JP2002355978A - Thermal ink jet recording head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To present conditions for preventing clogging of a liquid ejection recorder in which an ejection opening has a distance of depth part at the ejecting part. SOLUTION: Microparticles having size of Dp (μm) are dispersed into a liquid to produce a recording liquid which is then ejected from a fine ejection opening 4 to adhere onto a recording material thus performing recording. The end part of a channel serves, as it is, as the ejection opening 4 or the ejection opening 4 is formed independently at the end part of a channel wherein a relation Dp/t<=0.01 is satisfied for an ejection opening having a distance t (μm) at the depth part. When the outer corner part 4A1 has r shape (circular), shear drop at the corner part is 50 Dp or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thermal ink jet recording head, and more particularly to a thermal ink jet recording head using a recording liquid in which fine particles are dispersed.

[0002]

2. Description of the Related Art The non-impact recording method has recently attracted attention in that noise during recording is extremely small to a negligible level. Among them, a so-called ink jet recording method capable of high-speed recording and capable of performing recording on a so-called plain paper without requiring a special fixing process,
Some of the most influential recording methods have been proposed and various improvements have been proposed and commercialized, while others are still being put to practical use.

In such an ink-jet recording method, recording is performed by causing droplets of a recording liquid, called so-called ink, to fly and adhere to a recording member to perform recording. There are various methods as follows, depending on the generation method and the method for controlling the flying direction of the generated recording liquid droplet.

[0004] For example, in the Tele type system disclosed in US Pat. No. 3,060,429, droplets of a recording liquid are generated by electrostatic attraction, and the generated droplets of the recording liquid are transmitted to a recording signal. There is an electrostatic attraction type in which the electric field is controlled in accordance with the condition and recording is performed by selectively adhering the recording liquid droplets onto the recording member.

[0005] In addition, in the Sweet type disclosed in US Pat. No. 3,596,275 and US Pat. No. 3,298,030, small droplets of a recording liquid whose charge amount is controlled by a continuous vibration generation method are generated. There are a continuous flow type and a charge control type in which recording is performed on a recording member by flying a small droplet of which generated charge is controlled between deflection electrodes to which a uniform electric field is applied.

As another method, for example, a Hertz method disclosed in US Pat. No. 3,416,153, in which an electric field is applied between a discharge port and a ring-shaped charging electrode, and a continuous vibration generating method is used. There is a method of recording by generating and atomizing small droplets of a recording liquid. That is, in this method, the atomization state of the small droplet is controlled by modulating the electric field intensity applied between the discharge port and the charging electrode in accordance with the recording signal, and the image is recorded with the gradation of the recorded image.

Further, as another system, for example, there is a Stemme system disclosed in US Pat. No. 3,747,120. This system is fundamentally different from the above three systems in principle. That is, in each of the three methods, the droplets of the recording liquid ejected from the ejection port are electrically controlled while flying, and the droplets carrying the recording signal are selectively attached to the recording member. In contrast, this St
In the emme method, recording is performed by ejecting and flying a small droplet of a recording liquid from an ejection port in accordance with a recording signal. That is, Stem
In the me method, an electric recording signal is applied to a piezoelectric vibrating element attached to a recording head having a discharge port for discharging a recording liquid, and the electric recording signal is changed into mechanical vibration of the piezoelectric vibrating element. The recording is performed by ejecting a small droplet of the recording liquid from the ejection port according to mechanical vibration and attaching the droplet to a recording member, and is a so-called drop-on-demand type.

Further, as another method, there is a method proposed by the present applicant in Japanese Patent Publication No. 56-9429. This method is also a so-called drop-on-demand type in which small droplets of a recording liquid are ejected and ejected from an ejection port in accordance with a recording signal to perform recording, but the ink in the liquid chamber is heated to generate bubbles in the ink. This is a so-called bubble ink jet type in which ink droplets are ejected from ejection ports by the action of bubbles.

[0009] As described above, the ink jet recording method comprises:
There are various methods according to the principle, but what can be said in common is a so-called ink droplet of recording liquid.
The point is that the recording is performed by causing t) to fly and adhere to the recording member. As a recording liquid called this ink, a recording liquid in which a water-soluble dye is dissolved is generally used. However, in recent years, importance has been placed on water resistance and light resistance, and it is expected that a pigment having high robustness will be used as a colorant for a recording liquid for inkjet recording.

For example, Japanese Patent Application Laid-Open Nos. Hei 2-255875 and Hei 4-334870 disclose aqueous water-based pigment inks satisfying basic problems such as print quality, discharge characteristics, storage stability, and fixability. JP-A-4-57
JP-A-859 and JP-A-4-57860 disclose inks.

However, the pigment is not dissolved in the liquid medium as in the dye, but is dispersed, so that the stability in the liquid medium is poor, and the aggregation, sedimentation and separation of the pigment in the ink are reduced. The problem of generation and clogging of the nozzle portion has not been solved yet.

On the other hand, in recent years, the image quality and accuracy of the ink jet recording have been improved, and the discharge ports (nozzles) of the head used have conventionally been from φ33 μm to φ34 μm (about 900 μm ^{2 in} terms of area) to φ50 μm. ~ Φ51μ
m (approximately 2000 μm ^{2 in} terms of area), but a finer discharge port is required.
At that time, if a recording liquid in which a water-soluble dye is dissolved is used as the ink as in the related art, the problem of clogging can be solved because the dye is dissolved in the liquid medium. However, for pigment-based inks,
Clogging is a serious problem when a finer discharge port (for example, Φ25 μm or less, or opening area is less than 500 μm ² ) is obtained.

[0013]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and a first object of the present invention is to optimize the distance of the depth portion of the discharge port and the particle diameter to achieve a diameter of Φ25.
μm or less, or an extremely small discharge port with an opening area of less than 500 μm ² , realizes high-definition printing, and achieves high water resistance and high light fastness. Optimize the outside corner of the exit,
Provided is a highly reliable thermal inkjet recording head in which the pigment of the ink is less likely to accumulate and the ejection ports are not clogged.

A second object of the present invention is to provide a highly reliable thermal ink jet recording head which optimizes the surface roughness and the fine particle diameter of the depth portion of the discharge port, makes it difficult for the ink pigment to accumulate, does not cause clogging of the discharge port. .

A third object is to apply an ejection force to the ink so that the ink droplet ejection speed is equal to or higher than a certain value, thereby eliminating clogging of the ejection openings, and realizing stable ejection and high-quality recording. Provided is a thermal inkjet recording head.

[0016]

According to a first aspect of the present invention, a recording liquid is obtained by dispersing fine particles having a size of Dp (μm) in a liquid, and the recording liquid is instantaneously generated by heat. A thermal ink jet recording head which discharges from a fine discharge port by the action force of the ink and adheres to a recording medium to perform recording, wherein the end of the flow path is the discharge port as it is or When the discharge port is a discharge port having a separate discharge port formed at the end of the road, and the discharge port has an opening area of less than 500 μm ² and has a depth t of distance t, Dp / t ≤
A liquid jet recording apparatus having a discharge port having a head for discharging the recording liquid in which the fine particles are dispersed from the discharge port and a wiping mechanism for wiping an outer portion of the discharge port; (Chamfered shape) or r shape (circular shape), and the droop at the outer corner portion of the discharge port is c50Dp or less or r50Dp or less.

According to a second aspect of the present invention, the size of the liquid is D
Fine particles having a particle size of p (μm) are dispersed to form a recording liquid, and the recording liquid is discharged from a fine discharge port by the action of bubbles generated instantaneously by heat, and adheres to a recording medium to perform recording. In the thermal inkjet recording head, the discharge port is a discharge port in which the end of the flow path is the discharge port as it is or a discharge port in which a separate discharge port is formed at the end of the flow path, and the discharge port has a depth portion. When the discharge port has a surface roughness of R (s), 0.0
25 <Dp / R.

According to a third aspect of the present invention, in the second aspect of the present invention, an ejection force is applied to the recording liquid so that the ejection speed is 5 m / s or more.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the configuration and principle of an ink jet to which the present invention is applied will be described. As described above, there are various types of ink jet recording methods. Here, an example of a bubble ink jet type will be described as a representative example, but it is needless to say that the present invention is not limited to this method, but is applicable to all ink jet recording methods. However, among various types of ink jet recording methods, the so-called bubble ink jet recording method in which ink is heated to generate air bubbles is subjected to severe conditions (heat cycle), which leads to deterioration and accelerated chemical reaction. In addition, there is a technical problem that is more unfavorable for ink-jet such as clogging than other ink-jet recording methods in terms of dispersion instability of pigment and the like. The present invention is particularly suitably applied to the bubble inkjet recording method exposed to such severe conditions.

FIG. 1 is a view for explaining an example of a bubble ink jet recording head. FIG. 1 (A) is a perspective view of the head, FIG. 1 (B) is a perspective view of a lid substrate constituting the head,
FIG. 1C is a perspective view of the lid substrate viewed from the back side.
(D) is a perspective view of the heating element substrate, in which 1 is a lid substrate, 2 is a heating element substrate, 3 is a recording liquid inlet, 4 is a discharge port, 5 is a flow path, and 6 forms a liquid chamber. 7 is an individual (independent) control electrode, 8 is a common electrode, and 9 is a heating element.

FIG. 2 is a diagram for explaining the principle of ink droplet ejection of a bubble inkjet type ink jet. FIG. 2 (A) shows a steady state where the ink 10, surface tension and external pressure are in an equilibrium state at the ejection port surface. FIG. 2B shows a state in which the heating element 9 is heated until the surface temperature of the heating element 9 rises rapidly and a boiling phenomenon occurs in the adjacent ink layer, and fine bubbles 11 are scattered. Show.

FIG. 2C shows a state in which the adjacent ink layer rapidly heated over the entire surface of the heating element 9 is instantaneously vaporized, a boiling film is formed, and bubbles 11 grow. At this time, the pressure in the discharge port rises by the amount of the bubble that has grown, the balance with the external pressure on the discharge port surface is lost, and the ink column 10 'starts to grow from the discharge port.

FIG. 2D shows a state in which the bubble 11 has grown to a maximum, and ink corresponding to the volume of the bubble is pushed out from the discharge port surface. At this time, no current is flowing through the heating element 9 and the surface temperature of the heating element 9 is decreasing. The maximum value of the volume of the bubble 11 is slightly delayed from the timing of applying the electric pulse.

FIG. 2E shows a state in which the bubble 11 is cooled by ink or the like and starts to contract. Ink column 1
At the tip of 0 ', it moves forward while maintaining the pushed speed,
At the rear end, the ink flows backward from the discharge port surface into the discharge port due to a decrease in the pressure inside the discharge port due to the contraction of the bubble, and the ink column 1
There is a constriction 10 "at 0 '.

FIG. 2F shows a state in which the bubbles 11 further contract, the ink 10 comes into contact with the surface of the heating element 9, and the heating element surface is cooled more rapidly. On the discharge port surface, the external pressure is higher than the discharge port internal pressure, so that a large meniscus has entered the discharge port. The tip of the ink column is a droplet 12
And flying at a speed of 5 to 13 m / sec in the direction of the recording paper.

FIG. 2G shows that the bubbles are completely eliminated in the process in which the ink is again supplied (refilled) to the discharge ports by capillary action and returns to the state of FIG. 2A.

The general configuration and principle of a bubble ink jet recording head utilizing heat have been described above. However, as described above, the present invention is not limited to this method, and is applicable to all ink jet recording methods. Is what is done.

In the present invention, the recording liquid (ink) used in the above-described ink jet recording method uses a pigment having excellent water resistance and light resistance as a coloring agent of the recording liquid. However, when this pigment is used as a colorant for a recording liquid, the pigment is not dissolved in a liquid medium like a dye but is dispersed, so that the stability in the liquid medium is poor, and the There is a problem that aggregation, sedimentation and separation of the pigment occur and clogging of the nozzle portion occurs. In particular, clogging of the nozzle portion is a fatal problem for the ink jet because the ink is not ejected. Or, even if it is not clogged, it is difficult to eject ink droplets compared to the ink jet recording method using a normal dye as a colorant for the recording liquid for the above reasons, and stable ink droplet ejection and high precision dot position accuracy are achieved. There is a problem that it is difficult to support high-quality recording.

In order to solve the above-mentioned problems, the present invention has been made by studying the relationship between the material constituting the ink, the dimensions, shape, and properties of the nozzle portion, the pigment particle size used, the pigment content in the ink, and the like. It is. In the present invention, pigment ink is assumed. That is, the colorant in the recording liquid is not a dye dissolved in a solvent such as water, but a fine particle serving as a pigment dispersed therein.

The black pigment ink suitably applied to the present invention includes, for example, a black pigment having a neutral or basic pH, a tertiary amine salt or an acrylate monomer having a quaternary ammonium group. Alternatively, a dispersion treatment is carried out using a water-soluble polymer containing at least an acrylamide monomer as a component. For inks of other hues, for example, inks of yellow, magenta and cyan, pigments of these hues are also used. And a dispersion treatment using an anionic polymer dispersant having a carboxyl group or a sulfone group as a water-soluble group.

The pH of the black pigment referred to here is generally the pH of a solution obtained by dispersing a pigment in pure water in the same manner as in the method for measuring the physical properties of carbon black.
Refers to the H value. Further, when the recording material used for recording is plain paper, the interfacial tension of the black pigment ink is higher than that of the color ink in the interfacial tension of the ink with respect to the plain paper. It is preferable that the permeation speed of the black pigment ink is lower than the permeation speed of the color ink.

When color recording is performed on plain paper using the above-described ink, an image having good fixability, high density, and little boundary blur can be obtained. Also, a clear projected image can be obtained even when recording is performed on a recording material having transparency. And, needless to say, since the ink is a pigment ink, the resistance to light and water is extremely excellent as compared with the case where a conventional dye ink is used.

The polymer dispersant used in the present invention is obtained mainly by polymerization of a vinyl monomer. The cationic monomers constituting at least a part of the obtained polymer include the following tertiary monomers. And salts of quaternary amine monomers and their quaternized compounds.

That is, N, N-dimethylaminoethyl methacrylate [CH2 = C (CH3) -COO-C2H4N (CH3) 2],
N-dimethylaminoethyl acrylate [CH2 = CH-COO-C
2H4N (CH3) 2], N, N-dimethylaminopropyl methacrylate [CH2 = C (CH3) -COO-C3H6N (CH3) 2], N, N-dimethylaminopropyl acrylate [CH2 = CH-COO-C3H6N
(CH3) 2], N, N-dimethylacrylamide [CH2 = CH-C
ON (CH3) 2], N, N-dimethylmethacrylamide [CH2 =
C (CH3) -CON (CH3) 2], N, N-dimethylaminoethylacrylamide [CH2 = CH-CONHC2H4N (CH3) 2], N, N-dimethylaminoethylmethacrylamide [CH2 = C (CH3) -CON
HC2H4N (CH3) 2], N, N-dimethylaminopropylacrylamide [CH2 = CH-CONH-C3H6N (CH3) 2], N, N-dimethylaminopropylmethacrylamide [CH2 = C (CH3) -C
ONH-C3H6N (CH3) 2].

In the case of the tertiary amine, the compound forming a salt includes hydrochloric acid, sulfuric acid, acetic acid and the like.
Compounds used for the grading include methyl chloride, dimethyl sulfate, benzyl chloride, epichlorohydrin and the like. Among them, methyl chloride, dimethyl sulfate and the like are preferable in preparing a dispersant. The tertiary amine salt or the quaternary ammonium compound as described above behaves as a cation in water, and under neutralized conditions, acidity is a stable dissolution region. The content of these monomers in the copolymer is preferably in the range of 20 to 60% by weight.

Examples of the other monomers used in the constitution of the polymer dispersant include acrylic acid esters having a hydroxy group such as 2-hydroxyethyl methacrylate and acrylic acid esters having a long ethylene oxide chain in the side chain; Examples of hydrophobic monomers such as styrene monomers and water-soluble monomers soluble in water near pH 7 include acrylamides, vinyl ethers, vinylpyrrolidones, vinylpyridines, and vinyloxazolines. As the hydrophobic monomer, styrene,
Hydrophobic monomers such as styrene derivatives, vinyl naphthalene, vinyl naphthalene derivatives, alkyl esters of (meth) acrylic acid, and acrylonitrile are used. In the polymer dispersant obtained by copolymerization, a water-soluble monomer is used to make the copolymer stably exist in an aqueous solution.
Used in the range of 5 to 35% by weight, and the hydrophobic monomer is:
20 to improve the dispersing effect of the copolymer on the pigment
Preferably, it is used in the range of 40% by weight.

As the carbon black pigment (CI Pigment Black 7) used in the black ink of the present invention, # 2600, # 2300, # 990, # 980, #
960, # 950, # 900, # 850, # 750, #
650, MCF-88, MA-600, # 95, # 5
5, # 52, # 47, # 45, # 45L, # 44, # 4
0, # 33, # 32, # 30, # 25, # 20, # 1
0, # 5 (Mitsubishi Chemical), Printex95, Printex
90, Printex85, Printex80, Printex75, Print
ex45, Printex40, PrintexP, Printex60, Print
ex300, Printex30, Printex35, Printex25, P
rintex200, PrintexA, PrintexG, PrintexL6, P
rintexL (all made by Degussa), Raven850, Raven7
80 ULTRA, Raven 760 ULTRA, Raven 790
ULTRA, Raven520, Raven500, Raven41
0, Raven420, Raven430, Raven450, Raven4
60, Raven890, Raven1020 (all made in Colombia), Regal 415R, Regal330R, Regal250
R, Regal 995R, Monarch800, Monarch880,
Monarch900, Monarch460, Monarch280, Monar
ch120 (all manufactured by Cabot).

Pigments used for the yellow ink include CI Pigment Yellow 1, CI Pigment Yellow 2, CI Pigment Yellow 3, CI Pigment Yellow 12, CI Pigment Yellow 13, CI Pigment Yellow 14, CI Pigment Yellow 16, and CI Pigment Yellow 16.
Pigment Yellow 17, CI Pigment Yellow 7
3, CI Pigment Yellow 74, CI Pigment Yellow 75, CI Pigment Yellow 83, CI Pigment Yellow 93, CI Pigment Yellow 95, CI Pigment Yellow 97, CI Pigment Yellow 98,
CI Pigment Yellow 114, CI Pigment Yellow 128, CI Pigment Yellow 129, CI Pigment Yellow 151, and CI Pigment Yellow 154.

Pigments used in the magenta ink include CI Pigment Red 5, CI Pigment Red 7, CI Pigment Red 12, CI Pigment Red 48 (Ca), CI Pigment Red 48 (Mn), C.I.
I. Pigment Red 57 (Ca), CI Pigment Red 57: 1, CI Pigment Red 112, CI Pigment Red 123, CI Pigment Red 168, CI
Pigment Red 184, CI Pigment Red 202
And the like.

As the pigment used in the cyan ink,
CI Pigment Blue 1, CI Pigment Blue 2, C.I.
I. Pigment Blue 3, CI Pigment Blue 15:
3, CI Pigment Blue 15:34, CI Pigment Blue 16, CI Pigment Blue 22, CI Pigment Blue 60, CI Bat Blue 4, CI Bat Blue 60, and the like.

In addition to the above, when an intermediate color other than the three primary colors of red, green, blue and the like is required, it is preferable to use the following pigments alone or in combination. For example, CI Pigment Red 209, CI Pigment Red 122, CI Pigment Red 224,
CI Pigment Red 177, CI Pigment Red 1
94, CI Pigment Orange 43, CI Bat Violet 3, CI Pigment Violet 19, CI Pigment Green 36, CI Pigment Green 7, CI
Pigment Violet 23, CI Pigment Violet 37, CI Pigment Blue 15: 6, CI Pigment Blue 209 and the like.

Further, the following dyes may coexist in the color ink. Examples of the dye used in the yellow ink include CI Acid Yellow 1
1, CI Acid Yellow 17, CI Acid Yellow 23, CI Acid Yellow 25, CI Acid Yellow 29, CI Acid Yellow 42, CI Acid Yellow 49, CI Acid Yellow 61, CI Acid Yellow 71, CI Direct Yellow 12, CI Direct Yellow 24, CI Direct Yellow 26, CI
Direct Yellow 44, CI Direct Yellow 8
6, CI Direct Yellow 87, CI Direct Yellow 98, CI Direct Yellow 100, CI Direct Yellow 130, CI Direct Yellow 142, and the like.

The dyes used in the magenta ink include CI Acid Red 1, CI Acid Red 6, C.I.
I. Acid Red 8, CI Acid Red 32, CI Acid Red 35, CI Acid Red 37, CI Acid Red 51, CI Acid Red 52, CI Acid Red 80, CI Acid Red 85, CI Acid Red 87, CI Acid Red 92 CI Acid Red 94, CI Acid Red 115, CI Acid Red 180, CI Acid Red 254, CI Acid Red 256, CI Acid Red 289, CI Acid Red 315, CI Acid Red 317, CI Direct Red 1, CI Direct Red 4. , CI Direct Red 13, CI Direct Red 17, CI Direct Red 23, CI Direct Red 28, CI Direct Red 31, CI Direct Red 62, CI
Direct Red 79, CI Direct Red 81, C.
I. Direct Red 83, CI Direct Red 89,
CI Direct Red 227, CI Direct Red 2
40, CI Direct Red 242, CI Direct Red 243, and the like.

Dyes used for cyan ink include:
CI Acid Blue 9, CI Acid Blue 22, CI
Acid Blue 40, CI Acid Blue 59, CI Acid Blue 93, CI Acid Blue 102, CI Acid Blue 104, CI Acid Blue 113, CI
Acid Blue 117, CI Acid Blue 120, C.I.
I. Acid Blue 167, CI Acid Blue 229,
CI Acid Blue 234, CI Acid Blue 25
4, CI Direct Blue 6, CI Direct Blue 2
2, CI Direct Blue 25, CI Direct Blue 71, CI Direct Blue 78, CI Direct Blue 86, CI Direct Blue 90, CI Direct Blue 106, CI Direct Blue 199, and the like. However, even when these dyes coexist, the pigment particle size and the pigment content in the ink need to be within the ranges described below.

In the present invention, when the pigment is dispersed using the above-mentioned cationic water-soluble polymer as a dispersant,
Pigments whose isoelectric point is adjusted to 6 or more, or those having a neutral or basic pH of a simple aqueous dispersion characterizing the pigment, for example, 7 to 10 Certain pigments are preferred in terms of dispersibility. This is understood to be due to the strong ionic interaction between the pigment and the cationic water-soluble polymer.

In order to obtain an aqueous dispersion of fine particles of a pigment using the above materials, it is preferable to employ the following method. (1) In the case of carbon black: carbon black is premixed in a cationic dispersant solution, subsequently milled in a high shear rate disperser, diluted, and then centrifuged to remove coarse particles. . afterwards,
Materials for the desired ink formulation are added and, optionally, subjected to aging. Thereafter, centrifugation is performed to finally obtain a pigment dispersion having a desired average particle size. The pH of the ink thus produced is 3 to
It is preferred to be in the range of 9.

(2) In the case of pigments of other hues: Basically the same as carbon black except that an anionic dispersant is used. However, in the case of an organic pigment that is difficult to reduce the particle size, a surfactant treatment is performed simultaneously with or during the synthesis of the pigment to suppress crystal growth of the pigment particles and to improve wettability. It is desirable to use pigments. The pH of the ink thus prepared is preferably in the range of 5 to 10. The average particle size of both the carbon black ink and the color ink is 0.02 to 1
The range of μm is essential for the stability of the dispersion,
Preferably, it is in the range of 0.03 to 0.4 μm. This is an essential condition from the viewpoint of the stability of the dispersion. However, from the viewpoint of indispensable for the so-called ink jet that discharges ink from a fine opening, considering the average particle size, it is necessary to consider the fineness of the fine opening, that is, the discharge port. Clogging needs to be taken into account, which will be described later. A good surface tension of the ink is in a range of 10 to 60 dyn / cm.

When recording on plain paper using these inks, it is preferable that the black pigment ink has a high interfacial tension with the paper in view of the clarity of the recorded characters. On the other hand, the color ink preferably has a high penetration rate in order to reduce bleeding (color bleed) due to mutual diffusion between the color inks. Therefore, it is preferable that the interfacial tension with paper is low. As described above, when the black ink is acidic and has a high interfacial tension, and the color ink is basic and has a low interfacial tension, the tendency of the black ink to flow into the color ink side is reduced, and the black ink and the color ink have a lower interfacial tension. There is virtually no color bleed. The interfacial tension between the ink and the paper is measured by, for example, a device commercially available as a dynamic wettability tester (a device using the Wilhelmy method, manufactured by WET-3000 Resca Corporation) or the like. Quantity. A high interfacial tension means that the contact angle with plain paper is 90 ° or more even in a short time of 1 second to several seconds, and a low interfacial tension means that the contact angle is 90 ° or less.

The dispersant used in the color ink used in the present invention is an alkali-soluble water-soluble aliphatic tree, and has a weight average molecular weight of 1,000 to 30,000, preferably 3,000 to 15, 000. In particular,
Hydrophobic monomers such as styrene, styrene derivatives, vinylnaphthalene, vinylnaphthalene derivatives, alkyl esters of acrylic acid and alkyl esters of methacrylic acid;
Copolymers composed of hydrophilic monomers such as α, β-ethylenically unsaturated carboxylic acids and their aliphatic alcohol esters, acrylic acid, methacrylic acid, maleic acid, itaconic acid, fumaric acid and derivatives thereof, and salts thereof. It is. The copolymer may have any structure such as random, block and graft, and the acid value is in the range of 100 to 430, preferably 130 to 360.

As the dispersant used in the present invention, a water-soluble polymer such as polyvinyl alcohol and carboxymethyl cellulose, a water-soluble resin such as naphthalenesulfonic acid formaldehyde condensate and polystyrenesulfonic acid can be used. . However, an alkali-soluble water-soluble oily tree has the advantage that the viscosity of the dispersion can be reduced and the dispersion is easy. The amount of these dispersants used is determined experimentally using the selected pigment and dispersant, but the amount of resin dissolved without adsorbing on the pigment is 4% by weight or less in the ink. Is preferred.

In order to use the above dispersant in an aqueous system, a base is required. Suitable bases therefor include ethanolamine, diethanolamine, triethanolamine,
N-methylethanolamine, N-ethyldiethanolamine, 2-amino-2-methylpropanol, 2-ethyl-2-amino-1,3-propanediol, 2-
Organic bases such as (2-aminoethyl) ethanolamine, tris (hydroxymethyl) aminomethane, ammonia, piperidine, morpholine, β-dihydroxyethylurea, and inorganic bases such as sodium hydroxide, potassium hydroxide, and lithium hydroxide. No. The optimum base type varies depending on the type of the selected pigment and dispersant, but is preferably a non-volatile, stable, and high water retention property. The amount of the base used is basically used from the amount calculated from the acid value of the dispersant as the amount of the base required for neutralizing the same. In some cases, more than the equivalent of acid is used. This is performed for the purpose of improving the dispersibility, adjusting the pH of the ink, adjusting the recording performance, improving the moisture retention, and the like.

The solvent used in the ink of the present invention is an organic solvent miscible with water. Organic solvents can be divided into three groups as described below. That is,
A first group of solvents that has high moisture retention, is difficult to evaporate, and has excellent hydrophilicity. A second group of solvents that has good wettability to organic and hydrophobic surfaces and has good evaporation and drying properties. It is a third group of solvents (monohydric alcohols) having low viscosity.

The solvents belonging to the first group include ethylene glycol, diethylene glycol, triethylene glycol, tripropylene glycol, glycerin,
2,4-butanetriol, 1,2,6-hexanetriol, 1,2,5-pentanetriol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, dimethylsulfoxide, die Acetone alcohol, glycerin monoallyl ether, propylene glycol, butylene glycol, polyethylene glycol 300, thiodiglycol, N-methyl-2-pyrrolidone, 2-pyrrolidone, γ-butyrolactone, 1,3-
Dimethyl-2-imidazolidinone, sulfolane, trimethylolpropane, trimethylolethane, neopentyl glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monoallyl ether, diethylene glycol monomethyl ether, diethylene glycol Monoethyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, β-dihydroxyethyl urea,
Urea, acetonylacetone, pentaerythritol,
1,4-cyclohexanediol and the like can be mentioned.

Solvents belonging to the second group include hexylene glycol, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, ethylene glycol monophenyl ether, diethylene glycol diethyl ether, diethylene glycol monobutyl ether, and diethylene glycol monoisobutyl. Ether, triethylene glycol monobutyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether Ter, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, glycerin monoacetate, glycerin diacetate, glycerin triacetate, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether acetate, cyclohexanol, 1,2- Cyclohexanediol, 1-butanol, 3-methyl-1,5-pentanediol, 3-hexene-2,5-diol, 2,3-butanediol,
Examples thereof include 1,5-pentanediol, 2,4-pentanediol, and 2,5-hexanediol.

The solvents belonging to the third group include ethanol, n-propanol, 2-propanol, 1-methoxy-2-propanol, furfuryl alcohol, tetrahydrofurfuryl alcohol and the like. It is preferable that the total amount of the water-soluble solvent as described above is generally in the range of 5 to 40% by weight based on the whole ink.

A surfactant, a pH adjuster, a preservative and the like can be added to each aqueous pigment ink constituting the ink of the present invention. The surfactant is useful for preparing a color ink having a high permeability, a heating heater in a bubble ink jet system, and adjusting wettability to the surface of a discharge nozzle. The material can be appropriately selected from existing commercial products. To summarize the physical properties of each ink composed of the above materials, the black ink has a high surface tension (approximately 3).
0 to 60 dyn / cm), while the color ink preferably has a low surface tension (approximately 10 to 40 dyn / cm).

When color recording is performed on plain paper using the black aqueous pigment ink and the color ink of the present invention as described above, black characters and the like are clear, and images and graphs and black characters are clearly displayed. Even if they are adjacent to each other, there is no mutual bleeding and each is clear.

When the color ink of the present invention is used, the recording material may be any of ordinary plain paper (for example, high quality paper, medium quality paper or bond paper), coated paper, OHP plastic film and the like. Can be used. As described above, the present invention can be applied to all ink jet recording methods, and is particularly suitable for use in an ink jet recording method of a type in which ink is ejected by a bubbling phenomenon of ink due to thermal energy. Is extremely stable and does not generate satellite dots. However, in this case, it may be necessary to adjust thermal physical properties, for example, specific gravity, thermal expansion coefficient, thermal conductivity, and the like.

Next, more characteristic points of the present invention will be described. As described above, the present invention relates to a so-called ink jet recording method in which ink is ejected from a fine opening, and clogging at an ejection port is fatal to the ink jet recording method.
This is the case using pigment ink in which fine particles are dispersed in a solvent, as in the present invention, rather than using dye ink, the pigment is not dissolved like dye but only dispersed. Therefore, clogging is more likely to occur. Further, in the present invention, an ink jet recording head having an unprecedented fine ejection opening, for example, an ejection opening having a diameter of 25 μm or less (in terms of area, less than 500 μm ² ) is assumed. It is a very serious problem.

Incidentally, the clogging is derived from the principle of the ink jet recording system in which ink is ejected from a fine opening. In other words, this occurs because the opening is fine. Therefore, there is a close relationship between the dimensions, shape, and properties of the opening, that is, the discharge port, and the size of the pigment, which may be called foreign matter in the ink.

In view of this point, the present invention pays attention to each dimension, shape, and property of the discharge port and the size of the pigment particles.
It is a finding of the difficulty of clogging and their relationship. Specifically, inks having different pigment particle diameters are prepared, and ink jetting is performed for a certain period of time using an ink jet recording head whose dimensions, shape, and properties are known, and then left for a certain period of time to perform ink jetting. The operation was restarted and clogging of the discharge port was examined. In this case, not only the complete obstruction of the discharge port, but also partial clogging and the prior signs (slight clogging) leading to it were considered as clogging and tested.

The head used was an ink jet recording type head using thermal energy having a configuration as shown in FIG. However, the head shown in FIG. 1 shows a head in which the end of the flow path is the discharge port as it is, but the head used in the experiment is, as shown in FIG. A nozzle plate 20 having nozzles 21 formed at the same arrangement density is provided (note that in FIG. 3, FIG. 3A shows a state before the nozzle plate 20 is attached to the head shown in FIG. 1A). FIG. 3B is a perspective view showing the situation.
Is a perspective view after the nozzle plate 20 is attached). The number of discharge ports (nozzles) shown in FIGS. 1 and 3 has only four discharge ports for simplicity of explanation, but the number of discharge ports actually used was The number is 128 and the array density is 400 dpi. Also,
The size of the heating element was 22 μm × 90 μm, the resistance value was 110Ω, the driving voltage for ink ejection was 24 V, the driving pulse width was 6.5 μs, and the driving frequency was 12 kHz. In addition, three types of heads (H1 to H3) were prepared for the recording head, each having a discharge port diameter of Φ25 μm and a different discharge port thickness (distance of a depth portion of the discharge port) (thickness of each discharge port). T = 40 μm (H1), 50 μm (H
2), 60 μm (H3)).

The ink used has the following composition and manufacturing method, but has a pigment particle size of 0.005 to 4
Samples having a diameter of up to μm were prepared and tested in combination with heads H1 to H3 having different ejection apertures. In addition, the condition for leaving after the ink is ejected for a certain period of time is that the substrate is left for 10 hours in an atmosphere at a temperature of 40 ° C. and a humidity of 30%.

The method for producing the ink is described below. An acid value of 290 consisting of styrene / acrylic acid / ethyl acrylate;
Using an aqueous solution obtained by dissolving a copolymer P having a weight average molecular weight of 5,000 and a glass transition temperature of 77 ° C. using monoethanolamine, an anthraquinone pigment Pigment Red-1 was used.
77 dispersions D1 to D20 were prepared.・ Copolymer P aqueous solution (solid content 15% by weight) 40 parts ・ Pigment Red-177 (Chromophtal Red A2B, manufactured by Ciba Geigy) 24 parts ・ Diethylene glycol 20 parts ・ Isopropyl alcohol 10 parts ・ Water 130 parts

These materials were placed in a batch type vertical sand mill (made by Imex), filled with glass beads of 1 mm diameter as a medium, and subjected to a dispersion treatment for 3 hours while cooling with water. After the dispersion, a crude dispersion having a viscosity of 30 cP and a pH of 9.8 was obtained. The dispersion was centrifuged to remove coarse particles, and dispersions D1 to D20 in which the average particle size of the pigment was changed to 0.005 to 4 μm by changing the conditions of centrifugation variously. These dispersions were diluted with water, diethylene glycol, ethylene glycol monobutyl ether (60:25:15 weight ratio) and had a viscosity of 3c.
P, red basic inkjet inks R1 to R20 having a surface tension of 40 dyn / cm and a pH of 9.5 were obtained. The solids content of the final preparation was about 7.5% by weight. The final pigment content in these inks is 5% by weight.

The average particle size was measured by a particle size distribution analyzer ELS-800 (manufactured by Otsuka Electronics Co., Ltd.) by a dynamic light scattering method, and the average amount was indicated by a value obtained from the initial gradient of the autocorrelation function. . Tables 1 to 3 show the results of examining the state of clogging by combining these inks R1 to R20 and heads having different thicknesses of the above-described ejection openings (distances at the depths of the ejection openings). .

[0067]

[Table 1]

[0068]

[Table 2]

[0069]

[Table 3]

From the above results, the pigment particle diameter Dp and the distance (nozzle thickness) t at the depth of the discharge port are: Dp / t ≦
It can be seen that if the relationship of 0.01 is satisfied, stable ink ejection without clogging can be obtained. Note that, depending on the configuration of the head, the flow path and the discharge port (nozzle) may be continuously connected, but the distance (nozzle thickness) t of the depth part of the discharge port (nozzle thickness) in the present invention. Means a distance and a thickness of a portion substantially constituting the nozzle.

Next, another feature of the present invention will be described.
As described above, the colorant in the recording liquid of the present invention is not a dye dissolved in a dissolution medium such as water, but a fine particle as a pigment dispersed therein. According to the above-described results, even in the case of such a so-called pigment ink, if the relationship between the pigment particle diameter and the distance (nozzle thickness) at the depth of the discharge port is within a certain range, clogging may not occur. Okay, to use these pigment inks to eject ink droplets,
In addition to clogging, it is necessary to eject ink droplets on a recording medium, such as paper, in a stable manner and with high accuracy at a target position.

Here, the relationship between the distance t (nozzle thickness) at the depth of the discharge port, which is often related to clogging, and the distance L from the discharge port surface to a recording medium such as paper was examined. The heads used were the above-described heads H1 to H3, had a discharge aperture of 25 μm, had 128 nozzles, and had an array density of 400 dpi. The size of the heating element is 22 μm × 90 μm, its resistance value is 110Ω, the driving voltage for ink ejection is 24 V, the driving pulse width is 6.5 μs, and the driving frequency is 12 kHz.

The ink used was the aforementioned ink R5 for a red basic ink jet head. A matte coat NM made by Mitsubishi Paper Mills was used as a recording medium, and the distance from the discharge port surface of the head to the recording medium was changed. By performing a printing experiment and evaluating the pixel position accuracy on the recording medium, it was evaluated whether high-quality recording (high dot position accuracy) could be obtained. In the case of a head having a small ejection port and using a pigment ink, which is difficult to eject as compared with the conventional ink jet head as in the present invention, in order to find a slightly better condition, it is considered that the gravitational action also has an effect. The direction in which ink droplets are ejected in a direction substantially perpendicular to the
The different injection directions were evaluated. Table 4 shows the results.

[0074]

[Table 4]

In Table 4, ○ indicates that the deviation from the target dot position is within 1/4 dot, Δ indicates that the deviation from the target dot position is 1/4 dot or more, and
When it is within the dots, x indicates that the deviation from the target dot position is 1/2 dot or more. The size of one dot is about Φ60 μm.

From the above results, even if the head used in the present invention has a small ejection port, uses a pigment ink, and is hard to eject compared to the conventional head, the distance from the ejection port to the recording surface is 100 tons. By performing the following, it can be seen that stable ejection can be performed, high dot position accuracy can be obtained, and high image quality recording can be realized. In particular, the injection direction is vertical,
It can also be seen that the effect is increased by using the gravitational action.

It should be noted that the present invention is not necessarily limited to completely vertical, and it is said that it is more effective if gravity is used. Therefore, when actually using the present invention, even if it is not possible to make the ejection direction completely vertical due to the restriction on the configuration of the printer, it is necessary to make the ejection downward so that the gravitational action can be used at all. It just needs to be.

Next, still another feature of the present invention will be described. As described above, the colorant in the recording liquid of the present invention is:
It is not a dye dissolved in a solvent such as water, but a fine particle serving as a pigment dispersed therein. However, this pigment does not dissolve in a liquid medium like a dye,
Due to the dispersion, the stability in the liquid medium is poor, and aggregation, sedimentation, and separation of the pigment of the ink are likely to occur. In particular, depending on the shape of the discharge port, the aggregated pigment may easily accumulate and accelerate clogging.

In the liquid jet recording apparatus of the present invention having the clogging factor as described above, the reliability maintenance / recovery apparatus is an essential component. As a reliability maintenance and recovery device,
A structure is used in which the dirt on the outer surface of the discharge port is wiped off with a blade made of rubber, plastic, metal, or the like, or with a moisture absorbing member such as a sponge. Needless to say, it is also essential to cap the ejection port portion of the head. Here, an example of a specific mechanism of such a wiping structure will be described. For example, in the case of a serial printer type in which the head reciprocates and prints in front of the recording medium, a moisture absorbing member such as a blade or a sponge is provided near the home position of the carriage on which the head is mounted, and the ejection port of the head is provided. By arranging it so as to be in contact with the surface, the wiping operation is performed by the relative movement between the discharge port surface due to the movement of the carriage and the moisture absorbing member such as a blade or a sponge.

In this wiping operation, what is most problematic is who at the outer corner of the discharge port. 4 to 6 are views showing the state of the outer corner portion of the discharge port.
Shows the shape of the outer corner portion (4A ₁ ) having an r shape (circle), and FIG. 5 shows the shape of the outer corner portion (4A ₂ ) having a c shape (chamfered shape). Ideally, the outer corner (4A ₃ ) should have a sharp s shape (right angle shape) as shown in FIG. If this wiping the ejection extraoral side by reliability maintenance and recovery mechanism (wiping), if turned sharp shape (4A ₃ parts of FIG. 6), whereas the unnecessary ink ejection extraoral side cleanly removed, It is also evident from the fact that if there is anyone in the outer corner portion, the ink remaining in that portion inevitably dries and solidifies, and the precipitated pigment tends to accumulate. The precipitated pigment causes clogging. However,
From the viewpoint of mass production processing of the discharge port, it is costly to make the outer corner portion of the discharge port a completely sharp shape, and it is not always advisable to make the shape completely sharp.

The present invention has been made in view of the above-mentioned circumstances, and it has been experimentally determined to what extent the outer corner portion of the discharge port can be suppressed to prevent pigment precipitation / clogging. It has been clarified. Specifically, heads having different sizes at the outer corners of the discharge ports were prepared, and the same clogging test as described above was performed. That is, a head in which the size of the outer corner portion of the discharge port is changed based on the H2 head described above is prepared, and the ink is supplied to R5, R7, R9 and R6, R9.
8. A clogging test was performed using R10. As for the size of the outer corner portion of the discharge port, a c-shaped one and an r-shaped one were prepared, but a small r-shaped one could not be prepared. Note that such c
For the chamfering of the shape or the r-shape, a sharply shaped Ni nozzle was originally prepared without chamfering, and the chamfering (shape) was formed by chemical etching and electrolytic etching.

The other conditions are the same as those described above. The discharge diameter is Φ25 μm, the number is 128, and the array density is 400 dpi. The size of the heating element is 22 μm × 90 μm, its resistance value is 110Ω, the driving voltage for ink ejection is 24 V, the driving pulse width is 6.5 μs, and the driving frequency is 12 kHz. The conditions for leaving were the same, but this time, the discharge port surface was wiped off with a rubber blade, and then left. The results are shown in Tables 5 and 6.
Here, ○ indicates that no clogging occurred, and Δ indicates 128
In the case of one of the 128 pieces, the ejection was disturbed, and in the case of one of the 128 pieces, clogging occurred (clogging can be clearly determined).

[0083]

[Table 5]

[0084]

[Table 6]

From the above results, when the reliability is ensured by wiping the outer portion of the discharge port of the head for discharging the recording liquid in which the recording liquid in which the fine particles are dispersed from the discharge port, the recording liquid is dispersed. If the droop (chamfer) of the outer corner portion of the exit is c-shaped or r-shaped, it is c50Dp or less or r50Dp or less.
It can be seen that the pigment does not accumulate in any part and no clogging occurs.

Next, still another feature of the present invention will be described. As described above, the colorant in the recording liquid of the present invention is not a dye dissolved in a solvent such as water, but is a dispersion of fine particles as a pigment. Poorly, aggregation, sedimentation and separation of the pigment in the ink are likely to occur. In particular, depending on the properties of the discharge port, the aggregated pigment may easily accumulate and accelerate clogging. Specifically, it is the surface property of the discharge port, that is, the surface roughness. In particular, the surface roughness of the inner wall portion where the recording liquid actually flows.

The present invention has been made in view of the above circumstances, and it is experimentally clarified how much the surface roughness of the inner wall of the discharge port can be prevented to prevent the occurrence of pigment deposition / clogging. It was made. Specifically, heads having different surface roughness of the inner wall portion of the discharge port were prepared, and the same clogging test as described above was performed. That is, a head is prepared in which the surface roughness R of the inner wall portion of the discharge port (the depth portion of the discharge port indicated by the above-described distance t) is changed based on the H2 head described above.
A clogging test was performed using R5, R9, and R11 inks. The nozzle was SUS3 with a thickness t = 50 μm.
No. 04 was machined by electric discharge machining so that the discharge port diameter became Φ25 μm, and the surface roughness R was changed by changing the conditions of electric discharge machining.
Were prepared from 0.1 s to 5 s. The surface roughness R was calculated by SEM observation.

The other conditions are the same as those described above. The number of ejection ports is 128 per head and the arrangement density is 400 dpi. The size of the heating element is 22
μm × 90 μm, the resistance value is 110Ω, the driving voltage for ink ejection is 24 V, and the driving pulse width is 6.5 μm.
s, the driving frequency is 12 kHz. The conditions of leaving are the same. Table 7 shows the results. Here, ○ indicates that no clogging occurred, Δ indicates that even one of the 128 nozzles disturbed the injection, and x indicates that one of the 128 nozzles had a clogging (which can be clearly identified as clogging) ).

[0089]

[Table 7]

From the above results, the size of the liquid is Dp
(Μm) in a liquid jet recording apparatus in which a pigment ink in which fine particles are dispersed is ejected from a fine ejection port and adheres to a recording medium to perform recording, the ejection port has a surface roughness R in the depth portion. In the case of (s), 0.025 <
It can be seen that if the combination is selected so as to be Dp / R, highly reliable ink droplet ejection without clogging can be obtained.

Next, still another feature of the present invention will be described. In a liquid jet recording apparatus using a so-called pigment ink as in the present invention, not only the condition for clogging is very severe compared to that of a conventional dye ink, but also a conventional dye ink is used. In addition, there is a problem that it is difficult to stably eject ink droplets as compared with a nozzle having a large ejection opening diameter. Therefore, here, a method of driving the head of the liquid jet recording apparatus according to the present invention was studied.

The heads used were H4 to H6 heads shown in Table 8, and the ink used was R5. The ink used for the reference head is a dye ink, and its composition is glycerin: 18.0%, ethyl alcohol: 4.7
%, Water: 75.0%, dye (Acid Red 35): 2.
3%.

[0093]

[Table 8]

Using these heads and inks, heads H4 to H6 have driving voltages for ink ejection of 18V to 2V.
4V, drive pulse width 6.5μs, drive frequency 12k
Hz, the reference head has a drive voltage of 28
V to 30 V, drive pulse width 7 μs, drive frequency 3 k
Hz, conditions for stable injection were examined. The term “stable” as used herein means that a good ink droplet is formed and a flight without fluctuation is performed. The results are shown in Table 9, and Table 10 shows Reference Examples.

[0095]

[Table 9]

[0096]

[Table 10]

From the above results, in order to stably eject the pigment ink with an ink jet head having a fine discharge port which has not existed conventionally as in the present invention, the flying speed is 5 m.
It can be seen that it is necessary to set the driving conditions so that the speed is higher than / s, and to apply the ejection force to the ink. In addition, it can be seen that a conventional head having a large discharge aperture and using a dye ink is stable even if the flying speed is somewhat low. This is because ink droplets ejected from a head having a larger ejection aperture than conventional ones are less susceptible to disturbances because of their large mass, but as in the present invention, ink droplets having smaller ejection apertures than ever before The ink droplets ejected from the head have a very small mass, and are susceptible to disturbances. Therefore, it is considered that the ink droplets cannot be stably ejected unless ejection is performed at a somewhat high speed. . This experiment was performed using a so-called bubble ink jet head. However, even in the case of a piezo type head, similarly, the driving conditions were set so that the flying speed was higher than 5 m / s, and the ink was ejected to the ink. Needless to say, it is necessary to apply an acting force.

[0098]

According to the first aspect of the present invention, a thermal ink jet recording head for dispersing a pigment, which is a fine particle as a colorant, to form a recording liquid is subjected to heat and is placed in a severe condition. Since the distance of the depth part and the diameter of the fine particles have been optimized, an extremely fine discharge port which is not conventionally used such that the opening area is less than 500 μm ² is used,
Achieved high-definition printing, high water resistance and high light resistance, and optimized the drooping of the outer corners of the discharge port, making it difficult for the ink pigment to collect and clogging the discharge port. Reliability has improved.

According to the second aspect of the invention, a thermal ink jet recording head in which a pigment, which is fine particles as a coloring material, is dispersed and used as a recording liquid is subjected to heat and is placed in a severe state. Since the surface roughness and the fine particle diameter of the portion were optimized, the pigment of the ink was less likely to accumulate, the clogging of the discharge port was eliminated, and the reliability was improved.

According to the third aspect of the invention, a thermal ink jet recording head in which a pigment, which is a fine particle as a coloring material, is dispersed and used as a recording liquid is subjected to heat and is placed in a severe state. Since the ejection force is applied to the ink so as to be greater than or equal to a certain value, not only is the clogging of the ejection port eliminated, but also stable ejection and high-quality recording can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining an example of a bubble ink jet recording head.

FIG. 2 is a diagram for explaining the principle of ink droplet ejection of a bubble inkjet type inkjet.

FIG. 3 is a diagram illustrating an example of an inkjet head having a nozzle plate.

FIG. 4 is a diagram showing an example in a case where a discharge portion at an outer corner portion of a discharge port is r-shaped (circular).

FIG. 5 is a diagram illustrating an example in which a discharge portion at an outer corner portion of a discharge port has a c shape (chamfered shape).

FIG. 6 is a diagram illustrating an example of a case where a discharge portion at an outer corner portion of a discharge port has a sharp shape (right angle shape).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Lid board, 2 ... Heating element board, 3 ... Recording liquid inflow port, 4
... Discharge port, 5 ... Channel groove, 6 ... Common liquid chamber, 7 ... Individual lead electrode, 8 ... Common lead electrode, 9 ... Heating element, 10 ... Ink, 10 '... Ink column, 11 ... Bubble, 12 ... Liquid drop.

Claims (3)

[Claims] A recording liquid is prepared by dispersing fine particles having a size of Dp (μm) in a liquid, and the recording liquid is discharged from a fine discharge port by the action of bubbles generated instantaneously by heat. A thermal ink jet recording head for performing recording by adhering to a recording medium, wherein the discharge port has the end of the flow path as it is or the discharge port is formed separately at the end of the flow path Discharge port,
In addition, when the ejection port has an opening area of less than 500 μm ² and has a depth t of a distance t, in a liquid jet recording apparatus where Dp / t ≦ 0.01, A head for discharging a recording liquid in which fine particles are dispersed, and a wiping mechanism for wiping an outer portion of the discharge port, wherein a shape of an outer corner portion of the discharge port is c-shaped (chamfered) or r-shaped (circular); The droop at the outer corner of the discharge port is c50Dp or less or r
A thermal ink jet recording head having a density of 50 Dp or less. 2. A recording liquid, in which fine particles having a size of Dp (μm) are dispersed in a liquid, and the recording liquid is discharged from a fine discharge port by the action of bubbles generated instantaneously by heat. In a thermal ink jet recording head that performs recording by adhering to a recording medium, the discharge port may be a discharge port in which an end of the flow path is used as it is or a discharge port is separately formed at an end of the flow path. A thermal ink jet recording head, characterized in that, when the outlet is an outlet having a surface roughness R (s) in a depth portion, 0.025 <Dp / R. 3. The recording liquid has a discharge speed of 5 m / s.
3. The thermal ink jet recording head according to claim 2, wherein the ejection action force is applied as described above.