JP2000131667A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To display a high luminance image by suppressing a loss of an emission beam due to a light diffusing plate. SOLUTION: This device holds a liquid crystal layer 9 between an upper part substrate 5 and a lower part substrate 1, and is constituted of providing a reflection layer 2 having a reflective function formed on the inner surface of the lower part substrate 1, an optical film 11 containing a polarizing plate and a phase difference plate laminated on the upper layer of the upper part substrate 5, a light transmission body 13 for an auxiliary light source arranged on the upper part of the optical film 11 and a touch panel 15 arranged further on the upper part. In such a case, the light diffusing plate 12 is arranged upward the light transmission body 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device in which at least one of an auxiliary light source and a touch panel is disposed on a display surface side of a liquid crystal panel in a reflection mode.

[0002]

2. Description of the Related Art A liquid crystal display device used as a display means of a personal computer or another monitor irradiates an image generated on a liquid crystal panel with illumination light and emits the transmitted light or reflected light to the display surface side. To visualize.

That is, this type of liquid crystal display device generally uses a liquid crystal panel in which a liquid crystal layer is interposed between a pair of substrates having pixel selection electrodes and the like, and the alignment state of liquid crystal molecules in a selected pixel portion. The image is generated by changing. Since the generated image is not in a visible state by itself, the liquid crystal panel is irradiated with light from the outside to illuminate the liquid crystal panel, and the transmitted light or the reflected light is observed.

As a light source of the illumination light, there are a light source provided on the back surface of the liquid crystal panel, a so-called backlight, and a light source using extraneous light. In particular, in the case of a PDA (small portable data terminal) having a limited power supply capacity, since the mounted power supply itself is small, the liquid crystal display device does not include an active light source such as a backlight as an illuminating light source. In many cases, this is used as illumination light. However, in order to enable use in an environment where there is little ambient light or no external light, an auxiliary light source is arranged so that it can be used in a dark environment.

A liquid crystal display device using external light is of a reflection type in many cases. A reflection layer made of a mirror-finished metal film or the like is provided on the inner surface of a substrate (lower substrate) opposite to the display surface side substrate (upper substrate). The image is visualized by reflecting extraneous light incident through the substrate on the observation side and emitting the reflected light from the upper substrate. This type of liquid crystal display device is called an internal reflection type. A type in which a reflection plate is provided on the back surface of the lower substrate is also known.

When an auxiliary light source is used in a reflection type liquid crystal display device, a light guide is laminated on an upper substrate of a liquid crystal panel,
In general, the light of a linear lamp disposed at the edge of the light guide is propagated through the light guide to form a planar illumination light source.

Further, some PDAs have a so-called touch panel for directly inputting data or the like from a display surface with a pen or a finger. Such a touch panel is laminated on an upper substrate of a liquid crystal panel, or on a light guide that constitutes the auxiliary light source when the auxiliary light source is provided.

FIG. 7 is a schematic cross-sectional view for explaining a configuration example of a liquid crystal display device constituting a conventional reflection type liquid crystal display device, and is a simple matrix type (STN type) in which a touch panel for pen input is provided on a display surface. Is shown.

In FIG. 1, 1 is a lower substrate (lower glass substrate), 2 is a reflective layer preferably made of a metal layer, 3 is a protective film,
4 is a lower electrode (transparent electrode), 5 is an upper substrate (upper glass substrate), 6 is a color filter, 7 is a protective film, 8 is an upper electrode (transparent electrode), 9 is a liquid crystal layer, 10 is a sealing material, 11 Denotes an optical film including a retardation plate and a polarizing plate, 12 denotes a light diffusion plate, 13 denotes a light guide, 14 denotes a light source (linear lamp), and 15 denotes a touch panel for inputting information. Note that an alignment film for defining the alignment direction of the liquid crystal molecules constituting the liquid crystal layer is applied to the upper surfaces of the lower electrode 4 and the upper electrode 8, respectively, but is omitted in the figure.

The inner surfaces of the lower substrate 1 and the upper substrate 5, that is, the surfaces on which the lower electrode 4 and the upper electrode 8 are formed are opposed to each other and bonded together at a predetermined gap. The periphery is sealed to form a liquid crystal panel.

An optical film 11 composed of a retardation plate and a polarizing plate is laminated on the upper substrate 5 side of the liquid crystal panel. On this optical film 11, a light diffusing plate 12 in which silica fine particles are applied to a transparent plate is laminated, and effectively takes in external light incident from various upper surfaces and diffuses reflected light to the outside. Modulated light (display light) emitted from the liquid crystal panel is effectively emitted. Note that the light diffusion plate 12 may be one in which silica fine particles are applied on the optical film 11.

Above the light diffusing plate, a light guide 13 constituting an illumination light source is laminated, and a linear lamp 14 is provided along one side edge thereof to constitute a so-called front light. . In a PDA, this front light is generally called an auxiliary light source, and the linear lamp 14 is turned off in a bright environment, and is turned on in an environment with little or no external light to illuminate the liquid crystal panel from the front side. It is configured as follows.

The light guide 13 constituting the front light
A so-called touch panel 15 for inputting information from a screen is stacked on the upper surface of the touch panel. Generally, the touch panel 15 is an input unit that configures XY coordinates with respect to the screen of the liquid crystal panel, and detects the coordinates of a portion pressed by a pen, a finger, or the like based on a change in electric resistance or capacitance of the portion.

Incidentally, peripheral parts such as a drive circuit board for applying a voltage corresponding to display information to the lower electrode 4 and the upper electrode 8 of the liquid crystal panel are not shown.

The external light L ₁ incident through the touch panel 15, the light guide 13 and the optical film 11 is transmitted to the upper substrate 5.
From the liquid crystal panel, and is reflected by the reflective layer 2 formed on the inner surface of the lower substrate 1 and emitted from the upper substrate 5 again. The emitted light L ₂ is to be modulated by the image formed by the liquid crystal molecules constituting the liquid crystal layer 2, it is possible to recognize an image visually by observing the output light L _2.

The phase difference plate 5 constituting the optical film 11 compensates for the coloring of the emitted light, and the polarizing plate emits only the modulated light of the image component passing through the liquid crystal layer 9 and the light diffusing plate 12
Has a function of eliminating unevenness of incident light and obtaining uniform brightness.

The touch panel 15 directly inputs required information from a screen by pressing with a pen or the like, displays the information on a liquid crystal panel, and stores the information in a storage unit (not shown).
Used for reproduction, etc.

[0018]

[SUMMARY OF THE INVENTION However, the conventional liquid crystal display device, after the external light L ₁ that is joined to the liquid crystal panel is reflected by the reflective layer 2, a part that has been diffused by the light diffusion plate 12 lights since L ₃ is returned to the specular reflection and the liquid crystal panel side in the light guide 13 and the touch panel 15, the outgoing light L ₂ and that amount decreases, the screen brightness is lowered.

An object of the present invention is to solve the above-mentioned problems of the prior art, part of the light diffusing emitted light is diffused by the plate L ₂ is a high-brightness image display by reducing the back toward the liquid crystal panel It is an object of the present invention to provide a liquid crystal display device which is enabled.

[0020]

The above object is achieved by disposing a light diffusing plate provided on a liquid crystal panel above the light guide.

That is, the present invention is characterized in that it is configured as described in the following (1) and (2).

(1) A liquid crystal layer is sandwiched between an upper substrate and a lower substrate, and a reflection layer having a reflection function formed on the inner surface of the lower substrate, and a polarizing plate laminated on the upper layer of the upper substrate. An optical film including a phase difference plate, a light guide for an auxiliary light source disposed on the optical film, and a touch panel further disposed thereon, wherein the light diffusion plate is disposed above the light guide. did.

According to this configuration, most of the reflected light from the liquid crystal panel diffused by the light diffusion plate is emitted to the observation side.
The brightness of the display screen is not reduced.

(2) A color filter film is provided on the inner surface of one of the upper substrate and the lower substrate in (1).

With this configuration, most of the reflected light from the liquid crystal panel diffused by the light diffusion plate and color-modulated by the color filter is emitted to the observation side, so that the luminance of the display screen of the color image is not reduced.

It should be noted that the present invention is not limited to the above configuration, and does not depart from the technical idea of the present invention.
Various modifications are possible.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to examples.

FIG. 1 is a schematic sectional view for explaining a first embodiment of a liquid crystal display device according to the present invention, wherein 1 is a lower glass substrate as a lower substrate, 2 is an aluminum thin film as a reflection layer, and 3 is A protective film made of an antioxidant film such as SiO ₂ ,
4 is a lower transparent electrode as a lower electrode, 5 is a lower glass substrate as an upper substrate, 6 is a color filter of three colors (R, G, B), and 7 is a liquid crystal layer which is protected from contaminants oozing out of the color filter. And a protective film made of a transparent organic material for flattening the surface, 8 is an upper transparent electrode as an upper electrode, 9 is a liquid crystal layer made of a liquid crystal composition, and 10 is a liquid crystal layer between the upper substrate and the lower substrate. It is a sealing material such as an epoxy resin that is sealed, bonded and fixed as a liquid crystal panel.

On the surface (upper side) of the liquid crystal panel on the upper glass substrate 5 side, an optical film 11 composed of a retardation plate and a polarizing plate is laminated.

A grid-like light-shielding film (black matrix) is formed between the respective colors R, G, and B constituting the color filter 6 as necessary, and a protective film 7 is formed thereon.

In this embodiment, the aluminum thin film which is a reflection layer having specular reflectivity is formed by an aluminum evaporation method. A multilayer film for improving the reflectance may be formed on the surface of the aluminum thin film, and a protective film 3 for protecting aluminum from corrosion and flattening the surface is formed thereon. Note that the reflection layer is not limited to aluminum, and another metal film or a non-metal film may be used as long as the reflection layer has a specular reflection property. This protective film is usually made of a transparent organic material, on which a lower transparent electrode 4 for driving a liquid crystal panel is formed.

The polarization degree and the polarization axis of the polarizing plate constituting the optical film 11 disposed on the upper surface of the upper glass substrate, and the Δnd of the retardation plate are determined by known methods.
Design to an optimal value determined from the twist angle and the tilt angle.

Above the liquid crystal panel on which the optical film 11 is installed, a resin plate made of transparent acrylic or the like is surface-treated as an auxiliary light source for use in a dark environment such as indoors or at night with little external light. Is provided on the liquid crystal panel side. This light guide 13
A linear lamp 14 such as a cold-cathode fluorescent lamp is arranged along one edge of the light guide, and the illumination light is introduced into the light guide 13. This type of lighting device is generally called a front light.

FIG. 2 is a plan view for explaining an example of the front light in FIG. 1, and FIG. 3 is an explanatory view of a main part of FIG.
2 is a sectional view of a main part along the line AA in FIG. 2, and FIG.
FIG. The front light includes a light guide 13 and a linear lamp 14, and the light introduced from the linear lamp 14 is directed toward the liquid crystal panel on the upper surface (the surface opposite to the liquid crystal panel) of the light guide 13. Pattern 13a is formed.

As shown in FIG. 3A, the pattern 13a is formed by fine concave portions carved on the surface of the light guide 13. In this embodiment, the concave portion has a trapezoidal cross-section, and as shown in the top view of FIG. 4B, the facing slope on the side of the linear lamp 14 is inclined as the distance from the linear light source increases. The corners are formed so as to relax. By providing such a concave portion, the linear lamp 14 can be formed.
From the entire light guide 13 to the liquid crystal panel.

Above the light guide 13 constituting the front light, a touch panel 15 for inputting information is stacked. The touch panel 15 has a known structure in which a resistor is sandwiched between a glass substrate and a transparent film.

On the surface on the display surface side of the touch panel 15, a light diffusing plate 12 having a light diffusing function is formed by forming fine and random scratches on the surface of a transparent film such as transparent polyethylene terephthalate. . The surface of the light diffusing plate 12 is provided with a transparent reinforcing coating that resists the pressure and friction of the pen when inputting information.

According to this embodiment, the difference in the refractive index at the interface between the constituent layers (upper glass substrate, optical film, light guide, touch panel) until the light reflected by the reflection layer of the liquid crystal panel reaches the light diffusion plate. All the light (emission light) that has passed through the light diffusion plate is emitted outside the liquid crystal display device as diffused light. For this reason, a decrease in the luminance of the display screen is suppressed, and a high-luminance image display can be obtained.

FIG. 4 is a schematic cross-sectional view for explaining a second embodiment of the liquid crystal display device according to the present invention. The components constituting this embodiment are the same as those of the first embodiment. A repeated description is omitted.

In this embodiment, the light diffusion plate 12 is connected to the light guide 13.
1 except that it is installed on the upper surface (the surface on the touch panel side). In this embodiment, the light diffusing plate 12 is laminated on the upper surface of the light guide 13, and the light emitted from the liquid crystal panel passing through the light diffusing plate 12 is scattered at a deep angle and a very small portion of the light is emitted from the touch panel. 12, only regular reflection occurs at 12
Light loss is smaller than in the conventional configuration described in the above section, and therefore, a decrease in the luminance of the display screen is suppressed, and a high-luminance image display can be obtained.

FIG. 5 is a schematic sectional view for explaining a third embodiment of the liquid crystal display device according to the present invention. The components constituting this embodiment are the same as those of the first and second embodiments. Therefore, repeated description is omitted.

In the present embodiment, the light diffusing plate 12 is laminated on the lower surface of the touch panel 12, and the light emitted from the liquid crystal panel passing through the light diffusing plate 12 is partially scattered at a deep angle. The light is only specularly reflected at the interface between the touch panel 12 and the air, and the loss of light is smaller than in the conventional configuration described with reference to FIG. it can.

FIG. 6 is a perspective view illustrating a configuration example of a portable information terminal as an example of an electronic apparatus on which the liquid crystal display device according to the present invention is mounted. The portable information terminal (PDA) comprises a main body 20 and a cover 21 attached to the main body 20 so as to be openable and closable with a hinge. The liquid crystal display device 22 according to the present invention is mounted on the main body 20.

Input of information from the display surface of the liquid crystal display device 22 is performed by tracing an input portion on the display screen with a pen 23 stored in a storage portion 24 provided in a part of the cover 21.

The shape and structure of this type of portable information terminal are not limited to those shown in the figure, but may be variously provided with various shapes, structures and functions.

The present invention is not limited to a liquid crystal display device having a touch panel as described above, but may be a device having no front light, a device having only a touch panel, or other general reflective liquid crystal. The present invention can be similarly applied to a display device.

[0047]

As described above, according to the present invention,
Part of the emitted light diffused by the light diffusion plate can be reduced from returning to the liquid crystal panel side, and high-luminance image display can be obtained in various electronic devices using a reflection-type liquid crystal display device. .

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view for explaining a first embodiment of a liquid crystal display device according to the present invention.

FIG. 2 is a plan view illustrating an example of a front light in FIG.

FIG. 3 is an explanatory diagram of a main part of FIG. 2;

FIG. 4 is a schematic sectional view for explaining a second embodiment of the liquid crystal display device according to the present invention.

FIG. 5 is a schematic sectional view for explaining a third embodiment of the liquid crystal display device according to the present invention.

FIG. 6 is a perspective view illustrating a configuration example of a portable information terminal as an example of an electronic device on which the liquid crystal display device according to the present invention is mounted.

FIG. 7 is a schematic cross-sectional view illustrating a configuration example of a liquid crystal display device that constitutes a conventional reflective liquid crystal display device.

DESCRIPTION OF SYMBOLS 1 Lower substrate 2 Reflective layer 3 Protective film 4 Lower electrode 5 Depressed substrate 6 Color filter 7 Protective film 9 Liquid crystal layer 10 Sealing material 11 Optical film 12 Light diffusing plate 13 Light guide 14 Linear lamp 15 Touch panel .

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[Procedure amendment]

[Submission date] November 19, 1999 (1999.11.
19)

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Fig. 4

[Correction method] Change

[Correction contents]

FIG. 4

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) G09F 9/00 311 G09F 9/00 311Z 366 366E (72) Inventor Yoshikuni Nagashima 3300 Hayano, Mobara-shi, Chiba Pref. Hitachi, Ltd. Electronic Devices Division (72) Inventor Masaru Suzuki 3300 Hayano, Mobara-shi, Chiba Prefecture Hitachi, Ltd.Electronic Devices Division (72) Inventor Teruji Saito 3681 Hayano, Mobara-shi, Chiba Prefecture F-term in Hitachi Device Engineering Co., Ltd. Reference) 2H091 FA02Y FA11X FA14Z FA23X FA32X FA41X FB02 FB08 LA16 2H093 NC72 ND08 NE06 5G435 AA03 BB12 BB16 CC12 DD11 EE23 FF03 FF05 FF06 FF08 FF12 FF15 GG22 HH04 HH05 LL07 LL11

Claims (2)

[Claims] A liquid crystal layer sandwiched between an upper substrate and a lower substrate, wherein a reflection layer having a reflection function formed on an inner surface of the lower substrate and a polarizing plate laminated on an upper layer of the upper substrate have a phase difference. A liquid crystal display device comprising: an optical film including a plate; a light guide for an auxiliary light source disposed on the optical film; and a touch panel further disposed on the optical film. A liquid crystal display device disposed above. 2. The liquid crystal display device according to claim 1, wherein a color filter film is provided on an inner surface of one of the upper substrate and the lower substrate.