JP2000319566A - U.v ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a U.V ink using a monomer or oligomer for a ultraviolet curable resin as a varnish and retaining printability and film strength in a good state notwithstanding temperature change in an environment when applied. SOLUTION: This ink is made to have viscosity of 2-8 Pa.s when measured at 23 deg.C and a shear rate of 100 (1/s). The vanish preferably has viscosity of >=450 Pa.s (especially >=1,000 Pa.s) when measured at 23 deg.C and a shear rate of 20 (1/s). Addition of pigment, powder as a viscosity adjusting agent and the like to the vanish enables the ink to meet the condition of viscosity. The powder preferably is added in an amount of <=10 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultraviolet-curable ink, and more particularly to an ultraviolet-curable ink suitable for stencil printing, which exhibits excellent printability and film strength irrespective of temperature changes in the use environment. .

[0002]

2. Description of the Related Art An ultraviolet curable ink using an ultraviolet curable resin as a varnish is disclosed in Japanese Patent No. 266000 of the present applicant.
0 and Patent No. 2612318. When stencil printing is performed using an ultraviolet-curable ink, the ink can be immediately cured by irradiating the printed sheet with ultraviolet light, so that there is an advantage that drying properties are good and problems such as set-off are eliminated.

However, since the main component of the ultraviolet-curable ink is an ultraviolet-curable resin, there is a problem that the viscosity changes greatly with temperature. In other words, at high temperatures, the viscosity of the ink decreases and the density of the printed matter increases, causing bleeding in the printed image, making it impossible to obtain clear printed matter.At low temperatures, the viscosity of the ink increases and the printing density decreases. In addition, blurring occurs in a printed image, and a clear printed matter cannot be obtained.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ultraviolet curable ink which can obtain a good printed matter irrespective of a change in the temperature of a use environment and which has excellent film strength after printing. Aim.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies on the above-mentioned objects, and as a result, have found that an ultraviolet-curable ink using an ultraviolet-curable resin monomer or oligomer as a varnish, the ink having a temperature of 23 ° C. Measured share rate 10
It has been found that an ultraviolet curable ink characterized in that the viscosity at 0 (1 / s) is from 2 to 8 Pa · s maintains good printability irrespective of temperature changes in the use environment. completed. Shear rate 100 (1/1 /
If the viscosity at the time of s) is lower than 2 Pa · s, the viscosity of the ink decreases when the operating environment temperature rises, and the density of the printed matter becomes too high, causing blurring of the printed image and obtaining a clear printed matter. I can't. On the other hand, if the viscosity of the ink at a shear rate of 100 (1 / s) measured at 23 ° C. is higher than 8 Pa · s,
When the temperature of the use environment is lowered, the viscosity of the ink is increased, so that a sufficient print density cannot be obtained, the printed image is blurred, and a clear printed matter cannot be obtained.

It is desirable that the varnish used in the ultraviolet curable ink of the present invention has a viscosity of 450 mPa · s or more, preferably 1000 mPa · s or more at a shear rate of 20 (1 / s) measured at 23 ° C. If the viscosity of the varnish at a shear rate of 20 (1 / s) measured at 23 ° C is less than 450 mPa · s, the viscosity of the entire ink will decrease, and if a large amount of powder is added to increase the ink viscosity, printing will occur. Later film strength is reduced.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The ultraviolet curable ink of the present invention comprises
Primarily, a varnish made of an ultraviolet curable resin, a photo initiator,
It is constituted by adding a coloring agent such as a pigment, a viscosity modifier and the like.

In the present invention, the varnish corresponds to a vehicle of the ink, and is composed of an oligomer or monomer of a UV-curable resin. The viscosity of the varnish can be adjusted by changing the amount of the oligomer and the monomer.

Examples of the UV-curable resin include various oligomers of urethane-based, epoxy-based, polyester-based, and polyol-based (meth) acrylic acid-modified resins;
A monomer or the like is used.

As oligomers, for example, epoxy acrylate, epoxy acrylated acrylate, urethane acrylate, unsaturated polyester, polyester acrylate, polyether acrylate, vinyl acrylate and the like are used. Pentenyl ethyl acrylate, isobornyl acrylate, phenol ethylene oxide modified acrylate, polyfunctional acrylate as tripropylene glycol diacrylate, 1,6-hexanediol diacrylate, bisphenol A diglycidyl ether diacrylate, tetraethylene glycol diacrylate, trimethyl Propane triacrylate, pentaerythritol triacrylate, pentaerythritol tet Laacrylate and dipentaerythritol hexaacrylate.

As the photoinitiator, generally available ones can be used, for example, Irgacure 651, Irgacure 184, Darocure 1173, Irgacure 907,
Irgacure 369 (from Ciba-Geigy), or Kayacure DETX, Kayacure ITX (from Nippon Kayaku), Sorvathrone BIPE, Sorvathrone BIBE (from Kurokin Kasei), Lucirin TPO (from BASF), benzophenone,
One or a mixture of two or more of acetophenone, 4-4'bisdiethylaminobenzophenone, benzyl, benzoin, benzoin ethyl ether and the like is used. Furthermore, n-butylamine, triethylamine, p-
An aliphatic amine such as ethyl dimethylaminobenzoate or an aromatic amine may be used in combination. The photoinitiator is generally added in an amount of 1 to 20% by weight based on the total amount of the ultraviolet curable ink.

As the colorant, various dyes such as inorganic pigments such as carbon black, titanium dioxide and navy blue, organic pigments such as phthalocyanine pigment, insoluble azo pigment, soluble azo pigment and quinacridone pigment, and disperse dyes can be used. Can be. In general, the content of the colorant is
It can be 1 to 30% by weight.

As the viscosity modifier, organic bentonite,
Organic hectorite, various waxes, calcium carbonate, silica, starches, metal soap, quartz, glass, powders such as polytetrafluoroethylene (Teflon (trade name)) are used, and if necessary, commercially available gelling Agents and the like may be used in combination.

Further, the ultraviolet curable ink of the present invention includes:
If necessary, various additives such as known photoinitiator, pigment dispersant, antioxidant, preservative, fungicide, silicone oil, surfactant, surface lubricant, defoamer, light stabilizer, etc. May be added, and a polymerization inhibitor such as hydroquinone or a nitroso compound may be added for the purpose of preventing gelation during storage.

The ultraviolet curable ink of the present invention is, for example,
The varnish and other predetermined components can be mixed by stirring and then kneaded with a kneader such as a three-roll mill.

The ink of the present invention having a predetermined viscosity can be prepared by changing the amount of the powder component added to the varnish. In the present invention, examples of the powder component include, among the above components, a viscosity modifier for various powders in addition to the pigment. If the amount of the powder component contained in the varnish is too large, the film strength after printing the ink is reduced,
Excessive addition of powder components to the varnish should be avoided. In order to prepare an ink having a predetermined viscosity according to the present invention, it is desirable to contain a powder component of 30% by weight or less, preferably 20% by weight or less based on the total amount of the ink. In particular, a shear rate of 20 (1 / s) measured at 23 ° C
When a varnish having a viscosity of 1000 mPa · s or more is used and a powder component of 10% by weight or less based on the total amount of the ink is contained in the varnish, an ink excellent in both printability and film strength can be obtained. preferable.

[0017]

The present invention will be described below in more detail with reference to examples. In the following examples, “parts” means “parts by weight”.

Examples 1 to 20 and Comparative Examples 1 to 7 After all the components were mixed according to the compositions shown in Tables 1 and 2, powder components such as a pigment and a viscosity modifier were dispersed with three rolls. A stencil printing ink was obtained.

Test Example (1) Measurement of Viscosity For the inks of the above Examples and Comparative Examples, using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd.), The viscosity of the varnish component (ultraviolet curable resin oligomer and monomer) at a shear rate of 20 (1 / s) was measured. Table 3 shows the results.

(2) Printing Test Using the inks of the above Examples and Comparative Examples, printing was performed under the following printing conditions using a digital stencil printing machine RISOGRAPH (registered trademark) SR7200 (manufactured by Riso Kagaku Kogyo KK). The ink was cured by xenon flash irradiation according to the following curing conditions.

Printing conditions: printing temperature: low temperature 5 ° C., normal temperature 23 ° C., high temperature 35 ° C. Printing speed: 120 sheets / min Printing paper: Neutral paper (Product name: ideal paper thinner)

Ink curing conditions: Xenon flash Output: 0.85 J / cm ² Flash once Made by USHIO Inc.

A plate of a fine-text original was prepared, and the fine-printed portion (200th sheet) of the resulting printed image was observed with an optical microscope and evaluated according to the following evaluation criteria. Table 3 shows the results.

Criteria for evaluation of low-temperature printing suitability: X: markedly decreased density (faint fine lines are blurred, there is a problem in practical use) Δ: decreased in density (slight jumps in thin lines are observed, but within the practical range) Slight decrease in density (no fine line skipping, no practical problem)

Criteria for evaluation of suitability for high-temperature printing: X: Significant increase in density (fine characters are destroyed, there is a problem in practical use) Δ: Increase in density (small swollen fine characters are observed, but within practical range) O: Slight density Ascending (I do not feel the bulge of the fine line, there is no problem in practical use)

· Comprehensive evaluation of printability: ○: low or high temperature printability, or either ○ or △ ×: low or high temperature printability, either ×

(3) Measurement of film strength The ink was transferred onto coated paper using a grind gauge and then cured. The scale of 10 μm was rubbed back and forth five times with a clock meter, and the state of the ink film was visually evaluated according to the following evaluation criteria.

[0028]

[0029]

[Table 1]

[0030]

[Table 2]

The following terms in Tables 1 and 2 correspond to the following compounds. Monomer 1: dipentaerythritol hexaacrylate (DPHA) (manufactured by Toagosei Co., Ltd.). Monomer 2: phenol / ethylene oxide-modified acrylate (manufactured by Toagosei Co., Ltd.). Monomer 3: Trimethylolpropane ethylene oxide-modified triacrylate. Monomer 4: bisphenol F ethylene oxide-modified diacrylate (manufactured by Toagosei Co., Ltd.). Monomer 5: ditrimethylolpropane tetraacrylate (manufactured by Toagosei Co., Ltd.). Monomer 6: bisphenol A ethylene oxide-modified diacrylate (manufactured by Toagosei Co., Ltd.). Oligomer: Epoxy acrylate oligomer (manufactured by Harima Chemicals, Inc.). Photoinitiator 1: Irgacure 369 (manufactured by Ciba Geigy). Photoinitiator 2: Kayacure DETX-S (Nippon Kayaku Co., Ltd.)
Made). Carbon: Furness carbon (manufactured by Mitsubishi Chemical Corporation). Dispersant: Solsperse S24000GR (Zeneca). Viscosity modifier: BENTON38 (manufactured by RHEOX). Other powders: quartz powder in Example 15, glass powder in Example 16, and Teflon powder in Examples 17 and 18. Polymerization inhibitor: hydroquinone.

[0032]

[Table 3]

As is clear from Table 3, the share rate is 10
When the ink viscosity (23 ° C.) at 0 (1 / s) is lower than 2 Pa · s, printability at high temperatures is poor (Example 1 vs. Comparative Example 1), and the viscosity is higher than 8 Pa · s. In this case, the printability at low temperature was poor (Example 15 vs. Comparative Examples 2 to 7). Thus, it was shown that when the viscosity was in the range of 2 to 8 Pa · s, an ink having low temperature dependency was obtained. In addition, the varnish viscosity at a shear rate of 20 (1 / s) (23
° C) is lower than 450 mPa · s, it is shown that the film strength is inferior when printed on coated paper, even though there is usually no problem when printing on plain paper (Examples 19 and 2).
0). Therefore, like printing on coated paper,
If sufficient film strength is required, the varnish viscosity is 450m
It is desirable to use an ink having a viscosity of Pa · s or more and the ink viscosity in the range of 2 to 8 Pa · s. In particular, it was shown that when the varnish viscosity was 1000 mPa · s or more, the printability was excellent at both low and high temperatures, and sufficient film strength was obtained (Examples 8 to 1).
3).

Example 21 An ink was prepared in the same manner as in Example 1 except that the photoinitiator alone was changed to the photoinitiator shown in Table 4, and a digital stencil printing machine SR
After printing with 7200 (trade name, manufactured by Riso Kagaku Co., Ltd.), curing was performed using a metal halide lamp (UV lamp) and a xenon flash, respectively. The ink curing conditions were the same for xenon flash and the following conditions for metal halide lamps.

Ink curing conditions: Metal halide lamps: Output: 100 W / cm Transfer speed: 80 m / min 1 pass Nippon Battery

The state of the cured film was evaluated according to the following evaluation criteria in the same manner as in the measurement of the film strength in the above test examples. Table 4 shows the results.

[0037]

[0038]

[Table 4]

The results in Table 4 show that it is better to use an acetophenone-based or thioxanthone-based photoinitiator. However, in terms of curability, it is more preferable to use an acetophenone-based photoinitiator.

[0040]

As described above in detail, according to the present invention, 2
Use a varnish having a viscosity of preferably 450 mPa · s or more, particularly preferably 1000 mPa · s or more, at a shear rate of 20 (1 / s) measured at 3 ° C., and use powder or the like as a pigment or a viscosity modifier. By adding an appropriate amount, the viscosity of the ink at a shear rate of 100 (1 / s) measured at 23 ° C. is 2 to 8 Pa · s.
Therefore, an ultraviolet curable ink which is excellent in printability and has sufficient film strength and suitable for stencil printing is provided, regardless of the temperature change in the use environment.

Continued on the front page F term (reference) 4J039 AB01 AD04 AD21 AE04 AE05 AE06 AE07 AF03 BA16 BA21 BA23 BA25 BB01 BC16 BC19 BE01 BE27 BE33 CA04 EA06 EA36 EA48

Claims (8)

[Claims] 1. An ultraviolet-curable ink using an ultraviolet-curable resin monomer or oligomer as a varnish, wherein the shear rate of the ink measured at 23 ° C. is 100 (1 / s).
An ultraviolet-curable ink characterized in that the viscosity at the time of 2 to 8 Pa · s. 2. The ultraviolet curable ink according to claim 1, wherein the varnish has a viscosity at a shear rate of 20 (1 / s) measured at 23 ° C. of 450 mPa · s or more. 3. The ultraviolet curable ink according to claim 1, wherein the varnish contains a powder component. 4. The ultraviolet curable ink according to claim 1, wherein the varnish has a viscosity of 1000 mPa · s or more at a shear rate of 20 (1 / s) measured at 23 ° C. 5. The varnish is 10% based on the total amount of the ink.
The ultraviolet-curable ink according to claim 4, wherein the ultraviolet-curable ink contains a powder component of not more than weight%. 6. The ultraviolet curable ink according to claim 3, wherein the powder component comprises a pigment and a viscosity modifier. 7. The method according to claim 1, wherein the viscosity modifier is organic bentonite,
The ultraviolet curable ink according to claim 6, which is selected from the group consisting of organic hectorite, waxes, calcium carbonate, silica, starches, metallic soap, quartz, glass, and powder of polytetrafluoroethylene. 8. The ultraviolet-curable ink according to claim 1, which contains an acetophenone-based photoinitiator.