JPH04371847A - Ink jet head - Google Patents

Abstract

PURPOSE:To increase a volume fluctuation amount to ensure a high degree of integration, obtain superior high-frequency characteristics, and perform stable printing. CONSTITUTION:An ink jet head consists of a piezoelectric element having drive parts and a cover plate 6 at least having flow paths and nozzles. In the construction of the cover plate 6, a photosensitive resin layer 6b is laminated on a roughly molded cover plate 6a having a plurality of parallel flow paths 8, and fine nozzles 7 and flow paths 9 are formed in the photosensitive resin layer 6b so that the flow path 8 and the flow path 9 can form a single flow path of a three-dimensional form tapered toward the open part of the nozzle 7.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a head section of an inkjet recording apparatus, and more particularly to the structure of an on-demand inkjet head using piezoelectric elements.

0002

[Prior Art] A droplet ejection pressure control method in which an electrical signal is applied to a recording head equipped with a piezoelectric element to eject recording droplets only when necessary, converts it into a pressure wave, and ejects a droplet using the pressure wave. The on-demand inkjet recording method generates pressure pulses in response to electrical signals, so the drive circuit is simple and the structure is simple. FIG. 3 is a diagram for explaining an example of a conventional inkjet head, in which 11 is a piezoelectric body, 12 is a slit, 13 is a drive unit, 15 is a cover plate, 16 is a groove (channel 18), and 17 19a is a common electrode, 19b is an individual electrode, 20 is an elastic body (filler), and 21 is an adhesive.

In FIG. 3, a piezoelectric body 11 is provided with a plurality of parallel slits 12 to form convex portions, and the convex portions are alternately arranged as driving portions 13 and non-driving portions 14. The piezoelectric body 11 has a groove 1 provided corresponding to the drive section 13.
It is joined to a cover plate 15 having a diameter of 6. In the illustrated case, the end face of the non-driving part 14 of the piezoelectric body 11 illustrated in FIG.
The end faces of the partition walls 17 that define the grooves 16 are used as bonding surfaces to be bonded with an adhesive 21. By joining, the groove 16 becomes a flow path (pressurized liquid chamber) 18 having a cross section closed by the drive section 13 of the electric body 11. The channel 18 communicates with a nozzle (not shown) at one end and a liquid chamber (not shown) that supplies ink at the other end. In addition, the common electrode 19a and the fixed electrode 19b
An elastic body 20 is filled in to prevent the insulation from being deteriorated and to reinforce the driving part 13. The elastic body 20 is made of an insulating material having good filling properties and a low Young's modulus so that when the drive unit 13 is driven, the displacement of the drive unit 13 does not lift the partition wall 17 of the cover plate 15.

In the above-mentioned inkjet head, when a voltage pulse is applied between the individual electrode 19b of the drive section selected based on image information and the common electrode, the drive section is displaced in the thickness direction. As a result, the volume of the flow path 18 decreases, generating pressure waves and ejecting ink droplets from the nozzle. Channel 1
The amount of decrease in volume No. 8, that is, the amount of volume variation Q, affects drive efficiency and high frequency response, and is preferably larger.

The volumetric variation (Q) is defined by the width (W) and length (L) of the driving portion of the piezoelectric element in the flow path 18 and the displacement amount (δ) of the driving portion. That is, the volumetric variation amount (Q) is expressed by the following equation. Q=W×L×δ Here, in order to increase the volume variation amount (Q), each factor in the above equation may be increased. However, increasing the width (W) of the drive section reduces the degree of integration, and increasing the displacement (δ) increases the applied voltage, which is disadvantageous in terms of the drive circuit. Here, the length (L) is considered to be the most advantageous factor, but the length (L)
Increasing the flow path means increasing the pipe resistance of the flow path. However, when the conduit resistance increases, when the driving frequency is increased, the liquid supply cannot follow the flow, making high frequency response impossible. This means that the printer cannot perform high-speed printing, so an increase in conduit resistance must be avoided. From the above, in order to create an inkjet head with excellent high-frequency wave response, it is not necessary to increase the width (W) of the channel 18, but to increase the height direction, that is, the height of the groove of the channel 18. It is selected to lower the conduit resistance by

Originally, it would be ideal for the cover plate 15 to have the channel section and nozzle section integrally formed by resin molding, which would improve productivity and reduce costs. narrow opening, e.g. 40-50μ
It is very difficult to create a shape of m (micrometer) by molding, and it is also difficult to obtain the precision required for the nozzle part. Furthermore, the actual situation is that the molded product has burrs due to molding, making it impossible to obtain an ideal nozzle shape. On the other hand, it is conceivable to form the entire flow path and nozzle with photosensitive resin, but it is difficult to create a three-dimensional shape with a taper in the depth direction in order to reduce the resistance of the flow path. It is also difficult to remove the particles to a depth of about 70 to 100 μm.

[0007] As a known document related to the present invention, for example, there is an "ink jet recording head" described in Japanese Patent Laid-Open No. 1-125241. The "inkjet recording head" includes a photosensitive resin layer provided on a substrate having a thermal energy generating element and cured, a channel groove formed in the thermal energy generating element part, and a photosensitive resin layer formed on the upper surface of the photosensitive resin layer. This is a flat top lid that is joined together. The interval between the wall portions forming the flow path of the flow path groove is wide at the active portion where the thermal energy generating element is arranged, and narrow at the discharge port side. Therefore, although the planar shape of the flow path can be arbitrarily selected, the depth of the flow path is determined by the thickness of the photosensitive resin layer. It is extremely difficult to arbitrarily form the channel depth and width three-dimensionally using only a photosensitive resin.

[0008]

[Purpose] The present invention has been made in view of the above-mentioned circumstances.The present invention has been made in order to increase the amount of volume variation caused by driving a piezoelectric element for printing. To make it possible to manufacture a cover plate of an inkjet head with stable characteristics and at low cost, which has a flow path shape that increases the size and is highly integrated, and further has a flow path shape that reduces the pipe resistance in the flow path and has excellent high frequency characteristics. The purpose is to

[0009]

[Structure] In order to achieve the above objects, the present invention provides (1)
A piezoelectric element in which driving parts and non-driving parts are arranged alternately by a plurality of parallel grooves, and a cover plate having grooves corresponding to the driving parts of the piezoelectric element and partitioned by side walls, A flow path having a nozzle is formed by the drive part, the side wall, and the groove, and liquid is drawn from the nozzle by applying displacement in the thickness direction to the drive part of the piezoelectric element. In an inkjet head that ejects droplets, the lid plate is composed of a coarsely formed substrate and a finely formed photosensitive resin, and the finely formed photosensitive resin is integrally bonded to the coarsely formed substrate. (2) In the above (1), the lid plate is composed of a resin substrate and a photosensitive resin substrate formed on the resin substrate, and the resin substrate has a flowchart having a tapered portion. The present invention is characterized in that a passage is provided, and a finely formed nozzle portion is provided on the photosensitive resin substrate. Hereinafter, the present invention will be explained based on examples.

FIG. 2 is a diagram for explaining the schematic structure of the inkjet head of the present invention, in which 1 is a piezoelectric element;
2 is a groove, 3 is a filler, 4 is a driving part, 5 is a partition (non-driving part), 6 is a lid plate, 6a is a roughly formed substrate, 6b is a photosensitive resin layer, 7 is a nozzle, and 8 is a partition .

In the figure, the piezoelectric element 1 is usually a laminated piezoelectric element, which can be driven at a low voltage. The piezoelectric element 1 is provided with a plurality of parallel grooves 2, and the grooves 2 alternately partition drive parts 3 and partition walls 4. The groove 2 is filled with a filler 3. The filler 3 serves to insulate the electrodes (not shown) of the piezoelectric element 1 and to reinforce the drive section 3. Normally, when the drive unit 3 is displaced, the partition wall 4 is also pushed up, causing mutual interference, but in order to reduce the amount of push up, an elastic agent with a low Young's modulus is used. Lid plate 6
, a roughly molded substrate 6a and a photosensitive resin layer 6 for fine molding.
It consists of b.

FIGS. 1(a) and 1(b) are diagrams for explaining an embodiment of the lid plate in the inkjet head of the present invention, and FIG. 1(a) is a partial perspective view of the lid plate, and FIG. 1(b) is a partial perspective view of the lid plate. ) is a sectional view taken along arrow AA in Figure (a), in which 8 is a molding flow path, 8a is a tapered part, 9 is a photosensitive resin flow path, and 9a is a convergence part, which has the same effect as in Figure 2. The parts that do so are given the same symbols.

In the figure, the roughly formed substrate 6a serves as the substrate for the lid plate 6 which has a three-dimensional formed channel section 8 that does not require high forming precision, and is designed to reduce the flow path resistance due to the flow of ink. For example, a tapered shape 8a is provided near the outlet. The roughly formed substrate 6a is
Primarily, moldable materials such as resin or glass plates are used. The resin must not only be moldable but also have excellent solvent resistance and heat resistance. For example, polyether, sulfone and polysulfone are suitable.

The micro-molded photosensitive resin layer 6a is a photosensitive resin layer such as a dry film resist that forms a highly precise and fine nozzle portion 7 and a flow path 9. As a dry film resist, SR300 manufactured by Hitachi Chemical Co., Ltd. and Tokyo Ohka Co., Ltd. (
Co., Ltd. SP750 or the like is used to form the roughly formed substrate 6a.
A photosensitive resin layer 3b is laminated using the substrate as a substrate, and then a mask is placed thereon and exposed. Since the dry film resist is of a negative type, after exposure, the unexposed areas are removed by diluting with 1-1-1 trichloroethane. Thereafter, main heat treatment is performed at 135 to 145° C. and UV (ultraviolet light) curing is performed. Through the above steps, the roughly formed substrate 6a and the photosensitive resin layer 6b are tightly adhered to each other, and the lid plate 6 having the fine nozzle portion 7 can be integrally formed.

[0015] The lid plate 6 integrates the piezoelectric element 1 with an adhesive or the like between the partition wall part 5 and the partition wall part 8 so that the flow path 9 of the lid plate 6 corresponds to the driving part 4 of the piezoelectric element 1. They are glued together to form an inkjet head. The inkjet head applies voltage pulses to the drive unit 4 selected based on image information to displace it, generate a volume variation Q of the flow path 9, and eject droplets from the nozzle 7. Formed channel 8
, 9 have a shape that converges from the width direction and depth direction toward the nozzle part 7, making it easier to concentrate pressure waves and improving the discharge performance of bubbles generated from the inside and outside of the flow channels 8 and 9. Make it.

[0016]

[Effects] As is clear from the above explanation, according to the present invention, the depth of the flow path for increasing the amount of volume variation due to the drive of the piezoelectric element can be increased. A photosensitive resin layer is laminated on the molded lid plate to form a fine nozzle part and flow path, so the flow path can be formed three-dimensionally and smoothly without steps with excellent concentration of pressure waves and bubble discharge. It is possible to form a flow path. As a result, a highly integrated inkjet head with excellent precision and high frequency characteristics can be provided.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining one embodiment of a cover plate in an inkjet head of the present invention.

FIG. 2 is a diagram for explaining the schematic configuration of an inkjet head of the present invention.

FIG. 3 is a diagram for explaining an example of a conventional inkjet head.

[Explanation of symbols]

8... Molding flow path section, 8a... Taper section, 9... Photosensitive resin flow path, 9a... Convergence section.

Claims (2)

[Claims] 1. A piezoelectric element in which driving parts and non-driving parts are arranged alternately by a plurality of parallel grooves, and a cover plate having grooves corresponding to the driving parts of the piezoelectric element and partitioned by side walls. A non-driving part of the piezoelectric element is joined to a side wall of the lid plate, and a flow path having a nozzle is formed by the driving part, the side wall, and the groove, and a displacement in the thickness direction is applied to the driving part of the piezoelectric element. In the inkjet head that ejects droplets from the nozzle, the lid plate is composed of a coarsely formed substrate and a finely formed photosensitive resin, and the cover plate includes a finely formed photosensitive resin on the roughly formed substrate. An inkjet head characterized by integrally bonding a synthetic resin. 2. The lid plate is composed of a resin substrate and a photosensitive resin substrate formed on the resin substrate, and the resin substrate is provided with a flow path having a tapered portion, and the photosensitive resin substrate is provided with a flow path having a tapered portion. 2. The inkjet head according to claim 1, further comprising a finely formed nozzle portion.