JPH035992B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a droplet forming device used in a recording device or the like, and particularly to a droplet forming device that ejects liquid as small droplets from an orifice of a liquid chamber containing the liquid to form a droplet on a recording material. The present invention relates to a droplet forming device that performs recording etc. by adhering to a droplet.

[Conventional technology]

Various devices of this type have been proposed and various improvements have been made. For example, Utility Model Publication No. 49-16757, Special Publication No. 51-39495, Japanese Patent Publication No. 45698-1973, Japanese Patent Publication No. 110230-1970,
51-132036, JP 51-128227, JP 52-
No. 102039 etc. are known.

The present invention provides a new droplet forming device that has a completely different configuration from those devices.

[Problem that the invention seeks to solve]

The main purpose of the present invention is to solve the technical problems that the prior art could not solve in this type of device.

Another object of the present invention is to provide a droplet forming device that is compact and capable of high-density recording by devising the arrangement of the heating element and the liquid guide section.

[Means for solving problems]

The present invention, which solves the above-mentioned problems, includes a substrate on which a heating element that generates thermal energy for ejecting liquid is formed; A plurality of ink jet head blocks each having an orifice and a liquid guide portion forming a liquid chamber for supplying the liquid to the heating element portion have upper and lower area surfaces of a plate common to each of the plurality of ink jet head blocks. It is characterized by being provided in.

Still another object of the present invention is to form droplets in which a large number of heating elements can be arranged in high density by arranging heating elements, liquid guiding parts, and control elements on the upper and lower surfaces of one plate, respectively. The goal is to provide equipment.

In addition, it is a further object of the present invention to provide a device that is easy to maintain and manage.

〔Example〕

FIG. 1 is a schematic diagram showing some details of the droplet forming apparatus of the present invention. In the figure, heating elements H1 to H7 and lead electrodes 11 to 1D7 are formed on the surface of a substrate SS1. The plurality of heating elements H1 to H7 have the same area and the same resistance value. Board SS
1 is covered with a liquid guide portion, such as a plate GL1 having grooves M1 to M7, and forms a plurality of liquid chambers and orifices at the joint with the substrate SS1. The blade GL1 is provided with an ink supply chamber ND that supplies, for example, recording ink to a plurality of liquid chambers, and is also provided with an inlet IS that introduces ink from an ink tank (not shown).

FIG. 2 is a diagram in which the heating elements and orifices of FIG. 1 are increased in number (for example, 32), and a cassette-type ink jet head block for recording is formed. DA1 in the figure is a diode array containing a large number of diodes to prevent wraparound, and OP1
is an ink supply pipe that is detachable from the blade GL1, and when this is removed, the entire board SS1 will be removed from the main body.

FIG. 3 is a sectional view showing an example of a connection configuration between the ink supply pipe OP1 and the ink introduction port IS. Packing FH into the inlet IS drilled in Plaid GL1
has been inserted and is undergoing O-ring OR. O-ring OR is held by flange FG. flange
FG is inserted into ink supply pipe OP1,
The ink supply pipe CP1 is equipped with a spring SP1 that presses the packing FH and the flange FG to prevent ink leakage.

This diagram shows the ink supply pipe for cassette printing.
This shows an example of how to smoothly attach and detach OP1, and the ink supply pipe OP1 due to the cassette
Although the connection method is not limited, it is desirable to connect the ink supply pipe OP1 using a pressure bonding means as shown in this figure. FL is a filter. Furthermore, if the pipe FP1 is made flexible, it can be easily bent during attachment and detachment, so attachment and detachment operations can be performed without any trouble.

FIG. 4 is a perspective view showing one embodiment of the present invention, in which the aforementioned cassette type ink jet head blocks are fully assembled and arranged alternately above and below one common support plate. In the figure, odd-numbered blocks JB1,
JB3,...JBn, even numbered blocks JB2,
Join JB4,...JBn. Ink IK is supplied to each block by an ink tank IT, an ink pipe IP, core block common distribution pipes OP and EP, and block distribution pipes OP1 to OPn. Pipe OP1~ connected to each block
As shown in the example of FIG. 7, OPn can be attached to and detached from each plate and has flexibility, so OP1 to OPn can be conveniently bent when attached or detached.

DA1 to DAn are diode arrays that are the same as those shown in FIG. 2, and are connected to respective lead electrode groups on the heating element-attached substrates SS1 to SSn by solder. Due to this mutually shifted arrangement, the interval Q between the orifices OF1 and OF2 becomes the same on the upper and lower sides as shown in FIG. 5, and it is possible to ensure an equal orifice interval Q in all the full-multi lines.

In the above configuration, when a defective chip occurs while recording on the recording paper PP, the recording paper PP
Dots are missing in the corresponding areas above. When this is discovered, since the chips are distributed, it is easy to find the defective chip and replace it with a soldering iron.

FIG. 6 is a wiring diagram for time-division driving in the devices shown in FIGS. 4 and 5. FIG. Heating elements 1H1 to 1H3 as shown in the diagram
2 form one block, and there are a total of 1792 heating elements 1H1 to 56H32 in 56 blocks, and each heating element is connected to a control element such as a diode 1.
Total of 56 chips with d1 to 1d32 as 1 chip
It is connected to 1792 diodes 1d1 to 56d32. Each diode has wiring 1P1~56
It is connected to image information input terminals P1 to P32 through P32.

The other end of the heating element, 1H1 to 1H32, is the wiring 1D1 to
1D32 is connected to the chip selection signal input terminal D1. Heating elements 2D1 to 2D32...56
D1-56D32 are similarly connected to chip selection signal input terminals D2-D56, respectively. Heating elements 1H1 to 1H are mounted on the aforementioned substrate SS1 with heating elements.
32, diodes 1d1 to 1d32 and a group of lead electrodes are wired. Another cassette is similarly provided with a heating element, a diode, and a group of lead electrodes.

Terminals D1 to D56 and P1 to P32 are connected to a time division drive circuit (not shown) via a flexible printed board. In the case of the above configuration, each block is time-divisionally driven with a duty of 1/56, for example, to generate heat in each liquid chamber and cause the droplets to fly. Although it is possible to use multilayer wiring to satisfy the above wiring requirements, in any case, connectors are provided to connect the cassettes.

7 and 8 are schematic diagrams of a copying machine or facsimile recording device to which the above-mentioned full multi-ink jet head and time-division drive system are applied. It has a reading section RD for reading. As shown in Fig. 7, a document platen PG made of glass or the like is formed on the top of the reading section RD.
A document is placed on this document table PG. A document table cover PK for fixing the document is provided on the top of the document table PG.

At the bottom of the document platen PG, there is a rod-shaped light source BL that illuminates the document, and the light emitted from the light source BL is effectively illuminated by the document platen.
A reflector RM installed to illuminate the PG, and a self-scanning photodetector with multiple photodetectors arranged in a straight line.
An optical unit LS including a CS and an optical lens for forming an image of the original onto the light receiver CS is provided integrally with the light receiver CS. This optical unit LS and light receiver CS are fixed to a carriage CA. carriage
CA is driven in the Q direction or returns to the opposite direction by a screw G rotated by the motor MO on the guide rails R1 and R2. It is also assumed that the main scanning direction of the self-scanning light receiver CS sequentially scans the document surface in the P direction. Therefore the carriage
By moving CA (sub-scanning direction Q), the information of the original placed on the document platen PG is sequentially imaged onto the light receiver CS, and if the light-receiving elements are sequentially read out (main scanning), the information of the document placed on the document table PG is imaged from the light receiver CS. It is possible to obtain sequential signals obtained by raster scanning the original.

In this embodiment, the document table PG is fixed and the carriage CA is movable, but a structure in which the carriage CA is fixed and the document table PG is movable may be used. When performing copy recording, the carriage CA moves in the Q direction and raster-scans the information on the document table in the P direction. At this time, the recording paper PP in the recording section records in the R direction while moving in the S direction in FIG. 4, for example, at a speed equal to the moving speed of the carriage CA in the Q direction.

The image information obtained by the reading section RD is sent via a buffer memory to the inkjet head of the recording section shown in FIG. 4, and recording is performed in parallel with reading.
For example, page information that has been read once may be stored in a memory and then recorded again.

The self-scanning photoreceiver CS consists of a number of photodetectors that convert optical input into electrical signals, and can process these signals in time series. Examples include CCD image sensors, MOS image sensors, and the like. In this copying/recording device, the width of the document table in the P direction is 216 mm (almost equal to the width direction of A4 paper), and a 1728-bit light receiver is used.
Consider the case of using a CCD linear image sensor. Assuming that the output ink jet head is a full-line multi-head with 1792 nozzles and a width of 224 mm for signal processing reasons, the image sensor and ink jet head can obtain a resolution of 8 images/mm.

Now, the 28 block nozzle arrays above the heat sink plate are the odd number group, and the 28 block nozzle arrays below are the even number group, and the vertical orifice gap between the odd and even groups is 8 mm.
64 lines. As mentioned above, the CCD sensor CS is a 1728-bit line sensor that scans each scanning line and outputs a voltage level according to image information. This voltage level is converted into a binary value by a digitizing circuit AD shown in FIG. 8 when the level is black and white, and multivalued by an analog-to-digital converter or the like when gradation (halftone) is required.

For the sake of simplicity, considering binarization, the digitization circuit AD consists of a comparator that compares the output voltage of the CCD sensor CS with the reference voltage (slice level). Outputs a value signal. This digitized data is stored in a 32-bit shift register SR.
The data is input serially to the computer, converted to parallel data, and output, and then processed in 32-bit units. The data output in parallel by the shift register SR is once held in the 32-bit latch circuit L1 and then transferred to the memory section. The memory section is memory M1 and memory M2.
The memory M1 consists of an odd block group JB1,
The memory M2 stores the data of the even block groups JB2, JB4, . . . . The data held by latch circuit LA1 is alternately written into memories M1 and M2 every 32 bits. Memories M1 and M2 are, for example, RAMs (random access memories), and their storage capacity is 32 bits for memory M1 and 56K bits for memory M2. One word of memory consists of 32 bits, so memory M1 has one word and memory M2 has one word.
consists of 1792 words. Also, memory M
The outputs of 1 and M2 are the enable signal lines L4 and L5.
When is at a high level, it is assumed to be in a high impedance state, a so-called three-state state.

Data selectively read from memories M1 and M2 is once held in a 32-bit latch circuit LA2. At this time, the states of memory M1 and memory M2 are as follows:
When one of the latch circuits is in the write state, the other is in the read state, and when one of the latch circuits LA1, LA2 is holding data in memory M1, the other is holding data in memory M2.

Therefore, the data in the memory M1 and the data in the memory M2 are alternately held in the ripple circuit LA2.
The data held in the latch circuit LA2 is output to 32 NAND gates NG1 to NG32, but the NAND gates NG1 to NG32 are controlled by the transistor TP1 depending on the timing PG of the print command signal line L10 from the control circuit CC and the contents of the latch circuit LA2.
- Selectively operate TP32. transistor
The collector terminals of TP1 to TP32 are connected to image information input terminals P1 to P32 of the inkjet head driving matrix IJM.

The 56 block selection signal input terminals D1 to D56 of the inkjet matrix IJM are connected to the collectors of the transistors TD1 to TD56.
Transistors TD1 to TD56 are decode circuit DC
is sequentially scanned by the output of . decoding circuit
DC is a 6-line to 56-line decoder and is controlled by six signal lines L11 from the control circuit CC. The control circuit CC is a circuit that generates signals for controlling each of the above elements, and the reference clock is made of a crystal oscillator.

FIG. 9 is a schematic partial cross-sectional view of another example of an ink jet head. tapered metal plate
Substrates S1 and S2 with heating elements are bonded on HS, and S
1 and S2 are joined to grooved plates G1 and G2, and liquid chambers W1 and W2 are formed on both sides of the metal plate HS.

The ejection direction of the recording droplets ejected from the orifice O1 of one liquid chamber W1 is I1, and the ejection direction of the recording liquid droplets ejected from the orifice O2 of the other liquid chamber W2 is I2, and the ejection direction of the recording liquid droplets ejected from the orifice O2 of the other liquid chamber W2 is I2. the same line of
Head over the DP.

FIG. 10 shows another example of the structure of the substrate with a heating element, which can be manufactured simply and at low cost, and further improves the packaging density. That is, the selection electrodes P1 to P6 and the like are arranged as shown in the figure above the heating element resistance layer H to form the heating parts 1H2, 3H2, 3H4, 5H4, and 5H6. For example, to select 1H2, P1, P
It is only necessary to selectively apply a driving pulse to 2. P5
If you select P4, 5H4 will generate heat. It is easy to configure the selection circuit in this way. This configuration eliminates the need to etch the H layer, making it extremely simple. Of course, a predetermined portion may be etched if necessary.

11, 12, and 13 are diagrams for explaining an example of the principle of droplet formation that can be used in the apparatus of the present invention.

As shown in FIG. 11, the recording liquid IK is supplied from the direction P into a droplet wall W whose tip is formed into a nozzle and constitutes a droplet ejection head. Now, in a portion of width Δl in the liquid chamber W1 at a distance of l from the orifice OF,
When an electric pulse is applied to the heating element H1, the heating element H1 starts to increase in temperature. When the heating element H1 reaches a temperature higher than the vaporization temperature of the recording liquid in the chamber W1, bubbles B are generated on the heating element H1. Bubbles B are heating elements H1
grows and rapidly increases its volume as the temperature rises. As a result, the pressure in the liquid chamber W1 increases rapidly, and the recording liquid existing in Δl by the volume increased by the bubble B rapidly moves in the direction of the orifice OF and in the opposite direction. A portion of the recording liquid existing in the portion l in the liquid chamber W is discharged from the orifice OF. The ejected recording liquid becomes a liquid column and is connected to the orifice OF, and the liquid column that comes out of the orifice OF stops growing when the bubble B reaches its maximum, but the tip of the liquid column has not been fed until this point. kinetic energy is stored. In addition, when the bubble B collides with the ceiling surface of the Δl portion of the liquid chamber W1, the direction of the force is changed to the longitudinal direction of the orifice side.
Its driving force will be further increased.

Next, by cutting off the electric pulse applied to the heating element H1, the temperature of the heating element H1 gradually decreases. Due to the temperature drop, bubble B begins to shrink in volume a little later than when the electric pulse ends. As the volume of the bubble B shrinks, recording liquid is supplied to the Δl portion from the orifice OF side and from the P direction. As a result, the recording liquid in the portion of the liquid column grown from the orifice OF near the orifice OF is drawn back into the chamber W1. As a result, the kinetic energy at the tip of the liquid column and the orifice
The direction of the kinetic energy of the liquid column near OF is reversed, and the tip of the liquid column separates and becomes a recording droplet ID, which flies toward the recording member PP and attaches to a predetermined position on the recording member PP. do. Bubbles B on heating element H1
When the liquid disappears, the recording liquid volume drawn back into the chamber W1 is smaller than the volume of the liquid chamber W1, and the orifice OF
Although the liquid level (meniscus) recedes from the surface, it completely returns to the initial state because new recording liquid is always supplied from the P direction. After the electric pulse is cut, bubble B gradually contracts due to gradual heat dissipation.
The meniscus gradually returns to its original state. Therefore, destruction of the meniscus and excessive retreat can be prevented, and the next discharge can be performed promptly.

The size of the droplet ID discharged from the orifice OF is determined by the amount of thermal energy applied, the width of the portion Δl that is affected by thermal energy, the inner diameter d of the liquid chamber W, the distance l from the orifice OF to the heating element H1, and the liquid IK.
equipment conditions, such as the pressure applied to the
It depends on the physical properties of the material such as IK's specific heat, thermal conductivity, coefficient of thermal expansion, and viscosity.

FIG. 12 t0 to t9 are schematic diagrams showing the ejection process of recording liquid (hereinafter referred to as ink).
OF, the ink chamber W, and the heating element H1 are shown, and the ink
IK is supplied from arrow P. The meniscus, or the interface (liquid level) between the ink IK and the outside air, is indicated by IM.
Let B be the bubbles generated on the heating element H1.

FIG. 13A shows an example E of the driving electric pulse, and the horizontal axis t0 to t9 indicates the time corresponding to FIG. 12 t0 to t9. T in Figure 13B is the heating element H1
Fig. 13 shows a temperature change, that is, a change in a thermal signal.
Figure C is a diagram showing changes in the volume of bubbles B. At t0, the state before discharge is shown, and between t0 and t1
At tp, an electric pulse E is applied to the heating element H1. tp
As shown in , the temperature rise of the heating element H1 is released at the same time as the electric pulse E is applied. At t1, the temperature of the heating element exceeds the vaporization temperature of the ink, and bubbles B begin to form, and the liquid level IM swells in proportion to the pressure applied to the ink IK by the bubbles B from the orifice surface. There is. At t2, the liquid level IM further swells as the bubbles B grow further.
At t3, the electric pulse E falls as shown in FIG. 13A, and when the temperature of the heating element H1 reaches the maximum as shown in FIG. 13B, the liquid level IM further swells.
A liquid column begins to form. At t4, as shown in FIG. 13B, the heating element temperature T has begun to fall, but as shown in FIG. 13C, the volume of the bubble B has reached its maximum.
The liquid surface IM swells and forms a liquid column. t5
Then bubble B starts to shrink. The ink IK near the orifice OF is drawn into the ink chamber W by the amount that the bubble B contracts. As a result, the liquid level IM is constricted at the portion indicated by the arrow Q. At t6, the bubble B further shrinks and separates into the droplet ID and the liquid surface IM'. At t7, droplet ID
is discharged and flies, the bubble B further contracts, and the liquid level IM' further approaches the orifice OF surface. At t8, the bubble B is about to disappear, the liquid level IM further retreats, and it is drawn into the inner surface from the orifice OF. t
At 9, ink IK is supplied, and then at t0
Return to state. Here, as shown in FIG. 13B,
Since the fall time of the thermal signal T is longer than its fall time, this property can be used to gradually retreat the meniscus from t6 to t9 without destroying it.

From the above explanation, the shape of the electric pulse and thermal signal applied to the heating element H1 is an important factor for stable ejection of the recording liquid IK, and the contraction of air bubbles is an important factor when separating recording liquid droplets. It is easily possible to control contraction with the shape of electrical pulses. Further, the ejection speed of droplets can be similarly controlled using electric pulse shapes. Furthermore, the droplet ejection frequency can also be increased by using the electric pulse shape.

As described above, the present invention has the remarkable effect that a so-called on-demand type inkjet recording apparatus has an extremely simple structure and can easily achieve high density recording.

For example, the above-mentioned Utility Model Publication No. 16757, 1973, and JP-A-1989-1999.
No. 1102030 and the like are non-on-demand types, and the equipment is complex and large, making it extremely difficult to increase density.

Furthermore, the above-mentioned Special Publication No. 53-45698 (page 4, column 8, lines 5-7), JP-A-51-132036, JP-A-51-
No. 128227, JP-A No. 52-102039, etc., it can be configured more compactly, and heating elements are placed above and below a single plate.
The placement of the liquid guide and control elements makes it possible to arrange an extremely large number of heating elements at a high density, and since each component can be placed over a wide area, it is extremely easy to find defective parts and replace them. This has a synergistic effect.

Further, according to the droplet forming device according to the present invention, it is possible to stabilize the diameter of the ejected droplets, stabilize the ejection cycle, and increase the speed of the ejection frequency, and it is extremely simple in structure and requires no microfabrication. Because it is easy to do, the droplet forming head itself can be made much smaller than conventional ones, and because of its simple structure and ease of processing, it is extremely easy to create multiple nozzles, which are essential for high-speed ejection. can be realized. In addition, in the case of multi-nozzle design, the structure of the discharge orifice of the head can be arbitrarily designed as desired, and therefore, the head can be made into blocks and mass-produced very easily. It has remarkable characteristics.

[Brief explanation of drawings]

Figures 1 and 2 are perspective views of an example of the present invention, and Figure 3 is a perspective view of an example of the present invention.
The figure is a partially enlarged sectional view, Figure 4 is a perspective view showing the overall configuration, Figure 5 is a front view, Figure 6 is an example of the drive circuit, and Figure 7 is an information input section of a copying machine, etc. Fig. 8 is a block diagram thereof, Fig. 9 is a perspective view showing the
FIG. 10 is a further example of the present invention, FIG.
12 and 13 are diagrams for explaining an example of the principle of droplet formation. {H1-H7, 1H1-56H32}... Heating element, GL1-GLn... Liquid guide section, {1l1-56
l32, 1D1~56D32, P1~P6}...
Electrode group.

Claims (1)

[Scope of Claims] 1. A substrate on which a heating element that generates thermal energy for ejecting a liquid is formed, an orifice that is bonded to the substrate in correspondence with the heating element of the substrate and for ejecting the liquid, and A plurality of ink jet blocks each having a liquid guide portion forming a liquid chamber for supplying the liquid to the heating element portion are provided on upper and lower surfaces of a support plate common to each of the plurality of ink jet head blocks. A droplet forming device characterized by: 2. The droplet forming device according to claim 1, wherein the plurality of ink jet head blocks are arranged alternately in the upper and lower regions of a common plate. 3. The droplet forming device according to claim 1, wherein control elements corresponding to each of the heating elements are arranged above and below the support plate, respectively. 4. The droplet forming apparatus according to claim 3, wherein a pixel information input section for selectively causing the heating element to generate heat is connected to the control element.