JP2009283377A - Planar light source and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain excellent brightness uniformity as a whole even when a plurality of light guide plates are aligned in a planar light source and a liquid crystal display device. <P>SOLUTION: The planar light source 1 is constituted by aligning a plurality of light units 4 in a plurality of rows in such a state that light guide plates 3 are arranged adjacently to one another, wherein each of the light units 4 includes an LED light source and one of the light guide plates 3 for emitting planar light from a main face side by changing the optical path of the light entering from the LED light source and guided, the LED light source being disposed at an end face 3a of a base end side which is a light incident face, and the end face 3a of the base end side of each of the light guide plates 3 aligned in a row in a fixed direction is arranged in a direction different from directions of the light guide plates 3 in 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. However, in the backlight method, color mixing properties and luminance unevenness are in inverse proportion to thickness, making it difficult to reduce the thickness. 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, as in the technique described in Patent Document 1, when the light source direction is arranged in the same direction in all the arranged light guide plates, the height of the luminance distribution is the same between adjacent columns and is emphasized to each other. Since the luminance distribution is biased as a whole, there is a disadvantage that the luminance uniformity is lowered.

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

  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 proximal end facet is arranged in a different direction from the light guide plates in the other rows.

  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 as the light incident surface in a different direction from the light guide plates in the other adjacent rows. The incident directions are different, the brightness distributions of adjacent columns are different, and the brightness is averaged to obtain good brightness uniformity as a whole.

  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 direction of the base end side end surface that is the light incident surface is different for each row or column. The luminance distribution between adjacent rows or columns can be averaged to obtain good luminance uniformity as a whole.

  Further, in the planar light source of the present invention, the light guide plate has a triangular shape or a pentagonal or more polygonal shape, and is arranged in a triangular lattice array or a polygonal lattice array composed of a plurality of columns, rows and diagonal rows. The fixed direction row is a horizontal row, a vertical row, or a diagonal row. That is, in this planar light source, triangular or pentagonal or more polygonal light guide plates are arranged in a triangular lattice array or a polygonal lattice array, and the columns in the certain direction are horizontal rows, vertical columns, or diagonal rows. Therefore, even if triangular or pentagonal or more polygonal light guide plates are arranged corresponding to various screen shapes, the light incident direction differs for each of the horizontal, vertical, or diagonal rows, and the overall condition is good. Brightness uniformity can be obtained.

  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 with the base end side end surface as the light incident surface in a different direction from the light guide plates in other adjacent rows. Adjacent columns have different luminance distribution levels, and good luminance uniformity can be obtained as a whole. 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 such that the base end side 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 up and down in FIG. The light emission surface of the LED light source 2 is installed in the vertical 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 a row in a certain direction are provided with a base end side end surface 3 a that is a light incident surface in a different direction from the light guide plates 3 in other adjacent rows. In other words, in the present embodiment, the light guide plates 3 arranged in the vertical column are arranged with the proximal end surface 3a in a direction different from that of the other adjacent light guide plates 3, and the light of the light unit 4 is arranged for each column. Incident directions are arranged vertically symmetrically. For example, in FIG. 1, the light incident direction is set upward in the leftmost column, and the light incident direction is set downward in the adjacent column. In this way, the light incident direction is changed up and down alternately for each 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, plates and sheets in which silica particles or the like 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 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 panel body in which liquid crystal such as TN liquid crystal or STN liquid crystal is sealed with a sealing material in a gap between an upper substrate and a lower substrate each having a transparent electrode, an alignment film, and a polarizing plate; , With.

  Thus, in the planar light source 1 according to the embodiment, the light guide plates 3 arranged in a row in a fixed direction are arranged with 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 rows. Therefore, the incident direction of light is different for each adjacent column, the luminance distribution is different between adjacent columns, the luminance is averaged, and good luminance uniformity as a whole can be obtained.

Further, since the rectangular light guide plates 3 arranged in a matrix are arranged so that the direction of the base end side end surface 3a that is a light incident surface is different for each column, the luminance distribution between adjacent columns is an average. As a whole, good luminance uniformity can be obtained.
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 and third 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 is arranged so that the orientation of the base end side end surface 3a that is the light incident surface is different for each column. On the other hand, in the planar light source 21 of the second embodiment, as shown in FIG. 5, the light guide plate 3 is arranged so that the orientation of the base end side end surface 3a that is the light incident surface is different for each row. It is. Further, the second embodiment is different in that the light units 24 are arranged in 10 vertical rows and 4 horizontal rows.

In the planar light source 21 of the second embodiment, the light guide plate 3 is disposed so that the proximal end surface 3a, which is a light incident surface, extends in the vertical direction, and the LED emits light in the horizontal direction. The light emitting surface of the light source 2 is installed in the horizontal direction, and the light incident directions of the light units 24 are arranged symmetrically in each row.
In other words, in the second embodiment, the light guide plates 3 arranged in a column are arranged with the proximal end surface 3a in a different direction from the other light guide plates 3 in the adjacent column.

  Therefore, also in the second embodiment, the rectangular light guide plates 3 arranged in a matrix are arranged so that the direction of the base end side end surface 3a that is the light incident surface is different for each row. The brightness distribution between them is averaged, and as in the first embodiment, good brightness uniformity can be obtained as a whole.

  The difference between the third embodiment and the first embodiment is that the light guide plate 3 is rectangular in the first embodiment, whereas the planar light source 31 of the third embodiment is as shown in FIG. The hexagonal light guide plates 33 are arranged in a hexagonal lattice arrangement (honeycomb lattice arrangement), and the orientation of the proximal end surface 33a is changed so that the light incident direction is different for each oblique row.

  That is, in the third embodiment, the light incident direction of the light unit 34 is different for each row in the oblique direction, and the position of the proximal end surface 33a that is the light incident surface with respect to the oblique row adjacent to each oblique row is determined. The six sides of the hexagon are set to different sides. In FIG. 6, a row surrounded by an imaginary line is one of oblique rows in which the base end side end surface 33 a is set in the same direction.

  Therefore, in the third embodiment, the hexagonal light guide plates 33 are arranged in a hexagonal lattice pattern, and the direction of the base end side end surface 33a is changed so that the light incident direction is different for each oblique row. The luminance distribution between adjacent diagonal rows is averaged, and good luminance uniformity as a whole can be obtained. In the third embodiment, the direction of the base end side end surface 33a is changed so as to be different for each diagonal row, but may be changed for each diagonal row or each horizontal row in another direction.

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

  First, as shown in FIG. 7 (a), in all four light guide plates 3 arranged in a matrix, the base end side end surface 3a is arranged in the same direction as a conventional example as a comparative example, Table 1 (a) shows the results of measuring the luminance of each part obtained by dividing the main surface of the light guide plate 3 into nine parts when the incident direction of light from each LED light source 2 is set in the same direction.

  Further, as an example of the present invention, as shown in FIG. 7B, as in the first embodiment, the base end side end surface 3a is vertically symmetrically different for each vertical column in the four light guide plates 3. Table 1 (b) shows the result of measuring the luminance of each part obtained by dividing the main surface of the light guide plate 9 into nine parts when the light incident directions from the LED light sources 2 are different from each other. Shown in Table 1 shows the average luminance value in the horizontal direction. Furthermore, about these results, the luminance distribution in the vertical direction and the horizontal direction of the comparative example (same arrangement) and the present embodiment (symmetric arrangement) is shown in FIGS.

From these measurement results, in this example, the luminance distribution in the vertical direction is not much different from that in the comparative example, but the luminance distribution in the horizontal direction is averaged compared to the comparative example, and the average value of luminance is the maximum value and the minimum value. It can be seen that the difference from the value is small, and the luminance uniformity is improved.
Thus, in this embodiment, since the light incident direction of the light guide plate 3 is reversed between adjacent columns, the luminance distribution between the adjacent columns is averaged, and overall good luminance uniformity is obtained. Is obtained.

  In addition, in the said Example, since the brightness | luminance at the time of arranging the 4 light-guide plates 3 in 2x2 is measured, the difference between a comparative example and an Example is comparatively small, but the number of the light-guide plates 3 to arrange is set. As the number 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 the first and second embodiments, a rectangular light guide plate is used, but a square light guide plate may be adopted.
In the third embodiment, a hexagonal light guide plate is used, but a polygonal light guide plate other than a triangular or hexagonal shape may be employed. By appropriately selecting and arranging such a polygonal light guide plate, it is possible to cope with various screen shapes.

In addition, it is possible to emit light of any color using RGB-LEDs as LED light sources. For example, as an RGB-LED, when 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 a single 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 the 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. 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 prior art example and an Example. It is a graph which shows the luminance distribution of the vertical direction in the Example and comparative example of the planar light source and liquid crystal display device which concern on this invention. It is a graph which shows the luminance distribution of a horizontal direction in the Example and comparative example of the planar light source and liquid crystal display device which concern on this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1, 21, 31 ... Planar light source, 2 ... LED light source (light source), 3, 33 ... Light guide plate, 3a, 33a ... Base end side end surface, 4, 24, 34 ... Light unit, 10 ... Liquid crystal display device, 11 ... Liquid crystal display panel, 12A ... 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 faces in different directions 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,
The light guide plate is triangular or pentagonal or more polygonal and is arranged in a triangular lattice array or polygonal lattice array consisting of a plurality of columns, rows and diagonal rows,
The planar light source characterized in that the row in the certain direction is a row, a column, or a diagonal row. A liquid crystal display panel;
A liquid crystal display device comprising: the planar light source according to any one of claims 1 to 3 disposed on a back surface side of the liquid crystal display panel.

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