JP2002023160A - Optical element and display device provided with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical element and a display device having excellent brightness in a wide angular range, improving viewing angle characteristics of dark brightness observed from the front side in a conventional display device and further improving undesirable reflection. SOLUTION: The optical element changes a direction of light propagating through a light transmission region with a light controlling layer and pulls the light out of the upper surface of a light transmission plate and is at least provided with the translucent light transmission plate making incident light from an end face guided to the light transmission region, the light controlling layer arranged on the lower side of the light transmission plate and varying optical characteristics of the incident light with an electric field, at least a pair of electrodes generating the electric field in the light controlling layer, a reflection surface reflecting the incident light and a wavelength transforming means transforming the light emitted to the outside of the light transmission region through the light controlling layer into light with a specified wavelength in the visible ray region. Also the display device is constructed with this kind of the optical element and an illuminating means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical element applicable to a large-screen color display and the like and a display device using the optical element.

[0002]

2. Description of the Related Art A display device using a light guide plate and a liquid crystal is conventionally known. As an example, a display device that uses a light guide plate and a ferroelectric liquid crystal and applies an AC electric field near the relaxation frequency of the goldstone mode to the ferroelectric liquid crystal to cause scattering in the liquid crystal layer (for example,
Japanese Patent Application Laid-Open No. 6-347543) and a display device using a light guide plate and a polymer-dispersed liquid crystal (for example, see Japanese Patent Application Laid-Open No. 6-347790) have been proposed.

However, in the display device disclosed in Japanese Patent Application Laid-Open No. 6-30543, since application of an AC voltage is indispensable, simple matrix driving, thin film transistors (TFTs)
There is a problem that bit map display cannot be performed by active matrix driving such as driving.

[0004] The display device disclosed in Japanese Patent Application 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) A polymer dispersed liquid crystal that operates at a low voltage is not suitable for displaying a moving image because of its low response speed. (3) In a display device using a polymer-dispersed liquid crystal, multiplexing by simple matrix driving is difficult 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 a bitmap display. (4) It is said that it is difficult for a display device using a polymer-dispersed liquid crystal to achieve good color display as compared with a monotone display.

Further, in any of the above-described display devices, light on the observer side is reflected by a 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 deteriorate.

Japanese Patent Application Laid-Open No. H11-183902 discloses a display device which realizes color display using a light guide and a polymer dispersed liquid crystal. FIG. 9 illustrates an example of the display device disclosed here. The display device shown in FIG. 9 includes a color filter 2 on the surface of the liquid crystal display 1, a light absorber 5 on the back surface of the light guide 4 on which the illumination means 3 is provided, and 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 sandwiching the
a and 7b are formed on each of the two transparent substrates 8a and 8
b. The illumination means 3 includes a light source 9 and a reflection mirror 10. Note that reference numeral 11
Indicates a smoked film. Light incident from the end face of the light guide 4 guides the light through the transparent substrate 8b and the liquid crystal display 1, and
The light is scattered in an image or a character set in a scattering region (portion A in the figure) of the polymer-dispersed liquid crystal 6, converted into colored light by the color filter 2, and emitted.

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

However, in the display device configured as described above, the liquid crystal display is provided on the upper surface (that is, the front surface as viewed from the observer) than the light guide plate. A transparent substrate must be used. Further, although a polymer-dispersed liquid crystal is used for the light control layer of the liquid crystal display, there is no description about a means for avoiding the above-mentioned problem that is observed when the polymer-dispersed liquid crystal is used. Therefore, when a polymer dispersed liquid crystal is used in a display device illuminated from the back, a liquid crystal display can be driven, but has disadvantages such as a small number of pixels, a low response speed, and a high definition. It is not practical to use it as a display device that requires moving image display.

In order to solve the above-mentioned conventional problems, the present inventors have proposed a display device using a light guide plate and a polymer dispersed liquid crystal (see Japanese Patent Application No. 11-212893). FIG. 1 shows an example of the display device disclosed here.
1 is shown. As shown in FIG. 11, the optical element is provided on a lower surface of a light-transmitting light guide plate 20 that receives light from an end face and guides the light.
Translucent first electrode 21, light control layer 22, reflection film 2
3, a light absorbing film 24, a second electrode 25, and an insulating substrate 26 in that order. Further, the light control layer 22 includes:
It is made of a polymer-dispersed liquid crystal whose scattering degree changes 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 includes
It is preferable to use a reverse mode polymer-dispersed liquid crystal composed of a low-molecular liquid crystal dispersed in a liquid crystal polymer. Light control layer 22 of reverse mode polymer dispersed liquid crystal
Becomes a uniform birefringent thin film when no electric field is applied, and becomes a scattering state (portion A in the figure) when an electric field is applied. In the optical element thus configured, active matrix driving can be performed by dividing either the first electrode 21 or the second electrode 25 for each pixel. In the drawings, reference numeral 27 indicates a light source, and reference numeral 28 indicates a lens, which constitutes an illuminating unit 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. In the optical element having the structure shown in FIG. This corresponds to a configuration in which the active matrix drive type is provided by providing 25 for each pixel unit. As shown in FIG. 4, an electrode provided for each pixel (indicated by a dotted line in the figure), that is, a pixel electrode 25 'is provided with a switching element 30 for selectively applying a voltage to the electrode. 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 configuring the optical element and the display device using the optical element as described above, the display device disclosed in Japanese Patent Application No. 11-212893 can increase the output light intensity, improve the display contrast, and scatter due to external light. This enables display characteristics to be improved such as light reduction and enlargement of the screen.

[0011]

However, in the conventional display device that extracts light from the light guide plate by utilizing the scattering and transmission characteristics of the light control layer, the scattering characteristics inevitably have large forward scattering. Considering the display characteristics, it is desirable to make the scattering of the light control layer more isotropic.However, in the conventional display device, the scattering characteristics should be made closer to isotropic scattering while satisfying the conditions such as the drive voltage of the light control layer. Is difficult in practice. As described above, in the conventional display device, the forward scattering increases, so that the ratio of the emitted light to be emitted at a wide angle increases, and the scattering intensity in the front direction relatively decreases (that is, at a wide angle). (The brightness is high and the brightness is low at the front).

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to improve the viewing angle characteristics and improve the reflection in a conventional display device, and thereby to provide an optical element having better display characteristics and a display device using the optical element. It is to provide.

[0013]

The present inventors have made intensive studies on a display device which overcomes the above-mentioned conventional problems, and as a result, have found that the optical device and the optical element disclosed in Japanese Patent Application No. 11-212893 by the present inventors. It has been found that display characteristics can be remarkably improved by making improvements to make light emitted outside the light guide region by the light control layer closer to isotropic scattering while making use of the excellent characteristics of the display device.

That is, the optical element according to the present invention comprises:
An optical element for extracting light from the upper surface of the light guide plate by changing the direction of light propagating in the light guide region by the light control layer, and a light-transmitting light guide plate for guiding incident light from the end surface to the light guide region; ,
A light control layer provided below the light guide plate and changing the optical characteristics of the incident light by an electric field, at least one pair of electrodes that generate an electric field in the light control layer, and a reflection surface that reflects the incident light, Wavelength conversion means for converting light emitted outside the light guide region by the light control layer into light having a predetermined wavelength in a visible light region.

[0015] Whether the wavelength conversion means is provided on the upper surface of the light guide plate through a gap or is provided on the upper surface of the light guide plate via a layer having a refractive index lower than that of the light guide plate. Alternatively, it is preferably provided on the lower surface of the reflection surface.

It is preferable that the wavelength conversion means is a phosphor which emits fluorescence when excited by light emitted outside the light guide region by the light control layer.

It is preferable that the wavelength converting means is composed of phosphors emitting red, green and blue fluorescent light, respectively, and that the respective phosphors are arranged in a lattice pattern corresponding to the electrodes.

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

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

A display device according to the present invention includes an optical element and illumination means for causing light to enter the optical element, and any one of the above-described optical elements is used as the optical element.

It is preferable that the illumination means has a light source for emitting light having a wavelength in the ultraviolet region.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical element according to the present invention is an optical element for extracting 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, the light being incident from an end face. A light-transmitting light-guiding plate that guides light to the light-guiding region, a light control layer provided below the light guide plate, and changing an optical characteristic 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 light emitted outside the light guide region by the light control layer into light having a predetermined wavelength in a visible light region. At least.

The location of the wavelength conversion means is arbitrary,
In order to perform wavelength conversion efficiently, it is preferable to provide the light guide plate on the upper surface (the front surface as viewed from the observer) or the lower surface of the reflection surface. When wavelength conversion means is provided on the upper surface of the light guide plate, a layer having a refractive index lower than that of the light guide plate (for example, a dielectric multilayer film) is inserted between the wavelength conversion means and the light guide plate and bonded. Or simply glue them together through a gap.

Here, the term "wavelength converting means" broadly means means for converting the wavelength of light to another wavelength. In the present invention, however, in particular, the output light component of the display device, that is, the light control layer is used. This means means capable of converting light emitted outside the light guide region into light having a predetermined wavelength in the visible light region. More specifically, a method of converting an outgoing light component such as ultraviolet light into fluorescence having isotropic scattering characteristics is shown. Therefore, in the present invention, it is preferable that the wavelength conversion means be made of a phosphor that emits fluorescence when excited by an emitted light component emitted outside the light guide region by the light control layer. By providing such a wavelength conversion means in the optical element, 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) fluorescent light as the wavelength converting means, it is possible to realize good color display.

The phosphor is preferably one which is efficiently excited by the emitted light component, emits isotropic bright light, and does not decrease in luminance even after long use. Although these use forms are not particularly limited, for example, a phosphor-containing or light-transmitting film coated with a phosphor (hereinafter, also referred to as a fluorescent film) or a phosphor itself coated Can be used. Suitable phosphors include, for example, R, manufactured by EXCITON, respectively.
HODAMINE 640 (red), COUMARIN 5
40A (green) and COUMARIN 460 (blue).

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 wavelength conversion means. Is not limited at all, but the main components 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, in the optical element according to the present invention, since the emitted light component is extracted from the upper surface (front surface) of the light guide plate, the light guide plate is arranged on the front surface as viewed from the observer. Therefore, if a relatively durable 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 made of a material whose optical characteristics such as diffractive ability or scattering ability change due to an external field such as an electric field or a magnetic field. One of suitable materials for forming the light control layer is a polymer-dispersed liquid crystal.

The term "polymer-dispersed liquid crystal" as used herein refers to any thin film composed of a composite of a polymer resin and a liquid crystal, in which a polymer resin in which liquid crystal droplets are distributed is a continuous region. The ret type, the polymer ball type in which both the polymer resin and the liquid crystal are continuous regions, or the 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, and host-guest liquid crystals. Can be used. For example, when an electric field is generated in the light control layer by applying a voltage to the electrodes 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. Transmit light when an electric field is applied.

On the other hand, the light control layer can be formed by using a reverse mode polymer dispersed liquid crystal which exhibits an operation opposite to that of the above polymer dispersed liquid crystal. The reverse mode polymer-dispersed liquid crystal indicates a thin film in which a low-molecular liquid crystal is dispersed in a liquid crystalline polymer. For example, a liquid crystal such as E-7 (manufactured by Merck Japan KK) and a liquid crystal such as UCL002 (Dainippon Ink Co., Ltd.) )
And the like. The mixture can be prepared by irradiating a mixture composed of a liquid crystal monomer such as a liquid crystal monomer and a liquid crystal monomer 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 from the liquid crystalline polymer occurs. That is, the light control layer made of the reverse mode polymer dispersed liquid crystal transmits light when no electric field is applied, and scatters light when the electric field is applied. In the transmissive state of the light control layer, scattering does not occur in any direction, so that display with excellent viewing angle characteristics and high contrast can be performed even in an oblique direction. As described above, since the reverse mode polymer dispersed liquid crystal needs to align the liquid crystalline polymer together with the low molecular dispersed liquid crystal, an alignment film is provided so as to sandwich the liquid crystal layer and the alignment direction of the liquid crystal molecules is aligned. Is preferred.

The response characteristics of the reverse mode polymer dispersed liquid crystal are inverted from those of general polymer dispersed liquid crystals. Therefore, it is possible to prevent light emission from the gap between the electrodes, which is observed when the electrodes are divided in a general optical element using a polymer-dispersed liquid crystal for the light control layer, and display with high contrast is possible. Further, in the scattering state of the optical element using the reverse mode polymer-dispersed liquid crystal, there is a feature that scattering in the optical axis direction is small and scattering in the direction perpendicular to the optical axis direction is large. Therefore, when such an optical element is applied to a display screen, an efficient display in which directivity is provided in the direction of the user by making the optical axis direction perpendicular to the user's line of sight is made. The device can be realized.

For details of the reverse mode polymer-dispersed liquid crystal, refer to the technical report of the Institute of Television Engineers of Japan, IDY 96-50, pp. 137-142, by Dai Akita and Sato.

The thickness of the light control layer configured as described above is not particularly limited, and can be changed according to desired optical characteristics. However, the thickness of the light control layer must be uniform throughout. Needless to say, to obtain a uniform light control layer, a transparent substrate with a smooth surface is used, but microspheres with a uniform particle size are included as spacers in the polymer dispersed liquid crystal constituting the light control layer. You may. 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. Generally, the electrodes are divided into a plurality of pieces in an arbitrary form to enable light to be extracted from a desired position of the optical element. Note that a light absorbing film may be provided in order to reduce light emission between the electrode and the divided electrode. In addition, as described above, by forming the light control layer using the reverse mode polymer-dispersed liquid crystal, light emission between the electrodes can be significantly improved.

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 electrode and the substrate on the back side (the driving electrode and the driving substrate) are not necessarily required.
Need not be transparent. Therefore, a printed wiring board on which electrodes and the like can be easily mounted can be used. As a result, it is possible to take out the electrode on the back surface through the through electrode or the like, and it is not necessary to take out the wiring from the end face of the optical element. Also, by mounting a driving electronic circuit on the back surface via the through electrode, a bitmap display can be realized. Further, a plurality of drive boards can be arranged in a tile shape, which facilitates upsizing. The details of the through electrode and the back electrode will be described later.

The "reflection surface" is for mirror-reflecting 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. A reflective film (for example, a low-refractive-index single-layer film) having direction selectivity that does not totally reflect light is provided separately on the optical element. As another mode, an electrode may be manufactured from a material that specularly reflects light, and the electrode itself may be used as a reflection surface to simplify the optical element. By providing a light absorbing film on either the upper surface or the lower surface of the reflection surface, it is possible to prevent the user from seeing the reflection surface.

When the dielectric multilayer film is used as a reflection surface, by changing the thickness of the dielectric multilayer film, guided light can be reflected and other light can be transmitted. Reflection is not visible from the outside, and good characteristics can be realized. In addition, since the dielectric multilayer film has no electric conductivity, light can be reflected 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 one example of a display device based on the present invention. The display device shown in FIG. 1 is schematically composed of an optical element and illumination means. The optical element includes a light guide plate 100 and the light guide plate 10.
0, a transparent electrode 102 provided on the lower surface of the transparent electrode 101 via a transparent substrate 101, a light control layer 103 provided on the lower surface of the transparent electrode 102, a reflective 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 a lower surface of the electrode 106 Wavelength conversion means 108 on the upper surface of the light guide plate 100 via a gap.
And Here, the light control layer 103 is made of a 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 the reverse mode polymer-dispersed liquid crystal is provided with an alignment film (shown by a thick line in the figure) so as to sandwich the light control layer.

FIG. 2 is a plan view schematically showing an example of a fluorescent film serving as a wavelength conversion means. As shown in FIG. 2, the wavelength conversion means is configured by arranging fluorescent films each containing a red (R), green (G), and blue (B) phosphor in a lattice pattern. In the figure, reference numeral 200 denotes one pixel unit, and the divided electrodes (pixel electrodes) are arranged so as to correspond to each pixel unit. By providing such a 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 a voltage to the electrodes, a good color display can be realized.

In the display device shown in FIG. 1, since the reflection surface 104 is provided on the upper surface than the electrode 106, the light guided through the light guide plate 100 is reflected before reaching the electrode 106, and
6 and light loss due to electrode ends can be reduced.

Incidentally, 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 performs specular reflection, and may also serve as a reflection surface. In addition, by polishing the entire end surface of the light guide plate to a smooth surface and further providing the reflection film 109 on those end surfaces except for a portion where light enters, it is possible to improve the characteristics of confining light in the light guide plate.

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

The illuminating means is for allowing light to enter from the end face of the light guide plate, and is provided on the end face of the light guide plate 100. In the display device shown in FIG.
Are a light source 113 of a cold-cathode tube ultraviolet lamp and the light source 113
And a lens 114 for condensing light from the lens on the end face. As another mode, the lighting means may be constituted by a light source and a reflector 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 illuminating means is not particularly limited as long as light can be efficiently incident.

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 substance serving 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 the incident light, but ultraviolet light is the most practical. There is no particular limitation as long as the light source emits ultraviolet light, for example, a metal halide lamp,
A cold cathode fluorescent lamp, an ultraviolet LED, or the like can be used as a 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 as the wavelength converting means according to the type of the incident light.

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

Although the direction of light incident on the light guide plate 100 is various, attention is focused on incident light in a specific direction, and the direction is indicated by an arrow in the figure. When the light control layer 103 is formed using a reverse mode polymer dispersed liquid crystal, the light control layer 103 is normally in a transmission state. Therefore, if no voltage is applied between the opposing electrodes, the light that guides the light guide plate 100 will
The light is confined in the light guide region including the light control layer 103 and the light control layer 103. On the other hand, when a voltage is applied between the opposing electrodes to generate an electric field in the light control layer, the light control layer enters a transmission state. Therefore, the light that guides the light guide plate 100 is scattered and emitted from the upper surface (front surface) of the light guide plate.

That is, when a voltage is applied only to the electrode 106 ', only the portion of the light control layer corresponding to the electrode to which the voltage is applied is in a scattering state, and all other regions are in a 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, by reaching the polymer-dispersed liquid crystal region in the scattering state and scattering, the propagation direction is changed,
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 may be divided in any manner. For example, the electrodes may be divided into strips or display pixels.

The display device shown in FIG. 1 has a fluorescent film as wavelength conversion means 108 on the upper surface of light guide plate 100 (the front surface as viewed by an observer). When light such as ultraviolet light that has propagated 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 tends to be emitted at an angle close to the light guide plate. For this reason, the display characteristics are largely dependent on the viewing angle and the front luminance is low. However, in the present invention, by providing the optical element with wavelength conversion means such as a fluorescent film, it is possible to convert the emitted light component from the light guide plate into fluorescent light in the visible light region having isotropic scattering characteristics.
By converting the emitted light component into fluorescent light in the visible light region showing isotropic light emission in this way, a good display device having no viewing angle dependence and having no uneven brightness and contrast over a wide range can be realized. Can be.

By the way, the present inventors have filed Japanese Patent Application No.
No. 2,128,933 discloses various optical elements and display devices composed of a light guide plate and a polymer dispersed liquid crystal. It will be readily understood by those skilled in the art that the wavelength conversion means of the present invention can be applied to such optical elements and display devices, and similar effects can be obtained.

Hereinafter, embodiments of the display device according to the present invention will be described more specifically 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, but can be variously modified without departing from the gist thereof.

Embodiment 1 FIG. 3 is a side sectional view schematically showing a display device according to this embodiment. The display device according to this embodiment has substantially the same structure as the display device of FIG. 1 described above, but differs 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 illumination means 112 is provided on both end faces of the light guide plate 100. 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 includes a light guide plate 100 and a transparent electrode 102 provided on the lower surface of the light guide plate 100 via a transparent substrate 101, as in FIG. 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 the light control layer 103 is stacked for each of the divided substrates. Further, wiring is taken out from each electrode 106 through the substrate, and the wiring is collected and wired using the multilayer substrate 300.

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

First, a glass substrate 7059 (cornin
g (manufactured in the United States) on a light guide plate by sputtering or the like.
A TO film is formed. A grid-like electrode is arranged on another substrate, wiring is taken out from each electrode by penetrating the substrate, and wiring is collected using a multilayer substrate, and a drive circuit is mounted on the back surface. A light absorbing film is provided by applying a black resist on the opposite surface, and a dielectric multilayer film is deposited to form a reflecting surface.

Next, a liquid crystal of E-7 (manufactured by Merck Japan KK) containing microspheres having a diameter of, for example, about 50 microns on a glass substrate, and a liquid crystal monomer UCL002 (manufactured by Dainippon Ink KK) Is applied, and a substrate on which a drive circuit is mounted on the back surface is adhered on the mixture without gaps.
The light control layer of the reverse mode polymer-dispersed liquid crystal is manufactured by exposing 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 to ultraviolet light from the glass substrate side. The surfaces of the transparent electrode and the dielectric multilayer film sandwiching the light control layer vertically are subjected to an orientation treatment in advance. The light guide plate is brought into close contact with the thus obtained laminate. Finally, a slight gap is provided on the other substrate surface (the surface of the light guide plate), and a film coated with a 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 lower refractive index than the light guide plate is inserted between the wavelength conversion means and the light guide plate. Is also 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 light propagating through the light guide plate is emitted from the light guide plate and irradiates the fluorescent film 108. . When the fluorescent film 108 serving as the wavelength conversion means is irradiated with the light emitted from the light guide plate 100, the phosphor of the fluorescent film is excited to emit fluorescent light in the visible light region. Since the fluorescent light from the fluorescent film is isotropic, it is possible to realize good display characteristics that are not dependent on the viewing angle and have uniform brightness and contrast over a wide range. In addition, a color display can be realized by using a fluorescent film composed of phosphors of three colors of red, green and blue as shown in FIG. 2 as the wavelength converting means. Further, a light absorbing film 105 provided on the lower surface of the reflection surface 104
Thus, reflection can be suppressed, so that a decrease in contrast can be suppressed even in a dark room.

In the present embodiment, the case where the substrate (drive substrate) 107 used for driving is divided into two is illustrated, but the division type can be changed as required. In addition, by using an adhesive polymer-dispersed liquid crystal such as a reverse mode polymer-dispersed liquid crystal as the light control layer, the divided drive substrates can be tiled and arranged in a tile shape. By bonding and arranging in a tile shape in this manner, the drive substrate is fixed and hardly displaced. Further, by sharing the light guide plate when the screen is enlarged, the joint can be hidden.

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

The illumination means 112 applied to the display device according to the present embodiment is a light source 113 to which ultraviolet rays are introduced from a metal halide lamp 400 via an optical fiber 401.
And a reflective film 115 surrounding the light source 113, and such an illuminating 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
g (manufactured in the United States) on a light guide plate by sputtering or the like.
A TO film is formed. Using this substrate and another substrate, for example, a liquid crystal of E-7 (manufactured by Merck Japan KK) containing microspheres having a diameter of about 50 μm and a liquid crystal monomer UCL002 (Dainippon Ink Co., Ltd.) )), And the mixture is exposed to ultraviolet light to polymerize the liquid crystal monomer. In this way, a light control layer of a reverse mode polymer dispersed liquid crystal composed of a composite of a polymer liquid crystal and a low molecular liquid crystal is manufactured. The surface of each transparent electrode sandwiching the light control layer vertically is subjected to an alignment treatment in advance. Next, a reflective surface is formed by depositing a dielectric multilayer film on one substrate surface. Further, a light absorbing film is formed on the multilayer film obtained as described above, for example, by applying a black resist. Finally, a slight gap is provided on the other substrate surface (the surface of the light guide plate), and a film coated with a 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 lower refractive index than the light guide plate is inserted between the wavelength conversion means and the light guide plate. Is also good.

When wiring (see FIG. 1) is applied to the display device configured 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 light propagating through the light guide plate is emitted from the light guide plate and irradiates the fluorescent film 108. . When the fluorescent film 108 is irradiated with ultraviolet light, the fluorescent material emits fluorescent light in an isotropic visible light region. As described above, by converting ultraviolet light 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. As a wavelength conversion means, FIG.
Color display can be realized by using a fluorescent film composed of phosphors of three colors of red, green and blue as shown in FIG. Further, the light absorption layer provided on the lower surface of the substrate can suppress glare, and can suppress a decrease in 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 Embodiment 2 except that the reflection surface 104 is formed from an aluminum film deposited on a substrate. It is composed. Here, the light control layer 103 is made of a polymer dispersed liquid crystal in a normal mode, and the wavelength conversion means 108 is made 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 illuminating means 112 comprises a light source 113 of a cold cathode fluorescent lamp.
And a reflection film 115 surrounding the light source 113. Such illumination means 112 are provided on both end surfaces of the light guide plate 100.

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

First, a glass substrate 7059 (cornin
g (made in the United States) is formed by sputtering or the like to form an ITO film serving as a light guide plate. Using this substrate and another substrate, a liquid crystal of E-7 (manufactured by Merck Japan Ltd.) containing microspheres having a diameter of about 20 microns, and a NOA
-63 (Norland Products, Inc.)
(U.S.A.) and a mixture containing an ultraviolet-curable resin, and then further subjected to ultraviolet exposure. In this way, an optical control layer of a polymer dispersed liquid crystal having a thickness equal to the diameter of the microsphere is manufactured.

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

The display device thus constructed uses a general polymer-dispersed liquid crystal as the light control layer, and therefore 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 light is incident from the light guide plate, the light control layer 103 is in a scattering state in a region corresponding to the electrode 106 ′ to which no voltage is applied. The ultraviolet light propagating through the light guide plate is emitted from the light guide plate and irradiates the fluorescent film 108. When the fluorescent film 108 is irradiated with ultraviolet light, the fluorescent material emits fluorescent light in an isotropic visible light region. As described above, by converting the ultraviolet light 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 achieved. Characteristics can be realized. In addition, a color display can be realized by using a fluorescent film composed of phosphors of three colors 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 mirror reflection and also serving as the reflection surface 104, the optical element applied to the display device can be simplified.

As described above, in the first to third embodiments, the display device having the wavelength conversion means on the upper surface (front surface) of the light guide plate is exemplified. However, the same effect can be obtained when the wavelength conversion means is provided on the lower surface of the reflection surface. Can be Such a display device will be exemplified in the following embodiments.

(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 reflection surface. You. 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 applied to the lower surface of the reflection surface. Note that an alignment film (shown by a thick line in the figure) is provided so as to sandwich the light control layer 103 made of the reverse mode polymer-dispersed liquid crystal.

In the display device according to this embodiment, the illuminating means 112 is a light source 113 to which ultraviolet rays are introduced from a metal halide lamp 400 via an optical fiber 401.
And a reflection film 115 surrounding the light source 113, and such an illumination 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
g (manufactured in the United States) on a light guide plate by sputtering or the like.
A TO film is formed. Using this substrate and another substrate, E containing microspheres having a diameter of about 50 microns was used.
A mixture of liquid crystal such as -7 (manufactured by Merck Japan KK) and a liquid crystal monomer UCL002 (manufactured by Dainippon Ink and Chemicals, Inc.) is sandwiched, and is further exposed to ultraviolet light to polymerize the liquid crystal monomer. In this way, a light control layer of a reverse mode polymer dispersed liquid crystal composed of a composite of a polymer liquid crystal and a low molecular liquid crystal is manufactured. The surfaces of the transparent electrode and the dielectric multilayer film sandwiching the light control layer vertically 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, for example, a black resist. Further, after a phosphor is applied to the surface of the light absorption film, a dielectric multilayer film is deposited to form a reflection surface.
Finally, irradiating means having a light source connected to the metal halide lamp via an optical fiber is provided at one end of the light guide plate.

When wiring (see FIG. 1) is applied to the display device constructed as described above and 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 is obtained. The liquid crystal is in a scattering state, and ultraviolet light propagating in the light guide region leaks to the lower surface of the reflection surface. The ultraviolet light leaking from the light guide region is converted into fluorescent light in the visible light region by a phosphor provided on the lower surface of the reflection surface. That is, the ultraviolet light leaking from the reflecting surface irradiates the phosphor, and the phosphor is excited to generate fluorescence. The fluorescent light generated in this way reaches the outside of the display device via the light guide plate.

As described above, since the ultraviolet light propagating through the light guide region is converted into isotropically scattered fluorescence and emitted, there is no dependency on the viewing angle, and there is no unevenness in brightness and contrast in a wide range. And good display characteristics can be realized. As a wavelength conversion means, FIG.
Color display can be realized by using a fluorescent film composed of phosphors of three colors of red, green and blue as shown in FIG. Further, the light absorbing layer provided on the back surface of the substrate makes it possible to suppress glare, and to suppress a decrease in contrast even in a dark room.

(Embodiment 5) FIG. 7 is a side sectional view showing a display device according to this embodiment. An 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. A reflecting surface 104 provided; a wavelength converting means 108 provided on a lower surface of the reflecting surface 104; a light absorbing film 105 provided on a lower surface of the wavelength converting means 108; A plurality of electrodes 700a forming a pair for each divided unit
And 700b, and a substrate 107 provided on the lower surface of the electrodes 700a and 700b. The electrodes used in this embodiment are paired electrodes on the same plane for each pixel unit, and when a voltage is applied to these electrodes, an electric field is generated in the in-plane direction.

As an example of such an electrode, comb electrodes 800a and 800b provided in one pixel are shown in FIG. In the drawing, reference numeral 801 denotes a through electrode that penetrates through the substrate 107 and is connected to the electrodes 800a and 800b, respectively. By providing a back electrode via this through electrode 801, back drive can be realized. Note that such a comb-shaped electrode can be easily manufactured by uniformly depositing an electrode such as aluminum on a substrate and patterning the electrode according to a photolithography technique.

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 applied on the lower surface of the reflection surface.

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

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

First, an alignment-treated 7059 (cor)
A liquid crystal E-7 (Merck Japan Co., Ltd.) containing microspheres having a diameter of about 50 μm was formed using a glass substrate such as Ning Co. (U.S.A.) and a substrate on which electrodes forming a pair on the same plane were formed. )) And a liquid crystal monomer UCL002 (manufactured by Dainippon Ink and Chemicals, Inc.), and the mixture is exposed to ultraviolet light to polymerize the liquid crystal monomer. In this way, a light control layer of a reverse mode polymer dispersed liquid crystal composed of a composite of a polymer dispersed liquid crystal and a low molecular liquid crystal is manufactured. On the substrate surface on which the electrodes are formed, for example, a light absorption layer is formed by applying a black resist, a phosphor is subsequently applied, and a reflective multilayer is formed by depositing an oriented dielectric multilayer film. I do. Finally, irradiation means provided with a cold-cathode tube ultraviolet lamp as a light source is provided at both ends of the light guide plate.

When wiring (see FIG. 1) is applied to the display device configured as described above and ultraviolet rays are 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 ultraviolet light propagating in the light guide region leaks to the lower surface of the reflection surface. The ultraviolet light leaking from the light guide region is converted into fluorescent light in the visible light region by a phosphor provided on the lower surface of the reflection surface. That is, the ultraviolet light leaking from the reflecting surface irradiates the phosphor, and the phosphor is excited to generate fluorescence. The fluorescent light generated in this way reaches the outside of the display device via the light guide plate.

As described above, by converting the ultraviolet light propagating in the light guide region into the fluorescent light in the visible light region that isotropically scatters and emitting the fluorescent light, there is no dependency on the viewing angle, and the luminance and the contrast are wide. Good display characteristics without unevenness can be realized. Further, by using a fluorescent film composed of three color phosphors of red, green and blue as shown in FIG.
Color display can be realized. In addition, the light absorption layer on the back surface of the substrate makes it possible to suppress glare, and to suppress a decrease in 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 according to the present invention, the following effects are mainly obtained.

(1) By converting outgoing light components into fluorescent light, which is an isotropic light emission, it is possible to eliminate the dependence on the viewing angle and to realize good display characteristics without uneven brightness and contrast over a wide range. It becomes possible.

(2) It is possible to prevent reflection from an observer by providing a light absorbing layer on the optical element or adjusting the thickness of the dielectric multilayer film forming the reflection 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 or the like on which electrodes and the like can be easily mounted can be used. A 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 driving substrates in a tile shape, a color bitmap display by matrix driving and TFT driving becomes possible.

(5) Since the light guide plate has a structure for taking out light from the upper surface, the use of a relatively strong light guide plate can protect the liquid crystal display device from external impact, thereby improving the reliability of the display device. It becomes possible.

[Brief description of the 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 illustrating an example of a wavelength conversion unit 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 one 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 a pair of electrodes in a pixel unit applied to the optical element according to the present invention.

FIG. 9 is a side sectional view schematically showing one 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 an electrode provided for each pixel applied to a conventional optical element.

[Explanation of symbols]

 Reference Signs List 1 liquid crystal display 2 color filter 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 reflection mirror 11 smoke film 12 ultraviolet fluorescent glass 13 Ultraviolet lamp 14 Ultraviolet 15 Colored light 20, 100 Light guide plate 21, 102 First electrode (transparent electrode) 22, 103 Light control layer 23, 104 Reflective surface 24, 105 Light absorbing film 25, 106 Second electrode 26, 107 Substrate 28, 114 Lens 29, 112 Illumination means 30 Switching element 31 Signal electrode 32 Scan electrode 101 Transparent substrate 108 Wavelength conversion means 109, 115 Reflective film 110, 801 Through electrode 111 Back electrode 200 Pixel unit 300 Multilayer substrate 400 Metal halide lamp 401 Light Fiber 700a, 7 0b electrode 800a, 800b comb-shaped electrode

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 9/30 G02F 1/1335 530 5G435 (72) Inventor Hidetaka Tanaka 2-3-3 Otemachi 2-chome, Chiyoda-ku, Tokyo No. 1 Within Nippon Telegraph and Telephone Corporation (72) Inventor Katojo Uehira 2-3-1 Otemachi, Chiyoda-ku, Tokyo F-term within Nippon Telegraph and Telephone Corporation (reference) 2H038 AA55 BA06 2H089 HA04 JA04 KA04 KA08 2H091 FA14X FA23X FA34X FA41X FA43X FD01 LA16 LA19 5C058 AA06 AB01 BA31 BA35 5C060 BA04 BA07 BC01 BE05 BE10 DA04 DB03 HD00 JA00 JA08 5G435 AA01 AA04 BB12 BB16 CC09 CC12 DD11 EE22 FF08 HFF11 FF14 H15

Claims (11)

[Claims] 1. An optical element for extracting light from an upper surface of a light guide plate by changing a direction of light propagating through a light guide region by a light control layer, and transmitting incident light from an end surface to the light guide region. A light guide plate, a light control layer provided below the light guide plate and changing the optical characteristics of the incident light by an electric field, at least one pair of electrodes for generating an electric field in the light control layer, and the incident light. An optical element having at least a reflecting surface for reflecting light and wavelength conversion means for converting light emitted outside the light guide region by the light control layer into light having a predetermined wavelength in a visible light region. . 2. The optical element according to claim 1, wherein the wavelength conversion means is provided on an upper surface of the light guide plate via a gap. 3. The optical element according to claim 1, wherein the wavelength conversion means is provided on an upper surface of the light guide plate via a layer having a refractive index lower than that of the light guide plate. 4. The optical element according to claim 1, wherein said wavelength conversion means is provided on a lower surface of said reflection surface. 5. The light-emitting device according to claim 1, wherein the wavelength conversion means is a phosphor that emits fluorescence when excited by light emitted outside the light guide region by the light control layer. An optical element according to item 1. 6. The apparatus according to claim 1, wherein said wavelength converting means comprises phosphors respectively emitting red, green and blue fluorescence, and each phosphor is arranged in a lattice corresponding to said electrode. 6. The optical element according to any one of 1 to 5. 7. The optical element according to claim 1, wherein the incident light is light having a wavelength in an ultraviolet region. 8. The optical element according to claim 1, wherein the light control layer is made of a polymer dispersed liquid crystal. 9. The optical element according to claim 8, wherein the polymer dispersed liquid crystal comprises a composite of a polymer liquid crystal and a low molecular liquid crystal. 10. A display device comprising an optical element and an illuminating unit for making light incident on the optical element, wherein the optical element is the optical element according to claim 1. A display device characterized by the above-mentioned. 11. The display device according to claim 10, wherein said illumination means has a light source for emitting light having a wavelength in an ultraviolet region.