JP2010097784A - Planar light source and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a planar light source and a liquid crystal display wherein excellent luminance uniformity and appearance are obtained as a whole even if a plurality of light guide plates are arranged in a row. <P>SOLUTION: The planar light source 1 includes a plurality of light units 4 having a light source and a light guide plate 3 which includes the light source arranged at a base side end face 3a being a light incident face and emits light entered and guided from the light source in plane form from a main face side by changing its optical path, arranged in a plurality of rows with the light guide plates 3 in mutually adjacent state. The light guide plates 3 arranged in a row in a certain direction have the base side end faces 3a arranged at the different positions in the arrangement direction from the light guide plates 3 of the other adjacent rows. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a planar light source for illuminating a liquid crystal display panel and the like and a liquid crystal display device including the same.

Liquid crystal display devices for image display are widely used for large displays such as thin television devices and thin monitors. This liquid crystal display device uses a backlight unit that emits light from the back side of the liquid crystal display panel to increase the brightness of the display screen.
The backlight unit includes a light guide plate and a light source such as an LED disposed on a side end surface of the light guide plate, guides light from the light source, and emits the light from the entire main surface toward the liquid crystal display panel. ing.

  In recent years, with the increase in size of liquid crystal television devices, there has been a further demand for weight reduction and thickness reduction. It was. In addition, a backlight unit using a light guide plate with a light source on the side edge surface, when an injection molding method is adopted as a method for producing a large light guide plate, when producing a large area and thin type In addition, there is a limit that the resin is difficult to transfer and fill in the entire shape. In addition, in order to sufficiently fill the resin, it may be solved by increasing the molding machine size and increasing the injection pressure. However, since a large molding machine requires a lot of equipment costs, It is difficult to adopt.

  For this reason, for example, Patent Document 1 has proposed a tandem surface light source device in which a fluorescent lamp is provided as a light source in each of a plurality of wedge-shaped light guide blocks arranged. In this surface light source device, a large light-emitting area is obtained by arranging a plurality of adjacent light guide blocks so as to overlap each other without using a large light guide plate. In this surface light source device, the fluorescent lamps of the light guide blocks arranged are all arranged so that light enters the light guide block from the same direction.

JP-A-11-288611 (FIG. 7)

However, the following problems remain in the conventional technology.
That is, when the light guide plates are arranged in a plurality of rows as in the technique described in Patent Document 1, since the light sources are installed at the same position in the arrangement direction between the adjacent light guide plates, Since the brightness distribution is the same in the arrangement direction and dark portions and the like are emphasized with each other and the brightness distribution is biased as a whole, there is a disadvantage that the brightness uniformity is deteriorated and the appearance is deteriorated. In particular, light is not sufficiently transmitted to a portion where the horizontal and vertical lines overlap (a central portion of the cross portion), which is a connecting portion of light guide plates that are evenly arranged, and the appearance is adversely affected as a dark portion.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a planar light source and a liquid crystal display device that can obtain good luminance uniformity and appearance as a whole even when a plurality of light guide plates are arranged. To do.

  The present invention employs the following configuration in order to solve the above problems. That is, the planar light source of the present invention has a light source and the light source arranged on the base end side end surface which is a light incident surface, and the light incident and guided from the light source is converted into an optical path and emitted in a planar shape from the main surface side. A plurality of light units each having a plurality of light units arranged in a plurality of rows with the light guide plates adjacent to each other, wherein the light guide plates arranged in a row in a certain direction are adjacent to each other. The base end side end surface is arranged at a position different from the light guide plates of the other rows in the arrangement direction.

  In this planar light source, the light guide plates arranged in a row in a certain direction are arranged with the base end side end faces at different positions in the arrangement direction from the light guide plates in other adjacent rows. The luminance distributions are different, the levels of the luminance distributions are different between adjacent columns, and the luminances are averaged to obtain good luminance uniformity and appearance as a whole. In particular, the luminance is improved and the appearance can be improved in the portion where the vertical and horizontal lines overlap (the central portion of the cross portion) that is the connecting portion of the light guide plates.

  Further, in the planar light source of the present invention, the light guide plate is formed in a square shape or a rectangular shape and arranged in a matrix shape including a plurality of columns and rows, and the columns in the certain direction are rows or columns. It is characterized by that. That is, in this planar light source, the square or rectangular light guide plates arranged in a matrix are arranged so that the position of the base end side end surface is different in the arrangement direction for each row or column. Therefore, the luminance distribution between the rows or columns can be averaged to obtain good luminance uniformity and appearance as a whole.

  Moreover, the planar light source of the present invention is characterized in that the light guide plates arranged in a row in a certain direction have the base end side end faces arranged in a different direction from the light guide plates in other adjacent rows. That is, in this planar light source, the light guide plates arranged in a row in a certain direction are arranged with the base end side end surface that is a light incident surface in a different direction from the light guide plates in other adjacent rows, so that each adjacent row The incident directions of light are different, the brightness distributions of adjacent columns are further different, and the brightness is further averaged to obtain better brightness uniformity and appearance as a whole.

  The liquid crystal display device of the present invention comprises a liquid crystal display panel and the planar light source of the present invention disposed on the back side of the liquid crystal display panel. In other words, since the liquid crystal display device includes the planar light source of the present invention, good luminance uniformity can be obtained, and a large-area image display with good appearance can be obtained.

The present invention has the following effects.
That is, according to the planar light source according to the present invention, the light guide plates arranged in a row in a certain direction are arranged adjacent to the light guide plates in other rows in the arrangement direction at the base end side end surfaces at different positions. The luminance distribution in the arrangement direction is different for each column, the luminance distribution is different between adjacent columns, the luminance is averaged, and good luminance uniformity and appearance as a whole can be obtained.
Therefore, by installing multiple small-sized light guide plates that do not require a large molding machine or mold processing and can be manufactured easily and at low cost, large size can be realized, and overall brightness uniformity and appearance are excellent. A good planar light source can be obtained. In addition, according to the liquid crystal display device provided with the planar light source, it is possible to obtain a large-area image display with good appearance due to good luminance uniformity.

  Hereinafter, a planar light source and a liquid crystal display device according to a first embodiment of the present invention will be described with reference to FIGS. In each drawing used in the following description, the scale is appropriately changed to make each member a recognizable size.

  The planar light source 1 in the present embodiment is a backlight unit of a liquid crystal display device. As shown in FIGS. 1 and 2, a plurality of LED light sources (light sources) 2 and the LED light sources 2 are arranged on a light incident surface. A plurality of light units 4 including a light guide plate 3 disposed on a certain base end side surface 3a and changing the optical path of light incident and guided from the LED light source 2 and emitting the light from the main surface side in a plane shape are guided to each other. A plurality of rows are arranged with the optical plates 3 adjacent to each other.

  The light guide plate 3 has a rectangular shape and is arranged in a matrix composed of a plurality of columns and rows. In particular, in the planar light source 1 of the present embodiment, the shape and the number of installed light guide plates 3 are determined so that the mainstream aspect ratio is 16: 9 with a large-sized backlight. In this embodiment, the long side direction is a horizontal row and the short side direction is a vertical row, and the light units 4 are arranged in 8 vertical rows and 6 horizontal rows.

  In this planar light source 1, the light guide plate 3 is disposed so that the proximal end surface 3a, which is a light incident surface (light incident surface), extends in the horizontal direction in FIG. 1, and the light emission direction is the upper direction in FIG. The light emission surface of the LED light source 2 is installed in the upward direction in FIG. 1 so as to be in the direction (longitudinal direction). In addition, the arrow in a figure has shown the incident direction of the light with respect to the light-guide plate 3. FIG.

  Further, in the planar light source 1, the light guide plates 3 arranged in the vertical column (vertical column) are arranged with the proximal end surface 3a at a position different from the light guide plates 3 in the other adjacent columns in the arrangement direction (vertical direction). ing. That is, in the present embodiment, the light guide plates 3 arranged in the vertical column are shifted in the arrangement direction (vertical direction) with respect to the other adjacent light guide plates 3 and are alternately arranged in the vertical direction. The light unit 4 is installed in the position. For example, in FIG. 1, the light guide plate 3 in the column adjacent to the right (second column from the left) is slightly shifted upward by a predetermined amount with respect to the light guide plate 3 in the leftmost column (first column from the left). Furthermore, the light guide plates 3 in the column adjacent to the right (third column from the left) are slightly shifted downward by a predetermined amount with respect to the second light guide plate 3, and the first row and the arrangement direction ( The base end side end surface 3a is arranged at the same position in the vertical direction. Thus, the position of the base end side end surface 3a is changed up and down alternately for every column.

The light guide plate 3 is made of, for example, transparent polycarbonate resin or acrylic resin.
The light guide plate 3 is installed on the rigid substrate 5 in a state of being fixed to, for example, a bezel (not shown). Each LED light source 2 is connected to a flexible printed circuit board (not shown) fixed to the bezel.

  A plurality of light incident prisms (not shown) having a V-shaped cross section, for example, are formed in a region facing the LED light source 2 on the base end side end surface 3 a of the light guide plate 3. Further, for example, a white dot pattern (not shown) is formed on the light emitting surface which is the main surface of the light guide plate 3. In addition, you may give other optical shapes, such as a fine optical shape of a prism shape or a lenticular lens shape, for example to a light-projection surface or its opposing surface. For example, when a prism-shaped fine optical shape is applied, the vertex angle of the prism is set larger as the distance from the LED light source 2 increases. In addition, the prism having an unequal side cross section is used, and as the apex angle increases, the depth of the prism shape is set deeper or the prism pitch is set narrower.

  The LED light source 2 is a white LED that is installed with the distal end surface, which is a light emitting surface, facing the proximal end surface 3a. This white LED is, for example, a semiconductor light emitting element on a substrate sealed with a resin material. As the semiconductor light emitting element, for example, a blue (wavelength λ: 470 to 490 nm) LED element or ultraviolet light (wavelength λ: less than 470 nm). An LED element is formed by laminating a plurality of semiconductor layers of a gallium nitride compound semiconductor (for example, an InGaN compound semiconductor) on an insulating substrate such as a sapphire substrate.

  Further, the resin material for sealing the semiconductor light emitting element is mainly composed of a silicone resin and, for example, a YAG phosphor is added. This YAG phosphor converts white light or ultraviolet light from a semiconductor light emitting element into yellow light and generates white light by a color mixing effect. The LED light source 2 has a reflective frame formed on the side of the resin material other than the tip surface so that light is emitted only from the tip surface. As the white LED, various types other than the above can be adopted.

  The liquid crystal display device 10 of the present embodiment is a display device applied to a liquid crystal display such as a large liquid crystal television device, for example. As shown in FIG. 4, the liquid crystal display panel 11 and the liquid crystal display panel 11 And the planar light source 1 disposed on the back side.

That is, the liquid crystal display device 10 is arranged on the planar light source 1 composed of the plurality of light units 4 and the plurality of light guide plates 3 arranged, and diffuses the light from the light guide plates 3 to achieve in-plane light intensity. Diffusing plate 12A for uniforming, diffusing sheet 12B disposed on the diffusing plate 12A, and upward irradiation light directed to the liquid crystal display panel 11 from the diffusing sheet 12B disposed on the diffusing sheet 12B And the liquid crystal display panel 11 disposed on the prism sheet 13, and the reflection sheet 14 disposed on the lower surface of the light guide plate 3.
In the present embodiment, the screen side of the liquid crystal display panel 11 and the light emission surface side of the planar light source 1 are described as the surface side or the upper surface side.

  The diffusion plate 12A and the diffusion sheet 12B are, for example, a plate and a sheet in which silica particles are dispersed in a transparent resin such as an acrylic resin or a polycarbonate resin.

  The prism sheet 13 is a transparent sheet-like member for condensing light from the diffusion sheet 12B on the upper surface side, and has a prism portion having a plurality of parallel ridge lines on the upper surface side. Further, the prism sheet 13 is set to a position where the ridge line of the prism portion is twisted with respect to the optical axis of the LED light source 2, and in particular to the optical axis of the LED light source 2 as a direction in which high upward directivity is obtained. It is set parallel to the orthogonal direction.

  The reflection sheet 14 is a metal plate, film, foil or the like having a light reflection function, and a film provided with a silver vapor deposition film is employed in the present embodiment. Note that an aluminum metal vapor deposition film or the like may be employed instead of the silver vapor deposition film. The reflection sheet 14 is stuck on the bezel with a double-sided tape (not shown). The reflective sheet 14 may be a white reflective sheet.

  The liquid crystal display panel 11 is a transmissive or transflective liquid crystal display panel. For example, in the case of the transmissive liquid crystal display panel 11, a TFT liquid crystal method, an STN liquid crystal method, or a TN device in which a liquid crystal material is sealed in a gap between an upper substrate and a lower substrate each having a transparent electrode, an alignment film, and a polarizing plate. A panel body such as a liquid crystal system is provided.

  As described above, the planar light source 1 according to the embodiment is configured so that the light guide plates 3 arranged in a row (vertical row) in a certain direction are different from the light guide plates 3 in other rows in the arrangement direction (vertical direction). 3a is arranged, the luminance distribution in the arrangement direction (vertical direction) is different for each adjacent column, the luminance distribution is different between adjacent columns, the luminance is averaged, and the luminance is uniform as a whole You can get sex and appearance.

That is, since the rectangular light guide plates 3 arranged in a matrix are arranged so that the positions of the base end surface 3a are different in the arrangement direction for each column, the luminance distribution between adjacent columns is averaged. As a whole, good brightness uniformity and appearance can be obtained. In particular, the luminance of the connecting portion of the light guide plate 3 where the vertical and horizontal lines overlap (the central portion of the cross portion) is improved and the appearance can be improved.
Therefore, in the liquid crystal display device 10 that employs the planar light source 1 as a backlight unit, good luminance uniformity can be obtained, and a large-area image display with good appearance can be obtained.

  Next, second to fourth embodiments of the planar light source and the liquid crystal display device according to the present invention will be described below with reference to FIGS. In the following description of each embodiment, the same constituent elements described in the above embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  The difference between the second embodiment and the first embodiment is that, in the first embodiment, the light guide plate 3 has the vertical direction as the arrangement direction, and the position of the base end side end surface 3a is different in the arrangement direction for each column. In contrast, in the planar light source 21 of the second embodiment, as shown in FIG. 5, the light guide plate 3 has the light guide plate 3 on the base end side in the array direction for each row, with the horizontal direction as the array direction. The point is that the positions of the end faces 3a are shifted so as to be different.

  That is, in the second embodiment, the light guide plates 3 arranged in the horizontal rows in FIG. 5 are arranged so as to be shifted in the arrangement direction (left and right direction) with respect to the other adjacent light guide plates 3. The light units 4 are alternately shifted left and right. For example, in FIG. 5, the light guide plate 3 in the upper row (second row from the bottom) is slightly shifted leftward by a predetermined amount with respect to the light guide plate 3 in the lower row (first row from the bottom). Furthermore, the light guide plates 3 in the row adjacent to the top (third row from the bottom) are slightly shifted to the right by a predetermined amount with respect to the light guide plate 3 in the second row and are arranged in the arrangement direction ( The proximal end surface 3a is arranged at the same position in the left-right direction). Thus, the position of the base end side end surface 3a is changed to right and left alternately for every row.

  Therefore, also in the second embodiment, the rectangular light guide plates 3 arranged in a matrix are arranged adjacent to each other because the positions of the base end side end faces 3a are shifted in the arrangement direction (horizontal direction) for each row. The luminance distribution between the rows is averaged, and good luminance uniformity and appearance as a whole can be obtained as in the first embodiment.

  The difference between the third and fourth embodiments and the first and second embodiments is that, in the first and second embodiments, the light guide plates 3 arranged in a column are in the same direction as the light guide plates 3 in other adjacent columns. In the surface light sources 31 and 41 of the third and fourth embodiments, as shown in FIG. 6 and FIG. The light guide plates 3 arranged in the (column) are arranged with the proximal end surface 3a in a different direction from the light guide plates 3 in other adjacent rows.

  That is, in the third and fourth embodiments, the light guide plates 3 arranged in the vertical column are arranged with the proximal end surface 3a in a different direction from the other light guide plates 3 in the adjacent vertical column, and the light is written for each column. The light incident directions of the units 4 are arranged symmetrically in the vertical direction. For example, in FIGS. 6 and 7, the light incident direction is set downward in the leftmost column, and the light incident direction is set upward in the adjacent column. In this way, the light incident direction is changed up and down alternately for each column.

  As described above, in the third and fourth embodiments, the light guide plates 3 arranged in a row (column) in a certain direction have the base end side end surface 3a that is a light incident surface in a different direction from the light guide plates 3 in other adjacent columns. Therefore, the incident direction of light is different for each adjacent column, the brightness distribution level is further different between adjacent columns, and the brightness is more averaged, resulting in better brightness uniformity and appearance as a whole. Obtainable.

  Next, the planar light source and the liquid crystal display device according to the present invention will be specifically described with reference to FIGS.

  First, as shown in FIG. 8A, the four light guide plates 3 are arranged in two rows in the vertical and horizontal directions, and the positions of the base end side end surfaces 3a in the arrangement direction are the same in the rows adjacent to each other as in the prior art. FIG. 9 shows the result of measuring the overall luminance distribution of the comparative example.

On the other hand, as a first embodiment of the present invention, as shown in FIG. 8B, four light guide plates 3 are arranged in two rows and two in the vertical direction (vertical direction). FIG. 10 shows the result of measuring the entire luminance distribution in the same manner in the case where the positions of the proximal end face 3a are shifted in the vertical direction between adjacent columns.
Furthermore, as a second embodiment of the present invention, as shown in FIG. 8 (c), four light guide plates 3 are arranged in two rows in vertical and horizontal directions and adjacent to each other in the horizontal (horizontal) direction. FIG. 11 shows the result of measuring the overall luminance distribution in the same manner in the case where the positions of the proximal end surface 3a are shifted in the left-right direction between the rows.

As can be seen from these results, in the comparative example described above, the central portion of the four light guide plates 3 was a dark portion, whereas the first embodiment in which the vertical columns were shifted in the vertical direction and the horizontal rows in the horizontal direction. In the second embodiment in which the positions are shifted, the brightness is improved at the center of the four light guide plates 3 (the portion where the light guide plates 3 are connected and the vertical and horizontal lines overlap), and the appearance is improved. Yes.
Thus, in each Example of this invention, since the position of the base end side surface 3a of the light-guide plate 3 has shifted | deviated and arranged in the sequence direction between adjacent rows, the luminance distribution between adjacent rows is an average. As a result, good luminance uniformity is obtained as a whole.

  In addition, in each said Example, since the brightness | luminance at the time of arranging the 4 light-guide plates 3 in 2x2 is measured, although the difference between a comparative example and an Example is comparatively small, the number of the light-guide plates 3 to arrange | position As the value increases, the difference between the prior art and the present invention increases. That is, when the present invention is applied to an actual large-sized liquid crystal television apparatus or the like, the effects of the present invention appear more remarkably because more light guide plates 3 and light units 4 are arranged.

  In addition, this invention is not limited to said each embodiment, A various change can be added in the range which does not deviate from the meaning of this invention.

For example, in each of the above embodiments, a rectangular light guide plate is used, but a square light guide plate may be adopted. In addition to the rectangular light guide plate, a light guide plate formed in another shape such as a triangular shape may be used.
Further, in the third and fourth embodiments, the light guide plates arranged in the column are arranged with the base end side end surface as the light incident surface in a different direction from the other light guide plates in the adjacent column. The light plate may be a planar light source in which a proximal end surface that is a light incident surface is arranged in a direction different from that of the other adjacent light guide plates.

In addition, it is possible to emit light of any color using RGB-LEDs as LED light sources. For example, as an RGB-LED, an LED in which a red LED element (R), a green LED element (G), and a blue LED element (B) are mounted in one package is used as a light source, or one light guide plate emits light from each other. Different LED light sources may be arranged. In these cases, by controlling the applied current in each LED, it becomes possible to illuminate with light of various colors for the entire planar light source or for each light unit.
In addition, although the LED light source was employ | adopted as a light source, you may employ | adopt other light sources, such as a fluorescent tube.

  In the backlight unit of each of the embodiments described above, one diffusion plate and one diffusion sheet are used, but either one may be omitted, or a backlight unit using a plurality of at least one may be used. Further, the diffusion plate or the diffusion sheet may be a backlight unit arranged between the prism sheet and the liquid crystal display panel. That is, for the brightness unevenness adjustment, the installation positions and the number of sheets are appropriately set in consideration of the number and haze of these diffusion plates and diffusion sheets.

In addition, although one prism sheet is used, a backlight unit employing two prism sheets may be used.
In each of the above embodiments, a diffusion plate, a diffusion sheet, and a prism sheet having a size corresponding to the size of the liquid crystal display panel are employed, but these are divided into a plurality of light guide plates and arranged side by side. You may employ | adopt the structure to do.

FIG. 3 is a plan view showing a planar light source in the planar light source and the liquid crystal display device according to the first embodiment of the present invention. FIG. 2 is a simplified perspective view showing four adjacent light units surrounded by an imaginary line in FIG. 1 in the first embodiment. FIG. 2 is a simplified plan view showing four adjacent light units surrounded by an imaginary line in FIG. 1 in the first embodiment. In this embodiment, it is an expanded longitudinal cross-sectional view of the principal part which shows the planar light source and light unit except a bezel and a rigid board | substrate. It is a top view which shows a planar light source in 2nd Embodiment of the planar light source and liquid crystal display device which concern on this invention. It is a top view which shows a planar light source in 3rd Embodiment of the planar light source and liquid crystal display device which concern on this invention. It is a top view which shows a planar light source in 4th Embodiment of the planar light source and liquid crystal display device which concern on this invention. In the Example of the planar light source and liquid crystal display device which concerns on this invention, it is a top view which shows the light unit arrangement | positioning of a comparative example, 1st Example, and 2nd Example. It is a figure which shows luminance distribution in the comparative example of the planar light source and liquid crystal display device which concern on this invention. It is a figure which shows luminance distribution in 1st Example of the planar light source and liquid crystal display device which concern on this invention. It is a figure which shows luminance distribution in 2nd Example of the planar light source and liquid crystal display device which concern on this invention.

Explanation of symbols

  1, 2, 31, 41, planar light source, 2, LED light source (light source), 3, light guide plate, 3 a, proximal end surface, 4, light unit, 10, liquid crystal display device, 11, liquid crystal display panel, 12 A ... Diffusion plate, 12B ... Diffusion sheet, 13 ... Prism sheet, 14 ... Reflection sheet

Claims (4)

A plurality of light sources, and a light guide plate that is arranged on a base end side end surface that is a light incident surface and that changes the light path of the light that is incident and guided from the light source and emits the light from the main surface side in a planar shape. The light unit is a planar light source configured by arranging a plurality of rows with the light guide plates adjacent to each other,
The planar light source, wherein the light guide plates arranged in a row in a certain direction are arranged with the base end side end surface at a different position in the arrangement direction from the light guide plates in other adjacent rows. The planar light source according to claim 1,
The light guide plate is square or rectangular and is arranged in a matrix consisting of a plurality of columns and rows,
The planar light source characterized in that the row in the certain direction is a row or a column. The planar light source according to claim 1 or 2,
The planar light source, wherein the light guide plates arranged in a row in a certain direction are arranged with the base end side end faces in different directions from the light guide plates in other adjacent rows. A liquid crystal display panel;
A surface light source according to any one of claims 1 to 3, which is disposed on the back side of the liquid crystal display panel.