JP2003131204A - Liquid crystal display element and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display element with which a display showing an excellent light diffusion property is obtained and a method for manufacturing the liquid crystal display element with which degree of the light diffusion is simply controlled. SOLUTION: A light diffusion layer 6 comprising light scattering particles 7 nearly uniformly distributed on an upper surface of a reflection film 5 disposed between a liquid crystal layer 9 and a rear substrate 1B with >=50% filling factor and coated with a coating material 8 having a refractive index different from that of the light scattering particles 7 is formed.

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, and more particularly to a reflective liquid crystal display device having a light diffusion layer inside the liquid crystal display device and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, a reflective liquid crystal display device having a light diffusion layer inside a liquid crystal display device has been developed.

For such a liquid crystal display device, two large-sized substrates, one for a front substrate and one for a rear substrate, are prepared, and the transparent electrode and the alignment film are laminated and formed on the front substrate.
A reflective film, a light diffusing layer, a transparent electrode, and an alignment film are sequentially laminated on the rear substrate, and large substrates are attached by a peripheral sealing material so that the alignment films face each other to form a multi-substrate. Then, the multi-substrate is cut into a stick shape or a single cell shape to open a liquid crystal injection port, and liquid crystal is injected from the liquid crystal injection port into a cavity surrounded by the bonded substrate and the peripheral sealing material. Inject and then
The liquid crystal injection port is sealed with a sealing material and further divided into individual liquid crystal display elements.

By the way, in the reflection type liquid crystal display element as described above, when the incident light is specularly reflected by the reflection film, it is very bright at the regular reflection angle, but extremely dark at other angles. Since the viewing angle is limited, a diffusion layer is provided to widen the viewing angle.

The method of manufacturing the diffusion layer will now be described. Conventionally, a resin as a binder mixed with a large number of diffusion particles is formed in a substantially central portion on a large-sized rear substrate on which the reflection film is formed. It was dripped onto and was applied with a spinner.

[0006]

However, according to such a conventional method of manufacturing a diffusion layer, rotation of the spinner causes a centrifugal force to act on the diffusion particles mixed in the binder, so that the diffusion particles have a large size. There was a problem that it was unevenly distributed on the rear substrate.

When the large-sized rear substrate in which the diffusion particles are unevenly distributed is divided into single liquid crystal display elements in the above-described manufacturing process, for example, the liquid crystal display elements divided from the vicinity of the center of the mother substrate and the individual liquid crystal display elements are separated. There is a problem in quality control that the light diffusion performance is different for each display element.

Therefore, according to the present invention, it is possible to easily control the liquid crystal display element in which the diffusing particles are evenly distributed to obtain a display exhibiting a good light diffusing property and the degree of the light diffusing. A manufacturing method is provided.

[0009]

In order to achieve the above object, a liquid crystal display element according to claim 1 of the present invention has a front substrate and a rear substrate sandwiching a liquid crystal layer, and the liquid crystal layer and the rear substrate are combined. The filling factor is 50 on the upper surface of the reflective film disposed between them.
%, The light diffusing layer is formed by covering the scattering particles which are substantially uniformly distributed with a coating material having a refractive index different from that of the scattering particles.

According to the present invention, when external light is incident, the light diffusing layer is refracted at a predetermined refractive index when it is transmitted through the coating material and when the scattering particles are transmitted. By refracting the light when the scattering particles are transmitted and when the coating material is transmitted, it is possible to scatter and reflect external light incident on the liquid crystal display element. At this time, by distributing the scattering particles on the upper surface of the reflective film so as to be substantially uniform, the degree of light diffusion on the display screen can be made uniform, and a good display result can be obtained.

According to a second aspect of the present invention, in the liquid crystal display element according to the first aspect, the difference in refractive index between the coating material and the scattering particles is 0.1 or more. Is characterized by.

According to the present invention, refraction / scattering of incident light can be increased.

Further, a method of manufacturing a liquid crystal display element according to a third aspect of the present invention is a method of manufacturing a liquid crystal display element in which a liquid crystal is sealed in a gap in which a front substrate and a rear substrate are arranged to face each other. A reflective film is formed on the rear substrate, and scattering particles are substantially evenly dispersed on the upper surface thereof so that the filling rate is 50% or more, and the scattering particles are covered with a coating material having a refractive index different from that of the scattering particles. The light diffusing layer is formed by coating.

According to the present invention, by changing the refractive index of the scattering particles or changing the filling rate of the scattering particles,
The degree of light diffusivity can be easily changed, and the light diffusivity can be easily controlled.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS.

As shown in FIG. 1, the liquid crystal display element of this embodiment has two transparent substrates 1A and 1B made of a material such as glass, which are arranged in parallel with each other at a distance. The outer circumference between these transparent substrates 1A and 1B is sealed by a peripheral seal portion 2.

Of these, the transparent electrode 3A is formed on the lower surface of the upper transparent substrate (hereinafter, front substrate) 1A.
Are arranged in close contact with each other, and on the lower surface of the transparent electrode 3A, an alignment film 4A for controlling the alignment of liquid crystal molecules according to the applied voltage is provided.

On the other hand, on the upper surface of the transparent substrate (hereinafter, rear substrate) 1B located below, a reflective film made of a metal material such as aluminum for reflecting incident light is provided. The light diffusion layer 6 is disposed on the upper surface. In the present embodiment, the light diffusion layer 6 is formed by covering the scattering particles 7 that are substantially uniformly distributed so that the filling rate is 50% or more with a coating material 8 having a refractive index different from that of the scattering particles 7. Has been formed. Further, in the present embodiment, as the coating material 8, a material having a refractive index different from that of the scattering particles 7 by 0.1 or more is selected and used. Here, the filling rate refers to the ratio of the total projected area of the scattering particles 7 to the surface area of the reflective film 5.

On the upper surface of the light diffusion layer 6, IT
A transparent electrode 3B made of O or the like is provided, and an alignment film 4B is provided above the transparent electrode 3B so as to be in close contact therewith.

A liquid crystal is enclosed in a cavity surrounded by the substrates 1A and 1B and the peripheral sealing material 2 to form a liquid crystal layer 9. Further, the substrates 1A and 1B are formed.
A plurality of spherical spacers 10 are interposed between the alignment films 4A and 4B in order to keep the distance between B accurately constant.

As shown in FIG. 2, the liquid crystal display device having the light diffusion layer 6 having the above-described structure allows external light transmitted through the liquid crystal layer 9 to pass through the coating material 8 in the light diffusion layer 6. Also, when the scattering particles 7 are transmitted, they are refracted at a predetermined refractive index, and the reflected light reflected by the reflecting film 5 is also similarly scattered particles 7.
By refracting the light when passing through and when passing the coating material 8,
It is possible to appropriately diffuse the external light incident on the liquid crystal display element to perform a desired display. In FIG. 2, refraction of external light with an incident angle to the light diffusion layer 6 of 0 ° is illustrated by an arrow, and the scattering particles 7 have a filling rate of about 50.
The case is shown as being distributed as a percentage.

In particular, in this embodiment, the refractive index difference between the coating material 8 and the scattering particles 7 is 0.1 or more, so that the refraction / scattering of external light can be increased. it can.

Further, since the scattering particles 7 are distributed in the surface substantially uniformly and at a filling rate of 50% or more, the scattering reflection of the external light can be made substantially uniform on the display screen. Therefore, good display can be performed.

Now, a method of manufacturing the above-mentioned liquid crystal display device will be described.

In the production of the liquid crystal display element of this embodiment, two large-sized transparent substrates 1 which can divide a single liquid crystal display element in the production process are used. The two large-sized transparent substrates 1 are subjected to a patterning process and an alignment treatment process, respectively.

Specifically, a glass substrate is used as the transparent substrate 1 which is the front substrate 1A, and I is provided on one side thereof.
The transparent electrode 3A made of TO is patterned and formed into a predetermined shape. Then, a polyimide film having a thickness of 20 to 80 nm, preferably 40 to 50 nm is laminated on the upper surface of the transparent electrode, and a predetermined alignment treatment is performed by rubbing this.
The alignment film 4A is formed.

In the present embodiment, a glass substrate is also used as the other transparent substrate 1 which is the rear substrate 1B facing the front substrate 1A. Then, the semi-transmissive reflective film 5 is formed on one surface thereof. Then, on the upper surface of the reflective film 5,
The filling rate of the scattering particles 7 coated with a thermoplastic adhesive layer was 5
It is distributed substantially uniformly so as to be 0% or more by using a known dry type or wet type spraying device.

Then, the adhesive layer is heated to a melting temperature to fix the scattering particles 7 to the surface of the reflective film 5.

After that, the reflecting film 5 on which the scattering particles 7 are arranged.
A scattering material 7 and a coating material (protective film OP) 8 having a refractive index different from that of 0.1 or more are coated thereon by using a spinner to form a light diffusion layer 6 having a smooth upper surface and light diffusivity. . This embodiment is. Since the coating material 8 is applied by the spinner after the scattering particles 7 are fixed, the problem of uneven distribution of the scattering particles, which has been conventionally generated, can be solved.

Further, the method of applying the coating material is not limited to the method of using the spinner which makes the upper surface of the light diffusion layer 6 smooth, and the step of fixing the scattering particles 7 becomes unnecessary.
Flexographic printing, offset printing, roll coat printing, bar code printing and the like may be used.

As the scattering particles 7, desired fine particles having various refractive indexes can be used, and the degree of light diffusivity can be adjusted by selecting the scattering particles 7 having different refractive indexes. it can. Further, a plurality of types of scattering particles 7 having different refractive indexes may be mixed and uniformly distributed. Further, it is desirable that the refractive index of the adhesive layer is different from the refractive index of the scattering particles 7 or the coating material by 0.1 or more.

By distributing the filling rate of the scattering particles 7 to 50% or more, a liquid crystal display device having a high level of light diffusivity can be obtained.

Then, after the transparent electrode 3B made of ITO is patterned and formed in a predetermined shape on the upper surface of the light diffusion layer 6, a polyimide film is laminated to a thickness of 20 to 80 nm, preferably 40 to 50 nm. Then, a predetermined alignment treatment is performed by rubbing to form the alignment film 4B.

Next, on the front substrate 1A, a sealing material is applied and partitioned for each single liquid crystal display element to be divided in a later step, and a peripheral sealing portion 2 is formed.

Also, spacers 10 are scattered on the rear substrate 1B. In this embodiment, the peripheral seal portion 2 and the spacers 10 are formed on different transparent substrates 1. However, the peripheral seal portion 2 is formed when the density of the spacers 10 is increased. Spacers 10 may also be scattered on the substrate 1 side.

Next, the front substrate 1A and the rear substrate 1
B and B are accurately overlapped so that the alignment marks (not shown) formed on the respective substrates 1A and 1B are aligned with each other, and thermocompression bonding is performed, and a seal hardening process is performed to obtain a thickness approximately the same as the diameter of the spacer 10. A bonded substrate (not shown) having a hollow portion is obtained.

The large-sized bonded substrate thus obtained is
A plurality of stick-shaped substrates (not shown) are cut so that each liquid crystal inlet (not shown) formed in the peripheral seal part 2 of the single liquid crystal display element is opened, and in this state, the liquid crystal inlet is cut. Liquid crystal is injected from. After that, the liquid crystal injection port is sealed with a sealing material (not shown), and then the stick-shaped substrate is further divided to obtain a single liquid crystal display element having the above-described configuration.

In the case of a color liquid crystal display element, for example, a color filter film may be arranged between the transparent electrode 3B and the light diffusion layer 8. Further, a diffusion layer having a roughened surface may be arranged below the reflection film 5.

According to such a method of manufacturing a liquid crystal display element, the degree of light diffusivity can be easily changed by changing the refractive index of the scattering particles 7 or changing the filling rate of the scattering particles 7. As a result, the light diffusion property can be easily controlled.

A more specific embodiment will be described below. In addition,
In the following examples, the processing performed on the substrate which will be the rear substrate 1B of the liquid crystal display element and the effects of the liquid crystal display element using the rear substrate 1B thus produced will be described.

First, in order to form an adhesive layer on the surface of particles (spacer made by NATCO) having a diameter of 3 μm and a refractive index of about 1.54, which is mainly composed of styrene / siloxane, the melting temperature is 80 ° C. The particles were mixed in a solution of an adhesive having a refractive index of about 1.38 to prepare scattering particles 7 having an adhesive layer.

In this embodiment, the reflective film 5 made of aluminum and having a thickness of 20 nm is formed on the upper surface of the transparent substrate 1B made of glass so as to be semi-transmissive.
The scattering particles 7 were distributed on the upper surface of the reflective film 5 by a known spraying device so that the filling rate was about 75% and the upper surface of the reflective film 5 was uniformly covered. Then, it was placed in an oven at 90 ° C. for 30 minutes to fix the scattering particles 7 on the transparent substrate 1B. Then, a transparent acrylic resin having a refractive index of about 1.4 (SS6963 manufactured by JSR Corporation) was applied as a coating material 8 by a spinner so as to have a film thickness of about 5 μm to coat the scattering particles 7. After that, temporary drying is performed for 6 minutes on a hot plate at 100 ° C, and then at 240 ° C for 1
Post-baking was performed for a period of time to cure and form the light diffusion layer 6. By forming the light diffusion layer 6 in this way,
A liquid crystal display device having uniform diffusivity over the entire surface could be produced.

Further, when the rear substrate was treated in the same manner as in the above-mentioned embodiment with the filling rate of the scattering particles 7 set to 85% to form a liquid crystal display element, the level of light diffusivity was the liquid crystal in the above-mentioned embodiment. It was higher than the display device.

The present invention is not limited to the above-mentioned embodiment, but can be variously modified as necessary.

For example, the transparent substrate is not limited to a glass substrate, and a plastic substrate made of polycarbonate, polyarylate, polyether sulfone or the like may be used.

[0046]

As described above, according to the liquid crystal display element and the method for manufacturing the same according to the present invention, it is possible to uniformly distribute the diffusing particles to obtain a liquid crystal display element exhibiting good diffusivity. Further, it is possible to easily control the degree of light diffusion.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing an embodiment of a liquid crystal display element according to the present invention.

FIG. 2 is an explanatory diagram showing an example of refraction (light diffusion) of incident light and reflected light in the light diffusion layer of FIG.

[Explanation of symbols]

1 transparent substrate 1A front board 1B rear board 2 Peripheral seal 3 transparent electrodes 3A (front substrate side) transparent electrode 3B (rear substrate side) transparent electrode 4 Alignment film 4A (front substrate side) alignment film 4B (rear substrate side) alignment film 5 Reflective film 6 Light diffusion layer 7 scattering particles 8 coating material 9 Liquid crystal layer 10 Spacer

Claims (3)

[Claims] 1. A front substrate and a rear substrate sandwiching a liquid crystal layer, wherein the upper surface of a reflective film disposed between the liquid crystal layer and the rear substrate is substantially filled with a filling rate of 50% or more. A liquid crystal display device comprising: a light diffusion layer in which scattering particles uniformly distributed are covered with a coating material having a refractive index different from that of the scattering particles. 2. The liquid crystal display device according to claim 1, wherein a difference in refractive index between the coating material and the scattering particles is 0.1 or more. 3. A method of manufacturing a liquid crystal display device, wherein a liquid crystal is sealed in a gap in which a front substrate and a rear substrate are opposed to each other, wherein a reflective film is formed on the rear substrate, and a filling rate is provided on an upper surface thereof. So as to be 50% or more, and the light diffusing layer is formed by coating the scattering particles with a coating material having a refractive index different from that of the scattering particles. Manufacturing method.