JPH02286247A - Liquid jet recording device - Google Patents

Abstract

PURPOSE:To obtain a heating element substrate having high radiation of heat and to improve ink-droplet delivery performances of a superhigh density arrangement multi-nozzle head by forming a lower layer composed of at least a heat accumulation layer and a heat conduction layer. CONSTITUTION:A lower layer 20 is composed of a heat conduction layer 20-1 and a heat accumulation layer 20-2 provided on said layer 20-1. The heat conduc tion layer, provided under the heat accumulation layer, allows heat generated by a heating part to be rapidly released from the heating part. Hence, the heat conductive layer is made up of such material that has a thermal conductiv ity higher than that of a substrate and heat accumulation layer, i.e. made up of materials having thermal conductivity higher than that of glass and alumina. Materials for the heat conduction layer are those having softening and melting points of 300 deg.C or higher, e.g. copper, aluminum, nickel, and further SiC, BeO, AlN etc. Consequently, regardless of kind of substrate, excellent delivery perfor mance can be achieved, particularly in a superhigh density multi-nozzle head of 16 pieces/mm or higher.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid jet recording device, and more particularly to an inkjet printer.

The duck shell non-impact recording method has recently attracted attention because the noise generated during recording is so small that it can be ignored. Among them, high-speed recording is possible,
However, the so-called inkjet recording method, which allows recording on plain paper without the need for special fixing treatment, is an extremely powerful recording method, and various methods have been proposed and improvements have been made to improve the quality of products. Some have been developed, and efforts are still being made to put them into practical use.

In this type of 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 types of methods depending on the control method used to control the flight direction of the generated recording liquid droplets.

First, the first method is the Tel type method, which is disclosed in, for example, U.S. Pat. Recording is performed by controlling the droplets with an electric field in accordance with a recording signal to selectively attach recording liquid droplets onto a recording member.

To explain this in more detail, an electric field is applied between the nozzle and the accelerating electrode to eject a negatively charged recording liquid droplet from the nozzle, and the ejected recording liquid droplet is converted into a recording signal. Accordingly, the droplet is caused to fly between x and y deflection electrodes configured to be electrically controllable, and the droplet is selectively deposited on the recording member by changing the intensity of the electric field to perform recording.

The second method is a method (Sweet method) disclosed in, for example, U.S. Pat. No. 3,596,275, U.S. Pat. A device that records on a recording member by generating small droplets of recording liquid with a controlled amount of charge and flying the generated droplets between deflection electrodes to which a negative electric field is applied. It is.

Specifically, the orifice (discharge port) of a nozzle, which is a part of the recording head to which the piezo vibrating element is attached.
A charged electrode configured to have a recording signal applied thereto is arranged at a predetermined distance in front of the piezo vibrating element, and an electric signal of a constant frequency is applied to the piezo vibrating element to mechanically vibrate the piezo vibrating element, A small droplet of recording liquid is ejected from the iη ejection port. At this time, a charge is electrostatically induced in the recording liquid droplet discharged by the single charge electrode, and the droplet is charged with an amount of charge corresponding to the recording signal. When a droplet of recording liquid with a controlled amount of charge flies between deflection electrodes to which a constant electric field is uniformly applied, it is deflected according to the amount of charge added, and the droplet carries the recording signal. 6 A third method is disclosed, for example, in U.S. Pat.
16153, the method disclosed in JalW (Ile
This is a method in which an electric field is applied between a nozzle and a ring-shaped charging electrode, and small droplets of recording liquid are generated and atomized by a continuous vibration generation method to perform recording. That is, in this method, the atomization state of small droplets is controlled by modulating the electric field strength applied between the nozzle and the charged electrode according to the recording signal.
To record a recorded image with its gradation.

The fourth method is, for example, the method disclosed in US Pat. No. 3,747,120 (Stea+me method), and this method is fundamentally different in principle from the above three methods.

That is, in all three methods, the droplets of recording liquid ejected from the nozzle are electrically controlled while they are in flight, and the droplets carrying the recording signal are selectively attached to the recording member. In contrast, this Stemme method
Recording is performed by ejecting small droplets of recording liquid from an ejection port in response to a recording signal.

In other words, in the SteIIms method, f! ! Applying an electrical recording signal, converting this electrical recording signal into mechanical vibration of a piezo vibrating element, and ejecting small droplets of recording liquid from the ejection port according to the mechanical vibration to make them adhere to the recording member. Recording is performed using .

These four conventional methods each have their own advantages, but there are also points that can be solved in the other method.

That is, in the first to third methods, the direct energy for generating droplets of the recording liquid is electrical energy, and the deflection control of the droplets is also electric field control.

Therefore, although the first method is simple in structure, it requires a high voltage to generate droplets, and it is difficult to use a multi-nozzle recording head, making it unsuitable for high-speed recording.

The second method allows the recording head to have multiple nozzles and is suitable for high-speed recording, but it has a complicated structure, and the electrical control of recording liquid droplets is sophisticated and difficult, and satellite dots are placed on the recording member. There are problems such as easy occurrence of.

The third method has the feature that an image with excellent gradation can be recorded by atomizing liquid droplets.
On the other hand, there are various problems such as it is difficult to control the atomization state, fogging occurs in the recorded image, and it is difficult to configure the recording head with multiple nozzles, making it unsuitable for high-speed recording.

The fourth method has relatively many advantages compared to the first to third methods. In other words, the structure is simple, and since recording is performed by ejecting recording liquid from the ejection opening of the nozzle on-demand, it is possible to reduce the number of small droplets that fly as in the first to third methods. During.

It is unnecessary to collect droplets that are not needed for recording an image, and like the first and second methods.

It has great advantages such as there is no need to use a conductive recording liquid and there is a large degree of freedom regarding the material of the recording liquid.

On the other hand, it is difficult to make the recording head multi-nozzle because there are problems in processing the recording head, and it is extremely difficult to miniaturize the piezoelectric vibrating element having the desired resonance number. Since the recording liquid droplets are ejected into flight using the mechanical energy of the mechanical vibration of the piezo vibrating element, it has the disadvantage that it is not suitable for high-speed recording.

Furthermore, Japanese Patent Application Laid-Open No. 48-9622 (corresponding to the above-mentioned US Pat. No. 3,747,120) discloses, as a modification,
It is described that thermal energy is used instead of using mechanical vibration energy by means such as the piezo vibration element described above.

That is, the above-mentioned publication describes a so-called bubble jet liquid jet recording device that uses a heating coil that directly heats liquid as a pressure increasing means instead of a piezo vibrating element to generate steam that causes a pressure increase. There is.

However, in the above publication, the liquid ink in the bag-shaped ink chamber (liquid chamber), which has only one opening through which liquid ink can go in and out, is directly heated and vaporized by energizing the heating coil as a pressure increasing means. However, there is no suggestion as to how to heat the liquid when discharging the liquid continuously. Since the head is provided in the deepest part of the bag-shaped liquid chamber far from the liquid ink supply path, the head structure is complicated and it is not suitable for continuous repeated use at high speed.

Moreover, based on the technical content described in the above publication.

The generated heat, which is important in practical use, makes it impossible to quickly prepare for the next liquid discharge after discharging the liquid.

As described above, conventional methods have advantages and disadvantages in terms of structure, high-speed recording, multi-nozzle recording heads, generation of satellite dots, and fogging of recorded images. There was a restriction that it could only be applied.

The bubble jet recording method described above is an excellent recording method that can easily achieve high density and high integration. It is necessary to arrange the array at an ultra-high density of 16 lines/mm or more.

Also, if the density is ultra-high, the pixel diameter will naturally become smaller, and the number of dots to be printed on the paper will inevitably increase, so if you think about it simply, it will take a lot of time to form one image. . Therefore, it is necessary to form ink droplets at a high frequency, such as over 4 KHz. That is, 4K
It is necessary to drive the heating element at a high frequency exceeding Hz. Furthermore, it is also necessary to form a multi-array of heating elements and form images at high speed. In particular, when used in a copier or the like, a highly integrated head with more than 256 nozzles is practically required, and optimally, a so-called full-line type head is desirable.

However, such ultra-high density of 16 nozzles/mm or more and high integration exceeding 256 nozzles.

There are still problems to be solved in order to realize high frequency drive exceeding 4K Hy. In particular, the so-called heat dissipation, which allows the heat generated by the heating element to quickly escape without accumulation, has been a major problem.

Conventionally, the structure of the heating element substrate in the bubble jet recording method includes a heat storage layer, as shown in Japanese Patent Publication No. 61-59913, on a ceramic, glass, or silicon substrate.
Electrothermal converter (heating element).

The electrode and protective layer were laminated with JtII. especially,
Silicon is preferably used as the substrate because of its excellent heat dissipation properties. However, the silicon substrate is 1
For example, in the case of an A 4 Full Line type multi-array head, a substrate length of at least 210 mm is required, and it is currently extremely difficult to obtain a silicon substrate of this length. Therefore, conventionally, when making a line type head, the head is divided into blocks and the blocks are arranged in a staggered manner on the same support plate, as shown in Japanese Patent Application Laid-Open No. 55-13E253. has been used. However, this method has the drawback that precision is required for positioning each block, and that ejection characteristics vary depending on the block. Particularly in the case of an ultra-high density array of 16 lines/mm or more, even a slight error in alignment between blocks can greatly affect the dot position accuracy on the recording surface.

This required extremely high-precision alignment, which caused a decline in yield.

In the case of glass substrates, alumina substrates used in thermal heads, etc., due to thermal conductivity, when ultra-high density, high integration, and high frequency drive are used, heat dissipation is not sufficient and the head temperature increases. This resulted in problems such as an increase in image quality, the occurrence of satellite dots, and poor frequency response, resulting in a significant drop in image quality.

Furthermore, as shown in Japanese Patent Application Laid-Open No. 62-231761, using a SiC ceramic substrate is very expensive compared to alumina, and if a full line type is used, it will require an extremely expensive head. There was a drawback that it became

In addition, Japanese Patent Application Laid-open No. 1553/1983 also describes A as a substrate.
Q201, a head using AQN in addition to SiC is disclosed. However, AQN is produced in small quantities, there are concerns about stable supply, and it is expensive. moreover,
Since the AQN active surface reacts with moisture and decomposes, when used as a heating element substrate, it poses a problem in manufacturing or use, complicating the manufacturing process, tightening management, or requiring protective films etc. This creates the need for protection due to

Furthermore, JP-A No. 61-100464 discloses an example in which a substrate material having a thermal conductivity of 2W/c or more than 11°C is used.
In the specification, the above-mentioned S
In addition to iC, metals such as aluminum and copper are mentioned, but when these are used as a substrate, it is necessary to pay sufficient attention to the insulation between them and the electrodes. That is, a sufficiently dense and thick insulating layer is required between the electrode layer and the substrate. Furthermore, aluminum and copper have very large expansion coefficients, and the thermal expansion caused by driving one heating element cannot be ignored when the density is 16 pieces/mm or more.

As described above, none of the conventional substrate configurations are satisfactory.

U-Ma The present invention was made to solve the above-mentioned drawbacks, and its main purpose is to provide a heat generating substrate with an excellent heat dissipation property, which has a completely different structure from the conventional technology.

Another purpose is to improve the ink droplet ejection performance of an ultra-high density array multi-nozzle head of 16 nozzles/mm or more.

Yet other objectives include dispensing at higher speeds (e.g. 4K
Hz) is aimed at improving the ink droplet ejection performance of a multi-nozzle head.

Still another object is to provide a full-line head at low cost.

In order to achieve the above object, the present invention provides (1) an ejection orifice for ejecting recording liquid as droplets, a liquid path communicating with the ejection orifice, and the recording medium in the liquid path. A liquid jet recording device comprising a thermal energy generator for applying thermal energy to a liquid, and the thermal energy generator is provided on a lower layer laminated on a substrate, wherein the lower layer has at least a heat storage layer. or (2) an ejection orifice for ejecting the recording liquid as droplets, a liquid path communicating with the ejection orifice, and the recording liquid in the liquid path. a thermal energy generating body for applying thermal energy, the thermal energy generating body is provided on a lower layer laminated on the substrate, and the lower layer is composed of at least a heat storage layer and a heat transfer layer. In the liquid jet recording device, the thermal conductivity of the heat transfer layer is 0.
．． 58J/5-C11・℃ or higher, or (3) the heat transfer layer has at least a portion not provided between the adjacent thermal energy generating bodies. It is.

Hereinafter, the present invention will be explained based on examples.

First, the principle of ink ejection using a bubble jet that preferably implements the present invention will be explained based on FIG.

(a) is a steady state, in which the surface tension of the ink 2 and the external pressure are in equilibrium on the orifice surface.

In (b), the heater 3 is heated until the surface temperature of the heater 3 rises rapidly and a boiling phenomenon occurs in the adjacent ink layer, and microbubbles 4 are scattered.

(c) shows a state in which the adjacent ink layer that is rapidly heated on the entire surface of the heater 3 is instantaneously vaporized to form a boiling film, and the bubbles 4 grow. At this time, the pressure inside the nozzle increases by the amount of bubble growth, and the balance with the external pressure on the orifice surface is lost, causing an ink column to begin to grow from the orifice.

(d) shows a state in which the bubbles have grown to their maximum, and ink 2 corresponding to the volume of the bubbles is pushed out from the orifice surface. At this time, no current is flowing through the heater 3, and the surface temperature of the heater 3 is decreasing. The maximum value of the volume of the bubble 4 is slightly delayed from the timing of electric pulse application.

(e) shows a state in which the bubble 4 has been cooled by ink and has started to contract.The tip of the ink column moves forward while maintaining the extruded speed, and the rear end of the column moves forward as the bubble contracts. Due to the decrease in internal pressure, ink flows back into the nozzle from the orifice surface, creating a constriction in the ink column.

In (f), the air bubbles 4 are further contracted, and the ink comes into contact with the heater surface, causing the heater surface to be cooled even more rapidly. At the orifice surface, the external pressure is higher than the nozzle internal pressure, so the meniscus is largely moving into the nozzle.

The tip of the ink column becomes a droplet and drops 5 to 10 times toward the recording paper.
It is flying at a speed of m/sec.

In (g), the air bubbles have completely disappeared in the process of refilling the orifice with ink by capillary action and returning to the state of (a). 8 is a flying ink droplet.

FIG. 3 is an overall perspective view of a bubble jet recording head based on the above jetting principle. In the figure, 9 is a heating element substrate, 10 is a lid substrate, 11 is an ink supply port, and 12 is an orifice.

FIG. 1 is a diagram for explaining an embodiment of a liquid jet recording device according to the present invention, and is a diagram for explaining the structure of a bubble generating means using a heating resistor. Front partial view seen from the orifice side of the head, Figure 1(b)
1(a) is a cutaway partial view taken along the dotted chain line X-X. In FIG. , 17 is a heat acting part, 1B is a heat generating part, 19 is a heat acting surface, 20 is a lower layer, 21 is a heating resistance layer, 22 is a protective layer, 23° 24 is an electrode, 25 is a channel wall, A predetermined number of grooves with a predetermined density and a predetermined width and depth are provided on the surface of the substrate 13 on which the generation portion 18 is provided, and the orifice 15 and the liquid discharge portion 16 are connected so as to be covered with the lid substrate 14. It has a formed structure.

The liquid discharge section 16 has an orifice at its end for discharging droplets, and thermal energy generated by the heat generation section 18 acts on the liquid to generate bubbles, causing a rapid state change due to expansion and contraction of the volume. The heat acting part 17 is the place where
have.

The heat acting part 17 is located above the heat generating part 18.

A heat acting surface 19 that comes into contact with the liquid of the heat generating section 18 is the bottom surface.

The heat generating section 18 is a lower layer 20. provided on the substrate 13.
A heat generating resistor layer 21 provided on the lower layer 20, electrodes 23 and 24 are provided on the surface of the heat generating resistor layer 21 for supplying electricity to the heat generating resistor layer 21 in order to generate heat. . The electrode 23 is.

The electrode 24 is a common electrode for the heat generating section of each liquid discharging section, and the electrode 24 is a selective electrode for selectively generating heat in the heat generating section of each liquid discharging section. It is provided.

Examples of the material for the substrate 13 include glass, ceramics, metal, and silicon, but in the case of a multi-nozzle head or even a full-line head, glass or alumina can be used as a large-area substrate. It is preferable because it can be obtained at low cost.

The lower layer 20 is composed of a heat transfer layer 20-1 and a heat storage layer 20-2 provided thereon. The heat transfer layer is a layer provided under the heat storage layer and whose purpose is to quickly release heat generated from the heat generating part from the heat generating part. Therefore, the heat transfer layer is formed of a material having higher thermal conductivity than the substrate and the heat storage layer. That is, the thermal conductivity of glass is approximately 0.017J.
/5-cm・℃, thermal conductivity of alumina 0.32J/5-
Greater than C11・℃, that is, the thermal conductivity is 0.32J
/s-c! It is formed of a material with a temperature greater than +・℃. The material for the heat transfer layer is a material that satisfies the above conditions and has a softening point and melting point of 300° C. or higher, taking into account that the temperature of the heat generating part will rise to nearly 300° C.

For example, copper, aluminum, nickel, platinum, gold, silver,
Zinc, iron, tungsten, magnesium, silicon, calcium, cobalt, molybdenum, chromium, niobium, beryllium, iridium, palladium, etc., as well as their alloys and mixtures, as well as SiC, Be01AQN
, cubic BN, diamond-like carbon, etc. These materials are laminated on a substrate to a thickness of usually 0.05 μm or more, preferably 0.1 to 100 μm, by a known thin film forming method such as sputtering or CVD.

On this heat transfer layer, a thin film of SiO is formed as a heat storage layer using a vacuum thin film forming method such as sputtering or CVD. The heat storage layer is created by using a vacuum thin film formation method.
A thin film with a desired thickness can be formed with good film formation properties, and its composition can be controlled, and the film thickness is usually 0.1.
The thickness is 50 μm, preferably 1 to 10 μm.

Useful materials for forming the heating resistance layer 21 include, for example, tantalum-3in mixtures, tantalum nitride, nichrome, silver-palladium alloys, silicon semiconductors,
Or hafnium, lanthanum.

Examples include borides of metals such as zirconium, titanium, tungsten, molybdenum, niobium, chromium, and vanadium.

Among these materials constituting the heating resistance layer 21, metal borides are particularly excellent, and among them, hafnium boride has the best properties.
Next, zirconium boride.

The order is lanthanum boride, tantalum boride, vanadium boride, and niobium boride.

The heating resistance layer 21 is made of the above-mentioned material by photolithography, electron beam evaporation, sputtering, CVD,
It can be formed using a technique such as plasma CVD. What is the film thickness of the heating resistor M21?

So that the heat generating part per unit time is as desired.

Its area, material, and shape and size of the heat-acting part.

Furthermore, it is determined according to the actual power consumption, etc. 1 In the normal case, it is 0.001 to 5 μm, preferably 0.
．． 01 to 1 μm.

As the material constituting the electrodes 23 and 24, many commonly used electrode materials can be effectively used, and specifically, for example, AQ, Ag, and Au.

Examples include metals such as Pt and Cu, and alloys thereof,
Using these materials, it is provided at a predetermined position with a predetermined size, shape, and thickness by a method such as vapor deposition or sputtering.

The characteristics required for the protection IQ22 are such that the heat generated in the heat generating resistor layer 21 is not prevented from being effectively transferred to the recording liquid, and the heat generated by the heat generating resistor layer 21 is protected from the impact force when the recording liquid or bubbles disappear.
This means protecting 1. Examples of useful materials for forming the protective layer 22 include silicon oxide, magnesium oxide, aluminum oxide, tantalum oxide, and zirconium oxide, which can be used by electron beam evaporation, sputtering, CVD, plasma CVD, It can be formed using a thin film forming method such as a vapor phase growth method. The thickness of the protective layer 22 is usually 0.01 to 10 tt.
m, preferably 0.1 to 5 μm, optimally 0.1 to 3 μm
It is desirable to set it to m.

Further, an electrode protective layer may be provided on the electrode portion of the protective layer 22 except for the heat acting portion 17. The characteristics required of the electrode protective layer include excellent ink resistance, excellent heat resistance, and good electrical insulation. Therefore.

It has good film forming properties and few pinholes, and is suitable for the ink used.
It is required not to swell or dissolve. Many materials that satisfy the above conditions can be used as the material constituting the electrode portion BJd. For example, silicone resin, fluororesin, aromatic polyamide, addition polymerization type polyimide, metal chelate polymer, titanate ester, epoxy resin, phthalate resin,
Thermosetting phenol resin, P-vinyl phenol resin,
In addition to the above-mentioned organic materials, it is recommended to use resins such as Zyrox resin and triazine resin, and organic materials that are extremely easy to process using fine photolithography, if a high-density multi-orifice type recording head is to be manufactured. desirable.

A flow path is formed using a photosensitive resin on the heating element substrate configured as described above. A cavitation-resistant resin such as photosensitive polyamide varnish or photosensitive polyimide varnish is applied using a coating means such as a spinner or a roll coater.

The layer thickness of the photosensitive resin is not particularly limited, but considering its practicality as an inkjet recording head, it is at least about 5 to 100 μm, preferably about 1 μm.
It is desirable that the thickness is 0 to 50 Pm, most preferably 15 to 50 μm. Therefore, it is preferable that the photosensitive resin can be laminated to such a thickness. Photosensitive polyamide varnish, namely Printite EF95. Dobron (Toρ10n)
, Nylonprint, or photosensitive polyimide, i.e. Photonice VR-3
140 and Selectilux HTR-2 are preferably used.

The substrate on which the photosensitive resin is laminated in this manner is subjected to treatments such as exposure or development as described below to form an ink channel wall made of the photosensitive resin.

In the following, the photosensitive resin will mainly be Photonease VR-31.
40 will be described as an example, but the method for forming the ink flow path wall may be any method depending on the photosensitive resin used.

Prebaking is performed as necessary on the substrate laminated with photosensitive resin. After the prebaking is completed, a photomask having a desired pattern is placed on the Photonice VR-3140, and then exposure is performed through this photomask.

After the exposure, the unexposed part of Photonice VR-3140 is treated with developer DV-505 for Photonice VR-3140.
Grooves that are to be used as ink flow channels are formed by developing the film using a etchant and dissolving and removing the unexposed portions.

After dissolving and removing the unexposed portions, post-baking is performed to harden the exposed portions of the Photonice VR-3140 remaining on the substrate, and the Photonice VR-3140, which is an ink flow channel wall with a desired pattern on the substrate, is formed. Although a method for forming a liquid type photosensitive resin such as 0 or more Photonease VR-3140 that forms a cured film has been described, it can also be formed using a photosensitive dry film. The substrate thus formed and a lid substrate for forming the ceiling portion of the channel are bonded via an adhesive layer.

As the material of the lid substrate, the same material as that of the first heating element substrate can be used. That is, silicon, glass, ceramics, etc. A photosensitive dry film is provided in a semi-cured state on a substrate made of these materials, and after bonding to the substrate in which grooves are formed, heat is applied to fully cure the film, and the heating element substrate and the lid substrate are bonded.

Next, the present invention will be explained in detail.

(a) Head A; On the glass substrate, there is a Sin as a heat storage layer.
, is 3 μm, and Ta-8in is used as the heating element layer.

A head having the above-mentioned structure was prototyped, having a heat generating portion laminated with 2,000 layers of AQ as an electrode, 2 μm of SiO as a protective layer, and 1,500 layers of Ta as a second protective layer.

(b) Head B: After sputtering 1 μm of aluminum as a heat transfer layer over the entire surface of the glass substrate, a storage layer and a heat generating layer are formed as in head A.

Electrodes and protective layers were provided.

(Q) Head C: A heat-transfer layer of SiC having a thickness of 5 μm was provided on the entire surface of the glass substrate by CVD, and then a heat generating portion similar to that of Head A was provided.

(d) Head D: Attach the glass substrate to the RF power supply side in the vacuum device, and
A high-frequency electric field (13°, 56 MHz) is applied to the parallel plate electrodes in a gas atmosphere consisting of hydrogen and hydrogen. A heat transfer layer of diamond-like carbon made of carbon atoms and hydrogen atoms was provided on top. The thermal conductivity of the diamond-like carbon obtained by the so-called plasma CVD method was 0.8 J/5-cm·°C.

A heat generating portion similar to that of head A was provided on this heat transfer layer.

(e) Head C: After providing Cr as a heat transfer layer on the entire surface of the glass substrate by sputtering to a thickness of 1 μm.

A heat generating part similar to that of head A was provided.

(f) Head C: Zinc was provided as a heat transfer layer on the entire surface of the glass substrate by sputtering to a thickness of 1 μm, and then a heat generating portion similar to Head A was provided.

Using these heads, drive voltage 23V, pulse width 5μ
Droplets were ejected at a driving frequency of 4.2 KHz, and variations in droplet velocity and ejection direction were evaluated after 5 minutes.
The results are shown in Table 1 below.

The number of heating elements in heads A to F is 512 in total, and the arrangement density of heating elements is 16 pieces/mm and 24 pieces/11 pieces.
Two types of m were evaluated.

Table 1: O very small variation (2% or less) O small variation (5% or less) Δ variation slightly large (5% to 10%) When the situation was observed with a microscope, it was found that in the case of head A, minute irregular bubbles were appearing everywhere on the substrate around the first heating element shortly after the start of driving, and furthermore, in the heating part. In this case, the bubbles grow and contract repeatedly without completely disappearing, and then become large bubbles that do not grow or contract and adhere to the heating element, which eventually destroys the heating element, which is the cause of non-ejection. there were. In the case of head B, the above phenomenon was not observed, and the bubbles continued to grow and disappear normally. From these results, it is clear that the heat transfer layer allows stable bubble growth and disappearance without heat accumulation in the substrate.
This shows that the variation in droplet velocity was small and stable ejection could be performed. Also, from the results in Table 1, the thermal conductivity of the heat transfer layer is 0.58J/5-CI! The temperature is preferably 1.degree. C. or higher, and 2. OJ/5-cll·°C or higher is optimal.

In addition, although the droplet velocity of head F is stable, there are variations in the ejection direction, and heads B, C,
Looking at the expansion coefficients of the heat transfer layers D and H.

Head B=31.5X10"/deg, head C=4.
8 x 10°'/dag.

Head D = 4, 5 X 10-'/deg, Head E = 11 X I O"/dog, Head F = 3
9.7 x 10-"/deg, the head F is very large, and the expansion coefficient of the glass substrate is 0.54 x
Even when compared with 10-'/deg, the difference is extremely large. This is because the heat transfer layer expands due to heat, causing variations in the discharge direction. Also, cracks, etc. occur, and the heat generating part This was because it was destroyed. From this, the coefficient of linear expansion of the heat transfer layer should be as small as possible and should not be significantly different from that of the substrate or heat storage layer, and is usually 31.5 x 10-
'/deg, or even 11 X 10-'/deg
It is preferably less than or equal to 4.8X10-''
/dag or less is optimal.

Therefore, among the above-mentioned materials, preferred are aluminum, cadmium, gold, silver, Dungesten, iron, copper,
Single substances such as nickel, platinum, magnesium, molybdenum, beryllium, niobium, chromium, cobalt, iridium, palladium, silicon, and calcium, as well as alloys and mixtures thereof.

Beo, Sin, ADN, cubic BN, diamond-like carbon, among others, Si.

Be01SiC, AQN, cubic BN, and diamond-like carbon are excellent in terms of thermal conductivity, S expansion coefficient, electrical properties, etc.

Note that diamond-like carbon is i-
It is sometimes called carbon, and due to its crystallinity, it is also called amorphous carbon.

There is also Tiremond thin film, which is crystalline and has a structure similar to that of natural diamond due to its lattice spacing.

Here, it will be referred to as diamond-like carbon.

Next, another embodiment of the present invention will be described.

Fig. 4 shows an example of the pattern of the heat transfer layer 20-1. In Fig. 0, 40 is a heat transfer layer, and 41-1 to 41-5 are not provided with a heat transfer layer. Part (cutting part), 42-1 to 4
Reference numeral 2-4 indicates a portion where a heat generating resistor layer is laminated. FIG. 5 shows a heat storage layer 20-2 on the heat transfer layer having the pattern shown in FIG. Heat generating resistance layers 21-1 to 21-3, protective layer 22, channel wall 25.
It is a YY sectional view of the head in which the lid substrate 14 is laminated. As can be seen from these, each heating resistance layer 21-1.21-
2. A heat transfer layer is provided below 21-3, but since there is an incision between adjacent heat generating resistor layers, for example 1
The heat generated in the heat generating resistor layer 21-1 is transmitted through the heat transfer layer to the adjacent heat generating resistor layer 21-2.
If bubbles are generated even though layer 2 is not driven, or if heat generating resistor layers 21-1 and 21-2 are driven at the same time or with a slight time difference, the ejection characteristics may be affected ( In addition, heat is radiated from each heat generating resistor layer along the flow path direction, which satisfies the purpose of the heat transfer layer described above. The above crosstalk appears more prominently as the distance between the heating elements becomes shorter.

With the heat transfer layer pattern as shown in Figure 4, the above-mentioned (c) and (d)
) was made and the droplet velocity was evaluated. The number of heating elements in the head is 512, the arrangement density is 16, the driving voltage and pulse width are the same, and the driving frequency is 5KHz.
and each heating element was driven simultaneously. The results are shown in Table 2.

As can be seen from these results, even though the H dynamic frequency was made stricter, the variation in droplet velocity was reduced to 5% or less.

In the embodiment of the present invention, a pattern as shown in FIG. 4 is used, but all patterns as shown in FIG. 6 suitably realize the present invention.

In Fig. 6, (a) shows a structure in which many small cuts are provided in the heat transfer layer between the heat generating parts to reduce the lateral heat transfer efficiency, and (b)
(C) has a cut-out part that is sufficiently longer than the heat generating part.
The heat transfer layer is separated into each heat generating part.

In addition, in the present invention, since there is a cut next to the heat generating part that expands the most, this cut serves to absorb thermal expansion, and there is no need to consider thermal expansion as described above. In addition, in the case of a material with low thermal expansion as described above, it also has the characteristic that the stability in the discharge direction is further increased. especially.

In the case of FIGS. 6(b) and (c), that is, when the cut portion is sufficiently longer than the length of the heating element (for example, twice or more), or
When the heat transfer layer is separated for each heating element, there is almost no need to consider thermal expansion.

FIG. 7 is a diagram showing yet another bubble generating means. In this example, a pair of discharge electrodes 7o arranged on the inner wall side of the thermal energy application section receive a high voltage pulse from a discharge device 71, A discharge is caused in the recording liquid, and the heat generated by the discharge instantly forms bubbles.

8 to 15 are diagrams showing specific examples of the discharge electrode shown in FIG. 7, respectively. In the example shown in FIG. 8, the electrode 70 is shaped like a needle to concentrate the electric field and efficiently It is designed to cause a discharge (with low energy).

In the example shown in FIG. 9, two flat plate electrodes are used so that air bubbles are stably generated between the electrodes. The position of one generated bubble is more stable than with a needle-shaped electrode.

The example shown in FIG. 10 is one in which the electrode has a substantially coaxial hole. The holes in the two electrodes serve as guides, making the position of one generated bubble even more stable.

The example shown in FIG. 11 is a ring-shaped electrode, which is basically the same as the example shown in FIG. 10, and is a modified example thereof.

In the example shown in FIG. 12, one side is a ring-shaped electrode and the other side is a needle-shaped electrode. The ring-shaped electrode aims to stabilize the generated bubbles, and the needle-shaped electrode aims to improve efficiency by concentrating the electric field.

In the example shown in FIG. 13, one ring-shaped electrode is formed on the wall surface of the thermal energy application section. In addition to the effects of the example shown in FIG. 12, this is aimed at ease of manufacturing by forming electrodes in a two-dimensional manner on the substrate. A plurality of such planar electrodes can be easily manufactured with high density by vapor deposition (or sputtering) or photoetching techniques. Particularly effective for multi-arrays.

The example shown in FIG.

The ring-shaped electrode forming portion of the example shown in FIG. 13 is shaped along the outer periphery of the electrode and is raised one step higher than the surrounding area. This is also aimed at the stability of a single generated bubble, and is more stable than the one shown in FIG. 12 by adding a three-dimensional guide.

The example shown in FIG.

Contrary to the example shown in FIG. 14, the ring-shaped electrode forming part is made to fall downward from the periphery, and as expected,
The generated bubbles are stably formed.

As is clear from the above explanation, the present invention has the following effects.

(1) In the liquid jet recording apparatus according to the first aspect, since the heat transfer layer is provided, good ejection performance can be obtained regardless of the type of substrate. In particular, in an ultra-high density multi-nozzle head of 16 nozzles/lll1 or more, good ejection performance can be obtained, whereas in the past it was impossible to eject due to accumulation. Furthermore, it becomes possible to use a substrate such as glass or alumina that can be obtained at low cost and with a large area, making it possible to obtain a full-line head at low cost. Extremely good heat dissipation can be achieved even in high frequency drive exceeding 4 KHz.

(2) As claimed in claim 2, between the heat energy and energy generators,
Using a liquid jet recording device that has a part without a heat transfer layer, ultra-high density of 16 lines/mm or more is achieved at 4 KHz.
Good ejection can be achieved even if the drive exceeds the above. In addition, it is possible to extremely reduce variations in droplet velocity and perform stable ejection without causing crosstalk due to heat. Further, it is possible to perform good ejection without causing variations in the ejection direction due to thermal expansion of the heat transfer layer.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining an embodiment of a liquid jet recording apparatus according to the present invention, and is a diagram for explaining the configuration of a bubble generating means using a heating resistor. (a) is a partial front view of the recording head as seen from the orifice side, (b) is a partial view taken along the line X-X in (a), and Figure 2 shows ink ejection by bubble jet. 3 is an overall perspective view of the bubble jet recording head, FIG. 4 is a diagram showing an example of the heat transfer layer pattern of the present invention, and FIG. 6(a) to 6(c) are diagrams showing other patterns; FIG. 7 is a diagram for explaining an example of a bubble generating means using electric discharge; FIGS. 8 to 15 are views showing specific examples of the discharge electrode shown in FIG. 7, respectively. 13... Substrate, 14... Lid substrate, 15... Orifice, 1G... Liquid discharge part, 17... Heat action part, 18
...Heat generation part, 19... Heat action surface, 20... Lower layer, 20-1... Heat transfer Jef, 20-2... Heat storage layer, 21... Heat generating resistance layer. 22... Protective layer, 23.24... Electrode, 25...
channel wall. Patent Applicant: Ricoh Co., Ltd. Figure 1 (b) Figure 3 □ Figure 2 Figure 4 (e) O =: tQI Figure (b > Figure (C) Figure Figure Figure Figure Figure Figure figure

Claims (1)

[Scope of Claims] 1. An ejection orifice for ejecting recording liquid as droplets, a liquid path communicating with the ejection orifice, and thermal energy for applying thermal energy to the recording liquid in the liquid path. In the liquid jet recording device, the thermal energy generating body is provided on a lower layer laminated on a substrate, the lower layer comprising at least a heat storage layer and a heat transfer layer. A liquid jet recording device featuring: 2. It has an ejection orifice for ejecting the recording liquid as droplets, a liquid path communicating with the ejection orifice, and a thermal energy generator for applying thermal energy to the recording liquid in the liquid path. In the liquid jet recording device, the thermal energy generating body is provided on a lower layer laminated on a substrate, and the lower layer includes at least a heat storage layer and a heat transfer layer, wherein the heat transfer layer is at least adjacent to the lower layer. A liquid jet recording device characterized in that it has a portion that is not provided between the matching thermal energy generating bodies.