JPH0237300B2 - EKITAIFUNSHAKIROKUHO - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid jet recording method, and particularly to a liquid jet recording method in which recording is performed by flying a recording liquid in the form of droplets.

Non-impact recording methods have recently attracted attention because the noise generated during recording is so small that it can be ignored. Among these, the so-called inkjet recording method (liquid jet recording method), which is capable of high-speed recording and can record on so-called plain paper as a recording material without the need for special fixing treatment, is an extremely powerful recording method. Various methods have been devised so far, some have been improved and commercialized, and efforts are still being made to put them into practical use.

In this inkjet recording method, recording is performed by causing droplets of a recording liquid called ink to fly and adhere to a recording member. There are several methods for controlling the flying direction of the droplets, but they can be broadly classified into two methods. For example, one of these methods is USP3060429, USP3596275, USP3298030,
The other method is described in publications such as USP3416153.
It is described in detail in publications such as USP3683212, USP3747120, and USP3946398.

To summarize here, the former method uses a continuous vibration generation method to generate a droplet flow with a controlled amount of charge.
By flying the generated droplet flow with a controlled amount of charge between deflection electrodes to which a uniform electric field is applied, recording can be performed on a recording member, or a nozzle and a ring-shaped charged An electric field is applied between the electrodes and a continuous vibration generation method is used to generate droplets, which are atomized and recorded. The latter is a so-called drop on demand liquid jet recording method, in which all of the generated droplets are attached to the surface of the recording material for recording, so it is different from other methods. In recent years, wealth has been attracting attention because it does not require liquid recovery.

In this method, an electrical recording signal is applied to a piezo vibrating element attached to a recording head that has an ejection orifice that ejects recording liquid as droplets, and this electrical recording signal is transmitted to the piezo vibrating element's mechanical device. Recording is performed by ejecting and flying droplets from the orifice in accordance with the mechanical vibrations and adhering them to the recording member.

However, while each of the conventional systems has its own advantages, there are also points that are essential or that could be solved.

That is, in the former method, the direct energy for generating a droplet or a droplet stream is electrical energy, and the deflection control of the droplet is also controlled by an electric field. For this reason, a high voltage is required to generate droplets or a droplet stream, and it is difficult to make the recording head multi-orifice, especially multi-orifice at high density, so it is not suitable for high-speed recording.

There are problems such as the structure is complicated, the electrical control of the flight direction of the droplet flow is difficult and sophisticated, and satellite dots are likely to occur on the recording member.

The method of atomizing the ejected droplets is difficult to precisely and precisely control the atomization state, fogging occurs in the recorded image, and it is difficult to use a multi-orifice recording head, making it unsuitable for high-speed recording. There are various problems such as:

In the latter method, there are problems in processing the recording head, and it is extremely difficult to miniaturize the piezoelectric vibrating element with the desired resonance number, so it is difficult to miniaturize the recording head and make it multi-orifice. It is difficult, and because droplets are ejected and ejected using the mechanical energy of the mechanical vibration of the piezo vibrating element, it is not suitable for high-speed recording, and there is a relatively high incidence of satellite dots and fogging of recorded images. It has its drawbacks.

As described above, the conventional method has several problems in terms of structure, high-speed recording, recording head manufacturing, multi-orifice design, especially high-density multi-orifice design, generation of satellite dots, and fogging of recorded images. However, there are essential shortcomings and points that can be improved.
There was a restriction that it could only be applied to applications that took advantage of its advantages.

In response to this, the applicant proposed in Japanese Patent Application No. 118798/1983 a liquid jet recording method based on a completely new concept that can solve the above-mentioned problems.

The present invention relates to improvements in the recording method disclosed in Japanese Patent Application No. 52-118798, particularly when recording is performed using a laser beam.

In the recording method using a laser beam disclosed in Japanese Patent Application No. 52-118798, in order to maximize its characteristics, a discharge orifice for jetting liquid in a predetermined direction is installed at the end of the recording method. A plurality of flow passages are arranged in the discharge orifice and have a heat acting portion at a position where the acting force generated therein is effectively transmitted in the direction of the discharge orifice.
A multi-orifice recording head having a structure communicating with a common liquid chamber for supplying liquid to each is applied. The structure of such a recording head is
Since it is much simpler than conventional recording heads, the flow channels can be arranged with a density comparable to the resolution of the recorded image. Therefore, it is essential to accurately irradiate a laser beam onto the heat-active portions of these highly densely arranged channels. For example, if the laser beam is not accurately irradiated onto the heat-effecting part that should be irradiated, and the irradiation spot hits the heat-effecting part of an adjacent flow path, droplets may be ejected from the discharge orifice of that flow path, or However, even if no ejection occurs, it is inevitable that the irradiation efficiency will be significantly reduced. In addition, if we want to improve the accuracy of the laser beam scanning system in order to accurately irradiate the heat-acting part with the laser beam, extremely high precision is required, which requires advanced manufacturing of the optical system, etc. that makes up the scanning system. techniques are required and therefore cause a significant increase in the cost of the equipment.

Furthermore, when achieving irradiation accuracy on the scanning system side as described above, it is necessary to replace the recording head, or the position of the recording head may be worn out for some reason, or the arrangement of the flow channels may be changed. When the state changes, the scanning system must be adjusted again, which is an inconvenience, and this poses a problem in terms of maintainability of the apparatus.

In view of the above points, the above-mentioned patent application filed in 1972-
In order to maximize the characteristics of the recording method disclosed in No. 118798, it is necessary to be able to accurately irradiate each of the heat-acting parts with a laser beam, and to have a high degree of precision in the scanning system itself. What is desired is a recording method that can be provided at low cost.

The present invention has been made in view of the above points, and is characterized by having a discharge orifice at the end thereof for discharging droplets in a predetermined direction, and the acting force generated therein is directed toward the discharge orifice. A flow path having a heat acting part at a position where heat is effectively transmitted to the
By arranging a plurality of laser beams and irradiating the heat effecting part with a laser beam, a sharp state change is caused in the liquid in the heat action part, and an acting force based on the state change causes,
In the liquid jet recording method, in which droplets are ejected from the ejection orifice and recorded by adhering them to the recording surface, the amount of laser beam irradiated onto each heat-acting part in one scan is used to detect the flow path position. The flow path position detection scan and the droplet ejection scan are performed using the same beam scan to detect the flow path position, and the droplet ejection is performed based on the detection signal. It is a liquid jet recording method that controls timing.

The liquid jet recording method of the present invention can accurately irradiate each heat-acting part with a laser beam, and the precision of the beam scanning system itself is not required so that the cost can be reduced. It can be easily visualized that the maintainability of the device is relatively low.

The present invention will be specifically described below with reference to the drawings.

An overview of the recording principle according to the present invention will be explained with reference to FIG.

FIG. 1 is an explanatory diagram for explaining the recording principle according to the present invention.

A desired pressure is applied inside the nozzle 101 by a suitable pressurizing means such as a pump, and the pressure P is such that it is discharged by the discharge orifice 102 or is not discharged from the orifice 102 by itself. A liquid 103 for recording is being supplied. Now, orifice 1
Liquid 1 in the nozzle 101 at a distance l from 02
03a is acted upon by thermal energy in a portion of width △l (thermal action part). Due to the sudden state change of liquid 103a, the amount of liquid 103 existing within width l of nozzle 101 changes depending on the amount of thermal energy acting on it.
Part or all of the liquid b is ejected from the orifice 102 and flies in the form of a droplet in the direction of the recording member 104, and adheres to a predetermined position on the recording member 104.

To explain this point more specifically, the heat acting part △
When thermal energy is applied to the liquid 103a in the heat acting part Δl, a sudden change in state including the generation of bubbles occurs instantaneously in the liquid 103a in the heat acting part Δl, and this change in state causes Depending on the applied force, part or all of the liquid 103b existing within the width l is discharged from the orifice 102. Thus, the action of thermal energy is stopped or the liquid 10 is discharged from the liquid supply side toward the discharge orifice 102.
If the movement of 3 occurs, or if the amount of liquid discharged is instantly replenished according to the thermal effect △l, the liquid 10
The bubbles generated in 3a are instantly reduced in volume and either disappear or are reduced to an almost negligible volume.

The discharged amount of liquid is caused by the contraction of the volume of bubbles, by capillary action in the nozzle 101, by forced pressure, or by a combination of two or more of these. The action replenishes the inside of the nozzle 101.

The size of the formed droplet 105 depends on the amount of thermal energy, the width Δl of the portion 103a that is affected by the thermal energy of the liquid present in the nozzle 101, the volume of the liquid 103a within Δl, If the nozzle 101 is cylindrical, the average inner diameter d at the width l, or if the nozzle 101 is not cylindrical, the average cross-sectional area at the radius l, and the position of the orifice 102 determine the effect of thermal energy. It depends on the distance l to the receiving position, the pressure P applied to the liquid, the specific heat, thermal conductivity, coefficient of thermal expansion, heat of vaporization, etc. of the liquid. Therefore, by changing any one or more of these elements that can be controlled, the size of the droplet 105 can be easily controlled, and the size of the droplet 105 can be adjusted to any desired diameter. It is possible to record on the recording member 104 with a spot diameter of . In particular, being able to arbitrarily change the distance l means that the position of application of thermal energy during recording can be changed as desired, and therefore the amount of generated thermal energy per unit time can be changed. At least the size of the droplets 105 formed can be arbitrarily controlled during recording, and a recorded image with gradation can be easily obtained.

In the present invention, the heat acting portion Δl of the nozzle 101
Thermal energy acting on the liquid 103a may be provided or generated temporally continuously, or may be provided or generated discontinuously by turning on and off in pulses, but continuous recording is not possible. If you do
In order to improve the droplet generation frequency, it is preferable to repeatedly supply or generate droplets discontinuously in a pulsed manner.

In the recording principle applied to the present invention, by applying thermal energy to the liquid in the heat acting portion Δl in a temporally discontinuous manner, it is possible to cause the applied thermal energy to carry recorded information. That is, by applying thermal energy to the liquid 103a in the heat action section Δl in accordance with the recording information signal, a state change is caused in the liquid 103a in the heat action region Δl in accordance with the signal. Therefore, any of the formed droplets 105 can carry recording information, and therefore all of them can be transferred to the recording member 104.
It is possible to record by attaching it to Clogged,
A so-called drop-on demand recording method can be implemented.

When applying thermal energy to the liquid 103a in a pulsed manner, the amplitude and width of the pulse at this time can be easily selected and changed as desired, so the size and unit of the droplet can be adjusted. The number N ₀ of droplets generated per time can be controlled very easily.

The liquid 103 in the heat acting part △l is discontinuously stored without recording information being carried by the applied thermal energy.
When acting on a, it is applied repeatedly at a certain constant frequency.

The frequency in this case is determined by taking into account the type of liquid used and its physical properties, the shape of the nozzle, the volume of liquid in the heat acting part Δl, the liquid supply rate into the nozzle, the orifice diameter, the recording speed, etc. It is determined as appropriate depending on the request, but usually 0.1 to 1000KHz,
The frequency is preferably 1 to 1000 KHz, most preferably 2 to 500 KHz.

In this case, the pressure applied to the liquid 103 is caused by thermal energy being provided to the liquid 103a or by the pressure applied to the liquid 103a.
The orifice 102 is not generated in the
It may be set to a level at which the liquid 103 is ejected, or it may be set to a level at which the liquid 103 is not ejected. Heat acting part △ at any pressure
At 1, the liquid 103a undergoes a thermal action and undergoes a state change, and by repeating this state change, it is possible to form a droplet stream with a desired droplet generation frequency.

The droplets formed in such a state are controlled according to recording information by other means such as charge control, electric field control, or air flow control, and recording is executed.

Generating thermal energy based on laser beam irradiation and causing the liquid to undergo a sharp state change, for example, a state change including the generation of bubbles due to vaporization, is in the heat acting part △l. Either the liquid itself absorbs the laser beam and generates heat, or a heat converter that absorbs the laser beam and generates heat is provided in the heat acting part △l, and the thermal energy generated by the heat converter is transferred to the heat acting part △l. This is achieved by acting on a certain liquid. The heat converter may be provided in direct contact with the inner wall surface or outer wall surface of the heat acting portion Δl of the nozzle 101, or may be provided with a substance with good thermal conductivity interposed therebetween, but either In this case as well, the structure and arrangement are such that the thermal energy generated from the heat converter can be effectively applied to the liquid 103a.

Alternatively, at least the wall of the heat acting portion Δl of the nozzle 101 may be made of a heat converter. The heat converter is selected depending on the wavelength of the laser beam to be irradiated, and is made of a material that has an absorption region in the wavelength region of the laser beam. If such a laser beam absorbing material has film properties and adhesive properties, it is sufficient to directly form a coating film on a predetermined portion of the outer wall of the heat acting portion Δl of the nozzle 101.
If the laser beam absorbing material has no or weak coating properties or adhesive properties, it may be mixed and dispersed in a suitable binder that has coating properties and adhesive properties and is heat resistant to form a coating film. . Many commonly known dyes and pigments can be used as the laser beam absorbing material. For example, when infrared rays are used as the electromagnetic wave, dyes and pigments can be used as infrared absorbing exothermic agents.

Next, one preferred embodiment of the liquid jet recording method of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a merely schematic explanatory diagram illustrating a preferred embodiment of the liquid jet recording method of the present invention.

FIG. 2a is a schematic perspective view for explaining the configuration of an embodiment of the apparatus of the present invention. In the figure, a laser beam emitted by a laser oscillator 201 is guided to an entrance aperture of an acousto-optic modulator 202. In the modulator 202, the laser beam is modulated in intensity according to the input of the recording information signal to the modulator 202. The optical path of the modulated laser beam is bent toward the beam expander 204 by the reflecting mirror 203 and enters the beam expander 204 . The beam diameter of the modulated laser beam is expanded by the beam expander 204 while it remains a parallel beam. Next, the laser beam whose beam diameter has been expanded is a polygon 205.
is incident on the The polygon 205 is attached to the rotating shaft of a hysteresis synchronous motor 206 and rotates at a constant speed. polygon 2
Although it is not specified in 05, it is usually used in the recording field.
It is fed by the sheet feeding means being used and transported over the drum 216 by the sheet transport means.

The recording start signal is generated based on the start detection signal output from the detection means 217 when the laser beam is detected by the scanning start detection means 217, and thereafter recording is performed at a timing based on the flow path detection. The laser beam swept horizontally is reflected by the reflecting mirror 2 by the f-theta lens 207.
08 to a predetermined position of each channel of a channel array 210 aligned at the tip of a full-line high-density multi-orifice recording head 209. Due to the imaging of the laser beam onto the channel array 210, the recording liquid in each nozzle is affected by thermal energy;
Droplets of recording liquid are ejected from orifices provided at the tips of each flow path to perform recording on the recording member 211 . Each flow path of the recording head has a supply pipe 2.
Recording liquid is supplied from a liquid storage tank 214 through a common liquid chamber provided inside the common liquid chamber member 213 and the common liquid chamber member 213 . The recording member 211 shown in the figure is in the form of a sheet, and a large number of recording members 211 are stored in a cassette 215 in synchronization with a recording signal, as shown in FIG. 2b. , a recording head 20 used in the apparatus of FIG. 2a.
9 is a schematic perspective view as seen from the channel array 210 side, and FIG. 2c is a cross-sectional view of the laser beam section.

On the front surface of the recording head 209, a channel array 210 is provided with an orifice density of 10/mm over a total length of 300 mm.

An irradiation section 218 is provided on the upper surface of the channel array member 219 provided in the channel array 210 so that a laser beam is focused and irradiated on a predetermined position of each heat acting section 226.
is provided.

The channel array 210 is composed of liquid channels 224 parallel to each other and isolated from each other in the channel array member 219, and each channel 224 of the irradiation unit 218 is connected to the orifice of each channel 224 constituting the channel array 210. Every time the laser beam is irradiated on the part corresponding to
The droplet 223 is ejected and flies toward the surface of the recording member 211.

Each of the liquid channels 224 communicates with a common liquid chamber provided inside the common liquid chamber member 213,
The structure and dimensions are determined so that the liquid chamber can be smoothly supplied from the common liquid chamber to the flow path 224 as necessary.

In order to provide a predetermined number of channels 224 at a desired pitch, the channel array member 219 has grooves forming the liquid channels 224 formed by an etching process corresponding to the number of channels to be formed. An irradiation surface 2 for irradiating a laser beam onto the plate 221 and the heat acting portion 226, respectively.
It consists of a groove cover 222 provided with 18,
The groove plate 221 and the groove cover 222 are precisely positioned and bonded using a suitable adhesive.

An irradiation section 218 is provided above the heat application section 226 provided at a predetermined position from the orifice 225, with dimensions, structure, and material determined so that the heat application section 226 is efficiently and effectively irradiated with the laser beam. It is provided.

In the channel structure shown in FIG. 2c, a groove is formed in a part of the groove cover 222 by etching, mechanical cutting, etc. to reduce the wall thickness and provide good transparency to the laser beam. Select the material, and
A heat converter 227 having a function of absorbing a laser beam and generating heat is provided on the bottom surface of the heat acting section 226 of the groove plate 221.

Now, when the laser beam 228 is irradiated through the irradiation unit 218 so as to converge on the heat converter 227,
The heat converter 227 absorbs the laser beam and generates heat, and the heat acts on the liquid 220 in the heat acting section 226 . The liquid that has been exposed to the heat acting part undergoes a steep state change, and the acting force based on the state change causes the liquid to form a droplet 223.
is ejected from the ejection orifice 225.

If the liquid filling the liquid flow path 224 absorbs the laser beam and generates heat, causing a sufficiently rapid state change, it is not necessary to provide the heat converter 227, and the irradiation section 218 is made transparent to the laser beam 228. It is sufficient if it is made of good quality materials.

Furthermore, in the nozzle structure shown in FIG. 2c, the groove cover 222 and the irradiation section 218 are made of the same material, but the irradiation section 218 can be made of a material that satisfies the characteristics and functions required for the irradiation section 218. The groove cover 222 may be made of a different material.

However, as shown in the figure, it is preferable to use an integrated structure from the viewpoint of ease of construction and cost reduction.
The heat converter 227 may be provided on the irradiation section 218 side. In this case, it is advantageous if the irradiation section 218 itself is made of a heat converter, since the energy loss of the laser beam at the irradiation section 218 can be eliminated.

In addition, when the liquid 220 of the heat action section 226 absorbs the laser beam and generates heat, the bottom surface of the heat action section 226 (the side opposite to the laser beam incident side) is used to efficiently use the energy of the laser beam. ) is provided with a reflective member made of a metal surface or a mirror surface, for example, so that the laser beam that has passed through the liquid in the heat-acting section 226 is reflected by the reflective member and passes through the liquid again. As the energy progresses, it is absorbed and energy efficiency can be improved.

By the way, when the transmission type is used to detect the flow path position as shown in FIG. The laser beam 228 that irradiates the part other than the liquid flow path 224 passes through the groove plate 221 and reaches the diffusion plate 22.
9 at a detection level. The laser beam 228 is blocked in the flow path 224 and the diffuser plate 22
9 is not irradiated or is irradiated at a low level. The flow path position detector 230 is composed of a plurality of photodetecting elements such as photodiodes, phototransistors, or photomultipliers. The stray light guide 231 is for blocking light other than the laser beam.

In this embodiment, the flow path position was detected using a transmission type, but a reflection type may also be used.

Next, the timing of laser irradiation based on flow path position detection will be explained with reference to FIG.

In FIG. 3, 1 indicates the flow path pattern. 2 shows flow path position detection signals detected when droplets are ejected from the second and third orifices from the left. In other words, the flow path is irradiated with an insufficient amount of light to eject a droplet, and the second and third laser beams from the left are used to cause droplet ejection based on the edge trigger of the detected signal.
This is done for the second channel. Irradiation at a level sufficient for detection is performed in a channel that does not allow droplets to be ejected. The signal from the channel position detector 230 is amplified and binarized at the level shown by the broken line 2, resulting in a signal as shown in 3. Based on the edge trigger of this signal, a pulse as shown in 4 is generated to set a predetermined pulse width or irradiation time to a predetermined value. In other words, signal 4 becomes a signal that accurately reflects the flow path pattern.
The data signal inputted from a computer or the like shown at 5 is logically ANDed with the signal shown at 4, and finally becomes a signal 6 to be inputted to the modulator 202. As shown at 6, the signal input to the modulator 202 is normally at a level that irradiates with an amount of light sufficient for detection, and irradiates a strong laser beam only to the flow path where the droplet is to be ejected. The processing of the signal from the flow path position detector 230 will be explained using the block circuit diagram shown in FIG.

In FIG. 4, the signal from the flow path position detector 230 is input from a terminal 401, is amplified by an amplifier circuit 402, and then sliced at a predetermined level by a comparator 403 to become a binary signal. .
Based on the edge trigger, the mono-multivibrator 404 generates a pulse of a predetermined width.
On the other hand, a data signal is connected to the terminal 405,
A pulse according to the data is outputted by the gate circuit 406, and thereafter inputted to a modulator control circuit (not shown). In the modulator control circuit, a bias is applied for photodetection, and the laser beam is modulated so that a sufficient amount of light irradiates the heat-acting part only when ejecting a droplet. Although not shown in FIG. 4, the trigger signal from comparator 403 is used as a data transfer clock to terminal 405.

As explained above, according to the liquid jet recording method of the present invention, a laser beam can be accurately irradiated with a predetermined amount of light at a predetermined position in a flow path with a simple configuration and at a predetermined timing with good responsiveness and faithfulness to the recording signal. Irradiation can be easily carried out.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram for explaining the outline of the recording principle related to the present invention, FIG. 2a is an explanatory diagram schematically shown for explaining a preferred embodiment of the present invention, FIG. 2b is a schematic partial perspective view of the recording head 209 used in the apparatus shown in FIG. 2a, FIG. 2c is a schematic sectional view thereof, and FIG.
Timing chart, Figure 4 shows flow path detector 23
2 is a block circuit diagram when processing signals starting from 0. FIG. 101...Nozzle, 102...Discharge orifice, 1
03...liquid, 104...recording member, 105...droplet, 201...laser oscillator, 202...acousto-optic modulator, 203...reflector, 204...beam expander, 205...polygon, 206...motor, 207...f- θ lens, 208...reflector, 2
09... Recording head, 210... Channel array, 211... Recorded member, 212... Supply pipe, 213... Common liquid chamber member, 214... Liquid storage tank, 215... Cassette, 2
DESCRIPTION OF SYMBOLS 16...Drum, 217...Detection means, 218...Reflector, 219...Flow path separate member, 220...Liquid, 221
...Groove plate, 222...Groove lid, 223...Droplet, 224...
Liquid flow path, 225...Discharge orifice, 226...Heat action section, 227...Heat converter, 228...Laser beam, 229...Diffusion plate, 230...Flow path position detector,
231...Stray light guide.

Claims (1)

[Claims] 1. A plurality of flow channels each having a discharge orifice at the end thereof for discharging droplets in a predetermined direction, and a heat acting portion at a position where the acting force generated therein is effectively transmitted in the direction of the discharge orifice. Book arrangement,
By irradiating the heat acting part with a laser beam,
Liquid jet recording in which a sharp state change is caused in the liquid in the heat acting part, and the action force based on the state change causes droplets to be ejected from the ejection orifice and attached to the recording surface to perform recording. In this method, two levels are set for the amount of laser beam irradiated to each heat-acting part in one scan, one for flow path position detection and one for droplet discharge, and the flow path position detection scan and droplet discharge scan are performed. A liquid jet recording method characterized in that the flow path position is detected by performing the same beam scanning, and the timing of droplet ejection is controlled based on the detected signal.