JPH08166585A - Reflection type liquid crystal display device - Google Patents

Abstract

PURPOSE: To provide a reflection type liquid crystal display device in which misalignment of display colors is prevented and a bright display is obtd. in a bright state. CONSTITUTION: The reflection type liquid crystal display device consists of a first substrate 1 and a second substrate 2 facing each other to hold a liquid crystal layer 8 in between. A first transparent electrode 4 and a first oriented film 6 are formed don the liquid crystal layer side of the first substrate 1. A color filter layer 9 covered with a flattening layer 10, second transparent electrode 5, and second oriented film 7 are successively formed on the liquid crystal layer side of the second substrate 2. A polarizing plate 3 is disposed on the incident light side (outer surface) of the first substrate 1, and a reflecting plate 11 is disposed between the second substrate 2 and the color filter layer 9 covered with the flattening layer 10. By this method, the transmission optical length of the incident light and reflected light can be decreased and the distance Δd' between the incident position of the incident light and the outgoing position of the reflected light is reduced so that the incident light and reflected light can transmit through a same pixel and a same color filter layer 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflective liquid crystal display device, and in particular, a polarizing plate is provided only on the outer side of a (first) substrate on the light incident side, and a (second) substrate on the reflective side is provided. The present invention relates to a reflective liquid crystal display device in which a light reflector in a bright state is increased by providing a reflector between the color filter layer and the color filter layer.

[0002]

2. Description of the Related Art In a conventional reflective liquid crystal display device, first and second substrates are arranged so as to face each other with a liquid crystal layer in between, and a first liquid crystal layer side of the first substrate is provided. Transparent electrode and first alignment film, a first polarizing plate provided outside the first substrate, a color filter layer sequentially provided on the liquid crystal layer side of the second substrate, and a second transparent electrode. And a second alignment film, and a second polarizing plate and a reflecting plate which are sequentially provided on the outer side of the second substrate.

FIG. 6 is a cross sectional view showing an example of the known reflection type liquid crystal display device, and shows only a part of the cross section of the reflection type liquid crystal display device.

In FIG. 6, reference numeral 21 is a light incident side (first) substrate made of a transparent material, 22 is a reflection side (second) substrate made of a transparent material, 23 is a first polarizing plate, and 24 is a Second
Polarizing plate, 25 is a first transparent electrode, 26 is a second transparent electrode, 27 is a first alignment film, 28 is a second alignment film, 29 is a liquid crystal layer, 30 is a color filter layer, and 31 is flat. Chemical layer, 3
2 is a metal reflector.

Then, the first substrate 21 and the second substrate 22
Are arranged and arranged so as to sandwich the liquid crystal layer 29 and face each other. A first polarizing plate 23 is provided on the light incident side (outer side) of the first substrate 21, and a first transparent electrode extending in one direction is provided on the liquid crystal layer 29 side (inner side) of the first substrate 21. 25 and the first alignment film 27 are provided respectively, and the first alignment film 27 is provided so as to cover the first transparent electrode 25 and the exposed portion of the first substrate 21. A metal reflection plate 32 is provided outside the second substrate 22 via a second polarizing plate 24, and a liquid crystal layer 29 side (inside) of the second substrate 22 is covered with a flattening layer 31. The color filter layer 30 is provided, and the color filter layer 30 is provided above the color filter layer 30, that is, the planarization layer 31.
A second transparent electrode 26 and a second alignment film 28 extending in a direction orthogonal to the first transparent electrode 25 are provided on the upper side of the second alignment film 28. In this case as well, the second alignment film 28 has the second transparent electrode 26. It is provided so as to cover the electrode 26 and the exposed portion of the planarization layer 31. An AC driving power supply (no figure number) is connected between the first transparent electrode 25 and the second transparent electrode 26, and although not shown in FIG. 6, the first substrate 21 and the first transparent electrode 26 are connected to each other.
A thin film transistor is arranged between the transparent electrode 25 and the transparent electrode 25.

In the known reflection type liquid crystal display device having the above structure, when the incident light as shown in FIG. 6 is incident, the incident light is the first polarizing plate 23 and the first substrate 2.
1, first transparent electrode 25, first alignment film 27, liquid crystal layer 2
9, second alignment film 28, second transparent electrode 26, color filter layer 30, flattening layer 31, second substrate 22, second
Reaching the metal reflecting plate 32 through the respective polarizing plates 24 of
It is reflected there. Next, the reflected light is reflected by the second polarizing plate 24, the second substrate 22, the color filter layer 30, the flattening layer 31, the second transparent electrode 26, the second alignment film 28,
A liquid crystal layer 29, a first alignment film 27, a first transparent electrode 25,
It is emitted as reflected light to the outside of the reflective liquid crystal display device through the first substrate 21 and the first polarizing plate 23, respectively, and is observed by an observer. In this case, the liquid crystal layer 29 between the first transparent electrode 25 and the second transparent electrode 26, through which the light is transmitted (the liquid crystal layer 29 in this portion respectively constitutes different pixels) was in a transparent state. When the observer can observe the reflected light sufficiently, the first
Liquid crystal layer 29 between the transparent electrode 25 and the second transparent electrode 26 of
When the (pixel) is in an opaque state, the observer cannot observe the reflected light.

[0007]

In the known reflection type liquid crystal display device, when an observer observes the reflected light from the surface of the reflection type liquid crystal display device, it is orthogonal to the surface of the reflection type liquid crystal display device. The observation is often performed from an angle direction (slightly oblique direction) other than 90 ° with respect to the surface of the reflective liquid crystal display device, rather than from the direction (directly above). When observing from the angle direction other than 90 ° with respect to the surface of the reflective liquid crystal display device, the incident position of the incident light and the reflected light and the exit position of the surface of the reflective liquid crystal display device become different. As shown in FIG. 6, the distance between the incident position of the incident light and the reflected light and the emission position is Δd.

By the way, in the known reflection type liquid crystal display device, when the distance Δd is widened to a certain extent or more, as shown by the solid line in FIG. 6, a pixel through which incident light passes and a pixel through which reflected light passes through are formed. As a result, the color filter layer 30 that transmits incident light and the color filter layer 30 that transmits reflected light become different, as shown by the dotted line in FIG. 6, and as a result, However, when the observer observes the reflected light, there is a problem that the display color is displaced.

On the other hand, in the known reflection type liquid crystal display device, the incident light and the reflected light are transmitted through the first polarizing plate 23 and the second polarizing plate 24, respectively, and for convenience, they are transmitted through the polarizing plate four times. Therefore, there is a problem that the loss of incident light and reflected light at the time of transmission through the polarizing plates 23 and 24 becomes large, and bright display cannot be performed in a bright state.

The present invention eliminates such a problem, and an object of the present invention is to provide a reflection type liquid crystal display device capable of preventing the occurrence of display color shift and performing bright display in a bright state. To provide.

[0011]

In order to achieve the above object, the present invention provides a first and a second substrate which are arranged so as to face each other with a liquid crystal layer interposed therebetween, and the liquid crystal of the first substrate. A first transparent electrode and a first alignment film respectively provided on the layer side, and a color filter layer, a second transparent electrode and a second alignment film sequentially provided on the liquid crystal layer side of the second substrate. And a polarizing plate provided outside the first substrate and a reflection plate provided between the second substrate and the color filter layer.

[0012]

In the above means, the reflecting plate is provided between the (second) substrate on the reflecting side and the color filter layer, so that the incident light incident on the surface of the reflective liquid crystal display device is A polarizing plate, a light-incident side (first) substrate, a first transparent electrode, a first alignment film, a liquid crystal layer, a second alignment film, a second transparent electrode, and a color filter layer, respectively, and a reflection plate. While the reflected light from the reflector plate reaches the color filter layer,
The reflected light is emitted to the outside of the reflective liquid crystal display device through the second transparent electrode, the second alignment film, the liquid crystal layer, the first alignment film, the first transparent electrode, the first substrate, and the polarizing plate, respectively. To be done.

As described above, according to the above-mentioned means, as compared with the known reflection type liquid crystal display device, the incident light and the reflected light are transmitted by the amount of transmitting twice each through the second polarizing plate and the second substrate. Since the optical path length is shortened, even if the incident light is incident on the surface of the reflective liquid crystal display device at the same angle as that of the known reflective liquid crystal display device, the incident position of the incident light and the reflected light The interval Δd ′ is shorter than the same interval Δd in a known reflective liquid crystal display device, and the probability that a pixel transmitting incident light and a pixel transmitting reflected light are different by that amount,
Further, the probability that the color filter layer that transmits the incident light and the color filter layer that transmits the reflected light are different from each other is considerably reduced, and it is possible to prevent the deviation of the display color from occurring.

Further, in the above-mentioned means, since the polarizing plate is provided only on the outer side of the (first) substrate on the light incident side and the polarizing plate is not provided on the (second) substrate on the reflecting side, the incident light and The reflected light only passes through the polarizing plate once.

As described above, according to the above-mentioned means, the number of times the light transmitted through the polarizing plate is transmitted is halved as compared with the known reflection type liquid crystal display device, so that the light transmission loss in the polarizing plate can be halved. This makes it possible to perform bright display in the bright state.

[0016]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a cross sectional view showing a first embodiment of a reflective liquid crystal display device according to the present invention, and shows only a part of the cross sectional structure of the reflective liquid crystal display device.

In FIG. 1, reference numeral 1 denotes a light-incident side (first) substrate made of a transparent material, 2 denotes a reflection-side (second) substrate made of a transparent material, 3 a polarizing plate, and 4 a first substrate. Transparent electrode, 5
Is a second transparent electrode, 6 is a first alignment film, 7 is a second alignment film, 8 is a liquid crystal layer, 9 is a color filter layer, 10 is a flattening layer, and 11 is a metal reflector.

Then, the first substrate 1 and the second substrate 2 are
The liquid crystal layer 8 is arranged and arranged so as to face each other. First
A polarizing plate 3 is provided on the light incident side (outer side) of the substrate 1, and on the liquid crystal layer 8 side (inner side) of the first substrate 1, a large number of first transparent electrodes extending parallel to one direction. 4 (2 in FIG. 1
(Only a book is shown) and a first alignment film 6 are respectively provided so that the first alignment film 6 covers a large number of first transparent electrodes 4 and exposed portions of the first substrate 1. It is provided. On the liquid crystal layer 8 side (inside) of the second substrate 2, first, a metal reflection plate 11 is provided, and a color filter layer 9 covered with a flattening layer 10 is provided on the metal reflection plate 11. On the upper side of the color filter layer 9, that is, on the upper side of the flattening layer 10, a large number of second transparent electrodes 5 (only one is shown in FIG. 1) extending parallel to the first transparent electrodes 4 in the orthogonal direction. Are provided) and a second alignment film 7 are provided, respectively, and the second alignment film 7 is provided so as to cover the multiple second transparent electrodes 5 and the exposed portions of the planarization layer 10. An AC driving power supply (not shown) is connected between the first transparent electrode 4 and the second transparent electrode 5, and a thin film transistor is provided between the first substrate 1 and the first transparent electrode 4. (Not shown) is arranged. In this case, the metal reflector 11 is
For example, it is formed on the second substrate 2 by aluminum vapor deposition. The liquid crystal layer 8 has a twist angle of 240 °, for example. Further, the color filter layer 9 individually transmits each color of red (red), green (green), and blue (blue).

Next, FIG. 2 is a cross-sectional view showing the operation of the reflection type liquid crystal display device of the first embodiment with incident light and reflected light transmission optical paths, and is a known reflection type liquid crystal display. FIG. 6 shows a cross-sectional configuration diagram with a transmission optical path in the apparatus.
It corresponds to.

In FIG. 2, the same components as those shown in FIG. 1 are designated by the same reference numerals. In this case, the solid line shown in FIG. 2 shows the light transmission path in the reflection type liquid crystal display device of the first embodiment, while the dotted line shown in FIG. 2 shows the known reflection type liquid crystal display device. 2 shows a transmission optical path of light in FIG.

The operation of the reflection type liquid crystal display device of the first embodiment having the above construction will be described with reference to FIG.

When incident light is incident as shown in FIG. 2, the light is reflected by the polarizing plate 23, the first substrate 1, the first transparent electrode as shown by the solid line in FIG. 4, the first alignment film 6, the liquid crystal layer 8, the second alignment film 7, the second transparent electrode 5, the color filter layer 9 and the flattening layer 10, respectively, reach the metal reflection plate 11 and are reflected there. It Next, the reflected light from the metal reflection plate 11 is, as also shown by the solid line in FIG. 2, the color filter layer 9 and the planarization layer 1.
0, the second transparent electrode 5, the second alignment film 7, the liquid crystal layer 8, the first alignment film 6, the first transparent electrode 4, the first substrate 1, and the polarizing plate 3, respectively The reflected light is emitted to the outside of the display device, and the light is observed by an observer.
In this case, the liquid crystal layer 8 between the first transparent electrode 4 and the second transparent electrode 5 through which the incident light and the reflected light are transmitted (the liquid crystal layer 8 in this portion respectively constitutes different pixels) When in the transparent state, the observer can sufficiently observe the reflected light, whereas the liquid crystal between the first transparent electrode 4 and the second transparent electrode 5 through which the incident light and the reflected light are transmitted. It is a known reflective liquid crystal display device that the observer cannot observe the reflected light when the layer 8 (which constitutes each separate pixel as described above) is in the opaque state. Is the same as.

Here, comparing the light transmission optical path in the reflection type liquid crystal display device of the first embodiment with the light transmission optical path in the known reflection type liquid crystal display device, in the known reflection type liquid crystal display device, 2, when incident light is incident as shown in FIG. 2, the light is the same as the transmission optical path shown by the solid line in FIG. 2 until it passes through the color filter layer 9 and the flattening layer 10. After that, as shown by the dotted line in FIG. 2, the light passes through the second substrate 11 and the second polarizing plate 24 (see FIG. 6), reaches the metal reflection plate 11, and is reflected there. Then, the reflected light from the metal reflection plate 11 is again reflected by the second polarizing plate 24 as shown by the dotted line in FIG.
(See FIG. 6) and after passing through the second substrate 11, the color filter layer 9 and the planarization layer 10, the second transparent electrode 5,
The reflected light is emitted as reflected light to the outside of the reflective liquid crystal display device through the second alignment film 7, the liquid crystal layer 8, the first alignment film 6, the first transparent electrode 4, the first substrate 1, and the polarizing plate 3, respectively. To be done.

As described above, in the known reflection type liquid crystal display device, since the light transmission optical path length does not fall below about twice the thickness of the reflection type liquid crystal display device, the light is incident on the surface of the reflection type liquid crystal display device. The distance Δd between the light incident position, the reflected light and the emission position is relatively long. In the known reflection type liquid crystal display device, the incident light and the reflected light respectively pass through the polarizing plate 3 and the second polarizing plate 24 (see FIG. 6), so that in the polarizing plate 3 and the second polarizing plate 24, Light transmission loss occurs.

On the other hand, in the reflection type liquid crystal display device of the first embodiment, as described above, the light is not transmitted through the second substrate 11 and the second polarizing plate 24 (see FIG. 6). Since the transmission optical path length is shortened to approximately twice the thickness of the reflective liquid crystal display device or less, the distance Δ between the incident position of the incident light and the reflected light and the emitting position on the surface of the reflective liquid crystal display device is Δ.
d'is considerably shorter than the interval Δd.

As described above, in the reflection type liquid crystal display device of the first embodiment, the pixels (liquid crystal layer 8) through which the incident light is transmitted.
The probability that the pixel and the pixel (liquid crystal layer 8) through which the reflected light is transmitted is significantly smaller than that of a known reflection type liquid crystal display device.
Further, the probability that the color filter layer 10 that transmits incident light and the color filter layer 10 that transmits reflected light is different is significantly reduced as compared with a known reflective liquid crystal display device.
The occurrence of display color shift can be greatly reduced.
By the way, according to the reflection type liquid crystal display device of the first embodiment, when the incident angle θ of the light shown in FIG. 2 is within ± 36 °, the occurrence of display color shift is reduced. .

Further, in the reflection type liquid crystal display device of the first embodiment, the incident light and the reflected light respectively enter the polarizing plate 3.
Since the light is transmitted only one by one, only the light transmission loss that occurs in the polarizing plate 3 is required, and the reflectance in the bright state can be improved by about 23% as compared with the known reflection type liquid crystal display device. It was

Next, FIG. 3 is a sectional view showing the second embodiment of the reflection type liquid crystal display device according to the present invention, and shows only a part of the reflection type liquid crystal display device. is there.

In FIG. 3, reference numeral 12 is a thin film transistor (TFT), 13 is a black matrix, and the same components as those shown in FIG. 1 are designated by the same reference numerals.

The thin film transistor 12 is disposed and formed between the first substrate 1 and the first transparent electrode 4, and one thin film transistor 12 is disposed and formed for each pixel.
The black matrix 13 is arranged and formed on the first substrate 1 between the first transparent electrodes 4 and between the second transparent electrodes 5.
The liquid crystal layer 8 having a twist angle of 90 ° is used. Further, the other structure of the second embodiment is the same as the structure of the first embodiment shown in FIG. 1, and therefore the description of the other structure will be omitted.

The operation of the second embodiment, especially the operation when the incident light and the reflected light are transmitted through the reflection type liquid crystal display device, is almost the same as the operation of the first embodiment. Therefore, the description of the operation of the second embodiment will be omitted.

According to the second embodiment, when the incident angle .theta. Of light is within. +-. 34.degree., The occurrence of display color shift is reduced, and the known reflection type liquid crystal display device is provided. The reflectance in the bright state could be improved by about 33% as compared with the above.

In the second embodiment, in the case where only the thin film transistor 12 is arranged and formed and the black matrix 13 is not provided, when the incident angle θ of light is within ± 28 °, display is performed. The occurrence of color shift was reduced, and the reflectance in the bright state could be improved by about 33% as compared with the known reflective liquid crystal display device.

Next, FIG. 4 is a cross sectional view showing a third embodiment of the reflection type liquid crystal display device according to the present invention, and shows only a part of the cross section constitution of the reflection type liquid crystal display device. .

In FIG. 4, reference numeral 14 is a retardation plate, and other components that are the same as those shown in FIG. 1 are designated by the same reference numerals.

The retardation plate 14 is provided between the first substrate 1 and the polarizing plate 3, and has a Δn · d of 600, for example.
nm. Further, the other configurations in the third embodiment are the same as the configurations of the first embodiment shown in FIG. 1, and therefore the description of the other configurations will be omitted.

Also in the operation of the third embodiment, except that the incident light and the reflected light are transmitted by passing through the retardation plate 14,
Since the operation is almost the same as that of the first embodiment, the description of the operation of the second embodiment will be omitted.

Here, FIG. 5 is a characteristic diagram showing the spectral reflectance in the third embodiment. FIG. 5A shows the case where no complementary color filter is used, and FIG. 5B shows the complementary color filter. It shows the characteristics when is used.

In FIGS. 5A and 5B, the vertical axis represents the reflectance expressed in%, and the horizontal axis represents the light wavelength expressed in nm.

As shown in FIG. 5A, the retardation plate 1
In the reflection type liquid crystal display device of the third example having No. 4, when the light wavelength was about 500 nm, it was possible to obtain a spectral reflectance characteristic of about 50% at maximum in the bright state.

Further, as shown in FIG. 5B, in the reflective liquid crystal display device of the third embodiment having the retardation plate 14, complementary color pigments of cyan, magenta and yellow are used as the color filter 10. By performing mixed color additive display, it is possible to obtain spectral reflectance characteristics of up to 60% or more in the bright state when the light wavelength is about 600 nm.
Compared with the reflection type liquid crystal display device of the third embodiment having the retardation plate 14 shown in FIG.
It was possible to improve it by about%.

In the third embodiment, the retardation plate 1
The arrangement position of 4 is not limited to the one provided between the first substrate 1 and the polarizing plate 3, but may be provided inside the first substrate 1, or the liquid crystal of the first substrate 1 may be provided. It may be provided on the layer 8 side.

[0044]

As described in detail above, according to the present invention, the second polarizing plate and the (second) substrate on the reflection side are respectively provided twice as compared with the known reflection type liquid crystal display device. Since the transmission optical path lengths of the incident light and the reflected light are shortened by the amount of transmission, even if the incident light is incident on the surface of the reflective liquid crystal display device at the same angle θ as that of the known reflective liquid crystal display device,
Distance Δd ′ between the incident position of incident light and the reflected position of light
Is considerably shorter than the same interval Δd in the known reflection type liquid crystal display device, and the probability that a pixel transmitting incident light differs from a pixel transmitting reflected light, and a color filter transmitting the incident light. The probability that the layer and the color filter layer through which the reflected light passes will be significantly smaller,
This has the effect of significantly reducing the occurrence of display color shift.

Further, according to the present invention, the number of times of transmission of light passing through the polarizing plate is halved as compared with the known reflection type liquid crystal display device, so that the transmission loss of light in the polarizing plate can be halved. Thereby, there is also an effect that bright display can be performed in the bright state.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional configuration diagram with incident light and reflected light transmission optical paths for explaining the operation of the reflective liquid crystal display device of the first embodiment.

FIG. 3 is a cross-sectional configuration diagram showing a second embodiment of a reflective liquid crystal display device according to the present invention.

FIG. 4 is a cross-sectional configuration diagram showing a third embodiment of a reflective liquid crystal display device according to the present invention.

5 is a characteristic diagram showing a spectral reflectance in the third embodiment shown in FIG.

FIG. 6 is a cross-sectional configuration diagram showing an example of a known reflective liquid crystal display device.

[Explanation of symbols]

 1 Light-incident side (first) substrate 2 Reflection-side (second) substrate 3 Polarizing plate 4 First transparent electrode 5 Second transparent electrode 6 First alignment film 7 Second alignment film 8 Liquid crystal Layer 9 Color filter layer 10 Flattening layer 11 Metal reflector 12 Thin film transistor (TFT) 13 Black matrix 14 Phase difference plate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Osamu Ito 7-1-1, Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi Research Laboratory, Hitachi Ltd. (72) Tatsuhisa Fujii 3300, Hayano, Mobara-shi, Chiba Shares Company Hitachi Ltd. Electronic Device Division (72) Inventor Tomohide Ohira 3300 Hayano, Mobara, Chiba Prefecture Hitachi Electronic Device Division (72) Inventor Tatsunori Fumikura 3681 Hayano Mobara, Chiba Hitachi Device Engineering Co., Ltd.

Claims (6)

[Claims] 1. A first substrate and a second substrate which are arranged to face each other with a liquid crystal layer in between, a first transparent electrode and a first transparent electrode which are respectively provided on the liquid crystal layer side of the first substrate. In a reflective liquid crystal display device including an alignment film, a color filter layer provided on the liquid crystal layer side of the second substrate, a second transparent electrode, and a second alignment film, A reflective liquid crystal display device, wherein a polarizing plate is provided on the outside and a reflector is provided between the second substrate and the color filter layer. 2. The reflective liquid crystal display device according to claim 1, wherein the color filter layer is covered with a flattening film. 3. The reflection type liquid crystal display device according to claim 2, wherein the color filter layer uses a complementary color pigment of cyan, magenta and yellow. 4. A space between the first substrate and the polarizing plate is 1
4. The reflective liquid crystal display device according to claim 1, wherein one or more retardation plates are inserted and arranged. 5. The reflection type device according to claim 1, wherein a thin film transistor is formed and arranged between the first substrate and the first transparent electrode and the first alignment film. Liquid crystal display device. 6. The reflective liquid crystal display device according to claim 1, further comprising a black matrix layer disposed on the first substrate between the first transparent electrodes.