JPS6040393B2 - pressure sensitive recording material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a new pressure-sensitive recording paper, and more particularly to a carbon-free pressure-sensitive recording paper that has significantly improved color density and print fastness when pressure-printed. It is something.

Another object of the present invention is to provide a pressure-sensitive recording paper that is comprehensively superior in terms of manufacture and use. Usually, pressure-sensitive recording paper is made of electron-donating leuco dyes such as crystal violet lactone, benzoyl leucomethylene blue, mafkite green lactone, rhodamine anilinolactam, and 3-diethylamino-6-methyl-7-anilinofluorane, which are used in non-volatile oil-based solvents. Electron-accepting substances such as activated clay, acid clay, attaparsiyat, various phenol resins, organic carboxylic acids or their metal salts, or acidic substances such as solid acids are suitable. It consists of a base paper coated with a binder, and when the coated sides of both papers are stacked facing each other and pressure is applied by writing or using a typewriter, etc.
The capsule in the pressurized part is destroyed and the leuco dye comes into contact with the acidic substance, producing color. In addition, a large number of copies can be obtained by sandwiching an inner sheet coated with an acidic substance on the surface and a capsule containing leuco dye on the back side between the upper sheet and the lower sheet. Conventionally, activated clays represented by acid clay and phenol resins represented by formaldehyde polycondensates of phenylphenol have been widely used as acidic substances for this purpose, but recently a third acidic substance (color developer) has been widely used. Organic carboxylic acid metal salts, typified by metal salts of salicylic acid converters, have emerged as agents.

However, these three types of color developers each have their own advantages and disadvantages in terms of color development ability, stability, storage stability, printability, printing fastness, economic efficiency, etc., and it is difficult to find the ideal color developer. It has not been. Now, a wide range of research has been conducted on methods for improving the color-developing ability of the color-developing layer (i.e., the acidic substance coated layer) of the inner paper and lower paper of pressure-sensitive recording paper. When the resin-kaolin layer contains a metal salt selected from the group consisting of zinc, tin, calcium, magnesium, strontium, manganese, cornolet, nickel, etc., such as zinc chloride, the coloring ability is improved and the coloring of the colored image is reduced. Discloses what has been achieved. Furthermore, in Japanese Patent Publication No. 49-10855, when an organic acid is adsorbed to an inorganic pigment such as titanium oxide, zinc oxide, barium sulfate, or calcium sulfate and applied to a transfer paper (that is, to form a complexion layer), the above-mentioned inorganic pigment It is written that more vivid and robust coloring can be obtained by the effect of the and acid, and this clearly shows that the polyvalent metal compound has a coloring improving effect and a coloring image stabilizing effect. On the other hand, Tsubaki Publication No. 49-10856 discloses that when an organic acid metal salt (e.g., zinc salicylate) and a metal oxide (e.g., zinc oxide) are used in combination, the coloring ability becomes particularly remarkable and the color image also becomes more solid. It is being announced.

Furthermore, according to Japanese Patent Publication No. 49-13451, when aromatic carboxylic acids or their anhydrides (benzoic acid, benzoic anhydride, salicylic acid, etc.) coexist with metal compounds (e.g. zinc oxide), the It states that it has strong head color ability and strong color resistance to light. JP-A-51-127817 discloses that coatings with formulations such as hydroxy-substituted aromatic carboxylic acid derivatives and Group D metal oxides, carbonates, etc. can minimize the use of materials and provide improved stability. It is stated that the image forming speed can be increased. Some of the well-known documents that describe the effectiveness of metal compounds, typified by zinc compounds, in improving the activity of color formers made of organic acids can be cited.

However, looking at the implementation methods, the current situation is that in many cases, organic acids and metal compounds are closely mixed and coated in the color developing layer of the middle paper and bottom paper (on the same side of the support). Self-coloring pressure-sensitive recording paper coated with both pressure-sensitive dye (leuco dye)-containing microcapsules and a color developer can be seen as a variation of the color-developing layer and readable print-forming layer; layer).

When pressure printing is performed with the color developing layer made of an organic acid and a metal compound facing the coated surface of the upper paper, the microcapsules on the upper paper are torn and the leuco dye solution, which is the core substance, is transferred to the complexion layer. However, because coloring agents are usually applied as a solid or powder, the rate of dissolution of the color developer into the solvent controls the rate of color development (so-called rate of color development). For this reason, conventionally,
Particularly in cold weather, it takes time to dissolve the color developer in the transferred solvent, and the color density after pressure printing does not become high, which is very inconvenient. Furthermore, the head coloring agent must be uniformly applied to the developing layer, which essentially causes yellowing due to sunlight and increased costs. As a countermeasure against these problems, Tokubatsu Publication No. 81608/1983 and Japanese Unexamined Patent Application Publication No. 48/1973
According to the content disclosed in Publication No. 8-8291, a leuco dye (electron-donating organic coloring agent) and an organic acidic substance (electron-accepting organic acidic substance) are dissolved in a solvent, and if necessary, a coloring inhibitor is added. The original method is to enclose them in the same microcapsule.

However, this is because ■ To provide practical coloring properties, when the required amount of organic acidic substance is dissolved in a solvent together with leuco dye, a considerable coloring reaction occurs, and when this substance is encapsulated, the capsules are also colored and it is difficult to coat them. This will damage the appearance of the paper.

■ When a volatile substance such as alcohol, glycol, ketone, ether, or amine is used as a color inhibitor, the color density after printing is extremely slow, and many of these color inhibitors are hydrophilic and cannot be encapsulated. There were many problems in putting it into practical use because it was extremely difficult.
The present inventors have worked hard to solve these problems and improve coloring performance.
We have completed a pressure-sensitive recording system that has comprehensively improved various characteristics such as cost and appearance of copy paper. That is, the present invention (1) dissolves an organic carboxylic acid in a mixed solvent of an aromatic high-boiling solvent and a poorly water-soluble high-boiling polar solvent and encapsulates it into microcapsules.

■ Separately, the leuco dye is dissolved in an organic solvent and microencapsulated.

Mix ■■■, add adhesive and additives, and apply it to paper to make top (middle) paper.

■ A coating liquid containing a polyvalent metal compound is applied to paper, and the bottom (middle)
Paper.

This eliminates the coloring problem of the top (middle) paper, and also eliminates the need for coloring inhibitors, completely eliminating the associated problems such as high cost and difficulty adjusting coloring performance. It was decided to be resolved.

In this case, using a polar solvent as a solvent for dissolving organic carboxylic acids instead of aromatic solvents, which are widely used as solvents for pressure-sensitive recording paper, can easily dissolve organic carboxylic acids that are difficult to dissolve in aromatic solvents. Furthermore, organic carboxylic acids can be dissolved in a higher concentration than aromatic solvents, making it possible to reduce costs. Furthermore, although the reason for this is not clear, perhaps it is because the transfer rate is improved, the use of a polar solvent has the advantage that the final concentration is higher than when an aromatic solvent is used. However, when a polar solvent is used as capsule oil, depending on the type of color developer (acidic substance) applied to the bottom paper, the top paper and bottom paper may be overlapped and pressure is applied, resulting in dye-containing oil and organic carboxylic acid-containing oil. The speed of color development when transferred to the lower paper may be delayed. In other words, when active viscosity and phenolic resin are used alone as color developers, the color development speed is delayed due to polar solvents, and this may cause a delay in color development when various types of pressure-sensitive paper are combined. The disadvantage is that it is not compatible with all pressure-sensitive papers. Therefore, we investigated how to simultaneously achieve the two effects of increasing the solubility of organic carboxylic acids while maintaining the speed of color development, and found that it is preferable to use aromatic solvents and polar solvents in a ratio of 95:5 to 25:75. is 80:2
The intended purpose was achieved by using solvents mixed in a ratio of 0 to 50:50. In carrying out the present invention, the effect can be recognized even if the polyvalent metal compound is used alone to make the lower (middle) paper, but it is also possible to mix the polyvalent metal compound with an oil-soluble phenol resin and/or activated clay, Bottom (middle)
When making paper, it is necessary to use highly concentrated color development of phenolic resin or activated atomizer, sunlight fastness due to the synergistic effect with polyvalent metal compounds, improvement of setting properties of desensitizing ink or printing ink, and in some cases, organic carbon. Numerous property improvements are also possible, such as reduction in acid capsules.

In this case, pressure-sensitive recording paper with desired characteristics can be freely designed by changing the proportions of the polyvalent metal compound, phenolic resin, and activated clay. Examples of microencapsulation methods that have been practically used in the field of pressure-sensitive recording paper include '11
Phase separation (coacervation) method from aqueous solution (for example, U.S. Pat. No. 2,800,457, U.S. Pat. No. 2,8004)
Specification No. 58 or Japanese Patent Publication No. 38-1881
(methods shown in Publication No. 1, Special Publication Shobara-2 Group No. 1, etc.)
{2- Interfacial polymerization method (for example, Hakama Kosho-19574, Japanese Patent Publication No. 42-446, Japanese Patent Publication No. 42-771)
method disclosed in Japanese Patent Publication No. 47-1763, etc.) '3' monomer polymerization method (for example, Japanese Patent Publication No. 36-91
68, Tokusekki No. 51-907y, etc.), and the like.

In the top paper of the present invention, known microencapsulation methods could be effectively applied to both dye-containing microcapsules and organic carboxylic acid-containing microcapsules.
For organic carboxylic acid-containing microcapsules, please refer to the above-mentioned Japanese Patent Application Laid-open No. 51-907y, other Japanese Patent Publications No. 44-3495, and Japanese Patent Application No. 12058-1983 filed by the same applicant as the present application.
Microcapsules whose walls are basically made of a urea-formaldehyde polycondensate as described in Specification No. 8 (invention title "Microcapsules"), or Specification No. 52-11624 of Tokuiso Sho, which is filed by the same applicant as the present application. (name of the invention “
The best results were obtained when microcapsules whose walls were made of a melamine-formaldehyde polycondensate were used as described in "Microcapsules 4. Capsules".

The reason why other encapsulation methods are slightly inferior is probably because organic carboxylic acids are quite hydrophilic, so in coacervation method capsules in which gelatin is the main wall membrane, the internal phase is sufficiently extracted. This seems to be due to the fact that it cannot be prevented.
{21 This seems to be due to the fact that in the interfacial polymerization method, there is a possibility that the isocyanate compound, which is the raw material for the wall covering, may chemically react with the organic carboxylic acid. In contrast, for dye-containing capsules, the choice of encapsulation method was almost arbitrary, but to put it bluntly, microcapsules with a wall made of the above-mentioned urea-formaldehyde polycondensate or melamine-formaldehyde polycondensate were applied. When the best quality paper could be produced.

Perhaps wall membranes composed of these polycondensates give dense cells,
It's probably more expensive because it's a chemical-inclusive library. When other encapsulation methods were applied, undesired capsule breakage and contamination due to internal phase extrusion were sometimes observed. Specific examples of the organic carboxylic acids used in the present invention include formic acid, acetic acid, butyric acid, caproic acid, caprylic acid, belargonic acid, capric acid, lauric acid, oleic acid, palmidic acid, stearic acid, isostearic acid, and belargonic acid. Henic acid, linolenic acid,
Aliphatic carboxylic acids such as linoleic acid, adipic acid, octane-1,8-dicarboxylic acid, aralkyl carboxylic acids such as phenyl acetic acid, p-chlorophenylacetic acid, B-phenylpropionic acid, phenylsuccinic acid, benzoic acid, p-tolylic acid, Ortho-chlorobenzoic acid, para-nitrobenzoic acid, salicylic acid, ortho-chlorobenzoic acid.

Rosalicylic acid, metaoxysalicylic acid, paraoxysalicylic acid, anisic acid, gallic acid, phthalic acid, trimellitic acid, diphenic acid, paraisopropylbenzoic acid,
2,4-Creotic acid, 5-methylsalicylic acid, 5-tert-butylsalicylic acid, 3-phenylsalicylic acid, 3,5-di-secondarybutylsalicylic acid, 3,5
-Di-tert-butylsalicylic acid, 3-methyl-5
-tert-tertiary amyl salicylic acid, 3,5-tertiary amyl salicylic acid, 5-isoamyl salicylic acid,
5-cyclohexylsalicylic acid, 3,5-di-Q-methylbenzylsalicylic acid, 3,5-di-QQ-dimethylbenzylsalicylic acid, 1-hydroxy-2-naphthoic acid, 2-hydroxy-1-naphthoic acid, 3-hydroxy-
2 naphthoic acid, naphthalic acid, 4 nitronaphthalic acid,
Examples include aromatic carboxylic acids such as 3-hydroxynaphthalic acid, oxybenzoic acid, or a polycondensate of formaldehyde with oxybenzoic acid or a derivative thereof. Among these, salicylic acid derivatives have been particularly useful. Examples of polyvalent metal compounds used in the color developing layer of the bottom paper and inner paper of the present invention include magnesium, calcium strontium, barium, zinc, nickel, tin, manganese, co/
Examples include oxides, hydroxides, carbonates, basic carbonates, silicates, and phosphates of aluminum, titanium, aluminum, antimony, iron, vanadium, and the like. Oxides were particularly useful. Aromatic solvents used in the present invention include diarylalkanes, alkylnaphthalenes,
Solvents commonly used as pressure-sensitive paper solvents such as hydrogenated terphenyl solvents can be used.

Examples of poorly water-soluble high-boiling polar solvents include phthalate esters such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, methyl phthalylethyl glycolate, and butyl benzyl phthalate. Dimethyl adipate, diisopropyl adipate, dibutyl adipate, dioctyl adipate,
Dibasic aliphatic carboxylic acid esters such as dioctyl azelate, dibutyl sebacate, dioctyl sebacate, dibutyl maleate, and dioctyl fumarate. Ethylene glycol-mono-n-butyl ether acetate,
Esters or ethers of polyols such as diethylene glycol-mono-n-butyl ether acetate, triethylene glycol dimethyl ether, triacetin. Phosphate esters such as octyl diphenyl phosphate. Polar solvents such as these which are poorly soluble in water and have a boiling point of 150° C. or higher can be used. The pressure-sensitive material and the active viscosity of the phenolic resin used in the present invention may be appropriately selected from known and publicly available materials.As the pressure-sensitive dye, an electron-donating leuco dye is used. IJ stalviolet lactone, 3-diethylamino-6-methyl-7
Typical examples include ``Ani1'' nofluorane and benzoylleucomethylene blue.

As for oil-soluble phenolic resins, Japanese Patent Publication No. 42-2014
The substituted phenol-formalin polycondensation resin described in Publication No. 4 is a typical example, and as the activated clay, inorganic solid acids such as kaolin, bentonite, attapulgite, zeolite, silica gel, activated clay, acid clay, etc. can be used. . In the present invention, paper is used as a typical flat support, but various nonwoven fabrics, plastic films, metal foils, etc., or composite sheets made by combining these with silk (for example, resin coated paper) can also be effectively used. Next, the effects of the present invention will be specifically described using Examples and Comparative Examples.

Example 1 (Preparation of top paper) {1} A microcapsule dispersion containing a leuco dye solution was prepared as follows.

(In this specification, all "parts" refer to parts by weight, and "%" refers to parts by weight.)
All represent weight percentages. ) 10 parts of a 10% aqueous solution of ethylene-maleic anhydride copolymer, 1 part of urea, 1 part of resolmin and 20 parts of water were mixed to form a solution, and the pH was adjusted to 3.5 using an aqueous sodium hydroxide solution. .

Crystal violet lactone (hereinafter abbreviated as CVL)
7.2 is an allyl alkane solvent manufactured by Nippon Oil Co., Ltd./
-Dissolved in 172.8 parts of SAS296 to obtain a dye solution. This dye solution was emulsified and dispersed in the above mixed aqueous solution to prepare an oil droplet emulsion. Next, 25 parts of a 37% formaldehyde aqueous solution was added and the temperature of the system was maintained at 55°C while stirring. After 2 hours, a wall film mainly composed of urea-formaldehyde polycondensate was formed around the oil bottle.

I finished the encapsulation after a further 2 hours of trouble. [2- An organic carboxylic acid-containing microcapsule dispersion was prepared as follows.

10% aqueous solution of ethylene-monohydric maleic acid copolymer 10
Mix 1 part of urea, 1 part of resorcin, and 20 parts of water to make a solution, and make a solution using sodium hydroxide aqueous solution.
Adjusted to H3.5.

27 parts of 3,5-di-tertiarybutylsalicylic acid was mixed with Hysol SAS 296 and 8 parts of diisopropyl adipate.
It was dissolved in 153 parts of a solvent mixed at a ratio of 0:20 and emulsified and dispersed in the above mixed aqueous solution to form an oil-in-water emulsion with oil droplets of 4 to 8 microns.

Next, 25 parts of a 37% formaldehyde aqueous solution was added, and the temperature of the system was maintained at 55 qo while crossing the ocean. After worshiping her for 4 hours, I finished Capsess.

(3) Pressure-sensitive recording paper was prepared as follows.

'1' dye capsule 10 anchors (solid content)
Wheat starch 25 parts Oxidized starch aqueous solution 1 part (solid content) Add water
A total of 54 paints like Ikari Kakujo Kotoki were prepared, part 1
/To 1st generation ■ 5 parts (solid content) of capsules containing 3.5-tertiary butylsalicylic acid are mixed, and the basis weight is approximately 40.
The mixture was coated onto the base paper using a tater so that the total solids coating amount was approximately 5 days/day, and dried to obtain a top paper.

Almost no coloration was observed on the coated surface. Example 2 (Preparation of lower paper) 2 parts of zinc oxide was dispersed in a ball mill for 2 hours with 0.6 part of ammonium salt of styrene-maleic anhydride copolymer and 8 parts of water.

Add 20% of dispersion and 1.5% of SBR latex and apply on base paper with a basis weight of approximately 40mm/final so that the solid content after drying is 3mm, and dry to make zinc oxide base paper. did. Comparative Example 1 (Preparation of top paper for comparison) As a solvent for dissolving the 3,5-di-tertiarybutylsalicylic acid of Example 1, Ysol SAS296 and DiSop were used.

A comparative paper was prepared in substantially the same manner as in Example 1, except that diisopropyl adipate alone was used as the solvent instead of the mixed solvent of pyr adipate. Comparative Example 2 (Preparation of lower paper for comparison) A lower paper for comparison containing a phenol resin in the coating layer was produced as follows.

The above-mentioned coating material was prepared and applied onto a base paper having a basis weight of about 40 m/m at a total solids coating amount of about 6 m/m and dried to obtain a base paper for comparison.

Example 3 (Performance test of pressure-sensitive recording paper according to the present invention) The upper paper and the lower paper produced in Examples 1 and 2 and Comparative Examples 1 and 2 were combined (in 4 different ways) with their coated surfaces facing each other. The mixture was then passed through a super calendar with a linear pressure of 100k9' to develop color.

In all samples, color development was observed only on the bottom paper, and no color development was observed on the top paper.

Table 1 summarizes the measured values of color density after 1 minute and 2 hours for each combination. Table 1 Upper paper Example 1 Comparative example 1 Organic carbon Organic carbon lower paper For acid capsules Use of solvent for acid capsules Example 2 of using polar solvent 0.35 0.38 (zinc oxide) 0.43 0.44 Comparative example 2
0.30 0.07 (phenol resin) 0.
47 0.46 In the color development density measurement value column, the upper row shows the density after 1 minute, and the lower row shows the density after 24 hours.

The concentration was measured using a photometer manufactured by Tokyo Koden ■. As shown in Table 1, when zinc oxide base paper is used, the initial density and color density are almost the same even when a mixed solvent is used or when an appropriate solvent is used alone, but under phenolic resin (not containing zinc oxide) When paper was used, the final concentration did not change, but when a polar solvent was used alone, the initial concentration was low, but when a mixed solvent was used, a practically sufficient initial concentration was obtained.

In addition, the lower paper colored by the combination of Example 1 and Example 2, and the lower paper colored by the combination of Example 1 and Comparative Example 2 were used as commercially available European PVC film sheets (Japanese plasticizer was used as a plasticizer). Table 2 shows the concentrations obtained when the samples (containing a large amount of Rukiruftanot) were placed one on top of the other, a certain weight was placed on them, and the samples were left at 60 circles for 24 hours, along with the concentrations before the test.

Table 2 Before test After test Example 10 Example 2 0.43 0.38 Example 10 Comparative example 2 0.47 0.12 When the soft PVC sheet was brought into contact with the coloring surface, the combination in the present invention There was only slight color discoloration, and there was a significant improvement in fastness to chemicals that are likely to be encountered in daily life.

Example 4 {1} In the production of the CVL-containing microcapsule dispersion of Example 1, 10.8 parts of 3-jethylamino-6-methyl-7-anilinofluorane (hereinafter abbreviated as ODB) was used instead of CVL. ,/Isol SAS296169. ODB in the same manner as '1} of Example 1 except that the fire part is used.
A dispersion containing microcapsules was prepared.

'2) In Example 1 (■), 18 parts of salicylic acid was used instead of 27 parts of 3,5-di-tert-butylsalicylic acid, and a mixed solvent of 1:1 mixture of Yizol SAS 296 and dibutyl malate was used as a mixed solvent. Salicylic acid-containing microcapsules were prepared in substantially the same manner as in Example 1 [2] except that the following procedure was used.

Glue paper was prepared as follows.

Prepare the above paint, mix 5 parts (solid part) of salicylic acid-containing microcapsules to 1'1 of the paint, and apply the total solid content on base paper with a basis weight of about 40 mm/strength to about 5 parts. It was applied in the evening and evening, dried, and a top paper was prepared.

The coated surface was slightly colored. t4} Next, a phenol resin and zinc oxide were combined to produce a bottom paper.

The above-mentioned coating material was prepared and applied onto a base paper having a basis weight of about 40 m/m at a total solids coating amount of about 6 m/m, and dried to prepare a base paper.

{5} The coated surfaces of the upper paper and the lower paper produced in this example were placed opposite each other, and color was developed through a linear pressure of 100 k9/that super calender.

The concentration after 1 minute is 0. The concentration after two total intervals was 0.55.

Claims (1)

[Scope of Claims] 1 (1) Leuco dye-containing microcapsules and (2) organic carboxylic acid are formed on one side of a planar support in a ratio of an aromatic high-boiling solvent to a poorly water-soluble high-boiling polar solvent of 95: 5-2
Sheet I, which is obtained by coating a mixed coating liquid with organic carboxylic acid-containing microcapsules obtained by dissolving in a mixed solvent with a ratio of 5:75, and a coating containing a polyvalent metal compound on the other side of Sheet I. Sheet II and/or Sheet III formed by applying a coating liquid containing a polyvalent metal compound onto another flat support
A pressure-sensitive recording material characterized by a combination of. 2. The pressure-sensitive recording material according to claim 1, wherein the poorly water-soluble high-boiling polar solvent is a dibasic carboxylic acid ester. 3. The pressure-sensitive recording material according to claim 1, wherein a coating liquid containing a polyvalent metal compound is combined with an oil-soluble novolak type phenolic resin and/or activated clay. 4 The organic carboxylic acid-containing microcapsules are substantially
Urea-formaldehyde polycondensation resin, urea-melamine
Claim 1, which is a microcapsule whose wall film is a polycondensation resin selected from the group consisting of formaldehyde polycondensation resin and melamine-formaldehyde polycondensation resin.
Pressure-sensitive recording material described in Section 1. 5. The pressure-sensitive recording material according to claim 1, wherein the organic carboxylic acid is salicylic acid or a derivative thereof. 6. The polyvalent metal compound according to claim 1, wherein the polyvalent metal compound is a compound selected from the group consisting of polyvalent metal oxides, hydroxides, carbonates, basic carbonates, phosphates, and silicates. Pressure sensitive recording material. 7. The pressure-sensitive recording material according to claim 6, wherein the polyvalent metal salt is zinc.