JP2001125105A - Reflective liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device with which both a reflective display using external light and a transmissive display using backlight illumina tion are feasible and high contrast is obtained both in the reflective and transmis sive displays in the single polarizing plate mode device equipped with only one polarizing plate. SOLUTION: The reflective liquid crystal display device is provided with a first polarizing plate 11, a first optical retardation plate 13, a twisted optical retardation plate 12, an STN(supertwisted nematic) liquid crystal element 21 containing a semitransmissive reflection layer 9 inside, a second optical retardation plate 18, a second polarizing plate 17 and a backlight 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a liquid crystal display device, and more particularly to a single polarizing plate type reflection plate which comprises a reflector inside a liquid crystal display element and one polarizing plate to realize a bright monochrome display and a color display. The present invention relates to a liquid crystal display device.

[0002]

2. Description of the Related Art Conventionally, a reflection type liquid crystal display device comprises a pair of polarizing plates and a reflecting layer disposed outside one of the polarizing plates.
TN (twisted nematic) liquid crystal element, STN
(Super twisted nematic) A reflection type liquid crystal display device provided with a liquid crystal element is mainly used. However, in this method, there is a problem that the brightness is low, and furthermore, since the reflection layer is outside the glass substrate, a shadow is generated on the display, resulting in poor visibility.

As a countermeasure against the above-mentioned problem of poor visibility, a reflection type liquid crystal display device of a single polarizing plate type capable of displaying with one polarizing plate has been proposed. In this means, the polarizing plate is 1
Since the number of sheets is two, the brightness can be improved as compared with the conventional reflection type liquid crystal display device using two polarizing plates.

[0004] In a single polarizer type liquid crystal display device, the problem of display shadow can be solved by forming a reflection layer inside the liquid crystal display element.

This single-polarizer type liquid crystal display device is composed of one polarizing plate, one retardation plate, and a liquid crystal element having a reflective layer therein. It has been disclosed.

[0006]

However, in the single polarizer type liquid crystal display device using one retardation plate described above, a low reflectance is realized only for a specific wavelength, and a low reflectance is obtained for all wavelengths. The rate cannot be realized.

In order to obtain a good black display, a single polarizing plate type liquid crystal display device using two retardation plates has been developed, but sufficient contrast has not yet been obtained.

In addition, a single polarizing plate type liquid crystal display device using a compensation layer having a structure twisted in the direction opposite to the twisting direction of the liquid crystal layer instead of the phase difference plate has been disclosed. It is difficult to achieve low reflectivity over wavelength. A single polarizing plate type liquid crystal display device using a compensation layer having this twisted structure is disclosed in, for example, JP-A-10-123.
No. 505.

Further, in the above-mentioned prior art single polarizer type liquid crystal display device, since the reflection layer does not transmit light, a backlight cannot be provided, and the display can be viewed in a place where external light is weak or at night. Could not.

Therefore, a half mirror made of thin film aluminum formed by a vapor deposition method is used as the reflective layer, or an opening for each pixel is provided in the reflective layer, and the display is performed by the backlight light in a place where external light is weak or at night. A transflective liquid crystal display device has been developed.

However, in the case of a single-polarizer type liquid crystal display device, there is only one polarizing plate at the time of reflective display using external light, and good black-and-white display is possible with incident light reciprocating through the liquid crystal element. In addition, it is necessary to design an optical element such as a liquid crystal element or a retardation plate.

On the other hand, at the time of transmissive display using a backlight, the liquid crystal element is transmitted only once, and it is necessary to design the liquid crystal element and the optical element so that good black-and-white display can be obtained in this state. It was difficult to obtain high contrast for both display and transmissive display.

A liquid crystal display device in which an opening for each pixel is provided in a reflective layer is disclosed in, for example, Japanese Patent Application Laid-Open No. 10-282488. There is no description as to how to achieve good contrast display between the reflective display and the transmissive display.

[0014] The first object of the present invention is to solve the above-mentioned problems of the prior art, and to obtain black having a low reflectance over all wavelengths in a reflection display using external light, thereby achieving high contrast. It is an object of the present invention to provide a reflective liquid crystal display device which is bright and has good visibility.

A second object of the present invention is to provide a single polarizing plate system capable of performing reflective display by external light and transmissive display by backlight illumination, and obtaining high contrast in both reflective display and transmissive display. To provide a transflective liquid crystal display device.

[0016]

In order to achieve the above object, in a reflection type liquid crystal display device according to the present invention, a first substrate having a reflection layer and a first electrode and a first substrate having a second electrode are provided. The twist angle between the two substrates and the pair of substrates is 180 °.
An STN liquid crystal element holding a nematic liquid crystal twisted at up to 260 °, a torsional retarder provided outside the second substrate, and a first retarder provided outside the torsional retarder And a first polarizing plate provided outside the first retardation plate, wherein the Δnd value indicating the amount of birefringence of the STN liquid crystal element is 0.7 to 0.84 μm, and The retardation value R indicating the amount of birefringence of the retardation plate is 0.14 to
0.24 μm, and the intersection angle α between the slow axis of the first retardation plate and the absorption axis of the first polarizing plate is 60 ° to 8 °.
It is characterized by 5 °.

Further, the reflection type liquid crystal display device according to the present invention comprises a first substrate having a transflective reflection layer and a first electrode, a second substrate having a second electrode, and the pair of substrates. An STN liquid crystal element holding a nematic liquid crystal twisted at a twist angle of 180 ° to 260 °, a twisted phase difference plate provided outside the second substrate, and provided outside the twisted phase difference plate A first retardation plate, a first polarizing plate provided outside the first retardation plate, a second retardation plate provided outside the first substrate, and an outside of the second retardation plate And a backlight provided outside the second polarizing plate, wherein the Δnd value indicating the amount of birefringence of the STN liquid crystal element is 0.7 to 0.84 μm, and The retardation value R indicating the amount of birefringence of the retardation plate of No. 1 is 0.14.
And the intersection angle α between the slow axis of the first retardation plate and the absorption axis of the first polarizing plate is 60 ° to 0.24 μm.
85 °, and the retardation value of the second retardation plate is approximately 1
/ 4 wavelength.

Further, the reflection type liquid crystal display device according to the present invention comprises a first substrate having a transflective reflection layer and a first electrode, a second substrate having a second electrode, and the pair of substrates. An STN liquid crystal element having a nematic liquid crystal twisted in a twist angle of 180 ° to 260 ° and a second liquid crystal element;
Twisted phase difference plate provided outside the first phase difference plate, a first polarizing plate provided outside the first phase difference plate, a first polarizing plate provided outside the first phase difference plate, and the first substrate A second retardation plate provided outside the first retardation plate, a third retardation plate provided outside the second retardation plate, a second polarizing plate provided outside the third retardation plate, and a second A backlight provided outside the polarizing plate, and Δn indicating the amount of birefringence of the STN liquid crystal element.
The d value is 0.7 to 0.84 μm, and the retardation value R indicating the amount of birefringence of the first retardation plate is 0.14 to 0.2.
4 μm, and the slow axis of the first retardation plate
The crossing angle α with the absorption axis of the polarizing plate is 60 ° to 85 °, and the slow axis of the second retardation plate and the slow axis of the third retardation plate are substantially orthogonal to each other, The wavelength dependence of the phase difference value of the second phase difference plate is different from the wavelength dependence of the phase difference value of the third phase difference plate, and the phase difference value of the second phase difference plate and the third phase difference plate are different. Is characterized in that the difference from the phase difference value is approximately 1/4 wavelength.

Further, in the reflection type liquid crystal display device according to the present invention, the first substrate having the semi-transmissive reflection layer and the first electrode, the second substrate having the second electrode, and the pair of substrates are provided. An STN liquid crystal element having a nematic liquid crystal twisted in a twist angle of 180 ° to 260 ° and a second liquid crystal element;
Twisted phase difference plate provided outside the first phase difference plate, a first polarizing plate provided outside the first phase difference plate, a first polarizing plate provided outside the first phase difference plate, and the first substrate A second retardation plate provided outside the first retardation plate, a third retardation plate provided outside the second retardation plate, a second polarizing plate provided outside the third retardation plate, and a second A backlight provided outside the polarizing plate, and Δn indicating the amount of birefringence of the STN liquid crystal element.
The d value is 0.7 to 0.84 μm, and the retardation value R indicating the amount of birefringence of the first retardation plate is 0.14 to 0.2.
4 μm, and the slow axis of the first retardation plate
And the slow axis of the second retardation plate substantially intersects with the slow axis of the third retardation plate at an angle of 60 ° to 85 °. The phase difference value of the second phase difference plate is approximately １ ／ wavelength, and the phase difference value of the third phase difference plate is approximately １ ／ wavelength.

(Operation) The reflection type liquid crystal display device of the present invention comprises:
As an optical element of a single polarizing plate type liquid crystal display device, one twisted phase difference plate and one phase difference plate are used. The twist direction of the twisted phase difference plate is opposite to the twist direction of the STN liquid crystal element, and the twist angle of the twisted phase difference plate is smaller than the twist angle of the STN liquid crystal element. The Δnd value indicating the amount of birefringence of the torsional retardation plate is set to STN.
By making the Δnd value of the liquid crystal element 0.14 to 0.22 μm smaller, the substantial phase difference value generated between the STN liquid crystal element and the twisted phase difference plate is set to １ ／ wavelength.

However, with this alone, the phase difference values at all wavelengths cannot be reduced to １ ／ wavelength, and perfect black cannot be obtained. Therefore, by adding one retardation plate, changing the retardation value of the retardation plate from 0.14 μm to 0.24 μm, and changing the wavelength dependence of the retardation value, the retardation value of the short wavelength can be reduced. As a result, the phase difference value of the long wavelength becomes large, and as a result, the F / λ value obtained by dividing the phase difference value F by the wavelength λ can be kept constant at に お い て at all wavelengths.

That is, the linearly polarized light transmitted through the polarizing plate becomes circularly polarized light at all wavelengths, is reflected by the reflection layer, and is again reflected by S
When the light passes through the TN liquid crystal element, the twisted phase difference plate, and the phase difference plate, it becomes linearly polarized light whose polarization direction is rotated by 90 ° at all wavelengths, is absorbed by the polarizing plate, and a perfect black display can be obtained.

Further, the Δnd value of the STN liquid crystal element, the phase difference value of the phase difference plate, the Δnd value of the twisted phase difference plate, the arrangement angle of the phase difference plate, the arrangement angle of the twisted phase difference plate, and the arrangement angle of the polarizing plate are set as follows. By optimizing using optical simulation and actual measurement data, in the normally black mode reflection display, the reflectance can be reduced at all wavelengths in the visible light region, and a good black display can be obtained. High-contrast display with bright white display is possible.

On the other hand, in the transmissive display, the light emitted from the backlight passes through a polarizing plate provided on the back surface of the liquid crystal element and a retardation plate having a retardation value of 波長 wavelength, and further has a semi-transmissive reflection layer. And is incident on the liquid crystal element. Since the amount of birefringence of the liquid crystal element is equivalent to １ ／ wavelength due to the twisted phase difference plate and the phase difference plate, the phase difference plate provided on the back surface of the liquid crystal element so as to subtract the birefringence amount of the liquid crystal element Is disposed, the light emitted from the backlight reaches the polarizing plate on the viewing side as it is. Therefore, when the transmission axis of the polarizing plate on the backlight side and the transmission axis of the polarizing plate on the viewing side are arranged orthogonally, good black display can be obtained.

When a voltage is applied to the liquid crystal element, the amount of birefringence of the liquid crystal element changes, and good white display can be obtained for both reflective display and transmissive display. A single-polarizer-type liquid crystal display device with high contrast can be provided.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) The structure of a liquid crystal display device in the best mode for carrying out the present invention will be described below with reference to the drawings.

(Configuration of Liquid Crystal Display: FIGS. 1, 2 and 3) First, the configuration of the liquid crystal display according to the first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view for explaining components of the liquid crystal display device according to the first embodiment of the present invention, FIG. 2 is a plan view in which a pixel portion is enlarged, and FIG. FIG. Hereinafter, the configuration of the liquid crystal display device of the present invention will be described with reference to FIGS.

As shown in FIG. 1, the liquid crystal display device of the present invention comprises an STN liquid crystal element 20, a twisted phase difference plate 12 provided above the STN liquid crystal element 20, and a first phase difference plate 13.
And the first polarizing plate 11.

The first polarizing plate 11, the first retardation plate 13, and the twisted retardation plate 12 are integrated with an acrylic adhesive, and are also attached to the STN liquid crystal element 20 with an acrylic adhesive. .

The STN liquid crystal element 20 has a reflective layer 7 made of aluminum having a thickness of 0.1 μm, a protective film 8 made of an acrylic material having a thickness of 2 μm, and a first electrode 3 made of ITO which is a transparent electrode material. A first substrate 1 made of a glass plate having a thickness of 0.5 mm and a second substrate
A second substrate 2 made of a glass plate having a thickness of 0.5 mm on which the electrodes 4 are formed, a sealing material 5 for bonding the first substrate 1 and the second substrate 2, and a first substrate 1 And a nematic liquid crystal 6 oriented in a counterclockwise twist of 240 ° sandwiched between the second substrate 2 and the second substrate 2.

The transmittance between the first electrode 3 and the second electrode 4 made of ITO is important in terms of brightness. Also, IT
The lower the sheet resistance value of O, the thicker the film thickness and the lower the transmittance. In the embodiment of the present invention, the second electrode 4
Since a data signal is applied, the influence of crosstalk is small, and a sheet resistance of 100 ohms and a thickness of 0.05
Using μm ITO, the average transmittance is about 92%.

Since a scanning signal is applied to the first electrode 3, the first electrode 3 has a sheet resistance value of 1 to reduce crosstalk.
The average transmittance is as low as about 89% using ITO of 0 ohm and 0.3 μm thickness. However, as in the embodiment of the present invention,
Brightness can be improved by using a transparent electrode having a transmittance of 90% or more for at least one of the substrates. As shown in FIG. 2, the intersection of the first electrode 3 and the second electrode 4 becomes a pixel.

The reflective layer 7 is formed by sputtering an aluminum thin film, and has a thickness of 0.03 to protect the surface.
μm silicon oxide (SiO ₂ ) was formed on the surface by a sputtering method, and was formed in a rectangular shape around the pixel as shown in FIG. Further, it is more preferable that the surface shape of the reflective layer 7 is provided with irregularities to give scattering properties, thereby improving the viewing angle characteristics.

The twisted phase difference plate 12 is made of a liquid crystalline polymer having a twisted structure by using triacetyl cellulose (T
AC) film and polyethylene terephthalate (PE)
T) A film in which the film is oriented after being subjected to an orientation treatment, brought into a liquid crystal state at a high temperature of about 150 ° C., adjusted to a twist angle, rapidly cooled to room temperature, and the twisted state is fixed.

Alternatively, a twisted state is fixed to a separately prepared film which has been subjected to an orientation treatment, and then a liquid crystal polymer is transferred to a TAC film. In the embodiment of the present invention, the twist angle is set. Tc is -22
At 0 °, the Δnd value Rc indicating birefringence uses a clockwise twisted phase difference plate 12 of 0.61 μm.

It is preferable that the first polarizing plate 11 is as bright as possible and has a high degree of polarization. In the embodiment of the present invention, a material having a transmittance of 45% and a degree of polarization of 99.9% was used. When a non-reflection layer having a reflectance of about 0.5% is formed on the surface of the first polarizing plate 11 by coating several layers of an inorganic thin film having a different refractive index by a vacuum evaporation method or a sputtering method, the first polarizing plate 1
By reducing the surface reflection of No. 1, the transmittance is improved and the brightness is increased, and the contrast is improved by lowering the black level, which is more preferable.

However, since an inorganic thin film is expensive, a coating type non-reflective film coated with one or two layers of an organic material has recently been developed, and the reflectivity is somewhat high at about 1%. It is inexpensive and can be used as a non-reflective layer even with these non-reflective films.

The first retardation plate 13 is a transparent film of polycarbonate (PC) having a thickness of about 70 μm and a retardation value F1 at a wavelength of 0.55 μm of 0.2.
μm.

Next, the arrangement of the components will be described with reference to FIG. An alignment film (not shown) is formed on the surfaces of the first electrode 3 and the second electrode 4, and as shown in FIG. 3A, the first substrate 1 is positioned on the right with respect to the horizontal axis. 30 ° rise
By rubbing in the direction, the lower liquid crystal molecule alignment direction 6
a becomes + 30 °, and the upper substrate liquid crystal molecule alignment direction 6b becomes −30 ° by rubbing the second substrate 2 in the downward right direction at 30 °. In a nematic liquid crystal having a viscosity of 20 cp,
A revolving substance called chiral material is added and twist pitch P
Is adjusted to 10 μm, and the twist angle Ts = 240 in the counterclockwise direction.
(4) The twisted STN liquid crystal element 20 is formed.

The difference Δ in the birefringence of the nematic liquid crystal 6 used
n is 0.15, and the cell gap d between the first substrate 1 and the second substrate 2 is 5.2 μm. Therefore, Δ represents the amount of birefringence of the STN liquid crystal element 20 represented by the product of the birefringence difference Δn of the nematic liquid crystal 6 and the cell gap d.
The second value Rs is 0.78 μm.

The absorption axis 11a of the first polarizing plate is arranged at + 40 ° with respect to the horizontal axis. Twisted phase difference plate 12
As shown in FIG. 3B, the lower molecular orientation direction 12a is arranged at + 60 ° with respect to the horizontal axis, the upper molecular orientation direction 12b is arranged at −80 °, and the twist angle is clockwise. Tc = 220 °, and the difference ΔT =
Ts−Tc = 20 °, and the difference ΔR = Rs−
Rc = 0.17 μm.

The slow axis 13a of the first retardation plate is arranged at -30 ° with respect to the horizontal axis, and the crossing angle with the absorption axis 11a of the first polarizing plate is 70 °.

(Effects of the First Embodiment: FIGS. 1, 3,
FIG. 14) Next, effects of the liquid crystal display device according to the embodiment of the present invention will be described with reference to the drawings.

Lower molecular orientation direction 12 of torsional retardation plate 12
When the intersection angle between a and the upper liquid crystal molecule alignment direction 6b of the STN liquid crystal element 20 is about 90 °, the birefringence amount of the STN liquid crystal element 20 and the birefringence amount of the twisted phase difference plate 12 are subtracted.

Therefore, in the embodiment of the present invention, ST
The birefringence of the N liquid crystal element 20 and the birefringence of the twisted phase difference plate 12 are subtracted, and ΔR = 0.17 μm.
Since the nematic liquid crystal 6 of the liquid crystal element 20 is twisted, the actual retardation value is 0.1 corresponding to a quarter wavelength.
It is about 4 μm.

Further, in the embodiment of the present invention, the lower molecular arrangement direction 12a of the twisted phase difference plate 12 and the STN liquid crystal element 2
0, the crossing angle of the upper liquid crystal molecule alignment direction 6b is 90 °, and the twist angle Tc of the torsional retardation plate 12 is S
By making the twist angle smaller than the twist angle Ts of the TN liquid crystal element 20, the display color is corrected so that good white display and black display can be obtained.

The twist angle Tc of the torsional retardation plate 12 is
If the twist angle Ts of the STN liquid crystal element 20 is too small, the subtraction of the birefringence becomes insufficient. Therefore, the difference ΔT = Ts−Tc = 10 ° to 30 ° of the absolute value of the twist angle is preferable. Further, the difference in the amount of birefringence ΔR = Rs−Rc = 0.14−
Display was possible at 0.22 μm.

When the crossing angle between the absorption axis 11a of the first polarizing plate and the slow axis 13a of the first retardation plate is 90 °, no phase difference is generated, but the embodiment of the present invention is not limited to this. like,
By setting the intersection angle between the absorption axis 11a of the first polarizing plate and the slow axis 13a of the first retardation plate to 70 °, a slight phase difference is generated, and the phase difference for each wavelength is corrected. ing.

FIG. 14 shows the reflection characteristics of the single polarizer type liquid crystal display device used in the embodiment of the present invention. Curve 34
Indicates a black display state when no voltage is applied to the liquid crystal display device according to the embodiment of the present invention, and a curve 35 indicates a white display state when an on-voltage is applied. A curve 36 shows, for comparison, a black display state when no voltage is applied to a liquid crystal display device of a single polarizing plate system using only a normal PC and a quarter wavelength plate as a retardation plate.

In FIG. 1, the linearly polarized light entered from the first polarizing plate 11 is divided into a first retardation plate 13 and a torsional retardation plate 1.
2 and the nematic liquid crystal 6, it becomes circularly polarized light over all wavelengths and reaches the reflective layer 7.

The circularly polarized light reflected by the reflection layer 7 passes through the nematic liquid crystal 6, the twisted phase difference plate 12 and the first phase difference plate 13 again, and returns to linearly polarized light whose linear direction is rotated by 90 °. 14 is absorbed by the polarizing plate 11 of FIG.
4, a complete black display is obtained.

The liquid crystal display of the prior art using a single retardation plate and using a single polarizing plate, as shown by the curve 36 in FIG. 14, leaks light of short wavelength and long wavelength, and complete black display. No, the display becomes purple black and the contrast is reduced.

Next, when a voltage is applied between the first electrode 3 and the second electrode 4, the nematic liquid crystal 6 rises, and the substantial Δnd value of the STN liquid crystal element 20 decreases. Therefore, the linearly polarized light that has entered from the first polarizing plate 11 returns to elliptically polarized light or linearly polarized light by transmitting through the first retardation plate 13, the twisted retardation plate 12, and the nematic liquid crystal 6.

By applying this voltage, the STN liquid crystal element 20
Is substantially equal to the retardation value of the torsional retardation plate 12, the generated birefringence can be made substantially zero. Therefore, the linearly polarized light incident from the first polarizing plate 11 returns as it is without rotating.
As shown in FIG. 5, a bright and good white display can be obtained.

As described above, the first polarizing plate 11, the first retardation plate 13, the twisted retardation plate 12, and the STN liquid crystal element 20 having the reflection layer 7 therein provide good reflection display using external light. It is possible to provide a reflection type liquid crystal display device of a single polarizing plate type capable of obtaining a high black display and a bright white display and a high contrast display.

(Modification of First Embodiment) In the first embodiment of the present invention, as the STN liquid crystal element 20, 24
Although a STN mode liquid crystal element having a twist of 0 ° is used, a similar reflective liquid crystal display device can be obtained with an STN liquid crystal element having a twist angle of 180 to 260 °.

In the embodiment of the present invention, a liquid crystal polymer film in which the twist state is fixed at room temperature is used as the twist retardation plate 12, but a part of the liquid crystal molecules is bonded to the chain polymer molecules. However, if a temperature-compensated twisted phase difference plate whose Rc changes depending on temperature is used, brightness and contrast in a wide temperature range from high to low temperatures are improved, and a better reflective liquid crystal display device can be obtained.

In the embodiment of the present invention, the reflection layer 7 is formed separately from the first electrode 3. However, the first electrode is formed of a thin metal film such as aluminum or silver, so that the reflection layer 7 is formed. The structure can be simplified by using the reflective electrode that is also used. Further, although a shadow appears on the display, the same effect can be obtained even if the reflective layer 7 is disposed outside the first substrate 1.

In the embodiment of the present invention, PC is uniaxially stretched as the first retardation plate 13, and the refractive index nz in the Z-axis direction is such that the refractive index nx in the stretching direction is perpendicular to the refractive index nx in the stretching direction. n
For y, a retardation plate satisfying nx> ny = nz was used, but a so-called Z-type retardation plate which is multiaxially stretched and nx>nz> ny or polyvinyl alcohol (PVA) is used. ) And polypropylene (PP), the same effect can be obtained by stretching a retardation plate.

(Second Embodiment) Next, the configuration of a liquid crystal display device according to a second embodiment of the present invention will be described. The liquid crystal display device according to the second embodiment can also perform transmissive display by adding a second retardation plate, a second polarizing plate, and a backlight to the liquid crystal display device according to the first embodiment. This is a transflective liquid crystal display device.

(Structure of Liquid Crystal Display Device: FIGS. 4, 5 and 6) The structure of the liquid crystal display device according to the second embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a cross-sectional view illustrating components of a liquid crystal display device according to a second embodiment of the present invention. FIG. 5 is an enlarged plan view of a pixel portion.
FIG. 3 is a plan view showing an arrangement relationship of components. Hereinafter, FIG.
The configuration of the transflective liquid crystal display device of the present invention will be described with reference to FIGS.

As shown in FIG. 4, the liquid crystal display device of the present invention comprises an STN liquid crystal element 21, a twisted phase difference plate 12 provided above the STN liquid crystal element 21, and a first phase difference plate 13.
, A first polarizing plate 11, a second retardation plate 18 provided below the STN liquid crystal element 21, a second polarizing plate 17, and a backlight 16.

The first polarizing plate 11, the first retardation plate 13, and the twisted retardation plate 12 are integrated with an acrylic adhesive, and are also attached to the STN liquid crystal element 21 with an acrylic adhesive. . Further, the second polarizing plate 17 and the second retardation plate 18 are integrated with an acrylic adhesive,
The liquid crystal element 21 is also attached with an acrylic adhesive.

The STN liquid crystal element 21 has a transflective layer 9 of 0.02 μm thick made of aluminum, a protective film 8 of 2 μm thick made of an acrylic material, and a 0.3 μm thick made of ITO which is a transparent electrode material. A first substrate 1 made of a glass plate having a thickness of 0.5 mm on which the first electrode 3 is formed, and a second electrode 4 made of ITO having a thickness of 0.05 μm
Is formed, a second substrate 2 made of a glass plate having a thickness of 0.5 mm, a sealing material 5 for bonding the first substrate 1 and the second substrate 2, a first substrate 1 and a second It is formed from a counterclockwise 240 ° twisted nematic liquid crystal 6 sandwiched between the substrate 2.

As shown in FIG. 5, the first electrode 3 and the second
The portion that intersects with the electrode 4 becomes a pixel.

The semi-transmissive reflection layer 9 is a so-called half mirror in which a part of light is transmitted and the remaining light is reflected by making the thickness of aluminum very thin. In the embodiment of the present invention, by setting the film thickness of aluminum to 0.02 μm, about 10 to 20% of light is transmitted and the remaining 80 to 90% of light is reflected. As described above, a rectangular shape was formed around the pixel.

The torsional retarder 12 and the first retarder 13
And the first polarizing plate 11 are the same as those used in the first embodiment.

The second retardation plate 18 is a quarter-wave plate having a thickness of about 70 μm obtained by stretching polycarbonate, a retardation value F3 of 0.15 μm at a wavelength of 0.55 μm, and 0.14 μm. It is important for the second polarizing plate 17 to have a high degree of polarization, and a material having a transmittance of 44% and a degree of polarization of 99.99% was used.

The backlight 16 includes a light guide plate having a fluorescent lamp or an L light.
It is possible to use an electroluminescent (EL) plate or the like with an ED attached thereto, but in the embodiment of the present invention, an EL having a thickness of about 1 mm and emitting white light is used.
A plate was used.

Next, the arrangement of the components will be described with reference to FIG. The STN liquid crystal element 21 shown in FIG.
Since the arrangement relationship from the upper side to the upper side is the same as that of the first embodiment, it is omitted.

The second element disposed below the STN liquid crystal element 21
As shown in FIG. 6A, the slow axis 18a of the phase difference plate is disposed at + 85 ° with respect to the horizontal axis, and the absorption axis 17a of the second polarizing plate is -50 ° with respect to the horizontal axis. Placed in the first
Is orthogonal to the absorption axis 11a of the polarizing plate.

(Effect of Second Embodiment: FIGS. 4 and 5
FIG. 6) Next, the effects of the liquid crystal display device according to the embodiment of the present invention will be described with reference to the drawings. The reflection display is the same as the effect of the first embodiment, and a display with good contrast is possible.

The transmissive display with the backlight 16 turned on will be described. Light emitted from the backlight 16 becomes linearly polarized light by the second polarizing plate 17. This linearly polarized light is
Is incident at an angle of 45 ° with respect to the slow axis 18a of the phase difference plate 18 of FIG. About 8 in the transflective layer 9
The split is reflected, but the remaining 20% of the light is transmitted.

When no voltage is applied to the STN liquid crystal element 21, the twisted phase difference plate 12 and the STN liquid crystal element 21
And the first retardation plate 13, the birefringence is equivalent to １ ／ wavelength over almost all wavelengths. Therefore, when the second retardation plate 18 is arranged as in the embodiment of the present invention, the second retardation plate 18
Is subtracted by the phase difference generated by the STN liquid crystal element 21, the twisted phase difference plate 12, and the first phase difference plate 13 to become 0, and is orthogonal to the absorption axis 17a of the second polarizing plate. And is emitted as linearly polarized light.

Therefore, the absorption axis 11a of the first polarizing plate
And the absorption axis 17a of the second polarizing plate are orthogonal to each other,
The incident light is not transmitted and black display is performed.

Next, when a voltage is applied between the first electrode 3 and the second electrode 4, the nematic liquid crystal 6 rises, and the substantial Δnd value of the STN liquid crystal element 21 decreases. Therefore, the linearly polarized light incident from the second polarizing plate 17 becomes circularly polarized light when passing through the second retardation plate 18, but is transmitted through the twisted retardation plate 12 and the STN liquid crystal element 21, It becomes elliptically polarized light or linearly polarized light.

Assuming that the phase difference generated in the STN liquid crystal element 21 by this voltage application is 波長 wavelength, the second polarizing plate 1
7, the linearly polarized light incident from the torsion retarder 12 and the first
Is rotated 90 ° by transmitting through the phase difference plate 13 of
Through the first polarizing plate 11, a good white display can be obtained.

As described above, in the reflective display using external light, the first polarizing plate 11, the first retardation plate 13, the twisted retardation plate 12, and the STN liquid crystal element 21 including the transflective layer 9 are provided. Gives good black display and bright white display,
A second retardation plate 18 and a second
A semi-transmissive reflection type liquid crystal display device of a single polarizing plate type in which the backlight 16 is turned on in an environment with little external light by providing the polarizing plate 17 and the backlight 16. Can be provided.

(Modification of Second Embodiment) In the embodiment of the present invention, the transflective layer 9 is formed of an aluminum thin film having a thickness of 0.02 μm. When the thickness is from 03 μm to 0.01 μm, a part of the light is transmitted and can be used as a half mirror.

In the embodiment of the present invention, the transflective layer 9
Although an aluminum thin film was used as the above, it is also possible to use a thin film of an aluminum alloy or silver, or a multilayer film of aluminum and an inorganic oxide to improve the reflectance.

In the embodiment of the present invention, the phase difference generated by the second phase difference plate 18 is arranged to be subtracted from the phase difference generated by the STN liquid crystal element 21. And the phase difference generated by the STN liquid crystal element 21 are added so as to be equivalent to 波長 wavelength, and the absorption axis 17a of the second polarizing plate is set in parallel with the absorption axis 11a of the first polarizing plate. It is also possible to arrange.

(Third Embodiment) Next, the configuration of a liquid crystal display device according to a third embodiment of the present invention will be described. The liquid crystal display device according to the third embodiment is different from the liquid crystal display device according to the second embodiment in that two retardation plates are provided below the liquid crystal element, a diffusion layer is provided, and the shape of the transflective layer is different. It is different from the form.

(Structure of Liquid Crystal Display: FIGS. 7, 8 and 9) The structure of the transflective liquid crystal display according to the third embodiment of the present invention will be described with reference to the drawings. FIG. 7 is a cross-sectional view for explaining the components of the liquid crystal display device according to the third embodiment of the present invention, FIG. 8 is a plan view in which a pixel portion is enlarged, and FIG. FIG. Hereinafter, the configuration of the liquid crystal display device of the present invention will be described with reference to FIGS.

As shown in FIG. 7, the liquid crystal display device of the present invention comprises an STN liquid crystal element 22, a diffusion layer 15 provided above the STN liquid crystal element 22, a twisted phase difference plate 12, a first phase difference Plate 13, first polarizing plate 11, second retardation plate 18 provided below STN liquid crystal element 22, third retardation plate 19, second polarizing plate 17, and backlight 16.

The first polarizing plate 11, the first retardation plate 13, and the twisted retardation plate 12 are integrated with an acrylic adhesive. Further, the second retardation plate 18 and the third retardation plate 19
The second polarizing plate 17 is integrated with an acrylic adhesive, and the STN liquid crystal element 22 is also attached with an acrylic adhesive.

The STN liquid crystal element 22 has a transflective layer 14 of 0.1 μm thick made of aluminum, a protective film 8 of 2 μm thick made of an acrylic material, and a 0.3 μm thick made of ITO which is a transparent electrode material. A first substrate 1 made of a glass plate having a thickness of 0.5 mm on which the first electrode 3 is formed, and a second electrode 4 made of ITO having a thickness of 0.05 μm
Is formed, a second substrate 2 made of a glass plate having a thickness of 0.5 mm, a sealing material 5 for bonding the first substrate 1 and the second substrate 2, and a first substrate 1 and a second substrate 2. And the nematic liquid crystal 6 twisted 240 ° counterclockwise and held between the substrate 2 and the substrate 2.

As shown in FIG. 8, the first electrode 3 and the second
A portion that intersects with the electrode 4 becomes a pixel, and a rectangular transflective layer 14 is provided around the pixel. In the transflective layer 14, an opening 25 is provided for each pixel by a photolithography process. Since the film thickness of aluminum is thicker than that of the second embodiment, the aluminum layer is a complete reflection layer except for the opening, and the transmittance and the reflectance can be adjusted by the area of the opening. In the embodiment of the present invention, the area of the opening is 15 pixels of the pixel area.
%, So that about 15% of the light is transmitted and the remaining 8%
5% of light was reflected.

The diffusion layer 15 is provided to scatter the light reflected by the transflective layer 14 and obtain a bright display with a wide viewing angle. Light incident from the outside is preferably scattered and transmitted forward as much as possible, and less backscattering is preferable because high contrast can be obtained. Here, a scattering adhesive having a thickness of 30 μm in which fine particles are mixed with the adhesive is used as the diffusion layer 15.
It is also used as an adhesive between the TN liquid crystal element 22 and the twisted phase difference plate 12.

Further, since the diffusion layer 15 is made of a material having almost no phase difference and hardly changing the polarization state, the diffusion layer 15 is formed between the second substrate 2 and the first polarizing plate 11 or the first polarization plate. Although it may be arranged anywhere on the surface of the polarizing plate 11,
In order to reduce display blur, it is preferable to be as close to the second substrate 2 as possible. Further, it is preferable that the thickness of the second substrate 2 is as small as possible because display blur is reduced. In the embodiment of the present invention, the thickness is set to 0.5 mm. Further, the thickness of the second substrate is reduced to 0.4 mm, and the thickness of the first substrate is reduced to 0.5 mm.
Then, it is also possible to make the second substrate thinner than the first substrate.

The first polarizing plate 11 and the second polarizing plate 17
The torsional retarder 12, the first retarder 13, and the backlight 16 are the same as those used in the second embodiment.

The second retardation plate 18 is a transparent film having a thickness of about 70 μm obtained by stretching polycarbonate (PC).
The phase difference value F2 at the wavelength of 0.55 μm is 0.36 μm. The third retardation plate 19 is a transparent film having a thickness of about 100 μm obtained by stretching polypropylene (PP) and having a wavelength of 0.1 μm.
The phase difference value F3 of 55 μm is 0.50 μm.

The second device disposed below the STN liquid crystal element 22
The retardation axis 18a of the third retardation plate is disposed at −5 ° with respect to the horizontal axis, and the retardation axis 19a of the third retardation plate is disposed at + 85 ° with respect to the horizontal axis. The phase difference value F2 of the second phase difference plate and the phase difference value F3 of the third phase difference plate are subtracted, and the effective phase difference value is ΔF = F3-F2 =
0.14 μm.

Next, the effect of the phase difference plate will be described. FIG. 13 shows the wavelength dependence of the retardation value of the retardation plate used in the embodiment of the present invention. The horizontal axis indicates the wavelength of light, and the vertical axis indicates the phase difference value of the phase difference plate. A curve 31 indicates the phase difference value of the second phase difference plate 18, a curve 32 indicates a phase difference value of the third phase difference plate 19, and a curve 33 indicates the second phase difference plate 1.
8 is a phase difference value when the third and third phase difference plates 19 are overlapped orthogonally.

Since the material of the second phase difference plate 18 is PC having a large wavelength dependence of the refractive index, the phase difference value of the short wavelength becomes large as shown by the curve 31. On the other hand, since the material of the third retardation plate 19 is PP having a small wavelength dependence of the refractive index, the phase difference value of the short wavelength is almost the same as the phase difference value of the long wavelength as shown by the curve 32. Hardly change.

Therefore, when the second retardation plate 18 and the third retardation plate 19 are overlapped orthogonally so that the retardation value is subtracted, as shown by the curve 33, the shortness around 0.4 μm is obtained. The wavelength phase difference value can be made smaller than the long wavelength phase difference value around 0.7 μm.

Therefore, the value of F / λ obtained by dividing the phase difference value F by the wavelength λ of light can be reduced to approximately に わ た り over all wavelengths, and a so-called broadband 波長 wavelength plate can be formed. Becomes possible.

However, in a normal quarter-wave plate, the phase difference value of the short wavelength is larger than the phase difference value of the long wavelength, so that the F / R value obtained by dividing the phase difference value F by the wavelength λ is It becomes larger than １ ／, and becomes smaller than で は at a long wavelength. As a result, the polarization state changes for each wavelength.

(Effect of Third Embodiment: FIGS. 7 and 8
FIG. 9) Next, effects of the liquid crystal display device according to the embodiment of the present invention will be described with reference to the drawings. The reflection display is the same as that of the third embodiment.
By using the second and first retardation plates 13, it is possible to display a good contrast.

Next, the transmissive display with the backlight 16 turned on will be described. Light emitted from the backlight 16 becomes linearly polarized light by the second polarizing plate 17. The linearly polarized light is incident at an angle of 45 ° with respect to the slow axis of the wide-band quarter-wave plate formed by the third and fourth phase difference plates 18 and 19, and becomes circularly polarized light. Transflective layer 14
Thus, about 70% is reflected, but the remaining 30% of the light is transmitted.

When no voltage is applied to the STN liquid crystal element 22, the twisted phase difference plate 12 and the STN liquid crystal element 22
The first birefringent plate 13 has a birefringence of 複 wavelength over almost all wavelengths. When arranged as in the embodiment of the present invention, the phase difference generated between the second phase difference plate 18 and the third phase difference plate 19 is equal to the STN liquid crystal element 22, the twisted phase difference plate 12, and the first position. The light is subtracted by the phase difference generated by the phase difference plate 13 and becomes zero, and is emitted as linearly polarized light in the same direction as the absorption axis 17a of the second polarizing plate.

Since the absorption axis 11a of the first polarizing plate and the absorption axis 17a of the second polarizing plate are orthogonal to each other, the incident light is not transmitted and black display is performed. Then, the second retardation plate 18 and the third
By using the retardation plate 19, a better black display was obtained than in the second embodiment.

Next, when a voltage is applied between the first electrode 3 and the second electrode 4, the nematic liquid crystal 6 rises, and the substantial Δnd value of the STN liquid crystal element 22 decreases. Therefore, the linearly polarized light incident from the second polarizing plate 17 becomes circularly polarized light by passing through the second retardation plate 18 and the third retardation plate 19.
By passing through the N liquid crystal element 22, it becomes elliptically polarized light or linearly polarized light.

Assuming that the phase difference generated in the STN liquid crystal element 22 by this voltage application is ４ wavelength, the linearly polarized light incident from the second polarizer 17 is distorted by the torsional retarder 12 and the first retarder. 13, the light is rotated by 90 °, so that the light can pass through the first polarizing plate 11 and a good white display can be obtained.

As described above, in the reflective display using external light, the first polarizing plate 11, the first retardation plate 13, the twisted retardation plate 12, and the STN liquid crystal element 22 including the transflective layer 14 are provided. Provides a good black display and a bright white display, and includes a second retardation plate 18, a third retardation plate 19, a second polarizing plate 17, and a backlight 16 below the STN liquid crystal element 22. Thus, a transflective liquid crystal display device of a single polarizing plate type which can provide a display with good contrast can be provided by turning on the backlight 16 in an environment with little external light.

Further, by using the transflective layer 14 having an opening 25 for each pixel, when the opening 25 is made larger, the liquid crystal display device which emphasizes transmissive display is provided. It is possible to support a liquid crystal display device that emphasizes display.

(Modification of Third Embodiment) In the embodiment of the present invention, the second retardation plate 18 is provided with a PC and a third
Although PP is used for the retardation plate 19, if the wavelength dependence of the refractive index is different, a certain effect can be obtained. Good contrast was also obtained when polyarylate was used for the second retardation plate 18 and polyvinyl alcohol was used for the third retardation plate 19.

Further, in the embodiment of the present invention, the phase difference value F2 of the second phase difference plate 18 is 0.36 μm,
The phase difference value F3 of the phase difference plate 19 is 0.5 μm, but if the relationship of ΔF = F3−F2 = 0.14 μm is maintained, the phase difference value F2 and the phase difference value F3 are different. Also,
Similar effects can be obtained.

(Fourth Embodiment) Next, the configuration of a transflective liquid crystal display device according to a fourth embodiment of the present invention will be described. The liquid crystal display device according to the fourth embodiment includes:
The types and arrangement angles of the second retardation plate 18 and the third retardation plate 19 are different from those of the third embodiment.

(Structure of the liquid crystal display device: FIG. 7, FIG. 8, FIG. 1)
0) The configuration of the transflective liquid crystal display device according to the fourth embodiment of the present invention will be described with reference to the drawings. The configuration of the liquid crystal display device according to the fourth embodiment is the same as that of the third embodiment shown in FIGS.

The second retardation plate 18 is a transparent film having a thickness of about 70 μm obtained by stretching PC, and has a retardation value F2 = 0.14 μm at a wavelength of 0.55 μm, which is equivalent to １ ／ wavelength.
The third retardation plate 19 is also a transparent film having a thickness of about 70 μm obtained by stretching PC and having a retardation value F3 = 0.55 μm.
It is set to 0.28 μm, equivalent to 波長 wavelength.

Next, the arrangement of the components will be described with reference to FIG. The arrangement relationship above the STN liquid crystal element 22 shown in FIG. 10B is the same as that of the first embodiment, and therefore will not be described.

The second device disposed below the STN liquid crystal element 22
As shown in FIG. 10A, the slow axis 18a of the third retarder is disposed at -35 ° with respect to the horizontal axis, and the slow axis 19a of the third retarder is With respect to the horizontal axis, and the absorption axis 17a of the second polarizing plate is -5 ° with respect to the horizontal axis.
It is arranged at 0 ° and is orthogonal to the absorption axis 11a of the first polarizing plate.

(Effect of Fourth Embodiment: FIGS. 7 and 1)
0) Next, effects of the liquid crystal display device according to the embodiment of the present invention will be described with reference to the drawings. For the reflection display,
This is the same as the third embodiment, and the use of the torsional phase difference plate 12 and the first phase difference plate 13 enables a display with good contrast.

Next, the transmissive display with the backlight 16 turned on will be described. In the third embodiment, two retardation plates having different wavelength dependences of the refractive index are used. However, even if a material having the same wavelength dependence of the refractive index is used, circularly polarized light is obtained in all visible light regions. A broadband quarter-wave plate that can be converted can be obtained.

The phase difference value F2 is 0.14 corresponding to a quarter wavelength.
μm, the phase difference value F3 is 1 /
Third phase difference plate 19 of 0.28 μm corresponding to two wavelengths
Are overlapped so that the intersection angle becomes 60 ° as shown in FIG.
The phase difference value of the total number of sheets is 0.14 μm and the wavelength is 0.4 μm.
m is shorter than 0.14 μm at a short wavelength around 0.1 m.
At long wavelengths around 7 μm, it is larger than 0.14 μm.
Further, the substantial slow axis of the two lenses is intermediate between the slow axis 18a of the second retardation plate and the slow axis 19a of the third retardation plate, and is -5 ° with respect to the horizontal axis. Direction.

That is, even if the retardation plate is made of a material having the same wavelength dependence of the refractive index, by using two retardation plates, the retardation value of the short wavelength is smaller than the retardation value of the long wavelength. It is possible to form a 波長 wavelength plate. That is, the F / R value obtained by dividing the phase difference value F by the wavelength λ can be reduced to almost 1/4 over the entire visible light region, and as a result, circularly polarized light can be obtained at all wavelengths in the visible light region. Can be

Light emitted from the backlight 16 becomes linearly polarized light by the second polarizing plate 17. Since this linearly polarized light is incident at an angle of 45 ° with respect to the substantial slow axis synthesized by the two retardation plates 18 and 19,
It becomes circularly polarized light. About 70% is reflected by the transflective layer 14, but the remaining 30% of the light is transmitted.

When no voltage is applied to the STN liquid crystal element 22, the twisted phase difference plate 12 and the STN liquid crystal element 22
The first birefringent plate 13 has a birefringence of 複 wavelength over almost all wavelengths. When arranged as in the embodiment of the present invention, the phase difference generated between the second phase difference plate 18 and the third phase difference plate 19 is equal to the STN liquid crystal element 22, the twisted phase difference plate 12, and the first position. The phase difference generated by the phase difference plate 13 is subtracted to become 0, and the absorption axis 1 of the second polarizing plate is set.
The light is emitted as linearly polarized light in the same direction as 7a.

Since the absorption axis 11a of the first polarizing plate is orthogonal to the absorption axis 17a of the second polarizing plate, the incident light is not transmitted, and a black display is obtained. Further, by using the second retardation plate 18 and the third retardation plate 19, a better black display was obtained than in the second embodiment.

Next, when a voltage is applied between the first electrode 3 and the second electrode 4, the nematic liquid crystal 6 rises, and the substantial Δnd value of the STN liquid crystal element 22 decreases. Therefore, the linearly polarized light incident from the second polarizing plate 17 becomes circularly polarized light by passing through the second retardation plate 18 and the third retardation plate 19, but the torsional retardation plate 12 and the ST
By passing through the N liquid crystal element 22, it becomes elliptically polarized light or linearly polarized light.

Assuming that the phase difference value generated in the STN liquid crystal element 22 by this voltage application is equivalent to １ ／ wavelength, the linearly polarized light incident from the second polarizing plate 17 is
By rotating through 90 ° by transmitting through the first retardation plate 13 and the first phase difference plate 13, it is possible to transmit through the first polarizing plate 11 and obtain a good white display.

As described above, in the reflective display using external light, the first polarizing plate 11, the first retardation plate 13, the twisted retardation plate 12, and the STN liquid crystal element 22 including the transflective layer 14 are provided. Provides a good black display and a bright white display, and includes a second retardation plate 18, a third retardation plate 19, a second polarizing plate 17, and a backlight 16 below the STN liquid crystal element 22. Thus, a transflective liquid crystal display device of a single polarizing plate type which can provide a display with good contrast can be provided by turning on the backlight 16 in an environment with little external light.

(Modification of Fourth Embodiment) In the embodiment of the present invention, the slow axis 18a of the second retardation plate is disposed at -35 °, and Slow axis 19a +
Although arranged at 25 °, the intersection angle is 60 ° even if the slow axis 18a of the second retardation plate is located at + 55 ° and the slow axis 19a of the third retardation plate is located at −65 °. If so, a similar effect can be obtained.

(Fifth Embodiment) Next, the configuration of a liquid crystal display device according to a fifth embodiment of the present invention will be described. The liquid crystal display device of the fifth embodiment differs from the configuration of the fourth embodiment in that the shape of the semi-transmissive reflection plate is different and that color display is possible by providing a color filter. I have.

(Configuration of Liquid Crystal Display: FIGS. 11 and 12)
The configuration of the liquid crystal display device according to the fifth embodiment of the present invention will be described with reference to the drawings. FIG. 11 is a cross-sectional view for explaining components of a liquid crystal display device according to a fifth embodiment of the present invention, and FIG. 12 is an enlarged plan view of a pixel portion.
The arrangement relation of the components is the same as that of the fourth embodiment shown in FIG. Hereinafter, the configuration of the liquid crystal display device of the present invention will be described with reference to FIGS.

The liquid crystal display of this embodiment is similar to that of FIG.
As shown in FIG. 3, the STN liquid crystal element 23, the diffusion layer 15 provided on the STN liquid crystal element 23, and the twisted phase difference plate 12
, The first retardation plate 13, the first polarizing plate 11, and the ST
A second retardation plate 18 provided below the N liquid crystal element 23,
It comprises a third retardation plate 19, a second polarizing plate 17, and a backlight 16.

The first polarizing plate 11, the first retardation plate 13, and the twisted retardation plate 12 are integrated with an acrylic adhesive, and are attached to the STN liquid crystal element 23 by the diffusion layer 15. . Further, the second retardation plate 18 and the third retardation plate 1
9 and the second polarizing plate 17 are integrated with an acrylic adhesive, and also attached to the STN liquid crystal element 23 with an acrylic adhesive.

The STN liquid crystal element 23 has a transflective layer 9 made of aluminum and having a thickness of 0.02 μm and a thickness 1 made of three colors of red filter R, green filter G and blue filter B.
Glass having a thickness of 0.5 mm on which a color filter 10 having a thickness of μm, a protective film 8 having a thickness of 2 μm made of an acrylic material, and a first electrode 3 having a thickness of 0.3 μm made of ITO as a transparent electrode material are formed. A first substrate 1 made of a plate and ITO
Substrate 2 made of a 0.5 mm thick glass plate on which a 0.05 μm thick second electrode 4 made of
A sealing material 5 for bonding the first substrate 1 and the second substrate 2 to each other; and a 240 ° counterclockwise twisted nematic sandwiched between the first substrate 1 and the second substrate 2. It is formed from the liquid crystal 6.

The semi-transmissive reflection layer 9 is a so-called half mirror in which a part of light is transmitted and the remaining light is reflected by making the film thickness of aluminum extremely thin. In the embodiment of the present invention, the thickness of aluminum is set to 0.02 μm, which is the same as that of the first embodiment, so that 10 to 20%
About 80% to 90% of the light was reflected, and a rectangular shape was formed around the pixel as shown in FIG.

The first polarizing plate 11 and the twisted phase difference plate 12
The first retardation plate 13, the diffusion layer 15, and the second polarizing plate 17 are the same as those used in the fourth embodiment.

The second retardation plate 18 and the third retardation plate 1
9 and the second polarizing plate 17 are the same as those used in the fourth embodiment.

As the backlight 16, it is possible to use the same white EL as in the first to fourth embodiments. However, in the embodiment of the present invention, in order to improve the saturation and the brightness, the backlight 16 is used. A side light system in which a three-wavelength fluorescent tube was attached to a light plate was used.

The color filter 10 includes a red filter R,
It is composed of three colors, a green filter G and a blue filter B.
As shown in FIG. 2, in the embodiment of the present invention, a vertical stripe shape parallel to the second electrode 4 is used. The width of each color filter is formed wider than the width of the second electrode 4 so that no gap occurs. If there is a gap between the color filters 10, the incident light increases and becomes brighter,
It is not preferable because white light is mixed with the display color and the color purity is reduced.

In order to improve the brightness, the color filter 10 preferably has a maximum transmittance in the spectral spectrum as high as possible, and the maximum transmittance of each color is 80%.
% Or more, and most preferably 90% or more. Further, the minimum transmittance in the spectrum must be as high as 20% to 50%.

As the color filter 10, a pigment dispersion type, a dyeing type, a printing type, a transfer type, an electrodeposition type and the like can be used.
A pigment dispersion type in which a pigment is dispersed in an acrylic or PVA-based photosensitive resin is most preferred because of its high heat resistance and good color purity.

In order to obtain a color filter having such a high transmittance, a semi-transmissive reflective layer 9 of an aluminum thin film is formed on the first substrate 1, and the surface of the semi-transmissive reflective layer 9 is inactivated by anodizing. After that, 10-15% of pigment is added to the photosensitive resin.
The compounded color resist is applied to the first substrate 1 using a spinner, and an exposure process and a development process are performed.
A color filter 10 having a high transmittance was formed even at about μm.

The arrangement of the components is the same as that of the fourth embodiment shown in FIG. 10 and will not be described.

(Effect of Fifth Embodiment: FIG. 11) Next, the effect of the liquid crystal display device of the embodiment of the present invention will be described with reference to the drawings. Since the color filter 10 has no birefringence at all, the reflection display is the same as that of the fourth embodiment, and the use of the twisted phase difference plate 12 and the first Display of contrast is possible.

[0139] By combining the ON and OFF states of the display pixels, color display is possible. For example, turning on the red filter R (white) and turning off the green filter G and the blue filter B (black) enables red display.

The transflective liquid crystal display device according to the embodiment of the present invention has a high reflectance and a contrast ratio of 1.
Since a high value of 0 or more was obtained, a bright color display with high chroma was obtained even in a reflective display in which the backlight 16 was not lit.

Next, the transmissive display with the backlight 16 turned on will be described. Since the transflective layer 9 and the color filter 10 do not have birefringence, the transmissive display is the same as in the fourth embodiment. Therefore, the backlight 16
Is converted into linearly polarized light by the second polarizing plate 17 and becomes circularly polarized light by passing through the third retardation plate 19 and the second retardation plate 18. About 80% is reflected by the transflective layer 9, but the remaining 20% is transmitted.

When no voltage is applied to the STN liquid crystal element 23, the twisted phase difference plate 12 and the STN liquid crystal element 23
The first birefringent plate 13 makes the birefringence amount equivalent to 屈折 wavelength over almost all wavelengths. Therefore, the second
The phase difference generated between the phase difference plate 18 and the third phase difference plate 19 is the same as that between the STN liquid crystal element 23, the twisted phase difference plate 12 and the first
Is subtracted by the phase difference generated by the phase difference plate 13 of the second polarizing plate to become 0, and the light is emitted as linearly polarized light in the direction orthogonal to the absorption axis 17a of the second polarizing plate.

Since the absorption axis 11a of the first polarizing plate and the absorption axis 17a of the second polarizing plate are orthogonal to each other, the incident light is not transmitted and black display is performed. Then, when a voltage is applied between the first electrode 3 and the second electrode 4, white display is achieved with the same effect as in the fourth embodiment.

As described above, the first polarizing plate 11, the first retardation plate 13, the twisted retardation plate 12, the diffusion layer 15, the STN liquid crystal element 23 including the transflective layer 9 and the color filter 10, Accordingly, in the reflective display using external light, a color display with good contrast is possible, and the second retardation plate 18, the third retardation plate 19, and the second polarizing plate By providing the backlight 17 and the backlight 16, the backlight 16 is turned on in an environment where external light is small, so that a single-polarization-plate-type liquid crystal display device that can obtain good color display can be provided.

(Modification of Fifth Embodiment) In the embodiment of the present invention, the color filter 10 is provided on the first substrate 1, but the second electrode 4 is provided inside the second substrate 2. It is also possible to form a color filter 10 between the first substrate 2 and the second substrate 2. However, the color filter 10 is
It is preferable to provide the protective film 8 because the protective film 8 can serve both as the flattening of the color filter 10 and the function as an insulating layer between the transflective film 9 and the first electrode 3.

Further, in the embodiment of the present invention, three colors of red, green and blue are used as the color filters 10;
Similarly, bright color display can be achieved by using three color filters of yellow and magenta.

In the embodiment of the present invention, the surface of the aluminum thin film is inactivated by anodic oxidation as the transflective layer 8 so as to withstand the cleaning line in the color filter manufacturing process. A transparent oxide film such as silicon oxide (SiO ₂ ) can be formed thereon by a sputtering method or a chemical vapor deposition method (CVD method).

[0148]

As is apparent from the above description, according to the present invention, an STN liquid crystal element having a first polarizing plate 11, a first retardation plate 13, a twisted retardation plate 12, and a reflection layer 7 is provided. According to 20, a single-polarizer-type liquid crystal display device that can provide a high-contrast and bright reflective display using external light can be provided.

Further, according to the present invention, the STN liquid crystal element 21 including the first polarizing plate 11, the first retardation plate 13, the twisted retardation plate 12, the transflective layer 9, and the second By using the phase difference plate 18, the second polarizing plate 17, and the backlight 16, reflection display by external light and transmission display by backlight illumination are possible, and high contrast is obtained in both reflection display and transmission display. The obtained single polarizing plate type liquid crystal display device can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is an enlarged plan view showing a pixel portion of the liquid crystal display device according to the first embodiment of the present invention.

FIG. 3 is a plan view showing an arrangement relationship of the liquid crystal display device according to the first embodiment of the present invention.

FIG. 4 is a plan view illustrating an arrangement relationship of a liquid crystal display device according to a second embodiment of the present invention.

FIG. 5 is an enlarged plan view illustrating a pixel portion of a liquid crystal display device according to a second embodiment of the present invention.

FIG. 6 is a plan view illustrating an arrangement relationship of a liquid crystal display device according to a second embodiment of the present invention.

FIG. 7 is a sectional view illustrating a configuration of a liquid crystal display device according to a third embodiment of the present invention.

FIG. 8 is an enlarged plan view of a pixel portion of a liquid crystal display device according to a third embodiment of the present invention.

FIG. 9 is a plan view illustrating an arrangement relationship of a liquid crystal display device according to a third embodiment of the present invention.

FIG. 10 is a plan view illustrating an arrangement relationship of a liquid crystal display device according to a fourth embodiment of the present invention.

FIG. 11 is a sectional view illustrating a configuration of a liquid crystal display device according to a fifth embodiment of the present invention.

FIG. 12 is an enlarged plan view of a pixel portion of a liquid crystal display device according to a fifth embodiment of the present invention.

FIG. 13 is a drawing showing wavelength dependence of a phase difference value of a phase difference plate used in a liquid crystal display device according to a third embodiment of the present invention.

FIG. 14 is a drawing showing spectral reflectance characteristics in the liquid crystal display device according to the first embodiment of the present invention.

[Explanation of symbols]

1: first substrate 2: second substrate
3: first electrode 4: second electrode 5: sealing material
6: Nematic liquid crystal 6a: Lower liquid crystal molecular alignment direction 6b: Upper liquid crystal molecular alignment direction 7: Reflective layer 8: Protective film 9: Semi-transmissive reflective layer (half mirror) 10:
Color filter 11: First polarizing plate 11a: Absorption axis of first polarizing plate 12: Twisted phase plate 12a: Lower molecular orientation direction of twisted phase plate 12b: Upper molecular orientation direction of twisted phase plate 13: First 1 retardation plate 13a: slow axis of first retardation plate 14: transflective layer (with opening) 1
5: Diffusion layer 16: Backlight 17: Second polarizing plate 17a: Absorption axis of second polarizing plate 18: Second retardation plate 18a: Slow axis of second retardation plate 19: Third Retardation plate 19a: Slow axis of third retardation plate 20, 21, 22, 23: STN liquid crystal element R: Red filter G: Green filter
B: Blue filter

Claims (9)

[Claims] A first substrate having a reflective layer and a first electrode; a second substrate having a second electrode; and a twist angle between the first substrate and the second substrate. 180 ° ~
An STN liquid crystal element holding a nematic liquid crystal twisted at 260 °, a twisted phase difference plate provided outside the second substrate, and a first phase difference provided outside the twisted phase difference plate And a first polarizing plate provided outside the first retardation plate, wherein the Δnd value indicating the amount of birefringence of the STN liquid crystal element is 0.7.
a retardation value R from 0.1 μm to 0.84 μm and indicating the amount of birefringence of the first retardation plate
Is 0.14 μm to 0.24 μm, and an intersection angle α between the slow axis of the first retardation plate and the absorption axis of the first polarizing plate is 60 ° to 85 °. Reflective liquid crystal display device. 2. A first substrate having a transflective layer and a first electrode, a second substrate having a second electrode, and a twist angle between the first substrate and the second substrate. Is 180
An STN liquid crystal element holding a nematic liquid crystal twist-oriented at an angle of from 260 ° to 260 °, a torsional retarder provided outside the second substrate, and a first torsional retarder provided outside the torsional retarder A phase difference plate, a first polarizing plate provided outside the first phase difference plate, a second phase difference plate provided outside the first substrate, and provided outside the second phase difference plate A second polarizing plate; and a backlight provided outside the second polarizing plate, wherein a Δnd value indicating a birefringence amount of the STN liquid crystal element is 0.7.
a retardation value R from 0.1 μm to 0.84 μm and indicating the amount of birefringence of the first retardation plate
Is from 0.14 μm to 0.24 μm, and the intersection angle α between the slow axis of the first retardation plate and the absorption axis of the first polarizing plate is 60 ° to 85 °, and A reflection type liquid crystal display device, wherein the phase difference value of the second phase difference plate is approximately 1/4 wavelength. 3. A first substrate having a transflective layer and a first electrode, a second substrate having a second electrode, and a twist angle between the first substrate and the second substrate. Is 180
An STN liquid crystal element holding a nematic liquid crystal twist-oriented at an angle of from 260 ° to 260 °, a torsional retarder provided outside the second substrate, and a first torsional retarder provided outside the torsional retarder A phase difference plate, a first polarizing plate provided outside the first phase difference plate, a second phase difference plate provided outside the first substrate, and a second phase difference plate provided outside the second phase difference plate. A third retardation plate provided, a second polarizing plate provided outside the third retardation plate, and a backlight provided outside the second polarizing plate, a birefringence of the STN liquid crystal element. Δnd value indicating the amount is 0.7
a retardation value R from 0.1 μm to 0.84 μm and indicating the amount of birefringence of the first retardation plate
Is 0.14 μm to 0.24 μm, and the intersection angle α between the slow axis of the first retardation plate and the absorption axis of the first polarizing plate is 60 ° to 85 °, and The slow axis of the second phase difference plate is substantially orthogonal to the slow axis of the third phase difference plate, and the wavelength dependence of the phase difference value of the second phase difference plate and the third axis
Is different from the wavelength dependence of the phase difference value of the phase difference plate, and the difference between the phase difference value of the second phase difference plate and the phase difference value of the third phase difference plate is approximately １ ／ wavelength. A reflective liquid crystal display device, characterized in that: 4. A first substrate having a transflective layer and a first electrode, a second substrate having a second electrode, and a twist angle between the first substrate and the second substrate. Is 180
An STN liquid crystal element holding a nematic liquid crystal twisted from 90 ° to 260 °, a torsional retarder provided outside the second substrate, and a first torsional retarder provided outside the torsional retarder A phase difference plate, a first polarizing plate provided outside the first phase difference plate, a second phase difference plate provided outside the first substrate, and a second phase difference plate provided outside the second phase difference plate. A third retardation plate provided, a second polarizing plate provided outside the third retardation plate, and a backlight provided outside the second polarizing plate, a birefringence of the STN liquid crystal element. Δnd value indicating the amount is 0.7
a retardation value R from 0.1 μm to 0.84 μm and indicating the amount of birefringence of the first retardation plate
Is 0.14 μm to 0.24 μm, and the intersection angle α between the slow axis of the first retardation plate and the absorption axis of the first polarizing plate is 60 ° to 85 °, and The slow axis of the second phase difference plate and the slow axis of the third phase difference plate intersect at approximately 60 °, and the phase difference value of the second phase difference plate is approximately １ ／ wavelength. Wherein the retardation value of the third retardation plate is approximately 波長 wavelength. 5. The twist direction of the twisted phase difference plate has an inverse twisted structure with the STN liquid crystal element, and the twist angle of the twisted phase difference plate is 10 ° to 30 ° smaller than the twist angle of the STN liquid crystal element. The Δnd value indicating the amount of birefringence of the twisted phase difference plate is 0.14 μm to 0.2 from the Δnd value of the STN liquid crystal element.
The reflective liquid crystal display device according to claim 1, 2, 3, or 4, which is smaller by 2 μm. 6. The liquid crystal display device according to claim 1, wherein at least one of the first substrate and the second substrate has a plurality of colors. A reflective liquid crystal display device comprising a color filter. 7. The reflective liquid crystal display according to claim 1, wherein a diffusion layer is provided outside the second substrate. apparatus. 8. The reflection type liquid crystal display device according to claim 2, wherein a metal thin film having a thickness of 0.03 μm to 0.01 μm is used as the transflective layer. 9. The reflective liquid crystal display device according to claim 2, wherein a metal thin film having an opening for each pixel is used as the transflective layer.