JP2898998B2 - Carbonless pressure-sensitive copy paper - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a coating composition for carbonless copying paper having a coating layer of microcapsules, and more particularly to a carbonless pressure-sensitive copying paper. Color development, stain resistance,
The present invention relates to a carbonless pressure-sensitive copying paper excellent in high density smear suitability.

(B) Prior Art Carbonless pressure-sensitive copying paper is usually produced by coating a microcapsule containing a colorless leuco dye and a color developing agent on a paper serving as a support, each of which is independently applied to the support. It is coated and used as upper paper and lower paper, and is coated on both sides and is generally used as middle paper. A plurality of these sheets are appropriately combined, and the microcapsules are destroyed by applying physical pressure by writing pressure, typing pressure, etc., and the leuco dye in the capsules is colored by contact with the developer to form a recorded image. It is obtained.

In general, the following two conditions are required for the quality conditions required for carbonless pressure-sensitive copying paper and the main conditions required for production.
Items.

1. A dark and clear image can be obtained in a short time, and there is no deterioration over time.

2. When color development is not intended, that is, ・ Manufacturing process of carbon-free pressure-sensitive copy paper ・ Various printing and cutting processes ・ No contamination during storage and handling in sheet or rolled state .

It is difficult to fully satisfy both of the above two items because they have conflicting properties.However, it is necessary to devise factors such as microcapsule manufacturing conditions, types and amounts of buffers, and types and amounts of binders. Have made improvements and many suggestions have been made for them.

Not only in the production of pressure-sensitive copying paper, but also in the production of general coated paper, the high concentration of the coating liquid is used to reduce the energy during drying of the coated paper as much as possible and to increase the coating speed. Is being planned.

As the means, improvement of the liquid property of the coating liquid, a method of applying the coating method and the like have been performed. In particular, in pressure-sensitive copying paper, a method using a low-viscosity microcapsule emulsion or a low-viscosity binder, and Improvements have been made by methods such as scraping off the coating liquid.

However, when high-density coating is performed by combining the above-described means, the obtained pressure-sensitive copying paper causes a decrease in stain resistance due to rubbing during actual use, greatly increasing the quality as a carbonless pressure-sensitive copying paper. The result is impaired.

As described above, not only the design of the coating liquid but also the coating method and the liquid concentration at the time of coating greatly affect the quality of the multiplication carbonless pressure-sensitive copying paper.

(C) Problems to be Solved by the Invention The present invention is intended to improve the quality of conventional carbonless pressure-sensitive copying paper.
And to overcome the problems in the production, and specifically, to increase the color development sensitivity.

That is, a clear image can be obtained even on a large number of copies.

Prevents contamination when color development is not intended.

In other words, as the types of contamination: ・ Dynamic friction stains generated when rubbing; ・ Static pressure stains applied during storage in rolled state, printing, or guillotine cutting; ・ Leaving in a heated or humidified state for a long time Although dirt and the like resulting from capsule destruction at the time can be raised, in any case, excellent stain resistance is exhibited.

Improves high-concentration smear suitability.

That is, even at a low scraping pressure, specifically a low air discharge pressure with an air knife coater, the coating liquid can be easily scraped off, and the deterioration of the characteristics can be minimized.

An object of the present invention is to provide a carbonless pressure-sensitive copying paper that satisfies all of the above items.

(D) Means for Solving the Problems As means for solving the above problems, a composition having a pH of 7 or more containing a microcapsule containing an electron-donating color forming agent, a buffer, a binder alkali-soluble emulsion and water is supported. It is solved by providing it on the body.

The alkali-soluble emulsion of the present invention, for example,
It is produced by copolymerizing a relatively hydrophilic monomer such as an acrylate compound such as methyl acrylate or ethyl acrylate, or a methacrylate compound, or vinyl acetate with an unsaturated carboxylic acid. Examples of the type of the saturated carboxylic acid include unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, isocrotonic acid, and vinyl acetic acid, and unsaturated dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid.

Further, the alkali-soluble emulsion of the present invention keeps its form as an emulsion on the acidic side, but has the property that the carboxy group is neutralized, dissociated and dissolved by the addition of an alkali, and a water retention or thickening action is produced. . Water retention or thickening action depends on the type of unsaturated carboxylic acid, the type of copolymer component, and the copolymerization ratio.For example, in the type of unsaturated carboxylic acid, acrylic acid is better than methacrylic acid or itaconic acid Acrylic acid copolymer emulsion is particularly preferred in the present invention because of its large water retention or thickening effect.

The alkali-soluble emulsion used in the present invention has a solid content of 5%, a pH of 7.0, and a B-type viscosity at a temperature of 20 ° C. and 60 rpm of 50%.
It is preferably between 0 and 20,000 cps. If the viscosity is less than this range, the stain resistance decreases, which is not preferable.

On the other hand, if the viscosity is higher than this, the suitability for high-concentration smearing is impaired, resulting in an undesirable result.

It is particularly preferable that the number of parts of the alkali-soluble emulsion to be added is 0.2 to 20 parts per 100 parts of the capsule solid.

If the amount is less than this range, the stain resistance tends to decrease, and if the amount is greater than this range, the color development sensitivity tends to decrease and the suitability for high-density smearing tends to be impaired.

The composition of the present invention, that is, the pH of the coating solution is in the range of 7 to 12, and the solid concentration is in the range of 15 to 40%, for example, the solid concentration.
B-type viscosity at 20% adjustment (20 ℃, 60rpm) is 10 ~ 100cps
The solid content and viscosity are adjusted according to the coating method.

In addition, if necessary, various additives such as a liquid property adjusting agent (viscosity and pH), an antifoaming agent, various activators, waxes and lubricants are used based on ordinary techniques.

As the color developing agent for the color developing sheet used in combination with the upper paper obtained by the present invention, a known color developing agent such as a phenol resin compound and a metal salicylate compound is used.

The coating liquid of the present invention is applied with a normal coating liquid (coater),
It is dried, but specifically, air knife coater, blade knife coater, bar coater, roll coater,
A size press coater or the like is used.

As the support, acid paper or neutral paper mainly containing cellulose fibers is usually used, but synthetic paper may be used at all.

(E) Example Next, an example and a comparative example are shown.

 The following numerical values are all expressed in parts by dry weight.

Example 1. Hydrophobic substance Crystal violet lactone (CVL) (2 g) Benzoyl leucomethylene blue (BLMB) (1 g) dissolved in 100 g of KMC-113 (trade name, oil manufactured by Kureha Chemical Co., Ltd.) by heating.

The above hydrophobic substance (dye oil solution) was emulsified in 100 g of a 5% aqueous solution of pH 4.0 in which Scripset 520 (Monosanto, styrene-maleic anhydride copolymer) was dissolved together with a small amount of sodium hydroxide. . Melamine 10g, 37
When 25 g of 25% formalin and 65 g of water were adjusted to pH 9 with sodium hydroxide and heated to 60 ° C., the mixture became transparent in 15 minutes, and a melamine-formalin precondensate was obtained. This initial condensate was added to the emulsion, the solution temperature was adjusted to 60 ° C., and stirring was continued. As a result, the formation of capsules was confirmed in 30 minutes. The capsule particle size was about 5 microns.

100 parts of the microcapsules having the melamine-formaldehyde resin as a wall membrane, 35 parts of wheat starch as a buffer, and 48% carboxy-modified SBR as a binder
20 parts solid part, Primal ASE-75 manufactured by Rohm and Haas Co., Ltd. as alkali-soluble emulsion (solid content 5%, PH7.0, B-type viscosity at 20 ° C 60 rpm 4,000
0cps) A coating liquid for carbonless copy paper having a solid content of 25% and a solid content of 5 parts was obtained. 20% aqueous solution of caustic soda
Water was added to prepare a coating solution having a solid content of 20% and a pH of 7.2. The B-type viscosity of this coating solution at 20 ° C. and 60 rpm was 22 cps.

40 g / m ^{2 of} this coating solution was applied by air knife coating method.
When coated continuously on high quality paper at a speed of 80 m / min, a carbonless pressure-sensitive copying paper excellent in color development and stain resistance was obtained.

Example 2. The amount of the 20% aqueous sodium hydroxide solution added in Example 1 was increased,
A coating solution having a solid content of 20% and a pH of 11.0 was prepared. 20 ℃ of this coating liquid,
The B-type viscosity at 60 rpm was 20 cps.

When this coating solution was continuously applied by the A knife coating method in the same manner as in Example 1, a carbonless pressure-sensitive copying paper having good color development and stain resistance was obtained.

Example 3 Hydrophobic Substance A substance obtained by heating and dissolving 2 g of crystal violet lactone (CVL) and 1 g of benzoyl leucomethylene blue (BLMB) in 100 g of KMC-113 (trade name, oil manufactured by Kureha Chemical Co., Ltd.).

50% of a 10% aqueous solution of a hydrolyzate of EMA-31 (manufactured by Monosanto, ethylene-maleic anhydride copolymer), 5 g of urea, 0.5 g of resorcinol and 100 g of water were adjusted to pH 3.5 with a 20% aqueous sodium hydroxide solution. Prepared and emulsified the above hydrophobic substance (dye oil solution).

12.5 g of 37% formalin was added to the system, and the mixture was stirred at 55 ° C. for 2 hours. After formation of capsules was observed, the system was cooled to room temperature. The capsule particle size was about 4 microns.

The obtained urea-formaldehyde resin has 100 parts of solid microcapsules having a wall film, 30 parts of cellulose fine powder as a buffer, 17 parts of 20% PVA solid as a binder,
Primal ASE-7 as an alkali-soluble emulsion
A coating liquid for carbonless copy paper having a solid content of 23% and containing 0.5 parts by weight of 5 solid parts was obtained. To this, a 20% aqueous solution of caustic soda and water were added to prepare a coating solution having a solid content of 20% and a pH of 8.0. 20
The type B viscosity at 60 ° C. and 60 rpm was 32 cps.

When the coating solution was applied with an air knife coater in the same manner as in Example 1, a carbonless pressure-sensitive copying paper having good color development and stain resistance was obtained.

Comparative Example 1 A coating solution having a solid content of 20% and a pH of 5.5 was prepared in the same manner as in Example 1 except that the 20% aqueous sodium hydroxide solution was not used. The B-type viscosity of this coating solution at 20 ° C. and 60 rpm is 10 cps
Met.

Comparative Example 2 A coating solution having a solid content of 20% and a pH of 6.0 was prepared in the same manner as in Example 3 except that the aqueous 20% sodium hydroxide solution was not used. The B-type viscosity of this coating solution at 20 ° C. and 60 rpm was 23 cps.

Comparative Example 3 Alkali-soluble emulsion ASE-7 used in Example 1
The same composition was used except for using No. 5. PH at 20% solids
The B-type viscosity at 7.2, 20 ° C. and 60 rpm was 10 cps.

Comparative Example 4 Alkali-soluble emulsion ASE-7 used in Example 2
A coating liquid was prepared with the same composition except for using No. 5. At a solid content of 20%, the viscosity of the B-form at pH 11.0, 20 ° C. and 60 rpm is 10c.
ps.

Comparative Example 5 Alkali-soluble emulsion ASE-7 used in Example 3
A coating liquid was prepared with the same composition except for using No. 5. B-type viscosity at 20 ° C and 60 rpm at a solid content of 20% and pH 8.0 is 25 cps
Met.

The coating solutions of Comparative Examples 1, 2, 3, 4, and 5 were applied using an air knife coater in the same manner as in the examples. Comparing the obtained carbonless copy paper under Examples 1, 2, and 3, when the paper was rubbed against the lower paper, the stain was remarkable, and the entire surface of the lower paper was easily colored during use. It had poor commercial value.

(F) Effect of the Invention As is clear from the above, the alkali-soluble emulsion as in the present invention is added to the coating solution containing the microcapsules containing the electron-donating color former, and the support is smeared at a pH of 7 or more. As a result, it was possible to obtain a carbonless pressure-sensitive copying paper having excellent effects in stain resistance and suitability for high-density smearing without impairing the color developability.

Claims (2)

(57) [Claims] 1. A microcapsule containing an electron-donating color former, a buffer, a binder, and a copolymer formed by copolymerization of an unsaturated carboxylic acid with one or more monomers selected from (meth) acrylate compounds and vinyl acetate. A carbon-free pressure-sensitive copying paper provided on a support by adjusting the composition containing 0.2 to 20 parts of the solid portion based on 100 parts of the above microcapsules to the alkali-soluble emulsion to be adjusted to pH 7 to 12. 2. An alkali-soluble emulsion having a solid content of 5.
%, PH 7.0, B-type viscosity at 20 ° C. and 60 rpm is 500 to 20,000.
2. The carbonless pressure-sensitive copying paper according to claim 1, wherein the pressure-sensitive copying paper has 0 cps.