JPH06155916A - Material for forming thermal recording layer - Google Patents

Abstract

PURPOSE:To provide a material capable of forming a thermal recording layer excellent in printing preservability such as water resistance, or plasticizer resistance and background color development preventing properties. CONSTITUTION:In a material for a thermal recording layer containing a leuco dye, a color developer reacting with the leuco dye under heating to form a color and a binder component, a carboxyl group-containing aqueous polymer (A) and an oxazoline group-containing aqueous polymer (B) are used as the binder component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel heat-sensitive recording layer-forming material, and more specifically, it has excellent print storability such as water resistance and plasticizer resistance, and excellent fog (background color) prevention property. The present invention relates to a heat-sensitive recording layer-forming material which can form a heat-sensitive recording layer and can be suitably used for producing heat-sensitive recording paper such as labels and printer paper.

[0002]

2. Description of the Related Art In recent years, a thermosensitive recording paper having a dye-based thermosensitive recording layer formed by combining a leuco dye and a phenolic acidic substance has been widely used in the fields of printers, labels, etc. The demands for quality improvement are also diversified and sophisticated. Along with this, attempts have been made to improve the storability of printing such as water resistance and plasticizer resistance.

As those methods, there is an attempt to provide a transparent protective layer on the heat-sensitive recording layer (Japanese Patent Laid-Open No. 29383/1990), and a carboxyl group-modified polyvinyl alcohol binder is used without providing a protective layer. Attempts have been made to use a small amount of an epoxy compound having two or more epoxy groups or an ethyleneimine compound having two or more ethyleneimine groups as a waterproofing agent (JP-A-60-219088).

[0004]

The method of providing a protective layer on the heat-sensitive recording layer slightly improves the storability of prints, but the formation of the protective layer causes a drawback of poor thermal response. In addition, the method of using a small amount of waterproofing agent,
Since the water resistance agent is a low molecular weight compound, the storage stability of the print such as water resistance and plasticizer resistance is not sufficient.

An object of the present invention is to provide a heat-sensitive recording layer forming material capable of forming a heat-sensitive recording layer having excellent print storage stability such as water resistance and plasticizer resistance.

[0006]

In order to solve the above-mentioned problems, the present invention provides a material for forming a heat-sensitive recording layer containing a leuco dye, a developer which reacts with the leuco dye by heating to develop a color, and a binder component. In the above, there is provided a material for forming a heat-sensitive recording layer, which comprises using a carboxyl group-containing aqueous polymer (A) and an oxazoline group-containing aqueous polymer (B) as a binder component.

The carboxyl group-containing aqueous polymer (A) constituting the binder component used in the present invention is not particularly limited, but in general, carboxyl group-modified polyvinyl alcohol, carboxyl group-containing acrylic emulsion, carboxyl group-containing styrene-butadiene latex, etc. Is often used. Among these, carboxyl group-modified polyvinyl alcohol is particularly preferable in terms of strength and durability of the coating film.

The carboxyl group-modified polyvinyl alcohol (A) means that the carboxyl group-containing polymerizable monomer such as acrylic acid, methacrylic acid or itaconic acid is copolymerized with vinyl acetate and then partially or completely suspended. The commercially available products are K polymers KL-118, KL-318, and KL-50 manufactured by Kuraray Co., Ltd.
6, KM-118, etc.

The oxazoline group-containing aqueous polymer (B) constituting the binder component used in the present invention is an addition-polymerizable oxazoline (a) and at least 1 if necessary.
It is formed by polymerizing another monomer (b) of a kind.

In the present invention, the addition-polymerizable oxazoline (a) is represented by the following general formula 1.

[0011]

[Chemical 1]

[In the formula 1, R 1, R 2, R 3 and R 4 each independently represent a hydrogen atom, a halogen atom, an alkyl group, an aralkyl group, a phenyl group or a substituted phenyl group, and R 5
Represents an acyclic organic group having an addition-polymerizable unsaturated bond. ]
Specific examples include 2-vinyl-2-oxazoline, 2-
Vinyl-4-methyl-2-oxazoline, 2-vinyl-
5-methyl-2-oxazoline, 2-isopropenyl-
2-oxazoline, 2-isopropenyl-4-methyl-
2-oxazoline, 2-isopropenyl-5-ethyl-
2-oxazoline can be mentioned, and one kind or a mixture of two or more kinds selected from these groups can be used. Among them, 2-isopropenyl-2-oxazoline is industrially easily available and suitable.

The amount of the addition-polymerizable oxazoline (a) used is not particularly limited, but is preferably 5% by weight or more in the polymer (B). If the amount is less than 5% by weight, the degree of curing is insufficient and the durability and water resistance of the heat-sensitive recording layer tend to be impaired.

In the present invention, the other monomer (b) means
There is no particular limitation as long as it is a monomer that cannot react with an oxazoline group and is copolymerizable with the addition-polymerizable oxazoline (a). For example, methyl (meth) acrylate, butyl (meth) acrylate, ( (Meth) acrylic acid esters such as 2-ethylhexyl (meth) acrylate and methoxypolyethylene glycol (meth) acrylate; sodium (meth) acrylate, potassium (meth) acrylate, ammonium (meth) acrylate ( (Meth) acrylic acid salts; unsaturated nitriles such as (meth) acrylonitrile;
Unsaturated amides such as (meth) acrylamide and N-methylol (meth) acrylamide; vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; α-olefins such as ethylene and propylene. ; Vinyl chloride,
Vinylidene chloride, halogen-containing α, β- such as vinyl fluoride
Unsaturated monomers; α, β-unsaturated aromatic monomers such as styrene and α-methylstyrene.
One kind or a mixture of two or more kinds can be used.

The oxazoline group-containing aqueous polymer (B) is
The addition-polymerizable oxazoline (a) and optionally at least one other monomer (b) can be produced by solution polymerization or emulsion polymerization in an aqueous medium by a conventionally known polymerization method. The aqueous medium that can be used is not particularly limited as long as it can be mixed with water, but, for example, water, methanol, ethanol, propanol, isopropanol, butanol, tertiary butanol, ethylene glycol, ethylene glycol monomethyl ether, ethylene. Examples thereof include glycol monobutyl ether, diethylene glycol, acetone and methyl ethyl ketone.

In the present invention, the carboxyl group-containing aqueous polymer (A) and the oxazoline group-containing aqueous polymer (B)
The blending ratio with is not particularly limited, but the polymer (B) is 1 to 1 with respect to 100 parts by weight of the aqueous polymer (A).
A range of 00 parts by weight is preferred. If the amount is less than 1 part by weight, the degree of curing will be insufficient, the durability and water resistance of the thermosensitive recording layer will be impaired, and if it exceeds 100 parts by weight, the adhesion of the thermosensitive recording layer to the substrate will tend to be impaired. It is in.

The heat-sensitive recording layer comprises the known material for forming a heat-sensitive recording layer of the present invention in which a known leuco dye, a color developer, and various additives and auxiliaries, if necessary, are dispersed in the above-mentioned binder component. It can be obtained by coating and drying on a sheet-shaped support such as a plastic film.

As the leuco dye, known leuco compounds of triphenylmethane dyes, fluorane dyes, phenothiazine dyes, auramine dyes, spiropyran dyes, indolinophtalide dyes and the like can be used. Specific examples of such leuco dyes include 3,3-bis (p-dimethylaminophenyl) phthalide and 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet lactone). 3,3-bis (p-dimethylaminophenyl) -5-diethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-bis (p-dibutylaminophenyl) phthalide , 3-cyclohexylamino-6-chlorofluorane, 3-dimethylamino-5,
7-Dimethylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7,8-benzfluorane, 3-diethylamino-6-methyl-7-chlorofluor Oran, 3- (Np-tolyl-N-ethylamino)-
6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3- (N-
(3'-Trifluoromethylphenyl) amino) -6-
Diethylaminofluorane, 2- (3,6-bis (diethylamino) -9- (o-chloroanilino) xanthyl benzoate lactam), 3-diethylamino-6-methyl-7- (m-trichloromethylanilino) fluorane,
3-dimethylamino-7- (o-chloroanilino) fluorane, 3-dibutylamino-7- (o-chloroanilino) fluorane, 3-N-methyl-N-amylamino-
6-methyl-7-anilinofluorane, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-
Anilinofluorane, 3-diethylamino-5-methyl-7-dibenzylaminofluorane, benzoylleucomethylene blue, 6'-chloro-4'-methoxy-benzoindolino-pyrrilospirane, 5'-bromo-3'-
Methoxy-benzoindolino-pyrrilospirane, 3-
(2'-hydroxy-4'-dimethylaminophenyl)
-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- (2'-hydroxy-
4'-dimethylaminophenyl) -3- (2'-hydroxy-4'-chloro-5'-methylphenyl) phthalide, 3-morpholino-7- (N-propyl-trifluoromethylanilino) fluorane, 3- Pyrrolidino-7-
Trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7- (N-benzyl-trifluoromethylanilino) fluorane, 3-pyrrolidino-7-
(Di-p-chlorophenyl) methylaminofluorane,
3-diethylamino-5-chloro-7- (α-phenylethylamino) fluorane, 3- (N-ethyl-p-toluidino) -7- (α-phenylethylamino) fluorane, 3-diethylamino-7- (α -Methoxycarbonylphenylamino) fluorane, 3-diethylamino-5-methyl-7- (α-phenylethylamino) fluorane, 3-diethylamino-7-piperidinofluorane, 2-chloro-3- (N-methyltoluidino) -7-
(Pn-butylanilino) fluorane, 3- (N-benzyl-N-cyclohexylamino) -5,6-benzo-7-α-naphthylamino-4′-bromofluorane,
3-diethylamino-6-methyl-7-mesitidino-
4 ', 5'-benzofluorane etc. can be mentioned.

The color-developing agent compounded in the material for forming the heat-sensitive recording layer is a compound which reacts with the above-mentioned leuco dye upon heating to develop a color, and is a phenolic substance, an organic or inorganic acid compound, or an ester or salt thereof. Etc. can be used, for example, gallic acid, salicylic acid, 3-isopropylsalicylic acid, 3-cyclohexylsalicylic acid, 3,5
-Di-tert-butylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid, 4,4'-isopropylidenebisphenol, 4,4'-isopropylidenebis (2-
Chlorophenol), 4,4'-isopropylidene bis (2,6-dibromophenol), 4,4'-isopropylidene bis (2,6-dichlorophenol), 4,
4'-isopropylidenebis (2-methylphenol), 4,4'-isopropylidenebis (2,6-dimethylphenol), 4,4'-isopropylidenebis (2-tert-butylphenol), 4,4 ' -Sec-butylidene bisphenol, 4,4'-cyclohexylidene bisphenol, 4,4'-cyclohexylidene bis (2-methylphenol), 4-tert-butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol, 3,5-xylenol, thymol, methyl-4-hydroxybenzoate, 4-hydroxyacetophenone, novolac type phenol resin, 2,2′-thiobis (4,6-dichlorophenol), catechol, Resorcin, hydroquinone, pyrogallol, phloroglycin, furo Loglysine carboxylic acid, 4-tert-octylcatechol, 2,2'-
Methylenebis (4-chlorophenol), 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 2,2'-dihydroxydiphenyl, ethyl p-hydroxybenzoate, propyl p-hydroxybenzoate, p- Butyl hydroxybenzoate, benzyl p-hydroxybenzoate, p-chlorobenzyl p-hydroxybenzoate, o-chlorobenzyl p-hydroxybenzoate, p-methylbenzyl p-hydroxybenzoate, p
-Hydroxybenzoic acid-n-octyl, benzoic acid, zinc salicylate, 1-hydroxy-2-naphthoic acid, 2-hydroxy-5-naphthoic acid, zinc 2-hydroxy-6-naphthoate, 4-hydroxydiphenyl sulfone, 4 −
Hydroxy-4′-chlorodiphenyl sulfone, bis (4-hydroxyphenyl) sulfide, 2-hydroxy-p-toluic acid, zinc 3,5-di-tert-butylsalicylate, tin 3,5-di-tert-butylsalicylate , Tartaric acid, oxalic acid, maleic acid, citric acid, succinic acid, stearic acid, 4-hydroxyphthalic acid, boric acid, thiourea derivatives and the like.

Further, the above-mentioned material for forming a heat-sensitive recording layer, together with the above-mentioned binder, leuco dye, and color developer, if necessary, a conventional additive such as a sensitizer, a filler, a surfactant, or a heat-fusible agent is used. You may use together an active substance. In this case, as the filler, for example, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, inorganic fine powder such as surface-treated calcium or silica, and the like, Urea-formalin resins, styrene / methacrylic acid copolymers, organic fine powders such as polystyrene resins can be mentioned, and examples of the heat-fusible substance include higher fatty acids or esters thereof,
In addition to amides or metal salts, various waxes, mixtures of aromatic carboxylic acids and amines, phenyl benzoates, higher linear glycols, dialkyl 3,4-epoxy-hexahydrophthalates, higher ketones, other heat-resistant materials. Examples include fusible organic compounds having a melting point of about 50 to 200 ° C.

[0021]

In the material for forming a heat-sensitive recording layer of the present invention, the carboxyl group-containing aqueous polymer (A) and the oxazoline group-containing aqueous polymer (B) are used as binder components, so that the ionic interaction between the carboxyl group and the oxazoline group is By the action or the reaction of forming a covalent bond, the heat-sensitive recording layer becomes strong, and the heat-sensitive recording paper having excellent print storage stability such as water resistance and plasticizer resistance can be produced. Further, fogging can be prevented by the oxazoline group trapping an acidic component that causes background color formation. Therefore, the heat-sensitive recording layer forming material of the present invention can be used for the production of heat-sensitive recording paper,
It can be used very suitably.

[0022]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited to the following examples.
In the following, "%" means "% by weight" and "part" means "part by weight" unless otherwise specified.

-Production Example 1 (Production Example of Polymer (B))-116 parts of deionized water and V-50 (Wako Pure Chemical Industries, Ltd.) were placed in a flask equipped with a stirrer, a reflux condenser, a nitrogen introducing tube and a thermometer. Polymerization initiator (2,2′-azobis (2-amidinopropane) dihydrochloride) (4 parts) manufactured by a corporation was charged and heated to 70 ° C. while gently flowing nitrogen gas. A monomer composed of 48 parts of methoxypolyethylene glycol acrylate (ethylene glycol is an average 9-mer, NK ester AM-90G manufactured by Shin-Nakamura Chemical Co., Ltd.) and 32 parts of 2-isopropenyl-2-oxazoline, which had been adjusted in advance. The mixture was added dropwise from the dropping funnel in 1 hour. Nitrogen gas was kept flowing during the reaction to keep the temperature in the flask at 70 ± 1 ° C. After completion of the dropping, the mixture was kept at the same temperature for 6 hours and then cooled to obtain an oxazoline group-containing polymer aqueous solution (1) having a nonvolatile content of 41.5%, pH 7.0 and a viscosity of 290 centipoise.

-Production Example 2 (Production Example of Polymer (B))-782.4 parts of deionized water and Hitenol N-08 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) were placed in the same flask as in Production Example 1. 128 parts of a 15% aqueous solution of oxyethylene nonylphenyl ether sulfate ammonium salt) was charged, the pH was adjusted to 9.0 with an appropriate amount of aqueous ammonia (28%), and the mixture was heated to 70 ° C. while gently flowing nitrogen gas. 64 parts of a 5% aqueous solution of potassium persulfate was injected thereinto, and subsequently 288 parts of butyl acrylate and styrene 2 which had been prepared in advance.
88 parts and 2-isopropenyl-2-oxazoline 64
The monomer mixture consisting of parts was added dropwise over 3 hours.
Nitrogen gas was kept flowing during the reaction to keep the temperature in the flask at 70
The temperature was kept at ± 1 ° C. After maintaining the same temperature for 2 hours after completion of dropping, the internal temperature was raised to 80 ° C. and stirring was continued for 1 hour to complete the reaction. Then, it is cooled and the nonvolatile content is 39.8%, p
An aqueous dispersion of an oxazoline group-containing polymer (2) having H8.0 and a viscosity of 25 centipoise was obtained.

-Examples 1 to 4 and Comparative Examples 1 to 3 Liquids A and B having the formulations shown in Table 1 were mixed for 48 hours using a ball mill to prepare dispersions A and B.
Liquid A and liquid B were mixed, and liquid C having the composition shown in Table 1 was further mixed to prepare a material for forming a heat-sensitive recording layer. This heat-sensitive recording layer-forming material was applied to one side of a high-quality paper (basis weight: 50 g / m 2) and dried at room temperature for 2 days to form a heat-sensitive recording layer with an application amount of 7 g / m 2, to obtain a heat-sensitive recording paper.

[0026]

[Table 1]

A release paper coated with a silicone resin was coated with an acrylic pressure-sensitive adhesive layer at a coating amount of 20 g / m 2 on the back surface of these thermal recording papers. The heat-sensitive adhesive label was obtained by sticking the pieces together and then cutting out to an appropriate size.

Next, the heat-sensitive adhesive label sample obtained as described above was printed by a label printer, and a color-forming test, a sticking test and various storability tests were conducted. The results are shown in Table 2. The method of each test is as follows.

Color density: The color was printed with a label printer, and the color developed portion was measured with a Macbeth densitometer.

Background density: The non-printed portion was measured with a Macbeth densitometer.

Plasticizer resistance: The color was printed with a label printer, the sample was coated with a polyvinyl chloride sheet, and the densities of the sample before coating and after 72 hours at room temperature were compared.

Water resistance: The color was printed with a label printer, the sample was immersed in normal temperature water, and the densities were compared before and after 24 hours from the immersion.

Oil resistance: The color was printed with a label printer, sesame oil was applied to the sample, and the densities before application and after 24 hours from application were compared.

Sticking: Sticking sound at the time of printing, printing failure, etc. were tested.

[0035]

[Table 2]

As is clear from Table 2, the heat-sensitive recording paper obtained by using the material for forming a heat-sensitive recording layer of the present invention is excellent in print storability such as water resistance and plasticizer resistance, and background color prevention. It is a thing.

[0037]

INDUSTRIAL APPLICABILITY The heat-sensitive recording layer forming material of the present invention uses the carboxyl group-containing aqueous polymer (A) and the oxazoline group-containing aqueous polymer (B) as the binder component, and therefore the ion of the carboxyl group and the oxazoline group is used. The heat-sensitive recording layer is strengthened by a reaction that produces a physical interaction or a covalent bond, and a heat-sensitive recording paper having excellent print storage stability such as water resistance and plasticizer resistance can be obtained. Further, fogging can be prevented by the oxazoline group trapping an acidic component that causes background color formation. Therefore, it is useful for manufacturing thermal recording paper such as labels and printer paper.

[0038]

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[Procedure amendment]

[Submission date] December 22, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

[In the formula 1, R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom, a halogen atom, an alkyl group, an aralkyl group, a phenyl group or a substituted phenyl group, and R ⁵
Represents an acyclic organic group having an addition-polymerizable unsaturated bond. ]
Specific examples include 2-vinyl-2-oxazoline, 2-
Vinyl-4-methyl-2-oxazoline, 2-vinyl-
5-methyl-2-oxazoline, 2-isopropenyl-
2-oxazoline, 2-isopropenyl-4-methyl-
2-oxazoline, 2-isopropenyl-5-ethyl-
2-oxazoline can be mentioned, and one kind or a mixture of two or more kinds selected from these groups can be used. Among them, 2-isopropenyl-2-oxazoline is industrially easily available and suitable.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0024

[Correction method] Change

[Correction content]

-Production Example 2 (Production Example of Polymer (B))-782.4 parts of deionized water and Hitenol N-08 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) were placed in the same flask as in Production Example 1. 128 parts of a 15% aqueous solution of oxyethylene nonylphenyl ether sulfate ammonium salt) was charged, the pH was adjusted to 9.0 with an appropriate amount of aqueous ammonia (28%), and the mixture was heated to 70 ° C. while gently flowing nitrogen gas. 64 parts of a 5% aqueous solution of potassium persulfate was injected thereinto, and subsequently 288 parts of butyl acrylate and styrene 2 which had been prepared in advance.
88 parts and 2-isopropenyl-2-oxazoline 64
The monomer mixture consisting of parts was added dropwise over 3 hours.
Nitrogen gas was kept flowing during the reaction to keep the temperature in the flask at 70
The temperature was kept at ± 1 ° C. After maintaining the same temperature for 2 hours after completion of dropping, the internal temperature was raised to 80 ° C. and stirring was continued for 1 hour to complete the reaction. Then, it is cooled and the nonvolatile content is 39.8%, p
An aqueous dispersion of an oxazoline group-containing polymer (2) having H8.0 and a viscosity of 25 centipoise was obtained.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0025

[Correction method] Change

[Correction content]

-Examples 1 to 4 and Comparative Examples 1 to 3 Liquids A and B having the formulations shown in Table 1 were mixed for 48 hours using a ball mill to prepare dispersions A and B.
Liquid A and liquid B were mixed, and liquid C having the composition shown in Table 1 was further mixed to prepare a material for forming a heat-sensitive recording layer. This heat-sensitive recording layer-forming material was applied to one side of a high-quality paper (basis weight: 50 g / m ² ) and dried at room temperature for 2 days to form a heat-sensitive recording layer with an application amount of 7 g / m ² to obtain a heat-sensitive recording paper. It was

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] 0027

[Correction method] Change

[Correction content]

On the back surface of these thermal recording papers, a release paper coated with a silicone resin is provided with an acrylic pressure-sensitive adhesive layer on the silicone resin surface so that the coating amount is 20 g / m ² And then cut out into an appropriate size to obtain a heat-sensitive adhesive label.

Claims (2)

[Claims] 1. A heat-sensitive recording layer-forming material comprising a leuco dye, a developer which reacts with the leuco dye when heated to develop a color, and a binder component, wherein a carboxyl group-containing aqueous polymer (A) and oxazoline are used as binder components. A material for forming a heat-sensitive recording layer, which comprises using a group-containing aqueous polymer (B). 2. The heat-sensitive recording layer forming material according to claim 1, wherein the carboxyl group-containing aqueous polymer (A) is a carboxyl group-modified polyvinyl alcohol.