JPH11109350A - Backlight device and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress generation of optical loss, and secure necessary brightness without increasing of power consumption. SOLUTION: A backlight device 1 has a light source 2 for emitting light and a transparent light guide plate 4 for propagating the light from an incident end face therethrough, and a color separation element 5 is arranged on the incident end face of the light guide plate 4. Thus, the light emitted from the light source is color-separated through the color separation element 5 and enter into the inside of the light guide plate 4 from the incident end face of the light guide plate 4 the incident light is propagated into inside of the light guide plate 4 keeping the color-separated state and the light is emitted from the light exit face of the light guide plate 4. The liquid crystal display device 11 is made up by combining the backlight device 1 having the above composition with a liquid crystal element 12 controlled to change over scattering state to/ from transmitting state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a backlight device and a liquid crystal display device.

[0002]

2. Description of the Related Art In recent years, it has been proposed to use a liquid crystal display device called a dispersion type in constructing a direct-view display and the like. Such as a liquid crystal element in which a liquid crystal layer is sandwiched between a pair of substrates provided with electrodes for use in a liquid crystal display, that is, a polymer dispersed liquid crystal element in which a scattering state and a transmission state are controlled to be switched based on whether or not an electric field is applied. It is configured using a simple liquid crystal element. By the way, a backlight is not often used in such a method, but it is known that a backlight is used to obtain a bright display. However, the conventional T
Since sufficient contrast cannot be ensured by a backlight used in an N-type liquid crystal element, a method of arranging a light source on a side surface of a light guide plate and placing a black plate on a back surface is adopted.

[0003] Therefore, the backlight device at this time is provided with a light source for emitting light, and a transparent light guide plate, for example, acryl or the like, through which light incident from at least one incident end face facing the light source propagates inside. And a light guide plate in the form of a rectangular flat plate manufactured using the above method. When it is necessary to realize color display with a liquid crystal display device including such a backlight device and a liquid crystal element, an absorption type color filter is arranged between the liquid crystal element and the backlight device. Is done.

[0004]

However, the absorption type color filter used for realizing color display with the above-mentioned conventional liquid crystal display device is inevitable to cause a certain large light loss. As long as the absorption type color filter is disposed between the liquid crystal element and the backlight device, the transmittance of the liquid crystal element when it becomes transparent is reduced. In addition, when an absorption type color filter is used, the brightness of the display screen is reduced. Therefore, it is necessary to secure the brightness of the display screen, and the power consumption of the light source increases. I was

SUMMARY OF THE INVENTION The present invention has been made in view of these inconveniences, and it is possible to suppress the occurrence of light loss and to increase the required brightness of a display screen without increasing power consumption. It is an object of the present invention to provide a backlight device capable of ensuring high brightness and a liquid crystal display device configured using the backlight device.

[0006]

A backlight device according to the present invention comprises a light source for emitting light, and a transparent light guide plate through which light incident from an incident end surface propagates.
The light guide plate is characterized in that an element for color separation is arranged on an incident end face of the light guide plate. In the backlight device having such a configuration, since the color separation element is disposed on the incident end face of the light guide plate, the light emitted from the light source is subjected to color separation by the color separation element. The light enters the inside of the light guide plate from the incident end face of the light guide plate. become.

A liquid crystal display device according to the present invention is configured by combining a backlight device having the above configuration and a liquid crystal element whose switching between a scattering state and a transmission state is controlled. Therefore, it is possible to configure a liquid crystal display device capable of performing color display without using an absorption type color filter as in the related art, and to suppress the occurrence of light loss and to increase the required display screen without increasing power consumption. Brightness can be ensured.

[0008]

A backlight device according to a first aspect of the present invention includes a light source for emitting light, and a transparent light guide plate through which light incident from an incident end surface propagates. The light guide plate is characterized in that an element for color separation is arranged on the incident end face. A backlight device according to a second aspect of the present invention includes a light-parallelizing element that collimates light between a light source and a color-separating element included in the backlight device according to the first aspect. It is characterized by having.

A backlight device according to a third aspect of the present invention is characterized in that the color separating element according to the first or second aspect is an interference filter array. A backlight device according to claim 4 of the present invention is a mirror sequential color separation optical system element in which the color separation element of the backlight device according to claim 1 or 2 is configured using an interference filter. It is characterized by the following.

A backlight device according to a fifth aspect of the present invention includes a light source that emits light and a transparent light guide plate through which light incident from an incident end surface propagates. Characterized by having a light propagation region of The backlight device according to claim 6 of the present invention is:
Each of the light propagation regions of the light guide plate according to the fifth aspect is divided corresponding to each color separated by the color separation element.

A backlight device according to a seventh aspect of the present invention is the backlight device according to the sixth aspect, wherein the light guide plate of the backlight device comprises:
A step of laminating and joining resin sheets to be divided into light propagation regions corresponding to each color separated by the color separation element, and joining the obtained laminate along a direction coinciding with a lamination direction of the resin sheets. And a step of polishing the cut surface after cutting.

The liquid crystal display device according to claim 8 of the present invention,
The backlight device according to any one of claims 1 to 6 is combined with a liquid crystal element whose scattering state and transmission state are controlled to be switched. The liquid crystal display according to the ninth aspect of the present invention provides the liquid crystal display according to the eighth aspect.
The liquid crystal element included in the liquid crystal display device described in (1) is a polymer dispersion type liquid crystal element or a polymer network type liquid crystal element.

(Embodiment 1) FIG. 1 is a side view schematically showing a main part of a backlight device according to the present invention, FIG. 2 is a plan view thereof, and FIG. 3 is a simplified procedure of manufacturing a light guide plate. FIG. 4 is a plan view showing a modification of the color separation element. Note that reference numeral 1 in these figures indicates a backlight device.

Backlight device 1 according to the present embodiment
As shown in FIGS. 1 and 2, light incident from at least one incident end face of the fluorescent tube 2 functioning as a light source for emitting light and the fluorescent tube 2 surrounded by the light collector 3 is provided. It comprises a transparent light guide plate propagating inside, that is, a rectangular flat light guide plate 4 made of a transparent resin such as acrylic. An interference filter having an array shape functioning as a color separation element, that is, red (R), green (G), and blue (B), which are alternately and repeatedly arranged in parallel, are located immediately before the light incident surface of the light guide plate 4. An interference filter array 5 having three primary color portions is arranged, and each of the three primary color portions in the interference filter array 5 has the same size as a pixel pitch of a liquid crystal element described later.

When such an interference filter array 5 is arranged on the incident end face of the light guide plate 4, of the light emitted from the fluorescent tube 2, light other than a predetermined wavelength is used as an interference filter. Since the light is reflected by the array 5 toward the light source, no light loss occurs in principle. Although not shown, the other end surface of the light guide plate 4 at a position facing the incident end surface where the fluorescent tube 2 and the interference filter array 5 are arranged may be the same incident end surface. In the case of a configuration, the fluorescent tube 2 and the interference filter array 5 functioning as a light source are also arranged at positions facing the incident end face on the other side.

Further, between the fluorescent tube 2 as a light source and the interference filter array 5 as a color separating element, a prism sheet functioning as a light collimating element for collimating light, that is, in this case, A prism sheet 6 for parallelizing light along the width direction of the light guide plate 4 is interposed and disposed.
Then, the light emitted from the fluorescent tube 2 is
Are collimated while passing through, and pass through the interference filter array 5, and the light that has passed through the interference filter array 5 and has been color-separated enters the inside of the light guide plate 4 from the incident end face. . The light collimating element at this time is not limited to the prism sheet 6, and may be, for example, a collimating lens having a semicircular cross section.

Further, at this time, the light guide plate 4 has a multilayer structure including a plurality of light propagation regions 4a,... Corresponding to each color separated by the interference filter array 5, and has an acrylic sheet. Are provided between the light propagation regions 4a,... Corresponding to a single sheet or the like, and a reflection layer 4b made of an aluminum thin film for reflecting light. Therefore, the light incident from the incident end face of the light guide plate 4 propagates in each of the corresponding light propagation regions 4a while being color-separated from R, G, and B, and the light exit surface of the light guide plate 4 For example, from the surface, R, G, B
Then, light that is color-separated is emitted. In addition,
In this light guide plate 4, since the reflection layers 4b,... Are provided between the light propagation regions 4a,.
It is unlikely that light propagating inside each of these will enter another adjacent light propagation region 4a.

Therefore, when the backlight device 1 according to the present embodiment is used, it is not necessary to use an absorption type color filter which is indispensable in a conventional liquid crystal display device capable of color display. The liquid crystal display device capable of color display can be easily configured by combining the liquid crystal device 1 with a liquid crystal element. In this case, it is preferable that the thickness of each of the light propagation regions 4a,... Is equal to the pixel pitch of the liquid crystal element. It goes without saying that the thickness may be the same as the pixel pitch of the liquid crystal element. However,
When the thickness of each of the light propagation regions 4a,... And the pixel pitch of the liquid crystal element are the same, there is an advantage that the alignment margin is unnecessary.

Next, the procedure for manufacturing the light guide plate 4 will be described with reference to the process chart shown in FIG. First, FIG.
As shown in the figure, a large number of acrylic sheets 7 having a thickness of about 0.3 mm are prepared, and each acrylic sheet 7
After forming an aluminum thin film 8 by vapor deposition on one side of the above, several hundred to several thousand acrylic sheets 7 on which the aluminum thin film 8 is formed are laminated in a vacuum while being divided into a plurality of times. I do. Continuing with FIG.
As shown in (b), after these acrylic sheets 7 are joined while being pressed along the laminating direction, while the laminated body 9 integrated by the joining is arranged along the direction coinciding with the laminating direction of the acrylic sheets 7, Cutting is performed at predetermined thicknesses according to a cutting line X in the drawing.

As a result, as shown in FIG. 3 (c), an acrylic plate 10 having a rectangular flat plate shape was produced. When the cut surface of the acrylic plate 10 was polished,
This means that the light guide plate 4 constituting the backlight device 1 according to the present embodiment has been manufactured. In the acrylic plate 10 manufactured according to such a procedure, each of the acrylic sheets 7 corresponds to the light propagation region 4a of the light guide plate 4, and the aluminum thin film formed on one side of each acrylic sheet 7 Reference numeral 8 corresponds to the reflection layer 4b. That is, the light guide plate 4 is formed by laminating and joining the acrylic sheet 7 that becomes the light propagation region 4a divided corresponding to each color separated by the interference filter array 5, and the obtained laminate 9 It is manufactured through a process of cutting along the direction coinciding with the laminating direction of the acrylic sheet 7 and then polishing the cut surface.

In the present embodiment, the color separating element is the interference filter array 5, but the color separating element is not limited to the interference filter array 5. Color separation element as shown,
That is, it is also possible to use the mirror sequential color separation optical system element 11 configured using an interference filter. That is, the mirror-sequential color separation optical system element 11 includes a plurality of light transmission layers stacked and integrated with each other in a direction having an inclination angle of 45 degrees with respect to the transmission direction of the light emitted from the fluorescent tube 2. Have a multi-layer structure composed of the light transmitting layers 11a,.
13 and an internal reflection layer 14 made of an aluminum thin film are arranged in parallel while being alternately repeated.

In this case, the interference filter 12
Transmits only red (R) light and reflects green (G) and blue (B) light, and the interference filter 13 transmits only blue (B) light and reflects green (G) light. On the other hand, the internal reflection layer 14 reflects all light, and a light transmission layer opposed to the mirror-sequential type color separation optical system element 11 via the internal reflection layer 14 is provided on the light incident surface of the element 11. 11
An external reflection layer 15 made of an aluminum thin film which is formed so as to cover the surfaces of a,... and reflects light toward the light source is provided. The mirror sequential color separation optical system element 11 having such a configuration is manufactured according to the same procedure as that for manufacturing the light guide plate 4 having a multilayer structure.

Therefore, if the mirror-sequential color separation optical system element 11 having such a configuration is arranged immediately before the incident end face of the light guide plate 4, the light emitted from the fluorescent tube 2 is mirror-sequential. The color separation is performed by the color separation optical system element 11, and the red (R) light that has passed through the interference filter 12 propagates inside the light propagation region 4 a at the corresponding position of the light guide plate 4. . At this time, the green (G) light reflected by the interference filter 12 and also reflected by the interference filter 13 propagates inside the corresponding light propagation region 4a of the light guide plate 4,
Similarly, the blue (B) light that has passed through the interference filter 13 and has been reflected by the reflection layer 14 similarly propagates inside the light propagation region 4a provided at the corresponding position of 4.

Therefore, like the backlight device 1 in which the interference filter array 5 is arranged on the incident end face of the light guide plate 4, the backlight device 1 including the mirror sequential color separation optical system element 11 is also provided. From the light exit surface of the light guide plate 4, light that has been color-separated in advance into R, G, and B is emitted. Therefore, even when the backlight device 1 having such a configuration and the liquid crystal element are combined with each other, it is not necessary to use an absorption type color filter, and a liquid crystal display device capable of color display can be easily provided. Can be configured as follows.

(Embodiment 2) FIG. 5 is a simplified side view showing a main part of a liquid crystal display device according to the present invention. This liquid crystal display device uses the backlight device described in Embodiment 1. It is constituted by. In FIG. 5, reference numeral 11 denotes a liquid crystal display device, and reference numeral 12 denotes a liquid crystal element. In FIG. 5, parts and portions that are the same as those in FIGS. 1 and 2 are denoted by the same reference numerals.

The liquid crystal display device 11 according to the present embodiment
A liquid crystal element such as a polymer dispersed liquid crystal element in which a scattering state and a transmission state are controlled to be switched, that is, a composite 14 composed of a polymer and a liquid crystal is sandwiched between a pair of glass substrates 13 facing each other. The liquid crystal element 12 having a structure is disposed on the light emitting surface side of the backlight device 1, and the backlight device 1 and the liquid crystal element 12 have an adhesive, for example, a refractive index substantially equal to that of glass. The bonding is performed using an adhesive 15 such as silicon gel. Nothing is arranged on the back side of the light guide plate 4 included in the backlight device 1 here, and the back surface of the light guide plate 4 is in contact with air. In addition,
The fact that nothing is arranged on the back side of the light guide plate 4 is intended to increase the brightness of the display screen by external light, but a black plate (not shown) is arranged on the back side of the light guide plate 4. Needless to say, when a black plate is provided, the brightness is reduced while the black display is improved, and the contrast is improved.

The liquid crystal element 12 at this time is not limited to a polymer dispersed type liquid crystal element, but may be a polymer network type liquid crystal element or an IRIS type liquid crystal element (SI
D97 DIGEST page 1023). However, when a polymer dispersion type liquid crystal element or a polymer network type liquid crystal element capable of securing a sufficient scattering intensity is used as the liquid crystal side view 12, a sufficient contrast can be obtained. Also,
It is not always necessary to integrate the backlight device 1 and the liquid crystal element 12, but if they are joined with an adhesive 15 such as silicon gel, the interfacial reflection between them can be reduced. There is an advantage. Furthermore, although not shown, the backlight device 1 and the liquid crystal element 12 are not only joined with the adhesive 15 but also,
It is also possible to adopt a configuration in which the light guide plate 4 of the backlight device 1 is also used as one glass substrate 13 provided in the liquid crystal element 12.

In the liquid crystal display device 11 configured as described above, not only the display content can be visually recognized from the front surface side of the liquid crystal element 12 located on the upper side, but also in the related art, In spite of not using the essential absorption type color filter, color display is possible. That is, in the liquid crystal display device 11, the following operation is performed, and as a result, color display is possible. The configuration according to the present embodiment is effective when the liquid crystal element 12 has a large screen, and is effective when the dot pitch is large.

First, the liquid crystal element 12 included in the liquid crystal display device 11 is controlled to switch between a scattering state and a transmission state based on whether or not an electric field is applied. After that, the light propagates in a state where the light is confined together with the light guide plate 4 of the backlight device 1, so that the display screen cannot be visually recognized from outside the liquid crystal element 12 at this time. On the other hand, when a part of the liquid crystal element 12 is in a scattering state due to the application of an electric field, light propagating inside the light guide plate 4 provided in the backlight device 1 is also scattered. Bright spots are observed from the outside. And at this time,
Since each of these luminescent spots emits R, G, and B colors separated by the interference filter array 5 or the like, a color-displayed display screen can be visually recognized from outside the liquid crystal display device 11. Becomes

The liquid crystal element 12 included in the liquid crystal display device 11 according to the present embodiment has a structure in which a composite 14 composed of a polymer and a liquid crystal is sandwiched between a pair of glass substrates 13. When the thickness of the glass substrate 13 is large, the color may be blurred. Therefore, it is desirable that the thickness of the glass substrate 13 constituting the liquid crystal element 12 is thinner. When the thickness of the glass substrate 13 is 0.7 mm or less, color bleeding is not visually recognized. That is, the liquid crystal display device 11 according to the present embodiment
Now, the prism sheet 6 included in the backlight device 1 will be described.
It is considered that since the incident light is collimated, the color blur does not easily occur. It has been confirmed that when the light guide plate 4 of the backlight device 1 is also used as the glass substrate 13 of the liquid crystal element 12, color bleeding can be almost completely suppressed.

[0031]

As described above, in the backlight device according to the present invention, since the color separation element is disposed on the incident end face of the light guide plate, the light emitted from the light source is used for the color separation element. After being color-separated, the light enters the inside of the light guide plate from the incident end face of the light guide plate. The light is emitted from the light emission surface. Therefore, in a liquid crystal display device using this backlight device, color display can be easily performed without using an absorption type color filter, which is conventionally required, and it is possible to suppress the occurrence of light loss. In addition to this, it is possible to obtain an effect that required brightness of a display screen can be secured without increasing power consumption.

[Brief description of the drawings]

FIG. 1 is a simplified side view showing a main part of a backlight device according to the present invention.

FIG. 2 is a plan view thereof.

FIG. 3 is a process diagram showing a simplified procedure for manufacturing a light guide plate.

FIG. 4 is a plan view showing a modification of the color separation element.

FIG. 5 is a simplified side view showing a main part of the liquid crystal display device according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 backlight device 2 fluorescent tube (light source) 4 light guide plate 5 interference filter array (element for color separation) 11 liquid crystal display device 12 liquid crystal element

Claims (9)

[Claims] 1. A light source for emitting light, and a transparent light guide plate through which light incident from an incident end surface propagates inside, and a color separation element is arranged on the incident end surface of the light guide plate. A backlight device. 2. The backlight device according to claim 1, wherein a light collimating element for collimating light is disposed between the light source and the color separating element. apparatus. 3. The backlight device according to claim 1, wherein the color separation element is an interference filter array. 4. The backlight device according to claim 1, wherein the color separating element is a mirror sequential type color separating optical system element formed by using an interference filter. Backlight device. 5. A light source for emitting light, and a transparent light guide plate through which light incident from an incident end surface propagates, wherein the light guide plate has a plurality of light propagation regions. Backlight device characterized. 6. The backlight device according to claim 5, wherein each light propagation region of the light guide plate is divided corresponding to each color separated by the color separation element. Backlight device. 7. The backlight device according to claim 6, wherein the light guide plate is formed by laminating resin sheets to be light propagation regions divided corresponding to each color separated by the color separation element. A backlight device characterized by being produced through a joining step and a step of cutting the obtained laminate along a direction coinciding with the lamination direction of the resin sheet and polishing the cut surface. . 8. A liquid crystal display device comprising a combination of the backlight device according to claim 1 and a liquid crystal element whose scattering state and transmission state are controlled to be switched. . 9. The liquid crystal display device according to claim 8, wherein the liquid crystal element is a polymer dispersed liquid crystal element or a polymer network liquid crystal element.