JPH0549032B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a pressure-sensitive recording sheet, and more particularly to a pressure-sensitive recording sheet that utilizes a color-forming reaction between an electron-donating colorless dye and an electron-accepting compound. (Prior art) A pressure-sensitive recording sheet is produced by dissolving an electron-donating colorless dye (hereinafter referred to as a coloring agent) in a suitable solvent, and placing a microcapsule layer containing microcapsules in which oil droplets are encapsulated on a support. Coated paper, electron-accepting compound (hereinafter referred to as color developer)
A lower paper coated with a color developer layer containing on another support, and in some cases, a middle paper coated with a microcapsule layer on one side of the support and a color developer layer on the other side. or one in which the capsule and the color developer are contained on the same side of the support, or one in which the capsule or the developer is contained in the support and the other is coated. There are things etc. These pressure-sensitive recording papers are, for example,
No. 2505470, No. 2505489, No. 2550471, No. 2505470, No. 2505489, No. 2550471, No.
It is described in No. 2730457, No. 3418250, etc. The performance that a pressure-sensitive recording sheet should have is (1) sufficient color density, (2) no fogging,
(3) The solidity of the colored material after coloring is sufficient; (4)
Appropriate color hue and suitability for copying machines, (5) S/
(6) The coloring body has sufficient chemical resistance. Among these, there is a particularly strong demand for (3) regarding blue color development, and in order to satisfy this condition, the present inventors used p-substituted aminophenylindolphthalide as a color former and a phenolic hydroxyl group as a color developer. It is proposed to use an organic acid with a retention period of more than 1 month. However, when using capsules containing the coloring agent prepared by the most well-known gelatin coacervate method, fogging occurs when water adheres (water immersion coloring).
It has been found that there are serious drawbacks such as color transfer and color transfer (humidity-resistant fog) during storage under high humidity. (Object of the Invention) Therefore, the object of the present invention is to provide a pressure-sensitive recording sheet which has a color former having good fastness and which does not have the above-mentioned drawbacks. (Structure of the Invention) An object of the present invention is to provide a pressure-sensitive recording sheet using an electron-donating colorless dye contained in a capsule and an electron-accepting compound, as the colorless dye having the following general formula (): (In the formula, R and R' may be the same or different and represent an alkyl group having 1 to 10 carbon atoms,
R ₁ represents an alkyl group having 1 to 12 carbon atoms or a phenyl group, which may have an alkoxy group or a phenyloxy group as a substituent, and R ₂ represents an alkyl group having 1 to 8 carbon atoms or a phenyl group. , Y represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms). A salicylic acid derivative or a metal salt thereof having two C7-20 aralkyl groups as substituents is used, and the main membrane material of the capsule is polyurethane, polyurea, polyurethane polyurea, or melamine/formaldehyde resin. This was achieved using a pressure-sensitive recording sheet. The main membrane material of the capsule used in the present invention is:
Polyurethane, polyurea, polyurethane polyurea or melamine/formaldehyde resin, formed by interfacial, internal or external polymerization. In the above general formula (), when R ₂ is an alkyl group, the sum of the carbon numbers of R, R', Y, R ₁ and R ₂ is 11 or more, or the sum of the carbon numbers of R ₁ and Y is 4 or more , when R ₂ is a phenyl group, R, R', Y,
It is preferable that the sum of the carbon numbers of R ₁ and R ₂ is 14 or more because the solubility of the color former in an organic solvent increases. Some examples of these include 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-
2-methylindol-3-yl)phthalide, 3
-(4-diethylamino-2-ethoxyphenyl)
-3-(1-isoamyl-2-methylindol-3-yl)phthalide, 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-β-ethoxyethyl-2-methylindole-3- )
phthalide, 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-β-phenoxyethyl-2-methylindol-3-yl)phthalide,
3-(4-dibutylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindole-
3-yl)phthalide, 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2
-phenylindol-3-yl)phthalide, 3
-(4-N-cyclohexyl-N-ethylamino-2-ethoxyphenyl)-3-(1-ethyl-2
-methylindol-3-yl)phthalide, 3-
(4-N-ethyl-N-isoamylamino-2-
isoamyloxyphenyl)-3-(1-ethyl-
2-methylindol-3-yl)phthalide, 3
-(4-diethylamino-2-methylphenyl)-
3-(1-ethyl-2-methylindole-3-
yl)phthalide, 3-(4-N-cyclohexyl-N-ethylamino-2-ethoxyphenyl)-
3-(1-ethyl-2-methylindole-3-
yl)phthalide, 3-(4-N-butyl-N-ethylamino-2-methylphenyl)-3-(1-ethyl-2-methylindol-3-yl)phthalide, 3-(4-diethylaminophenyl) -3-
(1-ethyl-2-methylindol-3-yl)
Phthalide, 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-hexyl-2-methylindol-3-yl)phthalide, 3-(4-diethylamino-2-ethoxyphenyl)-3-( 1-
octyl-2-phenylindol-3-yl)
Examples include phthalide. Among the p-substituted aminophenyl indolyl fururide derivatives according to the present invention, 4-substituted amino-2-alkoxyphenyl indolyl phthalide is preferred from the viewpoint of its various color development properties. The color developer used in the pressure-sensitive recording sheet according to the present invention is a salicylic acid derivative or a metal salt thereof having one or two aralkyl groups having 7 to 20 carbon atoms as a substituent. To give some examples, 3
-Methyl-5-benzylsalicylic acid, 3-phenyl-5-(α,α-dimethylbenzyl)salicylic acid, 3,5-di-(α-methylbenzyl)salicylic acid, 5-(p′-α′-methylbenzyl- p-α-
Examples include methylbenzyl)salicylic acid, 5-α-(α-methylbenzyl)phenethylsalicylic acid, and metal salts thereof (eg, zinc salt, aluminum salt, calcium salt, etc.). These may be used alone or in combination. The pressure-sensitive recording sheet according to the present invention is made of a combination of a specific color forming agent and a color developing agent, and the developed dye is significantly more stable than dyes produced from existing color forming agents, and can withstand long-term light irradiation. It is particularly advantageous in terms of long-term preservation of records, as it hardly causes discoloration or fading even when exposed to heat, humidity, or humidity. In the pressure-sensitive recording sheet according to the present invention, the p-substituted aminophenyl indolyl phthalide is a well-known triphenylmethane phthalide compound, a fluoran compound, a phenothiazine compound, or an indolyl azaphthalide compound. , leucoauramine compounds, rhodamine lactam compounds, triphenylmethane compounds, triazene compounds, and spiropyran compounds. In this case, it is preferable to use the color former of the present invention in an amount of 60% or more from the viewpoint of improving properties. Generally, a coloring agent is used alone or in combination, and a solvent (alkylated naphthalene, alkylated diphenyl,
Synthetic oils such as alkylated diphenylmethane, alkylated terphenyl, and chlorinated paraffin; vegetable oils such as cotton oil and castor oil; animal oils; mineral oils, or mixtures thereof, etc.) are dissolved in microcapsules, and then incorporated into microcapsules. A color forming agent sheet is obtained by coating it on a support such as paper, high quality paper, plastic sheet, resin coated paper, etc. Neutral paper is particularly preferred as the support. Since the color former combination of the present invention has good solubility in synthetic oils such as alkylated naphthalene, alkylated diphenyl, and alkylated diphenylalkane, it has the advantage that it can be used in combination with paraffinic oils having low solubility. In addition to the coloring agent, there is no problem in adding ultraviolet absorbers, antioxidants, etc. as additives to the microcapsules, especially to improve the stability of the coloring agent in the capsule before use and the coloring of the capsule. It is preferable to add benzotriazole type ultraviolet absorbers, hindered Tomian type antioxidants, hindered phenol type antioxidants, aniline type antioxidants, quinoline type antioxidants and the like. The color developer, alone or in combination with other color developers, is dispersed in a binder such as styrene-butadiene latex or polyvinyl alcohol, and applied together with the pigment to a support such as paper, plastic sheet, resin-coated paper, etc. A developer sheet is thereby obtained. The amount of color former and developer used depends on the desired coating thickness,
It depends on the form of the pressure-sensitive copying paper, the capsule manufacturing method, and other conditions, so it may be selected as appropriate depending on the conditions.
It is easy for one skilled in the art to determine this amount to use. (Examples of the Invention) Examples are shown below, but the present invention is not limited to these examples. Examples and Comparative Examples Preparation of color developer sheet Add 10 parts of the color developer shown in Table 1 to 20 parts of 1-isopropylphenyl-2-phenylethane and add 90
The mixture was heated and dissolved at ℃. This was added to 50 parts of a 2% polyvinyl alcohol (PVA-117 manufactured by Kuraray) aqueous solution, and 0.1 part of a 10% dodecylbenzenesulfonic acid triethanolamine salt aqueous solution was added as a surfactant. An emulsifier was prepared so that the diameter was 3μ. Next, 80 parts of calcium carbonate, 20 parts of zinc oxide,
A dispersion of 1 part of sodium hexametaphosphate and 200 parts of water was prepared using a Keddy Mill, and after mixing the above emulsion, 10% of sodium hexametaphosphate was added as a binder.
Prepared by adding 100 parts of PVA-117 (manufactured by Kuraray) aqueous solution and 10 parts (as solid content) of carboxy-modified SBR latex (SN-307, manufactured by Sumitomo Nogatux) and adding water to make the solid content concentration 20%.
A coating liquid (A) was obtained. Next, using 10 parts of the color developer, 20 parts of Silton clay, 60 parts of calcium carbonate, 20 parts of zinc oxide, 1 part of sodium hexametaphosphate, and 200 parts of water, use a sand grinder to uniformly grind the particles to an average particle size of 3μ. Dispersed. First, 16 parts of 10% PVA-103 (manufactured by Kuraray) aqueous solution was added to the obtained dispersion, and then 10% PVA-117 was added.
(manufactured by Kuraray) 100 parts of aqueous solution and carboxy modification
10 parts (as solid content) of SBR latex (SN-307 manufactured by Sumitomo Nogatsu Tax) were added, and water was added to adjust the solid content concentration to 20% to obtain a coating liquid (B). Coating liquid (A) and coating liquid (B) in terms of color developer A/B = 50/
50 g/m ² base paper, coated with an air knife coater so that the solid content was 5.0 g/m ² , and dried to obtain a color developer sheet. Preparation of capsule sheet containing color former Melamine/formaldehyde resin capsule Partial sodium salt of polyvinylbenzenesulfonic acid (manufactured by National Starch Co., Ltd.)
VERSA, TL500, average molecular weight 500000) was added to 95 parts of hot water at about 80°C with stirring and dissolved. Dissolve in approximately 30 minutes and then cool. The pH of the aqueous solution was 2 to 3, and a 20% by weight aqueous sodium hydroxide solution was added thereto to adjust the pH to 4.0.
On the other hand, 100 parts of diisopropylnaphthalene in which 3.5% of the coloring agent shown in Table 1 was dissolved was emulsified and dispersed in 100 parts of a 5% aqueous solution of a partial sodium salt of the polyvinylbenzenesulfonic acid to form an emulsion having a particle size of 4.5μ in average diameter. I got the liquid. Separately, 6 parts of melamine, 11 parts of a 37% by weight aqueous formamidehyde solution, and 30 parts of water were heated to 60°C and stirred.
After 30 minutes, a transparent mixed aqueous solution of melamine, formaldehyde and melamine-formaldehyde initial condensate was obtained. The pH of this mixed aqueous solution was 6-8. Hereinafter, this mixed aqueous solution of melamine, formaldehyde, and melamine-formaldehyde initial condensate will be referred to as an initial condensate solution. Add and mix the initial condensate solution obtained by the above method to the above emulsion, and while stirring.
The pH was adjusted to 6.0 with a 3.6% by weight phosphoric acid solution, the liquid temperature was raised to 65°C, and stirring was continued for 360 minutes.
This capsule liquid was cooled to room temperature and adjusted to pH 9.0 with 20% by weight sodium hydroxide. To this capsule dispersion, 200 parts of a 10% by weight polyvinyl alcohol aqueous solution and 50 parts of starch particles were added, and water was added to adjust the solid content concentration to 20% to prepare a coating liquid of a microcapsule dispersion. This coating solution was coated on a 50 g/m ² base paper using an air knife coater so that a solid content of 5 g/m ² was applied and dried to obtain a color former-containing capsule sheet used in the present invention. Polyurethane urea capsule: 8 g of a polyvalent isocyanate compound (3 moles of tolylene diisocyanate/1 mole of trimethylolpropane adduct) as a wall film-forming substance in an oily liquid containing 3.5% of the color former shown in Table 1 dissolved in 30 g of diisopropylnaphthalene. and 1 g of a polyvalent hydroxy compound (ethylenediamine-propylene oxide adduct) were mixed at a temperature of 20° C. or lower to prepare a primary solution. Next, 3 g of polyvinyl alcohol and 1.5 g of sodium salt of carboxymethylcellulose were dissolved in 44 g of water at 20°C. Furthermore, 0.1 g of funnel oil (emulsifier) was added to prepare a secondary solution. While stirring the secondary solution vigorously, the primary solution was poured to form an oil-in-water emulsion. The size of the oil droplets
When the temperature reached 4.5 μ, the stirring was weakened, and then 100 g of water at 20°C was added to this emulsion.
The temperature of the system was gradually increased to 75°C and maintained at this temperature for 60 minutes. Into the capsule liquid thus obtained, 25 g of a 15% aqueous solution of polyvinyl alcohol, 42 g of solid content of carboxy-modified SBR latex,
20g of starch particles (average particle size 15μ) were added. Then, water was added to adjust the solid content concentration to 20% to prepare a coating solution. This coating solution was applied onto a 50 g/m ² base paper using an air knife coating machine and dried to give a microcapsule sheet at a dry weight of 5 g/m ² . Gelatin Capsules 20 parts of acid-treated gelatin with an isoelectric point of 8.0 and 20 parts of gum arabic are dissolved in 120 parts of water at 40°C, 0.4 parts of sodium alkylbenzenesulfonate is added as an emulsifier, and the color former shown in Table 1 is added. 200 parts of dipropylnaphthalene dissolved at 3.5% was added with vigorous stirring to emulsify it, and when the emulsification reached 4.5μ, 200 parts of water at 40°C was added to suppress the progress of emulsification. While stirring, 420 parts of water at 30°C was further added, and 20% acetic acid was added to adjust the pH of the system to 4.4. The liquid was further cooled to 8°C while stirring, and then 1.0 part of 37% formaldehyde and
1.5 parts of 20% glutaraldehyde was added. Next, pour 60 parts of a 10% carboxymethylcellulose aqueous solution, then drop a 25% sodium hydroxide solution to adjust the pH to 9.5, and then lower the liquid crystal temperature to 30%.
Microcapsules with hardened walls were obtained by heating to .degree. 10% for this capsule dispersion
A coating liquid of a microcapsule dispersion was prepared by adding 200 parts of a polyvinyl alcohol aqueous solution and 50 parts of starch particles, and adjusting water so that the solid content concentration was 20%. This coating solution was applied to a base paper of 50 g/m ² to a solid content of 5 g/m ² and dried using an air knife coater to obtain a coloring agent-containing capsule sheet to be used for comparison. A pressure-sensitive recording sheet was prepared by combining the color developer sheet and color former-containing capsule sheet obtained as described above as shown in Table 1, and the performance of each combination was compared. Each color developer sheet and color former-containing capsule sheet were placed facing each other, and the fog (water immersion color development, overlapping moisture fog resistance) was compared with respect to the following items, and the results are shown in Table 1. (a) Water immersion color development A developer sheet soaked in water and a capsule sheet containing a color former were layered and air-dried, and the fog density on the surface of the capsule containing the color former was measured using a Beckman DB spectrophotometer. (b) Layer moisture resistant fogging A color developer sheet and a capsule sheet containing a color former are layered and a pressure of 100g/ ^cm2 is applied at 50℃ relative humidity.
The fogging of the color developer sheet after being left under 90% high humidity for 24 hours was visually evaluated. It can be seen from Table 1 that remarkable effects can be obtained by the present invention. 【table】

Claims (1)

[Scope of Claims] 1. In a pressure-sensitive recording sheet using an electron-donating colorless dye contained in a capsule and an electron-accepting compound, the colorless dye has the following general formula (): (In the formula, R and R' may be the same or different and represent an alkyl group having 1 to 10 carbon atoms,
R ₁ may have an alkoxy group or a phenyloxy group as a substituent. represents an alkyl group having 1 to 12 carbon atoms or a phenyl group, _R2 represents an alkyl group having 1 to 8 carbon atoms or a phenyl group, and Y is a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or a phenyl group having 1 to 12 carbon atoms; (representing an alkoxy group of A pressure-sensitive recording sheet, characterized in that the main film material of the capsule is polyurethane, polyurea, polyurethane polyurea or melamine/formaldehyde resin.