JPH07146657A - Flat panel type display device and its production - Google Patents

Abstract

PURPOSE:To use PLZT with simple constitution and to enable driving with a low voltage by packing a PLZT layer into the respective spacings between one set of matrix-form electrodes on a transparent substrate and providing both outside surfaces of the transparent substrate with polarizing plates. CONSTITUTION:Both surfaces of the display substrate 7 constituted by providing both sides of the PLZT layer 4 which is a ferroelectric substance with the electrodes 2a, 2b and forming respective pixels in a matrix form are provided with the polarizing plates 8a, 8b and further the rear surface side is provided with a light source 9. Namely, both of the one comb-shaped electrode 2a and the other comb-shaped electrode 2b of one set of the electrodes on one substrate are formed to a comb shape and the respective comb teeth are arranged with each other to provide the structure that these teeth face each other. The PLZT layer 4 is so deposited as to coat the spacings between the comb teeth facing each other of both comb-shaped electrodes 2a, 2b and the respective comb teeth. Then, the secondary electro-optic effect of the PLZT is obtd. by impressing a voltage between one set of these electrodes 2a, 2b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat panel type display device and its manufacturing method. More details, PLZT
The present invention relates to a flat panel type display device using OLED and its manufacturing method.

[0002]

2. Description of the Related Art As a flat panel type display device, a light emitting type LED or plasma display (PDP) is used, or a light receiving type liquid crystal display device (LCD) is used. The light emitting type generally consumes a large amount of electric power, and a liquid crystal display device which consumes a small amount of electric power has recently been conveniently used.

This liquid crystal display device, as shown in FIG.
For example, two transparent substrates 21 and 22 made of glass or the like are provided with electrode films 23 and 24 made of ITO or SnO ₂ and alignment films 25 and 26 made of polyimide, respectively. , 22 are stuck in a certain space,
A liquid crystal material is filled in the gap to form a liquid crystal layer 28,
Polarizing plates 29 and 29 are provided on both sides of the two transparent substrates 21 and 22, respectively.
30 is provided, and the backlight 31 is arranged on the back surface side of the display surface.

In this liquid crystal display device, the change in the orientation of the molecules of the liquid crystal caused by the voltage applied to both electrode films 23 and 24 and the light transmittance of the backlight 25 disposed on the back surface side by the polarizing plate are Characters and figures that are changed and assembled with pixels are displayed.

On the other hand, a transparent ceramic P which is a ferroelectric substance
Since the light transmittance and the refractive index of LZT are easily controlled by an electric field, LZT has attracted great attention as an electro-optical material such as an optical shutter.

PLZT is a ceramic obtained by adding a small amount of lanthanum oxide (La ₂ O ₃ ) to lead zirconate titanate (Pb (Zr _1-x Ti _x ) O ₃ ) (Pb
_1-y La _y ) (Zr _1-x Ti _x ) O ₃ is meant.

The secondary electro-optical effect of PLZT is as shown in FIG. 9, in which a PLZT layer 10 is arranged between two polarizing plates 11 and 12 whose polarization directions are orthogonal to each other, and the PLZT layer 10 has a This is a phenomenon in which, when an electric field orthogonal to the traveling direction is applied, the light transmittance changes depending on the angle θ between the linearly polarized light that has passed through the polarizing plate 11 (hereinafter referred to as incident polarized light) and the electric field direction. The transmitted light becomes maximum when the angle θ between the incident polarized light and the direction of the electric field is 45 °, and the transmitted light becomes 0 when the angle θ is 0 ° or 90 °. It is known that the applied voltage V that gives the maximum transmitted light is given by the following equation.

V = d {λ (2k−1) / (n ³ Rt)} ^1/2 (1) where d is the thickness of the PLZT in the direction of electric field application, λ is the wavelength of incident light, and k is a positive value. An integer, n is the refractive index of PLZT (about 2.5), R is a quadratic electro-optic coefficient determined by the composition of PLZT, and t is the thickness of the incident light of PLZT in the traveling direction (optical path length).
Is.

Utilizing this property, an optical shutter for turning on / off light transmission has been considered (for example, "Transparent Ceramics PLZT-Application as Optical Shutter" by Murano, Solid State Physics, Vol. 21, Vol. No. 9, 1986). Examples of the application of this optical shutter include an example of a color separation electronic shutter of a color viewfinder, that is, an example of converting an image of a black and white cathode ray tube into a color image using a three primary color separation color filter and a PLZT electronic shutter, and an application example to a PLZT projector. It is disclosed in the same paper.

[0010]

However, in the optical shutter using the PLZT as described above, the applied voltage derived from the equation (1) must be made extremely high, and it is easy to operate at a low voltage such as in a liquid crystal display device. It is not suitable for use as a display device and has not been put to practical use.

On the other hand, in a liquid crystal display device, a liquid crystal material has to be filled in a narrow gap of a transparent substrate, which requires a large number of manufacturing steps, a small number of manufacturing steps, and a flat panel type display using PLZT which is highly reliable. Development of the device is desired.

The present invention solves such a problem and provides a PLZ
An object of the present invention is to provide a flat panel type display device having a simple structure that can be driven at a low voltage by using T.

[0013]

In the display device of the present invention, a set of electrodes is provided in a matrix on a transparent substrate, and a space between the electrodes of the set is filled with a PLZT layer.
Polarizing plates are respectively provided on both outer surfaces of the transparent substrate.

The fact that the one set of electrodes is formed in a comb shape and the comb teeth of the comb-shaped electrodes are alternately arranged so as to face each other makes it possible to reduce the electrode gap and reduce the gap. It is preferable to efficiently emit light in the pixel with a voltage.

The PLZT is composed of PbZrO ₃ and Pb.
It is preferable that the composition of TiO ₃ and La is formed to have a memory effect so that the display image can be stored as it is.

According to the method of manufacturing a flat panel type display device of the present invention, (a) one set of electrodes forming each pixel is formed in a matrix on a transparent substrate and the one set of electrodes of each pixel arranged in one direction is formed. Forming a first wiring connecting one of the electrodes, (b) depositing a PLZT layer on the transparent substrate provided with the one set of electrodes, and (c) depositing a PLZT layer on the other electrode of the one set of electrodes. The PLZT contact hole is provided for making contact.
A second wiring connected to the other electrode of the pair of electrodes through the contact hole, and (e) polarizing plates provided on both surfaces of the transparent substrate. It is a thing.

Further, in another method of manufacturing the flat panel type display device of the present invention, (f) a plurality of second wirings extending in one direction are provided in parallel between the pixels on the transparent substrate, and (g) a second wiring. An insulating film is provided on the transparent substrate provided with wiring, and then a contact hole for making contact with the second wiring is provided in the insulating film, and (h) each pixel is formed between the second wirings. Forming a plurality of one set of electrodes, and forming a first wiring connecting one electrode of the one set of electrodes of each pixel arranged in a direction intersecting with the second wiring, and
The other electrode of the set of electrodes is connected to the second wiring through the contact hole, (i) a PLZT layer is deposited on a transparent substrate provided with the set of electrodes, (j) Polarizing plates are provided on both outer surfaces of the transparent substrate.

[0018]

According to the present invention, since PLZT is filled between a pair of electrodes provided on a transparent substrate, a secondary electro-optical effect of PLZT can be obtained by applying a voltage to the pair of electrodes. Therefore, it operates as a display device with a simple structure.

Further, one set of electrodes of each pixel is formed in a comb shape so that comb teeth are alternately arranged to face each other, and a PLZT layer is deposited between the one set of electrodes to form a narrow electrode gap. It is possible to apply an electric field to the PLZT layer with a
It can obtain the secondary electro-optical effect of LZT, can be driven at a low voltage, and operates as a display device having a large aperture ratio.

Further, it can be manufactured simply by patterning electrodes on the transparent substrate, depositing PLZT, and providing contact holes for contacting the wiring. The number of manufacturing steps is very simple and the reliability of PLZT is improved because it is not damaged. .

Further, the first wiring and the second wiring are provided via an insulating film of silicon nitride or the like, and PLZ is formed thereon.
By depositing the T layer, it is not necessary to provide a contact hole in the PLZT layer which is difficult to process.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for manufacturing a display device of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory view of one pixel of a manufacturing process of a display substrate of an embodiment of a flat panel type display device of the present invention, FIG. 2 is a sectional view taken along the line AA of FIG. 1D, and FIG. 1D is a cross-sectional explanatory view taken along the line BB, FIG. 4 is a plan explanatory view showing the arrangement of pixels of the flat panel type display device of the present invention, and FIG. 5 is a side view thereof.

The flat panel type display device of the present invention is shown in FIG.
As shown in a plan view and a side view in FIG. 5, polarizing plates 8a and 8b are provided on both sides of a display substrate 7 in which electrodes are provided on both sides of a PLZT layer which is a ferroelectric substance and each pixel is formed in a matrix. Is provided, and the light source 9 is further provided on the back surface side.

The relationship between PLZT and electrodes of each pixel is shown in FIG.
The structure is shown in FIG. 2D and FIG. That is, one comb-shaped electrode 2a and the other comb-shaped electrode 2b of one set of electrodes on one substrate are both formed in a comb shape, and the comb teeth are alternately arranged to face each other. , The gap between the comb teeth of the two comb-shaped electrodes 2a and 2b facing each other, and the PLZT layer 4 so as to cover them.
Have been deposited. As described above, in order to give the PLZT layer an electro-optical effect, the applied voltage given by the above equation (1) is required, and for example, 0.53 mm.
A large voltage of about 160 V must be applied with an electrode gap of about 5 to 10 V as in a normal liquid crystal display device.
In order to operate the PLZT at a certain degree, the thickness (electrode interval) d of the PLZT in the direction of applying an electric field must be about 0.5 to 1.5 μm. As a result of intensive studies by the present inventors in order to form a PLZT having a narrow width between electrodes, as shown in FIG. 1D, a pair of electrodes on one substrate are formed in a comb shape. , PL that contributes to the display over a wide area in the pixel by narrowing the electrode gap by arranging the comb teeth alternately so as to face each other
It has been found that a ZT layer is provided.

First, the dimension of the width d (see FIG. 3) between the electrodes in the electric field direction of the PLZT layer 4 for operating at a low voltage will be examined. With the thickness t of the PLZT layer 4 in the incident light direction as a parameter, the wavelengths of the incident light are 350 nm and 800 nm.
Consider the following two points.

Tables 1 and 2 show the wavelength λ (nm) of the incident light, the thickness t (μm) of the comb-shaped electrode, and the distance d between the pair of comb-shaped electrodes.
(Μm) and the applied voltage V are shown in the table. The numerical values in the table are the comb-shaped electrode spacing d (μm) that gives the maximum transmitted light.
Is shown. Table 1 shows the case where the electrode thickness t = 1 μm, and Table 2 shows the case where the comb-shaped electrode thickness t = 0.5 μm.

[0027]

[Table 1]

[0028]

[Table 2]

From all the tables, the distance d between the comb-shaped electrodes is proportional to the applied voltage V, and the distance d between the comb-shaped electrodes is 1/2.
Therefore, it can be seen that the applied voltage V may be 1/2.

Therefore, the width of each electrode is 2 to 3 μm, and the electrode gap d is formed to be 0.5 to 1.5 μm.
The dimension of the ZT layer in the direction of applying the electric field is about 0.5 to 1.5 μm, and the thickness t of the electrode is set to about 0.5 to 1.0 μm. Can be switched. Therefore, the unidirectional wiring 3a
And a direction intersecting with it (in the example shown in FIG. 1, the wirings 3a and 3
Although an example in which b is orthogonal is shown, it is not necessary to be orthogonal) The desired pixel can be turned on by controlling the voltage applied to the wiring 3b. Although the length L of the comb tooth varies depending on the size of the pixel, for example, a pixel of 100 μm × 300 μm is formed with a length of about 300 μm. Further, the number of comb teeth is also a schematic diagram shown in the figure and can be arbitrarily set according to the size of the pixel, but the gap between the electrodes may be set to about 0.5 to 1.5 μm as described above. Preferably, each of the above-mentioned pixel sizes has about 10 to 15 comb teeth. In addition, a plurality of comb-shaped electrodes having comb teeth opposed to each other may be provided in one pixel, and one electrode and the other electrode may be connected to form one set of counter electrodes. Moreover, since the comb teeth of the comb-shaped electrodes are alternately arranged, the electric fields in the mutually opposite directions are applied to the adjacent PLZT layers, but the light transmittance becomes 180 ° when rotated by 180 °. The display characteristics are not affected because they are the same.

As the electrode material, a metal film such as chromium or aluminum can be used. PLZT has PbZrO ₃ and PbTiO ₃ as shown in the phase diagram of FIG.
The property differs depending on the ratio of ₃ and La, and the composition having the secondary electro-optical effect shown in FIG. 8 is used.
On the other hand, a composition having a memory effect is also preferable in that the display content can be stored, the electro-optical effect is exhibited, and information can be stored. As shown in FIG. 5, polarizing plates 8 are arranged on both sides of the display substrate 7 so that the polarization axes are orthogonal to each other, and the light source 9 is provided on the back side of the display surface.
Are arranged to form the display device of the present invention. Furthermore, a desired pixel is driven by connecting an external drive circuit and an electrode terminal portion, and the desired light can be displayed by turning on and off the transmitted light together with the polarizing plate 8. In addition, when displaying using external light,
Instead of the light source 9, a reflector having the same size as the display surface may be arranged on the back surface side of the display substrate 7.

Next, a method for manufacturing the flat panel type display device of the present invention will be described.

In FIG. 1, a metal film is provided on a transparent substrate 1 such as glass by sputtering or the like, a photoresist layer is formed, exposed through a mask, and then patterned by etching (hereinafter, referred to as "patterning"). A series of steps from exposure to patterning is called a photolithography step), and the comb-shaped electrodes 2a, 2b, the first
The wiring 3a is formed. The comb-shaped electrodes 2a and 2b are arranged at regular intervals, and the comb teeth are alternately arranged so as to face each other. The first wiring 3a is connected to one end of the comb-shaped electrode 2a (see FIG. 1A). 1
One pixel 6 is formed by a pair of comb-shaped electrodes 2a and 2b. The first wiring 3a is formed between the adjacent pixels 6.

Next, the PLZT layer 4 is deposited on the transparent substrate 1 by, for example, the CVD method (see FIG. 1B).
Thereby, the PLZT layer 4 is formed between the pair of comb-shaped electrodes 2a and 2b and so as to cover these electrodes.

Next, contact holes 5 are formed in the PLZT layer 4.
Are formed by dry etching such as reactive ion etching (RIE) (see FIG. 1C).

Next, a metal film of, for example, chromium or aluminum is provided on the PLZT layer 4 by sputtering and the second wiring 3 is formed by a photolithography process.
b is formed. The second wiring 3b is connected with the first wiring 3a by PL.
One electrode 2b of each pixel which is formed between adjacent pixels 6 and which intersects with each other through the ZT layer 4 and which is arranged in the horizontal direction.
Are connected. The first wiring 3a and the second wiring 3b are electrically separated by the PLZT layer 4. As a result, the comb-shaped electrode 2b and the second wiring 3b of each pixel arranged in the horizontal direction are connected via the contact holes 5, respectively. In addition,
The first wiring 3a and the second wiring 3b are drawn out to the ends of the transparent substrate to form electrode terminal portions (not shown), and are connected to a drive circuit (not shown) by TAB or the like.

Through the above steps, the transparent substrate 1 as shown in FIG.
A display substrate 7 on which a large number of pixels 6 are arranged in a matrix is formed.

Next, a method of manufacturing a display substrate of another embodiment of the display device of the present invention will be described. This method is a method of forming a display substrate without etching PLZT, which is difficult to etch.

6 to 7, a metal film made of chromium, aluminum, or the like is formed on the transparent substrate 1 such as glass by a sputtering method or the like, and the second wiring 3b is formed by a photolithography process (see FIG. 6 (a)).

Next, a transparent insulating layer 20 made of, for example, silicon nitride is formed on the transparent substrate 1, and a contact hole for connecting the second wiring 3b to the comb-shaped electrode 2b formed in the next step. 5 is formed by dry etching such as RIE (see FIG. 6B).
The insulating layer 20 adheres also between the opposing electrodes, but if it is thin, it may be left as it is or may be removed by etching.

Next, a metal film is provided on the transparent insulating layer 20 in the same manner as described above, and the comb-shaped electrodes 2a and 2b and the first wiring 3a are formed by a photolithography process. The comb-shaped electrodes 2a and 2b are arranged at regular intervals, and the comb-teeth portions are alternately arranged so as to face each other. One pixel 6 is formed by a pair of comb-shaped electrodes 2a and 2b. The first wiring 3a is connected to one end of the comb-shaped electrode 2a, and the second wiring 3b is connected to one end of the comb-shaped electrode 2b through the contact hole 5 (see FIG. 6C). ).

Next, the PLZT layer 4 is deposited by, for example, the CVD method (see FIG. 6D). As a result, the PLZT layer 4 is formed between the pair of comb-shaped electrodes 2a and 2b and so as to cover these electrodes, as in the above-described embodiment.

[0043]

According to the present invention, a display device having a simple structure using PLZT can be obtained, the cost can be reduced, and the flat panel display which is robust against temperature change and external force and has high reliability. The device can be obtained.

Further, by forming the electrodes in a comb shape, it is possible to obtain a flat panel type display device capable of being driven at a low voltage and having a large aperture ratio and capable of bright display.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a manufacturing process of a display substrate used in a flat panel display device of the present invention.

FIG. 2 is a cross-sectional explanatory view taken along the line AA of FIG.

FIG. 3 is a cross-sectional explanatory view taken along the line BB of FIG.

FIG. 4 is an explanatory diagram of arrangement of pixel electrodes on a display substrate.

FIG. 5 is a side view showing an embodiment of the flat panel type display device of the present invention.

FIG. 6 is an explanatory diagram of a manufacturing process of a display substrate of another embodiment of the flat panel type display device of the present invention.

FIG. 7 is a cross-sectional view taken along the line CC of FIG.

FIG. 8 is a phase diagram of PLZT.

FIG. 9 is an explanatory diagram of a secondary electro-optical effect of PLZT.

FIG. 10 is a cross-sectional explanatory diagram of a liquid crystal display device.

[Explanation of symbols]

 1 transparent substrate 2a, 2b comb-shaped electrode 4 PLZT layer 6 pixel 8 polarizing plate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Makoto Takamura, 21 Mizozaki-cho, Saiin, Ukyo-ku, Kyoto ROHM Co., Ltd.

Claims (5)

[Claims] 1. A set of electrodes is provided in a matrix on a transparent substrate, and PLZ is provided in each gap of the set of electrodes.
A flat panel type display device in which a T layer is filled and polarizing plates are respectively provided on both outer surfaces of the transparent substrate. 2. The flat panel display according to claim 1, wherein each of the pair of electrodes is formed in a comb shape, and the comb teeth of the comb-shaped electrodes are arranged alternately so as to face each other. apparatus. 3. The PLZT is made of PbZrO ₃ and PbTi.
2. The flat panel display device according to claim 1, wherein the composition of O ₃ and La is formed to have a memory effect. 4. (a) 1 in which each pixel is formed on a transparent substrate
A pair of electrodes is formed in a matrix, and one of the pair of electrodes of each pixel arranged in one direction is connected to the first electrode;
Wiring is formed, (b) a PLZT layer is deposited on the transparent substrate provided with the one set of electrodes, and (c) a contact hole for contacting the other electrode of the one set of electrodes is formed in the PLZT layer. A second wiring connected to the other electrode of the one set of electrodes through the contact hole, and (e) polarizing plates provided on both outer surfaces of the transparent substrate. Flat panel type display device manufacturing method. 5. (f) A plurality of second wirings extending in one direction are provided in parallel between pixels on a transparent substrate, and (g) an insulating film is provided on the transparent substrate provided with the second wirings. And then forming a contact hole for contacting the second wiring in the insulating film, and (h) forming a plurality of one set of electrodes forming each pixel between the second wiring and Forming a first wiring connecting one electrode of the one set of electrodes of each pixel arranged in a direction intersecting with the second wiring, and
The other electrode of the set of electrodes is connected to the second wiring through the contact hole, (i) a PLZT layer is deposited on a transparent substrate provided with the set of electrodes, (j) A method of manufacturing a flat panel type display device, characterized in that polarizing plates are provided on both outer surfaces of the transparent substrate.