JPH10228027A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the liquid crystal display device which has visibility even in a dark place by forming an ITO film of an electrode film of an observer-side electrode plate and constituting an electrode film of a back electrode plate by sandwiching a silver allow thin film with specific thickness between transparent oxide films. SOLUTION: The observer-side electrode plate 2 and back electrode plate 3 are arranged opposite each other, and a liquid crystal material 40 is charged between both the electrode plates. The observer-side electrode plate 2 consists of a reflection preventive film 83 which is arranged on the observer-side top surface of a transparent substrate 70, a scatter film 60 arranged on the other surface, and an ITO film 50 which is arranged as an electrode on the scatter film 60 and drives liquid crystal and an oriented film. Further, the back electrode plate 3 consists of a light-reflective and light-transmissive electrode film 30 of three-layered constitution, which is arranged as an electrode on the observer-side surface of the back transparent substrate 20 and has a silver alloy thin film of 12 to 70nm in film thickness for driving the liquid crystal sandwiched between a lower transparent oxide thin film and an upper transparent oxide thin film, and an oriented film.

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 a liquid crystal display device having visibility in a bright place, in a high light place and in a dark place. About.

[0002]

2. Description of the Related Art A main part of a liquid crystal display device is constituted by a pair of opposing electrode plates provided with electrodes capable of applying a voltage to each pixel, and a liquid crystal material sealed between the electrode plates. By applying a voltage between the two electrodes, the alignment state of the liquid crystal material is changed for each pixel, and light transmitted through the liquid crystal material is controlled to perform screen display.

In such a liquid crystal display device, external light such as room light or natural light is made incident from an electrode plate located on the viewer side of the liquid crystal display device, and the incident light is reflected on a back electrode having light reflectivity. A reflection type liquid crystal display device that reflects light on a plate and displays a screen with the reflected light is known.

[0004] Further, as a liquid crystal display device, a backlight type or a light guide type in which a light source (lamp) is arranged on the back surface or side surface of an electrode plate located on the back side of the liquid crystal display device and light enters from the back electrode plate side. There is known a transmission type liquid crystal display device having a built-in lamp.

[0005]

However, the visibility of this conventional reflection type liquid crystal display device depends on the intensity of external light. That is, in a high-light place with strong external light (for example, illuminance of several thousand lux or more) such as outdoors and a bright place such as indoor (for example, illuminance of several hundred lux), the visibility is good, but the garage, In a dark place such as a bedroom where external light is weak (for example, illuminance of several tens of lux), the visibility is very poor. An object of the present invention is to provide a liquid crystal display device which solves the problem that such a conventional reflective liquid crystal display device has very poor visibility in a dark place.

[0006] The visibility of a conventional transmissive liquid crystal display is also affected by the intensity of external light. That is, the visibility is good in the dark place and the bright place, but very poor in the high light place. An object of the present invention is to provide a liquid crystal display device which solves the problem that such a conventional transmission type liquid crystal display device has very poor visibility in a high light place.

[0007]

According to a first aspect of the present invention, in a liquid crystal display device comprising a pair of opposed electrode plates, an electrode film of an observer side electrode plate is an ITO film,
The liquid crystal display device is characterized in that the electrode film of the back electrode plate has a three-layer structure in which a silver alloy thin film having a thickness of 12 nm to 70 nm is sandwiched between a lower transparent oxide thin film and an upper transparent oxide thin film.

Next, the invention described in claim 2 of the present invention is:
2. The liquid crystal display device according to claim 1, wherein the thickness of the silver alloy thin film is in a range of 30 nm to 70 nm.

Next, the invention according to claim 3 of the present invention provides:
2. The liquid crystal display device according to claim 1, wherein the thickness of the silver alloy thin film is in a range of 12 nm to 30 nm.

Next, the invention described in claim 4 of the present invention is:
2. The liquid crystal display device according to claim 1, wherein at least the upper transparent oxide thin film has a thickness of 10 nm to 2 nm.
A liquid crystal display device having a range of 00 nm.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, in a liquid crystal display device (1) of the present invention, an observer-side electrode plate (2) and a back electrode plate (3) are arranged to face each other. A liquid crystal material (40) is sealed between the electrode plates.

The observer-side electrode plate (2) is disposed on the observer-side surface of the observer-side transparent substrate (70), and is an antireflection for reducing reflected light on the surface due to external light and preventing glare. A film (83), a light scattering film (60) disposed on another surface of the observer-side transparent substrate (70) for obtaining a matte display quality such as a blank surface, and a scattering film (60). ) For driving a liquid crystal disposed as an electrode on the ITO film (5).
0) and an alignment film (not shown).

The back electrode plate (3) is a silver alloy thin film (12 nm to 70 nm) for driving liquid crystal, which is disposed on the observer side surface of the back transparent substrate (20) as an electrode. 32) comprises a three-layer light-reflective and light-transmissive electrode film (30) sandwiching a lower transparent oxide thin film (31) and an upper transparent oxide thin film (33), and an alignment film (not shown). ing.

The antireflection film (83) disposed on the observer-side surface of the observer-side transparent substrate (70) has a titanium oxide layer /
It is composed of four layers of silicon oxide layer / titanium oxide layer / silicon oxide layer, and the reflected light is reduced by interference of light in these four layers. The reflectivity of the four-layer antireflection film (83) is about 0.5%.

As shown in FIG. 1, the scattering film (60) on the viewer-side transparent substrate (70) is composed of two layers: a scattering layer for scattering light and a flattening layer for flattening the scattering layer. Have been.

The scattering film (60) is prepared by first forming a material for the scattering layer (composition: cerium oxide powder (average particle size: 0.7 μm, solid content ratio: 25%) on the observer-side transparent substrate (70). Fluorine-based transparent resin (refractive index: 1.41; solid weight ratio: 75%) is applied to the entire surface by a spin coater and dried to provide a scattering layer having a thickness of about 1.5 μm.

Next, on the scattering layer, the above-mentioned fluorine-based transparent resin is used as a material for the flattening layer, and the whole surface is applied and dried by a spin coater to provide a flattening layer having a thickness of about 1.5 μm. ) Is about 3.0 μm.

Next, an ITO film (50) {composition: 90% by weight of indium oxide, 10% by weight of tin oxide} is formed on the scattering film (60) by sputtering, and then patterned by photolithography. And an ITO film (50) as a pattern electrode.

As shown in FIG. 2, the light reflecting / light transmitting electrode film (30) on the rear transparent substrate (20) has a three-layer structure.

First, the lower transparent oxide thin film (31) {composition:
Indium oxide 70%. Cerium oxide, tin oxide,
Approximately 4% of titanium oxide total 30%
Then, a silver alloy thin film (32) {composition: 2 atomic% of gold, the balance of silver} is deposited to a thickness of about 12 nm to 70 nm by a sputtering method.

Subsequently, the upper transparent oxide thin film (33)
｛Composition: 80% indium oxide. By forming a film of cerium oxide, tin oxide, or titanium oxide 20% in any thickness in a range of about 10 nm to about 200 nm by a sputtering method, a three-layer light-reflective / light-transmissive electrode film is formed. (30) is deposited.

Subsequently, the light reflecting / light transmitting electrode film (30) having a three-layer structure is patterned by photolithography to form a light reflecting / light transmitting electrode film (30) as a pattern electrode. In addition, the liquid crystal material (4) between the observer side electrode plate (2) and the back electrode plate (3) arranged opposite to each other.
As 0), a phase-transition guest-host liquid crystal is used.

[0023]

[Table 1]

[0024]

[Table 2]

Table 1 shows light-reflective / light-transmissive electrode films (3
0) has a three-layer structure of {transparent substrate on observer side (70) / film thickness 4
0 nm lower transparent oxide thin film (31) / silver alloy thin film (3
2) / 75 nm thick upper transparent oxide thin film (33) / medium (n = 1.5)}, which is an intermediate layer of a three-layer light-reflective / light-transmissive electrode film (30) Alloy thin film (32)
4 is a simulation result showing changes in reflectance and transmittance when the film thickness of the sample is changed. FIG.
The result at 700 nm is shown.

Table 2 shows that the three-layer structure of the light-reflective / light-transmissive electrode film (30) is as follows: {observer-side transparent substrate (70) / 40 nm-thick lower transparent oxide thin film (31) / silver alloy Thin film (32) / 46 nm thick transparent oxide thin film (33) /
Medium (n = 1.5)}, and a three-layer light-reflecting property
A silver alloy thin film (3) which is an intermediate layer of the light transmitting electrode film (30)
It is a simulation result which looks at the change of the reflectance and the transmittance | permeability when changing the film thickness of 2). In FIG. 9, 400n
The results for m to 700 nm are shown.

As shown in Table 1, for example, when the thickness of the silver alloy thin film (32) is 50 nm, the reflectance of the light-reflective / light-transmissive electrode film (30) is 88.4%. , Transmittance is 8.9%.

The liquid crystal display device (1) using the light-reflective / light-transmissive electrode film (30) made of the silver alloy thin film (32) having a thickness of 50 nm is mainly used as a reflective liquid crystal display device. . At this time, when a voltage is applied between the two electrode plates, the antireflection film (83), the observer-side transparent substrate (70), the scattering film (60), the ITO film (50), the liquid crystal 88. of the light incident on the material (40) with a diameter
The light reflecting / light transmitting electrode film (30) reflects 4%.

The liquid crystal display device (1) having a reflectivity of 88.4% has good visibility as a reflection type liquid crystal display device in a high light place and a bright place.

On the other hand, when the liquid crystal display device (1) is used as a transmission type liquid crystal display device, a light source (R) incident from the back surface of the liquid crystal display device (1) when a voltage is applied between both electrode plates. 8.9% of the light from the lamp (not shown)
Is transmitted.

Since the liquid crystal display device (1) having a transmittance of 8.9% has a transmittance of not 0%, it can be used in a dark place where external light is weak (for example, illuminance of several tens of lux) such as a garage or a bedroom. Are visible as a transmission type liquid crystal display device.

FIG. 3 illustrates such a function.
In a high light place and a light place, the externally incident light a incident on the pixel (A) to which a voltage is applied between the two electrode plates passes through the liquid crystal material (40), and becomes a light reflective / light transparent electrode film. The light is reflected as reflected light a ^' at (30). In addition, externally incident light b incident on the pixel (B) to which no voltage is applied between the two electrode plates is shielded by the liquid crystal material (40).

In a dark place, as shown in FIG. 4, incident light c from a light source (lamp) (not shown) on the back surface which enters the pixel (A) to which a voltage is applied between the two electrode plates. Is transmitted as transmitted light c ^′ through the light-reflective / light-transmissive electrode film (30) and the liquid crystal material (40). Further, incident light d from a light source (lamp) (not shown) on the rear surface, which enters the pixel (B) to which no voltage is applied between the two electrode plates, passes through the light-reflective / light-transmissive electrode film (30). , And is shielded by the liquid crystal material (40).

That is, the liquid crystal display device (1) according to the present invention has both functions of a reflection type liquid crystal display device and a function of a transmission type liquid crystal display device. The function can be used properly.

The liquid crystal display device (1) according to the present invention has good visibility as a reflection type liquid crystal display device in a high light place and a bright place. In a dark place (for example, illuminance of several tens of lux) where external light is weak, such as a garage or a bedroom, the transmissive liquid crystal display device has visibility.

As shown in Table 2, when the thickness of the silver alloy thin film (32) is 15 nm, for example,
The reflectance of the light transmitting electrode film (30) is 7.2%, and the transmittance is 90.4%.

The liquid crystal display (1) using the light-reflective / light-transmissive electrode film (30) made of the silver alloy thin film (32) having a thickness of 15 nm is mainly used as a transmissive liquid crystal display. . At this time, when a voltage is applied between the two electrode plates, 90.4% of light from a light source (lamp) (not shown) incident from the back surface of the liquid crystal display device (1).
%.

The liquid crystal display device (1) having a transmittance of 90.4% has good visibility as a transmission type liquid crystal display device in a dark place and a bright place.

On the other hand, when the liquid crystal display device (1) is used as a reflection type liquid crystal display device, the antireflection film (83) and the observer side from the observer side when a voltage is applied between both electrode plates. The light-reflective / light-transmissive electrode film (30) allows 7.2% of the light incident through the transparent substrate (70), the scattering film (60), the transparent oxide electrode film (50), and the liquid crystal material (40). It will reflect.

The liquid crystal display device (1) having a reflectivity of 7.2% has a reflectivity of 7.2%, but can be used in a high-light place (for example, an illuminance of several thousand lux or more) where external light is strong as in clear weather. In this case, a sufficient amount of reflected light is obtained correspondingly, and the reflective liquid crystal display device has visibility.

When such a function is described with reference to FIG. 4, in a dark place and a bright place, a light source (lamp) (see FIG. The incident light c from the not-shown light) passes through the light-reflective / light-transmissive electrode film (30) and the liquid crystal material (40) and is transmitted as transmitted light c ^′ . In addition, a light source (lamp) on the back surface (not shown) which enters the pixel (B) to which no voltage is applied between the two electrode plates
Incident light d from the light reflecting / light transmitting electrode film (30)
Through the liquid crystal material (40).

In a dark place, as shown in FIG. 3, externally incident light a incident on the pixel (A) to which a voltage is applied between the two electrode plates passes through the liquid crystal material (40). Reflective
The light is reflected by the light transmitting electrode film (30) as reflected light a ^' . In addition, externally incident light b incident on the pixel (B) to which no voltage is applied between the two electrode plates is shielded by the liquid crystal material (40).

That is, the liquid crystal display device (1) according to the present invention has both the function of a transmission type liquid crystal display device and the function of a reflection type liquid crystal display device. The function can be used properly. The liquid crystal display device (1) according to the present invention has good visibility as a transmissive liquid crystal display device in a dark place and a bright place.

Further, in a high light place (for example, an illuminance of several thousand lux or more) where the outside light is strong such as under fine weather, the reflection type liquid crystal display device has visibility.

The liquid crystal display device (1) according to the present invention is not limited to a phase-change guest-host liquid crystal, but a TN (twisted nematic) liquid crystal, an STN (super twisted nematic) liquid crystal, a HAN (hybrid aligned nematic) liquid crystal, and a BTN (bistable). The present invention is also applied to a (twisted nematic) liquid crystal, a cholesteric liquid crystal, a liquid crystal in a parallel alignment or a vertical alignment.

FIG. 5 shows an example of a TN liquid crystal display device. In this case, as shown in FIGS. 6 and 7,
The polarizing film (12, 82), the retardation film (11, 81), and the optical rotation compensating film (not shown) are provided. The liquid crystal display device (1) according to the present invention includes:
A color filter for colorization may be provided. Further, a switching element for driving a liquid crystal such as a thin film transistor or an MIM diode may be provided on any of the transparent substrates.

The silver alloy element of the silver alloy thin film (32) suppresses the movement of silver which easily moves in the thin film.
Heavy elements such as gold and lead are preferred. Copper, nickel, magnesium, aluminum and the like may be added in small amounts.

The material of the transparent oxide electrode films (31, 33) sandwiching the silver alloy thin film (32) is indium oxide,
Conductive oxides such as tin oxide and zinc oxide are preferred. It is more preferable to use a mixed oxide obtained by adding an oxide having a high refractive index, such as titanium oxide, cerium oxide, zirconium oxide, or tantalum oxide, to these.

The higher the refractive index of the transparent oxide thin film, the better the optical characteristics of the three-layer electrode. The composition of the lower transparent oxide thin film (31) of the three-layered electrode may be different from that of the upper transparent oxide thin film (33). Further, a low-refractive-index fluoride, a high-refractive-index oxide, or an organic material film may be laminated on the upper transparent oxide thin film (33).

When the liquid crystal display device (1) according to the present invention is used in a wristwatch, a mobile phone, a mobile terminal, or the like, the visibility can be improved even in a dark place where external light is weak (for example, illuminance of several tens of lux) such as a garage or a bedroom. Liquid crystal display device with In addition, when used for a monitor of a video camera, the liquid crystal display device has visibility even in a high light place (for example, an illuminance of several thousand lux or more) where external light is strong such as under fine weather.

[0051]

According to the liquid crystal display device of the present invention, in a liquid crystal display device comprising a pair of opposed electrode plates, the electrode film of the observer side electrode plate is an ITO film, and the electrode film of the back electrode plate is:
Since it is a three-layered electrode film having both light reflectivity and light transmissivity in which a silver alloy thin film having a thickness of 12 nm to 70 nm is sandwiched between transparent oxide thin films, strong external light as in clear weather Not only in high-light places (for example, illuminance of several thousand lux) and in indoor places (for example, illuminance of several hundred lux), but also in dark places such as garages and bedrooms where external light is weak (for example, tens of lux), In such a case, a liquid crystal display device with high visibility can be provided. In addition, in a dark place such as a garage or a bedroom where external light is weak (for example, illuminance of several tens of lux) and a light place such as a room (for example, illuminance of several hundred lux),
It is possible to provide a liquid crystal display device having visibility even in a high light place (for example, an illuminance of several thousand lux or more) where external light is strong such as under fine weather.

[Brief description of the drawings]

FIG. 1 is a sectional view of a liquid crystal display device according to the present invention.

FIG. 2 is an enlarged sectional view of an electrode film of the present invention.

FIG. 3 is an explanatory diagram showing an optical path when a reflection display function is used.

FIG. 4 is an explanatory diagram showing an optical path when a transmission display function is used.

FIG. 5 is a sectional view of a liquid crystal display device using a TN liquid crystal.

FIG. 6 is an enlarged sectional view showing an antireflection film, a polarizing film, and a retardation film on a viewer-side transparent substrate.

FIG. 7 is an enlarged sectional view showing a polarizing film and a retardation film on a rear transparent substrate.

FIG. 8 is a graph showing a simulation result.

FIG. 9 is a graph showing another simulation result.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display device 2 ... Observer side electrode plate 3 ... Back electrode plate 10 ... Retardation film and polarizing film 11, 81 ... Retardation film 12, 82 ... Polarization film 70 ... Observer side transparent substrate 20 ... Back transparent substrate Reference Signs List 30: Light-reflective / light-transmitting electrode film 31: Lower transparent oxide thin film 32: Silver alloy thin film 3
3: Upper transparent oxide thin film 40: Liquid crystal material 50: ITO film 60: Scattering film 80: Antireflection film, polarizing film, and retardation film Light film 83: Antireflection film A: Voltage was applied between both electrode plates Pixel B: Pixel not applying a voltage between both electrode plates a: Externally incident light to the pixel to which the voltage is applied a ^′ : Reflected light of a b: Externally incident light to the pixel to which no voltage is applied c: Light incident on the pixel to which a voltage is applied from the back surface Light transmitted through c ^' ... c d ... Light incident from the back surface to the pixel to which no voltage is applied

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Koji Imayoshi, Inventor, 1-5-1, Taito, Taito-ku, Tokyo Inside Toppan Printing Co., Ltd.

Claims (4)

[Claims] In a liquid crystal display device comprising a pair of opposing electrode plates, an electrode film of an observer side electrode plate is an ITO film, and an electrode film of a back electrode plate has a thickness of 12 nm to 70 nm. A liquid crystal display device having a three-layer structure in which a silver alloy thin film is sandwiched between a lower transparent oxide thin film and an upper transparent oxide thin film. 2. The liquid crystal display device according to claim 1, wherein said silver alloy thin film has a thickness in a range of 30 nm to 70 nm. 3. The liquid crystal display device according to claim 1, wherein said silver alloy thin film has a thickness of 12 nm to 30 nm. 4. The liquid crystal display according to claim 1, wherein at least the upper transparent oxide thin film has a thickness of 10 nm to 2 nm.
A liquid crystal display device having a range of 00 nm.