JP2004086221A - Front light and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an illuminator in which double images and bright and dark fringes are suppressed, brightness and contrast ratio are made superior, high quality display is provided, projecting and recessing scratches and a change in quality of a reflecting means are reduced, warping of a light transmission body is reduced, reliability is improved and thickness, weight and cost are reduced, and to provide a display device provided with the illuminator. <P>SOLUTION: An illuminator 100 is provided with a light source 101, a light transmission body 102 that has an incident surface 102a, onto which light beams from the source 101 are made incident, a light emitting surface 102b from which light for illumination is emitted and an opposing surface 102c which is placed opposite to the surface 102b and a reflecting means 103 which is formed or arranged to the surface 102b or the surface 102c of the body 102 independent to the body 102. Light beams from the source 101 are made incident on the surface 102a of the body 102, propagated inside the body 102, reflected by the means 103 to emit the light for illumination. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a lighting device and a display device including the lighting device and a reflective liquid crystal display element.

A liquid crystal display device, which is one of display devices used for an information display system or an OA device, has a transmission type in which an image is displayed by controlling a transmitted light amount of light emitted from the outside, and a liquid crystal display device in which a reflected light amount is controlled to control an image. And a reflective type that displays

A transmissive liquid crystal display device is generally used with an illumination device called a backlight disposed on the back surface.

A reflective liquid crystal display device can display using ambient light, but the degree to which display luminance depends on the surrounding environment is extremely high, and especially in the darkness such as at night, the display may not be recognized at all. . Therefore, an illuminating device called a front light for illuminating the reflective liquid crystal display element from the front is necessary in case sufficient ambient light cannot be obtained.

FIG. 16 shows an example of the configuration of this reflective liquid crystal display device.

This reflective liquid crystal display device includes a reflective liquid crystal display element 900 in which a liquid crystal layer 903 is sandwiched between a pair of glass substrates 902a and 902b, and a reflective electrode 904 is provided on a rear glass substrate 902b. A polarizing plate 901a and a λ / 4 plate 901b are arranged on the front side of the layer 903. The transmission axis (or absorption axis) of the polarizing plate 901a and the slow axis (or fast axis) axis of the λ / 4 plate 901b are arranged at an angle of 45 °.

Among the illumination light, the linearly polarized light transmitted through the polarizing plate 901 a is converted into circularly polarized light by the λ / 4 plate 901 b and enters the liquid crystal layer 903. Here, when the liquid crystal layer 903 does not modulate the circularly polarized light, the direction of rotation of the circularly polarized light is reversed when reflected by the reflective electrode 904, and after transmitting through the λ / 4 plate 901b again, the transmission axis of the polarizing plate 901a. Since the light is absorbed as linearly polarized light orthogonal to the light, black is displayed.

In the case where the liquid crystal layer 903 of the reflective liquid crystal display element 900 modulates so as to reflect incident circularly polarized light while preserving the same, after transmitting through the λ / 4 plate 901b, a straight line matching the transmission axis of the polarizing plate 901a is obtained. Since the light is emitted as polarized light, white color is displayed.

The direction of the transmission axis of the polarizing plate 901a and the direction of the slow axis of the λ / 4 plate 901b are determined in consideration of the liquid crystal material, the direction of alignment, the characteristics of the viewing angle, and the like. Further, a λ / 2 plate may be disposed between the polarizing plate 901a and the λ / 4 plate 901b in order to compensate for a phase delay tolerance of the wavelength of the light of the λ / 4 plate 901b. Generally, the polarizing plate 901a, the λ / 2 plate, and the λ / 4 plate 901b are integrated with each other via an adhesive layer, and are attached to the reflective liquid crystal display element 900.

The reflective electrode 904 disposed on the back surface of the liquid crystal layer 903 has a microstructure (MRS) formed on the surface, and scatters light incident through the polarizing plates 901a, λ / 2 plates, and λ / 4 plates 901b. It is designed so that uniform display can be performed in a wide viewing angle range by reflecting light. Specifically, an MRS as an underlayer is formed by a photolithography process, and a reflective electrode 904 is formed by vacuum-depositing Al thereon.

FIG. 3 shows the scattering characteristics of the reflective electrode 904 provided with such an MRS in comparison with the scattering characteristics of a standard white plate (MgO). According to this, it can be seen that the reflective electrode provided with the MRS can efficiently scatter and reflect light incident within an incident angle of 30 ° in the front direction.

As described above, characters and images are displayed by controlling the modulation by the liquid crystal layer 903 for each pixel, and the three primary colors of red (R), green (G), and blue (B) arranged in each pixel are displayed. A color display can be performed by coloring through a color filter. Although there are various arrangement patterns of R, G, and B pixels, typical examples include a delta arrangement and a stripe arrangement shown in FIG. 17, and the arrangement is such that pixels are repeatedly arranged in a horizontal direction and a vertical direction. The number of pixels and the size of the pixels are also various. In the case of the reflection type liquid crystal display element of the delta arrangement, the number of horizontal pixels × the number of vertical pixels is 280 × 220 in the 2.0 type, and the pixel size is 145.5 μm in the horizontal direction. The vertical direction is 138.5 μm, and the 2.5 type has a specification that the number of pixels is 280 × 220 and the pixel size is 179.5 × 168.5 μm. In the stripe arrangement, for example, in the case of a 3.8-inch QVGA reflective liquid crystal display device, the specification is adopted that the number of pixels is 960 × 240 and the pixel size is 81 × 234.5 μm.

By the way, the above-mentioned front light has been conventionally proposed. For example, SID (Society for Information and Display) '95 and Digest to p. 375 (conventional example 1) shows a front light having a configuration shown in FIG. The front light 910 includes a light source 911, an incident surface 912a on which light from the light source 911 is incident, and a light guide 912 having an emission surface 912b and a facing surface 912c substantially perpendicular thereto. Periodic unevenness 913 is formed on the opposing surface 912c of the light guide 912, and the unevenness 913 has a propagation portion 913a substantially parallel to the emission surface 912b and an inclined reflection portion 913b.

In the front light 910, the light from the light source 911 is totally reflected directly or by the propagation portion 913 a of the periodic unevenness 913 formed on the emission surface 912 b and the opposed surface 912 c, and propagates inside the light guide 912. The light reaches the reflecting portion 913b of the periodic unevenness 913 formed on the facing surface 912c, and is reflected and emitted toward the emission surface 912b. Therefore, illumination light from the emission surface 912 b, that is, the emission surface of the front light 910 irradiates the reflective liquid crystal display element 920.
, SID (Sociality for Information Display) '95 Digest p. 375

However, in the conventional display device including the front light 910 and the reflective liquid crystal display element 920, the unevenness 913 formed on the opposing surface 912c of the light guide 912 appears on the outermost surface, so that the unevenness 913 is easily damaged. In addition, there are major problems in terms of deterioration of front light performance, display quality, productivity, and reliability.

When the light reflected by the reflective liquid crystal display element 920 passes through the light guide 912, the light is refracted in different directions by the propagation portion 913 a and the reflection portion 913 b of the unevenness 913 formed on the light guide 912. Therefore, there is a problem that the display of the reflective liquid crystal display element 920 is observed twice.

{Circle around (2)} The two types of light and dark fringes described below occur due to the periodically formed unevenness 913, which causes a problem of deteriorating the display quality of the reflective liquid crystal display element 920.

First, the reason why the first light and dark fringes occur will be described. Light incident from the light source 911 via the incident surface 912a of the light guide 912 propagates inside the light guide 912 and is reflected toward the emission surface 912b by the periodic unevenness 913 formed on the facing surface 912c. Most of the light is emitted from the light guide 912 to illuminate the reflective liquid crystal display element 920. However, about 4% of the surface reflection on the emission surface 912b is reflected and passes through the periodic unevenness 913 on the facing surface 912c to reach the observer. Therefore, the observer sees the light from the periodically arranged unevenness 913 through the periodic unevenness 913, so that the first light and dark fringes are observed. Similarly, first light and dark fringes are also generated by reflection on the surface of the reflective liquid crystal display element 920.

The second bright and dark fringes are the periodic unevenness 913 formed by the reflection light of the periodic unevenness 913 passing through the pixel pattern of the reflective liquid crystal display element 920, being reflected and formed again on the light guide 912. , Three periods occur due to interference. Even when the reflection type liquid crystal display element 920 is illuminated by ambient light without turning on the front light 910, the illumination light includes the periodic irregularities 913 formed on the light guide 912 and the pixels of the reflection type liquid crystal display element 920. Since the light passes through the pattern, is reflected and passes through the periodic unevenness 913 again, a second light and dark fringe is generated due to interference of these periods.

The first bright and dark fringes can be suppressed by reducing the surface reflection by disposing an anti-reflection layer on each of the emission surface 912 b of the light guide 912 and the surface of the reflective liquid crystal display element 920. . Here, the antireflection layer is a layer formed by a method such as vapor deposition or sputtering and having a thickness of about 0.1 μm and made of MgF ₂ , SiO _2, or the like. Say. Therefore, for example, the surface reflection can be easily reduced by attaching an antireflection film in which an antireflection layer is formed on a transparent film serving as a base material to the emission surface 912b of the light guide 912, and the first light and dark stripes can be reduced. Generation can be suppressed.

However, when the ambient temperature changes, warpage occurs due to the difference in the thermal expansion coefficient between the light guide 912 and the antireflection film, and a new problem arises in terms of reliability. Although a method of forming the above-described antireflection layer directly on the surface of the light guide 912 is also conceivable, since a thin film such as evaporation or sputtering is formed in a high-temperature environment, a heat-resistant material is applied to the light guide 912. In addition, there is a problem with the adhesion of the antireflection layer, and there is a concern about reliability.

In order to solve such a problem, the conventional example 1 protects the unevenness 913 formed on the light guide 912, and displays a double image, a first light and dark fringe, and a second image on the display of the reflective liquid crystal display element 920. There is also described a configuration in which an optical compensator is added to a front light in order to prevent the occurrence of light and dark fringes.

In this front light, as shown in FIG. 18B, the optical compensator 914 includes compensation unevenness 915 in which the unevenness 913 formed on the opposing surface 912c of the light guide 912 is transferred. The 912 and the optical compensator 914 have their irregularities facing each other via an air layer.

Therefore, the reflected light from the reflective liquid crystal display element 920 that receives the illumination light is refracted in different directions when passing through the propagation portion 913a and the reflection portion 913b of the unevenness 913 formed on the light guide 912, By refracting again when passing through the unevenness 915 of the optical compensator 914, the light travels in the same manner as when there is no unevenness. By disposing the optical compensator 914 having such a function, the unevenness 913 of the light guide 912 can be protected. In addition, it is possible to prevent the occurrence of a double image in the display of the reflective liquid crystal display element 20 and the occurrence of the first light-dark stripe and the second light-dark stripe due to the periodically formed unevenness 913.

However, the addition of the optical compensator 914 creates another new problem. For example, in order to obtain the above-described compensation effect, the gap between the light guide 912 and the optical compensator 914 must be as small as possible. However, if the gap is not uniform, interference fringes occur. Therefore, it is necessary to install the optical compensator 914 on the light guide 912 with very high accuracy. In addition, since the reflection at the new interface of the optical compensator 914 is added, the light reflected toward the observer increases, or the transmittance decreases, and the display of the reflection type liquid crystal display element 920 becomes darker. A problem occurs that the contrast ratio of Further, there is a problem that the display device is increased in size due to an increase in thickness.

The present invention solves the above-mentioned problems of the related art, and can suppress the occurrence of double images and bright and dark fringes, and can provide a bright, high-contrast ratio, high-quality display and a lighting device. It is an object of the present invention to provide a display device provided with:

Another object of the present invention is to provide an illuminating device that can reduce the damage and deterioration of unevenness in the reflecting means and the warpage of the light guide, and can improve the reliability, and a display device including the illuminating device. It is in.

Another object of the present invention is to provide a lighting device that can be made thinner, lighter, and less expensive, and a display device provided with the same.

The lighting device of the present invention has a light source, an incident surface on which light from the light source is incident, an emission surface that is substantially orthogonal to the incident surface, emits illumination light, and a facing surface facing the emission surface. A light guide, and a reflection unit formed or arranged separately from the light guide on an emission surface or a facing surface of the light guide, and the light is incident from the light source via an incident surface of the light guide. Light propagating inside the light guide is reflected by the reflection means to emit illumination light, thereby achieving the above object.

The lighting device of the present invention has a configuration in which a transparent flat plate and a reflecting unit are arranged to face each other to form a light guide space, and a light source is arranged on an end face of the light guide space. The light which enters the light guide and propagates in the light guide space is reflected by the reflection means to emit illumination light, thereby achieving the above object.

Preferably, the reflection means reflects light by a difference in refractive index between interfaces of the uneven shape.

Preferably, the reflecting means is constituted by a combination of two members having different refractive indexes, and an interface between the two members has an uneven shape, and reflects light by a difference in refractive index between the interfaces. I do.

Preferably, the concave-convex shape of the reflecting means has a prism shape, and has a propagating portion substantially parallel to an emission surface of the light guide and a tilted reflecting portion, and the light guide enters the light guide from the light source. Light that enters through a surface and propagates mainly through the propagation section is reflected by the reflection section to emit illumination light.

Preferably, the concave-convex shape in the reflecting means has a prism shape, has a refraction portion and a reflection portion inclined with respect to the transparent flat plate, and emits light incident on the light guide space from the light source. The illumination light is refracted at the interface of the refraction part, reflected by the reflection part, and emitted.

Preferably, when the concave and convex shape of the reflecting means is a total reflection angle due to a refractive index difference at the interface of the reflecting portion is α, the reflecting portion forms with respect to the emission surface of the light guide or the transparent flat plate. The angle β is expressed by the following equation (1) α−30 ° ≦ β ≦ α + 30 ° (1)
It satisfies the relationship of

Further, the display device of the present invention is a lighting device according to any one of the above, and a reflective liquid crystal display element that receives illumination light from the lighting device, controls the reflectance of each pixel, and displays an image. , Whereby the object is achieved.

Hereinafter, the operation of the present invention will be described.

According to the above configuration, the light guide has the incident surface on which the light from the light source is incident, the exit surface substantially perpendicular to the entrance surface, and the opposing surface facing the exit surface. Propagating the light. Reflecting means formed or arranged separately from the light guide on the light emitting surface or the opposing surface of the light guide reflects light propagating inside the light guide to emit illumination light.

The reflecting means can be configured to reflect light by a difference in refractive index at the interface of the uneven shape. The reflecting means may be configured by a combination of two members having different refractive indices, and an interface between the two members may have an uneven shape, and light may be reflected by a difference in refractive index at the interface.

Specifically, when the uneven shape is formed integrally with the light guide, the light guide is made of a transparent resin such as an acrylic resin, a polycarbonate resin, or an epoxy resin as a material, and the light guide is formed by reflection. The means can be molded simultaneously.

When the uneven shape is formed separately from the light guide, the uneven shape may be an acrylic resin, a polycarbonate resin, an epoxy resin, an ultraviolet curable resin, a thermosetting resin, or the like on an emission surface or a facing surface of the light guide. Can be formed using a transparent resin such as the above, and the choice of materials can be increased. That is, a material having reliability such as hardness and chemical resistance can be selected for the uneven shape.

According to the above configuration, since the light guide has a flat exit surface and a facing surface, it is possible to select many materials. For example, if glass is selected, the rigidity is higher than that of a transparent resin. Even when an anti-reflection film or the like is attached to a plane where is not disposed to improve the transmittance of the light guide, warpage caused by a temperature change or the like can be reduced, and reliability is increased.

In the case where the reflection means has a configuration using a reflection sheet, by bonding the reflection sheet and the antireflection film to the emission surface and the opposing surface, the transmittance of the light guide is improved, and both are balanced. It is possible to further reduce the warpage of the light guide caused by a temperature change or the like. Further, it is desirable that the films as both base materials are the same.

When the reflecting means has a configuration in which a member having unevenness and a refractive index layer having a different refractive index, preferably a low refractive index, are formed on the unevenness, the performance of the illumination device due to damage of the unevenness, deterioration, etc. The drop can be prevented. Here, the unevenness can be formed separately from the light guide on the emission surface or the opposing surface of the light guide, or may be a reflective sheet having unevenness formed on a transparent film, and a refractive index having a different refractive index. Reflection means can be used in combination with a layer. Further, the projections and depressions may be integrally formed on the emission surface or the opposing surface of the light guide, and may be combined with a refractive index layer having a different refractive index to form a reflection unit.

When the reflecting means is disposed on the opposite surface of the light guide, the reliability of the surface of the lighting device is improved by forming an antifouling film (water repellent layer), a hard coat layer, etc. on the surface of the low refractive index layer. The surface reflectance can be reduced by forming the antireflection layer. The antifouling film (water repellent layer), hard coat layer and antireflection layer can be easily obtained by disposing a protective film on which these are formed in advance on the surface of the low refractive index layer.

(4) When the reflecting means is arranged on the light emitting surface of the light guide, the unevenness is protected by the light guide, so that the reliability of the reflecting means can be improved. Further, an antifouling film (water-repellent layer), a hard coat layer, and an anti-reflection layer may be formed on the surface of the reflection means where the unevenness is not formed.

If the concave-convex shape in the reflecting means is a prism-shaped shape composed of a propagation portion substantially parallel to the emission surface of the light guide and an inclined reflection portion, light enters the light guide from the light source via the incident surface. The light propagates inside the light guide and reaches the reflective portion while being repeatedly reflected on the light emitting surface, the facing surface, or the uneven propagation portion of the light guide, reaches the reflective portion, is reflected by the refractive index difference at the interface, and is illuminated. And emitted. Therefore, when the unevenness in the reflecting means forms an interface with an air layer or a refractive index layer having a lower refractive index than the unevenness, total reflection occurs, and illumination light can be emitted more efficiently.

Assuming that the unevenness in the reflection means is the total reflection angle due to the difference in refractive index at the interface of the reflection portion, α, the angle β formed by the reflection portion with respect to the emission surface of the light guide is α−30 ° ≦ β .Ltoreq..alpha. + 30.degree.... It is desirable to adopt a configuration satisfying the relationship of equation (1).

This is because, as shown in FIG. 3, in a reflection type liquid crystal display device, the reflection characteristics of a reflection electrode on which a fine structure is formed are required to efficiently illuminate the reflection type liquid crystal display device and obtain a bright display. This is due to the need to illuminate within an angle of 30 °.

Specifically, for example, as shown in FIG. 6A, when the angle β formed by the uneven reflection portion with respect to the emission surface of the light guide is set to (α−30 °), the entire reflection surface interface is formed. The reflected light includes light having an emission angle of 30 ° with respect to the emission surface.

As shown in FIG. 6B, when β = α, light totally emitted at the interface of the reflection portion includes light emitted at an emission angle of 0 ° with respect to the emission surface, and the reflection type liquid crystal display is efficiently performed. The element can be illuminated.

As shown in FIG. 6C, when β = (α + 30 °), illumination light having an emission angle of 30 ° or less with respect to the emission surface is generated. However, when β> (α + 30 °), illumination light with respect to the emission surface is generated. The amount of illumination light having an emission angle of 30 ° or more increases, which is not suitable for illumination of a reflective liquid crystal display element.

On the other hand, considering only the amount of illumination light emitted from the illumination device, the amount of light increases as β approaches 0 °, and decreases as β increases.

Therefore, considering both the emission angle and the light amount of the illumination light, the reflecting portion is formed to have an angle of (α−30 °) or more and (α + 30 °) or less with respect to the emission surface of the light guide. Is desirable.

Next, a method for evaluating deterioration of display quality due to a double image of a display of the reflection type liquid crystal display element will be described.

As shown in FIG. 8, a reflective liquid crystal display element 32 having a light guide 31 disposed on the front surface is illuminated from above by a light source 30 such as a fluorescent lamp, and an observer 37 observes the display. Was evaluated for the degree of reduction in display quality due to the double image. FIG. 9 shows the relationship between the ratio (P2 / P1) of the reflection portion and the propagation portion of the unevenness obtained as a result of the evaluation and the double image. In FIG. 9, a circle indicates that a double image is not observed and the display quality is good, and a triangle indicates that a double image is slightly generated but does not hinder display recognition. The mark "x" indicates that the double image is remarkable and adversely affects the display quality. According to FIG. 9, if the ratio (P2 / P1) of the uneven reflection portion and the propagation portion is 0.2 or less, an effect is obtained for a double image, and if the ratio is 0.05 or less, good display is obtained. It can be seen that quality can be obtained.

Therefore, by forming the ratio (P2 / P1) of the length (P2) of the reflection portion to the length (P1) of the propagation portion of the unevenness serving as the reflection means to be larger than 0 and equal to or smaller than 0.2. The observer 37 views the display of the reflection type liquid crystal display element mainly through the propagation portion of the unevenness, and can suppress a double image generated by light reaching the observer 37 through the reflection portion. .

Further, as described above, when the anti-reflection layer is arranged on the surface of the lighting device, the surface reflection of the lighting device can be reduced and the transmittance can be improved. When applied to a display device, it is possible to provide a display device that can display a bright image with a good contrast ratio and a clear image. It is desirable that an anti-reflection layer is also formed on the surface of the reflection type liquid crystal display element. In this case, a display device which is brighter and has a good contrast ratio can be realized.

By the way, as described above, when the uneven shape as the reflecting means is formed periodically, in the lighting device provided with the light, the light reflected by the unevenness at the time of lighting, the emission surface of the lighting device, and the reflection type liquid crystal. Since the light is reflected on the surface of the display element and passes through the unevenness again to reach the observer, the first light and dark fringes are generated due to interference of the unevenness.

However, as described above, the formation of the first light and dark fringes can be suppressed by forming the antireflection layer on the emission surface of the lighting device and the surface of the reflective liquid crystal display element to reduce surface reflection.

Alternatively, when the reflective liquid crystal display element is configured to display an image using polarized light transmitted through the polarized light selective transmission means, the first polarized light selective transmission means is attached to the light exit surface of the light guide. The occurrence of light and dark stripes can be suppressed.

This is because, as described above, the polarized light selective transmission means arranged such that the transmission axis or absorption axis of the polarizing plate and the slow axis or fast axis of the λ / 4 plate make an angle of 45 °, Since the rotation direction is reversed when the polarized light is reflected, the polarized light is absorbed by the polarizing plate when it reaches the polarized light selective transmission means again. Therefore, by attaching the polarized light selective transmission means to the exit surface of the illumination device, the reflected light on the rear side of the polarized light selective transmission means, that is, on the surface of the polarized light selective transmission means and the reflection type liquid crystal display element can be absorbed. The occurrence of light and dark stripes can be suppressed. Further, for the same reason, a display device with a good contrast ratio can be provided.

(4) Further, by arranging the anti-reflection layer on the surface of the polarization selective transmission means and the reflective liquid crystal display element, the reflected light can be reduced, and the transmitted light increases, so that a brighter display can be achieved.

In the case where a touch panel is added as an input device to a display device including a reflective liquid crystal display element and a lighting device, the light guide and the touch panel can also be used. That is, the surface of the touch panel on the side of the reflective liquid crystal display element is the emission surface of the light guide, and the surface on the observer side is the facing surface of the light guide. The light incident through the incident surface of the light body is reflected by the reflection means, emitted from the illumination device as illumination light, and illuminates the reflective liquid crystal display element.

Reflection means can be obtained by forming irregularities of a transparent resin on the surface of the touch panel. Alternatively, it can be configured by attaching a reflective sheet having irregularities formed of a transparent resin on the surface of a transparent film. Further, a refractive index layer having a different refractive index, preferably a low refractive index, may be formed on the unevenness of the member having the unevenness to serve as a reflection means, and may be disposed on the surface of the touch panel. It is preferable that the reflection means is disposed on the reflection type liquid crystal display element side of the touch panel, that is, on the light exit surface of the light guide. This is because the viewer side of the touch panel receives an input by using a touch pen or the like, and therefore, if the projections and depressions are provided here, the projections and projections are damaged, and the performance of the illumination device is deteriorated due to deformation, thereby affecting display quality. .

According to this configuration, it is possible to avoid an increase in the size of the device caused by providing both the light guide and the touch panel as in a conventional display device, and to provide a display device that is inexpensive, thin, lightweight, and excellent in portability. Can be realized.

(4) In the lighting device having the light guide space, the transparent flat plate and the reflection unit are arranged to face each other to form a light guide space, and the light source is arranged on an end face of the light guide space. Then, the light that enters the light guide space from the light source and propagates through the light guide space is reflected by the reflection unit and emitted from the lighting device as illumination light.

反射 In this lighting device, the reflection means is composed of a number of irregularities. Therefore, when the present illuminating device is used for a reflective liquid crystal display element, the reflecting means is a large number of irregularities arranged on the surface of the transparent film, and the reflective film formed of the transparent film and the large number of irregularities forms the reflective liquid crystal. It is attached to the surface of the display element. Alternatively, a large number of concaves and convexes may be directly formed on the surface of the reflective liquid crystal display element to serve as a reflection unit. The irregularities can be formed by molding with a transparent resin such as an acrylic resin, a polycarbonate resin, or an epoxy resin, an ultraviolet curable resin, a thermosetting resin, or the like. A transparent flat plate and a glass plate made of a transparent resin can be used as the transparent flat plate disposed substantially parallel to the transparent flat plate. When a touch panel is provided as an input device, the touch panel can be applied as a transparent flat plate. It is desirable that the surface of these transparent flat plates be subjected to an antireflection treatment so as to reduce surface reflection and improve transmittance. With this configuration, a bright and high-contrast display device can be realized.

According to the above configuration, the weight of the lighting device can be reduced by using the light guide space.

If the concave-convex shape of the reflecting means is configured to have two inclined portions inclined with respect to the transparent flat plate forming the light guide space, that is, a prism shape having a refraction portion and a reflection portion, light enters the light guide space from the light source. The light propagates through the light guide space while repeating reflection by the transparent flat plate and the reflection means, reaches the unevenness, and is refracted at the interface of the refraction part due to a difference in refractive index at the interface, and the refracted light is reflected at the interface of the reflection part. Then, the reflected light is emitted as illumination light.

When the unevenness in the reflecting means is α, the total reflection angle due to the difference in the refractive index at the interface of the reflecting part is relative to a transparent flat plate in which the reflecting part is arranged substantially parallel to the reflecting means and the reflective liquid crystal display element. It is desirable that the angle β to be formed satisfies the relationship of α−30 ° ≦ β ≦ α + 30 ° (1).

More specifically, for example, as shown in FIG. 7A, when the angle formed by the reflective portion with respect to the transparent flat plate, that is, the angle β formed with respect to the reflective liquid crystal display element is (α−30 °). In addition, there is light whose total angle of reflection is 30 ° with respect to the normal to the transparent flat plate, that is, light whose incident angle with respect to the reflective liquid crystal display element is 30 °.

As shown in FIG. 7B, when β = α, the angle of incidence of the light totally reflected at the interface of the reflecting portion with respect to the perpendicular of the transparent flat plate or with respect to the reflective liquid crystal display element is 0 °. The presence of light can efficiently illuminate the reflective liquid crystal display device.

ΒAs shown in FIG. 7C, when β = (α + 30 °), illumination light having an angle with respect to the perpendicular of the transparent flat plate and an incident angle with respect to the reflective liquid crystal display element of 30 ° or less is generated. However, if β> (α + 30 °), the amount of illumination light whose angle to the perpendicular of the transparent flat plate and the incident angle to the reflective liquid crystal display element is 30 ° or more increases, which is not suitable for illumination of the reflective liquid crystal display element.

Therefore, by designing the angle β formed by the reflection portion with respect to the transparent flat plate according to the above equation (1), the reflection type liquid crystal display element can be efficiently illuminated and a bright display can be performed.

Considering the double image of the display of the reflection type liquid crystal display element caused by the unevenness in the reflecting means, the result shown in FIG. 9 shows that in the illumination device using the light guide space, the area (P1) where the unevenness as the reflecting means is not formed If the ratio (P2 '/ P1') of the region (P2 ') where the unevenness is formed with respect to (') is greater than 0 and less than or equal to 0.2, the display of the reflective liquid crystal display element is observed twice. It can be seen that good display quality can be obtained without any. More desirably, by setting the ratio (P2 '/ P1') to 0.05 or less, a clear display can be provided.

When an illuminating device having a light guiding space is arranged on the front surface of the reflective liquid crystal display element and illuminates the illuminating device, a glass plate, a transparent resin plate, or a touch panel can be applied to the transparent flat plate. By performing the anti-reflection treatment on the transparent flat plate, the transmittance of the lighting device is improved, and a bright and high-contrast display device can be realized.

In the case where the unevenness of the reflecting means is periodically formed in the lighting device having the above-described configuration, it is desirable that the direction of the streak is arranged so as not to coincide with the repeated horizontal direction of the pixel pattern of the liquid crystal display element.

When a lighting device provided with a reflecting means having periodic unevenness is arranged as a front light in front of the reflective liquid crystal display element, the unevenness of the reflecting means and the pixel pattern of the reflective liquid crystal display element interfere with each other, so that the second However, by giving an angle between the direction of the streaks on which the irregularities are formed and the direction of repetition of the pixel pattern, the cycle of the second light and dark stripes is shortened, and a phenomenon occurs in which the second light and dark stripes are eventually not observed. Because.

Specifically, in FIG. 4, an illuminating device provided with a reflection means having periodic irregularities is disposed in front of a reflection type liquid crystal display element having a 2.0-type or a 2.5-type delta arrangement. The result of observing the second light and dark fringes by giving an angle between the direction of the streak and the horizontal direction of the pixel pattern and finding the angle range in which the second light and dark fringes are not observed is shown. FIG. 5 shows the results of a similar experiment performed on a reflection type liquid crystal display device having a 3.8-type QVGA stripe arrangement.

According to FIGS. 4 and 5, although the angular range varies depending on the period of the unevenness, when the reflective liquid crystal display element has a delta arrangement, the angular range is 10 ° to 25 °, and 55 ° to 80 °, and the stripes. In the case of the arrangement, the second light and dark fringes are not observed in the angle range of 15 ° to 75 °, and good display quality can be obtained.

As described above, according to the lighting device of the present invention, it is possible to reduce the damage and deterioration of the unevenness in the reflecting means and the warpage of the light guide, thereby improving the reliability. According to the display device provided with the illumination device of the present invention, it is possible to suppress the occurrence of double images and bright and dark stripes, and to perform bright, high-contrast, high-quality display. In addition, the lighting device and the display device can be reduced in thickness, weight, and cost.

More specifically, since the light guide has a flat exit surface and an opposing surface, it is possible to take many choices of materials.For example, if glass is selected, the rigidity is higher than that of a transparent resin. Even when an antireflection film or the like is stuck on a flat surface to improve the transmittance of the light guide, the warpage caused by a change in temperature or the like can be reduced, and the reliability increases.

Specifically, when the uneven shape is formed integrally with the light guide, the light guide is made of a transparent resin such as an acrylic resin, a polycarbonate resin, or an epoxy resin as a material, and the light guide is formed by reflection. The means can be molded simultaneously.

When the uneven shape is formed separately from the light guide, the uneven shape may be an acrylic resin, a polycarbonate resin, an epoxy resin, an ultraviolet curable resin, a thermosetting resin, or the like on an emission surface or a facing surface of the light guide. Can be formed using a transparent resin such as the above, and the choice of materials can be increased. That is, a material having reliability such as hardness and chemical resistance can be selected for the uneven shape.

When the reflecting means has a configuration in which a member having unevenness and a refractive index layer having a different refractive index, preferably a low refractive index, are formed on the unevenness, the performance of the illumination device due to damage of the unevenness, deterioration, etc. The drop can be prevented.

In the case where the reflection means is configured to use a reflection sheet, the transmittance of the light guide can be improved by bonding the reflection sheet and the antireflection film to the emission surface and the opposing surface, and both of them can be improved. It is possible to reduce the warpage of the light guide caused by a temperature change or the like by taking a balance.

When the reflection means is disposed on the opposite surface of the light guide, the reliability of the surface of the lighting device is improved by forming an antifouling film (water repellent layer), a hard coat layer, etc. on the surface of the low refractive index layer. The surface reflectance can be reduced by forming the antireflection layer.

(4) When the reflecting means is disposed on the light emitting surface of the light guide, the unevenness is protected by the light guide, so that the reliability of the reflecting means can be improved.

(4) In the lighting device using the light guide space constituted by the reflection means and the transparent flat plate, the weight of the display device can be further reduced.

In the case where a touch panel is added as an input device to a display device including a reflective liquid crystal display element and a lighting device, the light guide and the touch panel can also be used. In this case, it is possible to reduce the thickness, weight, and cost of the display device, the portable information terminal, and the like.

If the concave and convex shape in the reflecting means is a prism-like shape composed of a propagation portion substantially parallel to the light emitting surface of the light guide and an inclined reflecting portion, an air layer or a refractive index layer having a lower refractive index than the concave and convex portions. When an interface is formed, total reflection occurs, and illumination light can be emitted more efficiently.

Assuming that the total reflection angle due to the difference in the refractive index at the interface of the reflecting portion is α, the angle β formed by the reflecting portion with respect to the light exit surface of the light guide or the transparent flat plate is (1). By satisfying the relationship of the expression, the reflective liquid crystal display element can be efficiently illuminated, so that a display device which is bright, has a good contrast ratio, and can perform high-quality display can be obtained.

Further, the ratio of the length of the reflecting portion to the length of the propagation portion of the unevenness as the reflecting means (P2 / P1), or the ratio of the area where the unevenness is formed and the area where the unevenness is not formed (P2 ′ / P1 ′). Satisfies a predetermined relationship, it is possible to suppress the occurrence of double images and bright and dark stripes of the reflective liquid crystal display element.

In addition, by arranging the polarization selecting means of the reflection type liquid crystal display element on the emission surface of the illumination device, a display device capable of performing bright, high-contrast ratio, high-quality display without causing bright and dark stripes is provided. can get.

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.

(Embodiment 1)
1 and 2 show a configuration example of a lighting device according to a first embodiment of the present invention and a display device including a reflective liquid crystal display device including the lighting device.

In the first embodiment, as shown in FIGS. 1 and 2, the lighting device 100 includes a light source 101, a light guide 102, a reflection unit 103, and an antireflection film 104. The reflection type liquid crystal display element 110 includes a polarization selective transmission unit 111, a pair of glass substrates 112a and 112b, a liquid crystal layer 113 interposed therebetween, and a reflection electrode 114 disposed on the back side thereof.

Specifically, a fluorescent tube was used as the light source 101, and a glass plate having a refractive index of 1.53 was used as the light guide 102. Here, in the light guide body 102, a surface on the side from which the illumination light of the illumination device 100 emits light is defined as an emission surface 102b, and a surface facing this is defined as an opposite surface 102c. As the reflecting means 103 formed by unevenness formed separately from the light guide 102 on the opposing surface 102c of the light guide 102, GRNDICRC-8720 manufactured by Dainippon Ink and Chemicals, Inc., which is an ultraviolet curable resin, was used. This UV-curable resin has a refractive index after curing of 1.52 and a rigidity of 2.1 × 10 ¹⁰ dyn / cm ² . Therefore, the refractive index is almost equal to that of the glass plate, and the rigidity is high, so that the glass is hardly damaged and high reliability can be obtained. This ultraviolet-curing resin is applied on a glass plate, a mold is arranged, the resin is cured by irradiating ultraviolet rays from the glass plate side, and the shape of the mold is transferred to form the reflection means 103 by unevenness. it can.

For the anti-reflection film 104, a TAC-HC / AR manufactured by Nitto Denko Corporation having an anti-reflection layer formed on a TAC film as a transparent base material is used, and an adhesive layer is formed on the emission surface 102b of the light guide 102. Pasted together.

The reflective liquid crystal display element 110 has a 2.0-type delta arrangement, the number of pixels is 280 × 220, and the pixel size is 145.5 × 138.5 μm.

As shown in the partial enlarged view of FIG. 2, the polarization selective transmission unit 111 includes a polarizing plate 111a, a λ / 2 plate 111b, and a λ / 4 plate 111c bonded together in this order via an adhesive layer. Four plates 111c are bonded to a glass substrate 112a. For the light incident on the polarization selective transmission unit 111, only linearly polarized light is selected by the polarizing plate 111a, and the angle of the slow axis (or fast axis) of the λ / 4 plate 111c with the λ / 2 plate 111b is set to 45 °. The λ / 4 plate 111c converts the linearly polarized light into circularly polarized light.

Therefore, the reflective liquid crystal display element 110 reflects the circularly polarized light, which has passed through the polarization selective transmission unit 111, of the ambient light or the illumination light from the illumination device 100 on the liquid crystal layer 113 for each pixel, and reflects the circularly polarized light on the reflection electrode 114. Then, an image is displayed by controlling the amount of light passing through the polarization selective transmission unit 111 again.

The reflective electrode 114 has a fine structure (MRS) formed on its surface in order to scatter and reflect incident light to provide an image of good display quality in a wide viewing angle range, and has a scattering characteristic as shown in FIG. Have.

Next, a description will be given of the reflecting means 103 using unevenness. As shown in the partially enlarged view of FIG. 1, the unevenness is composed of a propagation portion 103a substantially parallel to the emission surface 102b of the light guide 102, and a reflection portion 103b inclined with respect to the emission surface 102b. Accordingly, light from the light source 101 enters the light guide 102 via the incident surface 102a, and light that propagates while repeating total reflection reaches the uneven reflection portion 103b and is totally reflected at the interface. The light exits from the exit surface 102b of the light guide 102, that is, the exit surface 100a of the lighting device 100, and illuminates the reflective liquid crystal display element 110.

Here, according to the scattering characteristics of the reflective electrode 114 in the reflective liquid crystal display element 110 shown in FIG. 3, the illumination light within an incident angle of 30 ° is efficiently scattered and reflected in the front direction. It is desirable that it is within °.

Specifically, between the angle β formed between the reflecting portion 103b of the reflecting means 103 due to the unevenness and the emission surface 102b of the light guide 102 and the total reflection angle α at the interface between the reflecting means 103 and the air caused by the unevenness, The following formula (1),
α-30 ° ≦ β ≦ α + 30 ° (1)
The illumination light as described above can be obtained by designing the shape of the unevenness so that the relationship of

In the first embodiment, since the reflecting means 103 formed by the unevenness is made of a transparent resin having a refractive index of 1.52 and forms an interface with air, the total reflection angle α is expressed by the following equation (2).
α = sin ⁻¹ (1.0 / 1.52) = 41.8 ° (2)
Given by

Therefore, β was set to 40 ° which is almost equal to α.

It is possible to obtain illumination light having an emission angle with respect to the emission surface 102b of the light guide 102 and the emission surface 100a of the illumination device 100 substantially parallel thereto, that is, an incidence angle with respect to the reflective liquid crystal display element 110 of approximately 0 °. The liquid crystal display element 110 can be efficiently illuminated.

The period of the unevenness of the reflection means 103 and the direction of the streaks are determined according to FIG. 4 in order to prevent the deterioration of the display quality due to the second light and dark fringes generated by the interference with the pixel pattern of the reflection type liquid crystal display element 110. Were determined. That is, since the reflection type liquid crystal display element 110 has a 2.0 type delta arrangement, the reflection means 103 has a period P of 390 μm and a horizontal direction of the pixel pattern of the reflection type liquid crystal display element 110 as shown in FIG. And 14 °. This shortens the period of the second light and dark fringes due to interference between the reflective means 103, which is composed of periodically formed irregularities, and the pixel pattern of the reflective liquid crystal display element 110, and is not recognized by the observer. The display quality of the liquid crystal display element 110 is not impaired.

Further, of the irregularity period 390 μm of the reflection means 103, the length P1 of the propagation portion 103a is 370 μm on average and the length P2 of the reflection portion 103b is 20 μm on average, and the ratio of the reflection portion 103b to the propagation portion 103a (P2 / P1 ) Was set to about 0.05. Therefore, the observer views the display of the reflection type liquid crystal display element 110 mainly through the propagation section 103a, and can prevent a double image generated by the light reaching the observer through the reflection section 103b, which is favorable. The display quality was obtained.

Further, the antireflection film 104 disposed on the emission surface 102b of the light guide 102 has an effect of reducing the surface reflection of the light guide 102 and improving the transmittance. When observing the display, a bright display with a good contrast ratio can be performed. When the lighting device 100 is turned on, the reflection type liquid crystal display element 110 is used to suppress the occurrence of the first light and dark fringes caused by the reflecting means 103 due to the unevenness periodically formed on the opposing surface 102 c of the light guide 102. Display quality can be improved. For the same reason, it is desirable that the surface of the reflective liquid crystal display element 110, that is, the surface of the polarization selective transmission unit 111 is also subjected to an antireflection treatment.

Further, in the first embodiment, since a glass plate is used for the light guide 102, warpage caused by thermal expansion of the transparent resin and the antireflection film 104 forming the reflection unit 103 is reduced even in a high-temperature and low-temperature environment. And the reliability of the lighting device 100 is improved. Further, by selecting a resin having high rigidity and high degree as the transparent resin forming the reflection means 103, it is possible to prevent the performance from being deteriorated due to scratches or the like.

(4) With the illumination device 100 and the reflective liquid crystal display element 110 having the above-described configurations, a bright and high-quality image can be provided, and a highly reliable display device can be realized.

In the first embodiment, a fluorescent tube is used as a light source. However, any other light source such as an EL, an LED, and a combination of an LED and a rod-shaped light guide that uniformly irradiates the light incident surface of the light guide may be used. Any one may be used.

As the material of the light guide 102, a transparent resin typified by an acrylic resin, a polycarbonate resin, or an epoxy resin, in addition to glass, can be used as appropriate.

材質 The material of the reflection means 103 is not limited to an ultraviolet curable resin, and a thermosetting resin, an acrylic resin, a polycarbonate resin, a transparent resin represented by an epoxy resin, or the like can be appropriately used. In addition, the reflection unit 103 may be configured by attaching a reflection sheet in which a large number of irregularities made of a transparent resin are formed on a transparent base material to the light guide 102.

ほ か In addition to bonding the antireflection film 104 to the light exit surface 102b of the light guide 102, an antireflection layer may be formed directly on the light guide 102. Further, when the polarization selective transmission unit 111 includes a polarizing plate 111a and a λ / 4 plate 111c as in the reflection type liquid crystal display element 110 in the first embodiment, a polarization is used instead of the antireflection film 104. The selective transmission unit 111 may be attached to the emission surface 102b of the light guide 102.

凹凸 The period of the unevenness of the reflection means 103 and the direction of the streaks are not limited to those described above, and vary depending on the pixel pattern of the reflection type liquid crystal display element as shown in FIGS. That is, the direction of the streaks of the unevenness formed by the reflection means 103 shown in FIG. 2 differs depending on the period. However, when the pixel pattern is in a delta arrangement, as shown in FIG. It is desirable to have an angle of 25 ° to 25 ° and 55 ° to 80 °. When the pixel pattern has a stripe arrangement, it is desirable to have an angle of 15 ° to 75 ° as shown in FIG.

The selection of the types of the light guide 102, the reflection means 103, the antireflection treatment 104, and the polarization selective transmission means 111 is appropriately determined in consideration of the performance and reliability of the lighting device.

The reflection type liquid crystal display element 110 includes a polarization selective transmission unit 111, and is not limited to one that displays an image by modulating circularly polarized light, and may be a reflection type liquid crystal display element using various modes of liquid crystal molecules. it can.

(Embodiment 2)
10 and 11 show a configuration example of a lighting device according to the second embodiment of the present invention and a display device including a reflective liquid crystal display device including the lighting device.

In Embodiment 2, as shown in FIGS. 10 and 11, the lighting device 200 includes a light source 201, a light guide 202, a low refractive index layer 204, a protective film 205, and a polarized light selective transmission unit 211, Here, in the light guide 202, the surface of the illumination device 200 on the side from which the illumination light is emitted is defined as an emission surface 202b, and the surface facing the surface is defined as an opposite surface 202c. In the illumination device 200, the reflection means 203 forms a low refractive index layer 204 having a refractive index smaller than that of the light guide 202 on the surface of a large number of irregularities integrally formed on the emission surface 202 b of the light guide 202. The protective film 205 is further laminated on the low refractive index layer 204. The reflection type liquid crystal display element 210 includes a pair of glass substrates 212a and 212b, a liquid crystal layer 213 sandwiched therebetween, and a reflection electrode 214 disposed on the back side thereof.

Specifically, a fluorescent tube was used for the light source 201, and polycarbonate having a refractive index of 1.58 was injection-molded for the light guide 202, and concavities and convexities serving as the reflection means 203 were integrally formed on the facing surface 202c.

紫外線 UV curable resin DEFENSA7702A manufactured by Dainippon Ink and Chemicals, Inc. was applied to the low refractive index layer 204. This UV-curable resin has a refractive index of 1.38 after curing, and has a lower refractive index than polycarbonate, which is a material of the light guide 202.

(4) A PET film 205a was applied as a base material to the protective film 205, and a hard coat layer, an antireflection layer, and a layer 205b serving as an antifouling layer were formed on one surface as shown in a partially enlarged view of FIG.

The UV curable resin is applied on the irregularities serving as the reflection means 203 formed on the opposing surface 202c of the light guide 202, and a protective film 205 is further disposed. The refractive index layer 204 was formed, and the light guide 202 and the protective film 205 were integrated. Here, the protective film 205 is disposed such that the layer 205b serving as the hard coat layer, the antireflection layer, and the antifouling layer is on the outside.

As shown in a partially enlarged view of FIG. 11, the polarization selective transmission unit 211 includes a polarizing plate 211a, a λ / 2 plate 211b, and a λ / 4 plate 211c bonded in this order via an adhesive layer. 211a is bonded to the emission surface 202b of the light guide 202 via an adhesive layer. As for the light incident on the polarization selective transmission unit 211, only the linearly polarized light is selected by the polarizing plate 211a, the light is rotated by the λ / 2 plate 211b, and the λ / 4 plate 211c converts the linearly polarized light into circularly polarized light.

The reflection type liquid crystal display element 210 has a 2.5-type delta arrangement, the number of pixels is 280 × 220, and the pixel size is 179.5 × 168.5 μm.

Accordingly, by receiving ambient light passing through the polarization selective transmission unit 211 or illumination light from the illumination device 200 and controlling the amount of light reflected by the reflective electrode 214 and passing through the polarization selective transmission unit 211 again for each pixel. Display an image. Note that the reflective electrode 214 has a scattering characteristic as shown in FIG.

Next, the unevenness integrally formed on the facing surface 202c of the light guide 202 and the reflection means 203 by the low refractive index layer 204 will be described. As shown in the partial enlarged view of FIG. 10, the unevenness includes a propagation portion 203a substantially parallel to the emission surface 202b of the light guide 202, and a reflection portion 203b inclined with respect to the emission surface 202b. Accordingly, the light from the light source 201 enters the light guide 202 through the incident surface 202a, and the light that reaches the reflecting portion 203b is totally reflected at the interface with the low refractive index layer 204, and becomes light guide. The light exits from the emission surface 202b of the illumination device 202 and the emission surface 200a of the illumination device 200 to illuminate the reflective liquid crystal display element 210.

The reflective electrode 214 of the reflective liquid crystal display element 210 efficiently scatters and reflects illumination light within an incident angle of 30 ° in the front direction. Therefore, the angle β formed between the uneven reflection part 203b of the reflection means 203 and the emission surface 202b of the light guide 202, and the reflection means 203 of the The following equation (1) is calculated between the total reflection angle α at the interface of the irregularities.
α−30 ° ≦ β ≦ α + 30 ° (1)
It is desirable to design the shape of the concavo-convex shape so that the relationship described above is satisfied, and set the incident angle of the illumination light to the reflective liquid crystal display element 210 within 30 °.

In the second embodiment, the unevenness of the reflection means 203 is made of polycarbonate having a refractive index of 1.58, and the low refractive index layer 204 has a refractive index of 1.38. formula,
α = sin ⁻¹ (1.38 / 1.58) = 60.9 ° (3)
Given by

Therefore, β was set to 60 ° which is almost equal to α.

In this case, it is possible to obtain an illumination light having an emission angle with respect to the emission surface 202b of the light guide 202 and the emission surface 200a of the illumination device 200 substantially parallel thereto, that is, an incidence angle with respect to the reflective liquid crystal display element 210 of approximately 0 °. Thus, the reflective liquid crystal display element 210 can be efficiently illuminated.

(4) The unevenness period of the reflection means 203 and the direction of the formed streaks are suitable for the 2.5-type delta arrangement which is the specification of the reflection type liquid crystal display element 210 according to FIG. More specifically, as shown in FIG. 11, the period P was 390 μm, and was formed so as to form an angle of 14 ° with the horizontal direction of the pixel pattern of the reflective liquid crystal display element 210. Accordingly, the period of the second light and dark fringes due to interference between the reflection means 203 having irregularities formed periodically on the opposing surface 202c of the light guide 202 and the pixel pattern of the reflection type liquid crystal display element 210 is shortened. The display quality of the reflective liquid crystal display element 210 is not impaired by the observer without being recognized.

Further, of the irregularity period 390 μm as the reflection means 203, the length P1 of the propagation portion 203a is 370 μm on average, and the length P2 of the reflection portion 203b is 20 μm on average, and the ratio of the reflection portion 203b to the propagation portion 203a (P2 / P1). Was set to about 0.05. Therefore, the image of the reflection type liquid crystal display element 210 was not observed as a double image, and good display quality could be obtained.

The reflection means 203 is constituted by forming a low refractive index layer 204 on the surface of a large number of irregularities integrally formed on the facing surface 202 c of the light guide 202, and further comprises a low refractive index layer 204 on the low refractive index layer 204. Since the protective film 205 is attached, it is possible to prevent the reflection means 203 from being damaged or deteriorated. Further, since a hard coat layer and an antifouling layer are formed on the surface of the protective film 205, it is possible to prevent the protective film 205 from being damaged or stained. Therefore, it is very effective in maintaining the performance of the lighting device 200. Further, the antireflection layer can reduce the amount of light reflected from the surroundings by the illumination means 200 and increase the amount of light incident on the reflective liquid crystal display element 210, so that a bright display with a good contrast ratio can be performed. it can.

The polarization selective transmission unit 211 bonded to the light exit surface 202b of the light guide 202 is constituted by the polarizing plate 211a, the λ / 2 plate 211b, and the λ / 4 plate 211c as described above. Accordingly, when the circularly polarized light transmitted through the polarization selective transmission unit 211 is reflected by the polarization selective transmission unit 211 and the surface of the glass substrate 212a of the reflection type liquid crystal display element 210, the rotation direction is reversed, and the polarization selective transmission unit 211 is again transmitted. And is absorbed. That is, a decrease in the display contrast of the reflective liquid crystal display element 210 due to the surface reflection of the polarization selective transmission means 211 and the glass substrate 212a is solved. Further, an anti-reflection layer may be disposed on the surfaces of the polarization selective transmission unit 211 and the glass substrate 212a. In this case, the amount of light incident on the reflective liquid crystal display element 210 increases as the surface reflection decreases. Thus, a bright display can be performed.

(4) A bright and high-quality image can be provided by the illumination device having the above-described configuration and the reflective liquid crystal display element, and a highly reliable display device can be realized.

In the second embodiment, a fluorescent tube is used as the light source 201, but the light is uniformly applied to the incident surface 202a of the light guide 202 such as an EL, an LED, or a combination of an LED and a rod-shaped light guide. Any light source may be used.

As the material of the light guide 202, besides glass, an acrylic resin, a polycarbonate resin, a transparent resin represented by an epoxy resin, or the like can be appropriately used.

(4) The unevenness of the reflection means 203 may be formed integrally with the light guide 202, or may be formed separately from the light guide 202 by a transparent resin or the like. Further, a reflection sheet in which a number of irregularities made of a transparent resin are formed on a transparent substrate may be bonded to the light guide 202.

他 An anti-reflection layer may be disposed on the emission surface 202b of the light guide 202, in addition to the polarization selective transmission unit 211 being attached. In this case, it is desirable that an anti-reflection layer is also provided on the surface of the reflection type liquid crystal display element 210.

(4) The irregularity period of the reflection means 203 and the direction of the formed streaks are not limited to those described above, but change according to the pixel pattern of the reflection type liquid crystal display element 210 as shown in FIGS.

The reflection type liquid crystal display element 210 is not limited to one that displays an image by modulating circularly polarized light by using the polarization selective transmission unit 211, and a reflection type liquid crystal display element using various modes of liquid crystal molecules is applied. Can be.

(4) The selection of the type of each unit constituting the illumination device 200 and the reflection type liquid crystal display element 210 is determined in consideration of the performance and reliability of the display device.

(Embodiment 3)
12 and 13 show a configuration example of a lighting device according to Embodiment 3 of the present invention and a display device including a reflective liquid crystal display device including the lighting device.

In the third embodiment, as shown in FIGS. 12 and 13, the lighting device 300 includes a light source 301, a light guide 302, and a reflection sheet 303. The reflection type liquid crystal display element 310 includes a polarization selective transmission unit 311, a pair of glass substrates 312a and 312b, a liquid crystal layer 313 sandwiched therebetween, and a reflection electrode 314 disposed on the back side thereof.

Specifically, a fluorescent tube was used as the light source 301 and the light guide 302 was a touch panel. The touch panel is an input system that detects the position of the touch panel when the surface is pressed with a touch pen 320 or the like, and is mounted on a portable information terminal or the like. Here, in the light guide 302, a surface on the side from which the illumination light of the illuminating device 300 is emitted is referred to as an emission surface 302b, and a surface opposed thereto is referred to as an opposed surface 302c.

As shown in a partially enlarged view of FIG. 12, the reflection sheet 303 has a low refractive index layer 307 formed on the unevenness of a member 306 having unevenness as a reflection means. The base material 305 is bonded to an emission surface 302b of the light guide 302, which is the back surface of the touch panel, via an adhesive layer.

Specifically, a member 306 having a large number of irregularities is arranged by molding a polycarbonate having a refractive index of 1.58 on a PET film 304a as a base material. Further, an ultraviolet curable resin DEFENSA7702A manufactured by Dainippon Ink and Chemicals, Inc. is applied to the low refractive index layer 307, this is applied on the unevenness of the member 306, and the PET film 305 as the base material is disposed again. Irradiate ultraviolet rays to cure the ultraviolet curable resin. Here, the refractive index of the ultraviolet curable resin after curing is 1.38. The base material 304 has an anti-reflection layer 304b formed in advance on the surface of the PET film 304a on which the member 306 is not formed.

The reflection type liquid crystal display element 310 is a 3.8-type QVGA, that is, a stripe array having 960 × 240 pixels and a pixel size of 81 × 234.5 μm.

As shown in a partially enlarged view of FIG. 13, the polarization selective transmission unit 311 provided in the reflection type liquid crystal display element 310 is configured such that a polarizing plate 311a, a λ / 2 plate 311b, and a λ / 4 plate 311c are provided via an adhesive layer. The λ / 4 plate 311c is attached to the glass substrate 312a in this order.

Therefore, the reflection type liquid crystal display element 310 receives the circularly polarized light that has passed through the polarization selective transmission unit 311 out of the ambient light or the illumination light from the illumination device 300, is reflected by the reflection electrode 314, and transmits the polarization selective transmission unit 311 again. An image is displayed by controlling the amount of passing light for each pixel. The reflective electrode 314 has a scattering characteristic as shown in FIG.

Next, a description will be given of the uneven shape of the member 306, which is a reflection unit, formed on the reflection sheet 303. The projections and depressions include a propagation portion 306a substantially parallel to the emission surface 302b of the light guide 302, and a reflection portion 306b inclined with respect to the emission surface 302b. As described above, since the reflection sheet 303 is attached to the emission surface 302 b of the light guide 302, light from the light source 301 enters the light guide 302 via the incident surface 302 a to form the unevenness 306. The light reaches the reflection portion 306b, is totally reflected at the interface with the low refractive index layer 307, and is emitted from the emission surface 300a of the illumination device 300 to illuminate the reflection type liquid crystal display element 310.

The reflective electrode 314 of the reflective liquid crystal display element 310 efficiently scatters and reflects illumination light within an incident angle of 30 ° in the front direction. Therefore, between the angle β formed by the uneven reflection portion 306b of the member 306 and the emission surface 302b of the light guide 302 and the total reflection angle α at the interface between the unevenness of the member 306 and the low refractive index layer 307, Equation (1),
α-30 ° ≦ β ≦ α + 30 ° (1)
It is desirable to design the shape of the concavo-convex so as to satisfy the relationship described above, and set the incident angle of the illumination light to the reflective liquid crystal display element 310 within 30 °.

In the third embodiment, the unevenness of the member 306 is made of polycarbonate having a refractive index of 1.58, and the low refractive index layer 307 has a refractive index of 1.38.
α = sin ⁻¹ (1.38 / 1.58) = 60.9 ° (4)
Given by

Therefore, β was set to 60 ° which is almost equal to α.

In this case, it is possible to obtain illumination light having an emission angle with respect to the emission surface 302b of the light guide 302 or the emission surface 300a of the illumination device 300 substantially parallel thereto, that is, an incidence angle with respect to the reflective liquid crystal display element 310 of approximately 0 °. Thus, the reflective liquid crystal display element 310 can be efficiently illuminated.

The irregularity period of the member 306 and the direction of the streaks formed were suitable for the 3.8 type QVGA which is the specification of the reflective liquid crystal display element 310 according to FIG. Specifically, as shown in FIG. 13, the period P was set to 390 μm and formed at an angle of 23 ° with the horizontal direction of the pixel pattern of the reflective liquid crystal display element 310. This shortens the period of the second light and dark fringes due to interference between the reflecting means having a large number of irregularities formed periodically and the pixel pattern of the reflective liquid crystal display element 310, so that the light is not recognized by the observer and the reflection is not performed. The display quality of the liquid crystal display element 310 is not impaired.

Further, of the period 390 μm of the unevenness of the member 306 as the reflection means, the length P1 of the propagation portion 306a is 370 μm on average, the length P2 of the reflection portion 306b is 20 μm on average, and the length P2 of the reflection portion 306b is used as a light source. The design is such that the reflective liquid crystal display element 310 can be uniformly illuminated by setting the distance to be shorter as the distance is shorter and set as the distance is longer. At this time, since the ratio (P2 / P1) of the reflection unit 306b to the propagation unit 306a is about 0.05, the image of the reflection type liquid crystal display element 310 is not observed as a double image, and the display quality is good. Could be obtained.

The anti-reflection layer 304b formed on the PET film 304a, which is the base material of the reflection sheet 303, reduces the surface reflection of the illumination device 300 and improves the transmittance, so that the display of the reflection type liquid crystal display element 310 is bright and has a high contrast ratio. Can be good. For the same reason, it is desirable that the anti-reflection treatment is also applied to the opposing surface 302 c of the light guide 302 and the surface of the reflective liquid crystal display element 310, that is, the surface of the polarization selective transmission unit 311.

In the third embodiment, since the light guide and the touch panel are also used, the number of interfaces is reduced as compared with the conventional configuration in which each of the light guides and the touch panel is formed of a separate member. Since the amount of incident light increases, very bright display with a high contrast ratio can be performed. Further, an inexpensive, thin and lightweight display device and an information display system such as a portable information terminal can be realized.

In the third embodiment, a fluorescent tube is used as a light source. However, an EL, an LED, a combination of an LED and a rod-shaped light guide, or the like may be used.

The light guide is not limited to a touch panel, but may be a glass, an acrylic resin, a polycarbonate resin, a transparent resin represented by an epoxy resin, or the like as appropriate.

基材 Various combinations are also possible for the bases 304 and 305 constituting the reflection sheet 303, the member 306 having irregularities serving as reflection means, and the low refractive index layer 307. Further, the reflecting means formed on the base material may be directly disposed on the light emitting surface 302b of the light guide 302 via the low refractive index layer 307.

In addition to providing an anti-reflection layer 304b on the surface of the reflection sheet 303 facing the reflection type liquid crystal display element 310, as in the reflection type liquid crystal display element 310 of the third embodiment, the polarization selective transmission means 311 comprises a polarizing plate and λ. In the case of having / 4, polarized light selective transmission means may be attached.

(4) The period of the unevenness as the reflection means and the direction of the formed streaks are not limited to the above, but change according to the pixel pattern of the reflection type liquid crystal display element as shown in FIGS.

The reflection type liquid crystal display element 310 includes the polarization selective transmission unit 311, and is not limited to one that modulates circularly polarized light to display an image, and may employ a reflection type liquid crystal display element using various modes of liquid crystal molecules. it can.

種類 The selection of the type of each means constituting the lighting device 300 and the reflective liquid crystal display element 310 is determined in consideration of the performance and reliability of the display device.

(Embodiment 4)
14 and 15 show a configuration example of a lighting device according to a fourth embodiment of the present invention and a display device including a reflective liquid crystal display device including the lighting device.

In the fourth embodiment, as shown in FIGS. 14 and 15, an illumination device 400 includes light sources 401a and 401b, a reflection unit 403, and a transparent flat plate 406. The reflection unit 403 and the transparent flat plate 406 face each other. The light guide spaces 402 are formed substantially in parallel. Note that the transparent flat plate 406 is a touch panel. The reflection type liquid crystal display element 410 includes a polarization selective transmission unit 411, a pair of glass substrates 412a and 412b, a liquid crystal layer 413 sandwiched therebetween, and a reflection electrode 414 disposed on the back side thereof.

Specifically, fluorescent tubes are used for the light sources 401a and 401b, and both are arranged to face each other.

As shown in a partially enlarged view of FIG. 14, the reflection means 403 arranges a large number of prisms 404 made of polycarbonate having a refractive index of 1.58 on a PET film 405 as a base material to form irregularities. The opposite surface of 405 is bonded to the reflective liquid crystal display element 410 via an adhesive layer.

タ ッ チ パ ネ ル A touch panel 406 is disposed above the reflection means 403, and a space formed between the two is a light guide space 402.

The reflection type liquid crystal display element 410 is a 3.8-type QVGA.

As shown in a partially enlarged view of FIG. 14, the polarization selective transmission unit 411 provided in the reflection type liquid crystal display element 410 is configured such that the polarizing plates 411a, λ / 2 plates 411b, and λ / 4 plates 411c are provided via an adhesive layer. The λ / 4 plate 411c is bonded to the glass substrate 412a in this order.

Therefore, the reflection type liquid crystal display element 410 receives the circularly polarized light that has passed through the polarization selective transmission unit 411 out of the ambient light or the illumination light from the illumination device 400 and controls the amount of the reflected light for each pixel to form an image. indicate.

The reflective electrode 414 has a scattering characteristic as shown in FIG.

Next, the uneven shape of the reflection means 403 will be described. The unevenness is formed by arranging a large number of prisms 404 on a PET film 405 as a base material, and each prism 404 is formed by a transparent flat plate 406 or an emission light from which illumination light of an illumination device 400 substantially parallel thereto is emitted. It has a first inclined portion 404a and a second inclined portion 404b inclined with respect to the surface 400a.

Light that has entered the light guide space 402 from the light source 401a propagates through the light guide space 402, reaches the prism 404, is refracted at the interface between the first inclined portion 404a and the light guide space 402, and is refracted at the second inclined portion 404b. The light is totally reflected at the interface between the liquid crystal display device and the light guide space 402 to illuminate the reflective liquid crystal display element 410. Similarly, light incident on the light guide space 402 from the light source 401b reaches the prism 404, is refracted by the second inclined portion 404b, is totally reflected by the first inclined portion 404a, and is reflected by the reflection type liquid crystal display element 410. Light up.

The reflective electrode 414 of the reflective liquid crystal display element 410 efficiently scatters and reflects the illumination light within an incident angle of 30 ° in the front direction. Therefore, the angle β formed by the first inclined portion 404a and the second inclined portion 404b of the prism 404 with the emission surface 400a of the illumination device is between the total reflection angle α at the interface between the prism 404 and the light guide space 402. , The following formula (1),
α-30 ° ≦ β ≦ α + 30 ° (1)
It is desirable that the incident angle of the illumination light be within 30 °.

In the fourth embodiment, since the prism 404 is made of polycarbonate having a refractive index of 1.58 and the refractive index of the light guide space 403 is 1.0, the total reflection angle α is expressed by the following equation (5).
α = asin (1.0 / 1.58) = 39.2 ° (5)
Given by

Therefore, β was set to 40 ° which is almost equal to α.

In this case, it is possible to obtain illumination light having an emission angle with respect to the emission surface 400a of the illumination device 400, that is, an incidence angle with respect to the reflection type liquid crystal display element 410 of approximately 0 °, so that the reflection type liquid crystal display element 410 can be efficiently illuminated. it can.

(5) The unevenness period and the direction of the streaks formed in the reflection means 403 are suitable for the 3.8 type QVGA which is the specification of the reflection type liquid crystal display element 310 according to FIG. Specifically, as shown in FIG. 15, the period P was set to 500 μm and formed at an angle of 20 ° with the horizontal direction of the pixel pattern of the reflective liquid crystal display element 310. Accordingly, the cycle of the second bright and dark fringes due to the interference between the numerous irregularities formed periodically and the pixel pattern of the reflective liquid crystal display element 410 is shortened, so that the reflective liquid crystal display element is not recognized by the observer. The display quality of the display 410 is not deteriorated.

Further, of the period 500 μm of the unevenness of the reflecting means 403, the length P1 ′ of the area where no unevenness is formed is 475 μm on average, and the length P2 ′ of the area where the unevenness is formed is 25 μm on average. The length P2 'of the region is set shorter as it is closer to the light source and longer as it is farther from the light source, so that the reflective liquid crystal display element 410 can be uniformly illuminated. At this time, the ratio (P2 ′ / P1 ′) of the length of the region where the unevenness is formed to the length of the region where the unevenness is not formed is about 0.05. Was not observed as a double image, and good display quality was obtained.

In the fourth embodiment, since the light guide space 402 formed by the reflection means 403 and the touch panel 406 is used, the display device and the portable information terminal are cheaper and lighter than the configuration using the light guide. Information display system can be realized.

In the fourth embodiment, a fluorescent tube is used as a light source. However, an EL, an LED, a combination of an LED and a rod-shaped light guide, or the like may be used.

The reflecting means 403 may be formed by forming a large number of irregularities directly on the surface of the reflective liquid crystal display element 410, for example, in addition to the method of forming irregularities on the base material.

(4) The unevenness period of the reflection means 403 and the direction of the formed streaks are not limited to those described above, and change according to the pixel pattern of the reflection type liquid crystal display element as shown in FIGS.

The reflection type liquid crystal display element 410 includes a polarization selective transmission unit 411, and is not limited to one that modulates circularly polarized light to display an image, and may employ a reflection type liquid crystal display element using various modes of liquid crystal molecules. it can.

(4) The selection of the type of each means constituting the illumination device 400 and the reflection type liquid crystal display element 410 is determined in consideration of the performance and reliability of the display device.

1 is a cross-sectional view illustrating a display device including a lighting device and a reflective liquid crystal display element according to a first embodiment of the present invention. 1 is a perspective view illustrating a display device including a lighting device and a reflective liquid crystal display element according to a first embodiment of the present invention. FIG. 3 is a diagram illustrating the scattering and reflection characteristics of a reflective electrode used in a reflective liquid crystal display element. FIG. 7 is a diagram illustrating a relationship between a lighting device in which a second bright and dark fringe does not occur and a reflection-type liquid crystal display element in a delta arrangement. FIG. 7 is a diagram illustrating a relationship between an illumination device in which second bright and dark fringes do not occur and a reflective liquid crystal display element in a stripe arrangement. FIG. 3 is a first diagram illustrating an optimal shape of a reflection unit in the lighting device of the present invention. It is a 2nd figure explaining the optimal shape of the reflection means in the illumination device of this invention. FIG. 3 is a diagram illustrating a method for evaluating a double image in display of a reflective liquid crystal display element by the illumination device of the present invention. The degree of the double image in the display of the illumination device of the present invention and the reflection type liquid crystal display element is determined by the ratio of the reflection part and the propagation part (P2 / P1) of the unevenness, and the area of the area where the unevenness is formed and the area where the unevenness is not formed. It is a figure shown by the relationship of a ratio (P2 '/ P1'). FIG. 6 is a cross-sectional view illustrating a display device including a lighting device and a reflective liquid crystal display element according to a second embodiment of the present invention. FIG. 6 is a perspective view showing a display device including a lighting device and a reflective liquid crystal display element according to a second embodiment of the present invention. FIG. 11 is a cross-sectional view illustrating a display device including a lighting device and a reflective liquid crystal display element according to a third embodiment of the present invention. FIG. 9 is a perspective view illustrating a display device including a lighting device and a reflective liquid crystal display element according to a third embodiment of the present invention. FIG. 13 is a cross-sectional view illustrating a display device including a lighting device and a reflective liquid crystal display element according to a fourth embodiment of the present invention. FIG. 9 is a perspective view illustrating a display device including a lighting device and a reflective liquid crystal display element according to a fourth embodiment of the present invention. FIG. 3 is a diagram illustrating a configuration example of a reflective liquid crystal display element. 6A and 6B are diagrams illustrating an arrangement pattern of pixels of a reflection type liquid crystal display element, in which FIG. 7A illustrates a case of a delta arrangement and FIG. 7B illustrates a case of a stripe arrangement. FIG. 9 is a diagram illustrating a configuration example of a front light that is a conventional lighting device.

Explanation of reference numerals

30, 101, 201, 301, 401a, 401b, 911 Light source 31, 102, 202, 302, 912 Light guide 32, 110, 210, 310, 410, 920 Reflective liquid crystal display elements 33, 111, 211, 311; 411, 921 Polarization selective transmission means 34a, 34b, 112a, 112b, 212a, 212b, 312a, 312
b, 412a, 412b, 922a, 922b Glass substrate 35, 113, 213, 313, 413, 923 Liquid crystal layer 36, 114, 214, 314, 414, 924 Reflective electrode 37 Observer 100, 910 Illumination device (front light)
102a, 202a, 302a, 912a Incident surfaces 100a, 102b, 200a, 202b, 302b, 912b Outgoing surfaces 102c, 202c, 302c, 912c Opposing surfaces 103, 203, 913 Reflecting means (irregularities)
103a, 203a, 306a, 913a Propagation parts 103b, 203b, 306b, 913b Reflection parts 104 Antireflection films 111a, 211a, 311a, 411a Polarization plates 111b, 211b, 211b, 311b, 411b λ / 4 plates 111c, 211c, 311c, 411c λ / 2 plate 200, 300, 400 Lighting device 204, 307 Low refractive index layer 205 Protective film 205a Protective film substrate 205b Hard coat layer, antireflection layer, antifouling layer 303, 403 Reflection sheet (reflection means)
304, 305 Reflective sheet substrate 304a PET film 304b Antireflection layer 306 Member with irregularities 402 Light guide space 404 Prism 404a First inclined portion 404b Second inclined portion 405 Reflective sheet substrate 406 Transparent flat plate (touch panel)
914 Optical compensator 915 Compensation unevenness

Claims (2)

A light source,
An incident surface on which light from the light source is incident, an exit surface that is substantially orthogonal to the incident surface, and an exit surface from which illumination light exits, and a light guide having a facing surface facing the exit surface,
On the emission surface or the opposing surface of the light guide, provided with reflecting means molded or arranged separately from the light guide,
An antireflection film is provided on an emission surface of the light guide,
Light that enters from the light source through the incident surface of the light guide and propagates inside the light guide is reflected by the reflection unit and emitted as illumination light ,
A front light in which the illumination light is incident on a reflection type liquid crystal display device . A light source,
An incident surface on which light from the light source is incident, an exit surface that is substantially orthogonal to the incident surface, and an exit surface from which illumination light exits, and a light guide having a facing surface facing the exit surface,
On the emission surface or the opposing surface of the light guide, provided with reflecting means molded or arranged separately from the light guide,
The reflecting means reflects light according to the refractive index difference of the interface in the uneven shape,
The concavo-convex shape has a prism shape, and has a reflecting portion inclined with a propagation portion substantially parallel to an emission surface of the light guide, and a total reflection angle due to a refractive index difference at an interface of the reflecting portion. Is α, the angle β formed by the reflecting portion with respect to the light exit surface of the light guide or the transparent flat plate is expressed by the following equation (1): α−30 ° ≦ β ≦ α + 30 ° (1)
By satisfying the relationship
A front light that enters from the light source through the incident surface of the light guide, propagates inside the light guide, and mainly reflects light that propagates through the propagation portion at the reflection portion and emits it as illumination light When,
A reflective liquid crystal display element having a reflective electrode having a fine structure for displaying an image by receiving illumination light from the front light and controlling the reflectance for each pixel to display an image.

Images