JPH09179112A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a liquid crystal display device with which the deterioration in image quality by double images, etc., does not arise, the storage capacity of a liquid crystal layer is sufficiently largely obtd., the degradation in the yield is averted and the setting of the adequate thickness of the liquid crystal layer is possible by forming the liquid crystal layer having orientation twisted at a specific angle between substrates and specifying the product of the layer thickness and double refraction of the liquid crystal layer to specific values. SOLUTION: A liquid crystal panel 2 consists of two sheets of the substrates consisting of the upper substrate 5 and the lower substrate 6, the liquid crystal layer consisting of liquid crystal molecules 7 held between the substrates and electrodes 8 disposed on the substrates in order to impress voltages on the liquid crystal layer. The liquid crystal layer is provided with a polarizing plate 1 on its one side and is provided with a phase compensator 3 and a reflection plate 4 on the other side. The orientation direction of the upper liquid crystal molecules L1 on the polarizing plate side of the liquid crystal layer and the orientation direction of the lower liquid crystal molecules L2 on the phase compensator side have the orientation twisted about 45 deg. between the two substrates. The product of the layer thickness (d) and double refraction Δn of the liquid crystal layer has the value from 150 to 350mn.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION Liquid crystal display devices are widely applied as flat panel displays. Above all, a reflective liquid crystal display device that does not require a backlight is widely used in portable electronic devices that require low power consumption. The present invention relates to a reflective liquid crystal display device.

A reflective liquid crystal display device using an active matrix in which an active element (switching element) for individually controlling a voltage applied to a liquid crystal layer is formed on a substrate is excellent in display performance such as contrast and response speed. It is expected that the applications will be expanded.

As the active element, a three-terminal type thin film transistor (hereinafter referred to as a TFT), a two-terminal type diode or a metal insulator metal (hereinafter referred to as MIM).
Non-linear resistance element is used. The present invention relates to a reflective liquid crystal display device using an active matrix.

[0004]

2. Description of the Related Art Two substrates, a liquid crystal layer sandwiched between the substrates, an electrode provided on the substrate for applying a voltage to the liquid crystal layer, and at least one side of the liquid crystal layer. As a liquid crystal display device having a polarizing plate provided and a reflecting portion provided on one side of the liquid crystal layer, there are TN (twisted nematic) type and STN (super twisted nematic) type.
Type and ECB (electric field control birefringence) type are known.

In the TN type and the STN type, the liquid crystal layer has a 90-270 degree twisted orientation between the two substrates. The polarizing plates are provided on both sides of the liquid crystal layer, and the reflecting portions are provided outside one of the polarizing plates.

In order to obtain a sufficient contrast ratio and viewing angle when the TN type is used as an active matrix, the product Δn * d of the layer thickness d of the liquid crystal layer and the birefringence Δn is 400 nm to 500 nm (first minimum mode). Set to the range of.

In order to obtain a sufficient contrast ratio when the TN type is used in a passive matrix, the product Δn * d of the layer thickness d of the liquid crystal layer and the birefringence Δn is 900 nm to 1200.
It is necessary to set the range to nm (second minimum mode).

In order to obtain a sufficient contrast ratio in the STN type, the product Δn * d of the layer thickness d of the liquid crystal layer and the birefringence Δn is 80.
It is necessary to set it in the range of 0 nm to 1100 nm.

In the ECB type, the liquid crystal layer has a parallel alignment between the two substrates. The polarizing plate is provided on one side of the liquid crystal layer, and the reflecting portion is provided on the other side of the liquid crystal layer. In principle, the maximum contrast ratio is obtained when the product Δn * d of the layer thickness d of the liquid crystal layer and the birefringence Δn has a value of ¼ with respect to the wavelength λ of light. Since the central wavelength λ of visible light that influences the contrast ratio is 400 to 600 nm, in order to obtain a sufficient contrast ratio, the product Δn * d of the layer thickness d of the liquid crystal layer and the birefringence Δn is in the range of 100 nm to 150 nm. It is necessary to

[0010]

The above-mentioned TN type,
The STN type or ECB type reflective liquid crystal display device has a problem that the range of the product Δn * d of the layer thickness d of the liquid crystal layer and the birefringence Δn is considerably limited.

The birefringence Δn of the liquid crystal layer is 0.05 in terms of material.
Although about 0.25 has been reported, the selection range is limited in view of other characteristics required for the display device. As a result, the allowable range of liquid crystal layer thickness is limited.

A typical Δn of a liquid crystal material for an active matrix is about 0.08 to 0.10.
When n is large, the DC characteristics of the liquid crystal material are deteriorated, and problems such as reliability and printing are likely to occur. In addition, Δn in the range below this
In the liquid crystal material, the steepness of the transmittance-voltage characteristic is deteriorated, and the contrast ratio and the viewing angle characteristic are deteriorated.

In the active matrix, the liquid crystal layer serves as a storage capacitor. In the case of an active matrix using TFTs, an auxiliary capacitance may be added, but in any case, it is advantageous to secure a capacitance of a sufficient value in the liquid crystal layer. In particular, when a two-terminal switching element such as MIM is used, the number of steps and costs increase, and the auxiliary capacitance is hardly provided. In this case, the storage capacitance is only the liquid crystal layer, and a sufficiently large capacitance of the liquid crystal layer is required as compared with the capacitance of the switching element.

Since the capacitance C of the liquid crystal layer is proportional to the dielectric constant ε of the liquid crystal layer and inversely proportional to the thickness d, it is advantageous that the liquid crystal layer thickness d is small in order to earn the capacitance C of the liquid crystal layer.

However, in the TN type active matrix, Δn is used in a liquid crystal material having Δn in the range of 0.08 to 0.10.
* If the d is to be 400 nm or more, the liquid crystal layer thickness d is 4
There is a problem that it is difficult to obtain a sufficient liquid crystal capacitance C because the thickness cannot be set to less than or equal to μm.

On the other hand, in the ECB type active matrix, Δn is used for the liquid crystal material having Δn in the range of 0.08 to 0.10.
When * d is set to be 100 nm to 150 nm, the liquid crystal layer thickness d is in the range of 1 μm to 1.8 μm. In this case, it is possible to obtain a sufficient liquid crystal capacitance C, but there is a problem that the liquid crystal layer is too thin and the manufacture is difficult. 2
A liquid crystal layer having a thickness of μm or less is experimentally possible, but it is also sensitive to small dust and foreign matter in mass production. There are many causes of defects such as electrical shorts between the upper and lower substrates, liquid crystal layer thickness (cell gap) abnormality, etc., and the yield drops sharply below 2 μm.

TN type and S as passive matrix
Typical Δn of the liquid crystal material used for the TN type is 0.15
Is about 0.2. If it is smaller than that, the range of Δn * d required to obtain a high contrast ratio is 800 to 1200 nm.
The liquid crystal layer thickness d for maintaining the above condition becomes as thick as 5 μm or more, and the slow response speed is further reduced. Further, a material having a larger Δn than that has a problem in reliability and the like.

One of the other drawbacks of the TN type and STN type reflective liquid crystal display devices is that a polarizing plate is required between the liquid crystal layer and the reflective portion. In the case of the reflection type, it is necessary to make the distance D between the liquid crystal layer, which is a light modulation layer, and the reflection portion close. In particular, when the distance D is large with respect to the pixel size G, a double image due to parallax with respect to obliquely incident light deteriorates the image quality.

A general polarizing plate is a plastic plate, and it is difficult to provide it inside a substrate holding a liquid crystal layer. Therefore, the polarizing plate is usually provided between the substrate and the reflecting portion. As a result, the distance D between the liquid crystal layer and the reflector is usually 0.5 mm to 1.1 mm with the substrate having a thickness of:
The thickness is about 0.6 to 1.3 mm depending on the polarizing plate having a thickness of 0.1 mm to 0.2 mm.

In the reflection type liquid crystal display device used for a wristwatch, a calculator or the like, the pixel size S is large and about 1 mm, so that a distance D of this extent does not cause a big problem. However, in a small electronic notebook, a portable computer, or the like, the pixel size is small, which is 0.5 mm or less, and at such a distance D, deterioration of image quality due to a double image is a serious problem.

In the ECB type, the polarizing plate need only be in front of the liquid crystal layer and on the observer side, and not on the reflecting portion side. Therefore,
It is also possible to provide the reflecting portion on the liquid crystal layer side of the substrate, and it is possible to easily deal with the double image problem as compared with the TN type or STN type.

As described above, in the conventional TN type or STN type reflection type liquid crystal display device, the liquid crystal layer thickness cannot be reduced, so that the storage capacity of the active matrix cannot be increased. However, there is a problem that the image quality is deteriorated by the double image.

On the other hand, the conventional ECB type reflective liquid crystal display device has a problem that the liquid crystal layer is too thin to secure the yield regardless of the active matrix or the passive matrix.

The object of the present invention is to solve the problems of the conventional examples,
An object of the present invention is to provide a reflective liquid crystal display device in which the image quality is not deteriorated by a double image and the storage capacity of the liquid crystal layer is sufficiently large, but the liquid crystal layer thickness can be appropriately set so as not to deteriorate the yield. .

[0025]

In order to achieve the above object, the liquid crystal display device of the present invention has two substrates, a liquid crystal layer sandwiched between the substrates, and a voltage is applied to the liquid crystal layer. A liquid crystal display device having an electrode provided on the substrate, a polarizing plate provided on one side of the liquid crystal layer for this purpose, and a phase compensator and a reflection section provided on the other side of the liquid crystal layer. , The liquid crystal layer has an orientation twisted by about 45 degrees between the two substrates, and the layer thickness d of the liquid crystal layer is
And the birefringence Δn have a value between 150 nm and 350 nm.

Further, the liquid crystal display device of the present invention comprises two substrates, a liquid crystal layer sandwiched between the substrates, an electrode provided on the substrate for applying a voltage to the liquid crystal layer, A liquid crystal display device comprising a polarizing plate provided on one side of a liquid crystal layer and a phase compensator and a reflection section provided on the other side of the liquid crystal layer, wherein the liquid crystal layer has a thickness of about 45 between two substrates. It has a twisted orientation, the product of the layer thickness d of the liquid crystal layer and the birefringence Δn has a value between 150 nm and 350 nm, and the retardation of the phase compensator has a value between 100 nm and 160 nm. Characterize.

Further, the liquid crystal display device of the present invention comprises two substrates, a liquid crystal layer sandwiched between the substrates, an electrode provided on the substrate for applying a voltage to the liquid crystal layer, An active element provided on the substrate for controlling the voltage supplied to the electrodes, a polarizing plate provided on one side of the liquid crystal layer, and a phase compensator and a reflection section provided on the other side of the liquid crystal layer. And a liquid crystal layer having a thickness of about 4 between the two substrates.
It has a twisted orientation of 5 degrees, and is characterized in that the product of the layer thickness d of the liquid crystal layer and the birefringence Δn has a value between 150 nm and 350 nm.

Further, the liquid crystal display device of the present invention comprises two substrates, a liquid crystal layer sandwiched between the substrates, an electrode provided on the substrate for applying a voltage to the liquid crystal layer, An active element provided on the substrate for controlling the voltage supplied to the electrodes, a polarizing plate provided on one side of the liquid crystal layer, and a phase compensator and a reflection section provided on the other side of the liquid crystal layer. And a liquid crystal layer having a thickness of about 4 between the two substrates.
It has a twisted orientation of 5 degrees, the product of the layer thickness d of the liquid crystal layer and the birefringence Δn has a value between 150 nm and 350 nm, and the retardation of the phase compensator has a value between 100 nm and 160 nm. Is characterized by.

Further, the liquid crystal display device of the present invention comprises two substrates, a liquid crystal layer sandwiched between the substrates, an electrode provided on the substrate for applying a voltage to the liquid crystal layer, A liquid crystal display device comprising a polarizing plate provided on one side of a liquid crystal layer, and a phase compensator and a reflection section provided on the other side of the liquid crystal layer, wherein a polarization transmission axis of the polarizing plate and a polarization of the liquid crystal layer. The orientation of the liquid crystal molecules on the plate side is substantially parallel or orthogonal to each other, the liquid crystal layer has an orientation twisted by about 45 degrees between the two substrates, and the optical axis of the phase compensator and the phase compensator side of the liquid crystal layer It is characterized in that it has an angle of about 45 degrees with the alignment direction of the liquid crystal molecules.

The liquid crystal display device of the present invention comprises two substrates, a liquid crystal layer sandwiched between the substrates, an electrode provided on the substrate for applying a voltage to the liquid crystal layer, A liquid crystal display device comprising a polarizing plate provided on one side of a liquid crystal layer, and a phase compensator and a reflection section provided on the other side of the liquid crystal layer, wherein a polarization transmission axis of the polarizing plate and a polarization of the liquid crystal layer. The orientation of the liquid crystal molecules on the plate side is substantially parallel or orthogonal to each other, the liquid crystal layer has an orientation twisted by about 45 degrees between the two substrates, and the optical axis of the phase compensator and the phase compensator side of the liquid crystal layer It is characterized in that it is substantially parallel or substantially orthogonal to the alignment direction of liquid crystal molecules.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION FIG.
FIG. 3 is a block diagram of an active matrix liquid crystal display device using terminal type switching elements. The matrix display panel 23 has data lines D1, D2 ,. . , DM and scan line S
1, S2 ,. . , SN are arranged in a matrix, and the liquid crystal pixels 21 and the two-terminal switching elements 22 are installed corresponding to the intersections.

The data lines D1, D2 ,. . , DM is supplied with a data signal from the data line driver circuit 24, and the scanning lines S1, S2 ,. . , SN includes scan line driver circuit 25
The scan signal is supplied from the data line driver circuit 24 to the data line driver circuit 24 and the scan line driver circuit 25.
A control circuit and a power supply circuit 26 for processing 7 are connected.

The liquid crystal display device of the embodiment of the present invention will be described in detail below. FIG. 1 is a cross-sectional view of a liquid crystal display device according to an embodiment of the present invention when no voltage is applied, and an explanatory view showing a polarization state at each position.

The liquid crystal panel 2 includes two substrates, an upper substrate 5 and a lower substrate 6, a liquid crystal layer composed of liquid crystal molecules 7 sandwiched between the substrates, and the substrate 5 for applying a voltage to the liquid crystal layer. , 6
It is composed of the electrode 8 provided above. A polarizing plate 1 is provided on one side of the liquid crystal layer, and a phase compensator 3 and a reflection plate 4 serving as a reflection section are provided on the other side of the liquid crystal layer.

The observer is located on the left side of the polarizing plate 1 and recognizes the display state by the reflected light 10 with respect to the incident light 9.

The upper part of FIG. 1 shows the angular relationship of each optical element. The liquid crystal molecules on the polarizing plate side of the liquid crystal layer are the upper liquid crystal molecules L.
1. When the liquid crystal molecule on the phase compensator side is the lower liquid crystal molecule L2, the orientation direction L1 of the upper liquid crystal molecule and the orientation direction L2 of the lower liquid crystal molecule have an orientation twisted by about 45 degrees between the two substrates 5 and 6. ing.

As shown in the upper part of FIG. 1, the polarization axis P1 of the polarizing plate 1 and the alignment direction L1 of the upper liquid crystal molecules are substantially parallel to each other. The optical axis O1 of the phase compensator and the alignment direction L2 of the lower liquid crystal molecules have an angle of about 45 degrees.

The lower part of FIG. 1 shows the polarization state of the propagating light at each position. The incident light 9 having the natural polarized light 11 of the horizontal component and the vertical component is transmitted by the polarizing plate 1 and only the horizontal polarized light 12 is incident on the liquid crystal panel. Approximately 4 for LCD panel
Due to the optical rotatory power of the liquid crystal molecules twisted at 5 degrees, like 13
The polarization direction rotates about 45 degrees and enters the phase compensator. The linearly polarized light 13 becomes circularly polarized light or elliptically polarized light 14 by the phase compensator and enters the reflection plate 4. When the light is reflected by the reflection plate 4, it becomes circularly polarized light or elliptically polarized light 15 of which the rotation direction is reversed and enters the phase compensator 3 again. After passing through the phase compensator 3, it becomes linearly polarized light 16 again and enters the liquid crystal panel 2.
In the liquid crystal panel 2, the polarized light is rotated again by about 45 degrees due to the optical rotatory power, and is emitted as the linearly polarized light 17 which is substantially orthogonal to the incident polarized light 12, so that it is absorbed by the polarizing plate 1 and the reflected light 10 has a substantially small light amount. As described above, in the state where no voltage is applied as shown in FIG. 1, almost no reflected light is emitted and the state becomes a dark state.

FIG. 2 is a cross-sectional view of the liquid crystal display device of the embodiment of the present invention shown in FIG. 1 in a voltage applied state, and an explanatory view showing polarization states at respective positions.

The difference from FIG. 1 lies in the alignment state of the liquid crystal molecules of the liquid crystal panel 2. Liquid crystal molecules 7 because voltage is applied
The orientation direction of (1) is perpendicular to the two substrates 5 and 6.

The lower part of FIG. 2 shows the polarization state of the propagating light at each position. The incident light 9 having the natural polarized light 11 of the horizontal component and the vertical component is transmitted by the polarizing plate 1 and only the horizontal polarized light 12 is incident on the liquid crystal panel 2. In the liquid crystal panel 2, since the liquid crystal molecules 7 stand in the direction perpendicular to the substrates 5 and 6, they lose their optical rotatory power and enter the phase compensator 3 with almost no rotation of the polarization direction. Since the optical axis O1 of the phase compensator 3 and the polarization direction 13 are substantially coincident with each other, the optical compensator does not have any effect on the polarization direction and forms the linearly polarized light 14 as the reflection plate 4.
Incident on. The polarization direction 15 does not change even after being reflected by the reflecting plate 4. Also on the return path, the optical axis O1 of the phase compensator 3 and the polarization direction 1
Since 5 coincides with each other, the polarization state 16 does not change, and even after passing through the liquid crystal panel 2, linearly polarized light 17 that is substantially parallel to the incident polarized light 17 is obtained.
And exit. Therefore, it is hardly absorbed by the polarizing plate 1, and the reflected light 10 has a large light amount. As described above, in the voltage applied state of FIG. 2, a large amount of reflected light is emitted and becomes a bright state.

FIG. 6 is a diagram showing the relationship between the product Δn * d of the layer thickness d of the liquid crystal layer and the birefringence Δn and the contrast ratio of the display device in the embodiment of FIG. Δn * d is 150n
It can be seen that there is a peak of contrast at a value between m and 350 nm.

FIG. 7 is a characteristic diagram showing the relationship between the product Δn * d of the layer thickness d of the liquid crystal layer and the birefringence Δn and the viewing angle characteristic of the display device in the embodiment of FIG. It can be seen that the smaller Δn * d is, the wider the viewing angle characteristic is. In Figure 6, Δn *
Although a tentative contrast ratio is obtained even when d is 350 nm or more, it can be seen that the best performance is obtained when Δn * d is between 150 nm and 350 nm, considering the viewing angle characteristics of FIG. 7.

FIG. 8 is a characteristic diagram showing the relationship between the retardation R of the phase compensator and the contrast ratio of the display device in the embodiment of FIG. R is 100 nm to 160 nm
It can be seen that a good contrast ratio can be obtained in the range of.

In the examples described in FIGS. 1 and 2, the polarization axis of the polarizing plate and the alignment direction of the liquid crystal molecules on the polarizing plate side of the liquid crystal layer were substantially parallel. However, a similar effect can be obtained even if the polarization axis of the polarizing plate and the alignment direction of the liquid crystal molecules on the polarizing plate side of the liquid crystal layer are substantially orthogonal.

FIG. 3 is a cross-sectional view of a liquid crystal display device according to another embodiment of the present invention when no voltage is applied, and an explanatory view showing a polarization state at each position.

The liquid crystal panel 2 includes two substrates, an upper substrate 5 and a lower substrate 6, a liquid crystal layer composed of liquid crystal molecules 7 sandwiched between the substrates, and the substrate 5 for applying a voltage to the liquid crystal layer. , 6
It is composed of the electrode 8 provided above. A polarizing plate 1 is provided on one side of the liquid crystal layer, and a phase compensator 3 and a reflection plate 4 serving as a reflection section are provided on the other side of the liquid crystal layer.

The upper part of FIG. 3 shows the angular relationship of each optical element. The liquid crystal molecules on the polarizing plate side of the liquid crystal layer are the upper liquid crystal molecules L.
1. When the liquid crystal molecule on the phase compensator side is the lower liquid crystal molecule L2, the orientation direction L1 of the upper liquid crystal molecule and the orientation direction L2 of the lower liquid crystal molecule have an orientation twisted by about 45 degrees between the two substrates 5 and 6. ing.

As shown in the upper part of FIG. 3, the polarization axis P1 of the polarizing plate 1 and the alignment direction L1 of the upper liquid crystal molecules have a relationship of about 45 degrees. The optical axis O1 of the phase compensator and the alignment direction L2 of the lower liquid crystal molecules have an angle substantially parallel to each other.

The lower part of FIG. 3 shows the polarization state of the propagating light at each position. The incident light 9 having the natural polarized light 11 of the horizontal component and the vertical component is transmitted by the polarizing plate 1 and only the horizontal polarized light 12 is incident on the liquid crystal panel. Approximately 4 for LCD panel
Due to the optical rotatory power of the liquid crystal molecules twisted at 5 degrees, like 13
The polarization direction rotates about 45 degrees and enters the phase compensator. Since the optical axis O1 of the phase compensator 3 and the polarization direction 13 substantially coincide with each other, the optical compensator does not have any effect on the polarization direction and enters the reflection plate 4 as the linearly polarized light 14. The polarization direction 15 does not change even after being reflected by the reflecting plate 4. Phase compensator 3 on the return route
Since the optical axis O1 of and the polarization direction 15 coincide with each other, the polarization state 1
6 does not change and enters the liquid crystal panel 2. LCD panel 2
Then, the liquid crystal molecules are twisted by about 45 degrees and rotated by about 45 degrees, and after passing, they are emitted as linearly polarized light 17 which is substantially parallel to the incident polarized light 12. Therefore, it is hardly absorbed by the polarizing plate 1, and the reflected light 10 has a large light amount. As mentioned above,
In the state in which no voltage is applied as shown in FIG. 3, a large amount of reflected light is emitted and becomes a bright state.

FIG. 4 is a cross-sectional view of the liquid crystal display device according to the embodiment of the present invention shown in FIG. 3 when a voltage is applied, and an explanatory view showing a polarization state at each position.

The difference from FIG. 3 lies in the alignment state of the liquid crystal molecules of the liquid crystal panel 2. Liquid crystal molecules 7 because voltage is applied
The orientation direction of (1) is perpendicular to the two substrates 5 and 6.

The lower part of FIG. 4 shows the polarization state of the propagating light at each position. The incident light 9 having the natural polarized light 11 of the horizontal component and the vertical component is transmitted by the polarizing plate 1 and only the horizontal polarized light 12 is incident on the liquid crystal panel 2. In the liquid crystal panel 2, since the liquid crystal molecules 7 stand in the direction perpendicular to the substrates 5 and 6, they lose their optical rotatory power and enter the phase compensator 3 with almost no rotation of the polarization direction. Linearly polarized light 1 by the phase compensator 3
3 becomes circularly polarized light or elliptically polarized light 14 and enters the reflection plate 4. When the light is reflected by the reflection plate 4, it becomes circularly polarized light or elliptically polarized light 15 of which the rotation direction is reversed and enters the phase compensator 3 again. After passing through the phase compensator 3, it becomes linearly polarized light 16 again and enters the liquid crystal panel 2. Since the liquid crystal panel 2 loses its optical rotatory power, the polarized light does not rotate and is emitted as a linearly polarized light 17 that is substantially orthogonal to the incident polarized light 12. Therefore, the polarized light 1 is absorbed by the polarizing plate 1, and the reflected light 10 has an almost small amount of light. Become. As described above, in the voltage applied state of FIG. 4, almost no reflected light is emitted and the state becomes a dark state.

Also in the embodiments of FIGS. 3 and 4, the layer thickness d of the liquid crystal layer is
The relationship between the product Δn * d of the birefringence Δn, the contrast ratio of the display device, and the viewing angle characteristic shows almost the same tendency as in FIGS. 6 and 7, and Δn * d is the best between 150 nm and 350 nm. Performance is obtained.

In the embodiments of FIGS. 3 and 4, the relationship between the retardation R of the phase compensator and the contrast ratio of the display shows a tendency almost similar to that of FIG. 8, and R from 100 nm to 16 nm.
A good contrast ratio can be obtained in the range of 0 nm.

In the examples of FIGS. 3 and 4, the optical axis of the phase compensator was substantially parallel to the alignment direction of the liquid crystal molecules on the phase compensator side of the liquid crystal layer when no voltage was applied. However, the same effect can be obtained even if the optical axis of the phase compensator and the alignment direction of the liquid crystal molecules on the phase compensator side of the liquid crystal layer are substantially orthogonal.

[0057]

As described above, in the liquid crystal display device of the present invention, a high contrast ratio and a good viewing angle are possible due to the novel structure. Also, since there is only one polarizing plate on the incident side, the distance between the liquid crystal layer and the reflection part can be reduced, and the TN type or STN
The deterioration of the image quality due to the double image, which is a defect of the mold, can be improved.

In the liquid crystal display device of the present invention, the contrast ratio and viewing angle characteristics can be optimized by setting the product of the layer thickness d of the liquid crystal layer and the birefringence Δn to a value between 150 nm and 350 nm.

In the liquid crystal display device of the present invention, the retardation R of the phase compensator has a value between 100 nm and 160 nm, whereby the contrast ratio can be optimized.

In the liquid crystal display device of the present invention, when used in an active matrix, the liquid crystal layer thickness d is 4.4 μm or less.
Can be set, and sufficient storage capacity can be secured.

In the liquid crystal display device of the present invention, the thickness d of the liquid crystal layer can be set in the range of about 1.8 μm to 4.4 μm, which avoids a decrease in yield and an increase in equipment investment cost due to excessive cleansing. It is possible to do

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a liquid crystal display device according to an embodiment of the present invention when no voltage is applied, and an explanatory view showing polarization states at various positions.

FIG. 2 is a cross-sectional view of a liquid crystal display device according to an embodiment of the present invention when a voltage is applied, and an explanatory diagram showing a polarization state at each position.

FIG. 3 is a cross-sectional view of a liquid crystal display device according to another embodiment of the present invention when no voltage is applied, and an explanatory view showing polarization states at various positions.

FIG. 4 is a cross-sectional view of a liquid crystal display device according to another embodiment of the present invention when a voltage is applied, and an explanatory view showing a polarization state at each position.

FIG. 5 is a block diagram of a two-terminal type active matrix liquid crystal display device of the present invention.

FIG. 6 is a characteristic diagram showing the relationship between the contrast ratio of the liquid crystal display device of the present invention and the product Δn * d of the layer thickness d of the liquid crystal layer and the birefringence Δn.

FIG. 7 is a characteristic diagram showing the relationship between the viewing angle characteristics of the liquid crystal display device of the present invention and the product Δn * d of the layer thickness d of the liquid crystal layer and the birefringence Δn.

FIG. 8 is a characteristic diagram showing the relationship between the contrast ratio of the liquid crystal display device of the present invention and the retardation R of the phase compensator.

[Explanation of symbols]

 1 Polarizing Plate 2 Liquid Crystal Panel 3 Phase Compensator 4 Reflector 5 Upper Substrate 6 Lower Substrate 7 Liquid Crystal Molecule 8 Electrode 9 Incident Light 10 Reflected Light 21 Liquid Crystal Pixel 22 Two-Terminal Switching Element 23 Matrix Display Panel 24 Data Line Driver Circuit 25 Scanning Line driver circuit 26 Control circuit and power supply circuit P1 Polarizing axis of polarizing plate L1 Upper liquid crystal molecule L2 Lower liquid crystal molecule O1 Optical axis of phase compensator

Claims (6)

[Claims] 1. Two substrates, a liquid crystal layer sandwiched between the substrates, an electrode provided on the substrate for applying a voltage to the liquid crystal layer, and provided on one side of the liquid crystal layer. A liquid crystal display device having a polarizing plate and a phase compensator and a reflection portion provided on the other side of the liquid crystal layer, wherein the liquid crystal layer has an orientation twisted by about 45 degrees between two substrates, Layer thickness d of liquid crystal layer and birefringence Δn
The liquid crystal display device is characterized in that the product of has a value between 150 nm and 350 nm. 2. Two substrates, a liquid crystal layer sandwiched between the substrates, an electrode provided on the substrate for applying a voltage to the liquid crystal layer, and provided on one side of the liquid crystal layer. A liquid crystal display device having a polarizing plate and a phase compensator and a reflection portion provided on the other side of the liquid crystal layer, wherein the liquid crystal layer has an orientation twisted by about 45 degrees between two substrates, Layer thickness d of liquid crystal layer and birefringence Δn
Has a value between 150 nm and 350 nm, and the retardation of the phase compensator is 100 nm to 160 nm.
A liquid crystal display device having a value between. 3. A substrate, two liquid crystals, a liquid crystal layer sandwiched between the substrates, an electrode provided on the substrate for applying a voltage to the liquid crystal layer, and a voltage supplied to the electrode are controlled. Therefore, a liquid crystal display device having an active element provided on the substrate, a polarizing plate provided on one side of the liquid crystal layer, and a phase compensator and a reflection section provided on the other side of the liquid crystal layer. The liquid crystal layer has a twisted orientation of about 45 degrees between the two substrates, and the product of the layer thickness d of the liquid crystal layer and the birefringence Δn is 150 nm to 350 nm.
A liquid crystal display device having a value between. 4. A substrate, two liquid crystals, a liquid crystal layer sandwiched between the substrates, an electrode provided on the substrate for applying a voltage to the liquid crystal layer, and a voltage supplied to the electrode are controlled. Therefore, a liquid crystal display device having an active element provided on the substrate, a polarizing plate provided on one side of the liquid crystal layer, and a phase compensator and a reflection section provided on the other side of the liquid crystal layer. The liquid crystal layer has a twisted orientation of about 45 degrees between the two substrates, and the product of the layer thickness d of the liquid crystal layer and the birefringence Δn is 150 nm to 350 nm.
And the retardation of the phase compensator is 10
A liquid crystal display device having a value between 0 nm and 160 nm. 5. A pair of substrates, a liquid crystal layer sandwiched between the substrates, an electrode provided on the substrates for applying a voltage to the liquid crystal layer, and provided on one side of the liquid crystal layer. A polarizing plate, and a phase compensator and a reflection portion provided on the other side of the liquid crystal layer, wherein a polarizing axis of the polarizing plate and an alignment direction of liquid crystal molecules on the polarizing plate side of the liquid crystal layer Are substantially parallel or substantially orthogonal, and the liquid crystal layer has an orientation twisted by about 45 degrees between the two substrates, and the optical axis of the phase compensator and the orientation direction of the liquid crystal molecules on the phase compensator side of the liquid crystal layer are approximately 45. A liquid crystal display device characterized by having an angle of degrees. 6. A substrate, two substrates, a liquid crystal layer sandwiched between the substrates, an electrode provided on the substrate for applying a voltage to the liquid crystal layer, and provided on one side of the liquid crystal layer. A polarizing plate, and a phase compensator and a reflection portion provided on the other side of the liquid crystal layer, wherein a polarizing axis of the polarizing plate and an alignment direction of liquid crystal molecules on the polarizing plate side of the liquid crystal layer Are substantially parallel or substantially orthogonal, and the liquid crystal layer has an orientation twisted by about 45 degrees between the two substrates, and the optical axis of the phase compensator and the orientation direction of the liquid crystal molecules on the phase compensator side of the liquid crystal layer are substantially parallel. Alternatively, a liquid crystal display device characterized by being substantially orthogonal.