JP3518237B2 - Liquid crystal display - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device that performs both display utilizing external light and display utilizing 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 and room illumination light and a display utilizing light from a light source provided in the display device. There is one.

As this two-way display type liquid crystal display device, there is conventionally one in which a backlight is arranged behind a liquid crystal display element having a semi-transmissive reflection plate on the back surface side, and the backlight is composed of an LE element. Is used, or a light source in which a light source such as a fluorescent lamp is arranged so as to face an end surface of a light guide plate made of a transparent plate.

This liquid crystal display device performs a reflection type display utilizing external light when external light of sufficient brightness is obtained,
When external light of sufficient brightness is not obtained, the backlight is turned on to perform transmissive display, and in reflective display using external light, the external light incident from the front surface of the liquid crystal display element is The light reflected by the semi-transmissive reflection plate of (1) again passes through the liquid crystal display element and is emitted to the front surface thereof. Further, in a transmissive display that utilizes the light of the backlight, the light that has passed through the semi-transmissive reflector of the light from the backlight becomes the incident light to the liquid crystal display element, and that light passes through the liquid crystal display element. It goes out to the front.

[0005]

However, the above-mentioned conventional method 2
The way-display type liquid crystal display device has a low light utilization efficiency both in the display utilizing external light and in the display utilizing the light from the backlight, and therefore, the external light from the backlight is utilized even when the external light is utilized. The problem is that the display is dark even when using light.

This is because the semi-transmissive reflection plate reflects and transmits incident light at a reflection / transmittance ratio according to its characteristics. Therefore, in the reflection type display utilizing external light, of the incident external light, The amount of light according to the transmissivity of the semi-transmissive reflector is transmitted to the back side of the semi-transmissive reflector to become loss light. This is because the amount of light corresponding to the reflectance of the semi-transmissive reflector is reflected by the semi-transmissive reflector and becomes lost light.

Moreover, the conventional liquid crystal display device has high front luminance (luminance of light emitted in the front direction of the liquid crystal display element) when utilizing light from the backlight, and a display without parallax can be obtained. However, when using outside light, the front luminance is low and parallax also occurs.

That is, when using external light, the two-way display type liquid crystal display device is diagonally above the screen, that is, in the direction perpendicular to the front surface of the liquid crystal display element, as in a normal reflection type liquid crystal display device. It is used by selecting the orientation of the device so that external light is mainly taken in from the direction inclined to the upper edge side of the screen.In that case, in the conventional liquid crystal display device, the direction perpendicular to the front surface of the liquid crystal display element is used. One side (upper edge of the screen)
External light that is incident from a direction that is tilted at an angle is reflected at a reflection angle that corresponds to the incident angle, so the output direction of that light is opposite to the vertical direction (the bottom of the screen). Therefore, sufficient front luminance cannot be obtained.

Further, in the conventional liquid crystal display device, the incident direction of external light is a direction inclined to one side with respect to the vertical direction, and the emitted direction of the reflected light is a direction inclined to the opposite side. , The deviation between the incident direction of external light and the outgoing direction of its reflected light is large, and therefore the pixel displayed by the reflected light of the light transmitted through the pixel region of the liquid crystal display element and the reflected light There is a large parallax in which the pixel displayed by light emitted through the pixel region is shifted.

According to the present invention, both the external light and the light from the light source can be utilized with high efficiency to make both the display utilizing the external light and the display utilizing the light from the light source bright, and
Whether you use outside light or light from a light source,
It is an object of the present invention to provide a two-way display type liquid crystal display device capable of obtaining a display of high quality with high front luminance and small parallax.

[0011]

Means for Solving the Problems Each electrode is formed.
A pair of front and back boards, provided between the pair of front and back boards
Liquid crystal layer, affixed to the outside of each of the front and back substrates
A pair of polarizing plates, and a liquid crystal display device having a reflection means provided on the back side, a light guide plate arranged on the front face of the liquid crystal display device, and at least one end face of the light guide plate facing each other. The light guide plate has a front surface that is inclined with respect to the back surface from one end to the other end.
The external light incident from the front surface is emitted to the back surface.
Then, the light from the light source incident from the end face is tilted.
Emitted to the back side by reflection of the inner surface of the formed surface
Then, the light emitted from the liquid crystal display element that is incident from the back surface while being incident on the liquid crystal display element is emitted to the front surface,
The reflecting means reflects light, which is emitted from the light guide plate and is incident on the liquid crystal display element in a direction inclined with respect to a direction perpendicular to the front surface, toward a direction close to the vertical direction. It is a thing.

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 external light is used, a liquid crystal display element is used. External light incident on the front surface of the light guide plate disposed on the front surface of the liquid crystal is transmitted through the light guide plate, enters the liquid crystal display element, is reflected by the reflecting means on the rear surface thereof, and is emitted to the front surface of the liquid crystal display element. However, the light passes through the light guide plate and is emitted to the front surface.

When a light source arranged facing at least one end face of the light guide plate is turned on, light from the light source is taken into the light guide plate from the end face and guided through the light guide plate to the back surface thereof. The light emitted to the front surface of the liquid crystal display element after being emitted to the front surface of the liquid crystal display element after being reflected by the reflecting means is emitted to the front surface through the light guide plate.

That is, this liquid crystal display device performs a reflective display both when external light is used and when light from a light source is used. Therefore, the reflection means has a high reflectance for incident light. It may be one that reflects light.

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, even when displaying using the external light, the light from the light source is used. Even when the display is performed, a sufficiently bright display can be obtained.

Moreover, in this liquid crystal display device, the light incident on the liquid crystal display element in a direction inclined with respect to the direction perpendicular to the front surface thereof is reflected by the reflection means toward the direction close to the vertical direction. Therefore, high front luminance can be obtained both when using the external light and the light from the light source, and the incident directions of the external light and the light from the light source are inclined with respect to the vertical direction. However, since the deviation between the incident direction of the light and the emitting direction of the light reflected by the reflecting means (the direction close to the vertical direction) is small, the incident light transmitted through the pixel region of the liquid crystal display element The parallax seen between the pixel displayed by the reflected light and the pixel displayed by the light of the reflected light that passes through the pixel area and is emitted is also reduced.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The liquid crystal display device of the present invention emits external light incident from the front surface and light from a light source incident from the end surface to the rear surface of the liquid crystal display element having the reflecting means on the rear surface. A light guide plate that allows the light emitted from the liquid crystal display element to be incident on the liquid crystal display element and the light emitted from the liquid crystal display element to be emitted to the front surface. By performing the display, it is possible to use the reflection means that reflects the incident light with a high reflectance, and use the outside light by utilizing the outside light and the light from the light source with high efficiency. Both the display and the display using light from the light source are made brighter, and further, by the reflection means, the light incident on the liquid crystal display element in a direction inclined with respect to the direction perpendicular to the front surface thereof is directed in the vertical direction. In the closer direction Only by reflecting, even when utilizing the light from the light source even when using external light, high front luminance and is obtained so as to obtain an indication of less good quality parallax.

In this liquid crystal display device, it is desirable that the light guide plate is provided in a state where there is no space between the back surface of the liquid crystal display device and the front surface of the liquid crystal display element. It is possible to increase the efficiency of light transmission / reception between the liquid crystal display element and the liquid crystal display element, and further improve the utilization efficiency of external light and light from the light source.

Further, in this liquid crystal display device, even if the reflecting means is a reflecting plate in which a plurality of inclined reflecting surfaces are continuous, a reflecting film is provided on the back surface of a prism sheet in which a plurality of prism portions are continuous. It may be one.

[0020]

1 is a cross-sectional view of a liquid crystal display device according to a first embodiment of the present invention in which the hatching of a light guide plate is omitted, in which the left side is the upper edge side of the screen and the right side is the lower edge side of the screen. .

This liquid crystal display device has a reflecting means 2 on the back side.
A light guide plate 30 having an area facing at least the entire display area of the liquid crystal display element 10 is arranged on the front surface of the liquid crystal display element 10 including 0, and a light source 32 is arranged so as to face one end surface of the light guide plate 30. It was done.

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

Although not shown in the drawing, active elements made of TFTs (thin film transistors) are provided on the inner surface of the back substrate 11a so as to correspond to the respective pixel electrodes 12, and the TFTs of the respective pixel electrode rows are provided. Line for supplying a gate signal to each pixel electrode and TF of each pixel electrode column
A data line for supplying a data signal to T is wired, and each pixel electrode 12 is connected to a TFT corresponding to the electrode.

On the other hand, on the inner surface of the front side substrate 11a, red, green, and blue color filters 14R, 14G, and 14B are provided alternately corresponding to the respective pixel electrodes 12, and these color filters 14R are also provided. , 14
Transparent protective film (insulating film) 1 formed over G and 14B
5, a single film transparent counter electrode 16 facing all of the pixel electrodes 13 is provided, and an alignment film 13a is formed thereon.

Then, the front side substrate 11a and the back side substrate 1
1b is joined via a frame-shaped sealing material 17,
A liquid crystal layer 18 is provided in a region surrounded by the sealing material 17 between the substrates 11a and 11b.

The molecules of the liquid crystal of the liquid crystal layer 18 are controlled by the alignment films 13a and 13b in the alignment directions in the vicinity of the front and back substrates 11a and 11b, and a predetermined twist angle (for example, approximately 90) is formed between the substrates 11a and 11b. Twist orientation at (°).

Further, polarizing plates 19a and 19b are attached to the outer surfaces of the front and back substrates 11a and 11b, respectively, and the reflecting means 20 is arranged behind the polarizing plate 19b on the back surface side.

The reflecting means 20 reflects the light incident on the liquid crystal display element 10 from a direction inclined with respect to the front surface thereof toward the direction close to the vertical direction. In this embodiment, As the reflection means 20, a reflection plate 21 in which a plurality of inclined reflection surfaces 21a are continuous is used.

That is, the reflecting plate 21 has a plurality of laterally long reflecting surfaces 21 along the width direction of the reflecting plate 21 on its surface.
a is formed so as to be continuous in the width direction and parallel to each other, and each of the reflection surfaces 21a is inclined with a uniform inclination angle from one side edge to the other side edge in the width direction. Is a face.

The inclination angle of each inclined reflection surface 21a of the reflection plate 21 is in the range of 1 ° to 70 °, preferably 1 ° to 30 °.
And more preferably in the range of 5 ° to 20 °, and the arrangement pitch of the inclined reflection surfaces 21a is 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. It is set smaller.

The reflecting plate 21 is provided with its inclined reflecting surfaces 21a oriented in the main direction of taking in external light when the liquid crystal display device performs display using external light.

As described in the section [Problems to be Solved by the Invention], the main direction of taking in the outside light is the screen diagonally above the screen, that is, with respect to the direction perpendicular to the front surface of the liquid crystal display element 10. Is inclined toward the upper edge side of the liquid crystal display element 10. Therefore, the reflecting plate 21 makes the length direction of each inclined reflecting surface 21a substantially parallel to the horizontal axis of the screen and directs the inclined surface toward the upper edge side of the liquid crystal display element 10. It is provided in a closed state.

Next, the light guide plate 30 arranged on the front surface of the liquid crystal display element 10 will be described.
Is a transparent plate made of glass, acrylic resin, or the like, and one surface of the front and back surfaces thereof is a surface inclined with respect to the other surface.

The light guide plate 30 used in this embodiment has its surface inclined from one end to the other end of the light guide plate 30. Although the inclination is exaggerated in the drawing, the inclination angle of this surface ( The angle with respect to the back surface of the light guide plate 30 is 1 ° to 10 °
Is set, preferably in the range of 2 ° to 5 °, and more preferably in the range of 2 ° to 5 °.

The light guide plate 30 emits external light entering from the front surface and light from the light source 32 entering from the end surface to the back surface to enter the liquid crystal display element 10 and from the liquid crystal display element 10 entering from the back surface. Of the light emitted from the light source 32 is emitted to the front surface, and the end face having the larger height of the both end faces is a face for taking in light from the light source 32 (hereinafter referred to as a light source light taking-in end face).

The light guide plate 30 is arranged so that the light source light-trapping end surface faces the upper edge side of the screen, which is the main outside light-trapping side, and the entire back surface thereof is a transparent adhesive (even a double-sided adhesive sheet). It is provided on the front surface of the liquid crystal display element 10 so that there is no space between the light guide plate 30 and the liquid crystal display element 10 by adhering it to the front surface of the liquid crystal display element 10 by means of (31).

As described above, the light guide plate 30 is provided without a space between the back surface thereof and the front surface of the liquid crystal display element 10 because the light between the light guide plate 30 and the liquid crystal display element 10 is provided. This is to increase the transfer efficiency of.

The adhesive 31 has substantially the same refractive index as either the light guide plate 30 or the front side polarizing plate 19a which is the front member of the liquid crystal display element 10 or has an intermediate refractive index between the two. Those having a refractive index of are desirable.

Further, the light source 32 has a straight tubular fluorescent lamp 33 having a length extending over the entire length of the end surface of the light guide plate 30 and light emitted from the fluorescent lamp 33 to the periphery thereof toward the end surface of the light guide plate 30. It consists of a reflector 34 that reflects light. The reflector 34 is in the shape of an elliptic cylinder having a light exit on one side.

The light source 32 is arranged on the side of the light source light receiving end surface of the light guide plate 30 with the emission port of the reflector 34 facing the light source light receiving end surface of the plate 30.

This liquid crystal display device is of a two-way display type which performs both display utilizing external light and display utilizing light from the light source 32, and the light source 32 has sufficient brightness. Used when outside light is not available.

First, the display utilizing external light will be described. At this time, the external light incident from the front surface of the light guide plate 30 arranged on the front surface of the liquid crystal display element 10 is indicated by an arrow A in FIG. The light that passes through the light guide plate 30 in the thickness direction thereof, enters the liquid crystal display element 10, is reflected by the reflecting means 20 on the back surface side thereof, and goes out to the front surface of the liquid crystal display element 10 passes through the light guide plate 30. And emits to the front.

In this case, since the external light is mainly taken in from diagonally above the screen (the direction inclined to the upper edge side of the screen with respect to the direction perpendicular to the front surface of the liquid crystal display element 10), most of the external light is the above. Although incident on the surface of the light guide plate 30 from an oblique direction, the light is refracted at the interface between the surface of the light guide plate 30 and the outside air (air), and becomes light in a direction with a smaller angle with respect to the vertical direction. And enters the light guide plate 30.

External light that has entered the light guide plate 30 from its front surface is emitted to the back surface of the light guide plate 30 and enters the liquid crystal display element 10. In that case, in this embodiment, the light guide plate 30 is moved to the outside. Since there is no space between the back surface and the front surface of the liquid crystal display element 10, the external light incident on the light guide plate 30 can be efficiently incident on the liquid crystal display element 10.

This is because the light transmission / reception efficiency between the light guide plate 30 and the liquid crystal display element 10 may or may not be a space between the back surface of the light guide plate 30 and the front surface of the liquid crystal display element 10. This is because they are different.

That is, the external light incident on the light guide plate 30 from its front surface passes through the light guide plate 30 in the thickness direction and travels to the back surface thereof, but out of the light, it is emitted to the back surface of the light guide plate 30. Is light incident on the interface between the back surface of the light guide plate 30 and a layer adjacent thereto at an angle of incidence smaller than the critical angle for total reflection, and at an angle of incidence greater than the critical angle for total reflection on the interface. The incident light is totally reflected at this interface.

The total reflection critical angle of the interface depends on the difference in the refractive index of light between the light guide plate 30 forming the interface and its adjacent layer. The larger the difference in refractive index, the greater the total reflection critical angle. large.

Therefore, when the adjacent layer is an air layer having a refractive index of about 1, that is, the light guide plate 30 and the liquid crystal display element 1.
When the space between 0 and 0 is a space, the incident angle range (angle range smaller than the total reflection critical angle) of the light transmitted through the interface becomes small, and the total reflection amount at this interface becomes large.

This is the same when the light emitted to the back surface of the light guide plate 30 is incident on the liquid crystal display element 10. If the space between the light guide plate 30 and the liquid crystal display element 10 is a space, the liquid crystal display element 10 will be described. The incident angle range of the light transmitted through the interface between the air layer and the air layer becomes small, and the total reflection amount at this interface increases.

However, as in this embodiment, the light guide plate 30
The entire back surface of the liquid crystal display element 1 is provided with a transparent adhesive 31.
When the light guide plate 30 is attached to the front surface of the liquid crystal display device 10 in a state where there is no space between the back surface of the light guide plate 30 and the front surface of the liquid crystal display device 10, the light guide plate 30 and the liquid crystal display device 10 are provided.
Since the difference between the refractive index of the front-side polarizing plate 19a and the refractive index of the pressure-sensitive adhesive layer therebetween is small, at the interface between the back surface of the light guide plate 30 and the pressure-sensitive adhesive layer and the interface between the liquid crystal display element 10 and the pressure-sensitive adhesive layer. Since the critical angle for total reflection is small and the incident angle range of light transmitted through these interfaces is large, the efficiency of light transmission / reception between the light guide plate 30 and the liquid crystal display element 10 is increased, and the light guide plate 30 is increased. The external light incident on the liquid crystal display device 10 can be efficiently incident on the liquid crystal display element 10.

The light incident on the liquid crystal display element 10 is
The light is transmitted through the front side polarizing plate 19a to become linearly polarized light, and the light is sequentially transmitted through the liquid crystal layer 18 and the back side polarizing plate 19b and is incident on the reflecting means 20, which is perpendicular to the front surface of the liquid crystal display element 10. Is reflected in a direction close to the normal direction. 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 filters 14R, 14G,
The colored light is transmitted through 14 bB.

That is, since the external light mainly taken in from diagonally above the screen is refracted at the interface between the surface of the light guide plate 30 and the outside air (air) and enters the light guide plate 30 as described above, the light guide plate 30. The incident direction of the external light incident on the liquid crystal display element 10 from is a direction in which the angle with respect to the direction perpendicular to the front surface of the liquid crystal display element 10 is smaller than the incident direction to the surface of the light guide plate. Is a direction inclining to the outside light intake side to some extent with respect to the vertical direction.

However, in this embodiment, the reflecting means 2 is used.
The reflection plate 2 in which a plurality of inclined reflection surfaces 21a are continuous is defined as
1, the reflection plate 21 is attached to each inclined reflection surface 21a.
Is provided in the main direction of taking in external light, the light incident on the liquid crystal display element 10 obliquely from the above direction is directed to a direction close to a direction perpendicular to the front surface of the liquid crystal display element 10. Can be reflected.

The direction of the light reflected by the reflector 21 is
The inclination angle of each inclined reflection surface 21a of the reflection plate 21 (angle with respect to a plane parallel to the front surface of the liquid crystal display element 10) θ and the incident angle of light to the reflection plate 21 determines the reflection plate 21.
The incident angle of light to ψin, the reflection angle of the light is ψout (all are angles with respect to the direction perpendicular to the front surface of the liquid crystal display element 10)
Then, in the case of θ = 5 °, ψin = −30 ° and ψout = + 20 ° ψin = −20 ° and ψout = + 10 ° When θ = 10 °, ψin = −30 ° and ψout = + 10 ° ψin = −20 ° and ψout = 0 ° θ = 15 °, ψin = −30 ° ψout = 0 ° ψin = −20 ° and ψout = −10 ° θ = 20 °, ψin = −30 ° At ψ out = −10 ° ψ in = −20 °, ψ out = −20 °.

Here, the − angle is a tilt angle with respect to the vertical direction toward the outside light intake side (the upper edge side of the screen), and the + angle is the opposite side with respect to the vertical direction (the lower edge side of the screen). ), And the incident angle ψin is the angle of − as described above.

Therefore, the more desirable tilt angle θ of the tilted reflection surface 21a is in the range of 5 ° to 20 °. If the tilt angle θ of the tilted reflection surface 21a is set in this range, the light is incident on the liquid crystal display element 10. Most of the reflected light can be reflected in the direction of ± 20 ° with respect to the vertical direction.

The reflected light from the reflecting means 20 is reflected by the back side polarizing plate 19b, the liquid crystal layer 18, and the front side polarizing plate 19a.
And are sequentially emitted to the front surface of the liquid crystal display element 10, and the light enters the light guide plate 30 from the rear surface thereof and is emitted to the front surface of the light guide plate 30. Note that, of the reflected light, the light that passes through the pixel region of the liquid crystal display element 10 and exits passes through the color filters 14R, 14G, and 14bB and is colored in that color.

Also at this time, since there is no space between the back surface of the light guide plate 30 and the front surface of the liquid crystal display element 10, the light emitted from the liquid crystal display element 10 can be efficiently incident on the light guide plate 30.

Next, the display using the light from the light source 32 will be described. The light source 32 is used when the external light of sufficient brightness cannot be obtained. As shown by the arrow B in FIG. 1, the light from the light source 32 is taken into the light guide plate 30 from the light source light taking-in end face, guided through the light guide plate 30, and emitted to the back surface thereof.

In this case, the light that has entered the light guide plate 30 from the light source end face of the light source is reflected by the front and back surfaces of the light guide plate 30 and is zigzag-reflected between the front and back surfaces to be guided in the light guide plate. Since the critical angle of total reflection at the interface between the surface of the light guide plate 30 and the outside air (air) is large and the critical angle of total reflection at the interface between the back surface and the adhesive 31 is small, the light source light taken into the light guide plate 3 is efficiently converted. The light can be well emitted to the back surface of the light guide plate 30, and since the back surface of the light guide plate 30 and the front surface of the liquid crystal display element 10 are adhered by the adhesive 31 so that there is no space between them, The light emitted to the back surface of the light plate 30 can be efficiently incident on the liquid crystal display element 10.

Then, the light incident on the liquid crystal display element 10 is the same as the above-mentioned external light transmission path, and the liquid crystal display element 1
0 is transmitted to enter the reflection means 20, and the reflection means 20
As a result, the light is reflected in a direction close to the direction perpendicular to the front surface of the liquid crystal display element 10.

Also at this time, the direction of the light reflected by the reflection means 20 depends on the inclination angle θ of each inclined reflection surface 21a of the reflection plate 21 which is the reflection means 20 and the incident angle of the light to the reflection plate 21. However, if the tilt angle θ of the tilted reflection surface 21a is in the range of 5 ° to 20 °, most of the light incident on the liquid crystal display element 10 is directed in the range of ± 20 ° with respect to the vertical direction. Can be reflected.

The reflected light from the reflection means 20 is transmitted through the liquid crystal display element 10 and emitted to the front surface thereof in the same manner as the external light transmission path, and the light is incident on the light guide plate 30 from the rear surface thereof. The light is emitted to the surface of the light guide plate 30. Also at this time, since there is no space between the back surface of the light guide plate 30 and the front surface of the liquid crystal display element 10, the light emitted from the liquid crystal display element 10 can be efficiently incident on the light guide plate 30.

Even when the light from the light source 32 is used, the light passing through the pixel area of the liquid crystal display element 10 passes through the color filters 14R, 14G and 14bB and is colored in that color.

That is, the above-mentioned liquid crystal display device performs the reflection type display both when using the external light and when using the light from the light source 32. Therefore, the reflecting means 2 is used.
0 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 32 can be used with high efficiency, a sufficiently bright display can be obtained both when using the external light and when displaying using the light from the light source 32. be able to.

In the above embodiment, the light guide plate 30 is used.
Is provided in a state where there is no space between the back surface thereof and the front surface of the liquid crystal display element 10, it is possible to increase the light transmission / reception efficiency between the light guide plate 30 and the liquid crystal display element 10, Therefore, it is possible to further improve the utilization efficiency of the external light and the light from the light source 32 and further brighten the display.

Moreover, according to the above liquid crystal display device, the light incident on the liquid crystal display element 10 in the direction inclined with respect to the direction perpendicular to the front surface of the liquid crystal display element 10 is directed toward the direction close to the vertical direction by the reflection means 20. Since the light is reflected, high front luminance can be obtained regardless of whether the external light or the light from the light source 32 is used, and the incident directions of the external light and the light from the light source 32 are relative to the vertical direction. Even if the light is tilted, the deviation between the incident direction of the light and the emitting direction of the light reflected by the reflecting means 20 (direction close to the vertical direction) is small, so parallax can be reduced.

FIG. 2 is a partially enlarged sectional view showing a state of parallax generation in a display utilizing the external light of the liquid crystal display device. In this liquid crystal display device, the incident direction of the external light to the liquid crystal display element 10 is Even in the oblique direction, since the emission direction of the light reflected by the reflection means 20 is close to the vertical direction,
The deviation between the incident direction and the outgoing direction is small, and therefore, the pixel d1 displayed by the reflected light of the light transmitted through the pixel area D of the liquid crystal display element 10 and the pixel area of the reflected light is transmitted. The parallax that is seen by the emitted light is deviated from the displayed pixel d2 and is small. This parallax is almost the same also in the display using the light from the light source 32.

In the conventional two-way display type liquid crystal display device, as described in the section [Problems to be Solved by the Invention], the deviation between the incident direction of external light and the outgoing direction of its reflected light is large. A part of the reflected light of the light transmitted through the pixel region and incident on the other pixel regions adjacent to each other at an interval, and color display is performed by the additive color mixture as in the above embodiment, In a liquid crystal display device having color filters of three colors of red, green, and blue, the color filters of these two pixel regions do not absorb and emit, and color display is performed by subtractive color mixing. Magenta, yellow, and cyan. In the liquid crystal display device including the color filters of three colors, the light obliquely incident on the peripheral portion of the pixel region is 2
Color mixture occurs by passing through the two color filters. However, according to the liquid crystal display device of the above-described embodiment, the incident direction of light and the reflection thereof are reflected regardless of whether external light is used or light from the light source 32 is used. Since the deviation from the emission direction of the light is small, the light does not pass through the two pixel regions and enter the two color filters. Therefore, a high quality color image can be displayed.

Further, 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 surface of the light guide plate 30 is improved. Almost no decline.

FIG. 3 is a partially enlarged sectional view showing the direction of emitted light of the liquid crystal display device and the reflection direction of external light on the surface of the light guide plate. The external light reflected on the surface of the light guide plate 30 is indicated by a broken line in the figure. As described above, the light travels in an oblique direction at a reflection angle corresponding to the incident angle with respect to the surface of the light guide plate, but the light emitted from the liquid crystal display device is emitted in a direction close to vertical as described above.

The display image of the liquid crystal display device is observed from the front direction with respect to 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. Since the surface reflected light traveling in an oblique direction is almost invisible, the surface reflected light is not superposed on the image light emitted from the liquid crystal display device and the contrast is not deteriorated.

Furthermore, since the above-mentioned liquid crystal display device performs the reflective display both when using the external light and when using the light from the light source 32, the liquid crystal display element is different from the conventional liquid crystal display device. The degree of freedom in designing 10 is high, and it is possible to easily design.

That is, in the conventional liquid crystal display device, the display utilizing the external light is the reflective display, the display utilizing the light of the backlight is the transmissive display, and the reflective display utilizing the external light is the display. In this case, the incident light from the front surface side is transmitted and reflected by the liquid crystal display element, and the light is again transmitted through the liquid crystal display element and emitted to the front surface side, whereas the transmission type utilizing the light of the backlight. In the display, the incident light from the back side is transmitted through the liquid crystal display element and is emitted to the front side, so that it is possible to compensate for the difference in display color caused by the difference in the light transmission path between the reflective display and the transmissive display. It is necessary to design a liquid crystal display element.

In this respect, in the liquid crystal display device of the above-mentioned embodiment, both the display utilizing the external light and the display utilizing the light from the light source 32 are reflection type displays, and the light transmission paths are almost the same in any of the displays. Therefore, the design of the liquid crystal display element 10 is easy.

FIGS. 4 and 5 are cross-sectional views of the liquid crystal display device according to the second and third embodiments of the present invention in which the hatching of the light guide plate is omitted, and these embodiments show the back surface of the liquid crystal display element 10. The reflecting means 20 provided on the side is provided with a prism sheet 22 or 23 in which a plurality of prism portions are continuous,
Reflective film (preferably specular reflective film) provided on the back surface
24 and 24. The second and third embodiments are the same as the first embodiment described above except that the reflecting means 20 is different. Therefore, the duplicate description is given the same reference numeral in the drawings. And omit.

The prism sheet 22 used in the second embodiment shown in FIG. 4 has a plurality of laterally long prism portions 22a along the width direction on the front surface of a transparent plate made of glass or acrylic resin. The prism portions 22a each have a right-angled triangular cross-section with one side vertical and the other side inclined.

The prism sheet 22 has an inclined surface of each prism portion 22a as a main direction of taking in external light (obliquely above the screen) when the liquid crystal display device performs display using external light. Are provided in the opposite direction.

In the case of this embodiment, the reflective film 24 is
It is possible to use a thin metal plate having a reflecting surface or a flat substrate made of glass or the like with a metal film deposited or plated on the surface, which is attached to the back surface of the prism sheet 22 with a transparent adhesive. Alternatively, a metal film may be deposited or plated on the back surface of the prism sheet 23 to form the reflection film 24.

The prism sheet 23 used in the third embodiment shown in FIG. 5 has a plurality of laterally long prism portions 23a along the width direction on the back surface of a transparent plate made of glass or acrylic resin. The prism portions 23a are formed continuously in the width direction and are parallel to each other, and each of the prism portions 23a has an isosceles triangular cross-sectional shape in which both side surfaces are inclined at substantially the same angle.

The prism sheet 23 has one inclined surface on one side of each prism portion 23a directed toward the main direction of taking in external light when the liquid crystal display device is to perform display using external light, and the opposite side. Is provided so as to face the inclined surface in a direction opposite to the direction in which the outside light is taken in.

In the case of this embodiment, the reflective film 24 is
A thin metal plate having a reflecting surface, or a flat substrate made of glass or the like having a metal film deposited or plated on the surface thereof is used, and the reflecting film 24 is provided on the surface of each prism portion 23a of the prism sheet 23. Is attached to the top of the prism sheet with a transparent adhesive, or is placed so as to be closely opposed to the back surface of the prism sheet 23,
A space is provided between the inclined surfaces on both sides of a and the reflection film 24.

In each of the second and third full-time working examples, the arrangement pitch of the prism sheets 22a and 23a of the prism sheets 22 and 23 is determined by the pixel area in the vertical direction of the screen of the liquid crystal display element 10. It is desirable to set the pitch equal to or smaller than the arrangement pitch of.

The reflecting means 20 consisting of the prism sheets 22 and 23 and the reflecting film 24 provided on the back surface of the prism sheet 22 and 23 reflects the light obliquely transmitted through the liquid crystal display element 10 as shown by the arrows in FIGS. The prism portions 22a and 23a of the prism sheets 22 and 23 are refracted and reflected by the reflection film 24, and the light is further refracted by the prism portions 22a and 23a and emitted in a direction close to the vertical direction.

Therefore, also in the liquid crystal display devices of the second and third embodiments, the light incident on the liquid crystal display element 10 from the direction inclined with respect to the direction perpendicular to the front surface thereof is
Since the light is reflected toward the direction close to the vertical direction by the reflection means 20, high front luminance can be obtained and parallax can be reduced when using external light or light from the light source 32. .

The reflecting means 20 used in the third embodiment has the prism portion 23a of the prism sheet 23.
However, since both sides thereof have an isosceles triangular cross-sectional shape that is inclined at substantially the same angle, the prism portion 23a
The incident light from the direction in which the one inclined surface faces each other and the incident light from the direction in which the opposite inclined surface faces each other can be reflected toward the direction close to the vertical direction.

Therefore, when the reflecting means 20 of the third embodiment is used, the light guide plate 30 is arranged with its light source light-trapping end face facing away from the main outside light-trapping side. The light source 32 may be arranged so as to face the light-trapping end surface.

Further, in the first to third embodiments, the light source 32 is provided on one side, but when the reflecting means 20 of the third embodiment is used, the light sources 32 are arranged on both sides. May be.

FIG. 6 is a sectional view showing a liquid crystal display device according to a fourth embodiment of the present invention, in which the hatching of the light guide plate is omitted. In this liquid crystal display device, the reflection means 20 provided on the back surface side of the liquid crystal display element 10 is the same as that of the third embodiment, and on the front surface of the liquid crystal display element 10, almost the upper half of the display area of the liquid crystal display element 10 is used. And two lower light guide plates 30a and 30b facing each other, respectively, with one light guide plate 30a having the light source light capturing end face directed toward the main outside light capturing side (the upper edge side of the screen) and the other light guiding plate 30a. The light source 30 is arranged with the light source end faces of the light plates 30b facing the opposite side (the lower edge side of the screen), and the light sources 32 are arranged so as to face the light source end faces of the light guide plates 30a and 30b, respectively.

In this embodiment, the two light guide plates 3 are
0a and 30b are adhered to the front surface of the liquid crystal display element 10 with a transparent adhesive (may be a double-sided adhesive sheet) 31 on the entire back surface of the liquid crystal display element 1
Liquid crystal display element 1 so that there is no space between
It is provided on the front of 0.

The liquid crystal display device of this embodiment uses two light guide plates 30a and 30b facing the upper half area and the lower half area of the screen.
Except for the point that the light source 32 is arranged opposite to a and 30b, the other configuration is the same as that of the above-mentioned third embodiment, and therefore duplicate explanations are given the same symbols in the drawings and omitted.

In this liquid crystal display device, the light from one light source 32 of the two light sources 32 arranged on both sides of the liquid crystal display device is guided by the one light guide plate 30a so as to reach substantially the upper half of the display area of the liquid crystal display element 10. The light from the other light source 32 is made incident and guided by the other light guide plate 30b so that the liquid crystal display element 10
In this liquid crystal display device, the luminance per unit area of the light source light incident on the liquid crystal display element 10 is increased so that the light from the light source is emitted from the light source. The display utilizing light can be made brighter.

FIG. 7 is a sectional view showing a liquid crystal display device according to a fifth embodiment of the present invention, in which hatching of a light guide plate is omitted. This liquid crystal display device uses the reflecting means 20 provided on the back surface side of the liquid crystal display element 10 of the third embodiment, and has an area on the front surface of the liquid crystal display element 10 that faces at least the entire display area. The two light guide plates 30 and 30 'were arranged such that one light guide plate 30 had a light source light receiving end face directed to the main outside light intake side, and the other light guide plate 30' had a light source light receiving end face directed to the opposite side. In this state, the light sources 32 are arranged so as to be stacked on top of each other, and the light sources 32 are arranged so as to face the light source light receiving end faces of the light guide plates 30 and 30 '.

In this embodiment, the two light guide plates 3 are
Reference numerals 0 and 30 'are the same as the light guide plate 30 used in the first to third embodiments, and the inner light guide plate 30 adjacent to the liquid crystal display element 10 has the inclined surface directed to the front side. In this state, the entire back surface is attached to the front surface of the liquid crystal display element 10 with a transparent adhesive (may be a double-sided adhesive sheet) 31 so that there is no space between the liquid crystal display element 10 and the liquid crystal display element. It is provided on the front surface of 10.

Also, the outer light guide plate 30 'laminated on the front side.
Is in a state in which the inclined surface is directed to the back side and the light source light intake end surface is directed in the direction opposite to the light source light intake end surface of the inner light guide plate 30, and the inclined surface (rear surface) is the inner light guide plate 30. It is arranged so as to be close to and parallel to the inclined surface (surface).

In the liquid crystal display device of this embodiment, substantially another light guide plate 30 'is arranged on the surface of the light guide plate 30 of the liquid crystal display device of the third embodiment, and the light guide plate 30' is also provided. The light source 3 facing the light source end face of the light plate 30 '
Since 2 is added, duplicate description will be omitted by attaching the same reference numerals to the drawings.

In this liquid crystal display device, light from one light source 32 of the two light sources 32 arranged on both sides of the liquid crystal display device is guided by the inner light guide plate 30 to be incident on the entire display area of the liquid crystal display element 10. The light from the other light source 32 is guided by the outer light guide plate 30 'and transmitted through the inner light guide plate 30 to be incident on the entire display area of the liquid crystal display element 10. Also in the device, the luminance per unit area of the light source light incident on the liquid crystal display element 10 can be increased, and the display utilizing the light from the light source can be made brighter.

FIGS. 8 and 9 are sectional views showing the liquid crystal display devices according to the sixth and seventh embodiments of the present invention, in which the hatching of the light guide plate is omitted. These liquid crystal display devices are
The light from the light source 32 is made incident on the light guide plate 30 as light substantially parallel to the back surface (the surface facing the liquid crystal display element).

The liquid crystal display device of the sixth embodiment shown in FIG. 8 corrects the emitted light from the light source lamp 33 and the reflected light from the reflector 34 into parallel light at the exit of the reflector 34 of the light source 32. A condensing lens 35 for emitting light is provided, and other configurations are the same as those in the first embodiment described above. In addition, the condenser lens 35 includes a reflector 34.
The lens may be a laterally long convex lens along the length direction of the light emission port of or a parallel Fresnel lens.

Further, in the liquid crystal display device of the seventh embodiment shown in FIG. 9, the light source 3 is provided on the end face of the light guide plate 30 for taking in the light source.
A condenser lens portion 36 for correcting the light from the light source 4 to be parallel light and making the light incident on the light guide plate 30 is provided. The other structure is the same as that of the first embodiment described above. The condensing lens 36 may be a horizontally long convex lens along the length direction of the light source light taking-in end surface of the light guide plate 30 or a parallel Fresnel lens. It may be attached to the end face of the light plate 30 for taking in the light source, or may be integrally formed with the light guide plate 30.

According to the liquid crystal display devices of the sixth and seventh embodiments, the light from the light source 32 is corrected to be parallel light and is made incident on the light guide plate 30, so that it is incorporated into the light guide plate 30. The light from the light source 32 can be made to enter the liquid crystal display element 10 more efficiently.

That is, since the emitted light from the light source lamp 33, the reflected light from the reflector 34, and the light directed in random directions are taken into the light guide plate 30 as they are, the surface of the light guide plate 30 among them is taken. Light that travels to the interface with the outside air at an angle smaller than the critical angle for total reflection is transmitted through the interface and exits to the surface of the light guide plate to be leaked light.

However, as in the sixth and seventh embodiments, the light from the light source 32 is corrected into parallel light and the light guide plate 30 is corrected.
When the light is incident on the surface of the light guide plate 30, almost no light travels to the interface between the surface of the light guide plate 30 and the outside air at an angle smaller than the critical angle for total reflection, so that light leakage to the surface of the light guide plate is reduced.
Most of the light from the light source 32 can be emitted from the back surface of the light guide plate 30 and incident on the liquid crystal display element 10.

The liquid crystal display device shown in FIG. 8 and FIG. 9 is a liquid crystal display device according to the first embodiment, which is a device for correcting the light from the light source 32 into parallel light and making it enter the light guide plate 30. The optical lenses 35 and 36 are added.
The second to fifth methods are to make the light from the light source 32 into parallel light and make it enter the light guide plate 30 as in the seventh embodiment.
It can also be applied to the liquid crystal display device of the above embodiment.

In the sixth and seventh embodiments,
The light from the light source 32 is corrected into parallel light by the condenser lenses 35 and 36 and is incident on the light guide plate 30.
Even if the light source lamp 33 of the light source 32 has a characteristic of emitting light in the direction toward the light source light receiving end face of the light guide plate 30, light close to parallel light is made incident on the light guide plate 30 and the light is efficiently emitted. It can be made incident on the liquid crystal display element 10, and the effect can be further enhanced by using the light source lamp having the above characteristics and the condenser lenses 35 and 36 in combination.

That is, FIG. 10 is an enlarged cross-sectional view showing a modified example of the light source 32. The light source 32 has a light source lamp 33 which emits light over its entire length on the side surface facing the light source light receiving end surface of the light guide plate 30. In addition to using the fluorescent lamp with an aperture in which the radiating part is formed, a condenser lens 35 is provided at the exit of the reflector 34 as in the sixth embodiment.

The fluorescent lamp with aperture has a fluorescent material layer 33b provided on the inner peripheral surface of the glass tube 33a except one side portion of the glass tube 33a. The fluorescent material layer 33b emits fluorescent light. Of these, the light emitted from the outer peripheral surface thereof is emitted to the periphery of the lamp, while the light emitted from the inner peripheral surface of the fluorescent material layer 33b is emitted from the light emitting portion (aperture) without the fluorescent material layer 33b. Therefore, the light emitted from the light emitting portion is a light having a high brightness and a light flux that is small in spread and is close to parallel light.

That is, the light source 32 causes the light emitting portion of the light source lamp 33, which is the fluorescent lamp with the aperture, to emit light close to parallel light with high brightness and a small light flux spread, and the light is condensed by the condensing lens 35. The light is further corrected by the light source plate 33 to be incident on the light guide plate 30 and is radiated from the light source lamp 33 to the surroundings thereof.
The light reflected at 4 is also made to be parallel light by the condenser lens 35 and incident on the light guide plate 30, and if such a light source is used, it becomes parallel light with higher brightness. It is possible to cause close light to be incident on the light guide plate 30 and efficiently enter the light to the liquid crystal display element 10.

In the light source 32 shown in FIG.
Although the condenser lens 35 is provided at the emission port of the reflector 34, the condenser lens may be provided on the light source light receiving end face of the light guide plate 30 as in the seventh embodiment.

As the light source lamp 33 of the light source 32,
When using a light emitting plate having a characteristic of emitting light in the direction toward the light source end face of the light guide 30 such as the fluorescent lamp with an aperture, there is no condenser lens for correcting the light from the light source into parallel light. Good.

The liquid crystal display element 10 used in each of the above-mentioned examples has polarizing plates 19a and 19b on the front and back surfaces thereof, but the liquid crystal display element 10 has a polarizing plate only on its front surface side. In this case, the inner surface of the rear substrate 11b of the display element 10 may be provided with a reflection unit that reflects light incident from a direction inclined with respect to the vertical direction toward the direction close to the vertical direction. Good.

The liquid crystal display element 10 used in each of the above embodiments is of the 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 twist-aligned at a twist angle of 180 ° to 270 °. , A phase transition effect type that displays black and white and a color colored by a color filter by adding a black dichroic dye to the liquid crystal, or a color filter that utilizes the birefringence effect of the liquid crystal It may be a birefringence effect type or the like for obtaining a colored display without using.

[0115]

According to the liquid crystal display device of the present invention, the external light incident from the front surface and the light from the light source incident from the end surface are emitted to the front surface of the liquid crystal display element having the reflecting means on the rear surface side. A light guide plate that allows the light emitted from the liquid crystal display element to be incident on the liquid crystal display element and the light emitted from the liquid crystal display element to be emitted to the front surface. Since the display is performed, it is possible to use, as the reflection means, one that reflects the incident light with high reflectance, and therefore, the outside light and the light from the light source are used with high efficiency to use the outside light. Both the display and the display utilizing light from the light source can be brightened.

Moreover, according to this liquid crystal display device, the reflection means reflects the light incident on the liquid crystal display element from the direction inclined with respect to the front surface thereof toward the direction close to the vertical direction. Therefore, it is possible to obtain good quality display with high front luminance and small parallax regardless of whether external light is used or light from a light source is used.

In the liquid crystal display device of the present invention, it is desirable that the light guide plate is provided in a state where there is no space between the back surface of the light guide plate and the front surface of the liquid crystal display element. It is possible to increase the light transmission / reception efficiency between the light guide plate and the liquid crystal display element, and further improve the utilization efficiency of the external light and the light from the light source.

[Brief description of drawings]

FIG. 1 is a sectional view of a liquid crystal display device according to a first embodiment of the present invention, in which hatching of a light guide plate is omitted.

FIG. 2 is a partial enlarged cross-sectional view showing a state of parallax generation in a display utilizing external light of the liquid crystal display device.

FIG. 3 is an enlarged cross-sectional view of a part showing a direction of emitted light of the liquid crystal display device and a direction of reflection of external light on the surface of the light guide plate.

FIG. 4 is a sectional view showing a liquid crystal display device according to a second embodiment of the present invention, in which hatching of a light guide plate is omitted.

FIG. 5 is a sectional view of a liquid crystal display device according to a third embodiment of the present invention, in which hatching of a light guide plate is omitted.

FIG. 6 is a sectional view showing a liquid crystal display device according to a fourth embodiment of the present invention, in which hatching of a light guide plate is omitted.

FIG. 7 is a sectional view of a liquid crystal display device according to a fifth embodiment of the present invention, in which hatching of a light guide plate is omitted.

FIG. 8 is a sectional view of a liquid crystal display device according to a sixth embodiment of the present invention, in which hatching of a light guide plate is omitted.

FIG. 9 is a sectional view showing a liquid crystal display device according to a seventh embodiment of the present invention, in which hatching of a light guide plate is omitted.

FIG. 10 is an enlarged cross-sectional view showing a modified example of the light source in the liquid crystal display device of the present invention.

[Explanation of symbols]

10 ... Liquid crystal display element 19a, 17b ... Polarizing plate 20 ... Reflecting means 21 ... Reflector 21a ... Inclined reflective surface 22, 23 ... Prism sheet 22a, 23a ... Prism 24 ... Reflective film 30, 30'30a, 30b ... Light guide plate 31 ... Adhesive 32 ... Light source

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-5-158033 (JP, A) JP-A-7-333606 (JP, A) JP-A-8-6016 (JP, A) JP-A-61-1 270731 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G02F 1/13357 F21V 8/00 601 G02F 1/1335 520

Claims (4)

(57) [Claims] 1. A pair of front and back substrates each having electrodes formed thereon.
A plate, a liquid crystal layer provided between the pair of front and back substrates,
A pair of front and back substrates that are affixed to the outside of each pair
A liquid crystal display device including a light plate and a reflection means provided on the back surface side; a light guide plate arranged on the front face of the liquid crystal display device; and a light source arranged so as to face at least one end face of the light guide plate. And the front surface of the light guide plate faces from the one end to the other end with respect to the back surface.
It is formed by tilting the
The light emitted from the light source , which is emitted from the back surface and is incident from the end surface, is inclined to form a back surface by reflection on the inner surface of the front surface.
The light emitted from the liquid crystal display element that is emitted from the surface side to enter the liquid crystal display element and from the back side is emitted to the front surface, and the reflecting means emits the light guide plate to the liquid crystal display element. A liquid crystal display device, characterized in that light incident from a direction inclined with respect to a direction vertical to the front surface is reflected toward a direction close to the vertical direction. 2. The liquid crystal display device according to claim 1, wherein the light guide plate is provided in a state where there is no space between the back surface of the light guide plate and the front surface of the liquid crystal display element. 3. The liquid crystal display device according to claim 1, wherein the reflecting means comprises a reflecting plate in which a plurality of inclined reflecting surfaces are continuous. 4. The liquid crystal display device according to claim 1, wherein the reflecting means comprises a prism sheet in which a plurality of prism portions are continuous, and a reflecting film provided on the back surface thereof. .