JP2007042524A - Light source device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light source which can make uniform luminescence of a surface of a diffuser sheet and illuminate a display unit such as a liquid crystal with a uniform light without unevenness, even if there is no wide distance between a diffuser sheet and an outer electrode rare gas fluorescent lamp. <P>SOLUTION: A light source is provided with a plurality of outer electrode rare gas fluorescent lamps of which the inner surface of a cylindrical bulb 10 is coated by phosphor 12 and has a pair of outer electrodes 11 on an outer surface along a cylindrical axis and which are placed in a reflecting mirror 2 in parallel in a plurality of number, and a diffuser sheet 3 is placed in front of the reflecting mirror 2. An electrode 11 facing the diffuser sheet passes through a center of the bulb and cross a virtual line perpendicular to the diffuser sheet on a plane crossing the cylindrical axis of the cylindrical bulb 10. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light source device using an external electrode rare gas fluorescent lamp used in a backlight device or a liquid crystal display device.

  As a light source used in a backlight device, a liquid crystal display device, etc., an external electrode rare gas fluorescent lamp (hereinafter referred to as a “external electrode rare gas fluorescent lamp”) having a pair of external electrodes spaced apart from each other along the longitudinal direction of the outer surface of the tubular bulb. Simply called a lamp).

  In this lamp, a high frequency alternating voltage is applied between a pair of external electrodes to generate a rare gas discharge of xenon in the discharge space to emit ultraviolet rays, and the ultraviolet rays are formed on the inner surface of the tube bulb. The phosphor is excited, visible light is emitted from the phosphor, and visible light is emitted from the gap between the pair of external electrodes (hereinafter also referred to as a light emitting portion) to the outside of the lamp.

Japanese Patent Application Laid-Open No. 2001-155527 is known as a light source device that uses this lamp and uses light emitted from a light emitting portion.
A light source device using an external electrode rare gas fluorescent lamp will be described with reference to FIG.
The external electrode rare gas fluorescent lamp 1 has a pair of external electrodes 11 on the outer surface along the tube axis, and a phosphor is formed on the inner surface of the tube-type bulb so that light between the pair of electrodes is light. Visible light is emitted from the emission part A.
Reference numeral 2 denotes a reflection mirror, and a plurality of, in this example, four lamps 1 are arranged in the reflection mirror 2 at intervals so as to be substantially parallel. A diffusion plate 3 is disposed in front of the reflection mirror 2. Has been placed.

FIG. 7 is an explanatory view of the arrangement state of the lamps in the reflection mirror in the light source device shown in FIG.
In a plane perpendicular to the tube axis of the bulb 10, an imaginary line α passing through the center P of the bulb 10 and perpendicular to the diffusion plate 3 is drawn, and another imaginary line β perpendicular to the imaginary line α at the center P is drawn, A pair of external electrodes 11 are formed on the outer surface of the bulb 10 at a position intersecting with the virtual line β.

  Then, the direct light radiated from the light emitting portion A and the reflected light reflected by the reflection mirror 2 enter the diffusion plate 3 and are combined, and the traveling direction of the light is changed in the diffusion plate 3. Uniform light diffused from the surface 3A is emitted and uniformly illuminates a display device such as a liquid crystal in front of the diffusion plate 3.

JP 2001-155527 A

The result of measuring the luminance on the diffusion plate of the light source device shown in FIG. 6 is shown in graph a of FIG.
In the figure, the vertical axis indicates the luminance, and the horizontal axis indicates the position in the direction orthogonal to the tube axis of the external electrode rare gas fluorescent lamp disposed in the light source device. Is the position where the lamp center is 30 mm, 60 mm, 90 mm, or 120 mm.

As shown in the graph a, the brightness of the diffuser plate at the position facing the lamp is larger than the brightness of the diffuser plate at the position not facing the lamp, and even when the diffuser plate is used, the brightness of the surface of the diffuser plate is It turns out that it is not fully equalized.
Specifically, in the graph a, the difference between the maximum luminance and the minimum luminance is about 600 cd / m ^2, and the luminance of the surface of the diffusion plate is clearly uneven.

A diffuser plate is one in which light is diffused and emitted from the surface, but the brightness of the surface of the diffuser plate becomes uniform when light uniformly enters the entire back surface of the diffuser plate within a certain range. It is.
More specifically, when the light flux density defining the light component that is perpendicularly incident on the back surface of the diffuser plate is uniform throughout the back surface of the diffuser plate, the luminance of the surface of the diffuser plate is also uniform.

Next, the relationship between the light emitted from the lamp and the light flux density will be described.
FIG. 8 is a diagram showing the relationship between the light emitted from the surface of the external electrode rare gas fluorescent lamp and the diffusion plate.
The lamp is coated with phosphor over the entire circumference of the inner surface of the bulb, and diffused light is emitted from the bulb surface as a whole.
FIG. 8 is a schematic diagram of light emitted from the bulb surface at two points (Y, Z), and La and Ld pass through the Y and Z points from the tangent line passing through the Y and Z points on the bulb surface. The light is perpendicular to the normal direction, and Lc, Lb, Le, and Lf are diffused light with the Y and Z points as base points. Note that the total luminous flux emitted from the Y point and the Z point is considered to be the same.
A point Y is a position where a virtual line α passing through the valve center P and perpendicular to the diffusion plate 3 is drawn, and the virtual line α intersects the valve surface.

The light emitted from the Y point has a larger La flux in the normal direction than Lb and Lc. Similarly, the light emitted from the Z point has the Ld luminous flux in the normal direction as Le. , Larger than Lf.
Further, when the light of La and Le is parallel, both lights become light perpendicularly incident on the diffusion plate 3, and the light flux density on the back surface of the diffusion plate is defined by these lights.
However, in La and Le, La has a larger luminous flux, and as a result, the luminous flux density at the position 3P on the back surface of the diffusion plate where the light La is incident is equal to the light flux density at the position 3P ′ on the back surface of the diffusion plate where the light Le is incident. Therefore, the brightness of the surface of the diffusion plate at the position 3P where the light La is incident is higher than that of other portions.

  In addition, at the back surface positions 3P and 3P ′ of the diffuser plate 3 where the light La and the light Le are incident, there is also light incident obliquely emitted from other bulb surfaces other than the light La and Le incident vertically. Light incident from an oblique direction has a small luminous flux and is diffused in a complicated manner inside the diffusion plate, and it cannot be analyzed from which position on the surface of the diffusion plate. It is not considered.

  Returning to FIG. 7 and continuing the explanation, the position 3P where the virtual line α intersects the back surface of the diffusion plate 3 has the highest light flux density than the other positions of the diffusion plate 3 as described in FIG. As a result, the luminance of the surface of the diffusion plate 3 facing the 3P position is the highest as compared with other portions.

  Further, in the region between the lamps, there is no light source, and the light reflected by the reflecting mirror on the back of the lamp passes, and a part of this light is incident on the diffuser plate perpendicularly. However, the light reflected by the reflecting mirror and incident perpendicularly to the diffuser is much smaller than the light perpendicularly incident on the 3P position of the diffuser, and is reflected by the reflective mirror and reflected by the diffuser. However, the light incident perpendicularly to the surface of the light does not reach the level of the light flux density on the back surface of the diffuser plate.

  Further, when the distance between the diffuser plate and the lamp is short, the diffused light from the lamp cannot be sufficiently spread. Therefore, at a position other than the 3P position of the diffuser plate 3, the light emitted from the lamp is applied to the diffuser plate. On the other hand, the component light incident perpendicularly becomes too small, and the light flux density on the back surface of the diffuser becomes even more uneven. If this uneven state is severe, increase the distance between the diffuser and the lamp. As a result, the apparatus becomes large, and the thickness of the flat panel display is increased, thereby reducing the merchantability.

  The present invention has been made to solve such a problem, and it is possible to make the luminance of the surface of the diffusion plate uniform without greatly separating the distance between the diffusion plate and the external electrode rare gas fluorescent lamp. An object of the present invention is to provide a light source device that can uniformly illuminate a display device such as a liquid crystal with uniform light.

  In the light source device according to claim 1, a plurality of external electrode rare gas fluorescent lamps, in which a fluorescent material is applied to the inner surface of a tube-type bulb and a pair of external electrodes are provided on the outer surface along the tube axis, are provided in the reflection mirror. In the light source device, which is arranged in parallel with each other and a diffusion plate is arranged in front of the reflecting mirror, the electrode facing the diffusion plate passes through the center of the bulb in a plane perpendicular to the tube axis of the tubular bulb, and the diffusion plate It intersects with an imaginary line perpendicular to.

  According to the light source device of the present invention, the external electrode facing the diffusion plate of the external electrode rare gas fluorescent lamp passes through the center of the bulb in a plane perpendicular to the tube axis of the tubular bulb, and is an imaginary line perpendicular to the diffusion plate. By blocking a part of the light emitted from the lamp, the brightness of the surface of the diffusion plate becomes uniform, and a display device such as a liquid crystal can be illuminated uniformly with uniform light. Is.

FIG. 1 is an explanatory diagram of a light source device of the present invention.
The external electrode rare gas fluorescent lamp 1 has a pair of external electrodes 11 along the tube axis on its outer surface.
The reflection mirror 2 is a white polycarbonate resin, and includes a flat bottom plate 21 located on the back surface of the lamp 1 and a side plate 22 erected on the periphery of the bottom plate 21. In the reflection mirror 2, A plurality of, in this example, four lamps 1 are arranged at intervals so as to be substantially parallel.

A diffusion plate 3 is disposed in front of the reflection mirror 2. The diffusion plate 3 is a plate-like body having a thickness of 0.1 mm, and the diffusion plate 3 is disposed at a position 10 mm away from the outer surface of the facing lamp 1.
The diffusing plate 3 is a translucent polycarbonate resin, and has a function of diffusing incident light inside and emitting diffused light from the surface 3A to improve luminance uniformity. A plurality of diffusion sheets may be overlapped to form a diffusion plate.

The external electrode type rare gas fluorescent lamp will be described with reference to FIGS.
FIG. 3 is a sectional view taken along line XX in FIG.
The tube-type bulb 10 of the external electrode type rare gas fluorescent lamp 1 is made of soft glass having an outer diameter of 8 mm, a thickness of 0.4 mm, and a length of 1050 mm. The inner surface of the bulb 10 is made of a rare earth phosphor, a halophosphate phosphor or the like. A phosphor 12 is formed, and the internal space of the bulb 10 is filled with 16 kPa of xenon gas.
On the outer surface of the bulb 10, external electrodes 11 baked with a silver paste having a width of 1 mm, a thickness of 3 μm, and a length of 740 mm are arranged so as to face each other on the bulb tube axis.

  Such a lamp 1 applies a high-frequency alternating voltage or the like between a pair of external electrodes 11 to generate a rare gas discharge of xenon in the discharge space, and radiates ultraviolet rays. The phosphor 12 formed on the surface is excited, visible light is emitted from the phosphor 12, and visible light is emitted from the light emitting portion A between the pair of external electrodes to the outside of the lamp.

FIG. 4 is an explanatory diagram of the arrangement state of the lamps in the reflection mirror in the light source device of the present invention. In particular, the positional relationship between the external electrode 11 of the lamp 1 and the diffusion plate 3 will be described in detail.
A virtual line α passing through the center P of the valve 10 and perpendicular to the diffusion plate 3 is drawn on a plane perpendicular to the tube axis of the valve 10. Then, the external electrode 11 facing the diffusion plate is formed so that the center 11P in the width direction of the external electrode 11 is positioned on the outer surface of the bulb 10 at a position intersecting with the virtual line α.

  By providing the external electrode 11 at this position, light incident on the position 3P where the imaginary line α intersects the back surface of the diffusion plate 3 is shielded, so that a portion where the light flux density is high in the entire back surface of the diffusion plate 3 is lowered. Therefore, the light flux density in the entire back surface of the diffusion plate 3 can be made uniform, and the surface brightness of the surface 3A of the diffusion plate 3 can be made uniform.

The luminance distribution on the diffusion plate of the light source device in which the external electrode 11 is provided at this position is shown in graph b in FIG.
In the graph b, the difference between the maximum luminance and the minimum luminance is about 200 cd / m ² , and it can be seen that the luminance of the surface of the diffusion plate is surely uniform as compared with the light source device (graph a) of FIG.

FIG. 5 is an explanatory view showing another example in which the arrangement state of the lamps in the reflection mirror in the light source device of the present invention is different. In particular, the positional relationship between the external electrode and the diffusion plate will be described in detail.
A virtual line α passing through the center P of the valve 10 and perpendicular to the diffusion plate 3 is drawn on a plane perpendicular to the tube axis of the valve 10. An external electrode 11 facing the diffusion plate is located on the outer surface of the bulb 10 at a position intersecting with the virtual line α, and the center 11P in the width direction of the external electrode 11 is located on the left side of the drawing from the virtual line α. It is displaced in the direction.
Also in this embodiment, the external electrode 11 facing the diffusion plate is arranged on the outer surface of the bulb 10 at a position intersecting with the virtual line α.

  That is, also in this embodiment, the light incident on the position 3P where the virtual line α intersects the back surface of the diffuser plate 3 can be shielded, and the portion where the light flux density is high in the entire back surface of the diffuser plate 3 is lowered. The light flux density in the entire back surface of the diffusion plate 3 can be made uniform, and the surface brightness of the surface 3A of the diffusion plate 3 can be made uniform.

The luminance distribution on the diffusion plate of the light source device in which the external electrode 11 is provided at this position is shown in the graph c in FIG.
In the graph c, the difference between the maximum luminance and the minimum luminance is about 250 cd / m ² , and it can be seen that the luminance of the surface of the diffusion plate is surely uniform as compared with the light source device (graph a) shown in FIG.

  That is, according to the light source device of the present invention, the brightness of the surface of the diffusion plate is higher than that of the conventional light source device as shown by graphs b and c in FIG. 9 without increasing the distance between the diffusion plate and the lamp. Therefore, a display device such as a liquid crystal can be illuminated uniformly with uniform light.

It is explanatory drawing of the light source device of this invention. It is explanatory drawing of the external electrode type rare gas fluorescent lamp of this invention. It is XX sectional drawing in FIG. It is explanatory drawing of the arrangement | positioning state of the lamp | ramp in the reflective mirror of this invention, and is especially explanatory drawing of the positional relationship of the external electrode and diffuser plate of a lamp | ramp. It is explanatory drawing from which the arrangement | positioning state of the lamp | ramp in the reflective mirror of this invention differs, and is especially explanatory drawing of the positional relationship of the external electrode and diffuser plate of a lamp | ramp. It is explanatory drawing of the light source device using an external electrode type | mold rare gas fluorescent lamp. In the light source device of FIG. 6, it is explanatory drawing of the arrangement | positioning state of the lamp | ramp in a reflective mirror, and is especially explanatory drawing of the positional relationship of the external electrode and diffuser plate of a lamp | ramp. It is a schematic diagram of the light radiated from the bulb surface of the external electrode rare gas fluorescent lamp. It is experiment data explanatory drawing which measured the brightness | luminance on the diffusion plate of a light source device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 External electrode rare gas fluorescent lamp 11 External electrode 12 Phosphor 2 Reflecting mirror 21 Bottom plate 22 Side plate 3 Diffusion plate A Light emission part

Claims (1)

A plurality of external electrode rare gas fluorescent lamps, which are coated with phosphor on the inner surface of the tube bulb and have a pair of external electrodes along the tube axis on the outer surface, are arranged in parallel in the reflection mirror, and in front of the reflection mirror. In the light source device in which the diffusion plate is arranged in
The electrode facing the diffusion plate passes through the center of the bulb and intersects with an imaginary line perpendicular to the diffusion plate on a plane orthogonal to the tube axis of the tubular bulb.

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