JP3524273B2 - Inkjet recording method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus in which an ink is ejected and ejected as small droplets from an ejection port (orifice), and the small droplets adhere to a recording material to perform recording. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving a head and an inkjet recording method using this method, and more particularly to a method for driving an inkjet recording head that eliminates bleeding (feathering) and color bleeding between different colors (bleeding) and realizes high color development. And an inkjet recording method.

[0002]

2. Description of the Related Art Conventionally, as inks for ink jet recording, water-based inks have been mainly used in terms of safety and odor, and various water-soluble dyes or pigments are mixed with water, or water and a water-soluble organic solvent. Dissolved or dispersed in a liquid medium consisting of
Further, an ink containing a moisturizing agent, a dye dissolution aid, a fungicide, etc., if necessary, is known.

In addition, ink jet recording is capable of ejecting several thousand drops or more of ink per second, and high-speed recording is easy, noise is small, colorization is easy, and resolution is high. It has many advantages such as being possible and being able to record on plain paper, and has been remarkably popular for several years.

Further, due to the recent price reduction, high performance, and standardization of the GUI environment of personal computers, the demand for high color development, high quality, high robustness, high resolution recording, and high speed recording is also increasing in image recording of printers and the like. A technical idea is being proposed in which the coloring material component is left as much as possible on the surface of the paper to make the edges of the recording dots clear and to reduce feathering and bleeding.

The following various methods are known as means for suppressing feathering and bleeding that have been conventionally known. First, as a first example, Japanese Patent Laid-Open No. 58-13675.
Japanese Patent Laid-Open No. 3-172362 discloses a method of adding polyvinylpyrrolidone to an ink to control the absorption and spread of recording dots on a paper. Is added to the ink to control ink absorption and dot spread.

Further, as a third example in which the sol-gel transition phenomenon is applied to an ink, JP-A-62-181372, JP-A-1-272623, etc., give a gel at room temperature and become a sol state by heating. It is stated that the recording is performed on the recording material in the sol state and returns to the gel state by cooling the ink, so that the permeation of the ink into the paper can be suppressed.

Also, as a recent fourth example, Japanese Patent Laid-Open No. 6-4
Japanese Patent No. 9399 discloses an ink in which a compound having a reversible thermal gelation property is added to an ink, which has good color developability, fixability, little bleeding, and excellent storage stability and reliability of printed matter. Ink jet recording methods and devices using ink are disclosed. This technical background is based on the phenomenon that when an aqueous solution of a specific water-soluble polymer is heated, the water solubility decreases and the solution becomes cloudy (this temperature is called a cloud point). Representative water-soluble polymers include, for example, N-isopropylacrylamide, polyvinyl methyl ether, polyethylene oxide, hydroxypropyl cellulose and the like. Since the solubility of these polymers has a negative temperature coefficient, they become separated and precipitated from the solution at a temperature above the cloud point. In the deposited state, a hydrophobic microgel is generated and the viscosity of the solution is reduced.
When recording is performed on the recording material in the deposited state, the original viscosity is restored due to the temperature drop on the surface of the recording material; that is, it is possible to suppress the permeation into the recording material by increasing the viscosity of the ink. is there.

On the other hand, as a fifth example, M. Croucher et al.
In addition to pointing out the problems with conventional homogeneous inks, we have proposed a heterogeneous ink that uses latex as a future inkjet ink (MDCroucher and
MLHair; Ind.Eng.Chem.Res.1989,28,1712-1718 "Desig
n Criteria and Future Directions in Inkjet InkTech
nology ").

On the other hand, US Pat. No. 4,246,154 discloses (1) an ink in which fine particles of a vinyl polymer colored with a dye are anionically stabilized.
Further, in US Pat. No. 4,680,332, (2)
A heterogeneous ink is disclosed in which a water-insoluble polymer containing an oil-soluble dye and having a nonionic stabilizer bound thereto is dispersed in a liquid medium. Further, US Pat. No. 5,100,471 proposes a water-based ink comprising (3) a solvent and colored particles consisting of a silica core in which a polymer core and a dye are covalently bonded, and a clearer color on paper. It is characterized in that it is formed, is stable to temperature, and has high water resistance.

On the other hand, as a sixth example, Japanese Patent Laid-Open No. 3-240586 proposes a non-aqueous ink in which colored particles coated with a resin that swells in a dispersion medium are dispersed in kerosene or the like. . This proposal states that it is particularly effective in preventing image bleeding and preventing clogging of droplet discharge nozzles.

[0011]

In the first and second examples of the conventional example described above, since the permeation into the paper is suppressed, the ink remains for a long time without permeating on the paper and there is a problem in fixing property. There is. There is also a problem that bleeding occurs. In the third example, the sol-gel transition ink may have fluidity due to changes in the storage temperature of the printed matter, and there is a problem of color mixing stains and transfer stains due to image runoff.

The fourth example is that the ink containing a reversible thermogelling compound uses water-soluble cellulose ethers,
Since the increase in viscosity due to the temperature drop is slow, it is not suitable for a method of recording one pixel at a high speed within several tens of msec, such as ink jet recording. When used for inkjet recording, the upper limit of viscosity when ejecting ink is 20 mPa · sec.
It must be used with a low viscosity as follows, and it is difficult to obtain a sufficient thickening effect.

On the other hand, of the fifth example, (1) the anionically stabilized ink has a problem that the pH range for stable dispersion is narrow and the selection range of the dye is small. In addition, there is a drawback that the spread of recording dots on the paper is small and it is difficult to obtain the required optical density (OD value). Further, in terms of shortening the fixing time required for high-speed recording, since the fixing depends only on evaporation and permeation as in the conventional image forming means, a sufficient effect cannot be obtained.

(2) In the ink containing the oil-soluble dye and dispersed in the water-insoluble polymer to which the nonionic stabilizer is bound, although the selection range of the dye is expanded, it depends on the evaporation and the penetration as in the above. Since it is a fixing mechanism, it is not possible to obtain a sufficient effect in shortening the fixing time. Further, bleeding is also disadvantageous because it takes time to fix between adjacent dots.

Further, (3) the dispersion ink having the polymer core / silica shell structure is excellent in the dispersion stability of the pigment, but it does not have a special means for aggregating the coloring material on the paper surface, so that There is a problem that the concentration is not sufficient.
Further, since the image fixing means depends only on evaporation and permeation, there is a problem that a sufficient effect for shortening the fixing time cannot be obtained and bleeding occurs. Incidentally, a problem common to the above three examples is that since the adherence of the color material particles to the paper surface is not taken into consideration, the scratchability of the recorded image is poor.

Further, in the sixth example, since kerosene is used as the dispersion medium, there are problems with odor and safety.

Here, the transfer of ink to paper will be considered. In general, regarding the transfer phenomenon of liquid to paper, Lucas-
Washburn's equation is known. When the liquid transfer amount is V, the paper roughness index is V _r , the absorption coefficient is K _a , the transfer time is T, and the wetting start time is T _w , the liquid is water. , The following formula (2)
Can be expressed as

[0018] [In the formula (2), K _a relates to the physical properties of both paper and ink and is represented by the following formula (3).

[0019] [In the formula (3), r is the capillary radius, γ is the surface tension of the liquid, θ is the contact angle, and η is the viscosity of the liquid. ]]

[0020] From equation (2), to leave a coloring material to the surface of the paper can only slow down the penetration of liquid; that it is necessary to reduce the K _a (evaporation by reducing the K _a You can save time.). The physical properties of the ink for that are:
It is understood that the surface tension should be small, the viscosity should be large, and the contact angle should be large. However, since there are restrictions on the physical properties of ink for inkjet recording, adjustment of K _a is not easy.

On the other hand, when the liquid is a non-aqueous solvent such as ethanol, the wetting time T _w in the formula (2) can be neglected, so that the fixing can be speeded up, but K _a also becomes large and the penetration becomes large. Since the effect is large, the amount of "feathering" increases in the image. Furthermore, in equation (3), cos θ
Since the item (1) is determined by the combination of ink and paper, it may be good or bad depending on the type of paper. That is, the non-selectivity of the paper cannot be satisfied. It is considered that the problems described above can occur even with the conventional color material-dispersed ink as long as the fixing unit for the recorded image depends only on the permeation and the evaporation.

Accordingly, the object of the present invention is to solve the problems of feathering and bleeding while achieving high optical density while the ink fixing means for fixing ink on paper in image formation does not depend only on evaporation and permeation. Another object of the present invention is to provide a driving method of the above and an inkjet recording method using this method.

[0023]

The above object can be achieved by the present invention described below. That is, the present invention is to heat the heating elements of the recording head in accordance with the recording signal, ink is heated foam in contact with the element by ejecting ink from above SL head, inkjet performing recording with a ink the recording method, the upper Symbol ink, water at transition temperature
Thermoreversible thickening polymer compound and color material that phase separate from solution
The thermoreversible thickening polymer having a nitrogen-containing ring is a liquid medium containing a
Alkylene oxide adducts of active hydrogen compounds with vinyl
50% by weight with a structural carboxylic acid ester as a constitutional unit
A vinyl polymer containing at least, an ink jet recording, wherein the average heat flux from the upper Symbol surface of the heating element to the ink (q _O) drives said head so as to satisfy the following relation (1) Is the way. [Where κ is thermal conductivity, S is the effective area of the heating element,
V is the volume of ink ejected in one drive, T _B is the temperature of the ink that causes bubbles, T _O is the temperature of the ink before ejection,
T _P is a transition temperature of the ink that causes a rapid change in viscosity of the ink, and α is a correction constant: 1.5. ]

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have the following restrictions.
Assuming that the ink is a liquid in which the coloring material and the solvent are in a uniform state regardless of the temperature, a change in the state is triggered by the temperature, and the coloring material and the solvent separate and behave on the recording material. We have proposed a method of efficiently flying the ink by using the ink.

The explanation of the improvement of the performance of the recorded image according to the present invention will be made mainly on the state change of the thermoreversible thickening polymer material in the ink. Here, the thermoreversible thickening polymer means a polymer material that undergoes phase separation from an aqueous solution in a reversible manner at a transition temperature or higher. The state change of the thermoreversible thickening polymer means that the polymer, which is dissolved and dissociated in the ink at room temperature, becomes associated with each other at a certain temperature (transition temperature) or more, resulting in a rich high viscosity. It becomes a liquid and forms a state in which the coloring material is bonded to the polymer. By recording on the recording material in this state, a rich color material phase remains on the surface of the recording material, and a dilute solvent phase permeates into the recording material, resulting in excellent color development and prevention of bleeding. Realizes sharpness of the edge of a recorded image and recording stability. The above-mentioned state change must be reversible in order to correspond to a wide range of environmental temperature during recording.

However, when the reliability in a wide temperature range is not required for practical use, for example, the internal temperature of the device for printing using the ink used in the present invention is the temperature at which such a polymer material changes its state. It is not always necessary to use a polymer material whose state change is reversible, when it is clear that the value does not exceed. It is a requirement of the present invention to cause a state change in a certain temperature range or higher to cause thickening or gelation, and reversibility is not always a requirement. For example, JP-A-63-239
The method for driving an inkjet recording head according to the present invention is also effective for an ink or the like using a protein such as ovalbumin which is denatured at 72 ° C. and elastically gels as disclosed in JP-A-81. In the following, the detailed description of the present invention mainly shows an ink using a thermoreversible thickening polymer as an example. However, this polymer material is used for the present invention. It does not limit the range.

When actually recording by the ink jet system, when the ink droplets are ejected from the recording head, the low viscosity of the ink is more advantageous for high speed recording.
It is also conceivable to discharge the ink in a state of low viscosity during the operation of the recording apparatus, heat the recording material to a transition temperature or higher, and record on the recording material to realize the above phenomenon.

In this case, since "ink temperature <recording material temperature", the surface of the recording material is cooled at the moment when the ink adheres to the surface of the recording material. There is a slight time delay in rising. Since the viscosity of the ink is kept low until the temperature rises, the ink permeates into the recording material according to the Lucas-Washburn equation. As a result, when the temperature of the ink is raised from the beginning and all of the coloring material is left on the surface of the recording material, there is a possibility that a problem may occur in the scratchability of the recorded image. This problem of scratching is solved. However, not only a device for heating the recording material in advance is required, but since such a device has a large heat capacity and a large area for heat dissipation, it is difficult to heat the recording material as desired. Extremely poor thermal efficiency.

In addition to the heating time delay described above, a considerable amount of time is required for the ink to actually change its state even if the ink is heated to the transition temperature or higher. This is because even if the ink at room temperature is heated to the transition temperature or higher within a short period of time, polymer association does not occur instantaneously, but a time delay always occurs. On the contrary, even if the heat energy that instantaneously heats the average temperature of the ejected ink to the transition temperature or higher is applied before ejection, the increase in viscosity and other property changes do not immediately appear, and the ejection performance is hardly affected. Means no. Therefore, the effect in this case is almost the same as the case where the recording material is heated in advance.

The transition temperature that causes a change in the state of the ink is higher than the ambient temperature (room temperature) in which the recording apparatus is normally used, and the thickening of the ink by the temperature is effective (the temperature difference before and after the state change). 35 to 10
It is desirable to set the temperature in the range of 0 ° C. Above 100 ° C,
It is not preferable because it causes a significant increase in viscosity due to evaporation of water in the ink.

The present invention will be described in more detail with reference to the preferred embodiments. Thermally reversible type thickening high content children in Lee ink of the present invention, the aqueous solution or aqueous suspension and the like thickened with a constant temperature (transition temperature) or above and the temperature - the relationship viscosity Ri Ah in a reversible polymer, 50% by weight structural units of vinyl carboxylic acid ester (a) alkylene oxide adducts of active hydrogen compound having a nitrogen-containing ring
Or water-soluble vinyl polymer containing (A) Ru der.

The above-mentioned active hydrogen compound having a nitrogen-containing ring is a compound having active hydrogen for addition of a nitrogen-containing ring and an alkylene oxide. Specifically, the nitrogen-containing alicyclic compound is an aziridine ring. Having aziridine, 2-methylaziridine; having a pyrrolidine ring, pyrrolidine, 2-methylpyrrolidine, 2-pyrrolidone, succinimide; having a piperidine ring, piperidine, 2-methylpiperidine, 3,5- Dimethylpiperidine, 2-ethylpiperidine, 4-piperidinopiperidine, 4-pyrrolidinopiperidine, ethylpipecolate; those having a piperazine ring, 1-methylpiperazine, 1-methyl-3-ethylpiperazine; morpholine ring As having, morpholine, 2-methyl Ruhorin, 3,5-dimethyl morpholine; and ε- caprolactam.
Further, examples of the nitrogen-containing unsaturated cyclic compound include 3-pyrroline, 2,5-dimethyl-3-pyrroline, 2-hydroxypyridine, 4-pyridylcarbinol, 2-hydroxypyrimidine and the like. Of these, preferred are nitrogen-containing alicyclic compounds, more preferred are those having a piperidine ring and those having a morpholine ring, and most preferred are those having a morpholine ring. Further, as the above-mentioned alkylene oxide, specifically, ethylene oxide, propylene oxide and butylene oxide are preferable.

In the examples of the present invention, the transition temperature of the thermoreversible thickening polymer as described above can be easily adjusted by adjusting the kind and the number of added moles of these alkylene oxides. For example, when ethylene oxide is used, the transition temperature increases as the number of addition moles increases, and when propylene oxide or butylene oxide is used, the transition temperature decreases when the number of addition moles increases. 1 to 20 as the number of moles of alkylene oxide added
The amount is preferably mol, and more preferably 1 to 5 mol.

The vinyl-based carboxylic acid ester (a) which is a constitutional unit of the water-soluble vinyl-based polymer (A) used in the present invention is an alkylene oxide addition of the above-mentioned active hydrogen compound having a nitrogen-containing ring. The vinyl carboxylic acid used in the present invention includes acrylic acid, methacrylic acid (hereinafter collectively referred to as (meth) acrylic acid), maleic acid, vinyl. Examples thereof include benzoic acid and derivatives thereof, and particularly preferable examples include (meth) acrylic acid and (meth) acrylic acid derivatives.

In addition, as described above , an activity having a nitrogen-containing ring is used.
The water-soluble vinyl polymer (A) having an ester (a) of an alkylene oxide adduct of a water-soluble hydrogen compound and a vinyl carboxylic acid as a constitutional unit is a polymer of one or more kinds of the above vinyl carboxylic ester (a). or a copolymer of the vinyl-based carboxylic acid esters (a) 1 or more other vinyl monomers (b), 50 weight or more vinyl carboxylic acid ester (a) 1 kind as a constituent unit %
The above may be contained.

Other vinyl monomers (b) used at this time include hydroxyethyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, N. -Vinyl-2-pyrrolidone, (meth) acrylic acid, (anhydrous) maleic acid, styrenesulfonic acid, N, N-dimethylaminoethyl (meth)
Acrylate, N, N-diethylaminopropyl (meth) acrylate, methyl (meth) acrylate, butyl (meth) acrylate, glycidyl (meth) acrylate, N-butyl (meth) acrylamide, N-cyclohexyl (meth) acrylamide, (meth) Acrylonitrile, styrene, vinyl acetate, vinyl chloride, butadiene, isoprene and the like are preferable.

The temperature range of thickening varies depending on the composition ratio of the vinyl carboxylic acid ester (a) among the monomers constituting the vinyl polymer (A). In order to make the temperature range as small as possible, the composition ratio of the vinyl carboxylic acid ester (a) is 50% by weight or more, and more preferably 70% by weight or more of the entire vinyl polymer (A).

When the above thermoreversible thickening polymer is used as an aqueous solution, the viscosity decreases as the temperature rises up to a certain transition temperature, but when it exceeds the transition temperature, the viscosity increases with a high odor. Furthermore, there is a characteristic that the temperature-viscosity relationship has almost no hysteresis. In addition, the 5 wt% aqueous solution is 1 ° C / min
When heated at a temperature rising rate of 40 mPa · sec / ° C. or higher at a transition temperature or higher,
A sufficient thickening effect on the recording material can be obtained. In addition, the transition temperature is easily adjusted to an arbitrary temperature by changing the type and the number of moles of added alkylene oxide in the vinyl carboxylic acid ester (a) constituting the thermoreversible thickening polymer as described above. Therefore, the present invention can be applied to various recording heads whose temperature rise characteristics vary depending on the form, recording method, and the like. However, since the transition temperature changes depending on the type, amount, etc. of the additive components such as salts, surfactants and solvents in the ink, it is necessary to adjust the transition temperature for the entire ink composition to be applied.

FIG. 1 shows that 5% by weight of the thermoreversible thickening polymer.
An example of the relationship diagram between the temperature of the aqueous solution and the viscosity is shown. The thermoreversible thickening polymer used at this time was 2- (2-morpholinoethoxy) ethyl methacrylate [an ester of morpholine with ethylene oxide (2 mol) and methacrylic acid] 1.
It was obtained by adding 00 parts by weight and 0.1 parts by weight of 2,2′-azobis (2,4-dimethylvaleronitrile) to an ampoule, freeze-deaeration, sealing, and polymerizing at 60 ° C. for 8 hours. is there. In the figure, the solid line shows the case where the temperature of the aqueous solution was raised at 1 ° C./min, the dotted line shows the case where the temperature was lowered at 1 ° C./min, and the transition temperature was 46 ° C.

In the examples of the present invention, the molecular weight and addition amount of the thermoreversible thickening polymer to be added are in the permissible range (1 to 20 mPa) of the viscosity of the ink for ink jet recording at room temperature.
・ Sec), the weight average molecular weight is 1
The range of 10,000 to 1,000,000 is preferable. Here, if the molecular weight exceeds 1,000,000, the molecular chain becomes too long, the re-dissolution rate decreases, and the spinnability is exhibited, which is not preferable. If the molecular weight is about 10,000 within the above range, the thickening effect is weak, so the addition amount must be increased, and it is preferably 2 to 10% by weight. Similarly, when the molecular weight is about 1,000,000,
Addition of a small amount shows a sufficient thickening effect, and the preferable addition amount is 0.005 to 3% by weight. The effects of the present invention can be sufficiently obtained by mixing and using those having different molecular weights.

Further, the ink used in the description of the present invention can obtain sufficient recording characteristics if it contains the thermoreversible thickening polymer, but in order to further improve the thickening effect above the transition temperature. For this purpose, it is effective to add a hydrophobic fine particle dispersion to the ink. That is, when the temperature is higher than the transition temperature, the hydration of the thermoreversible thickening polymer decreases and the polymer becomes hydrophobic, but if a hydrophobic (polymer) fine particle dispersion such as an acrylic emulsion coexists in this state, the thermoreversible Since the affinity between the type viscosity increasing polymer and the hydrophobic fine particle dispersion exceeds the affinity between the polymer and water, the fine particle dispersion in which the polymer is dispersed in the solution is rolled up and associated with each other, This is because the entire system thickens more than when the polymer alone is used. The increase rate of the thickening effect due to the coexistence of the fine particle dispersion varies depending on the type and the addition amount of the fine particle dispersion and the dispersant used, but in the experiments of the present inventors, the thickening effect of about 10 to 50% Was confirmed to rise.

Examples of the hydrophobic fine particle dispersion usable in the present invention include acrylic emulsions, styrene-acrylic emulsions, styrene-divinylbenzene emulsions, urethane emulsions, silicone-acrylic emulsions, and the like. Is 8 to 40% by weight, the particle size is 10 to 80 nm, and the pH is 6.0 to 8.5.
Of the hydrophobic polymer as described above in 0.1 to 1 in the ink.
It is recommended to add 0% by weight. The polymer should have high heat resistance and hardness, and the higher the degree of crosslinking, the more suitable it is for the ink jet recording system. Especially in the method of recording by applying thermal energy to the ink,
It is desirable that the heat resistant temperature of the polymer is equal to or higher than the critical temperature of water, which is the main ink solvent, specifically, 10%.
A polymer having a weight loss temperature Tb of 300 ° C. or higher is preferable. Among the above emulsions, a styrene-divinylbenzene system (Tb = 380 ° C.) having a particularly high degree of crosslinking is suitable.

Next, the coloring material contained in the ink used in the present invention will be described. First, a dye will be described as the first color material. The dye that can be used in the present invention may be any dye that interacts with the thermoreversible thickening polymer used in the present invention and promotes association of polymer chains at a transition temperature or higher. Dye, food dye,
Examples thereof include basic dyes and reactive dyes. These are mostly hydrophobic dye skeletons and several sulfonates (-SO
₃ M), carboxylic acid salt (-COOM), ammonium salt (NH ₄ X) and other solubilizing groups and hydrogen-bonding hydroxyl groups (-
OH), amino group (-NH _2), imino group (-NH-)
Etc., and can form a complex with the thermoreversible thickening polymer of the present invention.

The disperse dye itself is insoluble in water, but since it is used in combination with a polycyclic anionic surfactant such as naphthalene sulfonate as a dispersant, the apparent ionicity of the dye is the same as that of the direct dye. It is anionic and can be used similarly to the above dyes.

Specific examples of the dye include, for example, CIDire
ct Black17, CIDirect Black19, CIDirect Bla
ck62, CIDirect Black154, CIFood Black2,
CIReactive Black5, CIAcid Black52, CIProj
Black dyes such as et Fast Black2; CIDirect Yellow
11, CIDirect Yellow44, CIDirect Yellow8
6, CIDirect Yellow142, CIDirect Yellow33
0, CIAcid Yellow3, CIAcid Yellow38, CIBa
sic Yellow11, CIBasic Yellow51, CIDisperse
Yellow3, CIDisperse Yellow5, CIReactive Yel
Yellow dyes such as low2; CIDirect Red227, CID
irect Red23, CIAcid Red18, CIAcid Red5
2, CIBasic Red14, CIBasic Red39, CIDisp
Magenta dyes such as erse Red 60; CIDirect Blue1
5, CIDirect Blue199, CIDirect Blue168,
CIAcid Blue9, CIAcid Blue40, CIBasic Blue
41, CIAcid Blue 74, CI Reactive Blue 15, and other cyan dyes. In addition to these dyes, any of those having a reduced solubilizing group to enhance water resistance, a special grade of which sensitivity is sensitive to changes in pH, and the like can be used in the present invention. The concentration of the dye in the ink can be freely selected within the range of solubility, and is usually preferably in the range of 1 to 8% by weight based on the whole ink, and 3 for recording on cloth, metal (eg, alumite), etc. The range of 10 to 10% by weight is preferable, and the range of 0.1 to 10% by weight is preferable when the density of the recorded image is required.

Carbon black and organic pigments can also be used in the present invention as the second coloring material. These coloring materials are capable of interacting with the polymer compound of the present invention through the dispersant, because the dispersant is used together with the disperse dye. Such carbon black and organic pigments can be used as long as they are suitable for ink jet recording. Among them, the carbon black used for the black ink is manufactured by the furnace method or the channel method and has a primary particle diameter of 10 ˜40 mμ, specific surface area by BET method of 50 to 300 m ² / g, and DBP oil absorption of 40 to 150 ml / 100 g are desirable. Specific examples of such a material include carbon black (No. 2300, No. 900, MCF88, No. 33, No. 40, N manufactured by Mitsubishi Chemical Corporation)
o.45, No. 52, MA7, MA8, # 2200B, Raven1255, Raven1060 made by Colombia Carbon, Regal330 made by Cabot.
R, Regal660R, Mogul L, DEGUSSA Color Black FW
18, Printex 35, Printex U, etc.), carbon black surface oxidized or plasma treated, insoluble azo pigment, soluble azo pigment, phthalocyanine pigment, isoindolinone high-grade pigment, quinacridone high-grade pigment, dioxane violet. , Organic pigments such as perinone / perylene-based higher pigments can be used. As a coloring material classified into the above-mentioned pigments, so-called dyed lake in which a dye is dyed with an extender pigment can also be used as the coloring material of the present invention.

Further, as the third coloring material, there can be mentioned coloring material fine particles in which a dye is bound to the surface of the fine particles to render the dye water-insoluble. The color material fine particles described here are
A dye is chemically bonded to organic fine particles having a core / shell structure having a reactive group on the surface of a shell, and the reactive group is a carboxyl group, a hydroxyl group, an amino group, an epoxide group, an amide group, a hydroxymethyl group or It is selected from the isocyanate group.

The core portion of the organic fine particles having a core / shell structure is a styrene-divinylbenzene polymer having a high degree of cross-linking, and the one having the above-mentioned reactive group introduced into the shell on the surface thereof is used. The thickness of the shell is preferably about 30% of the particle diameter so that the dye can be sufficiently dyed. As a specific example of the organic fine particles having a core / shell structure, Fine Particle Dispersion S2467 manufactured by Nippon Synthetic Rubber Co., Ltd. is suitable. In particular, for use as a coloring material in the present invention, the property of S2467 is selected to have a particle size of 10 nm to 80 nm and a solid content of 10% by weight. When the surface shell of the organic fine particles is surface-modified with an amino group, it can be easily dyed with a dye by forming an ionic bond with an anionic dye ion like a direct dye, for example. Further, by modifying the shell on the surface of the organic fine particles with a carboxyl group, the shell can be dyed by forming an ionic bond with a dye having a cationic dye ion such as a basic dye. The coloring material fine particles after dyeing can be used as the coloring material of the present invention by handling in the same manner as the above-mentioned organic pigment, and also when the hydrophobic fine particle dispersion is added, the thickening effect is similarly obtained. Is improved.

The above-mentioned three kinds of coloring materials may be used individually, but the coloring material fine particles and the dye are mixed or used, or the coloring material fine particles and the carbon black or the organic pigment are mixed. When it is used, the water resistance is improved compared to the case where only the dye is used, and it is possible to enhance the fastness of the recorded image, and high color development due to an increase in the thickening effect and recording dots by containing particles. It is possible to further improve the quality of the recorded image, such as the edge of the image becomes sharper.

Water or a mixture of water and a water-soluble organic solvent is used as a liquid medium in which the above-mentioned components constituting the ink used in the present invention are dissolved or dispersed. Specific examples of the water-soluble organic solvent used in the ink of the present invention include amides such as dimethylformamide and dimethylacetamide; ketones such as acetone; ethers such as tetrahydrofuran and dioxane; polyethylene glycol and polypropylene. Polyalkylene glycols such as glycols; ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol and other alkylene groups having 2 to 6 carbon atoms Alkylene glycols containing atoms; glycerin; ethylene glycol monomethyl (or ethyl) ether, diethylene glycol monomethyl (or ethyl) ether, triethylene glycol monomethyi Lower alkyl ethers of polyhydric alcohols such as (or ethyl) ether; N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, triethanolamine, sulfolane, dimethyl sulfoxide, 2- Examples include cyclic amide compounds such as pyrrolidone and ε-caprolactam, and imide compounds such as succinimide.

In order to impart more excellent ink jet recording suitability such as reliability and storage stability to the ink used in the present invention having the above-mentioned constitution,
A moisturizing agent or a dissolution aid may be contained. Examples of such materials include 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2, 3-butanediol, 1,5-pentanediol, 1,7-heptanediol, 2-methyl-
2,4-pentanediol, 2-ethyl-1,3-hexanediol, glycerin, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol 200, dipropylene glycol,
Alkylene glycols such as 2,2′-thiodiethanol and 1,2,6-hexanetriol; alcohol amines such as monoethanolamine, diethanolamine and triethanolamine; dimethylformamide, dimethylacetamide, dimethylsulfoxide, sulfolane,
An aprotic polar solvent such as 1,3-propane sulfone;
1,2-dimethoxyethane, 1,2-diethoxyethane, 1,2-dibutoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, 2-methoxyethanol, 2-ethoxyethanol, 2- (methoxymethoxy) Ethanol, 2-butoxyethanol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, di Propylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl Ether, lower alkyl ethers of polyhydric alcohols, such as tripropylene glycol methyl ether; Other formamide, 2-pyrrolidone, N
-Methyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, sorbitol, urea, 1,3-bis (β-hydroxyethyl) urea and the like can be mentioned. The content of these additives in the ink is preferably in the range of 1 to 30% by weight based on the total amount of the ink.

When the above ink is used for ink jet recording, methanol, ethanol, propanol,
When an alkyl alcohol such as 2-propanol, 1-butanol or 2-butanol is contained, the dischargeability is improved,
It is even more effective. These alcohols are preferably contained in the range of 1 to 10% by weight based on the total amount of the ink. In the present invention, the ink may further contain additives such as a surfactant, a pH adjuster, a rust preventive, a fungicide and an antioxidant, if necessary.

Next, a means for ejecting and recording the ink will be described. The effect of the present invention is achieved by causing the above-mentioned average temperature of the ejected ink to reach the transition temperature or higher already described when the bubble is generated and kinetic energy is applied to the ink to eject the ink. It is more efficient than methods such as heating paper. However, the conventional heating method cannot sufficiently add heat energy to the ink.

The basic principle of the present invention will be described below.
Semi-infinite one-dimensional heat conduction in which a constant heat flux is generated from the surface boundary is expressed by the following equation (4). [In the formula, x is a position coordinate inside the ink which is separated from the surface of the heating element in the vertical direction, t is the time after the heat flux starts to be generated, T is the temperature of the ink at that position and time, and T ₀ is the heating start. The temperature of the previous ink, q ₀ is the average heat flux from the surface of the heating element to the ink, κ is the thermal conductivity, α is represented by κ / ρc, ρ is the density of the ink, and c is the specific heat of the ink.
Further, erf is a Gaussian error function and is defined by the following equation (5).

[0055] ]

FIG. 8 shows how heat is transferred from the surface of the heating element represented by this equation to semi-infinite water at 25 ° C. every 10 μsec. At this time, the heat flux from the surface of the heating element was calculated as a constant value of 55 [MW / m ² ]. It can be seen from the graph that most of the thermal energy remains within 10 μm from the surface of the heating element within the time of about 50 μsec.

A consideration about one-dimensional heat conduction will be added below. The actual heating element and ink placement is a three-dimensional structure. Originally, it is necessary to consider three-dimensional heat conduction, but as can be seen from FIG. 8, in the range of several tens of microseconds, the heat is not sufficiently far inside the ink as compared with the size of the heating element. Is not transmitted. Therefore, consideration can be added with high precision using an equation expressing one-dimensional heat conduction.

Equation (4) represents how heat is transferred to the ink after the heating of the ink is started. Here, the heat flow near the surface of the heating element will be examined. When x = 0 in the equation (4), the following equation is obtained.

[0059] By the way, the heat given to the ink by the heating element by the time t Q _give
Can be roughly estimated as follows. Q _give = Sq ₀ t (7) Here, S is the effective area of the heating element. On the other hand, the present invention is meaningless unless the average temperature of the ink ejected from the nozzle by heat bubbling exceeds the above-mentioned transition temperature.
The minimum amount of heat Q that the ink ejected should receive
_{When get} is estimated, the following formula (8) is obtained.

Q _get = ρcV (T _P −T ₀ ) ... (8) Here, V is the volume of ink to be ejected, and Q _give = Q
_{Assuming get} , the minimum required heating time t _give when the average heat flux from the heating element is q ₀ is obtained as follows.

T _give = ρcV (T _P −T ₀ ) / Sq ₀ (9) Here, T _P is a transition temperature (in a polymer substance, it is given by an average transition temperature).

By the time t _give , if water vapor bubbles are generated in the ink, the surface of the heating element is covered with gas to be in an adiabatic state, so that sufficient thermal energy is sufficient to cause the transfer of the ink. I will not be able to receive it.
Therefore, the ink near the surface of the heating element must not reach the ink bubbling start temperature T _B by this time. That is, the following expression (10) is an essential condition. T _(t) ≤ T _B ··· (10)

By summarizing the above, the following conditional expression (11) is obtained. Therefore, theoretically, it is a requirement of the ink jet recording method of the present invention to drive the heating element so as to at least satisfy the formula (11).

Here, the foaming start temperature T _B is not 100 ° C. which is the boiling point of water under 1 atm. With rapid heating, water overheats and boiling does not occur immediately. However, boiling occurs when heated above the critical temperature. Actually, foaming occurs even if the critical temperature is not reached for various reasons. For these, Stralen and Cole author “Boili
ng Phenomena ”McGraw-Hill, 1979. In addition, the foaming temperature of water was reported by Iida et al. in the 27th Japan Heat Transfer Symposium Proceedings (1990.5).

As the ink jet method used in the present invention, it is particularly preferable to use the ink jet method in which thermal energy is applied to ink to eject droplets by foaming of ink.

An example of the structure of a head, which is a main part of an ink jet recording apparatus utilizing heat energy as the above ink jet system, is shown in FIGS. 2, 3 and 4. Figure 2
FIG. 3A is a cross-sectional view of the head along the ink flow path, which will be described below. The head 1 is obtained by bonding a glass, ceramic, silicon or plastic plate or the like having a flow path (nozzle) 2 for passing ink and the heating element substrate 3 to each other. The heating element substrate 3 includes a protective layer 4 made of silicon oxide, silicon nitride, silicon carbide, etc., an electrode 5 made of aluminum, gold, aluminum-copper alloy, etc., and a high melting point of HfB ₂ , TaN, TaAl, etc. A heat generating resistor layer 6 made of a material, a heat storage layer 7 made of thermally oxidized silicon or aluminum oxide, and a substrate 8 made of a material having a good heat dissipation property such as silicon, aluminum or aluminum nitride. ing. Note that FIG. 3 is a cross-sectional view of the head 1 taken along line XY in FIG.

The electrode 5 of the head 1 having the above structure
When a pulsed electric signal is applied to the heating element substrate 3
However, since the area indicated by h rapidly generates heat, bubbles are generated in the ink in contact with this surface, and the meniscus 10 is projected by the generated pressure, and the ink is ejected from the nozzle 2 of the head 1.
Through the orifice 11, and becomes a small ink droplet 12 having a spherical shape, which flies toward the recording material 13. Figure 4
2 shows an external view of a multi-head in which many heads shown in FIG. 2 are arranged.

FIG. 5 shows an example of an ink jet recording apparatus incorporating the above head. In FIG. 5, reference numeral 61 is 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 has a recording head 65.
It is arranged at a position adjacent to the recording area by and is held in a protruding form in the movement path of the recording head 65. Also, 6
Reference numeral 2 denotes a cap of the ejection port surface of the recording head 65, which is arranged at a home position adjacent to the blade 61, moves in a direction perpendicular to the moving direction of the recording head 65, contacts the ink ejection port surface, and caps. Is provided.
Further, 63 is an ink absorber provided adjacent to the blade 61, and like the blade 61, is held in a form protruding in the movement path of the recording head 65.

The blade 61, the cap 62, and the ink absorber 63 constitute an ejection recovery section 64, and the blade 61 and the ink absorber 63 remove water, dust, and the like on the ink ejection port surface. Reference numeral 65 denotes a recording head which has an ejection energy generating means and ejects ink onto a recording material facing the ejection port surface where the ejection ports are arranged to perform recording.
Reference numeral 6 denotes a carriage on which the recording head 65 is mounted and which is moved.

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 65, 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 ejection recovery unit 64 is retracted from the movement path of the recording head 65, but the blade 61 is projected 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 65 to the home position is performed not only at the end of recording or at the time of ejection recovery, but also at the home position adjacent to the recording area at a predetermined interval while the recording head 65 moves in the recording area for recording. And the wiping is performed in accordance with this movement.

FIG. 6 is a diagram showing an example of an ink cartridge 45 in which ink is supplied to the head via an ink supply member, for example, a tube. Where 4
Reference numeral 0 is an ink containing portion containing the supply ink, 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. An ink absorber 44 receives the waste ink.
It is preferable for the present invention that the ink containing portion 40 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 separated as described above, but is also suitable for the one in which they are integrated as shown in FIG. Used. In FIG. 7, reference numeral 70 denotes a recording unit, in which an ink containing portion containing ink, for example, an ink absorber is contained, and the ink in the ink absorber has a head portion having a plurality of orifices. The ink is ejected from 71 as ink.

For the present invention, it is preferable to use polyurethane as the material of the ink absorber. Further, the structure may be such that the ink containing portion is an ink bag having a spring or the like provided therein, without using the ink absorber. Reference numeral 72 denotes an atmosphere communication port for communicating the inside of the recording unit with the atmosphere. The recording unit 70 is used in place of the recording head shown in FIG. 5, and is detachable from the carriage 66.

[0077]

EXAMPLES Now, the above-mentioned purely theoretical heat flux conditional expression (1)
1) requires some practical modifications. Therefore, the present invention will be specifically described below with reference to Examples and Comparative Examples, and heat flux values that are more practically suitable will be shown. First, examples and comparative examples of the method for driving an inkjet recording head of the present invention will be described. Here, it is assumed that an ink having a transition temperature of about 65 ° C. is used, and it is considered that the average temperature of the ink, which is about 25 ° C., reaches about 70 ° C. before ejection.

Example 1 and Comparative Example 1 A heating element (heater) classified as A in Table 1 below is used for the recording head. That is, the heater is formed on a Si substrate by first forming an oxide film layer of 1.0 μm of SiO ₂ , 0.
Heater material layer consisting of 065 μm HfB ₂ (sheet resistance 5
8.6Ω), a protective film layer made of 1 μm SiO ₂ , 0.05
A cavitation-resistant layer composed of a tantalum pentoxide (Ta ₂ O ₅ ) layer having a thickness of 0.6 μm and a tantalum (Ta) layer having a thickness of 0.6 μm is formed in this order. At this time, the size of the heater is 24
It is assumed to be μm × 28 μm and long in the direction of current flow.
Further, the total resistance of the heater and the circuit wiring is set to 92Ω. At this time, if a voltage of 11.3V is applied to the external circuit for 2.6 μsec as shown in FIG. 9, the ink near the heater surface is heated to 300 ° C. about 2.55 μsec after the start of the application of the drive voltage. Film boiling occurs and sufficient bubbling occurs to eject ink. At this time, the average temperature of the ink within 10 μm from the heater surface, which was initially 25 ° C., is about 35.5 ° C. The average temperature can be easily obtained by examining a graph similar to FIG. This drive method is standard as a conventional drive. A graph of heat flux at this time is shown in FIG. The graph that draws a sharp but smooth curve in this graph is 2.55 μse
The reason why it suddenly becomes 0 near c is that foaming occurs on the surface of the heater at this time, the heater is covered with gas and becomes adiabatic, and the heat flux becomes 0. After this point, the temperature of the heater surface rises rapidly. However, this method does not sufficiently increase the average temperature of the ink within 10 μm from the heater surface. This is because the heat flux from the heater surface is too large and the ink temperature near the heater surface exceeds the foaming temperature of 300 ° C. before sufficient heat is transferred to the ink. This example is referred to as Comparative Example 1. The average heat flux at this time is 2
It becomes 04 [MW / m ² ].

Next, the heat flux was made sufficiently small, and this is referred to as Example 1. In this example, the drive voltage is sufficiently lowered and only one drive pulse is applied to the heater. When the driving voltage is 5.7V, the ink temperature near the heater surface is 30
It takes about 24 μsec until it reaches 0 ° C and foams.
Becomes At this time, the average temperature of the ink within 10 μm from the heater surface is 69.7 ° C., and the ink can be sufficiently heated as compared with Comparative Example 1, and a remarkable effect is obtained. FIG. 15 shows the drive pulse of the voltage at this time.
In addition, FIG. 16 shows a time transition of the heat flux from the heater to the ink at this time. The average heat flux until foaming at this time is 7
It becomes 9.4 [MW / m ² ]. Further, FIG. 17 shows the time transition of the average temperature of the ink within 10 μm from the heater surface. In this example, ink at 25 ° C. can be heated up to approximately 70 ° C. without bubbling. The volume of the ink that has received the heat at this time is approximately 6.5 μl when the area of the heater and the thickness of the ink are approximately 24 μm × 27 μm × 10 μm.
Is. Note that this value is taken as the discharge volume for all of the examples and comparative examples listed in this specification.

Example 2 In the heating method of Example 1, since the driving voltage is relatively low, the nucleate boiling in which the heater surface is gradually covered with small water vapor bubbles without film boiling in which the water vapor is suddenly covered with water vapor may occur. May occur. This greatly affects the components of the ink, the surface roughness of the heater, the degree of purification of the ink, and the like.
When nucleate boiling occurs, the explosive growth of water vapor is hindered, and the ink ejection speed from the nozzle becomes slow, which may impair the printing quality.

Therefore, as Example 2, the same heater as that used in Example 1 is used, and the double pulse drive in which the drive voltage shown in FIG. 18 is set slightly higher is performed, and a good result is obtained. At this time, the driving voltage is 6.3 V, the first pulse width is 10 μsec, and the second pulse width is 9.8 μs.
ec, the interval between pulses is about 12 μsec
Is. In addition, the average temperature of the ink within 10 μm from the heater surface is 68.1 ° C., and it is possible to obtain the same effect as in Example 1. FIG. 19 is a time transition of the heat flux from the heater to the ink at this time. The heat flux reaches a substantially constant heat flux shortly after the start of heating, and when the application of the first drive pulse ends, the heat flux also immediately decreases. In this graph, the heat flux becomes negative until the second drive pulse is applied. This indicates that the temperature of the heater and the Si substrate became lower than that of the ink in contact with the surface of the heater, so that heat slightly flows back from the ink side to the heater and the Si substrate side. Of course, heat is diffused inside the ink, and the heat is diffused in a direction further away from the ink heater surface. The average heat flux before foaming at this time is approximately 57 [MW / m ² ]. In this example, the first drive pulse is used for heating until just before bubbling, and a pause period is provided for a while, waiting for the diffusion of heat concentrated in the ink near the surface, and then the pulse ( This is a system in which the ink is finally foamed and ejected by applying a second drive pulse). In this example, the application of the second drive pulse was started after the ink temperature on the heater surface dropped to about 100 ° C. FIG. 20 shows the heater surface 10 in this example.
It is a time transition of the average temperature of the ink within μm. It can be seen that the temperature hardly changes during the pulse rest period.

Third Embodiment Next, a third embodiment in which the driving voltage is further increased will be described.
In this example, the same heater as that used in Example 1 was used and the driving voltage was set to 7.5V. The ink is heated by driving five pulses of voltage as shown in FIG. In this case, the heat flux from the heater to the ink has a pulse train shape in response to the drive voltage, as shown in FIG. The peak heat flux at this time is 100 [MW / m ² ]
Is over. Especially when foaming, it has risen to 140 [MW / m ² ]. Therefore, more stable and powerful foaming occurs. Further, the average temperature of the ink within 10 μm from the heater surface by the time of foaming is 69.5 ° C. as shown in FIG. 23, and the same effect as in Examples 1 and 2 can be obtained. In this example, the voltage application was started for each subsequent pulse after the ink temperature near the heater surface dropped to about 180 ° C.

Example 4 and Comparative Example 2 In this example, heaters classified as B- in Table 1 below are used for the recording head. The difference from the heater A is S
The thickness of the oxide film layer provided on the i substrate was 1 μm for A, but 6.0 μm for B−. This oxide film is provided to reduce the amount of heat dissipated from the heater to the Si substrate side. A voltage is applied to this as shown in FIG. 11 which is a conventional driving method. The drive voltage is shown in Figure 9.
11.3 in the case of the heater configuration of A of Comparative Example 1 shown in FIG.
It was 10.5 V against V. The time transition of the heat flux from the heater to the ink at this time is shown in FIG. This graph is almost the same as the graph of Comparative Example 1 shown in FIG. The average heat flux is also 196 [MW / m ² ] and can be considered to be almost the same. This means that the same heat flux can be generated even if the driving voltage is different.
This example is referred to as Comparative Example 2.

Now, as Example 4, this heater configuration was driven by a single pulse of voltage as shown in FIG. The driving voltage at this time was 4.0V. Further, the time transition of the heat flux from the heater to the ink is shown in FIG. The average heat flux was 70.1 [MW / m ² ]. FIG. 26 shows the time change of the average temperature of the ink within 10 μm from the heater surface.

Example 5 In this example, the same heater as that used in Example 4 was used, and driving was performed by the double pulse of the voltage shown in FIG. At this time, the drive voltage is 5.8V. FIG. 31 shows the time transition of the heat flux from the heater to the ink. The average heat flux is 40.1 [MW / m ² ]. In this example, FIG.
It can be read that the backflow of heat is small as compared with Example 2 shown in FIG. The reason for this is that the oxide film layer has a thickness of 6.0 μm, which is thicker than 1.0 μm in the case of the heater used in Example 2.
This is because the heat insulating effect on the substrate is great. FIG. 32 shows a time transition of the average temperature of the ink within 10 μm from the heater surface. The average temperature of the ink within 10 μm from the heater surface reached 69.8 ° C.

Example 6 In this example, as shown in B- in Table 1 below, the thickness of the oxide film layer on the Si substrate was 6 μm, which is the same as that of the heater B- used in Example 5, but the protection was performed. The thickness of the film layer is 1 / B-
Double pulse drive is performed using the heater of 0.5 μm. The protective film layer is provided in order to prevent the heating element from being corroded by ink. By making the protective film layer thin, the thermal efficiency is further improved. The driving pulse at this time is shown in FIG. 27, and the time transition of the heat flux from the heater to the ink is shown in FIG. The average heat flux is 43.4 [MW / m ² ]. In addition, FIG. 29 shows the time transition of the average temperature of the ink within 10 μm from the heater surface.

Example 7 and Comparative Example 3 In this example, a heater classified as C in Table 1 below is used for the recording head. The heater has a structure in which a heater material layer (HfB ₂ ) is directly provided on a glass substrate, and at least only the heater material layer is heated directly or in contact with ink through an extremely thin film. This heater has extremely high heating efficiency. A voltage was applied by the conventional driving method as shown in FIG. FIG. 14 is a time transition of the heat flux from the heater to the ink at this time. The average heat flux from the start of heating to the time of foaming was 237 [MW / m ² ]. This example is referred to as Comparative Example 3.

In Example 7, the heater was used to drive by a single pulse of voltage as shown in FIG. The drive voltage at this time is 3.6V. Figure 3
4 is a time transition of heat flux from the heater to the ink.
The average heat flux is 79.9 [MW / m ² ]. FIG. 35 shows the time change of the average temperature of the ink within 10 μm from the heater surface. The average temperature reaches 70 ° C.

Example 8 Finally, the same heater as that used in Example 7 was used, and the double pulse driving shown in FIG. 36 was adopted.
The drive voltage is 4.0V. FIG. 37 is a time transition of the heat flux from the heater to the ink at this time. Since the heater used in this example does not have an oxide film layer (protective film), the driving voltage waveform shown in FIG. 36 and the shape of the graph showing the actual time transition of the heat flux from the heater to the ink are similar. . The average heat flux is 47.8 [MW / m ² ]. FIG. 38 shows the average temperature of the ink within 10 μm from the heater surface. In this example, the average temperature of the ink within 10 μm from the heater surface reaches 70.9 ° C.

Table 1: Structural example of heating element (heater) * All units are μm.

Table 2 below shows a list of specifications and results of each of the examples described above. The driving method described as “normal” is a comparative example using the conventional driving method, and the average temperature of ink within 10 μm from the heater surface is 35 in each case.
At about 38 ° C, the target of about 70 ° C has not been reached. The total amount of heat received by the ink is approximately 0.3-0.
It is 4 [μJ]. The average heat flux in Comparative Examples 1-3 is 20.
It is considerably large, about 0 to 240 [MW / m ² ], and the ink near the heater surface foams before the ink within 10 μm from the heater surface is sufficiently heated.

On the other hand, in the driving method of Examples 1 to 8, it was possible to reach the target temperature of about 70 ° C. In each case, the total amount of heat received by the ink is 1.2 to 1.3.
It was [μJ]. Looking at the average heat flux at these times,
It is in the range of 40 to 80 [MW / m ² ]. From these facts, regarding the driving method of the present invention, the heat flux of about 1/2 or less of the conventional driving method seems to be an approximate guide. However, more correctly, the standard is given as follows. For example, T _B = 300 ° C., T _P = 70 ° C., T ₀ = 25
C, the size of the heater is 24 μm × 28 μm, the amount of ejected ink is 6.7 pl, and the values of thermal conductivity and specific heat are obtained by calculating the average heat flux from the formula (11) when the value of water is used.
It is understood that the value may be 53 [MW / m ² ] or less. When this value is compared with the values of Examples 1 to 8 in Table 2 below, they are almost the same, but in reality, the constraints of various configurations of the heating element (heater) come into the heat conduction process. Therefore,
The correction constant α becomes necessary.

For this α, the value 53 obtained above is calculated.
[MW / m ² ] and the maximum value in Table 2, 79.
Using 9 [MW / m ² ], the value is calculated as 79.9 ÷ 53≈1.5.

Table 2: Specifications and results of Examples 1-8 and Comparative Examples 1-3

In the description of the present invention, the average temperature of the ink within 10 μm from the heater surface is mentioned. This is to show the upper limit of the average heat flux. The larger the average heat flux, the smaller the total amount of heat that can be given to the ink from the start of heating to the bubbling, so in the worst case, for example, a head configuration in which all of the ink on the heater surface is ejected (flat 4-10940). 8 and 16) of the issue). In the configuration of the head shown in FIG. 2, the ink on the heater may not be all ejected ink droplets. These differ depending on the individual heating element and nozzle configurations, but in any case, an average heat flux lower than the value shown here is required.

Among the examples of the driving method described above, the single pulse driving method, the double pulse driving method, the multi-pulse driving method and the like are known, for example, in Japanese Patent Laid-Open No. 5-31905. However, in the present invention, among the driving methods of the present invention, the inventors of the present invention remarkably remarkably use an ink containing a polymer material that causes a phase change by heat without heating the recording material by another means. In order to improve the printing quality, it is necessary to add a sufficient amount of heat to the ink to cause the phase change by using a heating element for ejecting the ink. For that purpose, it is essential to limit the heat flux. It was discovered and applied.

[0097]

As described above, according to the present invention, since the fixing of the ink to the recording material in the image formation does not depend only on the evaporation and the permeation, the high optical density (OD value) can be obtained. The problems of feathering and bleeding, which are indispensable for quality records, can be solved at the same time.
Further, in the method of the present invention, the state of the ink changes only by the temperature change, so that the pH and unevenness of the surface of the recording material can be applied to various recording materials such as transparency film, cloth, metal plate other than plain paper. It is useful because it is not affected by.

According to the present invention, the effect of the present invention can be obtained by efficiently heating the ink with a small heat capacity without requiring a device for preheating the recording material. INDUSTRIAL APPLICABILITY When the present invention is applied to an inkjet recording device, the effect is more remarkable.

[Brief description of drawings]

FIG. 1 is a temperature-viscosity relationship diagram of an aqueous polymer solution.

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

FIG. 3 is a cross-sectional view of a head portion of the inkjet recording device.

FIG. 4 is an example of a head having a plurality of nozzles of an inkjet recording apparatus.

FIG. 5 is a perspective view showing an example of an inkjet recording apparatus.

FIG. 6 is a vertical cross-sectional view showing an example of an ink cartridge.

FIG. 7 is a perspective view of a specification in which an inkjet recording head and an ink cartridge are integrated.

FIG. 8 is a graph showing how heat is transferred from the surface of the heating element to water.

FIG. 9 is a graph showing the drive voltage to the heater of Comparative Example 1.

FIG. 10 is a graph showing the change over time in heat flux from the heater to the ink in Comparative Example 1.

FIG. 11 is a graph showing the driving voltage to the heater of Comparative Example 2.

FIG. 12 is a graph showing changes over time in heat flux from the heater to the ink in Comparative Example 2.

FIG. 13 is a graph showing the drive voltage to the heater of Comparative Example 3.

FIG. 14 is a graph showing changes over time in heat flux from the heater to the ink in Comparative Example 3.

FIG. 15 is a graph showing the driving voltage to the heater of Example 1.

16 is a graph showing the time transition of heat flux from the heater to the ink of Example 1. FIG.

FIG. 17 is a graph showing the time transition of the average temperature of the ink within 10 μm from the heater surface of Example 1.

FIG. 18 is a graph showing the drive voltage to the heater of Example 2.

FIG. 19 is a graph showing the time transition of the heat flux from the heater to the ink of Example 2.

FIG. 20 is a graph showing the time transition of the average temperature of the ink within 10 μm from the heater surface of Example 2.

FIG. 21 is a graph showing the driving voltage to the heater of Example 3.

FIG. 22 is a graph showing the time transition of the heat flux from the heater of Example 3 to the ink.

FIG. 23 is a graph showing the time transition of the average temperature of the ink within 10 μm from the heater surface of Example 3.

FIG. 24 is a graph showing the driving voltage to the heater of Example 4.

FIG. 25 is a graph showing changes over time in heat flux from the heater to the ink in Example 4.

FIG. 26 is a graph showing the time transition of the average temperature of the ink within 10 μm from the heater surface of Example 4.

FIG. 27 is a graph showing the driving voltage to the heater of Example 6.

FIG. 28 is a graph showing the time transition of heat flux from the heater to the ink of Example 6.

FIG. 29 is a graph showing the time transition of the average temperature of the ink within 10 μm from the heater surface of Example 6.

FIG. 30 is a graph showing the drive voltage to the heater of Example 5.

FIG. 31 is a graph showing changes over time in heat flux from the heater to the ink in Example 5.

FIG. 32 is a graph showing the time transition of the average temperature of the ink within 10 μm from the heater surface of Example 5.

FIG. 33 is a graph showing the driving voltage to the heater of Example 7.

FIG. 34 is a graph showing the change over time in heat flux from the heater to the ink in Example 7.

FIG. 35 is a graph showing the change over time in the average temperature of the ink within 10 μm from the heater surface in Example 7.

FIG. 36 is a graph showing the drive voltage to the heater of Example 8.

FIG. 37 is a graph showing the change over time in heat flux from the heater to the ink in Example 8.

FIG. 38 is a graph showing the time transition of the average temperature of the ink within 10 μm from the heater surface of Example 8.

[Explanation of symbols]

1: Head 2: Flow path (nozzle) through which ink passes 3: Heating element substrate 4: Protective layer 5: Electrode 6: Heating resistor layer 7: Heat storage layer 8: Substrate 10: Meniscus 11: Orifice (fine hole) 12: Ink droplet 13: Recording material 40: Ink bag 42: Stopper 44: Ink absorber 45: Ink cartridge 51: Paper feed section 52: Paper feed roller 53: Paper ejection roller 61: Wiping member 62: Cap 63: Ink absorber 64: Discharge recovery unit 65: inkjet recording head 66: Carriage 67: Carriage guide shaft 68: Carriage drive unit 69: Driving belt 70: Recording unit 71: Head part 72: Air communication port

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-192605 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B41J 2/05 B41J 2/01 B41M 5 / 00 C09D 11/00

Claims (9)

(57) [Claims] 1. A heated heating elements in the print head in accordance with the recording signal, ink is heated foam in contact with the element by ejecting ink from above SL head, ink jet recording which performs recording with a ink in the method, the upper Symbol ink, heat friendly to phase separate from the aqueous solution at transition temperature
A thermo-reversible thickening agent that is a liquid medium that causes a rapid change in viscosity when heated , including a reverse-type thickening polymer compound and a coloring material.
The polymer is an alkyl of an active hydrogen compound having a nitrogen-containing ring.
Ester of lenoxide adduct and vinyl carboxylic acid
Vinyl-based polymerization containing 50% by weight or more as a structural unit
A body, an ink jet recording method characterized by average heat flux from the upper Symbol surface of the heating element to the ink (q _O) drives the upper Symbol head so as to satisfy the following relation (1). [Where κ is thermal conductivity, S is the effective area of the heating element,
V is the volume of ink ejected in one drive, T _B is the temperature of the ink that causes bubbles, T _O is the temperature of the ink before ejection,
T _P is a transition temperature of the ink that causes a rapid change in viscosity of the ink, and α is a correction constant: 1.5. ] Wherein the alkylene oxide adducts of active hydrogen compound having a nitrogen-containing ring, a piperidine ring or morpholine ring, as the alkylene oxide, ethylene oxide, claim 1 is a compound of propylene oxide or butylene oxide is added The inkjet recording method described in 1. 3. A molar number of addition of the alkylene oxides, the inkjet recording method according to claim 1 or 2 is 1 to 20. Wherein said thermally reversible thickening polymer, the ink in the range of 35 to 100 ° C., claim 1, having a transition temperature that causes a thickening 1 Inkjet recording method according to item. Wherein said thermally reversible thickening polymer, an ink jet recording method according to any one of claims 1 to 4 in the 1,000,000 molecular weight range 10,000 or more weight average molecular weight. Wherein said heating element, an ink jet recording method according to any one of claims 1 to 5 composed of a laminate comprising a heat generating resistor layer. 7. The ink-jet recording method according to any one of the recording signal according to claim 1 which is a pulse-like electrical signal 6. Wherein said colorant is an ink jet recording method according to any one of claims 1 to 7, which is a dye. Wherein said colorant is an ink jet recording method according to any one of claims 1 to 7, which is a pigment.