Inkjet printing head and inkjet printing head manufacturing method

An inkjet printing head is provided with an ink chamber forming member constructed of a ceiling plate and a glass thin plate which are made from identical photosensitive glass material. A plurality of groove-shaped recess are formed in parallel and at a regular pitch on one surface of the ceiling plate. The glass thin plate is integrally connected by heat treatment to a recess portion formation surface of the ceiling plate. With this arrangement, the inside of each of the recess covered with the glass thin plate serves as an ink chamber. In a manufacturing method of the ink chamber forming member, a photosensitive glass is coated to predetermined thickness on a support body. Subsequently, the photosensitive glass is subjected to pattern exposure via a mask plate. Through this process, the ultraviolet ray is applied to a portion which belongs to the photosensitive glass and corresponds to an area which is not masked, so that glass crystallization progresses only in this portion and a solubility to acid is developed. Then, the exposed photosensitive glass and the support body are immersed in an aqueous solution for chemical etching. Through this process, the exposed portion is melted to a specified depth, so that the plurality of recesses which serve as the ink chambers are formed. Subsequently, the photosensitive glass is crystallized through a heat treatment process for baking it, thereby obtaining the ceiling plate. Next, the ceiling plate is superposed on the glass thin plate, and the whole body is baked. Through this heat treatment, the ceiling plate and the glass thin plate are fused to be integrated into a body.

This application is based on application No. 9-18497 filed in Japan, the
 contents of which is hereby incorporated by reference.
 BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to an inkjet printing head for recording an
 image by discharging an ink drop from a nozzle according to an image
 signal and making this adhere to a recording medium such as a recording
 paper, and also relates to an inkjet printing head manufacturing method.
 2. Description of the Related Art
 There has been conventionally known an inkjet printing head for discharging
 an ink drop from a nozzle by pressurizing ink stored in an ink chamber by
 means of a piezoelectric actuator.
 In this type of inkjet printing head, there has been the general practice
 of forming a plurality of recess portions in an ink chamber forming
 member, covering the recess portions with a diaphragm and a nozzle plate
 formed of a thin plate of a metal or the like to this by fixation with an
 adhesive and making the inside of each of the aforementioned recess
 portions covered with this diaphragm and so forth serve as an ink chamber.
 As a method for forming such an ink chamber forming member, there is a
 forming method achieved by growing a metal layer into a specified pattern
 utilizing a resist by electroforming.
 However, when forming an ink chamber forming member by electroforming, a
 thick film is formed by controlling electrification of a metal plating
 liquid, and this has led to the problem that much time is required for
 obtaining a metal layer of a desired thickness and therefore the
 production cost increases. Furthermore, since the ink chamber is formed by
 fixing by the adhesive the diaphragm and so forth to the ink chamber
 forming member manufactured through the above processes, an assembling
 process with coating of the adhesive is required, and this has also caused
 a cost increase.
 OBJECTS AND SUMMARY
 It is an object of the present invention to provide an improved inkjet
 printing head and inkjet printing head manufacturing method.
 It is another object of the present invention to provide an easily
 manufacturable inkjet printing head and inkjet printing head manufacturing
 method.
 It is a further object of the present invention to provide a
 low-manufacturing-cost inkjet printing head and inkjet printing head
 manufacturing method.
 In order to achieve the above objects and other objects, an inkjet printing
 head of an embodiment comprises an ink chamber forming member constructed
 of a ceiling plate made of a photosensitive glass provided with a
 plurality of recess portions by pattern exposure and etching and a glass
 thin plate which is integrally connected to a recess portion formation
 surface of this ceiling plate by heat treatment, and the inside of each of
 the aforementioned recess portions covered with the glass thin plate
 serves as an ink chamber.
 In this inkjet printing head, it is preferable to form the aforementioned
 glass thin plate with a photosensitive glass raw material identical to
 that of the aforementioned ceiling plate. Furthermore, a nozzle
 communicating with the ink chamber may be formed on the ceiling plate by
 pattern exposure and etching.
 Furthermore, the inkjet printing head manufacturing method of an embodiment
 comprises an exposure process for subjecting a photosensitive glass to
 pattern exposure, an etching process for forming a plurality of recess
 portions by etching the exposed photosensitive glass, a heat treatment
 process for crystallizing the etched photosensitive glass and a connecting
 process for integrally connecting by a heat treatment the glass thin plate
 to the recess portion formation surface of the crystallized photosensitive
 glass.
 According to the aforementioned inkjet printing head and its manufacturing
 method, the ink chamber forming member can be manufactured in a shorter
 time than in a case where a member having a recess portion for an ink
 chamber is formed by electro forming, therefore allowing the production
 cost to be reduced. Since this is not the one in which the ink chamber is
 formed by fixing a plurality of members with an adhesive, the process for
 coating the adhesive is eliminated to allow the assembling process to be
 simplified. Furthermore, since the ink chamber wall surface made of glass
 has a good wettability for a watercolor ink, the flow of ink due to a
 capillary phenomenon becomes smooth and the generation of air bubbles can
 be prevented.
 In a case where the glass thin plate to be connected to the ceiling plate
 is formed of a photosensitive glass of the same raw material, an adhesive
 strength increases more than in a case where glass thin plates of
 different materials are connected together, thereby allowing a long
 operating life to be achieved.
 Furthermore, in a case where a nozzle communicating with the ink chamber is
 formed at the ceiling plate, there is no need for separately providing a
 nozzle plate, therefore allowing the production cost to be further
 reduced.

In the following description, like parts are designated by like reference
 numbers throughout the several drawings.
 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 Embodiments of the present invention will be described below with reference
 to the accompanying drawings.
 FIG. 1 is a perspective view showing the schematic construction of an
 inkjet printer 1.
 The inkjet printer 1 includes a recording sheet 2 which is a recording
 medium such as a paper, resin film or the like, a printing head 10 of an
 inkjet system, a carriage 4 for holding the printing head 10, slide shafts
 5 and 6 along which the carriage 4 is reciprocated in parallel with the
 recording surface of the recording sheet 2, a drive motor 7 for
 reciprocating the carriage 4 along the slide shafts 5 and 6, a timing belt
 9 for transforming the rotation of the drive motor 7 into a reciprocating
 motion of the carriage and an idling pulley 8.
 The inkjet printer 1 includes a platen 3 which concurrently serves as a
 guide plate for guiding the recording sheet 2 along a conveyance path, a
 paper pressing plate 11 for preventing the rising of the recording sheet 2
 between it and the platen 3 by pressing the sheet, a discharging roller 17
 for discharging the recording sheet 2 and a spur roller 19.
 The recording sheet 2 is fed into a recording section in which the printing
 head 10 and the platen 3 face each other by a paper feeder such as a
 manual or cut sheet feeder or the like. In this stage, the amount of
 rotation of a paper feeding roller (not shown) is controlled, so that the
 conveyance to the recording section is controlled.
 A piezoelectric element is used for the printing head 10. A voltage is
 applied to the piezoelectric element, thereby causing a distortion. This
 distortion changes the volume of the channel filled with ink. Due to the
 change in volume, the ink is discharged from the nozzle provided at the
 channel, so that recording on the recording sheet 2 is performed.
 The printing head 10 performs image recording by means of inks of four
 colors of Y (yellow), M (magenta), C (cyan) and K (black).
 The carriage 4 performs main scanning in the direction of row of the
 recording sheet 2 (in the transverse direction of the recording sheet 2)
 with the drive motor 7, the idling pulley 8 and the timing belt 9, and the
 printing head 10 mounted on the carriage 4 and records an image of one
 line. Every time the recording of one line is completed, the recording
 sheet 2 is fed in the vertical direction to be subjected to sub-scanning,
 and the next line is recorded.
 FIGS. 2 and 3 are views showing the inkjet printing head 10.
 This head 10 is provided with an ink chamber forming member 12 constructed
 of a ceiling plate 14 and a glass thin plate 16.
 A plurality of groove-shaped recess portions 18 are formed in parallel and
 at a regular pitch on one surface of the ceiling plate 14 by pattern
 exposure and etching as described later. The glass thin plate 16 is
 integrally connected by heat treatment to a recess portion formation
 surface of the ceiling plate 14. With this arrangement, the inside of each
 of the aforementioned recess portions 18 covered with the glass thin plate
 16 serves as an ink chamber 20. The ink chamber 20 has a
 rectangular-shaped section and is elongated as shown in FIG. 3. It is to
 be noted that the shape of the recess portion 18 is not limited to the
 elongated groove shape, and it may be a recess portion having a square
 shape, a circular shape or the like viewed from the recess portion
 formation surface side.
 As shown in FIG. 3, a nozzle plate 22 is adhered to one end surface of the
 ink chamber forming member 12. At the nozzle plate 22 is formed a tapered
 nozzle 24 communicating with one end of each ink chamber 20. To the other
 end surface of the ink chamber forming member 12 is adhered an orifice
 plate 28 having an ink inlet 26 corresponding to each ink chamber 20. To
 the orifice plate 28 is adhered an ink supply chamber forming member 32
 internally having an ink supply chamber 30.
 The ink supply chamber 30 is communicating with the ink chamber 20 via the
 ink inlet 26 and connected to an ink tank (not shown).
 The aforementioned nozzle plate 22, orifice plate 28 and ink supply chamber
 forming member 32 are also supported by a base plate 38 made of ceramic,
 metal, glass, plastic or the like.
 Between the aforementioned ink chamber forming member 12 and the base plate
 38 is fixed a diaphragm 40. The diaphragm 40 is made of a known
 piezoelectric material (e.g., PZT) and has its upper surface and lower
 surface provided with conductive metal layers (not shown) which function
 as a common electrode and an individual electrode, respectively, and are
 formed by plating, sputtering or a similar method. The diaphragm 40 is
 segmented by forming a plurality of separate grooves 42 through a dicing
 process, so that it is separated into a piezoelectric actuator 44 which
 faces the ink chamber 20 via the glass thin plate 16 and a support wall 46
 other than it. Each piezoelectric actuator 44 is polarized by applying at
 a high temperature a high voltage across the common electrode and the
 individual electrode located on the upper and lower sides.
 A manufacturing method of the aforementioned ink chamber forming member 12
 will be described next with specific material names and numeric values
 exemplified. As shown in FIG. 4, a photosensitive glass 52 is coated to a
 thickness of about 350 .mu.m on a support body 50. PEG-3C produced by HOYA
 CORP. is used for the photosensitive glass 52, and mirror-finished #7059
 glass, which is produced by Corning Inc., slightly coated with a wax for
 releasing use is used for the support body.
 Subsequently, as shown in FIG. 5, the aforementioned photosensitive glass
 52 is subjected to pattern exposure for 15 seconds with a G-line
 ultraviolet ray (or a broad ultraviolet ray is acceptable) at 250
 mJ/cm.sup.2 via a quartz glass plate 56 masked with a Cr layer 54. Through
 this process, the ultraviolet ray is applied to a portion 58 which belongs
 to the photosensitive glass 52 and corresponds to an area which is not
 masked by the Cr layer 54, so that glass crystallization progresses only
 in this portion 58 and a solubility to acid is developed.
 Then, the aforementioned exposed photosensitive glass 52 and the support
 body 50 are immersed in an 2N H.sub.2 SO.sub.4 aqueous solution for 30
 minutes for chemical etching. Through this process, the exposed portion 58
 is melted to a specified depth as shown in FIG. 6, so that the plurality
 of recess portions 18 which serve as the ink chambers 20 are formed.
 Subsequently, the photosensitive glass is crystallized through a heat
 treatment process for baking it at 90.degree. C. for 30 minutes, thereby
 obtaining the aforementioned ceiling plate 14.
 Next, as shown in FIG. 7, a glass material identical to that for use in
 manufacturing the photosensitive glass 52 is coated to a thickness of
 about 30 .mu.m on another support body 60, and this is baked at 90.degree.
 C. for 30 minutes, thereby obtaining the aforementioned glass thin plate
 16.
 Subsequently, the ceiling plate 14 and the support body 50 shown in FIG. 6
 are inverted as shown in FIG. 8 and superposed on the glass thin plate 16
 shown in FIG. 7, and the whole body is baked at 150.degree. C. for one
 hour with a load of 500 g/cm.sup.2 applied from above. Through this heat
 treatment, the ceiling plate 14 and the glass thin plate 16 are fused to
 be integrated into a body. Subsequently, by removing the support bodies 50
 and 60, the ink chamber forming member 12 is completed as shown in FIG. 9.
 According to the aforementioned manufacturing method of the inkjet printing
 head 10 and the ink chamber forming member 12, the ink chamber forming
 member 12 can be manufactured in a shorter time than in the case where a
 member having a recess portion for ink chamber use is manufactured by
 electroforming, therefore allowing the production cost to be reduced.
 Furthermore, the aforementioned ink chamber forming member 12 is obtained
 by integrally connecting the ceiling plate 14 with the glass thin plate 16
 through a heat treatment, not by fixing them with an adhesive, and
 therefore, the process for coating an adhesive is eliminated to allow the
 assembling process to be simplified.
 Furthermore, in regard to the ink chamber forming member 12, the ceiling
 plate 14 and the glass thin plate 16 to be connected to this are formed of
 an identical glass material. Therefore, the adhesive strength is increased
 further than in the case where glass thin plates of different materials
 are connected to each other, therefore allowing a long operating life to
 be achieved. It is also acceptable to connect glass thin plates of
 different materials with each other.
 In the aforementioned inkjet printing head 10, the ink supplied from the
 ink tank to the ink supply chamber 30 is stored in the ink chamber 20 via
 the ink inlet 26. When a drive voltage is applied across the common
 electrode and the individual electrode located respectively on the upper
 and lower surfaces in accordance with an image signal from a driver
 circuit (not shown) in this state, the piezoelectric actuator 44
 instantaneously extends to be deformed in the direction of thickness to
 thereby push the glass thin plate 16 toward the ink chamber 20 side. The
 ink in the ink chamber 20 pressurized by this is discharged as an ink drop
 from the nozzle 24 and adhered to a recording medium (not shown), thereby
 recording an image. When the voltage application is canceled, the
 piezoelectric actuator 44 is restored into its original state, and the ink
 is supplied from the ink supply chamber 30 into the ink chamber 20 by the
 capillary phenomenon. An ink flow thus occurs inside the ink chamber 20 in
 discharging and supplying the ink. However, since the glass-made wall
 surfaces on the four sides of the ink chamber 20 have a good wettability
 for the watercolor ink, the aforementioned ink flow becomes smooth, and
 the entry and generation of air bubbles can be prevented.
 Next, an inkjet printing head 70 of another embodiment will be described
 with reference to FIGS. 10 through 14. Since the construction and the ink
 discharging operation is the same as the aforementioned inkjet printing
 head 10 except for the nozzle position, no description is provided
 therefor.
 Although the nozzle 24 is provided by adhering the nozzle plate 22 to the
 end surface of the ink chamber 20 in the aforementioned inkjet printing
 head 10, a nozzle 72 communicating with each ink chamber 20 may be formed
 at an ink chamber forming member 13 as in the inkjet printing head 70
 shown in FIG. 10. In this case, a blocking plate provided with no hole is
 adhered to the end surface of the ink chamber forming member 12 in place
 of the nozzle plate 22.
 The ink chamber forming member 13 having the aforementioned nozzle 72 is
 manufactured as follows. First, as shown in FIG. 11, a fluorine containing
 coating material (not shown) is coated on the support body 50 on which a
 wax for releasing use is applied, and thereafter a photosensitive glass 74
 is coated on it to a thickness of about 80 .mu.m. Subsequently, it is
 subjected to pattern exposure of an ultraviolet ray via a quartz glass
 plate 86 masked with a Cr layer 84, thereby crystallizing a portion 76
 which belongs to the photosensitive glass 74 and becomes the nozzle 72. In
 this stage, by weakening the exposure conditions to 180 mJ/cm.sup.2 and 8
 seconds, the aforementioned portion 76 can be made to have a tapered
 shape.
 Next, as shown in FIG. 12, a photosensitive glass 78 is coated to a
 thickness of about 300 .mu.m on the aforementioned photosensitive glass
 74. Subsequently, as shown in FIG. 13, this photosensitive glass 78 is
 subjected to pattern exposure with an ultraviolet ray via the quartz glass
 plate 56 masked with the Cr layer 54, thereby crystallizing a portion 80
 which is to be a groove-shaped recess portion 18 for ink chamber 20 use.
 Then, by immersing these photosensitive glass 74 and photosensitive glass
 78 in an H.sub.2 SO.sub.4 aqueous solution to chemically etch the
 aforementioned portions 76 and 80 and then integrally baking them, a
 ceiling plate 15 having the nozzle 72 can be obtained as shown in FIG. 14.
 This process of connecting the glass thin plate 16 to the ceiling plate 15
 is the same as that in the case of the aforementioned ink chamber forming
 member 12 (see FIGS. 7 through 9).
 When the nozzle 72 is thus formed at the ink chamber forming member 13,
 there is no need for providing any separate nozzle plate, therefore
 allowing the production cost to be further reduced.
 Although the present invention has been fully described by way of examples
 with reference to the accompanying drawings, it is to be noted that
 various changes and modifications will be apparent to those skilled in the
 art. Therefore, unless such changes and modifications depart from the
 scope of the present invention, they should be construed as being included
 therein.