JPH02198854A - Ink-jet recorder - Google Patents

Abstract

PURPOSE:To increase the working speed of printing operation positively by incorporating a piezoelectric element into the spacer member of a head body and generating pressure oscillatory waves promoting the protrusion and return operation of an ink column at the time of the flying operation of ink by the piezoelectric element. CONSTITUTION:A spacer member 14 has a sheet-shaped ceramic group piezoelectric element 25 cut and molded in a U-shape at the pre-stage of sintering and burnt and formed, and electrodes 26, 27 evaporated onto both surfaces of the piezoelectric element 25, and one electrode 26 is brought into contact and arranged to a leading-out electrode 19 for the piezoelectric element in a first substrate 12, and the other electrode 27 is brought into contact and disposed to a positioning recessed section 28 shaped to a second substrate 13. A flexible sealing member 30 is arranged inside the spacer member 14, and the flexible sealing member 30 and the spacer member 14 are bonded by conductive adhesives. An image-signal input means 50 transmits a piezoelectric- element drive signal Dp over a piezoelectric-element drive means 54, and the piezoelectric element 25 of the spacer member 14 is driven by the piezoelectric-element drive means 54. Pressure oscillatory waves from the piezoelectric element 25 are transmitted directly to the ink in the ink chamber 14.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a so-called electrostatic attraction type inkjet recording device that causes ink to fly according to an electric field pattern based on image data. The present invention relates to an improvement of an inkjet recording device that speeds up the flying operation of ink by applying a voltage.

[Prior Art] As a conventional inkjet recording apparatus of this type, there is one disclosed in Japanese Patent Publication No. 59871/1983, for example.

As shown in FIG. 8, this head body 1 has an ink chamber 2 formed with a slit-shaped ink discharge section 2a and an ink reservoir section 2b communicating with the ink discharge section 1a. A large number of stylus electrodes 4 according to the pixel density are mounted on a flat substrate 3, which is a component of a part of the wall of the main body 1.
At the same time, a counter electrode 5 is provided at a portion facing the ink ejection section 2a, and a stylus drive voltage V corresponding to image information is applied to each of the stylus electrodes 4, while the above-mentioned Ink reservoir section 2b of head main body 1
A piezoelectric element 7 is provided on the bulging substrate 6, which is a component of the piezoelectric element 7, and a predetermined pulse signal p is applied to the piezoelectric element 7 to generate a predetermined pressure vibration wave (■) from the piezoelectric cord 7 inside the ink chamber 2. The ink (2) is applied to the ink (2) to promote the upward movement and return movement of the ink (1) in the ink ejection portion 2a, and the ink (2) corresponding to the image information is caused to fly toward the recording sheet 8 at high speed.

[Problems to be Solved by the Invention] However, in such an inkjet recording device, even if the pressure vibration wave V from the piezoelectric element 7 is simply applied to the ink chamber 2, the pressure vibration wave Discharge part 2
This resulted in a situation where the ink was not sufficiently transmitted to part 1 of the ink inside a, and the printing repetition frequency could not be set sufficiently high.

In order to solve the above-mentioned problems, the present inventors devised a configuration of the head main body in order to reliably transmit pressure vibration waves to the ink in the ink chamber, and came up with the present invention.

"Means for Solving the Problems" That is, the present invention has a head main body in which a slit-shaped ink chamber is formed, and stylus electrodes are arranged for each pixel density in a part of the ink ejection part of the ink chamber. A drive for selectively applying a control voltage according to image information between the recording head, a counter electrode disposed at a portion facing the ink ejection opening of the recording head, and the counter electrode and each of the stylus electrodes. The head main body includes a pair of substrates facing each other, and a spacer member interposed between the pair of substrates, the spacer member being entirely or partially composed of a piezoelectric element. The piezoelectric element is driven by a piezoelectric element driving means in order to generate a pressure vibration wave that promotes the upward movement and return movement of the ink column during the ink flying operation.

In such technical means, the recording head is
As long as a spacer member is interposed between a pair of substrates, it is not necessarily limited to those using a pair of flat substrates, but includes a wide range of devices such as those in which an ink reservoir is formed protruding from a part of the substrate. Furthermore, when the arrangement density of stylus electrodes is made finer in order to increase pixel density, ink is drawn from adjacent bit areas during the growth of the ink column, making it difficult to apply control signals to adjacent stylus electrodes simultaneously. In such a case, it is preferable to perform block division driving so as not to apply control signals to adjacent stylus electrodes at the same time. Furthermore, the width of the stylus electrode is preferably larger considering the selectivity of ink flight, but there must be some margin for leakage between adjacent stylus electrodes, and if the ink has low resistance There is naturally an upper limit to the flow rate from the viewpoint of not allowing a flow exceeding the drive N current value of the high voltage driver to flow, and from the viewpoint of suppressing power consumption.

Further, as the piezoelectric element constituting all or a part of the spacer member, various ceramics can be selected as long as it is piezoelectric and can be processed into a sheet shape.
Furthermore, the specific structure thereof may be either a single layer type or a laminated type. In addition, when a piezoelectric element is provided in a part of the spacer member, it is preferable to arrange a piezoelectric element or a plurality of piezoelectric elements so that pressure vibration waves are uniformly transmitted to the slit-shaped ink chamber. By installing an element, pressure vibration waves are efficiently transmitted to the ink inside the ink ejecting part 3! It is preferable to design it so that Furthermore, if the piezoelectric element of the spacer member is deteriorated by the ink, Design 1 is designed to cover the inner surface of the spacer member interposed between the pair of substrates with a flexible seal member. is preferred.

Furthermore, the counter electrode may be appropriately selected from roll-shaped, flat-plate, etc. as long as it can form an electrostatic field with the stylus electrode, but the counter electrode may also be used as a recording sheet conveyance member. It is preferable to design it so as to reduce the number of parts.

[Operation] According to the above-mentioned technical means, all or a part of the spacer member facing the slit-shaped ink chamber is made of a piezoelectric element, so that the piezoelectric element driving means drives the piezoelectric element at a predetermined timing. When driven, the pressure vibration waves from the piezoelectric element are directly transmitted to the ink in the ink chamber, thereby reliably promoting the upward movement and return movement of the ink column during the ink flying operation.

[Embodiments] Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.

FIG. 1 is a schematic explanatory diagram showing an embodiment of an inkjet recording apparatus to which the present invention is applied.

In the same figure, reference numeral 10 denotes a so-called electrostatic attraction type recording head, and a head body 11 of this recording head 10 is constructed of a flat first substrate made of an insulating material such as glass, as shown in FIG. 12, a metal flat second substrate 13 disposed opposite to the first substrate 12, and a U-shaped spacer member 14 interposed between both substrates 12 and 13. A slit-shaped ink chamber 15 with a gear roughness of about 50 μm is formed in 13Fl.

The first substrate 12 is provided with a large number of stylus electrodes 1 for each pixel density (8 dots/its in this embodiment).
6 (in this example, Ti
A high voltage driver 17 made of a polysilicon high breakdown voltage thin film transistor array is formed on the base side of the stylus electrode 16 by an H film process.

This high voltage driver 17 connects each of the stylus electrodes to +4
00 (V) and 0 (V) in a complementary manner, the high-voltage driver 17 and other circuits (not shown) are attached, and the stylus drive timing control means 51 (described later) is used as a whole. (see Figure 1). Note that reference numeral 018 is an extraction electrode of the high voltage driver 17 formed simultaneously with the stylus electrode 16 by a thin film process.

On the other hand, piezoelectric element extraction electrodes 19 are simultaneously formed on both sides of the first substrate 12 in the longitudinal direction by an R film process, and furthermore, an ink ejector for holding ejecting ink is formed on the inner surface of the first substrate 12. For example, a protective layer 20 (second protective layer 20) is formed by sputtering photosensitive polyimide or silicon dioxide so that only the area corresponding to the area, for example, the tip 200 μTrL of the stylus electrode 16 and the contact with the spacer member 14 of the piezoelectric element extraction electrode 19 are exposed. (not shown with virtual lines in the figure)
is provided.

Further, the second substrate 13 is made by attaching a plurality of ink supply tubes 21, each of which has a surface that contacts the spacer member 14 and an end of the ink discharge portion formed by polishing or the like. The ink supply tube 21 is arranged in a positional relationship such that it supplies ink approximately evenly to the effective printing width of the recording head 10, and also quickly resupplies ink when ink is consumed unevenly due to an uneven printing pattern. will be placed. The other end of the ink supply pipe 21 is connected to an ink reservoir (not shown), and the air pressure within the ink reservoir is adjusted and maintained at a predetermined pressure.

Furthermore, as shown in FIG. 3, the spacer member 14 is
A sheet-like ceramic piezoelectric element 25 which is cut into a U-shape as shown in FIG.
．． 27, the one electrode 26 is arranged in contact with the piezoelectric element extraction electrode 19 of the first substrate 12, and the other electrode 27 is arranged in a positioning recess 28 (spacer) formed in the second substrate 13. (formed in a shape corresponding to the member 14 and a flexible seal member 30 to be described later). A flexible seal member 30 is arranged inside the spacer member 14, and the flexible seal member 30 and the spacer member 14 are bonded together with a conductive adhesive (not shown).

The ink used in this example is an oil-based conductive ink with a Gat ratio of 10-7/Ω and a viscosity of 18 mP.
a5ec, surface tension 30 dyne/ffi.

Further, in FIG. 1, reference numeral 40 denotes a roll-shaped counter electrode disposed opposite to the ink ejection opening of the recording head 10 at a distance of about 300 μm.

Furthermore, in FIG. 1, reference numeral 50 denotes image signal input means 5 for inputting an image signal G sent from an external host.
1 is a stylus drive timing control means for selectively applying a stylus drive voltage to each stylus electrode 16 of the recording head 10 based on a stylus drive signal DS corresponding to the image signal G sent from the image signal input means 50;
2 is a counter electrode drive signal @Dr from the image signal input means 50
A counter electrode driving means 53 applies a predetermined drive voltage (-3 (V) in this embodiment) to the counter electrode 40 based on the voltage applied to the recording head 10 and the counter electrode 40 based on the voltage (see FIG. 4). A high-voltage power supply 54, which is a drive voltage supply source, applies a predetermined voltage to the piezoelectric element 25, which is a component of the spacer member 14, based on a piezoelectric element drive signal Do (see FIG. 4) from an image signal input means. This is piezoelectric element driving means.

In this embodiment, in order to prevent printing defects due to ink drawing when adjacent bits are printed simultaneously, various drive signals Dr, D (l is -line) including the stylus drive signal @DS are used. Block division driving is performed in which the bits are output multiple times during the printing cycle and divided into blocks as appropriate so that adjacent bits are not printed at the same time.

Next, the operation of the inkjet recording apparatus according to this embodiment will be explained.

Now, it is assumed that the bit of interest of the recording head 10 is set to the printing state in an arbitrary printing cycle, and the bit of interest of the recording head 10 is set to the non-printing state in the next printing cycle.

At this time, first of all, paying attention to the case where the bit of interest is set to the printing state, as shown in FIG. The piezoelectric element 25 of the spacer member 14 is driven by the piezoelectric element driving means 54 . In this state, the piezoelectric element 25 returns to its original state after being displaced by a predetermined amount (see FIG. 4), but the pressure vibration waves from the piezoelectric element 25 are directly transmitted to the ink in the ink chamber 14.

On the other hand, since there is a time interval T1 until the displacement of the pressure v11 cable 25 ends, in other words, the displacement d of the piezoelectric element 25 reaches a steady state, the image signal input means 50 After waiting for the time delay T1, the stylus drive signal Ds is sent to the stylus drive timing control means 51, and the counter electrode drive means 5
2, the counter electrode drive signal [)r is sent out.

At this stage, the stylus drive voltage (+400 in this embodiment) is applied to the stylus electrode 16 corresponding to the bit of interest.
(V)) is applied to the counter electrode 40, and a counter electrode driving voltage (-3 (V) in this embodiment) is applied to the counter electrode 40, and the voltage between the stylus electrode 16 and the counter electrode 40 corresponding to the bit of interest is applied. As shown in FIG. 5(a), a D electric field S is generated based on the image quotient difference, and the electrostatic attraction force due to this electrostatic field S acts on the ink portion (2) corresponding to the bit of interest.

Then, the ink portion I is the same as the static 1! The ink column 111 rises based on the attractive force and is conveyed to the front side of the counter electrode 40 and comes into contact with the recording sheet 41 side. This darkness,
Since the piezoelectric element 25 is displaced by a displacement lad (see FIG. 4), the pressure vibration waves from the piezoelectric element 25 are efficiently transmitted to the ink portion (I), and the ink portion I Since the pump pressure P and the pressure increase ΔP1 of the pressure sensing wave act on the ink column IH, the growth of the ink column IH is promoted.

Thereafter, when the application of the stylus driving voltage and the counter electrode driving voltage is stopped, the electrostatic field S disappears and the ink column IH becomes thinner due to its surface tension, as shown in FIG. 5 (1)). Initially, the ink column IH has the most constricted part as a boundary, and the ink on the side of the recording sheet 41 from the constriction is absorbed toward the recording sheet 41 side, and the ink from the constriction is absorbed into the recording head 1.
The ink on the 0 side is ink chamber 15#! Return to l. At this time, the piezoelectric cord 25 returns to the initial position from the displacement jid (see FIG. 4) during a predetermined time ffflT2 after the piezoelectric element drive signal @Dp is turned off. As the displacement m changes, the pressure of the pressure vibration wave from the piezoelectric element 25 decreases by ΔP2, and the ink that tries to return to the ink chamber 15 side
A pressure of P2 acts. For this reason, the raised ink column 1
11 returns to the ink chamber 15 side faster by the negative pressure of ΔP2.

Therefore, in such an operation process, the rising and returning speeds of the ink column IH become faster due to the influence of the pressure vibration waves of the piezoelectric element 25, and it becomes possible to realize high-speed printing accordingly.

In order to confirm such an operation process, we used the one shown in Fig. 8 as a comparative example, and generated a pressure vibration wave of a predetermined excitation frequency from the piezoelectric elements of the example and comparative example, and generated pressure vibration waves at the ink ejection port. When the amplitude of the ink meniscus was investigated, the results shown in FIG. 6 were obtained.

According to this, in the comparative example, even if a pressure vibration wave of approximately 100 Hz is generated, the mass of the flowing ink is large, and the bending of the ink container and slit section is affected, so that the ink discharge section cannot be reached. Although the pressure oscillation waves are not sufficiently transmitted, it is understood that in the example, even if a pressure oscillation wave of about 10,000 H2 is generated, the pressure oscillation waves are efficiently transmitted to the ink ejection section. still,
In the comparative example, it is possible to improve the transmission characteristics of pressure vibration waves by making the container of the ink reservoir smaller and increasing the rigidity of the ink container and the slit part, but in any case, it is possible to improve the transmission characteristics of pressure vibration waves. It is greatly limited compared to .

Further, in the above embodiment, when the upper limit of the printing repetition frequency at which the printing condition is good was investigated for each amplitude of the piezoelectric element 25, the results shown in FIG. 7 were obtained.

According to this, it is understood that the printing condition is good if the inkjet recording apparatus is operated within the area range A in FIG. At this time, it was confirmed that if the amplitude of the piezoelectric element 25 was set to about 0.8 μTrL, the printing repetition frequency could be increased to about 150 Hz. This is approximately twice the printing speed compared to the case where the piezoelectric element 25 is not driven, and the printing speed is approximately twice that of the case where the piezoelectric element 25 is not driven.
It is faster than . In FIG. 7, B indicates an area where printing blur occurs, C indicates an area where ink flows out, and D indicates an area where ink flows out before printing.

On the other hand, when focusing on the case where the bit of interest is set to the non-printing state, the image signal input means 50 first receives the piezoelectric element drive signal as shown in FIG.

(pulse width T) is sent to the piezoelectric element driving means 54, and the piezoelectric element 25 of the spacer member 14 is driven by the piezoelectric element driving means 54, but after waiting for a time delay T1, the counter electrode driving means 52 drives the piezoelectric element 25 of the spacer member 14. The counter electrode drive signal Qr is sent out only to this point.

At this time, the stylus is moved to the stylus electrode 16 corresponding to the bit of interest! lIJ voltage (+400 in this example)
V)) is not applied, an electrostatic field weaker than the electrostatic field S necessary for ink to fly is formed between the counter electrode 40 and the stylus electrode 16 corresponding to the bit of interest, and the corresponding The ink portion of the bit of interest is not raised toward the recording sheet 41 due to electrostatic attraction, and the bit of interest is not printed.

[Effects of the Invention] As explained above, according to the inkjet recording apparatus according to the present invention, a piezoelectric element is incorporated into all or a part of the spacer member of the head main body in which the slid-shaped ink chamber is formed, and the piezoelectric element Since a pressure vibration wave is generated that promotes the uplift and return movement of the ink column during the ink flying operation, it is possible to directly vibrate the ink in the ink chamber, and the ink column increases accordingly. It is possible to reliably promote the upheaval and return operations of the printer, and it is possible to reliably realize high-speed printing operations.

In particular, according to the inkjet recording apparatus according to the second aspect, since the flexible sealing member is interposed between the ink and the piezoelectric element of the spacer member, it is possible to avoid a situation where the ink comes into direct contact with the piezoelectric element. Deterioration of the piezoelectric element due to ink can be effectively prevented.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an embodiment of an inkjet recording apparatus according to the present invention, FIG. 2 is an exploded perspective view showing the configuration of a recording head according to the embodiment, and FIG. 3 is a diagram showing ■-■ in FIG. 2. 4 is a sectional view corresponding to a line, FIG. 4 is a timing chart showing the operating state of the inkjet recording apparatus according to the embodiment, and FIG.
Figures (a) and (b) are schematic diagrams showing the operating state of the inkjet recording device according to the example, and Fig. 6 is the relationship between the excitation frequency of the piezoelectric element and the ink meniscus of the inkjet recording device according to the example. FIG. 7 is a graph showing the relationship between the amplitude of the piezoelectric element and the printing repetition frequency of the inkjet recording device according to the embodiment, and FIG. 8 is an explanatory diagram showing an example of the conventional inkjet recording device. . [Explanation of symbols] 10... Recording head 11... Head body 12.13... Substrate 14... Spacer member 15... Ink chamber 16... Stylus electrode 25... Piezoelectric element 30. ...Flexible seal member 40...Counter electrode 50...Image signal input means (drive control means) 51...
- Stylus drive timing control means (drive control means) 52... Counter electrode drive means (drive control means) 53...
・High voltage electric m (drive control means) 54...Piezoelectric element drive means

Claims (1)

[Scope of Claims] 1) It has a head main body (11) in which a slit-shaped ink chamber (15) is formed, and a stylus electrode (16 ) is arranged, and this recording head (10)
A counter electrode (
40), and drive control means (50, 51, 52, 53) for selectively applying a control voltage according to image information between the counter electrode (40) and each of the stylus electrodes (16). In the inkjet recording apparatus, the head main body (11) includes a pair of substrates (12, 1) facing each other.
3) and a spacer member (14), which is entirely or partially composed of a piezoelectric element (25) and is interposed between the pair of substrates (12, 13), and the spacer member (14) is provided with a spacer member (14) that is entirely or partially composed of a piezoelectric element (25), and the spacer member (14) is provided with The piezoelectric element (25) is driven by the piezoelectric element driving means (54) in order to generate a pressure vibration wave that promotes the return movement.
). 2) The device according to claim 1, wherein the pair of substrates (1
2, 13) An inkjet recording apparatus characterized in that the inner surface of a spacer member (14) interposed between 2 and 13) is closed with a flexible seal member (30).