JP2001108957A - Liquid crystal display - Google Patents

Abstract

(57) [Problem] To realize a bright STN liquid crystal display device capable of displaying black and white accurately. SOLUTION: An STN is provided between first and second substrates 14 and 16.
It has a liquid crystal cell 10 in which a liquid crystal layer 12 is inserted, and a transflective layer 30 is provided on the second substrate side in this cell. If a reflective layer is used instead of the transflective layer 30, a reflective STN liquid crystal display layer is obtained. The first and second retardation plates 40 and 42 and the first polarizing plate 44 are arranged outside the first substrate of the liquid crystal cell 10 in this order. In a transflective LCD, the second
Circularly polarized light irradiating means 70 is arranged outside the substrate. Liquid crystal alignment twist angle θ _LC , delay axis direction θ 1 of first phase difference plate 40 with respect to liquid crystal alignment direction on first substrate side, first phase difference plate 40
The delay axis direction θ2 of the second phase difference plate 42 with respect to the delay axis of
By optimizing the values of the absorption axis θ3 of the first polarizing plate 44 with respect to the delay axis of the second retardation plate 42, the liquid crystal retardation Δn _LC · d _LC, etc., accurate display of black and white and bright display can be achieved. .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to an STN (Super Twist) in which the twist angle of the liquid crystal is larger than 90 degrees.
isted Nematic) type liquid crystal display device.

[0002]

2. Description of the Related Art Conventionally, as a method of increasing the twist angle of liquid crystal molecules between two electrodes to cause a sharp voltage-transmittance change and to perform a high-density dot matrix display, there has been proposed a STD method.
N-type liquid crystal display devices were known (TJ Scheffer and
J. Nehring, Appl. Phys. Lett. 45 (10) 1021-1023 (198
Four)).

In this method, the product Δn _LC · d _LC of the birefringence Δn _LC of the liquid crystal of the liquid crystal display element used and the thickness d _{LC of the} liquid crystal layer is used.
Was substantially set between 0.8 and 1.2 μm (Japanese Patent Application Laid-Open No. Sho 60-107020). In addition, good contrast can be obtained only with a specific combination of hues, such as yellow green and dark blue, and blue violet and light yellow, so that black and white display cannot be performed.

Therefore, a method for realizing a liquid crystal display device capable of monochrome display and having a high contrast has been conventionally proposed. For example, Japanese Patent Publication No. 3-18164 discloses that two liquid crystal cells having mutually opposite spirals are provided. A method has been proposed in which layers are stacked, a voltage is applied to only one cell, and the other liquid crystal cell is used as a mere optical compensator.

In Japanese Patent Publication No. Hei 3-50249,
It has been proposed to use a polymer film to optically compensate an STN liquid crystal cell.

[0006]

Recently, in a portable information terminal and the like, adoption of a reflection type liquid crystal display device has been proposed in order to further reduce the size and thickness and reduce power consumption.
Further, a reflection type liquid crystal display device having a semi-transmission function which can be used as a reflection type or a transmission type has begun to be proposed. In such a reflection type liquid crystal device, it is required to ensure appearance during reflection. The above-mentioned conventionally proposed STN liquid crystal cell is of a transmission type, and in order to use it as a reflection type, conventionally, a reflection plate may be provided outside the non-observation side of the liquid crystal cell.

However, in the configuration in which the reflector is disposed outside the cell, since the transparent substrate of the cell exists between the reflector and the liquid crystal layer, the occurrence of parallax cannot be prevented. And the light reflected and emitted outside the cell pass through different pixels. Therefore,
When observing the liquid crystal display device from an oblique direction, the shade of the displayed pixel becomes a double image as reflected on a reflection plate, and the display quality of the display device is reduced.

Further, when two polarizing plates are used in the same manner as in the transmission type STN liquid crystal cell, light is incident upon reflection and upon reflection.
Since the light passes through the polarizing plate a total of four times, the loss of light generated by the polarizing plate causes a problem that the light use efficiency is poor and the display becomes dark.

On the other hand, if one polarizing plate is used, the optical characteristics are different from those of a conventionally known two-plate polarizing plate type STN liquid crystal cell. Optical settings that are being optimized in transmissive STN liquid crystal cells are not available.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a reflection type in which a reflection layer is provided in an STN liquid crystal cell, a single polarizing plate is used, and optical compensation of the cell is performed by a retardation plate. It is an object of the present invention to realize an STN liquid crystal display device which is bright, has a small parallax, and has an optimum condition for enabling good black-and-white display.

Another object of the present invention is to realize a reflection type STN liquid crystal display device having an optimum characteristic even as a transflective type.

[0012]

In order to achieve the above object, a liquid crystal display of the present invention has the following features.

First, the liquid crystal display device of the present invention has a liquid crystal cell in which a liquid crystal layer is inserted in a gap between a first substrate having electrodes formed on opposing surfaces and a second substrate, respectively. A liquid crystal display device in which a first retardation plate, a second retardation plate, and a polarizing plate are arranged in this order outside the first substrate, and a reflective layer is formed on the second substrate side in the liquid crystal cell. Also,
In the liquid crystal layer, the twist angle θ _LC of the alignment direction of the liquid crystal molecules from the first substrate to the second substrate is ± 160.
゜ to ± 300 °, and the refractive index anisotropy Δn of the liquid crystal layer.
Retardation value [Delta] n _LC · d _LC of the liquid crystal layer, indicated by the product of the thickness d _LC of the the _LC liquid crystal layer, 0.30 .mu.m ≦
Δn _LC · d _LC ≦ 2.0 μm. Further, the angle of the slow axis direction of the first phase difference plate with respect to the alignment direction of the liquid crystal layer on the first substrate side is θ1, and the second phase difference with respect to the slow axis direction of the first phase difference plate is When the angle in the slow axis direction of the plate is θ2 and the angle in the absorption axis direction of the polarizing plate with respect to the slow axis direction of the second retardation plate is θ3, θ
1, θ2 and θ3 are 65 ° ≦ θ1 ≦ 90 ° and −25 ° ≧ θ, respectively, when the torsion angle θ _LC is set in a minus range, that is, in a range of −160 ° to −300 °.
When 2 ≧ −55 ° and 50 ° ≦ θ3 ≦ 80 ° are satisfied and the torsion angle θ _LC is set in the plus range, that is, in the range of 160 ° to 300 °, the above θ1, θ2, and θ3 are set.
, The relationship between the sign of the plus and minus signs and the sign of the sign in the range of −65 ° ≧ θ1 ≧ −90 °, 25 ° ≦
It is characterized by satisfying θ2 ≦ 55 ° and −50 ° ≧ θ3 ≧ −80 °. Note that, for example, the plus and minus signs express clockwise as plus and counterclockwise as minus.

In a STN liquid crystal display device having a reflective layer in a cell, by designing each optical element to satisfy such conditions, a bright reflective STN LCD without parallax is provided.
And the first and second retardation plates provide the STN
Coloring in the liquid crystal cell is compensated, and black and white can be displayed accurately.

Another feature of the present invention is that it has a liquid crystal cell in which a liquid crystal layer is inserted in a gap between the first and second substrates each having an electrode formed on the opposite surface side, and the first substrate of the cell has a liquid crystal layer. A liquid crystal display device in which a first retardation plate, a second retardation plate, and a polarizing plate are arranged in this order on the outside, and a reflective layer is formed on the second substrate side in the liquid crystal cell; In the liquid crystal layer, the twist angle θ _LC of the alignment direction of the liquid crystal molecules from the first substrate toward the second substrate is ± 160 ° to ± 3 °.
And the retardation value Δn _LC · d _LC of the liquid crystal layer represented by the product of the refractive index anisotropy Δn _LC of the liquid crystal layer and the thickness d _LC of the liquid crystal layer is 0.30 μm ≦ Δn _LC ·
When d _LC ≦ 2.0 μm and the torsion angle θ _LC is set in a minus range, that is, in the range of −160 ° to −300 °, θ1, θ2, and θ3 having the same definition as above.
Satisfies any of the following conditions (i) to (ix). Alternatively, the torsion angle θ _LC is in the positive range, that is, 160
(I) to (ix) when set in the range of
In which the directions of the plus and minus and the inequality sign in the relational expression are all reversed.

(I) -90 ° ≦ θ1 ≦ −60 °, −40 ° ≦ θ2 ≦ −30 °, 70 ° ≦ θ3 ≦ 80 °, (ii) 0 ° ≦ θ1 ≦ 20 °, -80 ° ≦ θ2 ≦ −60 °,
15 ° ≦ θ3 ≦ 40 °, (iii) 45 ° ≦ θ1 ≦ 55 °, 70 ° ≦ θ2 ≦ 80 °,
−60 ° ≦ θ3 ≦ −50 °, (iv) 80 ° ≦ θ1 ≦ 90 °, 65 ° ≦ θ2 ≦ 75 °, −
45 ° ≦ θ3 ≦ −35 °, (v) 60 ° ≦ θ1 ≦ 80 °, 55 ° ≦ θ2 ≦ 75 °, −
60 ° ≦ θ3 ≦ −55 °, (vi) 15 ° ≦ θ1 ≦ 30 °, -75 ° ≦ θ2 ≦ −65
°, -65 ° ≤ θ3 ≤ -55 °, (vii) 60 ° ≤ θ1 ≤ 70 °, -70 ° ≤ θ2 ≤ -55
°, 35 ° ≤ θ3 ≤ 55 °, (viii) 30 ° ≤ θ1 ≤ 55 °, -70 ° ≤ θ2 ≤ -50
°, -65 ° ≤θ3≤-40 °, (ix) -80 ° ≤θ1≤-70 °, 75 ° ≤θ2≤85
°, 50 ° ≦ θ3 ≦ 60 °.

The above (i) to (ix) or (i) to (ix) +
A reflective STN liquid crystal display device capable of bright display without parallax and capable of accurately displaying black and white can also be provided by designing so as to satisfy any of the conditions of-sign and ≤ ≥ sign reversed. realizable. In addition, + -sign, ≦
The relationship where the signs are reversed is, for example, 90 ° ≧ θ1 ≧ 60 °, 40 ° ≧ θ2 ≧ 30 °, −7 in the case of (i) above.
0 ° ≧ θ3 ≧ −80 °.

Another feature of the present invention is that, in the liquid crystal display device having the above-described configuration, the light incident from the one substrate side is used as the reflection layer formed on the second substrate side in the liquid crystal cell. A transflective layer having a function of reflecting and transmitting light incident from the second substrate side is to be adopted.

Still another feature of the present invention is a liquid crystal display device having a liquid crystal cell in which a liquid crystal layer is inserted in a gap between a first substrate having electrodes formed on opposite sides and a second substrate, respectively. A first retardation plate, a second retardation plate, and a first polarizing plate are arranged in this order outside the first substrate of the liquid crystal cell, and the second substrate side of the liquid crystal cell is arranged from the first substrate side. A semi-transmissive reflection layer having a function of reflecting incident light and transmitting light incident from the second substrate side is formed, and is incident from the first substrate side in accordance with a voltage applied to the liquid crystal layer. The reflected light is subjected to birefringence and reaches the transflective layer in a substantially circularly polarized state.

If such a semi-transmissive layer is used as the reflective layer, for example, when the outside light is very strong outdoors, it is used as a reflective type, and when it is dark indoors, the internal light source is turned on and the transmissive type is used. It can be used as For this reason, a bright image can always be displayed regardless of whether the external light is strong or weak. That is, a transflective STN liquid crystal display device can be realized by using such a transflective layer.

In addition, when light is reflected in the semi-transmissive reflection layer and is circularly polarized, the reflection characteristics are good,
For example, in an STN liquid crystal display device in a normally black mode, black display in the reflection mode is more accurate. In this case, by adopting a configuration in which a circularly polarized light irradiating unit or the like for irradiating the liquid crystal cell with circularly polarized light is disposed outside the second substrate of the liquid crystal cell, the transmission mode is a light source. The light irradiating means irradiates the liquid crystal cell with circularly polarized light, so that the light is in a circularly polarized state on the second substrate side (non-observation side of the display) of the liquid crystal cell in both the reflection mode and the transmission mode. Thus, high quality display with little difference even when the mode is switched is enabled.

In the above liquid crystal display device, it is preferable that the circularly polarized light irradiating means comprises a circularly polarized light source, or a broadband circular polarizer and a light source.

Further, in the above liquid crystal display device, the wide band circular polarizer is a cholesteric film. Alternatively, instead of the cholesteric film, the broadband circular polarizer comprises a λ / 4 retardation film, a λ
A configuration including a / 2 retardation film and a polarizing plate can also be adopted.

Further, the polarizer of the broadband circular polarizer may be a reflective polarizer that transmits linearly polarized light oscillating in a specific direction and reflects light oscillating perpendicularly to the specific direction. .

If there is an ideal broadband circularly polarized light source (a light source that emits circularly polarized light with respect to all visible wavelengths) as such a light source, it is preferable to use such a light source. Exists, there is an optimum axial relationship depending on the polarizing plate, the second and first retardation plates, the liquid crystal layer, and the circularly polarized light irradiation means used. Therefore, it is appropriate to evaluate the characteristics of the circularly polarized light irradiating means to be used and to optimally arrange them. In particular, in the present invention, it is preferable that right circularly polarized light or left circularly polarized light is incident on the liquid crystal cell from the broadband circular polarizer. Therefore, the optical characteristics of other optical elements (a retardation plate, a polarizing plate, a liquid crystal cell), particularly the optical characteristic axis relation of each element, are optimized depending on whether the right or the left is employed as the circularly polarized light. It is preferable to arrange them.

Another feature of the present invention is that in any one of the above liquid crystal display devices, it is indicated by the product of the refractive index anisotropy Δn1 of the first retardation plate and the thickness d1 of the first retardation plate. Retardation value Δn1 · d1 of the first retardation plate
The refractive index anisotropy Δn2 of the second retardation plate and the second
The total value Rs of the retardation value Δn2 · d2 of the second retardation plate indicated by the product of the thickness d2 of the retardation plate and the product
With respect to the retardation value Δn _LC · d _{LC of the} liquid crystal layer, Δn _LC · d _LC −m × 147.5-25 ≦ Rs ≦ Δn
_LC · d _LC −mx147.5 + 75 (where m = −2,
0, 1, 2).

Retardation value Δn _LC · d _{LC of} liquid crystal layer
On the other hand, if the total retardation value Rs of the first and second retardation plates is set so as to satisfy the above relationship, the number of optimal configurations that can achieve appropriate black and white display increases, so that the liquid crystal display device has Optimization is easy.

Still another feature of the present invention is that in any one of the above liquid crystal display devices, the retardation values of the first and second retardation plates at a wavelength of ₅₉₀ nm are Pr ₅₉₀ and a wavelength of 59.
The retardation value of the liquid crystal layer at 0 nm is Δn _LC · d
_LC590 , when the retardation values of the first and second retardation plates at a wavelength of 400 nm are represented by Pr ₄₀₀ and the retardation value of the liquid crystal layer at a wavelength of 400 nm are represented by Δn _LC · d _LC400 , the wavelength dispersion value of the liquid crystal layer [Δn _LC・ D _LC400 /
Δn _LC · d _LC590 ] to the ratio of the wavelength dispersion value [Pr ₄₀₀ / Pr ₅₉₀ ] of the first and second retardation plates is 0.98 to 0.98.
1.12.

By using the first and second retardation plates having the wavelength dispersion characteristics satisfying the above conditions, it is easy to optimize the optical characteristics of each member, and it is possible to improve the display quality of the reflection type, It is possible to realize a transflective STN liquid crystal display device.

Another feature of the present invention is that the relationship between the retardation Δn1 · d1 of the first phase difference plate and the retardation Δn2 · d2 of the second phase difference plate is Δn2 · d2.
> Δn1 · d1.

By using a retardation plate satisfying such a relationship, it is easier and more reliable to optimize the optical characteristics of each member as described above.

According to still another aspect of the present invention, in the liquid crystal display device according to any of the above, the retardation Δn1 · d1 of the first retardation plate, the retardation Δn2 · d2 of the second retardation plate, and the retardation of the liquid crystal layer. Value Δn _LC
· D _LC is the following: (i) satisfy any one of the ~ (iii). (i) Δn2 · d2 ≧ Δn _LC · d _LC /
2, Δn1 · d1 ≦ 150 nm, (ii) Δn2 · d2 ≧ Δ
_{n LC · d LC / 2,} Δn1 · d1 ≧ 400nm, (iii) Δ
n2 · d2 ≧ Δn _LC · d _LC × 2/5, 160 nm ≦ Δn
1 · d1 ≦ 220 nm.

By selecting the liquid crystal layer and the first and second retardation plates so as to satisfy such conditions, it is easier and more reliable to optimize the optical characteristics of each member, and an excellent display is achieved. A high quality reflective or transflective STN liquid crystal display device can be realized.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention (hereinafter, referred to as embodiments) will be described below with reference to the drawings.

[Embodiment 1] FIG. 1 shows a schematic configuration of a reflection type STN liquid crystal display device according to Embodiment 1, and FIG. 2 shows a configuration of a liquid crystal cell 10 of FIG. The liquid crystal cell 10 includes a first substrate 1 using a transparent substrate such as a glass substrate.
The liquid crystal layer 12 is inserted in the gap between the fourth substrate 4 and the second substrate 16. A first electrode 20 and a second electrode 22 made of a transparent conductive material such as ITO (Indium Tin Oxide) are formed on the sides of the first substrate 14 and the second substrate 16 facing the liquid crystal layer 12, respectively. The surface of each electrode is covered with an insulating layer 24, and an alignment layer 2 for controlling the initial alignment of liquid crystal molecules.
6 is formed on the insulating layer 24. A spacer 28 is mixed in the liquid crystal layer to keep the thickness of the liquid crystal layer constant. The reflective layer 18 made of, for example, Al is formed between the second substrate of the liquid crystal cell 10 and the liquid crystal layer 12, in the first embodiment, between the second electrode 22 and the second substrate 16. Light incident into the cell from the 14 side is reflected on its surface. Note that the insulating layer 24 can be omitted as necessary.

As shown in FIG. 1, a first retardation plate 40 made of a birefringent film, a diffusing plate 46, and a first position are provided outside the first substrate of the liquid crystal cell 10 corresponding to the viewing side as a display device. A second retardation plate 42 made of a birefringent film like the retardation plate 40 is arranged in this order, and the second retardation plate 42
A first polarizing plate 44 is further disposed outside the box.

In this liquid crystal display device, when the clockwise direction is represented by plus and the counterclockwise direction is represented by minus, in the liquid crystal layer 12, the twist angle in the alignment direction of the liquid crystal molecules from the first substrate 14 toward the second substrate 16. θ _LC is −160 ° ≧
θ _LC ≧ −300 °. More preferably, −180 ° ≧ θ
_LC ≧ −300 ° is preferable, and in the present embodiment, the twist angle θ _LC is −240 °, and an STN liquid crystal cell having a twist angle larger than 90 ° is configured. Of course, the twist angle θ _LC may be in a range of 160 ° ≦ θ _LC ≦ 300 °, that is, a clockwise twist angle. Also,
As the liquid crystal material, a liquid crystal having a positive dielectric anisotropy is used. In this cell 10, the refractive index anisotropy Δ
The retardation value Δn _LC · d _LC of the liquid crystal layer represented by the product of n _LC and the thickness d _LC of the liquid crystal layer is 0.30 μm
≦ Δn _LC · d _LC ≦ 2.0 μm. In addition,
It is preferable to mix a rotatory substance in the liquid crystal layer for the purpose of, for example, facilitating the maintenance of twist alignment.

As shown in FIG. 3, the angle of the slow axis direction of the first retardation plate 40 with respect to the orientation direction of the liquid crystal layer 12 on the first substrate 14 side is θ1, and the retardation of the first retardation plate 40 is θ1. When the angle of the second retardation plate 42 in the slow axis direction with respect to the axial direction is defined as θ2, and the angle of the absorption axis direction of the first polarizing plate 44 with respect to the slow axis direction of the second retardation plate 42 is defined as θ3, In the liquid crystal display device according to the first embodiment, when the torsion angle θ _LC is in a minus range (−160 ° to −300 °), θ 1
θ3 is the following No. 1 to No. The specifications are such that any one of the ten conditions is satisfied.

No. 1: 65 ° ≤ θ1 ≤ 90 °, -25
° ≧ θ2 ≧ −55 °, 50 ° ≦ θ3 ≦ 80 °, No. 2: -65 ° ≧ θ1 ≧ −90 °, −30 ° ≧ θ2
≧ −40 °, 70 ° ≦ θ3 ≦ 80 °, No. 3: 0 ° ≦ θ1 ≦ 20 °, −80 ° ≦ θ2 ≦ −6
0 °, 15 ° ≦ θ3 ≦ 40 °, No. 4: 45 ° ≦ θ1 ≦ 55 °, 70 ° ≦ θ2 ≦ 80
No., −60 ° ≦ θ3 ≦ −50 °, 5: 80 ° ≦ θ1 ≦ 90 °, 65 ° ≦ θ2 ≦ 75
°, -45 ° ≤ θ3 ≤ -35 °, 6: 60 ° ≦ θ1 ≦ 80 °, 55 ° ≦ θ2 ≦ 7
No. 5 °, −60 ° ≦ θ3 ≦ −55 °, 7: 15 ° ≦ θ1 ≦ 30 °, −75 ° ≦ θ2 ≦ −
No. 65 °, −65 ° ≦ θ3 ≦ −55 °, 8: 60 ° ≦ θ1 ≦ 70 °, −70 ° ≦ θ2 ≦ −
No. 55 °, 35 ° ≦ θ3 ≦ 55 °, 9: 30 ° ≦ θ1 ≦ 55 °, −70 ° ≦ θ2 ≦ −
No. 50 °, −65 ° ≦ θ3 ≦ −40 °, 10: −80 ° ≦ θ1 ≦ −70 °, 75 ° ≦ θ2
≦ 85 °, 50 ° ≦ θ3 ≦ 60 °.

When the torsion angle θ _LC is in the plus range, that is, 160 ° to 300 °, the above No. 1
-No. 10 so as to satisfy the condition that all of the plus and minus signs and the inequality sign in the relational expressions of θ1 to θ3 are reversed.

Specifically, No. 11 (−No. 1): −65 ° ≧ θ1 ≧ −90
°, 25 ° ≤ θ2 ≤ 55 °, -50 ° ≥ θ3 ≥ -80
°, No. 12 (-No. 2): 65 ° ≦ θ1 ≦ 90 °, 3
0 ° ≦ θ2 ≦ 40 °, −70 ° ≧ θ3 ≧ −80 °, No. 13 (-No. 3): 0 ° ≧ θ1 ≧ −20 °, 8
0 ° ≧ θ2 ≧ 60 °, −15 ° ≧ θ3 ≧ −40 °, No. 14 (−No. 4): −45 ° ≧ θ1 ≧ −55
°, -70 ° ≧ θ2 ≧ −80 °, 60 ° ≧ θ3 ≧ 50
°, No. 15 (-No. 5): -80?? 1? -90
°, -65 ° ≧ θ2 ≧ −75 °, 45 ° ≧ θ3 ≧ 35
°, No. 16 (−No. 6): −60 ° ≧ θ1 ≧ −80
°, -55 ° ≧ θ2 ≧ −75 °, 60 ° ≧ θ3 ≧ 55
°, No. 17 (−No. 7): −15 ° ≧ θ1 ≧ −30
No., 75 ° ≧ θ2 ≧ 65 °, 65 ° ≧ θ3 ≧ 55 °, 18 (−No. 8): −60 ° ≧ θ1 ≧ −70
°, 70 ° ≧ θ2 ≧ 55 °, −35 ° ≧ θ3 ≧ −55
°, No. 19 (−No. 9): −30 ° ≧ θ1 ≧ −55
No., 70 ° ≧ θ2 ≧ 50 °, 65 ° ≧ θ3 ≧ 40 °, 20 (-No. 10): 80 ° ≧ θ1 ≧ 70 °,
−75 ° ≧ θ2 ≧ −85 °, -50 ° ≧ θ3 ≧ −60
°.

The following (condition a) to (condition d) need not be satisfied, but by satisfying these, the specifications of the device capable of achieving the display quality desired as a reflection type STN LCD can be achieved. Since the number increases, optimization can be easily and reliably achieved.

(Condition a) The retardation value Δn1 · d1 of the first retardation plate, which is represented by the product of the refractive index anisotropy Δn1 of the first retardation plate 40 and the thickness d1 of the first retardation plate 40.
And the refractive index anisotropy Δn2 of the second retardation plate 42 and the second
The total value R of the retardation value Δn2 · d2 of the second retardation plate indicated by the product of the thickness d2 of the retardation plate 42 and the product
s (Δn1 · d1 + Δn2 · d2) , compared retardation value Δn _LC · d _{L C} of the liquid crystal _{layer, Δn LC · d LC -m ×} 1
47.5-25 ≦ Rs ≦ Δn _LC · d _LC −m × 147.5
+75 (where m = −2, 0, 1, 2).

(Condition b) The retardation values of the first and second retardation plates at a wavelength of ₅₉₀ nm are Pr ₅₉₀ and a wavelength 59, respectively.
The retardation value of the liquid crystal layer at 0 nm is Δn _LC · d
_{LC59 0} , when the retardation values of the first and second retardation plates at a wavelength of 400 nm are represented by Pr ₄₀₀ and the retardation value of the liquid crystal layer at a wavelength of 400 nm are represented by Δn _LC · d _LC400 , the wavelength dispersion value of the liquid crystal layer [Δn _LC・ D _LC400 / Δn
The ratio of the wavelength dispersion value [Pr ₄₀₀ / Pr ₅₉₀ ] of the first and second retardation plates to _LC · d _LC590 ] is set to be between 0.98 and 1.12.

(Condition c) The retardation Δn1 · d1 of the first retardation film and the retardation Δn2 · d1 of the second retardation film
d2 satisfies Δn2 · d2> Δn1 · d1.

(Condition d) The retardation Δn1 · d1 of the first retardation plate and the retardation Δn2 · d1 of the second retardation plate
The relationship between d2 and the retardation value Δn _LC · d _LC of the liquid crystal layer satisfies any one of the following conditions (i) to (iii).

[0047] (i) Δn2 · d2 ≧ Δn LC · d LC / 2, Δ
n1 · d1 ≦ 150nm, (ii ) Δn2 · d2 ≧ Δn LC · d LC / 2, Δn1 · d1 ≧
400nm, (iii) Δn2 · d2 ≧ Δn LC · d LC × 2 / 5,160n
m ≦ Δn1 · d1 ≦ 220 nm.

The first embodiment set to such conditions
The reflective STN liquid crystal display device operates as follows.

First, as external light incident on the first polarizing plate 44 from the device observation side, linearly polarized light in the direction orthogonal to the absorption axis of the first polarizing plate is extracted.
2. The light reaches the liquid crystal layer 12 through the first retardation plate 40. In the first embodiment, a liquid crystal cell of a negative mode (normally black) whose display luminance increases with the application of a voltage is employed. In the case of a white display mode, the liquid crystal layer 1 is used.
2 is applied to the substrate 14 so that the major axis direction of each liquid crystal molecule is
And rises toward the normal direction of 16. For this reason, the light that has entered the liquid crystal cell 10 through the second and first retardation plates 42 and 40 undergoes a slight birefringence while passing through the liquid crystal layer 12 to become elliptically polarized light and reaches the reflective layer 18. The light is reflected and reaches the first polarizing plate 44 through a path opposite to that at the time of incidence,
The light is emitted from the first polarizing plate 44 to the device observation side. Thereby, white is displayed.

In the black display mode, the first polarizing plate 44
Is polarized by the liquid crystal layer 12 oriented at a twist angle θ _LC of 240 °, is birefringent, becomes circularly polarized light, and is reflected by the reflective layer 18. The reflected circularly polarized light is applied to the liquid crystal layer 1.
2 and again undergoes birefringence and becomes linearly polarized light. That is, the second and first retardation plates 42 and 40 and the liquid crystal layer 1
2, the phase of the linearly polarized light incident from the first polarizing plate 44 is (2n + 1) π / 4 (where n =
0, 1, 2,...), The light that reaches the reflective layer 18 becomes circularly polarized light, and when it is reflected and passes through the liquid crystal layer 12 and the first and second retardation plates 40 and 42, the first (2n + 1) π / 2 with respect to the linearly polarized light incident from the polarizing plate 44
Only that phase is advanced. Therefore, the light incident from the first polarizing plate 44 and the light returned by reflection are in a linear polarization state in which the phase is completely inverted, and the first polarizing plate 4
4, light is shielded. Here, in the first embodiment, θ1 to θ3 satisfy the above conditions, and
Since the retardation value of the second retardation plate and the retardation value of the liquid crystal layer are set to have the above-described relationship, the polarization state (circular polarization state) of the reflection layer 18 passes through the liquid crystal layer. And the first and second retardation plates 40,
When the light reaches the first polarizing plate 44 via 42, the light becomes almost the same linearly polarized light over the entire wavelength range of the light. First polarizing plate 44
Is arranged so that its absorption axis is substantially parallel to the linearly polarized light, so that the light is blocked by the first polarizing plate 44 over the entire wavelength range, and black is accurately displayed.

Note that θ1 to θ3, Δn _LC · d _LC , Δn1
· D1 and Δn2 · d2 can be specifically specified as shown in Table 2 described later.
Optimum characteristics can be obtained by adopting the specification of o1.

It should be noted that the angle θ3 of the absorption axis of the first polarizing plate 44 with respect to the second retardation plate 42 can obtain the same reflection characteristic even when it is rotated by 90 °. in this way,
When the absorption axis of the first polarizing plate 44 is rotated by 90 °, if the right circularly polarized light is incident on the reflective layer 18, the light is changed to the left circularly polarized light, and the left circularly polarized light is incident on the contrary. If so, the same transmission characteristics can be obtained by changing to right circularly polarized light.

As described above, in the first embodiment, the liquid crystal cell 1
Although the configuration in which the diffusion plate 46 is provided outside of the substrate 10 has been described, the diffusion function is provided between the reflection layer 18 and the second substrate 16 in the cell 10 as shown by a dotted line in FIG. A configuration in which the provided uneven layer 36 is formed can also be adopted (see reference numeral 36 in FIG. 15 described later). When the uneven layer 36 is provided in the cell as described above, the use efficiency of external light is further increased, and the reflection intensity in a substantial use range (viewing direction range) of the liquid crystal display device can be improved.

Further, needless to say, the liquid crystal display device of the first embodiment can perform color display by forming a color filter (see reference numeral 32 in FIG. 16 described later) in the liquid crystal cell, for example.

Example 1 Next, a result of preparing a liquid crystal display device satisfying the above conditions as Example 1 and evaluating its characteristics will be described.

120 × 160 dots and 240 × 640
Using a dot size liquid crystal display panel, θ _LC : -240
゜, θ1: 82 °, θ2: −31 °, θ3: 74, Δn
_LC · d _LC : 0.65 nm, Δn1 · d1: 0.138 n
m, Δn2 · d2: a liquid crystal cell, a first retardation plate, a diffusion plate, a second retardation plate,
The first polarizing plate was arranged. For the obtained liquid crystal display device,
Multiplex drive was performed under the condition that the duty ratio was 1/120. As a comparative example, a conventional reflective STN liquid crystal display device using two upper and lower polarizing plates was prepared and driven under the same duty ratio of 1/120. The results of measuring the chromaticity coordinates and reflectance of white and black are shown in Table 1 below.

[0057]

[Table 1] In addition, the measurement of the reflectance was performed for the installed liquid crystal display device.
Light was emitted from a light source located at 20 ° from the panel normal direction, and the measurement was performed using a measuring instrument installed in the panel normal direction (see FIG. 14 described later). The reflectance is a numerical value when the brightness of the standard white plate is 100%.

As shown in Table 1, in Example 1, both chromaticity coordinates of white and black are targets (0.31, 0.31).
6), and particularly in the comparative example, the chromaticity coordinates of black are (0.225, 0.188), whereas the example 1
Thus, it can be understood that the chromaticity coordinates of black are (0.299, 0.317) and that black is accurately displayed. Further, in the first embodiment, since one polarizing plate is realized, the reflectance of white is remarkably improved as compared with the comparative example.

Further, the liquid crystal display device of the first embodiment is
In the first embodiment, even when multiplex driving is performed under the condition of 0 duty ratio, the chromaticity coordinates of white are (0.253,
0.273), chromaticity coordinates of black (0.293, 0.31)
6) was obtained, and black and white could be displayed accurately. Further, the reflectance of white was 34% and the reflectance of black was 4%, and a sufficiently bright display could be performed even under these conditions.

Embodiment 2 FIG. 4 shows a configuration of a liquid crystal display device according to Embodiment 2, and FIG. 5 shows a cross-sectional configuration of the liquid crystal cell of FIG. The first embodiment is a reflection type STN liquid crystal display device having a reflection layer in a liquid crystal cell, but the second embodiment is a transflective STN liquid crystal display device which can be used as a reflection type or a transmission type. . Liquid crystal cell 10
Outside the first substrate 14, a first retardation plate 40, a second retardation plate 42, and a first polarizing plate 44 are arranged in this order as in the first embodiment. The difference from the first embodiment is that a semi-transmissive reflective layer 30 in the liquid crystal cell 10 and a circularly polarized light irradiating means 70 serving as a light source in the transmission mode on the second substrate side of the liquid crystal cell 10 are provided. This is common to the first embodiment.

The transflective layer 30 reflects light incident from the observation side of the device, that is, from the first polarizing plate 44, and transmits light incident through the second substrate 16 from a light source disposed on the non-observation side of the device. It has a function of transmitting light, and is formed between the second substrate 16 and the second electrode 22 as shown in FIG. Note that a flattening layer 34 also having a function of insulating both is provided between the transflective layer 30 and the second electrode 22.

As the semi-transmissive reflection layer 30, it is preferable to use a material that has little depolarization and that has a small rotation of the polarization axis during reflection or transmission. For example, an Al half mirror or the like can be used. Further, an SiO ₂ film is laminated on the surface of the Al half mirror on the first substrate side, or SiO ₂ and T
By forming a layered structure of iO ₂ , it is possible to adjust the reflection color and control the reflection intensity. Transflective layer 3
The reflection at 0: the transmission intensity can be adjusted to, for example, about 9: 1 to 6: 4 by forming a hole in the Al layer or controlling the thickness of the layer when the layer is made of Al, for example. Also,
As an example, the color of light reflected by the transflective layer 30 is JI
S standard C light source (0.31, 0.31 on xy chromaticity coordinates)
When adjusted to approach 6), the reflectance is 71%,
The chromaticity coordinates of the reflected light are (0.310, 0.322), the transmittance is 10.3%, and the chromaticity coordinates of the transmitted light (0.278, 0.
274) can be realized.

The circularly polarized light irradiating means 70 provided on the non-observation side of the liquid crystal cell 10 can be constituted by a circularly polarized light source capable of directly emitting circularly polarized light. Alternatively, it can be constituted by a broadband circularly polarizing plate and a light source.
A cholesteric liquid crystal film can be used as the broadband circularly polarizing plate. The cholesteric liquid crystal film has a function of transmitting only the circularly polarized light turning right or left with respect to the incident light and reflecting the other, and by arranging this film between the light source and the liquid crystal cell 10, In addition, only predetermined circularly polarized light of the light source light can be emitted to the second substrate 16 side of the liquid crystal cell 10. In the example shown in FIG. 4, the circularly polarized light irradiating means 70 includes a light source 60 and a broadband circularly polarizing plate, and the broadband circularly polarizing plate includes a second polarizing plate 62 and a λ / 2 plate in order from the light source 60. 64 and a λ / 4 plate 66. The broadband circularly polarizing plate having the configuration shown in FIG. 4 includes a second polarizing plate 62, a λ / 2 and a λ / 4 plate 6.
By optimizing the characteristics of Nos. 4 and 66, the light from the light source is converted into circularly polarized light at all wavelengths. The second polarizing plate 62
Has the function of transmitting linearly polarized light in the direction perpendicular to the absorption axis of the polarizing plate and absorbing the rest of the light from the light source, but has the function of reflecting linearly polarized light in the direction of the absorption axis. By using the reflective polarizer, it is possible to improve the use efficiency of the light source light.

In the above configuration, the second embodiment
In the embodiment, the specifications are set so as to meet the following (condition A) to (condition F) as in the first embodiment. At least (A)
And (B) must be set to satisfy this.

(A) When the clockwise direction is represented by plus and the counterclockwise direction is represented by minus, the twist angle θ of the liquid crystal layer 12 is obtained.
_LC is ± 160 ° to ± 300 °. More preferably ±
180 ° ± 300 °, for example, θ _LC is set to −240 °. A liquid crystal material having a positive dielectric anisotropy is used as a liquid crystal material. In this liquid crystal cell 10, the retardation value Δn _LC · d _LC of the liquid crystal layer 12 is 0.30 μm ≦ Δn
_LC · d _LC ≦ 2.0 μm.

(B) The angle θ in the slow axis direction of the first retardation plate 40 with respect to the orientation direction of the liquid crystal layer 12 on the first substrate 14 side.
1, the angle θ2 of the second phase difference plate 42 in the slow axis direction with respect to the slow axis direction of the first phase difference plate 40, the absorption axis direction of the first polarizing plate 44 with respect to the slow axis direction of the second phase difference plate 42 Angle θ
No. 3 in the case where the torsion angle θ _LC is minus, that is, −160 ° to −300 °, as in the first embodiment. 1 to No. 10
Is set to satisfy any of the conditions. Alternatively, when the torsion angle θ _LC is plus, that is, 160 ° to 300 °,
No. 1 to No. 10 is set so as to satisfy the condition in which the directions of all the +-signs and the signs of the inequality signs of θ1 to θ3 are reversed in the relational expression defined by any one of the ten conditions. That is, No. 11-No. 20 are set so as to satisfy one of the conditions.

(C) The total value Rs (Δn1 · d1 + Δn2) of the retardation value Δn1 · d1 of the first phase plate 40 and the retardation value Δn2 · d2 of the second phase plate 42
Also for d2), as in the first embodiment, Δn _LC · d
_LC− mx147.5-25 ≦ Rs ≦ Δn _LC · d
_LC −mx147.5 + 75 (where m = −2, 0, 1,
Satisfies the relationship of 2).

(D) The wavelength dispersion value of the liquid crystal layer [Δn _LC · d
_{The ratio} of the wavelength dispersion value [Pr ₄₀₀ / Pr ₅₉₀ ] of the first and second retardation plates to _{LC 400} / Δn _LC · d _LC590 ] is also set to a value between 0.98 and 1.12. .

(E) The retardation Δn of the first retardation plate
1 · d1 and retardation Δn2 · d2 of the second retardation plate
Satisfies Δn2 · d2> Δn1 · d1.

(F) Retardation Δn of first retardation plate
1 · d1 and retardation Δn2 · d2 of the second retardation plate
And the retardation value Δn _LC · d _LC of the liquid crystal layer is
Any one of the following conditions (i) to (iii) is satisfied. (i) Δ
n2 · d2 ≧ Δn _LC · d _LC / 2, Δn1 · d1 ≦ 150
nm, (ii) Δn2 · d2 ≧ Δn LC · d LC / 2, Δn1 ·
d1 ≧ 400 nm, (iii) Δn2 · d2 ≧ Δn _LC · d _LC
× 2/5, 160 nm ≦ Δn1 · d1 ≦ 220 nm.

Tables 2 and 3 below show that

[Table 2]

[Table 3] It is an example of an actual setting value. No1 shown in Tables 2 and 3
If any of the specifications No. to No53 are adopted, accurate black and white display can be performed. Specifically, according to the specifications shown in Tables 2 and 3, when driving is performed under an optimum bias (1/16) at a duty ratio of 1/240, the reflectance of black is 0.1%.
At less than 8%, the chromaticity coordinate x satisfies x ≦ 0.31, and the white reflectance can satisfy 25% or more.

In particular, the specifications no1 (θ _LC : -240
゜, θ1: 82 °, θ2: −31 °, θ3: 74 °, Δ
_{n LC · d LC: 0.65μm,} Δn1 · d1: 0.138
μm, Δn2 · d2: 0.385 μm, incident light from the second substrate: left circularly polarized light) is most suitable.

FIGS. 6 to 9 show the total retardation value (retardation total value Rs) of the first and second retardation plates and the Δ of the liquid crystal.
The relationship between n _LC and d _LC is shown. 6 to 9
Is the thickness d _LC of the liquid crystal layer was fixed to 5 [mu] m, the liquid crystal of [Delta] n _LC
Is changed to change the value of Δn _LC · d _LC . In each of the figures, the vertical axis indicates that when each liquid crystal display device is driven at an optimal bias at a duty ratio of 1/240, the reflection black luminance is less than 0.8% and the reflection white luminance is 25% or more. 3, and the horizontal axis represents the total retardation value of the first and second retardation plates. Here, in order to change the linearly polarized light into the circularly polarized light, the phase of the incident light needs to be changed by (2n + 1) π / 4 (where n = 0, 1, 2,...) As described above. The total retardation value Rs is
It exists only at points that satisfy the above conditions. actually,
The total phase difference value Rs exists in a region having a certain width by adjusting the axis angle of each optical member,
As shown in each figure, the total phase difference value shows a periodic and discrete distribution characteristic. Further, this periodic discrete state is represented by Δn _LC
DLC changes as 0.6 μm (FIG. 6), 0.65 μm (FIG. 7), 0.70 μm (FIG. 8), 0.75 μm (FIG. 9), and each total phase difference The presence frequency of the specification in the value also changes, and here, 0.6 in FIG.
In the case of 5 μm, the abundance is the largest. Therefore, for example, by determining Rs and Δn _LC · d _LC so as to satisfy the above condition C, the abundance of the device specifications capable of realizing the required display characteristics increases, and the possible optical characteristics of each element of the device Since the degree of freedom of the value is increased and the margin in manufacturing is further widened, it is easy to optimize the apparatus.

Next, the wavelength dispersion ratio between the liquid crystal layer and the first and second retardation plates will be described. As shown in the above (Condition D), this wavelength dispersion ratio is determined by the wavelength dispersion value of the liquid crystal layer [Δn _LC
D _LC400 / Δn _LC · d _LC590 ] to the ratio of the wavelength dispersion value [Rs ₄₀₀ / Rs ₅₉₀ ] of the first and second retardation plates,
In the second embodiment, it is set between 0.98 and 1.12.

Table 4 below shows that

[Table 4] Different liquid crystals LC0 to LC11 and retarder materials (polycarbonate, polyarylate, polysulfone)
Of the chromatic dispersion value of the above. Wavelength dispersion values at wavelengths of 400 nm and 590 nm Δn · d ₄₀₀ , Δn ·
d ₅₉₀ can be obtained by the dispersion equation [a + b / (λ) ² + c / (λ) ⁴ ], and the right column of Table 4 shows the wavelength dispersion value Δn _LC · d _LC400 / Δn _LC · d of the liquid crystal layer. _LC590 and the wavelength dispersion values Pr ₄₀₀ / Pr ₅₉₀ of the first and second retardation plates.

FIG. 10 shows the characteristics of the wavelength dispersion values of the liquid crystal layer and the retardation plate with respect to the wavelength of the incident light. The solid lines indicate the wavelength dispersion characteristics of the liquid crystal layers LC0 to LC11 in Table 4 in ascending order of the intercept, and open squares, triangles, and circles indicate materials generally used as a retardation plate. It is a wavelength dispersion characteristic.

FIGS. 11 to 13 show the relationship between the chromatic dispersion of the liquid crystal layer [Δn _LC · d _LC400 / Δn _LC · d _LC590 ] and the chromatic dispersion of the first and second retardation plates [Rs ₄₀₀ / Rs ₅₉₀ ]. The graph shows the distribution of the abundance of the optimal specification at the total retardation value of each retardation plate when the chromatic dispersion ratio as a ratio is changed. In each of FIGS. 11 to 13, the thickness d _LC of the liquid crystal layer is 6
μm (FIG. 11), 5 μm (FIG. 12), 4 μm (FIG. 13)
The liquid crystal material is changed so that the value of Δn _LC · d _LC is constant at 0.65 μm, and Δn _LC is changed. The chromatic dispersion ratio in FIG. 11 is 1.003, and FIG.
2 is 1.041 and in FIG. 13 is 1.091. The abundance number of the optimal specification means that when each liquid crystal display device is driven at an optimal bias at a duty ratio of 1/240, the reflection black luminance is less than 0.8% and the reflection white luminance is 25% or more. The number of specifications such as 3 exists. 11 to 1
As can be seen from the comparison of No. 3, the abundance number of the optimum specification has a dependency on the chromatic dispersion ratio. In the examples of FIGS. 11 to 13,
Although a sufficient number of optimum specifications are obtained at any wavelength dispersion ratio, FIG. 11 shows the highest abundance. As described above, if the number of the optimal specifications is large, the degree of freedom in setting each member of the liquid crystal display device according to the required characteristics is increased, and the optical characteristics of each member (for example, , Θ and Δn · d) can be easily optimized.

In order to obtain such a high existence frequency,
The chromatic dispersion ratio is 0.98 to 1.1 in the second embodiment.
It is preferable that the wavelength dispersion value of the liquid crystal and the wavelength dispersion values of the first and second retardation plates are approximately the same, as can be understood from the comparison of FIGS. FIG.
When using a liquid crystal having a characteristic such as LC0, it is more preferable than polysulfone or polyarylate.
By using a polycarbonate having characteristics close to LC0 in a short wavelength region having a large characteristic difference as a retardation plate, appropriate phase compensation can be performed over the entire wavelength region. Conversely, when a liquid crystal having the characteristics of LC11 is used, it is appropriate to use, as the phase plate, polysulfone having characteristics similar to those on the short wavelength side where the characteristic difference is larger than that of polycarbonate.

The transflective STN liquid crystal display device of the second embodiment satisfying the above conditions operates in the reflection mode in the same principle as the first embodiment. That is, at the time of white display, the linearly polarized light incident from the first polarizing plate 44 passes through the liquid crystal layer 12 and is reflected by the transflective layer 30,
The light is returned to the first polarizing plate 44 while maintaining substantially the same linear polarization state, and is emitted from the first polarizing plate 44. When displaying black,
The linearly polarized light incident from the first polarizing plate 44 undergoes birefringence in the liquid crystal layer 12, becomes circularly polarized light on the surface of the transflective layer 30, and is reflected. The reflected circularly polarized light travels through the liquid crystal layer 12 again while undergoing birefringence, and is phase-compensated by the first and second retardation plates 40 and 42.
4 oscillates in the direction of the absorption axis. Therefore the first
The light is blocked by the polarizing plate 44, and black is displayed.

In the case of the transmission mode, first, the circularly polarized light emitted from the circularly polarized light irradiating means 70 reaches the semi-transmissive reflection layer 30 from the second substrate side, passes through the semi-transparent reflection layer 30 and passes through the liquid crystal layer. It is incident on 12. When a voltage is applied to the liquid crystal layer 12 and the liquid crystal layer 12 is in the white display mode, the circularly polarized light passes through the liquid crystal layer 12 while undergoing slight birefringence, and undergoes phase compensation by the first retardation plate 40 and the second retardation plate 42. Reaches the first polarizing plate 44. If the position of the first polarizing plate 44 is substantially circularly polarized, the first
A component in a direction orthogonal to the absorption axis of the polarizing plate 44 passes through the first polarizing plate 44, and light is emitted to the observation surface side of the device,
White is displayed.

In the case of black display in the transmissive mode, the light incident on the semi-transmissive reflective layer 30 from the second substrate 16 side has the same circularly polarized state as in the black display in the reflective mode. That is, for example, in the reflection mode, if the light is right circularly polarized at the time of reflection by the transflective layer, the light is also right circularly polarized in the transflective layer 30 in the transmission mode. Therefore, the circularly polarized light that has passed through the transflective layer 30 undergoes birefringence in the liquid crystal layer 12 oriented at a twist angle θ _LC of 240 ° to become linearly polarized light. In the second embodiment, θ1 to θ3 satisfy the above conditions, and
Since the retardation value of the second retardation plate, the retardation value of the liquid crystal layer, and the like are set to have the above-described relationship, the polarization state of the reflection layer 18 passes through the liquid crystal layer 12 and the first state. When the light reaches the first polarizing plate 44 via the second retardation plates 40 and 42, the light becomes substantially the same linearly polarized light over the entire wavelength range of the light. Since the first polarizing plate 44 is arranged so that its absorption axis is substantially parallel to the linearly polarized light, the first polarizing plate 44 blocks light in the entire wavelength range, so that the first polarizing plate 44 displays black in the transmission mode. Can accurately display black in almost the same manner as in black display in the reflection mode.

As described above, in the second embodiment, in the case of black display in the reflection mode and in the case of the transmission mode, the light is set to be in a circularly polarized state on the surface of the transflective layer 30 (the side facing the liquid crystal). Therefore, the reflection / transmission mode is switched for black display, and the polarization state of light in the transflective layer 30 does not change. Therefore, it is possible to accurately display black under almost the same conditions. Regarding white, the change in the polarization state in the liquid crystal layer 12 is very small in both the reflection and transmission modes, so that the light source 60 whose chromaticity coordinates show an appropriate value is used in both the reflection and transmission modes. It can be displayed accurately. Further, since the operation threshold voltage of the liquid crystal is the same in the reflection mode and the transmission mode, the color tone and the gradation are not changed at the time of mode switching, so that a display without a sense of incongruity is possible.

Although not shown, the surface of the first polarizing plate 44 is preferably provided with a low reflection coat and an anti-glare coat. Further, the phase difference plate is composed of the first, second, and second
Although three sheets are used, three or more retardation plates can be used. Further, in the above description, the diffusion layer 46 is disposed between the first retardation plate 40 and the second retardation plate 42,
The diffusion layer 46 may be provided between the first polarizing plate 44 and the liquid crystal cell 10, for example, the first retardation plate 40 and the liquid crystal cell 10.
The same characteristics can be obtained even when provided between (first substrate 14).

In the transmission mode, the circularly polarized light irradiating means 7
Regarding the device specification for injecting right circularly polarized light from 0, it is possible to change this to the left circularly polarized light specification. The same transmission characteristics can be obtained.

[Example 2] Next, a result of preparing a liquid crystal display device which satisfies the conditions described in Embodiment 2 as Example 2 and evaluating its characteristics will be described.

120 × 160 dots and 240 × 640
Using a dot size liquid crystal display panel, θ _LC : -240
゜, θ1: 82 °, θ2: −31 °, θ3: 74, Δn
_LC · d _LC : 0.65 μm, Δn1 · d1: 0.138 μ
m, Δn2 · d2: The liquid crystal cell 10, the first retardation plate 40, the diffusion layer 46, the second retardation plate 42, and the first polarizing plate 44 were arranged so as to satisfy the condition of 0.385 μm. Further, a circularly polarized light irradiation means 70 having the configuration shown in FIG. 4 was provided on the non-observation side of the liquid crystal cell. In addition, the second polarizing plate 6 constituting the broadband polarizing plate
2. A cholesteric liquid crystal film was used instead of the λ / 2 plate 64 and the λ / 4 plate 66, but the same effect was obtained.

As the transflective layer 30, an Al half-mirror with little depolarization (polarization rotation) was used. Also,
On top of this Al half mirror, SiO ₂ / TiO ₂ /
A layered structure of SiO ₂ is formed, and the reflection color is adjusted so as to approach the JIS standard C light source (0.31, 0.316 on xy chromaticity coordinates), and the ratio of reflection: transmission intensity is about 9: 1. Was controlled. Example 2 in controlling the ratio of reflection: transmission intensity
Then, both the case of controlling the thickness of Al and the method of making a hole were performed, but the same performance was obtained in both cases. Al
In the film thickness control described above, an intensity ratio of about 9: 1 could be realized by setting the Al film thickness to 180 °. Further, by reducing the Al film thickness, it was possible to control various ratios up to an intensity ratio of about 6: 4. Regarding the method of forming a hole in the Al layer, a hole having an area ratio of about 10% is formed to form 9:
An intensity ratio of about 1 can be realized, and 9: 1 by controlling the area ratio.
A semi-transmissive reflective layer having various ratios up to about 6: 4 could be formed. The surface of the first polarizing plate 44 was provided with a low reflection coat and an anti-glare coat.

Multiplex driving was performed on the obtained liquid crystal display device under the condition that the duty ratio was 1/120.
As a comparative example, a conventional reflective STN liquid crystal display device using two upper and lower polarizing plates was prepared, and the same duty ratio of 1 /
It was driven under the conditions of 120. In the liquid crystal display device of the second embodiment, the result of measuring the chromaticity coordinates and reflectance of white and black by driving in the reflection mode is the same as that of the first embodiment.
It became as shown in.

As in the first embodiment, the reflectivity was measured from a light source located at a position 20 ° from the panel normal direction to a liquid crystal display device installed as an object to be measured as shown in FIG. The measurement was performed by irradiating light and using a measuring instrument installed in the normal direction of the panel. The reflectance is a numerical value when the brightness of a reference white plate, which is a completely diffused paper, is 100%.

As shown in Table 1, the chromaticity coordinates of white and black approach the target (0.31, 0.316) without being different from that of the reflection type liquid crystal display device also in the second embodiment. In particular, in Example 2, the chromaticity coordinates of black are (0.2
99, 0.317), and black is accurately displayed. Further, in the second embodiment, in the case of the reflection mode, a single polarizing plate functions, so that the white reflectance is remarkably improved as compared with the comparative example.

Further, the liquid crystal display device of the second embodiment is
Even when multiplex driving is performed under the condition of 0 duty ratio, the chromaticity coordinates of white are (0.
253, 0.273), black chromaticity coordinates (0.293,
0.316) was obtained, and black and white could be accurately displayed. Further, the reflectance of white was 34% and the reflectance of black was 4%, and a sufficiently bright display could be performed even under these conditions.

[Embodiment 3] FIG. 15 shows a configuration of a liquid crystal cell of a liquid crystal display device according to Embodiment 3. This liquid crystal display device has the same transflective ST type as in the second embodiment.
N liquid crystal display device. The difference from the second embodiment is that, instead of the diffusion layer 46 arranged on the observation side of the apparatus in the second embodiment, a transflective layer having a diffusion function is provided on the liquid crystal panel 1.
It is formed within 0. The other configuration is the same as that of the second embodiment, and the description is omitted.

In the third embodiment, in order to provide the transflective layer 30 with a diffusing function, the surface of the transflective layer 30 has irregularities under the transflective layer 30, that is, between the transflective layer 30 and the second substrate 16. The formed uneven layer 36 is formed. The uneven layer 36 has a function of diffusing light and at the same time controlling the reflection directivity characteristics.
By using the liquid crystal display device in combination, the reflection intensity in the substantial use range (viewing direction range) of the liquid crystal display device is improved.

Such a liquid crystal display device is described in the second embodiment.
Similarly, in the reflection mode, driving was performed at a duty ratio of 1/120, and the reflectance and chromaticity coordinates were measured. As a result, the reflectance of white is about 103%, and the chromaticity coordinates of white (0.2
86, 0.323), the reflectance of black was about 8%, and the chromaticity coordinates of black were (0.309, 0.326).

Further, the measurement results of the reflectance and the chromaticity coordinates when the same driving is performed at a 1/240 duty ratio show that the white reflectance is about 85% and the white chromaticity coordinates (0.264, 0.2
82), about 7% reflectance of black, chromaticity coordinates of black (0.30
4,325).

As described above, by providing the structure of the third embodiment, in particular, the uneven layer 36 in the cell, the reflectance of white can be improved in each step without lowering the chromaticity of white and black. Therefore, a very bright screen can be realized even when used in the reflection mode.

As in the second embodiment, the specification in which the right circularly polarized light is incident from the circularly polarized light irradiating means is changed to the left circularly polarized light specification, and the specification in which the left circularly polarized light is incident is changed to the right circularly polarized light specification. Transmission characteristics are obtained.

[Fourth Embodiment] FIG. 16 shows the structure of a liquid crystal cell of a liquid crystal display device according to a fourth embodiment. The device of the fourth embodiment is the same as the transflective ST
N liquid crystal display device. The difference from the second embodiment is that in the fourth embodiment, a color filter 32 is formed in a liquid crystal cell to enable color display. The RGB color filters 32 are formed on the observation side in the liquid crystal cell, specifically, between the first substrate 14 and the first electrode 20. Other cell configurations and device configurations are the same as those of the second embodiment.

As the color filter 32, a color filter having lower color purity than that of a normal transmission type color filter for LCD is used. The luminous transmittance Y was 53%, which was adjusted so that each of the three colors of RGB was achromatic under the C light source. In the fourth embodiment, the filter having low color purity is used because, when used in the reflection mode, light passes through the color filter twice at the time of incidence and at the time of reflection. This is because the required color purity can be obtained and the high color reproducibility can be obtained when the light passes through the second time even if the color is not changed. Furthermore, if a transmission type color filter is used, light loss when passing through this filter twice becomes large.

The layout of the color filter is shown in FIG.
Any of (a), (b) and (c) can be adopted. In the layout of FIG. 17A, R, G, and B filters 32, each of which is associated with each pixel, are arranged side by side without interception between the filters. In the layout of FIG. 17B, different color filters between adjacent pixels partially overlap each other (for example, 5
(Overlap of 10 to 10 μm), and a color-mixed portion is formed in the region where they overlap each other. Then, light is shielded between adjacent pixels by the mixed color portion. In FIG. 17C,
A light-shielding black mask (black matrix) is formed at the boundary between each pixel, and a color filter 32 of each color is formed in each pixel region where the black mask is open.

A color liquid crystal display device having the structure of the liquid crystal display device of the fourth embodiment and using a panel of 120 × 160 × RGB dot size and a panel of 240 × 640 × RGB dot size was prepared. In the same manner as in Example 2, the reflective mode was driven at a duty ratio of 1/120, and the reflectance and chromaticity coordinates were measured. As a result, good results were obtained with a white reflectance of about 24.5% and a black reflectance of about 3.5%. The chromaticity coordinates of white are (0.268, 0.
318), the chromaticity coordinates of black are (0.297, 0.310)
Thus, a value close to the target coordinates (0.31, 0.316) was obtained, and black and white could be displayed accurately. Furthermore,
The measurement result when driven at 1/240 duty was about 20% of white reflectance and about 3% of black luminance. The chromaticity coordinates of white were (0.245, 0.277), and the chromaticity coordinates of black were (0.292, 0.309). Thus, sufficient characteristics were obtained even at a duty of 1/240. Note that, as in the above-described embodiment, the reflectance was set to 100% as the brightness of the reference white plate.

[Embodiment 5] FIG. 18 shows the structure of a liquid crystal cell of a liquid crystal display device according to Embodiment 5. This is a transflective color liquid crystal display device similar to that of the fourth embodiment. In the fourth embodiment, the diffusion plate 46 is provided outside the liquid crystal cell as in the configuration of FIG. 4, but in the fifth embodiment, as in the third embodiment, the diffusion plate 46 is replaced with a semi-transmissive device having a diffusion function. The reflection layer is formed in the liquid crystal panel 10. Other configurations are the same as those of the second and fourth embodiments, and a description thereof will be omitted.

Similarly to the third embodiment, the transflective layer 30 having a diffusion function is provided under the transflective layer 30, that is, the transflective layer 30.
Between the second substrate 16 and the second substrate 16. The uneven layer 36 has a function of diffusing light and simultaneously controlling the reflection directivity.
By using 6 in combination with the transflective layer 30,
The reflection intensity in a practical use range (viewing direction range) of the liquid crystal display device is improved.

As a liquid crystal display panel, 120 × 160 × R
A color filter having a size of GB dot and a size of 240 × 640 × RGB dot is provided on the inner surface of the liquid crystal cell.
The results obtained by measuring the characteristics of the color liquid crystal display device formed by forming are as follows. First, when the liquid crystal display device of the fifth embodiment is driven at 1/120 duty in the reflection mode, the obtained reflectance is 61% white reflectance.
, The black reflectance is about 5.3%, and the chromaticity coordinates of white are (0.
278, 0.327), and the chromaticity coordinates of black are (0.308,
0.318), and a good result was obtained. Especially uneven layer 3
6, the white reflectance is very high, and a bright and accurate black-and-white display is possible. Therefore, it is understood that a bright and clear color image can be displayed according to the configuration of the fifth embodiment.

Further, the measurement results when driven at a duty of 1/240 show that the white reflectance is about 50% and the black reflectance is 4.5.
%, And the chromaticity coordinates of white are (0.256,
0.286), and the chromaticity coordinates of black are (0.302, 0.31)
7), and accurate black and white display is possible. The reflectance of 100% is the brightness of the reference white plate as in the other embodiments.

[Embodiment 6] FIG. 19 shows a structure of a liquid crystal cell of a liquid crystal display device according to Embodiment 6. This liquid crystal display device is a color liquid crystal display device similar to that of the fourth embodiment, but differs from the fourth embodiment in that a color filter 32 is also formed on the second substrate 16 side of the liquid crystal cell. The other configuration is the same as that of the fourth embodiment, and the description is omitted. Color filter 3 formed on second substrate 16 side
2 used the one having the same specifications as the color filter 32 on the first substrate 14 side. That is, each color filter 32 has a lower color purity than a normal transmission type LCD color filter. Further, in both the transmission mode and the reflection mode, the balance of each of the three colors RGB is set to C.
Adjustment was made so as to be achromatic under the light source, and the luminous transmittance Y was 53%.

FIG. 20 shows another configuration of the sixth embodiment. In this liquid crystal display device, instead of the diffusion plate (diffusion plate 46 in FIG. 4) arranged outside the liquid crystal cell in the configuration of FIG. 19, the uneven layer 36 is replaced with the transflective layer 30 and the color filter 32 on the second substrate side. To improve the luminance as in the above-described third and fifth embodiments.

As shown in FIGS. 19 and 20, in the sixth embodiment, the color filters 32 having the same characteristics are formed on the first substrate side and the second substrate side, respectively. By employing such a configuration, in the reflection mode, light passes through the color filter 32 on the first substrate side twice, and in the transmission mode,
The light passes through both the color filter 32 on the second substrate side and the color filter 32 on the first substrate side.

FIG. 21 shows the difference in color reproducibility between the case where light passes through the color filter once (single pass) and the case where light passes twice (double pass). As is clear from FIG. 21, when the light beam passes twice, the area becomes wider on the chromaticity coordinates, and the color reproducibility is higher. This is because the color purity is improved by passing through the color filter twice. Here, as shown in FIGS. 16 and 18, when the number of color filters 32 is one, the number of times that light passes through the color filters 32 in the transmission mode is one less than in the reflection mode. The color reproducibility is lower than that. However, with the configuration of the sixth embodiment, similar color reproducibility can be realized in the reflection mode and the transmission mode.

[0110]

As described above, according to the present invention, by optimizing the optical characteristics and optical conditions, black and white can be accurately displayed in a reflective or transflective STN liquid crystal display device, and a bright image can be displayed. Can be displayed. Also,
Since black and white can be accurately displayed, a color image with good color reproducibility can also be displayed.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a reflective liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a cross-sectional configuration of the liquid crystal cell 10 of FIG.

FIG. 3 is a diagram illustrating a set angle with respect to an alignment direction of a liquid crystal on a first substrate side.

FIG. 4 is a diagram illustrating a configuration of a transflective liquid crystal display device according to a second embodiment of the present invention.

5 is a diagram showing a cross-sectional configuration of the liquid crystal cell 10 of FIG.

FIG. 6 is a diagram showing the relationship between the retardation of the liquid crystal and the abundance of the optimal specification in the liquid crystal display device according to the present invention.

FIG. 7 is a diagram showing the relationship between the retardation of the liquid crystal and the abundance of the optimal specification in the liquid crystal display device according to the present invention.

FIG. 8 is a diagram showing the relationship between the retardation of the liquid crystal and the abundance of the optimal specification in the liquid crystal display device according to the present invention.

FIG. 9 is a diagram showing the relationship between the retardation of the liquid crystal and the abundance of the optimal specification in the liquid crystal display device according to the present invention.

FIG. 10 is a diagram showing wavelength dispersion value characteristics of a liquid crystal layer and a retardation plate with respect to the wavelength of incident light in the liquid crystal display device according to the present invention.

FIG. 11 is a diagram showing a distribution of abundance numbers of optimal specifications when the chromatic dispersion ratio is changed in the liquid crystal display device according to the present invention.

FIG. 12 is a diagram showing a distribution of abundance numbers of optimal specifications when the chromatic dispersion ratio is changed in the liquid crystal display device according to the present invention.

FIG. 13 is a diagram showing a distribution of abundance numbers of optimal specifications when the wavelength dispersion ratio is changed in the liquid crystal display device according to the present invention.

FIG. 14 is a conceptual diagram illustrating a method for measuring the reflectance of a liquid crystal display device in Examples.

FIG. 15 is a diagram illustrating a cross-sectional configuration of a liquid crystal cell of a liquid crystal display device according to a third embodiment of the present invention.

FIG. 16 is a diagram illustrating a cross-sectional configuration of a liquid crystal cell of a liquid crystal display device according to a fourth embodiment of the present invention.

FIG. 17 is a diagram showing an example of the arrangement of color filters used in the present invention.

FIG. 18 is a diagram illustrating a cross-sectional configuration of a liquid crystal cell of a liquid crystal display device according to a fifth embodiment of the present invention.

FIG. 19 is a diagram illustrating a cross-sectional configuration of a liquid crystal cell of a liquid crystal display device according to a sixth embodiment of the present invention.

FIG. 20 is a diagram showing another sectional configuration of the liquid crystal cell of the liquid crystal display device according to Embodiment 6 of the present invention.

FIG. 21 is a diagram illustrating a difference in color reproducibility between a case where the color filter passes once and a case where the color filter passes twice in the liquid crystal display device of the present invention.

[Explanation of symbols]

Reference Signs List 10 liquid crystal cell, 12 liquid crystal layer, 14 first substrate, 16
2nd substrate, 18 reflective layers, 20 first electrodes, 22 second electrodes, 24 insulating layers, 26 alignment layers, 28 spacers,
30 transflective layer, 32 (first and second) color filters, 34 flattening layer, 36 uneven layer, 40 first retardation plate, 42 second retardation plate, 44 first polarizing plate, 46 diffusion plate, 60 light source, 62 second polarizing plate, 64 λ / 2
Plate, 66 λ / 4 plate, 70 circularly polarized light irradiation means.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Masao Ozeki 1150 Hazawacho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Asahi Glass Co., Ltd. F-term (reference) 2H089 HA24 HA25 QA05 QA11 QA16 RA10 SA04 SA07 SA12 SA18 SA19 TA12 TA14 TA17 2H091 FA02Y FA11Y FA15Y FB02 FB08 FC02 FC25 FC26 FD23 FD24 HA10 KA02 KA03 KA10 LA12 LA17 LA20

Claims (14)

[Claims] 1. A liquid crystal cell having a liquid crystal layer inserted in a gap between a first substrate having electrodes formed on an opposing surface and a second substrate, respectively. The first retardation plate, the second retardation plate and the polarizing plate are arranged in this order,
A liquid crystal display device having a reflective layer formed on a second substrate side in the liquid crystal cell, wherein a twist angle θ _LC of an alignment direction of liquid crystal molecules from the first substrate toward the second substrate in the liquid crystal layer is: , ± 160
゜ to ± 300 °, the refractive index anisotropy Δn _LC of the liquid crystal layer and the thickness d of the liquid crystal layer
Retardation value Δ of liquid crystal layer indicated by product with _LC
n _LC · d _LC is 0.30 μm ≦ Δn _LC · d _LC ≦ 2.0 μm
m, and the angle of the slow axis direction of the first retardation plate with respect to the orientation direction of the liquid crystal layer on the first substrate side is θ1, and the first
The angle in the slow axis direction of the second phase difference plate with respect to the slow axis direction of the phase difference plate is θ2, and the angle in the absorption axis direction of the polarizing plate with respect to the slow axis direction of the second phase difference plate is θ3. In this case, θ1, θ2, and θ3 are 65 ° ≦ θ1 ≦ 90 °, −65 ° when the torsion angle θ _LC is set in the range of −160 ° to −300 °, respectively.
When 25 ° ≧ θ2 ≧ −55 ° and 50 ° ≦ θ3 ≦ 80 ° or when the torsion angle θ _LC is set in the range of + 160 ° to + 300 °, −65 ° ≧ θ1 ≧ − A liquid crystal display device which satisfies 90 °, 25 ° ≦ θ2 ≦ 55 °, −50 ° ≧ θ3 ≧ −80 °. 2. A liquid crystal cell having a liquid crystal layer inserted in a gap between a first substrate having electrodes formed on an opposing surface and a second substrate, respectively, and outside the first substrate of the cell, The first retardation plate, the second retardation plate and the polarizing plate are arranged in this order,
A liquid crystal display device having a reflective layer formed on the second substrate side in the liquid crystal cell, wherein a twist angle θ of an alignment direction of liquid crystal molecules from the first substrate toward the second substrate in the liquid crystal layer. _LC is ± 160
゜ to ± 300 °, the refractive index anisotropy Δn _LC of the liquid crystal layer and the thickness d of the liquid crystal layer
Retardation value Δ of liquid crystal layer indicated by product with _LC
n _LC · d _LC is 0.30 μm ≦ Δn _LC · d _LC ≦ 2.0 μm
m, and the angle of the slow axis direction of the first phase difference plate with respect to the orientation direction of the liquid crystal layer on the first substrate side is θ1, and the second angle with respect to the slow axis direction of the first phase difference plate is When the angle of the retardation plate in the slow axis direction is θ2, and the angle of the polarizing plate in the absorption axis direction with respect to the slow axis direction of the second retardation plate is θ3, θ1, θ2, and θ3 are as follows. When the torsion angle θ _LC is in the range of −160 ° to −300 °, the following conditions (i) to (ix): (i) −90 ° ≦ θ1 ≦ −65 °, −40 ° ≦ θ2 ≦ − 3
0 °, 70 ° ≦ θ3 ≦ 80 °, (ii) 0 ° ≦ θ1 ≦ 20 °, −80 ° ≦ θ2 ≦ −60 °,
15 ° ≦ θ3 ≦ 40 °, (iii) 45 ° ≦ θ1 ≦ 55 °, 70 ° ≦ θ2 ≦ 80 °,
−60 ° ≦ θ3 ≦ −50 °, (iv) 80 ° ≦ θ1 ≦ 90 °, 65 ° ≦ θ2 ≦ 75 °, −
45 ° ≦ θ3 ≦ −35 °, (v) 60 ° ≦ θ1 ≦ 80 °, 55 ° ≦ θ2 ≦ 75 °, −
60 ° ≦ θ3 ≦ −55 °, (vi) 15 ° ≦ θ1 ≦ 30 °, -75 ° ≦ θ2 ≦ −65
°, -65 ° ≤ θ3 ≤ -55 °, (vii) 60 ° ≤ θ1 ≤ 70 °, -70 ° ≤ θ2 ≤ -55
°, 35 ° ≤ θ3 ≤ 55 °, (viii) 30 ° ≤ θ1 ≤ 55 °, -70 ° ≤ θ2 ≤ -50
°, -65 ° ≤θ3≤-40 °, (ix) -80 ° ≤θ1≤-70 °, 75 ° ≤θ2≤85
°, 50 ° ≦ θ3 ≦ 60 °, or when the torsion angle θ _LC is in the range of 160 ° to 300 °, the above (i) to (ix) Either of θ1 and θ
A liquid crystal display device which satisfies a condition expressed by reversing the directions of plus and minus signs and inequality signs in the range of 2 and θ3. 3. A liquid crystal display device comprising a liquid crystal cell in which a liquid crystal layer is inserted in a gap between a first substrate having electrodes formed on a facing surface side and a second substrate, respectively, wherein the first substrate of the liquid crystal cell is provided. A first retardation plate, a second retardation plate, and a first polarizer are arranged in this order outside of the liquid crystal cell. On the second substrate side of the liquid crystal cell, light incident from the first substrate side is reflected, and A semi-transmissive reflective layer having a function of transmitting light incident from the second substrate side is formed. According to a voltage applied to the liquid crystal layer, light incident from the first substrate receives birefringence. A liquid crystal display device, wherein the transflective layer arrives in a substantially circularly polarized state. 4. The liquid crystal display device according to claim 1, wherein the reflection layer formed on the second substrate side in the liquid crystal cell reflects light incident from the one substrate side, A liquid crystal display device comprising a transflective layer having a function of transmitting light incident from the second substrate side. 5. The liquid crystal display device according to claim 3, wherein a circularly polarized light irradiating means for irradiating the liquid crystal cell with circularly polarized light outside the second substrate of the liquid crystal cell. The liquid crystal display device, wherein is disposed. 6. The liquid crystal display device according to claim 5, wherein the circularly polarized light irradiating means is constituted by a circularly polarized light source or a broadband circular polarizer and a light source. 7. The liquid crystal display device according to claim 6, wherein the broadband circular polarizer is a cholesteric film. 8. The liquid crystal display device according to claim 6, wherein the broadband circular polarizer is a λ / 4 retardation film, λ / 2.
A liquid crystal display device comprising a retardation film and a polarizing plate. 9. The liquid crystal display device according to claim 8, wherein the polarizing plate of the broadband circular polarizer transmits linearly polarized light oscillating in a specific direction and oscillates vertically in the specific direction. A liquid crystal display device comprising a reflective polarizing plate for reflecting light. 10. The liquid crystal display device according to claim 7, wherein right-handed circularly polarized light or left-handed circularly polarized light is incident on the liquid crystal cell from the broadband circular polarizer. . 11. The liquid crystal display device according to claim 1, wherein a product of a refractive index anisotropy Δn1 of the first retardation plate and a thickness d1 of the first retardation plate. The second retardation indicated by the product of the retardation value Δn1 · d1 of the first retardation plate represented by the following expression, the refractive index anisotropy Δn2 of the second retardation plate, and the thickness d2 of the second retardation plate Plate retardation value Δ
and n2 · d2, the total value Rs of the relative retardation value Δn _LC · d _LC of the liquid crystal _{layer, Δn LC · d LC -m ×} 147.5-25 ≦ Rs ≦
Δn _LC · d _LC −mx147.5 + 75 (where m = −
2. A liquid crystal display device which satisfies the relationship of 2, 0, 1, 2). 12. The liquid crystal display device according to claim 1, wherein a retardation value of the first and second retardation plates at a wavelength of 590 nm is Pr ₅₉₀ , and a retardation value of the liquid crystal layer at a wavelength of 590 nm is Δn _LC · d _LC590 , when the retardation values of the first and second retardation plates at a wavelength of 400 nm are represented by Pr ₄₀₀ , and the retardation value of the liquid crystal layer at a wavelength of 400 nm is represented by Δn _LC · d _LC400 , Value Δn _LC · d _LC400 / Δn _LC · d
The liquid crystal display device a ratio of chromatic dispersion Pr ₄₀₀ / Pr ₅₉₀ of the first and second phase difference plate for _LC590, characterized in that is between 0.98 to 1.12. 13. The liquid crystal display device according to claim 1, wherein the relationship between the retardation Δn1 · d1 of the first retardation plate and the retardation Δn2 · d2 of the second retardation plate is: , Δn2 · d2> Δn1 · d1. 14. The liquid crystal display device according to claim 1, wherein the retardation Δn1 · d1 of the first retardation plate, the retardation Δn2 · d2 of the second retardation plate, and the retardation of the liquid crystal layer. The value Δn _LC · d _LC is defined by the following (i) to (iii)
Any one of the conditions (i) Δn2 · d2 ≧ Δn LC · d LC / 2, Δn1 · d1 ≦
150nm, (ii) Δn2 · d2 ≧ Δn LC · d LC / 2, Δn1 · d1 ≧
400nm, (iii) Δn2 · d2 ≧ Δn LC · d LC × 2 / 5,160n
A liquid crystal display device, wherein m ≦ Δn1 · d1 ≦ 220 nm is satisfied.