JPS6235883A - Binder for thermal recording paper - Google Patents

Abstract

PURPOSE:To obtain a binder for thermal recording which can be used with a high-speed printer or the like, by using an aqueous solution of a water-soluble copolymer of acrylic amide and/or methacrylic amide with N-vinylpyrrolidone in which the comonomer ratio by weight is specified. CONSTITUTION:The binder consists of an aqueous solution of a water-soluble copolymer comprising 50-80wt% of acrylic amide and/or methacrylic amide and 20-50wt% of N-vinylpyrrolidone. If the total amount of acrylic amide and/or methacrylic amide is less than 50wt%, color forming property of the thermal recording paper produced is poor, whereas if the amount is more than 80wt%, the effect on prevention of ground color development or ground fogging is lowered. The monomeric mixture is diluted with water so that the total concentration of the monomers (acrylic amide and/or methacrylic amide and N-vinylpyrrolidone) is 10-35wt%, a polymerization initiator is added to the diluted liquid, and the resultant mixture is brought into reaction for 0.5-3hr at a temperature of 60-90 deg.C in a nitrogen atmosphere.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a binder for thermal recording paper.

More specifically, the present invention relates to a binder for thermal recording paper that can be used in 8-speed thermal recording paper for facsimiles, high-speed printers for ticket issuing systems, high-speed printers for POS (point of sale) systems, and the like.

[Conventional technology and its problems]

In recent years, there has been a strong desire to improve printing speed in facsimiles, ticketing systems, etc., but when conventional binders mainly made of polyvinyl alcohol are used, recording problems such as background coloration and background fogging occur. There were problems such as a decrease in the whiteness of the background color of the paper, sticking, that is, adhesion to the thermal head during printing, and the resulting fading, and it was not compatible with high-speed printers.

In order to solve this problem, studies have been made to improve dyes, add whitening agents made of inorganic pigments such as titanium oxide, and select color developers. A material that satisfies performance, thermal response, cost, etc. has not yet been found.

Other conventionally used binders include water-soluble polymer binders such as starch, carboxymethyl cellulose, gum arabic, casein, gelatin, hydroxyethyl cellulose, styrene-maleic anhydride copolymers, and emulsion type binders. However, no binder has been found so far that has excellent thermal responsiveness (coloring density) and is practically satisfactory in terms of sticking properties, background coloring, background fogging, etc.

[Problems that Haimei attempts to solve]

In view of the above-mentioned problems, the inventors of the present invention have conducted intensive studies in order to create a binder that has excellent thermal responsiveness and is free from sticking properties, background color development, and background fogging, and has found that dyes, color developers, The dispersibility of pigments or binder strength is poor, and sticking occurs, but it is difficult to maintain color development.
We have discovered polyvinylpyrrolidone that exhibits excellent effects on skin fogging. After further investigation, we discovered that the above problems could be solved if a water-soluble copolymer obtained by copolymerizing polyvinylpyrrolidone with acrylamide and/or methacrylamide was used as a binder. The invention has been completed.

[Means to solve the problem]

The present invention contains 1% of acrylamide and/or methacrylamide and 20-50% of tovinyl bi-Olidone.
This invention relates to a binder for heat-sensitive recording paper consisting of an aqueous solution of any water-soluble copolymer (wt%).

〔Example〕

The heat-sensitive recording binder of the present invention is comprised of an aqueous solution of a water-soluble copolymer of 50 to 801% by weight of acrylamide and/or methacrylamide and 20 to 20% by weight of N-vinylpyrrolidone.

The acrylamide and/or methacrylamide has an affinity with paper and is a component for increasing binder force, that is, bonding force with paper, but the binder force is based on the 1CON82 group present in the molecule. It is believed that there are.

The N-vinylpyrrolidone is a component that has background coloring and background fogging prevention effects, but the mechanism of the background coloring and background fogging prevention effects is currently unknown.

Acrylamide and/or contained in the water-soluble copolymer
Alternatively, if the amount of methacrylamide is less than 50% by weight, that is, if the amount of N-vinylpyrrolidone exceeds 50% by weight, the color development of the thermal recording paper will be poor, and the amount of acrylamide and/or methacrylamide will be less than 50% by weight. In other words, N-vinylpyrrolidone is 2011%
If it is less than this, the effect of preventing background color development and background fogging will decrease, which is not preferable.

Next, a method for producing the binder of the present invention will be described, but the present invention is not limited to this method, and may be produced by other methods.

acrylamide and/or methacrylamide;
The total concentration of monomers including N-vinylpyrrolidone is
Dilute with water to a concentration of 10 to 35% by weight, preferably 15 to 30% by weight, add a polymerization initiator, and heat at 60 to 90°C.
The reaction is carried out in a nitrogen atmosphere at a humidity range of 0.5 to 3 hours.

Specific examples of the polymerization initiator include azo compounds such as azobisisobutyronitrile and azobiscyanobalate; persulfates such as ammonium persulfate and potassium persulfate; hydrogen peroxide, t-butyl peroxide, etc. The amount of the polymerization initiator used is preferably 0.1 to 3% by weight based on the monomer.

When the binder of the present invention obtained as described above has a low molecular weight copolymer, the coating strength of the obtained thermal recording paper is low and cannot be put to practical use. The viscosity increases and workability deteriorates, so do not lower the temperature to 25.
℃, viscosity at 20% concentration is 200~IO, 0O
The temperature and amount of polymerization initiator at the time of the first reaction are selected in order to adjust the OCP.

The binder for thermal recording paper of the present invention can be used in the same manner as conventional binders, but it can also be used in combination with other water-soluble and water-dispersible binders.

Furthermore, a color developer, filler, or color former may be added as appropriate.

Next, a more detailed explanation will be given using Examples and Comparative Examples.

Example 1 70 parts of acrylamide (1 part of heavy duty, same hereinafter), 30 parts of N-vinylpyrrolidone, and 400 parts of water were placed in a three-necked flask equipped with a thermometer and a nitrogen introduction tube, and nitrogen was bubbled for one hour. After that, raise the internal temperature to 70℃! Then, 1.0 parts of azobisisobutylnitrile was added as a polymerization initiator to initiate polymerization. After polymerization reaches the maximum temperature, 2
The binder was obtained as a 20% aqueous solution of the copolymer.

The viscosity of the obtained binder was 4.0OOc at a temperature of 25°C.
It was P.

Next, 2.5 parts of the obtained binder, 0.75 parts of crystal violet lactone (3,3-bis(P-dimethylaminophenyl)-6-dimethylaminophthalide) as a coloring agent, and 24.5 parts of water were added. I mixed it up and got solution A.

5.0 parts of the obtained binder, 3.0 parts of bisphenol A (4,4°-isopropylidene diphenol) as a color developer, 4.0 parts of calcium carbonate as a filler, and 0.0 parts of stearic acid amide as a color developer. 5 parts and 40.0 parts of water were mixed to obtain Solution B.

Next, liquid A and liquid B were each mixed in a ball mill for 48 hours, and then mixed and sufficiently stirred to obtain a coating liquid.

The obtained coating liquid was applied to 489/rrt high-quality paper using a wire bar, and the amount of adhesion when dry was 4.0 g/y.
A thermosensitive recording paper was obtained by adjusting the temperature to be d.

As a characteristic of the obtained thermal recording paper, a commercially available thermal facsimile (Panafax manufactured by Matsushita Electric Power Co., Ltd.)
UF-920) Please record the item mark '44tt.

Color density, background fog, and sticking property were measured using the following methods.

The results are shown in Table 1.

(Coloring density) The coloring density of the heat-sensitive layer surface of the thermal recording paper was measured using a Macbeth densitometer (R
D-514 Latten 8106), and those with a color density of 1.2 or higher were considered to have passed.

(Background fog) The color density of the non-printed heat-sensitive layer surface of the heat-sensitive recording paper was measured using a Macbeth densitometer fRD-514 Ratten $106), and those with a color density of 0.12 or less were judged to have passed.

(Sticking property) The degree of occurrence of the sticking phenomenon was visually evaluated. The evaluation criteria are as follows.

(Evaluation criteria) O: Printed image is not faded. ×: Printed image is faded. Examples 2 to 4 and Comparative Examples 1 to 2 70 parts of acrylamide of Example 1 and 30 parts of N-vinylpyrrolidone were added to the first A thermosensitive recording paper was obtained in exactly the same manner as in Example 1 except that the composition was changed to that shown in the table.

The properties of the obtained thermal recording paper were measured in the same manner as in Example 1.

The results are shown in Table 1.

〔Effect of the invention〕

The binder for thermal recording paper of the present invention does not reduce thermal responsiveness (coloring density) and does not develop background color or background fog, so it can be used as high-speed thermal recording paper for facsimiles, high-speed printers for ticketing systems, high-speed printers for POS systems, etc. This has the advantage that it can be suitably applied.

Claims (1)

[Claims] 1 Acrylamide and/or methacrylamide 5
A binder for thermal recording paper comprising an aqueous solution of a water-soluble copolymer of 0 to 80% by weight and 20 to 50% by weight of N-vinylpyrrolidone.