JPH07191315A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To measure the thickness of a liquid crystal cell with high precision by providing a metallic film for visible rays and infrared rays on the top surface of a 1st substrate which faces a 2nd substrate, and side a seal material. CONSTITUTION:The liquid crystal display device is produced by charging a liquid crystal material 6 in a cell constituted of the 1st substrate 1 provided with a switching element, the 2nd substrate 7 which faces the 1st substrate 1, and the seal material 5 arranged between the 1st and 2nd substrates 1 and 7. The matallic film 2 for visible rays and infrared rays is provided on the top surface of the 1st substrate 1 which faces the 2nd substrate 7, and outside the seal material 5. Consequently, the substrate 1 is irradiated with monochromatic light vertically and the intensity of light interference between reflected light on the lower surface of the transparent opposite substrate 7 and reflected light on the metallic film 2 is measured to calculate the distance between the opposite substrate 7 and metallic film 2 as the thickness of the liquid crystal cell. The thickness of this liquid crystal cell can be measured in a process after both the substrates 1 and 7 are stuck together.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device having a member for measuring the thickness of a liquid crystal cell between opposed substrates with high accuracy and reproducibility.

[0002]

2. Description of the Related Art To measure the thickness of a cell of liquid crystal material,
Optical methods are mainly used. Among them, the retardation method has been widely used conventionally. This retardation method utilizes the dielectric anisotropy of liquid crystal to determine the degree of rotation of the plane of polarization of incident light and measure the thickness. In addition, an optical interference method has also been conventionally widely used in which the intensity of the interference wave of reflected light is measured between a pair of substrates sandwiching a liquid crystal at various wavelengths. According to this method, when the structure of the pair of substrates facing each other is simple, clear interference fringes can be obtained, and the thickness of the liquid crystal cell can be accurately obtained.

[0003]

However, since the retardation method utilizes the dielectric anisotropy of the liquid crystal, the liquid crystal cell thickness cannot be measured before the liquid crystal is injected. Further, when the dielectric anisotropy Δε of the liquid crystal changes due to a reliability test or the like, an error occurs in the estimation of the liquid crystal cell thickness. Regarding the optical interference method, when a thin film transistor or the like for driving the liquid crystal is formed on one of the pair of opposing substrates, the transparent substrate and various opaque thin films are laminated on the opposing substrate. Therefore, the interference characteristic becomes complicated as shown in FIG. 5, and calculation of the liquid crystal cell thickness becomes practically impossible.

[0004]

Means and Actions for Solving the Problems
As a result of earnest efforts in view of the above problems, the following findings were obtained. That is, in order to measure the thickness of the liquid crystal material cell, the light interference method is used, and the light intensity is measured not on the portion filled with the liquid crystal material but on the outside of the sealing material. By using this method, the liquid crystal cell thickness can be accurately obtained before or after the liquid crystal material is injected.

FIG. 1 is a sectional view of a liquid crystal display device of the present invention. 1 is a semiconductor substrate including switching elements such as thin film transistors, 2 is a metal film used for wiring,
3 is a protective insulating film, 5 is a sealing material, and 7 is a transparent counter substrate. The bonding pad structure 4 is composed of the metal film 2 and the protective insulating film 3. 1 semiconductor substrate and 5
A liquid crystal material cell is constituted by the sealing material of 7 and the transparent counter substrate of 7, and the liquid crystal material is filled in the cell. The transparent counter substrate 7 also extends to the outside of the sealing material and extends above the bonding pad structure 4. The surface of the protective insulating film 3 and the surface of the metal film 2 in the liquid crystal material cell are on the same plane.

According to the present invention, monochromatic light is irradiated in a direction perpendicular to the substrate, the optical interference intensity between the light reflected on the lower surface of the transparent counter substrate 7 and the light reflected on the metal film is measured, and the counter substrate 7 is measured. The distance between and the metal film 2 is calculated, and the distance is used as the thickness of the liquid crystal cell.

FIG. 3 is a plan view of the liquid crystal display device of the present invention. It is preferable to provide a plurality of bonding pad structures 4 serving as reflective films in order to confirm the uniformity of the distance between the opposing substrates of the liquid crystal material cell.

Further, if the bonding pad structure is arranged at a position close to the sealing material at the portion where the sealing material is just bent, the size of the structure is about 100 μm square, so that the extra area of the liquid crystal cell is consumed. You can use the space effectively. If the upper part of a plurality of bonding pad structures is not covered with a transparent counter substrate, the structure can be used as a reference for measuring the intensity of reflected light.

Further, the metal film 2 may be provided below the sealing material 5.

That is, the present invention is configured by using a first substrate provided with a switching element, a second substrate facing the first substrate, and a sealing material arranged between the first and second substrates. In a liquid crystal display device in which a liquid crystal material is filled in the cell, a reflection plate for visible light and infrared rays is provided on the surface of the first substrate facing the second substrate and outside the sealing material. It is a liquid crystal display device.

At this time, it is preferable that the reflector is made of a metal or a metal compound.

At this time, the reflecting plate may be used as a bonding pad provided on the first substrate.

Further, at this time, it is preferable that the reflection plate is provided outside the portion close to the sealing material at the bending portion of the sealing material.

Further, at this time, the reflection plate may be provided below the sealing material.

Further, at this time, a plurality of the reflection plates may be provided.

Further, at this time, at least one of the plurality of reflectors is provided at a position where it does not overlap the second substrate when viewed along a direction perpendicular to the first substrate, and the like. The reflectors may be provided at a position where they overlap.

By carrying out the present invention, the thickness of the liquid crystal cell between the opposing substrates can be measured in the steps after the bonding of both substrates, and the value is a direct value which does not depend on the injected liquid crystal. can get. Further, since the reflector is produced at the same time when the bonding pad is produced during the process, the production cost can be reduced.

[0018]

【Example】

(Embodiment 1) A first embodiment using the cross-sectional view of the liquid crystal display device of FIG.
The embodiment will be described.

First, using a monochromator or the like, light with a known wavelength is made incident from the transparent substrate 7 side, and the intensity of the reflected light is measured. Since the metal film 2 totally reflects light of almost all wavelengths, the thickness of the liquid crystal cell can be obtained from the wavelength-reflection intensity characteristic (interference characteristic, FIG. 2).

Assuming that the distance between opposed substrates is d, the wavelength λ _{peak at} which the reflection intensity is strong is

[0021]

[Outer 1] The wavelength λ _valley with weak reflection intensity is

[0022]

[Outside 2] There is a relationship represented by. From this relationship, d can be obtained. Since the gap amount is approximately 4 μm, the light used is preferably infrared light or visible light.

(Embodiment 2) As another embodiment of the present invention,
In order to better understand the reflection characteristics of the metal film forming the bonding pad structure, it is possible to obtain the reflection characteristics of the metal film by using a bonding pad for external extraction existing in the liquid crystal cell.

Since the bonding pad is wire-bonded and an electric path is drawn out to the outside, there is usually no transparent substrate above the pad which interferes with the bonding. Therefore, there is no opposing transparent substrate on the pad, and no light interference occurs. Therefore, the pure reflection characteristic (λ-I0) of the metal film forming the pad can be obtained. By examining the ratio of the reflection characteristic of this metal film to the reflection characteristic (λ-I) of the liquid crystal cell gap, λ-I / I0, λ _peak , λ _valley , and therefore d can be obtained more accurately. Like Also, by performing such a correction, for example, several hundred Å on the pad.
It is also possible to reduce the weight due to the influence of the liquid crystal alignment film that exists with a certain thickness.

The present invention is not limited to the bonding pad structure for investigating the interference characteristics of the gap, and it is sufficient that the vicinity of the surface of the other substrate is a film that sufficiently reflects light. Therefore, the material thereof may be any of metal, metal oxide, and various film materials formed on the other substrate.

In order to improve the controllability of the gap amount, a seal is formed on the same structure as the light-reflecting portion for measuring the gap, and a spacer existing in the sealing material is pushed. It is also possible to directly monitor the crushed state (Fig. 4). As a result, the state of forming the seal material can be checked, so that the seal material can be formed while keeping the distance between both substrates uniform.

Further, as a matter of course, a structure in which the light-reflecting portion and the sealing material are continuous may be used.

[0028]

According to the present invention, the thickness of the liquid crystal cell can be measured with high accuracy by providing a simple structure. The currently obtained measurement accuracy is about ± 0.02 μm.
The measurement method is a direct method that does not depend on the liquid crystal to be injected, and the structure essential for building a liquid crystal cell such as a bonding pad is diverted, and by arranging it in the blank area of the liquid crystal cell, the cost required for manufacturing is reduced. It does not rise at all.

Further, by providing a plurality of the structures, it is possible to know the distribution of the gap amount, and it is possible to control the sealing material forming process.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

FIG. 2 is a diagram showing optical interference characteristics of the present invention.

FIG. 3 is a plan view of an embodiment of the present invention.

FIG. 4 is a sectional view of another embodiment of the present invention.

FIG. 5 is a diagram showing optical interference characteristics of a conventional example.

[Explanation of symbols]

 1, 41 Substrate 2, 42 Metal film 3, 43 Protective film 4 Structure 5, 45 Sealing material 6, 46 Liquid crystal 7, 47 Transparent substrate

Claims (7)

[Claims] 1. A cell formed by using a first substrate provided with a switching element, a second substrate facing the first substrate, and a sealing material arranged between the first and second substrates. A liquid crystal display device filled with a liquid crystal material, characterized in that a reflector for visible light and infrared rays is provided on the surface of the first substrate facing the second substrate and outside the sealing material. . 2. The liquid crystal display device according to claim 1, wherein the reflector is made of a metal or a metal compound. 3. The liquid crystal display device according to claim 1, wherein the reflection plate is used as a bonding pad provided on the first substrate. 4. The liquid crystal display device according to claim 1, wherein the reflection plate is provided outside a portion where the sealing material is bent and is close to the sealing material. 5. The liquid crystal display device according to claim 1, wherein the reflection plate is provided below the sealing material. 6. The liquid crystal display device according to claim 1, wherein the liquid crystal display device comprises a plurality of the reflection plates. 7. At least one of the plurality of reflectors is provided at a position where it does not overlap the second substrate when viewed along a direction perpendicular to the first substrate, and another reflector is provided. The liquid crystal display device according to claim 6, wherein the liquid crystal display device is provided at a position where the plates overlap.