JPH10298468A - Ink composition and image recording method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink composition which does not spread on a recording paper and is prevented from penetrating into the inner part of a recording paper, and can be used for forming an image of high concentration and high saturation. SOLUTION: This composition is an ink composition comprising water, a colorant and particles, wherein gel particles formed by the reaction of a gelatin and a gelatin-curing agent are used as such particles. This image-recording method is a method which records an image on a recording paper by jetting ink drops from a head, wherein an ink composition comprising water, a colorant and gel particles obtained by curing a gelatin is utilized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an ink composition and an image recording method using the same. For more information,
The present invention relates to an ink composition suitable for an ink jet printer containing specific fine particles and an image recording method using the ink composition.

[0002]

2. Description of the Related Art Recently, as an output device of information equipment such as a computer, an ink jet system, which has a low running cost, can obtain a high-definition image, and is easy to colorize, has attracted attention. As the ink for an ink jet printer, an aqueous dye solution has conventionally been mainly used. However, if the ink ejected from the nozzles and the flying ink adheres to the recording paper, the ink bleeds on the recording paper, the ink droplets at the time of flight become larger dots on the recording paper, or the ink flows inside the recording paper. There is a problem in that the density of the image recorded by penetrating the recording medium becomes low.

Conventionally, as a solution to the above-mentioned problems in the aqueous ink for ink jet, [A] a technique of adding fine resin particles for forming an image to an ink (Japanese Patent Publication No. 60-32663, Japanese Patent Application Laid-Open No. 239392
JP, JP-A-5-255628, JP-A-6-3
No. 40835) and a technique of adding dyed film-forming resin fine particles to ink (Japanese Patent Application Laid-Open No. 5-255567), [B] Image film obtained by blending resin fine particles and a cross-linking agent into ink and cross-linking the resin Technology (Japanese Patent Publication No. 7-4735)
No. 5), [C] an ink containing an oil-in-water emulsion using an oil or fat containing a coloring material (Japanese Patent Application Laid-Open No. 7-11181), and [D] an ink containing a compound having thermoreversible gelling properties ( JP-A-6-192605) and [E]
Inks containing water-soluble polymer colloids (U.S. Pat.
133, 803) have been proposed.

[0004]

However, although the inks [A] and [B] described above can reduce the bleeding on the recording paper to some extent, the bleeding of the ink into the recording paper fibers due to the capillary phenomenon is achieved. It is impossible to completely prevent the occurrence of high-density images, and even though it is effective to some extent in improving image density, it cannot prevent ink from penetrating into the recording paper. There is. In addition, since these inks are formed using resin fine particles that exhibit film forming properties at normal temperature, the resin fine particles need to be able to be fused at room temperature, and therefore have a relatively high glass transition temperature. There is a common problem that low resin fine particles must be used. Further, with the ink [A], there is a problem in that the image area becomes tacky when the environmental temperature during image recording increases, and this tendency increases as the environmental temperature increases. On the other hand, in the technique of ink [B], the image portion does not become tacky because the image film is crosslinked, but since the crosslinking agent added to the ink is a highly reactive substance, There are concerns about safety and stability.

[0005] The ink [C] has a drawback that high-boiling oils and fats remaining on the recording paper for a long period of time hinder image fixability. The ink [D] contains a compound having a thermoreversible gelling property. This compound is a homogeneous aqueous solution having a high viscosity at room temperature, but precipitates in water at a high temperature to form a low-viscosity fine particle dispersion. Ink is ejected with a low viscosity in a high-temperature head, and when the ink adheres to the recording paper, the temperature of the ink drops and the viscosity increases, so the ink deeply penetrates into the paper. Therefore, there is an advantage that a high density image can be obtained. However, since the ink [D] has a high viscosity, it is difficult to dry on the recording paper, so that the fixability immediately after printing becomes insufficient. When the thermal energy is applied to the head, the evaporation of water in the ink is promoted at the head ejection portion, and clogging due to the problem cannot be prevented. there were. In addition, all of the techniques of inks [A] to [D] have a common problem that image clarity is poor, that is, saturation is low. Further, although the ink [E] is effective in improving bleeding on the surface of the recording paper, it cannot sufficiently prevent the ink from penetrating into the recording paper, so that there is a limit in increasing the density of an image. .

[0006] The present invention has been made to solve the above-mentioned problems. That is, an object of the present invention is to provide an ink composition that does not cause ink bleeding on recording paper, can prevent penetration of the ink into the recording paper, and can provide a high-density and high-chroma image, particularly for inkjet. It is to provide a suitable ink composition. Another object of the present invention is to provide an ink composition capable of forming an image having good fixability immediately after printing. Further, another object of the present invention is to provide an image recording apparatus which does not become tacky even at a high environmental temperature, has excellent safety and stability, and is capable of image recording without applying thermal energy to a head. It is to provide an ink composition which can be used. Still another object of the present invention is to provide a good image recording method which does not cause clogging by using the above ink composition.

[0007]

The ink composition of the present invention contains water, a colorant and fine particles, and the fine particles are gel fine particles formed by a reaction between gelatin and a gelatin hardener. It is characterized by. Also, the image recording method of the present invention is an image recording method in which ink droplets are ejected from a head to perform recording on a recording medium, wherein the fine particles contain water, a colorant, and fine particles, and the fine particles are gelatin and a gelatin hardener. Characterized by using an ink composition that is a gel fine particle generated by the reaction with

According to the present invention, immediately after the ink adheres to the recording paper, the water in the ink evaporates or permeates into the recording paper, whereas the gel fine particles are trapped on the recording paper. Since the holes on the recording paper are closed, most of the colorant hardly bleeds on the recording paper and hardly penetrates into the recording paper, so that a high-density image can be formed on the recording paper. Further, when the colorant is a dye, the dye molecules are adsorbed on the surface of the gel fine particles without agglomeration, so that a very vivid color is formed, and an image with high chroma can be realized. When the colorant is a pigment, fine pigment particles cover the surface of the gel fine particles in an extremely thin layer, and the gel fine particles function as the extender pigment, so that it is assumed that the image shows high chroma.

In the ink composition of the present invention, since the compound constituting the gel exists in the ink as fine particles at normal temperature, the ink is ejected from the head with a low viscosity and adheres to the recording paper in a low viscosity state. At this time, the water of the ink adhering to the recording paper permeates the recording paper immediately after printing, while the gel fine particles are captured by the paper, and an image having good fixability is formed on the recording paper. In addition, since the gel fine particles used in the ink composition are flexible particles containing water, the gel fine particles can be deformed and adhere according to the unevenness of the recording paper surface, and can be colored as described above. Not only is it suitable for the fixability of the image because the agent is brought into close contact with the agent, but also because it has a crosslinked structure, it is possible to form an image having no tackiness even at a high temperature. Furthermore, the ink composition of the present invention does not contain any unreacted cross-linking agent, so there is no problem in safety, and energy is applied to the head as in an ink containing a compound having a thermoreversible gelling property. It is not necessary.

[0010]

Embodiments of the present invention will be described below in detail. The ink composition of the present invention contains water, a colorant, and fine particles. As the fine particles,
Gel fine particles, preferably hydrogel (hydrophilic gel), obtained by reacting gelatin with a gelatin hardener are used. Gels used in the present invention are described in "Polymer Compounds with a Three-Dimensional Network Structure Insoluble in All Solvents" as described in "New Edition Polymer Dictionary" (1988) published by Asakura Shoten, edited by the Society of Polymer Science, etc. The swollen body is defined.

In the present invention, as the gelatin used as a raw material for gel formation, any protein obtained by subjecting animal skin or bone to a known treatment method such as an alkali treatment or an acid treatment can be used. However, it is preferable to use those having an average molecular weight in the range of usually 61,000 to 67000. Examples of the gelatin hardener used for forming the gel include aldehydes such as aliphatic saturated aldehyde, aliphatic dialdehyde, aliphatic unsaturated aldehyde and aromatic aldehyde, and formaldehyde, acetaldehyde and propionaldehyde. Aliphatic saturated aldehydes are preferred.

The gel fine particles used in the present invention are usually produced as follows. First, water is added to gelatin to cause swelling, and the swollen gelatin is heated and dissolved to obtain an aqueous gelatin solution. Next, an aqueous solution containing a gelatin hardener is added to and mixed with the aqueous gelatin solution,
When this mixture is cooled, the crosslinking reaction is promoted and the mixture is gelled. The gel that has reached the swelling equilibrium state with this water is
Grinding in water using a wet grinding apparatus prepares a dispersion of gelatin gel fine particles. As the wet pulverizer, a known pulverizer such as a homogenizer, a colloid mill, a sand mill, or an ultrasonic disperser is used.

As the gel fine particles in the present invention, it is preferable to use those in which each particle is in a dispersed state. The average particle diameter is determined from the viewpoints of ease of production and adaptability to an ink jet nozzle. 0.01-3μ
m, and more preferably 0.0
5-1 μm.

The gel constituting the fine particles used in the present invention is a hydrogel containing water, and the content of water is in the range of 0.01 to 99.99% by weight.
Outside this range, the closure of the recording paper hole is insufficient,
For example, the adaptability to the inkjet nozzle may be reduced. That is, if the water content in the gel is less than 0.01% by weight, clogging is likely to occur in the nozzle portion of the ink jet.
If the content exceeds 9.99% by weight, the gel fine particles become too soft and pass through the paper holes, leaving many unblocked recording paper holes, and the colorant penetrates into the paper through these holes. As a result, the optical density decreases. The content ratio of the water is preferably 1.00 to 99.00% by weight,
More preferably, it is in the range of 50.00 to 99.00% by weight.

In the ink composition of the present invention, the gel fine particles are usually contained in the ink composition in an amount of 1 to 50% by weight. If the thickness is outside this range, the holes in the recording paper are not sufficiently closed, and the adaptability to the ink jet nozzles is reduced. That is, when the amount of the gel fine particles is less than 1% by weight based on the total amount of the ink, the number of the gel fine particles is too small, so that many holes of the recording paper which are not closed remain, and the colorant penetrates into the paper through these holes. As a result, the optical density is reduced, while the amount of gel fine particles is 50% by weight.
When the value exceeds, the viscosity of the ink increases remarkably, and it becomes difficult to discharge the ink from the inkjet nozzle. The proportion of the gel fine particles is preferably in the range of 5 to 35% by weight.

As the colorant used in the present invention, any colorant can be used as long as it has a good affinity for water as a main solvent and can be uniformly dispersed when used in combination with a dispersant or the like. As a typical example, a pigment, a water-soluble dye or a disperse dye is used. Among them, as the pigment, both organic pigments and inorganic pigments can be used. For example, for black and white, carbon blacks (CI Pigment Black 7) such as furnace black and channel black, aniline black (CI Pigment Black 1), and mixtures thereof are exemplified. For color printing, C.I. I. Pigment Yellow 1, 3, 12, 13, 14, 17, 24, 34, 3
5, 37, 42, 53, 55, 81, 83, 95, 9
7, 98, 100, 101, 104, 108, 109,
110, 117, 120, 138, 153, C.I. I. Pigment Violet 1, 3, 5: 1, 16, 19, 2
3, 38, C.I. I. Pigment Blue 1, 2, 15, 1
5: 1, 15: 2, 15: 3, 15: 4, 15: 6, 1
6 and the like and mixtures thereof. The addition amount of these pigments is preferably in the range of 1 to 30% by weight, and 1.5 to 12% by weight in order to exhibit the function as a colorant.
Is more preferable. In order to uniformly disperse these pigments, a dispersant may be added to the pigment in an amount of 0.01 to
It is desirable to add 1% by weight, and further perform a dispersion treatment using a ball mill or the like.

The water-soluble dye used as the colorant includes a direct dye or an acid dye. For example, C.I. I. Direct Black 9, 17, 19, 2
2, 32, 51, 56, 62, 69, 77, 80, 9
1, 94, 97, 108, 112, 113, 114, 1
17, 118, 121, 122, 125, 132, 14
6, 154, 166, 168, 173, 199, C.I.
I. Direct violet 7, 9, 47, 48, 5
1, 66, 90, 93, 94, 95, 98, 100, 1
01, C.I. I. Direct Yellow 8, 9, 11, 1
2, 27, 28, 29, 33, 35, 39, 41, 4
4, 50, 53, 58, 59, 68, 86, 87, 9
3, 95, 96, 98, 100, 106, 108, 10
9, 110, 130, 132, 144, 161, 16
3, C.I. I. Direct Blue 1, 10, 15, 22,
25, 55, 67, 68, 71, 76, 77, 78, 8
0, 84, 86, 87, 90, 98, 106, 201,
202, 244, 251, 280, C.I. I. Acid black 7, 24, 29, 48, C.I. I. Acid Violet 5, 34, 43, 47, 48, 90, 103,
C. I. Acid Yellow 17, 19, 23, 25, 3
9, 40, 44, 49, 50, 61, 110, 174,
218, C.I. I. Acid Blue 9, 25, 40, 4
1, 62, 72, 76, 80, 106, 112, 12
0, 205, 230, 271, 280, and the like, and mixtures thereof, but are not limited thereto.
The amount of these dyes to be added is determined depending on the type of the dyes and the properties required for the ink, and the like.
0% by weight, preferably 0.5 to 10% by weight.

The ink composition of the present invention may contain an aqueous resin emulsion or a water-soluble resin in order to further improve the fixability of an image formed on recording paper. As the resin of the aqueous resin emulsion,
For example, acrylic resin, acrylic silicone resin, vinyl acetate resin, polyester, polyurethane, vinyl chloride resin, polystyrene, styrene-butadiene copolymer,
Vinyl acetate-acryl copolymer, vinyl acetate-acrylamide copolymer, ethylene-vinyl acetate copolymer, epoxy resin, polyamide, silicone resin, chloroprene rubber and the like are used. Further, as the water-soluble resin, polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, polyvinyl pyrrolidone, acrylic resin,
Epoxy ester resins, phenol resins, alkyd resins, polyesters and the like are used.

Further, in order to further increase the density of an image in the ink composition, the above-mentioned coloring agent may be contained in the gel fine particles as necessary. In addition, if necessary, p such as potassium dihydrogen phosphate, sodium dihydrogen phosphate, etc.
H regulator, benzoic acid, dichlorophen, hexachlorophen, sorbic acid, etc. can be added for the purpose of antifungal, antiseptic, antirust, etc. Also, ethylene glycol, glycerin, various May be added.

The ink composition of the present invention can be produced by the following procedure, but is not limited thereto. First, an aqueous dispersion comprising a colorant and a dispersant was dispersed by a ball mill, and it was confirmed by microscopic observation and the like that the colorant particles were in a monodispersed state. Next, the gel dispersed in water in the solution was used. Fine particles are added and uniformly mixed by stirring. Thereafter, additives such as preservatives are further introduced, and after confirming that they are completely dissolved, the dispersion is filtered using, for example, a membrane filter having a pore size of 10 μm to remove dust and coarse particles. Thus, a recording ink composition is obtained.

[0021]

The present invention will be specifically described below with reference to examples. Example 1 First, an ink composition containing gel fine particles produced by a reaction between gelatin and a gelatin hardener using a water-based copper phthalocyanine pigment dispersion as a coloring agent was produced as follows. 2 parts by weight of gelatin (reagent) was mixed with 98 parts by weight of water to swell the gelatin with water, and then heated to 40 ° C. to dissolve the gelatin. To the obtained solution, 2 ml of a solution prepared by dissolving 2 parts by weight of a formalin aqueous solution (reagent, formalin concentration of 35% by weight or more) in 98 parts by weight of water was added, and the mixture was cooled to 25 ° C. to form a gelatin gel. Generated. A solution in which 90 parts by weight of water was mixed with 10 parts by weight of the produced gelatin gel was stirred at a high speed using a blender, whereby the gel was pulverized to obtain a gel fine particle dispersion of gelatin. Observation of this product with an optical microscope confirmed that a gelatin gel pulverized into fine particles of 1 to 2 μm was formed. 10 parts by weight of the obtained gelatin gel fine particle dispersion, 10 parts by weight of an aqueous copper phthalocyanine pigment dispersion (trade name: EP-700, manufactured by Dainichi Seika Kogyo Co., Ltd., solid content 35%) and acrylic silicone resin fine particles (product An ink composition was obtained by mixing 20 parts by weight of SW-135 (manufactured by Sanyo Kasei Kogyo Co., Ltd., solid content 35%, weight average molecular weight 15,000, particle diameter 0.1 to 0.2 μm).

Next, the obtained ink composition was coated on plain paper for a copying machine using a bar coater and dried at room temperature to obtain a solid image having a coated dry film formed on plain paper. . At that time, the type of the coating bar (roughness of the coating) of the bar coater was variously changed to obtain a plurality of solid images having different film thicknesses (image thicknesses). When the optical density (Optical Density) of the obtained image was measured, it was 1.5 when the image thickness was 3 μm and 4 when the image thickness was 4 μm.
In the case of 1.7 μm, an image having a high optical density was formed on plain paper. Further, when these solid images were visually observed, it was confirmed that the images exhibited vivid cyan coloring and were high-saturation cyan images. Further, when the longitudinal section of the solid image on the plain paper was observed with an optical microscope, the image was formed on the plain paper, and no permeation of the ink was found inside the plain paper.
Further, when a finger smudge test was performed on the image immediately after printing, the image fixability was good and the non-image portion was not contaminated.

A printing test was performed on plain paper using the ink composition described above in a commercially available ink jet printer. At that time, the inkjet printer
The viscosity was adjusted by diluting the ink composition with water so that the ink could fly. Observation of the printed dots of the obtained printed sample with a magnifying loupe and an optical microscope showed that there was no ink bleeding around the dots, and
Clear dots having high saturation and high image density were formed.
Further, water was sprayed on the solid image obtained by using the bar coater and the print sample obtained by using the printer to evaluate water resistance. As a result, each of these images was free from bleeding of the image due to water, did not diffuse the coloring agent, and had high water resistance.

Example 2 First, an ink composition containing gelatin gel fine particles dispersed in water using a phthalocyanine dye (acid blue 9) aqueous solution as a coloring agent was produced as follows. Example 1
Fine particle dispersion 10 of gelatin gel obtained in the same manner as described above.
Phthalocyanine dye containing acid blue 9 (parts by weight, trade name: Rakuto Brilliant Bl)
ue FCF, 10% by weight of 10% aqueous solution of Rakuto Chemical Co., Ltd. and fine particles of acrylic silicone resin (trade name: SW-
135, manufactured by Sanyo Chemical Industries, Ltd.), solid content 35%, weight average molecular weight 15,000, particle diameter 0.1 to 0.2 μm) 20
The ink composition was obtained by mixing parts by weight.

Next, the obtained ink composition was coated on plain paper for copying machines using a bar coater and dried at room temperature to obtain a solid image having a coated dry film formed on plain paper. . At that time, the type of the coating bar of the bar coater was variously changed to obtain a plurality of solid images having different film thicknesses. When the optical density of the obtained image was measured, the image thickness was 3.
1.7 μm for 3 μm and 6.0 μm for image thickness
Was 1.9, and an image with high optical density was formed on plain paper. Further, when these solid images were visually observed, it was confirmed that the images exhibited vivid cyan coloring and were high-saturation cyan images. Further, when a finger smudge test was performed on the image immediately after printing, the image fixability was good and the non-image portion was not contaminated. Further, when the longitudinal section of the solid image on the plain paper was observed with an optical microscope, the image was formed on the plain paper, and no permeation of the ink was found inside the plain paper.

A printing test was carried out on plain paper using the above-mentioned ink composition in a commercially available ink jet printer. At that time, the inkjet printer
The viscosity was adjusted by diluting the ink composition with water so that the ink could fly. Observation of the printed dots of the obtained printed sample with a magnifying loupe and an optical microscope showed that there was no ink bleeding around the dots, and
Clear dots having high saturation and high image density were formed.
Further, water was sprayed on the solid image obtained by using the bar coater and the print sample obtained by using the printer to evaluate water resistance. As a result, each of these images was free from bleeding of the image due to water, did not diffuse the coloring agent, and had high water resistance.

Comparative Example 1 An ink composition was obtained in exactly the same manner as in Example 1 except that water was used instead of the gelatin gel fine particle dispersion. Using this ink composition, a solid image was obtained on plain paper. When the optical density of the obtained image was measured, it was 1.4 when the image thickness was 3.2 μm and the image thickness was 5.9 μm.
m was 1.5, and both had low optical density. When these solid images were visually observed, it was confirmed that the images were cyan images with low saturation. Also, when the obtained image on plain paper was visually observed from the back side of the plain paper (the side opposite to the image surface), the color of the colorant was light,
It was confirmed that the ink slightly penetrated into the plain paper. Further, when the longitudinal section of the solid image on the plain paper was observed with an optical microscope, it was confirmed that the image was also formed inside the plain paper, and that the ink had penetrated into the plain paper. . Next, a printing test of this ink on plain paper was performed using the same commercially available inkjet printer as used in Examples 1 and 2. Observation of the printed dots of the printed sample with a magnifying loupe and an optical microscope revealed that ink bleeding was observed around the dots and that unclear dots having a low image density were formed.

Comparative Example 2 An ink composition was obtained in exactly the same manner as in Example 2 except that water was used instead of the gelatin gel fine particle dispersion. Using this ink composition, a solid image was obtained on plain paper. When the optical density of the obtained image was measured, it was 1.4 when the image thickness was 3.0 μm, and the image thickness was 5.9 μm.
m was 1.5, and both had low optical density. When these solid images were visually observed, it was confirmed that the images were cyan images with low saturation. Further, when the obtained image on the plain paper was visually observed from the back side of the plain paper, it was confirmed that the color of the colorant was light and the ink slightly penetrated into the plain paper. Further, when the longitudinal section of the solid image on the plain paper was observed with an optical microscope, it was confirmed that the image was also formed inside the plain paper, and that the ink had penetrated into the plain paper. . Next, a printing test of this ink on plain paper was performed using the same commercially available inkjet printer as used in Examples 1 and 2. Observation of the printed dots of the printed sample with a magnifying loupe and an optical microscope revealed that ink bleeding was observed around the dots and that unclear dots with low image density were formed.

[0029]

The ink composition of the present invention has no ink bleeding on the recording paper, can prevent the ink from penetrating into the recording paper, and has an extremely high density and high chroma printing quality. An excellent image can be formed. Further, when this ink composition is used, a good image having excellent fixability can be obtained immediately after printing without applying energy to the head, and the image portion has adhesiveness even at a high environmental temperature. It does not take on and has good safety. Therefore, an image recording method using this ink composition as a recording liquid is particularly suitable for an inkjet printer.

Claims (2)

[Claims] 1. An ink composition comprising water, a colorant and fine particles, wherein the fine particles are gel fine particles formed by a reaction between gelatin and a gelatin hardener. 2. An image recording method for recording on a recording medium by discharging ink droplets from a head, comprising: an ink composition containing water, a colorant and fine particles, wherein the fine particles are formed of gelatin and hardened gelatin. An image recording method using an ink composition that is gel fine particles generated by a reaction with an agent.