JPS63137886A - Composition of developer for pressure-sensitive recording paper - Google Patents

Abstract

PURPOSE:To improve the coloring performance, the surface strength and the antifading performance, by containing a hydroxide or an oxide of multivalent metal together with an aqueous polymer emulsion where an aromatic carboxylic acid metal salt is contained in emulsion particles in the composition of a developer for pressure-sensitive recording paper. CONSTITUTION:An aqueous polymer emulsion where an inorganic pigment and an aromatic carboxylic acid multivalent metal salt are contained in emulsion particles and a hydroxide or an oxide of multivalent metal are contained in the composition of a developer for pressure-sensitive recording paper. Preferably, the aromatic carboxylic acid multivalent metal salt is added by 2-100wt% for 100wt% of polymer in the aqueous polymer emulsion. Any monomer composition having adhesive force may be employed for composing the polymer in the aqueous polymer emulsion. Multivalent metal means a metal having valency higher than 2, and preferably 10wt% or more of its hydroxide or oxide is added for 100wt% of inorganic pigment.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a color developer composition for pressure-sensitive recording paper that has excellent color development and surface strength, and furthermore has excellent fade resistance.

(Prior art) Pressure-sensitive writing paper usually consists of an upper paper coated with microcapsules containing an electron-donating colorless leuco dye and an organic solvent, and an electron-accepting color developer that reacts with the colorless leuco dye to develop color. The microcapsules are destroyed by printing under pressure with a ballpoint pen or typewriter, etc., on top of the upper paper, and the colorless leuco dye in the microcapsules becomes organic. It moves to the lower paper together with the solvent and reacts with the color developer to form a colored recorded image on the coated surface of the lower paper. It is also possible to make multiple copies by inserting an inner sheet with a color developer layer on the front side and a microcapsule layer on the back side between the upper sheet and the lower sheet. Still another form is what is called a single recording sheet or single coloring paper in which both the microcapsules and color developer are coated on the same side of the sheet. The color developer sheet as used in the present invention includes all sheet-like materials containing a color developer, regardless of their form, as color developer sheets for pressure-sensitive copying paper.

Electron-accepting color developers used in color developer sheets include acid clay minerals such as acid clay, activated clay, attapulgide, and bentonite; acidic polymers such as p-phenylphenol resin; and aromatics such as salicylic acid derivatives. Examples include metal salts such as zinc salts of group carboxylic acids and aromatic carboxylic acids.

These color developers are usually used alone or in combination. The color developing sheet is made by adding inorganic pigments such as kaolin, calcium carbonate, talc, etc. to the coated area containing the color developer described above, and a binder for adhesively fixing these color developers and pigments to the base sheet. Water-soluble polymers such as starch, dextrin, casein, methyl cellulose, ethyl cellulose, carboxy ether cellulose, carboxy ether cellulose, hydroxyethyl cellulose, polyvinyl alcohol, polyacrylamide; styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer polymers, acrylonitrile-butadiene copolymers, vinyl acetate copolymers, acrylic acid ester copolymers, and carboxy-modified copolymers of these copolymers. A color developer paint is obtained by adding a seed or two or more types, and further blending a dispersant, a pH adjuster, etc. as necessary to obtain a color developer paint, and applying this color developer paint to a base sheet and drying it.

It goes without saying that the color development properties of a color developer sheet depend on the color development properties of the color developer, and various new color developers have been proposed, but from the viewpoints of color development, color development stability, paint formulation stability, etc. Recently, phenol resins and zinc salts of salicylic acid derivatives have been particularly frequently used.

Commonly used color developers are solid at room temperature, and these color developers are used in the form of dispersion in water.

(Problems to be Solved by the Invention) Demand for pressure-sensitive recording paper has shown remarkable growth in recent years, and requirements for its quality have also become more sophisticated. In particular, the color developing sheet, which serves as the coloring surface, is required not only to provide clear records but also to have improved surface strength that can withstand high-speed printing.

The color development properties of the color developer sheet are better as the amount of developer in the developer coating composition increases, but increasing the amount of developer not only becomes disadvantageous in terms of cost, but also reduces the surface strength of the coated surface. However, problems such as piling are likely to occur during high-speed printing.

After repeated studies to solve these problems, pressure-sensitive recording paper with excellent color development and surface strength was obtained by using an aqueous polymer emulsion containing polyvalent metal salts of aromatic carboxylic acids in emulsion particles. He discovered that this could be done and filed a patent application under Japanese Patent Application No. 128331/1983.

However, pressure-sensitive recording paper has a problem in that the density change in the colored portion gradually decreases over time after reaching a certain density. It is desired to improve the fading resistance of the colored portion of this pressure-sensitive recording paper.

Therefore, as a result of intensive research to provide a color developer composition for pressure-sensitive recording paper that has excellent color development and surface strength, as well as excellent fade resistance, we have completed the present invention. .

That is, an object of the present invention is to provide a color developer composition for pressure-sensitive recording paper that has excellent color development properties and surface strength, and also has excellent fade resistance.

(Means for Solving the Problems) An object of the present invention is to form a nonapolymer aqueous emulsion and a polyvalent metal hydroxide or oxide by incorporating an inorganic pigment and a polyvalent metal salt of an aromatic carboxylic acid into emulsion particles. This can be achieved by using a color developer composition for pressure-sensitive recording paper containing the following.

The aqueous polymer emulsion used in the present invention contains an aromatic carboxylic acid polyvalent metal salt in the polymer emulsion particles.

Methods for incorporating the polyvalent metal salt into the polymer emulsion particles include adding the polyvalent metal salt to the polymerization system during production of the polymer aqueous emulsion, and adding the polyvalent metal salt into the polymer aqueous emulsion particles after polymerization. In the present invention, any method can be used as long as the polyvalent metal salt is substantially contained in the particles of the aqueous polymer emulsion.

Methods for incorporating the polyvalent metal salt into the particles during polymerization include dissolving the polyvalent metal salt in monomers constituting the polymer, and dissolving the polyvalent metal salt in advance in a non-polymerizable organic solvent. and a method of mixing this solution with monomers,
There is a method in which a solution of the polyvalent metal salt is added to a monomer emulsion. Further, when the polyvalent metal salt has radical polymerizability, the polyvalent metal salt can be bonded to the polymer in the emulsion particles by copolymerizing with other monomers. When the polyvalent metal salt is used after being dissolved in a non-polymerizable organic solvent, it is preferable to distill off and recover the non-polymerizable organic solvent by vacuum distillation or the like after the completion of polymerization.

The method of incorporating the polyvalent metal salt into the aqueous polymer emulsion particles after completion of polymerization is to use an organic solvent that can swell the polymer in the aqueous polymer emulsion particles, and add the polyvalent metal salt to the organic solvent in advance. Dissolve the metal salt, add this solution to the polymer aqueous emulsion, stir it, allow the solution to be absorbed by the polymer in the polymer aqueous emulsion particles, and then distill off and recover the organic solvent by vacuum distillation etc. Examples include a method in which the polyvalent metal salt remains within the emulsion particles.

The polyvalent metal salt of aromatic carboxylic acid used in the present invention is a metal salt of aromatic carboxylic acid such as copper, lead, magnesium, calcium, zinc, aluminum, tin, or nickel.

Specific examples of aromatic carboxylic acids include benzoic acid, chlorobenzoic acid (0+m+p), and nitrobenzoic acid (O+m+P).
), toluic acid (o, m, p ), 4-methyl-3-
Nitrobenzoic acid, 2-chloro-4-nitrobenzoic acid, 2
．． 3-dichlorobenzoic acid, 2,4-dichlorobenzoic acid,
p-Inglobilbenzoic acid, 2.5-dinitrobenzoic acid, p-tart-butylbenzoic acid, N-phenylanthranilic acid, 4-methyl-3-nitrobenzoic acid, salicylic acid, m-hydroxybenzoic acid, p-hydroxy Benzoic acid, 3.5-dinitrosalicylic acid, 5-tert-butylsalicylic acid, 6-phenylsalicylic acid, 3-methyl-
5-tart-butylsalicylic acid, 3.5-di-tθr
t-Butylsalicylic acid, 3.5-di-tart-amylsalicylic acid, 3-cyclohexylsalicylic acid, 5-cyclohexylsalicylic acid, 3-methyl-5-yamylsalicylic acid, 5-yamylsalicylic acid, 3.5-dino5
ec-butylsalicylic acid, 5-nonylsalicylic acid, 2-
Hydroxy-3-methylbenzoic acid, 2-hydroxy-5
-tart-butylbenzoic acid, 2,4-cresotinic acid,
5.5-Methylenedisalicylic acid, acetaminobenzoic acid (o, m, p), 2.4-dihydroxy/benzoic acid, 2
, 5-dihydroxybenzoic acid, anacardic acid, 1-naphthoic acid, s, 5-c α, α-dimethylbenzyl salicylic acid, 3.5-di-α-methylbenzyl salicylic acid, 2
-naphthoic acid, 1-hydroxy-2-naphthoic acid, 2-
Examples include hydroxy-5-naphthoic acid, 2-hydroxy-1-naphthoic acid, thiosalicylic acid, 2-carboxybenzaldehyde, etc. In the present invention, it is essential to use polyvalent metal salts of these aromatic carboxylic acids. ,
Particularly preferred are zinc salts.

The amount of the polyvalent metal salt of aromatic carboxylic acid added to the aqueous polymer emulsion particles is not particularly limited, but is 2 to 1 part by weight per 100 parts by weight of the polymer in the aqueous polymer emulsion.
A range of 0.00 parts by weight is preferred. If it is less than 2 parts by weight, the intended effect of improving color development will be small, and if it exceeds 100 parts by weight, the ability as a binder for the aqueous polymer emulsion will be reduced, which is not preferable. Preferably it is in the range of 5 to 50 parts by weight.

The monomer composition constituting the polymer of the aqueous polymer emulsion used in the present invention is not particularly limited as long as it has adhesive strength.

Examples of monomers constituting the polymer include the following.

Aliphatic conjugated diolefins such as 1.3-butadiene, 2-methyl-1,3-butadiene, 2.3-dimethyl-1,3-butadiene, and halogen-substituted butadiene; styrene, α-methylstyrene, monochlorostyrene, vinyl Aromatic vinyl compounds such as toluene; methyl acrylate,
Examples include alkyl esters of acrylic acid and methacrylic acid such as methyl methacrylate, ethyl acrylate, butyl acrylate, and 2-ethyl-hexyl acrylate; and ethylenically unsaturated nitrile compounds such as acrylonitrile and methacrylonitrile. Furthermore, acrylic acid,
Unsaturated carboxylic acids such as methacrylic acid, itaconic acid, and maleic acid can also be used as comonomers to form carboxylated latexes. Furthermore, acrylic acid-β
-Hydroxyethyl, acrylamide, methacrylamide, N-methylolacrylamide, glycidyl methacrylate, divinylbenzene, etc. can also be used as a copolymer.

These monomers are combined to copolymerize as a monomer composition having adhesive strength. Examples include SB latex, NB latex, NB latex, acrylic ester latex, and carboxylated modifications thereof. Examples include latex.

In the present invention, it is a requirement that the polyvalent metal salt of an aromatic carboxylic acid be contained in the aqueous polymer emulsion particles, and the polymerization method itself of the aqueous polymer emulsion is not particularly limited, such as batch emulsion polymerization, Known emulsion heavy metal methods such as continuous emulsion polymerization can be employed, and various additives used in general emulsion polymerization, such as various known emulsifiers, polymerization initiators, chelating agents, and electrolytes, can be used.
Furthermore, the polymerization temperature can be selected from either high or low temperatures. Furthermore, known pH adjusters, dispersants, preservatives, etc. may be added to the aqueous polymer emulsion after completion of polymerization.0 Methods for incorporating the polyvalent metal salt during polymerization include dissolving it in monomers.

The polyvalent metal salt is dissolved in monomers in advance, and this is emulsified and subjected to a polymerization system. At this time, it may be dissolved in a mixture of each monomer of the copolymer composition, but it may also be dissolved in a specific monomer. Depending on the type of salt, the solubility of the polyvalent metal salt may not reach the desired amount.

In this case, the polyvalent metal salt may be dissolved in a non-polymerizable solvent in advance and then provided to the polymerization system. In this case, it is necessary to recover the solvent by distillation under reduced pressure after the emulsion polymerization is completed. The solvent used must have a high solubility of the polyvalent metal salt, a low boiling point, and be easy to recover.

Examples of solvents used include ethyl acetate, methyl ethyl ketone, and tetrahydrofuran.

The polyvalent metal salt can also be included after polymerization of the aqueous polymer emulsion. The polyvalent metal salt is dissolved in an organic solvent, and the solvent is added to the aqueous polymer emulsion and stirred. The solvent containing the polyvalent metal salt swells the polymer particles of the aqueous polymer emulsion, so that the particles contain the organic solvent and the polyvalent metal salt. Then, by vacuum distillation etc.
Only the organic solvent is distilled off and recovered to obtain an aqueous polymer emulsion containing the polyvalent metal salt in its particles. The solvent used must have a high solubility of the polyvalent metal salt, a high degree of swelling in the aqueous polymer emulsion, a low boiling point, and be easy to recover, but the type thereof is not particularly limited. Examples of solvents used include esters such as ethyl acetate, ketones such as methyl ethyl ketone, furan derivatives such as tetrahydro7rane, and halogenated hydrocarbons such as carbon tetrachloride and vinyl chloride. Metal hydroxides or oxides are hydroxides or hydroxides of polyvalent metals with a valence of 2 or more, such as magnesium, cadmium, aluminum, lead, titanium, calcium, cobalt, nickel, zinc, steel, tin, and manganese. Examples of hydroxides or oxides of polyvalent metals include zinc hydroxide, aluminum hydroxide, cadmium hydroxide, calcium hydroxide, cobalt hydroxide, nickel hydroxide, manganese hydroxide, and zirconium hydroxide. , scandium hydroxide, tin hydroxide, iron hydroxide, steel hydroxide, magnesium hydroxide, and other hydroxides; zinc oxide, aluminum oxide, barium aluminum oxide, cadmium oxide,
Gallium oxide, calcium oxide, chromium oxide, cobalt oxide, silicon oxide hydroxide, lead hydroxide oxide, nickel hydroxide oxide, manganese hydroxide oxide, tin oxide, titanium oxide,
Examples include oxides such as copper oxide, lead oxide, nickel oxide, barium oxide, magnesium oxide, and manganese oxide.

In the present invention, it is essential to use these hydroxides or oxides alone or in combination, and 10 parts by weight per 100 parts by weight of the inorganic pigment forming the color developer composition for pressure-sensitive recording paper. It is preferable to add the above amount. Addition amount is 10
If the amount is less than part by weight, the effect of addition is small and undesirable.
Any amount may be added as long as the proportion is 10 parts by weight or more,
It is also possible to replace all inorganic pigments with hydroxides or oxides.

When applying the aqueous polymer emulsion of the present invention to a color developer sheet, the above-mentioned known inorganic pigment is mixed with the polyvalent hydroxide or oxide of the present invention and, if necessary, a known color developer. , can be applied as a color developer composition.

In this case, the amount of the aqueous polymer emulsion of the present invention added is preferably 5 parts by weight to 40 m parts (solid content) per 100 parts by weight (solid content) of the color developer composition.

Further, the water-soluble polymer binder described above can be added to the color developer composition, and known polymer latexes may also be used in combination as binders as long as the effects of the present invention are not impaired.

In applying the color developer composition obtained in this way onto the base paper, a known method can be applied. For example, an air knife coater, a roll coater, a blade coater, etc. can be used. The colorant composition can be set to have a pigment concentration and paint viscosity suitable for the coating equipment to which it is applied. Furthermore, for the purpose of improving the coating suitability of the coating material, known dispersants, antifoaming agents, surfactants, viscosity modifiers, preservatives, and the like may be added.

(Effects of the Invention) Thus, according to the present invention, a hydroxide or oxide of a polyvalent metal can be used for pressure-sensitive recording paper together with an aqueous polymer emulsion in which a polyvalent metal salt of an aromatic carboxylic acid is contained in emulsion particles. By including it in the color developer composition, it becomes possible to produce pressure-sensitive recording paper that has excellent color development, surface strength, and furthermore, excellent fading resistance.

(Example) The present invention will be described in more detail with reference to Examples below. Note that parts and parts in Examples and Comparative Examples are based on weight unless otherwise specified.

In a pressure-resistant glass bottle with a volume of 1-e, water, an emulsifier, an inorganic salt, a chelating agent, and a polymerization initiator were added along with the monomers, molecular weight regulators, polyvalent metal salts of aromatic carboxylic acids, and non-monomers shown in Table 1. A polymerizable organic solvent was charged, and the reaction was carried out at 60°C for 15 hours with rotational mixing. Conversion rate is 99% in both cases
This has been reached. The obtained polymer latex was cooled with water to remove unreacted monomers and solvent, and then the pH of the latex was adjusted to 7 with NaOH.

The paint was adjusted according to the formulation shown in Table 2 so that the solid content concentration of the paint was 25%. The paint was applied to a base paper of 40 gr/nx'' in an amount of 4 to 5 gr/vt (solid content), and then dried to obtain a color developing sheet.

The performance of the obtained color developing sheet was evaluated by the following method.

■ Color development level Commercially available paper coated with microcapsules containing colorless A-ico dye is layered on a color development sheet, and then printed using an electric typewriter.
was used to print, the reflectance was measured after 1 hour, and the degree of color development (%) was determined using the following formula.

(2) Using a surface strength R printing suitability tester (Mei Seisakusho), picking test ink with a tank value of 12 was printed four times on the coated surface of the color developer sheet, and the state of powder falling off was sensory evaluated.

Evaluation was made on a 5-point scale based on the following criteria.

5 No powder falling 4 Very slight powder falling 3 Partly powder falling 2 Powder falling on the entire surface 1 Significant powder falling on the whole surface Measure the degree of color development after 1 hour and 3 days, and calculate the fading resistance (f) using the following formula.
I asked for

The above results are shown in Table 4.

A color developer sheet was prepared in the same manner as in the Examples using the formulations shown in Table 1, Table 2, Comparative Example, Table 3, and the performance of the color developer sheet was evaluated in the same manner as in the Examples. The results are shown in Table 4.

A color developing sheet was prepared using the same formulation as in the examples in Table 3, with the same amount of latex (solid content) and zinc aromatic carboxylate, and the color was developed, but the color was not developed to the extent that it could be compared with the examples. I couldn't.

Claims (1)

[Claims] A color developer composition for pressure-sensitive recording paper, comprising an aqueous polymer emulsion containing an inorganic pigment and a polyvalent metal salt of an aromatic carboxylic acid in emulsion particles, and a hydroxide or oxide of a polyvalent metal.