JPH10128806A - Nozzle plate, manufacturing method and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nozzle plate excellent in printing quality, low cost and excellent in mass productivity, and a method and an apparatus for manufacturing the same. SOLUTION: The surfaces of the cavities of a fixed mold 22 and a movable mold 23 are heated to a temperature not lower than the softening point of the molten resin material, and the molds 22 and 23 are assembled. Both dies 22, 23
Is put into a negative pressure state. The molten resin material is filled while maintaining the cavity 24a in a negative pressure state, and the core pins 32 are moved during or after the filling of the molten resin material to compress a portion where a plurality of nozzles are formed. .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a nozzle plate used for an ink jet head, and a method and an apparatus for manufacturing the nozzle plate.

[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, ink in the ink flow path is ejected as droplets from nozzles. In addition, there is known a configuration in which ink is introduced into an ink flow path from an ink introduction port when the volume is increased. Such an ink jet head prints characters, figures, and the like by ejecting ink droplets onto a recording medium in accordance with print data.

[0003] As this kind of ink jet head,
For example, as described in JP-A-63-247051, a plurality of parallel ink flow paths separated by piezoelectric ceramic partition walls are formed, and the other end is connected to ink supply means for supplying ink. Ink is ejected from the nozzles by changing the volume of the ink flow path by deforming the partition.

A method of manufacturing a nozzle plate having such nozzles is disclosed in, for example, Japanese Patent Application Laid-Open No. 3-297.
As described in JP-A-51-51, there is known a method of forming a nozzle by injection-molding a polymer resin material and then performing re-laser processing with an excimer laser device or the like.

[0005]

However, an excimer laser device or the like is a very expensive device, and the processing time of the nozzle, that is, the thickness of the portion where the nozzle is processed is proportional to the processing time.
Since the production cost of the nozzle plate is increased, there is a demand to reduce the thickness of the portion where the nozzle is processed as much as possible in order to shorten the processing time of the nozzle as much as possible.

On the other hand, if the nozzle can be formed simultaneously with the formation of the nozzle plate during injection molding, there is no need to perform post-processing using an excimer laser device or the like, and it is thought that production costs can be reduced. In this case, the tip surface of the core pin forming a nozzle having a diameter of several μm to several tens μm must be in contact with the opposite cavity wall surface at each mold clamping so that the core pin does not break, and the positioning control is performed. It was extremely difficult.

[0007] Even if such positioning control is performed well, the following problems have occurred in ordinary injection molding.

During injection molding, when the injected molten resin material collides with a core pin forming a nozzle, it flows around the core pin, splitting right and left, and merges again to fill the cavity. Cuts are likely to be formed at the confluence of the nozzles, and the nozzles do not have a clean shape, which has a negative effect on print quality.

Further, when the core pins are arranged in a plurality of rows and a plurality of columns with the high integration of the nozzles for improving the printing quality, the molten resin material becomes difficult to flow. It is necessary to increase the gap between the tip surface of the core pin and the cavity wall surface facing the core pin, or increase the thickness of the entire nozzle plate. However, if the gap is made thicker, the thickness of a portion to be processed by an excimer laser device or the like becomes thicker, which causes an increase in cost. Also, if the thickness of the entire nozzle plate is made thicker, the length of the core pin becomes longer. Since it is necessary to increase the length, the breakage rate of the core pin due to the injection pressure or the like during molding increases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a nozzle plate having excellent printing quality, low cost, and excellent mass productivity, and a method and apparatus for manufacturing the nozzle plate.

[0011]

According to the present invention, a molten resin material is filled in a cavity of an injection molding mold comprising a movable mold and a fixed mold, and ink is ejected onto a recording medium. A method of manufacturing a nozzle plate having a nozzle plate having a nozzle to be heated, the method comprising: heating a cavity surface of the movable mold and the fixed mold to a temperature equal to or higher than a softening point of the molten resin material; A first step of assembling the mold and the fixed mold, and, following the first step, a cavity formed by assembling the movable mold and the fixed mold with a negative pressure. A second step of filling the molten resin material while maintaining the cavity in a negative pressure state, and during or after the filling of the molten resin material, Move some or all of the nozzles to form multiple nozzles And a third step of compressing the site.

Therefore, the molten resin material is filled while the cavity is maintained in a negative pressure state, and a part or the whole of the movable mold is moved during or after the filling of the molten resin material, and a plurality of the molds are moved. Since the portion where the nozzle is formed is compressed, the injected molten resin material does not collide with the core pin forming the nozzle and flow around the core pin separately to the left and right. As a result, no trace of the confluence of the resin material is formed near the nozzle, and a nozzle plate having excellent printing quality is manufactured.
Also, during or after the filling of the molten resin material, part or all of the movable mold is moved, so that the flow of the molten resin material is not hindered, compression molding is performed, and the nozzle plate is easily It is formed thin.

The movable mold has a core pin forming a nozzle, and in a third step, at least the core pin is moved to compress a portion where a plurality of nozzles are formed, thereby forming a nozzle. In addition, since at least the core pin is moved, there is no need to increase the length of the core pin, and the probability of breakage of the core pin is reduced, which is advantageous in reducing costs.

Further, in the third step, a part where the plurality of nozzles are formed is made to be a thin part by moving a part or the whole of the movable mold, and the nozzle can be pierced in the thin part. . In this case, as a post-processing, it is necessary to process the re-nozzle by excimer laser processing or the like. However, since the portion where the nozzle is formed is a thin portion with a small thickness, the time required for the processing becomes shorter or shorter, and the cost is reduced. It is advantageous in aiming.

The nozzle plate according to the present invention is manufactured by the above-described manufacturing method and includes a plurality of nozzles, a plurality of nozzles perforated in a thin portion, and a resin material near the nozzles. No trace of the junction is formed, and the printing quality is excellent.

According to the manufacturing apparatus of the present invention, an injection molding die including a movable die and a fixed die is provided in a cavity.
In a nozzle plate manufacturing apparatus for filling a molten resin material and forming a nozzle plate having a nozzle for ejecting ink to a recording medium, a surface of a cavity of the movable mold and a fixed mold is formed of the molten resin material. Heating means for heating to a temperature higher than the softening point; negative pressure means for setting the inside of a cavity formed by assembling the movable mold and the fixed mold to a negative pressure state; and injection molding the molten resin material. When filling the cavity of the mold, during or after the melting of the molten resin material, moving part or all of the movable mold to compress a portion where a plurality of nozzles are formed. Prepare. Therefore, the temperature of the cavity surface can be maintained at a high temperature close to the melting temperature of the material from the start of filling to the completion of filling by heating by the heating hand, whereby the solidification rate of the resin material near the cavity surface is reduced, In addition, since molding can be performed at a low pressure without increasing the amount of movement of the movable mold, accurate position control is possible, and a nozzle plate is manufactured with high accuracy.

The compression means moves at least a core pin forming the nozzle, and can form the nozzle without performing processing by an excimer laser device or the like.

The heating means has a heating coil inserted between the movable mold and the fixed mold, and the heating coil is connected between the movable mold and the fixed mold. And a high-frequency heating means for heating the cavity surface by flowing a high-frequency current. Therefore, by the heating coil,
The cavity surface is heated without direct contact, preventing damage to the cavity surface.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the ink-jet head 1 has a flat piezoelectric ceramic plate 2 composed of polarized piezoelectric / electrostrictive elements, a ceramic cover plate 3, and a plurality of nozzles 4,. And a nozzle plate 5 provided with a nozzle plate.

A plurality of grooves (not shown) are formed in the piezoelectric ceramic plate 2, and metal electrodes (not shown) are provided on the upper half of the side walls of the grooves. The cover plate 3 has an ink inlet 6 and a manifold (not shown).

The piezoelectric ceramic plate 2 and the cover plate 3 are adhered by an epoxy-based adhesive, so that the ink-jet head 1 has a plurality of laterally spaced predetermined spaces covered with the upper surfaces of the grooves. An ink flow path 11 (see FIG. 2) is configured.

As shown in FIG. 2, the end faces of the piezoelectric ceramic plate 2 and the cover plate 3 are connected to the nozzles 4 corresponding to the positions of the ink passages 11, respectively.
The nozzle plate 5 is adhered. The nozzles 4 formed in the nozzle plate 5 include a tapered portion 4a and a nozzle hole 4b.
Or the three-dimensional shape, aperture and pitch of the ink jet head 1 determine the print quality.

Next, an apparatus for manufacturing the nozzle plate 5 will be described.

The apparatus 21 for manufacturing the nozzle plate 5
As shown in FIG. 3, a cavity 24a of an injection mold 24 including a fixed mold 22 and a movable mold 23 (see FIG. 5).
The nozzle plate 5 is filled with a molten resin material.
Is formed.

The above-mentioned apparatus includes a high-frequency heating means 26 as a heating means for heating the cavity surfaces of the fixed mold 22 and the movable mold 23 to a temperature higher than the softening point of the molten resin material, in addition to the usual mold temperature adjusting means 25. A vacuum pump 27 as a negative pressure means for setting a negative pressure inside a cavity 24a formed by assembling the movable mold 22 and the fixed mold 23, and injection molding the molten resin material. Cavity 24a of mold 24
During filling, during or after the melting of the molten resin material, by moving a part or all of the movable mold 23,
Pressing means 28, which is compression means for compressing a portion where a plurality of nozzles 4 are formed, is provided. Further, the fixed mold 22 located on the lower side is filled with a molten resin material through a resin supply nozzle 29.

A series of operations for manufacturing the nozzle plate 5 are controlled by the control means 30.

Further, as shown in FIG. 4, the movable mold 23 has an O-ring 31 provided around a molding recess 23a forming a cavity 24a for molding the nozzle plate 5, and has a recess 23a. A plurality of core pins 32 for forming the nozzles 4 are provided in a line, and the core pins 32 move during or after the melting of the molten resin material to form a plurality of nozzles 4.・ It compresses the part where is formed.

The high-frequency heating means 26 has a heating coil 34 inserted between the two dies 22 and 23. The heating coil 34 is inserted between the two dies 22 and 23. Is to be heated. The heating coil 34 heats without directly contacting the cavity surface, thereby preventing the cavity surface from being damaged. In addition,
Since the reciprocal of the distance between the heating coil 34 and the cavity surface is proportional to the temperature of the cavity surface, it is necessary to keep the distance constant.

Therefore, in order to manufacture the nozzle plate 5, first, the heating coil 34 is inserted between the two dies 22, 23, and a high-frequency current is supplied to heat the cavity surfaces of the two dies 22, 23.

Then, when the temperature of the cavity surface reaches a predetermined temperature, the heating by the high frequency heating means 26 is stopped, the heating coil 34 is moved to perform the mold clamping operation, and then the cavity 24a of the molten resin material is formed. Before the mold clamping operation is completed, suction from the inside of the re-cavity 24a is started by the vacuum pump 27 so that the injection into the inside becomes smooth.

After the resin supply nozzle 29 of the molding machine is brought into contact with and connected to the fixed mold 22, when the degree of vacuum in the cavity 24a increases, as shown in FIG. Inject the material R. The molten resin material R forms the nozzles 4,.
After passing through the vicinity, as shown in FIG. 5B, before the cavity 24a is completely filled, the core pins 32,.
Are moved until the upper end surfaces of the core pins 32,... Almost contact the opposing cavity surfaces (see FIG. 5C).

In this case, the temperature of the cavity surface can be maintained at a high temperature close to the melting temperature of the material from the start of the filling to the completion of the filling, whereby the solidification rate of the resin material near the surfaces of the dies 22, 23 becomes slow. The movement amount of the core pins 32, which are a part of the cavity 24a is about 1 mm or less and can be performed at a low pressure, so that extremely accurate position control becomes possible, and the core pins 32,. · Damage due to contact with the cavity surface is also prevented.

Then, the molten resin material R is transferred to the cavity 2
After the inside of the nozzle plate 5a is completely filled, the suction by the vacuum pump 27 is stopped, and the pressure-holding, cooling, mold-opening, and ejection processes, which are ordinary molding processes, are performed.
Is manufactured.

If the nozzle plate is manufactured as described above, the nozzle is formed simultaneously with the formation of the nozzle plate by the compression molding using the core pins 32,..., As in the conventional excimer laser apparatus. The nozzle can be formed without performing post-processing such as by using a nozzle plate having a clean shape without a break near the nozzle which adversely affects print quality. It has been confirmed that the ink jet head has good print quality.

In the above-described embodiment, after the molten resin material R passes through the vicinity of the core pins 32,... And before the molten resin material R is completely filled in the cavity 24a, the core pins 32,.
Are moved until they come into contact with the surface of the cavity, but after the molten resin material R has passed around the core pins 32,.
May be moved until the upper surface of the core pin contacts the opposing cavity surface.
However, in that case, it is desirable to provide an escape portion for the molten resin material accompanying the movement of the core pin.

Further, in the above-described embodiment, the nozzle is formed simultaneously with the injection molding of the nozzle plate 5. However, in order to prevent the tip surface of the core pin from being worn, the core pin is completely provided on the opposing cavity surface. Without contacting, stop several micrometers to about 10 μm before,
You may make it form the nozzle plate which made the site | part in which a nozzle is formed the thin part.

Further, as the material of the nozzle plate 5, a synthetic resin material is used, but ceramic powder or metal powder can also be used. That is, since high integration of nozzles is desired in the nozzle plate of the ink jet head as described above, if the molding die including the core pin is to be miniaturized as it is to achieve high integration, the molten resin material during injection molding is required. Has a large flow resistance, which is not preferable for injection molding. Therefore, if the ceramics or metal injection molding technology is used, the mold size can be set larger than the actual size, so that it is possible to correspond to an inkjet head in which nozzles are more highly integrated by using the same. is there. In this case, first, ceramic powder or metal powder is mixed and kneaded with a binder such as a resin material and injection-molded to obtain an injection-molded body. Then, the injection molded body is degreased, the resin material is removed from the injection molded body, and the obtained degreased body is sintered to obtain a nozzle plate. The degreased body shrinks by this sintering process,
Since the size of the nozzle is about 10 to 30% smaller than the size of the mold, the size and arrangement pitch of the nozzles on the mold side need to be larger than the final product in consideration of the shrinkage. As the ceramic powder or the metal powder, a powder of alumina, zirconia, silicon nitride, silicon carbide, stainless steel, or the like can be used.

The present invention is not limited to the above embodiment, but can be applied to the formation of a nozzle plate for various ink jet heads such as a so-called thermal jet type.

[0040]

The present invention is embodied in the above embodiment and has the following effects.

In the manufacturing method according to the present invention, the molten resin material is filled while the cavity is maintained in a negative pressure state, and a part or all of the movable mold is supplied during or after the filling of the molten resin material. Is moved to compress the portion where a plurality of nozzles are formed, so that the injected molten resin material collides with a core pin forming the nozzle and flows around the core pin in a left and right direction. There is no such thing.
As a result, no trace of the confluence of the resin material is formed near the nozzle, and a nozzle plate having excellent printing quality is manufactured. Further, since part or all of the movable mold is moved during or after filling with the molten resin material, compression molding can be performed without obstructing the flow of the molten resin material.

In the third step, at least the core pin of the movable mold is moved to compress a portion where a plurality of nozzles are formed, thereby forming a nozzle.
It is not necessary to increase the length of the core pin, and the probability of breakage of the core pin is reduced. In addition, since the nozzle is formed at the time of injection molding of the nozzle plate, it is not necessary to perform the excimer laser processing which was conventionally required, thereby reducing the process. The number and production equipment can be reduced, and the production cost can be greatly reduced.
It is also advantageous in terms of mass productivity.

Also, in the third step, a part where the plurality of nozzles are formed may be made a thin part by moving a part or the whole of the movable mold, and the nozzle may be pierced in the thin part. . In this case, as the post-processing, it is necessary to process the re-nozzle by excimer laser processing or the like. The time is shortened, which is advantageous in reducing costs.

The nozzle plate according to the present invention is manufactured by the above-described manufacturing method, is provided with a plurality of nozzles, or has a plurality of nozzles pierced in a thin portion. No trace of the part is formed, and the printing quality is excellent.

In the manufacturing apparatus according to the present invention, the temperature of the cavity surface can be maintained at a high temperature close to the melting temperature of the material from the start of filling to the completion of filling by heating by the heating means. Solidification speed can be reduced, and molding at low pressure becomes possible without increasing the moving amount of the movable mold.
Accurate position control becomes possible, and a nozzle plate can be manufactured with high accuracy.

Further, since the compression means moves at least the core pin forming the nozzle and forms the nozzle hole simultaneously with the molding, it is not necessary to perform post-processing by an excimer laser device or the like, and the nozzle plate can be simplified. Can be manufactured.

As the heating means, a heating coil is inserted between the movable mold and the fixed mold and a high-frequency current is applied to the heating coil to heat the cavity surface. Can be heated without direct contact, and damage to the cavity surface can be prevented.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a schematic structure of an inkjet head according to the present invention.

FIG. 2 is a sectional view showing the ink jet head.

FIG. 3 is an explanatory view showing a schematic structure of an injection molding apparatus for manufacturing a nozzle plate according to the present invention.

FIG. 4 is an explanatory view showing an injection mold for the nozzle plate.

FIGS. 5A and 5B are explanatory diagrams of a process of manufacturing a nozzle plate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ink jet head 4 Nozzle 5 Nozzle plate 11 Ink flow path 21 Nozzle plate manufacturing apparatus 22 Fixed side mold 23 Movable side mold 24 Injection mold 24a Cavity 26 High frequency heating means 27 Vacuum pump 28 Press means (compression means) 32 core pin 34 heating coil

Claims (8)

[Claims] 1. A nozzle plate having a nozzle for ejecting ink to a recording medium is formed by filling a molten resin material into a cavity of an injection molding mold including a movable mold and a fixed mold. A method of manufacturing a nozzle plate, comprising: heating a cavity surface of the movable mold and the fixed mold to a temperature equal to or higher than a softening point of the molten resin material; and forming the movable mold and the fixed mold. A first step of assembling the mold, and a second step of setting the cavity formed by assembling the movable mold and the fixed mold into a negative pressure state following the first step.
And after the second step, filling the molten resin material while maintaining the cavity in a negative pressure state, during or after the filling of the molten resin material, a part of the movable mold or A third step of moving the entirety and compressing a portion where a plurality of nozzles are to be formed. 2. The movable mold has a core pin forming a nozzle. In a third step, at least the core pin is moved to compress a portion where a plurality of nozzles are formed, thereby forming a nozzle. The method for manufacturing a nozzle plate according to claim 1, wherein 3. In a third step, a part or the whole of the movable mold is moved to make a portion where a plurality of nozzles are formed a thin portion, and a nozzle is perforated in the thin portion. The method for manufacturing a nozzle plate according to claim 1. 4. A nozzle plate formed by the manufacturing method according to claim 1 and comprising a plurality of nozzles. 5. Formed by the manufacturing method according to claim 3,
A nozzle plate having a plurality of nozzles perforated in a thin portion. 6. A nozzle plate having a nozzle for injecting ink onto a recording medium is formed by filling a molten resin material into a cavity of an injection mold including a movable mold and a fixed mold. A heating means for heating a cavity surface of the movable mold and the fixed mold to a temperature equal to or higher than a softening point of the molten resin material; and a mold comprising the movable mold and the fixed mold. Negative pressure means for setting the inside of the cavity formed by assembling into a negative pressure state; and when filling the molten resin material into the cavity of the injection mold, during or after the melting of the molten resin material, A compression means for moving a part or the whole of a mold to compress a portion where a plurality of nozzles are formed. 7. The nozzle plate manufacturing apparatus according to claim 6, wherein said compression means moves at least a core pin forming a nozzle. 8. The heating means has a heating coil inserted between the movable mold and the fixed mold, and connects the heating coil to the movable mold and the fixed mold. The nozzle plate manufacturing apparatus according to claim 6 or 7, wherein the apparatus is a high-frequency heating means inserted between the nozzle plates to heat a cavity surface by flowing a high-frequency current.