler being added to the recording layer of a thermal recording medium is preferably insoluble or not easily soluble to general solvents and preferably composed of spherical microparticles which are not aggregated easily. The organic filter has 50% volume mean grain size D50 determined from an accumulated volume distribution preferably in the range of 1-20μm and grain size preferably 1.1 times or less of the thickness of thermal recording layer. It is preferably composed of microparticies of polystyrene, PMMA, benzoguanamine resin, cellulose resin or silicon resin and linseed oil absorption of the organic filter is preferably 30ml/100g or above. Since the organic filter is added, friction between the film surface and a thermal head, thermal adhesion (sticking phenomenon) and adhesion of refuse due to thermal adhesion can be prevented.

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 utilizing a color-forming reaction between an electron-donating color-forming compound and an electron-accepting compound, and more particularly to a plate for gravure printing, offset printing and screen printing. Under film (for image forming) sheet, especially plate making under film (image forming) sheet for screen printing for textile printing, and also plate making under film (image forming) sheet for flexographic printing and image forming film for CAD The present invention relates to a useful thermosensitive recording medium.

[0002]

2. Description of the Related Art Conventionally, an electron-donating color-forming compound (hereinafter, referred to as an electron-donating color-forming compound) has been proposed.
Thermosensitive recording media utilizing a color development reaction between a color former and an electron-accepting compound (hereinafter also referred to as a developer) are widely known. In recent years, applications have expanded, and there is a demand for overhead projectors, for the second original drawing of diazo, or for design drawings, and further, as stencil film for plate making of gravure printing, offset printing, flexographic printing and screen printing. There are also requests.

For example, when used as an underlay film, (1) the light-shielding property in the ultraviolet wavelength region of the portion of the underlay film that should shield ultraviolet light, and the transmittance of the portion to be transmitted, (2) temperature and humidity Under the influence of light, the light-shielding property and transmittance in the ultraviolet wavelength range do not change so much as to become a problem during the required time (preservation). Easiness of inspection (drawing), (4) dimensional accuracy, (5) resolution, (6)
Although it is necessary to satisfy the requirements for physical strength that can withstand repeated use and (7) adhesion of head scum, the required performance level is becoming higher.

A heat-sensitive recording medium for an underlay film satisfying all of these required characteristics has not been obtained at present. Further, as a transparent thermosensitive recording medium which can be directly recorded by a thermal head, there is one proposed in Japanese Patent Application Laid-Open No. 1-99873. A fairly complicated process is required, such as encapsulating and applying a coating solution consisting of an emulsified dispersion obtained by emulsifying and dispersing a developer dissolved in an organic solvent that is hardly soluble or insoluble in water onto a transparent support. And there is a problem in that the transparency is insufficient.

[0005] Other heat-sensitive recording media having good transparency have a problem that the image stability of a color image formed by heat energy is poor. Further, when used as the underlay film for printing plate making, 360 nm to 450 nm
The contrast between the color image portion and the non-image portion cannot be obtained in the above wavelength range, so that it cannot be used as an underlay film for photosensitive plate making using a lamp of 360 nm to 450 nm. Also,
In a conventional transparent thermosensitive recording medium, the color tone is almost black, and when two or more underlay films of a black image are superimposed in the inspection work of an underlay film formed by an automatic tress or the like, the traces thereof are traced. There is also a problem that it is difficult to determine an image shift. This is because the colored image portion, especially 450 to 600 nm, which is easily recognized by the naked eye, has a strong absorption and looks black, and it is difficult to determine whether the image portions overlap or are displaced.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems encountered in the prior art in a heat-sensitive recording medium using a reaction between a color former and a developer. It has excellent sticking properties, and thermal energy is not transmitted to the thermosensitive recording medium due to the adhesion of head scum generated during printing. An object of the present invention is to provide an excellent heat-sensitive recording medium which is avoided.

[0007]

The object of the present invention is to provide a heat-sensitive recording layer comprising an electron-donating color-forming compound, an electron-accepting compound and a binder resin on a transparent support. A heat-sensitive recording medium, further comprising an over-layer mainly composed of a resin having substantially the same refractive index as the heat-sensitive recording layer, wherein the heat-sensitive recording layer contains an organic filler. " (2) a resin having a heat-sensitive recording layer mainly composed of an electron-donating color-forming compound, an electron-accepting compound and a binder resin on a transparent support, and further having a refractive index substantially the same as that of the heat-sensitive recording layer; Is a heat-sensitive recording medium provided with an over layer mainly composed of: a spherical organic filler in the over layer, and a 50% volume average particle diameter (D ₅₀ ) determined from the cumulative volume distribution of 1 ~ 5 μm
And (3) a composition comprising, as a main component, an electron-donating color compound, an electron-accepting compound and a binder resin on a transparent support. A heat-sensitive recording medium provided with a heat-sensitive recording layer, and further provided with an over-layer mainly composed of a resin having a refractive index substantially the same as that of the heat-sensitive recording layer, wherein the over-layer is obtained from a cumulative volume distribution. 50% volume average particle diameter inorganic filler (D ₅₀₎ is 0.7μm or less, and 50% volume average particle diameter determined by the cumulative volume distribution (D ₅₀₎ is allowed to contain an organic filler is in the range of 1~5μm The present invention has been found to be solved by a "thermosensitive recording medium characterized by the above-mentioned features."

Further, in the present invention, it has been found that particularly preferable results can be obtained when the following characteristics (4) to (14) are simultaneously obtained. (4) The organic filler contained in the heat-sensitive recording layer is spherical, and the 50% volume average particle diameter (D ₅₀ ) determined from the cumulative volume distribution is in the range of 1 to 20 μm. The heat-sensitive recording medium according to 1). (5) The thermosensitive recording according to the above (1) or (4), wherein the material of the organic filler contained in the thermosensitive recording layer is fine particles of polystyrene, PMMA, benzoguanamine resin, cellulose resin or silicone resin. Medium. (6) The heat-sensitive recording medium according to the above (1), wherein the organic filler contained in the heat-sensitive recording layer has a linseed oil absorption of 30 ml / 100 g or more. (7) The heat-sensitive recording medium according to (1), wherein the content of the organic filler contained in the heat-sensitive recording layer is less than 50% by weight of the solid content of the heat-sensitive recording layer. (8) The heat-sensitive recording medium according to the above (2) or (3), wherein the organic filler contained in the over layer has a linseed oil absorption of 50 ml / 100 g or more. (9) The thermosensitive recording medium according to the above (2) or (3), wherein the material of the organic filler contained in the over layer is fine particles of a silicone resin. (10) The above item (2) or (3), wherein the total content of the inorganic filler and the organic filler contained in the over layer is less than 50% by weight of the solid content of the over layer. Thermal recording medium. (11) The dynamic friction coefficient of the outermost surface of the thermal recording medium is 0.1
The heat-sensitive recording medium according to the above (1), (2) or (3), wherein: (12) The item (1), (2) or (3), wherein the surface roughness Rz (+ point average roughness) of the outermost surface of the thermosensitive recording medium is in a range of 1 to 4 μm. Thermal recording medium. (13) The electron-accepting compound contained in the heat-sensitive recording layer is an organic phosphoric acid compound represented by the following general formula (I) or (II), and the binder resin has a hydroxyl group or a carboxyl group in the molecule. The heat-sensitive recording medium according to the above (1), (2) or (3), characterized in that it contains.

[0009]

Embedded image (In the formula, R represents a linear alkyl group having 16 to 24 carbon atoms.)

[0010]

Embedded image (In the formula, R ′ represents a straight-chain alkyl group having 13 to 23 carbon atoms.) (14) A UV-curable resin and a resin in which a silicone segment is bonded to the overlayer in a block or graft form. (1), characterized in that
The heat-sensitive recording medium according to the item (2) or (3).

When a thermosensitive recording medium is used as an underprint, the dimensional accuracy of a printed image is involved in both the case where an underlay film is produced and the case where the produced underlay film is printed. However, when producing an underlay film, factors on the production device side have a greater effect than the film side. The factors include film feed accuracy and heat source position accuracy. In addition to the simple feed accuracy, when the heat source is a thermal head, feed unevenness occurs due to friction between the film surface and the thermal head, heat fusion (sticking phenomenon), and adhesion of head residues generated by the heat fusion. . The sticking phenomenon and the adhesion of head scum caused by thermal fusion are most related to the overlayer and the recording layer. Even if only the over layer is improved in lubricity and the film is strengthened, if the recording layer is soft and crushed when heated, it causes sticking and adhesion of head residues caused by heat fusion. Further, there is a change in the mechanical feed amount due to environmental conditions or a rise and fall in the temperature inside the machine, and similarly, expansion and contraction of the film due to a change in temperature. In addition, a change in tension at the time of feeding from a roll-shaped film due to a change in charging or a winding diameter of the film is also included. In addition, when the underlay film is baked, expansion of the underlay film due to the heat of the baking lamp is also a factor.

The accuracy required for an underlay film for printing or the like is ± 0.05 mm / 600 mm or less. On the above-mentioned film side, if the heat source is a thermal head, the friction between the film surface and the head, thermal fusion, environmental conditions, expansion and contraction of the film due to the rise and fall of the temperature inside the machine, and the charging of the film will affect the precision with the device. Come. In particular, the influence of friction between the film surface and the thermal head, thermal fusion (sticking phenomenon), and adhesion of head scum generated by thermal fusion are great, and these indexes include the dynamic friction coefficient and the surface roughness Rz of the film surface.

The definitions of the dynamic friction coefficient and the surface roughness Rz shown here are as follows. 1) Dynamic friction coefficient A stainless steel ball indenter having a diameter of 3 mm is placed on a horizontal film surface at room temperature, and a load of 50 g is applied thereto.
The value obtained by dividing the force acting on the indenter in the horizontal direction when running 10 mm at a speed of 0 mm / s by the load. 2) Surface roughness Rz (+ point average roughness) Rz was extracted from the roughness curve in the direction of the average line by a reference length difference, and measured from the average line of the extracted portion in the direction of longitudinal magnification. In this measurement, the sum of the average of the absolute values of the altitudes (Yp) of the highest to fifth peaks and the average of the absolute values of the altitudes of the lowest to fifth valleys (Yv) is obtained. This value is expressed in micrometers (μm).

In order to meet the above-mentioned demands for high precision, the present inventors have added a predetermined amount of an organic filler to the heat-sensitive recording layer to make the recording layer stronger against pressure, and to add a silicone in the over layer. By adding fine resin particles to make the surface roughness a predetermined roughness, or by making the friction coefficient of the outermost surface of the over layer 0.1 or less, friction between the film surface and the thermal head, heat fusion (sticking) Phenomenon) and the adhesion of head scum caused by thermal fusion were significantly improved.

Next, the thermosensitive recording medium of the present invention will be described in more detail. The organic filler to be added to the heat-sensitive recording layer of the heat-sensitive recording medium of the present invention is preferably one which is insoluble or hardly soluble in a general solvent, and more preferably spherical fine particles which are hardly aggregated. As for the organic filler, 50% volume average particle diameter determined by the cumulative volume distribution (D ₅₀₎ is from 1 to 20
μm, preferably 1.1 μm of the heat-sensitive recording layer thickness.
A particle size of 2 times or less is good. Furthermore, the organic filler is preferably made of fine particles of polystyrene, PMMA, benzoguanamine resin, cellulose resin, silicone resin,
Preferably, the linseed oil absorption of the organic filler is 30 ml.
/ 100g or more is good.

The particles having a volume average diameter of less than 1 μm generally have a large linseed oil absorption, and have good oil absorbency when the recording layer is liquefied during heating. Role is small. In addition, particles having a size exceeding 20 μm and having a thickness far exceeding the thickness of the heat-sensitive recording layer have a large role as a spacer, but the over-layer must be applied to a relatively large thickness in order to fill the irregularities of the heat-sensitive recording layer. There is a disadvantage that the thermal sensitivity of the heat-sensitive recording medium is deteriorated. Therefore, the organic filler to be added to the heat-sensitive recording layer preferably has an oil-absorbing property and an average particle diameter of 1.1 times or less the thickness of the heat-sensitive recording layer. The amount to be added to the recording layer depends on the thickness of the heat-sensitive recording layer,
Depending on the oil absorption of the organic filler and the average particle size of the organic filler, exceeding 50% by weight of the solid content of the heat-sensitive recording layer requires twice or more film thickness when the same concentration is obtained, resulting in an increase in cost. Since many side effects also occur, the usual addition amount is 2 to 30% by weight of the solid content of the heat-sensitive recording layer.
The degree is preferred. Next, specific examples of the organic filler will be described.

(1) Polystyrene-based fine particles SPG type manufactured by Soken Chemical, Techno Polymer SBX series manufactured by Sekisui Plastics, Fine Pearl PB series manufactured by Sumitomo Chemical Co., Ltd. Grandl PP series manufactured by Dainippon Ink and Chemicals, PB-200 manufactured by Kao Series, Nippon Synthetic Rubber MPP Series (2) PMMA-based fine particles Soken Chemical's MP-type MP type MX-type, Sekisui Chemical Co., Ltd. Techno-Polymer MB series (3) Benzoguanamine resin-based fine particles Nippon Shokubai Kasei Kogyo Eposter GP series (4 ) Cellulose resin fine particles Kanebo Bellfine series, Nisshinbo RC beads U series (5) Silicone resin fine particles Toray Dow Corning Silicone Trefill series and Toshiba silicone Tospearl series are listed as organic fillers. It is.

The electron-donating color-forming compound used in the present invention is itself a colorless or pale-colored dye precursor,
There is no particular limitation. For example, there are conventionally known fluoran compounds, and specific examples thereof include the following. 3-diethylamino-7-anilinofluoran, 3-di-n-butylamino-7-anilinofluoran, 3- (Nn-hexyl-N-ethylamino) -7-anilinofluoran, 3 -Diethylamino-
7-dibenzylaminofluoran, 3-diethylamino-5-methyl-7-dibenzylaminofluoran, 3-
Diethylamino-7-piperidinofluoran, 3-diethylamino-7- (o-chloroanilino) fluoran,
3-di-n-butylamino-7- (o-chloroanilino) fluoran, 3-dimethylamino-6-methyl-7
-Anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-di-n-butylamino-6-methyl-7-anilinofluoran, 3- (N-
n-propyl-N-methylamino) -6-methyl-7-
Anilinofluoran, 3- (N-isopropyl-N-methylamino) -6-methyl-7-anilinofluoran,
3- (Nn-butyl-N-ethylamino) -6-methyl-7-anilinofluoran, 3- (N-isobutyl-
N-methylamino) -6-methyl-7-anilinofluoran.

3- (Nn-amyl-N-methylamino) -6-methyl-7-anilinofluoran, 3- (N
-Isoamyl-N-ethylamino) -6-methyl-7-
Anilinofluoran, 3- (N-cyclohexyl-N-
Methyl) -6-methyl-7-anilinofluoran, 3-
(Nn-amyl-N-ethylamino) -6-methyl-
7-anilinofluoran, 3- (N-p-tolyl-N-
Ethylamino) -6-methyl-7-anilinofluoran, 3- (N-2-ethoxypropyl-N-ethylamino) -6-methyl-7-anilinofluoran, 3-pyrrolidino-6-methyl- 7-anilinofluoran, 3-
(N-tetrahydrofurfuryl-N-ethylamino)-
6-methyl-7-anilinofluoran, 3-diethylamino-7- (m-trifluoromethylanilino) fluoran, 3-diethylamino-6-methyl-7- (2 ′,
4'-dimethylanilino) fluorane, 3-diethylamino-6-chloro-7-anilinofluoran, 3-diethylamino-5-methyl-7- (α-phenylethylamino) fluoran, 3- (N-tolyl) —N-ethylamino) -7- (α-phenylethylamino) fluoran and the like.

Further, particularly preferred color formers used in the present invention are fluoran compounds represented by the following general formulas (III) to (VIII), and specific examples thereof include the following compounds.

[0021]

Embedded image (Wherein, R ₁ represents an alkyl group having 8 or less carbon atoms, R ₂ represents a hydrogen atom or an alkyl group having 4 or less carbon atoms, X represents fluorine,
Shows halogen atoms such as chlorine and bromine. )

[0022]

Embedded image (In the formula, R ₃ represents a hydrogen atom or an alkyl group having 8 or less carbon atoms, and R ₄ represents an alkyl group having 8 or less carbon atoms.)

[0023]

Embedded image (Wherein, R ₅ and R ₆ represent an alkyl group having 8 or less carbon atoms,
R ₇ represents a hydrogen atom, a lower alkyl group or a lower alkoxy group. )

[0024]

Embedded image (Wherein, R ₈ represents a hydrogen atom, R ₉ represents an alkyl group having 8 or less carbon atoms, R ₁₀ has a hydrogen atom, a lower alkyl group or a lower alkoxy group, and R ₁₁ has a hydrogen atom or 8 carbon atoms. The following alkyl groups are shown, and R ₁₂ represents an alkyl group having 8 or less carbon atoms, a phenyl group, or a substituted phenyl group.)

[0025]

Embedded image (In the formula, R ₁₃ represents an alkyl group having 8 or less carbon atoms, R ₁₄ represents a methyl group or an ethyl group, and R ₁₅ represents a hydrogen atom or 4 carbon atoms.
The following alkyl groups are shown. Y and Z each represent a hydrogen atom or a halogen atom such as fluorine, chlorine, and bromine. )

[0026]

Embedded image (Wherein, R ₁₆ represents an alkyl group having 8 or less carbon atoms, R ₁₇ represents a methyl group or an ethyl group, and R ₁₈ represents a hydrogen atom or 4 carbon atoms.
The following alkyl groups are shown. Y and Z each represent a hydrogen atom or a halogen atom such as fluorine, chlorine, and bromine. Also,
Ar represents a phenyl group or a benzyl group. )

[Specific examples of general formula (III)] 2- (o-chlorophenylamino) -6-ethylamino-7-methylfluoran, 2- (o-chlorophenylamino) -6
n-butylamino-7-methylfluoran, 2- (o-fluorophenylamino) -6-ethylamino-7-methylfluoran, 2- (o-chlorophenylamino) -6
-N-butylaminofluoran, 2- (o-chlorophenylamino) -6-n-hexylaminofluoran, 2
-(O-chlorophenylamino) -6-n-octylaminofluoran, 2- (o-fluorophenylamino)-
6-isoamylaminofluoran, 2- (o-fluorophenylamino) -6-n-octylaminofluoran.

[Specific examples of the general formula (IV)] 2- (o-nitrophenylamino) -6-diethylaminofluoran,
2- (o-nitrophenylamino) -6-di-n-butylaminofluoran, 2- (o-nitrophenylamino) -6- (N-ethyl-Nn-butylamino) fluoran, 2- ( o-nitrophenylamino) -6- (N
-Ethyl-N-isoamylamino) fluoran.

[Specific examples of the general formula (V)] 2-amino-6
-Diethylaminofluoran, 2-amino-6-di-n
-Butylaminofluoran, 2-amino-3-methyl-
6-diethylaminofluoran, 2-amino-3-methyl-6-di-n-butylaminofluoran, 2-amino-3-methyl-6- (N-ethyl-N-isoamylamino) fluoran, 2-amino -3-methoxy-6-diethylaminofluoran, 2-amino-3-methoxy-6
-Di-n-butylaminofluoran.

[Specific examples of the general formula (VI)] 2-methylamino-6-n-butylaminofluoran, 2-n-butylamino-6-n-butylaminofluoran, 2-n-octylamino- 6-ethylaminofluoran, 2-n-
Octylamino-3-methyl-6-n-butylaminofluoran, 2-phenylamino-6-ethylaminofluoran, 2-phenylamino-6-n-butylaminofluoran, 2-phenylamino-6-n -Octylaminofluoran, 2-phenylamino-3-methyl-6-
n-butylaminofluoran, 2-phenylamino-3
-Methyl-6-ethylaminofluoran, 2-phenylamino-3-methyl-6-n-hexylaminofluoran, 2-phenylamino-3-methyl-6-n-amylaminofluoran, 2-phenylamino -3-methyl-
6-isoamylaminofluoran, 2-phenylamino-3-methyl-6-n-octylaminofluoran, 2
-Phenylamino-3-methoxy-6-n-butylaminofluoran, 2-phenylamino-3-methoxy-6
-N-hexylaminofluoran.

[Specific examples of general formula (VII)] 2- (3 ',
4'-dichlorophenylamino) -6-ethylamino-
7-methylfluoran, 2- (3 ', 4'-dichlorophenylamino) -6-n-butylamino-7-methylfluoran, 2- (3'-chloro-4'-fluorophenylamino) -6 Ethylamino-7-methylfluoran,
2- (N'-methyl-N-3'-chlorophenylamino) -6-ethylamino-7-methylfluoran, 2-
(N-ethyl-N-3′-chlorophenylamino) -6
-Ethylamino-7-methylfluorane, 2- (N-methyl-N-4'-chlorophenylamino) -6-ethylamino-7-methylfluoran.

[Specific examples of the general formula (VIII)] 2-phenylamino-3-methyl-6-ethylamino-7-methylfluoran, 2-phenylamino-3-methyl-6-n-
Butylamino-7-methylfluoran, 2-phenylamino-3-ethyl-6-ethylamino-7-methylfluoran, 2-benzylamino-3-methyl-6-ethylamino-7-methylfluoran, 2 -Phenylamino-
3-chloro-6-ethylamino-7-methylfluoran, 2-phenylamino-3-chloro-6-n-butylamino-7-methylfluoran, 2-benzylamino-
3-chloro-6-ethylamino-7-methylfluoran and the like.

In the present invention, as the color developer for forming the color former, a phenolic compound and an organic phosphoric acid compound which are insoluble or hardly soluble in common solvents are preferable. Include gallic acid compounds, protocatechuic acid compounds, bis (hydroxyphenyl) acetic acid, and the like. Specific examples of organic phosphoric acid compounds include alkylphosphonic acid compounds, α-hydroxyalkylphosphonic acid, and the like. Among them, the organic phosphoric acid compound is excellent in terms of background fog and thermal sensitivity.

As a particularly preferred organic phosphoric acid compound, a phosphonic acid represented by the following formula (I) or (II) is used.

[0035]

Embedded image (Wherein, R represents a linear alkyl group having 16 to 24 carbon atoms)

[0036]

Embedded image (Wherein, R ′ represents a linear alkyl group having 13 to 23 carbon atoms)

Specific examples of the phosphonic acid represented by the general formula (I) include the following compounds. Hexadecylphosphonic acid, octadecylphosphonic acid, eicosylphosphonic acid, docosylphosphonic acid, tetracosylphosphonic acid and the like. Specific examples of the phosphonic acid represented by the general formula (II) include the following compounds. α
-Hydroxytetradecylphosphonic acid, α-hydroxyhexadecylphosphonic acid, α-hydroxyoctadecylphosphonic acid, α-hydroxyeicosylphosphonic acid,
α-hydroxytetracosylphosphonic acid and the like. In the present invention, the color developer is used alone or in combination of two or more. Similarly, the color former can be applied alone or in combination of two or more.

The average particle diameter of the developer used in the present invention is preferably 10 μm or less, more preferably 1 μm or less and not containing particles having a particle diameter of more than 1 μm. And the resolution can be improved.

As the binder resin used in the heat-sensitive recording layer, when a color-forming reaction occurs between the color-forming agent and the color-developing agent due to the force of heat energy or the like, the color-developing protons are attacked to form a ring-opening color. A material having an environment in which the surroundings of the dye color former are proton-rich and the color former is kept stable and the color former is hardly decolorized is preferable, for example, a compound containing a hydroxyl group or a carboxylic acid group in the binder resin, Further, it is a compound having a refractive index at room temperature in the range of 1.45 to 1.60.

As such a binder resin, for example, polyvinyl butyral (1.48 to 1.49), polyvinyl acetal (1.50), epoxy resin (1.5
5-1.61), ethylcellulose (1.46-1.4)
9), cellulose acetate (1.46-1.50),
Cellulose acetate butyrate (1.46 to 1.4)
9), cellulose acetate propionate (1.46)
-1.49), nitrocellulose (1.49-1.5)
1), styrene / maleic acid copolymer (1.50 to 1.
60) and the like. The numerical value in parentheses is the refractive index.
Further, the same as the above binder resin also when an acidic substance contained as an impurity in the binder resin and an ultraviolet absorber containing a hydroxyl group and a carboxyl group described below, an antioxidant, an antioxidant and the like are present in the recording layer. You can create an environment.

Further, the improvement of the light resistance of the heat-sensitive recording medium of the present invention can be achieved by including a light stabilizer in the heat-sensitive recording layer or the protective layer. As the light stabilizer used in the present invention, an ultraviolet absorber, an antioxidant, an antioxidant,
A quencher for singlet oxygen and a quencher for superoxide anion are used.

As the ultraviolet absorber, for example, 2,4-
Dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone, 4-dodecyloxy-2-hydroxybenzophenone, 2,2′-dihydroxy-4-
Methoxybenzophenone, 2,2'-dihydroxy-
4,4′-dimethoxybenzophenone, 2,2 ′, 1,
4′-tetrahydroxybenzophenone, 2-hydroxy-4-methoxy-2′-carboxybenzophenone,
2-hydroxy-4-oxybenzylbenzophenone,
2-hydroxy-4-chlorobenzophenone, 2-hydroxy-5-chlorobenzophenone, 2-hydroxy-
4-methoxy-4'-methylbenzophenone, 2-hydroxy-4-n-heptoxybenzophenone, 2-hydroxy-3,6-dichloro-4-methoxybenzophenone, 2-hydroxy-3,6-dichloro-4-ethoxy Benzophenone-based ultraviolet absorbers such as benzophenone and 2-hydroxy-4- (2-hydroxy-3-methylacryloxy) propoxybenzophenone; 2- (2 ′
-Hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-ditert-butylphenyl) benzotriazole, 2-
(2′-hydroxy-3′-tert-butyl-5 ′
-Methylphenyl) benzotriazole, 2- (2'-
(Hydroxy-4′-octoxy) benzotriazole,
2- (2'-hydroxy-3 ', 5'-ditert-butylphenyl) 5-chlorobenzotriazole, 2-
(3′-tert-butyl-2′-hydroxy-5 ′
-Methylphenyl) 5-chlorobenzotriazole, 2
Benzotriazole-based ultraviolet absorbers such as-(2'-hydroxy-5-ethoxyphenyl) benzotriazole, phenyl salicylate, p-octylphenyl salicylate, p-tert-butylphenyl salicylate, carboxylphenyl salicylate, methylphenyl salicylate, dodecylphenyl Salicylic acid phenyl ester type ultraviolet absorber such as salicylate or p-methoxybenzylidene malonic acid dimethyl ester,
2-ethylhexyl-2-cyano-3,3'-diphenyl acrylate, ethyl-2-cyano-3,3'-diphenyl acrylate, 3,5-ditert-butyl-
p-hydroxybenzoic acid, resorcinol monobenzoate which rearranges to benzophenone by ultraviolet rays, 2,
4-di-tert-butylphenyl, 3,5-di-tert-butyl-4-hydroxybenzoate and the like.

Examples of antioxidants and antioxidants include:
2,6-di-tert-butyl-4-methylphenol, 2,4,6-tri-tert-butylphenol,
Styrenated phenol, 2,2'-methylenebis (4-
Methyl-6-tert-butylphenol), 4,
4'-isopropylidenebisphenol, 2,6-bis (2'-hydroxy-3'-tert-butyl-5 '
-Methylbenzyl) -4-methylphenol, 4,4 '
-Thiobis- (3-methyl-6-tert-butylphenol), tetrakis- {methylene (3,5-ditert-butyl-4-hydroxyhydrocinnamate)} methane, p-hydroxyphenyl-3-naphthylamine, 2,2 , 4-Trimethyl-1,2-dihydroquinoline, thiobis (β-naphthol), mercaptobenzothiazole, mercaptobenzimidazole, aldol-2-naphthylamine, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate , 2,2,
6,6-tetramethyl-4-piperidyl benzoate,
Dilauryl-3,3'-thiodipropionate, distearyl-3,3'-thiodipropionate, tris (4-
(Nonylphenol) phosphite.

As singlet oxygen quenchers, carotenes,
There are pigments, amines, phenols, nickel complexes, sulfides and the like, for example, 1,4-diazabicyclo (2,2,2) octane, β-carotene, 1,3-cyclohexadiene, 2-diethylamino Methylfuran,
2-phenylaminomethylfuran, 9-diethylaminomethylanthraceacene, 5-diethylaminomethyl-6
-Phenyl-3,4-dihydroxypyran, nickel dimethyldithiocarbamate, nickel dibutyldithiocarbamate, nickel 3,5-di-t-butyl-4-hydroxybenzyl-o-ethylphosphonate, nickel 3,5-di-t -Butyl-4-hydroxybenzyl-o
-Butylphosphonate, nickel {2,2'-thiobis (4-t-octylphenolate)} (n-butylamine), nickel {2,2'-thiobis (4-t-octylphenolate)} (2- Ethylhexylamine), nickel bis (2,2′-thiobis (4-t-octylphenolate)}, nickel bis {2,2′-sulfonbis (4-octylphenolate)}, nickel bis (2
-Hydroxy-5-methoxyphenyl-NN-butylaldimine), nickel bis (dithiobenzyl), nickel bis (dithiobiacetyl) and the like.

As a quencher for a superoxyanion, superoxide dismutase and cobalt [III]
And complexes of nickel [II] and the like, but these examples do not limit the present invention. These may be used alone or in combination of two or more.

The substrate of the heat-sensitive recording medium of the present invention is a transparent support, and preferably has a refractive index at room temperature in the range of 1.45 to 1.60. For example, polyethylene terephthalate, a polyester film such as polybutylene terephthalate, a cellulose derivative film such as cellulose triacetate, a polypropylene, a polyolefin film such as polyethylene, a polystyrene film, or a transparent support obtained by laminating these are generally used. is there.

It is preferable to provide an adhesive layer between the recording layer and the heat-sensitive recording layer. As a material of the adhesive layer, generally, an acrylic resin, a saturated polyester resin, or the like, and a resin obtained by curing these are used.

To meet the above-mentioned demand for high precision, the head matching was improved by the following method even in the over layer. (1) Lubricant organic filler fine particles (silicone resin fine particles) were added to the over layer to reduce the friction coefficient of the outermost surface of the over layer to 0.1 or less. (2) The surface roughness of the over layer is adjusted to a predetermined roughness (1 to 4 μm).
m). By the methods (1) and (2), friction between the film surface and the thermal head, thermal fusion (sticking phenomenon), adhesion of head scum caused by thermal fusion, and the like were remarkably improved, and head matching was improved. The overlayer formed in the present invention has a great effect not only on the head matching property (dimensional accuracy) but also on the improvement of chemical resistance, water resistance, friction resistance and light resistance. Indispensable as an element.

Next, the overlayer of the present invention will be described in detail. The organic filler used in the over layer of the heat-sensitive recording medium of the present invention preferably has a spherical shape and a 50% volume average particle diameter (D ₅₀ ) of 1 to ₅ μm determined from the cumulative volume distribution. Oil absorption 50ml
/ 100g or more is good. More preferably, fine particles having lubricity such as silicone resin are preferable.
In order to improve the head matching property of the overlayer, an inorganic filler having a 50% volume average particle diameter (D ₅₀ ) of 0.7 μm or less determined from the cumulative volume distribution, and a 50% volume average particle size determined from the cumulative volume distribution are used. It is preferable to use an organic filler having a volume average particle diameter (D ₅₀ ) in the range of 1 to ₅ μm. The total amount of the inorganic filler and the organic filler to be added to the over layer is preferably less than 50% by weight of the solid content of the over layer in consideration of cost, head matching property and other characteristics.

Next, specific examples of the organic filler and the inorganic filler added to the over layer will be described. [Organic filler] (1) PMMA-based particles Soken Chemical's MP type MP type MX type, Sekisui Plastics Technopolymer MB series (2) Silicone resin-based particles Toray Dow Corning Silicone Trefill Series, Toshiba Silicone Tospearl Series Is an example of an organic filler. [Inorganic filler] kaolin, calcined kaolin, calcined clay, talc, calcium carbonate, titanium oxide, zinc oxide,
Examples of the inorganic filler include silica, colloidal silica, magnesium carbonate, magnesium oxide, aluminum hydroxide, and zinc hydroxide.

As the resin constituting the over layer of the present invention, a resin having the same refractive index as the binder resin constituting the heat-sensitive recording layer is used. Here, the fact that the refractive indices are the same means that they are substantially the same, and includes the case where they differ by about ± 5%. Its refractive index is 1.4 at room temperature.
Preferred are resins from 5 to 1.60.

Examples of such a resin include a water-soluble resin, an aqueous emulsion, a hydrophobic resin, an ultraviolet curable resin, an electron beam curable resin, and a resin in which silicone segments are bonded in a block or graft form. Included. Specific examples of the water-soluble resin include, for example, polyvinyl alcohol, modified polyvinyl alcohol, cellulose derivatives (methylcellulose, methoxycellulose, hydroxyethylcellulose, etc.), casein, gelatin, polyvinylpyrrolidone, styrene-maleic anhydride copolymer, diisobutylene- Maleic anhydride copolymer, polyacrylamide, modified polyacrylamide, methyl vinyl ether-maleic anhydride copolymer, carboxy-modified polyethylene, polyvinyl alcohol / acrylamide block copolymer, melamine-formaldehyde resin, urea-formaldehyde resin, etc. . Examples of the resin or the hydrophobic resin for the aqueous emulsion include polyvinyl acetate, polyurethane, styrene / butadiene copolymer, styrene / butadiene / acrylic copolymer, polyacrylic acid, polyacrylate, vinyl chloride, and the like.
Examples include vinyl acetate copolymer, polybutyl methacrylate, and ethylene / vinyl acetate copolymer. They are,
The resin may be used alone or as a mixture, and if necessary, a curing agent may be added to cure the resin.

Next, the most preferred UV-curable resin, electron beam-curable resin, and resin in which silicone segments are bonded in a block or graft form as the overlayer of the present invention will be described in detail. The type of the UV-curable resin used for forming the over layer is not limited as long as it is a monomer or oligomer (or prepolymer) which undergoes a polymerization reaction upon irradiation with ultraviolet light and cures to become a resin, and is known in the art. All can be used. Examples of such a monomer or oligomer include (poly) ester acrylate, (poly) urethane acrylate, epoxy acrylate, polybutadiene acrylate, silicone acrylate, and melamine acrylate.
(Poly) ester acrylate is obtained by reacting polyhydric alcohols such as 1,6-hexanediol, propylene glycol (as propylene oxide) and diethylene glycol with polybasic acids such as adipic acid, phthalic anhydride and trimellitic acid and acrylic acid. It is a thing. Examples of the structure are shown in (a) to (c). (A) adipic acid / 1,6-hexanediol / acrylic acid

[0054]

Embedded image (B) phthalic anhydride / propylene oxide / acrylic acid

[0055]

Embedded image (C) trimet acid / diethylene glycol / acrylic acid

[0056]

Embedded image

(Poly) urethane acrylate is obtained by reacting a compound having an isocyanate group such as tolylene diisocyanate (TDI) with an acrylate having a hydroxyl group. An example of the structure is shown in FIG.
HEA is 2-hydroxyethyl acrylate, H
DO stands for 1,6-hexanediol, and ADA stands for adipic acid. (D) HEA / TDI / HDO / ADA / HDO / TD
I / HEA

[0058]

Embedded image

Epoxy acrylates are roughly classified into bisphenol A type, novolak type and alicyclic type according to their structures. The epoxy groups of these epoxy resins are esterified with acrylic acid to make the functional groups acryloyl groups.
Examples of the structure are shown in (e) to (g). (E) Bisphenol A-epichlorohydrin type / acrylic acid

[0060]

Embedded image (F) phenol novolak-epichlorohydrin type /
Acrylic acid

[0061]

Embedded image (G) Alicyclic type / acrylic acid

[0062]

Embedded image

Polybutadiene acrylate has a terminal OH
Isocyanate or 1,2 polybutadiene
-A product obtained by reacting with mercaptoethanol or the like, and further reacting with acrylic acid or the like. (H)
Shown in (H)

[0064]

Embedded image The silicone acrylate is, for example, methacryl-modified by a condensation reaction (de-methanol reaction) between an organofunctional trimethoxysilane and a silanol group-containing polysiloxane, and a structural example thereof is shown in (i). (I)

[0065]

Embedded image

When an ultraviolet curable resin is used, a solvent may be used. Examples of the solvent include tetrahydrofuran, methyl ethyl ketone, methyl isophenyl isocyanate, etc., and an acrylic double bond. Examples of the compound to have include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and the like. The polyester diol is, for example, ADEKA NEW ACE Y4-30 (manufactured by Asahi Denka Kogyo KK), and the polyether triol is, for example, Sannics TP-400, Sannics GP-30.
00 (both manufactured by Sanyo Chemical Industries, Ltd.) and the like.

The molecular weight of the polyester part of the electron beam-curable acrylic-modified polyurethane resin is set at 200 to provide the heat-resistant slip layer with the required flexibility and toughness.
A range from 0 to 4000 is preferred. Further, the molecular weight of the entire electron beam-curable acrylic-modified polyurethane resin is preferably in the range of 20,000 to 50,000 for the same reason as described above. In this resin, when the number of functional groups is 5 or more, preferably 7 to 13, the effects such as acceleration of curing and improvement of hardness can be obtained.

On the other hand, the silicone-modified electron beam-curable resin has the following chemical structure.

[0069]

Embedded image (Where R is-(CH ₂ ) -n (n = 0 to
3), TDI is 2,4-tolylene diisocyanate, H
EM represents 2-hydroxyethyl acrylate, and x =
50 to 100 y = 3 to 6) Since this silicone-modified electron beam-curable resin has excellent coating properties, a uniform and thin coating can be formed satisfactorily.
Also, since it has a silicone functional group, the sliding effect is excellent.

When the electric wire-curable acrylic-modified polyurethane resin and the electron beam-curable silicone-modified resin are used in combination,
The ratio is 100 parts by weight of the electron beam-curable acrylic-modified polyurethane resin and 3 parts of the electron beam-curable silicone-modified resin.
It is desirable to add up to 0 parts by weight, preferably in the range of 5 to 20 parts by weight.

In the overlayer of the present invention, it is desirable to use a multi-functional electron beam-curable monomer in combination in order to promote curing and improve the heat resistance during the formation process. This monomer acts as a crosslinking accelerator and is advantageous in forming a complex and high-density crosslinked structure. Specific examples of such a monomer include trimethylolpropane triacrylate, tetramethylolmethanetetraacrylate, pentaerythritol triacrylate, dipentaerythritol hexatriacrylate, and the like. The monomer is preferably added in an amount of up to 50 parts by weight, preferably 20 to 50 parts by weight, per 100 parts by weight of the electron beam-curable acrylic-modified polyurethane resin. If the amount is more than 50 parts by weight, the lubricating hardening is weakened and the sliding effect is reduced.

The overlayer according to the present invention is a phosphazene-based resin having a repeating unit having a phosphazene skeleton represented by the following chemical formula, and is extremely excellent in heat resistance.

Embedded image-(P = N)-Specific examples include, but are not limited to, those represented by the following chemical formulas.

-[NP (A) a (B) b] n- (where a, b; a> 0, b ≧ 0, and a + b =
A is a real number that satisfies 2, A is a polymerization curable group such as a methacryloyloxyethyl group, and B is

[0073]

Embedded image Here, R _{1 to} R ₅ each represent a hydrogen atom, a chlorine atom, a bromine atom or a halogenated alkyl group having 1 to 4 carbon atoms,
M represents an oxygen atom, a sulfur atom or an imino group. )

The phosphazene resin represented by the above chemical formula, for example, A is a methacryloyloxyethyl group and b
= 0 can be produced by ring-opening polymerization of a compound represented by the following chemical formula.

[0075]

Embedded image

When a polymerizable and curable group such as a Bosfanzen resin represented by the above chemical formula is used, the resin is cured by ultraviolet rays, an electron beam, heating, or the like, thereby further improving mechanical strength.
Hardness and heat resistance are improved. In order to add lubricity to the over layer, a resin in which silicone segments are bonded in a block shape or a graft shape is used. By bonding in a block shape or a graft shape, sliding with the thermal head is improved, and scum is unlikely to adhere because silicone is copolymerized with the resin.

The silicone segment copolymerized with the resin has a siloxane bond and an alkyl group such as a methyl group bonded to a silicon atom, and has a hydroxyl group, a carboxyl group, an epoxy group, an amino group, An organopolysiloxane having a reactive functional group such as a mercapto group can be used. Examples of the trunk resin in which these silicone segments are bonded in a block shape or a graft shape include poly (meth) acrylate resin, polyvinyl butyral resin, polyvinyl acetoacetal resin, ethyl cellulose, methyl cellulose, cellulose acetate, and hydroxyethyl cellulose. ,
Cellulose acetate propionate, polyurethane resin, polyester resin, polyvinyl acetate resin, styrene acrylate resin, polyolefin resin, polystyrene resin, polyvinyl chloride resin, polyether resin, polyamide resin, polycarbonate resin Thermoplastic resins such as resin, polyethylene resin, polypropylene resin and polyacrylamide resin are used. Among these, preferred resins in terms of heat resistance and solvent solubility are poly (meth) acrylate resin, polyvinyl butyral resin, polyvinyl acetoacetal resin, cellulose acetate propionate, ethyl cellulose, and polyurethane resin.

The amount of silicone segments in these silicone-modified resins is preferably 1 to 30% by weight. If the content of the silicone segment is too small, the lubricity is low and sticking is liable to occur. If the content is too large, the adhesion of the resin and the adhesion to the lower layer are low and scum sticks easily occur. In addition, these resins modified with silicone have a binding ability and can be used alone or as a main component as an over layer.

As in the case of the heat-sensitive recording layer, a light stabilizer can be contained in the overlayer of the present invention to improve light resistance. The light stabilizer used in the present invention is an ultraviolet absorber, an antioxidant, an antioxidant, a quencher for singlet oxygen, a quencher for superoxide anion, and these are used in the heat-sensitive recording layer. The same ones are used.

The heat-sensitive recording medium of the present invention can be prepared by dispersing only the color developer in an organic solvent and then uniformly mixing the color former and the binder resin to prepare a coating solution for the heat-sensitive recording layer, or adding a binder to the organic solvent. Either disperse the developer uniformly in the binder resin solution in which the resin is dissolved, adjust the heat-sensitive recording layer coating solution by uniformly mixing the color former, etc., or in the organic solvent with the color developer and the developer together with the binder resin. The heat-sensitive recording layer is prepared by uniformly dispersing and adjusting the heat-sensitive recording layer coating solution, or applying the coating solution uniformly dispersed by any method on one side or both sides of the transparent support to form a heat-sensitive recording layer. It is manufactured by providing an over layer mainly composed of a resin.

Examples of the organic solvent for dissolving the binder resin include ethers such as dibutyl ether, isopropyl ether, dioxane, and tetrahydrofuran; acetone;
Ketones such as diethyl ketone, methyl ethyl ketone, methyl isobutyl ketone, methyl propyl ketone, ethyl acetate, isopropyl acetate, n-propyl acetate, and n-acetate
There are esters such as butyl and aromatic hydrocarbons such as benzene, toluene and xylene, which are used alone or in combination.

There are no particular restrictions on the method and amount of coating of the overlayer. However, the coating amount is preferably from 1 to 3 on the recording medium in consideration of the performance and economy of the overlayer.
20 μm range, more preferably 1 to 10 μm coating thickness
Is the range of the film thickness where the performance as the protective layer is sufficiently exhibited and the performance of the recording medium is not deteriorated. In the present invention, the above-described over layer is provided for improving the head matching property with respect to the thermal head related to the dimensional accuracy, and the antistatic layer is provided on the back surface for improving the antistatic property.

The antistatic layer is required to have an antistatic property such that the surface resistance is 10 ⁸ Ω / □ or less even under low humidity, so that the material is limited, and it is general to add a conductive metal oxide. No. An antistatic agent using a conductive metal oxide is generally expensive, but since the metal oxide itself has conductivity, it exhibits excellent antistatic properties even with a small amount of adhesion and has almost no transparency. Nothing. Examples of the conductive metal oxide include SnO ₂ , In ₂ O ₃ , ZnO, TiO ₂ , and Mg.
O, Al ₂ O ₃ , BaO, MoO ₃ or the like alone or P,
Examples include composite oxides mixed with Sb, Sn, Zn, and the like, but are not limited thereto. The finer powders of these metal oxides are preferably as fine as possible, and the finer the powder, the more excellent the transparency. In the present invention, excellent transparency is realized by setting the average particle size of the antistatic agent to 0.2 μm or less. Examples of the binder used by mixing with these include a water-soluble resin, an aqueous emulsion, a hydrophobic resin, an ultraviolet curable resin, and an electron beam curable resin. Examples of the water-soluble resin include polyvinyl alcohol, cellulose derivatives, casein, gelatin, styrene-maleic anhydride, and carboxy-modified polyethylene resin. Examples of the aqueous emulsion and the hydrophobic resin include polyvinyl acetate, polyurethane, vinyl chloride / vinyl acetate copolymer, polyester, polybutyl acrylate, polyvinyl butyral, polyvinyl acetal, and ethylene / vinyl acetate copolymer. These may be used alone or as a mixture, and if necessary, a curing agent may be added to cure the resin.

The type of the ultraviolet curable resin is not particularly limited as long as it is a monomer, oligomer or prepolymer which is cured by causing a polymerization reaction by ultraviolet rays, and known resins can be used. The type of the electron beam-curable resin is not particularly limited, but a particularly preferable electron beam-curable resin is a resin mainly composed of an electron beam-curable resin having a branched molecular structure of five or more functional groups having a polyester skeleton. The ratio of the metal oxide to the binder is preferably about 0.05 to 1 part by weight of the metal oxide per 1 part by weight of the binder,
Preferably, the amount is about 0.2 to 0.8 parts by weight. The formation of a recorded image on the transparent thermosensitive recording medium of the present invention varies depending on the purpose of use, but a hot pen, a thermal head, laser heating,
There is no particular limitation on thermal etching using light or the like. However, it is practically preferable to form an image using a thermal head.

[0085]

The present invention will be described in more detail with reference to the following examples. In the following, all parts and percentages are based on weight. Example 1 The following composition was dispersed in a table-top ball mill, and the volume average particle diameter of octadecylphosphonic acid was dispersed to 0.3 μm.
Further, Micropearl SPN-206 manufactured by Sekisui Chemical Co., Ltd.
(Volume average particle diameter: 6.0 μm) and 5.5 parts thereof were added and uniformly dispersed to obtain a recording layer coating liquid. [Recording layer coating solution] 2- (o-chlorophenylamino) -6-ethylamino-7-methylfluorane 10 parts Stearyl gal gallate 30 parts Polyvinyl butyral (refractive index 1.49, Denka Butyral # manufactured by Denki Kagaku Kogyo KK) 3000-2) 15 parts Toluene / methyl ethyl ketone (1/1) mixed solution 285 parts

The following solutions A and B were uniformly dispersed to about 0.5 μm, and further uniformly mixed with the solution C to prepare an overlayer coating solution. [Overlayer coating liquid] Liquid A Kaolin (UW-90 manufactured by Ryosan Shoji Co., Ltd.) 30 parts Silicone-modified polyvinyl butyral resin (SP-712 manufactured by Dainichi Seika, solid content 12.5%) 24 parts Methyl ethyl ketone 37 parts Liquid B stearin 3.3 parts of zinc acid Silicone-modified polyvinyl butyral resin (SP-712 manufactured by Dainichi Seika, solid content 12.5%) 2.6 parts Methyl ethyl ketone 4.1 parts Liquid C Silicone-modified polyvinyl butyral resin (SP- manufactured by Dainichisei Chemical 712, solid content 12.5%) 66 parts urethane acrylate-based UV-curable resin solution (refractive index 1.56, UNINDIC V9057 manufactured by Dainippon Ink and Chemicals, solid content 75%) 15 parts silicone oil (Shin-Etsu Chemical Co., Ltd.) X22-161AS) 1.5 parts Polyisocyanate compound (Nippon Polyurethane Industry) Ltd. Coronate L) 11.5 parts Toluene / methyl ethyl ketone (1/1) mixture 200 parts

[Coating Solution for Antistatic Layer] SnO ₂ -Sb / Polyester Emulsion Dispersion (Colcoat SP-2002 manufactured by Colcoat Co., Ltd.) 10 parts Methanol / water (1/2) mixed solution 90 parts [Preparation of thermosensitive recording medium] 75 μm Melinex 705
Apply the antistatic layer coating solution to one side of a polyester film (manufactured by ICI Japan) using a wire bar.
After drying, an antistatic layer having a thickness of about 0.3 μm was provided. On the opposite side, a recording layer coating solution is applied and dried using a wire bar to provide a heat-sensitive recording layer having a thickness of about 14 μm. Further, an overlayer coating solution is applied and dried on the recording layer using a wire bar to 80 W. Then, the composition was cured with an ultraviolet lamp having a thickness of about 3 μm, and an overlayer having a thickness of about 3 μm was provided.

Example 2 The following composition was dispersed in a table-top ball mill, and the volume average particle size of α-hydroxyoctadecylphosphonic acid was 0.3 μm.
m, and 2.75 parts of Soken Chemical's MX-1000 (volume average particle diameter 10.0 μm) were further added and uniformly dispersed to obtain a recording layer coating liquid. [Recording layer coating liquid] 2- (o-chlorophenylamino) -6-ethylamino-7-methylfluoran 10 parts α-hydroxyoctadecylphosphonic acid 30 parts polyvinyl butyral (refractive index 1.49, manufactured by Denki Kagaku Kogyo KK) Butyral # 3000-2) 15 parts Toluene / methyl ethyl ketone (1/1) mixed solution 285 parts

The following solutions A and B were uniformly dispersed to about 0.5 μm, and further uniformly mixed with the solution C to prepare an overlayer coating solution. [Overlayer coating solution] Liquid A Kaolin (UW-90, manufactured by Ryosan Corporation) 33 parts Silicone-modified polyvinyl butyral resin (SP-712, manufactured by Dainichi Seika, solid content 12.5%) 26 parts Methyl ethyl ketone 41 parts Liquid B stearin 3.3 parts of zinc acid Silicone-modified polyvinyl butyral resin (SP-712 manufactured by Dainichi Seika, solid content 12.5%) 2.6 parts Methyl ethyl ketone 4.1 parts Liquid C Silicone-modified polyvinyl butyral resin (SP- manufactured by Dainichisei Chemical 712, solid content 12.5%) 150 parts Urethane acrylate UV curable resin solution (refractive index 1.56, UNIDIC V9057 manufactured by Dainippon Ink & Chemicals, Inc., solid content 75%) 135 parts Silicone resin fine particles (Toshiba Silicone Co., Ltd.) Tospearl 105) 15 parts Silicone oil (SH2 manufactured by Toray Silicone Co., Ltd.) PA)) 1.5 parts Polyisocyanate compound (manufactured by Nippon Polyurethane Industry Co., Coronate HL) 20 parts Toluene / methyl ethyl ketone (1/1) mixture 180 parts

[Antistatic Layer Coating Solution] SnO ₂ -Sb / Polyester Emulsion Dispersion (Colcoat SP-2002 manufactured by Colcoat Co., Ltd.) 10 parts Methanol / water (1/2) mixed solution 90 parts [Preparation of thermosensitive recording medium] 75 μm Melinex 705
Apply the antistatic layer coating solution to one side of a polyester film (manufactured by ICI Japan) using a wire bar.
After drying, an antistatic layer having a thickness of about 0.3 μm was provided. On the opposite surface, a coating solution for the recording layer is applied using a wire bar and dried to provide a heat-sensitive recording layer having a thickness of about 13.5 μm, and a coating solution for the over layer is further applied and dried on the recording layer using a wire bar. After curing with UV lamp of 80W / cm, about 3μm
A thermosensitive recording medium of Example 2 was produced by providing a thick overlayer.

Example 3 The following composition was dispersed in a tabletop ball mill, and the volume average particle size of octadecylphosphonic acid was dispersed to 0.3 μm.
Further, Tospearl 145 (volume average particle diameter 4.5 μm, oil absorption 58 ml / 100 g) manufactured by Toshiba Silicone Co., Ltd.
Five parts were added and uniformly dispersed to obtain a recording layer coating liquid. [Recording layer coating solution] 2- (o-chlorophenylamino) -6-ethylamino-7-methylfluoran 10 parts Octadecylphosphonic acid 30 parts Polyvinyl butyral (refractive index 1.49, Denka Butyral # 3000 manufactured by Denki Kagaku Kogyo KK) -2) 15 parts Toluene / methyl ethyl ketone (1/1) mixed solution 285 parts

Each of the following solutions A was uniformly dispersed to about 0.5 μm, and further uniformly mixed with the solution B composition to prepare an overlayer coating solution. [Overlayer coating liquid] Liquid A Zinc stearate 5 parts Silicone-modified polyvinyl butyral resin (SP-712 manufactured by Dainichi Seika, solid content 12.5%) 4 parts Methyl ethyl ketone 6 parts Liquid B Urethane acrylate UV curable resin solution (refractive 200 parts Silicone resin fine particles (Tospearl 130 3 μm, Toshiba Silicone Co., Ltd., oil absorption 62 ml / 100 g) 15 parts Silicone resin fine particles (Toshiba Silicone Co., Ltd.) Tospearl 105 0.5 μm) 30 parts Silicone oil (Byk-344 manufactured by Big Chemie Japan) 3 parts Toluene / methyl ethyl ketone (1/1) mixed solution 145 parts

[Antistatic Layer Coating Solution] SnO ₂ -Sb / Polyester Emulsion Dispersion (Colcoat SP-2002 manufactured by Colcoat Co., Ltd.) 10 parts Methanol / water (1/2) mixed solution 90 parts [Preparation of heat-sensitive recording medium] 75 μm Melinex 705
Apply the antistatic layer coating solution to one side of a polyester film (manufactured by ICI Japan) using a wire bar.
After drying, an antistatic layer having a thickness of about 0.3 μm was provided. On the opposite side, a recording layer coating solution is applied and dried using a wire bar to provide a heat-sensitive recording layer having a thickness of about 14 μm. Further, an overlayer coating solution is applied and dried on the recording layer using a wire bar to 80 W. /3.5cm with UV lamp
A thermosensitive recording medium of Example 3 was produced by providing a thick overlayer.

Example 4 The following composition was dispersed in a table-top ball mill, and the volume average particle diameter of octadecylphosphonic acid was dispersed to 0.3 μm to prepare a recording layer coating liquid. [Recording layer coating solution] 2- (o-chlorophenylamino) -6-ethylamino-7-methylfluoran 10 parts Octadecylphosphonic acid 30 parts Polyvinyl butyral (refractive index 1.49, Denka Butyral # 3000 manufactured by Denki Kagaku Kogyo KK) -2) 15 parts Toluene / methyl ethyl ketone (1/1) mixed solution 285 parts

The following solutions A and B were uniformly dispersed to about 0.5 μm, and further uniformly mixed with the solution C to prepare an overlayer coating solution. [Overlayer coating solution] Liquid A Kaolin (UW-90 manufactured by Ryosan Shoji Co., Ltd.) 10 parts Silicone-modified polyvinyl butyral resin (SP-712 manufactured by Dainichi Seika, solid content 12.5%) 8 parts Methyl ethyl ketone 12.5 parts B Liquid Zinc stearate 3.3 parts Silicone-modified polyvinyl butyral resin (SP-712 manufactured by Dainichi Seika, solid content 12.5%) 2.6 parts Methyl ethyl ketone 4.1 parts Liquid C Silicone-modified polyvinyl butyral resin (Dainichi Seika SP-712, solid content 12.5%) 80 parts Urethane acrylate UV curable resin solution (refractive index 1.56, Unidick V9057 manufactured by Dainippon Ink & Chemicals, Inc., solid content 75%) 20 parts Silicone resin fine particles (Toshiba Silicone Tospearl 130 3μm) 15 parts Silicone oil (Shin-Etsu Chemical X) 2-161AS) 1.5 parts Polyisocyanate compound (manufactured by Nippon Polyurethane Industry Co., Ltd. Coronate L) 11.5 parts Toluene / methyl ethyl ketone (1/1) mixture 200 parts

[Antistatic Layer Coating Solution] SnO ₂ -Sb / Polyester Emulsion Dispersion (Colcoat SP-2002 manufactured by Colcoat Co., Ltd.) 10 parts Methanol / water (1/2) mixed solution 90 parts [Preparation of heat-sensitive recording medium] 75 μm Melinex 705
Apply the antistatic layer coating solution to one side of a polyester film (manufactured by ICI Japan) using a wire bar.
After drying, an antistatic layer having a thickness of about 0.3 μm was provided. On the opposite surface, a coating solution for the recording layer is applied and dried using a wire bar to provide a heat-sensitive recording layer having a thickness of about 13 μm. /3.5cm with UV lamp
A heat-sensitive recording medium of Example 4 was manufactured by providing a thick overlayer.

Example 5 The following composition was dispersed in a tabletop ball mill, and the volume average particle diameter of octadecylphosphonic acid was dispersed to 0.3 μm.
Further, Tospearl 145 (volume average particle diameter 4.5 μm, oil absorption 58 ml / 100 g) manufactured by Toshiba Silicone Co., Ltd.
Five parts were added and uniformly dispersed to obtain a recording layer coating liquid. [Recording layer coating solution] 2- (o-chlorophenylamino) -6-ethylamino-7-methylfluoran 10 parts Octadecylphosphonic acid 30 parts Polyvinyl butyral (refractive index 1.49, Denka Butyral # 3000 manufactured by Denki Kagaku Kogyo KK) -2) 15 parts Toluene / methyl ethyl ketone (1/1) mixed solution 285 parts

The following solutions A and B were uniformly dispersed to about 0.5 μm, and further uniformly mixed with the solution C to prepare an overlayer coating solution. [Overlayer coating solution] Liquid A Kaolin (UW-90, manufactured by Ryosan Corporation) 33 parts Silicone-modified polyvinyl butyral resin (SP-712, manufactured by Dainichi Seika, solid content 12.5%) 26 parts Methyl ethyl ketone 41 parts Liquid B stearin Zinc acid 10 parts Silicone-modified polyvinyl butyral resin (SP-712 manufactured by Dainichi Seika, solid content 12.5%) 7.8 parts Methyl ethyl ketone 12.2 parts Liquid C Silicone-modified polyvinyl butyral resin (SP-712 manufactured by Dainichiseika, 150 parts urethane acrylate UV curable resin solution (refractive index 1.56, Unidick V9057 manufactured by Dainippon Ink and Chemicals, solid content 75%) 135 parts Silicone resin fine particles (Tospearl manufactured by Toshiba Silicone Co., Ltd.) 130 3μm) 30 parts Silicone oil (Big Chemie Di) Bakery Byk-344) 3 parts Polyisocyanate compound (manufactured by Nippon Polyurethane Industry Co., Ltd. Coronate HL) 20 parts Toluene / methyl ethyl ketone (1/1) mixture 180 parts

[Antistatic Layer Coating Solution] SnO ₂ -Sb / Polyester Emulsion Dispersion (Colcoat SP-2002 manufactured by Colcoat Co., Ltd.) 10 parts Methanol / water (1/2) mixed solution 90 parts [Preparation of heat-sensitive recording medium] 75 μm Melinex 705
Apply the antistatic layer coating solution to one side of a polyester film (manufactured by ICI Japan) using a wire bar.
After drying, an antistatic layer having a thickness of about 0.3 μm was provided. On the opposite side, a recording layer coating solution is applied and dried using a wire bar to provide a heat-sensitive recording layer having a thickness of about 14 μm. Further, an overlayer coating solution is applied and dried on the recording layer using a wire bar to 80 W. /3.5cm with UV lamp
A heat-sensitive recording medium of Example 5 was manufactured by providing a thick overlayer.

Example 6 The following composition was dispersed in a table-top ball mill, and the volume average particle diameter of octadecylphosphonic acid was dispersed to 0.3 μm to prepare a recording layer coating liquid. [Recording layer coating solution] 2- (o-chlorophenylamino) -6-ethylamino-7-methylfluoran 10 parts Octadecylphosphonic acid 30 parts Polyvinyl butyral (refractive index 1.49, Denka Butyral # 3000 manufactured by Denki Kagaku Kogyo KK) -2) 15 parts Toluene / methyl ethyl ketone (1/1) mixed solution 285 parts

The following solutions A and B were uniformly dispersed to about 0.5 μm, and further uniformly mixed with the solution C to prepare an overlayer coating solution. [Overlayer coating liquid] Liquid A Urea / formalin-based organic filler (Nippon Kasei Co., Ltd.) 33 parts Silicone-modified polyvinyl butyral resin (Dainichiseika SP-712, solid content 12.5%) 26 parts Methyl ethyl ketone 41 parts Liquid B Zinc stearate 3.3 parts Silicone-modified polyvinyl butyral resin (SP-712 manufactured by Dainichi Seika, solid content 12.5%) 2.6 parts Methyl ethyl ketone 4.1 parts Liquid C Silicone-modified polyvinyl butyral resin (Dainichi Seika SP -712, solid content 12.5%) 150 parts Urethane acrylate UV curable resin solution (refractive index 1.56, UNIDIC V9057 manufactured by Dainippon Ink & Chemicals, Inc., solid content 75%) 135 parts Silicone resin fine particles (Toshiba Silicone) Tospearl 130 3μm) 30 parts Silicone oil (Toray Industries, Inc.) 1.5 parts polyisocyanate compound (Coronate HL manufactured by Nippon Polyurethane Industry Co., Ltd.) 20 parts Toluene / methyl ethyl ketone (1/1) mixed liquid 180 parts

[Antistatic Layer Coating Solution] SnO ₂ -Sb / Polyester Emulsion Dispersion (Colcoat SP-2002, manufactured by Colcoat Co., Ltd.) 10 parts Methanol / water (1/2) mixed solution 90 parts [Preparation of thermosensitive recording medium] 75 μm Melinex 705
Apply the antistatic layer coating solution to one side of a polyester film (manufactured by ICI Japan) using a wire bar.
After drying, an antistatic layer having a thickness of about 0.3 μm was provided. On the opposite surface, a coating solution for the recording layer is applied and dried using a wire bar to provide a heat-sensitive recording layer having a thickness of about 13 μm. /3.5cm with UV lamp
A thick over layer was provided, and a thermal recording medium of Example 6 was produced.

Example 7 The following composition was dispersed in a table-top ball mill, and the volume average particle diameter of octadecylphosphonic acid was dispersed to 0.3 μm to prepare a recording layer coating liquid. [Recording layer coating solution] 2- (o-chlorophenylamino) -6-ethylamino-7-methylfluoran 10 parts Octadecylphosphonic acid 30 parts Polyvinyl butyral (refractive index 1.49, Denka Butyral # 3000 manufactured by Denki Kagaku Kogyo KK) -2) 15 parts Toluene / methyl ethyl ketone (1/1) mixed solution 285 parts

The following solutions A and B were uniformly dispersed to about 0.5 μm, and further uniformly mixed with the solution C to prepare an overlayer coating solution. [Overlayer coating solution] Liquid A Kaolin (UW-90, manufactured by Ryosan Corporation) 33 parts Silicone-modified polyvinyl butyral resin (SP-712, manufactured by Dainichi Seika, solid content 12.5%) 26 parts Methyl ethyl ketone 41 parts Liquid B stearin Zinc acid 10 parts Silicone-modified polyvinyl butyral resin (SP-712 manufactured by Dainichi Seika, solid content 12.5%) 7.8 parts Methyl ethyl ketone 12.2 parts Liquid C Silicone-modified polyvinyl butyral resin (Dainichiseika SP-712, 150 parts urethane acrylate UV curable resin solution (refractive index 1.56, Unidick V9057 manufactured by Dainippon Ink and Chemicals, solid content 75%) 135 parts Silicone resin fine particles (Tospearl manufactured by Toshiba Silicone Co., Ltd.) 120 2μm, oil absorption 75ml / 100g) 30 parts silicon Oil (manufactured by BYK Chemie Japan Byk-344) 3 parts Polyisocyanate compound (manufactured by Nippon Polyurethane Industry Co., Coronate HL) 20 parts Toluene / methyl ethyl ketone (1/1) mixture 180 parts

[Coating Solution for Antistatic Layer] SnO ₂ -Sb / Polyester Emulsion Dispersion (Colcoat SP-2002 manufactured by Colcoat Co., Ltd.) 10 parts Methanol / water (1/2) mixed solution 90 parts [Preparation of thermosensitive recording medium] 75 μm Melinex 705
Apply the antistatic layer coating solution to one side of a polyester film (manufactured by ICI Japan) using a wire bar.
After drying, an antistatic layer having a thickness of about 0.3 μm was provided. On the opposite surface, a coating solution for the recording layer is applied and dried using a wire bar to provide a heat-sensitive recording layer having a thickness of about 13 μm. / Cm and cured with an ultraviolet lamp to provide an overlayer having a thickness of about 3 μm. Thus, a thermal recording medium of Example 7 was produced.

Comparative Example 1 A comparative example was prepared in the same manner as in Example 1 except that 5.5 parts of Micropearl SPN-206 (volume average particle size: 6 μm) manufactured by Sekisui Chemical Co., Ltd. was removed from the coating solution of the recording layer of Example 1. No. 1 heat-sensitive recording medium was produced. Comparative Example 2 A thermosensitive recording medium of Comparative Example 2 was produced in the same manner as in Example 3, except that the silicone resin fine particles Tospearl (manufactured by Toshiba Silicone) was removed from the overlayer of Example 3.

[Dynamic friction coefficient] Kyowa Interface Science Co., Ltd.
It measured using the dynamic friction coefficient measuring device on the following measurement conditions.
A stainless steel ball indenter having a diameter of 3 mm is placed on a horizontal sample surface at room temperature, and a load of 50 g is applied thereto.
The measurement was performed by running 10 mm at m / s. [Back surface resistance value] A heat-sensitive recording medium of 10 cm x 10 cm was used as a test piece, and a surface resistance value measuring device (HEWLETTPACKRD 4329A) was used.
HIGHT RESISTANCE METER). 1 minute discharge, 1 charge
Minute, measurement 1 minute, test voltage 10V, measurement environment 5 ° C, 30%
The value obtained by multiplying the RH and the measured value by 18.8 was defined as the surface resistance value. [Surface Roughness Rz] Rz was measured using Surfcom 570A, a surface roughness shape measuring instrument manufactured by Tokyo Seimitsu Co., Ltd. [Image density] Solid printing was performed under the following printing conditions using a thermal printing simulator manufactured by Okura Electric. (Printing conditions) Thermal head dot density: 8 dots / mm Applied power: 0.68 W / dot Pulse width: 0.70 msec Line period: 10 msec / line Printing length: 20 cm X-Rite 3 using a UV filter to print images
09 was used to measure the image density. [Head Matching (Sticking)] A solid image was printed using a thermal film printer manufactured by Ricoh Co., Ltd. The printing sound during printing and the solid image after printing were observed with an optical microscope, and the following rank evaluation was performed. ○: no sticking △ to ○: little sticking △: sticky ×: sticky violently [adhesion of head residue] A pattern including a solid image and a fine line image was printed using a thermal film printer manufactured by Ricoh Co., Ltd. and after printing. The thermal head was observed with a microscope, and the adhesion of head scum was evaluated according to the following rank. ：: no head residue adhered Δ〜: slight head residue adhered Δ: head residue adhered ×: head residue adhered severely * If severe head residue adhered, defects in dimensional accuracy and printed images occurred.

[0108]

[Table 1]

[0109]

As described above in detail and specifically, the heat-sensitive recording medium of the present invention has an organic filler added to the recording layer or the protective layer and has a dynamic friction coefficient of 0.1 or less on the surface.
Further, by setting the surface roughness Rz in the range of 1 to 4 μm, the head matching (sticking) and the adhesion of head scum are improved, and a remarkably excellent effect is exhibited.

Claims (14)

[Claims] 1. A heat-sensitive recording layer mainly comprising an electron-donating color compound, an electron-accepting compound and a binder resin provided on a support, and a resin having a refractive index substantially the same as that of the heat-sensitive recording layer. An over layer as a main component is provided,
A heat-sensitive recording medium characterized in that the heat-sensitive recording layer contains an organic filler. 2. The heat-sensitive material according to claim 1, wherein the organic filler has a spherical shape, and a 50% volume average particle diameter (D ₅₀ ) determined from a cumulative volume distribution is in a range of 1 to 20 μm. recoding media. 3. The material of the organic filler is polystyrene,
2. A fine particle of PMMA, benzoguanamine resin, cellulose resin or silicone resin.
Or the thermal recording medium according to claim 2. 4. The linseed oil absorption of the organic filler is 30.
2. The heat-sensitive recording medium according to claim 1, wherein the weight is not less than ml / 100 g. 5. The heat-sensitive recording medium according to claim 1, wherein the content of the organic filler in the heat-sensitive recording layer is less than 50% by weight of the solid content of the heat-sensitive recording layer. 6. An electron donating color compound on a transparent support,
A heat-sensitive recording medium comprising a heat-sensitive recording layer mainly composed of an electron-accepting compound and a binder resin, and an overlayer mainly composed of a resin having substantially the same refractive index as the heat-sensitive recording layer. Te, a spherical organic filler in the over-layer, and characterized in that the 50% volume average particle diameter determined by the cumulative volume distribution (D ₅₀₎ is obtained by incorporating an organic filler is in the range of 1~5μm Thermal recording medium. 7. An electron-donating color compound on a transparent support,
A heat-sensitive recording medium comprising a heat-sensitive recording layer mainly composed of an electron-accepting compound and a binder resin, and an overlayer mainly composed of a resin having substantially the same refractive index as the heat-sensitive recording layer. The 50% volume average particle diameter (D ₅₀ ) determined from the cumulative volume distribution in the over layer is 0.7 μm.
Thermosensitive recording medium, characterized in that less is inorganic filler, and 50% volume average particle diameter determined by the cumulative volume distribution (D ₅₀₎ is obtained by incorporating an organic filler is in the range of 1 to 5 [mu] m. 8. The linseed oil absorption of the organic filler is 50.
8. The heat-sensitive recording medium according to claim 6, wherein the heat-sensitive recording medium is at least 100 ml / 100 g. 9. The organic filler according to claim 6, wherein the material of the organic filler is fine particles of silicone resin.
The heat-sensitive recording medium according to the above. 10. The overlayer according to claim 6, wherein the total content of the inorganic filler and the organic filler in the overlayer is less than 50% by weight based on the solid content of the overlayer. Thermal recording medium. 11. The thermosensitive recording medium according to claim 1, wherein a dynamic friction coefficient of the outermost surface of the thermosensitive recording medium is 0.1 or less. 12. The surface roughness Rz of the outermost surface of the thermosensitive recording medium
8. The heat-sensitive recording medium according to claim 1, wherein (+ point average roughness) is in a range of 1 to 4 [mu] m. 13. An electron-accepting compound contained in the heat-sensitive recording layer is an organic phosphoric acid compound represented by the following general formula (I) or (II), and further comprising a hydroxyl group or a carboxyl group in the molecule. The thermosensitive recording medium according to claim 1, wherein the thermosensitive recording medium contains a group. Embedded image (In the formula, R represents a linear alkyl group having 16 to 24 carbon atoms.) (In the formula, R ′ represents a straight-chain alkyl group having 13 to 23 carbon atoms.) 14. An ultraviolet-curable resin and a resin in which silicone segments are bonded in a block or graft form to the over layer.
The heat-sensitive recording medium according to claim 6.