JP2001071509A - Ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain stable printing quality for a long time by a method wherein an ink-repellent film of a nozzle plate in an ink jet head is formed by using an FEP and a physical property of the coated film is improved. SOLUTION: There is provided an ink jet head having a nozzle plate which is constituted such that a mixture liquid of aqueous dispersion of tetrafluoroethylene/hexafluoropropylene copolymer (FEP) and silica sol particle dispersion is coated to be dried and is baked in a temperature of 300-400 deg.C, thereby applying an ink repellency treatment thereto.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet head capable of obtaining stable print quality over a long period of time.

[0002]

2. Description of the Related Art When ink droplets and dust adhere to the vicinity of a discharge nozzle of an ink jet head for an ink jet recording apparatus, the nozzle opening becomes dirty, the direction of the discharged ink droplet is bent, the discharge amount is reduced, or the discharge is stopped. And the resolution of the image is significantly reduced. It is also known that when the attached ink covers the entire surface of the nozzle opening, the ink droplet cannot be ejected. In addition, when the nozzle surface is wet with ink, a medium, for example, fine fibers of paper or cloth adheres, and when it comes into contact with the nozzle port, ejection may be hindered. The cause of contamination of the nozzle port is that the pressure applied to the ink remains after ejection, causing the ink in the nozzle to vibrate, causing the ink to overflow from the nozzle port, and the ink that collided with the medium to scatter and become small droplets. The head rebounds and adheres to the nozzle surface, the tail of the ejected ink droplet is broken, the generated satellite adheres, and the head suddenly accelerates at the end of the working range of the carriage equipped with the head,
It is considered that the deceleration causes a large change in the acceleration, and the ink overflows from the nozzle opening due to the inertial force.

[0003] In particular, if the ink overflowing from the nozzle opening due to residual vibration or inertia force is unevenly deposited on the circumference of the nozzle opening, the ejected ink droplets bend and the image is severely deteriorated. The ink around the mouth is treated with ink repellent to make it difficult for the ink to overflow from the nozzle mouth, or the overflowed ink is repelled on the ink-repellent surface to become small droplets, rolls around, and moves away from the nozzle mouth It is desirable not to hinder ejection of the next ink droplet.

[0004] Ink and dust adhering to the surface of the nozzle opening gradually accumulate and grow into large ink droplets, which come into contact with the nozzle opening. Therefore, the ejection is sometimes stopped, and the head is moved to a service station. A cleaning process is performed in which the head surface is wiped with a porous material such as a sponge or a rubber blade to remove attached ink and dust. At this time, if the nozzle opening is damaged by wiping, adhesion of dust and the like is further promoted.

For this reason, an ink repellent treatment has been performed so that ink does not adhere to the vicinity of the nozzle opening.

Various methods have been proposed for applying an ink-repellent treatment to the surface of the nozzle opening of an ink jet head. For example, Japanese Patent Publication No. 52-2482
No. 1, JP-A-56-21862 discloses a coating of a material having an ink-repelling property such as a fluororesin or a silicone resin.
No. 5441 and the like each disclose the use of tetrafluoroethylene-hexafluoropropylene copolymer (FEP) as the ink-repellent film. This FEP
Has a low surface energy (ink repellency) equivalent to that of polytetrafluoroethylene (PTFE), but has a lower viscosity at the time of heating and melting than PTFE, and applies an aqueous dispersion to form a uniform film by heating and melting. PTFE when forming
A uniform film can be obtained at a lower temperature and in a shorter time than at a lower temperature, and it is excellent in film forming processability.

[0007]

However, since FEP is a perfluorinated material and has a low surface energy, an ink-repellent film has a problem in adhesive strength to a nozzle plate. May occur.

The present invention has been made in view of the above circumstances, and an object of the present invention is to form an ink-repellent film of a nozzle plate of an ink jet head by using FEP to improve the physical properties of the film, and to provide the ink repellent film for a long time. And to assure stable printing quality.

[0009]

SUMMARY OF THE INVENTION The object of the present invention is to provide an aqueous dispersion of a tetrafluoroethylene / hexafluoropropylene copolymer (FEP) and a silica sol particle dispersion, which are coated, dried, and dried. In an ink jet head having a nozzle plate that has been ink-repellent by baking at a temperature of ° C., the infrared absorption spectrum of the film obtained by the ink-repellent treatment is derived from C-F ₂ symmetric stretching vibration 118.
0cm of peaks appearing between ^{-1 ~1130cm -1} infrared 2
1. The color ratios Dxy and Dyz are 0.9 to 1.1, respectively.
Wherein the calcination is performed for 30 minutes or more; and a fluorine-based aqueous dispersion of tetrafluoroethylene / hexafluoropropylene copolymer (FEP) is passed through a surface treatment by oxygen plasma treatment. An inkjet head having a nozzle plate made of polyimide, which has been subjected to ink-repellent treatment by applying, drying and baking at 300 to 400 ° C. a solution to which a cationic surfactant has been added; And the thickness of the film formed by the ink repellent treatment is 0.05 to 4 μm.

Hereinafter, the present invention will be described in detail.

The invention according to claim 1 is to increase the strength of the FEP ink repellent film by adding silica sol particles.
It has been found that other fillers have a weak chemical bonding force with FEP and are easily detached, but silica sol particles can achieve the purpose. The particle size of the silica sol particles is 0.1.
It is preferably in the range of 01 to 0.6 μm, and FE
P: silica sol in a weight ratio of 100: 0.05 to 10
It is preferably in the range of 0: 0.5.

The aqueous dispersion of FEP comprises fine particles of FEP,
ND-1 manufactured by Daikin Industries, Ltd., 120-J manufactured by DuPont, and the like are commercially available using a surfactant, water and other additives as components.

[0013] Claim invention according to 2, FEP ink repellent film infrared 2 peaks appearing between 1180cm ^-1 ~1130cm ^-1 derived from an alignment state to a C-F ₂ symmetric stretching vibration of the infrared absorption spectrum of When the color ratios Dxy and Dyz were evaluated as parameters, there was a correlation between the degree of orientation and durability, with Dxy being 0.9 to 1.1 and Dyz being 2.0 to 12.
It has been found that when it is 0, it has excellent durability.

The infrared two-color ratios Dxy and Dyz show a value of 1.00 when the ink repellent film is isotropic in the longitudinal direction x, the width direction y and the thickness z direction and is completely non-oriented. While x
Direction, the y direction is almost isotropic, but there is anisotropy in the thickness direction, that is, when FEP molecules are oriented in the thickness direction, Dxy shows a value of 0.90 to 1.10, , Dxz
Increases with the orientation strength in the thickness direction. In the ink-repellent film according to the present invention in which the durability has been improved by adding silica sol particles, as an example, the mixing ratio is FEP: silica sol = 100: 0.1 in weight ratio, and the polyimide film is plasma-treated on a polyimide film. Apply with a thickness of 0.1 μm, then 3
When heated at 30 ° C. for an hour, Dxy is 0.95 to 1.0.
5, Dxz shows a high value of 8.0 to 10.5. On the other hand, an ink-repellent film produced in the same manner except that silica sol particles were not added was inferior in durability, and Dxy was 0.95 to 1.0.
5, Dxz showed a low value of 0.9 to 1.1.

The ink-repellent film having excellent durability is substantially non-oriented in the x and y directions and oriented in the thickness direction z, and preferably has a Dxy of 0.90 to 1.10, Dyz.
Is from 2.0 to 12.0.

Here, the infrared two-color ratios Dxy and Dyz are obtained as follows.

Measurement of Infrared Spectra Using attenuated total reflection infrared spectroscopy (ATR-IR method), the measurement conditions were: prism: germanium, incident angle: 45 °, number of reflections: one, resolution: 4 cm ^{-1 and} data interpolation: 0. At 5 cm ⁻¹ , vertically polarized light and horizontally polarized light are incident on the incident surface composed of light incident on the sample surface and reflected light using a wire grid polarizer, and the infrared light (I
R) Measure the spectrum. This measurement is performed on the surface of the ink-repellent film with the incident direction parallel to the longitudinal direction and the width direction. The directions of the surface of the ink-repellent film for convenience at this time are defined as a longitudinal direction x, a width direction y, and a thickness direction z.

[0018] measuring the intensity of a peak derived from the C-F ₂ symmetric stretching vibration of calculation FEP ink repellent film of the infrared dichroic ratio Dxy and Dyz (strongest peak appearing between 1180cm ^-1 ~1130cm ^-1) . Assuming that the peak intensity is the wave number (αcm ⁻¹ ) at the peak top, α to α + 3
0 cm ^-1, the point having the smallest absorbance, and α to α-30
A point having the smallest absorbance in cm ^-1 is connected to the base point, and the intensity of the peak is measured and determined therefrom.
In this way, the absorbance when the plane of polarization is parallel to the plane of incidence (A
p) and the absorbance (As) when the plane of polarization is perpendicular to the plane of incidence are determined. This is called the longitudinal direction x and the width direction y of the surface of the ink repellent film.
And a total of four absorbances (Apx, Apx)
y, Asx, Asy) are measured, and Dx is calculated by the following calculation procedure.
Find y and Dxz.

1) Assuming that the refractive index of the FEP ink repellent film is n ₂ and the refractive index of the prism is n ₁ , α, β,
Calculate γ. θ is the incident angle, which is 45 ° here.

[0020]

(Equation 1)

The refractive index of the FEP ink repellent film (normally 1.
30-1.50) was measured with an ellipsometer.
The refractive index of the prism (germanium) is 4.00.

2) Four absorbances Apx, Apy, As
The following Kx, Ky, and Kz are calculated from x, Asy, and α, β, and γ.

[0023]

(Equation 2)

3) Dxy = Kx / Ky, Dxz = Kx /
Find Kz.

The details of the calculation procedure are described in P. A. Fl
oomoy, W.C. J. Schaffers, Spectrum
rochimica Axta, 22, 5 (1966)
And J. P. Hobbs, C.I. S. P. Sung, K .;
Krishnan, S .; Hill, Macromole
cules, 16, 193 (1983).

According to a third aspect of the present invention, in the ink repellent film according to the present invention, when the baking time is extended to 30 minutes or more,
It was found that the durability was improved, and this phenomenon was not observed in a film made of only FEP resin.

According to a fourth aspect of the present invention, an aqueous dispersion of FEP is applied to a nozzle plate made of polyimide because it is presumed that fine surface roughening occurs when surface treatment is performed by oxygen plasma treatment. 300-40 after drying
It has been found that baking at 0 ° C. improves the adhesiveness of the coating. On the other hand, when the coating unevenness is strongly developed and the uniformity of the ink-repellent film is deteriorated, the fluorine-based cation is added to the dispersion. This can be solved by adding a surfactant.

It is preferable that the fluorinated cationic surfactant is selected from the compounds represented by the general formulas 1) to 6), and specific examples thereof include the following compounds.

[0029] _{s-1 C 9 F 19 SO} 2 NHC 3 H 6 N + (CH 3) 3 · I - s-2 C 9 F 19 SO 2 NHC 3 H 6 N + (CH 3) 3 · Br - s _{-3 C 8 F 17 SO 2 N} (CH 3) C 3 H 6 N + (CH 3) 3 · I - s-4 C 8 F 17 SO 2 N (CH 3) C 3 H 6 N + (CH 3 ^{_{) 3 · Br - s-5}} C 6 F 13 SO 2 NC 2 H 4 N + (C 2 H 5) 3 · I - s-6 C 8 F 17 SO 2 N (CH 3) (C 2 H 5) ^{_{C 3 H 6 N + (CH}} 3) 3 · Cl - s-7 C 9 F 19 N + (CH 3) 3 · I - s-8 C 8 F 17 N + (CH 3) 3 · Br - s- ^{_{9 C 8 F 17 N + (}} C 2 H 5) 3 · I - s-10 C 6 F 13 N + (CH 3) 3 · Cl - s-11 C 9 F 19 C 2 H 4 SCH 2 COOC 2 H ^{_{4 N + (CH 3) 3}} · I - s-12 C 8 F 17 C 2 H 4 SCH 2 COOC 2 H 4 N + (CH 3 ^{_{3 · Br - s-13 C}} 6 F 13 C 2 H 4 SCH 2 COOC 2 H 4 N + (C 2 H 5) 3 · Cl - s-14 C 8 F 17 CONHC 3 H 6 N + (CH 3) ^{_{3 · I - s-15 C}} 8 F 17 CONHC 3 H 6 N + (CH 3) 3 · Br - s-16 C 6 F 13 CONHC 2 H 4 N + (C 2 H 5) 3 · Cl - s- _{17 C 9 F 17 O-C} 6 H 4 -SO 2 NHC 3 H 6 N + (CH 3) 3 · I - s-18 C 9 F 17 O-C 6 H 4 -CH 2 N + (C 2 H ^{_{5) 3 · Cl - s-}} 19 C 9 F 17 O-C 6 H 4 -CONHC 3 H 6 N + (CH 3) 3 · I - s-20 C 9 F 17 O-C 6 H 4 -SO 2 ^{_{NHC 3 H 6 N + (CH}} 3) 3 · Br - s-21 C 9 F 17 O-C 6 H 4 -CH 2 N + (CH 3) 3 · Br - s-22 C 9 F 17 O-C _{6 H 4 -CONHC 3 H 6 N} + (C 2 H 5) 3 · Cl - s-2 _{3 C 9 F 17 OCH 2 CH} 2 N + (CH 3) 3 · I - s-24 C 9 F 17 (OCH 2 CH 2) 2 N + (CH 3) 3 · Br - s-25 C 9 F 17 ^{_{OCH 2 CH 2 N + (C}} 2 H 5) 3 · Cl - invention according to claim 6, made the coating film thickness uniform by the invention according to claim 4 and 5, even with a dilute coating solution It can be applied stably, and the thickness of the ink repellent film is 0.05 to 4
It can be formed even with a thin film having a thickness of μm, and is particularly preferable when processing a nozzle hole with a laser.

Although it is common to form a nozzle hole in a nozzle plate using an excimer laser, the laser workability is a factor that affects the variation in injection. The FEP resin has a disadvantage that the absorption of ultraviolet light is small and the processability by the excimer laser is not so good, but this can be dealt with by making the thickness of the ink-repellent film thin.

It is also possible to use a stainless steel plate as the nozzle plate, pre-punch the nozzle holes with a punch, and print an ink-repellent film by flexographic printing. There is an advantage that printing is not performed on the nozzle holes due to the structure of a flexographic printing machine (for example, RK Easy Proof manufactured by Matsuo Sangyo Co., Ltd.).

[0032]

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

Example 1 An oxygen plasma treatment (13.56 MHz, 200 W, 10 Pa, 3 Pa) was performed using a 125 μm-thick polyimide sheet (UPIREX, manufactured by Ube Industries, Ltd.) as a nozzle plate.
), A coating solution having the following composition was applied using a wire bar so that the dry film thickness became 0.8 μm, and baked at 330 ° C. for the following time to perform an ink-repellent treatment.

Aqueous FEP dispersion (Neoflon ND-1 manufactured by Daikin Industries, Ltd.) 10 parts by weight Silica sol particle dispersion (Catalyst Chemical Industry Co., Ltd., Cataroid S-3OH) 0.02 parts by weight Water 90 parts by weight As a comparative ink-repellent treatment, the same treatment was carried out except that the composition of the coating liquid was composed of 10 parts by weight of the above neoflon ND-1 and 90 parts by weight of water.

<Evaluation of Durability> To simulate the cleaning process, a urethane rubber blade having a thickness of 2 mm, a length of 20 mm, and a width of 10 mm was set upright to the ink-repellent film surface, and was laid horizontally with a 1 mm overlap state. Was rubbed so that the ink repellent film was scraped and peeled, and evaluated according to the following criteria.

○: Cleaning durability of 50,000 times or more Δ: Cleaning durability of 10,000 times to less than 50,000 times ×: Cleaning durability of less than 10,000 times <Infrared absorption two-color ratio measurement> Dxy, D by the above-described method
xz was determined.

The results are shown below.

Firing time FEP film Containing silica sol particles Durability Dxy Dyz Durability Dxy Dyz None × 1.01 1.16 × 0.99 1.15 3 minutes × 1.01 1.63 △ 1.00 3.60 10 Min × △ 30 min × ○ 100 min × 1.06 1.54 ○ 0.96 3.54 300 min × ○ Example 2 A stainless steel plate having a thickness of 100 μm was used as a nozzle plate, and a coating solution having the following composition was applied to a wire bar. And dried at 380 ° C. for 2 hours to perform an ink-repellent treatment.

FEP aqueous dispersion (Neoflon ND-1 manufactured by Daikin Industries, Ltd.) 50 parts by weight Silica sol particle dispersion Particle size and mixing ratio 50 parts by weight of water shown below The evaluation results are shown below.

Silica sol particle size FEP: Silica sol Durability Dxy Dxz (μm) (weight ratio) 0.01 to 0.02 100: 0.05 ○ 0.01 to 0.02 100: 0.5 ○ 0.07 to 0.09 100: 0.02 △ 0.07 to 0.09 100: 0.05 ○ 0.07 to 0.09 100: 0.2 ○ 0.07 to 0.09 100: 2 △ − 100: 0 × 0.99 1.15 0.3 100: 0.02 Δ 0.92 1.62 0.3 100: 0.05 0.96 3.54 0.3 100: 0.2 ０．９ 0.96 3 .38 0.3 100: 2 △ 1.06 1.10 0.6 100: 0.02 △ 0.6 100: 0.05 ○ 0.6 100: 0.5 ○ 0.6 100: 2 △ Implementation Example 3 A 125 μm thick polyimide sheet (described above) was used as a nozzle plate. Using oxygen plasma treatment (13.56 MH)
z, 200 W, 10 Pa, 3 minutes), and then applying a coating solution having the following composition with a wire bar so that the dry film thickness becomes 1.0 μm, and baking at 350 ° C. for 10 minutes to perform an ink-repellent treatment. Sample No. 1 to 6 were produced.

FEP aqueous dispersion (manufactured by Daikin Industries, Ltd., Neoflon ND-1) 50 parts by weight Surfactant (shown below) 1 part by weight Water 49 parts by weight As Comparative 1, a 125 μm thick polyimide as a nozzle plate After washing with isopropyl alcohol (IPA) using the sheet (described above), a coating solution having the following composition is applied with a wire bar so that the dry film thickness becomes 0.3 μm,
The ink was repelled by baking at 350 ° C. for 10 minutes.

25 parts by weight of FEP aqueous dispersion (manufactured by Daikin Industries, Ltd., NEOFLON ND-1) Surfactant: 1 part by weight of s-2 74 parts by weight of water As a comparison 2, oxygen plasma treatment was performed instead of IPA cleaning ( (13.56 MHz, 200 W, 10 Pa, 3 minutes), and the ink-repellent treatment was performed in the same manner as in Comparative Example 1 except that a coating solution composed of 25 parts by weight of the FEP aqueous dispersion and 75 parts by weight of water was used.

In Comparative Example 3, ink-repellent ink was prepared in the same manner as in Comparative Example 1 except that after washing with isopropyl alcohol (IPA), a coating solution having the following composition was applied with a wire bar so that the dry film thickness became 5.0 μm. Processing was performed.

50 parts by weight of FEP aqueous dispersion (NEOFLON ND-1 manufactured by Daikin Industries, Ltd.) Surfactant: 1 part by weight of s-2 50 parts by weight of water (Evaluation of coatability) Visual uniformity of coated film Was observed and evaluated according to the following criteria.

：: Uniform coating surface △: Coating omission is observed in a very small portion X: Non-uniform film thickness due to liquid.

(Evaluation of Film Adherence) In the same manner as in the evaluation of durability in Example 1, rubbing was performed 10,000 times, and the presence or absence of peeling of the ink-repellent film was observed.

(Evaluation of Nozzle Workability) Nozzle hole processing was performed using an excimer laser, and the state of the processed surface was observed and evaluated according to the following criteria.

：: A clean machined surface Δ: Partially defective ×: Defect with film peeling

The above results are shown together.

Sample No. Surfactant Coating property Film forming property Nozzle workability 1 s-2 ○ ○ ○ 2 s-8 ○ ○ ○ 3 s-13 ○ ○ ○ 4 s-14 ○ ○ ○ 5 s-17 ○ ○ ○ 6 s-25 ○ Comparative 1 s-2 × ○ − Comparative 2 None ×--Comparative 3 s-2 ○ △ 比較 In Comparative 2, the ink repellent film was not uniformly formed. Could not be evaluated.

[0051]

According to the present invention, it is possible to obtain an ink jet head having excellent durability of the ink repellent treatment.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C057 AF70 AF93 AG07 AP02 AP13 AQ03 4H020 BA12 BA21 4J038 CD121 CD131 HA446 KA20 MA08 MA10 MA12 PA07 PA19 PB11 PC08

Claims (6)

[Claims] 1. Coating, drying and mixing of an aqueous dispersion of a tetrafluoroethylene / hexafluoropropylene copolymer (FEP) and a silica sol particle dispersion.
An ink jet head having a nozzle plate that has been subjected to an ink repellent treatment by baking at 00 ° C. 2. A derived from C-F ₂ symmetric stretching vibration of the infrared absorption spectrum of the film by the ink-repellent 1180
Infrared 2 peaks appearing between cm ^-1 ~1130cm ^-1 dichroic ratio Dxy and Dyz respectively 0.9～1.1,2.0
2. The inkjet head according to claim 1, wherein the number is from 1 to 12.0. 3. The ink jet head according to claim 1, wherein the baking is performed for 30 minutes or more. 4. Applying a solution obtained by adding a fluorine-based cationic surfactant to an aqueous dispersion of a tetrafluoroethylene / hexafluoropropylene copolymer (FEP) through a surface treatment by an oxygen plasma treatment, drying and drying the solution.
An ink jet head having a nozzle plate made of polyimide, which has been ink-repellent by baking at 400 ° C. 5. The ink jet head according to claim 4, wherein the surfactant is selected from compounds represented by the following general formula. _{1) Rf-SO 2 N (} R 1) (CH 2) m N + (R 2) 3 ·
^{X - 2) Rf-N +} (R 2) 3 · X - 3) Rf-C 2 H 4 SCH 2 COOC 2 H 4 N + (R 2) 3 ·
X ^- in [1) ~4), Rf represents a perfluoroalkyl group, R ₁ is _{^{H-, CH 3 - - 4)}} Rf-CONH (CH 2) m N + (R 2) 3 · X or C Represents ₂ H ₅ —, R ₂
Represents CH ₃ — or C ₂ H ₅ —, and X represents Cl, Br or I.
And m represents an integer of 1 to 3. ] _{5) C 9 F 17 O-} C 6 H 4 -R 3 -N + (R 2) 3 · X - 6) C 9 F 17 (OCH 2 CH 2) m N + (R 2) 3 · X - In [5) and 6), R ₃ represents —SO ₂ NHC ₃ H ₆ —,
Represents —CH ₂ — or —CONHC ₃ H ₆ —, and R ₂ , X and m have the same meanings as those in formulas 1) to 4). ] 6. The ink jet head according to claim 4, wherein the thickness of the film formed by the ink-repellent treatment is 0.05 to 4 μm.