JPH0312632A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To reduce the weight of the element and to decrease production defects by integrally forming at least either of 1st and 2nd substrate by holding a polarizer and an optical phase element between a pair of uniaxially stretched films. CONSTITUTION:The 1st and 2nd substrates 1, 2 are held at a specified spacing in such a manner that the respective 1st main planes 1a, 2a face each other. The 1st substrate 1 is formed to the integral structure as a transparent flexible substrate having the functions of the polarizing plate and the phase plate by holding, for example, a polyvinyl alcohol (PVA) film having the function of the polarizing plate as the polarizer and, for example, a PVA film having a desired phase difference as the optical phase element between a pair of, for example, polyethylene terephthalate films. The weight over the entire part of the display device is reduced and the defects occurring in a sticking stage, etc., are decreased.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a birefringence control type liquid crystal display.

(Prior art) There are TN type, DS type, and GH type for liquid crystal display depending on the operation mode.
Although there are many types such as type, DAP type, and thermal writing type, TN type liquid crystal displays are used in most products, including wristwatches, calculators, and measuring instruments. However, with the demand for increased display capacity and larger display area, problems such as insufficient contrast and narrow visual range have emerged in TN type liquid crystal displays. Development was expedited.

In recent years, birefringence control type liquid crystal displays such as the SBE (super twisted bias fringe effect) type described in Japanese Patent Application Laid-Open No. 107020/1980 have been developed as liquid crystal displays that meet such demands. The utensils are attracting attention.

The structure of these birefringence-controlled liquid crystal displays consists of two 4-transparent substrates with a transparent electrode formed on at least one side facing each other, the periphery of which is sealed to form a cell, and a nematic liquid crystal inside the cell. is included. The distance between opposing boards is 3 to 12
Cyclohexane-based, ester-based, biphenyl-based, and pyridimine-based liquid crystals are used as nematic liquid crystals. A chiral agent is added to the nematic liquid crystal, and the molecular axis of the liquid crystal molecules! From 800
It is twisted between the upper and lower substrates at an angle of 3600°. The liquid crystal molecules have a pretilt angle in which the molecular axis is tilted relative to the plane of the substrate by more than 5° due to the movement of the alignment layer on the substrate.

In an SBE type liquid crystal display with a molecular axis twist of 2700, polarizing plates are preferably arranged on the outer front and rear surfaces of the substrate, so that the transmission axis of the front polarizing plate is relative to the molecular orientation direction of the front substrate. The best configuration is when the transmission axis of the rear polarizing plate is approximately 30 degrees counterclockwise or approximately 60 degrees clockwise with respect to the alignment direction of the rear substrate.

Among these, the former configuration is displayed in bright yellow in the unselected state,
A black display is obtained in the selected state (yellow mode), and the latter configuration provides a deep blue display in the non-selected state, and becomes transparent in the selected state (blue mode). Also, in other birefringent liquid crystal displays, the background color is not achromatic.

On the other hand, there has been a proposal to make the background color achromatic, as disclosed in Japanese Patent Application Laid-Open No. 64-514. This is a display that utilizes birefringence, such as an SBE type liquid crystal display.
The value of R=△n++d*cos'θ related to (0) is 0
．． 3 and 0.7, the background and lighting spectra are made close to flat, and black and white display is performed.

However, it is extremely difficult to set contrast, whiteness, and transmittance to the desired values simply by setting R between G, 3, and 0.7 and adjusting the absorption axis (or polarization axis) of the polarizing plate. This is difficult, especially in transmissive liquid crystal display devices that use a transmissive liquid crystal display and are illuminated from the back. The rate was decreasing.

For this reason, a birefringent liquid crystal display equipped with a member having the function of a phase plate between two polarizing plates was developed in Japanese Patent Application Laid-Open No. 61-189.
520, Japanese Patent Laid-Open No. 61-189521, etc., and even in transmission type liquid crystal display devices, liquid crystal displays with sufficient achromaticity, contrast, and transmittance have been obtained. .

(Problem to be Solved by the Invention) The member having the function of a phase plate described above may be, for example, a liquid crystal cell in which the twist direction of the nematic liquid crystal molecules is completely opposite to that of the liquid crystal display on the driving side, These are organic films etc. that have been subjected to a stretching process, and if these are cast or pasted, the product will be extremely heavy and the cost will be nearly double that of conventional liquid crystal display devices. Although the latter solves the disadvantage of the former in terms of weight, it requires an additional step of pasting, resulting in a significant drop in product yield due to defects such as dust and air bubbles.

The present invention aims to solve the above-mentioned problems, and aims to reduce weight, reduce manufacturing defects, and improve yield.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides first and second substrates having conductive electrodes formed on the first main surface side, and a molecular axis that is at an angle of 1° with respect to the plane of the first and second substrates. a nematic liquid crystal having a large pretilt angle θ and sandwiched between the first and second substrates with a torsion in the range of 180° to 360°, the refractive index anisotropy Δn of the nematic liquid crystal; and layer thickness d
(am), and a value of R=Δn·dacos'θ as a product of the pretilt angle θ(0) is between 0.4 and 0.8; At least one of the two is integrally formed by sandwiching a polarizer and an optical retarder between a pair of uniaxially stretched films.

(Function) In the present invention, by using a film substrate in which a polarizer and an optical retardation plate are sandwiched between a -axially stretched film as at least one of the substrates, the substrate has the functions of a conventional polarizing plate and a phase plate. However, the thickness of the liquid crystal display is significantly reduced, making it thinner, and the substrate is a film, reducing the overall weight of the liquid crystal display.

Furthermore, since it is possible to perform a separate step of placing or attaching a member having the function of a phase plate, the yield of products is improved by reducing defects caused by the attaching step and the like.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

The first main surface 11.2> side 1 of the first and second substrates 1 and 2 is made of, for example, ITO (Indium Tin), respectively.
conductive electrodes 3 and 4 made of oxide) are formed, and the first and second substrates 1.2 have their respective first main surfaces Is,
Approximately '1.2* are facing each other. The spacing is maintained at Onm.

Also, the first main surfaces 11°2 of the first and second substrates 1.2! On the sides, alignment layers 5 and 6 made of, for example, polyimide are formed so as to cover the conductive electrodes 3 and 4, and the periphery thereof is sealed with a sealing agent 7 made of, for example, an ultraviolet curing adhesive. ing. and the first and second substrates 1.2
A nematic liquid crystal 8 to which a chiral agent is added is sandwiched between them, and the molecular axis of the nematic liquid crystal 8 is in the range of 1800 to 3600 between the first and second substrates 1.2, for example, 270° counterclockwise due to the action of the chiral agent. With the twist of
Due to the action of the alignment layers 5, 6, a pretilt angle θ of approximately 10', which is greater than 1°, is provided with respect to the planes of the first and second substrates 1, 2. Further, the refractive index anisotropy Δn of the nematic liquid crystal 8 is about 0.094, and R=Δn as the product of the refractive index anisotropy Δn of the nematic liquid crystal 8, the layer thickness d1, and the pretilt angle θ(') '(1" The values of cos2θ are 0.4 and 0
．． It is about 0.64 between 8 and 8.

The first substrate 1 is a pair of uniaxially stretched films, for example, polyethylene terephthalate (PE) having a thickness of about 100 μm.
T) For example, a polyvinyl alcohol (PVA) film having a polarizing plate function as a polarizer and a polyvinyl alcohol (PVA) film having a desired retardation as an optical retarder are sandwiched between the films to form a polarizing plate and It is integrally formed as a transparent flexible film substrate that functions as a phase plate.

A neutral polarizing plate 9 is attached to the second main surface 2b side of the second substrate 2. Here, the polarization axes of the first substrate 1 and the polarizing plate 9 made of film are approximately 100° clockwise and approximately 1° clockwise with respect to the orientation direction of the first substrate 1, respectively.
The angle is set to 35°, and the arrangement relationship between the polarizer of the first substrate 1 and the polarizing plate 9 corresponds to a case near the blue mode.

Then, the refractive index anisotropy Δn' and the layer thickness d' of the first substrate 1
R' as the product of (jm) = △n'φd' is 0,
32jm, and the stretching axis and the orientation direction of the first substrate 1 are:
It is set at about 70° clockwise with respect to the orientation direction.

Behind the polarizing plate 9 of the liquid crystal display 10 having the above configuration (
In the lower part of the figure), the illumination unit 11 is a flat light source that is a combination of a light bulb or a fluorescent light and a light guide body, or an EL (
An electroluminescent (electroluminescent) lamp is provided to provide uniform illumination over the entire surface of the liquid crystal display lO. Further, a liquid crystal display 10 is provided on the side surface (left and right in the drawing) of the second substrate 2.
As the drive circuit section 12, a circuit board 14 on which an electronic component 13 is mounted is electrically connected to the conductive electrode 4 on the protrusion of the second board 2 by a connecting means 15, for example, a flexible sheet or a heat seal. In this way, the first substrate 1
As a whole, a liquid crystal display device including a liquid crystal display lO is configured such that external light, which is ambient light, enters from the second principal surface 1b side of the screen, and back illumination light from the illumination unit 11 enters from the polarizing plate 9 side. It is shaped.

As described above, by using a film substrate in which a polarizer and an optical retarder are sandwiched between a uniaxially stretched film as the first substrate 1, the first substrate 1 can be replaced with a polarizing plate that has conventionally been polymerized on a glass substrate. The first substrate 1 is a film, and the weight of the entire liquid crystal display 10 can be significantly reduced.

Additionally, since it is possible to eliminate the process of separately arranging or pasting a component that functions as a phase plate, defects caused by the pasting process, etc. are reduced, which significantly improves product yield and reduces costs. can.

Furthermore, since the first substrate 1 itself has a laminated structure of films, problems caused by waviness, warping, etc. caused by each film itself can be corrected, and display quality can be significantly improved.

Further, by arranging the first substrate 1 made of a film with a polarizer and an optical retardator interposed close to the eight liquid crystal layers, the contrast ratio is significantly improved compared to the conventional one.

In addition, in the embodiment, the second substrate 2 may also be a flexible film substrate in which, like the first substrate 1, a polarizer is sandwiched between a pair of uniaxially stretched films such as polyethylene terephthalate.

〔Effect of the invention〕

According to the present invention, by using a film substrate in which a polarizer and an optical retarder are sandwiched between a uniaxially stretched film as at least one of the substrates, the substrate can be replaced with a polarizing plate and an optical retarder, which have conventionally been polymerized on a glass substrate. It has the function of a phase plate, significantly reducing the thickness of the liquid crystal display, and
By using a film as the substrate, the weight of the entire liquid crystal display can be significantly reduced.

Additionally, since it is possible to eliminate the process of separately arranging or pasting a component that functions as a phase plate, defects caused by the pasting process, etc. are reduced, which significantly improves product yield and reduces costs. can do.

Furthermore, since the substrate itself has a laminated structure of films, it is possible to correct problems caused by waviness, warping, etc. caused by each film itself, and display quality can be significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of a liquid crystal display according to the present invention. 1..First substrate, No. 11.First principal surface, 2..Second substrate,
21...First principal surface, 3...Conductive electrode, 4...Conductive electrode,
8. Nematic liquid crystal, 10. Liquid crystal display. $1 this board $l soil surface) $2 base line li surface count 4 electrode nematic tail crystal po ε8 謬(tλ elephant

Claims (1)

[Claims] (1) First and second electrodes with conductive electrodes formed on the first main surface side
a substrate, the molecular axis being 1 with respect to the plane of the first and second substrates;
has a pretilt angle θ greater than
and a nematic liquid crystal sandwiched between the second substrates with a twist in the range of 180° to 360°, and the refractive index anisotropy Δn and layer thickness d(μ
m), and R= as the product of the pretilt angle θ (°)
In a liquid crystal display in which the value of Δn・d・cos^2θ is between 0.4 and 0.8, at least one of the first and second substrates is a pair of uniaxially stretched films with a polarizer and an optical A liquid crystal display characterized by being integrally formed with a phase shifter sandwiched therebetween.