JPH09327924A - Nozzle plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use almost all inks, to mold in a thin state, and to extend selecting ranges of an NWC agent and adhesive so that release of a connecting part from an actuator scarcely occurs by using liquid crystal polymer as a raw material. SOLUTION: A nozzle plate 1 is coated on one surface of a board 2 formed of a liquid crystal polymer(LCP) with a liquid repellent film 3. Many nozzles 4 for injecting ink 5 are formed in a plurality of rows, in place. The board 2 is adhered on the other surface with an actuator 6 by adhesive 7. As the board 2, a nonreinforced grade LCP is used. The film 3 is coated with fluororesin after the board 2 is molded. Thereafter, micropores penetrating the film 3, board 2 and adhesive 7 are opened by laser processing, and the nozzles 4 are formed. Since the LCP is used for the board 2, almost all inks can be used. Since the thermal expansion coefficient of the board 2 is near that of the actuator 6, its release scarcely occurs. Since its heat resistant temperature is high, selecting ranges of adhesives are extended.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nozzle plate used in a print head for an inkjet printer, and more particularly to a nozzle plate whose material is liquid crystal polymer.

[0002]

2. Description of the Related Art Conventionally, as a drop-on-demand type ink jet head, for example, the volume of an ink flow path is changed by deformation of piezoelectric ceramics, and when the volume is reduced, the ink in the ink flow path is ejected as a droplet from a nozzle. In some cases, ink is introduced into the ink flow path from the ink introduction port when the volume is increased. Then, ink droplets are ejected from a nozzle at a required position in accordance with required print data to form a desired character or image on a paper surface facing the inkjet head. As this type of ink jet head, for example, there is one described in JP-A-63-247051. This ink jet head forms a plurality of parallel ink flow paths separated by piezoelectric ceramic partitions, one end of the ink flow path communicates with the nozzle of the nozzle plate, and the other end supplies ink. The ink is ejected from the nozzle by changing the volume of the ink flow path by the deformation of the partition wall. A method of forming a nozzle plate of an inkjet head having a plurality of ink ejection ports as described above using an injection molding technique is well known. As a manufacturing method thereof, for example, as disclosed in Japanese Patent Application Laid-Open No. 3-297651, there is known a method of forming an ink ejection port by laser processing using an excimer laser device or the like after injection molding with a polymer resin material. ing. However, the excimer laser device is a very expensive device, and the processing time,
That is, since the production cost of the nozzle plate has increased in proportion to the thickness of the portion to be processed, it has been required to reduce the thickness of the processed portion. Further, PSF (polysulfone) is generally used as the material of the nozzle plate.

[0003]

[Problems to be Solved by the Invention] However, PSF
The nozzle plate formed by using has the following problems. <1> Depending on the type of ink used, for example, a pigment,
The nozzle plate may be eroded by the ink containing the dye or other solvent. Therefore, the nozzle plate may be broken or melted, so that the types of ink that can be used are limited. <2> Further, as the nozzles are highly integrated to improve the resolution, core pins of a mold for forming the nozzles of several μm to several tens μm are arranged in a plurality of rows and a plurality of columns. On the other hand, since PSF has a high melt viscosity and poor fluidity in the mold, it cannot be filled in the ordinary injection molding method unless the injection pressure is increased and the wall thickness around the nozzle portion is increased. However, if the wall thickness is increased, the length of the fine core pin becomes long, and in addition, if the injection pressure is high, the core pin frequently breaks. Molding is possible even if only the wall thickness is increased without changing the length of the core pin, but there is a problem in that the number of processed parts by the excimer laser increases and the production cost increases. That is, as the nozzle plate, a material that can be made thinner than PSF has been required.

<3> Further, in an ink jet printer, a piezo type actuator is widely used as an ink jet head for ejecting ink. One surface of the nozzle plate is adhered to the actuator, and the ink pushed out by the actuator is ejected from the nozzles formed on the nozzle plate. PZT (lead zirconate titanate) is generally used for a piezo type actuator. However, PSF (nozzle plate) has a larger coefficient of thermal expansion than PZT (actuator). Specifically, the coefficient of thermal expansion of PZT is 0.2 to 0.3.
× to 10 ^-5 in the range of mm / mm / ℃, the thermal expansion coefficient of the PSF is ^{5.6 × 10 -5 mm / mm /} ℃. That is, the expansion coefficient when the temperature changes by 1 ° C. is 5 × 10 ⁻⁵ mm
/ Mm or more different. Therefore, there is a possibility that the size of the nozzle plate and the size of the actuator may be different due to a large temperature rise due to long-term use, or the size of the nozzle plate and the actuator may be separated due to the difference in the ambient temperature used.

<4> The heat distortion temperature of PSF is 174.
Since it is ℃, NWC (non-wet coat) that forms a liquid repellent film that coats the ink ejection surface of the nozzle plate
In the selection of the adhesive agent and the adhesive agent used for adhering the nozzle plate and the actuator, the heat curing temperature is 17
Limited to those below 4 ° C. In particular, the fluorine-based NWC agent, which is a material having good liquid repellency, tends to have better adhesion to the nozzle plate and better durability when the heat curing temperature is higher. That is, a material having a high heat resistant temperature has been required for the nozzle plate.

The present invention has been made to solve the above problems. <1> Almost all inks can be used, <2> Thin-wall molding is possible, <3> Peeling between an actuator and a joint is less likely to occur. , <4> NWC agent, a wide selection range of the adhesive agent is used, and an object thereof is to provide a nozzle plate capable of forming a clean nozzle hole.

[0007]

To achieve the above object, the nozzle plate of the present invention is a nozzle plate having nozzle holes for ejecting ink, and the material is liquid crystal polymer (LCP). Characterize. In particular, the liquid crystal polymer is more preferably a semi-aromatic liquid crystal polyester.

Liquid crystal polymer (LCP) forms a liquid crystal in a molten state, and when stress is applied in a molten state, molecular chains are oriented in one direction and the melt viscosity is lowered. Further, when cooled as it is, the molecules are solidified while being oriented and stabilized. for that reason,
It has excellent moldability, high strength and high elastic modulus. Among the LCPs having such characteristics, the semi-aromatic polyester is an LCP having low crystallinity and therefore has a low orientation and is particularly excellent in moldability and precision. The use of LCP as the material of the nozzle plate has the following effects against the problems when the conventional PSF is used.

<1> LCP can be used regardless of the type of ink since it is not affected by most organic solvents. <2> Further, since the melt viscosity is low, the molding can be performed with a pressure of a fraction of that in the case of molding with PSF, so that an extremely thin molded product can be formed.

<3> Further, since the thermal expansion coefficient of the LCP is close to the thermal expansion coefficient of the actuator, peeling of the joint portion with the actuator is unlikely to occur. Specifically, as a characteristic of LCP, the coefficient of thermal expansion is 2.8 × 10 ⁻⁵ mm / mm / ° C. The coefficient of thermal expansion of the actuator is 0.2 to 0.3 × 10
^-5 mm / mm / ° C, and the thermal expansion coefficient of the conventional PSF is 5.6 x 10 ^-5 mm / mm / ° C. Therefore, LC
The coefficient of thermal expansion of P is about half that of PSF, which is closer to the coefficient of thermal expansion of the actuator, so that peeling of the bonded portion does not easily occur even if the temperature changes. <4> Furthermore, the heat distortion temperature of LCP is 180 ° C and PS
Since it is higher than F, in the selection of NWC agent and adhesive, the range of types that can be used is wider than PSF. Therefore, it is possible to improve the adhesion performance and the durability performance.

Although the LCP has excellent properties as described above, it has a problem in molding as described below. First, in general LCP, fine powder such as glass fiber may be mixed as a filler in order to increase strength and flame retardancy. This is called the reinforced grade of LCP. However, on the other hand, the nozzle holes of the nozzle plate are generally formed by laser processing. In that case, a clean hole cannot be formed in the reinforced grade in which the filler such as the filler is contained in the LCP as the material of the nozzle plate. That is, since the laser heat is not uniformly absorbed by the LCP and the filler, the filler may remain.

On the other hand, in the case of the non-reinforced grade containing no LCP filler, a force is applied to the molding surface to cause fluffing. For example, fluffing is likely to occur during ultrasonic cleaning or wiping after molding. This is probably because the unfilled non-reinforced grade has a stronger orientation of the molecular chains in the flow direction than the reinforced grade.

For the above reasons, when both the reinforced grade and the non-reinforced grade are used as the nozzle plate, clean nozzle holes cannot be formed. As a result, the ink cannot be ejected properly because the ink droplets ejected from the nozzles may fluctuate in the flight direction due to the bending of the ink droplets, or the ejection timing of the ink may fluctuate.

In order to solve the above problems, the nozzle plate of the present invention is characterized in that a fluororesin liquid repellent film is formed on the outer surface thereof. In particular, it is more preferable that the fluororesin liquid-repellent film is a solvent-soluble fluoropolymer having a heterocycle. Furthermore, the thickness of the fluororesin liquid repellent film is preferably 0.1 μm or more and 3 μm or less.

As a material for the nozzle plate, an unfilled non-reinforced grade is used. As a result, a clear hole is formed by laser processing. Furthermore, by forming a fluororesin liquid-repellent film on one surface of the nozzle plate in advance before forming holes in the nozzle plate, it is possible to prevent fluffing after forming the nozzle holes. Since the other surface uses an adhesive for adhering to the actuator, it is possible to prevent fluffing. Further, if the fluororesin liquid-repellent film is a solvent-soluble fluoropolymer having a heterocycle, since the adhesiveness is good, it is possible to form a thinner film without deforming the nozzle plate. Specifically, 0.1
It can be formed to a thickness of 1 μm. Forming a film thinner than 0.1 μm is not desirable because the effect as a liquid repellent film is lost. Alternatively, a fluorine- or silicon-based liquid-repellent film can be used, in which case 2 to 3 μm.
Can be any thickness. Forming thicker than 3 μm
Not only is it unnecessary, but it also becomes difficult to form a clean nozzle due to penetration into the nozzle during hole processing.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1A is a front view showing the nozzle plate of the present invention, and FIG. 1B is a perspective view of the same as seen from the front direction. As shown in FIGS. 1A and 1B, a nozzle plate 1 has a liquid-repellent film 3 applied to one surface of a substrate 2 formed of LCP, and has a large number of nozzles for ejecting an ink 5 at appropriate places. 4 are formed in a plurality of rows. The actuator 6 is bonded to the other surface of the substrate 2 with an adhesive 7.

The substrate 2 uses a non-reinforced grade LCP without filler. Here, it is a semi-aromatic polyester, and LC-5000 is used as a product of Unitika Ltd. under the trademark "Rod Run" series. The substrate 2 may be molded by injection molding or using a film-like LCP product.

The liquid repellent film 3 is formed by coating the substrate 2 with a fluororesin which can be baked at a temperature of 180 ° C. or less after the substrate 2 is formed. 180 ° C. is the heat distortion temperature of LCP. As a coating method, a method such as spin coating or dip coating is used, and the adhesion surface with the actuator is masked. Here, as the liquid-repellent film 3, a solvent-soluble fluoropolymer having a heterocycle is coated to a thickness of 0.1 to 1 μm and used. In FIG. 1B, W represents the thickness of the liquid repellent film 3, and here W = 0.1 to 1 μm. In addition to this, a fluorine-based or silicon-based liquid repellent film may be coated to a thickness of 1 to 3 μm and used.

After that, by laser processing using an excimer laser or the like, minute holes are formed to penetrate the substrate 2 and the liquid repellent film 3. This becomes the nozzle 4. And the substrate 2
An adhesive 7 for adhering to the actuator 6 is coated on the other surface thereof to adhere to the actuator 6. Other than this, the following steps may be performed. After forming the liquid-repellent film 3 on the substrate 2, the other surface of the substrate 2 is bonded to the actuator 6 with the adhesive 7. After that, by laser processing using an excimer laser,
A small hole is formed through the liquid repellent film 3, the substrate 2, and the adhesive 7 to form the nozzle 4. At this time, since the substrate 2 uses the unfilled LCP, the filler is not left in the nozzle 4 portion and a clean hole is formed. After making a hole, ultrasonically clean it to wash away debris. At this time, since the liquid repellent film 3 and the adhesive 7 are coated on both surfaces of the substrate 2,
It is possible to prevent fluffing in ultrasonic cleaning and wiping.

As described above, since the nozzle plate 1 of the present invention uses LCP which is a semi-aromatic polyester for the substrate 2, almost all inks can be used.
Further, even if the nozzles are highly integrated to improve the resolution, the molding can be performed with a thin wall, the damage to the core pin of the mold is extremely reduced, and the laser processing cost can be reduced to reduce the cost. Further, since the coefficient of thermal expansion of the actuator 6 is close to that of the actuator 6, peeling from the actuator 6 is unlikely to occur. Further, since the heat resistant temperature is high, the selection range of materials that can be used as the liquid repellent film 3 and the adhesive 7 is widened.

Further, since the nozzle plate 1 of the present invention is coated with a solvent-soluble fluoropolymer having a heterocycle as the liquid-repellent film 3 on one surface thereof and an adhesive 7 on the other surface thereof, holes are drilled by a laser. A clean hole can be formed by processing, and there is no fluffing caused by ultrasonic cleaning or wiping during use. Therefore, since the nozzle shape is clean, there is no variation in the flight direction of the ink droplets ejected from the nozzles due to the bending of the droplets or variation in the ink ejection timing. Therefore, the ink is properly ejected, and high print quality can be obtained.

[0022]

As described above, since the nozzle plate of the present invention uses the liquid crystal polymer as its material, the nozzle plate is not eroded by the ink solvent,
Almost any ink can be used in an inkjet printer. Furthermore, since the nozzle plate of the present invention uses liquid crystal polymer as its material, it can be molded thin even if the nozzles are highly integrated to improve the resolution, so that the core pin of the mold is not damaged. The number is extremely small, and the laser processing cost is also reduced, so that the cost can be reduced. Furthermore, since the nozzle plate of the present invention uses a liquid crystal polymer as its material, the difference in the coefficient of thermal expansion from PZT, which is the material of the actuator, becomes small, and peeling of the joint with the actuator due to temperature change occurs. Hateful.

Furthermore, since the nozzle plate of the present invention uses a liquid crystal polymer as its material, it has a high heat resistance temperature and a wide selection range of liquid repellent film agents and adhesives. Further, a fluororesin liquid-repellent film is formed on the outer surface of the nozzle plate by 0.1
Since the coating is 3 μm thick, it is possible to form a clean nozzle hole without fluffing. Thereby, proper ink ejection can be obtained and a print head with high print quality can be formed.

[Brief description of drawings]

FIG. 1A is a front view of a nozzle plate according to an embodiment of the present invention, and FIG. 1B is a perspective view seen from the front direction.

[Explanation of symbols]

 1 Nozzle plate 2 Substrate 3 Liquid repellent film 4 Nozzle 7 Adhesive

Claims (5)

[Claims] 1. A nozzle plate in which nozzle holes for ejecting ink are formed, wherein the material is liquid crystal polymer (LCP). 2. The nozzle plate according to claim 1, wherein the liquid crystal polymer is a semi-aromatic liquid crystal polyester. 3. The nozzle plate according to claim 1, wherein a liquid repellent film made of a fluororesin is formed on the outer surface of the nozzle plate. 4. The nozzle plate according to claim 3, wherein the liquid repellent film made of fluororesin is a solvent-soluble fluoropolymer having a hetero ring. 5. The method according to claim 3 or 4, wherein the fluororesin liquid repellent film has a thickness of 0.1 μm or more and 3 or more.
A nozzle plate having a diameter of not more than μm.