JPH03147885A - Color former sheet for non-carbon pressure sensitive paper - Google Patents

Abstract

PURPOSE:To obtain a color former sheet for non-carbon pressure sensitive paper which can prevent the deterioration of a color forming performance under storage and an unwanted color contamination under storage during production processes by incorporating a phosphoric-esterified wheat starch of a specific particle diameter in the color former sheet coated with color former-containing microcapsules and a binder. CONSTITUTION:In a color former sheet, a phosphoric-esterified wheat starch having an average particle diameter of 10-60mum is incorporated, an alkali thickening-type styrene-butadiene copolymer emulsion is used as a binder, and a synthetic resin is used as a capsule film of a microcapsule. In this manner, an apparent effect can be obtained. The phosphoric-esterified wheat starch can be produced by a method in which an orthophosphoric liquid prepared to be pH5-6.5 is infiltrated into a wheat starch, predried, heated, and classified. The loading amount of the phosphoric-esterified wheat starch is 15-100 pts.wt. per 100 pts.wt. of the microcapsules. This color former has no or little possibility of unwanted color contamination and the reduction of a color forming performance under storage caused by light and nitrogen oxides.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Industrial Application Field The present invention relates to carbonless pressure-sensitive copying paper, and more particularly to microcapsules containing an electron-donating dye of a color former sheet for carbonless pressure-sensitive copying paper. The present invention relates to a coloring agent sheet for carbonless pressure-sensitive copying paper containing a new substance that prevents a decrease in coloring ability due to light and prevents unnecessary capsule destruction.

(B) Prior Art A carbonless pressure-sensitive copying paper using an electron-donating dye and an electron-accepting acidic substance is disclosed in, for example, US Pat. No. 2,505,489.
As described in detail in the specification of No. 4480052, basically, a color former sheet coated with an electron-donating dye (hereinafter referred to as a color former) and an electron-accepting acidic substance (hereinafter referred to as a color developer) are used. It consists of a color developer sheet coated with
The coloring agent is dissolved in a high boiling point solvent and incorporated into microcapsules.

Microencapsulation is carried out by a coacervation method, an in-situ method, an interfacial polymerization method, etc. Coloring agents include crystal violet lactone, 3-3bis(P-dimethylaminophenyl)phthalide, and 3-(P-dimethylaminophenyl)phthalide.
Acyl derivatives such as triallylmethanephthalide series such as dimethylaminophenyl)-3-(2-methylindol-3-yl)-6-dimethylaminophthalide and benzoyl, aminoyl, and VivaOyl of methylene blue; 3 −
diethylamino-6-methyl-7-chlorofluorane,
There are xanthine phthalides such as 3-diethylamino-7-dibenzylaminofluorane, which are also used in the present invention.

Examples of high boiling point solvents that dissolve color formers include alkylnaphthalenes represented by diisopropylnaphthalene, diallylakanes represented by 1-phenyl-1-xylylethane, alkyl biphenyls represented by isopropylbiphenyl, and triallyl derivatives thereof. Aromatic hydrocarbons such as dimethanes, alkylbenzenes, benzylnaphthalenes, diallylalkylenes, and allylindanes; Carboxylic acid ester compounds represented by dibutyl phthalate and dioctyl maleate; represented by tricresyl phosphate phosphoric acid ester compounds; vegetable oils such as castor oil, soybean oil, and cottonseed oil, or their modified oils; high-boiling fractions of natural products (consisting of aliphatic hydrocarbons) such as mineral oils, etc.
Also used in the present invention.

The color developer may be an inorganic color developer such as acid clay, natural clay minerals such as acpal guide, activated clay obtained by treating acid clay with mineral acid, or semi-synthetic solid acids described in JP-A-57-15996. As organic color developers, various phenolic compounds, novolac type phenolic resins, polyvalent metal salts of aromatic carboxylic acids, and recently proposed JP-A-63-18672 are used.
Polyvalent metallized salicylic acid resins described in No. 9 and No. 63-254124 have already been used.

Carbonless pressure-sensitive copying paper is produced by applying microcapsules containing a color former to the back side of a support such as paper, drying the color former sheet to the top paper, and applying a color developer to the surface of the support such as paper and drying. The developed color developer sheet is used as the bottom paper, and when the coated surfaces of the top paper and the bottom paper are overlapped and printed under pressure using a writing or dot printer, the microcapsules in the pressure area are destroyed and the color developer and color developer that flow out are destroyed. Upon contact, a color reaction occurs and a colored image is obtained.

Furthermore, since carbonless pressure-sensitive copying paper requires and is required to copy a large number of sheets, a color developer is coated on the surface of a support such as paper, and microcapsules are coated on the back side of the paper and then dried. A large number of copies can be made by combining a large number of lower sheets and inner sheets, such as upper sheet, middle sheet, middle sheet, etc., using a single sheet containing the agent as an inner sheet.

(C) Problems to be Solved by the Invention Carbonless pressure-sensitive copying paper, which requires or requires a large number of copies, is mainly used as slips and office paper.

Normally, the important characteristics when used as slips and office paper are: - Clear and high color image density.

■No decline in coloring ability during storage.

■No unnecessary colored stains occur.

etc. Increasing the amount of color former or color developer applied is effective as a method for making colored images clear and high in density. However, it is preferable to use organic color developers, and among them, polyvalent metallization of salicylic acid resin is effective. Particularly preferred. A method to prevent the deterioration of coloring ability due to the influence of sunlight, fluorescent lights, indoor nitrogen oxides, etc. during storage is to add ultraviolet absorbers, antioxidants,
There are methods of mixing and dissolving anti-aging agents, or mixing white pigments such as zinc oxide and titanium oxide in the coating layer of the color developer sheet, but these color developer sheets are economically expensive and lack preventive effects. There are also disadvantages such as the color developer sheet is subject to significant wear, and the colored image is pale and lacks saturation (watery).

In addition, in the carbonless copying paper manufacturing process or printing process, as a method for preventing unnecessary colored stains due to slight contact, rubbing, etc., it is possible to
The fine powder of starch or starch derivative described in Japanese Patent No. 7-1178 is used. Dye-free microcapsules containing an evaporable liquid such as xylene or a non-evaporable liquid described in Japanese Patent Publication No. 47-20972 are used. Heat-expandable microspheres with an average particle diameter of 30 μm and containing hydrocarbon are used as capsule membranes made of the vinylidene chloride-acrylic acid ester copolymer described in JP-A-48-32013. Unexamined Japanese Patent Publication 1973
An aggregate of polyvinyl chloride resin particles having a glass transition point (Tg) or lower as described in Japanese Patent No. 78422 is used. Japanese Patent Application Publication No. 5
A tertiary material such as kaolin with a diameter of 20 to 35 μm as described in Japanese Patent No. 4-143325 is used. Polyurethane particles having an average particle diameter of 3 to 150 μm as described in Japanese Patent Publication No. 64-3673 are used. The cellulose fiber powder described in US Pat. No. 2,711,375-u is used. Although different from the subject of the invention, Japanese Patent Application Laid-Open No. 5F-128492 discloses a method for preventing colored stains on self-coloring carbonless pressure-sensitive double paper in which a color forming agent and a color developer are provided in the same coating layer. 10~
30 μm steel powder particles are used. Tokuko Showa 64-1035
Examples include using a pulp powder having a weight average fiber length of 20 to 80 μm as described in Report No. 7.

When the present inventors confirmed the effect as a so-called buffering agent (stilt agent) to prevent these colored stains through experiments, they found that cellulose fiber powder (Bap Jlp powder) and
The fine powder of starch or starch derivative having a diameter of 40 .mu.m caused little color staining and was usable for practical use. However, since cellulose fiber powder has a high water absorption property, the viscosity becomes high when an air knife coater coating solution for a color former sheet is prepared. To do this, the water is diluted and applied to lower the viscosity, which increases the drying load on the coater and increases thermal energy. Furthermore, fine powders of starch and starch derivatives were not effective in preventing a decrease in coloring ability during storage.

Therefore, an object of the present invention is to provide an excellent carbonless pressure-sensitive copying paper coloring agent sheet that prevents the coloring ability of the coloring agent sheet from deteriorating during storage and does not cause unnecessary coloring stains during the manufacturing process or during storage. The goal is to provide the following.

(D) Means for Solving the Problems As a result of extensive experiments and research, the inventors of the present invention have found an excellent carbonless pressure-sensitive copy that does not lose its coloring ability during storage and does not cause coloring stains. Developed a color former sheet for paper.

That is, in the present invention, the color former sheet has an average particle size of 10 to 60 μm.
This objective was achieved by including phosphoric acid esterified wheat starch of m, and was further achieved by using an alkali-thickened styrene-butadiene copolymer emulsion as a binder and by making the capsule membrane of the microcapsules a synthetic resin. You can get the following effect.

The phosphoric acid esterified wheat starch used in the present invention is a monoester type phosphoric acid ester wheat starch including a diester type. The average particle diameter is 10 to 60 μm, particularly preferably 15 to 30 μm.

If it is less than 10 μm, colored stains cannot be prevented, and if it exceeds 60 μm, it may be difficult to prevent color stains during production using an air knife coater for a long time.
Coarse wheat starch particles are scraped off by the air knife, and the amount of wheat starch increases accordingly, making it impossible to obtain a uniform coloring agent sheet.

The method for producing phosphoric acid esterified wheat starch used in the present invention involves impregnating wheat starch with an orthophosphoric acid solution adjusted to pH 5 to 6.5, pre-drying the water to 10%, and then
It is obtained by heating at ~170°C for 1 to 15 hours and then classifying. The reason why the effect of preventing the decline in coloring ability during storage is obtained is not clear, but it is thought to be related to the decrease in hydrophilicity of the wheat starch surface due to phosphoric acid esterification.

The amount of phosphoric acid esterified wheat starch used in the present invention is 15 to 100 parts by weight, particularly preferably 25 to 60 parts by weight, per 100 parts by weight of microcapsules.

If it is less than 15 parts by weight, the effect of preventing colored stains will be small;
If the amount exceeds parts by weight, the density of the colored image will decrease.

The alkali-thickened styrene-butadiene copolymer emulsion used in the present invention is described in JP-A No. 64-49678, and has the property that the viscosity increases when the pH of the coating liquid shifts to the alkaline side. It is an emulsion.

The capsule membrane material of the microcapsules used in the present invention is
Synthetic resins such as polyurethane, epoxy resin, polyurea, urea-formalin resin, melamine-formalin resin, etc., which have moisture and heat resistance and solvent resistance, and particularly preferably a capsule membrane of melamine-formalin resin microencapsulated by an in-situ method. It is.

In the present invention, a water-soluble polymeric binder such as polyvinyl alcohol, an antifoaming agent, a penetrating agent, a dispersing agent, an alkaline agent for increasing pH, etc. are mixed as desired to form a coating liquid for a color former sheet.
Coating and drying is done using an air knife coater, three-roll coater, bar coater, or curtain coater.

(E) Examples Preferred embodiments and excellent effects of the present invention will be specifically explained below using the most typical examples. Note that all parts below are parts by weight, and all % represents weight %.

Example 1 200 parts of high boiling point oil (KMC-113 manufactured by Kureha Chemical Co., Ltd.) in which 7 parts of crystal violet lactone (CVL) was dissolved
) to 5% styrene maleic anhydride copolymer aqueous solution (pH
5,0) and emulsified to have an average particle size of 6 μm.

Next, 20 parts of 40% melamine-formalin initial condensate water-soluble acid (Sumilets Resin, manufactured by Sumitomo Chemical Co., Ltd.) was added to the above emulsion, the temperature was brought to 75°C, and after reacting for 2 hours, 20%
The pH was adjusted to 9.0 with an aqueous sodium hydroxide solution, and the mixture was cooled to room temperature to obtain a 40% microcapsule dispersion.

The 40% microcapsule dispersion thus obtained was used as a coating liquid for color former sheets in the following formulation. Apply this coating liquid to 140 g/n (3.5 g/n on high-quality paper).
The coating was applied using an air knife coater and dried to obtain an rrf (absolutely dry solid content) to obtain a coloring agent sheet.

[Coating liquid for color former sheet]

40% microcapsule dispersion 250 parts Phosphated wheat starch 25 parts (average particle size 10 μm
) 48% alkali-thickened styrene-butadiene copolymer emulsion 42 parts added water
400 parts Example 2 The 40% microcapsule dispersion obtained in Example above was used as a coating liquid for a color former sheet in the following formulation.

The coating amount of this coating liquid is 3゜5g/rr on high quality paper of 140 g/rd. (absolutely dry solid content) was coated and dried using an air knife coater to obtain a coloring agent sheet.

[Coating liquid for color former sheet]

40% microcapsule dispersion 250 parts Phosphated wheat starch (average particle size 10 μm) 50 parts 48% alkali-thickened styrene-butadiene copolymer emulsion
50 parts added water 52
0 parts Example 3 The 40% 74 micropcel dispersion obtained in Example 1 was made into a coating liquid for a color former sheet in the following formulation.

This coating liquid was applied to a high-quality paper with a basis weight of 40 g/m and an amount of 4°5.
The coating was applied using an air knife coater and dried to obtain a color forming agent sheet so as to give g/rtf (absolutely dry solid content).

[Coating liquid for color former sheet]

40% microcapsule dispersion 250 parts Phosphated wheat starch (average particle size 10 μm) 100 parts 48% alkali-thickened styrene-butadiene copolymer emulsion
65 parts added water 74
0 parts Example 4 A coloring agent sheet was obtained in the same manner as in Example 2, except that the same amount of phosphoric acid esterified wheat starch (average particle size 10 μm) used in Example 2 was replaced with an average particle size of 30 μm.

Example 5 A coloring agent sheet was obtained in the same manner as in Example 2, except that the phosphorylated wheat starch (average particle size 10 μm) used in Example 2 was replaced with an average particle size of 60 μm.

Comparative Example 1 The phosphoric acid esterified wheat starch (average particle size 10 μm) used in Example 2 was replaced with corn starch (average particle size 10 μm).
A coloring agent sheet was obtained in the same manner except that the same amount was replaced with m).

Comparative Example 2 A coloring agent sheet was obtained in the same manner as in Example 2, except that the same amount of phosphoric acid esterified wheat starch (average particle diameter 10 μm) was replaced with potato starch (average particle diameter 10 μm).

Comparative Example 3 A coloring agent sheet was obtained in the same manner as in Example 2, except that the same amount of phosphoric acid esterified wheat starch (average particle diameter 10 μm) was replaced with rice flour (average particle diameter 10 μm).

Comparative Example 4 A color former sheet was obtained in the same manner except that the same amount of the 48% alkali-thickened styrene-butadiene copolymer emulsion used in Example 2 was replaced with a 48% styrene-butadiene copolymer emulsion. .

Comparative Example 5 A color former sheet was obtained in the same manner except that the same amount of phosphoric acid esterified wheat starch (average particle size 10 μm) used in Example 2 was replaced with acetate esterified wheat starch (average particle size 10 μm). Ta.

Comparative Example 6 A coloring agent sheet was obtained in the same manner as in Example 2, except that the same amount of phosphoric acid esterified wheat starch (average particle size 10 μm) used in Example 2 was replaced with an average particle size of 5 μm.

Comparative Example 7 A coloring agent sheet was obtained in the same manner as in Example 2, except that the same amount of phosphoric acid esterified wheat starch (average particle size 10 μm) used in Example 2 was replaced with an average particle size of 75 μm.

(Test method) ◎The non-uniformity of the color former sheet obtained by using phosphated wheat starch with an average particle size of over 60 μm in the color former sheet coating liquid for a long time was evaluated.

The coating liquids for color former sheets of Examples r to 5 and Comparative Examples 1 to 3 were applied for 1 hour using an air knife coater. Immediately after the start of coating, the color former sheet was taken at the end of the coating, and the smoothness of the coated surface was measured using a Beck smooth needle.

Furthermore, it was combined with a commercially available Mitsubishi NCR paper (N-40), passed through a super calendar to develop color, and the colored area was measured with a color difference meter to obtain the following values. The smaller the value, the higher the color density.

Reflectance of color developing area Color density (%) = x, 100 Reflectance of blank paper area ◎Evaluation of color stain
Layer a commercially available Mitsubishi NCR paper with a width of 15 cm and place 350
A 0g colored stain test weight was placed on the paper and the lower paper was pulled at a constant speed.The degree of colored stain on the lower paper was measured using a color difference meter, and the following values were determined. The larger the value, the less the colored stain.

Reflectance of colored area Colored stain (%') = X100 Reflectance of white paper area The agent sheet was combined with a commercially available Mitsubishi NCR paper sheet, and the mixture was passed through a super calendar to develop color, and the colored area was measured with a densitometer to obtain the following values. The larger the value, the less the decline in coloring ability.

D concentration after exposure Coloring ability (%) = X100 Untreated D concentration Table 1 Table 2 Table 3 Evaluation ○ Excellent effect, △ No effect, × Problematic, (F) Effect Microcapsules containing a color former and binding As mentioned above, the coloring agent sheet coated with the coloring agent contains phosphoric acid esterified wheat starch having an average particle size of 0 to 60 μm according to the present invention,
Furthermore, by using an alkali-thickened styrene-butadiene copolymer emulsion as a binder and using a synthetic resin for the capsule membrane of the microcapsules, there is no unnecessary coloring and staining, and it is resistant to light and nitrogen oxides during storage. We were able to develop an excellent color-forming agent sheet for carbonless pressure-sensitive copying paper with little loss of color-forming ability.

Claims (2)

[Claims] (1) Carbonless pressure-sensitive copying in which synthetic resin membrane microcapsules containing an electron-donating dye and a coloring agent sheet coated with a binder contain phosphoric acid esterified wheat starch with an average particle size of 10 to 60 μm. Coloring agent sheet for paper. (2) The color former sheet for carbonless pressure-sensitive copying paper according to claim (1), wherein the binder is an alkali-thickened styrene-butadiene copolymer emulsion.