JPH09198909A - Reflecting mirror, lighting system, and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To guide the light from the rear of a fluorescent tube to a light guide plate by forming a reflecting mirror with reflecting surfaces having a cross sectional shape of a flattened involute curve and reflecting surfaces connected to expand the opening section of the reflecting mirror. SOLUTION: A reflecting mirror 11 is formed with reflecting surfaces 11a1, 11a2 and reflecting surfaces 11b1, 11b2. The reflecting surface 11b1 and the reflecting surface 11a1 are symmetrical with respect to the xz-plane, and the reflecting surface 11b2 and the reflecting surface 11a2, are symmetrical with respect to the xz-plane. The reflecting surface 11a1 is in the range that (x) is larger than the x-coordinate xc of a connection point Ca, i.e., x>=xc, and its shape is shown by the locus of x=(r)×cosθ+f(θ)×(r)×θ×sinθ, y=(r)×sinθ-f(θ)×(r)×θ×cosθ. The reflecting mirror 11 is formed with the reflecting surfaces having such a cross sectional shape and the reflecting surfaces connected to expand the opening section of the reflecting mirror 11, and the light from the rear of a fluorescent tube can be guided to a light guide plate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for improving light utilization efficiency of a backlight which is a lighting device in a liquid crystal display device. More specifically, the present invention relates to the shape of a reflection mirror that guides light emitted from a rod-shaped light source such as a fluorescent tube to a light guide unit.

[0002]

2. Description of the Related Art In a backlight which is an illumination device of a conventional liquid crystal display device, light emitted rearward (in the direction opposite to the light guide means) from a fluorescent tube which is a light source is effectively used. Regarding the shape of the reflecting mirror for leading to the above, the Japanese Patent Laid-Open No. 64-40815 and Japanese Patent Laid-Open No. 6-2
It is disclosed in JP-A-65886 and JP-A-7-128665.

Each of the publications discloses a reflection mirror having an involute linear cross-sectional shape that is symmetrical with respect to a plane including the central axis of the fluorescent tube.

[0004]

However, there is a problem in that the specific shape of the reflecting mirror shown in FIG. 5 of JP-A-6-265886 is not disclosed.

Further, Japanese Patent Application Laid-Open No. 7-128665 discloses a reflection mirror having an involute curve as a cross-section as an extended line. However, since the opening of the reflection mirror becomes large, the once widened opening is formed into a light guide plate. It is necessary to have a mirror part for focusing according to the area of the light-incident end face of the. Therefore, there is a problem that the mirror as a whole becomes large and the shape becomes complicated.

Further, Japanese Patent Application Laid-Open No. 64-40815 discloses a concept of reducing the aperture of the reflection mirror, but there is a problem that the specific shape is not disclosed.

The present invention solves such a problem by increasing the aperture of the mirror, that is, the thickness of the mirror, while having the function of guiding the light emitted to the rear of the fluorescent tube to the light guide means. It is an object of the present invention to provide a mirror that is suppressed and easy to manufacture, and to provide a bright illuminating device and a bright-looking liquid crystal display device.

[0008]

The reflecting mirror of the present invention comprises:
When an orthogonal coordinate system composed of an x axis, ay axis and az axis orthogonal to each other is set, the first reflective surface and the second reflective surface are symmetrical with respect to the xz plane, and the first reflective surface is formed. When the xy cross-sectional shape of the surface is such that r is a radius of a reference circle centered on the z axis and θ is an angle measured from the x axis along the xy plane in the range of x ≧ xc,

[0009]

[Equation 1]

[0010]

[Equation 2]

[0011]

(Equation 3)

Is represented by the locus of the point (x, y) represented by
When x is in the range of xc ≧ x, it is characterized by being represented by a straight line parallel to the x-axis or increasing y as x becomes negative.

The illuminating device of the present invention is a illuminating device having a rod-shaped light source, a reflection mirror, and a light guiding means, wherein the central axis extending in the longitudinal direction of the rod-shaped light source is az axis, and the z axis is orthogonal to the z axis. An axis extending in a direction opposite to the light guide means is an x axis,
It is characterized in that the reflection mirror has the shape of the reflection mirror of the present invention when an orthogonal coordinate system in which an y-axis is an axis orthogonal to the x-axis and the z-axis is set.

A liquid crystal display device of the present invention is characterized by including the above-mentioned lighting device of the present invention.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The structures of a reflecting mirror and an illuminating device of the present invention will be described with reference to FIGS. FIG. 1 depicts an illumination device with a reflecting mirror, the cross section of which is shown in FIG.

Light emitted from the fluorescent tube 10 serving as a rod-shaped light source is converted into planar light for illuminating a liquid crystal panel (not shown) by a light guide plate 12 which is a light guide means. Fluorescent tube 1
Behind 0 (the direction opposite to the light guide plate) is a reflection mirror 11.
Is arranged.

Of the light emitted from the fluorescent tube 12, the light emitted to the front (the direction in which the light guide plate is present) enters the light guide plate 12 directly from the light incident end face 12c of the light guide plate 12, and the light emitted to the rear is a reflection mirror. 1
After being reflected by 1, the light enters the light guide plate 12 through the light incident end face 12c.

Light-scattering bodies 14 that scatter light are printed in dots on the back surface 12b of the light guide plate 12, and a reflection sheet 13 is arranged below the light-scattering bodies 14. The light introduced into the light guide plate 12 is totally reflected on the light guide plate front surface 12a, and the light guide plate rear surface 12 is obtained.
Light that propagates in the light guide plate while repeating scattering or total reflection at b and does not satisfy the conditions for total reflection is the light guide plate surface 12a.
And illuminates the liquid crystal display panel disposed on the light guide plate surface 12a.

Next, the structure of the reflection mirror 11 will be described in detail with reference to FIG. FIG. 2 is a cross-sectional view orthogonal to the longitudinal direction of the fluorescent tube 10, in which the light entering portions of the reflection mirror 11 and the light guide plate 12 are enlarged and drawn. The reflection mirror 11 has a shape obtained by extending the cross-sectional shape in the direction perpendicular to the paper surface, that is, in the longitudinal direction of the fluorescent tube.

The reflection mirror 11 has reflection surfaces 11a1 and 11a.
2 and reflecting surfaces 11b1 and 11b2.
The reflection surface 11b1 is symmetrical with respect to the reflection surface 11a1 with respect to the xz plane, and the reflection surface 11b2 is symmetrical with respect to the reflection surface 11a2 with respect to the xz plane. In the present invention, the four reflecting surfaces 11a1
The shapes of 11a2, 11b1 and 11b2 are specified, and the outer shape of the reflection mirror 11 may be any shape.

The central axis in the longitudinal direction of the fluorescent tube 10 is the z axis, and a point on this axis is the origin, and x is orthogonal to this central axis.
Set the axis and y-axis. The positive direction of the x-axis is set to the direction away from the light guide plate 12. At this time, the surface 12a of the light guide plate 12 and the liquid crystal display panel are arranged parallel to the xz plane.

In the reflecting surface 11a1, x is a connection point Ca (xc,
yc) is larger than the x coordinate xc, that is, x is x ≧ x
It is a reflective surface in the range of c, and its shape is

[0023]

[Equation 1]

[0024]

[Equation 2]

It is the locus of the point (x, y) represented by

Here, r is the radius of the reference circle 20 and takes a value equal to or larger than the outer diameter of the fluorescent tube 10. Also, f (θ) is a function with the angle θ as a variable, including the case where it is a constant value regardless of θ.

[0027]

(Equation 3)

It is necessary to satisfy the condition of.

When f (θ) is 1 regardless of θ, this curve becomes an involute curve, and the opening of the reflection mirror becomes large. On the other hand, when f (θ) is 0 regardless of θ, it becomes a circle, and it is behind the fluorescent tube (+ x direction).
Much of the light that exits is reflected back to the fluorescent tube.

In order to guide the light emitted to the rear of the fluorescent tube toward the light guide plate while suppressing the opening of the reflection mirror from increasing,

[0031]

(Equation 3)

It is necessary to satisfy the condition of.

As in the case of the involute curve, the reflecting surface once swells in the + x direction (behind the fluorescent tube 10) as y increases from the position of y = 0 in FIG. 2 and then again in the -x direction (fluorescence). In front of the tube 10, that is, the light guide plate 1
By bending in the 2 direction),
Light emitted in the x direction, that is, rearward, can also be reflected to the light guide plate side.

When the curves expressed by the equations 1, 2 and 3 are extended to the range where x is xc ≧ x, a curve 11a3 shown by a broken line in FIG. 2 is obtained. In this case, the thickness W of the opening 11c of the reflection mirror 11 is the maximum thickness W of the reflection mirror.
Since the size becomes smaller than m, the mold becomes complicated when the reflection mirror is manufactured by the injection molding method.

In order for the mold to be easily removed during injection molding, it is necessary that the opening of the reflection mirror is at least not narrow. For that purpose, the reflection mirror having the cross-sectional shape represented by the equations (1), (2) and (3) is parallel to the xz plane before trying to narrow the aperture as shown by the broken line 11a3 in FIG. Or, it should be connected to the surface where the opening is to be widened. As the connection surface, any surface may be used as long as it has a structure that widens the opening, but it may simply be a flat surface. In FIG. 2, the reflecting surfaces 11a2 and 1a
1b2 corresponds to this connection surface.

The connection point Ca is selected such that the tangent to the curve representing the cross-sectional shape of the reflecting surface 11a1 is parallel to the x-axis or is a straight line having an inclination such that y increases as x becomes negative. Be done.

The coordinates of the connection point Cb are (xc, -yc), which are symmetrical with respect to the connection point Ca with respect to the x axis.

The opening 11c of the reflection mirror 11 has a light guide plate 1
2 is connected to the light incident end face 12c, which is one end face of the light source 2.

By arranging the liquid crystal display panel on the surface 12a side of the illumination device described above, it is possible to configure a liquid crystal display device that looks bright while suppressing an increase in the thickness of the illumination device.

[0040]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.

(Embodiment 1) FIG. 2 shows a cross-sectional shape of a first embodiment of a reflecting mirror used in the illuminating device of the present invention.

The reflecting surface of the reflecting mirror 11 is the reflecting surface 1.
It is composed of 1a1 and 11a2 and reflecting surfaces 11b1 and 11b2. Since the reflecting surface 11b1 is symmetrical with the reflecting surface 11a1 and the reflecting surface 11b2 is symmetrical with the reflecting surface 11a2 with respect to the xz plane, only the reflecting surface 11a1 and the reflecting surface 11a2 have the following shapes.

The xy cross-sectional shape of the reflecting surface 11a1 is expressed by the equation 1,
In Expression 2, r = 1.5 mm, f (θ) = (1-0.
It is the locus of (x, y) when 4θ / π).

The coordinates (xc, yc) of the connection point Ca between the reflecting surfaces 11a1 and 11a2 are xc = 0.300 mm and yc = 2.954 mm.

Reflecting surface 11a connected to reflecting surface 11a1
The xy cross-sectional shape of 2 is a straight line with an inclination of Δy / Δx = −0.280, and the coordinates (xp, yp) of the end point P of the reflection mirror opening 11c is xp = −1.500 mm yp = 3. It becomes 457 mm.

A reflection mirror having a reflection surface of such a shape can be formed by injection molding of acrylic resin. However, since the opening of the reflection mirror expands outward, it is necessary to remove the mold after molding. Will be easier.

Reflecting surfaces 11a1, 11a2, 11b1, 1
Silver or Al is vapor-deposited on 1b2.

The opening 11c of the reflection mirror has a thickness Wa of about 6.9 mm, and is connected to the light incident end face 12c which is one end face of the light guide plate 12 having a thickness of 6.9 mm.

The outer diameter of the fluorescent tube 10 is 2 mm, and there is a space of 0.5 mm between the fluorescent tube 10 and the apex 21 of the reflection mirror.

(Embodiment 2) FIG. 3 shows a sectional shape of a second embodiment of the reflection mirror used in the illuminating device of the present invention.

The reflecting surface of the reflecting mirror 30 is composed of reflecting surfaces 30a1 and 30a2 and reflecting surfaces 30b1 and 30b2. The reflecting surface 30b1 is the same as the reflecting surface 30a1.
Since the reflecting surface 30b2 is symmetrical with the reflecting surface 30a2 with respect to the xz plane, only the reflecting surface 30a1 and the reflecting surface 30a2 have the following shapes.

The xy cross-sectional shape of the reflecting surface 30a1 is expressed by the equation 1,
In Expression 2, r = 1.5 mm, f (θ) = (1-0.
It is the locus of (x, y) when 4θ / π).

The coordinates (xc, yc) of the connection point Ca between the reflecting surface 30a1 and the reflecting surface 30a2 are: xc = -0.412mm yc = 3.051mm, and the curves expressed by the equations (1), (2) and (3) The tangent line at the connection point Ca of is parallel to the x-axis.

The xy cross-sectional shape of the reflecting surface 30a2 is a straight line parallel to the x-axis, and the coordinates (xp, yp) of the end point P of the reflecting mirror opening 30c are xp = -1.500 mm and yp = 3.051 mm. .

The curve 3 drawn by the broken line in FIG.
0a3 is a curve obtained by extending the reflecting surface 30a1 to the range where x is xc ≧ x.

The thickness Wa of the opening of the reflection mirror 30 is about 6.1 mm, which is connected to the light incident end face 32c which is one end face of the light guide plate 32 having a thickness of 6.1 mm.

A reflection mirror having a reflection surface having such a shape can be formed by injection molding of acrylic resin. Reflective surfaces 30a1, 30a2, 30b1, 30b2
Is deposited with silver or Al.

The outer diameter of the fluorescent tube 10 is 2 mm, and there is a space of 0.5 mm between the fluorescent tube 10 and the apex 31 of the reflection mirror.

(Embodiment 3) FIG. 4 shows the sectional shape of a third embodiment of the reflection mirror used in the illuminating device of the present invention.

The reflecting surface of the reflecting mirror 40 is the reflecting surface 4
0a1 and 40a2 and reflecting surfaces 40b1 and 40b2. Since the reflecting surface 40b1 and the reflecting surface 40b2 are symmetrical with respect to the reflecting surface 40a1 and the reflecting surface 40a2 with respect to the xz plane, only the reflecting surface 40a1 and the reflecting surface 40a2 have the following shapes.

The xy cross-sectional shape of the reflecting surface 40a1 is given by
In Expression 2, it is a locus of (x, y) when r = 1.5 mm and f (θ) = 0.65.

The coordinates (xc, yc) of the connection point Ca between the reflecting surface 40a1 and the reflecting surface 40a2 are as follows: xc = -0.420mm yc = 3.062mm.

The xy cross-sectional shape of the reflecting surface 40a2 has an inclination of Δ.
It is a straight line of y / Δx = −0.182, and the coordinates (xp, yp) of the end point P of the reflection mirror opening 40c are as follows: xp = −1.500 mm yp = 3.258 mm

The curve 4 drawn by the broken line in FIG.
0a3 is a curve obtained by extending the reflecting surface 40a1 to the range where x is xc ≧ x.

A reflection mirror having a reflection surface of such a shape can be formed by injection molding of acrylic resin. However, since the opening of the reflection mirror expands outward, it is possible to remove the mold after molding. It will be easier.

Reflecting surfaces 40a1, 40a2, 40b1, 4
Silver or Al is vapor-deposited on 0b2.

The thickness Wa of the opening 40c of the reflection mirror is about 6.5 mm, and it is connected to one end surface of the light guide plate 42 having a thickness of 6.5 mm.

The outer diameter of the fluorescent tube 10 is 2 mm, and the fluorescent tube 10 and the apex 41 of the reflection mirror are spaced apart by 0.5 mm.

FIG. 5 shows the sectional shapes of the reflecting surfaces of Examples 1 to 3, and r = 1.5 mm and f in Formula 1 and Formula 2.
The involute curve with (θ) = 1 and the circle with r = 1.5 mm and f (θ) = 0 in Expressions 1 and 2 are shown in an overlapping manner.

The connected reflecting surface 51 in the first embodiment,
Connected reflective surface 52 in Example 2 and Example 3
It can be seen that the connected reflective surface 53 at is between the involute curve 54 and the circle 55.

The thickness Wi of the opening in the case of the involute curve 54 was 9.4 mm, the thickness Wa of the opening in the case of Example 1 was 6.9 mm, and Wa in the case of Example 2 was 6.1.
mm, and Wa = 6.5 mm in the case of Example 3 is considerably larger.

The reflecting surface 51 of the first embodiment or the reflecting surface 52 of the second embodiment has a larger bulge in the + x direction (backward of the fluorescent tube) than the shape of the reflecting surface 53 of the third embodiment. That is, the effect of sweeping the light emitted to the rear of the fluorescent tube toward the light guide plate is enhanced.

Although the embodiments of the illuminating device of the present invention have been described above, the coefficients of the equations (1) and (2) expressing the shape of the reflection mirror or the functional form of f (θ) are the numerical values used in the embodiments or The light guide plate is not limited to the functional form, and various types of light guide plates may be used.

[0074]

The reflection mirror used in the illumination device of the present invention has a reflection surface having a bulge rearward of the fluorescent tube which is a light source and having a cross-section like a crushed involute curve and a reflection mirror opening. Thus, it is possible to suppress an increase in the thickness of the reflection mirror while guiding as much light as possible to the rear of the fluorescent tube to the light guide plate, and it is possible to achieve high productivity.

Further, by using the reflection mirror according to the present invention, it is possible to provide a bright illuminating device capable of guiding more light emitted from the light source to the light guide plate while suppressing an increase in thickness. Have.

Further, the liquid crystal display device of the present invention has an effect that it is possible to provide a liquid crystal display device that looks bright while suppressing an increase in the thickness of the entire liquid crystal display device by using the illumination device of the present invention.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of a lighting device of the present invention.

FIG. 2 is a sectional view of a first embodiment of the reflection mirror of the present invention.

FIG. 3 is a sectional view of a second embodiment of the reflection mirror of the present invention.

FIG. 4 is a sectional view of a third embodiment of the reflection mirror of the present invention.

FIG. 5 is a diagram comparing the cross-sectional shape of the reflection mirror of the present invention with the cross-sectional shape of an involute curve.

[Explanation of symbols]

 10 Fluorescent tube 11, 30, 40 Reflecting mirror 11a1, 11a2, 11b1, 11b2 Reflecting surface 11a3, 30a3, 40a3 Curve 21, 31, 41 Mirror vertex 30a1, 30a2, 30b1, 30b2 Reflecting surface 40a1, 40a2, 40b1, 40b2 Reflecting Surface 11c, 30c, 40c Reflection mirror opening 12, 32, 42 Light guide plate 12a Light guide plate front surface 12b Light guide plate back surface 12c, 32c Light guide plate entrance end face 13 Reflective sheet 14 Light scatterer 20 Reference circles Ca, Cb Connection point Wa Reflective mirror thickness of opening 51 Reflective surface shape of Example 1 52 Reflective surface shape of Example 2 53 Reflective surface shape of Example 3 54 Involute curve 55 Yen

Claims (3)

[Claims] 1. When an orthogonal coordinate system composed of an x-axis, a y-axis and a z-axis which are orthogonal to each other is set, it is composed of a first reflecting surface and a second reflecting surface which are symmetrical with respect to the xz plane,
The xy cross-sectional shape of the first reflecting surface is a radius of a reference circle centered on the z axis with r in the range of x where x ≧ xc, θ
Where is the angle measured along the xy plane from the x-axis, [Equation 2] (Equation 3) Is represented by the locus of the point (x, y) represented by, and x is xc ≧ x
In the range of, the reflecting mirror is characterized by being represented by a straight line parallel to the x-axis or increasing y as x goes negative. 2. A lighting device having a rod-shaped light source, a reflection mirror, and a light guide means, wherein a central axis extending in the longitudinal direction of the rod-shaped light source is az axis, and the light guide means is orthogonal to the z axis. The reflection mirror according to claim 1, wherein when the orthogonal coordinate system is set such that an axis extending in the opposite direction is an x axis and an axis orthogonal to the x axis and the z axis is ay axis. An illuminating device having the shape of. 3. A liquid crystal display device comprising the lighting device according to claim 2.