JPH09175021A - Thermal recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal recording material for a transparent or a translucent thermal recording medium contributing to the improvement of a matching quality with a thermal head, i.e., the generation of less head refuse and being almost free from the occurrence of a sticking phenomenon. SOLUTION: A recording medium consists of a thermal recording layer formed mainly of an electron-donative coloring compound, an electron-receptive compound and a binder resin on a transparent or a translucent support, and a protecting layer formed on the thermal recording layer. In this case, the protecting layer contains an ultraviolet ray-curable resin, a resin obtained by copolymerizing a silicone component in a graft or a block fashion, a crosslinking agent which chemically reacts with this resin and an inorganic or an organic filler.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light-transmissive heat-sensitive recording medium utilizing a color-forming reaction between an electron-donating color-forming compound and an electron-accepting compound, and particularly to gravure printing, offset printing and screen printing. Stencil sheet (for image formation) sheet, screen printing stencil sheet for stencil sheet (for image formation) sheet, further for overhead project (hereinafter abbreviated as OHP) image forming film sheet and for CAD The present invention relates to a transparent or translucent thermal recording medium which is useful as an image forming film, particularly as a block film for a silver halide light-sensitive material.

[0002]

2. Description of the Related Art Conventionally, electron-donating color-forming compounds (hereinafter referred to as
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. Thermal recording media are generally paper, synthetic paper,
A thermosensitive recording layer containing a thermochromic composition as a main component is provided on a support such as a plastic film, and a colored image can be obtained by heating with a thermal head, a thermal pen, a laser beam or the like. Compared to other recording materials, this type of recording material can perform recording in a short time with a relatively simple device without performing complicated processing such as development and fixing, and has less noise and environmental pollution. In addition to being used for copying books, documents and the like due to advantages such as low cost, it is widely used as a recording medium in various fields such as electronic computers, facsimiles, ticket vending machines, labels and recorders.

A thermochromic composition used for such a recording medium generally comprises an electron-donating color compound (color former),
This color-forming agent is composed of an electron-accepting compound (color-developing agent) that develops color when heated, and examples of the color-developing agent include a lactone, a lactam, or a colorless or pale-colored leuco dye having a spiropyran ring, and a color-developing agent. Various acidic substances such as organic acids and phenolic substances are used. The recording medium in which the color former and the developer are combined has the advantages that the color tone of the obtained image is clear, the whiteness of the background is high, and the weather resistance of the image (dye image) is excellent. It is widely used.

In recent years, as the thermal recording medium has replaced other conventional recording systems and the demand has increased, there is an increasing demand for improving the quality of the thermal recording medium used in this thermal recording system. As one example, it is used as an overhead projector, a diazo second original drawing film, a design drawing film, and a gravure printing, offset printing and screen printing plate making film with a high contrast between the image part and the background part. There is a need for transparent thermal recording media.

Japanese Patent Laid-Open No. 1-9 discloses a transparent thermosensitive recording medium.
9879, in producing a transparent thermosensitive recording medium, a color former is microencapsulated,
Further, a coating solution composed of an emulsified dispersion obtained by emulsifying a color developer dissolved in a water-insoluble or insoluble organic solvent is coated on a transparent support. Another method proposed is that described in JP-A-5-104859. This is a solvent that dissolves a color former and a binder resin, and an organic acid that is a poorly soluble or insoluble developer in the solvent is finely dispersed, and this dispersion liquid and the dissolved binder resin and color former are mixed and stirred. The coating solution thus obtained is applied onto a transparent support, and the surface of the resulting heat-sensitive recording layer having fine irregularities is filled with a protective layer mainly composed of a resin. It is supposed to be formed.

These transparent and translucent thermal recording media are
The transparency is good, but the matching quality with the thermal head is insufficient. For example, at the time of printing, the heat-fusible substance of the thermal recording medium melts, causing head scraps to cause print fading, head wear, electrode disconnection, and sticking (the thermal recording medium sticks to the head due to heat load). However, a phenomenon in which an abnormal image is generated) occurs, or a problem more than that seen in general thermal paper occurs, and improvement is desired.

[0007]

SUMMARY OF THE INVENTION Therefore, the object of the present invention is to improve the matching quality with the thermal head, which is a drawback of the conventional transparent and semitransparent thermal recording media, that is, to reduce the occurrence of head shavings and the occurrence of sticking. It is to provide a thermosensitive recording material that is hard to do.

[0008]

Means for Solving the Problems As a result of intensive studies, we have found a thermosensitive recording layer containing an electron-donating color-forming compound, an electron-accepting compound and a binder resin as a main component on a transparent or semitransparent support. In a transparent thermosensitive recording medium having a protective layer provided on the recording layer, a resin obtained by copolymerizing a silicon component in the protective layer in a graft form or a block form, a cross-linking agent that reacts with the resin, an inorganic or organic filler. Further, the inventors have found that the above problems can be solved by containing an ultraviolet curable resin, and further studied further to reach the present invention.

Further, in the heat-sensitive recording material, by incorporating an isocyanate compound in the protective layer,
Further, it has been found that the above problem can be more sufficiently solved by incorporating metal soap and / or amino-modified silicone oil in the protective layer. Furthermore, the content of the ultraviolet curable resin is 10 wt% with respect to the total solid content of the protective layer.
-50% by weight, and the ratio of the resin in which the silicone component is copolymerized in the form of graft or block and the ultraviolet curable resin is set to 1: 9 to 7: 3 in weight ratio, the above-mentioned problems can be further satisfactorily achieved. Turned out to be resolved.

A conventional transparent or semitransparent heat-sensitive recording medium comprises a heat-sensitive recording layer provided on a transparent or semitransparent film, and further a protective layer laminated thereon. Too much emphasis is placed on the effect of absorbing heat melt, heat resistance, and a large amount of filler that has the effect of cleaning the head shavings cannot be used in the thermal recording medium, which causes a large amount of head shavings and sticking. At the moment, it is easy to do.

In order to improve the problems in matching with these thermal heads, it is desirable to use a protective layer in terms of function, and in order to improve matching, the protective layer has high heat resistance and thermal release. A material having good binding property and further having good binding property is preferable. Further, other functions of the protective layer include transparency of the recording medium, improvement of chemical resistance, water resistance, light resistance, and abrasion resistance. It is preferable that the material is also useful for these.

As the material used for the protective layer of the present invention, there are inorganic and organic fillers having high heat resistance and an effect of cleaning head shavings and having good head matching property, and the surface smoothness is not extremely lowered. Also, it can be used to the extent that transparency is not deteriorated. The filler preferably has a particle size of 3 μm or less. Also, 10
An oil supply amount of at least ml is preferably used. As these inorganic and organic fillers, one or more fillers commonly used in this type of thermal recording medium can be selected.

Specific examples thereof include inorganic pigments such as calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide zinc hydroxide, barium sulfate, kaolin, talc, surface-treated calcium carbonate and silica, and urea formalin. Examples thereof include resins, styrene / methacrylic acid copolymers, and organic resin powders such as polystyrene.

As the resin material having a high heat resistance used in the protective layer of the present invention, a cured resin having a three-dimensional network structure is preferable, but in the case of producing a thermal recording medium, high temperature treatment at 60 ° C. or higher cannot be performed. Therefore, an ultraviolet curable resin is useful because of its high productivity. The UV-curable resin is not particularly limited in its kind as long as it is a monomer, oligomer or prepolymer which undergoes a polymerization reaction upon irradiation with UV rays to be cured and becomes a resin, and various known resins can be used.

Examples of such monomers or oligomers include (poly) ester acrylate, (poly) urethane acrylate, epoxy acrylate, polybutadiene acrylate, silicone acrylate, and melamine acrylate. (Poly) ester acrylate is 1,
It is obtained by reacting a polyhydric alcohol such as 6-hexanediol, propylene glycol (as propylene oxide) or diethylene glycol with a polybasic acid such as adipic acid, phthalic anhydride or trimellitic acid and acrylic acid. Examples of the structure are shown in (a) to (c).

(A) Adipic acid / 1,6-hexanediol / acrylic acid

[0017]

Embedded image (B) Phthalic anhydride / Propylene oxide / Acrylic acid

[0018]

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

[0019]

Embedded image

The (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 is an abbreviation for 1,6-hexanediol, and ADA is an abbreviation for adipic acid. (D) HEA / TDI / HDO / ADA / HDO / TD
I / HEA

[0021]

Embedded image

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

[0023]

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

[0024]

[Chemical 6] (G) Alicyclic type / acrylic acid

[0025]

Embedded image

Polybutadiene acrylate has a terminal OH
Isocyanate or 1,2 polybutadiene
-Mercaptoethanol or the like is reacted, and then acrylic acid or the like is further reacted. Its structural example (h)
Shown in (H)

[0027]

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)

[0028]

Embedded image

When the UV curable resin is used, a solvent may be used. Examples of the solvent in this case include tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, chloroform, carbon tetrachloride, ethanol, isopropyl alcohol, Organic solvents such as ethyl acetate, butyl acetate, toluene and benzene can be mentioned.
Further, instead of these solvents, a photopolymerizable monomer can be used as a reactive diluent for easy handling.

Examples of the photopolymerizable monomer are 2-ethylhexyl acrylate, cyclohexyl acrylate, butoxyethyl acrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, polyethylene glycol diacrylate, trimethylolpropane triacrylate, pentaeryi. Examples include trit triacrylate.

Conventionally, as a transparent or translucent thermal recording medium, a structure mainly composed of an ultraviolet curable resin and a filler has been studied as a protective layer structure having high heat resistance in view of matching quality with a thermal head. However, there is a limit to the constitution of the protective layer having a high heat resistance, and sticking always occurs during printing. Therefore, in the present invention, in order to improve the sticking, the protective layer is devised so as to have thermal releasability.

As a result of intensive studies, we have found that the inclusion of a lubricating resin in which the silicon component is copolymerized in the form of blocks or grafts in the above-mentioned protective layer structure is very effective in reducing the occurrence of head shavings and preventing sticking. I found it effective.

The resin in which the silicon component is copolymerized in a block or graft form is not particularly limited, but a resin having good heat resistance is preferable. For example,
Silicon modified poly (meth) acrylic acid ester, polyvinyl butyral, polyvinyl acetoacetal, cellulose acetate propionate, cellulose acetate, cellulose acetate butyrate, ethyl cellulose, polyurethane, polyester and the like can be used.

The protective layer structure composed of the filler, the ultraviolet curable resin and the slip resin is excellent in matching quality with the thermal head and can be used as a sufficiently transparent and semitransparent thermal recording medium. It was found that the inclusion of a crosslinking agent in the protective layer did not cause sticking even at higher printing energy.
The cross-linking agent is a substance that reacts with the resin to form a three-dimensional structure, and examples of the cross-linking agent include isocyanate compounds, epoxy compounds, amino resins and the like.

Preferred crosslinking agents in the present invention are isocyanate compounds such as tolylene diisocyanate,
4,4-diphenylmethane diisocyanate, 1,5-
Naphthalene diisocyanate, triphenylmethane triisocyanate, tolidine isocyanate, xylene diisocyanate, hexamethylene diisocyanate and its modified products, dicyclohexylmethane diisocyanate, isophorone diisocyanate and the like can be used. The proportion of the isocyanate compound in the protective layer is preferably 3 to 30%, but is not particularly limited.

Further, the protective layer containing the ultraviolet curable resin, the filler, the lubricating resin in which the silicon component is bonded in the form of block or graft and the isocyanate compound improves the matching quality with the thermal head. However, there are cases in which head debris adheres to the head during high-energy printing. Once attached, the solvent resistance is so good that it cannot be cleaned with an alcohol-based head cleaner, which may cause a problem.

In order to deal with such a case, it has been found that by adding metal soap and / or amino-modified silicone oil to the protective layer, it is possible to prevent head residue on the head even during high energy printing. It was The metal soap is a metal salt of C10 or more fatty acid, and for example, barium stearate, calcium stearate, zinc stearate, aluminum stearate, magnesium stearate, stearic acid and the like can be used, and the ratio of the metal soap in the protective layer is 0. It is preferably 5 to 10%, but is not particularly limited.

The amino-modified silicone oil is a silicone oil having an aminopropyl group or N- (2-aminoethyl) aminopropyl group in the molecule. It is chemically active, unlike dimethyl silicone oil, because it has a reactive amino group. The ratio of amino-modified silicone oil in the protective layer is preferably 0.5-10%,
There is no particular limitation.

In the present invention, the content of the ultraviolet curable resin is preferably 10 wt% to 50 wt% of the total solid content of the protective layer. If the content is too small, the effect of improving heat resistance is small. On the contrary, when the amount is larger than this, the amount of the resin or organic or inorganic filler in which the silicon component contained in the protective layer is copolymerized in a graft form or a block form is relatively decreased, and the matching property with respect to the thermal head, descend.

In the present invention, the ratio of the resin obtained by copolymerizing the silicon component in the form of graft or block and the ultraviolet curable resin is preferably in the range of 1: 9 to 7: 3. If it is too small, the lubricity is insufficient, and if it is too large, the heat resistance is insufficient, which is not preferable for head matching.

The thermal recording medium of the present invention will be described in detail below. In the heat-sensitive recording medium of the present invention, the protective layer and the heat-sensitive layer have almost the same refractive index. Even if the refractive index of the protective layer and the refractive index of the heat-sensitive layer are different, if the respective layers are uniform in refractive index, have no unevenness in film thickness, and if the interface is flat, light that is physically transmitted will be refracted. When printing is performed on gauze with transmitted light using, for example, an image developed in the heat-sensitive layer as an underlay film for plate making of screen printing, high resolution is exhibited. But actually,
Not all of them are sufficient, and the reality is that the resolution is greatly reduced especially when the interface is not flat. It is also observed that the difference in the refractive index increases the reflectance at the interface and reduces the transparency. In the present invention, the problems of this interface can be solved by making the refractive indexes of the protective layer and the heat sensitive layer substantially the same for the above two reasons.

The color former used in the present invention is a compound exhibiting an electron donating property, and is applied alone or as a mixture of two or more kinds, but it is a colorless or pale color dye precursor,
It is not particularly limited and conventionally known ones, for example, triphenylmethanephthalide, triallylmethane, fluoran,
Leuco such as phenothidiane, thioferoran, xanthene, indophthalyl, spiropyran, azaphthalide, chromenopyrazole, methine, rhodamine anilinolactam, rhodamine lactam, xazoline, diazoxanthene, bislactone, etc. Compounds are preferably used.

Examples of such compounds are shown below, but the present invention is not limited thereto. 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) fluorane, 2-anilino-3-methyl-6- (N-gec-butyl-N-ethylamino) fluorane, 2-anilino-3-methyl-6- (N-sec
-Butyl-N-ethylamino) fluorane, 2-anilino-3-methyl-6- (Nn-amyl-N-ethylamino) fluorane, 2-anilino-3-methyl-6-
(N-isoamyl-N-ethylamino) fluorane, 2
-Anilino-3-methyl-6- (Nn-propyl-N
-Isopropylamino) fluoran, 2-anilino-3
-Methyl-6- (N-cyclohexyl-N-methylamino) fluorane,

2-anilino-3-methyl-6- (N-ethyl-p-toluidino) fluorane, 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-diethylaminofluoran,
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-dibutylaminofluorane, 2- (m-trifluoromethylanilino) -6-diethylaminofluorane, 2- (p-acetylanilino) -6- (N- n-amyl-N-n-
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-dimethylani Rino) fluorane, 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-phenyl) Ethylamino)-
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-propylaniline (Lino) fluorane, 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) fluorane, 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) fluorane, 2-amino-6- (N-ethyl-p-chloroanilino) fluorane, 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-chloro-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-diethylaminofluoran, 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) fluorane, 2- (p-chloroanilino) -6- (Nn-octylamino) fluorane, 2
-(P-Chloranilino) -6- (N-n-partimylamino) fluorane, 2- (p-chloranilino) -6
-(Di-n-octylamino) fluorane, 2-benzoylamino-6- (N-ethyl-ptoluidino) fluorane, 2- (o-methoxybenzoylamino) -6-
(N-ethyl-p-toluidino) fluorane, 2-dibenzylamino-4-methyl-6-diethylaminofluorane, 2-dibenzylamino-4-methoxy-6- (N
-Methyl-p-toluidino) fluorane, 2-dibenzylamino-4-methyl-6- (N-ethyl-p-toluidino) fluorane, 2- (α-phenylethylamino)
-4-Methyl-6-diethylaminofluorane, 2-
(P-toluidino) -3- (t-butyl) -6- (N-
Methyl-p-toluidino) fluorane,

2- (o-methoxycarbonylanilino)
-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) fluorane, 2- (α-phenylethylamino) -4-chloro-6-diethylaminofluorane, 2- (N-benzyl-p-trifluoromethylanilino) -4-chloro-6-diethylaminofluorane, Two
-Anilino-3-methyl-6-pyrrolidinofluorane,
2-anilino-3-chloro-6-pyrrolidinofluoran, 2-anilino-3-methyl-6- (N-ethyl-N
-Tetrahydrofurfurylamino) fluoran, 2-mesitidino-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) fluorane, 2-piperidino-6-diethylaminofluorane,

2- (N-n-propyl-p-trifluoromethylanilino) -6-morpholinofluorane, 2-
(Di-N-p-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) xanthyl benzoate 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) fluorene spiro (9,3 ′)-6′-dimethylaminophthalide, 6′-
Chloro-8'-methoxy-benzoindolino-spiropyran, 6'-bromo-2'-methoxy-benzoindolino-spiropyran and the like.

Next, the color developing agent used in the present invention is an electron-accepting compound, and various conventionally known electron-accepting color developing agents can be used. More preferably, in the present invention,
It is an electron-accepting color developer containing a long-chain alkyl group in the molecule as shown in Japanese Patent Application No. 3-355078. 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, or 1 carbon atom
A metal salt of mercaptoacetic acid having an aliphatic group of 0 to 18, an alkyl ester of caffeic acid having an alkyl group of 5 to 8 carbon atoms, an acidic phosphoric acid ester having an aliphatic group of 16 or more carbon atoms, and the like. Aliphatic groups include linear or branched alkyl groups, alkenyl groups, halogen,
It may have a substituent such as an alkoxy group or an ester. Particularly preferred developers in the present invention are represented by the following general formula (1)
Alternatively, it is an organic phosphoric acid compound represented by the general formula (2).

[0053]

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

[0054]

Embedded image (In the formula, R'represents a linear alkyl group having 13 to 23 carbon atoms)

In the heat-sensitive recording medium of the present invention, the developer is 1 to 20 parts, preferably 2 to 10 parts, per 1 part of the color former. The color developer can be used alone or in combination of two or more kinds, and also in the case of the color developer, it can be applied alone or in combination of two or more kinds.

Preferred as the binder resin used in the heat-sensitive recording layer is a resin having a hydroxyl group or a carboxyl group in the molecule. Examples of such resins include polyvinyl acetals such as polyvinyl butyral and polyvinyl acetoacetal, ethyl cellulose, cellulose acetate, cellulose acetate propionate, cellulose derivatives such as cellulose acetate butyrate, and epoxy resins. However, the present invention is not limited to this. The binder resin is used alone or in combination of two or more.

The heat-sensitive recording layer is uniformly dispersed or dissolved in an organic solvent together with a color former, a developer and a binder resin,
This is applied to a transparent support and dried to produce a coating, but the coating method is not particularly limited. The dispersed particle size of the recording layer coating liquid is 1
It is preferably 0 μm or less, more preferably 5 μm or less, and 1
μm or less is more preferable. The film thickness of the recording layer is about 1 to 50 μm, preferably about 3 to 20 μm, although it depends on the composition of the recording layer and the use of the thermal recording medium. If necessary, various additives used in ordinary thermosensitive recording paper can be added to the coating liquid for the recording layer for the purpose of improving coatability or recording characteristics.

The transparent support used in the present invention is not particularly limited, and polyester films such as polyethylene terephthalate and polybutylene terephthalate, cellulose derivative films such as cellulose triacetate, polyolefin films such as polypropylene and polyethylene, polystyrene films or the like. It is common to use a laminated transparent film or the like.

In the present invention, a protective layer is provided on the thermosensitive recording layer. As described above for the protective layer, an ultraviolet curable resin,
Filler, a silicone component is a block or is characterized by containing a lubricating resin that is bonded in a graft form, further for improving quality, an isocyanate compound,
It is characterized by containing metallic soap and amino-modified silicone oil. However, the function expected of the protective layer is not limited to the matching quality with the thermal head, and as described above, there are various properties such as transparency and storability, and other materials may be contained.

Therefore, in addition to the above resins, the following resins are used as the protective layer material. Specific examples include hydrophobic resins such as ethyl cellulose, cellulose acetate propionate, cellulose acetate butyrate, polyvinyl butyral, polyvinyl acetal, polyester cellulose acetate, polyurethane, polyacrylic acid ester, vinyl chloride / vinyl acetate copolymer, polyacrylic. Acid, polyvinyl acetate, polystyrene, ethylene / vinyl acetate copolymer and the like can be mentioned.

Further, other than the above-mentioned metallic soap and amino-modified silicone oil as additives, a lubricant similar to that used in the heat-sensitive recording layer,
Additives such as ultraviolet absorbers, antioxidants, antifoggants, and dispersants can be added. The preferred protective layer thickness is 0.3.
10 to 10 μm, and more preferably 0.5 to 5 μm. If the protective layer is too thin, the storage layer and the function as a protective layer, such as matching with a thermal head, are insufficient.If the protective layer is too thick, the thermal sensitivity of the recording medium decreases and the cost is disadvantageous. It is.

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EXAMPLES The present invention will now be described in more detail by way of examples. In the following, all parts and percentages are based on weight.

Example 1 The following composition was ground by a ball mill to a particle size of 0.3 μm and dispersed to prepare a recording layer coating liquid. (Liquid A) 3-diethylamino-6methyl-7-anilinofluorane 4 parts Octadecylphosphonic acid 12 parts Polyvinyl butyral (Denka Butyral # 3000-2 manufactured by Denki Kagaku Kogyo Co., Ltd.) 6 parts Toluene 57 parts Methyl ethyl ketone 57 parts

The coating solution prepared as described above is applied to a thickness of 75 μm.
(Liquid A) was coated on a polyester film (Teijin HMW-75) having a thickness of m and then dried to form a heat-sensitive recording layer having a thickness of 13 μm. Next, (B liquid) is applied onto this recording layer, dried, and cured with an 80 W / cm ultraviolet lamp,
A protective layer having a thickness of 3 μm was formed. (Liquid B) Urethane acrylate UV curable resin (Dainippon Ink and Chemicals Unidic C7-157, solid content 75%) 120 parts Silicon modified polyvinyl butyral (silicon segment content 20 wt%, solid content 12.5%) 160 parts Kaolin (UC manufactured by Engelhard Co., Ltd.) 100 parts Methyl ethyl ketone 600 parts Tolylene diisocyanate isocyanate compound (Coronate L solid content 75% manufactured by Nippon Polyurethane Industry Co., Ltd.) 10 parts

Example 2 A thermal recording layer was formed on a polyester film in the same manner as in Example 1. Next, apply (C liquid) on this recording layer,
It was dried and cured with an 80 W / cm ultraviolet lamp to form a protective layer having a thickness of 3 μm. (C liquid) Urethane acrylate ultraviolet curing resin (Dainippon Ink and Chemicals Unidic C7-157, solid content 75%) 100 parts Silicon modified polyvinyl butyral (silicon segment content 20 wt%, solid content 12.5%) 200 parts Kaolin (UC manufactured by Engelhard Co., Ltd.) 100 parts Tolylene diisocyanate isocyanate compound (Coronate L solid content 75% manufactured by Nippon Polyurethane Industry Co., Ltd.) 40 parts Methyl ethyl ketone 560 parts

Example 3 A thermal recording layer was formed on a polyester film in the same manner as in Example 1. Next, apply (D liquid) on this recording layer,
It was dried and cured with an 80 W / cm ultraviolet lamp to form a protective layer having a thickness of 3 μm. (D liquid) Urethane acrylate-based UV curable resin (Dainippon Ink and Chemicals Unidic C7-157, solid content 75%) 100 parts Silicon modified polyvinyl butyral (silicon segment content 20 wt%, solid content 12.5%) 200 parts Kaolin (UC manufactured by Engelhard Co., Ltd.) 100 parts Tolylene diisocyanate isocyanate compound (Coronate L solid content 75% manufactured by Nippon Polyurethane Industry Co., Ltd.) 40 parts Zinc stearate (toluene dispersion solid content 75%) 55 parts Methyl ethyl ketone 500 parts

Example 4 A thermosensitive recording layer was formed on a polyester film in the same manner as in Example 1. Next, apply (E liquid) on this recording layer,
It was dried and cured with an 80 W / cm ultraviolet lamp to form a protective layer having a thickness of 3 μm. (E liquid) Urethane acrylate-based UV curable resin (Dainippon Ink and Chemicals Unidick C7-157, solid content 75%) 100 parts Silicon modified polyvinyl butyral (silicon segment content 20 wt%, solid content 12.5%) 200 parts Kaolin (UC manufactured by Engelhard Co., Ltd.) 100 parts Tolylene diisocyanate isocyanate compound (Coronate L solid content 75% manufactured by Nippon Polyurethane Industry Co., Ltd.) 40 parts Amino-modified silicone oil 5 parts Methyl ethyl ketone 550 parts

Example 5 A thermosensitive recording layer was formed on a polyester film in the same manner as in Example 1. Next, apply (F liquid) on this recording layer,
It was dried and cured with an 80 W / cm ultraviolet lamp to form a protective layer having a thickness of 3 μm. (F liquid) Urethane acrylate-based UV curable resin (Dainippon Ink and Chemicals Unidic C7-157, solid content 75%) 10 parts Silicon modified polyvinyl butyral (silicon segment content 20 wt%, solid content 12.5%) 400 parts Kaolin (UC manufactured by Engelhard Co., Ltd.) 50 parts Tolylene diisocyanate isocyanate compound (Coronate L solid content 75% manufactured by Nippon Polyurethane Industry Co., Ltd.) 40 parts Methyl ethyl ketone 600 parts

Example 6 A thermal recording layer was formed on a polyester film in the same manner as in Example 1. Next, apply (G liquid) on this recording layer,
It was dried and cured with an 80 W / cm ultraviolet lamp to form a protective layer having a thickness of 3 μm. (G liquid) Urethane acrylate ultraviolet curing resin (Dainippon Ink and Chemicals Unidick C7-157, solid content 75%) 20 parts Silicon modified polyvinyl butyral (silicon segment content 20 wt%, solid content 12.5%) 10 parts Kaolin (UC manufactured by Engelhard Co., Ltd.) 5 parts Tolylene diisocyanate isocyanate compound (Coronate L solid content 75% manufactured by Nippon Polyurethane Industry Co., Ltd.) 1 part Methyl ethyl ketone 130 parts

Comparative Example 1 A thermosensitive recording layer was formed on a polyester film in the same manner as in Example 1. Next, apply (solution H) on this recording layer,
It was dried and cured with an 80 W / cm ultraviolet lamp to form a protective layer having a thickness of 3 μm. (H liquid) Urethane acrylate-based UV curable resin (Dainippon Ink and Chemicals Unidic C7-157, solid content 75%) 133 parts Polyether-modified silicone oil 3 parts Kaolin (UC manufactured by Engelhard Co.) 100 parts Methyl ethyl ketone 264 parts

Comparative Example 2 A thermal recording layer was formed on a polyester film in the same manner as in Example 1. Next, apply (I liquid) on this recording layer,
It was dried and cured with an 80 W / cm ultraviolet lamp to form a protective layer having a thickness of 3 μm. (Liquid I) Silicon-modified polyvinyl butyral (silicon segment content 20 wt%, solid content 12.5%) 800 parts Kaolin (UC manufactured by Engelhard) 100 parts Methyl ethyl ketone 1600 parts

Evaluation of Debris Adhesion A black solid was printed under the following printing conditions using a thermal printing device of Okura Electric. Printing conditions Thermal head dot density: 8 dots / mm Platen pressure (line pressure) 6 kg / A4 Printing power (29.9 mJ / mm ² , applied pulse width 0.7)
ms and 38.4 mJ / mm ² , applied pulse width 0.9 m
s) Line cycle: 10 ms / line Print length: 3 m After printing, the state of dust adhered to the thermal head was observed with a metallurgical microscope, and evaluation was made on the heating element and behind the heating element according to the scale shown in Table 1 and Table 2 below. . Debris on the heating element

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[Table 1] Behind heating element

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[Table 2]

Sticking Evaluation The black solid print samples subjected to the above-mentioned evaluation of adhesion of dust were evaluated according to the scale shown in Table 3 below. Sticking

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[Table 3] The transparent thermosensitive recording media obtained in the above Examples and Comparative Examples were evaluated as above, and the results are shown in Table 4. Evaluation results

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[Table 4]

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As described above in detail and specifically,
The heat-sensitive recording medium of the present invention has an extremely excellent effect that dust is hardly adhered to any area of the thermal head during printing and sticking hardly occurs.

Claims (5)

[Claims] 1. A heat-sensitive recording layer containing an electron-donating color-forming compound, an electron-accepting compound and a binder resin as a main component is provided on a transparent or semi-transparent support, and a protective layer is further provided on the recording layer. In the transparent heat-sensitive recording medium, the protective layer contains an ultraviolet curable resin, a resin obtained by copolymerizing a silicon component in a graft form or a block form, a crosslinking agent that reacts with the resin, and an inorganic or organic filler. Thermosensitive recording material. 2. The heat-sensitive recording material according to claim 1, wherein the crosslinking agent in the heat-sensitive recording material is an isocyanate compound. 3. The heat-sensitive recording material according to claim 1, wherein the protective layer of the heat-sensitive recording material contains a metal soap and / or an amino-modified silicone oil. 4. The ultraviolet curable resin contained in the protective layer is 10 wt% to 50 w based on the total solid content of the protective layer.
It is t%, The thermal recording material in any one of Claims 1-3. 5. The weight ratio of the resin in which the silicon component contained in the protective layer is copolymerized in the form of graft or block to the ultraviolet curable resin is 1: 9 to 7: 3. The heat-sensitive recording material according to claim 4.