JPH1039808A - Illumination device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an illumination device with which the irradiation with nearly uniform and high luminance is possible in use of a liquid crystal display device as a direct overhead type back light. SOLUTION: This illumination device has a reflection type casing 8 which has an openably formed front surface and is formed with a reflection surface having ruggedness in a specified direction on its inside bottom wall surface, cold cathode low-voltage discharge lamps 9 which are arranged in the recessed parts 8a' of the inside bottom wall surface of this reflection type casing 8 and form flat planar light emitting parts, mirror finished reflection films 8c which are formed and arranged on the projecting part 8b surfaces of the reflection type casing 8 and a diffusion transparent plate 10 which is mounted freely attachably and detachably in the aperture of the reflection type casing 8. The mirror finished reflection films 8c formed and arranged on the projecting part 8c surfaces incline at an angle of nearly 45 deg. or the projecting part 8b surfaces form slopes of nearly 45 deg.. In addition, these slopes are coated and formed with the mirror finished reflection films 8c.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat illuminating device suitable for a direct backlight for a liquid crystal display device such as a word processor, a personal computer, and a liquid crystal television.

[0002]

2. Description of the Related Art For example, a backlight illumination device for a liquid crystal display device such as a word processor, a personal computer, and a liquid crystal television uses a cold-cathode low-pressure discharge lamp (cold-cathode fluorescent lamp) as a light source. It is often used to display a liquid crystal surface by irradiating substantially uniform light to the surface.

FIG. 5 is an exploded perspective view showing the basic structure of a conventional backlight illumination device. FIG.
In the drawings, 1 is a reflection type casing having a shallow dish shape with a front surface formed to be openable, and 2 is the reflection type casing 1
A cold-cathode low-pressure discharge lamp arranged in a plane and electrically connected thereto. Here, the reflective casing 1 is made of, for example, a polycarbonate resin or a polycarbonate resin-mixed weather-resistant resin.

The cold cathode low-pressure discharge lamp 2 is formed, for example, by connecting a plurality of U-shaped cold cathode fluorescent lamps in series at a connection terminal portion 3 and using both ends as power supply terminals.
Further, reference numeral 4 denotes a lamp holder made of an elastic material such as rubber, which is mounted and arranged on the power supply terminal side of the cold cathode low-pressure discharge lamp 2, and 5 is a synthetic resin system which is removably mounted in the opening of the reflective casing 1. Is a diffusion transmission plate.

The bottom wall 1a of the reflective casing 1 is
Uneven surface in a certain direction (stripe-like projections 1b are formed)
The concave and convex surface functions as a reflective surface, and the cold cathode low-pressure discharge lamp 2 is locked by a locking piece 1c such as a bent portion 2a and arranged and mounted in the reflective casing 1 in a planar manner. . The cold-cathode low-pressure discharge lamp 2 has a lamp holder 4 sandwiched and supported by a pair of support mechanisms 6 integrally provided on the side wall 1d of the reflective casing 1,
It is fixed and mounted in the reflective casing 1. In the above configuration, both ends of the cold-cathode low-pressure discharge lamp 2 are fitted to and supported by the support mechanism (support groove) 6 via the lamp holder 4 because the minute bulb is deformed due to the thermal expansion that occurs at the time of lighting and during use. The external force due to the impact or vibration of the lamp is absorbed by the rubber-based elastic material holder 3 to prevent the cold cathode low-pressure discharge lamp 2 from being damaged and to provide electrical insulation.

[0006]

However, in the case of the lighting device having the above structure, there are the following disadvantageous problems.
That is, when the above-mentioned flat light source is used as a so-called direct-type backlight, it exhibits light distribution characteristics as shown in FIG. That is, as schematically shown in FIG.
Illumination light of the flat illumination device having the above-described configuration is emitted from the cold cathode low-pressure discharge lamp 2 and directly directed to the diffuse transmission plate 5;
Bottom wall 1a of reflective casing 1 (stripe-shaped convex surface 1
The reflected light in b) passes through the diffuse transmission plate 5 and irradiates the liquid crystal surface. Therefore, immediately above (directly above) the light emitting portion of the cold cathode low pressure discharge lamp 2 has a light distribution characteristic in which the luminance is high and the brightness between the light emitting portions of the cold cathode low pressure discharge lamp 2 is low. The light distribution characteristics as described above, in other words, exhibiting the stripe-like light distribution unevenness of the high luminance region and the low luminance region in a plane means that the liquid crystal display surface is non-uniformly irradiated with light. There is a problem in obtaining a high quality liquid crystal display.

As a countermeasure for the above-mentioned luminance unevenness, as shown in FIG.
Attempts have been made to form an aluminum layer 7 as a reflective layer on the bottom wall surface 1a that has been made into a convex surface 1b. In other words, by making the light reflection on the bottom wall surface 1a of the reflective casing 1 more efficient, it is possible to suppress the occurrence of uneven brightness or to make the diffuse transmission
Attempts have been made to reduce uneven brightness on the surface. But,
Even with such a configuration, the light distribution characteristics are as shown in FIG.
As described above, the problem of uneven brightness has not been solved yet.

The flat surface of the bottom wall of the reflective casing 1 is made into a mirror-reflective layer, and the surface made into the convex surface 1b is made white, and a light emission unevenness preventing film is disposed just above (directly above) the light emitting portion of the discharge lamp 2. The configuration is also known (JP-A-4-323687).
However, in this case, the configuration becomes complicated, the mass productivity is inferior, etc., and it cannot be said that it is sufficient as a measure against luminance unevenness. The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a lighting device capable of emitting substantially uniform high-luminance light when used as a direct backlight of a liquid crystal display device.

[0009]

According to a first aspect of the present invention, there is provided a reflection type casing having a front surface formed to be openable, and an inner bottom wall surface having a reflection surface with irregularities in a predetermined direction, and an inner bottom surface of the reflection type casing. A cold-cathode low-pressure discharge lamp, which is arranged in a concave portion of a wall surface and forms a planar light emitting portion, a mirror-like reflective film formed and arranged on a convex surface of the reflective casing, and an opening of the reflective casing. An illumination device having a diffuse transmission plate which is detachably mounted, wherein the specular reflection film formed and arranged on the convex surface is inclined at an angle of approximately 45 °. It is.

According to a second aspect of the present invention, there is provided a reflective casing in which a front surface is formed to be openable and an inner bottom wall surface is formed as a reflecting surface having irregularities in a predetermined direction, and is disposed in a concave portion of the inner wall surface of the reflective casing. A cold-cathode low-pressure discharge lamp forming a planar light-emitting part, and a projection formed on the reflective casing.
An illuminating device having a mirror-reflective film disposed thereon and a diffuse transmission plate detachably attached to an opening of the reflective casing, wherein the convex surface forms an approximately 45 ° inclined surface, and A lighting device characterized in that a specular reflection film is coated and formed on the inclined surface.

According to a third aspect of the present invention, in the lighting device according to the first or second aspect, the specular reflection film is formed of silver or a silver compound.

According to a fourth aspect of the present invention, in the lighting device according to any one of the first to third aspects, the cold-cathode low-pressure discharge lamp is flattened at a U-shaped bent portion.

That is, according to the present invention, the inner bottom wall surface of the reflective casing is formed as an uneven surface in a certain direction, and the cold cathode low-pressure discharge lamp is mounted and arranged in the concave area. The main point is that the reflection surface is set to a reflection surface with a 45 ° inclination angle and the reflection surface is a specular reflection layer. And by adopting such a configuration,
This is a high-quality, high-performance lighting device that not only eliminates and reduces the luminance unevenness of visible light generated by the cold cathode low-pressure discharge lamp, but also increases the reflection efficiency and the amount of light. The present invention has been made based on the following background. That is, the inventor of the present invention has determined that, on the bottom wall surface of the reflective casing, a region (concave portion) where the cold cathode low-pressure discharge lamp is mounted in a planar manner (a concave portion) and a region (convex portion) that forms a main reflection surface with respect to this concave portion. Various studies were conducted on the tilt angle, the reflection layer, and the like. As a result, when the angle of the main reflection surface is set to approximately 45 ° and the reflection surface is a mirror reflection layer, the brightness between the discharge lamp light emitting portions and the high brightness immediately above (directly above) the light emitting portions of the discharge lamp is high. It was confirmed that high luminance was exhibited, planar luminance unevenness was significantly reduced and eliminated, and the amount of light radiated through the diffusion transmission plate was also increased. Based on this finding, the present invention has provided an illuminating device capable of performing high-quality liquid crystal display with substantially uniform luminance over the entire surface.

In the present invention, the reflective casing is made of, for example, a polycarbonate resin or a mixture of a polybutadiene acrylonitrile resin containing a polycarbonate resin as a main component. In addition, the concave and convex reflecting surface formed in a certain direction (in the form of a stripe) on the inner bottom wall surface serves as an arrangement / mounting portion for a light emitting portion of a cold cathode low pressure discharge lamp having a flat concave surface region. The region functions as a reflector on the side of the light emitting unit. Therefore, the number, width and length of the concave regions and the number, height and spacing of the convex regions are appropriately selected and set according to the planar shape, tube diameter, tube length and the like of the cold cathode low pressure discharge lamp. Generally, in the case of a cold cathode low pressure discharge lamp having an outer tube diameter of about 4 to 5 mm, the width of the concave area is about 100 × 100 mm, and the interval between the convex areas is 14 to 18 mm.
The height is about 7 to 9 mm in mm.

In the present invention, the cold-cathode low-pressure discharge lamp, which is disposed in the recess on the inner bottom wall surface of the reflective casing and forms a planar light-emitting portion, is a so-called cold-cathode fluorescent lamp. A straight pipe-shaped parallel arrangement, a planar U-shape, a W-shape, a combination of U-shapes, a combination of W-shapes, or a combination of a U-shape and a W-shape are exemplified.

In the present invention, the specular reflection film formed and arranged on the convex surface of the inner bottom wall of the reflection casing is not particularly limited as long as it is made of a metal which can be mirror-finished, but silver and a silver compound are preferable. Further, the film thickness may be about 10 to 30 μm,
For example, it can be formed by an evaporation method or sputtering. However, the specular reflection film needs to be inclined and set at an angle of 45 ± 3 °, more preferably 45 °. Further, the diffusion transmission plate detachably attached to the opening of the reflection type casing is, for example, a light transmission plate such as a polycarbonate resin plate, an acrylic resin plate, and a glass plate. Resin plate is used.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment will be described below with reference to FIGS. 1, 2, 3 and 4. FIG.

FIG. 1 is a perspective plan view showing a basic configuration of the lighting apparatus, and FIG. 2 is a sectional view taken along line AA of FIG. In FIGS. 1 and 2, reference numeral 8 denotes a reflective casing made of a polycarbonate resin, which has a shallow dish shape having an open front surface and a bottom wall surface 8a serving as a reflective surface. Here, on the bottom wall surface 8a of the reflection type casing 8, a concave area 8a 'having a width of 7 mm and a convex area 8b having a height of 4 mm and a side surface inclination angle of 45 ° are alternately formed and arranged in a stripe shape. In addition, a mirror reflection layer 8c is formed on each inclined surface of the convex region 8b by vapor deposition of silver.

9 is a bottom wall of the reflection type casing 8
The cold cathode discharge lamp 9 is a flat cold cathode discharge lamp mounted and arranged in the concave area 8a 'of 8a. The cold cathode discharge lamp 9 is formed by combining a U-shaped cold cathode fluorescent lamp. That is, a plurality of U-shaped cold-cathode fluorescent lamps having an outer diameter of 3 to 4 mm and a total length of 200 to 260 mm are connected in series at the connection terminal portions as in the case shown in FIG. It is.

In this embodiment, a lamp holder mounted and arranged on the power supply terminal side of the cold-cathode low-pressure discharge lamp 9 according to the configuration shown in FIG. While being supported in a sandwiched manner by a supporting mechanism that is installed in place, a bent portion of the cold cathode low-pressure discharge lamp 9 is locked by a locking piece, and is arranged and mounted in a planar manner. A synthetic resin-based diffused transmission plate 10 is detachably attached to the opening 8 to constitute an illumination device.

When the illuminating device having the above configuration was turned on, and the light distribution characteristics radiated through the diffuse transmission plate 10 were measured and evaluated. As shown in FIG. 3, the light distribution characteristics showed almost no luminance unevenness. Was. That is, the light distribution characteristics of this flat-plate type illumination device depend on the cold cathode discharge lamp 9, the specular reflection layer 8c having an inclination angle of 45 °, and the diffusion transmission plate 10.

The light emission of the cold cathode discharge lamp 9 is as follows.
As schematically shown in FIG. 4 on an enlarged scale, the light emitted from the cold cathode discharge lamp 9 and directly directed to the diffuse transmission plate 10 and the specular reflection of the bottom wall surface 8a of the reflective casing 8 (stripe-shaped uneven surface). The light reflected by the layer 8c and traveling toward the diffuse transmission plate 10 passes through the diffusion transmission plate 10. At this time, the reflection layer on the bottom wall surface 8a is
Since the mirror reflection layer 8c having a high reflection efficiency and facing the light emitting portion of the cold cathode discharge lamp 9 at an angle of 45 °, most of the light emitted to the side surface in the light emitting portion is reflected,
It will be directed to the diffuse transmission plate 10.

In other words, the mirror reflection layer 8c functions as an apparent light source (pseudo lamp) with respect to the cold cathode discharge lamp 9 which is an actual light source, so that the space between the light emitting portions of the adjacent cold cathode discharge lamps 9 is provided. Easily avoid or suppress low brightness.

When the lighting device is turned on, the amount of light radiated through the diffusion transmission plate 10 is about 300 lm (lumen), which is smaller than that of the above-mentioned conventional flat lighting device. 1.5 to 2.0 times, and it was also excellent in terms of brightness.

Therefore, the light distribution characteristic radiated through the diffusion transmission plate 10 has substantially uniform luminance over the entire surface irrespective of the mounting position of the cold cathode discharge lamp 9 and between the light emitting portions of the cold cathode discharge lamp 9. It is possible to irradiate a liquid crystal display surface (without luminance unevenness) with good visibility.

In this configuration example, the specular reflection layer
Although the inclination angle of 8c is set to 45 °, substantially the same operation and effect can be obtained in the range of 43 to 47 °. Furthermore, in the above configuration example, the mirror surface reflection layer 8c is formed by depositing silver on the surface of the convex region 8b in which the inclination angle of the side surface provided on the bottom wall surface 8a of the reflective casing 8 is 45 ° and the inclination angle is 45 °. Even if the inclination angle of the side surface of the region 8b is not approximately 45 °, the finally formed specular reflection layer
If the form and structure of 8c have an inclination angle of about 45 °, the same operation and effect as in the above configuration can be obtained.

The present invention is not limited to the configuration described above, and various modifications can be made without departing from the spirit of the invention. For example, a cold cathode discharge lamp
Instead of the combination of the U-shaped fluorescent lamps, a W-shaped fluorescent lamp may be used, or a configuration in which straight tube fluorescent lamps are arranged in parallel may be employed. Also, the specular reflection layer may be a sputtered layer instead of the silver deposition layer,
Instead of silver, an alloy having a silver diameter or a silver alloy may be used.

[0028]

According to the lighting device of the present invention, approximately 45
The mirror reflection layer set to ° acts as a pseudo-lamp, which gives a high brightness comparable to the high brightness just above (directly above) the light-emitting part of the discharge lamp between the light-emitting parts of the discharge lamp, greatly reducing unevenness in planar brightness. Thus, radiation light reduced and eliminated can be obtained. In addition, since the amount of light radiated through the diffusion transmission plate is also increased, high-quality liquid crystal display can be realized when used as a direct-type liquid crystal backlight in combination with the high luminance and the non-uniform luminance. A lighting device is provided.

[Brief description of the drawings]

FIG. 1 is a plan view perspectively showing an example of a configuration of a main part of a lighting device according to the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG. 1;

FIG. 3 is a diagram showing an example of light distribution characteristics of irradiation light of the illumination device shown in FIG. 1;

FIG. 4 is a schematic explanatory diagram of the light distribution characteristics shown in FIG.

FIG. 5 is an exploded perspective view showing a configuration of a main part of a conventional lighting device.

FIG. 6A is a light distribution characteristic diagram of irradiation light of a conventional lighting device,
(b) is a sectional view showing a schematic configuration of the lighting device.

7A is a cross-sectional view illustrating another schematic configuration of a conventional lighting device, and FIG. 7B is a light distribution characteristic diagram of irradiation light of the lighting device.

[Explanation of symbols]

 1, 8 ... reflective casing 1a, 8a ... bottom wall surface 1b, 8b ... convex area 1c ... armature piece 2, 9 ... cold cathode discharge lamp (fluorescent lamp) 2a ... bent portion 3 ... connection Terminal part 4 ... Lamp holder 5,10 ... Light diffusion transmission plate 6 ... Support mechanism (support groove) 7 ... Aluminum reflection layer 8a '... Concave area 8c ... Mirror reflection layer

Claims (4)

[Claims] 1. A reflective casing having a front surface formed to be openable and an inner bottom wall having a concave and convex reflecting surface in a predetermined direction, and a planar light emitting device disposed in a concave portion of the inner wall surface of the reflective casing. A cold-cathode low-pressure discharge lamp forming a portion, a specular reflection film formed and arranged on a convex surface of the reflection type casing, and a diffusion transmission plate detachably mounted on an opening of the reflection type casing. The specular reflection film formed and arranged on the convex surface is inclined at an angle of approximately 45 °. 2. A reflective casing having a front surface formed so as to be openable and an inner bottom wall surface having a reflecting surface having irregularities in a predetermined direction, and a light emitting element disposed in a concave portion of the inner bottom wall surface of the reflective casing and having a planar light emission. A cold-cathode low-pressure discharge lamp forming a portion, a specular reflection film formed and arranged on a convex surface of the reflection type casing, and a diffusion transmission plate detachably mounted on an opening of the reflection type casing. An illumination device, comprising: a convex surface forming an approximately 45 ° inclined surface, and a specular reflection film attached and formed on the inclined surface. 3. The lighting device according to claim 1, wherein the specular reflection film is formed of silver or a silver compound. 4. The lighting device according to claim 1, wherein the cold-cathode low-pressure discharge lamp is flattened at a U-shaped bent portion.