JPH04234732A - Liquid crystal electrooptical device - Google Patents

Abstract

PURPOSE:To obtain the liquid crystal optical device of a black and white display which is lighter in weight at a low cost. CONSTITUTION:A stretched polycarbonate substrate 4 having 500mum thickness is used as a 1st substrate 2 and electrodes 5 are provided thereon by forming the thin film of indium oxide tin and patterning the film. Further, an oriented film consisting of the thin film of polyimide is provided. On the other hand, a ferroelectric liquid crystal 11 and spacers 10 are inserted between the two substrates 2 and 3 and the circumference is fixed by an adhesive. The value of the product of the value n of the optical anisotropy possessed by the respective substrates 2, 3 and the thickness d of the substrates is specified, by which the inexpensive and light liquid crystal electrooptical device is obtd.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention proposes a device having means for black-and-white color compensation of a liquid crystal display device (FLC: ferroelectric liquid crystal, STN: super twisted nematic liquid crystal, etc.) exhibiting birefringence mode. It is.

0002

2. Description of the Related Art Conventionally, STN (super twisted nematic) type liquid crystal display devices have been widely used for display screens of computers, word processors, etc. Compared to previous TN (twisted nematic) type liquid crystal display devices, STN has steeper electro-optical characteristics of the liquid crystal material, which makes it possible to perform high time-division driving with a large amount of information, which was difficult with TN. It sparked the rise of notebook computers and notebook word processors.

In the conventional TN liquid crystal display device, which was first applied to electronic watches, desktop calculators, etc., the twist angle of liquid crystal molecules in the liquid crystal cell was approximately 90° as shown in FIG. Therefore, no birefringence mode occurred and there was no change in color due to the phase difference when passing through the liquid crystal layer. Therefore, it was possible to easily create two gradations of white and black.

However, when set to STN mode,
Since the twist angle is designed to be approximately 210 to 270 degrees as shown in FIG. 2, a birefringence mode occurs, causing a problem in which color changes occur due to phase difference when light passes through the liquid crystal layer. Normally, the color of light transmission/non-transmission is yellow/dark green (yellow-green mode) or light blue/non-transmissive based on the design value.
It was dark blue (blue mode) and was not suitable for colorization as the amount of information increased.

[0005] Accordingly, in order to return the shifted phase to a state close to the original state, a method of creating black and white by providing a phase difference compensating cell twisted in the opposite direction to the display cell on the optical path; Alternatively, there is a method in which a plastic phase difference compensating film is provided on the optical path to make the image black and white.

[0006] Another liquid crystal display device using birefringence mode, proposed by Clark Lagarwal et al., was a display using ferroelectric liquid crystal. Figure 3 shows its conceptual diagram.

Since ferroelectric liquid crystals have spontaneous polarization,
When the thickness of the liquid crystal layer is thinned until the spiral unwinds, a stable interfacial state (SSFLC) is created, and once an electric field is applied, a memory effect is obtained in which the transparent or non-transparent state continues even if the electric field is removed. I was able to do it. By utilizing this memory state, static display quality similar to that of a TFT active matrix LCD is possible.

The liquid crystal composition exhibiting chiral smectic ferroelectricity used in the panel has an optical anisotropy value (Δn) of approximately 0.14, so it transmits all three primary colors of light equally. In order to achieve this, it was necessary to reduce the thickness (d) of the liquid crystal composition to around 2 μm. By doing so, the product (Δnd) of the optical anisotropy value (Δn) of the liquid crystal composition and the thickness (d) of the liquid crystal composition could be adjusted to around 280 nm. FIG. 4 shows the spectral characteristics when (Δnd) is 280 nm. As we will see, 4
Blue light around 50 nm, green light around 550 nm, and 65
It can be seen that red light around 0 nm is transmitted almost uniformly.

However, since it is necessary to reduce the thickness (d) of the liquid crystal composition to around 2 μm, conductive foreign matter may get mixed in between the electrodes on the first and second substrates, causing electrical problems. Short-circuiting occurred, making normal display impossible and extremely reducing process yield. Therefore, in order to improve the yield, the thickness (d) of the liquid crystal composition should be increased by 3.
It became necessary to increase the thickness to around μm.

When the thickness (d) of the liquid crystal composition is increased to around 3 μm, the value of optical anisotropy (Δn) is around 0.14, so the product (Δnd) of these becomes 420 nm. As shown in FIG. 5, the spectral characteristics of the liquid crystal cell result in a yellow screen that does not transmit light in the vicinity of blue, making it unsuitable for colorization as the amount of information increases.

In order to return the shifted phase to a state close to its original state, the devised means includes a plastic phase difference compensation film (1) as shown in FIG. 6, similar to the STN liquid crystal display device. There are methods such as providing it on the optical path and converting it into black and white.

0012

Problems to be Solved by the Invention First of all, conventional liquid crystal electro-optical devices are heavy. In the case of a conventional liquid crystal display device composed of two glass substrates, the substrate portion alone weighs approximately 400 g in the case of an A4 size panel. In recent years, this has become an obstacle to reducing the weight of notebook computers, notebook word processors, and the like. In addition, in STN, when phase difference compensation is performed using a liquid crystal panel, an additional 400 g is added, which adds to the problem.

[0013] The next problem is that black-and-white conversion leads to an increase in cost. Glass substrates, retardation films, and polarizing films each account for approximately 1% of the material costs in the manufacturing cost of liquid crystal display devices.
They are 5%, 25%, and 20%, and are in second, third, and fourth place after drive IC, which ranks first. There was a need to reduce costs by eliminating some of these points.

[0014]

[Means for Solving the Problems] Therefore, the present invention is characterized in that a substrate constituting a liquid crystal display device is provided with a phase difference compensation function.

Specifically, in the case of STN, the product (Δnd) of the optical anisotropy value (Δn) and the substrate thickness (d) is 450n.
a first substrate having electrodes and leads made of an ITO (indium tin oxide) thin film or the like, and a means for uniaxially aligning a nematic liquid crystal composition, on a substrate having a wavelength of at least 400 nm to 700 nm; The product of the optical anisotropy value (Δn) and the layer thickness (d) (Δnd ) is 450
A nematic liquid crystal composition having a wavelength of nm to 900 nm is sandwiched. In this case, it can be effectively used as a reflective type liquid crystal display device.

Alternatively, the product (Δn·d) of the optical anisotropy value (Δn) and the substrate thickness (d) is 250 nm to 450 nm.
a first substrate having electrodes, leads, and means for uniaxially aligning a nematic liquid crystal composition, and a product (Δn) of the optical anisotropy value (Δn) and the thickness (d) of the substrate;
) is 250 nm to 450 nm, and the product ( Δnd) is 450 nm to 900 nm
A nematic liquid crystal composition is sandwiched therebetween. In this case, it can be effectively used as a transmissive type liquid crystal display device.

Furthermore, in the case of FLC, the value of optical anisotropy (Δ
The product (Δnd) of n) and substrate thickness (d) is 250 nm to 5
A liquid crystal composition exhibiting ferroelectricity by a first substrate having electrodes and leads on a substrate of 00 nm and a second substrate having electrodes and leads on a substrate that transmits light of at least 400 nm to 700 nm. and a means for performing at least initial orientation of the liquid crystal composition.

Alternatively, a first substrate having electrodes and leads and an optical anisotropy on a substrate whose product (Δnd) of the optical anisotropy value (Δn) and the substrate thickness (d) is 100 nm to 500 nm. The product (Δnd) of the value (Δn) and the substrate thickness (d)
A liquid crystal composition exhibiting ferroelectricity and a means for orienting the liquid crystal composition at least initially are sandwiched between a second substrate having electrodes and leads on a substrate having a diameter of 100 nm to 500 nm.

[0019]

Example 1 In this example, as shown in FIG. 7, a stretched polycarbonate substrate (4) with a thickness of 500 μm was used as the first substrate (2). The optical anisotropy value (Δn
) and the substrate thickness (d) (Δnd) was 315 nm.

I was deposited on this substrate by DC sputtering.
A TO (indium tin oxide) thin film was formed to a thickness of 1000 Å. Thereafter, using a photolithography method, patterning was performed in a stripe shape having a width approximately the same as one side of the display pixel electrode, thereby forming a first electrode (5). Thereafter, a polyimide thin film of 200 Å was printed and fired by a printing method, and then an alignment film (6) was provided by a rubbing method as a means for arranging liquid crystal molecules in a certain direction, thereby forming a first substrate.

On the other hand, the second substrate (3) includes: 1.
A 1000 Å film of ITO was formed on 1 mm soda lime glass (7) by DC sputtering. after that,
A first electrode (8) was patterned using a photolithography method into a stripe shape having a width approximately the same as one side of the display pixel electrode.

A ferroelectric liquid crystal (11) is placed between the first substrate (2) and the second substrate (3), and has a diameter of 2.6 μm to maintain the distance between the substrates made of resin. A spacer (10) made of silicon oxide was inserted, and the periphery thereof was fixed with an epoxy adhesive (9). The optical anisotropy value (Δn) of the ferroelectric liquid crystal at this time is 0.124, and (
Δnd) was 324 nm.

After that, the first electrode (2) and the third electrode (
A liquid crystal driving LSI was connected to the leads connected to 4) using the COG method, and a polarizing film was further attached to the outside of the substrate to obtain a liquid crystal display device.

FIG. 8 shows the configuration of the polarization axis, retardation axis, and liquid crystal molecule direction in this embodiment. (Δnd) is 324 nm
It is known that when phase difference compensation is not performed, spectral characteristics as shown in FIG. 9 are obtained. The spectral characteristics in this example are as shown in FIG. 10, and black and white has been realized.

Furthermore, in terms of weight, the weight is reduced by 45% compared to when glass is used for both substrates.

[0026]

Example 2 In this example, as shown in FIG. 11, a stretched polycarbonate substrate (13) with a thickness of 182 μm was used as the first substrate (12). The product (Δnd) of the optical anisotropy value (Δn) of this substrate and the substrate thickness (d) is 115 nm.
And so.

I was deposited on this substrate by DC sputtering.
A TO (indium tin oxide) thin film was formed to a thickness of 1000 Å. Thereafter, using a photolithography method, it was patterned into a stripe shape having a width approximately the same as one side of the display pixel electrode, thereby forming a first electrode (14). after that,
A polyimide thin film of 200 Å was printed and fired by a printing method, and then an alignment film (15) was provided by a rubbing method as a means for arranging liquid crystal molecules in a certain direction, thereby forming a first substrate.

On the other hand, as the second substrate (16), 320
A stretched polycarbonate substrate (17) with a μm thickness was used. The optical anisotropy value (Δn) of this substrate and the substrate thickness (d
) product (Δnd) was 200 nm.

[0029] On this substrate, by DC sputtering,
ITO was deposited to a thickness of 1000 Å. Thereafter, using a photolithography method, it was patterned into a stripe shape having a width approximately the same as one side of the display pixel electrode, thereby forming a second electrode (18).

[0030] First substrate (12) and second substrate (16)
A silicon oxide spacer (20) with a diameter of 2.6 μm is placed between the ferroelectric liquid crystal (19) and the resin substrate, and the periphery is covered with epoxy adhesive. (21) was fixed. The optical anisotropy value (Δn) of the ferroelectric liquid crystal at this time was 0.124, and (Δnd) was 324 nm.

[0031] After that, a liquid crystal driving LSI is connected to the leads connected to the first electrode (14) and the second electrode (18) using the COG method, and a polarizing film is attached to the outside of the substrate to connect the liquid crystal. Obtained a display device.

FIG. 12 shows the configuration of the polarization axis, retardation axis, and liquid crystal molecule direction in this example. (Δnd) is 324n
It is known that when m, the spectral characteristics as shown in FIG. 9 are obtained when phase difference compensation is not performed. The spectral characteristics in this example are as shown in FIG. 13, and black and white is realized.

Furthermore, in terms of weight, the weight is reduced by 90% compared to when glass is used for both substrates.

[0034]

Example 3 In this example, as shown in FIG. 14, a stretched polycarbonate substrate (21) with a thickness of 500 μm was used as the first substrate (20). The product (Δnd) of the optical anisotropy value (Δn) of this substrate and the substrate thickness (d) is 315 nm.
And so.

I was deposited on this substrate by DC sputtering.
A TO (indium tin oxide) thin film was formed to a thickness of 1000 Å. Thereafter, using a photolithography method, it was patterned into a stripe shape having a width approximately the same as one side of the display pixel electrode, thereby forming a first electrode (22). after that,
A polyimide thin film of 200 Å was printed and fired by a printing method, and then an alignment film (23) was provided by a rubbing method as a means for arranging liquid crystal molecules in a certain direction, thereby forming a first substrate.

On the other hand, as the second substrate (24), P
ITO was deposited to a thickness of 1000 Å on a uniaxially polarized substrate (25) made of VA by DC sputtering. Thereafter, using a photolithography method, patterning was performed in a stripe shape having a width approximately the same as one side of the display pixel electrode, thereby forming a second electrode (26).

[0037] First substrate (20) and second substrate (24)
A silicon oxide spacer (28) with a diameter of 2.6 μm is placed between the ferroelectric liquid crystal (27) and the resin substrate, and an epoxy adhesive is placed around it. (29) was fixed. The optical anisotropy value (Δn) of the ferroelectric liquid crystal at this time was 0.124, and (Δnd) was 324 nm.

[0038] After that, a liquid crystal driving LSI was connected to the leads connected to the first electrode (22) and the second electrode (26) using the COG method, and a polarizing film was attached to the outside of the first substrate. A liquid crystal display device was obtained.

The optical characteristics of the liquid crystal display device in this example were almost the same as in Example 1. Furthermore, in terms of weight, the weight is reduced by 90% compared to when glass is used for both substrates.

[0040]

Example 4 In this example, as shown in FIG. 15, a stretched diacetate substrate (28) with a thickness of 500 μm was used as the first substrate (27). The optical anisotropy value of this substrate (
The product (Δnd) of Δn) and substrate thickness (d) was 780 nm.

I was deposited on this substrate by DC sputtering.
A TO (indium tin oxide) thin film was formed to a thickness of 1000 Å. Thereafter, using a photolithography method, it was patterned into a stripe shape having a width approximately the same as one side of the display pixel electrode, thereby forming a first electrode (29). after that,
A polyimide thin film of 200 Å was printed and fired by a printing method, and then an alignment film (30) was provided by a rubbing method as a means for arranging liquid crystal molecules in a certain direction, thereby forming a first substrate.

On the other hand, as the second substrate (31), 1.1
ITO was deposited to a thickness of 1000 Å on soda lime glass (32) with a diameter of 10 mm by DC sputtering. after that,
A second electrode (33) was patterned using a photolithography method into a stripe shape having a width approximately the same as one side of the display pixel electrode. After that, a polyimide thin film is printed to a thickness of 200 Å using a printing method, and then baked to form a film, and then, using a rubbing method, an alignment film (34) is provided as a means of arranging liquid crystal molecules in a certain direction, and the second substrate is formed. And so.

[0043] First substrate (27) and second substrate (31)
A silicon oxide spacer (36) with a diameter of 6.8 μm is placed between the nematic liquid crystal (35) and the resin substrate, and an epoxy adhesive (37) is placed around it. ) was fixed. The optical anisotropy value (Δn) of the liquid crystal at this time is 0.121, and (
Δnd) was 820 nm.

[0044] After that, a liquid crystal driving LSI was connected to the leads connected to the first electrode (29) and the second electrode (33) using the COG method, and a reflective type polarizing film was also attached to one of the outer sides of the substrate. (38) and a transmission type polarizing film (39) was attached to the other side to obtain a liquid crystal display device.

FIG. 16 shows the configuration of the polarization axis, retardation axis, and liquid crystal molecule direction in this example. (Δnd) is 820n
It is known that when m, the spectral characteristics as shown in FIG. 17 are obtained if phase difference compensation is not performed. The spectral characteristics in this example are as shown in FIG. 18, and black and white is realized.

Furthermore, in terms of weight, the weight is reduced by 45% compared to when glass is used for both substrates.

[0047]

Example 5 In this example, as shown in FIG. 19, a stretched diacetate substrate (41) with a thickness of 500 μm was used as the first substrate (40). The optical anisotropy value of this substrate (
The product (Δnd) of Δn) and substrate thickness (d) was 305 nm.

On the other hand, as the second substrate (42), 500
A stretched diacetate substrate (43) with a μm thickness was used. The optical anisotropy value (Δn) of this substrate and the substrate thickness (d)
The product (Δnd) was 390 nm. Other steps are the same as in Example 4.

As a result, the weight is reduced by 90% compared to when glass is used for both substrates.

[0050]

Example 6 In this example, as shown in FIG. 20, a stretched diacetate substrate (44) with a thickness of 500 μm was used as the first substrate (43). The optical anisotropy value of this substrate (
The product (Δnd) of Δn) and substrate thickness (d) was 780 nm.

On the other hand, as the second substrate (45), PVA
A 1000 Å film of ITO was formed on a uniaxially polarized substrate (46) by DC sputtering. after that,
A second electrode (47) was patterned using a photolithography method into a stripe shape having a width approximately the same as one side of the display pixel electrode. Thereafter, a polyimide thin film of 200 Å was printed and fired by a printing method, and then an alignment film (48) was provided by a rubbing method as a means for arranging liquid crystal molecules in a certain direction, thereby forming a second substrate. Other steps are the same as in Example 4.

As a result, the weight is reduced by 90% compared to when glass is used for both substrates.

[0053]

[Effects of the Invention] With the structure of the present invention, the weight is reduced by 45 to 90% compared to a liquid crystal display device using a conventional glass substrate.
% reduction was realized, and in terms of manufacturing costs, 15% was achieved.
A reduction of ~25% has become possible, making it possible to supply lighter and cheaper liquid crystal display devices.

[Brief explanation of the drawing]

FIG. 1 shows the basic concept of a TN liquid crystal display device.

FIG. 2 shows the basic concept of an STN liquid crystal display device.

FIG. 3 shows the basic concept of an FLC liquid crystal display device.

FIG. 4 shows spectral characteristics when Δnd is 280 nm.

FIG. 5 shows spectral characteristics when Δnd is 420 nm.

FIG. 6 shows the structure of a liquid crystal display device with phase difference compensation using a plastic film.

FIG. 7 shows the structure of a liquid crystal display device according to an example.

FIG. 8 shows the configuration of the optical axis of the example.

FIG. 9 shows spectral characteristics when Δnd is 324 nm.

FIG. 10 shows spectral characteristics of Examples.

FIG. 11 shows the structure of a liquid crystal display device according to an example.

FIG. 12 shows the configuration of the optical axis of the example.

FIG. 13 shows spectral characteristics of Examples.

FIG. 14 shows the structure of a liquid crystal display device according to an example.

FIG. 15 shows the structure of a liquid crystal display device according to an example.

FIG. 16 shows the configuration of the optical axis of the example.

FIG. 17 shows spectral characteristics when Δnd is 820 nm.

FIG. 18 shows spectral characteristics of Examples.

FIG. 19 shows the structure of a liquid crystal display device according to an example.

FIG. 20 shows the structure of a liquid crystal display device according to an example.

Claims (6)

[Claims] Claim 1: Value of optical anisotropy (Δn) and substrate thickness (d)
A first substrate having electrodes and leads on a substrate whose product (Δnd) of 1. A liquid crystal optical device comprising a liquid crystal composition exhibiting dielectric properties and a means for orienting the liquid crystal composition at least initially. Claim 2: Value of optical anisotropy (Δn) and substrate thickness (d)
The product (Δnd) of the first substrate having electrodes and leads and the optical anisotropy value (Δn) and the substrate thickness (d) is 100 nm to 500 nm.
A liquid crystal characterized in that a liquid crystal composition exhibiting ferroelectricity and a means for performing at least initial orientation of the liquid crystal composition are sandwiched between a substrate having a diameter of nm to 500 nm and a second substrate having electrodes and leads. optical equipment. Claim 3: Value of optical anisotropy (Δn) and substrate thickness (d)
A first substrate having electrodes and leads on a substrate with a product (Δnd) of 250 nm to 500 nm, and a second substrate having electrodes and leads on a substrate having a uniaxial polarization direction. 1. A liquid crystal optical device comprising: a liquid crystal composition as shown in FIG. Claim 4: Optical anisotropy value (Δn) and substrate thickness (d
) having a product (Δnd) of 450 nm to 900 nm, a first substrate having electrodes and leads, and means for uniaxially aligning a nematic liquid crystal composition;
The optical anisotropy value (Δn
) and layer thickness (d) (Δnd) is 450 nm to 90
A liquid crystal optical device characterized by sandwiching a nematic liquid crystal composition having a thickness of 0 nm. 5. Optical anisotropy value (Δn) and substrate thickness (d
) has a product (Δn d) of 250 nm to 450 nm, a first substrate having an electrode, a lead, and a means for uniaxially aligning a nematic liquid crystal composition; The product (Δnd) of the substrate thickness (d) is 25
The optical anisotropy value (Δn) and the layer thickness (
A liquid crystal optical device characterized by sandwiching a nematic liquid crystal composition having a product (Δnd) of d) of 450 nm to 900 nm. Claim 6: Optical anisotropy value (Δn) and substrate thickness (d
) has a product (Δnd) of 450 nm to 900 nm, a first substrate having electrodes and leads, and means for uniaxially aligning a nematic liquid crystal composition; and a substrate having a uniaxial polarization direction; By means of a second substrate having electrodes and leads and means for uniaxially aligning the nematic liquid crystal composition, the product of the optical anisotropy value (Δn) and the layer thickness (d) (
A liquid crystal optical device characterized in that a nematic liquid crystal composition having a Δnd) of 450 nm to 900 nm is sandwiched therebetween.