JPH11236523A - Ink for image formation and image formation method using sane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink for image formation which uses a solvent mainly comprising water and can give a high-difinition image without exhibiting blur and without causing swelling after drying of an image part formed by the ink and to provide an image formation method using the same. SOLUTION: An ink for image formation which contains (A) a solvent mainly comprising water, (B) a colorant dispersible or soluble in the solvent, and (C) a thermal excitation-responsive polymer which is water-soluble at normal temp., becomes water-insoluble by heating, and is contained in the dissolved state is deposited in the form of an image on a recording medium and/or is given thermal energy with an external means, causing the thermal excitation- responsive polymer to enclose and fix the colorant. Thus, in image formation with the ink prepd. by using a solvent mainly comprising water, blur is prevented; a high-difinition image can be obtd.; swelling after drying of an image part formed by the ink is avoided; and a high-quality image is obtd. even on plain paper.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming ink capable of obtaining a high-definition image without bleeding on a medium by applying a thermal stimulus, and an image recording method using the same.

[0002]

2. Description of the Related Art An ink jet recording method is a recording method in which an image is formed by ejecting and flying a small droplet of ink from a fine nozzle and directly attaching the droplet to a recording member such as paper. Printers using this method are low cost, high quality,
Currently, printers are widely used as printers for offices and homes because of their small size and easy colorization. As the ink used in such a printer, a colorant (dye, pigment) dissolved and dispersed in a liquid medium such as water is used, and various additives are added as necessary. However, when recording on plain paper using such inks, image bleeding often occurs due to uneven penetration of the ink, and furthermore, sufficient image density cannot be obtained because the ink penetrates inside the plain paper. There are many. In addition, during color printing, other inks are successively overlapped before the previously attached ink is completely fixed, so that bleeding at a color boundary occurs.

As a general method for solving these problems, a dedicated coated paper provided with an ink absorbing layer on a recording medium surface is often used. However, especially in offices, so-called plain paper such as electrophotographic paper is generally used, and the exclusive coated paper is expensive, so that high-definition recording can be performed even on a medium that easily spreads, such as plain paper. There has been a demand for a new ink or recording method. As a means for achieving this, there is known a method in which a liquid composition exhibiting a bleeding prevention effect by acting on ink is attached to a recording medium prior to ejection of the ink. For example, JP-A-63-2999971 discloses that an anionic dye is contained after a liquid containing an organic compound having two or more cationic groups per molecule is deposited on a recording medium. A method for recording with ink is disclosed. Also,
JP-A-64-63185 discloses a method in which a colorless or light-colored liquid for insolubilizing a dye is applied prior to ink recording, and the dot diameter of the liquid on a recording medium is made larger than that of the ink. ing. However, these methods have a problem in that the overlap of the two liquids is shifted if the ink ejection accuracy or the ejection conditions fluctuate. In addition, in order to surely obtain the effect, it is necessary to apply a large amount of liquid other than ink on the recording medium. Another problem when recording on plain paper is that the paper is wavy due to the ejection of a large amount of ink. This has not been completely solved even with the use of a specially coated paper.

[0004]

On the other hand, in recent years, attention has been paid to materials whose physical properties change in response to various external stimuli, and applications to a wide range of fields including sensors have been attempted. Among them, polymers that undergo hydration and dehydration in response to external stimuli or polymer gels that contract and swell in response to external stimuli have been attracting interest mainly from the field of biochemistry. Applications to those utilizing characteristics and those utilizing sharp stimulus responsiveness such as intelligent preparations have been studied. Some ink jet recording inks containing such stimuli-responsive polymers and polymer gels have also been proposed. For example, Japanese Patent Application Laid-Open No. 1-227273 discloses a polymer which changes into a gel at room temperature and a sol at high temperature. There is disclosed a method of including the compound in the ink. According to this method, the ink is ejected in a heated state, and at the time of impact, the ink is cooled at room temperature to suppress gelation and bleeding.

Japanese Patent Application Laid-Open No. 5-148442 discloses a method in which polymer gel beads which swell and shrink according to the proton concentration are contained in an ink in a contracted state. It is stated that the gel beads in the ink swell due to the provision of protons from the recording member after landing, and as a result, quick drying of the entire ink is obtained. However, all of these methods increase the viscosity of the ink after landing, and have a problem that the drying time of the solvent is long because the solvent is confined, and the dots after drying are raised.
Accordingly, the present invention has been made in view of the above problems, and using an ink for image formation using a solvent containing water as a main component, bleeding is prevented, and a high-definition image is obtained. An object of the present invention is to provide an image forming ink in which a portion does not rise after drying and an image recording method using the same.

[0006]

In order to achieve the above object, the present invention provides an image forming ink containing a solvent containing water as a main component and a colorant dispersed or dissolved in the solvent. It is characterized by containing a heat stimuli-responsive polymer which is soluble and becomes water-insoluble by heating in a dissolved state. Further, the image forming method of the present invention, the image forming ink is adhered on a recording medium in the form of an image,
By applying thermal energy by an external means, the heat stimuli-responsive polymer in the ink embraces and fixes the colorant.

The operation of the present invention is as follows. In the present invention, a solvent containing water as a main component, a colorant dispersed or dissolved in the solvent, and a heat-stimulated responsive polymer that is water-soluble at room temperature and becomes water-insoluble by heating are contained in a dissolved state. By causing the image forming ink to adhere to the recording medium in the form of an image and / or applying thermal energy to the image forming ink by an external means, the heat stimuli responsive polymer in the ink changes the colorant. It is to hold and fix. Therefore, in image formation using an ink for image formation using a solvent containing water as a main component, bleeding is prevented, a high-definition image is obtained, and the image portion of the ink does not rise after drying, and furthermore, High quality images can be obtained even on plain paper.

[0008]

Embodiments of the present invention will be described below. The image forming ink of the present invention contains a solvent containing water as a main component, and a colorant that is dispersed or dissolved in the solvent, is water-soluble at ordinary temperature, and becomes water-insoluble by heating. In a dissolved state.

(Ink for forming an image) The solvent used in the ink for forming an image of the present invention contains water as a main component. That is, it is water alone or a mixed solvent of water and a water-soluble organic solvent. The water is desirably pure water or ultrapure water that has undergone a purification step such as ion exchange or distillation. The water-soluble organic solvent includes polyhydric alcohols having high boiling points and low volatility such as glycerin, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, hexylene glycol, polyethylene glycol, and polypropylene glycol. Used
Or their monoetherified, dietherified,
Esterified products such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether and the like are used, and N-methyl-2-pyrrolidone, 1.3
-Nitrogen-containing organic solvents such as dimethylimidazolidinone, tetrahydrofuran, monoethanolamine, N, N-dimethylethanolamine, N, N-diethylethanolamine, diethanolamine, Nn-butyldiethanolamine, triisopropanolamine and triethanolamine And other water-soluble organic solvents can be added in a range that does not cause printing flow or bleeding.

[0010] In addition, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, iso-butanol, tert-butanol, and water are used for the purpose of improving the drying property and the permeability to water as a main solvent. A highly volatile monohydric alcohol such as
As the colorant, conventionally known pigments and dyes are used, but those which easily interact with the heat stimuli-responsive polymer having a phase transition temperature or higher in a hydrophobic manner are preferable. Examples of pigments that can be used in the image forming ink of the present invention include organic pigments and inorganic pigments. For example, for black, carbon black such as furnace black, lamp black, acetylene black, and channel black (C Pigment Black 7), metals such as copper, iron (CI Pigment Black 11) and titanium oxide, and organic pigments such as aniline black (CI Pigment Black 1).

As the yellow pigment, inorganic yellow lead,
Cadmium yellow, yellow iron oxide, titanium yellow, ocher and the like. Examples of the acetoacetic acid arylide monoazo pigments of poorly soluble metal salts (Azo Lake) include C.I. I.
Pigment Yellow 1, 3, 65, 74, 97, 98,
133, 169 and allylic disazo acetoacetate pigments include C.I. I. Pigment Yellow 12, 13, 1
4, 17, 55, 81, and 83. Examples of the condensed azo pigment include C.I. I. Pigment Yellow 93, 94,
95. Further, benzimidazolone monoazo pigments include C.I. I. Pigment Yellow 120, 1
51, 154, 156, and 175. Examples of the isoindolinone pigment include C.I. I. Pigment Yellow 109, 110, 137, and 173.
In addition, C.I. I. Pigment Yellow 24, 99, 108, 123, C.I. I. Pigment Green 10, C.I. I. Pigment Yellow 117 and 153, and quinophthalone pigments such as C.I. I. Pigment Yellow 138 and the like.

Examples of the magenta pigment include inorganic cadmium red, red iron oxide, silver vermilion, lead red, and antimony vermilion. Examples of the azo lake-based azo pigments include C.I. I. Pigment Red 48, 49, 51, 53:
1, 54, 57: 1, 60: 1, 63, 64: 1, C.I.
I. Pigment Orange 17, 18, 19,
Examples of the insoluble azo type (monoazo, disazo type and condensed azo type) include C.I. I. Pigment Red 1, 2, 3,
5, 9, 38, 112, 114, 146, 150, 17
0, 185, 187, C.I. I. Pigment Orange 5,
13, 16, 36, 38, C.I. I. Pigment Brown 25, and C.I. I. Pigment red 144, 166, C.I. I. Pigment Orange 31 and the like.

As anthraquinone pigments which are condensed polycyclic pigments, C.I. I. Pigment Red 177, C.I.
I. Pigment Orange 40 and 168, and thioindigo pigments such as C.I. I. Pigment Red 88,
C. I. Pigment Violet 36 and 38, and C.I. I. Pigment Orange 43; and perylene pigments such as C.I. I.
Pigment Red 123, 149, 178, 179, 1
And quinacridone pigments such as C.I. I. Pigment Red 122, 206, 207, C.I. I. Pigment Violet 19; and other condensed polycyclic pigments such as pyrocholine pigments, red fluorpine pigments, and basic dye lake pigments such as C.I. I. Pigment Red 81 and the like.

Examples of the cyan pigment include inorganic ultramarine blue, navy blue, cobalt blue, cerulean blue, and the like.
As phthalocyanine-based compounds, C.I. I. Pigment Blue 15, 15: 1, 15: 2, 15: 3, 15: 4, 1
5: 6, 16, 17, C.I. I. Pigment Green 7,
36, C.I. I. Pigment Violet 23, and C.I. I. Pigment Blue 21, 22, 60, 64, and C.I. I. Pigment Violet 3 and the like. Further, a coloring agent called a so-called processed pigment in which a resin is coated on the surface of the coloring agent can be used in the same manner. The dyes that can be used in the image forming ink of the present invention include water-insoluble oil-soluble dyes, disperse dyes, and water-soluble direct dyes, acid dyes, basic dyes, food dyes, and reactive dyes. It can be used in a form dispersed or dissolved in a solvent.

The water-insoluble dyes include, for example, diarylmethane, triarylmethane, thiazole,
Methine, azomethine, xanthine, oxazine, azo and azo derivatives, anthraquinone derivatives,
A quinophthalone derivative, a spirodipyran-based dye, an isodorinospiropyran-based dye, a fluoran-based dye, or a rhodamine lactam-based dye are preferably used. For example, C.I. I. Disperse Yellow 51, 3, 54, 7
9, 60, 23, 7, 141, C.I. I. Disperse Blue 24, 56, 14, 301, 334, 165, 1
9, 72, 87, 287, 154, 26, 359, C.I.
I. Disperse threads 135, 146, 59, 1, 7
3, 60, 167, C.I. I. Disperse Violet 4, 13, 26, 36, 56, 31, C.I. I. Solvent Violet 13, C.I. I. Solvent Black 3,
C. I. Solvent Green 3, C.I. I. Solvent Yellow 56, 14, 16, 29, 105, C.I. I. Solvent Blue 70, 35, 63, 36, 50, 49, 1
11, 105, 97, 11, C.I. I. Solvent Red 135, 81, 18, 25, 19, 23, 24, 14
3, 146, 182, and the like.

As the water-soluble dye, for example, the following dyes represented by a color index are used. C. I. Acid Yellow 17, 23, 42, 44, 79, 142,
C. I. Acid Red 1, 8, 13, 14, 18, 2
6, 27, 35, 37, 42, 52, 82, 87, 8
9, 92, 97, 106, 111, 114, 115, 1
34, 186, 249, 254, 289, C.I. I. Acid Blue 9, 29, 45, 92, 249, C.I. I. Acid Black 1, 2, 7, 24, 26, 94, C.I.
I. Food yellow 3, 4, C.I. I. Food red 7,
9, 14, C.I. I. Food black 2, C.I. I. Direct Yellow 1, 12, 24, 26, 33, 44, 5
0, 142, 144, 86, C.I. I. Direct Red 1, 4, 9, 13, 17, 20, 28, 31, 39, 8
0, 81, 83, 89, 225, 227, C.I. I. Direct Orange 26, 29, 62, 102, C.I. I. Direct Blue 1, 2, 6, 15, 22, 25, 71,
76, 79, 86, 87, 90, 98, 163, 16
5, 199, 202, C.I. I. Direct Black 1
9, 22, 32, 38, 51, 56, 71, 74, 7
5, 77, 154, 168, C.I. I. Basic Yellow 1, 2, 11, 13, 14, 15, 19, 21, 2
3, 24, 25, 28, 29, 32, 36, 40, 4
1, 45, 49, 51, 53, 63, 65, 67, 7
0, 73, 77, 87, 91, C.I. I. Basic Red 1, 2, 12, 13, 14, 15, 18, 22, 2
3, 24, 27, 29, 35, 36, 38, 39, 4
6, 49, 51, 52, 54, 59, 68, 69, 7
0, 73, 78, 82, 102, 14, 109, 11
2, C.I. I. Basic Blue 1, 3, 5, 7, 9, 2
1, 22, 26, 35, 41, 45, 47, 54, 6
2, 65, 66, 67, 69, 75, 77, 78, 8
9, 92, 93, 105, 117, 120, 122, 1
24, 129, 137, 141, 147, 155, C.I.
I. Basic Black 2,8. Among the above-mentioned water-soluble dyes, those having a large molecular weight and a high organic value are used as they are, but those other than the above are preferably used by lowering the solubility in the ink solvent by adjusting pH or the like.

The image forming ink of the present invention contains a heat stimuli-responsive polymer which is water-soluble at normal temperature and becomes water-insoluble by heating. It is practically preferable that the temperature at which the heat stimuli responsive polymer becomes insoluble in water is in the range of 30C to 100C. The heat stimuli-responsive polymer is hydrophilic at room temperature, but transitions to hydrophobic as the temperature rises from the transition temperature. In other words, it dissolves (swells) in water in a temperature range from low to normal. However, they precipitate (shrink) at high temperatures.

FIG. 1 is a simplified diagram showing a state in which the above-mentioned heat stimuli responsive polymer precipitates from a dissolved state in water. By applying heat energy to the image forming ink by an external means, the heat stimuli responsive polymer in the ink embraces and deposits the colorant, thereby fixing the image forming ink. Specific examples of the heat stimuli-responsive polymer include polyvinyl alcohol partial acetate, polyvinyl methyl ether (PVME), various acrylamide derivatives, polyethylene oxide, polyvinyl methyl oxazolidinone, methyl cellulose, and the like. Ethers and compounds containing a structural unit represented by the following general formula 1 as an essential component are preferably used.

[0019]

Embedded image

These heat stimuli-responsive polymers are structurally a kind of amphiphilic substance consisting of a hydrophilic part and a hydrophobic part, and the hydrophilic part and the hydrophobic part consist of only the main chain or the main chain and the side. Consists of chains. The phase transition temperature of the heat stimuli-responsive polymer is determined by the properties and proportions of the hydrophilic part and the hydrophobic part. In the case of poly N-substituted acrylamide, the transition temperature changes depending on the kind and number of the substituent. For example, the phase transition temperatures of poly (N-ethylacrylamide), poly (N, N-diethylacrylamide), and poly (Nn-propylacrylamide) are 72 ° C., 32 ° C., and 2 ° C., respectively.
The temperature becomes 2 ° C., and the phase transition temperature decreases as the chain length or the number of substituted alkyl groups increases. The phase transition temperature can also be changed by copolymerizing these heat stimuli responsive polymers with other hydrophilic or hydrophobic monomers. That is, the phase transition temperature increases by copolymerization with a hydrophilic monomer, and conversely, the phase transition temperature decreases by copolymerization with a hydrophobic monomer. The degree of change in the phase transition temperature is determined by the properties of the monomers to be copolymerized and the copolymerization ratio.

The phase transition temperature is changed by the coexistence of an appropriate additive other than the above polymer composition. For example, even when an alcohol alone dissolves the heat stimuli-responsive polymer well, the alcohol lowers the phase transition temperature by mixing with water. Therefore, when an additive is added to the image forming ink of the present invention for the purpose of dispersion or the like, it is necessary to design the ink composition in consideration of a change in the phase transition temperature due to the addition. The determination of the phase transition temperature is performed by a differential scanning calorimeter (DSC) or by measuring the change in the light transmittance of the solution while slowly raising (lowering) the temperature of the sample.

The image forming ink according to the present invention may comprise one or more kinds of colorants, especially organic pigments, oil-soluble dyes, and disperse dyes. A copolymer resin of a hydrophilic monomer and one or more kinds of hydrophobic monomers (hereinafter, granulated resin) can be used. The method of coating a pigment using a granulated resin is as follows:
It is as follows. Pigment dispersion step The granulated resin is dissolved in an organic solvent in which the granulated resin is soluble and compatible with water, and a pigment is further added. This liquid is treated for several hours with a bead mill, a ball mill, a high-speed disperser or the like to grind the pigment. Solvent replacement step The above dispersion is mixed with water. Dispersion is performed with an ultrasonic homogenizer or the like to prevent aggregation at the time of addition.

Organic Solvent Removal Step The organic solvent used for pigment dispersion is removed from the above dispersion using a rotary evaporator or the like. As the amount of the organic solvent decreases, the portion of the granulated resin caused by the hydrophobic monomer precipitates on the surface of the hydrophobic colorant and covers the colorant. At the same time, the site caused by the hydrophilic monomer of the granulated resin swells in water,
The coated colorant particles are dispersion-stabilized. Post-dispersion step Post-dispersion is performed with an ultrasonic homogenizer or the like to make the particle size uniform.

The granulated resin is obtained by copolymerization of one or more kinds of hydrophilic monomers and one or more kinds of hydrophobic monomers,
As a whole, those which are soluble in the organic solvent in the above step and insoluble or poorly soluble in water are preferred. As the hydrophilic monomer used, acrylic acid, methacrylic acid, maleic acid,
Examples include itaconic acid or salts thereof. In addition, vinyl alcohol, ethylene glycol, vinylpyrrolidone, acrylamide, methacrylamide, and a monomer having a salt of a cationic functional group such as a quaternary ammonium or an amino group may also be used. In addition, a constituent monomer of a heat stimuli-responsive polymer having a phase transition temperature equal to or higher than room temperature can be used in the same manner. In this case, since the granulated resin has heat stimulus responsiveness, it is not necessary to further include a heat stimulus responsive polymer in the ink.

The hydrophobic monomer is not particularly limited, but is preferably one which dissolves well in the organic solvent in the above step. A solubility parameter value (hereinafter referred to as SP value) is used as an index of solubility. Generally, the SP value is known to indicate the compatibility and incompatibility of substances, but taking the relationship between a resin and its solvent as an example, the SP value indicates the degree of solubility of the resin in the solvent. If the difference between the SP values is small, the solubility of the resin in the solvent is large, and if the difference is large, the solubility is small and the resin becomes insoluble. For example, when tetrahydrofuran is used as the organic solvent, preferred hydrophobic monomers are those in which the SP value of a homopolymer of the hydrophobic monomer is close to the SP value of tetrahydrofuran (9.1). Examples of such homopolymers include polyethyl methacrylate (9.1), polypropyl methacrylate (9.0),
Polyethyl acrylate (9.2), polymethyl methacrylate (9.3), polypropyl acrylate (9.
0), polystyrene (9.1), polyvinyl acetate (9.
4) and the like. Further, in the image forming ink of the present invention, in addition to the above-mentioned materials, a surfactant, a pH adjuster, an antifoaming agent, a preservative, and the like may be used as necessary.

(Image Recording Method) In the image forming method of the present invention, the above-described image forming ink is adhered on a recording medium in an image form. The recording medium is synthetic paper (polyolefin, polystyrene, etc.), high quality paper, art paper, coated paper, cast coated paper, wallpaper, backing paper, synthetic resin or emulsion impregnated paper, synthetic rubber latex impregnated paper, synthetic resin Attached paper, paperboard and the like, plastic films and the like, or fabrics such as polyester, cotton, silk and non-woven fabric can be mentioned.

The image forming ink is deposited on the recording medium in the form of an image by various printing methods such as gravure printing and flexographic printing. For example, the image forming ink is deposited on a pen to form images, characters, etc. Ink-jet method that prints by hand-drawing or ejecting and flying small droplets of ink from nozzles, a method of applying image-forming ink to a stamp or transfer roller, and transferring the image-forming ink to a recording medium under pressure Is mentioned. In particular, an inkjet recording method is preferable for clearly forming an image. further,
According to the image forming method of the present invention, the image forming ink is adhered on a recording medium in an image form, and thereafter, the thermal energy is applied to the image forming ink by an external unit. Here, examples of the external means for applying heat energy include sending hot air with a drier, irradiating an infrared lamp or a flash lamp, leaving in an oven, placing a recording medium on a hot plate, and the like. Can be

[0028]

Embodiments of the present invention will be described below. Example 1 Preparation of Pigment-Based Ink In order to stably disperse a hydrophobic pigment in water, a base ink in which the pigment was granulated with an appropriate resin was prepared. 2 parts of dimethylacrylamide-methyl methacrylate copolymer resin (dimethylacrylamide / methyl methacrylate (weight ratio) = 70/30) I. Pigment Blue 15: 4 2 parts (MONASTRAL BLUE FGX, manufactured by Zeneca Corporation) 40 parts of tetrahydrofuran

44 g of the above composition was placed in a mixing vessel together with 80 g of glass beads, and dispersed for 3 hours using a dispersing machine (RC-5000, manufactured by Red Devil Co.). Subsequently, an ultrasonic homogenizer (US-30 manufactured by Nippon Seiki Seisakusho Co., Ltd.)
0T), while adding 256 g of ion-exchanged water,
Tetrahydrofuran was removed by evaporation using a rotary evaporator. The dispersion treatment was again performed by an ultrasonic homogenizer to obtain a cyan base ink.

Preparation and Evaluation of Thermal Stimuli-Responsive Ink Next, a 50% aqueous solution of polyvinyl methyl ether was added at a ratio of 1 part to 10 parts of the obtained base ink and sufficiently stirred. 1 μl of the obtained ink was dropped on plain paper maintained at a constant temperature. The suitability for plain paper was evaluated from the dot diameter after drying and the drying time. The results are shown in Table 1.

Comparative Example 1 Base Ink 10 of Example 1
1 part of ion-exchanged water was added to 1 part, and the mixture was sufficiently stirred. The obtained ink was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[0032]

[Table 1]

Example 2 A heat stimuli-responsive ink having the following composition was prepared.・ C. I. Basic Blue 9 0.1 part ・ 50% aqueous solution of polyvinyl methyl ether 3 parts ・ Ion-exchanged water 26.9 parts 1 μl of the obtained ink was dropped on plain paper maintained at a constant temperature. The suitability for plain paper was evaluated from the dot diameter after drying and the drying time. The results are shown in Table 2. Since the drying speed is high and the dot diameter is not widened at the transition temperature of polyvinyl methyl ether (38 ° C.), the polyvinyl methyl ether precipitates while releasing water in response to heat and simultaneously embraces the dye, It is fixed.

Example 3 The dye in Example 2 was replaced with C.I.
I. A heat stimuli-responsive ink was prepared in the same manner as in Example 2 except that Basic Red 1 was used. Table 2 shows the results of evaluating the suitability for plain paper in the same manner as in Example 2. As in Example 2, the transition temperature of polyvinyl methyl ether (38
° C), the drying speed was faster. Further, it was confirmed that the hydrophobic interaction increased with an increase in the temperature, and that the dot diameter was reduced. At 80 ° C., it was observed that a skin layer was formed on the surface of the droplet due to strong hydrophobic interaction and water was trapped. Therefore, the drying speed is slightly reduced, but since the surface is dry, the next ink is not bleeding even if it is overlaid.

Example 4 A heat stimuli-responsive ink having the following composition was prepared.・ C. I. Basic Red 1 0.1 part Poly-N-isopropylacrylamide l. 5 parts / ion-exchanged water 28.4 parts The obtained heat stimuli-responsive ink was evaluated for suitability for plain paper in the same manner as in Example 3, and the results are shown in Table 2. Although the phase transition temperature of poly-N-isopropylacrylamide is 32 ° C., the dot diameter is smaller and the drying speed is slower than in Examples 2 and 3.
This is because the hydrophobic interaction is strong, and a skin layer is easily formed on the surface of the droplet at a relatively low temperature equal to or higher than the phase transition temperature.

[0036]

[Table 2]

Example 5 A heat stimulus responsive ink having the following composition was prepared.・ C. I. Basic Red 1 0.1 part Poly-N-isopropylacrylamide 0.2 part Ion-exchanged water 29.7 parts The obtained ink was subjected to a printing test on plain paper using an inkjet printer MJ-800C manufactured by Seiko Epson Corporation. In order to heat the landed ink above the phase transition temperature, plain paper was heated with a dryer during recording. The obtained image was good without bleeding and without wrinkles due to rapid drying.

[0038]

As described above, the present invention provides a solvent containing water as a main component, a coloring agent dispersed or dissolved in the solvent, and a heat stimulus which is water-soluble at normal temperature and becomes insoluble by heating. The image forming ink containing the responsive polymer in a dissolved state is attached to a recording medium in an image form, and / or by applying heat energy to the image forming ink by an external means, the The heat stimulus responsive polymer embraces and fixes the colorant. Therefore, in image formation using an ink for image formation using a solvent containing water as a main component, bleeding is prevented, a high-definition image is obtained, and the image portion of the ink does not rise after drying, and furthermore, High quality images can be obtained even on plain paper.

[Brief description of the drawings]

FIG. 1 is a simplified diagram illustrating a state in which a heat stimuli responsive polymer precipitates from a dissolved state in water.

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[Procedure amendment]

[Submission date] April 27, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

Patent application title: Image forming ink and image forming method using the same

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0001

[Correction method] Change

[Correction contents]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink for forming an image capable of obtaining a high-definition image without bleeding on a medium by applying a thermal stimulus, and an image forming method using the same.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0005

[Correction method] Change

[Correction contents]

Japanese Patent Application Laid-Open No. 5-148442 discloses a method in which polymer gel beads which swell and shrink according to the proton concentration are contained in an ink in a contracted state. It is stated that the gel beads in the ink swell due to the provision of protons from the recording member after landing, and as a result, quick drying of the entire ink is obtained. However, all of these methods increase the viscosity of the ink after landing, and have a problem that the drying time of the solvent is long because the solvent is confined, and the dots after drying are raised.
Accordingly, the present invention has been made in view of the above problems, and using an ink for image formation using a solvent containing water as a main component, bleeding is prevented, and a high-definition image is obtained. An object of the present invention is to provide an image forming ink in which a portion does not rise after drying and an image forming method using the same.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction contents]

(Image Forming Method) In the image forming method of the present invention, the above-described image forming ink is deposited on a recording medium in an image form. The recording medium is synthetic paper (polyolefin, polystyrene, etc.), high quality paper, art paper, coated paper, cast coated paper, wallpaper, backing paper, synthetic resin or emulsion impregnated paper, synthetic rubber latex impregnated paper, synthetic resin Attached paper, paperboard and the like, plastic films and the like, or fabrics such as polyester, cotton, silk and non-woven fabric can be mentioned.

Claims (10)

[Claims] 1. An image forming ink containing a solvent containing water as a main component and a colorant dispersed or dissolved in the solvent, has a high thermal stimulus response that is water-soluble at normal temperature and becomes water-insoluble when heated. An image forming ink comprising a molecule in a dissolved state. 2. The image forming ink according to claim 1, wherein the temperature at which the heat stimulus-responsive polymer becomes insoluble in water is in the range of 30 ° C. to 100 ° C. 3. The image forming ink according to claim 1, wherein the heat stimuli responsive polymer is polyvinyl methyl ether. 4. The heat-stimulated responsive polymer is represented by the following general formula 1.
The image forming ink according to claim 1, further comprising a structural unit represented by the following formula: Embedded image 5. The image forming ink according to claim 1, wherein the colorant is a pigment. 6. The image forming ink according to claim 1, wherein the colorant is a dye. 7. An image forming method, comprising applying the image forming ink according to claim 1 on a recording medium in an image form. 8. An image forming ink according to claim 1, wherein heat energy is applied to the image forming ink by an external means, so that the heat stimuli responsive polymer in the ink embraces and fixes the colorant. Image forming method. 9. The heat stimuli responsive polymer in the ink is colored by applying the image forming ink according to claim 1 on a recording medium in an image form and applying heat energy by an external means. An image forming method, wherein an agent is held and fixed. 10. The image forming method according to claim 7, wherein the means for adhering the image forming ink on the recording medium in an image form is an ink jet recording method.