JPH10301109A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make both displays light as a liquid crystal display device displaying by using external light and by using light from a source of light and to allow the display using the light from the source of light to have a high front brightness and a small parallax. SOLUTION: In front of a liquid crystal display element 10 provided with a reflection plate 19, external light made incident from the front and light from a source of light made incident on an end face are made incident on a liquid crystal display element 10, and a light transmission plate 30 is arranged which emits the outgoing light from the liquid crystal display element 10 in front, and a reflective display is performed both in a case of using the external light and in a case of using the light from the source of light so that a reflection plate with a high reflectance can be used. Further, a refraction means 21 is provided which makes the incident light from the end face incident on the liquid crystal display element 10 almost in the vertical direction, and allows the display using the light from the source of light 30 to have a high front brightness without parallax.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a liquid crystal display device that performs both display using external light and display using light from a light source.

[0002]

2. Description of the Related Art As a liquid crystal display device, a so-called two-way display type which performs both a display utilizing external light such as natural light or indoor illumination light and a display utilizing light from a light source provided in the display device. There are things.

As a conventional two-way display type liquid crystal display device, there is a device in which a backlight is disposed behind a liquid crystal display device having a transflective reflector on the back side. And a light source in which a light source such as a fluorescent lamp is arranged to face an end face of a light guide plate made of a transparent plate.

This liquid crystal display device performs a reflection type display using external light when external light of sufficient brightness is obtained,
When external light with sufficient brightness cannot be obtained, the backlight is turned on to perform transmissive display. In the reflective display using external light, of the external light incident from the front of the liquid crystal display element. The light reflected by the semi-transmissive reflection plate passes through the liquid crystal display element again and is emitted to the front surface thereof. In a transmissive display using light from a backlight, light transmitted through a semi-transmissive reflector among light from the backlight becomes incident light on a liquid crystal display element, and the light is transmitted through the liquid crystal display element. The light is emitted to the front.

[0005]

SUMMARY OF THE INVENTION However, the above-mentioned conventional 2
The way display type liquid crystal display device has poor light use efficiency both in display using external light and in display using light from a backlight. When using light, there is a problem that the display is dark.

[0006] This is because the transflective plate reflects and transmits incident light at a reflection / transmittance according to its characteristics. Therefore, in a reflection type display using external light, the reflection of the incident external light is reduced. The amount of light corresponding to the transmittance of the semi-transmissive reflector is transmitted to the back side of the semi-transmissive reflector, resulting in loss light. This is because an amount of light corresponding to the reflectance of the semi-transmissive reflector is reflected by the semi-transmissive reflector and becomes loss light.

The present invention provides a two-way display type in which both a display using external light and a display using light from a light source can be brightened by using both external light and light from a light source with high efficiency. It is an object of the present invention to provide a liquid crystal display device.

[0008]

According to the present invention, there is provided a liquid crystal display device having a liquid crystal display device provided with a reflection means on a back side, a light guide plate disposed in front of the liquid crystal display device, and an end face of the light guide plate. The light guide plate is configured to emit light from the light source incident from the front surface and light from the light source incident from the end surface to the rear surface, and to enter the liquid crystal display element, Light emitted from the liquid crystal display element incident on the rear surface is emitted to the front surface, and light incident from the end surface is emitted from the rear surface in a direction close to a direction perpendicular to the front surface of the liquid crystal display device. A refracting means is provided.

This liquid crystal display device is of a two-way display type that performs both display using external light and display using light from a light source. When using light from the light source, The light from the light source is taken into the light guide plate from the end face thereof, guided through the light guide plate, emitted to the back surface, enters the liquid crystal display element, is reflected by the reflection means, and is emitted to the front surface of the liquid crystal display element. The light enters the light guide plate from the rear surface, passes through the light guide plate, and exits to the front surface.

When using external light, external light incident on the light guide plate disposed on the front surface of the liquid crystal display element from the front surface passes through the light guide plate and exits to the rear surface, and the light is transmitted to the liquid crystal display device. The light enters the display element and is reflected by the reflection means on the rear side of the liquid crystal display element, and exits the front surface of the liquid crystal display element. The light enters the light guide plate from the rear surface, passes through the light guide plate, and exits the front surface.

That is, this liquid crystal display device performs a reflection type display both when using external light and when using light from a light source. Therefore, the reflection means reflects incident light with high reflectance. What reflects may be sufficient.

Therefore, according to this liquid crystal display device, both the external light and the light from the light source can be used with high efficiency. Therefore, when displaying using the external light, the light from the light source is used. Also, when displaying, a sufficiently bright display can be obtained.

Further, in this liquid crystal display device, a light guide plate is arranged on the front surface of the liquid crystal display element, and a light source is arranged opposite to the end face. The light guide plate has the above-described refracting means. Therefore, the light from the light source can be made to enter the liquid crystal display element from a direction close to a direction perpendicular to the front surface of the liquid crystal display element. Since the light that passes through and exits to the front is emitted in a direction close to the vertical direction, a display using light from the light source can be a good display with high front luminance and almost no parallax.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A liquid crystal display device according to the present invention emits external light incident from the front surface and light from a light source incident from an end surface to the rear surface of a liquid crystal display device having a reflection means on the rear side. A light guide plate for emitting light emitted from the liquid crystal display element, which is incident on the liquid crystal display element from the back and emitted from the liquid crystal display element to the front, is arranged so that the reflection type is used both when using external light and when using light from a light source. By performing the display, it is possible to use the one that reflects the incident light with high reflectivity to the reflection means, and utilize the external light by using the external light and the light from the light source with high efficiency. And the display using light from a light source, and further, the light incident on the light guide plate from an end face thereof is directed to a direction close to a direction perpendicular to the front face of the liquid crystal display element. Let out from By providing folding means, a display using light from a light source disposed opposite to the end face of the light guide plate is a good display with high front luminance and almost no parallax. . In the liquid crystal display device according to the present invention, the light guide plate may be provided with the refraction means on the back surface or with the refraction means on the front surface.

[0015]

FIG. 1 is a sectional view of a liquid crystal display device according to a first embodiment of the present invention, in which the left side is the upper edge of the screen and the right side is the lower edge of the screen. This liquid crystal display device
On the front surface of the liquid crystal display element 10 provided with a reflection means on the back side,
A light guide plate 20 having an area facing at least the entire display area of the liquid crystal display element 10 is arranged.
The light source 30 is arranged so as to face one end surface of the light source.

The liquid crystal display element 10 is, for example, a TN (twisted nematic) type liquid crystal display element of an active matrix system, and of a pair of transparent substrates (glass substrates) 11a and 11b, an inner surface of a rear substrate 11b. Is provided with a plurality of transparent pixel electrodes 12 arranged in a matrix, and an alignment film 13b is formed thereon.

Although not shown in the drawing, on the inner surface of the rear substrate 11b, an active element composed of a TFT (thin film transistor) is provided in correspondence with each pixel electrode 12, and each pixel electrode row is provided with an active element. A gate line for supplying a gate signal to the TFT and a T
A data line for supplying a data signal to the FT is wired, and each of the pixel electrodes 12 is connected to a TFT corresponding to the electrode.

On the other hand, red, green, and blue color filters 14R, 14G, and 14B are provided alternately on the inner surface of the front substrate 11a so as to correspond to the pixel electrodes 12, respectively. 14R, 1
On the 4G, 14B, a transparent opposing electrode 15 in the form of a single film is provided, which opposes all of the pixel electrodes 13, and an alignment film 13a is formed thereon. Although not shown in the figure, the color filters 14R, 14G, 14
B is covered with a transparent protective film (insulating film), and the counter electrode 15 is formed on the protective film.

The pair of substrates 11a and 11b
Are joined via a frame-shaped sealing material 16, and a liquid crystal layer 17 is provided in a region between the substrates 11 a and 11 b and surrounded by the sealing material 16.

The liquid crystal molecules of the liquid crystal layer 18 are
The alignment direction in the vicinity of 1a and 11b is
a and 13b, respectively.
Twist orientation is performed at a predetermined twist angle (for example, approximately 90 °) between them.

Further, polarizing plates 18a and 18b are adhered to the outer surfaces of the substrates 11a and 11b, respectively, and a mirror reflector 19 is disposed as a light reflecting means behind the rear polarizing plate 18b. Have been.

On the other hand, the light guide plate 20 disposed on the front surface of the liquid crystal display device 10 emits external light incident from the front surface and light from the light source 30 incident from the end surface to the rear surface to be incident on the liquid crystal display device 10. At the same time, the light emitted from the liquid crystal display element 10 incident on the rear surface is emitted to the front surface. The light guide plate 20 used in this embodiment is the light incident on the rear surface of the light guide plate body 20a from the end surface. The prism sheet 21 is laminated as refraction means for emitting light from the rear surface in a direction close to a direction perpendicular to the front surface of the liquid crystal display element 10.

The light guide plate main body 20a is a wedge-shaped transparent plate whose front surface is inclined from one end to the other end so as to be closer to the back surface. , And a light capturing surface (hereinafter, referred to as a light source light capturing end surface) from the light source 30. In the drawing, the inclination of the front surface of the light guide plate body 20a is exaggerated, but the inclination angle (the angle with respect to the rear surface) is in the range of 1 ° to 10 °,
It is preferably in the range of 2 ° to 5 °, more preferably 3 ° to 5 °.
It is set to a range of 4 °.

The prism sheet 21 is formed by forming a plurality of horizontally long prism portions 21a extending in the width direction on one surface of a transparent plate so as to be parallel to each other in the width direction. Each of the prism portions 21a
It has a right triangular cross section in which one side is vertical and the other side is inclined.

The prism sheet 21 has a flat surface opposite to the surface on which the prism is formed facing the rear surface of the light guide plate main body 20a, and the longitudinal direction of each prism portion 21a is set to the light source light capturing end face of the light guide plate main body 20a. Be parallel,
The vertical side surface of each prism portion 21a is
Attached to the back surface of the light guide plate main body 20a by a transparent adhesive (not shown) (a double-sided adhesive sheet may be used) toward the light source light receiving end face a.

The light guide plate main body 20a and the prism sheet 21 are formed of a transparent material such as an acrylic resin, and preferably have the same refractive index of each light.
Further, it is preferable that the adhesive has a refractive index substantially the same as that of the light guide plate main body 20a and the prism sheet 21. If the refractive indices of the light guide plate main body 20a and the prism sheet 21 are substantially the same as those of the adhesive, the light transmission path from one of the light guide plate main body 20a and the prism sheet 21 to the other can be changed at the interface between the two. Has almost no refraction,
Further, it is possible to provide a linear path with little reflection and scattering at the interface between the light guide plate main body 20a and the prism sheet 21.

The light guide plate 20 has a liquid crystal display element with the light source light take-in end face of the light guide plate main body 20a and the vertical side surface of each prism portion 21a of the prism sheet 21 facing the main outside light take-in side. 10 and the top of each of the prism portions 21a is
Is supported by a support means (not shown) in a state of contacting or approaching the front surface of the optical disc.

That is, the two-way display type liquid crystal display device, when utilizing external light, is similar to a normal reflection type liquid crystal display device in the direction obliquely above the screen, that is, in the direction perpendicular to the front surface of the liquid crystal display element. The device is used by selecting the direction of the device so as to mainly take in external light from the direction inclined toward the upper edge of the screen.

Therefore, in this embodiment, the light guide plate 20
Are arranged with the light source light capturing end face of the light guide plate main body 20a and the vertical side surface of each prism portion 21a of the prism sheet 21 facing the upper edge side of the screen, which is the main capturing side of external light.

The arrangement pitch of the prism portions 21a of the prism sheet 21 is set equal to or smaller than the arrangement pitch of the pixel regions in the vertical direction of the screen of the liquid crystal display element 10. In the example shown in FIG. 1, the arrangement pitch of each prism portion 21 a of the prism sheet 21 is set to be approximately 1 / 1.5 of the arrangement pitch of the pixel region of the liquid crystal display element 10.

The light source 30 includes a straight tubular fluorescent lamp 31 having a length extending over the entire end face of the light guide plate 20 and directing light emitted from the fluorescent lamp 31 to the periphery thereof toward the end face of the light guide plate 20. It comprises a reflector 32 that reflects light. The reflector 32 has an elliptical cylindrical shape having a light exit on one side. The light source 30 is provided on the side of the light guide plate 20 with the reflector 32.
Of the light guide plate main body 20a is opposed to the light source light capturing end face of the light guide plate main body 20a.

This liquid crystal display device is of a two-way display type which performs both display using external light and display using light from the light source 30. The light source 30 has a sufficient brightness. Used when external light cannot be obtained.

First, the display using light from the light source 30 will be described. The light from the light source 30 is taken into the light guide plate 20 from its end face as shown by the arrow L1 in FIG. And emitted to the rear surface thereof, and enters the liquid crystal display element 10.

In this case, the light from the light source 30 is incident on the light guide plate main body 20a from the light source light take-in end face, and the front surface of the light guide plate main body 20a is on the rear side from the light source light take-in end side to the opposite side. Since the light is inclined so as to be closer, the light heading toward the front surface of the light guide plate 20 among the light incident on the light guide plate main body 20a from the light source light capturing end face is an interface between the front surface of the light guide plate main body 20a and the outside air (air). Is totally reflected by
The light is guided toward the back of the light guide plate 20.

Also, of the light incident from the light source light receiving end face, the light traveling toward the back surface of the light guide plate 20 and the light reflected on the front surface of the light guide plate body 20a (the interface with the outside air) are separated by the prism sheet. The light enters each of the prism portions 21a.

As described above, the prism portion 21a has a right-angled triangular cross section in which one side surface is vertical and the other side surface is inclined, and the vertical side surface of the prism portion 21a receives light from the light guide plate main body 20a. Because it is facing the end face,
The light incident on each of the prism portions 21a is incident on the inclined surfaces of the prism portions 21a from the direction facing the surfaces (the direction of the vertical side surface), and of the light, the inclined surfaces of the prism portions 21a are included. In other words, light incident on the interface between the air layer between the liquid crystal display element 10 and the inclined surface at an angle larger than the critical angle of the total reflection angle (closer to the vertical) is transmitted through this interface, and The light is emitted in the direction in which the angle with respect to the light becomes smaller, is emitted to the back surface of the light guide plate 20, and enters the liquid crystal display element 10.

The light incident on the inclined surface of the prism portion 21a at an angle smaller than the critical angle of the total reflection angle is:
The light is totally reflected by this inclined surface, but the light is
0a is reflected by the front surface of the prism portion 21a and is incident on another prism portion 21a, and the light incident on the inclined surface of the prism portion 21a at an angle larger than the critical angle of the total reflection angle passes through the interface and exits. Most of the light from the light source 30 taken into the light guide plate 20 can be emitted to the back surface of the light guide plate 20 and made incident on the liquid crystal display element 10 without loss.

The light incident on the liquid crystal display element 10 is transmitted through the front polarizing plate 18a and becomes linearly polarized light, and the light is transmitted through the liquid crystal layer 17 and the rear polarizing plate 18b in that order to form the reflecting plate 1.
9 is incident. Note that, of the light that has entered the liquid crystal display element 10, the light that has entered the pixel region is the color filter 14.
R, 14G and 14bB are transmitted to become colored light.

The light incident on the reflector 19 is reflected by the reflector 19, passes through the rear polarizer 18b, the liquid crystal layer 17, and the front polarizer 18a in order, and is emitted to the front of the liquid crystal display element 10. . Also at this time, of the light reflected by the reflection plate 19, the light transmitted through the pixel region of the liquid crystal display element 10 and emitted is the color filters 14R, 14G,
Transmits 14 bB and is colored to that color.

The light emitted from the liquid crystal display element 10 is light in the direction in which the angle of incidence light to the liquid crystal display element 10 with respect to the vertical direction is reduced as described above, and the light is reflected by the reflection plate (specular reflection). Since the light is reflected by the plate 19 at a reflection angle corresponding to the incident angle, the light is a light in a direction having a small angle with respect to the vertical direction.

The light emitted to the front surface of the liquid crystal display element 10 enters the light guide plate 20 from the back surface, passes through the light guide plate 20 in the thickness direction and is emitted to the front surface. The light emitted from the display element 10 first enters each prism portion 21a of the prism sheet 21 from its inclined surface and is refracted in a direction closer to the vertical direction, and further at the interface between the front surface of the light guide plate main body 20a and the outside air. Since the light is refracted in a direction closer to the vertical direction, the light emitted to the front surface of the light guide plate 20 is emitted in a substantially vertical direction.

Next, a display using external light will be described. In this case, external light incident on the light guide plate 20 disposed on the front surface of the liquid crystal display element 10 from the front surface is indicated by an arrow L2 in FIG. As described above, the light passes through the light guide plate 20 in the thickness direction, is emitted to the rear surface, and enters the liquid crystal display element 10.

In this case, as described above, the external light is mainly taken in from a diagonally upper part of the screen (a direction inclined toward the upper edge of the screen with respect to a direction perpendicular to the front surface of the liquid crystal display element 10). The light capturing direction is the above-described light source light capturing end side, and the front surface of the light guide plate main body 20a is closer to the rear surface from the external light capturing side (the same side as the light source light capturing end side) to the opposite side. External light incident on the light guide plate 20 from the front surface thereof,
a is refracted in a direction which is close to the vertical direction at the interface between the front surface and the outside air.
The light is refracted by a and becomes a light in a direction in which the angle with respect to the vertical direction is reduced, exits to the rear surface of the light guide plate 20, and enters the liquid crystal display element 10.

The light incident on the liquid crystal display element 10 is reflected by the reflection plate 19 in the same manner as the light transmission path from the light source 30 described above.
And is emitted to the front of the liquid crystal display element 10. Also at this time, the light transmitted through the pixel region of the liquid crystal display element 10 is
The light passes through the color filters 14R, 14G, and 14bB and is colored in that color.

The light emitted to the front surface of the liquid crystal display element 10 enters the light guide plate 20 from the back surface, and is first refracted by the prism portions 21a of the prism sheet 21 in a direction closer to the vertical direction. Light guide plate body 20
a is refracted in a direction closer to the vertical direction at the interface between the front surface and the outside air and is emitted to the front surface.

In this embodiment, the light guide plate body 2
0a and the direction of the light incident on the liquid crystal display element 10 and the direction of the light emitted from the front surface of the light guide plate are perpendicular to each other with respect to the light taken in from the light source 30. The direction of incidence on the liquid crystal display element 10 and the direction of emission from the front surface of the light guide plate when utilizing external light are designed as follows.
Although the inclination with respect to the vertical direction is larger to some extent than when the light from the light source 30 is used, it is much closer to the vertical direction than when the external light is directly incident on the liquid crystal display element 10.

That is, the above-mentioned liquid crystal display device performs a reflective display both when using external light and when using light from the light source 30.
May reflect incident light with high reflectance.

Therefore, according to this liquid crystal display device,
Since both the external light and the light from the light source 30 can be used with high efficiency, a sufficiently bright display can be obtained both when displaying using the external light and when displaying using the light from the light source 30. be able to.

In this liquid crystal display device, a light guide plate 20 is arranged on the front surface of the liquid crystal display element 10 and a light source 30 is arranged opposite to the end surface. The light from the light source 30 can be incident on the liquid crystal display element 10 from a direction close to the direction perpendicular to the front surface of the liquid crystal display element 10, so that the reflection on the rear surface of the liquid crystal display element 10 can be achieved. Board 19
Is reflected by the light guide plate 20 and exits the liquid crystal display element 10.
Since the light that passes through and exits to the front exits in a direction close to the vertical direction, a display using the light from the light source 30 is displayed.
The front luminance (the luminance of light emitted in a direction substantially perpendicular to the front surface of the liquid crystal display element 10) is high, and the parallax (the liquid crystal display element 1
A phenomenon in which a pixel displayed by reflected light of light that has been transmitted through the pixel region of 0 and a pixel displayed by light transmitted through the pixel region and emitted out of the reflected light appear to be shifted.
And a good display with almost no display.

That is, for example, in the liquid crystal display device, when the light guide plate 20 is constituted only by the light guide plate main body 20a, the light which is taken into the light guide plate main body 20a from the light source 30 and enters the liquid crystal display element 10 from the back thereof. The direction of
Since the light is reflected by the reflection plate 19 at a reflection angle corresponding to the incident angle, the light exits the liquid crystal display element 10 and passes through the light guide plate main body 20a to reach the front surface. The emission direction of the emitted light is also a direction greatly inclined with respect to the vertical direction, so that sufficient front luminance cannot be obtained.

Moreover, in this case, the direction of incidence of light on the liquid crystal display element 10 is a direction inclined to one side with respect to the vertical direction, and the direction of emission of the reflected light is a direction inclined to the opposite side. Therefore, there is a large shift between the incident direction of light and the emission direction of the reflected light, and therefore, a pixel that is displayed by reflected light of light that has passed through and entered the pixel region of the liquid crystal display element 10;
Parallax in which a pixel displayed by light transmitted through and emitted from the pixel region in the reflected light appears to be displaced is large.

However, as in the above embodiment, the light guide plate 20
Is constituted by the light guide plate main body 20a and the prism sheet 21 so that light from the light source 30 is incident on the liquid crystal display element 10 from a direction close to the vertical direction.
The light guide plate 2 is reflected by the light guide plate 9 and exits the liquid crystal display element 10.
The light exiting from the front and passing through 0 is emitted close to the vertical direction, so that sufficient front luminance can be obtained. In addition, the direction of incidence of light on the liquid crystal display element 10 and the direction of emission of reflected light thereof Is very small, and the parallax can be almost eliminated.

In the above embodiment, the light guide plate 20
Because the light source light capturing end side is arranged toward the external light capturing side, even in a display using external light,
External light incident on the light guide plate 20 from the front surface can be made to enter the liquid crystal display element 10 from a direction close to the vertical direction. Therefore, the emission direction of the light reflected by the reflector 19 is set close to the vertical direction. As a result, a sufficient front luminance can be obtained, and the difference between the incident direction of the light to the liquid crystal display element 10 and the emitting direction of the reflected light can be reduced, and the parallax can be almost eliminated.

In the above liquid crystal display device, since the emitted light is emitted in a direction close to the direction perpendicular to the front surface of the liquid crystal display element 10, the display contrast due to the reflection of external light on the front surface of the light guide plate 20 is reduced. There is almost no decline.

That is, since the external light mainly enters from obliquely above the screen, most of the external light reflected on the front surface of the light guide plate 20 depends on the incident angle with respect to the front surface of the light guide plate as shown by the broken line in FIG. Although the light goes obliquely at a reflection angle, the light emitted from the liquid crystal display device is also used for display using external light.
In the display using the light from the light source 30, the light is emitted in a direction close to the direction perpendicular to the front surface of the liquid crystal display element 10 as described above.

The display image of the liquid crystal display device is observed from the front of the screen. According to the liquid crystal display device, most of the light observed from the front direction is emitted from the liquid crystal display device. The reflected light from the front surface of the light guide plate 20 and reflected in the oblique direction reflected on the front surface of the light guide plate 20 is hardly visible. Absent.

Further, since the above-mentioned liquid crystal display device performs a reflection type display both when using external light and when using light from the light source 30, the liquid crystal display device is compared with a conventional two-way display type liquid crystal display device. In addition, the degree of freedom in designing the liquid crystal display element 10 is increased, and the liquid crystal display element 10 can be easily designed.

That is, in the conventional two-way display type liquid crystal display device, the display using external light is a reflection type display, the display using light of a backlight is a transmission type display, and the external light is used. In the case of a reflective display, incident light from the front side is transmitted through the liquid crystal display element and reflected, and the light is transmitted through the liquid crystal display element again and emitted to the front side, whereas the light of the backlight is transmitted. In the transmissive display used, since the incident light from the back side passes through the liquid crystal display element and exits to the front side, a difference in display color caused by a difference in the light transmission path between the reflective display and the transmissive display, etc. It is necessary to design a liquid crystal display element to compensate for the following.

In this respect, in the liquid crystal display device of the above embodiment, both the display using the external light and the display using the light from the light source 30 are of the reflection type, and the transmission path of the light is almost the same in any of the displays. Therefore, the design of the liquid crystal display element 10 is easy.

FIG. 2 is a sectional view of a liquid crystal display device according to a second embodiment of the present invention, in which the left side is the upper edge of the screen and the right side is the lower edge of the screen. The liquid crystal display device of this embodiment has a light guide plate 20 disposed on the front surface of the liquid crystal display element 10.
The lens sheet 22 is laminated on the back surface of the light guide plate main body 20a as a refraction means for emitting light incident from the light source light capturing end face in a direction close to a direction perpendicular to the front surface of the liquid crystal display element 10. Things. The light guide plate body 20a is the same as that used in the first embodiment.

The lens sheet 22 has a plurality of horizontally long condensing lens portions 22 along one width of the transparent plate.
are formed in parallel with each other in the width direction thereof, and these condenser lens portions 22a are formed of cylindrical lenses, and the optical axis of the lens is in a direction perpendicular to the surface of the lens sheet 22. It is in.

The arrangement pitch of the condensing lens portions 22a of the lens sheet 22 is equal to or smaller than the arrangement pitch of the pixel areas in the vertical direction of the screen of the liquid crystal display element 10 (in FIG. (Approximately 1 / 1.5 of the arrangement pitch of the pixel regions of the display element 10).

The lens sheet 22 has a flat surface opposite to the lens forming surface facing the back surface of the light guide plate main body 20a, and adjusts the length direction of each condenser lens portion 22a to the light source light of the light guide plate main body 20a. It is attached to the back surface of the light guide plate main body 20a by a transparent adhesive (not shown) (a double-sided adhesive sheet may be used) in parallel with the end face.

Also in this light guide plate 20, the light guide plate body 20a and the lens sheet 22 have the same refractive index of light, and the adhesive has the same refractive index as the light guide plate body 20a and the lens sheet 22. And the light guide plate body 20
The light transmission path from a to the lens sheet 22 from one side to the other should be a linear path with little refraction of light and little reflection and scattering at the interface between the light guide plate body 20a and the lens sheet 22. desirable.

The light guide plate 20 is disposed on the front surface of the liquid crystal display element 10 with the light source light capturing end face of the light guide plate body 20a facing the main side of capturing external light (upper edge of the screen). Each condenser lens portion 22a of the sheet 22
Are supported by supporting means (not shown) in a state where the top portion is in contact with or close to the front surface of the liquid crystal display element 10.

The liquid crystal display of this embodiment is different from the liquid crystal display of the first embodiment shown in FIG. 1 only in the configuration of the light guide plate 20. The description will be omitted by attaching the same reference numerals to the drawings.

The liquid crystal display device of this embodiment also performs reflective display both when using external light and when using light from the light source 30.
Since the reflection plate 19 provided on the back side of the device reflects incident light with high reflectance, both external light and light from the light source 30 can be used with high efficiency. Also, when displaying using light from the light source 30, a sufficiently bright display can be obtained.

In this liquid crystal display device, since the light guide plate 20 is provided with the refraction means composed of the lens sheet 22, the light taken into the light guide plate 20 from the light source 30 is indicated by an arrow L1 in FIG. As shown, the lens sheet 22
The light is refracted in the light collecting direction by each of the condensing lens portions 22a, and is incident on the liquid crystal display element 10 from a direction close to the direction perpendicular to the front surface thereof. Light emitted from the display element 10 and transmitted through the light guide plate 20 and emitted to the front surface can be emitted in a direction close to the vertical direction.

Further, since the light guide plate 20 is arranged with its light source light capturing end side facing the outside light capturing side, the light guide plate 20 enters the light guide plate 20 from the front surface even in a display using external light. External light can enter the liquid crystal display element 10 from a direction close to a direction perpendicular to the front surface of the liquid crystal display element 10 as indicated by an arrow L2 in FIG.
The direction of emission of the light reflected by 9 can be made closer to the vertical direction.

Therefore, both the display using light from the light source 30 and the display using external light have high front luminance,
In addition, good display with almost no parallax can be obtained, and the emitted light exits in a direction close to the direction perpendicular to the front surface of the liquid crystal display element 10, whereas the light guide plate 20
The light reflected on the front surface of the light guide 20 travels in an oblique direction as indicated by the broken line in FIG. 2, and therefore, there is almost no reduction in display contrast due to the reflection of external light on the front surface of the light guide plate 20.

The light guide plate 20 used in the first and second embodiments has a structure in which a prism sheet 21 or a lens sheet 22 as a light refracting means is bonded to the back of a light guide plate body 20a. The light guide plate 20 may be formed by integrally forming the refraction means.

FIG. 3 is a sectional view of a liquid crystal display device according to a third embodiment of the present invention, in which the left side is the upper edge of the screen and the right side is the lower edge of the screen. The liquid crystal display device of this embodiment has a light guide plate 20 disposed on the front surface of the liquid crystal display element 10.
On the back surface, a refraction means for integrally emitting light incident from the light source light receiving end face in a direction close to a direction perpendicular to the front surface of the liquid crystal display element 10 is formed integrally.

In other words, in this embodiment, the light guide plate 20 is provided on the back surface of a wedge-shaped transparent plate whose front surface is inclined so as to be closer to the back surface from the light source light receiving end side toward the opposite side. A plurality of horizontally long prism parts 21b having the same shape as the prism part 21a of the prism sheet 21 of the light guide plate 20 used in the example are formed in parallel in the width direction thereof.

In this embodiment, the light guide plate 20
Is adhered to the front surface of the liquid crystal display element 10 by a low-refractive-index adhesive 23 made of a transparent resin having a smaller refractive index of light. The adhesive 23 desirably has a refractive index as low as possible. The lower the refractive index of the adhesive 23, the greater the refraction of light at the interface between each prism portion 21b on the back surface of the light guide plate 20 and the adhesive 23. be able to.

In the liquid crystal display device of this embodiment, the light guide plate 20 is integrally formed with a plurality of prism portions 21b as a light refracting means on the back surface thereof. It is affixed to the front surface of the liquid crystal display element 10, but other configurations are the same as those of the liquid crystal display device of the first embodiment shown in FIG. Omitted.

The liquid crystal display device of this embodiment also performs reflective display both when using external light and when using light from the light source 30.
Since the reflection plate 19 provided on the back side of the device reflects incident light with high reflectance, both external light and light from the light source 30 can be used with high efficiency. Also, when displaying using light from the light source 30, a sufficiently bright display can be obtained.

In this liquid crystal display device, the light guide plate 20 has a plurality of prism portions 21b formed on the back surface thereof.
Since the light refracting means is provided, the light taken into the light guide plate 20 from the light source 30 is refracted by the prism portions 21b as shown by the arrow L1 in FIG.
0 is incident on the liquid crystal display device 10 from a direction close to the direction perpendicular to the front surface thereof, is reflected by the reflector 19 on the rear surface of the liquid crystal display device 10, exits the liquid crystal display device 10, passes through the light guide plate 20, and exits to the front surface. Can be emitted in a direction close to the vertical direction, and also in a display using external light, external light incident on the light guide plate 20 from the front thereof is indicated by an arrow L in FIG.
As shown by 2, the light is incident on the liquid crystal display element 10 from a direction close to the direction perpendicular to the front surface, and the emission direction of the light reflected by the reflection plate 19 can be made close to the vertical direction.

Therefore, both the display using light from the light source 30 and the display using external light have high front luminance,
In addition, good display with almost no parallax can be obtained, and the emitted light exits in a direction close to the direction perpendicular to the front surface of the liquid crystal display element 10, whereas the light guide plate 20
The light reflected on the front surface of the light guide 20 travels in an oblique direction as shown by a broken line in FIG. 3, and therefore, there is almost no reduction in display contrast due to reflection of external light on the front surface of the light guide plate 20.

FIG. 4 is a sectional view of a liquid crystal display device according to a fourth embodiment of the present invention, in which the left side is the upper edge of the screen and the right side is the lower edge of the screen. The liquid crystal display device of this embodiment has a light guide plate 20 disposed on the front surface of the liquid crystal display element 10.
Is integrally formed with a refraction means for emitting light incident from a light source light receiving end face in a direction close to a direction perpendicular to the front surface of the liquid crystal display element 10 on its front surface.

That is, in the present embodiment, the light guide plate 20 is provided on the front surface of a wedge-shaped transparent plate which is inclined so that the front surface is closer to the back surface from the light receiving end side toward the opposite side. A plurality of horizontally long prism portions 21c similar in shape and opposite in direction to the prism portions 21a of the prism sheet 21 of the light guide plate 20 used in the example are formed in parallel in the width direction thereof.

In this embodiment, the light guide plate 20
Is attached to the front surface of the liquid crystal display element 10 by a transparent adhesive (may be a double-sided adhesive sheet) whose back surface (flat surface) is not shown, and is disposed on the front surface of the liquid crystal display element 10.

It is preferable that the adhesive has a refractive index substantially the same as that of the light guide plate 20.
When the refractive index of the light guide plate 20 is substantially the same as that of the adhesive, the light transmission path from one of the light guide plate 20 and the liquid crystal display element 10 to the other is hardly refracted, and the light guide plate 20 and the liquid crystal display element 10 are hardly refracted. A linear path with little reflection and scattering at the interface with the substrate.

Further, in this embodiment, the front surface of the light guide plate 20, that is, the uneven surface on which the prism portions 21c are arranged is formed by a low refractive index resin (transparent resin) 24 having a smaller refractive index of light than the light guide plate 20. And the front surface of the light guide plate 20 is hardly stained. The flattening resin 24 preferably has a refractive index as low as possible.
The refraction of light at the interface between each prism portion 21c on the front surface of the light guide plate 20 and the flattening resin 24 can be increased.

The liquid crystal display device of this embodiment has a configuration in which the light guide plate 20 is integrally formed with a plurality of prism portions 21c as a light refracting means on the front surface thereof. Since the configuration is the same as that of the liquid crystal display device of the first embodiment shown, the same description is given to the drawings and the duplicated description is omitted.

The liquid crystal display device of this embodiment also performs reflective display both when using external light and when using light from the light source 30.
Since the reflection plate 19 provided on the back side of the device reflects incident light with high reflectance, both external light and light from the light source 30 can be used with high efficiency. Also, when displaying using light from the light source 30, a sufficiently bright display can be obtained.

In this liquid crystal display device, the light guide plate 20 has a plurality of prism portions 21c formed on the front surface thereof.
The light taken in the light guide plate 20 from the light source 30 is refracted by the prism portions 21b as shown by the arrow L1 in FIG.
0 is incident on the liquid crystal display device 10 from a direction close to the direction perpendicular to the front surface thereof, is reflected by the reflector 19 on the rear surface of the liquid crystal display device 10, exits the liquid crystal display device 10, passes through the light guide plate 20, and exits to the front surface. Can be emitted in a direction close to the vertical direction, and also in a display using external light, external light incident on the light guide plate 20 from the front thereof is indicated by an arrow L in FIG.
As shown by 2, the light is incident on the liquid crystal display element 10 from a direction close to the direction perpendicular to the front surface, and the emission direction of the light reflected by the reflection plate 19 can be made close to the vertical direction.

Therefore, both the display using light from the light source 30 and the display using external light have high front luminance,
In addition, good display with almost no parallax can be obtained, and the emitted light exits in a direction close to the direction perpendicular to the front surface of the liquid crystal display element 10, whereas the light guide plate 20
The light reflected on the front surface of the light guide 20 travels in an oblique direction as indicated by a broken line in FIG. 4, and therefore, there is almost no reduction in display contrast due to the reflection of external light on the front surface of the light guide plate 20.

In the liquid crystal display devices according to the first to fourth embodiments, the light source 30 disposed on the side of the light guide plate is
Although the one using the straight tubular fluorescent lamp 31 is used, the light source may be, for example, an LED array in which a plurality of LEDs (light emitting diodes) are arranged.

The liquid crystal display element 10 used in each of the above embodiments has polarizing plates 18a and 18b on its front and back surfaces. The liquid crystal display element 10 has polarizing plates only on its front side. A light reflecting means may be provided on the inner surface of the rear substrate 11b of the display element 10 in that case.

The liquid crystal display element 10 used in each of the above embodiments is of an active matrix type.
The liquid crystal display element 10 may be of a simple matrix type.

Further, the liquid crystal display element 10 is not limited to the TN type, but may be an STN (super twisted nematic) type in which liquid crystal molecules are twisted at a twist angle of 180 ° to 270 °. , A phase transition effect type, a method of adding black dichroic dye to liquid crystal to display black and white and a color colored by a color filter, or a color filter utilizing birefringence effect of liquid crystal A birefringence effect type that can obtain a colored display without using a material may be used.

[0092]

According to the liquid crystal display device of the present invention, external light incident from the front surface and light from a light source incident from the end surface are emitted to the rear surface of the liquid crystal display device having the reflection means on the rear surface side. A light guide plate for emitting light emitted from the liquid crystal display element, which is incident on the liquid crystal display element from the back and emitted from the liquid crystal display element to the front, is arranged so that the reflection type is used both when using external light and when using light from a light source. Since the display is performed, it is possible to use the reflection means that reflects incident light at a high reflectance, and therefore, the external light and the light from the light source are used with high efficiency to utilize the external light. Both the display and the display using light from the light source can be brightened.

Moreover, in this liquid crystal display device, a light guide plate is disposed in front of a liquid crystal display element, and a light source is disposed so as to face an end face of the liquid crystal display element. Since there is provided a refraction unit for emitting light from the rear surface in a direction close to a direction perpendicular to the front surface of the liquid crystal display element, the light from the light source is directed to the liquid crystal display element in a direction close to the direction perpendicular to the front surface. Therefore, light emitted from the light source is reflected by the reflection means, exits the liquid crystal display element, passes through the light guide plate, and exits toward the front exits in a direction close to the vertical direction. Can be a good display with high front luminance and almost no parallax.

[Brief description of the drawings]

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

FIG. 2 is a sectional view of a liquid crystal display device according to a second embodiment of the present invention.

FIG. 3 is a sectional view of a liquid crystal display device according to a third embodiment of the present invention.

FIG. 4 is a sectional view of a liquid crystal display according to a fourth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Liquid crystal display element 19 ... Reflecting plate 20 ... Light guide plate 20a ... Light guide plate main body 21 ... Prism sheet (refraction means) 21a ... Prism part 22 ... Lens sheet (refraction means) 22a ... Condensing lens parts 21b, 21c ... Prism part (Refractive means) 23 ... Low refractive index adhesive 24 ... Low refractive index resin for flattening 30 ... Light source

Claims (3)

[Claims] 1. A liquid crystal display device having a reflection means on the back side, a light guide plate disposed on a front surface of the liquid crystal display device, and a light source disposed opposite to an end face of the light guide plate. The light guide plate emits external light incident from the front surface thereof and light from the light source incident from the end surface to the rear surface to be incident on the liquid crystal display element, and emits light from the liquid crystal display element incident on the rear surface. And a refraction means for emitting light incident from the end face in a direction close to a direction perpendicular to the front face of the liquid crystal display element from the back face. Display device. 2. The liquid crystal display device according to claim 1, wherein said refraction means is provided on a back surface of said light guide plate. 3. The liquid crystal display device according to claim 1, wherein said refracting means is provided on a front surface of said light guide plate.