JP3030961B2 - Transparent thermal recording material - Google Patents

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 material. More specifically, the present invention relates to a light-transmissive heat-sensitive recording material having excellent quality in image color development, recording suitability, and storage stability, and having excellent transparency.

[0002]

2. Description of the Related Art A heat-sensitive recording material generally comprises a substantially colorless color-forming dye precursor such as an electron-donating leuco dye, A heat-sensitive coloring layer containing an organic acid developer such as a receptive phenolic compound and a binder as main components is provided, and these color-forming dye precursors and the developer are subjected to heat energy. To form a color recording image.

[0003] Such a thermosensitive recording material has the advantages that the recording apparatus is compact, inexpensive, and easy to maintain. For this reason, the output of an electronic computer, a facsimile, an automatic ticket vending machine, It is widely used for applications such as printers for scientific measuring instruments or printers for CRT medical measurements.

However, conventional thermosensitive recording materials in which a thermosensitive coloring layer containing a dye precursor, a color-developing substance and a binder as active ingredients are merely coated on a support, include light, water, heat, It is unstable with respect to plasticizers and oils, so that a temporal change in quality during storage has always been a problem.

In order to improve the storage stability as described above,
It has been proposed to provide a surface protective layer on the thermosensitive coloring layer and cover the surface protective layer. For example, JP-A-56-146794 discloses that a surface protective layer is formed by using a hydrophobic polymer compound emulsion or the like.
No. 199189 discloses that a water-soluble polymer compound or a hydrophobic polymer compound emulsion is provided as an intermediate layer on a thermosensitive coloring layer, and a surface protective layer is formed thereon using an oil-based coating liquid containing a hydrophobic polymer compound as a resin component. Is disclosed.

In the case where the above oil-based paint is applied on the heat-sensitive recording layer to form a surface protective layer, the solvent contained in the protective layer coating solution binds to the heat-sensitive coloring layer already formed. Agents and coloring components may be dissolved. In the recording of an image, the dissolution of the above components of the thermosensitive coloring layer may cause non-uniformity of the image, and therefore, in reality, the recording suitability is not satisfactory. In particular, when recording an image with rich gradation is required as in a video printer, it is important to design the structure of the recording material so as to prevent nonuniformity of the image on the recording material.

[0007]

The present invention solves the above-mentioned problems of the prior art, has excellent heat resistance, plasticizer resistance, oil resistance, etc., has long-term storage stability, and
Light transmission with high recording density , excellent gradation, and transparency equivalent to silver halide photographic film, and excellent recording aptitude without sticking phenomenon to thermal head in thermal recording operation It is intended to provide a thermosensitive recording material of the type.

That is, the present invention relates to a video printer (CR) which provides a photographic high-quality image which has been used in recent years.
Suitable for use as a film for a printer in a thermal image recording device for T-images) and for medical images (ultrasonic diagnosis, X-ray photography, etc.) requiring preservation, and OHP
It is an object of the present invention to provide an excellent transmission-type heat-sensitive recording material which can be used as a recording medium and a plotter.

[0009]

The heat-sensitive recording material according to the present invention has a support, a heat-sensitive color-forming layer and a protective layer. A transparent sheet material is used as the support, and the heat-sensitive color-forming layer is provided in the heat-sensitive color-forming layer. , A binder containing a hydrophobic polymer compound, a developer consisting of a specific bis (hydroxyphenyl) acetic acid compound, and a sensitizer consisting of a specific dicarboxylic acid ester compound. As an agent, in contrast to the solubility parameter of the binder in the thermosensitive coloring layer,
The above problem has been successfully solved by using a polymer compound soluble in a solvent having a specific solubility parameter.

That is, the transparent thermosensitive recording material of the present invention comprises:
A support, formed on at least one surface of the support,
And a substantially colorless dye precursor, a heat-sensitive color-developing layer containing, as a main component, a mixture of a color-developing agent that reacts with the dye precursor under heating to develop a color, and a binder. And a protective layer containing a mixture of a binder and a lubricant as a main component, (A) the support is made of a transparent sheet material, and (B) the thermosensitive coloring layer is
(A) As the binder, at least one kind of a hydrophobic polymer, and (b) Bis (hydroxyphenyl) acetic acid compounds represented by the following formula (I) as the developer:

Embedded image [However, in the formula (I), R ₁ represents a C ₁ -C ₄ alkyl group or a benzyl group. At least one selected from
And (c) dicarboxylic acid ester compounds represented by the following formula (II):

Embedded image [Wherein, in the formula (II), X represents a hydrogen atom, a methyl group, or a chlorine atom, and n represents 0 or an integer of 4 or less]
And (C) the binder contained in the protective layer is the following with respect to the solubility parameter (A) of the binder contained in the thermosensitive coloring layer. Solvent having a solubility parameter (B) that satisfies relational expression (i) or (ii): at least soluble in -1.1 ≧ (AB) (i) or + 1.1 ≦ (AB) (ii) It is characterized by containing one kind of polymer compound as a main component.

[0011]

The heat-sensitive recording material of the present invention comprises a support, a heat-sensitive coloring layer and a protective layer which are sequentially laminated from the bottom.

The support used in the present invention is made of a transparent sheet material, for example, a synthetic resin film or transparent paper. Examples of the transparent synthetic resin film include, for example, a film made of a polyester such as polyethylene terephthalate and polybutylene terephthalate, a film made of a cellulose derivative such as a cellulose triacetate film, a polypropylene film, and a film made of a polyolefin such as polyethylene, and And the like can be used.

As the transparent paper, tracing paper and synthetic pulp mixed paper have been known.
A transparent agent, i.e., a reactive resin, capable of hardening a relatively low-molecular liquid material into the paper layer after it has sufficiently penetrated into the paper layer in the presence of a catalyst or by heating or other means, is used.
A high-quality impregnated base paper having a rice basis weight of g / m ² , or a resin-impregnated transparent paper obtained by impregnating a base made of synthetic paper to make it transparent can be used. As the above-mentioned reactive resin for impregnation, amino resins or polyurethanes disclosed in JP-B-43-25927 and JP-B-51-36367 can be used, and further, other polyamides, polyamines and epoxy resins can be used. Alternatively, an ultraviolet curable or electron beam curable resin may be used.

The amount of the reactive resin adhered to the substrate is preferably 10 to 60% of the basis weight. It is preferable that the paper after the transparency has a transparency of 50% or more and an air permeability of 400 to 10,000 sec. The thickness of the support is not particularly limited, but it is generally preferable to have a thickness of 30 to 200 μm.

On at least one surface of the support, a thermosensitive coloring layer containing a dye precursor, a color developer and a binder is formed by a conventionally known coating method. In general, the weight of the thermosensitive coloring layer is preferably ³ to 10 g / m2.

In the present invention, the binder contained in the thermosensitive coloring layer contains at least one kind of hydrophobic polymer, and its solubility parameter (A) is used in the coating liquid for forming the protective layer. Between the solubility parameter (B) of the solvent to be used and -1.1 ≧ (AB) or + 1.1 ≦ (A
-B) is satisfied. The hydrophobic polymer compound is an organic solvent such as toluene (SP = 8.9),
It is preferable to use one that dissolves in However, such a binder, when mixed with each of the dispersions of the dye precursor and the developer, does not cause the mixed solution to develop color, aggregate, or increase the viscosity. It is preferable that the formed heat-sensitive coloring layer film can achieve toughness, no desensitization effect, and no sticking to the thermal head.

Therefore, in the present invention, as the binder for the heat-sensitive coloring layer, a binder composed of a hydrophobic polymer compound having a value as close as possible to the solubility parameter of the solvent used in the coating solution for forming the heat-sensitive coloring layer is used. Preferably, it is used. For example, when toluene is used as the solvent, it is preferable to use polymethyl methacrylate resin (SP = 9.45) as the hydrophobic polymer compound.

The dye precursor used in the present invention is a substantially colorless electron-donating compound capable of forming a color by reacting with a developer under heating. Examples of such a color-forming dye precursor include, for example, 2,2 - bis {4- [6'-
(N-cyclohexyl-N-methylamino) -3′-methylspiro (phthalide-3,9′-xanthen) -2 ′
-Ylamido] phenyl} propane, 3-diethylamino-6-methyl-7-anilinofluoran, 3-piperidino-6-methyl-7-anilinofluoran, 3- (N
-Methyl-N-cyclohexylamino) -6-methyl-
7-anilinofluoran, 3-diethylamino-7-chloroanilinofluoran, 3- [N-ethyl-N- (p
-Methylphenyl) amino] -6-methyl-7-anilinofluoran, 3-diethylamino-7- (metatrifluoromethyl) anilinofluoran, 3- (N-ethyl-N-tetrahydrofurfuryl) amino- 6-methyl-
7 - anilinofluoran, 3- ( N- isopentyl-N
-Ethylamino) -6-methyl-7-anilinofluoran, 3- (N, N-dibutyl) amino-6-methyl-7
-At least one member selected from fluoran compounds such as anilinofluoran can be used.

These dye precursors are preferably refined using a disperser such as a sand grinder or an attritor so that the average particle size is 0.7 μm or less.

The developer used in the present invention is an electron-accepting organic acidic substance capable of reacting with a color-forming dye under heating to form a color, and is a bis (hydroxy) compound represented by the above formula (I). phenoxyphenyl) are those containing at least one compound selected from acetic acid compounds. Compounds of formula (I) include, for example, methyl-bis (4-hydroxyphenyl) acetate, n-butyl-bis (4-hydroxyphenyl) acetate, and benzyl-bis (4
-Hydroxyphenyl) acetate and the like can be used. It is preferable that the color developer is finely divided by the same dispersion treatment as that of the dye precursor so that the average particle diameter becomes 0.7 μm or less.

In the present invention, the developer is usually used in an amount of 1 to 5 parts by weight, preferably 1.5 to 3 parts by weight, per 1 part by weight of the dye precursor.
It is mixed and used in parts by weight. The specific color developer in the present invention has a particularly low solubility in toluene and is effective for preventing background fog.

The thermosensitive coloring layer of the present invention contains at least one dicarboxylic acid ester compound represented by the formula (II) as a sensitizer. As the sensitizer compound of the formula (II), for example, dibenzyl oxalate, di (p-methylbenzyl) oxalate, di (p-chlorobenzyl) oxalate and the like can be used. This sensitizer is used for the dye precursor,
It is mixed and used in a ratio of 0.3 to 3 parts by weight, preferably 0.5 to 2 parts by weight. This sensitizer has an excellent sensitizing effect especially in combination with the bis (hydroxyphenyl) acetic acid compound used as the color developer.

The thermosensitive coloring layer of the present invention may contain a pigment, particularly a white pigment, if necessary. Such pigments include, for example, calcium carbonate, magnesium carbonate,
Kaolin, clay, talc, calcined clay, silica, diatomaceous earth, synthetic aluminum silicate, zinc oxide, titanium oxide, aluminum hydroxide, barium sulfate, surface-treated inorganic fine powders such as calcium carbonate and silica, and urea -Fine powders of organic resins such as formalin resin, styrene / methacrylic acid copolymer, and polystyrene resin.

In the heat-sensitive coloring layer, if necessary, auxiliary additives conventionally used in heat-sensitive recording materials, for example, fillers,
A small amount (10% or less based on the weight of the heat-sensitive coloring layer) of a surfactant, a heat-fusible substance (or a lubricant) or the like may be added.

Examples of the above-mentioned heat-fusible substance include fatty acid amides such as stearic acid amide, ethylene bisamide stearate, oleic acid amide, palmitic acid amide, coconut fatty acid amide, and behenic acid amide; zinc stearate; calcium stearate; Polyethylene wax,
Waxes such as carnauba wax, paraffin wax and ester wax, dimethyl terephthalate, dibutyl terephthalate, dibenzyl terephthalate, dibutyl isophthalate, phenyl 1-hydroxynaphthoate, 1,2-di (3-methyl Phenoxy) ethane, 1,2-diphenoxyethane,
1-phenoxy-2- (4-methylphenoxy) ethane, diphenyl carbonate, p-benzylbiphenyl, 2,
2'-methylenebis (4-methyl-6-tert-butylphenol), 4,4'-butylidenebis (6-tert-butyl-3-methylphenol), 1,1,3-tris (2-methyl-4-hydroxy -5-tert-butylphenyl) butane, 2,2'-methylenebis (4-ethyl-
6-tert-butylphenol), 2,4-di-tert-butyl-3-methylphenol, 4,4′-thiobis (3
Hindered phenols such as -methyl-6-tert-butylphenol) and 2- (2'-hydroxy-5 ')
-Methylphenyl) -benzotriazole, sensitizers such as 2-hydroxy-4-benzyloxybenzophenone,
It includes a lubricant, an antioxidant, an ultraviolet inhibitor and the like. Such a heat-fusible substance is generally a developer 1
It is preferable that the thermosensitive coloring layer contains the thermosensitive coloring layer in a proportion of 4 parts by weight or less with respect to part by weight.

In the present invention, in order to form a thermosensitive coloring layer, a coating solution containing the above-mentioned components and a solvent (for example, toluene) is prepared, and this is coated on a support by a known coating method, for example, a roller coating method or gravure. What is necessary is just to apply by a coating method or a wire coating method, and to dry this.

In the heat-sensitive recording material of the present invention, a protective layer mainly containing a mixture of a binder and a lubricant is formed on the heat-sensitive coloring layer. The protective layer contains, as a main component, a mixture of a binder made of a high molecular compound and a lubricant, and is formed by applying a coating solution containing these components and a solvent on the thermosensitive coloring layer. You.

The solvent used for the coating solution for forming the protective layer includes:
It is necessary that the coloring component and the binder in the thermosensitive coloring layer formed below the protective layer are not dissolved.
That is, the solubility parameter (B) of the solvent for forming the protective layer
Is required to be selected from a binder used in the thermosensitive coloring layer, for example, a solvent having a difference between the solubility parameter (A) such as polymethyl methacrylate (SP = 9.45) and -1.1 or less or +1.1 or more. It is.

The above polymethyl methacrylate (SP = 9.
When a protective layer is formed on the thermosensitive coloring layer containing 45) as a binder, the solvent of the coating liquid for forming the protective layer may be, for example, methylcyclohexane (SP = 7.8, (AB) =
+1.65), cyclohexane (SP = 8.2, (AB) =
1.25) can be used. In this case, as the binder for the protective layer, for example, poly-tert-butyl methacrylate (SP = 8.0) is preferably used. Further, for the thermosensitive coloring layer, as a coating solution solvent for forming a protective layer,
Water (SP = 23.4, (AB) =-13.95) can be used, and in this case, a hydrophilic polymer compound such as polyvinyl alcohol (SP = 8.0) can be used as a binder.

The lubricant contained in the protective layer is effective for smoothing contact between the thermal head and the surface of the heat-sensitive recording material and preventing sticking of the thermal head. Examples of such lubricant include higher fatty acid metal salts, solid waxes such as polyethylene wax and amide wax, fluorine-based compounds, phosphate-based surfactants, reaction-curable silicone oils, fluorinated alkyl-ester-modified silicones, and Polyester-modified silicone and the like can be used. The added amount of these lubricants is preferably 0.5 to 30 parts by weight based on the weight of the binder in the protective layer.

The coating amount of the protective layer is appropriately adjusted to such an extent that the heat conduction from the thermal head to the coloring layer is not hindered, but is usually preferably 0.1 to 10 g / m ² , More preferably, it is 0.2 to 5 g / m ² . In this case, a desired effect can be obtained without lowering the thermal sensitivity of the thermosensitive coloring layer.

[0032]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the scope of the present invention is, of course, not limited thereto. In each example, “parts” indicates “parts by weight” unless otherwise specified.

Example 1 A transparent thermosensitive recording sheet was produced by the following steps. (1) Preparation of Solution A (Dye precursor dispersion for thermosensitive coloring layer) 3- (N-isopentyl-N-ethylamino) -6-5 parts methyl-7-anilinofluoran 30% polymethyl methacrylate (SP = 9.45) 1 part of toluene solution 20 parts of toluene The above mixture was finely ground using a sand grinder until the average particle diameter became 1 μm or less.

(2) Preparation of Solution B (Thermosensitive Coloring Layer Western Developer Dispersion) Methyl-bis (4-hydroxyphenyl) acetate 25 parts Di (p-methylbenzyl) oxalate 10 parts 30% Polymethyl methacrylate in toluene Solution 10 parts Toluene 130 parts The above mixed solution was refined by the same method as for the above solution A until the average particle diameter became 1 μm or less.

(3) Preparation of solution C (for protective layer) 10% poly-tert-butyl methacrylate in methylcyclohex 60 parts Sun solution 50% alkyl fluoride-ester modified silicone 1.5 parts Methylcyclohexane solution Methylcyclohexane (SP = 7.8) 16 parts

(4) Formation of Thermosensitive Coloring Layer First, a coating solution for a thermosensitive coloring layer having the following composition was prepared. Solution A 20 parts Solution B 60 parts 30% solution of polymethyl methacrylate in toluene 22 parts Toluene 5 parts Next, this coating solution was placed on a surface of a 75 μm-thick polyethylene terephthalate (PET) film support.
The composition was applied to a dry weight of 7 g / m ² and dried to form a thermosensitive coloring layer.

(5) Formation of Protective Layer On the thermosensitive coloring layer, the above-mentioned liquid C was applied at a dry weight of 3 g / m ^2.
And dried to form a protective layer. By the above operation, a transparent thermosensitive recording material having a coating layer composed of a thermosensitive coloring layer and a protective layer on a support was obtained.

The above-mentioned heat-sensitive recording material was subjected to 17-gradation recording by using a thermo-sensitive video graphic printer, UP-930 (trade name, manufactured by Sony Corporation), and the anti-sticking property in this recording operation was evaluated. Was measured using a Sakura Densitometer PDA65 (trade name, manufactured by Konica Corporation). Further, the uniformity of the image was evaluated from the obtained 17-gradation recorded image. Table 1 shows the test results.

Example 2 The same operation as in Example 1 was performed. However, polyethylene was used instead of poly-tert-butyl methacrylate in the solution C (coating solution for the protective layer). Table 1 shows the test results of the obtained thermosensitive recording materials.

Example 3 The same operation as in Example 1 was performed. However, polyvinyl alcohol was used instead of poly-tert-butyl methacrylate in solution C (coating solution for protective layer), and water was used instead of methylcyclohexane. Table 1 shows the test results of the obtained thermosensitive recording materials.

Comparative Example 1 The same operation as in Example 1 was performed. However, toluene was used instead of methylcyclohexane in the solution C (coating solution for the protective layer). Table 1 shows the test results of the obtained thermosensitive recording materials.

Comparative Example 2 The same operation as in Example 1 was performed. However, methyl ethyl ketone was used instead of toluene in the solution C (coating material for the protective layer). Table 1 shows the test results of the obtained thermosensitive recording materials.

[0043]

[Table 1]

[Notes] * 1 ：: extremely excellent ○: good Δ: slightly poor ×: extremely poor * 2 ◎: no sticking to the thermal head, and no sticking sound was generated. ：: No sticking to the thermal head, but slight sticking sound was generated. Δ: Some sticking to the thermal head was observed, and the image was distorted. X: Frequent sticking to the thermal head, causing running failure of the recording material.

As is clear from Table 1, the heat-sensitive recording materials of the examples according to the present invention were used as light-transmitting recording materials.
Although satisfactory results were obtained, each of the comparative examples was unsatisfactory in any of the performances.

[0046]

According to the heat-sensitive recording material of the present invention, an extremely clear image and a non-image portion having high transparency can be formed.
It has extremely high practicality as a light transmission type heat-sensitive recording material.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-58051 (JP, A) JP-A-4-272890 (JP, A) JP-A-4-62088 (JP, A) JP-A-4-62088 70383 (JP, A) JP-A-2-214690 (JP, A) JP-A-2-9683 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41M 5/28-5 / 34

Claims (1)

(57) [Claims] 1. A support, a substantially colorless dye precursor formed on at least one surface of the support, and a developer which reacts with the dye precursor under heating to form a color,
A heat-sensitive color-forming layer containing a mixture of a binder and a binder as a main component; and a protective layer formed on the heat-sensitive color-forming layer and containing a mixture of a binder and a lubricant as a main component. (B) the thermosensitive coloring layer contains (a) at least one kind of a hydrophobic polymer compound as the binder, and (b) the following formula (I) as the color developer. Bis (hydroxyphenyl) acetic acid compounds represented by the following formula: Wherein, in the formula (I), R ₁ represents a C ₁ -C ₄ alkyl group or a benzyl group, and (c) a dicarboxylic acid represented by the following formula (II): Acid ester compounds: Wherein, in the formula (II), X represents a hydrogen atom, a methyl group, or a chlorine atom, and n represents 0 or an integer of 4 or less. And (C) the binder contained in the protective layer is different from the solubility parameter (A) of the binder contained in the thermosensitive coloring layer by:
Solvent having a solubility parameter (B) that satisfies the following relational expression (i) or (ii): -1.1 ≧ (AB) (i) or + 1.1 ≦ (AB) Soluble in (ii) A transparent thermosensitive recording material comprising at least one polymer compound as a main component.