JPH03234772A - Ink for ink-jet recording and its manufacture - Google Patents

Abstract

PURPOSE:To make it possible to form characters and images which do not spread on plain paper and to improve the marring resistance, storage stability, and light resistance by dissolving a polar resin in a non-polar insulating organic solvent, and adding and dispersing a pigment therein. CONSTITUTION:A polar resin (e.g. a rosin resin) and, if desired, a dispersant (e.g. sorbitan monooleate) are dissolved in a non-polar aliphatic hydrocarbon insulating organic solvent, and a pigment (e.g. carbon black) is added thereto. Then, the mixture is introduced into an apparatus for dispersing, such as a ball mill or an attritor, and dispersed until the average diameter is reduced to 0.03-0.5mum when the average diameter of the pigment is 1mum or below, thereby producing an ink for ink-jet recording having a viscosity of 20m Pa.S or below at 0-50 deg.C.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention allows ink droplets to fly and print characters and letters on a medium such as recording paper.
The present invention relates to an ink used in an inkjet recording device that forms images and a method for manufacturing the same.

[Prior Art] Conventionally, inkjet recording methods can be roughly divided into two types: continuous type and on-demand type. Inks used in such inkjet systems are mainly inks in which dyes are dissolved in water.

Water-based inks are currently used in which various water-soluble dyes are dissolved in water or a solvent consisting of water and a water-soluble organic solvent, and various additives are added as necessary. The advantages of these inkjet recordings are that the process is simple because it is direct recording, there is no noise because it is not an impact method, it is easy to create colors, high-speed recording is possible, and minute ink droplets are ejected. It has excellent features such as being capable of high-resolution recording, and its future potential is attracting attention.

[Problem to be Solved by the Invention] However, with the above-mentioned conventional technology, although it differs slightly depending on the method, inkjet recording is performed by ink soaking into the paper, so depending on the type of paper, the ink may bleed. The problem is that the periphery of the recorded dots is unclear, the print quality deteriorates, and a high-quality recorded image cannot be obtained.

Therefore, attempts have been made to solve the above problems. For example, in Japanese Patent Publication No. 55-29546, a specific surfactant is added to lower the surface tension and improve the ability of the ink to transfer to the paper. Products with increased absorbency have been proposed, and in Japanese Patent Publication No. 56-57862, a strong basic substance is added to raise the pH, and sizing agents and pulp agents, which are water-resistant treatment agents for plain paper, are chemically modified. A method of dissolving and controlling the spread and absorption of dots has been reported, and also published in Japanese Patent Publication No. 58-1367.
Publication No. 5 proposes a method in which polyvinylpyrrolidone with a molecular weight of 40,000 or more is added to the ink to control the spread of dots and the absorbability to the transfer paper, but these attempts have not completely solved the above problems. There are no countermeasures to resolve this issue.

In addition, water-based inks are the mainstream of inkjet inks, and as mentioned earlier, water-based inks are recorded by soaking into the paper, so they can be used on transfer materials that cannot soak in, specifically ○HP sheets, etc. Calendar paper and the like have the problem that it is difficult to print on them, and even if printing is possible, the scratch resistance is not ensured.

Therefore, the present invention solves these problems,
The purpose of this is to prevent characters and images from bleeding on plain paper in the inkjet recording method, in which minute droplets of ink are ejected from the recording head and the ink is deposited on the transfer target to perform printing. An object of the present invention is to provide an inkjet ink that enables high-density printing with clear outlines, is also capable of printing on HP sheets, etc., and has abrasion resistance, and a method for producing the same.

[Means for Solving the Problems] The inkjet ink of the present invention is composed of at least a pigment, a resin, and a non-polar insulating organic solvent, and a dispersant is added as needed.
The resin is a polar resin, and the pigment has a maximum particle size of 1 μm or less and an average particle size of 0.03 to 0.5 μm. Further, the method for producing an inkjet ink of the present invention comprises at least a pigment, a resin, and a non-polar insulating organic solvent, and a dispersant is added as necessary. After adding and dissolving a dispersant as necessary, add a pigment, and use a dispersion machine to obtain a pigment with a maximum particle size of 1 μm or less and an average particle size of CL, 03~
It is characterized by being dispersed to a range of 0.5 μm.

The behavior of the inkjet ink of the present invention on the transferred object is that the pigment, which is the coloring material, remains in the position at the moment it is ejected and adheres to the transferred object, and only the non-polar insulating organic solvent is transferred to the transferred object. It diffuses along the fibers or the surface and evaporates to dryness, as shown in Figure 1. The present inventors refer to 1 as a ring in the first drawing, and 2 as an outline. It is formed by penetrating objects (diffusing on OHP sheets, etc.), and evaporates and dries over time and disappears. In addition, the second diagram shows the state of ink dots on a transfer object when printing is performed using an inkjet ink consisting of a pigment particle size, a resin, and a non-polar insulating organic solvent that does not fall within the scope of the claims of the present invention. 3 in FIG. 2 is called a blur.

[Function] By containing the polar resin, the inkjet ink of the present invention suppresses the diffusion of the pigment, which is the coloring material, together with the non-polar insulating organic solvent on the transferred material, prevents bleeding, and furthermore, the pigment The maximum particle size is 1 μm or less, and the average particle size is 0
．． By being in the range of 03 to 0.5 μm, the binding between the pigment particles and the resin is improved, the outline becomes clearer, and after the solvent evaporates, the pigment is finely dispersed in the resin. This improves the resin strength and ensures the abrasion resistance of the print.

[Example 7] The present invention will be specifically explained with reference to Examples below, but the present invention is not limited thereto.

The ink of the present invention can be prepared by the method described in claim 2, in which a resin is added to a solvent, a dispersant is added and dissolved if necessary, a pigment is added, and the dispersion is performed using a ball mill, attritor sand mill, etc. The maximum particle size of the pigment in the machine is 1 μm.
In the following, it can be obtained by dispersing and forming a uniform dispersion system until the average particle size is in the range of 0.03 to 0.5 μm, and if necessary, filtering through a filter or the like to remove giant particles, dust, etc.

In terms of ink physical properties, when the operating temperature is set at 0 to 50°C, the ink viscosity varies depending on the stability of ink supply under high-speed response of the head and the stability of ink droplet formation and flight near the nozzle during ejection. 20a+Pa・S or less is required, and in order to achieve even higher speed response, 2.
0 to 10.0 mPa·S is more preferable.

Specific examples of the components of the ink are given below.

Pigments include inorganic pigments (carbon black), organic pigments (insoluble azo pigments, soluble azo pigments, phthalocyanine pigments, isoindolinone-based high-grade pigments, quinacridone-based high-grade pigments, perinone/perylene-based high-grade pigments), and the like. In addition, processed pigments whose particle surfaces are coated with resin or the like can also be used. These may be used in combination of two or more types depending on the case.

The solvent used is an aliphatic hydrocarbon, specifically Exxon's Isopar Phillips Oil Pillar Tsurutrol.
IP Solvent of Idemitsu Petrochemical Co., Ltd.; for petroleum naphtha, Naphtha No. 1 to No. 6 of Shell Petrochemical Co., Ltd.; for other hydrocarbons, Exxon's Solepets; Shell S, B, R1, and Shell of Shell Petrochemical Co., Ltd. There are sol, Vegasol from Mopil petroleum oil, etc., and the required characteristics are low toxicity, low flammability, and low odor.

Moreover, these can also be used in combination of two or more types depending on the case.

Specifically, the resins include ethyl cellulose, polyacrylic ester, linseed oil modified alkyd resin, polystyrene, polyvinyl chloride, chlorinated polypropylene, polyamide resin, coumaron indene resin, rosin resin, terpene phenol resin, and alkylphenol modified resin. There are polar resins such as xylene resins, among which terpene phenol resins and rosin resins are more preferred. In addition, from the viewpoint of ink storage stability, it is preferable that the ink is soluble in a solvent.
Furthermore, from the viewpoint of blocking of recorded matter after printing, the melting point or softening point of the resin is preferably 5°C or higher. Moreover, two or more types of these can be used depending on the case.

In addition, the dispersant to be added as appropriate may be any dispersant as long as it is compatible with the solvent or can stably disperse fine particles, and specific examples thereof include sorbitan fatty acid ester (sorbitan monooleate, sorbitan monooleate, sorbitan monolaurate, sorbitan sesquioleate, sorbitan trioleate, etc.), polyoxyethylene sorbitan fatty acid esters (polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, etc.), polyethylene glycol fatty acid esters (polyoxyethylene sorbitan monooleate, etc.) nonionic surfactants such as polyoxyethylene alkylphenyl ethers (polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, etc.) are suitable. In addition, two or more of these may be used in combination depending on the case.

A specific example is shown below.

(Example 1) Pigment Mitsubishi Carbon Black MA100
6.0wt% (manufactured by Mitsubishi Kasei Corporation) Dispersant -1-'/:I-ru TO-1061, 3wt%
(manufactured by Nikko Chemicals) Resin YS Polyster T80 15.0wt% (manufactured by Resource Chemicals) Solvent Isopar H77.7wt% (manufactured by Exxon Chemicals) An ink composition having the above composition was prepared by the manufacturing method described in claim 2. . Table 1 shows the maximum particle size and average particle size of the pigment in this ink composition.

To obtain this maximum particle size and average particle size, the attritor
0 hours of dispersion time was required. In addition, the maximum particle size and average particle size of the pigment were measured using an electrophoretic light scattering device iEL made by Tenba Electronics Co., Ltd.
Measured using S-800. (Hereinafter, all maximum particle diameters and average particle diameters were measured using the above device.) Then, using an inkjet recording device, general high-quality paper,
After bit image printing, character printing, etc. were performed on various transfer materials such as Boside paper, PPC paper, and OHP sheets, the following evaluations a1 to a5 were performed.

(al) Printing bleedability: After printing on various transfer materials, evaluate the presence or absence of ink bleed by visual or microscopic observation. - No bleed is seen in the print by visual or microscopic observation... Suitable ( ■) - Bleeding was observed in the print by microscopic observation - Appropriate (○) - Bleeding was observed in the print by visual inspection - Unsuitable (x) - Classification and evaluation was performed.

(a2) Printing outline: After printing on various transfer objects, the quality of the outline is evaluated by microscopic observation, and the outline is clear.
... Suitable (■) - Outline is unclear
... Classified and evaluated based on unsuitability (×).

(a3) Printing abrasion resistance: After printing on various transfer objects,
The presence or absence of stains caused by rubbing the printed surface with a clip under a load of 200 kg/cm was evaluated by the number of times of rubbing.・No stains after 30 or more reciprocations...Suitable (■)・20
It was classified and evaluated according to the following criteria: Occurred after 30 reciprocating frictions: Appropriate (0); Occurred after 20 reciprocal frictions or less: Unsuitable (x).

(a4) Ink storage stability: After leaving the ink at a high temperature of 70°C for 3 months, observe: - Sedimentation is observed, but it redisperses easily - Suitable (O) - Sedimentation is observed, but aggregation ( Hard cake) has not occurred...Suitable (○) Sedimentation and aggregation has occurred...Unsuitable (x) (a5) Nozzle clogging: Fill the inkjet recording device with ink and heat at 50℃
Leave the nozzle without a cap in the environment for one month,
The ink ejection status was evaluated and classified and evaluated as follows: Immediate ejection: suitable (O); ejection after a little delay or rubbing with a rubber plate: suitable (0); No ejection: unsuitable (x).

The results are shown in Table 1.

(Examples 2 and 3) With the same composition as in Example 1, the dispersion time was adjusted so that the maximum particle size of the pigment was 1 μm or less and the average particle size was in the range of 0.03 to 0.5 μm. An ink composition of Example 2.3 shown in Table 1 was obtained. Then, in the same manner as in Example 1, this ink composition is used for bit image printing, character printing, etc. on various transfer materials such as general high-quality paper, bond paper, PPC paper, and HP sheet using an inkjet recording device. After that, al-a5 was evaluated.

The results are shown in Table 1.

(Example 4) Pigment Printex 55 10.0 wt% (
Resin Super Ester A-7510.0 wt% (manufactured by Tenkawa Chemical Co., Ltd.) Solvent 1 Isopar H64.0 wt% (manufactured by Exxon Chemical Co.) Solvent 2 Scherzol A I6.0 wt% (manufactured by Exxon Chemical Co., Ltd.)
An ink composition having the above composition (manufactured by Shell Petrochemical Co., Ltd.) was added to the ink composition according to claim 2 using the manufacturing method oil described in claim 2. Shown below.

To obtain this maximum particle size and average particle size, the attritor
A dispersion time of 2 hours was required.

Then, using an inkjet recording device, ordinary high-quality paper,
After performing bit image printing, character printing, etc. on various transfer materials such as bond paper, PPC paper, and OHP sheets, a.
Evaluations were made from 1 to a5.

The results are shown in Table 1.

(Examples 5 and 6) With the same composition as in Example 4, the dispersion time was adjusted so that the maximum particle size of the pigment was 1 μm or less and the average particle size was in the range of 0.03 to 0.5 μm. An ink composition of Example 5.6 shown in Table 1 was obtained. Then, in the same manner as in Example 1, this ink composition was used to print bit images and characters on various transfer materials such as on-board paper, bond paper, PPC paper, and OHP sheets using an inkjet recording device. After performing the above, al-a5 was evaluated.

The results are shown in Table 1.

(Comparative Examples 1, 2, 3, and 4) Furthermore, as comparative examples, ink compositions having the compositions shown in Example 1.4 were prepared without using the manufacturing method described in Claim 2. The maximum particle size and average particle size of the pigment in each ink composition are also listed in Table 1.

Then, using an inkjet recording device, ordinary high-quality paper,
After bit image printing, character printing, etc. were performed on various transfer materials such as bond paper, PPC paper, and OHP sheets, evaluations of a1 to a5 were performed in the same manner as in the examples.

The results are also shown in Table 1.

(Comparative Example 5) Pigment Mitsubishi Carbon Frack MA100
6.0wt% (manufactured by Mitsubishi Kasei Corporation) Dispersant Niracol T 0-106 1.3wt
% (manufactured by Nikko Chemicals) Resin Highlets HRT200X 15.0wt%
(Mitsui Petrochemical Co., Ltd.) Solvent Isopar H77.7wt% (Exxon Chemical Co., Ltd.) As mentioned above, the polar resin terpene phenol copolymer (YS Polyster T
80: Instead of aliphatic hydrocarbon resin (manufactured by Resource Chemical Co., Ltd.), a non-polar resin, aliphatic hydrocarbon resin (Hiretz HRT 200)
X: manufactured by Mitsui Petrochemical Co., Ltd.) was added to an ink composition was prepared by the manufacturing method described in claim 2. The maximum particle size and average particle size of the pigment in each ink composition are also listed in Table 1.

Then, using an inkjet recording device, ordinary high-quality paper,
After bit image printing, character printing, etc. were performed on various transfer materials such as bond paper, PPC paper, and OHP sheets, evaluations of a1 to a5 were performed in the same manner as in the examples.

The results are also shown in Table 1.

As is clear from the table, the ink and manufacturing method of the present invention show good results in the evaluation of print bleeding, print outline, and print abrasion resistance. The diameter is 1 μm or less, and the average particle size is 0.03 to 0.5
Since it is within the μm range, it also satisfies the evaluation of ink storage stability and nozzle clogging.

[Effects of the Invention] As described above, by using the inkjet ink of the present invention and its manufacturing method, characters and images do not bleed on plain paper, which has been a problem in the past, and high density images with clear outlines can be produced. In addition, it can print on OHP sheets, etc., is scratch resistant, and does not clog.
It also has the advantage of good storage stability. Furthermore, the use of pigments also has the special effect of improving light resistance compared to conventional inks.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the state of ink dots on an object to be transferred when printing is performed using the inkjet ink of the present invention. FIG. 2 is a diagram showing the state of ink dots on transfer paper when printing is performed using an inkjet ink that does not fall within the scope of the claims of the present invention.・More than ring marks, contours, and blur

Claims (2)

[Claims] (1) An inkjet ink consisting of at least a pigment, a resin, and a non-polar insulating organic solvent, in which a dispersant is added as necessary, wherein the resin is a polar resin,
and an inkjet ink, wherein the pigment has a maximum particle size of 1 μm or less and an average particle size of 0.03 to 0.5 μm. (2) In a method for producing an inkjet ink consisting of at least a pigment, a resin, and a non-polar insulating organic solvent, and in which a dispersant is added as necessary, the resin is added to the solvent, and a dispersant is added as necessary. After addition and dissolution, a pigment is added and dispersed by a dispersing machine until the pigment has a maximum particle size of 1 μm or less and an average particle size of 0.03 to 0.5 μm. method for producing ink for