JP2507062B2 - Substrate for optical element, manufacturing method thereof and display device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element such as a display element and an optical shutter, and more particularly to a substrate for the optical element, a manufacturing method thereof and a display device.

Conventional Technology Conventional technology will be described below with reference to the drawings. Presently, the applied fields as optical elements include high-density ones such as shutters for printers, word processors as OA terminals, personal computers, televisions and the like.

Many of these applications have very high planarization needs, and flatness is particularly desired for large-sized display devices.

The liquid crystal element is currently most attracting attention when flatness is desired.

Liquid crystal elements are gaining market share from watches and calculators in the old days to OA terminals with a size of about 10 inches due to the recent increase in size. High-definition displays with a resolution of 640 x 400 dots have been introduced.

Most of such high-definition liquid crystal displays are XY
It is composed of a substrate having an electrode structure called a matrix.

With the XY matrix configuration, as shown in FIG. 3, two substrates 21, 22 are provided with strip electrodes 23, 24, respectively,
Generally, one of the strip electrodes is the scanning electrode or the X electrode 2
3, the other is called the signal electrode or Y electrode 24.

A voltage is applied to the scanning electrodes line-sequentially, and a voltage corresponding to the data is applied to the signal electrodes, so that display is performed.

In this scanning method, the field frequency is usually required to be 50 Hz or higher so that flicker does not occur, and the scanning line is
In the case of 400 lines, the frequency of the applied voltage waveform is 20 kHz, which is a fairly high frequency voltage waveform.

However, when a large-area display and a high-definition display panel are used, the driving frequency becomes high frequency as described above. Therefore, when a substrate with uniform electrode resistance is used as in the conventional case, the distance from the voltage supply end increases. There is a problem that the voltage waveform becomes dull and the display becomes uneven.

Means for Solving the Problems As described above, in order to solve the problems, the nonuniformity of the display is prevented by lowering the resistance of the electrodes as the distance from the voltage supply end increases.

By making the working electrode resistance non-uniform, the dullness of the voltage waveform is made uniform, and as a result, uniform display can be obtained.

Example A substrate for an optical element according to an example of the present invention will be described below with reference to the drawings.

(Example 1) The electrode attenuation of a normal XY matrix configuration is given by the following equation by considering an equivalent circuit as shown in FIG. Where 31 is the capacitance per unit length of the liquid crystal layer (C1), 32
Is the conductance per unit length of the liquid crystal layer (G1), 33 is the resistance per unit length of the scanning electrode (R), 34 is the conductance per unit length of the signal electrode (G2), and 35 is the electrode length (L). ), 36 represents the voltage (VS) at the transmitting end, and 37 represents the voltage (VR) at the receiving end.

The equivalent circuit of FIG. 4 can be converted into a general ladder-type distributed RCG circuit, and the equivalent circuits of C ₁ , G ₁ and G ₂ are given by equations (1) and (2).

C = C ₁ G ₂ ² / {(G ₁ + G ₂ ) ² + (wC ₁ ) ² } (1) G = {G ₁ G ₂ (G ₁ + G ₂ ) + G ₂ (wC ₁ ) ² } / {( G ₁ + G ₂ ) ² } (2) For such an equivalent circuit, v (x, t) = V
When a (x) exp (iwt) sinusoidal voltage is applied, the following telegraph equation holds.

dV ² / dx ² = (G + iwC) RV (3) Under the boundary condition that the equation (3) is V (0) = VR and x = 0 is the open end. From this, the effective value ratio of the voltage at the transmitting end and the receiving end, that is, the attenuation ratio VR / VS of the applied voltage is Becomes Further, when G can be ignored, that is, when the resistance value of the signal electrode is low and the resistance value of the liquid crystal layer is sufficiently high, C = C ₁ and G ₁ = 0, and the equation (5) becomes Becomes

As can be seen from formula (6), L, so that Z is constant,
Even if C, R, and f are changed, the same voltage decay rate will be given.

Further, considering a strip electrode having a width W, Where e: relative permittivity of liquid crystal, r is the surface resistance of the electrode, and Z is calculated from Eqs. (7) and (8). It can be seen that the voltage decay rate does not depend on the electrode width W.

Normally, when driving a matrix, a rectangular waveform is used instead of a sine waveform, and the voltage attenuation rate needs to be expanded into a sine wave by Fourier transform, but the same is true.

From the equation (9), Z is a function of L, and if Z is constant, the attenuation rate is constant from the equation (6).

In order to change the surface resistance r of the electrode so that Z becomes constant with respect to L, it is necessary to reduce the surface resistance of the electrode by a function of r = L ⁻² .

In practice, it is difficult to provide such a large difference between the transmitting end and the receiving end of the electrode, so as an experiment, we used an electrode with a surface resistance of 10 ohm / lo at the transmitting end and 40 ohm / lo at the receiving end. I was there. As the panel structure, a so-called TN (twisted nematic) panel having a 90-degree twist structure with liquid crystal selected as an optical element was used. As the parameters of the panel, L = 300mm, e = 9, liquid crystal resistivity 10
^The thickness was ¹¹ ohm · cm and the cell thickness d was 5 μm. At this time, when a rectangular wave of 10 kHz was applied from the transmitting end of the panel, the voltage attenuation was less conspicuous than that of a uniform resistance electrode having a surface resistance of 10 ohms / square.

Further, such electrode attenuation is not so noticeable in a small panel (since it largely depends on L), in this experiment, L
It was not very effective for panels of 150 mm or less (diagonal size of 8 inches or less as the size of the substrate).

(Example 2) As a method of manufacturing an electrode having a non-uniform surface resistance as described above, a substrate passing speed over a vapor deposition source in vacuum to form an electrode in a substrate shape as shown in FIG. Was changed.

In FIG. 1, when the glass substrate 11 passes through the vapor deposition source 12 (here, indium tin oxide is used), the moving speed is 1c from the front end to the final end of the glass substrate.
It was continuously changed from m / min to 4 cm / min. The glass substrate used had a size L of 300 mm and a diagonal of 15 inches. The evaporation method uses an electron beam method, and the degree of vacuum during evaporation is
It was 6X10 ^-6 Torr. By changing the moving speed of the plate, the film thickness of ITO (indium tin oxide) on the substrate was changed, and the surface resistance value was changed. The film thickness changed from 1000 angstroms to 4000 angstroms.

As a result, the resistance of the substrate changed from 10 ohms / lo to 40 ohms / lo from the tip to the end. The surface resistance value of the substrate was measured by the three-terminal method.

(Example 3) As a method for producing an electrode having a non-uniform surface resistance, a vapor deposition source 21 is placed in a vacuum as shown in FIG.
Is positioned at an angle θ23 with respect to the vapor deposition source, an ITO thin film was provided on the substrate by the electron beam method using the vapor deposition source similar to that in Example 2. At this time, θ was set to 30 degrees. At this time, the substrate was tilted so that the distance d1 from the vapor deposition source to the closest portion of the substrate was 300 mm and the distance d2 to the farthest portion was 600 mm. Since the vapor deposition film thickness is determined by the square of the distance, the surface resistance at the position closest to the vapor deposition source was 10 ohms / lot, while at the furthest position it was 40 ohms / lot.

The size of the substrate used was L 600 mm.

EFFECTS OF THE INVENTION The present invention has the effect of reducing the electrode resistance as the distance from the voltage supply end increases, thereby softening the voltage attenuation and preventing the unevenness of the surface.

[Brief description of drawings]

FIG. 1 is a schematic view of an apparatus for making the electrode resistance non-uniform in Embodiment 2 of the present invention, and FIG. 2 is a schematic view of the apparatus for making the electrode resistance non-uniform in Embodiment 3 of the present invention. FIG. 3 is a conventional XY matrix electrode configuration diagram, and FIG. 4 is a model diagram for establishing an electrode attenuation model of the present invention. 11 ... Substrate, 12 ... Deposition source.

Claims (16)

(57) [Claims] 1. A substrate for an optical element, which has a strip-shaped electrode as a voltage applying means, and the resistance of the strip-shaped electrode becomes smaller as the distance from the voltage supply end increases. 2. The optical element substrate according to claim 1, wherein the length of the substrate in the diagonal direction is 8 inches or more. 3. The optical element substrate according to claim 1, wherein the optical element has a matrix-structured electrode structure. 4. The optical element substrate according to claim 1, wherein the optical element is a liquid crystal element. 5. A manufacturing method for depositing a substance on a substrate to provide voltage applying means having a strip electrode on the substrate, wherein the strip electrode is formed by changing a moving speed of the substrate when depositing the substance on the substrate. The method for manufacturing an optical element substrate is characterized in that the resistance is reduced as the distance from the voltage supply end increases. 6. The method for manufacturing an optical element substrate according to claim 5, wherein the length of the substrate in the diagonal direction is 8 inches or more. 7. The method of manufacturing an optical element substrate according to claim 5, wherein the optical element has an electrode structure having a matrix structure. 8. The method for manufacturing an optical element substrate according to claim 5, wherein the optical element is a liquid crystal element. 9. A manufacturing method for depositing a substance on a substrate to provide voltage applying means having a strip electrode on the substrate, wherein the substrate is arranged obliquely with respect to a deposition direction of the substance. The method for manufacturing an optical element substrate is characterized in that the resistance is reduced as the distance from the voltage supply end increases. 10. The method for manufacturing an optical element substrate according to claim 9, wherein the length of the substrate in the diagonal direction is 8 inches or more. 11. The method of manufacturing an optical element substrate according to claim 9, wherein the optical element has a matrix-structured electrode structure. 12. The method for manufacturing an optical element substrate according to claim 9, wherein the optical element is a liquid crystal element. 13. A display device comprising an optical element substrate having a strip electrode as a voltage applying means, and the resistance of the strip electrode becoming smaller as the distance from the voltage supply end increases. 14. The display device according to claim 13, wherein an optical element substrate having a diagonal length of 8 inches or more is used. 15. The display device according to claim 13, wherein an optical element substrate having a matrix-structured electrode structure is used as the optical element. 16. The display device according to claim 13, wherein the optical element is a liquid crystal element.