JP3243799B2 - Manufacturing method of thermal recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a thermosensitive recording medium, and more particularly, to providing a protective layer mainly composed of a polysiloxane compound on a leuco coloring type thermosensitive recording layer. Accordingly, the present invention relates to a method for producing a thermosensitive recording medium having improved heat resistance, water resistance, and writing characteristics.

[0002]

2. Description of the Related Art A heat-sensitive recording material having a heat-sensitive recording layer containing a leuco dye and a color developer has a primary color developing property and requires no development.
Due to the advantages of paper quality close to ordinary paper, high color density, easy handling, etc., it is widely used. Particularly, this thermosensitive recording medium is facsimile, It is used in large quantities in fields such as various printers and ticketing machines.

However, since the leuco dye and the developer contained in the heat-sensitive recording layer are easily dissolved in various solvents, the heat-sensitive recording material is exposed to inks such as water-based ink pens and oil-based ink pens, adhesives and glues. White background color develops,
On the contrary, there is a disadvantage that the printed portion disappears. For the purpose of eliminating such disadvantages, Japanese Patent Publication No.
JP-A-30437 and JP-A-48-31958 disclose a thermosensitive recording medium in which a protective layer composed of various binders composed of organic polymer substances and a material obtained by adding a crosslinking agent to the binder is provided on the thermosensitive recording layer. . However, these conventional protective layers have a problem that heat resistance, water resistance, chemical resistance, writing characteristics, and the like are low.

[0004]

SUMMARY OF THE INVENTION The present invention provides a leuco coloring
By improving the protective layer provided on type heat-sensitive recording layer,
It is an object of the present invention to provide a method for producing a thermosensitive recording medium having excellent heat resistance, water resistance, chemical resistance, writing characteristics, and resistance to scratches.

[0005]

According to the present invention, there is provided a thermosensitive recording medium having a leuco coloring type thermosensitive recording layer on a support, wherein a polysiloxane compound is provided on the thermosensitive recording layer. An object of the present invention is to provide a method for producing a thermosensitive recording medium , comprising a protective layer as a main component. B
Protective layer of the present invention to provide the equalizer color forming heat-sensitive recording layer is for a main component a polysiloxane compound, Al
Coxysilane is hydrolyzed in the presence of an acid catalyst, then
Coat on thermal recording layer to cause polycondensation reaction,
Or by heating .

The coating liquid for the protective layer of the present invention is obtained by mixing alkoxysilane or a mixture of two or more alkoxysilanes, acid and water, and hydrolyzing the alkoxysilane while forming a uniform dispersion by high-speed stirring or the like. Prepare. The alkoxysilane or a mixture thereof is subjected to a hydrolysis reaction in the presence of an acid catalyst, and then a polycondensation reaction is caused by being applied to form a polysiloxane compound, which is cured at room temperature or by heating to form a protective layer. To form.

Usually, the hydrolysis of the alkoxysilane is carried out in an organic solvent such as alcohols, which is a common solvent of both, in order to make the mixing of the alkoxysilane and water uniform, but in the present invention, the common solvent is used. It is characterized in that a uniform aqueous solution is obtained by high-speed stirring or the like. For this reason, the protective layer coating liquid of the present invention has a low organic solvent content, and in particular, a coater (coating machine) having no explosion-proof device can be used. Since the coating liquid for the protective layer is unstable and easily gels, it is desirable to use the coating liquid immediately after preparation.

The alkoxysilane used in the coating liquid for the protective layer of the present invention is preferably an alkoxysilane having an alkyl group having 1 to 4 carbon atoms.
Preferred is a trialkoxysilane having 1 to 3 carbon atoms in the alkoxy, and examples thereof include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, and mixtures thereof.

The acid used in the protective layer coating solution of the present invention includes inorganic acids such as nitric acid and hydrochloric acid, and formic acid, acetic acid, propionic acid, maleic acid, chloroacetic acid, citric acid, benzoic acid, and the like.
Organic acids such as dimethylmalonic acid, glutaric acid, glycolic acid, malonic acid, toluenesulfonic acid and oxalic acid can be mentioned. The addition amount of such an acid is 0.01 to 3 parts by weight, preferably 0.5 to 1.5 parts by weight based on 100 parts by weight of the alkoxysilane. The reason for this definition is that if the amount is less than 0.01 part by weight, the hydrolysis of the alkoxysilane is insufficient, while if it exceeds 3 parts by weight, the coating liquid is apt to gel.

The proportion of water in the protective layer coating solution used in the present invention is at least the minimum amount required for complete hydrolysis of trialkoxysilane calculated from the reaction formula for complete hydrolysis of trialkoxysilane. . For example, 0.4 g or more of water is used for 1 g of methyltrimethoxysilane, and 0.3 g or more of water is used for 1 g of methyltriethoxysilane.

Therefore, the amount of water in the protective layer coating solution is 500 to 3000 per 100 parts by weight of the alkoxysilane.
Parts by weight, preferably 800 to 1500 parts by weight. Further, conventionally used fillers and lubricants can be added to the protective layer coating solution according to the purpose in the present protective layer. Further, an intermediate layer mainly composed of a conventionally used organic polymer substance may be provided between the present protective layer and the heat-sensitive layer.

Examples of the support used in the present invention include various types of paper such as recycled paper including high quality paper, medium quality paper, coated paper and waste paper, various nonwoven fabrics, plastic films, synthetic papers, metal foils and the like. . When paper is used as the support, the basis weight of the paper is 20 to 400 g / m ² , preferably 30 to 200 g / m ² . Dye-type and pigment-type heat-sensitive recording layers can be used for the heat-sensitive recording layer of the present invention. Among them, examples of leuco dyes used in the dye-type heat-sensitive recording layer include triallylmethane dyes, thiazine dyes, spiro dyes, lactam dyes, and various fluoran compounds.

Further, in the present invention, the developer used in combination with the leuco dye is not particularly limited, and has a property of liquefying, vaporizing or dissolving when the temperature rises. These are various color developing agents having a property of being colored upon contact. Developers that may be mentioned as typical specific examples include, for example, 4-tert-butylphenol, α-naphthol, 4-acetylphenol, hydroquinone monobenzyl ether, 4-hydroxybenzophenone, dimethyl 4-hydroxyphthalate, Aromatic carboxylic acids such as methyl 4-hydroxybenzoate and terephthalic acid, and phenolic compounds thereof, and aromatic carboxylic acids and polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin and nickel There are organic acidic substances such as salts.

One of the materials used for the pigment type thermosensitive recording layer is an organic acid heavy metal salt or an organic acid noble metal salt, and the other is an organic reducing agent, a sulfur compound, an amino compound, or the like. The preparation of a coating solution containing these is generally performed by dispersing the leuco dye and the developer together or separately by agitating a ball mill, an attritor, a sand grinder, etc., or a pulverizer using water as a dispersion medium, and preparing a coating solution. I do.

In such a coating solution, starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, styrene / maleic anhydride copolymer salt, styrene / butadiene copolymer are usually used as binders. Emulsions are 2 to 40% by weight of the total solids,
Preferably, it is used at a ratio of 5 to 25% by weight. Further, various auxiliaries can be added to the coating liquid as needed. For example, dispersants such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium salt of lauryl alcohol sulfate, metal salts of fatty acids, and the like, other antifoaming agents, fluorescent dyes, coloring dyes, and the like.

In the heat-sensitive recording medium of the present invention, the method for forming the heat-sensitive recording layer is not particularly limited, and the heat-sensitive recording layer can be formed according to a conventionally known technique.
For example, in a method of applying a heat-sensitive coating solution to a support, an appropriate coating device such as an air knife coater or a blade coater is used. The coating amount of the coating liquid is not particularly limited, but is generally in the range of ^{2 to} 15 g / m ² , preferably 3 to 10 g / m ² in terms of dry weight.

Further, an intermediate layer using an inorganic pigment such as calcined kaolin or silica or an organic pigment such as a plastic pigment can be provided between the support and the heat-sensitive recording layer.
Various known techniques in the thermal recording medium field can be added.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments, but the present invention is of course not limited to the scope of these embodiments. Production of thermosensitive recording medium A liquid and B liquid having the following compositions were prepared. Solution A leuco dye 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluoran (S-205, manufactured by Yamada Chemical) 10 parts by weight Polyvinyl alcohol 12% aqueous solution 30 {polystyrene ammonium acrylate 20 % Aqueous solution 2% water 8% or more was dispersed and prepared by a sand grinder until the average particle size became 1 μm. Solution B Bisphenol A 18 parts by weight m-terphenyl 22 << 12% aqueous solution of polyvinyl alcohol 50 >> 20% aqueous solution of polystyrene ammonium acrylate 3 << water 57 >> The above components are dispersed by a sand grinder until the average particle size becomes 1 μm. Prepared.

The above was prepared by dispersing with a homomixer for 10 minutes. Next, 50 parts by weight of the liquid A, 150 parts by weight of the liquid B, and 42 parts by weight of a 12% aqueous solution of polyvinyl alcohol were mixed to prepare a heat-sensitive coating liquid. The heat-sensitive coating solution prepared in this way was applied to a high quality paper of 50 g / m ² of rice tsubo and dried weight of 5 g / m ^2.
It was applied with a wire bar so as to obtain m ² and dried at 50 ° C. in an oven.

Example 1 0.5 g of acetic acid was added to 449.5 g of distilled water, and 50 g of methyltrimethoxysilane was gradually added thereto while stirring at a high speed to completely dissolve it. An aqueous solution of the hydrolyzate of methoxysilane was obtained. Using this aqueous solution, a dry coating amount of 3 was applied on the heat-sensitive layer prepared as described above.
g / m ² was applied with a wire bar and dried at 50 ° C. to obtain a thermosensitive recording medium.

Example 2 Instead of methyltrimethoxysilane of Example 1, methyltriethoxysilane was used to obtain an aqueous solution having a solid content of about 4%. Using this aqueous solution, a thermosensitive recording medium was obtained in the same manner as in Example 1. Comparative Example 1 Instead of the protective layer coating liquid containing methyltrimethoxysilane used in Example 1, a polyvinyl alcohol aqueous solution (PV
A-105 Kuraray Co., Ltd.) was used in the same manner as in Example 1 except that a 5% solution was used to obtain a thermosensitive recording medium.

Comparative Example 2 A 5% aqueous solution of den powder was used in place of the protective layer coating solution containing methyltrimethoxysilane used in Example 1.
A thermosensitive recording medium was obtained in the same manner as in Example 1. Comparative Example 3 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that a 5% aqueous solution of methylcellulose was used instead of the protective layer coating liquid containing methyltrimethoxysilane used in Example 1.

Comparative Example 4 A thermosensitive recording medium was obtained in the same manner as in Example 1, except that a 5% aqueous solution of casein was used instead of the protective layer coating solution containing methyltrimethoxysilane used in Example 1. . Comparative Example 5 Polyvinyl alcohol aqueous solution 700 used in Comparative Example 1
g to amorphous silica (Mizukasil P527 Mizusawa Chemical)
0 g was gradually added, and a dispersion of zinc stearate (Hydrin D-523 manufactured by Chukyo Yushi: solid content 3) was further added as a lubricant.
0%), and 33.3 g of this mixture was used.
A thermosensitive recording medium was obtained in the same manner as in Example 1.

Comparative Example 6 A heat-sensitive recording material was obtained in the same manner as in Example 1 except that phenyltrimethoxysilane was used instead of the protective layer coating solution containing methyltrimethoxysilane used in Example 1. The heat-sensitive recording materials obtained in Examples 1 and 2, and Comparative Examples 1 to 6,
A calendering process was performed using a gloss calender to obtain a thermosensitive recording medium having a recording surface with a Bekk smoothness of 1,000 seconds.

The thermosensitive recording media obtained in Examples 1 and 2 and Comparative Examples 1 to 6 were evaluated, and the results are shown in Table 1. Printing: Printing was performed under the following conditions using a thermal tester TH-PMD (manufactured by Okura Electric Co., Ltd.).・ Thermal head: KJT-256-8HGF1 (Kyocera) ・ Applied voltage: 24.0V ・ Pulse period: 2msec ・ Pulse time: 1.2msec 1.8msec The density of the recording part was measured using a Macbeth densitometer (RD-514). Measured. 1) Stinging resistance Using an image printer VP-35 (manufactured by Seiko Denshi), printing was performed at a printing rate of 100%, and the coloring state and sticking sound were evaluated.

[0026] 2) Chemical resistance Acetone was dropped onto the solid printed portion with a pulse width of 1.9 msec using a thermal tester TH-FMD, and the recorded portion was visually observed to examine the chemical resistance. The evaluation was x when fogging occurred, and ○ when fogging did not occur.

2-1 Water resistance: The recording portion was immersed in water for 24 hours, and the recorded portion was visually evaluated. 2-2 Oil resistance: The recording part was immersed in salad oil for 24 hours and evaluated visually. 2-3 Plasticizer resistance: Erasable rubber (Dragon homo PE-OI
A) was placed on the recording part, and the weight of 200 gf / cm ² was applied thereto and left for 3 days. Thereafter, the recording part was visually evaluated.

2-4 Highlighter resistance: Highlighter (ZEB)
Using RA PEN2), draw a line above the recording
Evaluation was made visually after day. Judgment ：: The recording portion hardly changed from that before storage. Δ: The recording part is legible. X: The recording portion is almost completely decolored.

[0029]

As is clear from the results of Comparative Examples 1 to 4 in Table 1, when an aqueous solution of a conventional organic polymer substance is used as a protective layer without adding a pigment or a lubricant, sticking is large and the printed portion is hardly printed. White spots occur. On the other hand, as is apparent from Comparative Example 5, sticking can be improved by adding a pigment or a lubricant, but in this case, the print density is greatly reduced.

On the other hand, as is clear from Examples 1 and 2 in Table 1, the heat-sensitive recording material of the present invention using a polysiloxane compound as the protective layer does not need to include a pigment or a lubricant in the protective layer. Because of its high heat resistance, there is no sticking, the printing density is high, and the chemical resistance is also excellent. Therefore, according to the present invention, a thermosensitive material having excellent heat resistance, water resistance, chemical resistance, and writing characteristics can be obtained.

[0031]

[Table 1]

Claims (1)

(57) [Claims] 1. A support, leuco color development-type heat-sensitive recording layer, in the manufacturing method of the heat-sensitive recording material having a protective layer in this order, charcoal
Alkyl groups having 1 to 4 carbon atoms and alkoxy having 1 to 3 carbon atoms
Alkyl trialkoxysilane having a group as a constituent is hydrolyzed in the presence of an acid catalyst, and then applied on a heat-sensitive recording layer to cause a polycondensation reaction. At room temperature or by heating, a polysiloxane compound is used as a main component. A method for producing a thermosensitive recording medium, comprising forming a protective layer as follows.