JP2010230835A - Reflective liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflective liquid crystal display device for achieving high light utilization ratio and the improvement of luminance uniformity by reusing leaking light. <P>SOLUTION: A side surface reflection plate 19 angled with respect to an end surface of a substrate 13 of a liquid crystal panel is disposed on a side surface opposite to a light source 11. Light passed through the end surface is reflected by the side surface reflection plate 19, the light is reflected by a reflection plate 17, and the light is further reflected by the side surface reflection plate 19 and is returned to a liquid crystal panel. In this constitution, light leaking from the end surface is recycled, and the light utilization efficiency of the light source is increased. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a reflective liquid crystal display device having a sidelight, and more particularly to measures for efficiently using light from a light source.

  Liquid crystal panels are used as display elements in many devices such as televisions and mobile phones because of their thinness and low power consumption. In particular, since the reflective liquid crystal display panel uses external light, the low power consumption effect is particularly high. However, when used in a dark place, it is necessary to use an external light source. There is a front light method as a method used in this case.

  The front light illuminates light from a light source such as a light emitting diode by providing a thin plate called a light guide plate on which a prism is formed on the viewing side of the liquid crystal panel and reflecting the light from the light source toward the liquid crystal panel.

  However, since the thickness of the liquid crystal panel is increased by adding a front light, the merit of thinness is reduced. Therefore, the substrate itself sandwiching the liquid crystal layer is used as a light guide plate, a fine polymer network is formed in the liquid crystal layer called polymer network liquid crystal (hereinafter referred to as PNLC), and the light scattering state is caused by the difference in refractive index between the liquid crystal and the polymer. By using a liquid crystal that realizes the above, a thinner direct incident type reflective liquid crystal display element can be realized. However, this method has a problem that a part of the light incident from the end face of the liquid crystal panel on the light source side passes through the end face on the side opposite to the light source side and the light from the light source cannot be used sufficiently effectively.

  As a solution to this problem, there is known a conventional technique in which a reflecting layer is closely attached to an end surface portion from which light is emitted or a liquid crystal panel is incorporated and closely attached to a frame having a light reflecting mechanism to return the light to escape to the front light side. (For example, refer to Patent Document 1).

JP 2002-268061 A (page 3-4, FIG. 1)

  However, it is difficult to bring the reflective layer into close contact with the end face portion of the liquid crystal panel unless the single face portion has flatness, and luminance reduction occurs due to light leakage or the like. SUMMARY OF THE INVENTION An object of the present invention is to solve the problem of losing light from a light source, and to provide a reflective liquid crystal display element that uses light with high efficiency by suppressing light leakage from the end face of a light guide plate opposite to the light source. .

  The present invention includes a liquid crystal panel having an upper substrate and a lower substrate having a reflecting plate, with a liquid crystal layer sandwiched between the upper substrate and the lower substrate, and a light source on the end face side of the liquid crystal panel. In the reflective liquid crystal display device, a side reflector is provided on an end surface opposite to an end surface of the liquid crystal panel on which the light source is disposed, the side reflector is opposed to the end surface of the liquid crystal panel, and the liquid crystal panel It is characterized by being arranged at an angle with respect to the display surface. Further, the reflection plate is arranged so as to protrude from the lower substrate toward the side reflection plate, and has a space surrounded by the end face of the liquid crystal panel, the reflection plate, and the side reflection plate.

Further, the side reflector and the reflector are integrated. The side reflector and the end face of the liquid crystal panel are disposed in contact with each other. Further, the space is filled with a material having a refractive index between the refractive index of air and the refractive index of the upper substrate or the lower substrate.

  In the reflective liquid crystal display device, by installing a metal plate on the opposite side of the light source, the light that escapes from the liquid crystal panel or the light guide plate can be reused, and the light use efficiency can be improved. A reflective liquid crystal display device with high brightness and high brightness uniformity can be provided.

It is sectional drawing of the reflection type liquid crystal display element of this invention. It is a principal part enlarged view of FIG. 1 in this invention. It is a principal part enlarged view in this invention. It is sectional drawing of the reflection type liquid crystal display element of this invention.

  The present invention is a reflective liquid crystal display device using a liquid crystal panel in which liquid crystal is sandwiched between an upper substrate and a lower substrate having a reflector, and having a light source on the end face side of the liquid crystal panel. On the end surface side opposite to the end surface side of the liquid crystal panel where the light source is disposed, the liquid crystal panel is disposed opposite to the end surface and at an angle with respect to the display surface of the liquid crystal panel. At this time, it is preferable to dispose at an angle of 45 °. The reflecting plate is arranged so as to protrude from the lower substrate toward the side reflecting plate, and forms a space surrounded by the end face of the liquid crystal panel, the reflecting plate, and the side reflecting plate. By forming such a space, the light emitted from the end face after being guided through the upper substrate of the liquid crystal panel is reflected by the side reflector, the reflector, and the side reflector again in the space, and is directed to the end face of the liquid crystal panel. And light can be returned. In this manner, by making light incident again on the liquid crystal panel, the light utilization rate of the light source is increased, the luminance of the liquid crystal panel on the end surface side facing the light source side is increased, and the luminance uniformity is improved.

  FIG. 1 is a cross-sectional view of the reflective liquid crystal display device of this embodiment. The liquid crystal panel includes an upper substrate 13 and a lower substrate 14, and each substrate is a polycarbonate substrate having a thickness of 125 μm. The upper substrate 13 and the lower substrate 14 are bonded with a sealant 16, and the sealant 16 is formed in a frame shape to bond the upper substrate 13 and the lower substrate 14 on four sides of the liquid crystal panel. . Transparent electrodes (not shown) are provided inside both substrates, and liquid crystal is sandwiched between the substrates. In this embodiment, the thickness of the liquid crystal layer 15 is 10 μm.

  The display format of the liquid crystal layer 15 is not particularly limited, such as TN (Twisted Nematic), VA (Vertical Alignment), and IPS (In Plane Switching), but the upper substrate 13 or the lower substrate 14 or both substrates are used as the light guide plate. In this case, PN (Polymer Network) LC or polymer-dispersed liquid crystal (PDLC) is used as the liquid crystal layer 15 in order to scatter light, change the traveling direction of light toward the reflector 17 or the substrate, and increase the luminance. It is preferable to use it. In addition, since a PNLC or PDLC liquid crystal panel does not require a polarizing plate, high luminance can be obtained.

  As the light source 11, a white light emitting LED is used. The light source 11 is a linear light source in which a prism is formed so that light is incident from one side of the liquid crystal panel. The light emitting portion has a thickness of 0.3 mm and a width of 42.7 mm. In order to prevent light leakage and to emit light only in the direction of the liquid crystal panel, the linear light source has a structure in which the reflective cover 12 covers the light emitting surface and the white light emitting LED light other than the incident surface. The material and shape of the reflective cover 12 are not limited, but a material having a higher reflectance and a structure that does not allow light to leak to other than the end face of the liquid crystal panel are preferable.

  On the outside of the lower substrate, a reflector 17 longer than the lower substrate 14 is disposed via an acrylic adhesive tape that is an adhesive layer 18 provided in the peripheral portion. The reflection plate 17 is a mirror surface, and is arranged so as to protrude from the lower substrate 14 to the side facing the light source 11. The protruding portion is used as a side reflection plate 19 so as to contact the corner of the upper substrate 13 of the liquid crystal panel. It bent | folded so that it might become 45 degrees with respect to the edge part. Thus, a space surrounded by the end face of the liquid crystal panel, the reflection plate 17 and the side reflection plate 19 was formed.

  FIG. 2 is an enlarged view of the space surrounded by the end face of the liquid crystal panel, the side reflector 19 and the reflector 17. The light 21 emitted from the end surface after being guided through the upper substrate 13 of the liquid crystal panel is reflected by the side reflector 19, guided to the reflector 17, reflected by the reflector 17 to the side reflector 19, and It acts to return light from the side reflector 19 to the end face of the liquid crystal panel. In this manner, by making light incident again on the liquid crystal panel, the light utilization rate of the light source 11 is increased, the luminance of the liquid crystal panel on the end surface side facing the light source side is increased, and the luminance uniformity is improved.

  The side reflector 19 is deformed so as to be easily attached to the liquid crystal panel by bending, and is attached so as not to cause light leakage by being in close contact with the corner of the end face of the liquid crystal panel. Further, the side reflector 19 is preferably attached at an angle of 45 ° with respect to the end face of the liquid crystal panel in order to make the reflectance as high as possible and easily return to the end face of the liquid crystal panel. Moreover, although the example in which the side reflector 19 and the reflector 17 are integrally formed is shown in FIG. 1, each may be arranged separately.

  The reflection plate 17 provided on the lower substrate 14 is attached to the lower substrate 14 via the adhesive layer 18, and the material is not limited. However, it is preferable that the reflection plate 17 has a high reflectance and can be easily attached. Further, in FIGS. 1 and 2, the reflector 17 and the lower substrate 14 are attached to the entire surface of the lower substrate 14 with an adhesive layer. May be.

  FIG. 3 is an enlarged view of the space surrounded by the end face of the liquid crystal panel, the reflector 17 and the side reflector 19. The same members as those in FIGS. 1 and 2 are denoted by the same reference numerals. However, the reflecting plate 17 and the side reflecting plate 19 are not integrally formed, but are formed of different materials, and are arranged in close contact with each other.

  In FIG. 3, a resin 31 is filled in a space surrounded by the end face of the liquid crystal panel, the reflecting plate 17, and the side reflecting plate 19. The resin 31 is a material having a refractive index between the refractive index of air and the refractive index of the substrate that mainly guides light from the light source. In this way, by filling the resin 31, the three surfaces of the space are brought into close contact with each other and the difference in refractive index is filled, so that when the light emitted from the end surface of the liquid crystal panel is incident again, reflection at the end surface is reduced and more efficient. Light can be incident again well. Therefore, it is preferable that the resin to be filled has substantially the same refractive index as that of the substrate used for the liquid crystal panel.

  In this embodiment, a silicone resin having a refractive index of 1.41 is filled as the resin 31 as a material having a refractive index between the refractive index of air and the refractive index of the substrate. In this configuration, since the refractive index of the space increases from 1.00 to 1.41 of air, the difference between the refractive index of 1.585 of the polycarbonate used for the upper substrate and the lower substrate of the liquid crystal panel becomes small. . Therefore, when the light emitted from the end face of the liquid crystal panel is reflected and reenters the liquid crystal panel, loss due to refraction is reduced, and light utilization efficiency can be increased.

FIG. 4 is a cross-sectional view of a reflective liquid crystal display device according to another embodiment of the present invention. On the viewing side of the upper substrate 13, a light guide sheet 41 for increasing the luminance is provided. The light guide sheet 41 is a plastic film provided with a prism, and is attached to the upper substrate 13 via an adhesive layer 42. In addition, as in FIG. 1, a high-efficiency utilization effect can be obtained by bringing the side reflector 19 into close contact with the corner of the end face of the light guide sheet 41 on the side facing the light source.

  Also in the configuration of FIG. 4, the light from the light source 11 is mainly guided in the light guide sheet 41, reflected by the prism toward the reflection plate 17, and reflected by the reflection plate 17 at the same time. By repeating the reflection in the direction, higher luminance could be provided.

  Further, as illustrated in FIG. 3, the space portion of FIG. 4 may be filled with a material having a refractive index between the refractive index of air and the refractive index of the substrate. In that case, higher luminance can be obtained.

11 Light source 12 Reflective cover 13 Upper substrate 14 Lower substrate 15 Liquid crystal layer 16 Sealing agent 17 Reflector 18 Adhesive layer 19 Side reflector 41 Light guide sheet 42 Adhesive layer

Claims (5)

A liquid crystal panel having an upper substrate and a lower substrate provided with a reflector, a liquid crystal panel sandwiching a liquid crystal layer between the upper substrate and the lower substrate, and a reflection provided with a light source on the end face side of the liquid crystal panel Type liquid crystal display device,
A side reflector is provided on an end face opposite to the end face of the liquid crystal panel in which the light source is disposed, the side reflector is opposed to the end face of the liquid crystal panel and is opposed to the display face of the liquid crystal panel. A reflection type liquid crystal display device, characterized in that it is arranged at an angle. The reflector is disposed so as to protrude from the lower substrate to the side reflector.
The reflective liquid crystal display device according to claim 1, further comprising a space surrounded by an end face of the liquid crystal panel, the reflecting plate, and the side reflecting plate.   The reflective liquid crystal display device according to claim 1, wherein the side reflector and the reflector are integrated.   4. The reflective liquid crystal display device according to claim 1, wherein the side reflector and the end face of the liquid crystal panel are disposed in contact with each other. 5.   The reflection according to any one of claims 2 to 4, wherein the space is filled with a material having a refractive index between a refractive index of air and a refractive index of the upper substrate or the lower substrate. Type liquid crystal display device.

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