JPH0789237A - Sheet for thermal recording - Google Patents

Abstract

PURPOSE:To provide a thermal recording sheet which shows a clear contrast between a transparent part and an opaque part and enables the transparent part of the recording section to be used as a color negative-type OHP film. CONSTITUTION:This sheet for thermal recording consists of a recording layer containing a coloring component of leuco dye and a coloring agent and a hydrophobic polymer emulsion and a protecting layer provided sequentially on a transparent support. In this sheet, the coloring component is used at a mixing ratio ranging from 3 to 50wt.% for the hydrophobic polymer emulsion. In addition, the minimum film forming temperature of the hydrophobic polymer emulsion is 50 to 150 deg.C.

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 sheet suitable for thermal head recording, and more particularly to a negative type overhead having a clear contrast between a transparent portion and an opaque portion and a transparent portion of the recording portion being colored. The present invention relates to a thermal recording sheet that can be used as a project film.

[0002]

2. Description of the Related Art Conventionally, overhead projects (O
As a sheet for HP), colored powder is fixed on the film by xerography, unevenness is generated on the surface of the heated portion due to shrinkage of the film, bubble generated inside the film by heating, or feeling There is a thermal transfer method. Further, there is also one in which a colorless or light-colored basic dye and a color developer are provided on a transparent support. However, each method has advantages and disadvantages, and development of a film for forming a clear image with a simpler method is being advanced. On the other hand, most of the conventional types are positive types, but recently, a colored negative type image forming film has been desired from the viewpoint of reducing eye fatigue as much as possible.

As a negative type image forming method, for example, a heat-sensitive recording medium utilizing heat fusion of polymer particles of a hydrophobic polymer emulsion (JP-A-60-44388) has been proposed. However, the present situation is that a recording body having a colored recording portion and excellent transparency has not yet been obtained.

[0004]

From the actual situation as described above,
An object of the present invention is to provide a thermosensitive recording sheet which has a clear contrast between the transparent portion and the opaque portion and which can be used as a negative type OHP film in which the transparent portion of the recording portion is colored.

[0005]

DISCLOSURE OF THE INVENTION The inventors of the present invention sequentially provide a transparent support with a recording layer containing a color-forming component composed of a leuco dye and a color former and a hydrophobic polymer emulsion, and a protective layer. In the heat-sensitive recording sheet, the coloring component is contained in an amount of 3 to 50% by weight based on the hydrophobic polymer emulsion.
It was found that the above object can be achieved by using a hydrophobic polymer emulsion having a minimum film-forming temperature in the range of 50 to 150 ° C., and completed the present invention.

[0006]

The present invention provides a heat-sensitive recording sheet in which a transparent support is provided with a recording layer containing a coloring component composed of a leuco dye and a color former and a hydrophobic polymer emulsion, and a protective layer in that order. The coloring component is used in the range of 3 to 50% by weight with respect to the hydrophobic polymer emulsion, and further, the hydrophobic polymer emulsion having a minimum film forming temperature (MTF) of 50 to 150 ° C. is used. When the content of the component is less than 3% by weight based on the hydrophobic polymer emulsion, O
When projecting with HP, a clear colored projection image cannot be obtained,
If it exceeds 50% by weight, the transparency of the recorded image will be lowered, and as a result, the projected image by OHP will be very blurred. Therefore, it is preferable to adjust the amount in the range of 5 to 35% by weight.

The recording layer of the present invention is formed in a cloudy state (opaque), and when a temperature higher than the MFT of the hydrophobic polymer is applied, the particles in the heated portion are melted by heat,
The heat-sensitive recording sheet of the present invention, which is fused and made transparent, uses this transparent portion as a print or an image. Therefore, if the MTF of the hydrophobic polymer emulsion is less than 50 ° C., the emulsion particles are fused and the opacity of the unrecorded portion is lowered when forming the recording layer, and the projected image becomes unclear with OHP. When the temperature exceeds 150 ° C., the recording sensitivity decreases.

Specific examples of the hydrophobic polymer emulsion having an MTF of 50 to 150 ° C. include, for example, vinyl acetate-ethylene-vinyl chloride type, ethylene-vinyl chloride type, vinyl chloride type and the like having a high hydrophobicity. Molecular emulsions are preferred. However, in this case, when the hydrophobic polymer emulsion is the only material that imparts opacity to the heat-sensitive layer, the heat fusion tends to be non-uniform, resulting in insufficient transparency and a projected image with poor contrast when projected with OHP. It is known that by incorporating a heat-fusible substance in the heat-sensitive layer, it is possible to obtain a heat-sensitive recording sheet in which the heat-melting is made uniform and the contrast between the opaque portion and the transparent portion is extremely good.

Specific examples of the heat-fusible substance include paraffin wax, caproic acid amide, capric acid amide, palmitic acid amide, stearic acid amide, oleic acid amide, erucic acid amide, linoleic acid amide, and linolenic acid amide. N-methylstearic acid amide, stearic acid anilide, N-methyloleic acid amide, benzanilide, linoleic acid anilide, N-ethylcapric acid amide, N-butyllauric acid amide, N-octadecylacetamide, N-oleinacetamide, N- Oleylbenzamide, N-stearylcyclohexylamide, polyethylene glycol, 1-benzyloxynaphthalene, 2-benzyloxynaphthalene, 1-hydroxynaphthoic acid phenyl ester, 1,2-diphenoxyethane, 1,4 Diphenoxybutane, 1,2-bis (3-methylphenoxy) ethane, 1,2-bis (4-
Methoxyphenoxy) ethane, 1-phenoxy-2-
(4-chlorophenoxy) ethane, 1-phenoxy-2
-(4-Methoxyphenoxy) ethane, terephthalic acid dibenzyl ester, oxalic acid dibenzyl ester, oxalic acid di (4-methylbenzyl) ester, p-benzyloxybenzoic acid benzyl ester, p-benzylbiphenyl, 1,5- Bis (p-methoxyphenoxy) -3-
Oxapentane, 1,4-bis (2-vinyloxyethoxy) benzene, p-biphenyl-p-tolyl ether, benzyl-p-methylthiophenyl ether, 2-
Examples thereof include compounds such as (2′-hydroxy-5′-methylphenyl) benzotriazole and 2-hydroxy-4-benzyloxybenzophenone.

In the heat-sensitive recording sheet of the present invention, as the leuco dye used in the recording layer, various known colorless or light-colored leuco dyes can be used, and specifically, for example, 3,3-bis (p-dimethylamino). Phenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2)
-Methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethylaminophthalide, 3-diethylamino-7-dibenzylamino-benzo [a] fluorane,
3- (N-ethyl-Np-tolyl) amino-7-N-
Methylanilinofluorane, 3-diethylamino-7-
Anilinofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3,6-bis (diethylamino) fluorane-γ-anilinolactam, 3-cyclohexylamino-6-chlorofluorane, 3-diethylamino-6- Methyl-7-chlorofluorane, 3-diethylamino-7-chlorofluorane, 3- (N-ethyl-
N-isoamyl) amino-6-methyl-7-anilinofluorane, 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7 -Anilino Fluoran, 3
-Di (n-butyl) amino-6-methyl-7-anilinofluorane, 3-di (n-pentyl) amino-6-methyl-7-anilinofluorane, 3-diethylamino-7
-(O-chlorophenylamino) fluorane, 3-di (n-butyl) amino-7- (o-chlorophenylamino) fluorane, 3-diethylamino-7- (o-fluorophenylamino) fluorane, 3-di (n- Butyl) amino-7- (o-fluorophenylamino) fluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluorane, 3- (N-ethyl-p)
-Toluidino) -6-methyl-7- (p-toluidino)
Fluorane, 3- (N-ethyl-N-furfurylamino) -6-methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3
-(N-methyl-Nn-propylamino) -6-methyl-7-anilinofluorane, 3,3-bis [1- (4
-Methoxyphenyl) -1- (4-dimethylaminophenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3,3-bis [1- (4-methoxyphenyl) -1 -(4-Pyrrolidinophenyl) ethylene-
2-yl] -4,5,6,7-tetrachlorophthalide,
3,3-Bis [1,1-bis (4-pyrrolidinophenyl) ethylene-2-yl] -4,5,6,7-tetrabromophthalide, 3-p- (p-anilinoanilino) anilino-6 -Methyl-7-chlorofluorane, 2,2-bis {4- [6 '-(N-cyclohexyl-N-methylamino) -3'-methylspiro [phthalide-3,9'-xanthen-2'-ylamino] ] Phenyl} propane,
3,6, -bis (dimethylamino) fluorene-9-spiro-3 '-(6'-dimethylamino) phthalide and the like can be mentioned. Of course, it is not limited to these, and two or more kinds may be used in combination as required.

Various materials are known for the color former used in combination with the leuco dye as described above, and examples thereof include the following. Inorganic acidic substances such as activated clay, attapulgite, colloidal silica, aluminum silicate,
4-tert-butylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol, 4-hydroxyacetophenol, 4-tert-octylcatechol, 2,2′-dihydroxydiphenol, 4,4′-
Isopropylidene bis (2-tert-butylphenol), 4,4'-sec-butylidene diphenol, 4-
Phenylphenol, 4,4'-isopropylidenediphenol (bisphenol A), 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 2,2'-
Methylenebis (4-chlorophenol), hydroquinone, 4,4'-cyclohexylidenediphenol, 4,
4'-dihydroxydiphenyl sulfide, hydroquinone monobenzyl ether, 4-hydroxybenzophenone, 2,4-dihydroxybenzophenone, 2,4
4'-trihydroxybenzophenone, 2,2 ', 4
4'-tetrahydroxybenzophenone, dimethyl 4-hydroxyphthalate, methyl 4-hydroxybenzoate,
Propyl 4-hydroxybenzoate, sec-butyl 4-hydroxybenzoate, pentyl 4-hydroxybenzoate, phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, 4
-Chlorophenyl hydroxybenzoate, phenylpropyl 4-hydroxybenzoate, phenethyl 4-hydroxybenzoate, -p-chlorobenzyl 4-hydroxybenzoate, -p-methoxybenzyl 4-hydroxybenzoate,
Phenolic compounds such as novolac type phenol resin and phenol polymer, benzoic acid, p-tert-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, 3-sec-butyl-4-hydroxybenzoic acid, 3-cyclohexyl-
Aromatic carboxylic acids such as 4-hydroxybenzoic acid and 3,5-dimethyl-4-hydroxybenzoic acid, 4,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-
Isopropoxydiphenyl sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4'-methyldiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 3,4-dihydroxydiphenyl sulfone, 3,4- 4-hydroxydiphenylsulfone derivative such as dihydroxy-4'-methyldiphenylsulfone, bis (3-tert-butyl-4-hydroxy-6-methylphenyl) sulfide, bis (2-methyl-4-hydroxy-6-tert-) Sulfide derivatives such as butylphenyl) sulfide, and further these phenolic compounds, 4- [2- (p-methoxyphenoxy) ethyloxy] salicylic acid, 4- [3- (p-tolylsulfonyl) propyloxy] salicylic acid, 5 -[P- (2-
Aromatic carboxylic acids such as p-methoxyphenoxyethoxy) cumyl] salicylic acid, salts of these aromatic carboxylic acids and the like with polyvalent metals such as zinc, magnesium, aluminum and calcium, and further 4,4′-bis ( p-
Examples thereof include organic acidic compounds such as tolylsulfourea) diphenylmethane.

The ratio of the leuco dye to the coloring agent used is appropriately selected according to the type of the leuco dye or the coloring agent used and is not particularly limited, but generally 1 part by weight of the leuco dye is used. 1 to 50 parts by weight, preferably 2 to
About 10 parts by weight of coloring agent is used. A coating for a recording layer containing a leuco dye and a coloring agent generally uses water as a dispersion medium,
It is prepared by dispersing together or separately by an agitator / crusher such as a ball mill, attritor, or sand mill.

If desired, various auxiliary agents can be added to the coating solution. For example, dispersants such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, and fatty acid metal salts. , Zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, and other waxes,
An antifoaming agent, a fluorescent dye, a coloring dye, etc. are appropriately added. .

Further, in the range which does not impair the effects of the present invention, various auxiliary agents such as sodium dioctylsulfosuccinate and dodecyl are contained in the aqueous coating liquid for recording layer (hereinafter, simply referred to as coating liquid). Dispersants such as sodium benzene sulfonate, sodium lauryl alcohol sulfate / sodium salt, fatty acid metal salts and the like, ultraviolet absorbers such as triazoles, other defoaming agents, fluorescent dyes, coloring dyes, antioxidants and the like are appropriately added. In addition, if necessary, starches such as grain starch, pregelatinized starch, oxidized starch, etherified starch and esterified starch, proteins such as gelatin, albumin and casein, carboxymethyl cellulose, celluloses such as hydroxyethyl cellulose, agar, It is also possible to add water-soluble natural polymer compounds such as polysaccharides such as sodium alginate and gum arabic, and water-soluble synthetic polymer compounds such as polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic acid, polyacrylamide, and maleic acid copolymers. it can. The addition of the above materials to the coating liquid is appropriately adjusted within a range that does not impair the desired effects of the present invention. Generally, it is preferably adjusted to 20% by weight or less based on the total solid content of the recording layer.

Specific examples of the transparent support used in the present invention include films of polyethylene, polyester, polypropylene, polyvinyl chloride, polystyrene, nylon and the like. The coating device for coating the coating liquid on the support is not particularly limited, but is generally known, for example, bar coater, air knife coater, rod blade coater, pure blade coater, short dwell coater, etc. A public device is used as appropriate. Of course, in the drying, as described above, the temperature at which the surface of the recording layer at the time of drying does not exceed either the melting temperature of MFT of the hydrophobic polymer compounded in the coating liquid for the recording layer or the melting temperature of paraffin wax. It is important to dry under the conditions. By the way, if the coating is dried at a temperature exceeding the above conditions, the coating film becomes transparent and the desired effect cannot be obtained. When a plastic film is used as the support, the coating efficiency can be increased by appropriately performing a pretreatment such as corona discharge or electron beam irradiation on the surface thereof.

The coating amount of the coating liquid is not particularly limited, but generally it is 1 to 30 g / dry weight.
m ² , more preferably adjusted in the range of about 1 to ²⁰ g / m ² . Further, by providing a protective layer on the heat-sensitive recording layer, it is possible to obtain a heat-sensitive recording sheet in which sticking and dust adhesion hardly occur. The adhesive component used for forming the protective layer of the present invention is a polyvinyl alcohol, a carboxyl group-modified polyvinyl alcohol, an acetoacetyl group-modified polyvinyl alcohol, a silicon-modified polyvinyl alcohol, or another modified polyvinyl alcohol. Examples of other water-soluble or water-dispersible polymer adhesive components that can be used in combination include hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, starch and its derivatives, casein, sodium alginate, polyvinylpyrrolidone, polyacrylamide, and styrene. -Maleic acid copolymer salt, polyurethane resin, urea resin, melamine resin, polyamide resin, epichlorohydridone polyamide resin, styrene-butadiene emulsion, styrene-acrylate emulsion, acrylic It includes such synthetic polymer emulsions such as an ester-based emulsion may be used in combination these same two types or more.

A pigment may be added to the protective layer within a range not impairing the transparency after recording, and specific examples thereof include calcium carbonate, zinc oxide, aluminum oxide, silicon dioxide, aluminum hydroxide and sulfuric acid. barium,
Zinc sulfate, talc, kaolin, clay, calcined kaolin,
Examples include inorganic pigments such as calcined clay and colloidal silica, organic pigments such as styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, and raw starch particles. It is generally desirable to adjust the amount used in the range of about 10 to 200 parts by weight with respect to 100 parts by weight of the adhesive component. Further, in the coating liquid for forming the protective layer, if necessary, a lubricant such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, a surfactant such as sodium dioctylsulfosuccinate, an antifoaming agent. It is also possible to appropriately add various auxiliaries such as.

Further, a curing agent such as glyoxal, boric acid, dialdehyde starch, or an epoxy compound may be added to further improve water resistance. The coating amount of the protective layer is adjusted to a dry weight of 0.5 to 12 g / m ² , preferably 1 to 10 g / m ² . As the coating method, the same method as the coating method of the heat-sensitive coating liquid is appropriately used. Needless to say, even when the protective layer coating liquid is dried, the surface temperature of the protective layer should be dried at a temperature which does not exceed either the MFT of the hydrophobic polymer contained in the recording layer or the melting start temperature of the paraffin wax. is important.

[0019]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.
Unless otherwise specified, parts and% in the examples mean parts by weight and% by weight, respectively.

Example 1 [Preparation of liquid A] 10 parts of 3-dimethylamino-7-chlorofluorane, 1,2-di (m-tolyloxy) ethane 25
Parts, 5 parts of a 5% aqueous solution of methyl cellulose, and 40 parts of water
The composition consisting of 1 part was pulverized with a sand grinder until the average particle size became 1 μm to obtain a liquid A.

[Preparation of Solution B] A composition consisting of 20 parts of 4-hydroxy-4′-isosopropoxydiphenyl sulfone, 5 parts of a 5% aqueous solution of methylcellulose, and 55 parts of water has an average particle diameter of 1 μm with a sand grinder. Was pulverized to obtain a liquid B.

[Formation of Recording Layer] Emulsion type paraffin wax excluding components having a melting start temperature of 64 ° C. or less (trade name: KW-622 / manufactured by Kyoo Kagaku Kogyo / solid content 30)
%) 10 parts, vinyl chloride emulsion (trade name: VINYBLANC 602 / manufactured by Nissin Chemical / 45% solid content / resin MFT = 130 ° C.) 35 parts, solution A 5 parts, and solution B 5 Part of the coating solution for the recording layer is applied onto a transparent polyethylene terephthalate film having a thickness of 75 μm by a wire bar so that the dry weight is 12 g / m ^2, and
A white opaque recording layer was formed by drying with a dryer at 90 ° C. for 90 seconds.

[Formation of protective layer] A composition comprising 80 parts of a 10% aqueous solution of silicone-modified polyvinyl alcohol, 5 parts of kaolin, 5 parts of a 30% aqueous dispersion of zinc stearate, and 10 parts of water is mixed and stirred to obtain The coating liquid thus obtained was coated on the above-mentioned thermosensitive recording layer with a wire bar so that the weight after drying was 4 g / m ^2, and dried with a dryer at 60 ° C. for 120 seconds to give a white opaque thermosensitive recording medium. Got the sheet.

Example 2 Example 2 was repeated except that 3,3-bis (p-dimethylaminophenyl) -6-dimethylphthalide was used in place of 3-dimethylamino-7-chlorofluorane in the preparation of solution A. A thermal recording sheet was obtained in the same manner as in 1.

Comparative Example 1 As Example 1 except that in the formation of the recording layer of Example 1, 35 parts of the vinyl chloride emulsion was replaced by SBR latex (solid concentration 45%) 35 having an MTF of 10 ° C. Similarly, a heat-sensitive recording sheet was obtained.

COMPARATIVE EXAMPLE 2 In the formation of the recording layer of the example, the heat sensitivity was the same as in Example 1 except that 25 parts of solution A and 25 parts of solution B were used in place of 5 parts of solution A and 5 parts of solution B. A recording sheet was obtained.

The four types of heat-sensitive recording sheets thus obtained were subjected to an applied energy of 2 to 5 mj / do by a heat-sensitive recording evaluation machine (trade name TH-PMD: manufactured by Okura Electric Co., Ltd.).
Recorded at t and evaluated. The haze value of the obtained transparent recorded image was measured with a haze number meter (trade name TC-H3: manufactured by Tokyo Electric Co., Ltd.). Further, the sharpness of the projected image obtained by projecting the heat-sensitive recording sheet after recording with an OHP machine was visually determined, and each result is shown in Table 1. Criteria for evaluating the sharpness of the projected image O ... Excellent sharpness. X: Poor definition.

[0028]

[Table 1]

[0029]

As is clear from the results shown in Table 1, the heat-sensitive recording sheet of the present invention is excellent in the contrast between the opaque portion and the transparent portion, and the recorded image is a negative type OHP.
It is a heat-sensitive recording sheet that can be used for applications.

Claims (1)

[Claims] 1. A heat-sensitive recording sheet comprising a transparent support, a recording layer containing a leuco dye and a color former, a recording layer containing a hydrophobic polymer emulsion, and a protective layer, which are sequentially provided on the transparent support. Is used in the range of 3 to 50% by weight with respect to the hydrophobic polymer emulsion, and the minimum film forming temperature of the hydrophobic polymer emulsion is 50 to 150 ° C.