JP2764050B2 - Coloring sheet for pressure-sensitive fortune paper - Google Patents

Description

The present invention relates to a color developing sheet for pressure-sensitive copying paper, which forms an image by reacting with a basic leuco dye. More specifically, the present invention relates to a color developing sheet characterized by using (A) a salicylic acid condensate polyvalent metal compound and (B) a semi-synthetic inorganic solid acid as an acidic color developer. [Prior art] Pressure-sensitive copying paper is also called carbonless paper, and it is a copy paper that can be colored by mechanical or shocking pressure, such as writing or a typewriter, and that can make multiple copies at the same time. There is a type referred to as a type or a type referred to as a single color developing paper. The color forming mechanism is based on a color forming reaction between an electron-donating colorless dye and an electron-accepting developer. The transfer type pressure-sensitive copying paper will be described below with reference to FIG. 1 as an example. A colorless color-developing pressure-sensitive dye is dissolved in a non-volatile oil on the back surface of the top paper 1 and the middle paper 2, and microcapsules 4 having a diameter of several microns to several tens of microns, which are wrapped with a polymer film such as gelatin, are applied. Have been. The surface of the middle paper 2 and the lower paper 3 is coated with a paint containing a color developing agent 5 having a property of causing a reaction and color development upon contact with the above-mentioned pressure-sensitive dye. To make a copy above-(medium)-
(Middle)-Overlapping in order from the bottom (the dye-containing coating surface and the developer-containing coating surface are opposed to each other), and when a local pressure such as a pen pressure 6 or a type pressing pressure is applied, the capsule 4 at that portion is broken. The pressure-sensitive dye solution is transferred to the developer 5 to obtain a copy record. Examples of the electron-accepting developer include (1) acid clay disclosed in US Pat. No. 2,712,507, inorganic solid acids such as Attapal Guide, and (2) acid-treated clay disclosed in JP-A-58-217389. Semi-synthetic solid acids obtained by introducing magnesium and / or aluminum components into minerals.
Substituted phenols and diphenols disclosed in JP-A-9309, (4) p-type disclosed in JP-B-42-20144
Substituted phenol-formaldehyde polymers, and (5) metal salts of aromatic carboxylic acids disclosed in JP-B-49-10856 and JP-B-52-1327 have been proposed and partially put to practical use. The performance conditions that the color developing sheet should have are: excellent color development that does not change immediately after the sheet is manufactured and after long-term storage, as well as little yellowing during storage and exposure to wide rays such as sunlight, and a color image that is robust and wide It does not easily disappear or fade due to wire, water or plasticizer. Conventionally-developed developers and sheets coated with them have advantages and disadvantages in performance. For example, inorganic solid acids are inexpensive, but adsorb gas and moisture in the air during storage, causing yellowing of the paper surface and deteriorating color-forming performance, and substituted phenols have insufficient color-forming properties, resulting in poor color image density. Low. The p-phenylphenol-novolak resin used as a p-substituted phenol formaldehyde polymer has excellent color development, but the coated paper is exposed to sunlight or stored (especially nitrogen oxides in air). ), And the color image is remarkably faded. Further, the metal salt of an aromatic carboxylic acid has good coloring properties, yellowing properties, and fading properties due to light, but it is still hard to say that it has sufficient resistance to water or a plasticizer. And the conventional pressure-sensitive copying paper color developing sheet, after coating production,
When stored for a long period of time or stored at a high temperature, there is a problem that the color forming ability, particularly the initial color forming density is lowered. [Problems to be Solved by the Invention] An object of the present invention is to provide a color developing sheet for pressure-sensitive copying paper using a novel color developing agent which has improved the above-mentioned disadvantages. [Means for Solving the Problems] The present inventors have made intensive studies to achieve the above object, and as a result, have completed the present invention. That is, the present invention relates to a method for preparing (A) a compound represented by the following general formula (I): (Wherein R ₁ represents an alkyl group having 1 to 12 carbon atoms, an aralkyl group, an aryl group or a cycloalkyl group.) A salicylic acid ester represented by the general formula (II) (Wherein, R ₂ and R _{3 each} represent a hydrogen atom or a methyl group, and R ₄ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms). After hydrolyzing the resin, the polyvalent metal salt of salicylic acid resin, which is reacted with a polyvalent metal salt, and magnesium and / or
Or a developer sheet for pressure-sensitive copying paper, comprising a developer layer containing a semi-synthetic solid acid into which an aluminum component has been introduced. The novel color developing sheet of the present invention has better color developing performance (especially, excellent color developing speed and low temperature color developing speed) as compared with the conventionally disclosed color developing sheet, and the generated image is composed of water, solvent , Has extremely excellent resistance to brown by light rays, etc., and has extremely low tendency to yellow due to gas on the paper surface and light rays, and is extremely advantageous in handling and preservability which is also excellent in printability and desensitizing printing characteristics. This has the advantage that the color developing sheet can be provided at low cost. Furthermore, the developer sheet of the present invention can be used after long-term storage or high-temperature storage, which has been regarded as a common problem in developer sheets using conventional inorganic or resin-based developers. Has a remarkable feature of remarkably improving the tendency of lowering the coloring performance (especially the coloring speed). The salicylic acid resin polyvalent metallized product (A) used in the present invention is obtained by the following method. That is, a styrene derivative is subjected to a Friedel-Crafts reaction with salicylates in the presence of a strong acid catalyst (hereinafter referred to as a first-stage reaction), and the resulting salicylate ester resin is hydrolyzed (hereinafter referred to as a second-stage reaction), Further, the salicylic acid resin after the hydrolysis is produced by reacting with a polyvalent metal salt (hereinafter referred to as a third-stage reaction). Salicylic acid resin produced in the first and second stages,
Heretofore, they have not been disclosed at all and have been newly discovered by the present inventors and separately filed for patent application (Japanese Patent Application No. 62-2018).
31). Examples of the salicylates used in the first-stage reaction include methyl salicylate, ethyl salicylate, n-propyl salicylate, isopropyl salicylate, n-butyl salicylate, isobutyl salicylate, tert-butyl salicylate, isoamyl salicylate, salicylate, -Tert-octyl, nonyl salicylate, dodecyl salicylate, cyclohexyl salicylate, phenyl salicylate, benzyl salicylate, -α-methylbenzyl salicylate, and the like, but are not limited thereto. Industrially preferred is inexpensive methyl salicylate. Next, styrene derivatives defined by the general formula (II) used in this reaction include styrene, o-methylenestyrene, m-methylenestyrene, p-methylenestyrene, o-ethylenestyrene, p-ethylenestyrene,
Examples include, but are not limited to, o-isopropylstyrene, m-isopropylstyrene, p-tert-butylstyrene, α-methylenestyrene, β-methylenestyrene, and the like. Industrially preferred is inexpensive styrene. The amount of the styrene derivative to be used is 1 to 20 mole ratio, preferably 2 to 10 mole ratio, based on the salicylic acid ester, and is in the range of 50 to 10,000 in average molecular weight of the resin. In this general reaction, a strong acid catalyst is generally used, and the reaction may be carried out in the presence of a solvent inert to the reaction. The salicylate resin obtained in the first-stage reaction is then hydrolyzed using an acid or alkali aqueous solution. In order to obtain the polyvalent metal compound used in the present invention from the salicylic acid resin obtained by hydrolysis in this way, several known methods can be applied. For example, (1) a resin is reacted with an alkali metal hydroxide, carbonate, or alkoxide to obtain an alkali metal salt of the resin or an aqueous solution, an alcohol solution, or a water-alcohol mixed solution thereof. This is a method of producing a reactive polyvalent metal salt by reacting the same. It is desirable to react about 0.5 to 1 g equivalent of a water-soluble polyvalent metal salt per 1 mol of salicylic acid in the resin. (2) It can be produced by mixing a resin with a polyvalent metal salt of an organic carboxylic acid such as formic acid, acetic acid, propionic acid, valeric acid, caproic acid, stearic acid or benzoic acid, followed by heating and melting. In some cases, a basic substance such as ammonium carbonate, ammonium bicarbonate, ammonium acetate, or ammonium benzoate may be added, and the mixture may be heated and melted. (3) Carbonate, oxide, water of resin and polyvalent metal It can be produced by using an oxide and heating and melting it with a basic substance such as an organic ammonium carboxylate such as ammonium formate, ammonium acetate, ammonium caproate, ammonium stearate and ammonium benzoate. The metal of the metal compound of the salicylic acid condensate used in the present invention is a metal excluding alkali metals such as lithium, sodium, and potassium.
Magnesium, aluminum, calcium, copper, zinc,
Tin, barium, cobalt and nickel. Of these, zinc is particularly effective. The polyvalent metal compound of the salicylic acid condensate used as the color developer of the present invention includes a benzotriazole-based, benzophenone-based, or nickel complex-based singlet oxygen quencher for further improving the light fastness and the like. The use of an appropriate amount of mixed melting is, of course, included in the embodiments of the present invention. The semi-synthetic inorganic solid acid used as the other component (B) of the present invention is described in JP-A-57-15996 or JP-A-5-15996.
It is derived from a clay mineral having a layer structure composed of a tetrahedron of silica as disclosed in JP-A-8-217389, and has a layer structure composed of a tetrahedron of the silica according to electron beam diffraction. It shows an analysis pattern based on crystals, but does not substantially show a diffraction pattern based on the layer structure according to X-ray diffraction, and contains at least silicon, magnesium and / or aluminum as elements other than oxygen. It is a white fine powder and can be obtained by subjecting a solid such as acid clay to acid treatment and then reacting with a magnesium and / or aluminum compound to re-introduce the magnesium and / or aluminum components. Such a semi-synthetic solid acid has color developing ability itself and has a large specific surface area, and is extremely useful as a pigment for coating white paper. A semi-synthetic solid acid developer having such a developing ability is
When used alone as a color developer for pressure-sensitive copying paper, the light fastness and water fastness of the color image are insufficient and practical use is difficult without any change, and the drawbacks of such a synthetic solid acid developer should be overcome. Proposals have already been made in JP-A-58-162375 and JP-A-58-162375.
162376, 58-162377, 58-162378, 60-20
No. 8282 and No. 61-49886. These are intended to improve the properties of the color developing sheet by using the semi-synthetic solid acid in combination with a phenol compound having a specific chemical structure, a polyvalent metal salt of a salicylic acid derivative, or a thiourea compound. However, the shortcomings of the semi-synthetic solid acid, the color image light resistance and insufficient water resistance, have not yet been completely solved, and in some cases, the yellowing tendency of the paper has been promoted, so that it has been put to practical use. Not in. As described above, the present invention is a color developing sheet containing (A) a novel polyvalent metal salicylic acid condensate and (B) a semi-synthetic solid acid as a color developer component. In order to produce the color developing sheet of the present invention, in addition to the color developing agents (A) and (B), if desired, other white pigments (for example, natural and synthetic metal oxides, hydroxides or carbonates), etc. Of course is included in the embodiment of the present invention. If necessary, a known acidic developer such as a phenol formaldehyde resin or a polyvalent metal salt of an aromatic carboxylic acid may be used in combination. In the present invention, generally, a polyvalent metallated salicylic acid condensate is used in advance in the form of an aqueous suspension of fine particles. In order to prepare the color developing sheet of the present invention, in addition to (a) salicylic acid co-condensation resin polyvalent metal compound (generally used as an aqueous suspension which has been finely pulverized in advance) and (B) a semi-synthetic solid acid,
(C) binders (eg, synthetic rubber latex, modified starches, polyvinyl alcohol or modified polyvinyl alcohols), (d) others (dusting inhibitors, fluorescent brighteners, viscosity property regulators, defoamers) Are mixed well, an aqueous coating liquid having a viscosity and a solid content corresponding to the coating method to be used is prepared in advance, and applied to a support such as paper or film and dried. As a coating method, an air knife coater, a bar coater, a blade coater, a gravure coater, a roll coater and the like are generally used. In the aqueous coating solution used in the present invention, (A) salicylic acid condensate polyvalent metallized product is 2 to 40% by weight of the total solid content,
(B) 30 to 90% by weight of semi-synthetic solid acid, binder component 5
~ 40% by weight is common. The ability of the semi-synthetic solid acid used in the present invention as a developer is most effectively exhibited when the system is weakly alkaline. Is common. The coating amount of the support of the water-based coating solution is a dry weight 1 g / m ² or more preferably from 2 to 10 g / m ^2. The color developing sheet of the present invention requires only a small amount of the color developer component and the coating liquid to be applied, and the concentration, viscosity, etc. of the aqueous coating liquid can be changed in a relatively wide range. Because of its excellent mechanical stability, both on-machine coating and off-machine coating are possible, which has great advantages not only in performance but also in the pressure-sensitive copying paper manufacturing process. [Action and Effect] The present invention provides a novel pressure-sensitive copying paper color developing sheet which is remarkably excellent in performance using (A) a novel polyvalent metal salicylic acid resin and (B) a semi-synthetic inorganic solid acid as a color developer. I do. The color developing sheet of the present invention differs from the conventionally known color developing sheet in physical properties to be provided as pressure-sensitive copying paper (1) and provides excellent color developing performance (color developing speed and density). In particular, the coloring performance (coloring speed) at low temperatures in winter or outdoors, which is a problem in using pressure-sensitive copying paper, is significantly improved. (2) The stability of the color former due to exposure to light or contact with a solvent such as a plasticizer is extremely excellent. (3) The color image has excellent water resistance, and does not disappear under humid conditions or contact with water. (4) Changes in coloring ability are extremely small even after long-term storage or storage at high temperatures. (5) the coated surface does not yellow even by contact with the gas component of the NO _X in the light or in the atmosphere. (6) It has extremely excellent features such as excellent printability and desensitized printing characteristics, and can be used in applications that were unsuitable for conventional pressure-sensitive paper, and its practical significance is extremely large. EXAMPLES Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples. Prior to Examples, a method for producing a color-developed sheet and a method for evaluating performance as a pressure-sensitive copying paper will be described below. The developer used in each example was wet-pulverized in the presence of a small amount of an anionic polymer surfactant to obtain an aqueous suspension having a solid content of 40% by weight (average particle size 2.5 μm). Next, an aqueous coating liquid having the following composition (solid content 35% by weight, pH 9.8) is prepared using this suspension. Standard aqueous coating liquid composition Solid weight ratio Developer 15 Semi-synthetic inorganic solid acid 100 Synthetic rubber latex 10 Oxidized starch 12 Anti-dusting agent 1 Remark Semi-synthetic inorganic solid acid Mizusawa Chemical Silyton SS-1 Synthetic gum latex Mitsui Higashi Pressure Polyrac 752-A Oxidized Starch Oji Corn Starch Ace B Dusting inhibitor Nissin Chemical DEF-922F The above aqueous coating solution was applied at 40 g / m ² using a Meyer bar coater.
Is applied to a high-quality paper at a dry application amount of 7 g / m ² to form a pressure-sensitive copying paper color developing sheet. The performance evaluation method of the thus obtained color-developed sheet as pressure-sensitive paper is as follows. (1) Coloring speed and concentration (implemented in a thermo-hygrostat at 20 ° C and 65% RH) Commercially available blue color paper (Chujo NW-40) with crystal violet lactone (CVL) as the main pressure-sensitive dye
Using T), the coated surfaces of the color-developed sheet (lower paper) obtained in the example are superposed on each other so as to face each other, and the color is embossed with an electronic typewriter. The reflectivity 30 seconds after and 24 hours after the embossing is measured with a Σ-80 color difference meter (manufactured by Nippon Denshoku) and displayed as Y value. (2) Constant-temperature color-forming speed After storing the color-developing sheet obtained in the example and a commercially available blue-colored upper paper (Jujo NW-40T) in a constant temperature room at 2 ° C. for a day and a night, the two coated surfaces are combined to obtain a linear pressure. The color is developed by passing through a calender roll of 50 kg / cm. The color density at 10 seconds after color development is measured with a Σ-80 color difference meter and displayed as a Y value. The smaller the Y value, the better the color development performance at low temperatures. (3) Lightfastness of Colored Image The developed sheet colored by the method of (1) is exposed to outdoor direct light at 6:00 on a sunny day, and the density of the colorized image after the test is indicated by a Y value. (4) Plasticizer resistance of a color image A melamine-formaldehyde resin film microcapsule having an average particle diameter of 50 μm containing dioctyl phthalate (DOP) as a core substance is prepared, and a coating solution containing a small amount of a starch-based binder is applied by an air knife coater. 5g / c dry coating amount on high quality paper
coating and drying m ² and so as to prepare the DOP microcapsule coated paper. The DOP microcapsule coated paper and the (1)
100K after facing the color development surface of the color developing sheet
It is passed through a super calender roll having a linear pressure of g / cm to uniformly infiltrate DOP on the color-developed surface. The density one hour after the test is indicated by a Y value using a Σ-80 color difference meter. The lower the Y value and the smaller the difference from the value before the test, the better the plasticizer resistance of the color image. (5) Water Resistance of Colored Image The developed sheet colored by the method of (1) was immersed in water for 2 hours, and the density change of the color image was observed with the naked eye. (6) yellowing of the color-developing sheet (6-1) on the basis of the NO _X yellowing JIS L-1055 [dyeings and nitrogen oxide gas fastness test method of the dye by the color-developing sheet NaNO ₂ (sodium nitrite) NO _X generated by the reaction between the H ₃ PO ₄ (phosphoric acid)
Store for 1 hour in a closed container in a gas atmosphere and check the degree of yellowing. One hour after the test, use a WB-80 color difference meter to indicate the WB value. WB value is large and means that there is less yellowing in about NO _X atmosphere a small difference between the WB value of untested sheet. (6-2) Yellowing due to light The developed color sheet is irradiated for 4 hours with a carbon kirk fade meter (manufactured by Suga Test Instruments), and after the test, the result is indicated by WB value using a Σ-80 color difference meter. WB value is large and untested sheet
The smaller the difference from the WB value, the smaller the yellowing due to light irradiation. (7) Heat resistance of the color developing sheet The evaluation was made by measuring the tendency of the color developing ability to decrease during storage for a long period of time or at high temperature (particularly, the change in color density immediately after color development). After storing each of the color developing sheets in a thermostat at 50 ° C for 100 hours, use a commercially available paper for blue coloring (Jujo NW-40)
Color is developed by passing through a calender roll with a linear pressure of 50 kg / cm in combination with T). The color densities at 10 seconds and 24 hours after color development are indicated by a Y value of Σ-80 color difference meter. Similarly, the smaller the change in the undeveloped color density in the color development test, the better the long-term storage and heat stability. Synthesis Example 1 15.2 g (0.1 mol) of methyl salicylate, 50 ml of 1,2-dichloroethane, and 3.75 g of 96% concentrated sulfuric acid were charged into a glass reactor, and 52 g (0.5 mol) of styrene was added with vigorous stirring.
It was added dropwise at 2 ° C. over 6 hours. Thereafter, aging was performed at the same temperature for 3 hours to complete the reaction. Next, 50 g of an 85% aqueous sulfuric acid solution was added to the reaction solution, and the mixture was heated to distill off 1,2-dichloroethane. 50 ml of acetic acid in this
And a hydrolysis reaction was performed under reflux for 18 hours. After the completion of the reaction, the reaction solution was poured into 300 ml of water and allowed to stand, whereby a brown resin precipitated. This was tilted, the upper layer of water was discarded, and the plate was further washed twice with 300 ml of warm water. The weight average molecular weight of the obtained salicylic acid co-condensation resin is 96.
It was 0. Put this resin in a separate reactor at a temperature of 150-160
A mixture of zinc benzoate (16.3 g) and ammonium bicarbonate (10 g) was added slowly at 30 ° C. in 30 minutes. After the addition, stirring was continued for 1 hour at the same temperature, and the mixture was discharged, cooled and pulverized to obtain 79.5 g of a zinc benzoate modified salicylic acid resin. According to JIS-K-2548, the softening point of this product was 82 ° C. as measured with a ring and ball softening point measuring device. This is called salicylic acid resin polyvalent metal [A]. Synthesis Example 2 Benzyl salicylate 22.8 g (0.1 mol), methylene chloride
A glass reactor was charged with 75 ml and 15.9 g of 96% concentrated sulfuric acid, and 83.2 g (0.8 mol) of styrene was added dropwise at a temperature of 5 to 12 ° C. over 8.5 hours to react. After aging at the same temperature for 3 hours,
The mixture was neutralized with dilute aqueous ammonia and separated to obtain a methylene chloride solution of the co-condensation resin. The weight average molecular weight of this co-condensation resin was 1380. Next, the solvent was distilled off while heating the solution,
Temperature. A 20% aqueous zinc chloride solution (35 g, 0.5 mol) was added dropwise to the slightly viscous co-condensation resin, and the mixture was stirred for 12 hours under reflux. Then, after heating and stirring at a temperature of 140 ° C. for 2 hours, 250 ml of toluene was added. Next, the temperature was maintained at 70 to 80 ° C., and 7.3 g (0.12 mol) of 28% aqueous ammonia was added dropwise thereto, followed by stirring for 1 hour. Then, the mixture was allowed to stand, and the lower aqueous layer was separated and removed. Then, the temperature was raised and toluene was distilled off. The reddish-brown resin solution was discharged, cooled, and then pulverized to obtain 93.5 g of a zinc-modified salicylic acid co-condensation resin. Its softening point is 76 ℃
Met. This is called salicylic acid resin polyvalent metal [B]. Synthesis Example 3 The same reaction was carried out using 38.4 g (0.3 mol) of p-methylstyrene in place of the reaction styrene in the first stage of Synthesis Example 1. Next, 80 g of a 10% aqueous sodium hydroxide solution was added to the reaction solution.
(0.2 mol), and the solvent was distilled off by heating and heating.
Next, a hydrolysis reaction was performed at a temperature of 100 to 10 ° C. for 12 hours. The reaction solution is a slightly cloudy solution, which is diluted with 850 ml of water and then diluted with a 5% aqueous solution of zinc sulfate 400%.
g (0.07 mol) was added dropwise over 3 hours at a temperature of 20-25 ° C. The deposited precipitate was filtered, washed with water and dried in vacuo to obtain 52 g of a white zinc salt of salicylic acid resin. The softening point was 112 ° C. This is called salicylic acid resin polyvalent metal [C]. Synthesis Example 4 A salicylic acid co-condensation resin having a weight average molecular weight of 720 was obtained in the same manner as in Example 1 except that α-methylstyrene was used instead of styrene in the reaction of Synthesis Example 1. 4.1 g (0.05 mol) of zinc oxide was added to this resin and reacted at a temperature of 140 to 150 ° C. for 2 hours to obtain 76 g of a zinc-modified red-brown transparent salicylic acid co-condensation resin. The softening point was 71 ° C. This is called salicylic acid resin polyvalent metal [D]. Example 1 Using the salicylic acid resin Zn compound [A] obtained in Synthesis Example 1 as a color developer, a color development sheet (1) was obtained with the standard aqueous coating liquid formulation. Example 2 Using the salicylic acid resin Zn compound [B] obtained in Synthesis Example 2 as a color developer, a color development sheet (2) was obtained according to the standard aqueous coating liquid formulation. Example 3 Using the salicylic acid resin Zn compound [C] obtained in Synthesis Example 3 as a color developer, a color developing sheet (3) was obtained with the above standard aqueous coating liquid formulation. Example 4 Using the salicylic acid resin Zn compound [D] obtained in Synthesis Example 4 as a color developer, a color development sheet (4) was obtained with the standard aqueous coating liquid formulation. Example 5 A developing sheet (5) was obtained in the same manner as in Example 2 except that in place of 100 parts of the semisynthetic solid acid (Silton SS-1), 80 parts of Shilton SS-180 and 20 parts of zinc oxide were used. Example 6 The procedure of Example 3 was repeated, except that in place of 100 parts of the semi-synthetic solid acid (Silton SS-1), 80 parts of Shilton SS-1 and 20 parts of light calcium carbonate (Okutama Kogyo TP-123) were used. Thus, a color developing sheet (6) was obtained. Comparative Example 1 Example 1 except that a Zn compound of a salicylic acid resin was not used.
In the same manner as in the above, a color developing sheet (7) was obtained. Comparative Example 2 A developer sheet (8) was obtained in the same manner as in Example 1 except that the same amount of P-phenylphenol formaldehyde resin (Mitsui Toatsu RB) was used as the developer [A]. Comparative Example 3 Instead of semi-synthetic solid acid (Silton SS-1), activated clay (Mizusawa Chemical, Shilton DR-) conventionally known as a developer was used.
A developer sheet (9) was obtained in the same manner as in Example 1 except that 1) was used. Comparative Example 4 Example 1 was repeated except that the same amount of a Zn-modified salicylic acid-p-nonylphenol-formaldehyde condensate (Schenectady Chemical HRJ-4002) was used as the developer [A].
A developer sheet (10) was obtained in the same manner as described above. Comparative Example 5 A developer sheet (11) was obtained in the same manner as in Example 1 except that Zn 3,5-di-tert-butylsalicylate was used as the developer [A]. Comparative Example-6 A color developing sheet (12) was obtained in the same manner as in Example 2 except that the same amount of light calcium carbonate was used instead of the semi-synthetic solid acid (Silton SS-1). Table 1 summarizes the performance evaluation results of the thus-obtained developed sheets of Examples and Comparative Examples as pressure-sensitive copying paper. As is clear from Table 1, the pressure-sensitive copying paper color developing sheet of the present invention is an unprecedented excellent color developing sheet satisfying the physical properties required for the pressure-sensitive copying paper.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing the structure of a pressure-sensitive copying paper. In FIG. 1, each symbol is as follows. 1 upper paper, 2 middle paper, 3 lower paper, 4 upper microcapsules, 5 developer, 6 writing pressure

   ────────────────────────────────────────────────── ─── Continuation of front page                   (56) References JP-A-1-133780 (JP, A)                 JP-A-58-217389 (JP, A)                 JP-A-57-15996 (JP, A)

Claims (1)

(57) [Claims] (A) General formula (I) (Wherein R ₁ represents an alkyl group having 1 to 12 carbon atoms, an aralkyl group, an aryl group or a cycloalkyl group.) A salicylic acid ester represented by the general formula (II) (Wherein, R ₂ and R _{3 each} represent a hydrogen atom or a methyl group, and R ₄ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms). A semi-synthetic solid acid obtained by introducing a magnesium and / or aluminum component into a clay mineral treated with (B) an acid, wherein the resin is hydrolyzed and then reacted with a polyvalent metal salt; And a color developing sheet for pressure-sensitive copying paper.