JP4013472B2 - Liquid crystal device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal device including a lighting device.
[0002]
[Prior art]
In recent years, with the miniaturization of electronic devices, liquid crystal panels have been used as display devices. In general, an illumination device is attached to the liquid crystal panel so that the liquid crystal panel can be used in a dark place.
[0003]
The illuminating device is disposed on the back side of the liquid crystal panel as a backlight composed of a light source such as a discharge tube or LED and a light guide plate for uniformly supplying light from the light source to the entire liquid crystal panel. In particular, as shown in FIG. 8, the sidelight type backlight has a light guide plate 102 disposed on the side of the light source 100 so as to face the liquid crystal panel 110. In this case, the light source 100 is formed, for example, by arranging a plurality of light emitting diodes (LEDs) 100a... On the light source substrate 104 at regular intervals. Further, the light guide plate 102 has a front surface 102b as a light emitting surface (outgoing surface) and a back surface and side surfaces as light shielding surfaces.
[0004]
In such a backlight, light from the LED 100 a enters the light guide plate 102 from the incident surface 102 a of the light guide plate 102, and is guided to the front surface of the output surface 102 b while being reflected by the inner surface of the light guide plate 102. At this time, a translucent diffusion sheet (prism sheet) 106 is affixed to the outside of the emission surface 102b (between the light guide plate 102 and the liquid crystal panel 110) in order to guide light more efficiently to the emission surface 102b. Is done.
Further, it is difficult to completely and efficiently shield light around the light source 100, and it is difficult to make all the light from the light source 100 incident on the incident surface 102 of the light guide plate 102. In other words, part of the light emitted from the light source may leak without entering the incident surface 102 of the light guide plate 102. Such leaked light not only has a possibility of adversely affecting other circuits and mechanical elements, but also causes a loss that does not contribute to illuminating the liquid crystal panel, thereby deteriorating illumination efficiency.
[0005]
[Problems to be solved by the invention]
However, in such a backlight, since the diffusion sheet 106 and the liquid crystal panel 110 are in direct contact with each other, the diffusion sheet 106 and the liquid crystal panel 110 may interfere with each other, and accordingly, interference fringes may be generated. Therefore, the display screen may be difficult to see.
[0007]
The present invention has been made paying attention to the above circumstances, and an object thereof is to provide a liquid crystal device capable of preventing interference fringes generated by interference between a diffusion sheet on a light guide plate and a liquid crystal panel. .
[0008]
[Means for Solving the Problems]
In order to solve the above-described problem, a liquid crystal device according to claim 1 includes at least one light source that emits light, a light guide plate, a diffusion plate placed on the light guide plate, and the diffusion plate. A liquid crystal panel mounted thereon, a spacer and an air layer are provided on a surface of the diffusion plate on the liquid crystal panel side, and the diffusion plate and the liquid crystal panel are mutually connected. It is characterized by being overlapped via the spacer and the air layer without contacting.
[0009]
According to the liquid crystal device described in claim 1, interference between the diffuser plate and the irradiated body is prevented, and interference fringes are prevented from being generated in the display area of the irradiated body.
[0010]
A liquid crystal device according to a second aspect is the liquid crystal device according to the first aspect, wherein the spacer has a thickness of 0.1 mm to 0.5 mm.
[0011]
According to the liquid crystal device described in claim 2, the interference between the diffuser plate and the object to be irradiated is almost certainly prevented, and the occurrence of interference fringes in the display area of the object to be irradiated is almost certainly prevented. The If the spacer thickness is 0.1 mm or less, the generation of interference fringes cannot be prevented. On the other hand, if the thickness of the spacer exceeds 0.5 mm, the entire liquid crystal device becomes thick, which hinders downsizing of the display device including the irradiated body.
[0012]
According to a third aspect of the present invention, in the liquid crystal device according to the first aspect, the spacer also serves as a light shielding plate.
[0013]
According to the liquid crystal device described in claim 3, it is possible to prevent light leakage and improve the illumination efficiency.
[0014]
According to a fourth aspect of the present invention, in the liquid crystal device according to the third aspect, the spacer includes white polyethylene terephthalate.
[0015]
According to the liquid crystal device described in claim 4, light is easily reflected, and light efficiency and display unevenness can be prevented to further improve the illumination efficiency.
[0016]
The liquid crystal device according to claim 5 is the liquid crystal device according to claim 3 or 4, wherein the spacer has an inner edge located in the vicinity of the display region of the irradiated object so that the display region is substantially the same. It is formed as a rectangular frame-like member extending so as to be defined.
[0017]
According to the liquid crystal device according to the fifth aspect, the light emitted from the light guide plate can be efficiently guided to the display area of the irradiated object without waste.
[0024]
The liquid crystal device described in claim 6 is characterized in that a diffusion sheet is used as the diffusion plate. Thereby, light can be uniformly irradiated to a to-be-irradiated body.
[0025]
The liquid crystal device described in claim 7 uses a prism sheet as a diffusion plate. Thereby, light can be uniformly irradiated to a to-be-irradiated body.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0033]
1 and 2 show a liquid crystal device 1 including an illumination device according to an embodiment of the present invention. As shown in the figure, the liquid crystal device 1 is mainly composed of a rectangular liquid crystal panel 60 as an irradiated body and a backlight as an illuminating device for supplying illumination light to the liquid crystal panel 60, and is a flat rectangular parallelepiped shape. Is formed. The backlight includes a plurality of light emitting diodes (LEDs) 20 as light sources, and a rectangular light guide plate 50 that uniformly supplies light from the LEDs 20 to the entire liquid crystal panel 60, and is disposed on the back side of the liquid crystal panel 60. Is done.
[0034]
The light guide plate 50 is placed in a housed state in a light shielding member 40 having a rectangular frame shape, and a side surface portion of the light guide plate 50 facing the LED 20 is formed as an incident surface 50 a that receives light from the LED 20. A rectangular diffusion sheet (prism sheet) as a diffusion plate that uniformly diffuses (diffuses) the light of the backlight and guides it to the liquid crystal panel 60 on the surface 50 b of the light guide plate 50 that is a light emitting surface (outgoing surface). 70 is attached. Further, between the diffusion sheet 70 and the liquid crystal panel 60, a rectangular frame-shaped contact prevention sheet 10 that prevents contact between the diffusion sheet 70 and the liquid crystal panel 60 is interposed. Then, the peripheral portions of the side surfaces and the upper surface (front surface) of the series of members including the liquid crystal panel 60 and the backlight, that is, the portions excluding the rectangular display region 60a of the liquid crystal panel 60 are covered with a cover 80 that also serves as a light shield. It has been broken. Here, the display area 60a of the liquid crystal panel 60 refers to an area represented as a lighting pixel by an electrode formed on the liquid crystal panel.
[0035]
The light shielding member 40 has a concave placement surface 44 on which the light guide plate 10 is placed, and a rectangular frame-like placement portion 40a on which the light guide plate 10, the sheets 10 and 70 thereon, and the liquid crystal panel 60 are placed. And a box-shaped light source accommodating portion 40b which is disposed on the side of the light guide plate 10 and forms an accommodating space S for accommodating the plurality of LEDs 20.
[0036]
As shown in FIGS. 1 to 4, the mounting portion 40 a has three side walls 45 a, 45 b that cover the three side surfaces excluding the incident surface 50 a of the light guide plate 50 and prevent light leakage from these side surfaces. 45c, and a bottom wall 45d that covers the back surface opposite to the light emitting surface 50b of the light guide plate 50 and prevents light leakage from the back surface. The light source accommodating portion 40b is disposed in the accommodating space S with three side walls 42a, 42b, and 42c that surround the plurality of LEDs 20 disposed in the accommodating space S from the side to prevent leakage of light to the outside. The upper wall 42d that covers the LED 20 to be formed from above is provided. An opening 43 that exposes the incident surface 50a of the light guide plate 50 to the accommodation space S is formed on the side of the light source accommodation portion 40b that faces the side wall 42c. Note that brackets 49 for attaching the liquid crystal device 1 to an attachment frame (not shown) via the light shielding member 40 are provided at the four corners of the light shielding member 40.
[0037]
In order to improve the light shielding performance of the light shielding member 40, at least the inner surface portion (light shielding surface) facing the light guide plate 50 and the LED 20 is painted white or coated (pasted) with a white sheet. In particular, in the present embodiment, the entire light shielding member 40 is painted white.
[0038]
The light guide plate 50 is provided on the concave mounting surface 44 of the light shielding member 40 so as to face the liquid crystal panel 60. In this case, as described above, of the four side surfaces of the light guide plate 50, the side surfaces not covered by the side walls 45a, 45b, and 45c of the light shielding member 40 are accommodated through the openings 43 of the light shielding member 40 so as to face the LEDs 20. The incident surface 50a is exposed to the space S.
[0039]
The light guide plate 50 is formed in a rectangular parallelepiped shape with a transparent acrylic resin. In this case, the exit surface (front surface) 50b of the light guide plate 50 and the back surface opposite to the exit surface (front surface) 50b are formed in parallel planes, and four side surfaces including the entrance surface 50a are perpendicular to the exit surface 50b. It is formed in a plane.
[0040]
In addition, in order to improve the light diffusion performance of the light guide plate 50, a light diffusion shaped protrusion may be formed on the surface of the light guide plate 50 by injection molding or the like. Further, all the surfaces of the light guide plate 50 may be formed as irregular reflection surfaces that are subjected to a textured process so that internally reflected light is diffusely reflected (and transmitted) and diffused. The transparent material forming the light guide plate 50 may be an acrylic resin, a transparent resin such as a polycarbonate resin or an amorphous polyolefin resin, an inorganic transparent material such as glass, or a composite thereof.
[0041]
The plurality of LEDs 20 positioned on the side of the light guide plate 50 are arranged on the light source substrate 30 with a certain distance from each other. Specifically, the plurality of LEDs 20 are supported by a support body 30a erected on the substrate 30. When the substrate 30 is attached to the light shielding member 40, the plurality of LEDs 20 supported by the support body 30a are replaced by the light shielding member. It is located in the 40 accommodation space S so as to face the incident surface 50 a of the light guide plate 50. At this time, the portion 30b of the substrate 30 facing the accommodation space S forms a part of the light source accommodation portion 40b so as to close the bottom of the accommodation space S, and the side walls 42a, 42b, 42c and the upper wall 42d of the light shielding member 40 are formed. At the same time, the light from the LED 20 is prevented from leaking outside. As the light source, in addition to the LED 20, a point light source such as a discharge tube (fluorescent tube) or a lamp or a linear light source can be used. Further, the number of LEDs 20 is arbitrary.
[0042]
Further, the diffusion sheet 70 placed on the light guide plate 50 is, for example, a surface of a transparent acrylic resin plate formed into a mat so as to reflect and refract light, and is emitted from the exit surface of the light guide plate. The light is uniformly dispersed (diffused) and guided to the liquid crystal panel 60.
[0043]
The liquid crystal panel 60 that faces the light guide plate 50 through the diffusion sheet 70 and the contact prevention sheet 10 described later includes a simple matrix type liquid crystal panel, a liquid crystal panel using active elements such as TFT and MIM, As a liquid crystal material, a liquid crystal panel using a polymer liquid crystal material in which a polymer is dispersed in liquid crystal can be used. In the case of a polymer-dispersed liquid crystal panel, it is not necessary to use a polarizing plate. Further, in the case of a simple matrix type liquid crystal panel, in particular, when an STN type liquid crystal is used, at least one retardation plate is disposed as necessary. Since it is a reflective liquid crystal panel, a brighter display can be obtained by using a liquid crystal panel that uses only one polarizing plate.
[0044]
FIG. 5 shows the contact prevention sheet 10 interposed between the diffusion sheet 70 and the liquid crystal panel 60. As illustrated, the contact prevention sheet 10 includes a rectangular frame portion 10a that functions as a spacer that separates the diffusion sheet 70 and the liquid crystal panel 60 by a predetermined distance to prevent contact therebetween. The frame portion 10 a is placed on the diffusion sheet 70 and has an opening 15 that guides light from the light guide plate 50 to the display area 60 a of the liquid crystal panel 60. An air layer is formed with the diffusion sheet 70. The frame portion 10a is set to have a thickness t of 0.1 mm to 0.5 mm in order to prevent interference fringes from occurring due to interference between the diffusion sheet 70 and the liquid crystal panel 60. In particular, in the present embodiment, t = 0.25 mm (250 μm) is set.
[0045]
Further, the contact prevention sheet 10 has a function as a light shielding plate in addition to a function as a spacer for preventing contact between the diffusion sheet 70 and the liquid crystal panel 60. Therefore, the contact prevention sheet 10 is formed of white PET (polyethylene terephthalate) as a whole, and has a flat plate-like extension portion 10b extending outward from the frame portion 10a in addition to the frame portion 10a. ing. When the contact prevention sheet 10 is viewed as a light shielding plate, the frame portion 10a forms a first light shielding portion that shields light from the light guide plate 50 (reflects toward the light guide plate 50), and the extension portion 10b A second light-shielding portion that prevents light from the LED 20 from leaking outside the light source housing portion 40 b through the opening 43 is formed.
[0046]
Specifically, as shown by a broken line in FIG. 6, when the frame portion 10 a is placed on the diffusion sheet 70 and overlapped with the liquid crystal panel 60, the inner edge thereof is the display area 60 a ( It is located in the vicinity of (indicated by a one-dot chain line in the figure). That is, the frame portion 10a extends with a width that substantially defines the display area 60a. In particular, in the present embodiment, the distance X between the outer edge of the display region 60a and the inner edge of the frame portion 10a is set to 0.5 to 1 mm. This distance X is set in a range where the inner edge of the frame portion 10a does not overlap the display area 60a. 1, 2, and 7, the extending portion 10 b extends from the opening 43 of the light source accommodating portion 40 b of the light shielding member 40 in a state where the frame portion 10 a is placed on the diffusion sheet 70. It extends into the accommodation space S and is arranged so as to cover all the LEDs 20 from above. In particular, in the present embodiment, the extending portion 10b is set to have such a width and length as to substantially completely close a gap formed between the light guide plate 50 side and the light shielding member 40 side by the opening 43. . In this case, it is desirable to form a closed space S1 surrounded by the extending portion 10b, the light guide plate 50 and the diffusion sheet 70, the side walls 42a and 42b of the light source housing portion 40b, and the support 30a of the substrate 30. In the present embodiment, the distance Y between the extending portion 10b and the LED 20 is not particularly limited, and can be appropriately set according to the position of the light guide plate 50.
[0047]
Next, operations of the illumination device and the liquid crystal device having the above-described configurations will be described.
[0048]
First, when the LED 20 emits light, the light from the LED 20 enters the light guide plate 50 from the incident surface 50 a of the light guide plate 50. At this time, light that is not directly incident on the light guide plate 50 from the LED 20 is also reflected by the inner surface of the light source housing portion 40b of the light shielding member 40, the substrate 30 (including the support 30a), or the extending portion 10b of the contact prevention sheet 10. However, the light is guided to the incident surface 50 a of the light guide plate 50. That is, in the present embodiment, the light source (LED 20) is isolated from the outside by the light source housing portion 40b of the light blocking member 40, and the opening 43 formed to expose the incident surface 50a of the light guide plate 50 to the light source is blocked. Thus, the extension part 10b of the contact prevention sheet 10 extends into the accommodation space S, and the light source accommodation part 40b and the extension part 10b jointly form a closed space S1. Therefore, almost all of the light from the LED 20 is incident on the incident surface 50 a of the light guide plate 50 without leaking outside.
[0049]
The light that has entered the light guide plate 50 in this way is multiple-reflected and diffused by the front and back surfaces of the light guide plate 50, and is uniformly diffused throughout the light guide plate 50. In this case, since the side surface and the back surface of the light guide plate 50 are covered from the outside by the light shielding member 40, there is no light transmitted from the side surface and the back surface to the outside, and all the light incident into the light guide plate 50 is diffusely reflected. Then, the light is diffused and emitted (uniformly) from the entire emission surface 50b of the light guide plate 50 with a substantially uniform energy density. That is, the light shielding member 40 guides the light in the light guide plate 50 and reaches the end surface again to return the light into the light guide plate 50, thereby improving the illumination efficiency.
[0050]
The light emitted from the emission surface 50 b of the light guide plate 50 is further uniformly dispersed (diffused) by the diffusion sheet (prism sheet) 70, and then passes through the opening 15 of the frame portion 10 b of the contact prevention sheet 10. 60 is illuminated. At this time, since the frame portion 10a extends so that the inner edge thereof is positioned in the vicinity of the display region 60a of the liquid crystal panel 60 and substantially defines the display region 60a, light deviating from the display region 60a is transmitted by the frame portion 10a. The light is reflected and returned again to the light guide plate 50 side, and is guided only to the display area 60 a through the opening 15. That is, the light is guided so as to be narrowed toward the display area 60a.
[0051]
As described above, in the illumination device and the liquid crystal device according to the present embodiment, the contact prevention sheet 10 as a spacer for preventing the diffusion sheet 70 and the liquid crystal panel 60 from contacting between the diffusion sheet 70 and the liquid crystal panel 60. It is inserted. Therefore, interference between the diffusion sheet 70 and the liquid crystal panel 60 is prevented, and occurrence of interference fringes in the display area 60a of the liquid crystal panel 60 is prevented. In order to prevent interference between the diffusion sheet 70 and the liquid crystal panel 60 and prevent interference fringes, the thickness t of the contact prevention sheet 10 is set to 0.1 mm to 0.5 mm as in the present embodiment. It is desirable to set to. If the thickness t of the contact prevention sheet 10 is 0.1 mm or less, the generation of interference fringes cannot be prevented. In addition, when the thickness t of the contact prevention sheet 10 exceeds 0.5 mm, the entire lighting device becomes thick, which hinders downsizing of the liquid crystal device 1.
[0052]
Further, in the illumination device and the liquid crystal device of the present embodiment, the contact prevention sheet 10 has a function as a light shielding plate in addition to a function as a spacer for preventing the diffusion sheet 70 and the liquid crystal panel 60 from contacting each other. Therefore, it is possible to prevent light leakage and improve illumination efficiency. In particular, in this embodiment, the extension part 10b of the contact prevention sheet 10 is closed with the light source accommodating part 40b and the substrate 30 to block the optical path between the LED 20 and the incident surface 50a of the light guide plate 50 from the outside. A space is formed, and the frame portion 10a extends so that the inner edge thereof is positioned in the vicinity of the display region 60a of the liquid crystal panel 60 and substantially defines the display region 60a. That is, the light from the LED 20 is guided into the light guide plate 50 without waste by the extending portion 10b that is the second light shielding portion, and the light emitted from the light guide plate 50 by the frame portion 10a that is the first light shielding portion. The liquid crystal panel 60 is efficiently led to the display area 60a without waste. When light that tries to escape from the opening 43 is prevented by the extending portion 10b, display unevenness of the liquid crystal panel 60 and unnecessary light leakage to the observer side due to unevenness of the irradiated light can be eliminated. Similarly, the frame portion 10a prevents display unevenness of the liquid crystal panel 60. That is, if light is absorbed by the frame portion 10a, display unevenness (light unevenness) occurs between the central portion and the peripheral portion of the display region 60a of the liquid crystal panel 60. In the present embodiment, however, the frame portion 10a. Thus, the light is reflected and the light is uniformly collected toward the display region 60a, so that display unevenness is eliminated. Thus, the contact prevention sheet 10 can improve illumination efficiency markedly more than before by the synergistic effect of the frame part 10a and the extension part 10b.
[0053]
Moreover, in this embodiment, since the contact prevention sheet | seat 10 is formed with white PET, light is easy to reflect, light leakage and display nonuniformity can be prevented, and illumination efficiency can further be improved.
[0054]
In the above embodiment, in order to improve the light shielding performance in the light source housing portion 40b and further increase the illumination efficiency, the portion 30b of the substrate 30 and the support 30a facing the housing space S are set to white. Also good. As a result, the entire inner surface of the shielding part (closed space S1) surrounding the LED 20 becomes white, and almost all of the light from the LED 20 can be incident on the incident surface 50a of the light guide plate 50 without leaking outside. . Therefore, the illumination efficiency is significantly improved as compared with the conventional case.
[0055]
Needless to say, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention. For example, instead of using the light shielding member 40, a reflective film may be formed on a surface other than the surface that is the emission surface 50 b of the light guide plate 50, that is, a side surface or a bottom surface. The reflective film may be a welded film or a foil attached. Moreover, the thing which smeared mercury may be used. When this reflective film is a vapor deposition film, a metal such as aluminum can be used as the vapor deposition material. Further, for example, in the embodiment of the present invention, only the contact between the diffusion plate and the irradiated object (liquid crystal panel) is shown, but the prism sheet (the condensing lens sheet) and the irradiated object (liquid crystal panel) are in direct contact. In this case, interference fringes are similarly generated in the display of the irradiated object (liquid crystal panel). Accordingly, in this case as well, interference fringes can be prevented by providing a spacer between the prism sheet and the irradiated body (liquid crystal panel).
[Brief description of the drawings]
FIG. 1 is a side sectional view of a liquid crystal device to which a lighting device according to an embodiment of the present invention is applied.
FIG. 2 is an enlarged cross-sectional view of the liquid crystal device of FIG.
3 is a side view of the liquid crystal device of FIG. 1 as viewed from the B direction.
4 is a side view of the liquid crystal device of FIG. 1 as viewed from the C direction.
5A is a plan view of a contact prevention sheet, and FIG. 5B is a side view of the contact prevention sheet.
6 is a plan view showing a state in which the contact prevention sheet of FIG. 5 is overlapped with a liquid crystal panel. FIG.
7 is a plan view taken along line AA in FIG. 1 (plan view of an illumination device with a liquid crystal panel removed). FIG.
FIG. 8 is a cross-sectional view of a conventional liquid crystal device.
[Explanation of symbols]
10 ... Contact prevention sheet (spacer)
20 ... LED (light source)
50 ... Light guide plate 50a ... Incident surface 50b ... Emission surface 60 ... Liquid crystal panel (irradiated body)
70 ... Diffusion sheet (diffusion plate)

Claims (7)

In a liquid crystal device comprising at least one light source that emits light, a light guide plate, a diffusion plate placed on the light guide plate, and a liquid crystal panel placed on the diffusion plate,
A spacer and an air layer are provided on the surface of the diffusion plate on the liquid crystal panel side,
The liquid crystal device, wherein the diffusion plate and the liquid crystal panel are not in contact with each other and are overlapped with each other through the spacer and the air layer.   The liquid crystal device according to claim 1, wherein a thickness of the spacer is set to 0.1 mm to 0.5 mm.   The liquid crystal device according to claim 1, wherein the spacer also serves as a light shielding plate.   The liquid crystal device according to claim 3, wherein the spacer includes white polyethylene terephthalate.   5. The spacer is formed as a rectangular frame-like member whose inner edge is positioned in the vicinity of the display area of the irradiated object and extends so as to substantially define the display area. The liquid crystal device according to 1.   The liquid crystal device according to claim 1, wherein the diffusion plate is a diffusion sheet.   The liquid crystal device according to claim 1, wherein the diffusion plate is a prism sheet.

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