JP2540297B2 - Thermal recording material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material having improved thermal sensitivity and head matching property.

[Prior Art] The demand for heat-sensitive recording materials is rapidly expanding as recording materials that are inexpensive and easy to maintain for recording machines.

However, recently, it is possible to record a clear image with high density even with a small amount of energy accompanying the speeding up of facsimiles, printers, parcode labels, etc.Also, the reliability of the obtained image, such as oils and fats such as fingerprints and plastic eraser, Mending tape, plasticizers contained in salt wraps, whiskey, sake, shochu, alcohol, water, etc. should not be erased or colored.
For example, there are demands for quality such as no sticking, head residue, and head wear.

In order to achieve high sensitivity, it is of course important to select the coloring material to be used, but the filler used together,
The addition amount of the binder and the like is important, and it is necessary to use it in the heat-sensitive color developing layer as little as possible. However, if this is reduced, the reliability of the image and the head matching property deteriorate.
In particular, there are image erasing due to oils and fats and plasticizers, layer peeling and sticking due to water and alcohol. In order to improve this drawback, it has been proposed to provide various overcoat layers on the thermosensitive coloring layer. However, when the overcoat layer is provided, the thermosensitive coloring layer is overcoated during printing. Since it will be in contact with the thermal head via
There is a drawback that heat conduction is hindered and the color development sensitivity is lowered.

Further, in the method of providing a conventionally known overcoat layer, it is necessary to increase the ratio of the binder and the filler in order to prevent oils and fats and the plasticizer from penetrating into the thermosensitive color developing layer, resulting in sticking. It is not easy to generate, and in order to prevent sticking, a filler has been used in the conventional method, but depending on the type of filler, head wear may occur, and since the high temperature treatment cannot be performed, the binder hardens and sticking occurs. However, there is a drawback that it takes a long time to improve.

〔Purpose〕

The present invention is a heat-sensitive recording material which develops a high density of color at low energy, has high oil resistance, water peeling resistance and reliability of a recorded image, and is excellent in head matching property without the above-mentioned problems. To provide.

〔Constitution〕

According to the present invention, a thermosensitive coloring layer containing a leuco dye and a color developer is provided on a support, and an overcoat layer is provided on the thermosensitive coloring layer. It contains 20 to 70% by weight of a binder in which a polymer and a waterproofing agent for the water-soluble polymer are used in combination, and 5 to 45% by weight of aluminum hydroxide as a filler, and the dry adhesion amount of the overcoat layer is 1.0. A heat-sensitive recording material is provided, which is characterized by having a weight ratio of up to 6.0 g / m ² .

That is, the present invention provides an overcoat layer using aluminum hydroxide as a filler and a binder in which a specific amount of a water-soluble polymer and a waterproofing agent for the water-soluble polymer are used together as a main component on a thermosensitive coloring layer. Is provided in a specific adhesion amount, whereby high sensitivity is maintained and oil resistance, water peeling resistance, image reliability, and head matching property are improved.

The overcoat layer of the present invention has little deterioration in color development sensitivity, and has improved oil resistance, water resistance and reliability of printed images,
Moreover, it functions as a layer for improving the head-matching property.

In the present invention, as the binder used in the overcoat layer, polyvinyl alcohol, starch and derivatives thereof, methoxycellulose, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose,
Cellulose derivatives such as ethyl cellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylic acid amide /
Acrylic ester copolymer, acrylic acid amide / acrylic acid ester / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, isobutylene /
It is a combination of a water-soluble polymer such as an alkali salt of a maleic anhydride copolymer, polyacrylamide, sodium alginate, gelatin, and casein and a water resistance agent for the water-soluble polymer, for example, a polyamide epichlorohydrin resin.

That is, in the present invention, the amount of the overcoat layer constituents used is 20 to 70% by weight for the binder, 5 to 45% by weight for aluminum hydroxide, and the dry adhesion amount of the overcoat layer. A preferable result is obtained by adjusting the amount to 1.0 to 6.0 g / m ² .

If the amount of the binder used is less than 20% by weight and the amount of aluminum hydroxide is more than 45% by weight, penetration prevention by oils and fats and plasticizers is insufficient, and the amount of the binder used is less than 70% by weight. Further, if the amount of aluminum hydroxide is less than 5% by weight, it takes a long time to function as an overcoat layer, which is not preferable.

Further, when the dry adhesion amount of the overcoat layer is less than 1.0 g / m ² , the oil resistance, the water peeling resistance, the effect of preventing sticking and the like are insufficient, and conversely the dry adhesion amount is 6.0 g / m ²
If it exceeds the range, the dynamic color density decreases, and the intended purpose of the present invention cannot be achieved.

The thermosensitive coloring layer of the present invention contains a leuco dye and a color developer as main components, and the leuco dye is applied alone or in combination of two or more kinds. What is applied to a heat-sensitive material is arbitrarily applied, and for example, leuco compounds of dyes such as triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, spiropyran-based, and indolinophtalide-based dyes are preferably used. Specific examples of such leuco dyes include, for example,
The following are mentioned.

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-dimethylethylaminophenyl) -6-chlorophthalide, 3,3-bis (p-dimethylaminophenyl) phthalide, 3,3-cyclohexylamino- 6-chlorofluorane, 3-dimethylamino-5,7-dimethylfluorane, 3-dimethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7,8-benzfluor Oran, 3-diethylamino-6-methyl-7-chlorofluorane, 3- (Np-tolyl-N-ethylamino) -6-methyl 7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2- {N- (3'-trifluoromethylphenyl) amino} -6-diethylaminofluorane, 2- {3, 6-bis (diethylamino) -9- (o-chlorianilino) xanthylbenzoic acid lactam}, 3-diethylamino-6-methyl-7- (m-trichloromethylanilino) furorane, 3-diethylamino-7- (o-chloroanilino ) Fluoran, 3-dibutylamino-7- (o-chloroanilino) fluorane, 3-N-methyl-N-amylamino-6-methyl-7-
Anilinofluoran, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3- (N, N-diethylamino ) -5-methyl-7- (N, N
-Dibenzylamino) fluorane, benzoyl leuco methylene blue, 6'-chloro-8'-methoxy-benzoindolinopyrilospirane, 6'-bromo-3'-methoxy-benzoindolinopyrilospiran, 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'-methoxy-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- (o-methoxycarbonylphenylamino) fluorane, 3-diethylamino-5-methyl-7- (α -Phenylethylamino) fluorane, 3-diethylamino-7-piperidi Fluoran, 2-chloro-3-(N-Mechirutoruijino)-7-(p
-N-butylanilino) fluoran, 3- (N-benzyl-N-cyclohexylamino) -5,
6-benzo-7-α-naphthylamino-4′-bromofluoran, 3-diethylamino-6-methyl-7-mesitidino-
4 ', 5'-benzofluoran and the like.

Further, as the developer used in the present invention, various electron-accepting substances that react with the leuco dye when heated to develop a color thereof are applied, and specific examples include phenolic compounds as shown below. Examples include substances, organic or inorganic acidic substances, their esters and salts, and the like.

Gallic acid, salicylic acid, 3-isopropylsalicylic acid, 3-cyclohexylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid, 4,4′-isopropylidenediphenol, 4,4′-isopropylidenebis (2-chlorophenol) ), 4,4′-isopropylidene bis (2,6-
Dibromophenol), 4,4'-isopropylidene bis (2,6-dichlorofere), 4,4'-isopropylidene bis (2-methylphenol), 4,4'-isopropylidene bis (2,6-dimethyl) Phenol), 4,4'-isopropylidene bis (2-tert-butylphenol), 4,
4'-sec-butylidene diphenol, 4,4'-cyclohexylidene bisphenol, 4,4'-cyclohexylidene bis (2-methylphenol), 4-tert-butylphenol, 4-phenylphenol, 4-hydroxydiphenol Phenoxide, α-naphthol, β-naphthol, 3,5
-Xylenol, thymol, methyl-4-hydroxybenzoate, 4-hydroxyacetophenone, novolac type phenolic resin, 2,2'-thiobis (4,6-dichlorophenol), catechol, resercin, hydroquinone, pyrogallol, phloroglycin, phloroglysin 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-vidroxybenzoate, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, p-chlorobenzyl p-hydroxybenzoate,
p-Hydroxybenzoic acid-p-methylbenzine, p-hydroxybenzoic acid-n-octyl, benzoic acid, zinc salicylate, 1-hydroxy-2-naphthoic acid, 2-hydroxy-6-naphthoic acid, 2-hydroxy-6. -Zinc 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, stearic acid, 4-hydroxyphthalic acid, boric acid and the like.

In the present invention, in order to bond and support the leuco dye and the color developer on a support, various conventional binders can be appropriately used. For example, polyvinyl alcohol, starch and its derivative, methoxycellulose. , Cellulose derivatives such as hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose and ethyl cellulose, polyacrylic acid soda, polyvinylpyrrolidone, acrylic acid amide / acrylic acid ester copolymer, acrylic acid amide / acrylic acid ester / methacrylic acid terpolymer, Styrene / maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, water-soluble polymers such as casein, polyvinyl acetate,
Polyurethane, styrene / butadiene copolymer, polyacrylic acid, polyacrylate, vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate, ethylene / vinyl acetate copolymer, styrene / butadiene / acrylic copolymer, etc. Latex can be used.

Further, in the thermosensitive coloring layer of the present invention, together with the leuco dye, the color developer and the filler, auxiliary additives commonly used in thermosensitive recording materials of this kind, for example, a surfactant, a thermoplastic substance (or a lubricant), etc. Can be used together. In this case, examples of the heat-fusible substance include higher fatty acids or esters, amides or metal salts thereof, various waxes, condensates of aromatic carboxylic acids and amines, phenyl benzoate esters, higher linear glycols. , 3,4-epoxy hexaahydrophthalic acid dialkyl, higher ketone,
Other examples include those having a melting point of about 50 to 200 ° C., such as other heat-fusible organic compounds.

The heat-sensitive recording material of the present invention can be prepared by a generally known method. For example, the leuco dye is
Separately the color developer, polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose,
The dispersion particle size is 1 with a dispersing machine such as a ball mill, an attritor or a sand mill together with an aqueous solution of a water-soluble polymer such as an alkali salt of styrene-maleic anhydride copolymer or starch.
After pulverizing and dispersing until it becomes ~ 3μ, if necessary, a filler, a heat-fusible substance dispersion liquid, an antifoaming agent and the like are mixed in a fixed formulation to prepare a thermosensitive coloring layer coating liquid. Further, the overcoat liquid is prepared by mixing or dispersing a binder, aluminum hydroxide and the like. Next, these coating solutions are sequentially applied and laminated on a support such as paper or synthetic paper to prepare the heat-sensitive recording material of the present invention.

〔effect〕

The heat-sensitive recording material of the present invention has a specific amount of an overcoat layer containing aluminum hydroxide and a binder in which a specific amount of a water-soluble polymer and a waterproofing agent for the water-soluble polymer are used in combination on the heat-sensitive color developing layer. When the amount is set to a certain amount, the color development sensitivity is less deteriorated, the oil resistance, the water peeling resistance and the image reliability are high, and the head matching property is excellent.

〔Example〕

Next, the present invention will be described in more detail with reference to Examples. The parts and% shown below are based on weight.

Example 1 Liquids [A] and [B] were prepared by pulverizing and dispersing a mixture having the following composition by a ball mill and an attritor until the volume average diameter became about 1.5 μm.

[A] liquid 3- (N-cyclohexyl-N-methyl) amino-6-methyl-7-anilinofluorane 20 parts by weight 10% aqueous polyvinyl alcohol solution 16 〃 water 64 〃 [B] liquid calcium carbonate 10 parts by weight 10 % Polyvinyl alcohol aqueous solution 16 〃 water 54 〃 Then, [A] solution: [B] solution = 1: 4 were mixed and stirred to prepare a thermosensitive color developing layer coating solution.

Further, a mixture having the following composition was dispersed by a sand mill to prepare an overcoat layer coating liquid.

Dry aluminum hydroxide 20 parts by weight of itaconic acid-modified polyvinyl alcohol alkali salt 10% aqueous solution 40 〃 zinc stearate 10 〃 polyamide epichlorohydrin resin 10 〃 water 20 〃 then these coating solutions in commercial wood-free paper of 50 g / m ² adhesion A thermosensitive recording material of the present invention was prepared by coating and drying the thermosensitive color developing layer so that the amount was 3.0 g / m ² and the overcoat layer was 3.0 g / m ² .

Example 2 Solution [C] Solution Bisphenol A 10 parts by weight Parabenzyldiphenyl 10 〃 Calcium carbonate 10 〃 10% polyvinyl alcohol aqueous solution 20 〃 Water 50 〃 are prepared in the same manner as the solution B of Example 1. Then [A] liquid:
Liquid [C] was mixed and stirred at a weight ratio of 1: 4 to prepare a thermosensitive recording material of the present invention in the same manner as in Example 1 as a thermosensitive color developing layer coating liquid.

Comparative Examples 1 and 2 Thermal recording materials of Comparative Examples were prepared in the same manner as in Examples 1 and 2 except that the overcoat layer was not provided in Examples 1 and 2.

Comparative Example 3 A thermal recording material of Comparative Example was prepared in the same manner as in Example 1 except that calcium carbonate was used in place of the aluminum hydroxide in the overcoat layer of Example 1.

Comparative Example 4 A thermal recording material of Comparative Example was prepared in the same manner as in Example 1 except that silica was used instead of aluminum hydroxide in the overcoat layer of Example 1.

For the above heat-sensitive recording materials, leave them at room temperature for 48 hours and then use a calender to set the Beck's smoothness to 700-1000 seconds. Dynamic color development sensitivity, image brownness, image whitening, oil resistance, water resistance, sticking Was tested. The results are shown in Table-1.

(1) Dynamic color development sensitivity ... Matsushita Electronics Co., Ltd., thermal transfer test 0.45 in a thermal printing experimental device with a thin film head.
W / dot, 1 line recording time 20ms / l, scanning line density 8 × 3.
Pulse width of 0.8, 1.2, 1.6, 2.0mse under the condition of 85 dots / mm
Printing was performed with c and the printing density was measured with a Macbeth densitometer RD-514.

(2) Brown ratio of the image ... With respect to the sample for which the dynamic color development sensitivity of (1) was measured, the print density of 1.0 to 1.2 (which is referred to as D ₀ ) was measured after leaving at room temperature for 15 days. (This is designated as D), and the image brownness rate was obtained according to the following.

(3) Whitening of image: The same test as in (2) was performed, and visually determined as follows.

○: Almost no white powder was generated △: White powder was generated, but there was no problem in practical use ×: Large amount of white powder was generated and not practical (4) Oil resistance: Except that 0.5 g / m ^{2 of} castor oil was attached to the image, (2) An experiment was conducted in the same manner, and the judgment was made as follows.

○: Image brown ratio less than 30% △: Image brown ratio 30 to 50% ×: Image brown ratio 50% or more (5) Water peeling resistance: Immerse the printed sample in water for 24 hours to test for layer peeling. The evaluation was performed as follows.

○: No layer peeling ×: Layer peeling (6) Sticking: Using the printer used for dynamic color development sensitivity, change head power to 0.6 W / dot and pulse width to 2.9 ms, and test for sticking. The evaluation was performed as follows.

○: No sticking ×: Sticking

Front page continuation (72) Inventor Akira Ichikawa 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) References JP-A-59-167291 (JP, A) JP-A-60-46295 (JP, A) JP-A-60-105589 (JP, A) JP-A-60-112487 (JP, A)

Claims (1)

(57) [Claims] 1. A thermosensitive recording material comprising a support, a thermosensitive coloring layer containing a leuco dye and a color developer, and an overcoat layer formed on the thermosensitive coloring layer.
Contains 20 to 70% by weight of a binder using a water-soluble polymer and a water-proofing agent for the water-soluble polymer, and 5 to 45% by weight of aluminum hydroxide as a filler, and is dried and adhered to the overcoat layer. A heat-sensitive recording material, characterized in that the amount is 1.0 to 6.0 g / m ² .