JPS60206655A - Liquid jet recording head - Google Patents

Abstract

PURPOSE:To maintain stabilized characteristics of liquid drop formation of an initial stage for a long time by establishing a surface roughness of the portion, at least, in which a liquid flow path in a substrate is provided as Ra<=0.1mum where an average roughness of the centerline according to Japanese Industrial Standard is Ra. CONSTITUTION:Pertaining to a liquid jet recording head of the type in which liquid drips are formed and discharged by an electrothermal converter 4, by maintaining the surface smoothness of a substrate below 0.1mum when an average roughness is Ra by the indication as defined by JIS (Japanese Industrial Standard), an overall durability is enhanced and yield rate of production is improved. The portion in which the surface roughness Ra is maintained below 0.1mum may be the whole surface area of the substrate, but the portions that are necessary for durability and production process are the areas under electrodes 12,13 or a heat generating resistor layers 11 that have a probability of contacting the liquid, and for the practical purposes it is sufficient enough to keep the surface smooth where there are concerned with the liquid such as a liquid chamber, liquid flow path, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a liquid jet recording head that performs recording by jetting liquid to form flying droplets.

[Prior art]

Liquid jet recording methods such as inkjet recording generate very little noise during recording, which can be ignored.
It has recently attracted attention because it is capable of high-speed recording and can be recorded on plain paper without the need for special processing such as fixing.

Among them, for example, the liquid jet recording method described in Japanese Patent Application Laid-Open No. 54-51837 and German Opening Publication (DOLS) No. 2843064 applies thermal energy to the liquid to generate the driving force for ejecting droplets. This method has different characteristics from other liquid jet recording methods in terms of the amount of information obtained.

That is, in the recording method disclosed in the above-mentioned publication, the liquid subjected to the action of thermal energy undergoes a state change accompanied by a sudden increase in volume, and the acting force based on this state change causes the tip of the recording head to change. Liquid is ejected from the orifice, and recording is performed by making flying droplets that are formed at this time adhere to a recording member.

In particular, the liquid jet recording method disclosed in DOL32843064 is
Since a recording head with a mancl orifice can be easily implemented, it has the feature that high resolution and high quality images can be obtained at high speed.

The recording head section of the device applied to this recording method includes an orifice provided for ejecting liquid, and a heat exchanger that communicates with the orifice and is a part where thermal energy acts on the liquid to eject droplets. The apparatus includes a liquid discharge part having a liquid flow path of which the action part is a part of the structure, and an electrothermal converter as a means for generating thermal energy.

This electrothermal converter includes a pair of electrodes, and a heat generating resistor layer connected to these electrodes and having a heat generating part in the Ichinose region that generates heat between these electrodes.

A typical example of the structure of such a liquid jet recording head is shown in the first example.
It is shown in Figure (A) and Figure 1 (B).

Here, 1 is a recording head for ejecting liquid, 2 is a substrate thereof, and 3 is a communication hole through which a recording liquid flows to the head. Furthermore, electrothermal converters 4 that generate thermal energy are arranged at predetermined intervals on the substrate 2, and three sides of these electrothermal converters 4 are arranged in a zigzag shape as shown in FIG. 1(A). A liquid flow path section 6 having a predetermined depth and width is further surrounded by the surrounding wall member 5 and has a predetermined depth and width.
A liquid chamber portion 8 is formed by the peripheral wall member 7 and the peripheral wall member 7.

Reference numeral 9 denotes a liquid discharge hole, that is, an orifice, which is formed at the upper surface of the electrothermal converter 4, that is, at the position of the discharge plate 10, which is directly above the heat acting surface 4A where the converter 4 maintains contact with the liquid. In the portion of the liquid flow path section 6 interposed between the heat acting surface 4A and the orifice 9, bubbles are generated in the liquid that has been supplied with generated thermal energy from the electrothermal converter 4 to increase its volume. A heat action area 6A is configured to cause rapid expansion and contraction.

Further, the electrothermal converter 4 includes a heat generating resistor layer 11 attached to the upper surface of the substrate 2 as shown in FIG.
and an individual electrothermal converter 4 and a selection electrode 13 for selectively generating heat from the FL, where the common electrode 1
2 and the selection electrode 13 are arranged so as to extend from the liquid chamber part 8 formed on both sides of the member 5 to the liquid flow path part 6, respectively.

Thus, the common electrode 12 and the individual selection electrodes 13 are electrically connected to the heating resistance layer 11, thereby forming the stain heat transfer converter 4, and the electrothermal converter formed in this way An upper layer 14 is further formed on the upper surface of the body 4 and the upper surface of the electrode 12.13, and the upper layer 14 fills the liquid flow path section 6 including the heat action area 6A with the heating resistance layer 11. The electrodes 12 and 13 are kept so as not to cause a chemical or physical reaction when they come into contact with the liquid, and are also prevented from short-circuiting between the electrodes 12 and 13 via the liquid. In the following description, the electric converter 4 and the upper layer 14 that covers its upper surface are referred to as the heat generating section 24, and the heat acting area 6A is also referred to as the heat generating section 24.
and the orifice 9 are collectively referred to as a liquid discharge section 25.

Furthermore, the upper layer 14 also has the role of preventing electrical leakage between adjacent electrodes, and in particular,
To prevent electrical leakage between each selection electrode 13, or to prevent electrical leakage caused by the electrodes 12 and 13 below each liquid flow path 6 coming into contact with the liquid for some reason and energizing them. Preventing corrosion is important, and for this purpose, an upper layer 14 having the function of a retention layer is provided at least on the electrodes 12 and 13 below the liquid flow path.In particular, The liquid flow path section 6 provided in each liquid discharge section 25 is
Upstream of each liquid discharge part 25, each liquid discharge part 25 communicates with each other via a common liquid chamber part 8 that constitutes a part of the flow path.
An electrode 12 connected to an electrothermal converter 4 provided in
and 13 is the heat action area 6A due to its design convenience.
Since the electrodes 12 and 13 are provided so as to pass under the common liquid chamber 8 on the upstream side of the
It was necessary to prevent the liquid from coming into contact with the liquid.

However, in a liquid jet recording head constructed in this way, the characteristics required for the upper layer 14 differ depending on the location where it is provided.

That is, for example, the heat generating part 24 is required to have excellent properties such as heat resistance, liquid resistance, liquid permeation prevention property, thermal conductivity, antioxidant property, and tear resistance. In other areas, it is required to have sufficiently excellent liquid permeation prevention properties, liquid resistance, and tear resistance, although they can be alleviated by thermal conditions.

By the way, there is currently no material for forming the upper layer 14 that fully satisfies all of the above-mentioned /ζ characteristics as desired.
Currently, some of these characteristics are relaxed.

That is, in the heat generating part 24, priority is given to heat resistance, thermal conductivity, and anti-oxidation property, while on the other hand, in the electrode coating part other than the heat generating part 24, priority is given to @j liquid property and liquid penetration prevention property. and tetanicity are priority conditions.

On the other hand, a substrate material such as ceramics is suitable for the substrate 2 because of its low cost, good workability, good electrical insulation and thermal conductivity, but in the case of a ceramic substrate, there are Since fine irregularities are formed, it is difficult to maintain coverage of the upper layer 14 at the stepped portions.

That is, if the coverage of the upper layer 14 is poor in relation to the roughness of the substrate surface, liquid may penetrate from that portion, causing electrolytic corrosion or electrical breakdown.

Therefore, taking these things into consideration, the surface of the substrate 2 should include at least the electrodes 12 and 13 and the heating resistor layer 11.
Smoothness is required that does not impair the coverage of the upper layer 14 at the portions that come into contact with the liquid.

However, there has been no conventional liquid jet recording head that has a substrate 2 and an upper layer 14 that satisfy all of these requirements, and that can comprehensively guarantee durability in use.

For example, Figures 2 (A), (B), and (C) show schematic cross sections of the substrate 2 in the conventional recording method in the order of their construction, and Figure 2 (4) shows the substrate 2 made of alumina ceramics. This is a cross section of a microscopic model of the main body of the board 2.

Therefore, 202 is a microcrystalline grain of alumina J, 203
is the binder and the void. FIG. 2(B) shows an electrothermal transducer 4 for performing liquid jet recording formed on the substrate 2 sintered in this way, where 11 is a heating resistance layer, 12A and 13A are heating resistance layers. This is an electrode layer. He's 14 years old.
is a retention layer, ie, an upper layer, for insulating the electrode layers 12A, 13A and the heating resistance layer 11 from liquid.

In the liquid contact portion of a liquid jet recording head formed through such a JJy shape sequence, as shown in FIG. 3(C),
Because defects 302 such as pinholes occur due to the surface roughness of the substrate 2 and the step coverage method, electrolytic corrosion is applied to the electrode layers 12A, 13A and the resistance layer 11 that come into contact with the liquid 210.
Furthermore, since the surface area of the resistance layer 110 is substantially large, a desired resistance value cannot be obtained, and the variation in resistance value becomes large due to the surface roughness.

Therefore, in order to solve these problems, it is conceivable to increase the thickness of the film laminated on the substrate 2, but from the viewpoint of thermal design, it is not permissible to simply increase the thickness.

〔the purpose 〕

In view of the above-mentioned points, the object of the present invention is to provide a liquid jet that has excellent overall durability in frequent repeated use and long-term continuous use, and is capable of stably maintaining good initial droplet formation characteristics over a long period of time. The purpose is to provide a recording head.

Furthermore, another object of the present invention is to provide a liquid jet recording head that is highly reliable in manufacturing and processing.

Furthermore, it is an object of the present invention to provide a liquid jet recording head that has a high manufacturing yield even when it has multiple orifices.

〔composition〕

In order to achieve such an object, the present invention includes an orifice for discharging a liquid to form flying droplets, a liquid flow path communicating with the orifice, and a liquid flow path provided on a substrate along the liquid flow path. In the liquid spray recording head having the liquid droplet and an energy generating body that generates energy for forming the liquid droplet, the surface roughness of at least the portion of the substrate where the liquid flow path is provided is equal to or less than the center line average roughness according to JIS. Ra in Ra
It is characterized by being ≦0.1 μm.

〔Example〕

Below, an example of forming such a smooth surface on a substrate will be explained with reference to the drawings, but before explaining the details, the basis for requiring such a smooth surface will be described. The layer 14 needs to have a thickness of 3 μm or less in view of the heat resistance required for the heat generating part 24. On the other hand, in order for the upper layer 14 to maintain its function as a retention layer, The present inventor has confirmed through experiments that the surface roughness of the substrate 2 on which the layer 14 is coated needs to be kept at 1/30 or less of the thickness of the upper layer 14 in terms of Ra.

Furthermore, regarding the resistance mll, the coverage of the upper layer 14 as a protective layer and the resistance layer 11 and the electrode layer 12 as described above are also considered.
Considering the efficiency of energy transfer between A and 13A, the film thickness must be kept at 3 μm or less, and from this point of view, the substrate surface roughness Ra should be determined by the film thickness of the upper layer 14. It is desirable to keep it at 1/30 or less.

Therefore, the present inventor has developed a liquid jet recording head of a type in which droplets are formed and ejected by the electrothermal transducer 4.
By keeping the surface smoothness of the substrate 2 at 0.1 μm or less in terms of Ra in 10-point average roughness specified by JIS, overall durability is increased and manufacturing yield is improved. I was convinced that I could do it.

Fig. 3 (4) shows a microscopic model of an example in which the surface roughness Ra < 0.1 μm has been obtained by polishing the surface of the substrate 2 of a conventional glass. By reducing the grain size, the surface smoothness can be reduced to Ra <
An example in which the thickness is set to 0.1 μm is shown. In other words, in Figure 3 (5), two people are using a smooth surface obtained by the polishing method.
In FIG. 3(B), 2B is a microcrystalline grain of alumina.

In this way, it is more desirable that the surface roughness Ra is 0.1 μm or less.

In addition, the part where the roughness Ra is kept at 0.1 μm or less may be the entire surface of the substrate 2, but the part that is necessary for durability and the manufacturing process should be the electrode that may come into contact with liquid. 12.1
3 or under the heat-generating resistor layer 11. Such work requires extremely fine processing technology, and in practical terms, it is necessary to process surfaces in a range related to liquid, such as the liquid chamber and liquid flow path. It is sufficient to hold it smooth.

In particular, it is preferable for the recording head 1 to have the surface of the substrate other than the liquid-contacted portion moderately curved, since this improves the degree of adhesion of the wiring to the substrate 2.

In this way, forming a smooth surface on the substrate 2 can be achieved by polishing the surface of the substrate 2 or by making the crystal grains forming the substrate 2 finer. The effects of the present invention can be obtained by, for example, making the substrate surface smooth by chemical etching.

However, in this case, if the etching rate between the binder and the crystal grains is not appropriately selected, a surface layer may form instead.

Furthermore, sputter etching using plasma in a vacuum, which is known as a physical etching method, or reactive plasma etching using a reactive gas or the like may be used.

Furthermore, the substrate 2 may be melted or the surface of the substrate may be smoothed by heating locally or only the surface layer to a high temperature. For example, there is also a method of heating using a laser or the like.

Furthermore, the substrate body can be constructed by providing a second substrate layer made of fine crystal grains on the normal substrate 2.

Furthermore, in the above explanation, the so-called side shooter type case in which the discharge direction is perpendicular to the electrothermal converter 4 has been described, but the so-called edge shooter type case in which the discharge direction is parallel to the electrothermal converter 4 has been described. It goes without saying that similar effects can be obtained with a type of liquid jet recording head.

Further, if necessary, an organic resin layer may be provided on the upper layer 14 to preserve defective portions, and a metal layer may be laminated to improve surface cavitation.

Through experiments, the inventor applied a rectangular voltage of 30 V of 10 pS to the electrothermal transducer 4 of the recording head 80
It was confirmed that the liquid was ejected from the orifice according to the applied signal by applying the signal at 0 Hz, and that flying droplets could be stably formed. In other words, in a conventional recording head using a substrate with poor planar smoothness, repeated formation of such droplets causes electrolytic corrosion of the At electrode and HfB2 resistor, and the resistance change rate of the resistor increases. Mainly, disconnection due to dielectric breakdown between electrodes,
The resistance value increases and ink stops being ejected, but
In this example, such failures can be prevented and the number of repetitions, that is, the number of durability can be increased.

Furthermore, when such a conventional substrate with poor smoothness is used, the yield during manufacturing is also reduced. The major causes of this are unevenness in resistance values, short circuits between electrodes and resistors, and work errors caused by difficulty in identifying pattern boundaries due to unevenness.According to the present invention, however, during manufacturing This also contributes to improved yields.

Table 1 below shows an example comparing the smoothness of the substrate surface, the yield rate, and the number of durability cycles.

Table 1 ◎ 90 inches or more Q 70% or more △ 50% or more ×
50% or less As is clear from the results in Table 1, the head of the present invention provided with a smooth layer was able to stably achieve durability of 10' cycles.

〔effect〕

As explained above, the flat 1'Tf property of the substrate of a liquid jet recording head is very important in the liquid contact area, and according to the present invention, the substrate surface has a JIS center line average roughness Ra of 0. A liquid jet recorder that is formed to a diameter of 1 μm or less, has excellent overall durability even under frequent repeated use and long-term continuous use, and can stably maintain good initial droplet formation characteristics over a long period of time. It is now possible to provide the head.

Furthermore, according to the present invention, not only the manufacturing yield but also the reliability can be significantly improved compared to the conventional method.

It goes without saying that the application of "Nao, Honmaru" is not limited to a recording head having a plurality of liquid ejecting orifices, but can also be applied to a recording head provided with a single orifice.

[Brief explanation of drawings]

FIG. 1(A) is a schematic exploded perspective view of an example of the configuration of a conventional liquid jet recording head, FIG. 1(J3) is a sectional view taken along line X-X, FIG. 2(A) and (B) is a cross-sectional view schematically showing the bonding state of fine particles on the surface of the substrate with only the substrate and with a seed layer formed on the substrate, and Figure 2 (0) is Figure 2 CB. 3(A) is a cross-sectional view schematically showing a state in which electrolytic corrosion occurs in the liquid-contacted part in the formation form shown in FIG. FIG. 3 is a cross-sectional view schematically showing a state in which the surface of the substrate can be bonded with microcrystalline particles. 1... Recording head 2... Substrate 2A... Polished surface 2B... Microcrystalline particle 3... Communication hole 4... Electrothermal converter 4A... Heat action surface 5... Surrounding wall Member 6... Liquid flow path section 6A... Heat action area 7... Surrounding wall member 8... Liquid chamber section 9... Orifice 10... Discharge plate 11... Resistance layer 12.13. ... Electrodes 12A, 13A, Electrode layer 14, Upper layer 24, ° Heat generating part 25, Liquid discharge part 202, Microcrystalline grains 203, Binder and cavity 210, Liquid 310 Defect part.

Claims (1)

[Scope of Claims] An orifice for ejecting liquid to form flying droplets, a liquid flow path communicating with the orifice, and a liquid flow path provided on a substrate along the liquid flow path to form the droplets. In the liquid jet recording head, the surface roughness of at least the portion of the substrate where the liquid flow path is provided satisfies a centerline average roughness Ra according to JIS of Ra≦0. A liquid jet recording head characterized in that the diameter is 1 μm. (Margin below)