JPH0915595A - Back light unit - Google Patents

Abstract

PURPOSE: To realize a ultra lightweight back light unit which is capable of having a large-sized light emitting surface having the high brightness and uneven brightness suppressed to the low level. CONSTITUTION: In the back light unit 1 of a both-side lighting system, four rectangular plate-shaped prism array parts 13 (1) to 13 (4), in which prism arrays 13 (1)p to 13 (4)p are formed on the upper surface, are joined together, straight line-like peak parts are almost in parallel with the longitudinal direction of both-light source units 3 and are formed into the gable roof shape so as to be positioned approximately in the middle of the both-light source units 3. A structure, in which a reflecting plate 15 is installed on the lower surface side, is included in this unit. In the two prism array parts 13 (1), 13 (4) on the outer side close to the light source units 3, the ridgelines of respective prisms are intersecting almost orthogonally with or are crossing the straight line-like peak parts of the gable roofs nearly at a right angle. In the two prism array parts 13 (2), 13 (3) on the inner side away from the light source unit 3, the ridgelines of respective prisms are almost in parallel with the straight line peak parts of the gable roofs.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a liquid crystal display device (Liquid
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight unit of a double-sided lighting system and a single-sided lighting system that can provide planar illumination from the back surface of a crystal display (LCD). In particular, the backlight unit according to the present invention is suitable for liquid crystal color televisions and liquid crystal display devices for office automation that require uniform high brightness.

[0002]

2. Description of the Related Art Recently, liquid crystal displays have attracted attention because of their thinness and low power consumption.
It has been adopted in some small TVs, and is also being considered for liquid crystal displays such as large TVs and large monitors. In such a liquid crystal display, a backlight unit for complementing its performance is indispensable, and the light emitting surface of the backlight unit is as uniform and as bright as possible in terms of visibility and reproducibility. There is a need.

On the other hand, as the size of the liquid crystal screen increases, the size of the backlight unit also inevitably increases, and the weight of the entire display increases. However, due to the universal market needs for lighter products, the weight can be increased. Must be kept as low as possible.

[0004]

It is conceivable to eliminate the light guide plate that occupies most of the weight of the backlight unit in order to reduce the weight of the liquid crystal display as a whole, and in particular to drastically reduce the weight. Forming a light-emitting surface that is uniform and has high brightness without any removal is a completely new approach to weight reduction, which is also an unknown technical theme.

Accordingly, an object of the present invention is to realize an ultra-lightweight backlight unit capable of having a large light-emitting surface with high brightness but with low brightness unevenness. .

[0006]

In order to solve the above problems, a first aspect of the present invention is directed to both sides including a light guide means and a pair of light source units arranged on both sides of the light guide means substantially in parallel with each other. In the lighting type backlight unit, the light guide means includes a reflection / prism section on the lower surface side, and a light guide section on the upper surface side.
A hollow cavity light guide part sandwiched between the reflection / prism part and the light guide part, and the reflection / prism part is formed by connecting four rectangular plate-shaped prism array parts each having a prism array formed on the upper surface thereof, Including a structure in which a linear peak is formed in a gable roof shape that is substantially parallel to the longitudinal direction of both light source units and is located approximately in the middle of both light source units, and a reflecting member is attached to the lower surface side The two prism array parts on the outer side close to the light source unit have the ridge lines of the prisms intersecting the straight peaks of the gable roof at substantially right angles or at right angles, and the two prism array parts on the inner side far from the light source unit are The structural feature is that the ridgeline of each prism is substantially parallel to the linear peak portion of the gable roof.

In order to solve the above-mentioned problems, a second aspect of the present invention is a one-side lighting type backlight unit including light guide means and a light source unit on one side of the light guide means, wherein the light guide means is a bottom surface. Side reflecting / prism section, a light guiding section on the upper surface side, and a hollow hollow light guiding section sandwiched between the reflecting / prism section and the light guiding plate section. The reflecting / prism section forms a prism array on the upper surface. The two rectangular plate-shaped prism arrays thus formed are connected to each other to form a one-way roof-shaped structure in which the linear peaks are substantially parallel to the longitudinal direction of the light source unit and are located far from the light source unit. The prism array portion on the side closer to the light source unit includes a structure in which a reflecting member is attached to the lower surface side, and the ridgeline of each prism intersects the straight ridge portion of the one-sided roof at a substantially right angle or a substantially right angle. A unit Prism array portion farther is characterized in configuration that ridge line of each prism is substantially parallel to the linear peaks of the shed roof.

[0008]

The ridge line of each prism of the prism array portion near the light source unit intersects the straight ridge portion at a substantially right angle or at a right angle, and the ridge line of each prism of the prism array portion far from the light source unit forms a straight ridge portion. Due to the action of the reflection / prism portions which are substantially parallel to each other, the luminance distribution is remarkably averaged and uniformed while the luminance of the light emitting surface is high. Further, since the hollow cavity light guide section is provided, the backlight unit becomes considerably lighter.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a cross section of a backlight unit according to a first embodiment of the present invention, but the components are exaggerated for clarity. The illustrated first embodiment is a so-called double-sided lighting type backlight unit 1, and both side portions thereof are arranged substantially parallel to each other (extend in a direction substantially perpendicular to the plane of the drawing). 3a, 3b). Each of the light source units 3 includes a plurality of fluorescent lamp tubes, specifically, cold cathode tubes and hot cathode tubes (in the illustrated embodiment, four hot cathode tubes (φ6.1 × 400 mm) on each side). It comprises a rod-shaped lamp 5 and a lamp holder 7 which covers the back side of these lamps 5 and has a reflection mirror (layer) formed on the inner surface and has a substantially semicircular cross section.

A hollow hollow light guide portion 9 having a cross-sectional shape like a drum with a constricted center is formed between both light source units 3. Light control plates 11 are symmetrically arranged substantially parallel to each other between the hollow light guide 9 and both light source units 3. The light control plate 11 has a rectangular thin plate shape (for example, a plate thickness of about 2 mm), is made of, for example, polymethylmethacrylate (PMMA) resin, and has an apex angle of about 90 degrees on the opposing surfaces. Row of prisms (prism array 11p)
However, the ridge line of each prism is formed so as to extend in a direction substantially perpendicular to the paper surface of FIG. 1 (in other words, a direction substantially parallel to the longitudinal direction of the light source unit 3 (or the lamp 5)).

The lower side of the hollow light guide section 9 is defined by four rectangular plate-shaped prism array sections 13 in which two inclined surfaces are connected in a mountain shape and are connected like a gable roof.
(1), 13 (2), 13 (3), and 13 (4).
The highest straight ridge in the center of this gable roof
It is substantially parallel to the longitudinal direction of both light source units 3 and is located approximately in the middle of both light source units 3. On the lower surface side of these prism array portions 13 (1) to (4), the light transmitted through the prism array portion is redirected in the light emitting surface (LCD emission surface) direction (vertically upward), so that silver or aluminum is formed on the upper surface. And a reflective layer (reflectance 96% (550 mm)),
For example, the reflection plate 15 formed of polyethylene terephthalate (PET) resin is provided.

On the upper surface of each of the prism array portions 13 (1) to 13 (4), rows of prisms (prism arrays 13 (1) p to 13 (4) p) having an apex angle of about 90 degrees are formed. .
Among these four prism array parts, the light source unit 3
From the inner side (in other words, adjacent to each other with the straight ridge portion as a boundary), two prism array portions 13 (2), 13
(3) Prism array 13 (2) p, 13 (3) p
Indicates that the ridgeline of each prism is substantially parallel to the linear peak (in other words, in a direction substantially perpendicular to the paper surface of FIG. 1, and in other words, substantially parallel to the longitudinal direction of the light source unit 3 (or the lamp 5). Extending in any direction). The remaining two prism array portions 13 (1), 13 on the outer side close to the light source unit 3
(4) Prism array 13 (1) p, 13 (4) p
The ridge line of each prism is substantially orthogonal to (or intersects at a substantially right angle) the straight ridge portion.

The upper side of the hollow light guide 9 is defined by two inclined surface light guide plates 17 (1), 17 (2) that are joined together like an inverted gable roof. Inclined surface light guide plate 1
On the lower surface (prism array surface) of each of 7 (1) and 17 (2), a row of prisms (prism arrays 17 (1) p, 17 (2) p) having an apex angle of approximately 135 degrees is formed asymmetrically. The ridgeline of each prism is substantially parallel to the linear ridge portion formed by the prism array portions 13 (2) and 13 (3) on the lower side.

Above the inclined surface light guide plates 17 (1) and 17 (2), the transparent plate 2 constituting the main part of the light emitting (diffusing) surface.
1, the diffusion plate 23, and the prism lens 25 are laminated in this order. The transparent plate 21 has a thin plate shape (for example, about 1 m).
m) and is formed of, for example, polymethylmethacrylate (PMMA) resin. The diffusion plate 23 is made of a resin plate material (for example, polyethylene terephthalate (PET) resin) whose surface is processed to have irregularities or a light diffusion material is mixed. The prism lens 25 has a film shape, and a prism array (not shown) is formed on the surface thereof. The order of laminating the transparent plate 21, the diffusion plate 23, and the prism lens 25 is appropriately determined according to the visual characteristics on the LCD side.

In the double-side lighting type backlight unit 1 of the present embodiment having the above configuration, the light emitted from the light source unit 3 (3a, 3b) enters the cavity light guide section 9 through the light control plate 11. Then, the light is transmitted through the prism array portions 13 (1) to 13 (4) on the lower surface side and is guided to the light emitting surface direction by the reflecting plate 15, and the transparent plate 21 and the diffusing plate 2
The light is emitted to the outside (in the vertically upward direction) through the prism 3 and the prism lens 25. While the light travels, mainly due to the characteristic arrangement configuration (orientation of the prism ridgelines) of the four prism array portions 13 (1) to 13 (4) on the lower surface side, the brightness on the light emitting (diffusing) surface is kept high. At the same time, the brightness distribution can be made extremely uniform. That is, on the light emitting surface, it is general that both sides near the light source are bright and the central part is dark, and the difference between them is large. However, according to the configuration of the present embodiment, both sides in terms of brightness (luminance distribution) are also The central part can be about the same.

In order to actually verify the excellent effect of the present embodiment, a comparative device 101 shown in FIG. 2 was produced, and a specific comparative experiment between this and the device 1 of the present embodiment was conducted. . It should be noted that this comparative device 101 is specially manufactured for this experiment, and is not a known technique. Both the device of the present example and the device of the comparative example are backlight units having a thickness of about 40 mm and a display area of about 573 mm × 312 mm, only the arrangement configuration of the prism array portion on the lower surface side is different, and the other components are The same was done (only different elements are labeled).

As can be understood from FIGS. 3 and 4 in which the prism array portions of the two devices 1 and 101 are exaggerated in plan view, the prism array 13 is included in the device 1 of the present embodiment.
(1) p to 13 (4) p prism ridges are oriented at right angles, parallel, parallel, and right angles from the left hand to the right hand in the figure with respect to the longitudinal direction of the light source units 3a and 3b (FIG. 3),
On the other hand, in the example device 101, the prism array 1
The prism ridges of 13 (1) p and 113 (2) p are all oriented parallel to the light source units 3a, 3b (in other words, the prism ridges are substantially parallel to the straight peaks of the gable roof). .

Regarding these two devices 1 and 101, at five measurement points (points) on a virtual straight line that crosses the light emitting surface, a point near each of the light sources 3a and 3b, a central point, and an intermediate point between them. The magnitude of the luminance [cd / mm ² ] was measured, and the luminance distribution state was plotted in FIG. In FIG. 5, a circle indicates a luminance distribution by the device 1 of the present embodiment shown in FIG. 1, and a circle indicates a luminance distribution by the comparative device 101. From the figure, it can be understood that in the device 1 of the present embodiment, the brightness at the center of the light emitting surface can be maintained high and the brightness is averaged / uniformized as a whole. The device 1 of the first embodiment described above was a backlight unit of a double-sided lighting system, but the second embodiment described next is a so-called one-sided lighting system backlight unit.
In addition, unless otherwise specified, the elements having the same names or reference numerals as those of the constituent elements of the first embodiment have substantially the same contents, and the duplicated description will be omitted.

Referring to FIG. 6, the backlight unit 61 of the second embodiment is provided with a light source unit 63 only on one side thereof. The light source unit 63 is different from the light source unit 3 of the device 1 of the first embodiment in that the lamp holder 67 has a V-shaped cross section, but is substantially the same as the above. On the front side in the lateral direction of the light source unit 63,
A hollow hollow light guide 69 having a triangular cross section is formed,
The light control plate 11 is disposed between the light source unit 63 and the hollow light guide section 69. The lower side of the hollow light guide portion 69 is defined by two rectangular plate-shaped prism array portions 73 (1) and 73 (2) that are joined together like a one-way roof. The highest straight ridge of this one-sided roof is
It is substantially parallel to the longitudinal direction of the light source unit 63 and is located on the side far from the light source unit 63. On the lower surface side of these prism array portions 73 (1) and 73 (2), the reflection plate 7
5 are provided. The prism array 73 (1) p of the prism array portion 73 (1) near the light source unit 63 is
The prism array 73 (2) of the prism array section 73 (2) on the side far from the light source unit 63, in which each prism ridge intersects the straight ridge of the one-sided roof at a substantially right angle or at a right angle.
In p, each prism ridge line is substantially parallel to the straight ridge of the one-way roof. The inclined surface light guide plate 77 defines the upper surface side of the hollow light guide portion 69, and is arranged so as to lower as it moves away from the light source unit 63. On the upper side of the inclined surface light guide plate 77, the transparent plate 21, the diffusion plate 23, and the prism lens 25 which constitute the main part of the light emitting (diffusing) surface.
Are stacked in this order. The elements described above are incorporated inside a predetermined housing 81. In the one-side lighting system backlight unit 61 of the second embodiment having the above-described configuration, as in the double-side lighting system device 1 of the first embodiment, while maintaining high brightness on the light emitting (diffusing) surface. At the same time, the brightness distribution can be made extremely uniform. That is, in the light emitting surface, a portion close to the light source is bright and a portion far from the light source is dark, and the difference is large. However, according to the configuration of the second embodiment, the portion close to the brightness (luminance distribution) is also included. The distant part can be made almost the same.

It should be noted that, as is common to the backlight unit devices of the first and second embodiments, each lamp of the light source unit has a lateral dimension corresponding to the dimension of the light emitting surface. In this case, there is no particular inconvenience, but if the size of one lamp cannot cover the size in terms of price and technology (current leakage, etc.), simply connecting two lamps will usually result in a dark lamp end. The joint part that is butted may be dark, which may darken the central part of the light emitting surface, but by arranging the two lamps so that they partially overlap near the center, the central part of the light emitting surface becomes brighter. can do. By incorporating such a device in the configuration of the present application, it is possible to further improve the luminance surface.

[0021]

As described above, according to the present invention, a light emitting surface having a high luminance and an ultra-light, large light emitting surface capable of suppressing the luminance unevenness to a low level as a whole can be provided. A light unit can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a first embodiment device of the present invention.

FIG. 2 is a schematic cross-sectional view of a comparative example device.

FIG. 3 is a plan view of a prism array section in the first embodiment device of FIG.

FIG. 4 is a plan view of a prism array section in the comparative example device of FIG.

FIG. 5 is a diagram showing a result of a comparative experiment regarding a luminance distribution using the device of the first example and the device of the comparative example.

FIG. 6 is a schematic cross-sectional view of a second embodiment device of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Backlight unit 3, 3a, 3b ... Light source unit 5 ... Lamp 7 ... Lamp holder 9 ... Cavity light guide part 11 ... Light control plate 13 (1), 13 (2), 13 (3), 13 (4) ... Prism array part 15 ... Reflective plates 17 (1), 17 (2) ... Inclined surface light guide plate 21 ... Transparent plate 23 ... Diffusion plate 25 ... Prism lens 61 ... Backlight unit 63 ... Light source unit 67 ... Lamp holder 69 ... Cavity Light guide part 73 (1), 73 (2) ... Prism array part 75 ... Reflector 77 ... Inclined surface light guide plate

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yuu Shiozawa 654 Kawawa-cho, Tsuzuki-ku, Yokohama-shi, Kanagawa Fujitsukasei Co., Ltd. (72) Inventor Takeshi Iijima 654 Kawawa-cho, Tsuzuki-ku, Yokohama-shi, Kanagawa Fujitsukasei Co., Ltd. (72) Inventor Akira Tanaka, 654 Kawawa-cho, Tsuzuki-ku, Yokohama-shi, Kanagawa Prefecture (72) Takashi Aoki Inventor Takashi Aoki 6-735 Kitashinagawa, Shinagawa-ku, Tokyo No. Sony Corporation (72) Inventor Kiyoshige Matsuura 6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation (72) Inventor Tomoya Tanino 6-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni -Inside the corporation

Claims (6)

[Claims] 1. A double-side lighting type backlight unit including a light guide means and a pair of light source units arranged on both sides of the light guide means substantially in parallel with each other. It includes a prism part, a light guide part on the upper surface side, and a hollow cavity light guide part sandwiched between the reflection / prism part and the light guide part. The reflection / prism part includes four prism arrays formed on the upper surface. The rectangular plate-shaped prism array parts are connected together to form a gable roof in which the linear peaks are substantially parallel to the longitudinal direction of both light source units and are located approximately in the middle of both light source units. The two outer prism array parts near the light source unit include a structure in which a reflecting member is attached to the side,
The ridgeline of each prism intersects the straight ridge of the gable roof at a substantially right angle or at a right angle, and in the two prism array portions inside the light source unit, the ridgeline of each prism is a straight ridge of the gable roof. A backlight unit that is substantially parallel to the section. 2. The light guide section on the upper surface side of the light guide means includes a prism array surface, and the ridge line of each prism is substantially parallel to the straight ridge portion of the gable roof.
Backlight unit described. 3. The light guide means includes a light control plate having a prism array on one side on both side surfaces facing the light source unit, and the ridges of the prisms are substantially parallel to the linear peaks of the gable roof. The backlight unit according to claim 1, wherein the backlight unit is provided. 4. A one-side lighting type backlight unit including a light guide means and a light source unit on one side of the light guide means, wherein the light guide means comprises a reflection / prism section on a lower surface side and a light guide unit on an upper surface side. It includes a light section and a hollow cavity light guide section sandwiched between the reflection / prism section and the light guide plate section. The reflection / prism section includes two rectangular plate-shaped prism array sections each having a prism array formed on the upper surface thereof. A structure that is formed by connecting them to form a one-way roof so that the linear peaks are substantially parallel to the longitudinal direction of the light source unit and located on the side far from the light source unit, and a reflecting member is attached to the lower surface side. In the prism array portion on the side closer to the light source unit, the ridgeline of each prism intersects the straight ridge portion of the one-sided roof substantially orthogonally or at a right angle, and the prism array portion on the side far from the light source unit is A backlight unit, wherein the ridge line of the beam is substantially parallel to the linear peaks of the shed roof. 5. The light guide section on the upper surface side of the light guide means includes a prism array surface, and the ridgeline of each prism is substantially parallel to the linear peak section of the one-sided roof. Backlight unit described. 6. The light guide means includes a light control plate having a prism array on one side facing the light source unit, and a ridgeline of each prism is substantially parallel to a straight peak of the one-sided roof. The backlight unit according to claim 4, wherein the backlight unit is provided.