JP2003140149A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To promote the portability of a cellular phone, etc., as a whole by making a liquid crystal display device used for a display screen of the cellular phone etc., commonly usable as another hand baggage. SOLUTION: This liquid crystal display device is formed of a structure laminated with a display liquid crystal layer with a back light, a scattering type liquid crystal shutter layer and a half mirror layer. The scattering type liquid crystal shutter layer is switched to a light transmission mode by a certain switch, by which the device is functioned as an ordinary liquid crystal and the scattering type liquid crystal shutter layer is switched to a light scattering mode, by which the device is functioned as a mirror. When this device is used as the display device of, for example, the cellular phone, the screen serves as an ordinary liquid crystal display screen during signal transmission and reception of mail or the like and on the other hand, the device lends itself to the mirror when the device is not used as the phone. Female is not required to put both of the cellular phone and the mirror in a small bag and is merely necessitated to put the cellular phone having this liquid crystal display device into the bag.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a mobile phone (PHS
Etc.), a personal digital assistant (so-called PDA), a display device of a personal computer, and the like.

[0002]

2. Description of the Related Art For mobile phones and the like, their small size,
From the viewpoint of light weight and low driving power, a liquid crystal display device is exclusively used as a display device, but the liquid crystal display device currently in use simply displays information such as characters and images. There is nothing. In recent years, the amount of information to be displayed on the screen has increased, and the character size has increased to improve visibility. It's starting.

[0003]

[Problems to be Solved by the Invention] In a mobile phone, the information processing unit (computer unit) and peripheral devices (antenna, speaker, etc.) are becoming smaller and smaller, and the keyboard unit is being made as small as possible. On the contrary, the display screen tends to be large as described above. The mobile phone literally has a utility value in that it is always carried, but such an increase in size is contrary to the portability, and the commercialability of the mobile phone or the like is impaired.

Therefore, the present invention intends to improve the portability of a mobile phone or the like as a whole by making the liquid crystal display device used for the display screen of the mobile phone or the like compatible with other mobile products.

[0005]

A liquid crystal display device according to the present invention is characterized by laminating a display liquid crystal layer with a backlight, a scattering type liquid crystal shutter layer, and a half mirror layer.

An example of such a configuration is shown in FIG. The display liquid crystal layer with a backlight (the backlight is not shown in the figure) is a liquid crystal device itself which has been conventionally used as a display device for mobile phones, home appliances and the like. The format may be any type such as TFT / STN / DSTN, color / monochrome, bitmap type / segment type, backlight type / sidelight type. In any case, it may be anything as long as image information such as characters and pictures is displayed on the surface by passing light from the back surface through the liquid crystal layer.

The term "half mirror layer" as used herein means that the light from the front surface is totally reflected or highly specularly reflected, while the light from the back surface (scattering type liquid crystal shutter layer) side is also transmitted at a high ratio. Is a layer having. For example, a glass plate or a transparent plastic plate on which a metal layer having an appropriate thickness is vapor-deposited (for example, chromium, silver, or gold vapor-deposited to a thickness of several to several tens of angstroms) has such a function.

The scattering type liquid crystal shutter layer is a shutter layer using liquid crystal and has a light scattering mode and a light transmitting mode. In the light-scattering mode, light incident from one surface is scattered in the liquid crystal and hardly exits from the other surface. In the light transmission mode, the light incident from one surface passes through without being scattered inside and directly exits from the other surface. As such a scattering type liquid crystal shutter layer, a PCW (Polymer Cell Wall) type liquid crystal optical shutter (Tadahiro Asada, Japanese Patent No. 3030973) can be preferably used. The PCW liquid crystal optical shutter has a structure in which a group of chiral nematic liquid crystal parcels (grains) surrounded by a transparent polymer solid thin film is inserted between two transparent electrode substrates. Yes,
While the voltage is not applied between both electrodes, the liquid crystal molecules in each grain form a spiral arrangement with the main axis in different directions (polydomain structure), so light is scattered and passes through the shutter. Not possible (light scattering mode). When a voltage is applied between both electrodes, the liquid crystal molecules of the entire device are aligned along the direction of the electric field, so that light passes through (light transmission mode).

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION While the scattering type liquid crystal shutter layer is in the light transmission mode, image information from the display liquid crystal layer passes through the scattering type liquid crystal shutter layer and also through the half mirror layer. Since it is displayed on the outermost surface, the user of the device can visually recognize the image information. On the other hand, while the scattering type liquid crystal shutter layer is in the light scattering mode, light from the display liquid crystal layer is scattered by the scattering type liquid crystal shutter layer and does not appear on the surface. Therefore, since only the reflected light comes from the half mirror layer to the user side, the half mirror layer acts as a mirror.

That is, the liquid crystal display device according to the present invention operates as a normal display liquid crystal by setting the scattering type liquid crystal shutter layer in the light transmission mode by some switch, and sets the scattering type liquid crystal shutter layer in the light scattering mode. This acts as a mirror. For example, when this is applied to a display device of a mobile phone, the screen becomes a normal liquid crystal display screen at the time of making a call or receiving a mail, while it can be used as a mirror when not used as a phone. Therefore, a woman does not need to put both the mobile phone and the mirror in a small bag, but only the mobile phone having the liquid crystal display device according to the present invention.

Here, as the switch for setting the scattering type liquid crystal shutter layer to the light transmission mode or the light scattering mode, a power switch of a mobile phone or the like may be used as it is, or a display mode / mirror surface may be used separately. A mode switch may be provided. Alternatively, it may be controlled by software, such as changing to a light scattering mode (mirror mode) when a keyboard or the like is not operated for a predetermined time.

For the scattering type liquid crystal shutter layer, PCW
Type liquid crystal optical shutter was briefly mentioned above,
Here, the configuration will be described in detail. The PCW type liquid crystal optical shutter basically consists of a) two electrode substrates and b) a dimming layer interposed between them. c) The light control layer b) is composed of a mixture of b1) 1 to 50% by weight (preferably 10 to 20% by weight) of a transparent polymer solid and b2) a chiral nematic liquid crystal, and d) this chiral nematic liquid crystal. b2) is 0.05 of the liquid crystal component.
It contains ~ 5% by weight of chiral dopant, and e) this chiral dopant is a mixture of cholesteric liquid crystal and ferroelectric liquid crystal exhibiting chiral smectic C phase. f) The ratio of the ferroelectric liquid crystal exhibiting the chiral smectic C phase to the total amount of the chiral dopant is 40 to 60% by weight.
Is desirable.

The electrode substrate a) is not particularly limited as long as it is transparent and has a conductive layer on its surface, and glass, a transparent resin sheet or the like can be used.

Chiral nematic liquid crystal constituting the light control layer
The nematic liquid crystal material of b2) has sufficient electric field response at room temperature, and when mixed with a polymer component, a polymer phase and a liquid crystal phase are mixed as different phases, and two more substrates are used. It is necessary that a large number of liquid crystal grains (in which a plurality of domains exist) surrounded by a polymer thin film be present. A general nematic liquid crystal can be used as long as it satisfies such conditions, and for example, biphenyl-based, phenylcyclohexane-based, cyclohexylcyclohexane-based, cyanobiphenyl-based, cyanophenylcyclohexane-based, cyanocyclohexylcyclohexane-based ones or these Can be mentioned. Among these, particularly preferred are cyanobiphenyl-based, cyanophenylcyclohexane-based, and cyanohexylcyclohexane-based compounds which are excellent in electric field response.

The cholesteric liquid crystal as a chiral dopant added to the nematic liquid crystal and the ferroelectric liquid crystal exhibiting the chiral smectic C phase have good miscibility with the nematic liquid crystal material and have a sufficient helical twisting power to the nematic liquid crystal material. Anything can be given. Specifically, each is not particularly limited as long as it exhibits a cholesteric phase and a chiral smectic C phase alone at room temperature, but a structure having a relatively non-bulky structure is preferable.

The concentration of the chiral dopant in the chiral nematic liquid crystal is preferably 0.05 to 5% by weight of the liquid crystal component, more preferably 0.3 to 0.5% by weight, considering the driving voltage and the response speed.

As the components of the chiral dopant, a cholesteric liquid crystalline substance and a ferroelectric substance exhibiting a chiral smectic C phase may be used alone or as a mixture. The component ratio in the case of mixing and using is not particularly limited, but in order to fully exert the effect of mixing two kinds of twisting forces, a ferroelectric liquid crystal exhibiting a chiral smectic C phase in the total amount of chiral dopant is used. It is preferably 40 to 60% by weight.

The polymer component interposed between the grains of the liquid crystal component is required to have a continuous structure in which the interface of the liquid crystal phase is covered with a thin film in order to fully develop the interfacial effect. In order to maintain the state in which the liquid crystal grains are encapsulated and kept in a liquid crystal grain, it is desirable to mix them with a liquid crystal component in the form of a prepolymer or a monomer, make a dispersed state, and then solidify at a suitable temperature by irradiation with ultraviolet light. By such treatment, the cholesteric liquid crystal is polymerized while maintaining the focal conic grain structure, so that the grain domains are enclosed in a thin film of the polymer. As such an ultraviolet light curable prepolymer, an acrylic or methacrylic prepolymer can be used.

Further, since a continuous liquid crystal domain is difficult to be formed when the ratio of the polymer component is high, the ratio of the polymer component in the light control layer is preferably 1 to 50% by weight, more preferably 10 to 15%. % By weight.

In addition, various optional components can be added to the light control layer. For example, a polymerization initiator such as benzophenone or 1-hydroxycyclohexyl phenyl ketone, a chain transfer agent, a dye, or the like is appropriately mixed and used depending on the properties of the liquid crystal component or the polymer component or the type and purpose of the intended display device. be able to.

The PCW type liquid crystal optical shutter can be manufactured as follows. First, in the isotropic phase state of the nematic liquid crystal component, a chiral dopant is added and mixed well, and then a polymer component (prepolymer) and an optional component are added and further stirred. This mixture is inserted between two transparent electrode substrates set at a predetermined interval using a spacer, and ultraviolet light is irradiated through the substrates to solidify the polymer component and form an opaque light control layer. .

The thickness of the light control layer is not particularly limited, but it is preferably 5 to 60 μm, more preferably 5 to 15 μm from the viewpoint of responsiveness.

Regarding the above PCW type liquid crystal optical shutter,
The present inventor has proposed, as an improved version thereof, a liquid crystal display device having improved contrast (light transmittance ratio between light scattering mode and light transmission mode) by adding a dichroic black dye to the light control layer ( Japanese Patent Application 2001-142894). Its structure is as follows.

A liquid crystal display device comprising two conductive substrates, at least one of which is transparent, and a light control layer interposed between the two substrates, wherein the light control layer is a transparent polymer. A chiral nematic liquid crystal encapsulation encased by a solid thin film, b) the chiral nematic liquid crystal, b1) 0.05 to 5% by weight of the liquid crystal chiral dopant, and b2) 0.001 of the liquid crystal. ~ 20% by weight (preferably 0.1-15% by weight)
%) Dichroic black dye, c) the chiral dopant, c1) cholesteric liquid crystal, c2) a ferroelectric liquid crystal exhibiting a chiral smectic C phase,
Is a mixture of.

The present inventor has also proposed a liquid crystal display device having a shutter portion of two layers (Japanese Patent Application No. 2001-15127).
3). There are two types of structures, each of which is as follows.

The first structure has a) two surface electrode substrates, at least one of which is transparent, and b) a dye-containing light control layer and a scattering light control layer interposed between the two substrates. C) the dye-containing dimming layer is composed of a nematic liquid crystal, a chiral nematic liquid crystal or a cholesteric liquid crystal mixed with a dichroic black dye, and d) the scattering dimming layer is covered with a thin film of a transparent polymer solid. It is composed of an assembly of parcels of chiral nematic liquid crystals, wherein the chiral nematic liquid crystal contains 0.05 to 5% by weight of a chiral dopant, the chiral dopant being a cholesteric liquid crystal and a ferroelectric exhibiting a chiral smectic C phase. It is a mixture with an organic liquid crystal.

In the second structure, a) two transparent surface electrode substrates and b) electrodes on both sides, which are inserted between the substrates with a gap between them. A layer-coated intermediate electrode substrate, and c) a dye-containing light control layer interposed between one surface electrode substrate and the intermediate electrode substrate, and another surface electrode substrate and the intermediate electrode substrate. And d) the dye-containing light control layer is 0.001 to 20% by weight (preferably 0.1% by weight).
1 to 15% by weight) consisting of a nematic liquid crystal mixed with a dichroic black dye, a chiral nematic liquid crystal or a cholesteric liquid crystal, e) The scattering dimming layer is a chiral nematic that is surrounded by a thin film of a transparent polymer solid. Consisting of an assembly of liquid crystal parcels, wherein the chiral nematic liquid crystal contains 0.05 to 5% by weight of a chiral dopant, the chiral dopant being a mixture of a cholesteric liquid crystal and a ferroelectric liquid crystal exhibiting a chiral smectic C phase. That is,

[Brief description of drawings]

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

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H088 EA02 EA33 GA02 GA03 GA04                       GA06 GA08 GA10 GA13 GA17                       HA28 JA06 JA08 JA17 MA20                 2H089 HA04 HA06 HA09 HA21 HA22                       HA23 JA03 JA04 JA05 KA03                       KA04 KA09 QA16 RA02 RA06                       RA13 TA17 UA09                 2H091 FA15X FA31X FA41Z FD04                       HA08 HA12 HA18 JA01 LA13                       MA10

Claims (4)

[Claims] 1. A liquid crystal display device comprising a display liquid crystal layer with a backlight, a scattering type liquid crystal shutter layer, and a half mirror layer laminated on each other. 2. The scattering type liquid crystal shutter layer comprises two transparent electrode substrates and a light control layer interposed between the two electrode substrates, and b) the light control layer is a transparent polymer. A chiral nematic liquid crystal encapsulation encapsulated by a solid thin film, c) the chiral nematic liquid crystal, b1) 0.05 to 5% by weight of the chiral dopant, and b2) 0.001% of the liquid crystal. Up to 20% by weight of a dichroic black dye, and d) the chiral dopant is a mixture of c1) a cholesteric liquid crystal and c2) a ferroelectric liquid crystal exhibiting a chiral smectic C phase. The liquid crystal display device according to claim 1. 3. The a) the scattering type liquid crystal shutter layer comprises two transparent electrode substrates and a dye-containing dimming layer and a scattering dimming layer interposed between the two electrode substrates, and b) the dye. The contained dimming layer is made of a nematic liquid crystal mixed with a dichroic black dye, a chiral nematic liquid crystal or a cholesteric liquid crystal, and c) the scattering dimming layer is made of a chiral nematic liquid crystal surrounded by a thin film of a transparent polymer solid. It is composed of an assembly of parcels, the chiral nematic liquid crystal contains 0.05 to 5% by weight of a chiral dopant, and the chiral dopant is a mixture of a cholesteric liquid crystal and a ferroelectric liquid crystal exhibiting a chiral smectic C phase. The liquid crystal display device according to claim 1, wherein 4. An intermediate electrode in which a) the scattering type liquid crystal shutter layer is interposed between a1) two transparent electrode substrates and a2) both substrates with a gap between each substrate. Substrate, a3) a dye-containing dimming layer interposed between one surface electrode substrate and an intermediate electrode substrate, and a scattering dimming layer interposed between the other surface electrode substrate and an intermediate electrode substrate. And b) the dye-containing light control layer is made of a nematic liquid crystal, a chiral nematic liquid crystal or a cholesteric liquid crystal mixed with a dichroic black dye, and c) the scattering light control layer is a thin film of a transparent polymer solid. Consisting of an assembly of parcels of chiral nematic liquid crystal encapsulated by, the chiral nematic liquid crystal containing 0.05-5 wt% chiral dopant, the chiral dopant exhibiting cholesteric liquid crystal and chiral smectic C phase. Ferroelectric liquid crystal The liquid crystal display device according to claim 1, which is a mixture of, features in that.