JP4544259B2 - Liquid crystal device - Google Patents

Description

  The present invention relates to an illumination device for illuminating an object to be irradiated, particularly a liquid crystal panel, and a liquid crystal device including the illumination device.

  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.

  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.

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 attached 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 to the emission surface 102b more efficiently. Is done.
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.

  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.

The present invention has been made paying attention to the above circumstances, and an object thereof is to provide a liquid crystal device including an illuminating device capable of improving the illumination efficiency by completely and efficiently shielding the periphery of the light source. There is to do.

In order to solve the above problems, a liquid crystal device according to claim 1 includes a liquid crystal panel having a display area, a light source comprising at least one light emitting diode emits light, and the incident surface for receiving light from said light source A light guide plate that faces the liquid crystal panel and has an exit surface that emits light incident from the entrance surface toward the liquid crystal panel; and a light guide plate opposite to the liquid crystal panel A light source comprising: a substrate provided; and a standing portion that supports the light source so as to face the incident surface and is erected with a height corresponding to a thickness of the light guide plate from the substrate. It has a board | substrate and the light-shielding member which has the light reflection property formed over the top part of the said standing part, and the area | region which overlaps with the said light-guide plate planarly, It is characterized by the above-mentioned.

According to the liquid crystal device of the first aspect, light from the light source can be efficiently incident on the incident surface of the light guide plate without waste. Therefore, it is possible to provide a liquid crystal device with significantly improved illumination efficiency, brightness, and low power consumption.

The liquid crystal device according to claim 2 is the liquid crystal device according to claim 1, wherein the light shielding member includes a first light shielding portion corresponding to an outer edge of a display area of the liquid crystal panel, and the first light shielding portion. and having a second light-shielding portion extending over the erected portion from.

According to the liquid crystal device according to the second aspect, the first light shielding portion and the second light shielding portion of the light shielding member having light reflectivity can prevent light leakage and improve the proof efficiency.

The liquid crystal device according to claim 3 is characterized in that a reflective member is provided on a surface of the light guide plate opposite to the liquid crystal panel.

According to the illumination device described in claim 3, light is easily reflected, and the illumination efficiency can be further improved.

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

  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.

  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. 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 other than the rectangular display area 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.

  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.

  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.

  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 (attached) with a white sheet. In particular, in the present embodiment, the entire light shielding member 40 is painted white.

  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 with the side walls 45 a, 45 b, 45 c 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.

  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.

  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.

  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.

  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.

  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.

  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.

  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 entirely formed of white PET (polyethylene terephthalate) 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.

  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.

  Next, operations of the illumination device and the liquid crystal device having the above-described configurations will be described.

  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.

  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.

  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.

  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.

  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.

  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.

  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 portion (closed space S1) surrounding the LED 20 becomes white, and substantially 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.

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, on the side surface or the 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.

It is a sectional side view of the liquid crystal device with which the illuminating device which concerns on one Embodiment of this invention is applied. It is an expanded sectional view of the liquid crystal device of FIG. It is the side view which looked at the liquid crystal device of Drawing 1 from the B direction. It is the side view which looked at the liquid crystal device of Drawing 1 from the C direction. (A) is a top view of a contact prevention sheet, (b) is a side view of a contact prevention sheet. It is a top view which shows the state which accumulated the contact prevention sheet | seat of FIG. 5 with the liquid crystal panel. It is the top view (plan view of the illuminating device which removed the liquid crystal panel) seen along the AA line of FIG. It is sectional drawing of the conventional liquid crystal device.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Contact prevention sheet (spacer), 20 ... LED (light source), 50 ... Light guide plate, 50a ... Incident surface, 50b ... Output surface, 60 ... Liquid crystal panel (irradiated body), 70 ... Diffusion sheet (diffusion plate).

Claims (3)

A liquid crystal panel having a display area; a light source comprising at least one light emitting diode that emits light;
A light guide plate having an incident surface that receives light from the light source, and an output surface that faces the liquid crystal panel and emits light incident from the incident surface toward the liquid crystal panel;
A substrate provided on the opposite side of the light guide plate from the liquid crystal panel, and the light source is supported so as to face the incident surface, and has a height corresponding to the thickness of the light guide plate from the substrate. A light source substrate having a standing portion that is erected,
A liquid crystal device comprising: a light-shielding member having light reflectivity formed over a top portion of the standing portion and a region overlapping the light guide plate in a planar manner . The light blocking member has a feature that it has a first light-shielding portion corresponding to the outer edge of the display area of the liquid crystal panel, a second light-shielding portion extending over the standing portion from said first light-shielding portion, a The liquid crystal device according to claim 1.   The liquid crystal device according to claim 1, wherein a reflection member is provided on a surface of the light guide plate opposite to the liquid crystal panel.

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