JPH0621255B2 - Non-aqueous ink for jet printing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a non-aqueous ink for jet printing for firing for marking the surface of a heat-resistant substrate such as ceramics, metal or glass.

<Prior Art and Problems to be Solved> In recent years, heat-resistant substrates such as ceramics have been widely used, and accordingly, a method of marking by firing has been proposed.

Conventionally, a screen printing method and a spray printing method have been widely adopted as marking methods, but there is a problem in that precise pattern marking is difficult. Therefore, a jet printing method that enables precise pattern marking has been considered.

By the way, since the ink used for jet printing needs to leave a marking film after firing, a metal-containing dye and an inorganic coloring pigment are blended.

However, in the ink for jet printing, since acrylic resin, polyester resin, alkyd resin, epoxy resin, etc. are usually used as the binder resin, the binder resin does not remain in the marking film when baked at a temperature of 1000 ° C. or higher, for example. Only metal dyes or inorganic coloring pigments are available. Therefore, there has been a problem that the adhesion of the marking film is insufficient.

Further, when a metal-containing dye is used, the ink storage stability is excellent, but there is a problem in that the visibility of the marking film is greatly deteriorated when firing is usually performed at a temperature of 1350 ° C. or higher.

On the other hand, when a heat-resistant inorganic coloring pigment is used, 1350 ° C
Even if the marking film is fired at the above temperature, the marking film has good visibility, but there is a problem in the storage stability of the ink that the inorganic color pigment easily precipitates and aggregates and is difficult to redisperse.

In view of such a situation, the present inventors have found that the marking film has good adhesion after firing in a jet printing method capable of marking a precise pattern, and the marking film can be formed even if fired at a temperature of 1350 ° C. or higher. The present invention has been achieved as a result of intensive research to develop an ink for jet printing which has good visibility and storage stability.

<Means for Solving the Problems> That is, the present invention provides the following components: (i) a solvent-soluble silicone resin, (ii) a heat-resistant inorganic color pigment having an average particle size of 3 μm or less, and (iii) an average particle size of 3 μm or less. Of the solvent-insoluble resin particles of (4), and (iv) a solvent that dissolves the component (i).

Hereinafter, the present invention will be described in detail.

The solvent-soluble silicone resin (i) which is a constituent of the ink of the present invention is typically a resin whose main part has the following three-dimensional structure.

(However, R ₁ , R ₂ , R ₃ , and R ₄ are either a methyl group, an ethyl group, or a phenyl group.) Such a silicone resin is a dehydration condensation of a small amount of residual silanol group (SiOH). The reaction promotes cross-linking to form a strong film.

In the present invention, since a silicone resin is used as a binder resin, the organic component is acid-decomposed after firing, and the skeleton component remains and remains as a silicon dioxide film, so that the adhesion of the marking film after firing can be maintained. It is estimated to be.

The number average molecular weight of the silicone resin is about 2,000 to 10,000 because of the adhesiveness of the marking film before firing (for example, at room temperature to 800 ° C.) and the ejection stability of ink droplets from the nozzle of an ink jet printer. It is suitable.

Further, as the silicone resin used in the present invention, a modified silicone resin obtained by reacting a silicone resin intermediate with a polyester, an acrylic resin or the like can be used in order to improve the adhesion before firing. However, the silicone resin used in the present invention should be one that does not react with moisture, oxygen, etc. in the atmosphere, and the one that reacts is not suitable because it causes nozzle clogging.

The heat-resistant inorganic coloring pigment (ii), which is a constituent of the ink of the present invention, is added to the marking film in order to improve its visibility.
(0 ° C or higher) Poor visibility after firing can be eliminated. In addition,
The heat-resistant inorganic color pigment as used in the present invention refers to an inorganic color pigment that maintains its coloring power even at high temperatures.

Specific examples of the inorganic color pigment (ii) include red iron oxide, cobalt blue, cerulean blue, chromium oxide, hydrated chromium oxide, cobalt green, cobalt chromium green,
Typical examples thereof include cobalt purple and Mars purple, but the invention is not limited thereto, and any inorganic coloring pigment having coloring power after firing can be used without particular limitation.

The inorganic color pigment (ii) should have an average particle size of 3 μm or less in order to prevent nozzle clogging and precipitation aggregation. However, an inorganic coloring pigment having a particle diameter larger than at least the nozzle diameter is not included.

The solvent-insoluble resin particles (iii), which is a constituent of the ink of the present invention, are present between the inorganic color pigments (ii) in the ink to prevent secondary aggregation from occurring, and the inorganic color pigments are precipitated. Is also added to improve redispersibility.

The resin particles (iii) are not particularly limited as long as they are resins that are insoluble in the solvent used, for example, various synthetic resins such as phenol resin, urea resin, melamine resin, polyester resin, epoxy resin, urethane resin, xylene resin, vinyl chloride resin. , Acrylic resin, styrene resin, polyamide resin,
Nylon resin, fluororesin, etc. can be used.

Particularly preferable resin particles (iii) having a spherical shape are preferable because the storage stability of the ink is improved and the nozzle is less likely to be clogged. Solvent-insoluble solvent-insoluble resin particles are also preferable.

The resin particles (iii) should have an average particle diameter of 3 μm or less in order to prevent nozzle clogging. However, at least resin particles having a particle diameter larger than the nozzle diameter are not included.

The solvent (iv) which is a constituent component of the ink of the present invention is an organic solvent which dissolves the component (i) and does not dissolve the component (iii), and desirably has good drying property and bleeding prevention property. There is no particular limitation, and the solvent used in the conventionally known jet printing non-aqueous ink can be used.

Specifically, alcohols such as methanol, ethanol and isopropanol, carbitols such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether and ethylene glycol monobutyl ether,
Typical examples thereof include ketones such as acetone, methyl ethyl ketone and cyclohexanone, and aliphatic esters such as ethyl acetate and butyl acetate.

The non-aqueous ink for jet printing of the present invention is mainly composed of the silicone resin (i), the inorganic color pigment (ii), the resin particles (iii) and the solvent (iv) described above, and if necessary various types. It is composed of a mixture of a dye, a curing catalyst, a modified resin, an electric conductivity adjusting agent, a surfactant and the like.

In the ink of the present invention, the blending amount of the silicone resin (i) is appropriately 1 to 20% by weight, preferably 2 to 7% by weight in the ink from the viewpoint of adhesion after firing. In addition, the blending amount of the inorganic color pigment (ii) is 1 to 1 in view of visibility, stability of ink and the like.
0 wt%, preferably 2-5 wt% is suitable.

The amount of the resin particles (iii) to be blended is appropriately 2 to 20% by weight, preferably 5 to 15% by weight, from the viewpoint of ink stability and film forming properties.

The solvent (iv) is blended in an amount of 40 to 95% by weight, preferably 70 to 90% by weight, in consideration of the viscosity and surface tension of the ink.

It is also possible to form the marking film in a state where the ink of the present invention is dried at room temperature to several hundreds of degrees Celsius without being baked, and therefore, in order to improve the visibility before baking, a solvent-soluble dye is added in an amount of 0.
It is preferable to add 2 to 5% by weight.

The non-aqueous ink for jet printing of the present invention is required to have properties suitable for inkjet printing, and therefore the viscosity of the ink is 1 to 10 CPS / 20 ° C and the specific resistance is 200 to 3
000Ωcm, specific gravity 0.8-1.2, surface tension 20-
It should be adjusted to 60 dynes / cm.

The ink of the present invention having such a composition and properties is used as an ink for inkjet printing by mixing and stirring each component, filtering and purifying with a filter having a pore size of 3 μm.

The ink jet printer can be applied to conventionally known printers, and examples thereof include a charge control system, an ink-on-demand system, and a system in which ink is ejected by a thermal head.

The marking film of the jet-printed ink is, for example, 10
Baking at 00 to 1500 ° C. forms a marking film having heat resistance.

<Effects of the Invention> Since the non-aqueous ink for jet printing of the present invention uses a silicone resin as a binder resin, not only the adhesiveness of the marking film before firing but also the adhesiveness after firing is much wider than that of the conventional ink. In addition, the marking film has good visibility after firing because it uses a heat-resistant inorganic pigment, and because it uses resin particles together, secondary aggregation of the inorganic coloring pigment does not easily occur and redispersion is possible. It also has good stability and excellent ink stability.

Hereinafter, the present invention will be described in more detail with reference to Examples. In the examples, "parts" and "%" are shown by weight.

Inks for jet printing were prepared by uniformly mixing the formulations shown in Tables 1 to 4 and Comparative Examples 1 to 3 and then filtering and purifying with a filter having a pore size of 3 μm.

Stability of the obtained ink when stored at 25 ° C. for 1 month; the marking film obtained by ejecting each of the above inks on alumina ceramics with an ink jet printer (nozzle diameter 60 μ) and drying at room temperature 600 ° C,
Each test of visibility and adhesion after baking for 15 minutes; visibility and adhesion after baking the marking film at 1500 ° C. for 15 minutes was performed, and the results are shown in the lower column of Table 1.

As is clear from Table 1, the ink of the present invention had good stability, visibility of the marking film, and adhesion.

On the other hand, the stability of the ink was poor in the comparative example containing no resin particles (iii). Further, in Comparative Example 2 in which a dye was added instead of the inorganic color pigment, the visibility after firing was poor. Furthermore,
Comparative Example 3 in which an acrylic resin was blended as a binder had poor adhesion after firing.

Claims (1)

[Claims] 1. The following components: (i) a solvent-soluble silicone resin, (ii) a heat-resistant inorganic color pigment having an average particle size of 3 μm or less, (iii) a solvent-insoluble resin particle having an average particle size of 3 μm or less, and (iv) A non-aqueous ink for jet printing for baking, which comprises a solvent that dissolves the component (i) as a main component.