JPH0649399A - Ink, ink jet recording method using the same, and apparatus wherein such ink is used - Google Patents

Abstract

PURPOSE:To obtain an ink improved in color development without detriment to the printing properties such as fixability and feathering, by blending an ink contg. a recording agent and a liq. medium with a specific compd. having reversible thermal gelation properties. CONSTITUTION:An ink contg. a recording agent and a liq. medium further comprises a compd. having reversible thermal gelation properties, a 2% aq. soln. of which shows a viscosity of 5 to 10,000cP as measured at 25 deg.C. Pref. examples of the compd. having such properties include water-soluble cellulose ethers such as hydroxypropyl cellulose and hydroxypropyl dimethyl cellulose, and polyvinyl acetal. An extremely high mol.wt. of the above-mentioned compd. is causative of clogging of a nozzle in ink jet recording, and not pref. from the viewpoint of the ejection properties of the resulting ink. On the other hand, an extremely low mol.wt. of the above-mentioned compd. prevents the resulting ink from satisfactorily exhibiting the function and effect thereof due to the gelation properties thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides high-speed, high-definition, high-quality full-color recording not only on coated paper but also on uncoated paper generally used in offices and households, so-called plain paper. And an ink jet recording method using the same and a device using the ink.

[0002]

2. Description of the Related Art In recent years, as an image forming method using an ink jet recording method, one of the technologies that is becoming more and more important is electrophotographic paper, note, report paper used in general offices and homes. , Non-coated paper such as stationery, bond paper, and continuous slip paper (hereinafter, in the present invention,
There is a strong demand for an image forming method capable of obtaining a high-definition full-color image with good color development and extremely little bleeding even for these papers (generally referred to as plain paper). Many proposals have been made.

For example, there have been many proposals relating to the improvement of ink mainly in the past. In JP-A-55-29546, a specific surfactant is added to the ink to reduce the surface tension of the ink, thereby reducing the paper surface tension. A method for increasing the permeability of the ink into the inside is disclosed, and in JP-A-55-57862, by adding a strongly basic substance to the ink, a paper sizing agent or a pulp material is chemically added at the time of applying the ink. A method for controlling the spread of dots and the ink absorbency by dissolving the ink in the ink is disclosed. Furthermore, in Japanese Patent Laid-Open No. 58-13675,
Addition of polyvinylpyrrolidone having a molecular weight of 40,000 or more to the ink, and Japanese Patent Laid-Open No. 172362/1993 discloses addition of a specific microemulsion to the ink to improve dot spread and ink absorbency. A method of controlling is disclosed.

As an example of using the solid-liquid phase change ink, US Pat. Nos. 3,653,932, 3,715,219, 4,390,369, and US Pat. Japanese Patent No. 4,490,731 and the like disclose an ink that is solid at room temperature but becomes liquid at a certain temperature or higher. This type of solid-liquid phase change ink is, after being ejected as a liquid, colliding with a recording material and immediately solidifying on the surface of the recording material.

Further, as an example of using a gel-sol transition ink, JP-A-62-181372, JP-A-1-
Japanese Patent No. 272623 discloses an ink which is in a gel state at room temperature but is transformed into a sol state by heating. This type of gel-sol transfer ink
Similar to the solid-liquid phase change ink, it is intended to return to a gel state after landing on a recording material to suppress ink bleeding.

[0006]

However, the above-mentioned prior art has the following problems.

That is, in the method of increasing the permeability of the ink into the paper by adding the surfactant to the ink, the fixability of the ink to the paper is improved, but a recording agent such as a dye in the ink is also added. Further, there is a problem that the color developability is deteriorated because it penetrates deeply into the paper. In the method of adding a strong base substance into the ink, neither ink bleeding nor fixability is sufficient for paper using a certain sizing agent, for example, neutral paper, and the safety of the ink to the human body is low. But there is a problem. Further, just adding a polymer or some kind of emulsion to the ink does not provide a sufficient effect in a region where the recording density of the ink is high, such as full-color recording. Also, with solid-liquid phase change ink, when the printed matter is exposed to extremely high temperatures during storage,
There is a problem that the ink is redissolved and the printed portion is destroyed. Further, the sol-gel transition ink also has a problem in the storability of the printed matter like the solid-liquid phase change ink.

As described above, various proposals have been made so far for improving the ink jet recording characteristics on plain paper, but the color development is still good for plain paper, and it seems that full color recording is performed. Even when two or more colors of ink are ejected onto the ink, bleeding and feathering do not occur,
Moreover, an ink having excellent fixability is not known.

Therefore, an object of the present invention is to provide a recorded image which has good coloring property even when recorded on plain paper, has excellent fixing property even when a plurality of colors of ink are ejected, and has very little ink bleeding. Ink that can be given and is excellent in storability of printed matter and that is excellent in reliability such as hardly causing clogging of nozzles of an inkjet recording head,
An object of the present invention is to provide an inkjet recording method using the ink and a device using the ink.

[0010]

The above object can be achieved by the present invention described below.

That is, according to the present invention, in an ink containing a recording material and a liquid medium, the viscosity of a 2% aqueous solution at 25 ° C. is 5%.
An ink containing a compound having a reversible thermal gelation property in the range of cP to 10,000 cP.

Further, the present invention provides an ink jet recording method for recording on a recording material by ejecting ink droplets containing a recording agent and a liquid medium from an orifice of a recording head according to a recording signal. , 2% at 25 ℃
The inkjet recording method is characterized by containing a compound having a reversible thermal gelation property in which the viscosity of the aqueous solution is in the range of 5 cP to 10000 cP.

Furthermore, the present invention provides an ink jet recording method for recording on a recording material by ejecting ink droplets containing a recording agent and a liquid medium from an orifice of a recording head according to a recording signal. , 2% at 25 ℃
It is characterized in that it contains a compound having a reversible thermal gelation property in which the viscosity of the aqueous solution is in the range of 5 cP to 10000 cP, and the applied amount of the ink to the recording material is 40 nl / mm ² or less. This is an inkjet recording method.

Furthermore, the present invention is an apparatus such as a recording unit, an ink cartridge, an ink jet recording apparatus, etc. on which the above ink is mounted.

[0015]

The compound having the reversible thermal gelation property described in the present invention is described, for example, in Polymer Review, Vol. 38,
No. 3, water-soluble cellulose ethers described on pages 133-137 (1981) can be used. The characteristics of these aqueous solutions of water-soluble cellulose ethers are that the temperature coefficient of the solubility of the water-soluble cellulose ethers is negative, so that the polymer microgel reversibly undergoes an aqueous phase transition as the temperature rises and falls. It is to repeat the separation from water and the dissolution in the aqueous phase. When the separation of this microgel from the aqueous phase occurs, the viscosity of the aqueous solution decreases discontinuously.

FIG. 7 is a schematic drawing of a typical viscosity-temperature curve obtained with the ink of the present invention. At a temperature T [H] higher than the gelation temperature (T [G]), which is the temperature at which the gel aggregates and separates from the aqueous phase due to the action of the compound having reversible thermal gelation property contained in the ink. The ink viscosity is lower than the viscosity near room temperature (T [R]). When ink jet recording is performed using the ink of the present invention, it is preferable to set the temperature of the recording head to T [H] in FIG. After the ink has landed on the recording material, it thickens and returns to its original viscosity, so that the recording agent does not unnecessarily penetrate deep into the recording material, and the recording agent remains on the surface of the recording material and color develops. The property becomes good. Further, regarding the lateral spread of the ink, the ink bleeding is suppressed due to the thickening effect.

(Preferred Embodiment) The present invention will be described in more detail with reference to preferred embodiments.

Examples of the compound having the reversible thermogelling property according to the present invention include hydroxypropyl cellulose.
Water-soluble cellulose ethers such as cellulose, hydroxypropyl dimethyl cellulose and polyvinyl acetal are preferred for use. Furthermore, in the ink of the present invention, among these compounds, it is necessary that the compound has a molecular weight in the range of 5 cP to 10000 cP when converted into the viscosity of a 2% aqueous solution at 25 ° C. Since the present invention utilizes the gelling property of the ink by containing the above compound, when the molecular weight of the above compound is extremely large, it is possible to precisely control the particle size of the gelled and agglomerated particles. It becomes difficult, and in inkjet recording,
This is a cause of nozzle clogging and is not preferable in terms of ink ejection characteristics. On the other hand, when the molecular weight is extremely small, the action and effect due to the gelling property of the ink cannot be sufficiently exhibited.

The compounds having the above-mentioned reversible thermal gelation properties can be used alone or as a mixture. The content of this compound in the ink varies depending on the kind of the dye or pigment used, the solvent, the additive, etc., but is 0.01 to 20% by weight, preferably 0% by weight in the ink. 0.05 to 10% by weight, more preferably 0.1 to 5% by weight. Setting the content of the compound having the reversible thermal gelation property to 20% by weight or less makes it possible to prevent nozzle clogging and improve recording characteristics such as ink ejection characteristics, especially in certain recording methods in inkjet recording. It is preferable in terms of the reliability of the head, and is 0.
It is preferable that the amount is 01% by weight or more in order to sufficiently exert the effect of the gelling property (viscosity change property).

The ink of the present invention is characterized by containing a compound having a reversible thermal gelation property as described above together with a recording agent, and other components include water and an organic solvent, and further, , Various dispersants, surfactants,
You may contain additives, such as a viscosity adjusting agent, a surface tension adjusting agent, a fluorescent color increasing agent, an antioxidant, a fungicide, and a pH adjusting agent.

The recording agent used in the ink of the present invention includes direct dyes, acid dyes, food dyes, reactive dyes, disperse dyes, vat dyes, soluble vat dyes, reactive disperse dyes, oil dyes, Examples include pigments and the like. The content of these recording agents in the ink is determined depending on the type of liquid medium components, the properties required for the ink, etc., but in the present invention, it is 0.2 to 20 relative to the total weight of the ink. %, Preferably 0.5 to 10% by weight, more preferably 1 to 5% by weight.

Examples of the organic solvent used in the ink of the present invention include methyl alcohol, ethyl alcohol,
n-propyl alcohol, isopropyl alcohol, n
-Butyl alcohol, sec-butyl alcohol, te
rt-butyl alcohol, isobutyl alcohol, n-
Alcohols such as pentanole and cyclohexanol;
Amides such as dimethylformamide and dimethylacetamide; ketones or keto alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol Oxyethylene or oxypropylene addition polymers such as ethylene glycol, propylene glycol, trimethylene glycol, etc.
, Alkylene glycols such as butylene glycol, 1,2,6-hexanetriol and hexylene glycol; thiodiglycol, glycerin; ethylene glycol monomethyl (or ethyl) ether, diethylene glycol monomethyl (or ethyl) ether, triethylene glycol monomethyl Lower alkyl ethers of polyhydric alcohols such as (or ethyl) ether; sulfolane,
N-methyl-2-pyrrolidone, 1,3-dimethyl-2-
Examples thereof include imidazolidinone. In the present invention, the content of the organic solvent is 1 to the total weight of the ink.
It is in the range of 50% by weight, preferably 2 to 30% by weight.

Although the above-mentioned organic solvents can be used alone or as a mixture, a preferable liquid medium composition is a mixture of water and one or more of the above organic solvents, more preferably, the organic solvent is, for example, diethylene glycol- , Triethylene glycol, a mixture with at least one water-soluble high-boiling solvent such as polyhydric alcohol such as glycerin,
Particularly preferably, the organic solvent is a mixture of the water-soluble high-boiling point solvent and monovalent alcohol.

In particular, the inclusion of the water-soluble high-boiling point solvent is preferable from the viewpoint of reliability of the recording head such as prevention of nozzle clogging and improvement of ink ejection characteristics in a certain recording method in ink jet recording.

Further, in the present invention, various salts may be added to the ink in order to adjust the gel point of the compound having the reversible thermal gelation property.

The ink of the present invention can be suitably used in general general ink jet recording systems, but in particular, it is particularly applicable to an ink jet recording method of the type in which the ink is ejected by the bubbling phenomenon of the ink due to the application of heat energy. It is suitable.

When ink jet recording is carried out using the above ink of the present invention, it is necessary to adjust the physical properties of the ink during non-operation and during operation (during ejection). In this case, the main purpose of the present invention is It is preferable to consider the matching (ejection characteristics, reliability, etc.) with the inkjet recording head to be used together with the printability for plain paper.

With respect to the above points, the preferable physical properties of the ink at the time of non-operation are a viscosity at 25 ° C. of 5 to 500 cP, preferably 10 to 100 cP, and particularly preferably 15 to 1 cP.
It is desirable to adjust to the range of 00cP, and 2
The surface tension at 5 ° C. is preferably adjusted in the range of 25 to 68 dyn / cm. The above-mentioned physical properties of the ink are in a preferable range in order to further improve the action and effect due to the gelling property of the ink and further improve the reliability of the recording head such as the ejection property of the ink and the prevention of clogging.

In addition, the preferable physical properties of the ink during operation are a viscosity of 0.5 to 5 cps, more preferably 0.5 to 3 cp.
s, the surface tension is preferably in the range of 25 to 68 dyn / cm, and in order to obtain such ink physical properties, the setting of the temperature during operation (the temperature indicated by T [H] in FIG. 7) is recorded. It is preferable to raise the temperature by 2 ° C. to 40 ° C. higher than the gelation point (the temperature indicated by T [G] in FIG. 7) by heating the head, and the operating temperature T [H] is 30 ° C.
It is desirable to adjust the temperature within the range of 80 ° C, more preferably 35 ° C to 60 ° C. The temperature of the gel point can be adjusted by the type, the molecular weight and the addition amount of the polymer having the reversible thermal gelation property to be used, and the solvent and the solvent amount to be used or the addition of an appropriate inorganic salt. Can also be adjusted by.

Of the above-mentioned physical properties of the ink, the viscosity of the ink at 25 ° C. (A)
And ink viscosity (B) at operating (recording) temperature
It is a particularly preferable embodiment that the ratio A / B is set to 5 or more in order to sufficiently exert the action and effect based on the gelling property of the ink of the present invention.

Furthermore, when ink jet recording is performed using the ink of the present invention, after ink droplets land on the recording material,
Alternatively, it is preferable to instantly reversibly change to a high-viscosity state upon landing, especially from the viewpoint of improving color development and printing quality (fixability, bleeding, etc.) of plain paper.
As described above, the content of the compound having the reversible thermal gelation property, the combined use of polyvalent alcohol as the liquid medium of the ink, the adjustment of the ink physical properties (viscosity, surface tension), etc. The action and effect can be further improved by changing the viscosity of the ink. In addition to these, the action and effect can be further improved by suppressing the amount of ink applied to a certain amount or less. That is, it is particularly preferable that the amount of the ink applied to the recording material is 40 nl / mm ² or less.

As a method and an apparatus particularly suitable for recording using the ink of the present invention, thermal energy corresponding to a recording signal is applied to the ink in the chamber of the recording head, and the thermal energy causes a droplet to be generated. Methods and apparatus.

An example of the head structure, which is the main part of the apparatus, is shown in FIGS. 1, 2 and 3. The head 13 is made by adhering a glass, ceramics or plastic plate having a groove 14 through which ink passes, and a heating head 15 (a head is shown in the figure, but not limited to this) used for thermal recording. Obtained. The heating head 15 includes a protective film 16 made of silicon oxide and an aluminum electrode 17.
-1, 17-2, a heat generating resistor layer 18 formed of nichrome or the like, a heat storage layer 19, and a substrate 20 having good heat dissipation such as alumina.
Has become

The ink 21 is a discharge orifice (fine hole) 2
2, the meniscus 23 is formed by the pressure P.

Now, when an electric signal is applied to the electrodes 17-1 and 17-2, the area indicated by n of the heating head 15 rapidly generates heat, and bubbles are generated in the ink 21 in contact therewith, and the pressure thereof is generated. Then, the meniscus 23 protrudes, the ink 21 is ejected, and becomes a recording droplet 24 from the orifice 22 and flies toward the recording material 25. FIG. 3 shows an external view of a multi-head in which many heads shown in FIG. 1 are arranged. The multi-head is manufactured by closely contacting a glass plate 27 having a multi-groove 26 and a heating head 28 similar to that described in FIG. 1 shows the head 13 along the ink flow path.
2 is a sectional view taken along line AB in FIG. 1.

In order to keep the ink of the present invention at its operating temperature (head temperature control temperature during recording), the substrate 20 is heated by a heating means (not shown) to adjust the entire head to a constant temperature. It may be carried out by such a method. In this way, the viscosity of the ink of the present invention held at the operating temperature becomes lower than that in the non-operating state by the action of the compound having the reversible thermal gelation property, and the ejection property of the head is sufficiently improved.

FIG. 4 shows an example of an ink jet recording apparatus incorporating the above head.

In FIG. 4, reference numeral 61 denotes a blade as a wiping member, one end of which is held by a blade holding member to become a fixed end, which is in the form of a cantilever. The blade 61 is arranged at a position adjacent to the recording area of the recording head, and in the case of this example, is held in a protruding form in the moving path of the recording head. Reference numeral 62 denotes a cap, which is disposed at a home position adjacent to the blade 61, and has a configuration in which it moves in a direction perpendicular to the moving direction of the recording head and contacts the ejection port surface to perform capping. Further, 63 is an absorber provided adjacent to the blade 61, and like the blade 61, it is held in a protruding form in the moving path of the recording head. The blade 61, the cap 62, and the absorber 63 constitute a discharge recovery section 64,
The blade 61 and the absorber 63 remove water, dust and the like from the ink ejection port surface.

Reference numeral 65 denotes a recording head which has an ejection energy generating means and ejects ink to a recording material facing the ejection port surface where the ejection ports are arranged for recording, and 66 denotes a recording head in which the recording head 65 is mounted. A carriage for moving 65. The carriage 66 is slidably engaged with the guide shaft 67, and a part of the carriage 66 is connected (not shown) to a belt 69 driven by a motor 68. As a result, the carriage 66 can move along the guide shaft 67, and the recording head 65 can move the recording area and its adjacent area.

Reference numeral 51 denotes a paper feeding section for inserting a recording material, and 5
A paper feed roller 2 is driven by a motor (not shown). With these configurations, the recording material is fed to a position facing the ejection port surface of the recording head, and is ejected to a paper ejection unit provided with a paper ejection roller 53 as the recording progresses.

In the above structure, when the recording head 65 returns to the home position after recording is completed, the cap 62 of the head recovery section 64 is retracted from the movement path of the recording head 65, but the blade 61 projects into the movement path. There is. As a result, the ejection port surface of the recording head 65 is wiped. When the cap 62 comes into contact with the ejection surface of the recording head 65 to perform capping, the cap 62 moves so as to project into the movement path of the recording head.

When the recording head 65 moves from the home position to the recording start position, the cap 62 and the blade 61 are in the same position as the above-mentioned position during wiping. As a result, the ejection opening surface of the recording head 65 is wiped even during this movement.

The above-described movement of the recording head to the home position is performed not only at the end of recording and at the time of ejection recovery, but also at the home adjacent to the recording area at a predetermined interval while the recording head moves in the recording area for recording. The wiper is moved to the position, and the wiping is performed along with the move.

FIG. 5 is a diagram showing an example of an ink cartridge in which the ink is supplied to the head through an ink supply member, for example, a tube. Here, 40 is an ink containing portion containing the ink for supply, for example, an ink bag, and a rubber stopper 42 is provided at the tip thereof. By inserting a needle (not shown) into this stopper 42,
The ink in the ink bag 40 can be supplied to the head. Reference numeral 44 is an absorber that receives waste ink. It is preferable for the present invention that the ink containing portion has a liquid contact surface with ink formed of polyolefin, particularly polyethylene. The ink jet recording apparatus used in the present invention is not limited to the one in which the head and the ink cartridge are separate from each other as described above, and is preferably used in the one in which they are integrated as shown in FIG.

In FIG. 6, reference numeral 70 denotes a recording unit in which an ink containing portion for containing ink, for example, an ink absorber is contained, and the ink in the ink absorber has a plurality of orifices. Head portion 71
It is configured to be ejected as an ink droplet from. It is preferable for the present invention to use polyurethane, cellulose or polyvinyl acetal as the material of the ink absorber. Reference numeral 72 denotes an atmosphere communication port for communicating the inside of the recording unit with the atmosphere. This recording unit 70 is shown in FIG.
The recording head is used instead of the recording head shown in FIG.

[0046]

EXAMPLES Next, the present invention will be specifically described with reference to Examples and Comparative Examples.

(Examples 1 to 7 and Comparative Examples 1 to 5) The water-soluble cellulose ethers shown in Table 1 were prepared as compounds having reversible thermal gelation properties. Table 2, viscosity at 20 ° C. for a 2% water-soluble respective compound (η), - 0CH ₃ group substitution degree (a), - by OC ₃ H ₅ OH group substitution degree (b) and the thermal gelation The aqueous solution viscosity lowering temperature (T [G]) is also described.

[0048]

[Table 1]

[0049]

[Table 2]

Examples 1 to 7 were prepared by mixing the components shown in Table 3.
Created ink. The ink is prepared by preparing an aqueous solution of water-soluble cellulose ether having a concentration of 20% by weight, and adding predetermined amounts of water, various organic solvents, dyes, and surfactants in that order to the predetermined water-soluble cellulose. -Adjusting the concentration of the ether, stirring for 5 hours, and then pressurizing and filtering with a membrane filter having a pore size of 0.22 µm to obtain four color inks of black, yellow, magenta, and cyan for each example. It was The numbers in the table represent the weight percentage of each component in the ink.

The compositions of the black inks of Examples 1 to 7 are shown in Table 3 below.

[0052]

[Table 3]

The yellow inks of Examples 1 to 7 were mixed with C.I.
I. Hood Black 2, in place of 3.0% by weight, C.I.
I. The composition was the same as in Table 3 except that the amount of Direct Yellow 86 was 2% by weight.

The magenta inks of Examples 1 to 7 were mixed with C.I.
I. Hood Black 2, in place of 3.0% by weight, C.I.
I. The composition was the same as in Table 3 except that Acid Red 35 was 2.5% by weight.

The cyan inks of Examples 1 to 7 were mixed with C.I. I.
Hood Black 2, in place of 3.0% by weight, C.I. I. The composition was the same as in Table 3 except that Direct Bull-199 was 3.0% by weight.

Further, as a comparative ink, a water-soluble cellulose cloth was prepared from each of the above-mentioned inks of Examples 1 to 5.
Tells (Compounds A to E in Table 1) were removed, and the ink was replaced with water to prepare inks, which were set as Comparative Examples 1 to 5, respectively.

[0057] Table 4 below, it was described and the viscosity eta ₂ at the operating temperature T [H] to the viscosity eta ₁ of the ink at 25 ° C. of each ink.

[0058]

[Table 4]

(Example 8 and Comparative Example 6) Recording density is 40
Four inkjet recording heads (for black ink, yellow ink, magenta ink, of a type having 256 nozzles at 0 DPI (dots / inch) and forming ink droplets by the action of thermal energy on the ink,
4 pieces for cyan ink) 1 in the main scanning direction of the head
A recording head for each color of the recording apparatus is used, which includes an ink jet recording apparatus provided with a heater that is arranged in a row and heats and holds the ink filled in each recording head at a predetermined temperature (T [H]; operating temperature). Is filled with the ink prepared in Examples 1 to 7 and Comparative Examples 1 to 5 through an ink supply system tube, and each recording head is heated to an operating temperature corresponding to the filled ink, and then commercially available. Inkjet recording was performed on electrophotographic paper. The amount of ink applied to the full-solid printing portion for each color is 10 nl / mm ² .

Coloring property, fixing property, and
The ink bleeding was evaluated by the following methods.

1. Fixability Evaluation Full solid printing (cyan ink and magenta ink with 100% duty solid printing) on commercially available electrophotographic paper, and after 10 seconds, 20 seconds, and 30 seconds, the printing part was printed with filter paper. Name: No. 5C, manufactured by Toyo Roshi Kaisha, Ltd., and rubbed and evaluated as follows. O: Almost no rubbing after 10 seconds. Δ: Almost no rubbing after 20 seconds. X: Rub after 30 seconds. Evaluation of color development 100% of each color The reflection density (D
D) was measured using a Macbeth RD-918 reflection densitometer and evaluated as the color developability. 3. Bleed of printing Character printing was performed with black ink, and then 100% yellow ink solid printing was performed, and the printing quality of the character was evaluated and ranked as follows.
○: Almost no bleeding △: Bleeding occurs and the outline of the character is slightly broken ×: Severe bleeding and the character is completely unreadable

Table 5 shows the evaluation results of the above three items.

[0063]

[Table 5]

As is clear from the results shown in Table 5 above, according to the ink and the ink jet recording method of the present invention, a recorded image having good printability on plain paper can be obtained as compared with the conventional ink. In particular, as compared with the conventional ink, the color developability can be further improved without deteriorating the printability such as the fixing property and the bleeding.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a head portion of an inkjet recording apparatus.

FIG. 2 is a cross-sectional view of a head portion of an inkjet recording device.

3 is an external perspective view of a head in which the head shown in FIG.

FIG. 4 is a perspective view showing an example of an inkjet recording apparatus.

FIG. 5 is a vertical sectional view of an ink cartridge.

FIG. 6 is a perspective view of a recording unit.

FIG. 7 is a schematic diagram of a temperature-viscosity curve of the ink of the present invention.

[Explanation of symbols]

 61 Wiping Member 62 Cap 63 Ink Absorber 64 Ejection Recovery Section 65 Recording Head 66 Carriage

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical display location B41J 2/05 B41M 5/00 E 9221-2H C09D 11/02 PTG 7415-4J 9012-2C B41J 3 / 04 103 B

Claims (27)

[Claims] 1. An ink containing a recording material and a liquid medium, wherein the viscosity of a 2% aqueous solution at 25 ° C. is 5 cP-100.
An ink comprising a compound having reversible thermogelation properties in the range of 00 cP. 2. The ink according to claim 1, wherein the content of the compound having the reversible thermal gelation property in the ink is in the range of 0.01 to 20% by weight. 3. The ink according to claim 1, which contains polyvalent alcohol as the liquid medium. 4. The ink according to claim 3, wherein the content of the polyvalent alcohol in the ink is in the range of 5 to 20% by weight. 5. The ink according to claim 1, wherein the compound having a reversible thermal gelation property is a water-soluble cellulose ether. 6. An ink jet recording method for recording on a recording material by ejecting ink droplets containing a recording agent and a liquid medium from an orifice of a recording head according to a recording signal, wherein the ink is at 25 ° C. An ink jet recording method, comprising a compound having a reversible thermogelation property in which a 2% aqueous solution has a viscosity in the range of 5 cP to 10000 cP. 7. The ink jet recording method according to claim 6, wherein the recording head is heated at the time of recording to raise the temperature of the ink. 8. The ink jet recording method according to claim 6, wherein the temperature of the recording head during recording is set to be equal to or higher than the thermal gelation temperature of the ink. 9. The ink jet recording method according to claim 6, wherein the ratio A / B of the viscosity A of the ink at 25 ° C. and the viscosity B of the ink at the temperature of the recording head during recording is 5 or more. 10. The temperature of the recording head during recording is 30.degree.
The ink jet recording method according to claim 6, wherein the ink jet recording method is performed within a range of 80 ° C. 11. The ink jet recording method according to claim 6, wherein the recording material is uncoated paper. 12. The ink jet recording method according to claim 6, wherein the ink droplets are formed by applying thermal energy to the ink. 13. An inkjet recording method for recording on a recording material by ejecting ink droplets containing a recording agent and a liquid medium from an orifice of a recording head in response to a recording signal, wherein the ink is at 25 ° C. A 2% aqueous solution containing a compound having a reversible thermal gelation property in the range of 5 cP to 10000 cP, and the amount of the ink applied to the recording material is 40 nl / mm ² or less. And an inkjet recording method. 14. The ink jet recording method according to claim 13, wherein the recording head is heated at the time of recording to raise the temperature of the ink. 15. The ink jet recording method according to claim 13, wherein the temperature of the recording head during recording is set to be equal to or higher than the thermal gelation temperature of the compound having the reversible thermal gelation property. 16. The temperature of the recording head during recording is set to be equal to or higher than the thermal gelation temperature of the ink.
The inkjet recording method described in 1. 17. The ink jet recording method according to claim 13, wherein a ratio A / B of the viscosity A of the ink at 25 ° C. and the viscosity B of the ink at the temperature of the recording head during recording is 5 or more. 18. The temperature of the recording head during recording is 30.degree.
The ink jet recording method according to claim 13, wherein the ink jet recording method is performed by setting the temperature in the range of 80 ° C. 19. The ink jet recording method according to claim 13, wherein the recording material is uncoated paper. 20. The ink jet recording method according to claim 13, wherein the ink droplets are formed by applying thermal energy to the ink. 21. An ink according to any one of claims 1 to 5, wherein in a recording unit including an ink containing portion containing ink and a head portion for ejecting the ink as ink droplets. Recording unit characterized by. 22. The head portion includes a head for ejecting ink droplets by applying thermal energy to the ink.
The recording unit according to 1. 23. An ink cartridge comprising an ink containing portion containing ink, wherein the ink is
<5> An ink cartridge comprising the ink according to any one of <5> to <5>. 24. An ink jet recording apparatus comprising a recording unit having an ink containing section containing ink and a head section for ejecting the ink as ink droplets, wherein the ink is any one of claims 1 to 5. An ink jet recording apparatus, which is the ink described above. 25. The head section includes a head for ejecting ink droplets by applying thermal energy to the ink.
4. The inkjet recording device according to item 4. 26. A recording head for ejecting ink droplets,
An ink according to any one of claims 1 to 5, wherein the ink is an ink cartridge having an ink containing portion containing the ink and an ink supplying portion for supplying the ink from the ink cartridge to a recording head. An inkjet recording apparatus characterized by the following. 27. The ink jet recording apparatus according to claim 26, wherein the recording head is a head which applies thermal energy to ink to eject ink droplets.