JP2003200575A - Ejector for ejecting liquid containing fine particles and ejection head for use therein - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an ejector for ejecting liquid containing fine particles from a fine opening and sticking it to an article being stuck in which the ejection opening is prevented from clogging even when a very fine ejection opening is employed by setting a diameter of fine particle optimal to the diameter of the ejection opening. <P>SOLUTION: Liquid dispersed with fine particles is ejected from a fine opening of Φ25 μm or less and stuck to an article being stuck. The size Dp of the fine particle and the size Do of the opening are set to satisfy a relation; 0.001≤Dp/Do≤0.01. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid ejecting apparatus for ejecting a recording liquid in which fine particles are dispersed and an ejecting head used in the liquid ejecting apparatus.

[0002]

2. Description of the Related Art The non-impact recording method has recently attracted interest in that noise generation during recording is negligibly small. Among them, the so-called inkjet recording method, which is capable of high-speed recording and can perform recording without requiring a special fixing process on so-called plain paper, is
There are extremely powerful recording methods, some of which have been proposed and improved in the past, and some of which have been commercialized, while others are still being put into practical use.

In such an ink jet recording method, recording is performed by ejecting droplets of a recording liquid, which is so-called ink, and adhering the droplets to a recording member for recording. There are various methods as described below, depending on the generation method and the method for controlling the flight direction of the generated recording liquid droplets.

For example, in the case of the Tele type method (Patent Document 1), the droplets of the recording liquid are generated by electrostatic attraction, and the generated recording liquid droplets are subjected to an electric field control according to a recording signal. There is an electrostatic suction type in which a recording liquid droplet is selectively adhered to a recording member to perform recording.

Further, in the case of the Sweet method (Patent Documents 2 and 3), a small droplet of the recording liquid of which the charge amount is controlled is generated by the continuous vibration generating method, and the generated charge amount is controlled. There are a continuous flow type and a charge control type in which recording is performed on a recording member by causing a droplet to fly between deflection electrodes to which a uniform electric field is applied.

Another method is the Hertz method (Patent Document 4), in which an electric field is applied between the discharge port and the ring-shaped charging electrode to generate small droplets of the recording liquid by the continuous vibration generating method. There is a system that records by converting. That is,
In this method, the atomization state of the droplet is controlled by modulating the electric field strength applied between the discharge port and the charging electrode according to the recording signal, and the gradation of the recorded image is produced and recording is performed.

Furthermore, as another method, there is a Stemme method (Patent Document 5). This method is fundamentally different in principle from the above three methods. That is, in all of the above-mentioned three methods, the droplets of the recording liquid ejected from the ejection port are electrically controlled during the flight, and the droplets carrying the recording signal are selectively deposited on the recording member. On the other hand, the Stemme method is used to perform recording by ejecting and ejecting a small droplet of recording liquid from an ejection port according to a recording signal. In other words, the Stemme method applies an electrical recording signal to a piezoelectric vibrating element attached to a recording head having a discharge port for ejecting a recording liquid, and converts this electrical recording signal into mechanical vibration of the piezoelectric vibrating element. Recording is performed by ejecting and ejecting small droplets of the recording liquid from the ejection ports according to the mechanical vibrations and adhering them to the recording member, which is a so-called drop-on-demand type.

Furthermore, as another method, there is a method (Patent Document 6) previously proposed by the present applicant. 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 according to 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 inkjet type in which ink droplets are ejected from an ejection port by the action force of bubbles.

As described above, the ink jet recording method is
There are various methods depending on the principle, but the common thing is that so-called ink droplets of a recording liquid are used.
t) is ejected and adhered to the recording member for recording. The recording liquid called this ink is generally a recording liquid in which a water-soluble dye is dissolved. However, in recent years, importance has been placed on water resistance and light resistance, and it is expected that a pigment having strong fastness will be used as a colorant for a recording liquid for inkjet recording.

For example, as water-based pigment inks for ink jets that meet the basic problems such as print quality, ejection characteristics, storage stability, and fixability, there are JP-A-2-255875 (Patent Document 7) and JP-A-4. -334870 (Patent Document 8), JP-A-4-57859 (Patent Document 9) and JP-A-4-57860 (Patent Document 1)
The ink described in 0) is disclosed.

However, since this pigment is not dissolved in a liquid medium like a dye but is dispersed, the stability in the liquid medium is poor, and the pigment in the ink is agglomerated, settled or separated. The problem of generation and clogging of the nozzle has not been solved yet.

On the other hand, in recent years, high quality and high accuracy of ink jet recording have been advanced, and the ejection port (nozzle) of the head used is conventionally Φ33 μm to Φ34 μm (about 900 μm ^{2 in} area) to Φ50 μm. ~ Φ51μ
m (generally about 2000 μm ^{2 in} area) was generally used, but finer ejection ports have been demanded.
At that time, if a recording liquid in which a water-soluble dye is dissolved is used as the ink as in the conventional case, the dye is dissolved in the liquid medium, so that the problem of anti-clogging property can be dealt with. However, for pigment-based inks,
The clogging is a serious problem when a finer ejection port (for example, Φ25 μm or less) is formed.

Further, the recording liquid in which the above pigment is dispersed is scraped off the ink passage of the ink jet recording head when used for a long time as if river water containing gravel erodes mountains. It has the effect of damaging it. Even if this is a simple ink passage, there is no problem of some damage and wear, but damage and wear of the ejection port portion affects the ink droplet ejection performance, which is a problem.

In particular, in recent years, high quality and high accuracy of ink jet recording have been advanced, and the ejection port (nozzle) of the head used is conventionally Φ33 μm to Φ34 μm (about 900 μm ^{2 in} area) to Φ50 μm. Φ51 μm
(Area of about 2000 μm ² ) was common, but finer ejection ports (for example, Φ25 μm or less, less than 500 μm ² in terms of area) have been required. At that time, as in the conventional case, the one having a relatively large ejection port has almost no influence on the ink droplet ejection performance (ejection stability, ink mass uniformity, etc.) even if it is slightly damaged or worn. This is not a problem because it does not exist, but in the case of a finer ejection port (for example, Φ25 μm or less), the ink droplet ejection performance (ejection stability, ink mass uniformity) even with slight damage or abrasion. Etc.), which is a serious problem.

[0015]

[Patent Document 1] US Pat. No. 30,604,29

[Patent Document 2] US Pat. No. 3,596,275

[Patent Document 3] US Pat. No. 3,298,030

[Patent Document 4] US Pat. No. 3,416,153

[Patent Document 5] US Pat. No. 3,747,120

[Patent Document 6] Japanese Patent Publication No. 56-9429

[Patent Document 7] Japanese Patent Application Laid-Open No. 2-255875

[Patent Document 8] Japanese Patent Laid-Open No. 4-334870

[Patent Document 9] Japanese Unexamined Patent Publication No. 4-57859

[Patent Document 10] JP-A-4-57860

[0016]

DISCLOSURE OF THE INVENTION The first object of the present invention is to provide a fine particle-containing liquid ejecting apparatus for ejecting a liquid in which fine particles are dispersed through a fine opening and adhering the adherend to an adherend. It is to prevent clogging of the ejection port even if a very fine ejection port with a fine particle diameter of Φ25 μm or less, which is not used in the past, is used.

The second purpose is to apply the relationship between the discharge diameter and the fine particle diameter to a plurality of kinds of liquids in which different fine particles are dispersed for each liquid and an ejecting device for ejecting the liquids to disperse various fine particles. This is to prevent the discharge port from being clogged even if a liquid is used.

A third object is to optimize the content rate of fine particles and the amount of solid content in the liquid in a fine particle-containing liquid ejecting apparatus for ejecting a liquid in which fine particles are dispersed from a fine opening and adhering it to an adherend. To prevent clogging of the discharge port.

The fourth object is to apply the relationship between the content rate of fine particles and the amount of solid content to a plurality of kinds of liquids in which different fine particles are dispersed for each liquid and an ejecting apparatus for ejecting the liquids.
Even if a liquid in which various fine particles are dispersed is used, it is to prevent the discharge port from being clogged.

A fifth object is to optimize the distance and the diameter of the fine particles in the depth portion of the discharge port in the fine particle-containing liquid ejecting apparatus for discharging the liquid in which the fine particles are dispersed from the fine discharge port and adhering it to the adherend. , .PHI.25 .mu.m or less, it is to prevent clogging of the ejection port even if a very fine ejection port which has not been used in the past is used.

A sixth object is that in a fine particle-containing liquid ejecting apparatus for ejecting a liquid in which fine particles are dispersed from a fine ejection port and adhering it to an adherend, the fine particle-containing liquid is easily ejected. It is to prevent clogging of the outlet and to realize stable injection.

A seventh object of the present invention is to provide a fine particle-containing liquid ejecting apparatus for ejecting a liquid in which fine particles are dispersed from a fine ejection port and adhering it to an adherend, when the ejection port portion is formed of resin. By optimizing the hardness,
The purpose of this is to eliminate damage and friction at the ejection port portion and to ensure stable ejection without deterioration of droplet ejection performance.

An eighth object is to optimize the diameter of fine particles in a fine particle-containing liquid ejecting apparatus for ejecting a liquid in which fine particles are dispersed from a fine ejection port and adhering it to an adherend, and forming the ejection port portion with resin. Even in such a case, stable droplet ejection can be obtained, and damage and friction of the ejection port portion are eliminated, so that droplet ejection performance is not deteriorated and stable ejection can be obtained for a long period of time.

A ninth object is to optimize the relationship between the ejection opening diameter and the fine particle diameter of the ejection head used in the above-mentioned fine particle-containing liquid ejecting apparatus to eliminate clogging of the ejection opening,
It is to improve reliability.

[0025]

A first aspect of the present invention is a fine particle-containing liquid ejecting apparatus for ejecting a liquid in which fine particles are dispersed from a fine opening and adhering the liquid to an adherend, wherein the opening has a diameter of 25 μm or less, The size of the fine particles is Dp,
When the size of the minute opening is Do, 0.001 ≦ D
It is characterized in that p / Do ≦ 0.01.

In a second aspect based on the first aspect, the liquid to which the fine particles are attached is a plurality of types of liquid in which fine particles different for each liquid are dispersed, and the fine openings are provided in the plurality of types of fine particles. It is characterized in that it corresponds to a liquid in which is dispersed.

A third aspect of the present invention is a fine particle-containing liquid ejecting apparatus for ejecting a liquid in which fine particles are dispersed from a fine opening and adhering it to an adherend, wherein the opening has a diameter of 25 μm or less, and the fine particles in the recording liquid. Of 2 to 10% by weight and the amount of the solid content containing the fine particles in the liquid is 15% by weight or less.

In a fourth aspect based on the third aspect, the liquid in which the fine particles are dispersed is a plurality of types of liquid in which fine particles different for each liquid are dispersed, and the fine openings are used in the plurality of types of fine particles. It is characterized in that it corresponds to a liquid in which is dispersed.

In a fifth aspect, a liquid in which fine particles having a size of Dp are dispersed is discharged from a fine discharge port,
In the fine particle-containing liquid ejecting apparatus to be adhered to an adherend, the discharge port is a discharge port in which the end of the flow channel is the discharge port as it is, or a separate discharge port portion is formed at the end of the flow channel, In addition, the discharge port is Φ25 μm or less, and when the discharge port has a distance t in the depth portion, Dp / t ≦ 0.01.

A sixth invention is characterized in that, in the fifth invention, the distance from the ejection port to the adherend surface is 100 t or less, and the liquid is ejected from the ejection port in the direction of gravity action. is there.

In a seventh aspect of the present invention, in a fine particle-containing liquid ejecting apparatus for ejecting a liquid in which fine particles are dispersed through a fine opening and adhering it to an adherend, the member including the opening is made of a resin material. The opening diameter is Φ25μ
m or less, and the hardness of the resin material is 65 to 120 on the Rockwell M scale.
According to the seventh aspect of the present invention, by optimizing the hardness of the resin, damage and friction of the discharge port portion are eliminated, the droplet ejection performance is not deteriorated, and stable ejection can be obtained. When the discharge port diameter is relatively large, the hardness of the resin is not optimized as in the present invention, and the discharge port portion is damaged,
Even if there is some friction, the ratio of the damage to the ejection orifice diameter and the magnitude of the friction is small, and therefore the droplet ejection performance is not deteriorated. However, in the case of using a very fine discharge port which has not been used in the past and has a discharge port diameter of Φ25 μm or less as the object of the present invention, the hardness of the resin is not optimized and If the damage and friction are left to occur, the ratio of the size of the damage and friction to the fine discharge port diameter is large, and the droplet discharge performance deteriorates significantly, which becomes a problem. As is clear from the above description, the present invention is particularly effective in the case of using a very fine discharge port having a discharge port diameter of Φ25 μm or less, which has not been heretofore used.

An eighth invention is characterized in that, in the seventh invention, the fine particles have a particle diameter of 0.02 μm to 0.2 μm.

The invention of claim 9 is characterized by an ejecting head which is used in the liquid ejecting apparatus containing fine particles according to any one of the first to eighth aspects and ejects droplets.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION First, the constitution and principle of an ink jet to which the present invention is applied will be explained. As mentioned above, there are various ink jet recording methods.
Here, a bubble ink jet type will be described as a typical example, but needless to say, the present invention is not limited to this method and is applicable to all ink jet recording methods. However, among various inkjet recording methods, the so-called bubble inkjet recording method, in which ink is heated to generate bubbles, is exposed to harsh conditions (heat cycle), so deterioration and chemical reaction are accelerated. In view of unstable dispersion of pigments, there is a technical problem that is more unfavorable for inkjet, such as clogging, than other inkjet recording methods. The present invention is particularly suitably applied to the bubble inkjet recording method exposed to such severe conditions.

1A and 1B are views for explaining an example of a bubble ink jet type recording head. FIG. 1A is a perspective view of the head, and FIG. 1B 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, and FIG.
(D) is a perspective view of a 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 is a liquid chamber. Area 7 for controlling, 7 is an individual (independent) control electrode, 8 is a common electrode, and 9 is a heating element.

Here, the lid substrate 1 can be manufactured by forming the flow path 5 and the liquid chamber 6 on a glass substrate or a metal substrate by a method such as etching. The most preferable manufacturing method is forming by plastic molding. It is a technique. Although it costs a little to manufacture the first mold, since it can be mass-produced after that, the manufacturing cost per piece can be very low. At this time, in the present invention, as will be described later, by appropriately selecting the hardness of the plastic used, damage and wear of the portion of the ejection port 4 are eliminated, and stable ink droplet ejection is obtained.

FIG. 2 is a diagram for explaining the principle of ink droplet ejection of a bubble inkjet type inkjet. FIG. 2A shows a steady state in which the ink 10, the surface tension, and the external pressure are in equilibrium on the ejection port surface. Figure 2 (B)
Is heated until the heating element 9 is heated and the surface temperature of the heating element 9 rapidly rises to cause a boiling phenomenon in the adjacent ink layer, and the minute bubbles 11 are scattered.

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

FIG. 2D shows a state in which the bubble 11 has grown to the maximum, and ink corresponding to the volume of the bubble is pushed out from the ejection port surface. At this time, no current is flowing in 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. 2 (E) 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 ', move forward while maintaining the pushed speed,
At the rear end portion, the ink flows back from the ejection port surface into the ejection port due to the decrease in the ejection port internal pressure as the bubbles contract, and
There is a neck 10 "at 0 '.

In FIG. 2F, the bubble 11 is further contracted, the ink 10 is in contact with the surface of the heating element 9, and the surface of the heating element is further rapidly cooled. On the surface of the discharge port, the external pressure is higher than the internal pressure of the discharge port, so that a large meniscus enters the discharge port. Droplets 12 at the tip of the ink column
And flies toward the recording paper at a speed of 8 to 13 m / sec.

In FIG. 2G, the bubbles are completely extinguished during the process in which the ink is supplied (refilled) to the ejection port again by the capillary phenomenon and returns to the state of FIG. 2A.

3 is different from the head shown in FIG. 1 in that a nozzle plate 20 is additionally provided at the tip of the flow path.
3A is a state before the nozzle plate 20 is attached, FIG.
(B) shows the state after attachment. In this case as well, this nozzle plate is formed in a resin (plastic) film by, for example, punching the nozzle 21 by an excimer laser, or by a method such as metal etching, electroforming, punching, etc. It is necessary to select the hardness appropriately as described later.

The above is the general structure and principle of the bubble ink jet recording head utilizing heat, but as described above, the present invention is not limited to this system and is applicable to all ink jet recording methods. It is what is done.

In the present invention, the recording liquid (ink) used in such an ink jet recording method uses a pigment having excellent water resistance and light resistance as a colorant for the recording liquid. However, when this pigment is used as a colorant for a recording liquid, the pigment does not dissolve in a liquid medium like a dye but is dispersed, so that the stability in the liquid medium is poor and There is a problem in that pigment agglomeration, sedimentation and separation occur, and the nozzle part is clogged. In particular, the clogging of the nozzle portion is a fatal problem for the inkjet because the ink is not ejected.

In order to solve this problem, the present invention has diligently studied the material constituting the ink, the structure of the nozzle portion, the particle size of the pigment used, the pigment content in the ink, and the like. The present invention is premised on pigment ink. That is, the colorant in the recording liquid is not a dye dissolved in a solvent such as water but a dispersion of fine particles which are pigments.

As described above, the present invention uses the recording liquid (ink) used in the ink jet recording method as a coloring agent for the recording liquid, although a pigment having excellent water resistance and light resistance is used. When this pigment is used as a colorant for recording liquid, the pigment is like abrasive particles dispersed in the liquid medium, and when the ink is used in large quantities, it damages the ink path of the inkjet head. There is a problem of making it wear out. In particular, scratches and abrasion of the ejection port portion are problematic because they affect the ink droplet ejection performance.

In order to solve this problem, the present invention diligently studied the hardness of the material forming the ejection port portion, the ink flow rate, the pigment particle size of the nozzle portion, and the like.

The black pigment ink suitably applied to the present invention is, for example, a black pigment having a neutral or basic pH, a salt of a tertiary amine or an acrylic ester monomer having a quaternary ammonium group. Alternatively, a water-soluble polymer containing at least an acrylamide monomer as a constituent component is subjected to a dispersion treatment, and inks of other hues, for example, inks of yellow, magenta, cyan, etc., are also treated with pigments of these hues. A dispersion treatment is carried out 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 p of the solution when the pigment is dispersed in pure water, as is used in the method for measuring the physical properties of carbon black.
H value. When the recording material used for recording is plain paper, the interfacial tension of the ink with respect to the plain paper is such that the interfacial tension of the black pigment ink is higher than that of the color inks. In regard to the ink permeation rate with respect to, the permeation rate of the black pigment ink is preferably slower than that of the color inks.

When color recording is performed on plain paper using the above inks, an image with good fixability, high density, and less boundary bleeding can be obtained. Further, a clear projected image can be obtained even when recording is performed on a recording material having transparency. And, needless to say, since it is a pigment ink, the resistance to light and water becomes very excellent as compared with the case of using a conventional dye ink.

The polymer dispersant used in the present invention is obtained mainly by polymerizing a vinyl monomer, and as the cationic monomer constituting at least a part of the obtained polymer, the following third monomer is used. Included are salts of secondary amine monomers and their quaternized compounds.

That is, N, N-dimethylaminoethyl methacrylate [CH2 = C (CH3) -COO-C2H4N (CH3) 2], N,
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-dimethylaminoethyl acrylamide [CH2 = CH-CONHC2H4N (CH3) 2], N, N-dimethylaminoethyl methacrylamide [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] and the like.

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

As the other monomer used for the constitution of the above-mentioned polymer dispersant, for example, 2-hydroxyethyl methacrylate, acrylic acid ester having a hydroxy group such as acrylic acid ester having a long ethylene oxide chain as a side chain, Hydrophobic monomers such as styrene-based 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, vinylnaphthalene, vinylnaphthalene derivatives, alkyl esters of (meth) acrylic acid, and acrylonitrile are used. The water-soluble monomer in the polymer dispersant obtained by the copolymerization is used in order to make the copolymer stably exist in the aqueous solution.
The hydrophobic monomer is used in the range of 5 to 35% by weight.
20 to enhance the dispersion effect of the copolymer on the pigment.
It is preferably used in the range of 40% by weight.

The carbon black pigment (CI pigment black 7) used in the black ink of the present invention includes # 2600, # 2300, # 990, # 980, and # 2600.
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 (Made by 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 (above, made by Degussa), Raven850, Raven7
80 ULTRA, Raven 760 ULTRA, Raven 790
ULTRA, Raven520, Raven500, Raven41
0, Raven420, Raven430, Raven450, Raven4
60, Raven 890, Raven 1020 (above, made in Colombia), Regal 415R, Regal 330R, Regal 250
R, Regal 995R, Monarch800, Monarch880,
Monarch900, Monarch460, Monarch280, Monar
ch120 (above, manufactured by Cabot) and the like.

The pigments used in 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.
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, CI pigment yellow 154 and the like.

As pigments used in magenta ink, 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
Etc.

The pigment used in the cyan ink is
CI Pigment Blue 1, CI Pigment Blue 2, C.
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 Vat Blue 4, CI Vat Blue 60 and the like.

In addition to the above, when intermediate colors other than the three primary colors such as red, green and blue are 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 dyes used in 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.

As the dye used in the magenta ink, 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.

The dye used in the cyan ink is
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. 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, the pigment content in the ink, and the like must be within the ranges described below.

In the present invention, when the above-mentioned cationic water-soluble polymer is used as a dispersant to disperse a pigment,
From the viewpoint of physical properties, preferred pigments are those having an isoelectric point adjusted to 6 or more, or those in which the pH of the simple aqueous dispersion characterizing the pigment has a neutral or basic pH, for example, 7 or more to 10 or less. Some pigments are preferable in terms of dispersibility. It is understood that this is because the ionic interaction force between the pigment and the cationic water-soluble polymer is strong.

In order to obtain a pigment fine particle aqueous dispersion using the above materials, the following method is preferably adopted. (1) In the case of carbon black: Premixing treatment of carbon black in a cationic dispersant solution, followed by milling with a disperser having a high shear rate, and dilution, followed by centrifugation to remove coarse particles. . afterwards,
Ingredients for the desired ink formulation are added and optionally aged. After that, centrifugal treatment is performed to finally obtain a pigment dispersion having a desired average particle size. The pH of the ink thus produced is 3 to
A range of 9 is preferable.

(2) For pigments having other hues: Basically the same as carbon black except that an anionic dispersant is used. However, in the case of organic pigments where it is difficult to reduce the particle size, a surfactant treatment is applied at the same time as the pigment synthesis or during the synthesis process to suppress crystal growth of the pigment particles and improve the wettability. It is desirable to use pigments. The pH of the ink thus produced is preferably in the range of 5-10. The average particle size of both carbon black ink and color ink is 0.02 to 1
The range of μm is essential for the stability of the dispersion,
It is preferably in the range of 0.03 to 0.4 μm. This is an essential condition from the viewpoint of the stability of the dispersion, but from the viewpoint that it is essential for so-called inkjet, which discharges ink from a fine opening, it is necessary to examine the average particle size to find that the fine opening Clogs need to be taken into account, which will be discussed later. The surface tension of good ink is in the 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 from the viewpoint of the clarity of the characters to be recorded. On the other hand, it is preferable that the color inks have a low interfacial tension with the paper, since it is preferable that the color inks have a high permeation rate in order to reduce bleeding (color bleeding) due to mutual diffusion between the color inks. 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 black ink is less likely to flow into the color ink side and the black ink and the color ink Color bleed is virtually gone. The above-mentioned interfacial tension between the ink and the paper is measured, for example, by a device commercially available as a dynamic wettability tester (a device using the Wilhelmy method, product name WET-3000 manufactured by Resca Co., Ltd.) and the like. Is the amount. High interfacial tension means that the contact angle to plain paper is 90 ° or more even in a short time of 1 second to several seconds, and low interfacial tension means that it is 90 ° or less.

The dispersant used in the color ink used in the present invention is an alkali-soluble water-soluble oily resin and has a weight average molecular weight of 1,000 to 30,000, preferably 3,000 to 15, The range is 000. In particular,
Hydrophobic monomers such as styrene, styrene derivatives, vinylnaphthalene, vinylnaphthalene derivatives, alkyl esters of acrylic acid, 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 their derivatives, and salts thereof Is. The copolymer may have any structure such as random, block or 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, it is also possible to use water-soluble polymers such as polyvinyl alcohol and carboxymethyl cellulose, water-soluble resins such as naphthalene sulfonic acid formaldehyde condensate and polystyrene sulfonic acid. . However, the alkali-soluble water-soluble oil has the advantage that the viscosity of the dispersion liquid can be reduced and the dispersion is easy. The amount of these dispersants used is experimentally determined by using the selected pigment and dispersant, but the amount of the resin dissolved without adsorbing to the pigment is 4% by weight or less in the ink. It is preferable.

A base is required to use the above dispersant in an aqueous system. 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 and β-dihydroxyethylurea, and inorganic bases such as sodium hydroxide, potassium hydroxide and lithium hydroxide Can be mentioned. The optimum base species varies depending on the type of pigment and dispersant selected, but is preferably non-volatile, stable and highly water-retaining. The amount of the base used is basically the amount calculated from the acid value of the dispersant, and each is used as the amount of base necessary for neutralizing it. In some cases, more than the equivalent amount of acid may be used. It is carried out for the purpose of improving dispersibility, adjusting pH of ink, adjusting recording performance, and improving moisturizing property.

The solvent used for the ink in the present invention is an organic solvent miscible with water. The organic solvent can be divided into three groups as described below. That is,
Highly moisturizing, hard to evaporate, hydrophilic first group solvent, good organic and hydrophobic surface wettability second solvent also evaporative dry, moderate wettability It is a low viscosity third group solvent (monohydric alcohols).

As the solvent belonging to the first group, ethylene glycol, diethylene glycol, triethylene glycol, tripropylene glycol, glycerin, 1,
2,4-butanetriol, 1,2,6-hexanetriol, 1,2,5-pentanetriol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, dimethylsulfoxide, dye 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, hentaerythritol,
1,4-cyclohexanediol etc. are 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, 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 Tell, 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,
1,5-pentanediol, 2,4-pentanediol, 2,5-hexanediol and the like can be mentioned.

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

It is possible to add a surfactant, a pH adjuster, an antiseptic, etc. to each of the aqueous pigment inks constituting the ink of the present invention. Surfactants are useful for preparing highly penetrating color inks, heating heaters in bubble ink jet systems, and adjusting the wettability of the ejection nozzle surface. The material can be appropriately selected from existing commercial products. Summarizing the physical properties of each ink composed of the above materials, black ink has a high surface tension (approximately 3
It is preferable that the color ink has a low surface tension (approximately 10 to 40 dyn / cm).

As described above, when color recording is performed on plain paper using the black aqueous pigment ink and color ink of the present invention, black characters and the like are clear, and images and graphs and black characters are Even if they are next to each other, there is no mutual blurring and they are clear.

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

Next, more characteristic points of the present invention will be described. As described above, the present invention relates to a so-called inkjet recording method in which ink is ejected from a minute opening, and clogging at the ejection port is fatal to the inkjet recording method.
This is not the case of using a dye ink, but the case of using a pigment ink in which fine particles are dispersed in a solvent as in the present invention, the pigment is not dissolved like a dye but is dispersed. Therefore, clogging is more likely to occur. Further, in the present invention, an ink jet recording head having a fine ejection opening diameter which is not available in the past, for example, an ejection opening diameter of Φ25 μm or less (less than 500 μm ^{2 in} terms of area) is assumed. This is a very serious problem.

By the way, the clogging is derived from the principle of the ink jet recording system in which ink is ejected from a minute opening. That is, it is caused because the opening is minute. Therefore, there is a close relationship between the size of the opening and the size of the pigment, which is a foreign substance in the ink.

In view of this point, the present invention pays attention to the size of the ejection port and the size of the pigment particles, and finds the degree of difficulty in causing clogging and their relationship. Specifically, an ink having different pigment particle diameters was prepared, and an inkjet recording head with a known ejection port size was used, and after ejecting ink for a certain period of time, leaving it for a certain period of time, restarting the ink ejection, It was examined whether or not the discharge port was clogged. In that case, not only complete obstruction of the discharge port but also partial clogging and a preceding sign leading to it (slight clogging) were regarded as clogging and tested.

The head used is an ink jet recording type head using the thermal energy having the structure shown in FIG. However, the head shown in FIG. 1 shows the one in which the tip of the flow path is the discharge port as it is, but the head used in the experiment, as shown in FIG. 4 is provided with the nozzle plate 20 having the nozzles 21 formed with the same array density as that in FIG. 4 (FIG. 3 (A) is a perspective view before the nozzle plate 20 is attached, and FIG. 3 (B) is a perspective view after the attachment. Is). Also, regarding the number of the discharge ports (nozzles), the one shown in FIGS. 1 and 3 has only four discharge ports for simplification of description, or is partially shown. The number of outlets used was 1
The number is 28 and the array density is 400 dpi. Further, the size of the heating element is 22 μm × 90 μm, the resistance value thereof is 110Ω, the driving voltage of the ink ejection is 24V,
The driving pulse width was 6.5 μs and the driving frequency was 12 kHz. In addition, recording heads H1 to H4 were prepared (each ejection port diameter was H1 = Φ25 μm, H2 = Φ20 μm).
m, H3 = Φ15 μm, H4 = Φ10 μm). Further, the thickness of the nozzle plate was all 40 μm.

The ink used had the following composition and production method, but had a pigment particle size of 0.005-1.
Prepare ones with different diameters up to μm
Tested in combination with H4. In addition, the conditions for leaving after ink ejection for a certain period of time are temperature 40 ° C. and humidity 30
% Atmosphere for 10 hours.

The method for producing the ink is shown below. Acid value 32 consisting of styrene / methacrylic acid / butyl acrylate
5, weight average molecular weight 11,000, glass transition temperature 84
The following carbon black dispersions D1 to D10 were prepared using an aqueous solution in which the copolymer P at 0 ° C. was dissolved using potassium. -Copolymer P aqueous solution (solid content 20% by weight) 40 parts-Carbon black MCF-88 (manufactured by Mitsubishi Chemical) 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 1 mm diameter glass beads as a medium, and dispersed for 3 hours while cooling with water. A crude dispersion having a viscosity of 17 cP after dispersion and a pH of 9.6 was obtained. This dispersion was centrifuged to remove coarse particles, and various conditions of centrifugation were changed to obtain dispersions D1 to D17 in which the average particle diameter of the pigment was changed to 0.005 to 1 μm. These dispersions were diluted with water to have a viscosity of 2.5 cP, a surface tension of 45 dyn / cm, p
Black basic inkjet ink B1 with H = 9.5
B17 was obtained. The solid content of the final preparation was about 7% by weight. The final pigment content in these inks is 5
% By weight. The average particle size was measured by a particle size distribution measuring device ELS-800 (manufactured by Otsuka Electronics Co., Ltd.) by the dynamic light scattering method, and the average amount was shown by a value obtained from the initial slope of the autocorrelation function.

Tables 1 to 4 show the results of investigating the occurrence of clogging by combining these inks B1 to B17 with the heads H1 to H4 having different ejection port diameters. However, Table 1 shows the head H1 (ejection port diameter Do = Φ25 μm)
Table 2 shows the case of the head H2 (ejection port diameter Do = Φ20 μm), Table 3 shows the case of the head H3 (ejection port diameter Do = Φ15 μm), and Table 4 shows the case of the head H4 (ejection port diameter Do = Φ10 μm).

[0086]

[Table 1]

[0087]

[Table 2]

[0088]

[Table 3]

[0089]

[Table 4]

From the above results, if the pigment particle diameter Dp and the discharge port diameter Do satisfy the relationship of 0.001≤Dp / Do≤0.01, stable ink ejection without clogging can be obtained. I understand. In the experiment, the discharge port is round, but in the case of other shapes (polygon),
It may be within the range converted by the area ratio.

Next, another feature of the present invention will be described.
As described above, the present invention is premised on the pigment ink. That is, the colorant in the recording liquid is not a dye dissolved in a solvent such as water but a dispersion of fine particles which are pigments. Therefore, the pigment content and the pigment dispersant content including the solid content in the ink have a great influence on clogging. Therefore, here, the relationship between their contents and the clogging of the discharge port was investigated.

The head used is the same as the head H2 (ejection port diameter Do = Φ20 μm), and the pigment particle diameter D
In the ink (B4) with p = 0.03 μm, its pigment content and styrene / methacrylic acid / as a pigment dispersant /
By changing the amount of the copolymer P composed of butyl acrylate,
The amount of solids in the final ink and the ease of clogging were examined. The method of the clogging test and the like are the same as those described above. The results are shown in Table 5.

[0093]

[Table 5]

From the above results, it is understood that the pigment content in the ink should be 1 to 10% by weight, and if it is more than that, clogging occurs. It is also understood that not only the pigment content but also the final solid content including the pigment must be 15% by weight or less. When the pigment content is 1% by weight, there is no risk of clogging, but when used only with this ink, the density is low and it is not practical. However, it can be suitably used as a light ink for a recording apparatus using a plurality of types of so-called dark and light inks. Further, even when only this ink is used, it is possible to add a dye to supplement the insufficient density.

Next, still another feature of the present invention will be described. Since the inkjet recording head to which the present invention is applied is generally suitable for color recording, the configuration of the color inkjet recording head to which the present invention is preferably applied will be described here.

FIG. 4 is a diagram showing an example of the ink jet head of the present invention. In the present invention, as shown in the figure, a plurality of ink ejection elements 31Y, 31M and 31C are formed. In this example, three color inks of yellow (Y), magenta (M), and cyan (C) are shown. It should be noted that, in this example and the following examples, the ink ejection elements and ejection ports for each color will be described with four or five for each color for the sake of simplicity, but in reality, each color is 64 to 51.
Two are preferably used.

FIG. 5 shows a diagram in which the recording head section of FIG. 4 is provided with an ink tank section 40 for supplying Y, M, and C inks, respectively. It should be noted that this drawing is a diagram showing the concept of the ink jet recording head of the present invention composed of the recording head portion and the ink tank portion, and differs from the actual one (described later).

FIG. 6 is a diagram showing the construction of a so-called serial printer in which the inkjet head according to the present invention is mounted on a carriage for recording. In the figure, 50 is the inkjet head according to the present invention, 51 is recording paper, and 52. Is a carriage, 53 is a guide rod of the carriage, 54 is a screw rod for moving the carriage, 55 is a recording paper conveying roller, 56 is a recording paper pressing roller, and as is well known, in the vertical direction (moving direction of the recording paper 51). ), The recording heads 50 (in the illustrated example, the heads shown in FIG. 5 are mounted) arranged in a row of Y, M, and C are reciprocally moved in front of the recording paper 51 in the X direction. Make a record. In the present invention, the recording paper is moved in the direction of the arrow Y in the drawing each time the carriage is scanned once. Therefore, the area printed by one scan is only the ejection element of the head, that is, the length of the ejection port array. Further, since Y, M, and C are arranged in a line in the vertical direction, full-color recording is performed for the first time because the printing areas of the Y, M, and C inks are overlapped by two or more scans. You can

Although the above description shows an example of three colors of Y, M, and C, the present invention is also applicable to an ink jet having a four-color ejection port array in which black (B) is added. To be done. An example of this is shown in FIG. 7. In this case, as shown,
In addition to the example shown in FIG. 4, an ink ejection element 31B for black is added.

FIG. 8 shows another example having a row of ejection ports of four colors. FIG. 4 shows an example in which the ink channels of each color are manufactured independently, but this figure shows an example in which the channels for four colors are integrally manufactured by molding the plastic 60. By doing so, the assembly cost can be significantly reduced.

Normally, a color ink jet recording apparatus is
One recording head as shown in FIG. 1 is filled with one color of ink, and a plurality of colors of this ink are stored in the carriage 7 as shown in FIG.
0 side by side. 71B, 71C, 71M, 71
Y is a recording head for ejecting each color ink of black, cyan, magenta, and yellow. This is partly to ensure reliability such as measures against clogging. For example, when the heads 71B, 71C, 71M and 71Y filled with four color inks are independently arranged on the carriage 70 as shown in FIG. 5, and if any one color head is clogged, The original state can be restored by replacing the head of one color.

On the other hand, in the present invention, as shown in FIGS.
A recording head for ejecting ink in a plurality of colors is integrally formed. As described above, considering recovery measures in the case of causing clogging, it is more advantageous to arrange heads filled with inks of plural colors independently on the carriage as shown in FIG. In the invention, as described above, since the pigment particle size, the content rate, or the solid content in the ink has been earnestly studied and optimized, the fear of clogging is eliminated. Therefore, it is not necessary to separately arrange the heads filled with the inks of plural colors on the carriage as shown in FIG. 5, and the assembly cost can be reduced, the compactness can be realized, and the dot position accuracy of the plural colors can be improved. Therefore, as shown in FIGS. 4 to 8, a recording head for ejecting ink of a plurality of colors is integrally formed.

The integral formation referred to here means the state shown in FIGS.
As in the bubble inkjet head shown in FIG. 8, not only an example in which the heating element substrate is a single common substrate, but also heads filled with a plurality of colors of ink as shown in FIG. 10, such as 71B and 71C, are used. , 71M, 71Y are also included. In this example, the tips 72B, 7 of the flow path are
2C, 72M, and 72Y show an example in which one common nozzle plate 73 is provided (FIG. 10A is a perspective view before the nozzle plate 73 is attached, and FIG. 10B is a perspective view after the attachment).
In this case, since a common single nozzle plate 73 is provided that is highly accurately drilled, assembled, and integrated, not only the manufacturing cost is reduced, but also the dot position accuracy of a plurality of colors is highly accurate. .

FIG. 11 shows a plurality of colors (in this example, Y, M,
This is an example in which a head unit capable of ejecting ink of three colors (C) is integrally formed with the ink container portion. FIG. 11A is an overall perspective view and FIG. 11B is an exploded perspective view. 10
Reference numeral 0 is a head unit, 101 is a head chip, 102 is a printed circuit, 103 is an upper lid, 104 is an ink container portion, 105 (105Y, 105M, 105C) is a sterless mesh filter, 106 (106Y, 106M,
106C) is a foam material containing ink, 107 is a bottom lid, and in this example, the head part and the ink container part communicating with it are divided into three parts, and the Y, M, and C inks are separately filled. It is a thing. In this way, the head unit that integrates multiple colors can be made very compact, and when mounted on a carriage, it is lightweight and compact, so a small carriage is sufficient, and the motor that drives the carriage is also compact, Energy saving can be realized.

FIG. 12 is a view for explaining an example in which the ink container integrated head unit for a plurality of colors shown in FIG. 11 has a structure in which only the ink container portion is separable, and FIG. Is an overall perspective view of the head unit 110, and FIG. 12B is a perspective view of the head unit 110 in which the recording head portion 111 and the ink container portion 112 are separated. As a result, even if a large amount of ink is consumed for printing a color image, only the ink container portion 112 needs to be replaced, so that cost reduction is realized. Moreover, the advantages of the color integrated head described with reference to FIG. 11 are maintained.

FIG. 13 is a view for explaining an example in which the ink container portion can be separated for each color of ink in the above-mentioned integrated head unit. FIG. 13A is a perspective view of the whole. FIG. 13B shows a recording head section 111 of the head unit 110 and ink containers 112 (112Y,
112M, 112C) is shown in a perspective view in a separated state.
The advantage of doing so is that the Y, M, and C inks are not always consumed at the same speed in color image printing, so if any of the inks in the examples of FIGS. Even if other ink remains when the ink disappears, the head unit or the entire integrated ink container must be replaced, which is disadvantageous in terms of running cost. By keeping the containers separate, it is possible to further reduce the running cost by replacing only the ink container that has run out.

As described above, the clogging is derived from the principle of the ink jet recording system in which the ink is ejected from the fine openings. That is, it is caused because the opening is minute. Therefore, there is a close relationship between each dimension, shape, and property of the opening, that is, the ejection port, and the size of the pigment, which is a foreign substance 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,
We found the relationship between the occurrence of clogging and the difficulty. Specifically, by mixing inks with different pigment particle diameters, using an ink jet recording head whose dimensions, shape, and properties are known, ink is ejected for a certain period of time, then left for a certain period of time, and then ejected. After restarting, the presence or absence of clogging of the discharge port was examined. In that case, not only complete obstruction of the discharge port but also partial clogging and a preceding sign leading to it (slight clogging) were regarded as clogging and tested.

The head used is an ink jet recording type head using the thermal energy having the structure shown in FIG. However, the head shown in FIG. 1 shows that the tip of the flow path is the discharge port as it is, but the head used in the experiment, as shown in FIG. The nozzle plate 20 having the nozzles 21 formed with the same arrangement density is provided. Also, regarding the number of the discharge ports (nozzles), the ones shown in FIGS. 1 and 3 have only four discharge ports for simplification of description, but the number actually used is The number is 128 and the array density is 400 dpi. The size of the heating element was 22 μm × 90 μm, the resistance value was 110Ω, the ink jet drive voltage was 24 V, the drive pulse width was 6.5 μs, and the drive frequency was 12 kHz. As the recording head, three types of heads (H1 to H3) were prepared, each having a discharge port diameter of Φ25 μm and a thickness of the discharge port portion (distance of the depth portion of the discharge port portion) changed (thickness of each discharge port portion). T = 40 μm (H1), 50 μm (H2), 60 μ
m (H3)).

The ink used had the following composition and production method, but had a pigment particle size of 0.005 to 4
What changed to [mu] m was prepared and tested in combination with heads H1 to H3 having different discharge port diameters. The condition of leaving after ink ejection for a certain period of time is to stand for 10 hours in an atmosphere of a temperature of 40 ° C. and a humidity of 30%.

The method for producing the ink is shown below. Acid value 290 consisting of styrene / acrylic acid / ethyl acrylate,
An anthraquinone pigment Pigment Red-1 was prepared by using an aqueous solution prepared by dissolving a copolymer P having a weight average molecular weight of 5,000 and a glass transition temperature of 77 ° C. with monoethanolamine.
77 dispersions D1 to D20 were prepared. -Copolymer P aqueous solution (solid content 15% by weight) 40 parts-Pigment Red-177 (Chromoftal 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 1 mm diameter glass beads as a medium, and dispersed for 3 hours while cooling with water. A crude dispersion having a viscosity of 30 cP after dispersion and a pH of 9.8 was obtained. This dispersion was centrifuged to remove coarse particles, and various conditions of centrifugation were changed to obtain dispersions D1 to D20 in which the average particle diameter of the pigment was changed to 0.005 to 4 μm. These dispersions were diluted with water, diethylene glycol, ethylene glycol monobutyl ether (60:25:15 weight ratio) to give a viscosity of 3c.
Red basic inkjet inks R1 to R20 having P, a surface tension of 40 dyn / cm, and a pH of 9.5 were obtained. The solid 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 measuring device ELS-800 (manufactured by Otsuka Electronics Co., Ltd.) by the dynamic light scattering method, and the average amount was shown by the value obtained from the initial slope of the autocorrelation function. . Tables 6 to 8 show the results of investigating the occurrence status of clogging by combining these inks R1 to R20 and the heads having different thicknesses of the ejection openings (distances of the ejection openings). .

[0114]

[Table 6]

[0115]

[Table 7]

[0116]

[Table 8]

From the above results, the pigment particle diameter Dp and the distance (nozzle thickness) t in the depth portion 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. It should be noted that, depending on the configuration of the head, the flow path and the discharge port (nozzle) may be connected continuously, but in the present invention, the distance (nozzle thickness) t in the depth portion of the discharge port is Means the distance and the thickness of the portion that substantially constitutes 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 solvent such as water but a dispersion of fine particles which are pigments. From the above results, even with such a so-called pigment ink, if the relationship between the pigment particle diameter and the distance (nozzle thickness) of the depth portion of the ejection port is within a certain range, clogging may not occur. Okay, to eject ink droplets with such pigment ink,
In addition to clogging, it is necessary to eject ink droplets on a recording medium such as paper with stable ejection and thereby with high precision at a target position.

Here, the relationship between the distance t (nozzle thickness) t in the depth portion of the ejection port, which is often associated with clogging, and the distance L from the ejection port surface to a recording medium such as paper was investigated. The heads used are the heads H1 to H3 described above, the ejection port 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, the resistance value is 110Ω, the ink jet drive voltage is 24 V, the drive pulse width is 6.5 μs, and the drive frequency is 12 kHz.

The ink used was the red basic ink jet head ink R5 described above, and MITSUBISHI PAPER mat coat NM was used as the recording medium, and the distance from the ejection 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 image quality recording (high dot position accuracy) could be obtained. It should be noted that, in the case of a head having a small ejection port and using a pigment ink as in the present invention, which is less likely to eject than a conventional one, it is considered that the gravity effect also has an influence in order to find even better conditions, Direction and the case of ejecting ink drops almost vertically
The jet direction was evaluated. The results are shown in Table 9.

[0121]

[Table 9]

In Table 9, ◯ indicates that the deviation from the target dot position is within 1/4 dot, and Δ indicates that the deviation from the target dot position is 1/4 dot or more, 1/2
When it is within the dots, x is when 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 in the case of the head of the present invention, which has a small ejection port and uses pigment ink, and ejection is more difficult than in the conventional case, the distance from the ejection port to the recording surface is 100 t. It can be seen that by the following, stable ejection can be performed, high-precision dot position accuracy can be obtained, and high-quality recording can be realized. Especially the injection direction is vertical,
It can also be seen that the effect is increased by utilizing the gravity effect.

Incidentally, the present invention is not necessarily limited to the complete vertical, but it is to be understood that it is more effective if the gravity action is utilized. Therefore, when actually using the present invention, even if the jetting direction cannot be made completely vertical due to the structural limitation of the printer, the jetting should be directed downward so that the gravitational force can be used even a little. It should be.

Next, a more characteristic point of the present invention will be described. As described above, the present invention relates to a so-called inkjet head recording method in which ink is ejected from a minute opening, and damage and abrasion of the ejection port portion caused by the pigment contained in the ink affect ink droplet ejection performance. It was made to solve it in order to exert.

In particular, in recent years, the high image quality and high definition of ink jet recording have been advanced, and the ejection openings (nozzles) of the heads used are conventionally Φ33 μm to Φ34 μm (about 900 μm ^{2 in} area) to Φ50 μm to Φ51 μm. (Area of about 2000 μm ² ) was common, but finer ejection ports (for example, Φ25 μm or less, less than 500 μm ² in terms of area) have been required.

At that time, as in the conventional case, the discharge port diameter is relatively large.
If the value is large, even if there is some damage or wear,
Due to the large discharge port of
The wear rate is almost negligible and
For droplet discharge performance (jet stability, ink mass uniformity, etc.)
Has almost no effect and is not a problem. But
And a finer discharge port (for example, Φ25 μm or less, surface
The product is 500 μm ²Less than)
Even if it is damaged or worn, since it is a fine discharge port,
The proportion of damage and wear in that size cannot be ignored, and
Ink droplet ejection performance (jetting stability, ink mass uniformity, etc.)
Will be affected.

By the way, it is considered that such damage and wear of the discharge port can be avoided by appropriately selecting the hardness of the material forming the discharge port. The present invention pays attention to this point and experimentally investigates the relationship between hardness and damage and wear of various materials. Specifically, by using a head as shown in FIG. 3 and forming the nozzle plate by changing the material and ejecting ink for a certain period of time, it is determined whether or not the ejection port is damaged or worn. This is an examination of whether or not the drop ejection performance is deteriorated. The head used is shown in Figure 3.
The inkjet recording type head using the thermal energy having the structure as shown in FIG. 3, the one shown in FIG. 3 shows only four ejection ports for simplification of description. The number of ejection ports actually used was 128, and the arrangement density thereof was 400 dpi.

The size of the heating element is 22 μm × 90.
The resistance was 110 Ω, the drive voltage for ink ejection was 24 V, the drive pulse width was 6.5 μs, and the drive frequency was 12 kHz. For the ejection port portion (nozzle portion), an experiment was conducted by preparing a head in which a nozzle plate made of various resin materials or metal materials was changed. Further, the discharge port diameters were prepared to be Φ25 μm (H1) and Φ20 μm (H2).

As a comparative reference example, the discharge port diameter is Φ50 μm.
I also prepared the one (reference head). In this case, the number of discharge ports is 48 and the array density is 180 dpi. The size of this heating element is 40 μm × 180
The resistance was 120Ω, the driving voltage for ink ejection was 30 V, the driving pulse width was 7 μs, and the driving frequency was 1.8 kHz. Nozzle plate thickness is 40μ
m. The hardness of various materials was evaluated by Rockwell hardness, but the actual hardness is not measured with the nozzle plate, but a test piece is made with the same material as the material forming the nozzle plate. It was measured by

The materials for forming the nozzle plate are shown in Table 10 together with the hardness. Hardness was mainly shown on the Rockwell M scale, but some metal materials were shown on the B scale (B scale is applied to those harder than those indicated on the M scale).

[0132]

[Table 10]

The ink used had the following composition and production method, but had a pigment particle size of 0.02 to 1 μm.
What changed to m was prepared, and it tested by combining with the head from which the ejection port diameter differs, and the head from which the ejection port part material differs.

The method for producing the ink will be described below. Acid value 265 consisting of styrene / acrylic acid / butyl acrylate,
Pigment Red 122 Dispersions D1 to D10 were prepared using an aqueous solution in which the copolymer P having a weight average molecular weight of 8,000 and a glass transition temperature of 67 ° C. was dissolved using ethanolamine. -Aqueous solution of copolymer P (solid content 15% by weight) 40 parts-Pigment Red 122 (Fast Gensueher Magenta RT, manufactured by Dainippon Ink) 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 AIMEX), filled with 1 mm diameter glass beads as a medium, and dispersed for 3 hours while cooling with water. A crude dispersion having a viscosity of 18 cp after dispersion and a pH of 9.5 was obtained. The dispersion was centrifuged to remove coarse particles, and various conditions of centrifugation were changed to obtain dispersions D1 to D7 in which the average particle diameter of the pigment was changed to 0.02 to 1 μm. This fine dispersion was diluted with water, diethylene glycol and ethylene glycol monobutyl ether (60:30:10 weight ratio) to give a viscosity of 3.3.
Magenta basic inkjet inks M1 to M7 having a cps, a surface tension of 35 dyne / cm and a pH of 9.3 were obtained. The solid content of the final preparation was about 7.5% by weight. The final pigment content in these inks is 5% by weight.
Is. The average particle size was measured by a particle size distribution measuring device ELS-800 (manufactured by Otsuka Electronics Co., Ltd.) by the dynamic light scattering method, and the average amount was shown by a value obtained from the initial slope of the autocorrelation function.

By combining these inks M1 to M7 with the above-mentioned heads having different ejection port diameters and heads having different ejection port materials, each ejection port has 5 × 10 ⁸ drops, and all 128 nozzles are ink. Droplets were discharged.
Tables 11, 12, and 13 show the results obtained by examining whether or not the ejection port portion is damaged or worn immediately after and after the ejection is started, and as a result, the ink droplet ejection performance is deteriorated.
Note. In the table, ○ indicates that the ejection opening was not damaged or worn, and the ink droplet ejection performance did not deteriorate.
Indicates that the ejection opening was damaged or worn, but the ink droplet ejection performance was not deteriorated, and x is that the ejection opening was damaged or worn, and the ink droplet ejection performance was deteriorated. .

[0137]

[Table 11]

[0138]

[Table 12]

[0139]

[Table 13]

From the above results, it can be seen that in the head having a large ejection port as in the comparative reference example, even if the ejection port portion is slightly damaged or worn, the ejection performance is not deteriorated. On the other hand, the discharge port diameter targeted by the present invention is Φ25μ.
If it is very fine as m or less, the damage or wear of the ejection port portion deteriorates the ink droplet ejection performance. Therefore, in order to perform stable ink droplet ejection, the ejection port portion may be damaged or worn. It can be seen that the conditions under which wear does not occur must be selected. The present invention is preferably applied even when the shape of the ejection port is not a circle but a rectangle or a trapezoid. In that case, Φ25 μm or less is equivalent to the area of about 500 μm.
It is less than m ² , and the present invention is applied to a discharge port having an area of less than about 500 μm ² even if it has a shape other than a circle.

Specifically, as can be seen from Tables 11 and 12, the resin material for forming the ejection port is changed to Rockwell M.
A material of 65 to 120 (S3 to S11) may be used on a scale. Further, the pigment particle size is 0.02 μm to 0.2 μm.
Ink in the range may be used. In addition, sample S
If the ink having a pigment particle size of 0.02 μm is used even if the particle size is less than 65 on the Rockwell M scale such as 1 and S2, the ink drop ejection performance does not deteriorate, but the usable ink is very limited. Therefore, it is not very practical.

Although all the above explanations have been made with reference to the bubble ink jet example, the present invention is not limited to this, and is applied to all ink jets having a fine ejection port and using a pigment ink. It is a thing. In addition, although the recording head example is also described by using an example of a single color ink,
It goes without saying that it can also be applied to color inkjet.

[0143]

EFFECTS OF THE INVENTION According to the present invention, in a fine particle-containing liquid ejecting apparatus for ejecting a liquid in which fine particles are dispersed from a fine opening and adhering it to an adherend, the diameter of the fine particle is optimum for the ejection port. Even when using a very fine ejection port which is not available in the past, the ejection port is not clogged and the reliability is improved.

Further, since the relationship between the discharge diameter and the fine particle diameter is applied to a plurality of kinds of liquids in which different fine particles are dispersed for each liquid and an ejecting device for ejecting the liquids, liquids in which various fine particles are dispersed are used. Even after that, the discharge port was not clogged and reliability was improved.

Further, in the fine particle-containing liquid ejecting apparatus for ejecting the liquid in which the fine particles are dispersed from the fine openings and adhering it to the adherend, the content rate of the fine particles in the liquid and the amount of the solid content are optimized. The discharge port is not clogged and reliability is improved.

Further, since the relationship between the content rate of fine particles and the amount of solid content was applied to a plurality of kinds of liquids in which different fine particles are dispersed for each liquid and an ejecting apparatus for ejecting the same, various fine particles are dispersed. Even if a different liquid is used, the discharge port is not clogged and the reliability is improved.

Further, in a fine particle-containing liquid ejecting apparatus for ejecting a liquid in which fine particles are dispersed from a fine ejection port and adhering it to an adherend, the distance of the depth portion of the ejection port and the fine particle diameter are optimized. Even if a very fine ejection port, which is not available in the past, is used as described below, the ejection port is not clogged and the reliability is improved.

Further, in the fine particle-containing liquid ejecting apparatus for ejecting the liquid in which the fine particles are dispersed from the fine ejection port and adhering it to the adherend, since the fine particle-containing liquid is easily ejected, the ejection port is clogged. Not only did it disappear, but stable injection was also realized.

Further, in the fine particle-containing liquid ejecting apparatus for ejecting the liquid in which the fine particles are dispersed from the fine ejection port and adhering to the adherend, in the present invention, when the member including the ejection port portion is formed of resin, By optimizing the hardness of the resin, damage and friction on the discharge port portion are spread, and stable jetting can be obtained without deterioration of droplet jetting performance. It should be noted that the present invention, by optimizing the hardness of the resin, eliminates damage and friction at the discharge port portion, does not deteriorate the droplet ejection performance, and enables stable ejection. When the discharge port diameter is relatively large, unlike the present invention, the hardness of the resin is not optimized, and even if there is some damage or friction at the discharge port portion, the ratio of the damage and friction amount to the discharge port diameter is large. Is small, the drop discharge performance is unlikely to deteriorate. However, in the case of using a very fine discharge port which has not been used in the past and has a discharge port diameter of Φ25 μm or less as the object of the present invention, the hardness of the resin is not optimized and If the damage and friction are left to occur, the ratio of the size of the damage and friction to the fine discharge port diameter is large, and the droplet discharge performance deteriorates significantly, which becomes a problem. As is clear from the above description, the present invention is particularly effective in the case of using a very fine discharge port having a discharge port diameter of Φ25 μm or less, which has not been heretofore used.

In a fine particle-containing liquid ejecting apparatus for ejecting a liquid in which fine particles are dispersed from a fine ejection port and adhering it to an adherend, since the fine particle diameter is optimized, when the ejection port portion is made of resin. In addition, stable droplet ejection can be obtained, and there is no damage or friction at the ejection port portion, deterioration of droplet ejection performance is eliminated, and stable ejection can be obtained for a long period of time.

Further, since the relationship between the ejection port diameter and the particle size of the ejection head used in the above-mentioned fine particle-containing liquid ejecting apparatus is optimized, clogging of the ejection port is eliminated and reliability is improved.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an example of a bubble inkjet 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 showing an example of an inkjet head having a nozzle plate.

FIG. 4 is a diagram showing an example of an inkjet head of the present invention.

5 is a diagram showing an example in which an ink tank is provided in the recording head unit of FIG.

FIG. 6 is a diagram illustrating an example of an inkjet head having a serial printer configuration.

FIG. 7 is a diagram showing an example having ejection port arrays of four colors.

FIG. 8 is a diagram showing an example in which heads of four colors are integrated.

FIG. 9 is a diagram showing an example in which heads of four colors are independently arranged on a carriage.

FIG. 10 is a diagram showing an example in which heads of a plurality of colors are stacked and integrated.

FIG. 11 is a diagram showing an example in which a head unit and an ink container section are integrally formed.

FIG. 12 is a diagram showing an example in which only the ink container portion is separable.

FIG. 13 is a diagram showing an example in which ink containers can be separated for each color of ink.

[Explanation of symbols]

1 ... Lid substrate, 2 ... Heating element substrate, 3 ... Recording liquid inlet, 4
... Discharge port, 5 ... Flow channel, 6 ... Common liquid chamber, 7 ... Individual lead electrode, 8 ... Common lead electrode, 9 ... Heating element, 10 ... Ink, 10 '... Ink column, 11 ... Bubble, 12 ... Liquid Drops, thirty
... Heating element substrate, 31Y, 31M, 31C, 31B ... Ink ejection element, 40 ... Ink tank, 50 ... Recording head, 51 ... Recording paper, 52 ... Carriage, 53 ... Guide rod, 54 ... Screw rod, 55 ... Recording paper Feed roller, 56
... Recording paper holding roller, 70 ... Carriage, 71B, 71
C, 71M, 71Y ... Head, 72B, 72C, 72
M, 72Y ... Discharge port, 73 ... Nozzle plate, 100 ... Head unit, 101 ... Head chip, 102 ... FPC, 1
03 ... Top cover, 104 ... Ink container part, 105 ... Filter, 106 ... Ink impregnating foam material, 107 ... Bottom cover,
110 ... Head unit, 111 ... Head part, 112 ...
Ink container part.

Claims (9)

[Claims] 1. A fine particle-containing liquid ejecting apparatus for ejecting a liquid in which fine particles are dispersed from a fine opening to adhere to an adherend, wherein the opening has a diameter of 25 μm or less, and the size of the fine particle is Dp. A fine particle-containing liquid ejecting apparatus, characterized in that when the size of the opening is Do, 0.001 ≦ Dp / Do ≦ 0.01. 2. The liquid to which the fine particles are attached is a plurality of types of liquid in which fine particles different for each liquid are dispersed, and has the fine openings corresponding to the liquid in which the plurality of types of fine particles are dispersed. The fine particle liquid ejecting apparatus according to claim 1, wherein: 3. A fine particle-containing liquid ejecting apparatus for ejecting a liquid in which fine particles are dispersed from a fine opening and adhering the liquid to an adherend, wherein the opening has a diameter of 25 μm or less, and the content ratio of the fine particles in the recording liquid is 2 to 10% by weight, and the amount of the solid content containing the fine particles in the liquid is 1
A fine particle-containing liquid ejecting apparatus characterized by being 5% by weight or less. 4. The liquid in which the fine particles are dispersed is a plurality of types of liquid in which different fine particles are dispersed for each liquid, and has the fine openings corresponding to the liquid in which the plurality of types of fine particles are dispersed. The fine particle-containing liquid ejecting apparatus according to claim 3, characterized in that. 5. A fine particle-containing liquid ejecting apparatus for ejecting a liquid in which fine particles having a size of Dp are dispersed from a fine ejection port and adhering the liquid to an adherend, wherein the ejection port is an end of a flow path. Is a discharge port in which the discharge port is formed as it is, or a discharge port is separately formed at the end of the flow path, and the discharge port is Φ25 μm or less and has a distance t in the depth portion thereof. , Then Dp / t
A fine particle-containing liquid ejecting apparatus characterized in that ≦ 0.01. 6. The distance from the discharge port to the adherend surface is 1
The fine particle-containing liquid ejecting apparatus according to claim 5, wherein the liquid is ejected from the ejection port in a gravity acting direction while being set to 00 t or less. 7. A fine particle-containing liquid ejecting apparatus for ejecting a liquid in which fine particles are dispersed through a fine opening and adhering it to an adherend, wherein a member including the opening is made of a resin material and has an opening diameter of Φ25 μm or less, and the hardness of the resin material is 65 to 5 on the Rockwell M scale.
120 is a fine particle-containing liquid ejecting apparatus. 8. The fine particles have a particle size of 0.02 μm.
The fine particle-containing liquid ejecting apparatus according to claim 7, characterized in that 9. An ejection head, which is used in the fine particle-containing liquid ejecting apparatus according to claim 1 and ejects a droplet.