JPH0375037B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a recording device, and more specifically, to a recording device that ejects recording liquid as small droplets from an orifice of a liquid chamber containing recording liquid and adheres to a recording material. The present invention relates to an inkjet recording method applied to an inkjet recording apparatus that performs recording.

[Prior Art] Many methods have been proposed for this inkjet recording apparatus, and various improvements have been made. For example, Utility Model Publication No. 49-16757,
JP 51-39495, JP 53-45698, JP 50-110230, JP 51-132036
No. 128227, Japanese Patent Application Laid-Open No. 1982-128227,
Publication No. 102039 is known.

[Technical Issues] However, in the conventional recording method, although the cause is unknown, the diameter of the ejected droplets becomes unstable in unique cases, and the ejection cycle and print quality are deteriorated. This has caused print defects and made high-speed recording unstable in high-density multi-nozzle configuration, which is an advantage for inkjet recording.

[Objective of the Invention] The present invention solves technical problems in inkjet recording that could not be solved by conventional techniques, and provides a novel inkjet recording method that is completely different in principle and concept from conventional methods. It is something.

The main object of the present invention is to provide an inkjet recording method that enables recording of gradation images without stabilizing the diameter of ejected droplets or impairing the recording speed.

More specifically, an object of the present invention is to provide an improved inkjet recording method that is well suited to high-speed recording and does not cause print defects or deterioration in print quality.

Another object of the present invention is to provide an inkjet recording method that can maintain a stable ejection state of recording droplets over a long period of time without requiring a complicated configuration.

[Summary of the invention] The present invention achieves the above main objectives,
Generates thermal energy in a heating element for recording, and causes a sudden change in state of ink in an ink ejection section corresponding to the heating element for recording, thereby converting an electric drive signal into a recording signal to cause ink to be ejected from the ink ejection section. In the ink jet recording method, an electric signal for preheating the recording heating element is supplied to the recording heating element according to the timing of supplying the electric drive signal to the recording heating element. - An inkjet recording method characterized by having signal supply timing to supply the recording heating element in the order of the electric drive signal.

According to the present invention, the signal supply timing for providing the preliminary heating electric signal is provided in the inkjet recording method for supplying the electric drive signal for ejecting the ink to the recording heating element in accordance with the recording signal, thereby preventing overheating. The inconvenience caused by the ink is solved, and the state of the recording heating element driven by the electric drive signal can be instantly adjusted to the desired state at the required time, which stabilizes the diameter of the ejected droplets or improves the recording speed. It is possible to record a gradation image without impairing the image quality. In any case, according to the recording method according to the present invention, the diameter of the ejected droplet can be stabilized, and high-speed recording is possible. In addition, since it does not require a complicated structure, the recording head itself can be made much smaller than conventional ones, and its structural simplicity and ease of processing make it suitable for high-speed recording. The essential multi-nozzle configuration can be realized extremely easily. Furthermore, in multi-nozzle configuration, the structure of the ejection orifice of the recording head can be arbitrarily designed as desired, and therefore it is extremely easy to form recording heads into blocks and mass-produce them. , etc. have remarkable characteristics. Furthermore, gradation images can be easily recorded without reducing the recording speed.

[Example] The present invention will be specifically explained in detail below with reference to the drawings.

FIG. 1 is a diagram for explaining an embodiment of the basic recording principle of the inkjet recording method of the present invention.

A recording liquid IK is supplied from the P direction into a recording liquid chamber wall W whose tip forming a recording head is formed into a nozzle. Now, in a portion of width Δl in the liquid chamber W1 at a distance l from the orifice OF, the heating element H1
When an electric pulse is applied to the heating element H1, the temperature starts to rise. 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. The bubbles B grow as the temperature of the heating element H1 rises, and their volume increases rapidly.
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 discharged recording liquid becomes a liquid column and passes through the orifice OF.
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 accumulated the kinetic energy that has been applied up to this point. Furthermore, when the bubble B collides with the ceiling surface of the Δl portion of the liquid chamber W1, the force changes its direction in the longitudinal direction toward the orifice, and its propulsive force is 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 is delayed slightly from the point at which the electric pulse ends, and its volume begins to shrink. bubble B
As the volume shrinks, recording liquid is replenished into the Δl portion from the orifice OF side and the P direction. As a result, the orifice OF of the liquid column grown from the orifice OF
The recording liquid near the area is drawn back to 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 volume of the recording liquid drawn back into the chamber W1 is smaller than the volume of the liquid chamber W1, and the orifice
This causes the liquid level (meniscus) to retreat from the OF surface, but
Since new recording liquid is always supplied from the P direction, the initial state is completely returned. After the electric pulse is cut off, the bubble B gradually contracts due to gradual heat dissipation, and 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 quickly.

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 the thermal energy, the inner diameter d of the liquid chamber W,
It depends on the distance l from the orifice OF to the heating element H1, the equipment conditions such as the pressure applied to the liquid IK, or the physical properties of the material such as the specific heat, thermal conductivity, coefficient of thermal expansion, and viscosity of the liquid IK. Furthermore, even if the laser beam LZP is instantaneously irradiated instead of the heating element described above, the bubble B is generated and disappears in the same way, and a single droplet is discharged. In this case, H1 in the Δl portion can be used for other purposes such as a reflection plate or a heat storage plate to make heat generation by the laser pulse LZP more efficient, but is not necessarily required.

FIG. 2 t0 to t9 are schematic diagrams showing the ejection process of recording liquid (hereinafter referred to as ink).
OF, ink chamber W and heating element H1 are shown and ink IK
is supplied from arrow P. meniscus or ink
The interface (liquid level) between IK and outside air is indicated by IM. Let B be the bubbles generated on the heating element H1.

FIG. 3A is an example of a driving electric pulse E,
The horizontal axis t0 to t9 indicates time corresponding to t0 to t9 in FIG. 2. T in FIG. 3B is a diagram showing the temperature change of the heating element H1, that is, a change in the thermal signal, and FIG. 3C is a diagram showing the volume change of the bubble B. At t0, a state before ejection is shown, and at tp between t0 and t1, an electric pulse E is applied to the heating element H1. As shown at tp, the temperature of the heating element H1 starts to rise at the same time as the electric pulse E is applied. t1 is a state in which the temperature of the heating element exceeds the vaporization temperature of the ink,
Bubbles B begin to form and the liquid level IM expands in proportion to the pressure applied to the ink IK by the bubbles B from the orifice surface. At t2, the bubble B grows further and the liquid level IM further swells. At t3, the electric pulse E falls as shown in FIG. 3A, and when the temperature of the heating element H1 reaches the maximum as shown in FIG. 3B, the liquid surface IM further swells and begins to form a liquid column. At t4, as shown in Figure 3B, the heating element temperature T has begun to fall, but as shown in Figure 3C, the volume of bubble B has reached its maximum, and the liquid surface IM further swells to form a liquid column. ing. At t5, bubble B begins 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 contraction of the bubble B further progresses, causing separation into the droplet ID and the liquid surface IM'. At t7, droplet ID is ejected and flies, bubble B further contracts, and the liquid level decreases.
IM′ further approaches the OF surface of the orifice. At t8, the bubble B is about to disappear, and the liquid level IM further retreats and is drawn into the inner surface from the orifice OF. At t9, ink IK is supplied, and then the state returns to t0. As shown in FIG. 3B, the fall time of the thermal signal T is longer than its rise time, so by utilizing this property, from t6 to t9, the thermal signal T gradually retreats to the extent that it does not destroy the meniscus. can be done.

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. Furthermore, the droplet ejection speed can be similarly controlled using electric pulse shapes. Furthermore, the droplet ejection frequency can also be increased by using the electric pulse shape.

4A, B, and C show various electric pulse waveforms E applied to the heating element H1, temperature changes T of the heating element H1, and volume changes B of bubbles in response thereto.

Ink droplets are suitably ejected with any of these electric pulse waveforms. The waveform at a is an extremely effective pulse waveform that does not require special specifications for the drive circuit. This is a specific example of a method of supplying an electric drive signal for ejecting ink from an ink ejecting section of the present invention shown in FIG. 3 to the recording heating element in accordance with a recording signal. In the waveform b, preheat bias heating is performed before the pulse rises to shorten the pulse width during droplet ejection. This supplies an electric signal for preheating the recording heat generating element to the recording heat generating element in the order of the preheating electric signal and the electric drive signal in accordance with the supply timing of the electric drive signal to the recording heat generating element. This is a specific example of signal supply timing. Discharge using this waveform caused bubbles to rise quickly and was effective in improving the discharge speed and response frequency. In addition, preheating is performed instantaneously and without waste only during recording, that is, when the electric drive signal is supplied to the recording heating element.
Since it is possible to prevent the recording liquid from becoming too warm and causing problems, high-speed recording can be achieved without the problem of a decrease in recording speed. The waveform in c is a reference example of the present invention, in which bias heating is performed at the falling edge of the pulse, and the meniscus can be retreated more gradually after droplet separation. This waveform prevented excessive intake of air into the liquid chamber after ejection, and smooth ejection was obtained during the next recording. Also in this case, since bias heating is performed only during recording, the bubbles completely disappear, which is effective for the next recording. The waveform in d is a reference example of the present invention, in which the droplets are separated smoothly and cooling is performed gradually to prevent the liquid level from receding too much. It is effective because the liquid level can be gradually receded without dropping. e is an effective pulse waveform that is a composite of the waveforms b and d described above.

As described above, it is only necessary to control the driving electric signal and the preliminary heating electric signal, and no external high resistance element is required. Particularly, a is preferable in terms of LSI functionality. Further, the laser pulse has a shape similar to that shown in a, and the above-mentioned effect functions similarly in the laser pulse as well.

FIG. 5 is a schematic diagram of an example of a recording head using the principles of the present invention. In the figure, the surface of the substrate SS1 includes heating elements H1 to H7 and lead electrodes 1e1 to 1D.
7 is formed. Multiple heating elements H1 to H7
have the same area and the same resistance value. The board SS1 is
Covered by plate GL1 with grooves M1 to M7 carved,
A plurality of liquid chambers are formed at the joint with the substrate SS1. The plate GL1 is provided with an ink supply chamber ND that supplies 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. 6 is a diagram in which the number of heating elements and orifices of FIG. 5 is increased (for example, 32) to form a cassette-type ink jet head block. figure
DA1 is a diode array containing many diodes to prevent wraparound, and OP1 is an ink supply pipe that is detachable from plate GL1. When this is removed, the entire board SS1 can be removed from the main body.

FIG. 7 is a sectional view showing an example of a connection configuration between the ink supply pipe FP1 and the ink introduction port IS. Packing FH into the inlet IS drilled in plate 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 FP1,
The ink supply pipe FP1 is equipped with a packing FH and a spring SP1 that presses 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 the FP1.
Although the connection method is not limited, it is desirable to connect the ink supply pipe FP1 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. 8 shows the above-mentioned cassette type inkjet recording head blocks fully assembled and arranged alternately above and below one common heat sink plate. Common heat sink plate in the figure
Odd number blocks JB1, JB3,...JBn on the top surface of HS
, and even-numbered blocks JB2, JB4,...JBn are joined to the bottom surface. Each block has an ink tank IT,
Ink pipe IP, common distribution pipe for each block
OP, EP and each block distribution pipe OP1~
Ink IK is supplied by OPn. The pipes OP1 to OPn connected to each block can be attached to and detached from each plate as shown in the example in FIG.
OPn is convenient and easy to bend.

DA1 to DAn are diode arrays that are the same as those shown in FIG. 6, and are connected to the respective lead wires on the heating element-equipped substrates SS1 to SSn. With this zigzag arrangement, the orifice OF1 is
The spacing Q between and OF2 is the same on the top and bottom, and it is possible to ensure an equal orifice spacing Q for all full-multi lines.

FIG. 10 is a wiring diagram for time-division driving in the devices shown in FIGS. 8 and 9. FIG. As shown in the figure, heating element 1H1~
1H32 forms one block, and there are a total of 172 heating elements 1H1 to 56H32 in 56 blocks, and each heating element is a diode 1d1 to 1d.
1792 diodes 1d1 to 56d32 are connected to the diodes 1d1 to 56d32. Each diode has wiring 1P1 to 56P32
It is connected to the image information input terminals P1 to P32 through the image information input terminals P1 to P32. The other ends of the heating elements 1H1 to 1H32 are connected to the block selection signal input terminal D1 by wirings 1D1 to 1D32. Heating elements 2D1 to 2D3
2...56D1 to 56D32 are similarly connected to block selection signal input terminals D2 to D56, respectively. A heating element 1 is placed on the cassette board SS1 mentioned above.
H1 to 1H32, diodes 1d1 to 1d32, and lead wires are wired. Another cassette is similarly equipped with a heating element, diode, and lead wire.

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 air bubbles in each liquid chamber and cause droplets to fly. Although it is possible to use multilayer wiring to satisfy the above wiring requirements,
In either case, a connector is provided to connect the cassettes.

FIGS. 11 and 12 are schematic diagrams of a copying machine or facsimile recording device to which the above-mentioned full multi-recording head and time-division drive system are applied. It has a reading section RD for reading. Reading section
As shown in Fig. 11, an original platen PG made of glass or the like is formed on the upper part of the RD.
Place the original on top. 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 receiver
CS is fixed to carriage CA. carriage
CA moves forward in the Q direction or backward in the counter Q direction by a screw G rotated by the drive of 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
The information on the document table is raster scanned in the P direction while moving 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. 8, 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 the buffer memory to the inkjet head of the recording section shown in Fig. 8, and recording is performed in parallel with the reading. You may record again later.

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 (approximately equal to the short side 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, assume that 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 gap spacing of the orifices in the vertical direction of the odd and even groups is 8 mm, 64
Line. 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 signal by a digitizing circuit AD shown in FIG. 12 when the level is black and white, and multivalued by an analog-to-digital converter or the like when gradation (half tone) is required.

For simplicity, considering binarization, the digitization circuit AD consists of a comparator that compares the output voltage of the CCD sensor and the reference voltage (slice level), and it can be divided into high level or low level depending on the input voltage. Outputs a value signal. This digitized data is serially input to a 32-bit shift register SR, converted into parallel data, and output, and thereafter 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 includes 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 the latch circuit L1 is alternately written into the memories M1 and M2 every 32 bits. Memories M1 and M2 are, for example, RAM (random access memory), etc., and memory M1 has a storage capacity of 32
The memory M2 is 56K bits. One word of the memory consists of 32 bits, so the memory M1 consists of one word and the memory M2 consists of 1792 words. It is also assumed that the outputs of the memories M1 and M2 are in a high impedance state, so-called three-state state, when the enable signal lines L4 and L5 are at high level.

Data selectively read from memories M1 and M2 is once held in a 32-bit latch circuit L2. At this time, the states of the memory M1 and the memory M2 are such that one is in the write state and the other is in the read state, and one of the latch circuits L1 and L2 is in the memory M
1, the other one is memory M2
holds data.

Therefore, the data in the memory M1 and the data in the memory M2 are alternately held in the latch circuit L2. The data held in the latch circuit L2 is output to 32 NAND gates NG1 to NG32, and the NAND gates NG1 to NG32 are controlled by the transistors TP1 to NG32 depending on the timing PG of the print command signal line L10 from the control circuit CC and the contents of the latch circuit L2. T.P.
32 is selectively operated. Transistor TP1
The collector terminal of ~TP32 is connected to the 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.

As described above, in the above embodiment, the pressure is rapidly increased by applying heat to the liquid chamber to form a liquid column, the pressure decreases to create a constriction in the liquid column, and the tip of the liquid column is separated to form droplets and fly. Because of this structure, the so-called on-demand type inkjet recording apparatus has an extremely simple structure and has the remarkable effect of facilitating high density printing.

For example, the above-mentioned Utility Model Publication No. 16757/1975, Japanese Patent Application Publication No. 1973
-110230 and the like are non-on-demand types, and the equipment is complicated and large, making it extremely difficult to increase the density.

In addition, the above-mentioned Japanese Patent Publication No. 53-45698 (page 4, column 8, lines 5 to 7), Japanese Patent Application Laid-Open No. 1982-132036,
Since it does not utilize the bubble bursting phenomenon as in JP-A No. 51-128227 and JP-A-52-102039, it is possible to record clear dots at high speed, and the droplets are approximately the same size as the bubbles. It has characteristics such as being able to form.

[Effects of the Invention] According to the present invention, in the inkjet recording method, the signal supply timing for providing the preliminary heating electric signal is set such that an electric drive signal for ejecting the ink is supplied to the recording heating element in accordance with a recording signal. This solves the inconvenience of ink caused by overheating, and the state of the recording heating element driven by the electric drive signal can be instantly adjusted to the desired state at the required time, so the diameter of the ejected droplets can be adjusted. It is possible to record gradation images without sacrificing stability or recording speed. In any case, according to the recording method according to the present invention, the diameter of the ejected droplet can be stabilized, and high-speed recording is possible.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the principle of the present invention, Fig. 2 is an explanatory diagram of its operation, Fig. 3 is a diagram of its waveform relations, Fig. 4 is a diagram of other waveform relations, Figs. 5, 6, and 7. 8 is a perspective view of an example of the fully multi-layered head shown in FIG. 6, FIG. 9 is a front view of FIG. 8, FIG. 10 is an example of the drive circuit, and FIG. 11 is a diagram of an example of the head configuration. 1 is a diagram showing an image input section of a copying machine or the like, and FIG. 12 is a block diagram thereof. W...recording liquid chamber, OF...orifice, IK...
Recording liquid, HI... heating element, IM... meniscus.

Claims (1)

[Claims] 1. Generating thermal energy in a heating element for recording,
an inkjet that supplies an electric drive signal to the recording heating element in response to a recording signal to cause a sudden change in the state of ink in the ink jetting unit corresponding to the recording heating element to cause the ink to be ejected from the ink jetting unit; In the recording method, an electric signal for preheating the recording heat generating element is applied to the recording heat generating element in the order of the preheating electric signal and the electric drive signal according to the supply timing of the electric drive signal to the recording heat generating element. An inkjet recording method characterized by having a timing for supplying a signal to the body.