JPS6014720B2 - Method for manufacturing heat-sensitive recording sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a heat-sensitive recording sheet, and more particularly to a method for producing a V-thermal recording sheet that forms a dye image with improved tenacity blur.

Thermosensitive recording sheets record images by utilizing physical and chemical changes in substances caused by thermal energy, and a large number of processes are being studied.

2. Description of the Related Art There has been a so-called wax-type V thermal recording sheet that utilizes physical changes in substances due to heat, and is used for electrocardiograms and the like. In addition, various types of color-forming machines have been proposed that utilize chemical changes caused by heat, but a two-component color-sensitive V thermal recording sheet is particularly representative. Two-component colored spear.
The V heat-sensitive recording sheet is produced by dispersing two types of thermally reactive compounds in the form of fine particles, mixing them with a binder, etc., so that the two types of thermally reactive compounds are separated by the binder, etc., and dispersing them on a support. One or both of them are melted by heating and the coloring reaction that occurs when they come into contact is used to obtain records.

These two types of heat-reactive compounds are generally called electron-donating compounds and electron-accepting compounds, and although there are many types of combinations, they can be broadly classified to form images of metal compounds. There are two types: those that form dye images, and those that form dye images. For forming images of metal compounds,
Using phenols and other organic reducing agents, chelating agents, sulfur compounds, and amino compounds as electron-donating compounds,
Some use organic metal salts as electron-accepting compounds.

These two react by heating to produce metals, metal compounds, metal sulfides, etc., giving colored images. Specifically, a combination of thiourea and heavy metal salt (US Pat. No. 2,740,895)
), a combination of gallic acid, etc. and a metal stearate (US Pat. No. 2,663,654-7), a combination of hydroquinone and silver behenate (US Pat. No. 3,031,329), a combination of hexamethylenetetramine and a tin compound (US Pat. No. 2,813,04)
3) etc. On the other hand, there is a method that uses an electron-donating colorless dye as an electron-donating compound and uses phenols or other acidic substances as an electron-accepting compound to form a dye image (Japanese Patent Publication No. 43-1416u Japanese Patent Publication No. 44-13
Spots 0).

These two-component color sensitive V thermal recording sheets have the following advantages: 1) Primary color development and no need for development; 2) When applied to paper, the quality of the paper is similar to that of regular paper; and 3) Easy handling. It has many advantages as a sheet.

In particular, those using colorless dyes as electron-donating compounds have further advantages such as (41) high color density, and '5) thermal recording sheets with various color hues can be easily produced, and have a large utility value. Therefore, it is most commonly used as a V-thermal recording material. Although a heat-sensitive recording sheet made of a combination of an electron-donating colorless dye and a Tsuruko-accepting compound has the above-mentioned advantages, it still has some drawbacks.

One of them is Jiriki yellowtail. In general, a two-component color-forming thermosensitive recording sheet using an electron-donating colorless dye (hereinafter referred to as a coloring agent) and a fin-accepting compound (hereinafter referred to as a complexing agent) is:
A color former (e.g., crystal violet lactone) and a color developer (e.g., bisphenol A) are each separately dispersed with the same binder (e.g., polypynyl alcohol) in soot until the particle size is a few microns. After pulverization and dispersion, the two are mixed, fillers, auxiliary agents, etc. are added, and the mixture is coated on a support such as paper or plastic film. However, in this case, the separation of the coloring agent and the complexion agent is not always sufficient, so mixing them causes the coating liquid to become colored, and the coated sheet also becomes lightly colored. This coloring is called Jikiburi. This soil quality not only deteriorates the quality of the V-thermographic recording sheet, but also
Even if an image is recorded, the contrast becomes low, which is not desirable. Various attempts have been made to reduce this soil fertility.

For example, a method of adding amines to the coating liquid to suppress color development of colorless dyes (e.g., Tokubatsu 1977-101943), {
21 Method of keeping the pH of coating liquid alkaline (Tokukan Sho 49-
11141)'3} A method of adding a basic inorganic pigment (for example, Hakama Sekisho 49-90142) has been proposed. However, these methods are countermeasures based on the assumption that the separation of the coloring agent and the complexion agent is insufficient, and as a result, soil burr will increase due to long-term storage or storage under high temperature and humidity. It has its drawbacks. Therefore, in order to prevent soil blurring, it is important to completely and stably separate the coloring agent and head coloring agent. It is thought that the state of separation of the color forming agent and the color developing agent is greatly influenced by the type of hydrolyzable polymer added when dispersing both.

This means that the type of water-soluble polymer added when dispersing the color former and color developer greatly affects the coloring of the coating liquid and the strength of the V-thermal recording sheet obtained by coating it. I know it will happen. In this regard, it is already known that polyvinyl alcohol and hydroxyethyl cellulose are excellent water-soluble polymers. (Hakama Kosho 45-14039 Tokukan Sho 48-17 Tsumugi 4) However, water-soluble polymers that are superior in terms of soil burr generation are not suitable for water-soluble polymers that have too high a viscosity or have poor water resistance of the coating film. There are many drawbacks, such as poor performance and high prices. In order to compensate for this shortcoming, other binders are mixed and used, but in general, the properties are averaged and the properties are averaged, making it impossible to obtain a coated sheet that is satisfactory in all respects, which is a dilemma. There is. Therefore, the object of the present invention is to
J is low, the strength of the coating film is excellent, the water resistance is excellent, and the application method is suitable.
An object of the present invention is to provide a thermal recording sheet that is excellent in terms of cost and a method for producing the same.

As mentioned above, the coating liquid used for manufacturing the V heat-sensitive recording sheet is prepared by separately dispersing the color former and the color developer in a water-soluble polymer solution, and then mixing the two dispersions. be done.

At this time, the same water-curing polymers used for dispersing color formers and color developers have conventionally been used. The present inventors used an electron-donating iq colorless dye (color former) and an electron-accepting compound (color developer) in the production of a heat-sensitive recording sheet, respectively.
It has been found that a V heat-sensitive recording sheet obtained by dispersing water-soluble polymers having different repeating units, mixing the two, and coating the same has suppressed tenacity.

That is, according to the present invention, a coloring agent is dispersed together with a water-soluble polymer A, and a complexion agent is dispersed with a water-soluble polymer B having a different repeating unit from the water-soluble polymer A (i.e., a different type). After that, by using a mixture of both, the color former and the color developer can be combined with the same type of water-soluble polymer (i.e., only either water-soluble polymer A or water-soluble polymer B). After being dispersed, it is possible to suppress the curling of the tied heat-sensitive recording sheet compared to when the two are mixed. This means that by dispersing either of the components of the coloring agent or the head coloring agent with a water-soluble polymer such as polyvinyl alcohol or hydroxyethyl cellulose, the occurrence of the well-known soil retention can be minimized. This shows that soil fertility is guaranteed.

On the other hand, the coating strength, water resistance, coating viscosity, cost, etc. of the coating sheet are approximately proportional to the amount of binder used, so it is not suitable for use as a water-repellent polymer added when dispersing other components. It has the advantage of being able to improve these characteristics without worsening the soil's fertility by selecting the right one.

Such an effect cannot be achieved if water-soluble polymer A and water-soluble polymer B are mixed in advance and used. In the present invention, the term "polymer having different repeating units" refers to a polymer having at least one different type of monomer unit forming a polymer chain.

Therefore, among polymers composed of two or more types of monomer units, it refers to those in which one or more types of constituent monomers are different, and the way they are arranged, that is, whether it is a random copolymer or not. It does not depend on whether it is an alternating copolymer or not. In natural polymers, not only the basic units that can be considered monomer units (for example, Q-D-lactose and 3-D-lactose) are different, but also their direct substitutes have different substituents and repeat units. It is a polymer. Therefore, hydroxyethylcellulose, methylcellulose, and hydroxymethylcellulose. base is a polymer with different repeating units. On the other hand, two types of polyvinyl alcohols with different saponity values (0 and 100% saponity)
) have the same monomer units and can be considered to differ only in their ratio, so they cannot be said to be polymers with different repeating units.

The polymers with different repeating units used in the present invention are:
It needs to be water soluble.

Generally, 100 evening water and 20qo are 1? Those that dissolve more than that are useful. According to the present invention, the above-mentioned water-soluble polymers having different repeating units are used in combination, and the following are examples of preferred combinations that can particularly suppress soil burr. It will be as shown in Table 1.

Of course, the present invention is not limited to only these combinations. Table 1 In Table 1, the effect remains the same even if the coloring agent is dispersed with the water-soluble polymer A and the complexing agent is dispersed with the water-soluble polymer B, or vice versa.

Furthermore, even if several water-soluble polymers are mixed and added at the time of dispersion, if the water-soluble polymer mixtures added when dispersing the color developer and color former are essentially different (the same Unless water-soluble polymers having repeating units are predominantly contained in both of them, a heat-sensitive recording sheet with little strength can be obtained. Commercially available water-soluble polymers can be used without any problem.

Specifically, polyvinyl alcohol has an attack degree of 400 to 2.
, 500, with a saponification degree of 80 to 99.8%. Particularly preferred for the present invention are polymerization degrees of 500 to 500.
2,000, and the saponification value ranges from 90 to 99.8%. Maleic anhydride-styrene copolymer, maleic anhydride-isobutylene copolymer, ice-free maleic acid-ethylene copolymer, etc. are generally alternating copolymers, but their degree of polymerization, distribution, etc. in commercial products are not disclosed. In many cases, the standard is determined as the value of the viscosity of the aqueous solution.

The degree of polymerization and molecular weight distribution do not limit the contents of the present invention in any way, but in order to keep the viscosity of the final coating liquid low, the viscosity should be 20 p or less when made into a 5% by weight aqueous solution. is preferred. Hydroxyethyl cellulose. The physical properties of cellulose derivatives such as carboxymethylcellulose and methylcellulose are influenced by the degree of introduction of substituents.

Generally, the degree of substitution of hydroxyethylcellulose is 1.0
~2.0, carboxymethylcellulose has 0.6 substituents
~1.0, but the effect of the present invention is not impaired by the degree of substitution, and the preferable range of the degree of substitution is determined mainly by the solubility in water. Starches include oxidized starch, esterified starch, and
There are etherified starches, Q-starches, Yanxiao dextrins, phosphorylated starches, etc., and these can be used depending on the required solubility, viscosity, coating strength, etc.

In addition, the effects of the present invention are not affected by the molecular weight, molecular weight distribution, etc. of the water-soluble binder used, and the selection is made in order to keep the viscosity of the final coated wave within an appropriate range. From this point of view, it is preferable that the viscosity in a 5% by weight aqueous solution be 20 p or less. The water-soluble polymer added at the time of dispersing the coloring agent and the complexing agent preferably ranges from 1 to 200% (by weight), more preferably from 5 to 100%, of the solid content for each dispersion.

In particular, good results can be expected by dispersing at least one of a color former and a color developer together with a water-soluble polymer in a proportion of 10 to 100% of the dispersed solid content. For dispersion, well-known methods such as ball mill, attritor, sand mill, etc. can be used.

Various pigments are added to the heat-sensitive recording sheet for the purpose of preventing adhesion to the recording head, etc., and these pigments can also be added at the time of dispersing the color former or color developer and dispersed at the same time. Other additives such as waxes, ultraviolet absorbers, and latex binders can be added, but in most cases these are added after the color former dispersion and developer dispersion are mixed.

The prepared coating solution is coated on a common support such as paper or a plastic film (for example, a polyester film) in an amount of 2 to 20 coats, and dried at a temperature of 90°C or less to obtain a V heat-sensitive recording sheet. It will be done. Next, the materials used in the present invention will be explained in more detail.The present invention is characterized in that the coloring agent and the complexion agent are each dispersed together with a water-soluble polymer containing at least repeating units. It is not limited to the material.

The coloring agent used in the present invention is called a leuco dye, and most of them are used as colorless dyes for pressure-sensitive recording paper.

These have the property of developing color by reacting with a color developer. Specifically, triarylmethane compounds, diphenylmethane compounds, xanthene compounds, thiazine compounds,
Examples include subiropyran compounds.

To illustrate some of these, triarylmethane compounds include 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (i.e., crystal violet lactone), 3,3-bis(p-dimethyl Aminophenyl) phthalide, 3-(p-dimethylaminophenyl)-3-(1,2-dimethylindol-3-yl)phthalide, 3-(p-dimethylaminophenyl)-3
-(2-methylindol-3-yl)phthalide, 3-(p-dimethylaminophenyl)-3-(2-phenylindol-3-yl)phthalide, 3,3-bis-(1
, 2-dimethylindol-3-yl)-5-dimethylaminophthalide, 3,3-bis(1,2-dimethylindol-3-yl)-6-dimethylaminophthalide, 3
,3-bis(9-ethylcarbazol-3-yl)-5
-dimethylaminophthalide, 3,3-pis(2-phenylindol-3-yl)-5-dimethylaminophthalide, 31p-dimethylaminophenyl-3-(1-methylpyrrol-2-yl)-6 -dimethyl-aminophthalide, etc., and diphenylmethane compounds include 4
．． 4'-bis-dimethylaminobenzhydrin benzyl ether, N-halophenyl leukoolamine, N-2,4,5-triclo. There are phenylleukoolamine, etc., and xanthene compounds include rhodamine-B-
Anilinolactamurodamine (p-nitroanilino)
lactam, rhodamine 8(p-chloroanilino)lactam, 7-dimethylamino-2-methoxyfluorane, 7
-diethylamino-2-methoxyfluorane, 7-diethylamino-3-methoxyfluorane, 7-diethylamino-3-chlorofluorane, 7-diethylamino-3
-Chloro-2-methylfluorane, 7-diethylamino-2,.3-dimethylfluorane, 7-diethylamino-(3-acetylmethylamino/)fluoran, 7-diethylamino-(3-methylamino/)fluoran, 3,7
- Diethylaminof/. Leolan, 7-diethylamino-3-(dibenzylamino)fluoran, 7-diethylamino-3-(methylbenzylamino)fluoran, 7
-diethylamino-3-(chloroethylmethylamino)
There are fluoran, 7-diethylamino/-3-(diethylamino)fluoran, etc., and thiazine compounds include:
There are benzoyl leucomethylene blue, p-nitrobenzyl leucomethylene blue, etc., and spiro compounds include 3-methyl-spirodinaphthopyran, 3-ethyl-spirodinaphthopyran, and 3,3'-dichlorospiro. Dinaphthopyran, 3-benzylspiro dinaphthopyran, 3-methylnaphtho-(3-methoxybenzo)
-Sviropyran, 3-bropyrusupirodibenzopyran, etc. These may be used alone or in combination. As head coloring agents, phenolic compounds, organic acids or metal salts thereof, oxybenzoic acid esters, clays, etc. are used. Phenol compounds have a melting point of 80°C to 25°C.
Those having a temperature of 0° C. are preferable, and those having two or more phenolic hydroxyl groups in the molecule are particularly preferable because they have a high coloring density.

The list of phenolic compounds is 4,4'-isopropylidene-diphenol (bisphenol A), p-te
Reptile phenol, 2,4-dinitropher/ol,
3,4-dichlorophenol, 4,4'-methylene bis(2,,6-dibutylphenol), p-phenylphenol, 4,4-cyclobentridenediphenol, 2,2'-methylenebis(4 In addition to 4,4'-thiobis(6-tert-butyl-m-cresol), sulfonyl diphenol, -ten-butylphenol-formalin condensate, p-phenylphenol-formalin condensate, etc.

Examples of organic acids or metal salts thereof include phthalic acid, dihydrophthalic acid, maleic acid, benzoic acid, gallic acid, o-toluic acid, p-toluic acid, salicylic acid, 3-rt-butylsalicylic acid, 3,5 - rt-butylsalicylic acid,
Useful examples include 5-Q-methylbenzylsalicylic acid, 3,5-Q-methylbenzylsalicylic acid, 3-[e-octylsalicylic acid, and their zinc, lead, aluminum, magnesium, and nickel salts. In particular, salicylic acid derivatives and their zinc salts and aluminum salts are excellent in terms of color development, fastness of colored images, and storage stability of recording sheets. Examples of oxybenzoic acid esters include ethyl p-oxybenzoate, butyl p-oxybenzoate, heptyl p-oxybenzoate, penzyl p-oxybenzoate, and the like.

Clays include activated clay, acid clay, attapaljite, and activated alumina.

A thermofusible substance is added when using a color developer having a curtain & dot of more than 250 qo or when attempting to develop color in a heat-sensitive recording sheet at a temperature lower than the melting point of the head colorant.

The thermofusible substance may be one that is compatible with either the coloring agent or the complexion agent and has a transverse point close to the desired coloring temperature. It is also effective to add a small amount of a color developer with a low point as a thermofusible substance. The filler is added for the purpose of preventing adhesion to the heat-generating head during recording on the V heat-sensitive recording sheet and preventing bleeding of a colored image.

Commonly used natural or synthetic fine powders include kaolin, talc, cellulose floc, calcium carbonate, magnesium carbonate, barium sulfate, aluminum hydroxide, zinc oxide, titanium oxide, magnesium oxide, fine polyethylene powder, and fine polyurethane powder. etc. These may be dispersed together with a color former or developer, or
Alternatively, as a binder that may be dispersed alone and added when mixing the color former dispersion and the pigment dispersion,
The water-soluble polymers shown in Table 1 can be used as binders as they are.

If necessary, a water-soluble polymer may be further added, or a latex binder may be added for the purpose of improving water resistance and coating strength. It is preferable that the latex binder used in the heat-sensitive recording sheet uses no emulsifier or is emulsified with an anionic multi-L quenching agent, and it is not preferable to use a cationic emulsifier.

For example, styrene-butadiene rubber latex,
Acrylonitrile-butadiene latex. Examples include methyl methacrylate-butadiene rubber latex and vinyl acetate emulsion. In addition, various waxes and metal soaps are added for the purpose of improving the flatness of the coated surface and improving the slipperiness, and if necessary, antifoaming agents, surfactants, etc. are added.

The present invention will be explained in more detail with reference to Examples below.

In each Example, the soil density and color density were measured using a Macbeth RD-51 base type reflection densitometer (using a Ratten 106 filter). The soil density was measured immediately after making the heat-sensitive recording sheet, and the color density was 150℃, with no spots.
Evening/Earth. The color was developed and measured under the condition of heating for 1 second. Example: As a coloring agent, 20 grams of Crystal Violet Lactone (manufactured by Hodogaya Chemical Co., Ltd.) was mixed with 100 grams of water-repellent polymer A (Table 2 below) prepared at a concentration of 5%, and 2 baits were placed in a pole mill with a capacity of 500 grams. A liquid A was prepared by dispersing the mixture over time.

4.4-isopropylidene diphenol (
Mitsui Toatsu Chemical Co., Ltd. "Bisphenol A") 10 times and kaolin (Georgia kaolin) 10 times were combined with 100 times of water-soluble polymer B (Table 2 below), which was made into a steel liquid at a concentration of 2.5%, to a capacity of 500. A liquid B was prepared by dispersing the mixture in a ball mill for 24 hours.

Add 3 parts of Part A, 40 parts of Part B, and further add styrene-butadiene rubber latex (Nippon Zeon LX407) [styrene content: about 6% by weight, solid content 50% by weight] 5 parts and paraffin wax emulsion [ Melting point of paraffin:
70 qo, solid content 5% by weight] Add 3 evenings, and after rope prayer, 5
0 evening/Applying amount 7.0 using a wire bar on that base paper
The mixture was applied in the evening and evening directions, and dried at 70°C for 1 minute to prepare heat-sensitive recording paper.

Water-soluble polymers A and B used and the obtained soil strength yellowtail concentration,
The relationship between the color density and the straightness of application was as shown in Table 2.
Table 2: Hydroxycetylcellulose: Fuji Chemical “HEC”
BL-15” Volipinyl Alcohol (Ken’i Masculinity 98
%, polymerization degree 1700): Kuraray's "PVAI17" Styrene-ice-free maleic acid co-Q polymer: Arabetsu Forestry Chemical Co., Ltd. "Borimalon 351" Isobutylene-ice-free maleic acid copolymer (polymerization degree 1,000): Kuraray " Oxidized starch: "Amicote #800" manufactured by Matsushita University Co., Ltd. Etherized starch: "Unique Gum C30" manufactured by Matsushita University Co., Ltd.
10" Table 2 shows that the thermal recording sheet obtained by dispersing color-forming Shinmachi and complexion agents together with water-soluble polymers of different repeating units, then mixing and coating them has significantly reduced soil strength. I understand.

Claims (1)

[Claims] 1. A method for producing a heat-sensitive recording sheet, which comprises dispersing an electron-donating colorless dye and an electron-accepting compound together with water-soluble polymers having different repeating units, and then mixing and coating the two.