JP2000158647A - Ink jet recording head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable ink jet recording head capable of having the resistance to fifty thousands or more times of wiping and surely wiping ink adhered to a nozzle face. SOLUTION: An ink repellent thin film 117 of an ink jet recording head body 11 is lower than a lower face of an auxiliary plate 12 to form a recess section. The recess section prevents an end section of the ink repellent thin film 117 from being directly pressurized by a tip of a wiper blade during the wiping so that peeling of the ink repellent thin film 117 is prevented. In order to ensure the wiping of the ink, it is necessary to make the recessed depth to be not greater than a double of a thickness of a diaphragm 112.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording head (hereinafter, abbreviated as a recording head) used in an ink jet recording apparatus (hereinafter, abbreviated as a recording apparatus) for performing recording by discharging ink as small droplets from nozzles. ).

[0002]

2. Description of the Related Art FIG. 4 is a conceptual view showing a main part of an example of a conventional recording apparatus, and FIG. 5 is a perspective partial sectional view showing a structure of a recording head 1 used in the recording apparatus. In the recording apparatus shown in FIG. 4, the recording head 1 travels along the guide shaft 2, and ink droplets ejected from the recording head 1 adhere to the recording paper 6 sent over the platen 5, and print recording is performed. Is done. The recording head 1 is shown in FIG.
As shown in FIG. 1, the recording head main body 11 and the auxiliary plate 12 are provided.

The recording head body 11 has a flow path substrate 11 having grooves on the front and back surfaces formed as ink flow paths from an ink supply section 114 to a nozzle 116 through an ink pressurizing chamber 115.
1, two vibrating plates 112 bonded to both surfaces thereof, and a piezoelectric element 113 bonded to the outer surface of the vibrating plate 112 corresponding to the ink pressurizing chamber 115 for each ink flow path. In this conventional example, the flow path substrate 111 is made of a single-crystal silicon wafer having a thickness of 0.76 mm, and the diaphragm 112 is made of Pyrex, a kind of borosilicate glass having a thermal expansion coefficient very close to that of silicon. Made of glass, its thickness is 0.03mm
It is. The flow path substrate 111 and the vibration plate 112 are joined by electrostatic joining, and the piezoelectric element 113 is joined by an adhesive.
26 ink passages are formed on one surface and 52 ink passages are formed on both surfaces at an interval of 508 μm. An example of the outer shape of the head main body 11 is 6.5 mm long, 18.6 mm wide, and 0.82 mm thick.

When a predetermined pulse voltage is applied to the piezoelectric element 113, the piezoelectric element 113 expands and contracts and vibrates integrally with the diaphragm 112 to pressurize the ink in the ink pressurizing chamber 115. As a result, the nozzle Ink droplets are ejected from. An ink-repellent film 117 is formed on the nozzle opening surface of the recording head main body 11 . This ink-repellent film 117 is formed in order to improve the cut of the ejected ink and to prevent the ink from adhering and remaining on the nozzle opening surface.

The auxiliary plate 12 is a component for protecting the recording head main body 11 from external impact. The recording head main body 11 is fitted in the center of the auxiliary plate 12, and the surface of the ink repellent film 117 of the recording head main body 11 is provided. And the lower surface of the auxiliary plate 12 are integrated so that they are flush with each other. The auxiliary plate 12 is made of an inexpensive polyphenylene ether resin having excellent ink resistance, and is formed by injection molding.

[0006] Such a recording head 1 is required to always normally eject ink. Therefore, the inner surface of the ink flow path is made hydrophilic by an alkali treatment or the like to prevent air bubbles from staying in the ink flow path. Further, an ink repellent film 117 made of a fluorine compound or the like is formed on the nozzle opening surface. This prevents ink from accumulating on the nozzle opening surface. When the nozzle 116 is clogged, when the ink ejection direction is abnormally deflected, or when the recording for a predetermined time has elapsed without causing nozzle clogging or ink deflection, the protective suction device (FIG. In 4, simply protector,
The ink in the ink flow path is sucked from the nozzle 116 by a nozzle 3 to remove foreign matter such as dust and air bubbles and dry ink in the ink flow path. The ink adhering to the surface of the 117 and the surface of the auxiliary plate 12 around it is wiped off to restore a normal print record.

The suction of the ink is performed by the protection device 3 provided in a portion outside the area of the recording paper 6. The protection device 3 connects the cap 31 and the pump 33 to a cap 31 for forming a closed space in close contact with the lower surface of the recording head 1, a pump 33 for depressurizing the inside of the cap 31 and sucking ink. And is moved up and down by a lifting mechanism (not shown).

When sucking ink, first, the recording head 1 is moved to a position immediately above the protective device 3, and then the cap 31 is pressed and adhered to the lower surface of the recording head 1 (the surface of the auxiliary plate 12) by an elevating mechanism. Then, the pressure in the cap 31 is reduced by driving the pump 33, and the ink in the ink flow path is
Suction from 6. The ink sucked by the pump 33 is collected in a waste ink container (not shown).

[0009] wiping the ink surface and the like of the ink repellent film 117 by the wiper 4 is in a state in which the wiper 4 is the height of the wiper 4 at a height to contact the lower surface of the recording head 1 is adjusted, FIG recording head 1 The process is executed by moving to the left from the state of No. 4.
FIG. 6 shows this ink wiping state. FIG.
The positional relationship between the wiper 4 and the recording head 1 is opposite to that in FIG. 4, but FIG.
(B) has shown the state of the latter half of wiping. Ink repellent film 117
The ink adhering to the surface of the wiper blade 41 is wiped by the tip of the wiper blade 41, moves downward along the side surface of the wiper blade 41, and is absorbed by the sponge. By making the sponge 42 absorb the ink, the surroundings are prevented from being stained with the ink. After the ink adhering to the surface of the ink-repellent film 117 and the surface of the auxiliary plate 12 around the surface of the ink-repellent film 117 are thus removed, print recording is started. The running speed of the recording head 1 at the time of ink wiping is as follows.
The speed is about 50 mm / sec.

Since the wiper 4 does not need to contact the recording head 1 at the time of normal printing and recording, the wiper 4 is attached to an elevating mechanism for vertically moving so as to be able to contact the recording head 1 only when wiping the ink. Is Hs40 °, thickness
It is made of a flat plate made of 0.5 mm silicone rubber, and its tip is rounded so as not to damage the surface of the ink-repellent film 117 and the surrounding auxiliary plate 12. In FIG. 6A, the length of the portion where the tip of the wiper 4 projects above the lower surface of the recording head 1 (the amount of bite) is 0.7 mm.
When ink is filled into the ink flow path, the above-described suction and wiping of ink are performed in exactly the same manner.

[0011]

When the recording head 1 is mounted on a facsimile, the wiping operation of the ink by the wiper 4 (hereinafter referred to as wiping) is performed about 50,000 times before the life of the recording apparatus. Accordingly, in order to use the recording head 1 without replacing it for the life of the recording apparatus, the surface of the recording head 1 rubbed by 50,000 wipings, that is, the ink-repellent film 117 formed on the nozzle opening surface and its surroundings It is necessary that the surface of the auxiliary plate 12 does not deteriorate. Above all, in particular, peeling of the ink repellent film 117 is a problem, and according to the results of experiments conducted by the inventor, it has been found that there is a case where peeling from the end of the diaphragm 112 occurs after about 10,000 wiping operations. .

An object of the present invention is to solve the above-described problem that the ink-repellent film 117 peels off during wiping, and
An object of the present invention is to provide a highly reliable recording head that can withstand wiping for more than ten thousand times and that can reliably wipe off ink adhering to the surface of an ink-repellent film and the surface of an auxiliary plate around the surface by wiping.

[0013]

The inventor of the present invention has investigated the state of peeling of the ink-repellent film mainly on the recording head from which the ink-repellent film has been peeled during wiping. As a result, it is understood that the important points are peeling of the ink-repellent film during wiping and whether the surface of the ink-repellent film of the recording head body projects or is recessed from the surface of the surrounding auxiliary plate. The relationship between the position of the surface of the ink-repellent film with respect to the surface and the presence or absence of peeling of the ink-repellent film was investigated, and the results shown in FIG. 7 were obtained. The horizontal axis in FIG. 7 is the position of the surface of the ink-repellent film with reference to the surface of the auxiliary plate (in FIG. 7, described as “the position of the nozzle opening surface with reference to the surface of the auxiliary plate”), and is concave. The case is indicated by negative (-), and the protruding case is indicated by positive. The vertical axis indicates the frequency of occurrence of nozzles (non-defective nozzles) in which the ink-repellent film was not peeled off after 50,000 times of wiping and nozzles (defective nozzles) in which the ink-repellent film was peeled off, and the bars indicated by hatching did not peel off. Nozzles, and solid black bars indicate the nozzles that peeled off.

The following can be said from the results of this investigation. 1)
When the surface of the ink-repellent film of the recording head body is at the same level as the surface of the auxiliary plate or is depressed, the ink-repellent film is not peeled at all. 2) When the protrusion is 10 μm or more, the ink-repellent film may be peeled off, and when the amount of protrusion is increased, the rate of peeling tends to increase.

If the surface of the ink-repellent film of the recording head body protrudes from the surface of the auxiliary plate, the ink-repellent film often peels off during wiping because the tip of the wiper blade is edged at the edge of the recording head body during wiping. It is presumed that this is due to the force acting to peel off the ink-repellent film from the edge portion where the ink-repellent film is considered to be most easily peeled off. Therefore, if the tip of the wiper blade is prevented from contacting the edge of the recording head body at the time of wiping, it can be expected that peeling of the ink-repellent film can be prevented.

Based on the above investigation results, in the present invention, a flow path substrate having an ink flow path formed of ink pressurizing chambers and nozzles is formed and joined to the ink flow path forming surface. Recording head body comprising a piezoelectric element joined to an outer surface of a vibrating plate and a vibrating plate corresponding to an ink pressurizing chamber, and an ink-repellent film formed on a nozzle opening surface, and an ink jet recording head In an ink jet recording head having an auxiliary plate for protecting the main body from external impact, the ink-repellent film is recessed from the surface of the auxiliary plate.

Since the ink-repellent film of the recording head body is recessed with respect to the auxiliary plate surface, the tip of the wiper blade contacts the edge of the recording head body during wiping, and a force is applied to the edge of the ink-repellent film at the edge. Has no effect. In the invention of claim 1, the recess of the ink-repellent film from the auxiliary plate surface is 0.1 to 2 times the distance from the nozzle to the auxiliary plate (the invention of claim 2).

If the ink-repellent film is slightly depressed from the surface of the auxiliary plate, the tip of the wiper blade contacts the edge of the recording head body during wiping and does not exert a force on the edge of the ink-repellent film at the edge. . On the other hand, if the dent is twice as long as the distance from the nozzle to the auxiliary plate, the surface of the ink-repellent film around the nozzle can be reliably wiped by the wiper due to the elastic deformation of the wiper.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to examples. It is to be noted that the same reference numerals are used for portions having the same functions as those of the conventional technology. FIG. 1 is a sectional view showing the structure of an embodiment of a recording head 1a according to the present invention.

As described in the section of "Means for Solving the Problems", according to the result of the investigation mainly on the recording head 1 from which the ink-repellent film 117 has peeled off at the time of wiping, 1)
If the surface of the ink-repellent film 117 of the recording head body 11 is at the same level as or lower than the lower surface of the auxiliary plate 12, the ink-repellent film 117 is not peeled off at all. 2) Ink-repellent film 117
If the surface of the
117 may peel off, and as the amount of protrusion increases, the rate of peeling tends to increase.

Therefore, the recording head 1a according to the present invention
This is based on the expectation that the ink-repellent film 117 can be prevented from peeling if the tip of the wiper blade does not contact the end of the ink-repellent film 117 of the recording head main body 11 during wiping. In other words, as shown in FIG. 1, in the recording head 1 a according to the present invention, the position of the surface of the ink-repellent film 117, which is the nozzle opening surface of the recording head main body 11 including the flow path substrate 111, is It is recessed from the lower level.

The amount of depression at the surface of the ink-repellent film 117 is determined by the following three requirements. 1) The ink-repellent film 117 does not peel off due to wiping. This requirement is the subject of the present invention itself,
As explained in the section “Means to solve the problem”
If the surface position of the ink-repellent film 117 is recessed from the lower surface of the auxiliary plate 12, peeling can be prevented. However, for reliable wiping of ink, which is the purpose of wiping, it is necessary to reliably wipe around the nozzle 116. According to the results of experiments and studies by the inventor, the amount of depression that satisfies this condition is less than twice the distance from the nozzle 116 to the auxiliary plate 12. In the case of the recording head body 11 having the configuration shown in FIG. 1, the distance from the nozzle 116 to the auxiliary plate 12 corresponds to the thickness of the diaphragm 112. In the embodiment in which the thickness of the vibration plate 12 was 30 μm, it was possible to reliably wipe off the adhered ink up to the depression amount of 60 μm.

2) Ink ejection is stable. If the position of the surface of the ink-repellent film 117, which is the nozzle opening surface, is more concave than the level of the lower surface of the auxiliary plate 12, the nozzle 11
The ink ejected from step 6 comes into contact with the inner wall of the auxiliary plate 12, and the ejected ink droplet changes the flight direction (deflects) or adheres to the inner wall to generate an ink pool, thereby making print recording impossible. there is a possibility. According to the results of the experimental study by the inventor, if the dent amount is within 140 μm, there is no deflection of the ejected ink droplets and no ink accumulation.

3) Complete sealing property can be ensured.
As described in the section of "Prior Art", when ink is sucked by the protection device 3, the recording head body 11 and the auxiliary plate 12 need to be fixed in a hermetically sealed state. On the other hand, when the adhesive or the like used adheres to the periphery of the nozzle 116 or enters the nozzle 116 when securing the adhesion in the hermetically sealed state, normal ink droplets are not ejected from the nozzle 116. In some cases, the ink is not ejected. In order to avoid such a situation, in this embodiment, a temporary fixing step using an adhesive and a hermetic sealing step using an adhesive sealing agent are used in combination.

First, the temporary fixing step will be described. The temporary fixing step was performed using an automatic machine because it was necessary to accurately position and fix the recording head body 11 and the auxiliary plate 12, which were small components. This step will be described with reference to FIGS. 2 and 3 showing the essential points of the temporary fixing step by the automatic machine.

1) The recording head main body 11 and the auxiliary plate 12 are set on a pallet 81 serving as a positioning jig. 2) An adhesive 83 is placed in a tray 82 serving as a predetermined container. As the adhesive 83 used here, High Super 30 manufactured by Cemedine Co., Ltd., which is an adhesive having a high viscosity, was used to prevent the adhesive 83 from flowing to the nozzle opening after application. This adhesive is an epoxy-based adhesive having a viscosity of about 1500 poise.

3) The start button of the automatic machine is pressed, and the following operation is automatically performed. 4) the arm 84 grasps the upper side surface of the recording head main body 11 lifts the recording head main body 11, moved to the application position of the adhesive 83 remain grabbed recording head main body 11 [FIGS. 2 (a)].

5) The needle 85 descends and the plate 82
The adhesive 83 in the inside is collected, and then rises to the original position again (FIG. 2B). 6) The needle 85 is turned 90 degrees and turned sideways, and the adhesive 83 is collected at the tip by the centrifugal force due to the rotation [FIG. 2 (c)].

7) Arm holding recording head body 11
84 moves, and the application of the adhesive 83 to the side surface of the recording head main body 11 is started. At this time, the position where the tip of the needle 85 starts to apply the adhesive 83 is 1 mm from the nozzle opening surface in the vertical direction.
The distance between the tip of the needle 85 and the side surface of the recording head body 11 is set to 0.1 mm (FIG. 3A).

8) Subsequently, the arm 84 moves and the needle 84
85 moves to a position where the tip of the adhesive 83 finishes applying the adhesive 83 (a position where the vertical direction is 3 mm from the nozzle opening surface and the distance between the tip of the needle 85 and the side surface of the recording head body 11 is 0.2 mm) [FIG. b)).

In the above-described step of applying the adhesive 83, if the distance between the tip of the needle 85 and the side surface of the recording head body 11 is increased, the amount of the adhesive 83 applied increases, and if the distance is reduced, the adhesive 83 decreases. On the other hand, as the application proceeds, the amount of the adhesive 83 at the tip of the needle 85 decreases, and the amount of application decreases. Therefore, balancing both of these
In order to apply a uniform thickness to the entire application position, it is effective to reduce the distance at the beginning of application and increase the distance at the end of application as described above.

9) The arm 84 further moves, and the tip of the needle 85 moves horizontally from the side surface of the recording head main body 11 to a position of 3 mm, and stops at that position for 3 seconds (FIG. 3C). 3
The second stop is for stopping the adhesive 83, but the adhesive 83 does not break when the stop position is less than 3 mm, and the separated adhesive 83 hangs when the stop position is more than 3 mm. Ink-repellent film 11 which is the nozzle opening surface
May adhere to 7.

10) After the arm 84 is rotated by 180 degrees and the opposite side surface of the recording head main body 11 is set to the needle 85 side, from 5)
The same step as step 9) is repeated, and the adhesive 83 is applied to the opposite side surface of the recording head main body 11 . 11) The arm 84 moves to the upper part of the auxiliary plate 12, and the adhesive is applied to the side.
The recording head main body 11 coated with 83 is inserted into the auxiliary plate 12 (FIG. 3D, but this drawing shows a state immediately before insertion).

At this time, the recording head body 11 is pushed into the pallet 81 until it is brought into contact with the pallet 81.
The ink repellent film of the recording head body 11 is formed by the 30 μm projection.
Position 117 is recessed by 30 μm from the lower surface of auxiliary plate 12.

[0035] The above pallet 81 is made of aluminum, it is polished to a high flatness, the ink repellent layer 11 of the recording head main body 11
7 is coated with a modified fluoropolymer film having a coating thickness of 30 μm to form projections.

[0036] 12) until the adhesive 83 is cured, as ink repellent film 117 of the recording head main body 11 continues to contact with a predetermined position of the pallet 81, a load is applied to each of the recording head main body 11 and the auxiliary plate 12 Can be This load is 100 g each
The curing condition is 20 ° C. for 1 hour. The man-hour for the above temporary fixing process is about 30 seconds per unit.

In the hermetic sealing method following the temporary fixing, an adhesive sealant having a relatively low viscosity is used, and the adhesive sealant is fed into the gap between the recording head main body 11 and the auxiliary plate 12 from the opposite side of the nozzle 116, A method of fixing and sealing the both is adopted.

In this method, the point is the flowability of the adhesive sealant. If the flowability is poor, the adhesive sealant does not sufficiently spread to the required part of the gap, and thus a sealing failure occurs. On the other hand, if the flowability is too good, the risk of the adhesive sealant flowing to the nozzle 116 side increases. In this example, a silicone-based adhesive sealant having excellent sealing properties and excellent ink resistance (product name TSE3995 manufactured by Toshiba Silicone Co., Ltd.) was used as the adhesive sealant.
The recording head was prepared by changing the amount of the dent by using, and if the amount of the dent was 100 μm or less, it was confirmed that there was no outflow of the adhesive sealant. The adhesive sealant has a viscosity of 15 to 35 poise.

A wiping test is carried out with the recording head 1a thus prepared, and the ink is reliably wiped off by all of the recording heads 1a.
Excellent results were obtained that no delamination of 7 occurred.

[0040]

According to the present invention, there is provided a flow path substrate in which a groove for an ink flow path including an ink pressurizing chamber and a nozzle is formed, and a vibration plate joined to the ink flow path forming surface. An ink jet recording head body composed of a piezoelectric element bonded to the outer surface of the diaphragm corresponding to the ink pressurizing chamber and an ink repellent film formed on the nozzle opening surface;
In an ink jet recording head comprising an auxiliary plate for protecting the ink jet recording head body from external impact, the ink-repellent film is recessed from the surface of the auxiliary plate, so that the tip of the wiper blade during wiping may be Does not contact the edge of the ink repellent film at the edge. Therefore, a highly reliable recording head that can withstand 50,000 or more wiping operations can be provided (the invention of claim 1).

In the first aspect of the present invention, the depression of the ink-repellent film from the auxiliary plate surface is 0.1 to 2 times the distance from the nozzle to the auxiliary plate. If the ink-repellent film is slightly depressed from the auxiliary plate surface, the tip of the wiper blade contacts the edge of the recording head body during wiping and does not exert a force on the edge of the ink-repellent film at the edge. On the other hand, if the dent is twice as long as the distance from the nozzle to the auxiliary plate, the surface of the ink-repellent film around the nozzle can be reliably wiped by the wiper due to the elastic deformation of the wiper. Therefore, it is possible to provide a highly reliable recording head that can withstand 50,000 or more wiping operations and that can reliably wipe off the ink adhering to the surface of the ink-repellent film and the peripheral surface of the auxiliary plate by wiping. (Invention of claim 2).

[Brief description of the drawings]

FIG. 1 is a sectional view showing the structure of an embodiment of a recording head according to the present invention.

2A and 2B show a temporary fixing step of the embodiment, in which FIG. 2A shows a state in which a recording head body is held on an arm, FIG. 2B shows a state in which an adhesive is collected by a needle, and FIG. A diagram showing a state in which a needle is rotated to apply an adhesive to a recording head body.

FIG. 3 shows a temporary fixing step of the embodiment following FIG. 2;
(A) is a diagram showing an initial state of adhesive application to the recording head body, (b) is a diagram showing a final state of adhesive application, and (c).
Is a diagram showing a state at the time of completion of adhesive application, and (d) is a diagram showing a state immediately before the recording head main body is inserted and bonded to the auxiliary plate

FIG. 4 is a conceptual diagram of a main part showing a configuration of an example of a recording apparatus according to a conventional technique.

FIG. 5 is a perspective partial sectional view showing the structure of a recording head used in the recording apparatus.

6A and 6B show a state of ink wiping by a wiper, and FIG.
Is a diagram showing a state before ink wiping, and (b) is a diagram showing a state in the latter half of wiping.

FIG. 7 is a bar graph showing the frequency of occurrence of ink-repellent film non-peeling nozzles and ink-repellent film peeling nozzles with respect to the position of the ink-repellent film surface relative to the auxiliary plate surface.

[Description of Signs] 1 , 1a Recording head 11 Recording head main body 111 Flow path substrate 112 Vibration plate 113 Piezoelectric element 114 Ink supply unit 115 Ink pressurizing chamber 116 Nozzle 117 Ink repellent film 12 Auxiliary plate 2 Guide shaft 3 Protective device 4 Wiper 41 Wiper blade 42 Sponge 5 Platen 6 Recording paper 81 Pallet 82 Plate 83 Adhesive 84 Arm 85 Needle

Claims (2)

[Claims] An ink pressurizing chamber corresponding to a flow path substrate formed with a groove for an ink flow path comprising an ink pressurizing chamber, a nozzle and the like, a vibration plate joined to the ink flow path forming surface, and the ink pressurizing chamber. Main body composed of a piezoelectric element bonded to the outer surface of a vibrating plate and an ink-repellent film formed on a nozzle opening surface, and an auxiliary for protecting the main body of the inkjet recording head from external impact And an ink-repellent film, wherein the ink-repellent film is recessed from an auxiliary plate surface. 2. The method according to claim 1, wherein the recess of the ink repellent film from the auxiliary plate surface is
2. The ink jet recording head according to claim 1, wherein the distance is 0.1 to 2 times the distance from the nozzle to the auxiliary plate.