JP2007310405A - Liquid crystal display device and portable terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device for performing bright double side display even in the dark. <P>SOLUTION: The liquid crystal display device is equipped with one side member constituted by forming a liquid crystal layer 13, and a translucent film 4, a color filter 3, and a transparent electrode 7 on a surface opposed to the liquid crystal layer 13 of a transparent substrate 1, another side member constituted by forming a transparent electrode 10 on the surface opposed to the liquid crystal layer 13 of the transparent substrate 2, and a flat panel light oppositely arranged on the surface opposed to the opposite surface of the liquid crystal layer 13 of the transparent substrate 2. Also, the color filter 3 is formed on a translucent film 4. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device in which a planar light formed by arranging a light source on the end face of a light guide plate is arranged on a liquid crystal display panel. Furthermore, the present invention relates to a portable terminal provided with the liquid crystal display device of the present invention.

  In recent years, liquid crystal display devices have advantages such as thinness, light weight, and low power consumption. Taking advantage of these advantages, they are widely used as display panels for computers, mobile phones, portable information terminals, and the like.

  Recently, especially for mobile phones, a type in which a mobile phone is carried with the lid closed during standby, and the lid is opened when an incoming call is received.

  According to such a type, functions such as displaying a clock even when carrying the mobile phone and displaying the other party are added, and the liquid crystal display device is divided into a main display unit and a sub display unit. Many mobile phones have been put on the market.

  In general, a liquid crystal display device used for a main display unit and a sub display unit uses a single liquid crystal display panel.

  However, liquid crystal display devices used for mobile phones are desired to have low power consumption and light weight, and the functions have evolved while portability is impaired.

  Prior art has been proposed to meet these requirements (see Patent Document 1).

  The proposed liquid crystal display device P will be described with reference to FIG. FIG. 7 is a cross-sectional view of a conventional reflective liquid crystal display device P.

  As shown in the figure, one transparent member 1 and the other transparent member 2 in which a transparent electrode made of striped ITO and an alignment film are sequentially disposed on a transparent substrate and the other transparent member 1 are formed. Spacers are dispersed so as to maintain a distance between both substrates with the other transparent member 2 (hereinafter, this distance between the substrates is referred to as an inter-substrate gap), and a sealing member is provided for sealing and filling with liquid crystal. Thus, the liquid crystal display device P is obtained.

In this liquid crystal display device P, a single liquid crystal display device is used, film compensation conditions are optimized in the respective areas of the display direction A and the display direction B, and both the front and back surfaces of the liquid crystal display device can be used in a reflective state. Displayed in reflection mode.
JP 2001-27756 A

  However, the above-described liquid crystal display device P has a problem in that when it is used in a dark place, it is of a reflective type, so that the amount of light is insufficient and cannot be seen at all.

  Even if an auxiliary light source such as a front light is used so that it can be viewed in the dark, the auxiliary light source must be provided on both sides of the display directions A and B. Therefore, the liquid crystal display device is not suitable for low power consumption and thinness.

  The liquid crystal display device according to the first aspect of the present invention includes a liquid crystal layer and one member formed by forming a transflective film, a color filter, and a transparent electrode on a surface of the transparent substrate facing the liquid crystal layer, A second member formed by forming a transparent electrode on a surface of the transparent substrate facing the liquid crystal layer; and a planar light disposed opposite to the surface of the second member opposite to the facing surface of the transparent substrate. The color filter is formed on the semipermeable membrane.

  In the liquid crystal display device, the planar light includes a light source and a light guide plate that guides light emitted from the light source, and the light guide plate transmits the light to the other member via the diffusion plate. It is preferable that a prism is formed so as to be incident substantially perpendicularly.

  In the present liquid crystal display device, it is preferable that the semi-transmissive film is formed only in a portion corresponding to the display region on the other member side.

  In the present liquid crystal display device, it is preferable that the other member further has a semi-transmissive film formed on the facing surface of the transparent substrate in the other member. Further, in the liquid crystal display device of the present configuration, the planar light is on a surface of the light guide plate opposite to the surface facing the other member and on a portion corresponding to the semi-transmissive film forming portion of the other member. More preferably, a light reflecting film is formed.

  The liquid crystal display device according to the second aspect of the present invention includes a liquid crystal layer and a member formed by forming a light reflection film, a color filter, and a transparent electrode on a surface of the transparent substrate facing the liquid crystal layer, A second member formed by forming a transparent electrode on a surface of the transparent substrate facing the liquid crystal layer; and a planar light disposed opposite to the surface of the second member opposite to the facing surface of the transparent substrate. The color filter is formed on the light reflecting film at a portion corresponding to the display area on the other member side.

  In the present liquid crystal display device, the light reflecting film is preferably formed only in a portion corresponding to the display region on the other member side.

  In the liquid crystal display device, the planar light includes a light source and a light guide plate that guides light emitted from the light source, and the light guide plate transmits the light to the other member via the diffusion plate. It is preferable that a prism is formed so as to be incident substantially perpendicularly.

  In the present liquid crystal display device, it is preferable that the other member further has a semi-transmissive film formed on the facing surface of the transparent substrate in the other member. Further, in the liquid crystal display device of the present configuration, the planar light is on a surface of the light guide plate opposite to the surface facing the other member and on a portion corresponding to the semi-transmissive film forming portion of the other member. More preferably, a light reflecting film is formed.

  A portable terminal according to the present invention includes at least one of the liquid crystal display device according to the first aspect of the present invention and the liquid crystal display device according to the second aspect of the present invention.

  As described above, according to the liquid crystal display device of the present invention, one member in which the semi-transmissive film, the transparent electrode, and the alignment film are sequentially stacked on the transparent substrate, and the transparent electrode and the alignment film are sequentially stacked on the transparent substrate. A planar light formed by arranging a light source on the end face of the light guide plate is disposed on the other member side of the liquid crystal display panel formed by facing the other member through a liquid crystal layer. In the apparatus configuration configured to reflect light by the semi-transmissive film, a prism configured to emit light emitted from the light source toward the liquid crystal display panel is provided on the outer surface of the light guide plate of the planar light. By adopting a configuration in which part of the light emitted from the planar light liquid crystal display panel passes through the area where the semi-transmissive film is not formed, the front and back of the display can be used, and a bright, thin and lightweight liquid crystal display device is obtained. It is done.

  In addition, as in the present invention, the transflective film may be replaced with a light reflecting film, which can similarly use the front and back of the display, and a bright, thin and light liquid crystal display device can be obtained.

  Hereinafter, the liquid crystal display device of the present invention will be described with reference to the drawings, taking an STN type simple matrix liquid crystal display device as an example.

Embodiment 1
FIG. 1 is a schematic sectional view of a liquid crystal display device S of this example. 2A is a perspective view of a planar light, and FIG. 2B is a schematic cross-sectional view. In these drawings, optical paths of light α, β, and γ are simply shown by arrows.

  As shown in FIG. 1, a translucent film 4, a color filter 3, a protective film 5 made of silica or synthetic resin, a transparent electrode 7 made of striped ITO, and the like on a transparent substrate 1 made of glass material or plastics material. An alignment film 8 made of polyimide or the like is sequentially formed, thereby forming the one member.

  The color filter 3 is formed by a photolithography method, in which a photosensitive resist previously prepared by a pigment dispersion method, that is, a pigment (red, green, blue, etc.) is applied on a substrate. In this photolithography method, a photosensitive resist is applied, and a photolithographic mask is used to perform the steps of exposure, development, etching, and peeling.

As for the other member, a transparent electrode 10 made of stripe-like ITO is formed on a transparent substrate 2 made of glass material or plastics material, and an alignment film 12 made of polyimide or the like is formed on the transparent electrode 10. . An insulating layer made of SiO ₂ or the like may be interposed between the transparent electrode and the alignment film.

The semi-transmissive film 4 may be formed of a semi-transmissive film made of a metal such as aluminum, chromium, SUS, aluminum alloy, or silver alloy, or a dielectric semi-transmissive film made of a laminate of TiO ₂ and SiO ₂ .

  Then, the transparent substrate 1 and the transparent substrate 2 are arranged so as to face each other so that the transparent electrode 7 and the transparent electrode 10 are orthogonal to each other, thereby providing a liquid crystal display unit, and spraying resin spacers 9 and maintaining the required inter-substrate gap. A sealing member mixed with spacers to be formed is formed on the outer peripheral portion in the facing surface of the transparent substrate 1 and the transparent substrate 2, a vacuum is formed between the transparent substrate 1 and the transparent substrate 2, and a liquid crystal is formed between the transparent substrate 1 and the transparent substrate 2. Is formed into a liquid crystal layer 13 and a certain pressure is applied to the outer surface of the transparent substrate 1 and the transparent substrate 2 to form a required gap between the substrates, and the opening into which the liquid crystal is injected is sealed with UV resin. By doing so, a liquid crystal display panel is obtained.

  Further, a retardation plate 15 and a polarizing plate 16 are disposed on the transparent substrate 1. Further, the transparent substrate 2 is provided with the diffusion plate 17, the phase difference plates 18 and 19, and the polarizing plate 20 in this order, and the planar light 21 is arranged, whereby the liquid crystal display device S is obtained.

  According to the planar light 21 shown in FIG. 2, one or a plurality of LEDs 22 are arranged as a light source. The light emitted from the LED 22 enters the light guide plate 23 made of synthetic resin or the like through the light guide rod 25, is reflected by the prism 24, and the optical path is changed to the liquid crystal display device side.

  The light guide rod 25 and the light guide plate 23 are formed of a resin material such as acrylic resin, polycarbonate, arton, or ZEONEX.

  A prism 24 is formed on the light guide plate 23 and is optimized so as to enter the liquid crystal display panel substantially perpendicularly.

  Specifically, the light emitted from the LED 22 is introduced as light α into the light guide plate 23 through the light guide rod 25 and is emitted to the liquid crystal display panel as light α ′ by the prism. In addition, the external light γ is transmitted without any change in the light guide plate. The light α ′ and the light γ are incident on the liquid crystal display panel, reflected by the semi-transmissive film 4 in the liquid crystal display panel, and emitted from the liquid crystal display panel as light β. This light β is transmitted through the light guide plate without any change.

  Thus, according to the liquid crystal display device S of the present invention, the LED 22 is lit in the dark, the light α ′ is used for the front surface used in the transmission mode, and the light β is used for the back surface used in the reflection mode. Yes.

  By the way, the back surface used in the present invention is a sub-display unit in which the display can be seen with the lid closed in, for example, a foldable mobile phone, and the front surface is displayed with the lid open when using a mobile phone. Refers to the main display section where

(Embodiment 2)
FIG. 3 is a schematic cross-sectional view of the liquid crystal display device T of this example. Also in this example, the planar light shown in FIG. 2 is used.

  In this liquid crystal display device T, the surface used in the transmissive state uses the fully transmissive panel method, and the surface used in the reflective state uses the transflective panel method.

  As shown in FIG. 3, the configuration of the liquid crystal display device T is characterized in that part of the light emitted from the planar light to the liquid crystal display panel passes through a region where the semi-transmissive film 4 is not formed.

  In this way, the semi-transmissive film 4 on the transparent substrate 1 is formed only in the display area portion used on the back surface, and is not used in the transmission portion on the front surface.

  According to the liquid crystal display device T having such a configuration, the light β is not different from the liquid crystal display device S, but the light α ″ is not absorbed by the semi-transmissive film 4, thereby comparing with the light α ′. Bright light is obtained.

  In practice, the standby screen is generally smaller than the front display panel, and the amount of information is smaller than the front screen. Therefore, by setting the area of the back surface narrow in advance, the light α ″ when using the surface can be brightened, and when the outside light is incident from the surface when the surface is used, it can be reflected by the semi-transmissive film 4. Since it disappeared, the contrast could be increased.

  Next, an improvement of the liquid crystal display device T having the above configuration will be described with reference to FIGS. Like the liquid crystal display device V shown in FIG. 8, a semi-transmissive film 4 is further provided on the transparent substrate 2 side of the surface display region with respect to the liquid crystal display device T, so that external light γ is used when the surface is used. May be.

  Further, as in the liquid crystal display device W shown in FIG. 9, light is applied to the prism surface of the planar light corresponding to the portion where the semi-transmissive film 4 provided on the transparent substrate 2 side is further formed. By forming the reflection film 26, the light α ′ can be made brighter.

  That is, by disposing the semi-transmissive film 4 between the transparent substrate 2 and the transparent electrode 10 of the liquid crystal display device T, a liquid crystal display device having both the display of the light α ′ and the display of the reflection state by the light γ is obtained. Furthermore, a brighter liquid crystal display device can be obtained by disposing the light reflecting film 26 on the prism surface of the planar light.

(Embodiment 3)
Next, the liquid crystal display device U will be described. FIG. 4 is a schematic cross-sectional view of the liquid crystal display device U of this example. Also in this example, the planar light shown in FIG. 2 is used.

  As shown in FIG. 4, the configuration of the liquid crystal display device U is substantially the same as that of the liquid crystal display device T. However, a light reflecting film 6 is provided in place of the semi-transmissive film 4 and the emitted light to the liquid crystal display panel of the planar light is further provided. A part thereof passes through a region where the light reflecting film 6 is not formed.

  According to the liquid crystal display device U, the reflection use area is completely limited to the use of the back surface, and thereby the display characteristics in the standby state can be improved.

  The light reflecting film 6 is formed of a metal such as aluminum, chromium, SUS, aluminum alloy, or silver alloy.

  In this way, the light reflection film 6 on the transparent substrate 1 is formed only in the display area portion used on the back surface, and is not used in the transmission portion on the front surface.

  According to the liquid crystal display device U having this configuration, the light β is not different from the liquid crystal display device S, but the light γ is not much absorbed by the light reflection film 6, thereby being brighter than the light β. Light is obtained.

  Also in the liquid crystal display device U of this example, as described in the improvement of the liquid crystal display device T described above with reference to FIGS. 8 and 9, the liquid crystal display device V is further transparent with respect to the liquid crystal display device U. The semi-transmissive film 4 may be disposed on the substrate 2 side, and thereby external light γ may be used when the surface is used. Similarly, as in the liquid crystal display device W, a light reflecting film 26 is formed on the prism surface of the planar light so as to correspond to the portion where the semi-transmissive film 4 provided on the transparent substrate 2 side is formed. 'Can be made brighter.

  Regarding the liquid crystal display devices S, T, U, V, and W having the above-described configuration, a diffusion plate is provided outside, but a scattering plate may be provided (not shown) inside. . In the present invention, the color liquid crystal display device has been verified, but the same effect can be obtained with a monochrome liquid crystal display device without a color filter.

  Next, the inventor evaluated the optical characteristics of the liquid crystal display device S, the liquid crystal display device T, and the liquid crystal display device U of the present invention, and the liquid crystal display device V and the liquid crystal display device W. Table 1 The results as shown in Fig. 1 were obtained.

  In Table 1, Example 1 is a liquid crystal display device S, Example 2 is a liquid crystal display device T, Example 3 is a liquid crystal display device U, Example 4 is a liquid crystal display device V, and Example 5 is a liquid crystal display device. W.

  As the evaluation panel, a panel having an effective display area with a diagonal size of 1.86 "was used. The optical characteristics were evaluated by measuring contrast and brightness, and comprehensively evaluating the visibility of the back and front. The brightness was measured using Minolta CS-100.

The measured value is indicated by (Y, x, y), and the larger “Y”, the brighter the image. The contrast is the ratio of the brightness “Ywhite” when displaying white to the brightness “Yblack” when displaying black.

  The table shows examples of the liquid crystal display devices S, T, U, V, and W and two comparative examples.

  Comparative Example 1 is the liquid crystal display device shown in FIG. 5, and Comparative Example 2 is the liquid crystal display device shown in FIG.

  For the symbols in the table, ◎ indicates a sufficiently practical evaluation, ○ indicates practical, but slightly lower performance, △ indicates practical, but further lower performance, requiring improvement In some cases, x indicates a case where it cannot be used practically.

  As is clear from the above results, the liquid crystal display device S has the merit that the display area can be made equal when the front and back sides are used because the semi-transmissive film is disposed on the entire surface.

However, when external light is incident, the contrast becomes low. Rather, the liquid crystal display device T in which the area of the semi-transmissive film is matched to the area of use on the back surface is more advantageous by limiting the use area of the front and back surfaces from the beginning. Further, in order to make the liquid crystal display device T a bright and high contrast display device, it is preferable to change the transflective film like the liquid crystal display device U to a reflective film. Further, it is more preferable that a semi-transmissive film, a reflective film, and the like are appropriately disposed as in the liquid crystal display devices V and W.

  Comparative examples 1 and 2 will be described below. In Comparative Example 1, a semi-transmission plate is arranged on the transparent substrate 2 side so as to ensure brightness when the front surface is used. The display is not visually recognized at all and is not practical.

  Comparative Example 2 is the same as Comparative Example 1 in that a transflective plate is disposed on the transparent substrate 2 side, and an auxiliary light source is disposed on the transparent substrate 1 side to improve the visibility when using the back surface. However, in the state where the auxiliary light source is not turned on during standby, only the external light γ is used, so that the light β ′ is not modulated by the liquid crystal layer as in Comparative Example 1, so that the display is not visually recognized at all. Not.

Mobile Terminal A mobile phone equipped with the liquid crystal display device of the present invention will be described with reference to FIG. According to this mobile phone, the liquid crystal display device of the present invention is disposed in a small casing 28. In addition, a transmitting / receiving antenna 29 is provided on the top of the housing 28, and a receiver 30 and a microphone 31 are formed on the surface.

  A portable terminal provided with the liquid crystal display device of the present invention will be described with reference to FIG. This portable terminal is shown as various information terminals other than a cellular phone. For example, there are a clock, a calculator, a game machine, a pedometer (registered trademark), a GPS, a POS, a handy terminal, an industrial instrument, and the like, but is not limited thereto. Also in this portable terminal, the liquid crystal display device of the present invention is disposed in a small casing 32.

  Thus, in these cellular phones and portable terminals, further miniaturization could be achieved by using the miniaturized liquid crystal display device of the present invention.

  It should be noted that the present invention is not limited to the above embodiment, and various changes and improvements can be made without departing from the scope of the present invention. For example, in the above-described embodiment, the STN type simple matrix type liquid crystal display device is described. However, in addition, a bistable type simple matrix type liquid crystal display device and a TN type simple matrix type liquid crystal display device are provided. In addition, the same effect can be obtained with an active matrix type liquid crystal display device.

  In addition, the device provided with the liquid crystal display device of the present invention is exemplified by a portable terminal. However, the present invention can also be applied to various devices using this liquid crystal display device as a display device. For example, in addition to sewing machines, stereos, musical instruments, videos, ATMs, copiers and facsimiles, they may be used for display boards of various display devices such as stations, restaurants, and display panels in factories.

It is sectional drawing of the liquid crystal display device S of this invention. A is a perspective view of a planar light, and FIG. B is a schematic cross-sectional view. It is sectional drawing of the liquid crystal display device T of this invention. It is sectional drawing of the liquid crystal display device U of this invention. 6 is a cross-sectional view of a liquid crystal display device of Comparative Example 1. FIG. 10 is a cross-sectional view of a liquid crystal display device of Comparative Example 2. FIG. It is sectional drawing of the conventional liquid crystal display device P. FIG. It is sectional drawing of the liquid crystal display device V of this invention. It is sectional drawing of the liquid crystal display device W of this invention. 1 is a front view of a mobile phone according to the present invention. It is a front view of the portable terminal which concerns on this invention.

Explanation of symbols

2 ... Transparent substrate 3 ... Color filter 4 ... Semi-transmissive film 5 ... Protective film 6 ... Completely reflective film 7, 10 ... Transparent electrodes 8, 12 ... Alignment film 9 .. Resin spacer 13... Liquid crystal layer 17...・ LED
23 ... resin light guide plate 24 ... prism 25 ... light guide rod 26 ... perfect reflector

Claims (11)

A liquid crystal layer;
One member formed by forming a transflective film, a color filter, and a transparent electrode on the surface of the transparent substrate facing the liquid crystal layer,
The other member formed by forming a transparent electrode on the surface of the transparent substrate facing the liquid crystal layer;
A planar light disposed opposite to the surface opposite to the facing surface of the transparent substrate in the other member,
The liquid crystal display device, wherein the color filter is formed on the semi-transmissive film. The planar light has a light source and a light guide plate that guides light emitted from the light source,
The liquid crystal display device according to claim 1, wherein the light guide plate is formed with a prism for allowing the light to enter the other member through the diffusion plate substantially perpendicularly. The liquid crystal display device according to claim 1, wherein the semi-transmissive film is formed only in a portion corresponding to the display region on the other member side. 4. The liquid crystal display device according to claim 1, wherein the other member further includes a semi-transmissive film formed on the facing surface of the transparent substrate in the other member. The planar light has a light reflecting film formed on a portion of the light guide plate opposite to the surface facing the other member and corresponding to a portion where the semi-transmissive film is formed on the other member. The liquid crystal display device according to claim 4, wherein: A liquid crystal layer;
One member formed by forming a light reflection film, a color filter, and a transparent electrode on the surface of the transparent substrate facing the liquid crystal layer,
The other member formed by forming a transparent electrode on the surface of the transparent substrate facing the liquid crystal layer;
A planar light disposed opposite to the surface opposite to the facing surface of the transparent substrate in the other member,
The liquid crystal display device, wherein the color filter is formed on the light reflecting film at a portion corresponding to the display region on the other member side. The liquid crystal display device according to claim 6, wherein the light reflecting film is formed only in a portion corresponding to the display region on the other member side. The planar light has a light source and a light guide plate that guides light emitted from the light source,
8. The liquid crystal display device according to claim 6, wherein the light guide plate is formed with a prism for allowing the light to enter the other member substantially perpendicularly through the diffusion plate. 9. The liquid crystal display device according to claim 6, wherein the other member further includes a semi-transmissive film formed on the facing surface of the transparent substrate in the other member. The planar light has a light reflecting film formed on a portion of the light guide plate opposite to the surface facing the other member and corresponding to a portion where the semi-transmissive film is formed on the other member. The liquid crystal display device according to claim 9. A portable terminal comprising the liquid crystal display device according to claim 1.

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