JPH03136894A - Binder for heat sensitive recording body - Google Patents

Abstract

PURPOSE:To remarkably improve the adhesive property while maintaining various properties such as color developing property etc. by making a solution of a copolymer of a predetermined amount of monomer which is copolymerizable with a predetermined weight of (meth)acrylamide and N- vinylpyrrolidone as an effective component. CONSTITUTION:A solution of a copolymer made of 52-98 weight % of (A) (meth) acrylamide, 1.0-18 weight % of (B) N-vinylpyrrolidone and, 1.0-30 weight % of monomer which is copolymerizable with (A) and (B) is used as an effective component. Moreover, where polyvinylalcohol is present, a solution of a copolymer made of 52-98 weight % of (meth)acrylamide, 1.0-18 weight % of N- vinylpyrrolidone and, 1.0-30 weight % of monomer copolymerizable with these is made an effective component.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a binder for a heat-sensitive recording material, and in particular provides a recording material that can obtain a coating liquid with a high solid content, has high sensitivity, and has good adhesiveness. This invention relates to a binder for a vine heat-sensitive recording material.

(Prior art) Thermosensitive recording materials generally consist of two components: a leuco dye such as crystal violet lactone or 3-diethylamino-6-methyl-7-anilinofluorane, and a color developer such as a phenolic substance. It is manufactured by applying a heat-sensitive composition in which a binder is added to a heat-sensitive component to impart binding properties to a sheet-like support to form a heat-sensitive layer. In this heat-sensitive recording material, one or both of the leuco dye and the color developer melts when heated, and when they come into contact, a chemical reaction occurs, resulting in color development and color recording. This type of heat-sensitive recording material has advantages such as easy printing and clear records, so it is widely used as a recording material for facsimiles, printers, and POS, for example.

Conventionally, water-soluble resins such as polyvinyl alcohol and polyacrylamide have been known as binders for heat-sensitive recording materials, but these all have insufficient adhesive properties.
As a result, there was a problem that the dye, developer, filler, etc. would peel off from the base paper. Furthermore, when the base paper was rolled up, so-called "powder blowing" occurred, which was not good for environmental hygiene. Furthermore, since the viscosity of the aqueous solution of the binder for heat-sensitive recording materials is high, when a heat-sensitive coating solution is prepared using the binder, the solid content concentration is also low, making it difficult to dry the heat-sensitive coating solution coated on the support. There is a disadvantage that it takes a long time and the productivity of the heat-sensitive recording medium is reduced. Note that if the drying temperature is increased, a coloring phenomenon will occur during the drying stage, so this method cannot be used as a commercial product.

(Problems to be Solved by the Invention) The present invention can solve a problem that could not be solved satisfactorily with conventional techniques, namely, significantly improve adhesion while maintaining various performances such as color development.

Another object of the present invention is to provide a binder for a thermosensitive recording material that can significantly improve the productivity of the thermosensitive recording material by sufficiently increasing the solid content concentration of the thermosensitive coating liquid.

(Means for Solving the Problems) In order to solve the above problems, the present invention δ et al. conducted intensive studies on copolymer components, and as a result, they used an aqueous solution of the specific copolymer shown below as an active ingredient. The present invention, which was the first to discover that the above problems could be solved completely, was completed for the first time based on this new knowledge.

That is, the present invention comprises: 11) (Al (meth)acrylamide 52-98% by weight, IOI N-vinylpyrrolidone 1.0-18ffi@%, and
(C1 Monomer 1 copolymerizable with the above IAI and (old)
, 0-30 weight! The present invention relates to a binder for a heat-sensitive recording material, characterized in that the active ingredient is an aqueous solution of a copolymer consisting of t.

In the river, (2) in the presence of polyvinyl alcohol, (^)
(Meth)acrylamide 52-98 weight 1 FBI N
- vinylpyrrolidone 1.0-18% by weight, and Ic
Monomer copolymerizable with IAI and +81 1.
The present invention relates to a binder for a heat-sensitive recording material, characterized in that the active ingredient is an aqueous solution of a copolymer having a weight of 0 to 30 weight molecules.

In the present invention, (meth)acrylamide (hereinafter referred to as monomer (A)) is an essential monomer and has the significance of increasing the adhesive strength of the resulting binder. N-vinylpyrrolidone (hereinafter referred to as monomer fB+) is an essential component in order to improve color development and staining resistance. In addition, the monomer (C1) copolymerized with the monomer iAl and the monomer (hereinafter referred to as monomer (C1)) is an essential component in order to adjust the glass transition temperature of the resulting binder.The monomer (C) is not particularly limited, but 1
For example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (
Various alkyl (meth)acrylates such as meth)acrylate, 2-ethylhexyl (meth)acrylate, stearyl (meth)acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate Examples include acrylate, glycidyl methacrylate, vinyl acetate, (meth)acrylonitrile, (meth)acrylic acid, and styrene. Among them, alkyl (meth)acrylates and (meth)acrylonitrile are preferred from the viewpoint of color development.

The amounts of the 84 monomers used are as follows. That is, the usage state of monomer (Al) is 52 to 98!
1%, preferably 60-90% by weight. If the amount used is less than 52 times Ni, the adhesive strength of the resulting binder tends to decrease, which is not preferable. Monomer (previously used amount is 1.0-181 amount i, preferably 5-15% by weight
It is said that If the amount used is less than 1 heavy duty i, it will not be sufficient in terms of color development or staking resistance, and 18
If it exceeds fEi%, the adhesive strength tends to decrease, which is not preferable. Monomer (the amount of C1 used is 1.0 to 30
@Amount i, preferably 1.0 to 20% by weight. If the amount used is less than 1.010, the color development will decrease and the amount of 30
II If it exceeds 1%, the adhesive strength decreases, which is not preferable.

Of the present invention, the second invention uses polyvinyl alcohol as an essential component in addition to the monomers (Al to monomer (C1). It is effective when it is desired to further improve the adhesive strength while retaining the characteristics of the binder of the invention, and is preferably used within a range that does not hinder the high concentration of the obtained binder.

The type of polyvinyl alcohol is not particularly limited,
Any conventionally known solvent can be used as long as it is water-soluble. That is, polyvinyl alcohol may be either a partially saponified product or a completely saponified product, or may be a modified polyvinyl alcohol such as silicon-modified, carboxyl-modified, or acetoacetyl-modified. degree is 75-100%
Partially saponified products or completely saponified products are preferred.The amount of polyvinyl alcohol used is determined appropriately taking various performances such as adhesiveness into consideration, and is usually 100% by weight based on the total amount of monomers (A) to (C1). Weight preferably 5-7
0m 1%. If the amount used is less than 1ti1%, the adhesive strength tends to be poor. Also 100 N
If it exceeds 1, the viscosity of the product will be too high and the stability over time will tend to be poor.

The method for packaging the copolymer, which is an active ingredient of the binder of the present invention, is not particularly limited and various methods can be employed.For example, it can be easily manufactured by the following method. first,
In addition to the method of charging predetermined amounts of monomer (A) monomer (previously) and monomer (C1) to a reaction container and stirring to form an aqueous solution, and then reacting simultaneously in the presence of a radical polymerization initiator, continuous dropping, split charging, etc. A method of supplying the monomer etc. to the reaction system by the method described above can also be adopted.On the other hand, when using polyvinyl alcohol,
Pour polyvinyl alcohol and water in predetermined amounts into a reaction vessel, stir to form an aqueous solution, and then add the monomer (
In addition to the method of adding Al-(C1 and reacting simultaneously in the presence of a radical polymerization initiator), it is also possible to adopt a method of supplying the monomer, etc. to the reaction system by a method such as continuous dropwise charging in one portion.

When using either of these methods, 1. Usually,
The reaction temperature is preferably about 20 to 95°C, and the reaction time is about 2 to 8 hours to complete the polymerization.In addition, the monomer concentration during polymerization is, of course, in any of the above-mentioned polymerization methods. In any other method, although not particularly limited, it is usually 10 to 50% by weight in the reaction mixture solution, preferably 15 to 4011%.

In addition, the radical polymerization initiator is not particularly limited, and any known water-soluble peroxide or azo compound such as hydrogen peroxide, ammonium persulfate, potassium persulfate, etc. can be appropriately selected and used, and the amount used. is usually about 0.1 to 5 parts per 100 parts of total monomers used in the present invention. In addition, a reducing agent may be used in combination with the radical 1 initiator to form a dox system, and a chain transfer agent such as mercaptans may be used to adjust the degree of polymerization and achieve the desired viscosity. can.

The thus obtained binder of the present invention usually has a pH of 4.
~7. Viscosity 500~100.000cps, solid content concentration lO~40! i 1% is good.

The binder of the present invention obtained above can be used for facsimile paper, printer paper, ticket paper for automatic ticket issuing machines, etc. as described above.
It can be used as a binder for various heat-sensitive recording media such as barcode paper for POS systems, and exhibits excellent adhesiveness, water resistance, color development, and storage stability. It goes without saying that known waterproofing agents such as epichlorohydrin-modified polyamide polyamine resins and amino-formaldehyde resins may be used in combination, if necessary. Furthermore, the staking resistance can be further improved by adding higher fatty acids, higher fatty acid amides, higher fatty acid metal salts, and the like.

In order to produce a 9J heat-sensitive recording material using the binder of the present invention, conventionally known methods can be employed as they are. That is, 5. Leuco dye and color developer are bonded onto various supports such as paper, synthetic paper, and film using the binder of the present invention and optionally additives such as fillers, waterproofing agents, and anti-sticking agents. 52 can be easily formed by at least forming a heat-sensitive layer.

As the leuco dye, various known ones can be used, and either lactone type or non-lactone type having a lactone ring in the molecule may be used, and triphenylmethane type and fluoran type lactone compounds are particularly suitable. .

Examples of fluoran compounds include 3-diethylamino-6-methyl-7-anilinofluoran.

2-anilino-3-methyl-6-dinithylaminofluorane, 2-anilino-3-methyl-6-(methylcyclohexylamino)fluoran, 2-anilino-3-methyl-6-(ethylisobenzylamino)fluoran .

2-(p-chloroanilino)-3-methyl-6-dinithylaminofluorane, 2-(p-fluoroanilino)-
3-Methyl-6-dinithylaminofluorane, 2-anilino-3-methyl-6-(p-toluidinoethylamino)fluoran, 2-(p-toluidino)-3-methyl-
6-dinitylaminofluorane, 2-(0-chloroanilino)-6-sibutylaminofluorane, 2-(o-fluoroanilino)-6-dinitylaminofluorane.

2-(o-fluoroanilino)-6-sibutylaminofluorane, 2-anilino-3-methyl-6-piperidinofluorane, 2-anilino-3-methyl-6-pyrrolidinofluorane, 2 -ethoxyethyl amyl 3-chloro-
6-Dinithylaminofluorane, 2-anilino-3-chloro-6-dinithylaminofluorane, 2-chloro-6
-dinithylaminofluorane, 2-methyl-6diethylaminofluorane, etc., and triarylmethane compounds include 3,3-bis-fp-dimethylaminophenol)-6-dimethylaminophthalide (also known as: crystal violet lactone), 3.3-bis-
(p-dimethylaminophenol)phthalide, 3-(p
-dimethylaminophenol)-311,2-dimethylaminoindol-3-yl)phthalide, etc.
These leuco dyes may be used alone or in combination.

Examples of the color developer include phenol compounds, organic acids or metal salts thereof, and oxybenzoic acid esters. Specific examples include p-octylphenol, p-tert-butylphenol,
! , tobis(p-hydroxyphenyl)propane, 2.
2-bis-(p-hydroxyphenyl)propane, 1.
1-bis(p-hydroxyphenyl)cyclohexane,
4.4-thiobisphenol, 4.4-sulfonyldiphenol, bis(3-allyl-4-hydroxyphenyl)-sulfone, novolac type phenolic resin, p-hydroxybenzoic acid ester, dimethyl 4-hydroxyphthalate, 5-hydroxy Examples include dimethyl isophthalate, 3.5-di-tert-butylsalicylic acid, 3.5-di-α-methylbenzylsalicylic acid, and polyvalent metal salts of aromatic carboxylic acids corresponding to the above.

The method for dispersing the leuco dye and color developer is not particularly limited, and any conventional method can be used. For example, the leuco dye and the color developer may be separately dispersed in the presence of a dispersant to a size of about several micrometers using a dispersion device such as a ball mill or sand mill. As the dispersant, water-soluble resins such as polyvinyl alcohol and methyl cellulose can usually be used.

The fillers are used to improve writability, whiteness, and staining resistance, and specific examples thereof include calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide,
In addition to inorganic fine powders such as silica, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, and talc, urea-formalin resin.

Examples include organic fine powder such as polystyrene resin.

Examples of the water-resistant agent include various known agents such as epichlorohydrin-modified polyamide polyamine resins and amino-formaldehyde resins.

Anti-sticking agents include waxes such as paraffin wax and microcrystalline wax, higher fatty acids such as valmitic acid and stearic acid, higher fatty acid amides such as stearic acid amide, and higher fatty acid metal salts such as zinc stearate and calcium stearate. can be given.

The ratio of the total amount of leuco dye, slI coloring agent, and filler to the binder used is usually 1: o, t to 1:
It is appropriate that it be l.

In addition, polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, methoxy cellulose, carboxy-modified polyvinyl alcohol, polyacrylamide, polyacrylic acid, starch and its derivatives, casein, gelatin, alkali salts of styrene-maleic anhydride copolymers, etc. There is no problem in using various known binders in combination within the range that does not reduce the performance of the heat-sensitive recording material binder of the present invention.

Applying the coating liquid obtained from the binder for heat-sensitive recording material of the present invention, additives, leuco dye and color developer to a support,
When drying to form a heat-sensitive layer, the concentration and viscosity of the coating solution are not particularly limited;
It is said to be about 0 to 50% and about 20 to 2000 cps. Although the coating method is not particularly limited, a wire bar, blade coater, air knife coater, roll coater, etc. can usually be used. Furthermore, the amount of coating is not limited and can be determined as appropriate by taking into account the type of heat-sensitive recording medium, etc., and it is usually sufficient to apply the coating so that the amount of solid content in the coating liquid is in the range of 3 to ISg/rn'. .

As described above, the heat-sensitive recording material obtained using the binder for heat-sensitive recording material of the present invention has excellent water resistance as it is, but a known overcoating agent can be coated thereon if desired. Specific examples thereof include polyvinyl alcohol and polyvinyl alcohol-acrylic graft copolymers.

The present invention will be explained in more detail below with reference to Reference Examples, Examples, and Comparative Examples; however, it goes without saying that the present invention is not limited to these Examples.

Reference Example 1 (Production of binder) 88 parts by weight of acrylamide (hereinafter simply referred to as parts), 10 parts of N-vinylpyrrolidone, 2 parts of n-butyl acrylate, and 400 parts of water were placed in a reaction vessel equipped with a stirrer and a uA flow cold steamer. After preparation and sufficient nitrogen replacement, lower the liquid temperature to 3.
The temperature was adjusted to 5°C, and then 0.5 parts of ammonium persulfate and 0.2 parts of sodium bisulfite were each added as aqueous solutions to initiate 1 polymerization. After the polymerization system reached 80 to 90°C, the reaction was continued for 2 hours. After the reaction was completed, the pH was adjusted with 28% aqueous ammonia. The obtained binder had a solid content concentration of 20%, a viscosity of 20,000 cps, and a PL of 6.
．． It was 0.

Reference Examples 2 to 8 and 15 to 16 In Reference Example I, polymerization was carried out in exactly the same manner as in Reference Example 1, except that the type or amount of the heavy polymer used was changed as shown in Table 1, and various binders were used. Obtained. Their solid content concentration, pH and viscosity are shown in Table 1.

Reference example 9 In a reaction vessel equipped with a stirrer and reflux condenser.

Polyvinyl alcohol (product name rPVA110J,■
Kuraray Kema 1 (polymerization degree 1000, saponification degree 98.5%) 1
267 parts of a 5% aqueous solution, 88 parts of acrylamide, 10 parts of N-vinylpyrrolidone, 2 parts of n-butyl acrylate, and 333 parts of water were charged, and after sufficient nitrogen substitution, the liquid temperature was adjusted to 35°C, and then 1 part of ammonium persulfate was added. 0.4 parts of sodium bisulfite were each added as an aqueous solution to initiate polymerization. After the polymerization system reached 80 to 90°C, the reaction was continued for 2 hours. After the reaction was completed, PTI was added with 28% aqueous ammonia. It was adjusted. The obtained binder had a solid content concentration of 20%, a viscosity of 38.000 cps, and a rho of 116.0.
Met.

Reference Examples 1O to 14 In Reference Examples 10 to 14, polymerization was carried out in exactly the same manner as in Reference Example 9, except that the type of monomer used or the door was changed as shown in Table 1, to obtain various binders. Their solid content concentration, pf113 and viscosity are shown in Table 1.

Examples 1 to 14 and Comparative Examples 1 to 2 (Preparation of heat-sensitive coating liquid) L1 Stand 1j 2-anilino-3-methyl-6-(toethylisobentylamino)-fluoran 10 parts Polyvinyl alcohol (trade name r 10% aqueous solution of PVA205J (manufactured by Kuraray) 5 parts water
Grind 18.3 parts with a ball mill until the average particle size is 3 μm or less,
The mixture was dispersed to obtain Solution A.

11 JJ Bisphenol A 30 parts r P
VA20SJ (7) 10% aqueous solution 7.5 parts water
48.2 parts were ground in a ball mill until the average particle size became 3 μm or less and dispersed to obtain B@.

Part A: 33.3 parts Solution B: 85.7 parts Light calcium carbonate: 30 parts Reference examples - 16 binder: 82 parts Zinc stearate
10 parts water
240 parts were stirred and mixed using a motor to obtain thermal coating #i (liquid C).

Using the heat-sensitive coating liquid obtained above, a heat-sensitive recording paper of the present invention was prepared according to the method shown below.

(Coating method) A coating amount (
The heat-sensitive recording material of the present invention was prepared by applying the coating liquid using a bar coater so that the solid content (solid content) was about 5 g, /rd, drying at 50° C. for 2 minutes, and further calendering at room temperature. I got paper.

(Evaluation Method) The heat-sensitive recording paper obtained above was evaluated in terms of color development, adhesive strength, and preservability according to the following methods. The results are shown in Table 2.

il+ Color development Printed using a commercially available heat-sensitive facsimile (manufactured by Matsushita Densen, Panafax 0F-22), and printed using a Sara9 crush meter PDA-6.
The color density of the printed portion (dynamic printing) and the color density of the background portion of the thermosensitive recording paper obtained using the thermal recording paper No. 5 (manufactured by Konica ■) were measured.

The higher the color density of the printed part and the lower the color density of the background part of the thermal recording paper, the better the color property.

(2) Adhesiveness (Tape Peeling) 1. Apply cellophane tape (made by Chiban, 24m) to the coated surface of the obtained thermal recording paper, and test the 180° peeling strength using a tensile tester (made by Toyo Bouldwin). The adhesion between the φ cut surface and the base paper surface was determined.

(3) Stizzing property The same thermal facsimile as used for coloring property measurement was used to print and record, and the blurring of the printed image was visually evaluated.

(Evaluation criteria) O: No fading Δ: Slightly fading The color density of the background area was measured.

The lower the color density of the background portion of the obtained thermal recording paper, the better the storage stability.

(Effects of the Invention) The binder for heat-sensitive recording materials of the present invention is used to form heat-sensitive layers having excellent adhesive properties on various supports.

That is, it not only imparts excellent color development and storage stability to the heat-sensitive recording material.

Since the solid content concentration of the heat-sensitive coating liquid during application is high, productivity can be significantly improved. Therefore, it is possible to provide a thermal recording material that is superior to the thermal recording material obtained by applying a conventional binder and meets today's requirements.

Arakawa Chemical Industry Co., Ltd. Table 2

Claims (5)

[Claims] (1) (A) (meth)acrylamide 52-98% by weight
, (B) 1.0 to 18% by weight of N-vinylpyrrolidone, and (C) monomer 1 copolymerizable with the above (A) and (B).
．． A binder for a heat-sensitive recording material, characterized in that the active ingredient is an aqueous solution of a copolymer consisting of 0 to 30% by weight. (2) (C) is an alkyl (meth)acrylate, (
The binder for a heat-sensitive recording material according to claim 1, wherein the binder is at least one selected from meth)acrylonitrile. (3) In the presence of polyvinyl alcohol, (A) (meth)
52 to 98% by weight of acrylamide, (B) 1.0 to 18% by weight of N-vinylpyrrolidone, and (C) the above (A)
A binder for a heat-sensitive recording material, characterized in that the active ingredient is an aqueous solution of a copolymer comprising 1.0 to 30% by weight of a monomer copolymerizable with (B) and (B). (4) The amount of polyvinyl alcohol used is
4. The binder for a heat-sensitive recording material according to claim 3, wherein the amount is 1 to 100% by weight based on the total amount of monomers B) and (C). (5) The above (C) is an alkyl (meth)acrylate, (
The binder for a heat-sensitive recording material according to claim 3 or 4, wherein the binder is at least one selected from meth)acrylonitrile.