JP3478784B2 - Optical element and display device provided with the optical element - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element applicable to large-screen color display and a display device using the optical element.

[0002]

2. Description of the Related Art Conventionally, a display device using a light guide plate and a liquid crystal has been known. As an example thereof, a light guide plate and a ferroelectric liquid crystal are used, and a display device which causes scattering in the liquid crystal layer by applying an AC electric field in the vicinity of the relaxation frequency of the Goldstone mode to the ferroelectric liquid crystal (for example,
JP-A-6-30543) and a display device using a light guide plate and polymer-dispersed liquid crystal (for example, see JP-A-6-347790).

However, in the display device disclosed in Japanese Unexamined Patent Publication No. 6-30543, it is necessary to apply an AC voltage, so that simple matrix driving and thin film transistor (TFT) are used.
There is a problem that it is not possible to perform bitmap display by active matrix driving such as driving.

Further, the display device disclosed in Japanese Patent Laid-Open No. 6-347790 has the following problems. That is, (1) it is difficult to use a TFT because a high voltage is required to drive the polymer dispersed liquid crystal. (2) Polymer-dispersed liquid crystals that operate at low voltage are not suitable for displaying moving images because of their slow response speed. (3) In a display device using a polymer dispersed liquid crystal, it is difficult to perform multiplexing by simple matrix driving because the driving voltage characteristic of scattering is not steep. That is, it is difficult to manufacture a transparent electrode for driving multiple pixels, and it is difficult to perform bitmap display. (4) It is difficult for a display device using polymer-dispersed liquid crystal to realize good color display as compared with monotone display.

Further, in any of the above-mentioned display devices, the light on the observer side is reflected by the reflection surface formed by the front surface or the back surface of the light guide plate (so-called reflection).
Therefore, there is a problem that display characteristics are deteriorated.

By the way, Japanese Patent Application Laid-Open No. 11-183902 discloses a display device which realizes a color display by using a light guide and a polymer dispersed liquid crystal. An example of the display device disclosed here is shown in FIG. The display device shown in FIG. 9 includes a color filter 2 on the front surface of the liquid crystal display 1, and a light absorber 5 on the back surface of the light guide 4 on which the illumination means 3 is provided. Is colored with a predetermined colored light. As can be seen from the figure, the liquid crystal display 1
Is a polymer-dispersed liquid crystal 6 and a transparent electrode 7 that holds the liquid crystal.
Two transparent substrates 8a and 8 on which a and 7b are respectively formed
b. The illumination means 3 is composed of a light source 9 and a reflection mirror 10. Note that reference numeral 11
Indicates a smoked film. The light incident from the end surface of the light guide body 4 is guided inside the transparent substrate 8b and the liquid crystal display 1,
The polymer dispersed liquid crystal 6 scatters at the image or character portion set in the scattering region (portion A in the figure), is converted into colored light by the color filter 2, and is emitted.

Further, in Japanese Patent Application Laid-Open No. 11-183902, as shown in FIG. 10, a liquid crystal display 1 (see FIG. 9).
There is also disclosed a display device in which an ultraviolet fluorescent glass 12 is provided on the surface of the liquid crystal display device and the ultraviolet light is emitted from the back surface of the liquid crystal display 1. Ultraviolet light 14 emitted from an ultraviolet lamp 13 provided on the back surface of the liquid crystal display 1 is a transparent region of the polymer dispersed liquid crystal (in the figure,
The image and the character portion set in (B portion) are transmitted, converted into a predetermined colored light 15 by the ultraviolet fluorescent glass 12, and emitted.

However, in the display device having such a structure, the liquid crystal display is provided on the upper surface (that is, the front surface when viewed from the observer) of the light guide plate. A transparent substrate must be used. Further, although polymer dispersed liquid crystal is used for the light control layer of the liquid crystal display, nothing is mentioned about means for avoiding the above-mentioned problems that are observed when the polymer dispersed liquid crystal is used. Therefore, when a polymer-dispersed liquid crystal is used in a display device that illuminates from the back surface, the liquid crystal display can be driven, but it has drawbacks such as a small number of pixels and a slow response speed, and high definition. It is not practical to use it as a display device that requires moving image display.

Therefore, in order to solve the above-mentioned conventional problems, a display device using a light guide plate and a polymer dispersed liquid crystal has been proposed by the present inventor (see Japanese Patent Application No. 11-212893). An example of the display device disclosed here is shown in FIG.
Shown in 1. As shown in FIG. 11, the optical element is provided on the lower surface of the translucent light guide plate 20 which guides light by entering the light from the end surface.
Translucent first electrode 21, light control layer 22, and reflection film 2
3, a light absorption film 24, a second electrode 25, and an insulating substrate 26 in this order. Further, the light control layer 22 is
It is made of a polymer-dispersed liquid crystal whose degree of scattering is changed by an electric field generated when a voltage is applied to the first electrode 21 and the second electrode 25. The light control layer 22 is
It is preferably composed of a reverse mode polymer dispersed liquid crystal formed by dispersing a low molecular weight liquid crystal in the liquid crystal polymer. Reverse mode polymer dispersed liquid crystal light control layer 22
Becomes a uniform birefringent thin film when no electric field is applied, and becomes a scattering state (A part in the figure) when an electric field is applied. In the optical element thus configured, active matrix driving becomes possible by dividing either the first electrode 21 or the second electrode 25 for each pixel unit. In the figure, reference numeral 27 indicates a light source and reference numeral 28 indicates a lens, which constitutes an illuminating means 29 in the display device.

FIG. 12 is a schematic plan view showing an example of a pixel electrode group in which an electrode is provided for each pixel unit and a voltage control means. The second electrode in the optical element having the configuration shown in FIG. This corresponds to a configuration in which 25 is provided for each pixel unit to be an active matrix drive type. As shown in FIG. 4, the electrodes provided for each pixel unit (indicated by a dotted line in the drawing), that is, the pixel electrodes 25 ', are provided with switching elements 30 for selectively applying a voltage to the electrodes. Further, signal electrodes 31 and scanning electrodes 32 are provided in a grid pattern so that a voltage can be independently applied to each switching element 30. By thus configuring the optical element and the display device using the optical element, the display device disclosed in Japanese Patent Application No. 11-212893 has an increased intensity of emitted light, improved display contrast, and scattering by external light. It is possible to improve display characteristics such as reduction of light and increase the screen size.

[0011]

However, in the conventional display device that takes out light from the light guide plate by utilizing the scattering and transmission characteristics of the light control layer, the scattering characteristic of the forward scattering is inevitable. Considering the display characteristics, it is desirable to make the scattering of the light control layer more isotropic, but in the conventional display device, the scattering characteristics should be closer to isotropic scattering while satisfying the conditions such as the drive voltage of the light control layer. Is practically difficult. As described above, in the conventional display device, since the forward scattering is large, the ratio of the emitted light emitted at a wide angle is large, and the scattering intensity in the front direction is relatively small (that is, at the wide angle). The brightness is bright and the brightness is dark on the front).

Therefore, an object of the present invention is to improve the viewing angle characteristics and the glare in a conventional display device, thereby providing an optical element having more excellent display characteristics and a display device using the optical element. Is to provide.

[0013]

DISCLOSURE OF THE INVENTION The inventors of the present invention have made earnest studies on a display device that overcomes the above-mentioned conventional problems, and as a result, the optical element disclosed in Japanese Patent Application No. 11-212893 by the inventors and It has been found that the display characteristics can be remarkably improved by taking advantage of the excellent characteristics of the display device and adding an improvement for making the light emitted outside the light guide region closer to isotropic scattering by the light control layer.

That is, the optical element according to the present invention has a translucent light guide plate for guiding the incident light from the end face to the light guide region, and an optical characteristic of the incident light provided below the light guide plate. a light control layer changing the electric field, at least a pair of electrodes to generate an electric field to the light control layer, the light
A reflection surface provided on the lower surface of the control layer for reflecting the incident light;
In the optical element that extracts the light from the upper surface of the light guide plate by changing the direction of light propagating in the light guide area by the light control layer, the light control layer is provided on the lower surface of the reflection surface by the light control layer. The wavelength conversion means for converting the light emitted to the outside into the light having a predetermined wavelength in the visible light region is provided.
It is characterized in that a light absorbing film is provided on the lower surface of the length converting means .

Further , the reflecting surface is a dielectric multilayer film.
Is preferred. Further, it is preferable that the reflection surface is a reflection film having direction selectivity.

The wavelength conversion means is preferably a phosphor that is excited by the light emitted outside the light guide region by the light control layer to emit fluorescence.

It is preferable that the wavelength conversion means is composed of phosphors which respectively emit red, green and blue fluorescences, and the phosphors are arranged in a grid pattern corresponding to the electrodes.

The incident light is preferably light having a wavelength in the ultraviolet range.

The light control layer is preferably composed of a polymer dispersed liquid crystal, and the polymer dispersed liquid crystal is preferably composed of a composite of a polymer liquid crystal and a low molecular weight liquid crystal.

A display device according to the present invention is characterized by including an optical element and an illuminating means for making light incident on the optical element, and using any one of the above-mentioned optical elements as the optical element.

It is preferable that the illumination means has a light source that emits light having a wavelength in the ultraviolet range.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION An optical element according to the present invention is an optical element that extracts the light from the upper surface of a light guide plate by changing the direction of light propagating in a light guide region by a light control layer, and A light-transmitting light guide plate for guiding the light to the light guide region, a light control layer provided below the light guide plate for changing the optical characteristics of the incident light by an electric field, and generating an electric field in the light control layer. At least one pair of electrodes, a reflection surface that reflects the incident light, and a wavelength conversion unit that converts the light emitted outside the light guide region by the light control layer into light having a predetermined wavelength in the visible light region. At least.

The wavelength conversion means may be installed at any place,
In order to perform wavelength conversion efficiently, it is preferable to provide the light guide plate on the upper surface (front surface as viewed by an observer) or on the lower surface of the reflection surface. When the wavelength conversion means is provided on the upper surface of the light guide plate, a layer (for example, a dielectric multilayer film) having a refractive index lower than that of the light guide plate is inserted and bonded between the wavelength conversion means and the light guide plate. Or simply bond the two together through a gap.

Here, the term "wavelength conversion means" means, in a broad sense, a means for converting the wavelength of light into another wavelength. In the present invention, however, the emitted light component of the display device, that is, the light control layer is used. It means a unit capable of converting light emitted outside the light guide region into light having a predetermined wavelength in the visible light region. More specifically, the one that converts emitted light components such as ultraviolet rays into fluorescence having an isotropic scattering characteristic is shown. Therefore, in the present invention, the wavelength conversion means is preferably made of a phosphor that emits fluorescence when excited by the emitted light component emitted outside the light guide region by the light control layer. By providing such an optical element with such wavelength conversion means, it is possible to improve the conventional viewing angle characteristics such that the brightness is bright at a wide angle and the brightness is dark at the front. Also,
By using phosphors that respectively emit red (R), green (G), and blue (B) fluorescence as the wavelength conversion means, good color display can be realized.

It is preferable that the phosphor is efficiently excited by the emitted light component to exhibit isotropic bright light emission, and the brightness does not decrease even when used for a long time. The use form of these is not particularly limited, but for example, as a translucent film containing a phosphor or coated with a phosphor (hereinafter, also referred to as a fluorescent film), or by coating the phosphor itself. Can be used. Examples of suitable phosphors include R manufactured by EXCITON.
HODAMINE640 (red), COUMARIN5
40A (green), COUMERIN 460 (blue), and the like.

The optical element of the present invention configured as described above is characterized in that the optical element for extracting the emitted light component from the upper surface (front surface) of the light guide plate is provided with the wavelength conversion means, and other configurations are provided. However, the main constituent members will be briefly described below.

For the "light guide plate", for example, ITO having excellent conductivity, transparency and workability can be used. This ITO is well known in the field of liquid crystal display devices. As described above, the optical element according to the present invention is characterized in that the emitted light component is extracted from the upper surface (front surface) of the light guide plate, so that the light guide plate is arranged on the front surface as viewed by the observer. Therefore, if a relatively strong light guide plate is used, the liquid crystal display device can be protected from external impact, and the reliability of the display device can be improved.

The "light control layer" is composed of a material whose optical characteristics such as diffractive power or scattering power are changed by an external field such as an electric field or a magnetic field. Polymer dispersed liquid crystal is mentioned as one of the suitable materials which comprise a light control layer.

The term "polymer dispersed liquid crystal" as used herein refers to an overall thin film composed of a polymer resin and a liquid crystal, and the polymer resin having liquid crystal droplets distributed in the polymer resin forms a continuous region. It may be a let type, a polymer ball type in which both the polymer resin and the liquid crystal are continuous regions, or a resin region in which liquid crystal particles are dispersed in the liquid crystal may be discontinuous.

Suitable polymer-dispersed liquid crystals used in the light control layer include, for example, nematic liquid crystals, smectic liquid crystals, cholesteric liquid crystals, host-guest liquid crystals, and the like, but generally thin films whose optical characteristics change depending on the external field. Can be used. For example, when a voltage is applied to the electrodes to generate an electric field in the light control layer to change the optical characteristics, the light control layer made of a general polymer dispersed liquid crystal scatters light when no electric field is applied. , Transmits light when an electric field is applied.

On the other hand, the light control layer can also be formed by using a reverse mode polymer dispersed liquid crystal that exhibits an operation contradictory to the above polymer dispersed liquid crystal. The reverse mode polymer dispersed liquid crystal refers to a thin film in which a low molecular weight liquid crystal is dispersed in a liquid crystalline polymer, for example, liquid crystal such as E-7 (manufactured by Merck Japan Ltd.) and, for example, UCL002 (Dainippon Ink and Chemicals Co., Ltd.). )
It can be produced by irradiating a mixture composed of a liquid crystal monomer such as that manufactured by the manufacturer) with ultraviolet rays to polymerize the liquid crystal monomer.

The reverse mode polymer dispersed liquid crystal becomes a film having a uniform refractive index distribution because the liquid crystalline polymer and the low molecular liquid crystal have birefringence when no electric field is applied,
When an electric field is applied, the low-molecular liquid crystal is oriented by the electric field and a difference in refractive index with the liquid crystalline polymer occurs. That is, the light control layer made of reverse mode polymer dispersed liquid crystal transmits light when no electric field is applied and scatters light when an electric field is applied. In the transmissive state of the light control layer, since scattering does not occur when viewed from any direction, it is possible to perform a display with excellent viewing angle characteristics and high contrast even from an oblique direction. As described above, in the reverse mode polymer dispersed liquid crystal, it is necessary to align the liquid crystalline polymer with the low molecular dispersed liquid crystal, and therefore, an alignment film is provided so as to sandwich the liquid crystal layer to align the alignment direction of the liquid crystal molecules. Is preferred.

The response characteristic of the reverse mode polymer dispersed liquid crystal is inverted from the response characteristic of general polymer dispersed liquid crystal. Therefore, it is possible to prevent light emission from the gap between the electrodes, which is seen when the electrodes are divided in an optical element using a general polymer-dispersed liquid crystal for the light control layer, and to display with high contrast. Further, in the scattering state of the optical element using the reverse mode polymer dispersed liquid crystal, the scattering in the optical axis direction is small, and the scattering in the direction perpendicular to the optical axis direction is large. Therefore, when applying such an optical element to a display screen, an efficient display in which the user's line of sight and the optical axis direction are perpendicular to each other is provided to have directivity in the direction of the user. The device can be realized.

For details of the reverse mode polymer-dispersed liquid crystal, see Technical Report IDY 96-50, pages 137 to 142, by the Akita, Sato et al.

The thickness of the light control layer configured as described above is not particularly limited and can be changed according to the desired optical characteristics. However, the thickness of the light control layer must be uniform throughout. In order to obtain a uniform light control layer, it goes without saying that a transparent substrate with a smooth surface is used, but the polymer-dispersed liquid crystal that constitutes the light control layer contains microspheres of uniform particle size as spacers. May be. Such spacers are well known in the art.

The "electrode" is not particularly limited as long as an electric field can be generated in the light control layer by applying a voltage to the electrode. In order to allow the light to be extracted from the desired position of the optical element, the electrodes are generally divided into a plurality in any form. A light absorption film may be provided in order to reduce light emission between the electrode and the divided electrodes. Further, as described above, by forming the light control layer using the reverse mode polymer dispersed liquid crystal, it is possible to remarkably improve the light emission between the electrodes.

By the way, as described above, the optical element according to the present invention has a structure for extracting light from the upper surface (front surface) of the light guide plate. In such an optical element, the electrodes and substrate on the back surface side (driving electrode and driving substrate) are not always required.
Need not be transparent. Therefore, it is possible to use a printed wiring board or the like on which electrodes and the like can be easily mounted. As a result, it is possible to take out the electrode on the back surface via the through electrode or the like, and it is not necessary to take out the wiring from the end face of the optical element. Further, a bitmap display can be realized by mounting a driving electronic circuit on the back surface through the through electrode. Furthermore, a plurality of drive substrates can be arranged in a tile shape, which facilitates size increase. The details of the through electrode and the back electrode will be described later.

The "reflecting surface" is for specularly reflecting the light propagating in the light guide region, and is, for example, a film made of a metal such as aluminum, a dielectric multilayer film, or light transmitted through a light guide plate. The optical element is separately provided with a reflective film (for example, a low-refractive index single-layer film) having a direction selectivity that does not totally reflect light. As another aspect, the electrode may be made of a material that specularly reflects light, and the electrode itself may be used as a reflecting surface to simplify the optical element. It is also possible to prevent the user from seeing the reflecting surface by providing a light absorbing film on either the upper surface or the lower surface of the reflecting surface.

When the dielectric multilayer film is used as the reflecting surface, the guided light can be reflected and the other light can be transmitted by changing the thickness of the dielectric multilayer film. The reflection of is not visible from the outside, and good characteristics can be realized. Further, since the dielectric multilayer film has no electrical conductivity, it can reflect light without disturbing the electric field.

Next, a display device to which the optical element according to the present invention is applied will be described. FIG. 1 is a side sectional view schematically showing an example of a display device according to the present invention. The display device shown in FIG. 1 is roughly composed of an optical element and an illuminating means. The optical element includes a light guide plate 100 and the light guide plate 10
0, the transparent electrode 102 provided on the lower surface of the transparent electrode 101 via the transparent substrate 101, the light control layer 103 provided on the lower surface of the transparent electrode 102, and the reflection surface 104 provided on the lower surface of the light control layer 103. A light absorbing film 105 provided on the lower surface of the reflecting surface 104, a plurality of electrodes 106 provided on the lower surface of the light absorbing film 105, spaced apart from each other and arranged in parallel, and provided on the lower surface of the electrode 106. Substrate 107, and wavelength conversion means 108 on the upper surface of the light guide plate 100 with a gap therebetween.
Have and. Here, the light control layer 103 is made of reverse mode polymer dispersed liquid crystal, the reflection surface 104 is made of a dielectric multilayer film, and the wavelength conversion means 108 is made of a fluorescent film. The light control layer 103 made of reverse mode polymer dispersed liquid crystal is provided with an alignment film (indicated by a thick line in the drawing) so as to sandwich the light control layer.

FIG. 2 is a plan view schematically showing an example of the fluorescent film which serves as the wavelength converting means. As shown in FIG. 2, the wavelength conversion means is configured by arranging fluorescent films each containing red (R), green (G), and blue (B) phosphors in a grid pattern. In the figure, reference numeral 200 indicates one pixel unit, and the divided electrodes (pixel electrodes) are arranged so as to correspond to each pixel unit. By providing such wavelength conversion means on the upper surface of the light guide plate or the lower surface of the reflection surface and controlling the application of voltage to the electrodes, good color display can be realized.

Since the display device shown in FIG. 1 has the reflecting surface 104 on the upper surface of the electrode 106, the light guided through the light guide plate 100 is reflected before reaching the electrode 106 and the electrode 10
The light absorption by 6 and the light loss by the electrode end can be reduced.

In order to simplify the structure of the optical element body, the light guide plate 100 and the transparent substrate 101 may be integrated. Further, the lower electrode 106 may be made of a material that specularly reflects, and may also serve as a reflecting surface. Further, by polishing the end faces of the entire light guide plate to be smooth and further providing the reflection film 109 on these end faces except the part where the light is incident, the light confining property in the light guide plate can be improved.

The wiring for driving the optical element is optional, but in the optical element according to the present invention, the lower electrode 10 is used.
Since it is not necessary to make 6 and the substrate 107 transparent, it becomes possible to apply a high voltage from the back electrode 111 via the through electrode 110 as shown in the figure. The through electrode 110 is formed by forming a fine hole penetrating the substrate 107 and filling the inside of the hole with a conductive material such as metal, and the electrode 106 and the back electrode 111 have a one-to-one relationship. Connect electrically. A drive circuit can be mounted on each of the back electrodes 111 or collectively on the plurality of back electrodes 111 to control the voltage application.

The illuminating means is for allowing light to enter from the end surface of the light guide plate, and is provided on the end surface of the light guide plate 100. In the display device shown in FIG.
Is the light source 113 of the cold cathode fluorescent lamp and the light source 113.
And a lens 114 for condensing the light from the end face on the end face. As another aspect, the illuminating means may be composed of a light source and a reflecting plate surrounding the light source. In the display device shown in FIG. 1, the illuminating means is provided at one end of the light guide plate, but the illuminating means may be provided at both ends of the light guide plate. As described above, the illumination unit is not particularly limited as long as it can efficiently enter light.

The light incident from the end face of the light guide plate by the illuminating means is not particularly limited, but it is preferable that the fluorescent material as the wavelength converting means can be efficiently excited. For example, ultraviolet light, visible light having a specific wavelength,
Infrared light or the like can be used as incident light, but ultraviolet light is the most practical. It is not particularly limited as long as it is a light source that emits ultraviolet rays, for example, a metal halide lamp,
Cold cathode fluorescent lamps, ultraviolet LEDs, etc. can be used as the light source. It will be easily understood by those skilled in the art that the wavelength can be efficiently converted by appropriately selecting the phosphor serving as the wavelength converting means according to the type of incident light.

Next, the operation of the display device configured as described above will be briefly described with reference to FIG.

Although the directions of the light incident on the light guide plate 100 are various, attention is paid to the incident light in a certain specific direction, which is indicated by an arrow in the figure. When the light control layer 103 is formed by using the reverse mode polymer dispersed liquid crystal, the light control layer 103 is usually in a transmissive state. Therefore, unless a voltage is applied between the electrodes facing each other, the light guided through the light guide plate 100 is emitted from the light guide plate 10.
0 and the light control layer 103 are confined in the light guide region. On the other hand, when a voltage is applied between the electrodes facing each other to generate an electric field in the light control layer, the light control layer becomes in a transmissive state. Therefore, the light guided through the light guide plate 100 is scattered and emitted from the upper surface (front surface) of the light guide plate.

That is, when the voltage is applied only to the electrode 106 ', only the light control layer corresponding to the electrode to which the voltage is applied is in the scattering state, and the other regions are all in the transparent state. Therefore, the incident light is guided by being reflected by the reflection surface 104, and propagates in the light guide region as long as the light control layer is transparent. Then, the propagation direction is changed by reaching and scattering the polymer dispersed liquid crystal region in the scattering state,
Generate an outgoing light component. In the display device shown in FIG. 1, the light extraction position is controlled by dividing one of the electrodes sandwiching the light control layer 103, but the electrode division method is arbitrary. For example, the electrodes may be divided into strips or display pixel units.

In the display device shown in FIG. 1, a fluorescent film is provided as the wavelength conversion means 108 on the upper surface of the light guide plate 100 (the front surface when viewed from the observer). When light such as ultraviolet rays propagating through the light guide plate is emitted from the light guide plate by changing the direction of the light in the light control layer, most of the light has a strong tendency to be emitted at an angle close to the light guide plate. As a result, the display characteristics have large viewing angle dependency and low front luminance. However, in the present invention, by providing the optical element with a wavelength conversion means such as a fluorescent film, it is possible to convert the emitted light component from the light guide plate into fluorescence in the visible light region having isotropic scattering characteristics.
Thus, by converting the emitted light component into fluorescence in the visible light region that exhibits isotropic emission, it is possible to realize a good display device that does not depend on the viewing angle and has uniform brightness and contrast in a wide range. You can

By the way, Japanese Patent Application No. Hei 11 by the present inventors
No. 212893 discloses various optical elements and display devices each composed of a light guide plate and polymer dispersed liquid crystal. It will be easily understood by those skilled in the art that the wavelength conversion means of the present invention can be applied to those optical elements and display devices and similar effects can be obtained.

The embodiments of the display device according to the present invention will be described below in more detail by way of examples, but these do not limit the present invention. Therefore, it is needless to say that the present invention is not limited to the embodiments described below and can be variously modified without departing from the scope of the invention.

(Embodiment 1) FIG. 3 is a side sectional view schematically showing a display device according to this embodiment. The display device according to the present embodiment has substantially the same structure as the display device of FIG. 1 described above, but is different in the following points. That is,
The illuminating means 112 is a light source 113 of an ultraviolet LED and the light source 1
The light-guiding means 112 is provided on both end surfaces of the light guide plate 100. Further, in the optical element, the lower surface of the light control layer is divided for each substrate and arranged in a tile shape.

As shown in FIG. 3, the optical element applied to the display device is the same as in FIG. 1, and the light guide plate 100 and the transparent electrode 102 provided on the lower surface of the light guide plate 100 via the transparent substrate 101. And the light control layer 103 provided on the lower surface of the transparent electrode 102 are integrated. However, in this embodiment, the lower surface of the light control layer 103 has a structure in which each of the divided substrates is laminated. Further, wiring is taken out from each electrode 106 through the substrate, and wiring is further collected using the multilayer substrate 300.

The display device of this embodiment can be manufactured as follows.

First, a glass substrate 7059 (cornin)
I will be a light guide plate by sputtering etc. on top of g company (USA) I
A TO film is formed. Lattice-shaped electrodes are arranged on another substrate, wirings are taken out from each electrode through the substrate, and wiring is further collected using a multilayer substrate and a drive circuit is mounted on the back surface. A black resist is applied to the opposite surface to form a light absorbing film, and a dielectric multilayer film is further vapor-deposited to form a reflecting surface.

Next, a liquid crystal of E-7 (manufactured by Merck Japan Co., Ltd.) containing microspheres having a diameter of, for example, about 50 microns and a liquid crystal monomer UCL002 (manufactured by Dainippon Ink Co., Ltd.) on a glass substrate. A mixture containing and is applied, and a substrate having a drive circuit mounted on the back surface is closely adhered on the mixture.
The mixture of the liquid crystal and the liquid crystal monomer sandwiched between the glass substrate and the substrate on which the driving circuit is mounted in this way is exposed to ultraviolet rays from the glass substrate side to produce a light control layer of reverse mode polymer dispersed liquid crystal. The surfaces of the transparent electrode and the dielectric multilayer film that sandwich the light control layer between the upper and lower sides are subjected to an alignment treatment in advance. The light guide plate is brought into close contact with the laminated body thus obtained. Finally, a slight gap is provided on the surface of the other substrate (surface of the light guide plate), and the film coated with the phosphor is arranged. In this embodiment, the gap is provided between the wavelength conversion means and the light guide plate, but a layer having a refractive index lower than that of the light guide plate is inserted between the wavelength conversion means and the light guide plate. Good.

The operation of the display device thus configured is as described above. In the region corresponding to the electrode 106 ′ to which the voltage is applied, the reverse mode polymer dispersed liquid crystal is in a scattering state, so that the ultraviolet rays propagating through the light guide plate are emitted from the light guide plate and illuminate the fluorescent film 108. . When the fluorescent film 108 serving as the wavelength conversion unit is irradiated with the light component emitted from the light guide plate 100, the phosphor of the fluorescent film is excited to emit fluorescence in the visible light region. Since the fluorescence from the fluorescent film is isotropic, there is no dependence on the viewing angle, and it is possible to realize good display characteristics without unevenness in brightness and contrast over a wide range. Further, color display can be realized by using a fluorescent film composed of three color phosphors of red, green and blue as shown in FIG. 2 as the wavelength converting means. Further, the light absorption film 105 provided on the lower surface of the reflection surface 104.
Since it is possible to suppress glare, it is possible to suppress deterioration of contrast even in a dark room.

In this embodiment, the case where the substrate (driving substrate) 107 used for driving is exemplarily divided into two is illustrated, but the division type can be changed as necessary. Further, by using an adhesive polymer dispersed liquid crystal such as a reverse mode polymer dispersed liquid crystal as the light control layer, it is possible to arrange the divided drive substrates by adhering them in a tile shape. By thus adhering and arranging in a tile shape, the drive substrate is fixed and is unlikely to shift. In addition, the seams can be hidden by sharing the light guide plate when increasing the screen size.

(Embodiment 2) FIG. 4 is a side sectional view showing a display device according to this embodiment. The optical element applied to the display device according to the present embodiment is provided with a light guide plate 100, a transparent electrode 102 provided on the lower surface of the light guide plate 100 via a transparent substrate 101, and a lower surface of the transparent electrode 102. And a plurality of electrodes 10 provided on the lower surface of the light control layer 103, spaced apart from each other and arranged in parallel.
6, a substrate 107 provided on the lower surface of the electrode 106,
The reflecting surface 104 provided on the lower surface of the substrate and the reflecting surface 1
The light absorbing film 105 provided on the lower surface of 04, and the wavelength converting means 108 on the upper surface of the light guide plate 100 with a gap.
Have and. Here, the light control layer 103 is made of reverse mode polymer dispersed liquid crystal, the reflecting surface 104 is made of a dielectric multilayer film, and the wavelength converting means 108 is made of a fluorescent film provided on the upper surface of the light guide plate. An alignment film (indicated by a thick line in the figure) is provided so as to sandwich the light control layer 103 made of reverse mode polymer dispersed liquid crystal.

The illumination means 112 applied to the display device according to this embodiment is a light source 113 into which ultraviolet rays are introduced from the metal halide lamp 400 via the optical fiber 401.
And a reflection film 115 surrounding the light source 113, and such an illumination means 112 is provided at one end of the light guide plate.

The display device of this embodiment can be manufactured as follows.

First, a glass substrate 7059 (cornin)
I will be a light guide plate by sputtering etc. on top of g company (USA) I
A TO film is formed. Using this substrate and another substrate, a liquid crystal of E-7 (manufactured by Merck Japan Ltd.) containing, for example, microspheres having a diameter of about 50 microns and a liquid crystal monomer UCL002 (Dainippon Ink and Chemicals Co., Ltd. The liquid crystal monomer is polymerized by sandwiching a mixture containing a) and) and further exposing to ultraviolet light. In this way, the light control layer of the reverse mode polymer dispersed liquid crystal composed of the composite of the polymer liquid crystal and the low molecular liquid crystal is prepared. The surface of each transparent electrode sandwiching the light control layer between the upper and lower sides is subjected to an alignment treatment in advance. Then, a reflective surface is formed by depositing a dielectric multilayer film on the surface of one of the substrates. Further, a light absorbing film is formed by applying, for example, a black resist on the multilayer film obtained as described above. Finally, a slight gap is provided on the surface of the other substrate (surface of the light guide plate), and the film coated with the phosphor is arranged. In this embodiment, the gap is provided between the wavelength conversion means and the light guide plate, but a layer having a refractive index lower than that of the light guide plate is inserted between the wavelength conversion means and the light guide plate. Good.

Wiring (see FIG. 1) is applied to the display device constructed as described above, and ultraviolet rays are incident from the light guide plate.
In the region corresponding to the electrode 106 ′ to which the voltage is applied, the reverse mode polymer dispersed liquid crystal is in a scattering state, so that the ultraviolet rays propagating through the light guide plate are emitted from the light guide plate and illuminate the fluorescent film 108. . When the fluorescent film 108 is irradiated with ultraviolet rays, the phosphor emits isotropic fluorescence in the visible light region. As described above, by converting the ultraviolet rays emitted at an angle close to the light guide plate into fluorescent light that isotropically scatters, there is no viewing angle dependency and there is no unevenness in brightness and contrast over a wide range, and good display characteristics. Can be realized. Further, as a wavelength conversion means, FIG.
Color display can be realized by using a fluorescent film composed of three color phosphors of red, green and blue as shown in FIG. Further, the light absorption layer provided on the lower surface of the substrate can suppress the reflection of light and can prevent the deterioration of the contrast even in a dark room.

(Embodiment 3) FIG. 5 is a side sectional view showing a display device according to this embodiment. The optical element applied to the display device according to the present embodiment is substantially the same as the optical element applied to the display device of the second embodiment, except that the reflecting surface 104 is formed of an aluminum film deposited on the substrate. Composed. Here, the light control layer 103 is composed of a normal mode polymer dispersed liquid crystal, and the wavelength conversion means 108 is composed of a fluorescent film provided on the upper surface of the light guide plate 100 with a gap.

In the display device according to this embodiment, the illumination means 112 is the light source 113 of the cold cathode fluorescent lamp.
And a reflection film 115 surrounding the light source 113, and such illuminating means 112 is provided on both end surfaces of the light guide plate 100.

The display device of this embodiment can be manufactured as follows.

First, the glass substrate 7059 (cornin)
An ITO film to be a light guide plate is formed on the g company (USA) by sputtering or the like. Using this substrate and another substrate, a liquid crystal of E-7 (manufactured by Merck Japan KK) containing microspheres with a diameter of about 20 microns and NOA
-63 (Norland Products, Inc.
(US) and a UV-curable resin, and a mixture is exposed to UV light. In this way, a polymer-dispersed liquid crystal light control layer having a thickness equal to the diameter of the microspheres is prepared.

Next, a reflecting surface is formed by evaporating aluminum on the surface of one of the substrates. In addition, a film coated with the phosphor is placed with a slight gap provided on the surface of the other substrate (the surface of the light guide plate). Although the gap is provided between the wavelength conversion means and the light guide plate here, a layer having a refractive index lower than that of the light guide plate may be inserted between the wavelength conversion means and the light guide plate. .

Since the display device constructed as described above uses a general polymer dispersed liquid crystal as the light control layer, it has a response characteristic different from that of the display device using the reverse mode polymer dispersed liquid crystal described above. Invert. That is, when wiring (see FIG. 1) is applied to the display device of this embodiment and ultraviolet rays are incident from the light guide plate, the light control layer 103 is scattered in the region corresponding to the electrode 106 ′ to which no voltage is applied. The ultraviolet light propagating in the adjacent light guide plate is emitted from the light guide plate and illuminates the fluorescent film 108. When the fluorescent film 108 is irradiated with ultraviolet rays, the phosphor emits isotropic fluorescence in the visible light region. As described above, by converting the ultraviolet rays emitted at an angle close to the light guide plate into fluorescent light that isotropically scatters, there is no viewing angle dependency and there is no unevenness in brightness and contrast in a wide range, and a good display is obtained. It becomes possible to realize the characteristics. Further, color display can be realized by using a fluorescent film composed of three color phosphors of red, green and blue as shown in FIG. 2 as the wavelength converting means. Further, by forming an electrode from a material capable of specular reflection and also serving as the reflection surface 104, the optical element applied to the display device can be simplified.

As described above, in Examples 1 to 3, the display device having the wavelength conversion means on the upper surface (front surface) of the light guide plate was illustrated, but the same effect can be obtained when the wavelength conversion means is provided on the lower surface of the reflection surface. To be Such a display device will be exemplified in the following examples.

(Embodiment 4) FIG. 6 is a side sectional view showing a display device according to this embodiment. The optical element applied to the display device according to the present embodiment is configured in substantially the same manner as the optical element applied to the display device of FIG. 1 except that the wavelength conversion means is provided on the lower surface of the reflecting surface. It Here, the light control layer is made of a reverse mode polymer dispersed liquid crystal, the reflection surface is made of a dielectric multilayer film, and the wavelength conversion means is made of a phosphor coated on the lower surface of the reflection surface. An alignment film (indicated by a thick line in the figure) is provided so as to sandwich the light control layer 103 made of reverse mode polymer dispersed liquid crystal.

In the display device according to the present embodiment, the illumination means 112 has a light source 113 into which ultraviolet rays are introduced from the metal halide lamp 400 via the optical fiber 401.
And a reflective film 115 surrounding the light source 113, and such an illuminating means is provided at one end of the light guide plate.

The display device of this embodiment can be manufactured as follows.

First, a glass substrate 7059 (cornin)
I will be a light guide plate by sputtering etc. on top of g company (USA) I
A TO film is formed. Using this substrate and another substrate, E containing microspheres with a diameter of about 50 microns
A mixture of a liquid crystal such as -7 (manufactured by Merck Japan Ltd.) and a liquid crystal monomer UCL002 (manufactured by Dainippon Ink and Chemicals) is sandwiched and further exposed to ultraviolet light to polymerize the liquid crystal monomer. In this way, the light control layer of the reverse mode polymer dispersed liquid crystal composed of the composite of the polymer liquid crystal and the low molecular liquid crystal is prepared. The surfaces of the transparent electrodes and the dielectric multilayer film that sandwich the light control layer between the upper and lower sides are subjected to an alignment treatment in advance.

Next, after forming an electrode on the surface of one of the substrates, a light absorbing film is formed by applying a black resist, for example. Further, after coating a phosphor on the surface of the light absorption film, a dielectric multilayer film is deposited to form a reflection surface.
Finally, an irradiation unit having a light source connected to the metal halide lamp via an optical fiber is provided at one end of the light guide plate.

Wiring (see FIG. 1) is applied to the display device thus constructed, and when ultraviolet rays are incident from the light guide plate, the reverse mode polymer dispersion in the region corresponding to the electrode 106 'to which the voltage is applied. The liquid crystal is in a scattering state, and the ultraviolet rays propagating in the light guide region leak to the lower surface of the reflecting surface. The ultraviolet light leaking from the light guiding region is converted into fluorescent light in the visible light region by the phosphor provided on the lower surface of the reflecting surface. That is, the ultraviolet light leaking from the reflecting surface irradiates the phosphor, and the phosphor is excited to generate fluorescence. The fluorescence thus generated reaches the outside of the display device via the light guide plate.

As described above, by converting the ultraviolet rays propagating through the light guide region into fluorescent light that isotropically scatters and emits the fluorescent light, there is no dependence on the viewing angle, and there is no unevenness in brightness and contrast in a wide range. Therefore, it becomes possible to realize good display characteristics. Further, as a wavelength conversion means, FIG.
Color display can be realized by using a fluorescent film composed of three color phosphors of red, green and blue as shown in FIG. Further, the light absorption layer provided on the back surface of the substrate makes it possible to suppress glare, and it is possible to suppress deterioration of contrast even in a dark room.

(Embodiment 5) FIG. 7 is a side sectional view showing a display device according to this embodiment. The optical element applied to the display device according to the present embodiment includes a light guide plate 100, a light control layer 103 provided on the lower surface of the light guide plate 100 via a transparent substrate 101, and a light control layer 103 on the lower surface of the light control layer 103. The reflecting surface 104 provided, the wavelength converting means 108 provided on the lower surface of the reflecting surface 104, the light absorbing film 105 provided on the lower surface of the wavelength converting means 108, and the lower surface of the light absorbing film 105. A plurality of electrodes 700a forming a pair for each divided unit
And 700b, and a substrate 107 provided on the lower surfaces of the electrodes 700a and 700b. The electrodes used in this embodiment are electrodes forming a pair on the same plane for each pixel unit, and when a voltage is applied to them, an electric field is generated in the in-plane direction.

As an example of such an electrode, FIG. 8 shows comb-shaped electrodes 800a and 800b provided in one pixel. In the figure, reference numeral 801 indicates a through electrode penetrating the substrate 107 and connected to the electrodes 800a and 800b, respectively. By providing the back electrode via the penetrating electrode 801, back driving can be realized. In addition, such a comb-shaped electrode can be easily manufactured by uniformly vapor-depositing an electrode such as aluminum on a substrate and patterning it according to a photolithography method.

Here, the light control layer is made of a reverse mode polymer dispersed liquid crystal, the reflecting surface is made of a dielectric multilayer film, and the wavelength converting means is made of a phosphor coated on the lower surface of the reflecting surface.

In the display device according to this embodiment, the illumination means 112 is the light source 113 of the cold cathode fluorescent lamp.
And a reflective film 115 surrounding the light source 113, and such illuminating means are provided on both end surfaces of the light guide plate.

The display device of this embodiment can be manufactured as follows.

First, the orientation-treated 7059 (cor) was used.
liquid crystal E-7 (Merck Japan Ltd.) containing microspheres with a diameter of about 50 μm using a glass substrate such as Ning Co. (USA) and a substrate on which electrodes paired on the same plane are formed. )) And a liquid crystal monomer UCL002 (manufactured by Dainippon Ink and Chemicals, Inc.) are sandwiched and further exposed to ultraviolet light to polymerize the liquid crystal monomer. In this way, the light control layer of the reverse mode polymer dispersed liquid crystal composed of the composite of the polymer dispersed liquid crystal and the low molecular liquid crystal is prepared. On the surface of the substrate on which the electrodes are formed, for example, a light absorption layer is formed by applying a black resist, then a phosphor is applied, and then a dielectric multilayer film subjected to orientation treatment is vapor-deposited to form a reflection surface. To do. Finally, irradiation means equipped with cold cathode fluorescent lamps as light sources are provided at both ends of the light guide plate.

Wiring (see FIG. 1) is applied to the display device thus constructed, and ultraviolet rays are made incident from the light guide plate.
In the region where the voltage is applied, the reverse mode polymer dispersed liquid crystal is in a scattering state, and the ultraviolet rays propagating in the light guiding region leak to the lower surface of the reflecting surface. The ultraviolet light leaking from the light guiding region is converted into fluorescent light in the visible light region by the phosphor provided on the lower surface of the reflecting surface. That is, the ultraviolet light leaking from the reflecting surface irradiates the phosphor, and the phosphor is excited to generate fluorescence. The fluorescence thus generated reaches the outside of the display device via the light guide plate.

As described above, the ultraviolet light propagating through the light guide region is converted into fluorescence in the visible light region which isotropically scatters and emitted, so that there is no dependence on the viewing angle and the brightness and contrast are wide in a wide range. It is possible to realize good display characteristics without unevenness. Further, as the wavelength conversion means, by using a fluorescent film composed of three color phosphors of red, green and blue as shown in FIG.
Color display can be realized. Further, the light absorption layer on the back surface of the substrate makes it possible to suppress glare, and it is possible to suppress deterioration of contrast even in a dark room. Further, since the electrodes provided on the same plane are used, the optical element applied to the display device can be simplified.

[0087]

As described above, according to the optical element and the display device based on the present invention, the following effects are mainly obtained.

(1) By converting the emitted light component into fluorescence which is isotropic emission, it is possible to eliminate the viewing angle dependency and to realize good display characteristics with uniform brightness and contrast in a wide range. It will be possible.

(2) It is possible to prevent reflection from the observer by providing a light absorbing layer on the optical element or adjusting the thickness of the dielectric multilayer film forming the reflecting surface.

(3) Since light is extracted from the upper surface of the light guide plate, the drive electrodes and the drive substrate do not necessarily need to be transparent, so that a printed wiring board on which electrodes and the like can be easily mounted can be used. The drive circuit can be provided on the back surface of the drive substrate via the through electrode.

(4) Since a large screen can be easily realized by arranging a plurality of drive substrates in a tile shape, it is possible to display a color bitmap by matrix drive and TFT drive.

(5) Since it has a structure for extracting light from the upper surface of the light guide plate, the liquid crystal display device can be protected from external impacts by using a relatively strong light guide plate, and the reliability as the display device is improved. It becomes possible.

[Brief description of drawings]

FIG. 1 is a side sectional view schematically showing an example of a display device according to the present invention.

FIG. 2 is a schematic diagram showing an example of wavelength conversion means applied to an optical element according to the present invention.

FIG. 3 is a side sectional view schematically showing an example of a display device according to the present invention.

FIG. 4 is a side sectional view schematically showing an example of a display device according to the present invention.

FIG. 5 is a side sectional view schematically showing an example of a display device according to the present invention.

FIG. 6 is a side sectional view schematically showing an example of a display device according to the present invention.

FIG. 7 is a side sectional view schematically showing an example of a display device according to the present invention.

FIG. 8 is a plan view schematically showing an example of electrodes forming a pair in a pixel unit, which are applied to the optical element according to the present invention.

FIG. 9 is a side sectional view schematically showing an example of a conventional display device.

FIG. 10 is a side sectional view schematically showing an example of a conventional display device.

FIG. 11 is a side sectional view schematically showing an example of a conventional display device.

FIG. 12 is a plan view schematically showing electrodes provided for each pixel unit applied to a conventional optical element.

[Explanation of symbols]

1 Liquid crystal display 2 color filters 3 lighting means 4 Light guide 5 Light absorber 6 Polymer dispersed liquid crystal 7a, 7b transparent electrode 8a, 8b transparent substrate 9, 27, 113 Light source 10 reflective mirror 11 smoked films 12 UV fluorescent glass 13 UV lamp 14 UV 15 colored light 20, 100 Light guide plate 21, 102 1st electrode (transparent electrode) 22, 103 Light control layer 23, 104 Reflective surface 24, 105 Light absorption film 25, 106 second electrode 26,107 substrate 28, 114 lenses 29,112 Lighting means 30 switching elements 31 signal electrode 32 scanning electrodes 101 transparent substrate 108 wavelength conversion means 109, 115 Reflective film 110,801 Through electrode 111 Back electrode 200 pixels 300 multi-layer board 400 metal halide lamp 401 optical fiber 700a, 700b electrode 800a, 800b comb-shaped electrodes

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI H04N 9/30 H04N 9/30 (72) Inventor Tomotake Uehira 2-3-1 Otemachi, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Within the corporation (56) Reference JP-A-6-308543 (JP, A) JP-A-10-186361 (JP, A) JP-A-2000-147494 (JP, A) Special Table 9-511588 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G02F 1/13357 G02B 6/00 331 G02F 1/1334 G09F 9/00 336 H04N 5/66 H04N 9/30

Claims (10)

(57) [Claims] 1. A translucent light guide plate for guiding incident light from an end face to a light guide region, and a light control layer provided below the light guide plate for changing the optical characteristics of the incident light by an electric field. A direction of light propagating in the light guide region, comprising at least a pair of electrodes for generating an electric field in the light control layer, and a reflection surface provided on the lower surface of the light control layer for reflecting the incident light.
In the optical element extracts light from the top surface of the light guide plate instead Ri by the light control layer, by the light control layer to the lower surface of the reflecting surface of the visible light region light emitted to the outside of the light guide region Provided with a wavelength conversion means for converting light having a predetermined wavelength,
Optical element characterized in that a Hikari吸 Osamumaku the surface. 2. The reflecting surface is a dielectric multilayer film.
The optical element according to claim 1, which is characterized . 3. A reflective film in which the reflective surface has direction selectivity.
The optical element according to claim 1, wherein Claims wherein said wavelength converting means is characterized by a phosphor that emits fluorescence when excited by light emitted to the outside of the light guide region by the light control layer 1, 2
Alternatively , the optical element according to item 3 . 5. The wavelength conversion means is composed of phosphors that respectively emit red, green and blue fluorescences, and each phosphor is arranged in a grid pattern corresponding to the electrodes. The optical element according to any one of 1 to 4 . 6. The optical element according to any one of claims 1 to 5, wherein the incident light is light having a wavelength in the ultraviolet range. 7. The optical element according to any one of claims 1 to 6, wherein the light control layer is characterized by comprising the polymer dispersed liquid crystal. 8. The optical element according to claim 7 , wherein the polymer-dispersed liquid crystal is a composite of polymer liquid crystal and low-molecular liquid crystal. 9. A display device comprising an optical element and an illuminating means for causing light to enter the optical element, wherein the optical element is the optical element according to any one of claims 1 to 8. A display device characterized by the above. 10. The display device according to claim 9 , wherein the illumination unit has a light source that emits light having a wavelength in the ultraviolet range.