JP2003080684A - Ink-jet recording head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink-jet recording head for easily performing filling of an ink and an apparatus for ink-jet recording. SOLUTION: In the ink-jet recording head with an nozzle discharging the ink and an ink liquid room communicating with the nozzle through an ink passage, before an aqueous recording ink is filled, a mixed liquid containing water, acetylene glycol or acetylene alcohol and glycerin and containing no coloring ingredient is filled from the ink liquid room to the nozzle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet recording head and an inkjet recording apparatus for performing color recording with high ejection reliability.

[0002]

2. Description of the Related Art Conventionally, before the initial filling of a water-based recording ink for liquid ink jet recording, a mixed solution in which a black dye having a surface-active action is dissolved or dispersed in water, an organic solvent or a mixture thereof. It has been prepared. Although these satisfy many characteristics in black monochrome printing, when ejecting ink of other colors or different organic solvents, the ejection characteristics or color characteristics deteriorate, so a large amount of cleaning liquid must be used to replace different inks. The cleaning process at was essential. Also, the time consumed for ink filling is 10
The amount of water-based recording ink consumed is 50 ml or more, and it is not environmentally preferable for disposal because it has no recovery mechanism.

Further, in ink jet recording, when high speed recording or continuous recording for a long time is performed, the ejection efficiency, ejection stability, ejection responsiveness, etc. of the ink liquid may decrease.
One of the reasons for this is that the ink causes bubbles in the liquid chamber of the recording head, which impedes the flow of ink near the minute ejection orifices, and the driving force for ink droplet ejection is absorbed by the bubbles. As a result, inconveniences such as the droplets not being ejected stably in response to the signal and the responsiveness being lowered occur.

Conventionally, various methods have been adopted as a method for removing unnecessary bubbles generated in ink. Patent No. 3037
In No. 512, hydrophilic treatment is carried out by injecting at least one ion of O ⁺ , H ⁺ , and Au ^{+ by} an ion implantation method into the surface of the material forming the ink wetted portion where the ink wetted portion is formed. A recording head is disclosed. Patent No. 3110314
In No. 6, the surface of the member that constitutes the inkjet head is treated with sulfuric acid / hydrogen peroxide mixture, which is a mixed solution of sulfuric acid and hydrogen peroxide solution, and then treated with a diethanolamine solution after the treatment with sulfuric acid / hydrogen peroxide solution. A hydrophilic treatment method has been proposed in which acid treatment is performed after deterioration. Patent No. 26
No. 71390 proposes a method of adjusting a filling liquid containing a black dye until the ink used for printing is initially filled in order to improve a printing defect caused by a problem of wettability between the head material and the ink. However, it was not compatible with color recording. In addition, JP 4-359071A, JP 4-359072A, JP 2000-154344A, JP 200
JP-A 1-267736 proposes an ink composition containing acetylene glycol and a colorant for the purpose of promptly penetrating ink droplets into a recording paper to improve the fixability.

[0005]

SUMMARY OF THE INVENTION In the present invention, the waste of ink in the complicated hydrophilic manufacturing process and the cleaning process at the time of ink filling or replacement found in the prior art is eliminated, and the low cost and environmental load are reduced. However, it is an object of the present invention to provide an inkjet recording head and an inkjet recording device which are suitable for color recording and do not cause print defects or deterioration in print quality at that time.

[0006]

Means for Solving the Problems The gist of the present invention for solving the above problems is that a mixed liquid containing no coloring component has a hydrophilic treatment effect, and a water-based recording ink can be quickly produced without any special means or treatment. It is an object of the present invention to provide an inkjet recording head that can be filled or replaced. Specifically, in an ink jet recording head having a nozzle for ejecting ink and an ink liquid chamber communicating with the nozzle, water, acetylene glycol or acetylene alcohol containing no coloring component before being filled with the aqueous recording ink. And filling the mixture liquid containing glycerin from the ink liquid chamber to the nozzle.

Particularly, the amount of glycerin added is 25 to 70 wt.
% (Weight percent), and this mixture is JIS-K
In the foaming power and foam stability test of 3362, it is desirable that the foam has a stability of 30 mm or less and a viscosity of 5 mPa · s or more at 25 ° C.

Further, by substituting the aqueous recording ink for this mixed liquid, the aqueous recording ink can be quickly filled.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The features of the present invention will be described below.

In the present invention, an ink jet recording head having a nozzle for ejecting ink and an ink liquid chamber communicating with the nozzle through an ink flow channel, particularly an ink contact portion including the ink flow channel and the ink liquid chamber. It is more effective for a recording head having no hydrophilic film. As an alternative to the complicated hydrophilic treatment, the present inventors have added a versatile mixed solution to various aqueous inks to impart a hydrophilic treatment effect that makes it easy to wet the liquid contact member, and perform a normal printing operation to form an ink liquid chamber and an ink flow. The present invention has been accomplished based on the idea of giving a hydrophilic effect to the road.

Ejection stability in ink jet recording has been achieved by hydrophilic treatment around the print head.
However, the study for realizing the low running cost in color recording, which is the greatest merit of inkjet recording, has not been sufficient. In particular, when a standard color is changed to a color specified by the printer user (custom color), different inks are ejected from the same nozzle, and color recording is performed, there is a concern that defects may occur. In particular, inks that use pigments as colorants often have different dispersion stabilizers, anti-drying agents, etc. for each color in order to control the characteristics, and since they are complicatedly prepared, they are versatile for various water-based inks. It is effective to wash with a mixed solution containing no coloring component.

When the surfactant was added, the contact angle with respect to the liquid-contacting part which was not subjected to the hydrophilic treatment was 30 ° or less at 25 ° C., which facilitated wetting. However, even when air was not entrained, bubbles were observed to be generated from the mixed liquid itself, and due to this, sufficient hydrophilic treatment or washing could not be performed. On the other hand, it can be improved by adding a small amount of acetylene glycol or acetylene alcohol or a mixture thereof to water and a glycerin solution of 25 wt% or more.

According to JIS-K3362 foaming power and foam stability test, the addition amount of glycerin was 25 wt%.
It was confirmed that the compositions of less than 1 had a foam stability of greater than 30 mm, whereas the mixed solution containing 25 wt% or more of glycerin had a foam stability of 30 mm or less and was exceptionally excellent in defoaming properties. The reason for this is not clear, but it may be based on the difference in compatibility between water and glycerin and acetylene glycol and acetylene alcohol.

Further, the contact angle of the ink composition at the ink contacting portion was 35 ° or less at 25 ° C. According to this,
The properties as a mixed liquid having both sufficient wettability and defoaming property were satisfied.

The viscosity of the mixed solution at 25 ° C. is preferably 5 mPa · s or more. If the viscosity is less than 5 mPa · s, sufficient hydrophilic treatment cannot be performed. A viscosity range of 5 to 15 mPa · s is more desirable.

The amount to be filled is not particularly limited as long as the mixed liquid fills the flow path of the head, but is preferably the minimum amount capable of obtaining the characteristics, and is preferably about 0.5 to 50 ml. . It is further preferable that the inkjet recording apparatus has a mechanism for collecting and reusing the mixed liquid and the recording ink.

Acetylene glycol and acetylene alcohol are important components for achieving the object of the present invention.
Specifically, Olfin B, P, Y, A, STG, SPC, E1004, E
1010, AK-02, Surfynol 104E, 104H, 104BC, 104D
PM, 104PA, 104S, 420, 440, 465, 485, SE, SE-F, 50
4, 61 (manufactured by Nisshin Chemical Industry) is used. The addition amount is
It is desirable to contain 0.01 to 5 wt%. Excessive addition promotes the generation of bubbles, and less than 0.01 wt% is less effective. However, this is not limited to a head that has been previously subjected to a treatment that facilitates temporary initial filling in the inside of the head or the ink chamber with a plasma asher having a hydrophilic effect, and addition of a small amount may be effective. .

In the present invention, glycerin is used for the purpose of promoting defoaming of acetylene glycol and acetylene alcohol. However, since it is added to a general aqueous recording ink to prevent the nozzle from drying, a mixed liquid is used. Has good compatibility with and does not cause any problems. Excessive addition increases the viscosity of the mixed solution and makes filling difficult.
It is desirable to include wt%. If it is 25 wt% or less, the defoaming effect cannot be obtained.

Further, in the present invention, after the ink jet recording head is filled with the liquid mixture, it is immediately replaced with the aqueous recording ink (in this case, the role of the liquid mixture is a cleaning liquid), or the liquid mixture is previously stored in the ink jet recording head. In the filled state, for example, it is filled as a temporary ink when shipped or not used (in this case, the role of the mixed liquid is a filled liquid), and is replaced with an aqueous recording ink when used.

As a method of replacing the mixed liquid with the aqueous recording ink, the mixed liquid is discharged from the head portion, and a pump connected to the nozzle of the ink jet recording head is driven to suck the mixed liquid, and the aqueous recording ink is discharged from the ink container. A method by an automatic suction operation for supplying the ink into the inkjet recording head,
There are pressure operation methods such as pressurizing the ink container to fill the nozzles with the water-based recording ink, but there is no limitation as long as it is a method in which bubbles are not taken in.

The water-based recording ink is not particularly limited, but a similar composition compatible with the mixed liquid, which does not corrode the print head or peripheral members or change the characteristics, is preferable. For example, ethylene glycol, propylene glycol, diethylene glycol and dipropylene glycol, triethylene glycol, pentamethylene glycol, polyethylene glycol (manufactured by Wako Pure Chemical Industries, Ltd.), methyl glycol, methyl diglycol, methyl triglycol, methyl polyglycol, butyl glycol. , Butyldiglycol, butyltriglycol, isobutylglycol (all manufactured by Nippon Emulsifier), etc. and methylpropylene glycol, methylpropylenediglycol, methylpropylenetriglycol, propylpropyleneglycol, propylpropylenediglycol, butylpropylene Glycol, butyl propylene diglycol, phenyl propylene glycol (above, Japan Propylene glycol-based ethers (e.g., emulsifiers), and other anionic surfactants such as carboxylic acid salts, sulfuric acid ester salts, sulfonic acid salts, and phosphoric acid ester salts, alkylamine salts, dialkylamine salts, tetraalkylammonium salts. Cationic surfactants such as benzalkonium salts, alkylpyridinium salts, imidazolinium salts, amphoteric surfactants such as carboxybetaine, sulfobetaine aminocarboxylic acid, and phosphoric acid ester salts, ether-based, ester-based, ether-ester based , Nitrogen-containing, specifically, polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene polyoxypropylene glycol, glycerin ester, sorbitan ester, sucrose ester, glycerin ester polyoxy Chiren'eteru, polyoxyethylene ether of sorbitan ester, polyoxyethylene ether of sorbitol ester, fatty acid alkanolamide, polyoxyethylene fatty acid amides, nonionic surfactants such as amine oxides can be used widely.

Examples of the physical property modifier include metal hydroxides such as KOH, various surfactants, alcohol amines such as diethanolamine and triethanolamine, phosphoric acid, alcohol amine salts of strong acids, ammonium salts, lower carboxylic acids, glycols. Acids, hydroxycarboxylic acids such as lactic acid, sodium benzoate, potassium sorbate, thiabendazole, fungicides such as benzimidazole, chelating agents, deoxidizers, defoamers, antistatic agents, conductivity imparting agents,
Various additives such as polymer surfactants can be used depending on the application. It is also possible to use acetylene glycol and acetylene alcohol added to the mixed solution.

As the dyes, direct dyes, acid dyes, food dyes, basic dyes, reactive dyes, disperse dyes, vat dyes,
Various dyes usually used in ink jet recording such as soluble vat dyes and reaction disperse dyes can be used. As the pigment, organic pigments and carbon black, which are well dispersed in the vehicle and have excellent weather resistance, are desirable.

In the present invention, the material of the nozzle plate and other ink flow path members is stainless steel, F
The material is not limited to metals such as e and Ni, and plastics such as acryl and polycarbonate, as well as silicon, glass, and ceramics can be used without any problem. There is no problem even if the nozzle is formed by using a method such as electroforming, machining or dry etching.

The recording head of the present invention has various modes such as line-type recording, serial-type recording, transfer-type (shuttle-type) recording, etc. for the on-demand type ink-jet recording recording head or recording method using a piezoelectric element. However, they are used without particular limitation. It is also possible to add a heating / drying process, a double-sided printing mechanism, a mixed liquid / ink collecting mechanism, etc. to the ink jet recording apparatus.

Further, this ink jet recording head is
A conventionally known inkjet printer that ejects ink droplets only when printing is required, for example, an office printer, a printer used for industrial marking,
It can be used in, but is not limited to, wide format printers, plate and plate making printers, label printers and all types of printers having this typical operation.

Next, the present invention will be specifically described with reference to examples, but the present invention is not limited to the examples.

[0028]

[Table 1]

Examples 1 to 4 A printing tester in which a plastic head was fixed to a direct printing plate making machine (SJ02A manufactured by Hitachi Koki) was used. This head has no hydrophilic treatment, the wettability of the aqueous recording ink is poor, and the contact angle between the commercially available yellow dye ink and the head material is 60 ° without treatment. Therefore, the mixed liquid A shown in Table 1 (Example 1) was used. ), B (Example 2), C (Example 3) and D (Example 4) were charged at room temperature. The contact angle is a contact angle meter (CONTAC manufactured by Kyowa Interface Science Co., Ltd.)
T ANGLEMETER CA-D) was used to measure the value 30 seconds after the ink was dropped at room temperature.

As a filling method, the mixture is supplied from the container into the head portion through the ink supply tube. When the pump connected to the nozzle is driven, suction starts and the mixed liquid is supplied from the container to the head.

The stability test of bubbles in the mixed solution is conducted according to JIS K-
Foaming force measuring device conforming to 3362 (Kiriyama Seisakusho, Ca
When measured at room temperature using t.No.JIS-197-1), all were 0 to 30 mm. The viscosity was measured by using a rotational viscometer (EDL model manufactured by Tokimec). 25
The viscosity at ° C was 5.1 to 9.2 mPa · s.

After filling with a commercially available yellow dye ink, first, the ink ejection speed is 3 kHz and the paper feed speed is 10 ips on the paper surface.
Print at a resolution of 300 (× 600) dpi
I went for a minute. The evaluation is that there is no non-ejection nozzle (○),
The occurrence of non-ejection nozzles was determined (x). The ink compositions of Examples 1 to 4 did not generate non-ejecting nozzles in the recording head having no hydrophilic film, and stable recording was possible.

The contact angle between the commercially available yellow dye ink and the head material was 15 to 26 °, and it was found to be a mixed solution having both defoaming property and sufficient wettability. Since the commercially available ink can be smoothly filled after filling the mixed liquid, the time consumed for filling is about 2 minutes and the amount of ink is 20 ml or less. [Examples 5 to 8] After evaluation of Examples 1 to 4, mixed solutions E (Example 5), F (Example 6) G (Example 7) shown in Table 1,
H (Example 8) was filled at room temperature, the commercial yellow dye ink was washed and replaced with the commercial blue pigment ink. Evaluation and filling of the mixed solution were carried out in the same manner as in Example 1. The foam stability of the mixed solution was 1 to 25 mm, and the viscosity was 5.0 to 8.3 mPa · s. The contact angle was 15 to 38 °, which was a characteristic suitable for ink jet recording having both defoaming property and sufficient wettability.

Since the commercially available ink can be smoothly filled after filling the mixed liquid, the amount of ink consumed for filling is 2
The amount was 5 ml or less, and the discharge was stable. [Comparative Example 1] 80 wt% purified water, 20 wt% glycerin
A mixture similar to that prepared by mixing was prepared, and the same measurement and evaluation as in Example 1 were performed to fill the mixture. The results are shown in Table 1. The viscosity at 25 ° C. was 2.5 mPa · s. Bubble stability is 10
It was mm. Since the contact angle of the ink is 65 °, which is large, the contact angle between the ink and the head material is large, and bubbles are generated due to the entrainment of air. Therefore, it is difficult to fill the ink and stable ejection cannot be performed.

[Comparative Example 2] A mixed liquid analog prepared by mixing purified water (100 wt%) and Olfine E1010 (5.5 wt%) was manufactured, and the same measurement and evaluation as in Example 1 were carried out and the mixture was filled. The results are shown in Table 1. Viscosity at 25 ℃ is 1.3mP
It was a ・ s. The foam stability was 60 mm. Since the contact angle was 13 °, the defoaming property was low when the mixed liquid analog itself foamed, so that it was difficult to fill the ink and stable ejection could not be performed.

[0036]

The ink jet recording head of the present invention is
It has a hydrophilic treatment effect by filling a mixed liquid that does not contain a coloring component with general versatility, and a large amount of cleaning liquid can be used for the complicated hydrophilic treatment process of wetted parts found in the prior art and for changing to a different ink. Since it eliminates the cleaning process, meets the demands of high speed and low price, and can easily create custom colors, it is possible to manufacture inkjet recording heads and inkjet recording devices that have a wide range of uses with significantly improved running costs. Becomes

Claims (4)

[Claims] 1. An ink jet recording head having a nozzle for ejecting ink and an ink liquid chamber communicating with the nozzle, which does not contain a coloring component before being filled with an aqueous recording ink,
An ink jet recording head, characterized in that a mixed liquid containing water, acetylene glycol or acetylene alcohol and glycerin is filled from the ink liquid chamber to the nozzle. 2. The mixed solution contains 25 to 70 wt of glycerin.
%, And the foam stability and foam stability test of JIS-K3362 are 30 mm or less in the ink jet recording head according to claim 1. 3. The ink jet recording head according to claim 2, wherein the viscosity of the mixed liquid is 5 mPa · s or more at 25 ° C. 4. An ink jet recording head having a nozzle for ejecting ink and an ink liquid chamber communicating with the nozzle, wherein a mixed liquid containing water, acetylene glycol or acetylene alcohol and glycerin is contained without the coloring component. An ink jet recording head, characterized in that the liquid chamber is filled up to the nozzle and the mixed liquid is replaced with an aqueous recording ink.