JP2004030990A - Backlight device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a backlight device without decreasing an effective luminous area and capable of surely retaining an intermediate part of a U-shaped cylindrical light source to a case. <P>SOLUTION: A reflective face 5 is formed on the bottom face of a case 1 having a rectangular plane shape, an opening of the case is covered with a diffusion plate 10, and a U-shaped cylindrical light source 3 is fitted to a side plate of the case so as to enable a pair of ends be mounted. The device is provided with first retaining parts 8, 9 for retaining the center of the cylindrical light source and second a retaining part 6 (6a) retaining a part adjacent to the center of one of the legs of the cylindrical light source erected at the bottom of the case. At lighting the cylindrical light source, the width of the second retaining part along the length direction of one of the legs is selected so that shades of the second retaining parts are not clearly formed on the surface of the diffusion plate, the temperature fall of a contact part of the U-shaped light source with the second retaining part is small, and the retaining strength of the cylindrical light source is kept high. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a backlight device mounted on a liquid crystal display device or the like.
[0002]
[Prior art]
Hereinafter, a conventional backlight device will be described with reference to FIG. 1 shows the backlight device as a whole. As shown in FIG. 8, the backlight device 1 has two or more lamps, that is, a plurality of linear cylinders, so as to pass between a pair of opposed side plates 2A and 2B of a casing 2 having a rectangular planar shape. The light sources (cold cathode discharge tubes) 30, 30 are arranged in parallel, a reflection surface 5 is formed on the inner surface of the housing 2, and a diffusion plate (not shown) is provided so as to cover the opening of the housing 2. It was composed.
[0003]
In this case, since the linear cylindrical light source 30 includes a glass tube, both ends of each linear cylindrical light source 30 are prevented in order to prevent the glass tube from being damaged by an impact or the like. Are attached to a pair of opposed side plates 2A, 2B of the housing 2 via holders 4a, 4b made of rubber, respectively.
[0004]
In such a conventional backlight device, since the two electrodes of each linear cylindrical light source are connected to the inverter transformer and the ground on the pair of side plates of the housing, the configuration of the electrical connection unit is complicated. There is a disadvantage. Also, two holders are required for each linear cylindrical light source.
[0005]
Therefore, as shown in FIG. 9, a backlight device using a U-shaped (U-shaped) cylindrical light source as a cylindrical light source has been conventionally proposed. In this case, both ends of the U-shaped cylindrical light source 3 are attached to one side plate 2A of a pair of side plates 2A and 2B facing each other of the housing 2 via holders 4a and 4b made of rubber, respectively. ing.
[0006]
In a backlight device using this U-shaped cylindrical light source, two U-shaped cylindrical light sources are used instead of two linear C-shaped light sources, so that two linear light sources are used. In the case of the cylindrical light source of (1), four electrical connection portions were required. However, in the case of one U-shaped cylindrical light source, only two electrical connection portions were required. The configuration is simplified.
[0007]
In the backlight device using the U-shaped (U-shaped) cylindrical light source 3 as shown in FIG. 9, it is necessary to hold an intermediate portion of the backlight device in the housing 2.
[0008]
Therefore, as shown in FIG. 10, the U-shaped cylindrical light source 3 is provided at the base between the pair of legs 3a and 3b on the side of the center 3c between the pair of legs 3a and 3b via the holders 4c and 4d made of rubber. To the side plate 2B. In this case, the central portion 3c of the U-shaped cylindrical light source 3 is located below the side plate.
[0009]
[Problems to be solved by the invention]
In the backlight device, the intermediate portion of the U-shaped cylindrical light source is held as shown in FIG. 10 because a portion for accommodating the center portion 3c is required, and the U-shaped cylindrical light source having the same size as the conventional one is required. As compared with the case where the light emitting device is used, the area of the effective light emitting portion is reduced, and the temperature of that portion is lowered.
[0010]
In view of the above, the present invention provides a backlight device in which a U-shaped cylindrical light source is attached to a casing, the area of the effective light emitting portion is not reduced, and the middle portion of the U-shaped cylindrical light source is provided. An object of the present invention is to propose a backlight device that can be securely held in a housing.
[0011]
[Means for Solving the Problems]
The present invention provides a housing having a rectangular planar shape, a reflection surface formed on an inner surface of the housing, a diffusion plate covering an opening of the housing, and a side plate having the housing, and a pair of end portions. A U-shaped cylindrical light source to be attached, a first holding portion that holds the central portion of the U-shaped cylindrical light source upright at the bottom of the housing, and an upright at the bottom of the housing. A second holding portion for holding a portion close to the center of one of the legs of the U-shaped cylindrical light source, and when the U-shaped cylindrical light source is turned on, a second surface is provided on the surface of the diffusion plate. 2, the shadow of the holding portion 2 is not clearly formed, the temperature drop of the contact portion with the second holding portion in the U-shaped cylindrical light source is small, and the holding strength of the U-shaped cylindrical light source is small. The width of the second holding portion is selected along the longitudinal direction of one leg of the U-shaped cylindrical light source so that the second holding portion is sufficient. It is a scaling apparatus.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an example of a backlight device according to an embodiment of the present invention will be described in detail with reference to FIGS. FIG. 1 is a plan view of the backlight device, and FIG. 2 is a cross-sectional view taken along line II-II of FIG.
[0013]
1 and 2, reference numeral 1 denotes a backlight device as a whole. Reference numeral 2 denotes a housing having a rectangular planar shape. Reference numeral 5 denotes a reflection surface formed on the inner surface of the housing 2. Reference numeral 10 denotes a diffusion plate that covers an opening of the housing 2. Here, the diffusion plate 10 includes a diffusion plate 10a having a total light transmittance of 50% and a diffusion sheet 10b thereon having a haze value of 78%.
[0014]
Reference numeral 3 denotes a U-shaped cylindrical light source (having a diameter of 3 mm in this example), and a pair of linear legs 3a and 3b and a linear central portion connecting the pair of legs 3a and 3b. 3c. Then, both ends of the U-shaped cylindrical light source 3 are attached to the side plate 2A with the housing 2 via holders 4a and 4b made of rubber.
[0015]
Then, the central portion 3 c of the U-shaped cylindrical light source is held by two holding portions 8 and 9 erected on the bottom of the housing 2. Instead of the holding parts 8 and 9, one holding part may be provided. In that case, the one holding portion stands upright on the bottom of the housing 2 so as to hold the center of the center 3c.
[0016]
Further, a portion of the U-shaped cylindrical light source 3 that is close to the central portion 3c of the one leg 3b is held by one holding portion 6 planted on the bottom of the housing 2. The holding portion 6 includes a holding portion 6a that holds one leg 3b of the U-shaped cylindrical light source 3, and a reinforcing portion 6b that connects the holding portion 6a and the side plate 2B facing the side plate 2A. Is done. The distance D between the reflecting surface 5 and the cylindrical light source 3 is 2 mm.
[0017]
The holding portions 8, 9 and the holding portion 6 work together to convert the U-shaped cylindrical light source 3 into the central portion 3 c and the two leg portions 3 a and 3 b orthogonal to the central portion 3 c on the central portion 3 c side, The intermediate portion of the U-shaped cylindrical light source 3 can be positioned so as to prevent movement of the legs 3a, 3b in the extending direction and the central portion 3c in the extending direction.
[0018]
By the way, when the U-shaped cylindrical light source 3 is turned on, a shadow of the holding portion 6 a of the holding portion 6 provided on one leg 3 b of the U-shaped cylindrical light source 3 is formed on the diffusion plate 10. Then, the backlight device cannot uniformly illuminate the liquid crystal display device. However, even when the width B of the holding unit 6a is large to some extent, if the distance A between the reflection surface 5 in the backlight device and the diffusion plate 10 is large, the shadow of the holding unit 6a of the holding unit 6 becomes It is difficult to form on the diffusion plate 10.
[0019]
In general, a fluorescent tube is used as the cylindrical light source. However, in a case where the width B of the holding portion 6a of the holding portion 6, which is a contact portion with the cylindrical light source, is large, the U-shaped cylindrical light source 3 is used. If the temperature of the contact portion decreases, mercury contributing to the emission of the fluorescent tube collects in that portion, and the emission luminance and life of the cylindrical light source may be reduced. Therefore, the width of the holding portion 6a of the holding portion 6 is reduced. Should be as narrow as possible.
[0020]
However, in order to obtain sufficient holding strength with respect to the U-shaped cylindrical light source 3 by the holding section 6, it is preferable that the width of the holding section 6a of the holding section 6 is wide.
[0021]
Therefore, the distance A between the reflection surface 5 and the diffusion plate 10 in the backlight device, the width B of the holding portion 6a of the holding portion 6, and the shadow of the holding portion 6a are clearly shown on the diffusion plate 10. An examination of whether it is formed or its shadow is negligibly faint is described below.
[0022]
In the case where the distance between the shadow portion and the non-shadow portion on the diffuser plate 10 is about 10 mm to 30 mm and the difference in brightness is 1% or less, human eyes recognize the uneven brightness. It is not possible.
[0023]
FIG. 3A is a view of the backlight unit of FIG. 1 at the coordinate points 0, 1, 2,... 198, 199 at equal intervals in the vertical and horizontal directions when the width B of the holding unit 6a of the holding unit 6 is 2 mm. represents the luminance contour lines, a, b represents the legs 3a, the position of the 3b of the cylindrical light source 3 of the respective U-shaped, P _B represents the center position of the width of the holding portion 6a of the holder 6. 3 to 7, the distance A from the back side of the diffusion plate 10a to the reflection surface 5 is 13.4 mm.
[0024]
L _a and L _{b in} FIG. 3B indicate characteristic curves of luminance changes on straight lines at positions a and b in FIG. 3A. The number on the left side of FIG. 3B indicates the luminance value (cd / m ² ), and one division is approximately 1% of the luminance value. Then, the brightness curve _{L b,} the maximum level value at the position _{P B} and _{L b0,} this is the standard brightness level.
[0025]
4A and 4B are similar to FIGS. 3A and 3B when the width of the holding portion 6a of the holding portion 6 is 4 mm. 5A and 5B are diagrams similar to FIGS. 3A and 3B when the width of the holding portion 6a of the holding portion 6 is set to 5 mm. 6A and 6B are diagrams similar to FIGS. 3A and 3B when the width of the holding portion 6a of the holding portion 6 is 6 mm.
[0026]
The brightness curve Lb in FIG. 4B, decrement the reference luminance level _{L b0} of the maximum level value _{L b1} at position _{P B} is 0.5%. The brightness curve Lb in FIG. 5B, the decrease amount with respect to the reference luminance level _{L b0} of the maximum level value _{L b2} at the position _{P B} is 1%. The brightness curve Lb in FIG. 6B, the decrease amount with respect to the reference luminance level _{L b0} of the maximum level value _{L b3} at the position _{P B} is 1.5%.
[0027]
As described above, in the case where the distance between the shadow portion and the non-shadow portion on the diffuser plate 10 is about 10 mm to 30 mm and the difference in luminance is 1% or less, human eyes cannot Since it is said that the luminance unevenness cannot be recognized, the width of the holding portion 6a of the holding portion 6 is 5 mm or less (FIGS. 3 to 5), that is, A / B ≦ 2.68, but exceeds 5 mm. (FIG. 6) is not preferred.
[0028]
7A and 7B are diagrams similar to FIGS. 3A and 3B when the width of the holding portion 6a of the holding portion 6 is fixed to 4 mm and the distance A between the reflection surface 5 and the diffusion plate 10 is changed. when the distance a between the diffusion plate 10 and the reflecting surface 5 is equal to or higher than a = 10.7 mm, the brightness curve Lb in FIG. 7B, decrement the reference luminance level _{L b0} of the maximum level value _{L b4} at the position _{P B} is It was found to be less than 1%.
[0029]
When comparing the example of the backlight device of FIG. 1 with the conventional backlight device of FIG. 10, the temperature of the contact portion of the U-shaped cylindrical light source 3 and the temperature of one of the pair of linear legs 3a or 3b are compared. Compared with the temperature at the center, the temperature difference of 5 ° C. or more occurred in the conventional example of the backlight device of FIG. 10, whereas the temperature difference was 1 ° C. in the example of the backlight device of FIG. It was able to be suppressed below.
[0030]
【The invention's effect】
According to the present invention, a housing having a rectangular planar shape, a reflection surface formed on the inner surface of the housing, a diffusion plate covering an opening of the housing, and a side plate having the housing have a pair of ends. A U-shaped cylindrical light source to which the unit is attached; a first holding portion that holds the central portion of the U-shaped cylindrical light source upright at the bottom of the housing; and an upright at the bottom of the housing. A second holding portion for holding a portion close to the center of one of the legs of the U-shaped cylindrical light source, and when the U-shaped cylindrical light source is turned on, , The shadow of the second holding portion is not clearly formed, the temperature of the contact portion with the second holding portion in the U-shaped cylindrical light source is small, and the U-shaped cylindrical light source is The width of the second holding portion along the longitudinal direction of one leg of the U-shaped cylindrical light source is selected so that the holding strength is sufficient. Runode, does not decrease the area of the effective light-emitting portion, moreover, it is possible to obtain a backlight device capable of holding the intermediate portion of the cylindrical light source U-shaped in securely housing.
[Brief description of the drawings]
FIG. 1 is a plan view of an example of a backlight device according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view taken along line II-II of FIG.
3A shows luminance contours at coordinate points at equal intervals in the vertical and horizontal directions of the backlight device in FIG. 1 when the width B of the holding unit is 2 mm.
6 shows a characteristic curve of luminance change on a straight line at positions a and b in B A.
FIG. 4A shows luminance contours at coordinate points at equal intervals in the vertical and horizontal directions of the backlight device in FIG. 1 when the width B of the holding unit is 4 mm.
6 shows a characteristic curve of luminance change on a straight line at positions a and b in B A.
5A shows luminance contours at coordinate points at equal intervals in the vertical and horizontal directions of the backlight device of FIG. 1 when the width B of the holding unit is 5 mm.
6 shows a characteristic curve of luminance change on a straight line at positions a and b in B A.
FIG. 6A shows luminance contours at coordinate points at equal intervals in the vertical and horizontal directions of the backlight device in FIG. 1 when the width B of the holding unit is 6 mm.
6 shows a characteristic curve of luminance change on a straight line at positions a and b in B A.
FIG. 7 is a graph showing brightness contours at coordinate points at equal intervals in the vertical and horizontal directions of the backlight device of FIG. 1 when the width B of the holding unit is 4 mm and the interval A between the reflection surface and the diffusion plate is 10.7 mm. Show.
6 shows a characteristic curve of luminance change on a straight line at positions a and b in B A.
FIG. 8 is a perspective view showing an example of a conventional backlight device.
FIG. 9 is a perspective view showing another example of a conventional backlight device.
FIG. 10 is a perspective view showing a reference example of the backlight device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Back light apparatus, 2 housings, 3 cylindrical light sources, 3a, 3b legs, 3c central part, 4a, 4b holder, 5 reflection surface, 6 holder, 6a holder of holder 6, 6b holder 6 8, 9 holding part, 10 diffusion plate, 10a diffusion plate, 10b diffusion sheet.

Claims (1)

A housing having a rectangular planar shape;
A reflecting surface formed on the inner surface of the housing;
A diffusion plate covering the opening of the housing,
A U-shaped cylindrical light source to which a pair of ends is attached to a side plate having the housing,
A first holding portion that holds a central portion of the U-shaped cylindrical light source that is erected on a bottom portion of the housing;
A second holding portion that holds a portion of the one leg portion of the U-shaped cylindrical light source that is upright at the bottom of the housing and that is close to the central portion,
When the U-shaped cylindrical light source is turned on, the shadow of the second holding portion is not clearly formed on the surface of the diffuser plate, and the second holding portion of the U-shaped cylindrical light source is not formed. The one leg of the U-shaped cylindrical light source of the second holding portion so that the temperature drop at the contact portion is small and the holding strength of the U-shaped cylindrical light source is sufficient. A backlight device characterized in that a width along a longitudinal direction of the portion is selected.

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