JPH10279866A - Hot melt solid ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a hot melt solid ink having basic performances and good printing quality and giving a print having good transparency and adhesion when used to give a print on printing paper or an OHP sheet by mixing a wax with a colorant and a resin having a specified viscosity and a specified weight-average molecular weight. SOLUTION: The wax (A) used in the solid ink has a melting point of 50-200 deg.C, is stable against heat and is exemplified by a petroleum wax, desirably paraffin wax. The colorant (B) used may be a dye or a pigment conventionally used in an oil-base ink composition. The resin (C) used has a viscosity of below 150 mPa.s at 140 deg.C and a weight-average molecular weight of 500 or above. This ink has a composition of 20-80 wt.% component A, 0.1-10 wt.% component B and 5-80 wt.% component C. The obtained solid ink is adjusted so that the viscosity at the time of delivery from nozzles may be 30 mPa.s.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state hot-melt ink at room temperature, that is, a so-called hot melt solid ink. More specifically, the present invention relates to a hot-melt solid ink having high transparency and adhesiveness, which is used for recording by heating and melting at a temperature higher than room temperature in an ink jet recording apparatus.

[0002]

2. Description of the Related Art Conventionally, as an ink jet recording system, for example, a so-called electric field control system in which ink is ejected by using electrostatic attraction; a so-called drop-on system in which ink is ejected by using a vibration pressure of a piezoelectric element. Demand system (pressure pulse system); various systems such as a so-called thermal ink jet system have been proposed in which ink is ejected using pressure generated by forming and growing bubbles by high heat. Obtainable.

[0003] In these ink jet recording systems, an aqueous ink using water as a main solvent and an oil-based ink using an organic solvent as a main solvent are generally used. Printed images using water-based inks generally have poor water resistance, whereas oil-based inks can provide printed images having excellent water resistance.

However, these water-based and oil-based inks are liquid at room temperature and penetrate rapidly when printed on recording paper, so that bleeding is likely to occur, and it is difficult to obtain a sufficient print density. Furthermore, since the ink is always liquid, precipitates such as dye aggregates are likely to be generated from the ink during storage, and these deposits block the ink flow path and the discharge port, and the reliability of the ink jet recording system. Was greatly reduced.

For the purpose of improving the drawbacks of these conventional solution-type inks, so-called hot-melt type oil-based inks for ink-jet recording have been proposed which use inks which are solid at room temperature and melt by heating. Specifically, US Pat. No. 3,653,932 discloses an ink containing a dialkyl sebacate,
U.S. Pat. No. 4,390,369 and JP-A-58-1
No. 08271, an ink containing a natural wax, Japanese Patent Application Laid-Open No. 59-22973, an ink containing a stearic acid, Japanese Patent Application Laid-Open No. 61-83268.
JP-A-62-48774 discloses an ink containing an acid or alcohol having 20 to 24 carbon atoms and further containing a ketone having a relatively high melting point. A thermosetting resin having, a solid organic solvent having a melting point higher than 150 ° C.,
Ink containing a small amount of dye substance
In JP-A-27, a coloring material, a first solvent which is solid at room temperature and liquefies when heated to a temperature higher than room temperature,
JP-A-62-295973 discloses an ink comprising a second solvent which is liquid at room temperature and has a high volatility, which dissolves a solvent of the formula (1), wherein a synthetic wax having a polar group and a dye soluble in the wax are used. Included inks and the like have been proposed.

[0006] These hot-melt type solid inks are mounted on a hot-melt ink-jet recording apparatus, turned into a liquid state by heating, discharged from a discharge apparatus in a liquid state, and printed and printed on a print medium. However, the conventional hot-melt type solid ink is mainly composed of wax, and wax is generally low in transparency,
When such an ink is printed on a print medium or the like, the resulting print has poor transparency. In particular, when such an ink is printed and printed on an OHP (overhead projector) sheet, the disadvantage of insufficient transparency appears remarkably, and a color image on the OHP sheet appears clearly by irradiation. And only dark images were obtained. Further, when the OHP sheet was bent or scratched, the adhesive strength was so low that the ink in the printing portion or the image portion was peeled off from the sheet. OHP
It is effective to add a resin as a means for imparting an adhesive force to the sheet for use, and as the amount of the added resin increases,
It is known that the transparency of the ink itself increases and the adhesive strength of the ink to the OHP sheet also increases. However, in general, the viscosity of resin alone is much higher than that of wax, and the greater the amount of resin added, the higher the melt viscosity of the ink, the more difficult it is to eject ink, and in the worst case, the ejection mechanism Ink clogging occurred in some areas. on the other hand,
As means for lowering the melt viscosity of the ink, it is conceivable to raise the ink heating temperature during ejection. However, considering the temperature rise inside the printer, which may affect the product life of the ejection mechanism or affect other parts, there is a limit to increasing the temperature of the ejection mechanism. As described above, the conventional hot melt type solid ink does not have sufficient transparency and adhesiveness.

[0007]

DISCLOSURE OF THE INVENTION The present invention maintains the basic performance and good print quality as a hot-melt type solid ink for an ink jet printer, and prints on a printing paper or an OHP sheet with good transparency and An object of the present invention is to provide a hot-melt type solid ink exhibiting adhesiveness.

[0008]

In order to achieve the above-mentioned object, the present invention relates to a hot-melt type solid ink for an ink jet printer which is solid at ordinary temperature and used by melting under heating. Is less than 150 mPa · s, more preferably 120 mPa · s.
It is characterized by containing a resin having a viscosity at 500C of less than 500 mPas and a weight average molecular weight of 500 or more.

In the present invention, the resin is printing paper or O.
It functions to impart adhesiveness to the HP sheet, impart transparency to the ink, control the viscosity of the ink, and suppress crystallization of the wax. In particular, with respect to controlling the viscosity of the ink, the viscosity of the wax is negligibly small compared to the viscosity of the resin, so the viscosity of the ink is determined by the viscosity of the contained resin. Is also good. The viscosity of the hot melt type solid ink changes depending on the melting temperature, and the viscosity decreases as the melting temperature increases. In practice, the hot melt type solid ink has a viscosity of 30 mPa · s when ejected by inkjet.
It is usually adjusted as follows. The viscosity of the ink itself can be adjusted to some extent by the temperature of the hot-melt solid ink discharged from the discharge mechanism, but consider the effect on the other parts due to the product life of the discharge mechanism and the rise in temperature inside the inkjet printer. There is a limit to raising the temperature. For this reason, the temperature at which the ink is ejected from the ejection mechanism is preferably set to 150 ° C. or lower, more preferably 130 ° C. or lower. In the present invention, the viscosity at 140 ° C. is less than 150 mPa · s and the weight-average molecular weight is 500 or more. By using the selected resin, even if the resin is added to the ink, the viscosity of the ink is increased. Since this is not performed, the content can be increased, so that the transparency of the ink can be increased. In addition, since the viscosity of the ink itself becomes relatively low, the ink ejection temperature can be lowered. For example, even if the ejection temperature is lowered to about 120 ° C., the ink can be ejected, so that the print quality is also improved. .

[0010]

DETAILED DESCRIPTION OF THE INVENTION The resin used in the present invention has a viscosity of less than 150 mP.s at 140.degree. C., preferably less than 500 mP.s at 120.degree. The viscosity is measured using a B-type viscometer. In addition, the molecular weight of the resin used in the present invention is obtained by gel permeation chromatography using a differential refractometer as a detector, or molecular weight fractionation by heating gas chromatography using a thermal conductivity meter as a detector, and obtained from the results. The weight average molecular weight Mw is 500 or more;
500 to 500,000 is desirable, and 600 to 400,
000 is more desirable, and 700 to 300,000 is most desirable. Even if the viscosity satisfies the above conditions, the resin is not suitable for use in the present invention if it has a Mw of less than 500 because it exhibits crystallinity close to that of a wax and has no transparency. The resin used in the present invention is M
It is a requirement that w is greater than 500 and the viscosity must be less than 150 mP · s at 140 ° C., preferably less than 500 mP · s at 120 ° C.

The resin used in the present invention is preferably an oil-soluble resin. As such a resin, for example,
Olefin resin, preferably polyethylene resin, polypropylene resin, or polyisobutylene resin, or vinyl resin, preferably ethylene-vinyl acetate copolymer resin, vinyl chloride-vinyl acetate copolymer resin, vinyl acetate resin, or ethylene-vinyl chloride -Vinyl acetate resin,
Acrylic resin, desirably methacrylate resin, polyacrylate resin, ethylene-ethyl acrylate copolymer resin, or ethylene-methacrylic acid copolymer resin, phenol resin, polyurethane resin, polyamide resin, polyester resin And, ketone resin, alkyd resin, rosin resin, hydrogenated rosin resin, petroleum resin, hydrogenated petroleum resin, maleic acid resin, butyral resin, terpene resin, hydrogenated terpene resin, Chromane-indene resin and the like. In the present invention, these may be used alone or in a mixture of two or more.

In the present invention, the resin is used in such an amount that the total amount of the resin is in the range of 5 to 80% by weight based on the total weight of the ink. If the content of the resin in the ink is less than 5% by weight, not only the melt viscosity sufficient for discharging by the ink jet recording method cannot be obtained, but also the transparency of the ink and the adhesion to the printing medium are obtained. I can't. On the other hand, when the content of the resin in the ink is more than 80% by weight, the melt viscosity of the ink becomes too high, so that it becomes difficult to discharge the ink at a working temperature of a printer head used for inkjet recording. At the same time, the penetration of the ink into the paper when attached to paper etc. becomes worse, and if the printing surface is rubbed with the hand etc., the ink will peel off from the paper etc.
Good printing quality cannot be maintained. Therefore, the total amount of the polyamide resin is preferably contained in the ink in the range of 10 to 60% by weight.

In the present invention, a wax having a melting point of 50 ° C. to 200 ° C. and being stable to heat is used. Specifically, petroleum wax, desirably paraffin wax or microcrystalline wax, vegetable wax, desirably candelilla wax, carnauba wax, rice wax, or jojoba solid wax, animal wax, desirably beeswax, lanolin Or whale wax, mineral wax, preferably montan wax, synthetic hydrocarbon, preferably Fischer-Tropsch wax or polyethylene wax, hydrogenated wax, preferably hydrogenated castor oil or hydrogenated castor oil derivative, modified wax, preferably Montane wax derivatives, paraffin wax derivatives, microcrystalline wax derivatives or polyethylene wax derivatives, and synthetic fats and oils such as higher fatty acids, preferably behenic acid and stearic acid Palmitic acid, myristic acid,
Or lauric acid, a ketone wax, desirably distearyl ketone, a higher alcohol, desirably stearyl alcohol, or behenyl alcohol, hydroxystearic acid, desirably 12-hydroxystearic acid or a 12-hydroxystearic acid derivative, or laurin as a fatty acid amide Acid amide, stearic acid amide, oleic acid amide, erucic acid amide, ricinoleic acid amide, stearic acid ester amide, palmitic acid amide, behenic acid amide, brassic acid amide, N-oleyl stearic acid amide, N-stearyl stearic acid amide, N-oleyl palmitic acid amide, N-stearyl erucic acid amide and the like can be mentioned. Also ketone,
Desirably stearone or laurone, amine, preferably dodecylamine, tetradecylamine or octadecylamine, or ester, preferably methyl stearate, octadecyl stearate, glycerin fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid ester, ethylene glycol fatty acid Any known wax such as an ester or a polyoxyethylene fatty acid ester, a polymerized wax, preferably an α-olefin maleic anhydride copolymer wax can be used without particular limitation. These waxes can be used alone or in combination of two or more.

The above-mentioned wax is used in such an amount that the total amount of the wax is in the range of 20 to 80% by weight based on the total weight of the ink. If the content of the wax in the ink is less than 20% by weight, the ink will not have sufficient transparency, and the characteristics of other additives will appear, so that the melting point of the ink will increase or become unstable. Thus, the ink does not melt sharply at the inkjet discharge temperature. On the other hand, if the content is more than 80% by weight, a melt viscosity sufficient to function as an ink cannot be obtained, and adhesion to printing paper becomes difficult.

As the coloring material used in the present invention, any of dyes and pigments conventionally used in oil-based ink compositions can be used. Pigments that are generally used in the technical field of printing, whether organic or inorganic, can be used. Specifically, for example, carbon black, cadmium red, molybdenum red, chrome yellow,
Cadmium yellow, titanium yellow, chromium oxide, viridian, titanium cobalt green, ultramarine blue, Prussian blue, cobalt blue, azo pigment, phthalocyanine pigment, quinacridone pigment, isoindolinone pigment, dioxazine pigment, sulene pigment Conventionally known pigments such as perylene-based pigments, perinone-based pigments, thioindigo-based pigments, quinophthalone-based pigments, metal complex pigments, etc., are particularly limited as long as the primary particle size is in the range of 10 to 100 nm. It can be used without. These pigments can be used in combination. Dyes can be used any of dyes conventionally used in oil-based ink compositions, but azo dyes, disazo dyes, metal complex dyes, naphthol dyes, anthraquinone dyes, indigo dyes, carbonium dyes,
Oil-soluble dyes such as quinone imine dyes, cyanine dyes, quinoline dyes, nitro dyes, nitroso dyes, benzoquinone dyes, naphthoquinone dyes, xanthene dyes, phthalocyanine dyes and metal phthalocyanine dyes are preferred. These dyes can be used in combination. In the present invention, both a dye and a pigment can be used as the coloring material, but it is desirable to use a soluble dye having excellent heat stability and solubility with other vehicles. In order for the ink to have sufficient color-forming ability, these coloring materials may be added in the ink in an amount of 0.1%.
It is preferably contained in an amount of 1 to 5% by weight, and preferably 0.5 to 3% by weight in consideration of the color developing ability when printing with a printer. Further, the dye does not precipitate from the ink due to a thermal change during operation of the printer. Further, as a guarantee that the pigment does not agglomerate, the content is more preferably 1 to 5% by weight.

The vehicle used in the present invention described above,
When using other vehicles or additives, they are all solid at room temperature, so that when preparing the hot melt type solid ink of the present invention, they are all melted at a temperature higher than the melting temperature, It is necessary to mix and disperse well, and if such an object can be achieved, the means for preparing the hot melt type solid ink of the present invention is not limited at all, and any means can be used. Good. The procedure for producing the hot melt type solid ink of the present invention will be described below. Each of the vehicles used in the present invention at the above-described ratio, and when other vehicles or additives are used, they are contained in a container at a ratio within a range not to impair the performance of the hot melt type solid ink of the present invention. The temperature is higher than the highest melting temperature among the melting temperatures of the charged and vehicle, additives when used, usually 70 ° to 250 ° C, preferably 100 ° to 20 ° C.
The mixture is heated and melted at a temperature of about 0 ° C., and then a coloring material is loaded. Once the vehicle, additives if used, etc. have been melted, the agitator is rotated at a speed and time sufficient to obtain a uniform mixture, typically at 200 to 10,000 RPM, preferably 500 to 5,000 RPM, usually Enough to several hours,
Preferably, the mixture is rotated for about 1 to 2 hours to sufficiently stir and mix the mixture. The stirring and mixing are performed until one drop of the mixture is taken on a slide glass and the absence of aggregates is confirmed by an optical microscope (about 200 times). After the completion of the stirring and mixing, the obtained mixture is subjected to filtration in a molten state through a filtration device to filter heterogeneous substances, and the substances that have passed through the filter are obtained as final hot-melt solid ink.

[0017]

EXAMPLES Specific examples are given below to illustrate the present invention. Example 1 As a resin, a polyamide resin having a viscosity of 94 mPa · s at 140 ° C. and a viscosity of 192 mPa · s at 120 ° C. (Versamide 756, softening point of 102 ° to 112 °)
C., manufactured by Henkel Co., Ltd.), and as waxes, Fischer-Tropsch wax (FTP-1005, melting point: 98 ° C., manufactured by Nippon Seiro) and stearic acid amide wax (Amide AP-1, melting point: 100 ° C., manufactured by Nippon Kasei Co., Ltd.) are listed below. Of the oil-soluble dye C.I. I. Solvent Y
yellow 162 (Neopen Yellow 0
75, manufactured by BASF). This was stirred and mixed with a dissolver at 1,000 RPM for about 1 hour. One drop of the mixture was taken on a slide glass, and the light microscope (200
No.), it was confirmed that there was no aggregate. The resulting mixture was filtered with a 0.8 μm glass fiber filter GA200 (Toyo Roshi Kaisha Co., Ltd.) using a hot filtration device manufactured by Toyo Roshi Kaisha.
), And the mixture passed through the filter was obtained as a hot melt type solid ink.

Versamide 756 18 parts by weight FTP-1005 60 parts by weight Amide AP-1 20 parts by weight Neopen Yellow 075 2 parts by weight

When the viscosity of the obtained ink at a melting temperature of 125 ° C. was measured using a B-type viscometer, it had a viscosity of 28.8 mPa · s. This temperature 125 ° C
Is the ejection temperature commonly used in hot-melt solid-state inkjet printers, and the hot-melt solid ink of the present invention has a viscosity that allows good ejection by the hot-melt solid-state inkjet printer head at this temperature. Was. 110 ° C
Was melted on a hot plate heated to 2 mm and coated on a sheet for OHP (PP-2500, manufactured by Sumitomo 3M) with a winding rod (winding diameter 0.9 mm). As a result, a clear and transparent ink film was obtained. Obtained. When the haze was measured with a Haze meter (manufactured by Suga Test Instruments Co., Ltd.), it was 22.9.
%Met.

When the above hot-melt type solid ink was mounted on an ink jet printer and printed at a discharge temperature of 125 ° C., there was no clogging of the printer head.
Clear printing was obtained on the recording paper.

Example 2 Hydrogenated petroleum resin having a viscosity of 90 mPa · s at 140 ° C. and 184 mPa · s at 120 ° C. (Alcon P-90, softening point 90 ° C., manufactured by Arakawa Chemical Industry Co., Ltd.) , Microcrystalline Arin wax (Hi-Mic 2095, melting point 101 ° C., manufactured by Nippon Seiro Co., Ltd.) and stearic acid amide wax (Amide AP95, melting point 107 ° C., manufactured by Nippon Kasei Co., Ltd.), oil-soluble dyes C.I. I. Solent Blue
Using 70 (Neopen Blue 808, manufactured by BASF) in the following amounts, a hot melt type solid ink was obtained according to the same procedure as described in Example 1.

Alcon P-90 30 parts by weight Hi-Mic 2095 50 parts by weight Amide AP95 18 parts by weight Neopen Blue 808 2 parts by weight

When the viscosity of the obtained hot melt type solid ink at 125 ° C. was measured in the same manner as in Example 1, it was found to have a viscosity of 26.3 mPa · s.
Similarly to the above, at this temperature, the hot melt type solid inkjet printer head had a viscosity that allowed good ejection. When this ink was coated on an OHP sheet according to the same procedure as that described in Example 1, a clear and transparent ink film was obtained. Haze
When the haze was measured with a degree meter (manufactured by Suga Test Instruments Co., Ltd.), it was 24.6%.

When the above hot melt type solid ink was mounted on an ink jet printer and printing was performed at an ejection temperature of 125 ° C., the printer head was not clogged.
Clear printing was obtained on the recording paper.

Comparative Example 1 As a resin, a polyamide resin having a viscosity of 150 mPa · s at 140 ° C. and a viscosity of 500 mPa · s at 120 ° C. (Versamide 55, softening point of 102 ° to 112 °)
C., manufactured by Henkel Co., Ltd.), and as the wax, urethane type wax (NPS6010, melting point: 75 ° C., manufactured by Nippon Seiro Co., Ltd.) and stearic acid amide wax (Amide AP-1,
Melting point: 100 ° C., manufactured by Nippon Kasei Co., Ltd.); I. Solvent Yellow 162
(Neopen Yellow 075, manufactured by BASF) was used in the following amount, and a hot melt type solid ink was obtained according to the same procedure as that described in Example 1.

Versamide 55 18 parts by weight NPS6010 60 parts by weight Amide AP-1 20 parts by weight Neopen Yellow 075 2 parts by weight

The viscosity of the obtained hot-melt solid ink at 125 ° C. was measured in the same manner as in Example 1. The viscosity was 32.9 mPa · s. At this temperature, the hot-melt solid ink jet printer head was used. Had a viscosity that was difficult to discharge. When this ink was coated on an OHP sheet according to the same procedure as described in Example 1, Examples 1 and 2
The transparency was clearly lower than that of the ink obtained in the above. When the haze was measured by a HAZE meter (manufactured by Suga Test Instruments Co., Ltd.), the value was as high as 51.1%.

Further, two or three drops of the above ink were put on a slide glass heated to 120 ° C. and melted, and a cover glass was placed on the glass and pressed lightly, and this was put on a Nikon microscope (XF-UNR). Observation with transmitted light revealed that many wax crystals were observed.

As is clear from the above, Examples 1 and 2
The hot-melt type solid ink obtained in (1) had a considerably lower melt viscosity and a much higher transparency than the hot-melt type solid ink obtained in Comparative Example 1.

[0030]

According to the hot melt type solid ink, by using a resin having a viscosity of less than 150 mP · s and a weight average molecular weight of 500 or more,
An ink having a high resin content, which could not be obtained conventionally, can be obtained. Accordingly, it is possible to provide an ink having high transparency and exhibiting the same adhesiveness as plain paper even to a printing medium such as OHP without permeability. Also, even if the content of the resin component in the ink is increased, the ink can be printed satisfactorily, the print quality is good, and the print medium is OHP even without increasing the ejection temperature of the ink. , Expresses clear colors with high transparency.

Claims (3)

[Claims] 1. A hot-melt solid ink comprising a wax, a coloring material and a resin having a viscosity at 140 ° C. of less than 150 mPa · s and a weight average molecular weight of 500 or more. 2. The hot melt according to claim 1, wherein the wax is present in an amount of 20 to 80% by weight, the coloring material is present in an amount of 0.1 to 10% by weight and the resin is present in an amount of 5 to 80% by weight, based on the total weight of the ink. Type solid ink. 3. A resin having a viscosity at 120 ° C. of 5
The hot melt type solid ink according to claim 1 or 2, wherein the hot melt type solid ink is less than 00mPa · s.