JP2003326698A - Heating type inkjet recording head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heating type inkjet recording head which can obtain a continuous discharge reliability even when used under a high temperature condition for a long term. <P>SOLUTION: In the heating type inkjet head which has a head plate including a plurality of nozzles for discharging ink, pressure chambers communicating with the nozzles, ink chambers for guiding the ink to the pressure chambers, and a discharge supporting means for applying a pressure to the ink in the pressure chambers, a flexible cable connected to supply a driving signal from an external driving circuit to the discharge supporting means, and a heating means mounted to the head plate, the flexible cable comprises a base layer, a conductor layer and a cover layer for coating the conductor layer. The base layer and the cover layer are formed of a polyimide resin. The reliability when the heating type inkjet recording head is used for a long term can be improved. Moreover, a workability improvement in registering an FPC and the head, or the like can be expected. Also a total thickness can be reduced by a constitution without an adhesive layer provided, so that an apparatus can be made compact and light-weight. <P>COPYRIGHT: (C)2004,JPO

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 that forms an image on a recording medium by ejecting ink droplets, and more specifically, it has a flexible cable including a base layer, a conductor layer, and a cover layer. The present invention relates to a heating type inkjet recording head.

[0002]

2. Description of the Related Art Inkjet recording apparatuses are currently used in various fields because of their lightness and small size, and low vibration and noise during recording, and various recording media to be printed are also available. Is becoming more popular. Examples of such an ink jet recording apparatus include a bubble method in which an ink droplet is ejected from a nozzle by the pressure of a bubble generated by energizing a heating resistor provided in a pressure chamber, or a vibration plate which constitutes a part of the pressure chamber. A piezo method in which the volume of the pressure chamber is changed by applying a voltage to a single-layer or laminated piezoelectric element provided in the ink droplet to eject an ink droplet from a nozzle is widely known.

In these ink jet recording apparatuses, since water-based inks or oil-based inks in which dyes / pigments are dissolved or dispersed in a solvent such as water / organic solvent are mainly used, the inks after landing on the recording medium are used. Image deterioration due to ink bleeding and delay of drying is a problem, and in order to solve these problems, an ink receiving layer for absorbing and holding ink is generally formed on the surface of the recording medium. Is. However, a pretreatment step is required to form the ink receiving layer on the recording surface, and a posttreatment step for removing the ink receiving layer may be further required after inkjet printing, which is extremely inefficient.

In recent years, attention has been paid to such a problem as to a heating type ink jet recording apparatus using a heat melting type ink which is solid at room temperature. Due to the nature of the phase change due to temperature, the heat-melting type ink has a special property because when it is ejected, the ink, which is a liquid, immediately solidifies or cures before it penetrates into the recording medium when it hits the surface of the recording medium. It has an advantage that high quality image formation without bleeding can be formed on various recording media such as paper, resin, cloth, leather, ceramics, metal and wood without forming an ink receiving layer. In addition, there is a problem such as clogging caused by thickening of ink due to solvent volatilization at rest and adhesion of dried matter (precipitate) around the nozzle, which has been a problem when conventional water-based ink or oil-based ink is used. It is also possible to suppress the occurrence.

In the heating type ink jet recording apparatus having such an advantage, the direct or indirect heating means for heating the heat-melting type ink to be fed above the softening point and maintaining the ink melted state, the ink tank, Also, the basic configuration is almost the same as that of the conventional inkjet recording apparatus except that it is installed on a head plate having a nozzle, a pressure chamber, an ink chamber, an ejection support unit, and the like.

The ink of the heating type ink jet recording apparatus has an appropriate temperature in order to maintain the viscosity of the ink so that the ink can be promptly shifted to the printing operation not only during printing but also during standby such as waiting. Held in. Although the ink temperature varies depending on the physical properties of the ink,
The temperature is set to 10 ° C to 50 ° C higher than the softening point of the ink used. Specifically, since the ink is heated and held at a predetermined set temperature within the range of 70 ° C. to 170 ° C., the temperature around the ink tank, the head plate, and the like is also about the same.

Especially when these devices are industrially used, since heating and maintaining at a predetermined temperature takes a long time, not only the ink tank and the head plate but also each member constituting the heating type ink jet head. As for the above, it is very important to use a material considering heat resistance in order to improve reliability for a long period of time.

As means for supplying a drive signal from an external drive circuit to the ejection support means of the head plate, a cover layer 61 composed of a resin film and an epoxy resin or acrylic resin adhesive as shown in FIG. A flexible cable configured by laminating a base layer 63 having the same structure as the cover layer and a conductor layer 62 made of a metal foil such as copper is generally used. One end of the flexible cable is connected to the head plate side having the ejection assisting means, and the other end is connected to the external drive circuit side for generating a signal based on image information.

However, when the conventional flexible cable is used in the heating type ink jet recording apparatus in which the normal heating temperature is 100 ° C. or more, for example, 130 ° C., the adhesive strength between the layers is deteriorated due to the deterioration of the adhesive layer, and the discharge assisting means is provided. It became impossible to supply a stable power supply to, and could not withstand continuous use for a long time.

Therefore, when the conventional heating type ink jet recording apparatus using a flexible cable is used for a long period of time, it is necessary to keep the temperature applied to the flexible cable low. When the heating temperature itself is lowered, the materials usable as ink are limited to those having a low melting point, so that it becomes impossible to give various characteristics to the formed image. Also, in the case of keeping the heat applied to the flexible cable below the heat resistant temperature by the head structure while maintaining the heating temperature,
The device itself becomes large and complicated, for example, the flexible cable connection part is separated from the heat source, and the heat dissipation part is provided between the connection part and the heat source.

[Problems to be Solved by the Invention]

The present invention is intended to solve the above problems, and an object thereof is to provide a heating type ink jet recording head capable of obtaining continuous ejection reliability even when used for a long period under high temperature conditions. To provide.

[0012]

Thus, the present inventor has
In the heating type ink jet recording head, it is possible to obtain a head with high ink ejection stability by setting the material composition of the flexible cable connected to supply the drive signal from the external drive circuit to a specific thing. The present invention has been completed based on this finding.

That is, the first aspect of the present invention is to provide a plurality of nozzles for ejecting ink, a pressure chamber communicating with the nozzles, an ink chamber for introducing ink into the pressure chambers, and ejection assisting means for applying pressure to the ink in the pressure chambers. In a heating type ink jet recording head, a head plate having: a flexible cable connected to supply a drive signal from an external drive circuit to the ejection assisting unit; and a heating unit attached to the head plate. The flexible cable is composed of a base layer, a conductor layer, and a cover layer covering the conductor layer, and the base layer and the cover layer are made of a polyimide resin, which is a heating type inkjet recording head. . The second aspect of the present invention
The heating type inkjet recording head according to claim 1, wherein the base layer of the flexible cable does not include an adhesive layer. A third aspect of the present invention is the heating type ink jet recording head according to claim 1 or 2, wherein the cover layer of the flexible cable does not include an adhesive layer. Fourth of the present invention
Is a heating type inkjet recording head according to any one of claims 1 to 3, wherein the haze value of the laminated portion including the base layer and the cover layer of the flexible cable is less than 40%. Furthermore, a fifth aspect of the present invention is the heating type ink jet recording head according to any one of the first to fourth aspects, wherein the ink is a hot-melt type ink that is solid at room temperature. A sixth aspect of the present invention is the heating type ink jet recording head according to the fifth aspect, wherein the temperature of the heat-melting type ink in the pressure chamber is 100 to 170 ° C.

According to the present invention, even if the temperature of the flexible cable itself rises due to the heat generated from the heating means, the base layer and the cover layer are made of a polyimide resin having excellent heat resistance, so that they can be used for a long time. Also, it becomes possible to supply the stable power to the discharge assisting means. Further, the stable supply of electric power makes it possible to eject desired ink droplets, and it is possible to maintain good image formation.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of a heating type ink jet recording head of the present invention will be described in detail with reference to configuration examples. FIG. 1 shows an example of a heating type ink jet recording apparatus equipped with the ink jet recording head of the present invention. In FIG. 1, the inkjet head unit 2 is positioned and fixed on a carriage 74 supported by a guide rail 71, and the carriage 74 is driven by a carriage motor 72 to reciprocate in a main scanning direction via a timing belt 73. You can do it. Further, the recording medium 75 fixed on the support means composed of the endless belt 76 is conveyed by a predetermined amount in the direction perpendicular to the main scanning direction (hereinafter, referred to as the sub scanning direction) by the conveyance rollers 77a and 77b which are rotationally driven. It By sequentially repeating the reciprocating movement of the head unit 2 and the conveyance of the recording medium, continuous recording is possible in the longitudinal direction of the recording medium.

The ink jet head unit 2 comprises an ink tank 3 for accommodating ink, and a head plate 10 for ejecting melted ink in response to an image signal from an external drive circuit. The material of the ink tank 3 is preferably a material having high thermal conductivity, such as aluminum, but is not limited to this. The ink tank 3 is provided with a tank heater (not shown) for heating the supplied ink and adjusting / maintaining the ink viscosity within a dischargeable range.

2, 3 and 4 show an example of the head plate 10, FIG. 2 is an exploded perspective view of each component, FIG. 3 is a sectional view parallel to the longitudinal direction of the piezoelectric element, and FIG. A sectional view perpendicular to the direction is shown. The head plate 10 is for supplying the ink supplied from the nozzle plate 11 in which the plurality of nozzles 16 are formed, the plurality of pressure chambers 18 formed corresponding to each nozzle 16 and the ink tank to each pressure chamber 18. Cavity plates 12 and 13 in which ink chambers 17 are formed, pressure chambers 18 formed by the cavity plates, a vibration plate 14 that closes the ink chambers 17, and a piezoelectric plate formed corresponding to each pressure chamber 18 via the vibration plate 14. It is composed of the element 15. A flexible cable 5 (hereinafter, referred to as FPC) is connected to the piezoelectric element 15, and one end thereof is connected to an external drive circuit (not shown) that generates a drive signal based on image information. When a drive signal is applied from this external drive circuit, the piezoelectric element 15 and the vibration plate 14 are deformed, and the ink in the pressurized pressure chamber 18 is ejected from the nozzle 16.

Further, a plate heater 4 for heating the head plate 10 is fixed to the head plate 10 at a position corresponding to the ink chamber 17 excluding the portion where the piezoelectric element 15 is arranged, by a thermosetting adhesive. . By appropriately controlling the heat generation temperature of the plate heater, the ink state is maintained within an appropriate viscosity range that can be ejected.

FIG. 6 shows an example of a cross-sectional structure showing the FPC 5 of the present invention. A base layer 63 made of a polyimide resin, a conductor layer 62 made of copper foil formed on the base layer 63, and a conductor layer 62 are provided. The cover layer 61 is made of a polyimide resin for coating. Of course, the base layer 6 of the present invention
3 and the cover layer 61 may include an adhesive layer made of a polyimide adhesive for adhering to the conductor layer 62. However, when the FPC of the present invention is prepared by the method described below without providing the adhesive layer. The total thickness of the FPC can be reduced,
As a result, the size and weight of the device can be reduced, which is preferable.

FIG. 7 shows an example of the manufacturing process of the FPC 5, but it is not limited to this. First, the base layer 6
Examples of the method of laminating the conductor layer 62 on the layer 3 include a plating method, a casting method, and a lamination method.

In the plating method, first, a thin conductor layer called a seed layer is formed on a polyimide film which has been pretreated, if necessary, by a method such as electroless plating, vacuum deposition or sputtering, and then the seed layer is formed. This is a method of forming a conductor layer having a required thickness by electrolytic plating, and it is possible to form a thin conductor layer. The casting method is a method of forming a base layer by applying a polyamic acid varnish, which is a precursor of polyimide, onto a conductor layer and then drying and imidizing the varnish. The lamination method is a method of thermocompression-bonding a film made of a thermoplastic polyimide resin on a conductor layer under high temperature and high pressure, and it is easy to manufacture a thick conductor layer.

The laminate produced by the above method is excellent in heat resistance because the base layer 63 and the conductor layer 62 are adhered to each other without an adhesive layer having low heat resistance such as epoxy resin / acrylic resin. A FPC is obtained. (Fig. 7a)

Next, the conductor layer 62 is formed into a predetermined circuit pattern. After a liquid resist or a dry film resist layer 64 is provided on the surface of the conductor layer 62 made of copper foil (FIG. 7b), exposure is performed by irradiating ultraviolet rays through a photomask 65 having a desired circuit pattern. (Fig. 7
c) By developing this resist layer 64, the resist in the portion exposed by ultraviolet rays is removed, and a mask pattern corresponding to a desired circuit pattern is formed on the conductor layer 62 by the resist layer 64. (Fig. 7d)

After the conductor layer 62 other than the circuit pattern is dissolved and removed by an etching solution such as ferric chloride (FIG. 7e), the resist layer 64 is removed to form a desired pattern (FIG. 7f). )

Next, in order to protect the circuit pattern of the conductor layer 62, the cover layer 61 is formed on the portion where insulation is required. The cover layer 61 is formed by a method of adhering a laminated material composed of a polyimide resin film and a thermoplastic polyimide adhesive (film cover lay), and a polyimide liquid cover coat ink having ultraviolet curability or thermosetting property. Either a method (ink coverlay) or a method using a photosensitive polyimide-based liquid or dry film-shaped coverlay (photosensitive coverlay) can be used.

Each cover layer forming step will be briefly described. In the case of a film cover lay, heat and pressure are applied by stacking and fixing the films with the openings corresponding to the connection terminals that can be conducted by processing such as NC drilling, punching, and laser processing in the aligned state (Fig. 7g). And adhere (Fig. 7h).

In the case of an ink cover lay, a liquid cover coat ink is printed by a screen printing method on a portion excluding connection terminals which can be conducted in advance (FIG. 7i),
Cure in UV oven or oven.

In the case of a photosensitive coverlay, the process is slightly different between the liquid form and the dry film form. In the case of a liquid, a photosensitive resin is applied on the entire surface by a screen printing method, a spray method or the like, and then dried to form a cover layer.
In the case of a dry film, a cover layer is formed by laminating the whole with a vacuum laminator or the like completely removing air (FIG. 7j). Then, after the pattern is exposed and baked by the photomask 65 according to the desired circuit pattern (FIG. 7k), development (FIG. 7l) is performed. Finally, it is cured in an oven to form a cover layer and insulate the conductor layer.

When a photosensitive coverlay is used, a pattern can be formed by using a photo process, and therefore extremely fine processing can be performed with high dimensional accuracy, which is preferable. F of the present invention manufactured by the above steps
The PC may be subjected to surface treatment such as gold plating or solder plating on the exposed electrode portion, if necessary. For the solder plating, it is preferable to use a material having a melting point higher than the ink heating temperature by 30 ° C. or more.

Further, in the FPC of the present invention, the haze value of the laminated portion composed of the base layer 63 and the cover layer 61 is preferably adjusted to less than 40%, particularly preferably less than 25%. If the haze value is less than 40%, the relative positions of the alignment mark and the piezoelectric element provided on the FPC and the head plate, respectively, can be adjusted even when the object to be bonded and the FPC are aligned in a state where they are not in close contact with each other and are apart from each other. You can clearly see through the. This is effective when connecting to the piezoelectric element using a liquid or paste-like conductive material. As mentioned above,
It is possible to achieve a highly accurate connection between the FPC connection portion and the piezoelectric element and improve connection workability.

FP of the present invention manufactured by the above-mentioned process
Since C is composed of a polyimide-based resin except for the conductor layer, the polyimide itself can sufficiently exhibit extremely high heat resistance. This means not only that the usable temperature becomes high, but also that there is little deterioration in a high temperature environment. From the above, the head of the present invention is preferably used as a head for hot-melt ink, and particularly preferably used as a hot-melt ink jet recording head in which the temperature in the ink pressure chamber reaches 100 to 170 ° C. In addition, for FPCs that do not have an adhesive layer, the overall thickness can be made thinner than the conventional FPC by the amount of the adhesive layer, so the device can be made smaller and lighter, and the transparency improves the positioning work during connection. It also has the effect of improving sex.

Hereinafter, the present invention will be described in more detail with reference to examples, but of course the present invention is not limited thereto.

[0033]

[Examples] The following evaluation tests were carried out on each Example and Comparative Example. 1) Heat resistance test The heating type ink jet recording heads of the respective examples and comparative examples were attached to an ink jet recording apparatus, and the ejection stability and durability during long-term driving were evaluated. Specifically, the number of non-ejection nozzles with respect to the number of evaluation target nozzles during continuous driving is shown by numerical values. Moreover, the appearance change of FPC was investigated. The evaluation criteria for the change in appearance over time are as follows. ◯: No change such as carbonization or peeling Δ: Some change such as carbonization or peeling is observed. X: The test conditions in which obvious changes such as carbonization and peeling are recognized are as follows. Heating temperature: 130 ° C. Applied voltage: 60 V Driving frequency: 5 kHz Driving period: 6 months Nozzle number: 32 Ink prescription: BE SQUARE 195 100 parts by weight (microcrystalline wax, manufactured by Toyo Petrolite Co., Ltd.) HOSTAPERM PINK E-02 1 part by weight ( Pigment, manufactured by Clariant) LANOX FP-1410N 0.3 parts by weight (dispersant: lanolin fatty acid polyhydric alcohol ester, manufactured by Nippon Seika Co., Ltd.) After dispersing the mixture using a heating type dispersion machine, impurities are removed by heating filtration. Then, it was left to cool at room temperature to prepare a uniform magenta hot melt ink.

2) Visibility test The haze value of the FPC shown in each Example and Comparative Example was measured. For the measurement, a haze meter (NDH-1001-DP) manufactured by Nippon Denshoku Industries Co., Ltd. is used and JIS-K is used.
It was carried out according to -7105. However, the measurement location was the laminated portion composed only of the base layer and the cover layer.
The smaller the number, the better the visibility. Further, the work of attaching the electrode and the FPC was actually performed, and the ease of alignment was evaluated according to the following criteria. ○: Alignment marks are easy to see and work △: Alignment marks are somewhat difficult to see and there is a problem in work ×: Alignment marks are difficult to see and alignment is difficult

Example 1 After forming a circuit of a conductor layer,
Double-sided F by the film coverlay method using the materials listed below
Created a PC. Base layer and conductor layer: Espanex (non-adhesive type; laminate of polyimide film 25 μm and rolled copper foil 35 μm, manufactured by Nippon Steel Chemical) Cover layer: Espanex SPC series (polyimide film 25 μm and polyimide adhesive 35 μm Laminated body, manufactured by Nippon Steel Chemical Co., Ltd. A sectional view of the completed FPC is shown in FIG. 8a. The total thickness was 0.215 mm. This FPC was attached to a head plate as shown in FIG. 2 and evaluated. The evaluation results are shown in Table 1.

Example 2 After forming the circuit of the conductor layer,
Single-sided FP with the ink coverlay method using the materials listed below
Created C. Base layer and conductor layer: Espanex (non-adhesive type; laminate of polyimide film 25 μm and rolled copper foil 18 μm, manufactured by Nippon Steel Chemical Co., Ltd.) Cover layer: Espanex SPI series (thermosetting polyimide cover coat ink 12 μm, Fig. 8b shows a cross-sectional view of the completed FPC. The total thickness was 0.055 mm. This FPC was attached to a head plate as shown in FIG. 2 and evaluated. The evaluation results are shown in Table 1.

Comparative Example 1 After forming the circuit of the conductor layer,
Double-sided F by the film coverlay method using the materials listed below
Created a PC. Base layer and conductor layer: TLF-521MR (polyimide film 25 μm, epoxy adhesive 25 μm, and rolled copper foil 35 μm laminated body, manufactured by Toshiba Chemical) Cover layer: TFA-577 (polyimide film 25 μm
A laminated body of m and an epoxy adhesive of 35 μm, manufactured by Toshiba Chemical) A sectional view of the completed FPC is shown in FIG. 8c. The total thickness was 0.265 mm. This FPC was attached to a head plate as shown in FIG. 2 and evaluated. The evaluation results are shown in Table 1.

[Comparative Example 2] After forming a circuit of a conductor layer,
One side F by the film coverlay method using the materials listed below
Created a PC. Base layer and conductor layer: TLF-521MR (multilayer of polyimide film 12.5 μm, epoxy adhesive 25 μm, and rolled copper foil 18 μm, manufactured by Toshiba Chemical) Cover layer: TFA-577 (polyimide film 12.5 μm
And epoxy adhesive 25 μm laminate, manufactured by Toshiba Chemical) A cross-sectional view of the finished FPC is shown in FIG. 8d. The total thickness was 0.093 mm. This FPC was attached to a head plate as shown in FIG. 2 and evaluated. The evaluation results are shown in Table 1.

Comparative Example 3 After forming the circuit of the conductor layer,
Single-sided FP with the ink coverlay method using the materials listed below
Created C. Base layer and conductor layer: Espanex (non-adhesive type; laminate of polyimide film 25 μm and rolled copper foil 18 μm, Nippon Steel Chemical Co., Ltd.) Cover layer: NPR-5BR (thermosetting epoxy cover coat ink 12 μm, Japan A cross-sectional view of the completed FPC is shown in FIG. 8e. The total thickness was 0.055 mm. This FPC was attached to a head plate as shown in FIG. 2 and evaluated. The evaluation results are shown in Table 1.

[Table 1]

[0040]

With the above construction, it is possible to improve the reliability of the heating type ink jet head during long-term use. Further, improvement in workability such as alignment of the FPC and the head can be expected. Further, according to the second aspect of the invention, since the adhesive layer does not exist, the overall thickness can be reduced, and the size and weight of the device can be reduced.

[Brief description of drawings]

FIG. 1 is an overall perspective view of a printer using a heating type inkjet recording head of the present invention.

FIG. 2 is an exploded perspective view of the heating type inkjet recording head of the present invention.

FIG. 3 is a cross-sectional view in a direction parallel to the longitudinal direction of the piezoelectric element of the heating type inkjet recording head of the present invention.

FIG. 4 is a cross-sectional view of the heating type inkjet recording head of the present invention in a direction perpendicular to the longitudinal direction of the piezoelectric element.

FIG. 5 is a cross-sectional view of a conventional FPC.

FIG. 6 is an FPC sectional view showing an embodiment of the present invention.

FIG. 7: F of the heating type inkjet recording head of the present invention
It is a PC manufacturing process.

8A and 8B are FPCs showing an embodiment of the present invention.
FIG. Further, (c) to (e) are FPC cross-sectional views showing a comparative example of the present invention.

[Explanation of symbols]

10 head plate 11 nozzle plate 12 Cavity plate 13 Cavity plate 14 diaphragm 15 Piezoelectric element 16 nozzles 17 Ink chamber 18 Pressure chamber 19 Ink supply port 2 head units 3 ink tank 4 plate heater 5 flexible cable 61 cover layer 62 conductor layer 63 Base layer 64 resist layer 65 photo mask

Claims (6)

[Claims] 1. A head plate comprising: a plurality of nozzles for ejecting ink; a pressure chamber communicating with the nozzle; an ink chamber for introducing ink into the pressure chamber; and ejection assisting means for applying pressure to the ink in the pressure chamber. A heating type inkjet recording head having a flexible cable connected to supply a drive signal from an external drive circuit to the ejection assisting means, and a heating means attached to a head plate, wherein the flexible cable is a base. A heating type ink jet recording head comprising a layer, a conductor layer and a cover layer covering the conductor layer, wherein the base layer and the cover layer are made of a polyimide resin. 2. The heating type ink jet recording head according to claim 1, wherein the base layer of the flexible cable does not include an adhesive layer. 3. The cover layer of the flexible cable does not include an adhesive layer.
The heating type inkjet recording head described in. 4. The heating type ink jet recording head according to claim 1, wherein a haze value of a laminated portion including the base layer and the cover layer of the flexible cable is less than 40%. 5. The heating type ink jet recording head according to claim 1, wherein the ink is a hot-melt type ink that is solid at room temperature. 6. The heating type ink jet recording head according to claim 5, wherein the temperature of the heat melting type ink in the pressure chamber is 100 to 170 ° C.