JP2507998B2 - Liquid crystal device - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a liquid crystal device.

[Technical background of the invention and its problems]

2. Description of the Related Art Recently, in optical writing in an optical writing type printer, image formation in a television receiver, and the like, a liquid crystal device in which a large number of minute shutter portions for controlling light transmission are arrayed is used.

This liquid crystal device is called a liquid crystal shutter and has a transparent substrate on which a large number of signal electrodes are arranged and a transparent substrate on which a common electrode is formed so as to face the signal electrodes so that the electrode formation surface is on the inside. It is configured to be opposed to each other with a liquid crystal interposed therebetween. That is, the signal electrode formed on one substrate and the common electrode formed on the other substrate respectively have a transparent electrode deposited on the surface of the substrate and exclude the portion (shutter electrode) through which light is transmitted to the surface of this transparent electrode. A liquid crystal that is formed by depositing a metal film on the transparent electrode in the signal electrode and the light transmitting portion of the transparent electrode in the common electrode facing the signal transmitting portion and both the light transmitting portions. A large number of shutter parts are formed in an array by. Then, by applying a voltage between the signal electrode and the common electrode to control the behavior of the liquid crystal molecules, each shutter part can be opened or closed.

Thus, in this liquid crystal device, the metal film deposited on the signal electrode and the transparent electrode of the common electrode defines the light transmitting portion of the transparent electrode, that is, the shutter electrode, and also serves to reduce the resistance of the electrode. .

Conventionally, in order to form a signal electrode and a common electrode on a substrate, a transparent electrode is formed on the entire surface of the substrate by a sputtering method or the like, then a metal film is formed on the entire surface of the transparent electrode by an evaporation method, and then photoetching is performed. By using the method, unnecessary portions of the transparent electrode and the metal film are removed to form a signal and a common electrode having a predetermined pattern.

However, in such a conventional electrode, since the metal layer is formed by the vapor deposition method, a vapor deposition apparatus is required to form the metal film, which requires a large manufacturing facility, and even for a large number of substrates at one time. It is not suitable for mass production because it is difficult to form a metal film by vapor deposition. Therefore, the conventional liquid crystal device has a problem in terms of equipment and productivity in forming the electrode provided on the substrate.

[Object of the Invention]

The present invention has been made based on the above circumstances, and an object of the present invention is to provide a liquid crystal device in which electrodes provided on a substrate can be formed with good productivity without using large-scale equipment, and the characteristics of the electrodes are improved. To do.

[Outline of Invention]

The liquid crystal device of the present invention, the transparent one substrate provided with an electrode, and the other transparent substrate provided with an electrode facing the electrode, the electrode formation surface is disposed inwardly facing each other through the liquid crystal,
In a liquid crystal device that constitutes a shutter unit that controls light transmission by electrodes facing each other of the both substrates and the liquid crystal, one of the electrodes of the both substrates is formed on a surface of the substrate. Transparent electrode, and a metal layer formed by chemical plating on the surface of the transparent electrode,
It is characterized in that the surface layer of the metal layer is composed of at least two conductive films including another metal layer formed by chemical plating by a substitution reaction.

Example of Invention

 The present invention will be described below with reference to embodiments shown in the drawings.

3 to 6 show an embodiment of a liquid crystal device, that is, a liquid crystal shutter of the present invention.

In the figure, 1 and 2 are substrates made of transparent glass plates.
Are opposed to each other and are mounted via a frame-shaped outer seal material 3 and linear inner seal materials 4, 4. A liquid crystal LC, for example, a liquid crystal for guest-host effect, is filled in a portion sandwiched between the inner sealing materials 4 and 4 in the gap between the substrates 1 and 2 and both ends of the outer sealing material 3.

On the inner surface of one substrate 1, a large number of signal electrodes S ... Are arrayed in the longitudinal direction at intervals. Signal electrode S ...
Is composed of the transparent electrode 5 and the metal film 6, and the transparent electrode 5
Is double-bonded to the inner surface of the substrate 1, and has two shutter electrodes 7 and 7 which are light transmitting portions located inside the inner sealing materials 4 and 4 and a terminal 8 which is led out to the outside of the outer sealing material 3 in one body. , The terminals 8 of the transparent electrodes S ... Are formed so as to lead out alternately left and right. The metal film 6 is deposited on the surface of the transparent electrode 5 other than the shutter electrodes 7, 7. The signal electrode S will be described later in detail. Incidentally, 9 is an alignment film formed on the inner surface of the substrate 1.

On the inner surface of the other substrate 2, two strip-shaped common electrodes are provided.
C and C are formed along the longitudinal direction, and this common electrode C and C
Is a row of one shutter electrode 7 ... And terminals 8 ... and the other shutter electrode 7 in each signal electrode S ... Of the substrate 1.
, And the terminals 8 ... Common electrode C, C
Is composed of a strip-shaped transparent electrode 10 adhered to the inner surface of the substrate 2 and a metal film 11 adhered to the surface of the transparent electrode 10, and the shutter of the signal electrodes S ... Portions facing the electrodes 7, ..., 7 are opened respectively, and each portion of the transparent electrode 10 facing the openings in the metal film 11 is formed as a large number of shutter electrodes 12 ,. ing. The common electrodes C, C will be described later. Note that 1
Reference numeral 3 is an alignment film formed on the inner surface of the substrate 2.

The shutter electrodes 7 ..., 7 ... of the signal electrodes S.
And the shutter electrode 12 of the common electrodes C, C facing this
, 12, and a large number of shutter parts A ..., A ...
Are configured and arranged.

Next, the signal electrodes S provided on the substrate 1 and the common electrodes C, C provided on the substrate 2 will be described.

First, the signal electrode S will be described with reference to FIG. The transparent electrode 5 is made of a material obtained by adding tin to indium oxide (In ₂ O ₃ ), and is formed on the surface of the substrate 1 by sputtering or the like to have a thickness of 200 to 300 Å. The metal film 6 is composed of a nickel layer 6A formed on the surface of the transparent electrode 5 by chemical plating by reduction reaction, and a metal 6B formed on the surface of the nickel layer 6A by chemical plating by substitution reaction, that is, displacement plating. is there. The thickness of the nickel layer 6A is approximately
The thickness of the metal layer 6 was 1100Å, the thickness of the gold layer 6B was about 900Å, and the total thickness of the metal film 6 was 2000Å. It is preferable that the thickness of the metal film 6 does not exceed 2500Å because the thin metal film 6 does not have a low resistance when it is thin, and the thick liquid crystal LC is disordered at the edge of the metal film 6. Therefore, the edge of the shutter portion A becomes unclear. The signal electrode S is formed by the following method. First, the transparent electrode 5 is formed on the surface of the substrate 1 by patterning into a predetermined signal electrode shape. Next, the surface of the transparent electrode 5 is activated by using palladium chloride and a reducing agent for pretreatment. Then, the substrate 1 is immersed in the plating solution of the plating bath, and the nickel layer 6A is formed on the surface by chemical plating by the reduction reaction of the transparent electrode 5. The plating solution contains metal salts (supplying metal ions necessary for plating), reducing agents (reducing and precipitating metal ions as metals), and buffering agents (precipitation of metal ions and changes in PH due to oxidation of reducing agents). Suppress)). In this case, due to the difference in redox potential between the surface of the substrate 1 and the transparent electrode 5, the transparent electrode 5
Nickel deposits only on the surface. Next, the substrate is immersed in a plating solution of a plating bath for displacement plating to perform displacement plating. In this case, the metal salt in the plating solution contains potassium cyanide and nickel cyanide, and due to the difference in ionization tendency, the surface of the nickel layer 6A is replaced with gold to form the gold layer 6B. According to the method of forming the metal film 6 on the surface of the transparent electrode 5 thus patterned, compared with the method of patterning the transparent electrode and the metal film on the entire surface of the substrate 1 and then patterning the metal. It is economical because it does not waste the expensive metal forming the film 6.

In the signal electrodes S ...
Is a surface layer because the gold layer 6B is formed on the surface of the transparent electrode 5 by reduction plating. The metal 6B can be firmly formed. The reason why the nickel layer is used as the base of the metal film 6 is that it has good adhesiveness to the transparent electrode, and that the surface layer is made of gold has a low electrode resistance and is stable to the external atmosphere. Because there is. The metal film 6 has a two-layer structure of nickel and gold and has a sheet resistance of 0.7Ω / Sg. This sheet resistance is much smaller than the sheet resistance 3 Ω / sg (film thickness 2000 Å) of the metal film made of chromium of the signal electrode in the conventional liquid crystal display device. Therefore, even if the number of the signal electrodes S increases, the resistance of the entire signal electrodes S can be suppressed to be low, and heat generation and driving waveform distortion due to the increase in resistance can be prevented.

Further, the common electrode C has the same structure as the signal electrode S. That is, as shown in FIG. 2, the metal film 11 includes a nickel layer 11A formed on the surface of the transparent electrode 10 by chemical plating utilizing a reduction reaction, and a gold layer 11B formed on the surface of the nickel layer 11A by displacement plating. It consists of and. Therefore, the same effect as in the case of the signal electrodes S ... Can be obtained.

In the liquid crystal display device thus configured, however, the metal film provided on the surface of the transparent electrode in the signal electrodes S ... and the common electrodes C, C is formed by chemical plating, that is, electroless plating. The equipment for forming the metal film is simple as compared with the case where the metal film is formed by electrolytic plating. Further, since the chemical plating is performed in an open atmosphere, a large amount of the object to be plated can be plated, and a large amount of metal film can be formed efficiently. Furthermore, by adopting chemical plating, it is possible to form a metal film having a constant film thickness and no pinhole. In addition,
The reason why chemical plating is used to form a metal film of an electrode provided on a substrate used for a liquid crystal display device is as follows. The signal electrode and the common electrode are separated from each other. Particularly, since the signal electrode is composed of an extremely large number of electrodes, it is difficult to electrically connect the electrodes, so that electrolytic plating cannot be performed. Since the resistance of the transparent electrode is large, a sufficient current cannot be passed by electrolytic plating, and the current value of each part of the transparent electrode is different, so that plating with a uniform film thickness cannot be performed.

Further, since the surface metal layer is formed by displacement plating on the surface of the metal film formed by reduction plating, the surface metal layer can be firmly formed and the durability of the metal film can be improved.

In addition, when forming the electrode on the substrate, it is not limited to the case of forming the metal film after patterning the transparent electrode,
It is also possible to adopt a method in which a transparent electrode is formed on the entire surface of the substrate, then a metal film is formed on the entire surface of the transparent electrode, and finally the metal film and the transparent electrode are patterned into an electrode shape.

Further, the electrode structure of the present invention may be applied to the electrodes provided on at least one of the pair of substrates.

〔The invention's effect〕

As described above, according to the liquid crystal device of the present invention, the electrode provided on the substrate, the transparent electrode formed on the substrate surface, the metal layer formed by chemical plating on the surface of the transparent electrode, and the surface of the metal layer Since the layer is composed of at least three conductive films including another metal layer formed by chemical plating by substitution reaction, the equipment for forming the metal film can be simplified, and the metal film can be formed in a large scale. You can do it efficiently. In addition, the metal film can have a metal layer strongly formed on the surface by displacement plating to improve durability.

[Brief description of drawings]

The drawings show an embodiment of the liquid crystal device of the present invention. FIGS. 1 and 2 are sectional views showing enlarged electrodes provided on a substrate, and FIG. 3 is a line III-III in FIG. 4 showing the liquid crystal device. FIG. 4 is an enlarged cross-sectional view taken along line 4, FIG. 4 is a plan view showing the inner surface of the signal electrode substrate,
FIG. 6 is a plan view showing the inner surface of the common electrode substrate, and FIG. 6 is an enlarged plan view showing the shutter portion. 1 ... Substrate, 2 ... Substrate, 5 ... Transparent electrode, 6 ... Metal film, 10 ...
Transparent electrode, 11 ... Metal film, LC ... Liquid crystal, S ... Signal electrode, C ...
Common electrode.

Claims (3)

(57) [Claims] 1. A transparent one substrate provided with an electrode and another transparent substrate provided with an electrode facing the electrode are arranged so as to face each other with a liquid crystal therebetween with an electrode formation surface inside. In a liquid crystal device that forms a shutter unit that controls light transmission by electrodes facing each other and the liquid crystal, one of the electrodes of the both substrates is transparent formed on the surface of the substrate. An at least three-layer conductive film consisting of an electrode, a metal layer formed on the surface of the transparent electrode by chemical plating, and another metal layer formed on the surface layer of the metal layer by chemical plating by a substitution reaction A liquid crystal device having a structure. 2. The conductive film comprises a transparent electrode, a nickel layer formed on the surface of the transparent electrode by chemical plating by a reduction reaction, and a surface of the nickel layer replaced by chemical plating by a substitution reaction. The liquid crystal device according to claim 1, wherein the liquid crystal device is formed of 3. The liquid crystal device according to claim 1, wherein the metal layer and the other metal layer are formed on the surface of the patterned transparent electrode.