WO1997029914A1

WO1997029914A1 - Optical switch and ink-jet printer

Info

Publication number: WO1997029914A1
Application number: PCT/JP1997/000384
Authority: WO
Inventors: Masatoshi Kimura; Masao Hiyane
Original assignee: Fujitsu Limited
Priority date: 1996-02-16
Filing date: 1997-02-13
Publication date: 1997-08-21
Also published as: DE19780213T1

Abstract

The printing speed and resolution of an ink-jet printer are improved by making the wiring pattern finer and increasing the number of individual driving circuits which are required for obtaining a line head, while avoiding high-voltage operation and the increase in cost of the printer. The ink-jet printer is constituted in such a way that ink jetting mechanisms respectively using piezoelectric bodies (3) are arranged in parallel and one electrode of the bodies (3) is independently connected to photoconductors, and then, the other electrodes of the bodies (3) are connected to the other electrodes of adjacent bodies (3). The ink jetting mechanisms emit ink by deforming one of the piezoelectric bodies (3) by selectively irradiating the corresponding photoconductor (5) with light (12) from an optical scanning device. The printer uses an optical switch.

Description

Description Optical switch and inkjet printer Technical field

The present invention relates to an optical switch using a capacitance object such as a piezoelectric element and a photoconductor, and to an ink jet printer using such an optical switch. The present invention can be conveniently applied to achieve a high-speed driving and high-density switch structure. Background art

In recent years, there has been remarkable progress in information processing equipment, and parallel signal processing has been performed everywhere. In image processing devices that use such parallel signal processing, higher densities and higher image quality have progressed, and in some cases, pixel densities of about 500 dpi (dots per inch), which is the limit of human recognition The fact is that it has already surpassed. In particular, in electrophotographic printers, which are becoming mainstream as office printers, in order to obtain pixels as small as about 10 / zm, (1) a laser beam focused to a beam diameter of about 10〃m is exposed. The electrostatic latent image is formed on the photosensitive drum by irradiating the electrostatic latent image on the photosensitive drum in accordance with a desired image pattern. (2) The charged toner obtained by subdividing this electrostatic latent image into several to sub-m By developing on the photosensitive drum using a photo sensor, a fine toner image with pixels of about 10 m is obtained.

—On the other hand, the inkjet printer, which is rapidly developing as a personal printer, is not an exception. However, in order to increase the density, it is necessary to reduce the pitch between the nozzles for the ink jet. (1) Insufficient ink jetting capability due to miniaturization of the ink jet pump, and (2) Injection of ink droplets from nozzles for each nozzle. However, it was difficult to configure the connection between the starter circuit and the ejection pump for individual control, which hindered the realization of high density. With the current print board wiring technology, the limit is to limit the nozzle arrangement interval to several lines per square meter, and especially the narrowing of the pitch at the connection between the ink injection pump and the starting circuit is already limited. Has been reached. Attempts have also been made to line up the inkjet head to achieve higher speeds. That is, a large number of injection nozzles are arranged in the line direction of the head, and ink jet printing is performed in parallel on a print medium for each line. When the head is sprayed, the head must be formed over the entire width of the printing surface, that is, over a width of about 100 mm. On the other hand, it is very difficult and expensive to form a lined ink jet head using a semiconductor fine pattern forming method suitable for the method.

Japanese Patent Application Laid-Open No. Sho 61-29343 discloses a conventional technique for controlling the driving state of a piezoelectric element by irradiating a photoconductor with light. This is related to an ultrasonic probe that transmits and receives ultrasonic signals, and has a structure in which a photoconductor is directly provided on one side of a piezoelectric element, and a transparent electrode is provided thereon, so that a light beam emitted from the transparent conductor side is emitted. By changing the shape and strength, the operating area of the piezoelectric element and the sensitivity (resistance) of the photoconductor are controlled, and when the piezoelectric element receives ultrasonic waves, the output of the piezoelectric element receiving the ultrasonic waves The voltage is taken out as an analog value.

As an ink jet recording apparatus using a photoconductive film, there is JP-A-61-79664. In this method, a recording element is formed of a photoconductive element in a piezoelectric element that deforms a pressure chamber of an ink nozzle, a recording electrode provided in the nozzle, and a counter electrode provided corresponding to the recording electrode. A high voltage is applied to the ink by forming a meniscus of the ink with the piezoelectric element, applying a voltage between the nozzle surface and the recording electrode, and irradiating the photoconductor provided on the nozzle surface with light. At the same time, electric charges are injected into the ink at the generated high voltage, and at the same time, the ink starts flying at the high charge level. Disclosure of the invention

As mentioned above, the speed of the ink jet printer is increased. To achieve high resolution, technologies that are indispensable for line heading are: (1) fine pattern wiring, (2) many It is important to realize individual drive circuits. It is also important to reduce power consumption in order to suppress heat generation from many individual drive circuit elements. For this purpose, it is desirable to use a constant voltage driving method even at a high voltage instead of a constant current driving method. Therefore, there arises a new problem in constant voltage driving: (3) suppression of high voltage. Furthermore, in order to make the ink jet head a line, not only the integration of the drive circuit, but also the problem of reducing the absolute price and lowering the price.

Accordingly, the present invention provides an ink jet printer device which realizes the four problems (1) to (4) described above, namely, wiring of a fine pattern, a large number of individual drive circuits, suppression of high voltage, and low cost. The task is to provide.

Another object of the present invention is to provide an optical switch which can be suitably used for driving an ink jetting mechanism of a head in an ink jet printer according to the present invention.

The present invention uses a photoconductor as a driving circuit for a piezoelectric element, and irradiates the photoconductor with light according to a signal pattern, thereby varying the voltage between both ends of the piezoelectric element (capacitance object). A light switch characterized by An optical multi-switch is provided by providing a switch and a plurality of nozzles for ejecting ink by mechanical displacement of the piezoelectric element, and providing individual photoconductors for each piezoelectric element. As a result, a multi-ink jet head printer is achieved, and all four problems (1) to (4) are solved.

Therefore, the optical switch of the present invention can switch the charging or discharging of the capacitance object (piezoelectric element) by irradiating the photoconductor connected to the capacitance object with light. The feature is that it is performed by using the

The capacitance object has a pair of electrodes, one of which is formed by the photoconductor, and the other of which is grounded.

The photoconductor has a first side connected to one electrode of the capacitive object, and a second side opposite to the first side, and the second side is a transparent conductor. The signal of the electric circuit connected to the transparent conductor is transmitted to the capacitance object by an optical switching effect of the photoconductor.

One electrode of the capacitance object is a good conductor electrode, the photoconductor is bonded to the good conductor electrode, and a side of the photoconductor opposite to the good conductor electrode is formed of a transparent conductor. A signal of an electric circuit connected to the transparent conductor is transmitted to the capacitance object by an optical switching effect of the photoconductor.

It is preferable that the capacitance object is composed of a piezoelectric body, and the piezoelectric body is deformed by a signal transmitted to the piezoelectric body by an optical switching effect of the photoconductor. It is desirable to extract mechanical output.

Further, the optical multi-switch of the present invention includes a plurality of capacitance objects (piezoelectric elements), and one electrode of each capacitance object is independently illuminated. The other electrode of each capacitance object is connected to the conductor, and the other electrode of the adjacent capacitance object is connected to the other electrode of the adjacent capacitance object, and performs switching of charging or discharging of each capacitance object. The method is characterized by performing the light switch effect by irradiating each photoconductor with light.

Furthermore, according to the ink jet printer device using the optical switch of the present invention, a plurality of ink jetting mechanisms using piezoelectric materials are arranged in parallel, and one electrode of each piezoelectric material is connected to each other. Independently connected to the photoconductor, and the other electrode of each piezoelectric body is connected to the other electrode of the adjacent piezoelectric body, and the light scanning means selectively irradiates the plurality of photoconductors with light. Thus, the ink is ejected from the ink ejecting mechanism by deforming the corresponding piezoelectric body.

As the optical scanning means, a laser optical system such as a laser light source, a rotating mirror or a vibrating mirror, and acoustic deflection can be used.

Further, according to the present invention, a photosensitive layer is connected to the piezoelectric element of an image forming apparatus including an ink supply path, an ink pressure chamber, an ink nozzle, and a piezoelectric element, and the photosensitive layer is irradiated with light according to an image pattern. Accordingly, in an ink jet printer using an optical switch, the piezoelectric element is deformed and the piezoelectric element is ejected from the ink nozzle by mechanical fluctuation. A switch circuit is connected between one electrode and the other electrode of the piezoelectric element, and a voltage having a polarity such that the photosensitive member can respond to light is applied to the photosensitive layer (5). A printer device characterized by the following is provided.

When a voltage of approximately 0 V is applied to the piezoelectric element, the ink pressure chamber expands, absorbs ink from the ink supply path, and is applied to the photosensitive element to the photosensitive layer. When a high voltage is applied, the ink pressure chamber may be configured to contract.

Conversely, when a voltage near 0 V is applied to the piezoelectric element, Then, the ink pressure chamber expands, absorbs ink from the ink supply path, and conversely, when the high voltage applied to the photosensitive layer is applied to the piezoelectric element, the ink chamber shrinks. It can also be configured. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a configuration diagram schematically showing an inkjet nozzle of the present invention.

FIG. 2 is a principle view of an ink jet nozzle using the optical switch of the present invention.

FIG. 3 shows a specific configuration example of the ink jet nozzle of the present invention. FIGS. 4 (a) and 4 (b) are diagrams for explaining a method of forming a diode 7 used in an ink jet head using the optical switch of the present invention.

Figure 5 shows a multiplexed circuit configuration that includes a piezoelectric element, a photoconductor film, and a diode.

Figure 6 shows the overall configuration of the ink jet printer.

Figure 7 is a schematic diagram of the print head.

FIG. 8 shows a configuration example of the optical switch of the present invention.

FIG. 9 shows another example of the configuration of the optical switch of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a configuration of an ink jet nozzle to which the present invention is applied. In the figure, 1 is a nozzle plate, 2 is an ink pressure chamber, and 3 is a piezoelectric element, which is configured as a piezoelectric injection device. The piezoelectric element 3 is a part of the inner wall of the ink pressure chamber 2, for example, the upper wall as shown in the figure. Is formed. When a voltage is applied to the piezoelectric element 3 and charging is performed, the piezoelectric element 3 is deformed from the broken line position to the solid line position in FIG. 1 and the pressure chamber 2 contracts, so that pressure is applied to the ink in the pressure chamber 2 Image recording by ejecting ink droplets through the nozzle holes 1 a of the nozzle plate 1. When the voltage application to the piezoelectric element 3 is stopped and the discharge is performed, the piezoelectric element 3 is deformed from the solid line position in FIG. 1 to the broken line position, the pressure chamber 2 expands, and the ink is absorbed into the pressure chamber 2. I do.

In this way, the piezoelectric element 3 contracts the pressure chamber 2 when applying a voltage, that is, when charging, ejects ink droplets, and expands the pressure chamber 2 during discharge to absorb ink in the pressure chamber 2. On the other hand, when voltage is applied, that is, during charging, the pressure chamber 2 expands to absorb ink into the pressure chamber 2, and when discharging, contracts the pressure chamber 2 to cause ink drop. May be deformed so as to inject water.

FIG. 2 is a diagram illustrating the principle of the ink jet printer of the present invention. FIG. 3 is a perspective view thereof. In FIG. 2, reference numeral 4 denotes a conductive film individually connected to each piezoelectric element 3, 5 denotes a photoconductor layer individually formed on each conductive film 4, and 6 denotes an individual photoconductor layer 5 , A common high-voltage circuit connected to the other surface, 7 is a diode individually connected to each photoconductor layer 5, and 8 is a ground short circuit (commonly provided for each diode 7). 9) is a common ink supply path, 10 is a platen, 11 is a print medium, and 12 is a scanning light. Reference numeral 13 denotes a transparent conductive film. 2 and 3, a plurality of pressure chambers 2 are arranged in the line direction with respect to the platen 10. The nozzle plate 1 has a nozzle hole 1a corresponding to each pressure chamber 2. The common ink supply passage 9 communicates with the individual pressure chambers 2 via the communication holes 9a.

One (upper) electrode of each piezoelectric element 3 is connected to one (upper) surface of an individual photoconductor eyebrow 5 via an individual conductive film 4. Individual One (upper) surface of the photoconductor layer 5 is connected to an individual diode 7 and the other (lower) surface is connected to a common high-voltage circuit 6. The electrodes on the other (lower) surface of the individual piezoelectric element 3 are connected to a common ground (switch) 8. The individual photoconductor layer 5 is selectively irradiated with the scanning light 12 of the laser beam via the transparent conductive film 13 o

As described above, in the present invention, by realizing a large number of drive circuit elements by the photoconductor layer 5 individually connected to the piezoelectric element 3, it is possible to increase the density and reduce the cost. Further, the control of the high voltage applied to the piezoelectric element 3 can be easily handled by applying the optical switching by the photoconductor layer 5.

FIGS. 4 (a) and 4 (b) are diagrams for explaining a method of forming a diode 7 used in an ink jet head using the optical switch of the present invention. First, an N-type silicon substrate 71 is prepared. Next, the surface of the single crystal of the N-type silicon substrate 71 is heated and oxidized to form a silicon oxide film (SiO ₂ film). This SiO ₂ film functions as a single-crystal protective film and at the same time acts to prevent diffusion of the doping agent. Next, a photosensitive chemical substance (not shown) called a photo resist is applied on the SiO ₂ film, and ultraviolet rays are irradiated through a mask (not shown). As a result, the SiO ₂ film is removed only in the region where the P-type diffusion layer is to be formed. Next, boron is diffused in an oxidizing atmosphere to form a P-type region 73. At the same time, a SiO ₂ film is formed on the surface. Next, the oxide film in the portions corresponding to the electrode portions is removed, and aluminum is formed by vapor deposition on the portions from which these oxide films have been removed, to form electrodes 74 and 75. The SiO ₂ film 72 as a protective film remains in portions other than the electrode forming portion.

Figure 5 shows a multi-circuit configuration. As described above, the piezoelectric element 3, the photoconductive film 5, and the diode 7 are provided for each ink jet nozzle. Is provided. One electrode of each piezoelectric element 3 (1 to n) is connected to one side of a separate photoconductor layer 5 (1 to n), and each connection portion is connected to one of the individual diodes 7. The other side of each diode 7 is commonly connected and connected to the ground via a common ground switch 8. The other sides of the individual photoconductor layers 5 (1 to n) are connected in common and connected to a high-voltage circuit (6). As described above, each of the photoconductor layers 5 (1 to! 1) is selectively driven by light irradiation.

FIG. 6 is an overall configuration diagram of an ink jet printer that drives nozzles using the optical switch of the present invention, and FIG. 7 is a schematic diagram of a print head. In these figures, 20 is a print head, 10 is a platen, 11 is paper, 24 is a paper cassette, 25 is paper staple force, and 30 is a control unit. In addition, 21 is an LED array, 22 is a self-optical lens, and 23 is a circuit board. As shown, the structure of the pressure chamber 2 and the multi-circuit configuration shown in FIG. 5 (excluding the common switch 8) ), An LED array 21, a self-occurring lens 22, and a circuit board 23 are mounted on a print head 20, and a control unit 30 including a common ground switch 8 is provided on the side of the printer body. The paper 11 is supplied from the paper cassette 24 to the platen 10, and printing is performed on the paper 11 on the platen 10 by the ink jet printing head 20. The printed paper 11 is accumulated on the paper stat force 25.

The LED array 21 is arranged in parallel to the arrangement direction of the nozzles 1 a, and can selectively irradiate light to the photoconductor layer 5 corresponding to a specific nozzle via the self-ox lens 22.

Next, the operation principle of the ink jet printer according to the present invention will be described with reference to FIGS. 2, 3, and 5 to 7. FIG.

① First, in the initial state, the common ground short circuit 8 is closed (that is, ) And short circuit all circuits. Then, by the action of the diode 7, the surface potential of the upper part of the photoconductor layer 5, that is, the piezoelectric element 3 becomes 0 V. At this time, the piezoelectric element 3 is set so that the pressure chamber 2 expands.

(2) Next, the common ground circuit 8 is opened (that is, turned off). In this state, the state described in (1) above is maintained as it is, and the surface potentials of all the piezoelectric elements 3 are 0 V.

(3) Next, the light beam 12 is scanned in accordance with the image signal pattern, and the individual photoconductor layers 5 are selectively irradiated with light via the transparent conductive film 13 (FIG. 3) to selectively irradiate the light. Is activated, the power supply voltage of the common high-voltage circuit 6 also appears on the opposite side of the photoconductor layer 5 (that is, the upper surface of the photoconductor layer 5), and this potential is transmitted via the conductive film 4 to the piezoelectric body. Applied to element 3. Then, the piezoelectric element 3 is deformed and the pressure chamber 2 is compressed. As a result, ink droplets are ejected from the compression chamber 2 through the nozzle holes la.

④Lastly, the common earth short circuit is closed again (that is, turned on), and since the surface potential of the piezoelectric element 3 that has ejected the ink is higher than the earth potential, the piezoelectric element 3 is discharged through the diode 7 and discharged. The surface of the body element 3 is set to the 0 V potential again. Then, the piezoelectric element 3 expands again in the direction in which the pressure chamber 2 expands, and ink is supplied from the common ink supply path 9 to the pressure chamber 2 via the individual communication holes 9a. In this way, all the piezoelectric elements 3 become 0 V potential and return to the initial state. That is, the pressure chamber 2 is filled with ink.

In the above operation principle, the irradiation of the light beam 12 causes the pressure chamber 2 of the ink to contract and eject the ink. However, when the method of applying the voltage is reversed, the photoconductor layer is formed. 5 irradiates light, the pressure chamber 2 expands and sucks ink, and a voltage of 0 V is applied to the piezoelectric element 3. Conversely, when the pressure is applied, the pressure chamber 2 is contracted so that ink can be injected.

As described above, in the present invention, a large number of drive circuit elements are realized by the photoconductor layer 5 individually connected to the piezoelectric element 3, thereby enabling a reduction in cost. Furthermore, since the voltage is controlled by applying the optical switching by the photoconductor layer 5, the high voltage to be applied to the piezoelectric element 3 can be easily controlled.

Theoretical consideration of the feasibility of optical switches

(a) Characteristics of photoreceptor for optical switch:

In order to realize an optical switch that can be used in the present invention, first, it is required that the ON / OFF ratio of the photoconductor is high, and second, that the ON resistance is small and no residual voltage remains. Is done. The characteristics of currently known inorganic photoconductor films are as follows.

〔table 1 〕

Characteristics of photoconductive film Item 0PC a-SiSe film thickness 10 ~ 30 zm 20 ~ 30 m ~ 60 m Relative permittivity 3 ~ 4 11-12 ~ 7

Mobility ^{^{/ 10- 5 ~l (T 7 cm}} 2 / Vs 0. l~10cm 2 / Vs ≥0. LcmVVs carrier lifetime Te ^{~ 1 s 10- 5 s 10 "} 6 s

Te product ≥10- ⁷ cm ² / Vs

Charging voltage 600 to 800 V to 500 V 600 to 1000 V Carrier transit time 0.125 ms to 150 ms 0.8 ns to 0.18 s 0.36 s to 0.6 us The OPC, a- There are Si and Se-based ones, and which photoconductor film can be applied to the ink jet printer of the present invention will be discussed later. (b) Regarding the piezoelectric element for driving the ink jet:

In the piezoelectric driving of an ink jet, for example, when a piezoelectric element having a capacitance of InF is driven at a voltage of 80 V, an injection ink amount lOOpl can be obtained. This value is the required ink amount at 240dpi. The electrical energy once stored in this piezoelectric element is 3.2〃J from 1Z2QV. Since particle velocity of the injected Lee ink particles is about 8 s, the injection I link is Mochisa ivy kinetic energy is calculated from ^1/2 m V 2, about ⁴ X 10- 4 jtz J, and the stored energy It is about 1/10000. That is, even if ink is ejected, the energy once accumulated in the piezoelectric element remains almost completely.

If the voltage applied to the piezoelectric element is increased to 500 V in order to obtain this electrostatic energy required for ink ejection, the capacitance of the piezoelectric element becomes 26 pFF. For example, if the thickness is increased six times, the area becomes It can be reduced by about an order of magnitude to 0.16 times. This is because, as can be understood from Figs. 1 to 3, in the piezo type, the area of the piezoelectric element 3 is designed to restrict the adjacent pitch, and therefore, the area of the piezoelectric element 3 can be reduced.分かる It turns out that it is extremely effective in reducing the size of the nozzle.

The above relationships are summarized in Table 2.

(Table 2)

Piezoelectric element Item Value

Article Resolution 240dp i

Case Injection amount l OOp l

Pressure Capacitance C 1 nF 26pF

Drive voltage 80 V 500 V

Stored energy 3.2 J 3.2 J

In general, in the direct drive method of the ink jet by the piezoelectric element, increasing the drive voltage increases the cost of the drive driver.

However, when an optical switch using the photoconductor layer 5 as a photoreceptor as in the present invention is used, the piezoelectric element can be driven by a high voltage without using a driving driver. It is advantageous for

(c) Regarding optical scanning conditions:

The optical scanning conditions are as follows.For example, if a printer device for 100 lines scans over an A4 size paper width direction of 190 mm at a recording density of 600 lines per inch and a resolution of 600 dpi, one line The total number of print dots per minute is 449 x 10 ³ , and the scan time per line is 0.6 seconds to 1.34 S per dot. In addition, since the number of optical scans for one row is 100, the scanning time interval per line is 6 ms. In the line head of the ink jet, the driving time of the piezo is s to obtain the required ink injection time, and the high speed limit of the ink suction cycle to the ink pressure chamber is about 10 kHz. (= 100 / zs), the scanning time of 6 ms per line is enough time for ink suction.

Table 3 summarizes the above relationships. (Table 3)

Examination result of optical scanning conditions Item Number Value

Maximum driving frequency of piezoelectric element lUkHz ― luu s * —-Required driving time of piezoelectric element from raw ~ 10 ^ S

Printing speed 100 lines (two 0.6 seconds)

Line spacing 6 lines inches (= 4.233 hidden lines)

Resolution 600dpi (= 42.33 / zm / dot)

Main scanning dot 600 / 25.4X 190 recitation (paper width) = 4,488 dot lines Scanning times 600 / 25.4X 4.233 (-line) = 100 times Total 0.6S / 100 times = 6 ms / 1 line

number

Total number of dots 448.8 X 10 ³ Z 0.6 seconds → 1.34 s / dot

Since the scanning time for one line is 6 ms, the optical carrier generated in the photoconductor (photoconductor) must pass through the photoconductor within at least 6 ms. As shown in Table 1, a photoconductor that satisfies this condition is an a-Si or Se photoconductor. Note that the 0PC, only the photosensitive member having 10- ⁵ ~10 ⁶ cm ² ZVs more mobility becomes applicable.

(d) About required light energy:

As shown in Table 2, the amount of charge stored in the piezoelectric element is 13 nC at 500 V. This means that the number of electrons is 8.125X10 ¹ °. When a semiconductor laser having a wavelength of 720 nm, the photon Nerugi one becomes 2.76 X 10- ^{1 9} J. Now, assuming that the light conversion efficiency of the photoreceptor is 100%, the required energy is

2.76X 10 " ^{1 9} JX 8.125 X 10 ^{1 G} = 2.22 x 10— ⁸ J

Becomes Assuming that this light energy is covered by the light scanning time per dot of 1.34 s shown in Table 3, the light energy per unit time is 16.6mW. Taking into account the optical attenuation due to the transparent conductive film and the optical aperture in the optical system, this can be achieved by using a semiconductor laser with a power of about 30 mW that has about twice the optical output.

Table 4 summarizes the above study results.

(Table 4)

Required light energy Item Consideration value

Pressure Drive voltage 500 V

Electric

Element capacitance 26pF

Child

13nC 8.125X10 ^{1 (1} (number of electrons)

Wavelength 720nm (semiconductor laser)

hC 6.626X 10— X 3 X10 ⁸

Optical energy —— = = 2.76X10— ^{l 9} J

Scan 720X 10 one ⁹

Required light energy 2.76X10 ^"IB JX8.125 X 10 '° number = 2.22 X 10- ⁸ J / dot need LD light amount 2.22X10- ⁸ J ÷ 1. = 16mW

(e) Light irradiation area of photoconductor

If the photoconductor (that is, the photoconductor layer 5) is regarded as the charge resistance of the piezoelectric element 3, it is necessary to discharge the charge accumulated in the piezoelectric element 26pF in at least one line scanning time of 6 ms. is there. That is, from the time constant of CR, the resistance R of the photoconductor is

R = 6 ms ÷ 26pF = 2.31 x 10 ⁸ Ω

Becomes Also, the resistance of the a-Si photoreceptor is about 10 ⁷ Ωcm, and the required area S of the photoreceptor is

S = 10 ⁵ Ω m X 20X 10- ⁶ ÷ 2.3 X 10 ⁸

= 8.65X 10 " ⁹ m ²

That is all. That is, an area of about 100 mC] is sufficient. Also, in this area, if the required LD light amount is provided, the required irradiation light amount is

^{2.22x 10 "B J ÷ (8.} 65 X 10- 9) = 2.5 J m 2

= 2.5x 10 ² J / cm ²

Becomes This value is about three orders of magnitude greater than the half-life exposure energy of a normal photoreceptor.

As described above, as a result of theoretical consideration of the feasibility of an optical switch, it has been found that the use of a-Si or Se-based It became clear that the optical switch applied in the invention was feasible.

(7) Configuration of optical switch

As for the concrete method of configuring the optical switch, two types as shown in FIGS. 8 and 9 can be considered. 8 and 9, members corresponding to those in FIGS. 1 to 7 are denoted by the same reference numerals. That is, 3 is a piezoelectric element (capacitance), 4 is a good conductor, 5 is a photoconductor, 6 is a high-voltage circuit, 8 is a ground switch, 12 is a light beam (electric signal), and 13 is a transparent conductive film ( Electrodes) and 15 are electrodes.

FIG. 8 shows the capacitance, that is, the photoconductor layer 5 formed on the piezoelectric element 3—a body type. 1) First, the switch 8 is short-circuited, and the voltage applied to the piezoelectric element 3 is substantially reduced. Set to 0 V. 2) Next, switch 8 is opened. 3) Light irradiation is performed from the transparent electrode 13 side of the photoconductor 5 according to the electric signal. Then, an optical carrier is generated only at the place where light is irradiated, the voltage applied to the transparent electrode 13 is applied to the good conductor 4, the voltage is applied to the piezoelectric element 3, and the piezoelectric element 3 outputs mechanical displacement. become. In the next cycle, switch 8 is shorted first, and the above operation is repeated. Thus, an optical switch is configured.

FIG. 9 shows the capacitance, that is, the photoconductive layer 5 formed directly on the piezoelectric element 3. Rather, the photoconductive layer 5 is formed at a position separated from the photoconductive layer 5 via the good conductor 4, and the operation principle is the same as that of the example of FIG. The advantage of FIG. 9 is that the size of the photoconductor (photoconductor) 5 in the optical switch portion can be any configuration without being limited to the size of the piezoelectric element 3.

Next, specific examples of the present invention will be described.

In the ink jet nozzles in Figs. 1 to 3, the nozzle plate indicated by 1 is composed of a SUS multilayer plate. 3 is a stacked piezoelectric element o

The photoconductor layer 5 is formed by applying a strip-shaped mask pattern on the PET film having a thickness of 100 μm so as to correspond to the cuts of each piezoelectric element, and then applying the transparent conductive film I T0. It is formed by vapor deposition. Next, a mask pattern in which a mask is opened only at a portion where a photosensitive layer is to be formed is attached, and a single-layer a-Si photosensitive member layer is formed by vacuum evaporation. Further, a conductive dry film is stuck on the photoreceptor film, and a substrate is stacked thereon. On the other hand, an individual diode 7 and a common electrode are formed on the Si substrate at a position remote from the ink jet substrate. Thereafter, the I T0 portion of the transparent conductive layer 13 and the electrode portion of the diode 7 are bonded with a conductive material. In this way, a multi-nozzle head as shown in FIGS. 1 to 3 was created.

The operation principle of the ink jet nozzle according to the embodiment of the present invention is as follows.

(1) The high voltage circuit 6 does not supply the piezoelectric body 3 with a voltage in a direction in which the pressure chamber 2 expands.

(2) The light beam 12 is scanned to selectively activate the photoconductive film 5 and supply electric charges to the piezoelectric body 3.

③ The selected piezoelectric body 3 deforms and sucks ink into the pressure chamber 3

高圧 The high voltage circuit 6 is cut off, but the diode 7 Isolated.

戻し Return the electrodes of all units to the ground potential and return the piezoelectric body to its original shape to contract the pressure chamber 2, and only the ink sucked into the pressure chamber 2 in the above item ③ is injected .

In the above operation, the unit not selected by the optical scanning is also coupled with the capacitor, so that a voltage is applied to the piezoelectric body 3 in the step ①, but the dielectric constant of the photoconductor 5 becomes 11 Since the dielectric constant of 3 has a difference of 2 digits or more from 1800 to 4600, if the area is the same and the thickness is the same, most of the voltage is received by the capacitor of the photoconductor film 5 and the value of 1 to 100 or less Only the voltage is applied to the piezoelectric body 3, and the design conditions of the thickness and the area are not affected by this problem.

In this embodiment, although the photoresponse speed is relatively slow, ink suction is selected by an optical switch so that an organic photoreceptor which can be constructed at a low cost is selected. By using an a-Si photoconductor or a Se photoconductor, which is faster than the above, it is also possible to select on the ejection side. In addition, it is needless to say that with the advent of organic photoconductors having a higher speed in the future, there is a possibility that optical switching can be performed on the ink jetting side.

Based on the above results, numerical studies were made on the feasibility of an ink jet printer using the optical switch of the present invention.

① Photoreceptor (photoconductive film) with fast response speed (see Table 1)

Light calibration Ria transit time ≤ 6 ms / 1 line (1.5 ppm, 600 dpi) in order to meet this condition, it is necessary that an optical calibration Li A mobility ≥ 10- ⁶ cm ² / Vs. Therefore, a-Si / Se-based photoreceptors and 0PC can be used as long as they are fast.

② Storage capacity of piezoelectric element (see Table 2)

Piezo element capacitance: 26pF 13nC electrostatic storage capacity at 500V drive voltage

③ Optical scanning conditions: 1.5 dpi and 600 dpi (see Table 3)

1) 1 line scanning time: 6 ms

2) One-dot irradiation time: 1.34 s

光 Required light energy (See Table 4)

• 13nC → 8.125X10 '. Pieces (number of electrons)

• 720nm semiconductor laser photon energy → 2.76 x 10- ^{1 9} J

'Necessary light energy: 2.22 x 10- ^{1 9} J Roh dot

• Required LD light amount: 16mW

光 Light irradiation area of photoconductor (photoconductive film): Possible with area 100 mC3

• CR time constant: 6 ms

→ Bright part resistance of photoconductor: 6 ms ÷ 26 pF = 2.31 X 10 ⁸ Ω

In addition, a numerical study on the high speed limit of the printer was performed. Table 5 shows the results. As basic conditions, the required maximum ink response speed is 100 s or less, and the resolution is 600 dpi.

(If the resolution is 300 dpi, 4 times speedup is possible.) [Table 5]

High speed limit

From the above, at LD = 50 mW, about 5 ppm at 600 dpi (about 20 ppm at 300 dpi) is possible, and about ΙΟΟρ for line solid-state light-emitting elements such as high-brightness LEDs. pm can be expected.

As described above, the embodiments of the present invention have been described in detail with reference to the accompanying drawings. However, the present invention is not limited to the above-described embodiments, and various forms, modifications, and variations are possible within the spirit and scope of the present invention. It should be noted that modifications are possible. Industrial applicability

By using the photoreceptor element (that is, photoconductor) of the present invention as described above, the optical switching element and the ink jet head are configured one-to-one. This eliminates the need for a drive driver having a high drive voltage with respect to the piezo element of the ink jet as in the past. A simpler configuration can be achieved using mirrors and line LEDs, which is advantageous for economy and miniaturization.

Claims

The scope of the claims

1. An optical switch characterized in that switching of charging or discharging of a capacitive object is performed by an optical switching effect by irradiating light to a photoconductor electrically connected to the capacitive object. Ji.

2. The capacitance object according to claim 1, wherein the capacitance object has a pair of electrodes, one of the electrodes is formed by the photoconductor, and the other electrode is grounded. Light switch.

3. The photoconductor has a first side connected to one electrode of the capacitance object, and a second side opposite to the first side, and the second side is formed of a transparent conductive material. The signal of an electric circuit connected to the transparent conductor is transmitted to the capacitance object by an optical switching effect of the photoconductor. Light switch.

4. One electrode of the capacitance object is a good conductor electrode, the photoconductor is joined to the good conductor electrode, and a side of the photoconductor opposite to the good conductor electrode is formed of a transparent conductor. The optical switch according to claim 2, wherein a signal of an electric circuit connected to the transparent conductor is transmitted to the capacitive object by an optical switch effect of the photoconductor. .

5. Equipped with a plurality of capacitance objects, one electrode of each capacitance object is independently connected to a separate photoconductor, and the other electrode of each capacitance object is It is connected to the other electrode of the capacitive object, and performs switching of charging or discharging of each of the capacitive objects by an optical switching effect by irradiating light to each of the corresponding photoconductors. Light multi-switch.

6. Each of the photoconductors has a first side connected to one electrode of each of the capacitance objects and a second side opposite to the first side, and the second side is connected to the second side. Each electric circuit composed of a transparent conductor and connected to the transparent conductor The optical multi-switch according to claim 5, wherein the signal is transmitted to each of the capacitance objects by an optical switching effect of each of the photoconductors.

7. One electrode of each capacitance object is a good conductor electrode, the photoconductor is joined to the good conductor electrode, and the opposite side of the photoconductor from the good conductor electrode is made of a transparent conductor. The optical multi-switch according to claim 5, wherein a signal of an electric circuit connected to the transparent conductor is transmitted to the capacitance object by an optical switch effect of the photoconductor. Tsuchi.

8. The optical switch according to any one of claims 1 to 7, wherein the capacitance object is formed of a piezoelectric body.

9. The piezoelectric body is deformed by a signal transmitted to the piezoelectric body by an optical switch effect of the photoconductor, and the deformation is taken out as a mechanical output. An optical switch according to claim 8,

10. A plurality of ink jetting mechanisms using piezoelectric bodies are arranged in parallel, one electrode of each piezoelectric body is connected to the photoconductor independently, and the other electrode of each piezoelectric body is adjacent. By connecting the other photoconductor to the other electrode of the piezoelectric body to be irradiated and selectively irradiating the plurality of photoconductors with light by a light scanning means, the corresponding piezoelectric body is deformed, and the ink is deformed. An ink jet printer using an optical switch, characterized in that the ink is ejected from an ejection mechanism.

11. The optical switch according to claim 10, wherein a laser optical system such as a laser light source, a rotating mirror or a vibrating mirror, and acoustic deflection is used as the optical scanning means. Ink jet printer device.

12. A method of selectively irradiating a plurality of photoconductors with laser light from a LED array via a self-ox lens. Item 11. An ink jet printer using the optical switch according to Item 11.

13. The optical switch according to claim 10, wherein the one electrode of each piezoelectric body is connected to a common ground switch connected to the ground via an individual diode. Ink jet printer using o

1 4. By connecting a photosensitive layer to the piezoelectric element of an image forming apparatus including an ink supply path, an ink pressure chamber, an ink nozzle, and a piezoelectric element, and irradiating the photosensitive layer with light according to an image pattern. An ink jet printer using an optical switch, wherein the piezoelectric element is deformed and the ink is ejected from the ink nozzle by mechanical fluctuation. Wherein a switch circuit is connected between one electrode and the other electrode of the piezoelectric element, and a voltage having a polarity such that the photosensitive layer can respond to light is applied to the photosensitive eyebrows. Characteristic printer equipment o

15. When a voltage of about 0 V is applied to the piezoelectric element, the ink pressure chamber expands and absorbs ink from the ink supply path, and conversely, the piezoelectric element applies the ink to the photosensitive layer. 13. The printer device according to claim 12, wherein the ink pressure chamber is configured to contract when the applied high voltage is applied.

16. When a voltage of about 0 V is applied to the piezoelectric element, the ink pressure chamber expands, absorbs ink from the ink supply path, and conversely applies the piezoelectric element to the photosensitive layer. 13. The printer device according to claim 12, wherein the ink chamber is configured to contract when the applied high voltage is applied.