JPH09290557A - Pressure-sensitive copying developing sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize the prevention of the blurring of an ink jet recording image and the lowering of the density of the image under the state getting wet with water by a method wherein the pH of the surface of a developing layer is specified in a pressure-sensitive copying developing sheet, which is prepared by providing the organic developer-containing developing layer on a support. SOLUTION: In this pressure-sensitive copying developing sheet, in which an organic developer is employed, in order to control the surface of a developing layer to the range of pH7 or lower, there is a method for applying a pH controller to the surface of the surface of the developing layer. In this case, as the pH controller, a hydrogencarbonate or the like is employed as well as an organo-hydrogencarbonate. In the ink jet recording system, in which the above- mentioned pressure-sensitive copying developing sheet is used, a water-based ink containing dye, which changes from water-soluble one to non-water-soluble one due to change of pH is used, for example a tetra-sodium salt of 1- hydroxy-2-(4-[3,5-dicarboxy-phenylazo]-7-sulfonate-1-i1)-3-sulfo-7-ami nonaphthalene or the like is cited.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensitive color developing sheet suitable for ink jet recording.

[0002]

2. Description of the Related Art A pressure-sensitive copying paper is composed of a paper on which a color-forming agent microcapsule composition mainly containing microcapsules containing an oily substance in which an electron-donating organic color-forming agent or the like is dissolved is coated on the back surface of a support. A medium paper on which a color developer composition mainly composed of an electron-accepting color developer that develops color when it comes into contact with the color developer is applied to the surface of the support, and the color former microcapsule composition is applied to the back surface And a lower paper coated with a developer composition on the surface of a support, and generally used in combination of upper paper-lower paper or upper paper-middle paper-lower paper in order of writing pressure, pressure of a printer, etc. The microcapsules are destroyed and the oil dissolving the color former transfers to the color developing layer,
The color is developed by reacting with the color developer. In addition, a self-coloring type pressure-sensitive copying paper in which a color former and a developer are coated on the same surface of a support so that pressure-sensitive recording can be performed with one sheet is also known as one form thereof.

Pressure-sensitive copying paper is used for various kinds of slips, and those slips have been conventionally used by form printing by offset printing, letterpress printing or the like. In recent years, along with the technical development of the ink jet recording method, an example in which the ink jet recording method is used for form printing has come to be seen. The inkjet recording method has the advantages that plate making is not required and the format can be changed easily. It can be used for printing small lots or variable information such as barcodes on slips. Ink-jet recording is also widely used for pressure-sensitive copying paper.

As the color developer used for pressure-sensitive copying paper,
Inorganic color developing agents such as acid clay, activated clay and attapulgite, and organic developing agents such as phenol-formaldehyde resin, polyvalent metal salt of salicylic acid derivative, polyvalent metal salt of terpene phenol resin and polyvalent metal salt of salicylic acid-containing copolymer. Coloring agents are known. In particular, the organic color developer has a high color density and has good light resistance, chemical resistance, temporal stability, and the like of the color image.

However, when the ink jet recording system is used for the pressure sensitive copying color developing sheet using the conventional organic color developing agent, the formed ink jet recording image does not have sufficient water resistance and the ink jet recording image when wet with water. However, there is a problem in that the image quality of the ink jet recording is deteriorated, and sufficient quality cannot be obtained.

In order to improve this, Japanese Patent Laid-Open No. 3-236
Japanese Patent Publication No. 986 describes that a cationic substance is mixed in the color developing layer of a pressure-sensitive copying sheet. However,
In order to reduce the viscosity of the color developing layer coating liquid or stabilize the viscosity, the coating liquid is usually preferably anionic, but when a cationic substance is added to the anionic color developing layer coating liquid, The coating liquid thickens or gels, which makes coating very difficult. Further, the cationic substance acts on the color developing agent to lower the color developing ability, and the color density of pressure sensitive recording is lowered, so that there is a problem that sufficient quality cannot be obtained as a pressure sensitive copying paper.

On the other hand, in the ink jet recording system, recording is carried out using an aqueous ink composed of an aqueous solvent and a water-soluble dye. In paragraph No. 0009 of JP-A-6-219044, it exists in the form of a water-soluble salt (for example, ammonium salt) in the ink, and is insolubilized on the surface of the paper on which it is attached (for example, counterion H
It is described as a dye that achieves both solubility in ink and water resistance of an image by replacing it with ⁺ to become an insoluble substance. Such a dye changes from water-soluble to water-insoluble due to a change in pH. I know that.

[0008]

DISCLOSURE OF THE INVENTION According to the present invention, in a color-developing sheet for pressure-sensitive copying using an organic color developer, when an ink jet recording system is used, bleeding of an ink jet recorded image when wet with water and An object of the present invention is to provide a color-developing sheet for pressure-sensitive copying paper which prevents a decrease in image density and maintains a sufficient color density as pressure-sensitive copying paper.

[0009]

SUMMARY OF THE INVENTION The present invention is a pressure-sensitive copying color developing sheet using an organic color developing agent, wherein the surface of the color developing layer is p.
It relates to a color-developing sheet for pressure-sensitive copying, which is in a range of H7 or less. Furthermore, the present invention is most suitable for printing using an inkjet recording system using an aqueous ink containing a dye that changes from water-soluble to water-insoluble due to a change in pH.

Generally, the color developing layer of the color developing sheet for pressure-sensitive copying contains pigments such as calcium carbonate and kaolin for the purpose of enhancing the color density and whiteness, and therefore the surface of the color developing layer is usually It is in an alkaline state.
However, when ink jet recording is carried out on such a color-developing sheet with a water-based ink containing a dye that changes from water-soluble to water-insoluble due to a change in pH, the insolubility of the dye hardly progresses, and only an ink jet recorded image having poor water resistance is obtained. I can't get it.

Therefore, as a result of intensive studies by the present inventors, in the case of a pressure-sensitive copying color developing sheet, the pH of the surface of the color developing agent layer is
When the pH is 7 or less, it was found that the ink jet recorded image does not bleed even if it gets wet with water and the density of the recorded image does not decrease, and the present invention has been completed. Also,
In the present invention, even if the pH of the surface of the color developing layer becomes small, the color density due to pressure-sensitive recording does not decrease, and the function as pressure-sensitive copying paper is sufficiently maintained.

In the present invention, the pH of the surface of the color developer layer may be pH 7 or less, and is adjusted within a range that does not impair other properties such as color density. The “pH” referred to in the present invention
Means a paper surface pH defined by the Japan Pulp and Paper Technology Association (J'TAPPI).

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in detail. In the present invention, in order to adjust the pH of the surface of the color developing layer to pH 7 or less, there are a method of adjusting the pH by a substance added to the coating liquid for the color developing layer and a method of applying a pH adjuster on the surface of the color developing layer. It is more effective to apply the pH adjusting agent on the surface without any adverse effect on the color developing ability of the color developing agent. As the pH adjuster, organic carboxylic hydrogen salts such as sodium hydrogen phthalate and potassium hydrogen phthalate, as well as hydrogen phosphate, hydrogen carbonate and the like can be used. These pH adjusting agents are applied alone or together with pigments, binders and the like. In addition, a water resistant agent, a sizing agent and the like can be added to the coating liquid containing the pH adjusting agent, if necessary. The coating amount of the pH adjusting agent coating liquid is appropriately adjusted and applied so as to obtain a target surface pH of the color developing layer.

As the electron-accepting developer used in the present invention, any of the organic acidic substances known as organic developers can be used. To give a concrete example, Japanese Examined Japanese Patent Publication Sho 42
No. 20144, phenol formaldehyde resin, phenol acetaldehyde resin, phenol acetylene resin, and polyvalent metal salts thereof; benzoic acid described in JP-B-49-55410 and JP-B-51-25174; 4-Methyl-nitrobenzoic acid, p-isopropylbenzoic acid, 2,5-dinitrobenzoic acid, p-tert-butylbenzoic acid, 4-methyl-3
-Nitrobenzoic acid, salicylic acid, m-hydroxybenzoic acid, p-hydroxybenzoic acid, 3,5-dinitrosalicylic acid, 5-tert-butylsalicylic acid, 3-phenylsalicylic acid, 3-methyl-5-tert-butylsalicylic acid, 3,5-di-tert-butylsalicylic acid,
3,5-di-tert-amylsalicylic acid, 5-cyclohexylsalicylic acid, 3-methyl-5-isoamylsalicylic acid, 5-isoamylsalicylic acid, 3,5-di-se
c-Butylsalicylic acid, 5-nonylsalicylic acid, 2-hydroxy-3-methylbenzoic acid, 2-hydroxy-5-
tert-Butylbenzoic acid, 5,5-methylenedisalicylic acid, acetaminobenzoic acid, 2,4-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, 3,5-di-
α, α-Dimethylbenzyl salicylic acid, 3,5-di-α
-Aromatic carboxylic acids such as methylbenzyl salicylic acid, 1-hydroxy-2-naphthoic acid, 2-hydroxy-3-naphthoic acid, 2-hydroxy-1-naphthoic acid, and those aromatic carboxylic acids and copper, lead, magnesium,
Metal salts with metals such as zinc, aluminum, tin, and nickel; polyvalent metal salts of carboxy-modified terpene phenolic resins described in JP-A-63-194876; salicylic acid novolak described in JP-A-48-8215. Resin: JP-A-62-176875, JP-A-63-530
92, JP-A-63-186729 and the like, copolymers of salicylic acid with alkoxyxylene, or compounds such as trialkylbenzenes and styrene derivatives, or polyvalent metal salts thereof; JP-A-63-13285.
Examples thereof include metal salts of oligobenzylated aromatic hydroxycarboxylic acids described in 7.

The pigment contained in the color developing layer of the present invention includes zinc oxide, titanium oxide, magnesium oxide, aluminum hydroxide, zinc hydroxide, kaolin, calcined kaolin,
Examples thereof include silica, barium sulfate, magnesium silicate, aluminum silicate, talc, etc., but are not limited thereto.

As the binder, a water-soluble polymer such as starch, sodium alginate, gum arabic, dextrin, glue, gelatin, casein, collagen, viscose, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, etc. and acetic acid. A vinyl emulsion, a styrene-butadiene copolymer emulsion or the like can be used, but these are not particularly limited.

The color developing layer coating liquid of the present invention may contain the above-mentioned color developing agents, pigments, binders and other various auxiliaries known in the field of pressure-sensitive copying paper production. The method for preparing the coating liquid is not particularly limited, and is appropriately prepared according to a conventional method. The type and amount of the color developer and various other components used in the present invention are determined according to the required performance and recording suitability, but the color developer is usually 1 to 20 relative to the total solid content of the color developing layer.
It is suitable to add about 50% by weight, about 50 to 95% by weight of pigment, and about 1 to 40% by weight of binder.

The method for applying the coating solution for the color developing layer is not particularly limited, and it is applied to a substrate such as paper or synthetic paper using an air knife coater, roll coater, blade coater, rod coater, curtain coater or the like.

In the ink jet recording system used for the pressure-sensitive copying color developing sheet of the present invention, an aqueous ink containing a dye which changes from water-soluble to water-insoluble by a change in pH is used. Such a dye is an acidic or direct dye, is present in the ink as a salt of a cation such as an alkali metal ion or ammonium ion, and is water-soluble, and after recording, the solvent evaporates to a cation that is a counter ion. It is known that ions are desorbed and replaced with H ⁺ to become a water-insoluble substance. In the present invention, any ink containing a dye having such a property may be used, and specifically, for example, JP-A-2
1-Hydroxy-2- (4- [3,5
-Dicarboxy-phenylazo] -7-sulfo-naphth-1-
Ilazo) -3-sulfo-7-aminonaphthalene tetrasodium salt and the like can be mentioned.

[0020]

EXAMPLES Hereinafter, the effects of the present invention will be described in detail with reference to examples and comparative examples, but the present invention is not limited to these examples. In addition, the part and% shown below show a weight part and weight%, respectively.

[Example 1] By a sand grinder,
18 parts of a 30% aqueous dispersion of 3,5-di (α-methylbenzyl) salicylic acid zinc salt having an average particle size of 2 μm, 100 parts of kaolin, 20% polyvinyl alcohol (trade name:
PVA-105, manufactured by Kuraray Co., Ltd.) 70 parts of an aqueous solution, 10 parts of a carboxy-modified SBR latex as a solid content, and 100 parts of water were mixed to prepare a coating material having a dry weight of about 60 g / m ^{2 on} a base paper of 60 g / m ^2. The developer was coated so that the coating amount was 6 g / m ^{2, and} the surface of the developer layer was adjusted to 6.8 by adjusting the surface pH of the developer layer by using an air knife coater and applying an aqueous solution of ammonium chloride. A color developing paper for pressure-sensitive copying paper was obtained.

[Embodiment 2] Pressure sensitive copying in which the surface pH of the color developing layer was 6.7 in the same manner as in Embodiment 1 except that the ammonium chloride aqueous solution of Example 1 was changed to a disodium hydrogen phosphate aqueous solution. A developer paper was obtained.

[Embodiment 3] A color-developing paper for pressure-sensitive copying having a surface pH of 6.8 in the color developing layer, in the same manner as in Example 1 except that the ammonium chloride aqueous solution of Example 1 was changed to an aluminum sulfate aqueous solution. Got

[Embodiment 4] With a sand grinder,
18 parts of a 30% aqueous dispersion of 3,5-di (α-methylbenzyl) salicylic acid zinc salt having an average particle size of 2 μm, 100 parts of kaolin, 20% polyvinyl alcohol (trade name:
PVA-105, manufactured by Kuraray Co., Ltd.) 70 parts aqueous solution, 10 parts of carboxy-modified SBR latex as a solid content, 100 parts of water were mixed, and a coating material whose pH was adjusted with ammonium chloride was 60 g / m using an air knife coater. ^It was applied to the base paper of No. ^{2 so} as to have a dry weight of about 6 g / m ² to obtain a color-developing paper for pressure-sensitive copying paper having a surface pH of the color-developing layer of 6.8.

Comparative Example 1 A color developing paper for pressure sensitive copying paper having a surface pH of the color developing layer of 7.2 was prepared in the same manner as in Example 1 except that the aqueous ammonium chloride solution was not applied. Obtained.

Comparative Example 2 A developer for pressure-sensitive copying paper having a surface pH of the developer layer of 7.3 was obtained by applying an aqueous solution of ammonium chloride in Example 1.

[Comparative Example 3] A pressure-sensitive copying developer paper having a surface pH of the developer layer of 7.2 was obtained by applying an aqueous solution of disodium hydrogen phosphate in Example 2.

[Comparative Example 4] With a sand grinder,
18 parts of a 30% aqueous dispersion of zinc 3,5-di (α-methylbenzyl) salicylate having an average particle diameter of 2 μm, 100 parts of calcium carbonate, 20% polyvinyl alcohol (trade name: PVA-105, Kuraray Co., Ltd.) 70) aqueous solution 70
Parts, carboxy-modified SBR latex as solids
Approximately 6 g / m ² dry weight of the coating composition containing 0 part and 100 parts water on the base paper of 60 g / m ² by using an air knife coater.
^It was applied so that the coating amount was ² , and the surface pH of the color developing layer was 7.
A color-developing paper for pressure-sensitive copying paper of 9 was obtained.

[Comparative Example 5] With a sand grinder,
18 parts of a 30% aqueous dispersion of 3,5-di (α-methylbenzyl) salicylic acid zinc salt having an average particle size of 2 μm, 100 parts of kaolin, 20% polyvinyl alcohol (trade name:
70 parts of PVA-105, Kuraray Co., Ltd. aqueous solution, 10 parts of carboxy-modified SBR latex as solid content, styrene methacrylic acid ester quaternary ammonium salt copolymer (Saftomer ST-3100, Mitsubishi Petrochemical Co., Ltd.) )
As a solid content, 2 parts and 100 parts of water were mixed to prepare a coating solution, but the viscosity was remarkably increased and coating was impossible.

The respective color developing papers described above were evaluated for recording suitability as pressure sensitive copying paper and ink jet printing suitability by the following methods, and the results are shown in Table 1. [Suitability of pressure-sensitive copying paper] Color density: Commercial top paper NW40T (Nippon Paper Industries Co., Ltd.)
) And developer paper are overlapped so that the application surfaces face each other,
After calendering at a linear pressure of 50 kg / cm, the color density after 24 hours is measured using a Macbeth densitometer (RD914, Wratten # 1).
06 filter, MAKUBETH) was used (the larger the value, the better the color development).

[Inkjet printing characteristics] Printing quality: Inkjet printer BJC-400J
(Canon Co., Ltd.) was used for printing, and the bleeding of the ink in the printed portion was judged as the target sheet. ○ No bleeding × With bleeding Water resistance: Printing was performed using the above-mentioned recording device, and after 24 hours had elapsed after printing, one drop of distilled water was dropped on the printed area to visually check the decrease in ink jet print density and the degree to which ink had melted. A judgment was made. ○ No decrease in print density × Some decrease in print density

[0032]

[Table 1]

As is clear from the results shown in Table 1, in the examples of the present invention in which the color developing layer was adjusted to pH 7 or less,
Practically satisfactory results were obtained in terms of both suitability for pressure-sensitive copying paper and suitability for inkjet printing, but in the case of Comparative Examples 1 to 4 in which the pH of the color developing layer was not adjusted to pH 7 or less, inkjet recording was performed. The printing quality was good, but the water resistance of the ink jet recorded image was extremely poor. Therefore, it can be seen that the pH of the surface of the color developing layer has a great effect on the water resistance of the ink jet recorded image.

[0034]

The color-developing color developing sheet for pressure-sensitive copying of the present invention prevents deterioration of the quality of an ink-jet recording image when it is wet with water when printed using an ink-jet recording system, and is used as a pressure-sensitive copying paper. It is a very excellent pressure-sensitive copying developer sheet that can maintain a sufficient color density.
Further, it is not necessary to add another additive such as a cationic substance to the color developing layer for imparting water resistance, which is industrially advantageous and highly practical.

Claims (2)

[Claims] 1. A pressure-sensitive color developing sheet comprising a support and a color developing layer containing an organic color developer, wherein the surface of the color developing layer has a pH of 7 or less. Development color sheet for copying. 2. The color-developing sheet for pressure-sensitive copying according to claim 1, wherein ink jet recording is carried out using an aqueous recording liquid containing a dye which changes from water-soluble to water-insoluble due to a change in pH.