JPH05193251A - Developing ink - Google Patents

Abstract

PURPOSE:To prevent contamination from occurring by blending a color developer, an inorganic pigment, a photocurable chemical compound and a photopolymerization initiator with an organic acid or the sodium salt of the organic acid, and thereby preparing a photocurable developing ink for pressure sensitive sheet. CONSTITUTION:Specified amount of color developer, photocurable chemical compound and thermal reaction polymerization inhibitor are blended and the blend is thermally dissolved to prepare a varnish. In addition, specified amount of inorganic pigment, photopolymerization initiator, organic acid or the sodium salt of organic acid, waxes and photocurable chemical compound are added to the varnish. Thus, the blend is kneaded using a three-roll mill to prepare the photocurable developing ink for pressure sensitive recording sheet. The typical examples of the photocurable chemical compound are aliphatic, alicyclic, aromatic 2 to 6 valent polyhydric alcohol, polyacrylate or polymethacrylate of polyalkyleneglycol. The typical examples of the photopolymerization initiator are benzoinalkylethers, acetophenones and benzylketals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photo-curable developer ink for pressure-sensitive recording sheets, and more particularly to a photo-curable developer ink for pressure-sensitive recording sheets in which the occurrence of scumming is prevented during offset printing.

[0002]

2. Description of the Related Art A color image is formed by a reaction between an electron-donating or proton-accepting colorless organic compound (hereinafter referred to as a color former) and an electron-accepting or proton-donating compound (hereinafter referred to as a developer). It has long been known to gain. Pressure-sensitive recording papers (for example, US Pat. Nos. 2,505,470 and 2,505,489) are used as concrete examples of this phenomenon.
Issue 2, Issue 2,505,471, Issue 2,548,366
Issue 2, Issue 2,712,507, Issue 2,730,456
Issue 2, Issue 2,730,457, Issue 3,418,250
No. 3,672,935), thermal recording paper (for example, Japanese Examined Patent Publication Nos. 43-4,160, 43-7,600 and 4).
5-14,039, US Pat. No. 2,939,009)
Etc. Furthermore, a printing method is known in which an ink containing a color-developing agent is supplied to a sheet coated with a color-developing agent to obtain a colored image (German Patent OLS 1,939,962).
The color developer has the properties defined previously, and examples thereof include clays, phenol resins, and metal salts of aromatic carboxylic acids.

In general, these color developing agents are usually applied on the entire surface of a support, and a desensitizing ink must be applied by printing to a portion where a user does not want to copy to prevent color development. .. This operation is very complicated and uneconomical because it requires two coatings. In order to solve this drawback, a method has been proposed in which a color-developing ink containing a color-developing agent is applied by printing on only a necessary portion of the support.

Among the color-developing inks used for such purposes, there is a photo-curable color-developing ink which does not use organic solvents such as acetic acid esters and alcohols.
No. 8,437, 52, 141,705 and 52.
-147,107 and the like. Certainly, the above photo-curable developer ink improves the ink drying property by being irradiated with light, so even if the developer ink is printed on the back side of a sheet coated with microcapsules containing a color-forming agent on one side, the color fog develops. It does not occur, and since it does not use an organic solvent, it has the advantages of fire protection, health and pollution problems.

[0005]

However, the conventional photo-curable color developing ink has a problem that background stain occurs when offset long-run printing is performed. As a result of various studies to solve the above problems, the present inventors have found that phosphoric acid contained in the fountain solution used during offset printing reacts with the developer to form a water-insoluble reaction product. Since it has the property of repelling water, it was found that it is the cause of the occurrence of scumming, and by adding an organic acid or a sodium salt of an organic acid to the color-developing ink, a water-insoluble reactant The present invention has been accomplished by finding that generation is suppressed and generation of background stain can be prevented.

Accordingly, it is an object of the present invention to provide a photo-curable developer color ink for pressure-sensitive recording sheets which does not cause scumming during offset printing. The above-mentioned object of the present invention is a photocurable developer ink for a pressure-sensitive recording sheet, which comprises a developer, an inorganic pigment, a photocurable compound and a photopolymerization initiator, wherein the ink is an organic acid or a sodium salt of an organic acid. Was achieved by including.

The present invention will be described in detail below. Examples of the organic acid used in the present invention include citric acid, tartaric acid, gluconic acid, lactic acid, glycolic acid, oxalic acid and adipic acid, and sodium salts of these organic acids are also used. Of these, citric acid, tartaric acid, and sodium gluconate are particularly preferable.

The amount of organic acid or sodium salt of organic acid used is 0.1 to 30% by weight, preferably 1 to 10% by weight, based on the color developer. Examples of the developer used in the present invention include metal salts of aromatic carboxylic acids and phenolic resins, and metal salts of aromatic carboxylic acids are preferable.
The content of this metal salt of aromatic carboxylic acid in the color developing ink of the present invention is preferably 25 to 35%.

The metal salts of aromatic carboxylic acids used in the present invention are, for example, US Pat. Nos. 3,864,146 and 3,98.
3,292, JP-B-51-25174, JP-A-62.
No. 19486, JP-A-63-254124 and the like. The aromatic carboxylic acid in the metal salt of the aromatic carboxylic acid is useful that having a hydroxyl group in the ortho or para position with respect to the carboxy group, among which salicylic acid derivatives are preferable, and substitution of alkyl group, aryl group, aralkyl group, etc. Those having a group and having a total number of carbon atoms of the substituents of 8 or more are preferable.

Specific examples of preferable metal salts of salicylic acid derivatives used in the present invention are 3,5-di-t-butylsalicylic acid, 3,5-di-t-octylsalicylic acid, and
3,5-di-t-nonylsalicylic acid, 3,5-di-t-
Dodecylsalicylic acid, 3-methyl-5-t-dodecylsalicylic acid, 3-t-dodecylsalicylic acid, 3-isododecylsalicylic acid, 5-cyclohexylcyclohexylsalicylic acid, 3,5-bis (α-methylbenzyl) salicylic acid, 3,5- Bis (α, α-dimethylbenzyl) salicylic acid, 3-methyl-5- (α-methylbenzyl) salicylic acid, 3- (α, α-dimethylbenzyl) -6-methylsalicylic acid, 3- (α-methylbenzyl)- 5-
(Α, α-Dimethylbenzyl) salicylic acid, 3- (α,
α-Dimethylbenzyl) -6-ethylsalicylic acid, 3-
Phenyl-5- (α, α-dimethylbenzyl) salicylic acid, 3- (α-methylbenzyl) -5-t-butylsalicylic acid, 3- (α-methylbenzyl) -5-t-octylsalicylic acid, 3- (α -Methylbenzyl) -5-t-
Examples include zinc salts, nickel salts, aluminum salts, calcium salts and the like of octyl salicylic acid, carboxy-modified terpene phenol resin, salicylic acid resin which is a reaction product of 3,5-bis (α-methylbenzyl) salicylic acid and benzyl chloride, and the like.

The photocurable compound used in the present invention is
(1) Aliphatic, alicyclic, araliphatic, aromatic polyhydric alcohols having 2 to 6 valences and polyacrylates or polymethacrylates of polyalkylene glycols, (2) aliphatic,
Alicyclic, araliphatic, polyhydric alcohol polyacrylate or polymethacrylate in a form obtained by adding an alkylene oxide to a polyhydric alcohol having a valence of 2 to 6;
(3) Polyacryloyloxyalkyl phosphate ester or polymethacryloyloxyalkyl phosphate ester, (4) Polyester polyacrylate or polyester polymethacrylate, (5) Epoxy polyacrylate or epoxy polymethacrylate, (6) Polyurethane polyacrylate Alternatively, polyurethane polymethacrylate, (7) polyamide polyacrylate or polyamide polymethacrylate, (8) polysiloxane polyacrylate or polysiloxane polymethacrylate may, for example, be mentioned. Of these, the compounds (1) and (2) are particularly preferable.

Examples of the photopolymerization initiator used in the present invention include benzoin alkyl ethers, acetophenones, benzyl ketals, benzophenones and thioxanthones. Of these, acetophenones are particularly preferable, and specifically, 2-methyl-1- [4- (methylthio) -phenyl] -2-morpholino-1-propanone, 2-hydroxy-2-methyl-1-phenyl- 1-
Propanon etc.

Examples of the inorganic pigment used in the present invention include white pigments such as titanium oxide and zinc oxide. The alumina pigment previously proposed by the applicant of the present invention is excellent in color developing ability and improves offset printing suitability. White (Japanese Patent Application No. 3-523)
No. 99) is preferably used. As other additives of the color developing ink of the present invention, a thermal reaction polymerization inhibitor, waxes and the like are added if necessary.

In the present invention, a method for producing a color developing ink may be a usual method. First, a color developing agent, a photocurable compound and a thermal reaction polymerization inhibitor are mixed and heated to dissolve to form a varnish. Then, a photopolymerization initiator, a pigment, a wax and, if necessary, a photocurable compound for adjusting fluidity are added to the varnish and the mixture is kneaded by a three-roll mill to complete the varnish.

The color-developing ink produced according to the present invention is spot-printed on a copy-needed portion using a printing machine on the surface of fine paper, the surface of a film base, the back surface of a sheet coated with microcapsules containing a coloring agent on one surface, and the like. The printed surface is immediately cured by irradiation with light. An offset method is used as the printing method. A mercury lamp, a metal halide lamp, or the like is used as the light irradiation source.

The coating amount of the color developing ink of the present invention is 0.5.
-3 g / m < ² >, preferably 1-2 g / m < ² >. The color-developing agent that develops color on the color-developed ink printing coated surface of the present invention is not particularly limited, but a triphenylmethanephthalide compound,
Examples thereof include fluoran compounds, phenothiazine compounds, indolylphthalide compounds, leuco auramine compounds, rhodamine lactam compounds, triphenylmethane compounds, triazene compounds, spiropyran compounds, and fluorene compounds. Specific examples of phthalides include U.S. Pat. Nos. 23,024 and 3,491,111.
No. 3,491,112, No. 3,491,11
6, No. 3,509,174, and specific examples of fluoranes are U.S. Pat. Nos. 3,624,107 and 3,62.
No. 7,787, No. 3,641,011, No. 3,4
No. 62,828, No. 3,681,390, No. 3,
920,510, 3,959,571, and specific examples of spiro dipyrans are described in US Pat. No. 3,971,808.
U.S. Pat. No. 3,775,424, U.S. Pat. No. 3,853,869, U.S. Pat. No. 4,246,318, and fluorene compounds are disclosed in Japanese Patent Application No. 61- No. 240989 and the like.

The color former is dissolved in a solvent, encapsulated and applied to a support. As the solvent, natural or synthetic oils can be used alone or in combination. Examples of the solvent include cottonseed oil, kerosene, paraffin oil, naphthene oil, alkylated biphenyl, alkylated terphenyl, chlorinated paraffin, alkylated naphthalene, diphenylalkane and the like. As a method for producing the color-forming agent-containing microcapsules, an interfacial polymerization method, an internal polymerization method, a phase separation method, an external polymerization method, a coacervation method and the like are used. A water-soluble binder or a latex binder is generally used for preparing a coating liquid containing a color-forming agent-containing microcapsule. Further, cellulose powder, starch particles, talc, etc. are added as a capsule protecting agent to obtain a color developer-containing microcapsule coating solution.

The color-developing ability of the surface printed with the color-developing ink of the present invention was confirmed by using the following color-forming agent-containing microcapsule sheet. (Preparation of Microcapsule Sheet Containing Coloring Agent) 5 parts of a partial sodium salt of polyvinyl sulfonic acid (manufactured by National Starch, VERSA, TL500, average molecular weight 500,000) was added to 95 parts of hot water at about 80 ° C. with stirring. Then melt and cool. The pH of the aqueous solution is 2
˜3, and a 20 wt% sodium hydroxide aqueous solution was added thereto to adjust the pH to 4.0. On the other hand, crystal violet lactone 4 parts and 3- [4- (diethylamino) -2
-Ethoxyphenyl] -3- (2-methyl-1-octyl-3-indolyl) -4-azaphthalide dissolved in 2 parts of 100 parts of diisopropylnaphthalene was added to 5% aqueous solution of a partial sodium salt of polyvinylbenzenesulfonic acid 1
It was emulsified and dispersed in 100 parts to obtain an emulsion having a particle size of 4.5 μm in average diameter. Separately, 6 parts of melamine and 11 parts of 37% by weight formaldehyde aqueous solution were heated and stirred at 60 ° C. for 3
After 0 minutes, a transparent mixed aqueous solution of melamine and formaldehyde and a melamine-formaldehyde initial condensation product was obtained.
The pH of this mixed aqueous solution was 6-8. Hereinafter, the mixed aqueous solution of melamine, formaldehyde, and melamine-formaldehyde precondensate will be referred to as an initial condensate solution.
The initial condensate solution obtained by the above method was added to and mixed with the above emulsion, the pH was adjusted to 6.0 with a 3.6 wt% hydrochloric acid solution while stirring, the liquid temperature was raised to 65 ° C. and 360 minutes. Continued to stir. The capsule solution was cooled to room temperature and adjusted to pH 9.0 with a 20 wt% sodium hydroxide aqueous solution. To this capsule dispersion, 200 parts of a 10 wt% polyvinyl alcohol aqueous solution and 50 parts of starch particles were added, and water was added to prepare a solid content concentration of 20% to prepare a color developer-containing microcapsule coating solution. This coating solution was applied to an original paper of 50 g / m ^{2 with} an air knife coater so that a solid content of 5 g / m ² was applied and dried to obtain a microcapsule sheet containing a color former. Hereinafter, the photocurable color developer ink for pressure-sensitive recording of the present invention will be specifically described with reference to examples, but the present invention is not limited to the examples.

[0019]

【Example】

Example 1 Zinc 3,5-di- (α-methylbenzyl) salicylate 5
0 part, di-trimethylolpropane tetraacrylate 20 parts, propylene oxide adduct of neopentyl glycol diacrylate 30 parts and N-nitrosophenylhydroxylamine ammonium salt 0.1 part 110 parts
The mixture was heated to 0 ° C. and uniformly dissolved to obtain a varnish. To 62 parts of this varnish, 4 parts of 2-methyl-1- [4- (methylthio) -phenyl] -2-morpholino-1-propanone, 3 parts of 2-hydroxy-2-methyl-1-phenyl-1-propanone, polyethylene 3 parts of wax, 3 parts of citric acid, 10 parts of titanium oxide, and 8 parts of alumina white are kneaded with a three-roll mill, and finally 10 parts of propylene oxide adduct of neopentyl glycol diacrylate is added,
A developer ink was obtained. Example 2 A color developing ink was obtained in the same manner as in Example 1 except that 3 parts of sodium gluconate was used instead of 3 parts of citric acid. Example 3 A color developing ink was obtained in the same manner as in Example 1 except that 3 parts of tartaric acid was used instead of 3 parts of citric acid. Comparative Example A developer ink was obtained in the same manner as in Example 1 except that 1 part of citric acid was not used. Example 4 40 parts of zinc 3- (α, α-dimethylbenzyl) -6-methylsalicylate, 20 parts of polyester acrylate oligomer, 30 parts of 1,6-hexanediol diacrylate
Parts and 0.1 part of N-nitrosophenylhydroxylamine ammonium salt were heated to 110 ° C. and uniformly dissolved to obtain a varnish. 2-Methyl-1- on 62 parts of this varnish
[4- (methylthio) -phenyl] -2-morpholino-
1-propanone 4 parts, 2-hydroxy-2-methyl-1
-Phenyl-1-propanone (3 parts), polyethylene wax (3 parts), citric acid (1 part), titanium oxide (10 parts), and alumina white (8 parts) were kneaded with a three-roll mill, and finally 1,
Add 10 parts of 6-hexanediol diacrylate,
A developer ink was obtained. Comparative Example 2 A colored ink was obtained in the same manner as in Example 2 except that 3 parts of citric acid was not used.

Using the metal halide lamp with an output of 8 kw so that the ink of 1.5 g / m ² can be printed on the surface of the ^high- quality paper of 50 g / m ² with the above-mentioned color-developing ink, the speed of 80 m / min 000 m was printed. The fountain solution used had the following composition. Water 1000 g Phosphoric acid (85%) 0.12 g Gum arabic 0.8 g Evaluation of the background stain of the printed sample and the color developing ability of the printed surface was performed by the following method. (1) Background stain of printed sample The printed sample at the time of printing 8,000 m was subjected to a spray checker containing a color former, and the background stain of the non-printed portion was visually determined. (2) Color development ability of the printed surface The printed sample and the microcapsule sheet containing the color former are combined to apply a load pressure of 300 kg / cm ² to develop the color.
The color density after one day was measured with a Macbeth reflection densitometer.

The results obtained are shown in Table 1 below.

[0022]

[Table 1]

[0023]

As shown in Table 1, the color-developing ink of the present invention has improved background stain without lowering the color-developing ability as compared with the color-developing ink for comparison.

Claims (1)

[Claims] 1. A photocurable developer ink for pressure-sensitive recording paper, which comprises a color developer, an inorganic pigment, a photocurable compound and a photopolymerization initiator together with an organic acid or a sodium salt of an organic acid.