KR20040091585A - Backlight and liquid crystal display device using the same - Google Patents

Abstract

PURPOSE: A backlight, and a liquid crystal display using the same are provided to improve the display quality of a backlight by suppressing brightness shading and color shading of light exited from a first diffusion plate. CONSTITUTION: A case(3) supports a plurality of light sources(4), having an opening at a part of an upper side. A first diffusion plate(1) is arranged adjacent to the opening of the case. A second diffusion plate(2) is arranged between the light sources and the first diffusion plate. Reflecting plates(7) are arranged on a bottom and a side of the case. Reflecting members(5) are arranged corresponding to the light sources for reflecting light emitted from the light sources. The light enters into the second diffusion plate after being repeatedly reflected between the reflecting members and the reflecting plate arranged on the bottom so that the light is dispersed around positions on the second diffusion plate corresponding to the light sources.

Description

BACKLIGHT AND LIQUID CRYSTAL DISPLAY DEVICE USING THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight for supplying light to a display device and a display device using the backlight, and is particularly preferred for application to a direct backlight and a liquid crystal display device using the backlight including a light source disposed directly below the display surface. will be.

In recent years, the use of a point light source such as a light emitting diode (LED) or a laser diode (LD) has been advanced as a backlight of a display device such as a liquid crystal display device. The backlight using the point light source uses red (R), green (G), and blue (B) three primary LEDs, which do not need to use mercury, compared to conventional backlights using, for example, cold cathode tubes. High color reproducibility can be obtained, or the life of the backlight can be extended. On the other hand, when a point light source is employed as the light source of the display device, the directivity of the emitted light is high, so that the luminance in the vicinity of the point light source tends to be higher than the luminance at a position far from the point light source, and as a result, the luminance unevenness and There was a problem that color unevenness occurred, which lowered the display quality. In a backlight in which a point light source is disposed directly below a display panel, a method of suppressing luminance unevenness and color unevenness is known. In the conventional backlight, the first backlight is formed by a frame body on a substrate on which a plurality of point light sources are disposed. The second light diffusion sheet was supported at a predetermined interval up and down, and one of the light diffusion sheets was integrally provided with a fluorescent material that fluoresced by the light of the point light source to suppress luminance unevenness (e.g., See, for example, Japanese Patent Application Laid-Open No. 2000-133006 (FIG. 2).

Further, another conventional technique is provided with a plurality of prism portions having a light diffusing sheet having a light diffusing property, a light emitting element disposed behind the light transmitting sheet, and a light emitting element and the light transmitting sheet and having a substantially V-shaped cross section. A prism sheet having a prism surface formed in rows and a flat portion formed on a surface opposite to the prism surface constitutes a backlight device, and the prism sheet is spaced apart from the light emitting element and the transparent sheet so that the prism surface faces the light emitting element side. By arranging apart from each other, luminance unevenness and color unevenness were suppressed (for example, see Japanese Patent Laid-Open No. 2002-49324 (Fig. 1)).

However, the above-mentioned prior art of Japanese Patent Application Laid-Open No. 2000-133006 (FIG. 2) is provided with two light diffusion sheets above the point light source to reduce luminance unevenness. In the 1st and 2nd light-diffusion sheet, the brightness | luminance of the vicinity of the position corresponding to a point light source became high, and there existed a problem that brightness unevenness and color unevenness generate | occur | produce.

Further, the prior art disclosed in Japanese Patent Laid-Open No. 2002-40324 (FIG. 1) also has a configuration in which the luminance unevenness is reduced by separating the prism sheet and the transparent sheet at a distance above the point light source, but with a diffusion function. Without the two sheets having the above structure, the luminance of the vicinity of the position corresponding to the point light source in the prism sheet and the translucent sheet also increases, resulting in the problem of luminance unevenness and color unevenness.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a backlight having a high display quality in which luminance unevenness and color unevenness are further suppressed, and a display device using the backlight.

1 is a cross-sectional view of a backlight according to a first embodiment of the present invention;

2 is a cross-sectional view of another backlight according to the first embodiment of the present invention;

3 is a cross-sectional view of another backlight according to a first embodiment of the present invention;

4 is a cross-sectional view of another backlight according to the first embodiment of the present invention;

5 is a cross-sectional view of a backlight according to a second embodiment of the present invention;

6 is a perspective view illustrating an arrangement of a point light source according to a second embodiment of the present invention;

7 is a perspective view of a point light source unit of a backlight according to a second embodiment of the present invention;

8 is a luminance distribution diagram in an array direction in which a plurality of point light sources of a backlight according to a second embodiment of the present invention are arranged;

9 is a cross-sectional view of a backlight according to a third embodiment of the present invention.

* Description of the symbols for the main parts of the drawings *

1: first diffuser plate 2: second diffuser plate

3: case 4: light source

5: reflection member 6: support member

7: reflector

The backlight of the present invention supports a light source, and has a case having an opening in at least a portion of an upper surface thereof, a first diffuser plate disposed close to the opening of the case, and disposed between the light source and the first diffuser plate. A backlight having a second diffuser plate and reflectors disposed on the bottom and side surfaces of the case, the backlight member comprising: a reflective member reflecting light from the light source disposed at a position corresponding to the light source in the second diffuser plate; A convex portion provided on a surface opposing the light source for diffusing light from the light source disposed at a position corresponding to the light source, a concave portion provided on a surface opposing the first diffuser plate disposed at a position corresponding to the light source Or any one of uneven parts formed by a mill and a small piece on a surface facing the first diffusion plate.

(First embodiment)

A first embodiment of the present invention will be described with reference to Figs. 1 is a cross-sectional view of a backlight according to a first embodiment of the present invention, and FIGS. 2 to 4 are cross-sectional views of another backlight according to the first embodiment of the present invention.

In FIG. 1, an opening is formed in at least a part of the upper surface of the case 3 supporting the point light source 4 directly below the display surface, and the first diffusion plate 1 is disposed to close the opening. do. In addition, the second diffusion plate 2 is disposed between the first diffusion plate 1 and the point light source 4 at a distance from the first diffusion plate 1. As the first diffusion plate 1 and the second diffusion plate 2, those having a light diffusion function, such as one having a concave-convex shape on both surfaces or one surface, or one using a milky white material as the material, are used. The first diffusion plate 1 and the second diffusion plate 2 are supported by the support member 6 and the case 3. Several supporting members 6 are provided at substantially the center of the backlight. At this time, the reflecting plate 7 which reflects the light from the point light source 4 is arrange | positioned at the side surface and the bottom surface of the case 3, and the opening part is provided in the position corresponding to the point light source 4 of the reflecting plate 7. The point light source 4 is arrange | positioned so that the light of the point light source 4 may be guide | induced in a backlight. Further, on the surface of the second diffusion plate 2 that faces the point light source 4, the reflection member 5 is formed at a position corresponding to the point light source 4. The reflecting member 5 may be formed by printing after the molding of the second diffusion plate 2, or may be attached to a reflecting member having adhesive force after molding, or the reflecting member 5 may be a second diffusion plate. In (2), as shown in Fig. 1, it may be placed on one of the surfaces facing the point light source 4 or the surface facing the first diffuser plate 1 and formed at a position corresponding to the point light source 4. In order to efficiently reflect the light from the point light source 4, it is preferable that it is formed on the surface facing the point light source 4 as shown in FIG.

With the above-described configuration, the light generated from the point light source 4 does not directly enter the second diffuser plate 2 in the second diffuser plate 2 in the region adjacent to the point light source 4, but is once a reflective member. Reflected by (5). Thereafter, the reflection is repeated between the reflecting plate 7 disposed on the bottom surface of the case 3 and incident on the second diffusion plate 2. Thereby, it becomes possible to disperse light in the second diffuser plate 2 without concentrating light in the vicinity of the position corresponding to the point light source 4. As a result, the light from the point light source 4 is further diffused until it is incident from the first diffuser plate 2 and exits from the first diffuser plate 1 to exit the first diffuser plate 1. Luminance unevenness and color unevenness are suppressed, and light becomes uniform luminance.

Next, Figs. 2 to 3 will be described. In Figs. 2 to 3, the same components as in Fig. 1 are denoted by the same reference numerals and the differences will be described. 2 to 3 do not have the reflecting member 5 of FIG. 1, and in FIG. 2, the point facing the point light source 4 of the second diffuser plate 2, and also corresponds to the point light source 4. The convex part 8 is integrally formed in the position to which it is made, In FIG. 3, in the surface which opposes the 1st diffuser plate 1 of the 2nd diffuser plate 2, it is also located in the position corresponding to the point light source 4 The recessed part 9 is formed integrally.

2 or 3, the reflection member of FIG. 1 is not necessary, so that the manufacturing cost can be reduced and the reliability can be improved, and the light from the point light source 4 can be projected by the convex portion 8 or the like. Instead of being directly emitted from the second diffusion plate 2 by the concave portion 9, the light is emitted by dispersing light in the transverse direction on the surface of FIG. 2 or FIG. Concentration in the vicinity of the position corresponding to 4) can be suppressed. As a result, the light from the point light source 4 is further diffused until it enters the second diffuser plate 2 and exits from the first diffuser plate 1, and emits the first diffuser plate 1. Luminance unevenness and color unevenness are suppressed, and light is made uniform.

Next, FIG. 4 is demonstrated. In FIG. 4, the same code | symbol is attached | subjected about the same component as FIG. 1-3, and the difference is demonstrated. FIG. 4 shows the second diffuser plate 2 instead of the configuration of forming the reflective member 5, the convex portion 8 or the recessed portion 9 in the second diffuser plate 2 in FIGS. In the surface opposite to the first diffuser plate 1, the uneven portion 10 is densely formed in the vicinity of the position corresponding to the point light source 4, and is sparse at a position far from the position corresponding to the point light source 4. To form the uneven portion 11 to.

By the configuration of FIG. 4 described above, the reflective member of FIG. 1 is not necessary, thereby reducing manufacturing costs and improving reliability, and by directly forming the uneven portions 10, the second diffuser plate 2 is directly formed. In this case, light is emitted near the position corresponding to the point light source 4 by dispersing light near the position corresponding to the point light source 4 in the transverse direction on the page of FIG. Concentration can be suppressed and it becomes possible to obtain the same effect as the said FIG. 4 illustrates a case where the uneven parts 10 and 11 are formed on the surface of the second diffusion plate 2 that faces the first diffusion plate 1, but the point light source ( The same effect can be obtained also when formed in the surface which opposes 4).

In addition, in FIG. 4, the uneven part 10 is densely formed in the vicinity of the position corresponding to the point light source 4, and the uneven part 11 is formed sparsely in the position far from the position corresponding to the point light source 4. In FIG. Although shown in relation to, when the outgoing light of the point light source 4 is mainly emitted in the lateral direction of the paper in Fig. 4, the position near the position corresponding to the point light source 4 (region where the light from the point light source is relatively small) The same effect can be obtained by forming a sparse uneven portion 10 and forming a dense uneven portion 11 at a position far away from the position corresponding to the point light source 4 (region where the light from the point light source is relatively large). It becomes possible. In this case, instead of the roughly formed concave-convex portion, either one of the surfaces facing the point light source or the surface facing the first diffuser plate 1, or both sides, for example, a region where the light from the point light source is relatively small. In rare cases, a light shielding pattern may be densely formed in a region where the light from the point light source is relatively high, or relatively less light from the point light source in the second diffuser plate at the time of forming the second diffuser plate. The region may be manufactured to have a high transmittance, and a region where a large amount of light from the point light source is relatively low may be produced to have a low transmittance.

At this time, in FIG. 4, the reflecting plate 7 has the convex part in the bottom face center part and a periphery part in the bottom face of the case 3, and the parts other than a bottom face center part and a periphery part have a recessed part near a bottom face. By setting it as such a structure, it becomes possible to make the light from the point light source 4 more uniform, and to suppress luminance unevenness and color unevenness. At this time, the shape of the reflecting plate may be used in combination with FIGS. 1 to 3 according to the present embodiment. In addition, in the reflecting plate 7 of FIGS. 1-4, the specular reflection member which reflects light in a horizontal direction in each figure is arrange | positioned in the position near the point light source 4, and is a position far from the point light source 4 In the center part and / or periphery part of the bottom face of the case 3, a brightness | luminance spot and a color spot can be suppressed further by arrange | positioning the diffuse reflection member which reflects light upwards in each figure. The shape and configuration of these reflecting plates may be used in combination with other embodiments described later. Further, the shape and configuration of the reflecting plate may be applied independently to the backlight of each embodiment, and in this case, the light from the point light source 4 is dispersed by the shape and configuration of the reflecting plate, and by the two diffusion plates Further spreading, it becomes possible to reduce luminance unevenness and color unevenness.

In addition, the reflecting plate 7 in FIG. 4 has a convex part in the bottom part center part and a peripheral part (region where the light from a point light source is relatively few) in the bottom face of the case 3, and parts other than a bottom part center part and a peripheral part (point The area having a relatively large amount of light from the light source is shown as a shape having a concave portion close to the bottom surface, but is not limited thereto, and may be a shape that directs light from the point light source to the opening of the case. What is necessary is just a shape which forms a convex part in a small area | region, and forms the recessed part near a bottom face of a case in the area | region where the light from a point light source is relatively many.

1 to 4, the distance between the point light source 4 and the second diffuser plate 2 shown in FIG. 1 is L1, the distance between the second diffuser plate 2 and the first diffuser plate 1. By setting L2 to a configuration that satisfies the relationship of L1? L2, luminance unevenness and color unevenness can be suppressed more reliably. In this embodiment, the reference point of the distance between L1 and L2 is the center point in the thickness direction with respect to the position of the first diffusion plate and the second diffusion plate, and the point light source 4 with respect to the position of the point light source 4. Let it be the position of light emitting element IC. When L2 is greater than or equal to L1, light can be diffused sufficiently between the first diffusion plate 1 and the second diffusion plate 2 as compared with the case where L2 is smaller than L1, resulting in luminance unevenness and color unevenness. It can be suppressed more reliably. In addition, with respect to L1, especially in the case of the configuration using the reflective member 5 (in the case of FIG. 1), by setting it small, the reflective member 5, which is the light shielding member, can also be formed or adhered accordingly accordingly, resulting Since the brightness of the backlight can be improved, it is preferable to set the configuration to satisfy the relationship of L1? L2.

(Second embodiment)

A second embodiment of the present invention will be described with reference to FIG. 5 is a cross-sectional view of a backlight according to a second embodiment of the present invention. In Fig. 5, the same components as in Figs. 1 to 4 are denoted by the same reference numerals and the differences will be described. In addition to the structure of FIG. 1, FIG. 5: In the 2nd diffuser plate 2, the uneven part 12 is formed in the surface which opposes the 1st diffuser plate 1, and the unevenness | corrugation in the surface which opposes the point light source 4 is shown. It is to have a flat surface without forming a.

By such a configuration, the surface of the second diffusion plate 2 in which the reflection member 5 near the reflection member 5 disposed on the surface of the second diffusion plate 2 facing the point light source 4 does not exist. Also, by reflecting a part of the light from the point light source 4 and repeating reflection several times between the reflecting plate 7 disposed on the bottom of the case 3, the light corresponds to the point light source 4. Concentration in the vicinity of the position can be further suppressed. As a result, the light from the point light source 4 is further diffused until it enters the second diffuser plate 2 and exits from the first diffuser plate 1, and emits the first diffuser plate 1. Luminance unevenness and color unevenness are suppressed, and light to be made becomes uniform luminance.

The point light sources 4 according to the first embodiment and the present embodiment are arranged in a line on the circuit board 16 to form the light source unit 17, as shown in FIG. It is held on the bottom. FIG. 6 is a perspective view illustrating an arrangement of the point light source 4 held in the case 3, and includes a first diffuser plate 1, a second diffuser plate 2, a reflector plate 7, a support member 6, and the like. The illustration is omitted. In the light source unit 17, by adjusting each of the arrangement intervals in the arrangement direction of each of the plurality of point light sources 4 arranged, it is possible to easily obtain an arbitrary luminance distribution in the X direction shown in FIG. For example, as shown in FIG. 7, the luminance distribution in the X direction of FIG. 6 is used by using the light source unit 17 in which the point light source 4 is arranged so that the center part in the X direction is dense and the end is sparse. Can be controlled as shown in FIG. In FIG. 8, the brightness | luminance of the center part of a X direction is made higher than the brightness | luminance of the edge part in a X direction, and high quality display is attained.

In addition, since the distance between the light sources is large in a region where the arrangement of the point light sources 4 is sparse, luminance unevenness and color unevenness are particularly likely to occur in the vicinity of the point light source 4. For this reason, by increasing the thickness dimension of the apparatus, it is necessary to increase the distance from the point light source 4 to the emission surface, promote the mixing of light from each point light source 4, and improve the display quality. However, in the backlight and the liquid crystal display device according to the first embodiment and the present embodiment, since the diffusion and reflection of the light can be promoted by using the second diffusion plate 2, sufficiently mixed light can be extracted. It is possible to easily reduce luminance unevenness and color unevenness without increasing the thickness dimension of the apparatus.

At this time, as the point light source according to the first to second embodiments, the first point light source emitting red (R) light, the second point light source emitting green (G) light, and blue using an LED The thing comprised by the 3rd point light source which emits light of (B) can be used. LEDs emitting monochromatic light of red (R), green (G), and blue (B) each have a higher luminous efficiency compared to LEDs emitting white light, and the red, green, and blue colors of color filters used in liquid crystal display devices are higher. Since the display device having high color reproducibility can be obtained by adjusting the transmission characteristics and the emission spectrum of the LED, it is preferable to use the three point light sources in combination.

(Third embodiment)

A third embodiment of the present invention will be described with reference to FIG. 9 is a cross-sectional view of a backlight according to a third embodiment of the present invention. In Fig. 9, the same reference numerals are given to the same constituent parts as Figs. 1 to 8, and the differences will be described. FIG. 9 shows a case where a line light source 13 such as a cold cathode tube is used without using a point light source as a light source as shown in FIGS. 1 to 8. The linear light source 13 is supported by the bottom surface of the case 3, and is arranged in the vicinity of an opening formed in at least a part of the upper surface of the case 3, and the linear light source 13. The diffusion sheet 14 is formed between and. In this specification, the diffusion sheet means that the thickness is about 0.05 mm to 0.30 mm. In order to support the diffusion sheet 14, the diffusion sheet 14 and the support plate 15 are supported by the support member 6 and the case 3, for example, using a support plate 15 made of transparent acrylic resin or the like. It is to be configured to support.

With the above configuration, also in the backlight using the linear light source, luminance unevenness and color unevenness can be suppressed and display with high display quality can be performed as in the above embodiment.

At this time, only the present embodiment has been described with respect to the example in which the diffusion plate is configured as the diffusion sheet and the support plate, but the diffusion plate according to the first to second embodiments is constituted by the diffusion sheet and the support plate as in the third embodiment. Needless to say, the same effect can be obtained. Further, the diffusion plate according to the above embodiment does not require thickness in particular, and may be a thin member as in the diffusion sheet as long as it is a member having rigidity that can be supported by the support member and the case.

In addition, by combining the backlight according to the first to third embodiments and a liquid crystal panel disposed at a position corresponding to an opening formed in the case outside the case and inserting a liquid crystal into a gap between two insulating substrates, the display is performed. A high quality liquid crystal display device can be obtained.

Also in the second and third embodiments, the distance between the point light source and the second diffusion plate shown in the first embodiment is L1, and the distance between the second diffusion plate and the first diffusion plate is L2. By satisfying the relationship L1? L2, luminance unevenness and color unevenness can be suppressed more reliably as in the first embodiment.

Although the first to third embodiments have described the case where the light source is supported on the bottom of the case, the present invention is not limited thereto, and the case where the light source is supported on the side surface of the case also includes the case where the light source is supported by the second diffuser plate. By forming any one of the reflecting member, the convex portion, the concave portion or the uneven portion of the above embodiment in a position where the light is most likely to be affected by the light, the same effect as in the above embodiment can be obtained.

As mentioned above, although the display apparatus which concerns on the said Example demonstrated using liquid crystal, it is not limited to this, Even if it applies to all the display apparatuses provided with the so-called backlight which has a light source behind a display surface, it does not interfere at all. Of course.

According to the present invention, it is possible to perform display with high display quality by suppressing luminance unevenness and color unevenness in a backlight used for a display device.

Claims (9)

A case supporting the light source and having an opening in at least a part of the upper surface; A first diffusion plate disposed close to the opening of the case; A second diffuser plate disposed between the light source and the first diffuser plate, In the backlight having a reflector plate disposed on the bottom and side surfaces of the case, A reflection member for reflecting light from the light source disposed at a position corresponding to the light source, and a surface facing the light source for diffusing light from the light source disposed at a position corresponding to the light source in the second diffusion plate; Any one of a convex portion provided in the concave portion, a concave portion provided on a surface facing the first diffuser plate disposed at a position corresponding to the light source, or a dense and sparse uneven portion formed on a surface facing the first diffuser plate. Backlight, characterized in that the portion is formed. The method of claim 1, And the reflecting member is formed or adhered to the position corresponding to the light source and to a surface facing the light source in the second diffusion plate. The method according to claim 1 or 2, In the second diffusion plate, a surface facing the light source is a smooth surface. The method according to any one of claims 1 to 3, The reflecting plate has a concave-convex portion on the bottom of the case. The method according to any one of claims 1 to 4, And said first diffusion plate and / or second diffusion plate are formed by combining a diffusion sheet and a support plate. The method according to any one of claims 1 to 5, The light source is a backlight, characterized in that the point light source. The method of claim 6, The arrangement interval of each point light source in the arrangement direction in which the said point light source is arranged in multiple numbers is dense at the center part, and is sparsely arranged at the edge part. The method according to any one of claims 1 to 7, A distance L1 between the second diffusion plate and the light source and a distance L2 between the first diffusion plate and the second diffusion plate satisfy a relationship of L1? L2. A liquid crystal panel, comprising: a backlight according to any one of claims 1 to 8, and a liquid crystal panel disposed at a position corresponding to an opening formed in the case from outside of the case, wherein a liquid crystal is inserted into a gap between two insulating substrates. A liquid crystal display device.