JP2685575B2 - Surface light source device - Google Patents

Description

The present invention relates to a surface light source device for use in a transmissive liquid crystal television, a transmissive liquid crystal display, or the like.

[Conventional technology]

As a conventional surface light source device in which a W-shaped fluorescent tube is arranged above a light reflection surface and a light diffusion / transmission plate is arranged above it, there is one described in JP-A-62-102226.

According to the technique described in JP-A-62-102226, a straight tubular fluorescent tube is used by using a U-shaped, S-shaped, or M-shaped (same as W-shaped) curved tubular fluorescent tube as a light source of a surface light source device. It is possible to obtain a larger number of luminous fluxes of the fluorescent tubes as compared with the case of using, and it is possible to improve the light guiding efficiency as compared with the case of using the straight tubular fluorescent tube, so that a bright surface light source device is obtained. be able to.

[Problems to be solved by the invention]

The above-mentioned prior art uses the W-shaped fluorescent tube as a light source, such as the specific shape of the W-shaped tube with respect to the shape of the light emitting surface of the surface light source device and the distance between the W-shaped tube and the light diffusion plate. The basic conditions were not taken into consideration, and there was a problem in realizing a high-performance surface light source device.

The target performance of the surface light source device in the transmissive liquid crystal display device is that the brightness is high, the brightness unevenness is small, and the power consumption is low. However, it is not always necessary to simply use the W-shaped fluorescent tube as the light source. However, the target performance cannot be satisfied.

By setting the size and shape of the W-shaped fluorescent tube that is optimal for the size and shape of the light irradiation surface, it is possible to obtain a surface light source device with low power consumption, high brightness, and less brightness unevenness. Setting the size and shape of is very important.

The object of the present invention is to set the size and shape of the W-shaped fluorescent tube that is optimal for the size and shape of the light irradiation surface, so that low power consumption, high brightness, less brightness unevenness, and a thin surface can be achieved. To obtain a light source device.

[Means for solving the problem]

In order to achieve the above object, the size of the W-shaped fluorescent tube,
The surface light source structure using the W-shaped fluorescent tube was optimized by, for example, setting the shape and size to be optimal for the light irradiation surface of the surface light source device and setting the distance between the W-shaped fluorescent tube and the light diffusion plate to the optimum distance. It is a thing.

[Action]

A structure in which the surface light source device is made thin by specifying the size and shape of the W-shaped fluorescent tube so that the light flux emitted from the fluorescent tube is relatively uniformly irradiated on the light irradiation surface on the light diffusion plate. However, the brightness of the light irradiation surface can be increased and the uneven brightness can be reduced. In addition, the tube shadow disappears on the light irradiation surface. Further, in the surface light source structure, it is possible to further improve the brightness and the light guiding efficiency by optimizing the constituent materials and the mutual shapes.

〔Example〕

Hereinafter, the present invention will be described with reference to examples. Fig. 1 (a)
Is a front perspective view of the first embodiment of the surface light source device of the present invention, and FIG. 1 (b) is a side sectional view thereof.

The basic configuration of the embodiment shown in FIGS. 1 (a) and 1 (b) is such that a W-shaped fluorescent tube 2 as a light source is arranged on a light reflecting plate 4, and a light diffusing / transmitting plate is arranged above the light reflecting plate 4 with a certain space. 3 is arranged. The light diffusion / transmission plate 3 forms the light irradiation surface 1 of the surface light source device.

FIGS. 1 (a) and 1 (b) further show the size and shape of the W-shaped fluorescent tube 2 with respect to the size and shape of the light irradiation surface 1 in the above-mentioned basic configuration as shown in (1), (2),
The settings are made as (3), (4), and (5).

(1) The relationship between the lateral distance L ₂ between the curved portions a ₁ and a ₂ and the curved portion a ₃ of the W-shaped fluorescent tube 2 and the lateral width L of the light irradiation surface 1 is 0.7 ≦ l ₁ / L
≦ 1.

(2) an effective light emitting portion width l ₂ of the fluorescent tube 2 arranged on the light irradiation surface 1, the relationship between the width L of the light irradiation surface 1 0.8 ≦ l ₂ / L ≦
Let it be 1.

(3) The relationship between the vertical width h of the fluorescent tube 2 and the vertical width H of the light irradiation surface 1 is set to 0.6 ≦ h / H ≦ 0.75.

(4) The straight line portions S ₁ and S ₂ and the straight line portions S ₃ and S _{4 of the} fluorescent tube 2 are arranged vertically symmetrical with respect to the center of the light irradiation surface.

(5) The distance d between the fluorescent tube 2 and the light diffusion / transmission plate 3 is set to 0.6 ≦ d / F ≦ 1.4 with respect to the tube diameter F of the fluorescent tube 2.

The surface light source device has the above (1), (2), (3),
By adopting the structures shown in (4) and (5), it is possible to make the light irradiation surface 1 have a high brightness, a small brightness unevenness, and a brightness distribution with no discomfort, and to make the surface light source device thinner. You can also measure.

Next, the above (1), (2), (3), (4), (5)
The reason why the surface light source device is made high-performance and thin by setting is described below.

(I) The curved portion l ₁ of the W-shaped fluorescent tube 2 is set as 0.7 ≦ l ₁ / L ≦ 1, and the effective light emitting portion width l ₂ is 0.8 ≦ l ₂
By setting such that / L ≦ 1, 1-on the light irradiation surface 1
The brightness of each part of 4,1-7,1-10,1-6,1-9,1-12 is set to the central part 1
It is possible to obtain a luminance distribution state in which there is little reduction in luminance with respect to the luminance of −8 and there is no discomfort.

(Ii) By setting the relationship between the vertical width h of the fluorescent tube 2 and the vertical width H of the light irradiation surface 1 to be 0.6 ≦ h / H ≦ 0.75, the tube shadow on the light irradiation surface 1 is not conspicuous and the irradiation is performed. Upper part 1-1 of surface 1
It is possible to reduce the decrease in brightness in 1-2, 1-3, and the lower portions 1-13, 1-14, 1-15 of the irradiation surface 1.

In Fig. 2, when 0.6 ≤ h / H ≤ 0.75, and h / H> 0.7
An example of the luminance distribution in the vertical direction of the irradiation surface 1 when 5 and when h / H <0.6 is shown.

When h / H> 0.75, the W-shape of the fluorescent tube is visually recognized on the irradiation surface 1, and when h / H <0.6, the upper and lower ends 1-1,
The brightness of 1-2, 1-3, 1-13, 1-14, and 1-15 is much lower than the brightness of the central portion 1-8, and the brightness distribution is not satisfactory as a surface light source. When 0.6 ≦ h / H ≦ 0.75, the above problem does not occur.

(Iii) By arranging the fluorescent tubes 2 symmetrically with respect to the center of the irradiation surface 1, the luminance distribution in the vertical direction can be made substantially vertically symmetrical, and as a result, the luminance of the irradiation surface 1 does not feel unnatural. It can be a distribution.

(Iv) When the distance d between the fluorescent tube 2 and the light diffusion / transmission plate 3 is d / F <0.6 with respect to the tube diameter F, the irradiation surface 1 is satisfied even when the above conditions (1) to (4) are sufficiently satisfied. It is very difficult to obtain a high luminance, a relatively uniform luminance distribution, and a comfortable distribution. That is, under the condition of d / F <0.6, it is necessary to use a light diffusion / transmission plate having a very low transmittance in order to reduce the unevenness of brightness. It is necessary to use a screen which is changed to a different value or partially reduces the transmittance significantly. In that case, even if the brightness of the fluorescent tube 2 is sufficiently high, the average brightness of the irradiation surface 1 becomes very low, resulting in very low efficiency.

Further, when d / F> 1.4, the brightness unevenness can be sufficiently reduced, but the average brightness tends to decrease, and it is not possible to set the distance d between the fluorescent tube 2 and the light diffusion transmission plate 3 larger than a specific value. It is disadvantageous in terms of brightness efficiency.

From the above, the relationship between the interval d and the pipe diameter F is 0.6 ≦ d / F ≦ 1.
By setting as shown in 4, high brightness and high efficiency can be achieved, and if 0.6 ≦ d / F ≦ 1 is also satisfied, sufficient thinning can be achieved.

3 (a) and 3 (b) are a lateral sectional view and a longitudinal sectional view, respectively, of a surface light source device according to a second embodiment of the present invention. The difference between the second embodiment and the first embodiment is that the W-shaped fluorescent tube 2 and the light reflecting plate 4 are separated by Δd. The relationship between the tube diameter F of the fluorescent tube 2 and Δd is 0 <Δd / F ≦ 0.3.

Next, the reason for setting as above will be described.
FIG. 4 shows an example of the relationship between Δd / F and the average luminance and luminance unevenness (luminance maximum point luminance / luminance minimum point luminance) of the irradiation surface when the depth D of the light reflecting surface is constant. According to the relationship shown in Fig. 4, the average brightness tends to increase until Δd / F is close to 0.3, and is almost constant above 0.3 and below 0.5. In addition, the brightness unevenness sharply increases when Δd / F> 0.3. As described above, from the relationship of FIG. 4, 0 <Δd / F ≦ 0.3 is set as the condition of Δd that the average brightness of the light irradiation surface 1 can be increased and the brightness unevenness does not increase.

The reason why the average brightness increases when the fluorescent tube 2 and the light reflection plate 4 are separated by Δd as compared with the case where the fluorescent tube 2 and the light reflecting plate 4 are closely attached is that the fluorescent tube 2 is emitted from the fluorescent tube 2 in FIGS. 3 (a) and 3 (b). It is considered that the light rays 6 reaching the light diffusing and transmitting plate 3 increase due to the reflected light from the light reflecting plate 4. Note that Δ
When d = 0, most of the light emitted below the fluorescent tube 2 is reflected by the light reflecting plate 4 and then enters the fluorescent tube 2, and at that time, it is absorbed and loss light is generated.

FIG. 5 is a vertical sectional view of a third embodiment of the surface light source device of the present invention. The difference between the third embodiment and the second embodiment is that the light reflecting surface formed by the light reflecting plate 4'is made substantially flat in the second embodiment, whereas it is formed by a plurality of curved surfaces. thing,
In addition, the fluorescent tubes are arranged so that the W-shaped fluorescent tubes 2 are located on the convex portions 4'-1 of the curved surfaces. The reflection surface depth D, which is the distance between the light diffusion / transmission plate 3 and the recess 4'-2 of the light reflection plate 4 ', is substantially the same as that in the second embodiment. When the difference in height between the convex portion 4'-1 and the concave portion 4'-2 is Δd ', it is 0 as in the second embodiment.
When <Δd ′ / F ≦ 0.3, the average brightness of the light irradiation surface 1 can be increased, and the brightness unevenness can be kept below a certain level.
In FIG. 5, if the shapes of the convex portion 4'-1 and the concave portion 4'-2 are optimized, the light is emitted from the fluorescent tube 2 and diffused by the light reflected by the light reflecting plate 4 '. It is possible to increase the amount of light 6 that reaches the transmission plate 3, and it is possible to increase the luminance and reduce the unevenness in luminance more than in the second embodiment.

As another method for separating the W-shaped fluorescent tube 2 and the light reflection plate 4 by Δd, the thickness Δd is provided only at a specific portion under the fluorescent tube 2.
Alternatively, a method may be used in which a convex object is provided, and the fluorescent tube 2 is placed on and fixed to the convex object.

Light reflection plate 4 in the structure of the surface light source device described above,
When a white titanium oxide-containing PBT (polybutylene terephthalate) resin is used as the 4'material and a milky white light diffusion / transmission stretched acrylic plate is used as the light diffusion / transmission plate 3, the average brightness of the light irradiation surface 1 is conventionally used. This can be further improved as compared with the case of using a white paint-coated aluminum light reflection plate and a milky white light diffusion / transmission extruded acrylic plate.

PBT containing 10% or more of white titanium oxide has better diffuse reflection performance than a white paint-painted aluminum plate (light reflectance of about 96
%), As a surface light source reflecting surface for performing multiple reflection, it more effectively acts to improve the light guiding efficiency from the W-shaped fluorescent tube 2 to the light irradiation surface 1. According to the measurement result by the prototype surface light source device, when the light reflection plate of PBT containing white titanium oxide is used, the average brightness of the irradiation surface 1 is increased by about 15% as compared with the light reflection plate made of aluminum painted with white paint. I was able to.

If the stretched acrylic plate is used for the light diffusion / transmission plate 3, it is possible to achieve a thin plate that cannot be achieved with the molded acrylic plate.
Therefore, even if the light reflecting plates 4 and 4 ′ are made of the PBT resin and the thickness of the light reflecting plates 4 and 4 ′ is increased as compared with when they are made of the aluminum plate, the stretched krill plate is used. By doing so, the thickness of the light diffusion / transmission plate can be reduced, so that the overall thickness of the surface light source device can be made equal to or less than that of the conventional configuration.

Next, based on the contents disclosed in the above embodiments, as an example of a prototype surface light source device, the structure of a surface light source device having a light irradiation surface diagonal of 5 inches will be described, which is different from the conventional surface light source device. Describe whether the performance has improved.

(1) Structure of prototype surface light source device (i) Light irradiation area L × H: 106 × 80 mm ² (ii) Surface light source device thickness D: 13 mm Thickness distribution: light reflection surface depth 11.5 mm, light reflection plate ( PBT resin) 0.9mm thick, light diffusion / transmission plate (milky white light diffusion / transmission stretched acrylic plate) thickness 0.6mm (iii) W-shaped fluorescent tube Tube diameter F: 6.2mm Width l ₁ : 0.85L, l ₂ :
0.93L, vertical width h: 0.68H (iv) The straight line portions S ₁ and S ₂ and the straight line portions S ₃ and S _{4 of the} W-shaped fluorescent tube are arranged substantially symmetrically with respect to the center of the light irradiation surface (v) Distance between W-shaped fluorescent tube and light diffusion / transmission plate d: 0.85F (2) Performance of prototype surface light source device (i) Light guiding efficiency (light irradiation surface luminous flux / W-shaped fluorescent tube luminous flux): 72% ... Straight tube , Or a U-shaped fluorescent tube, white paint-painted aluminum light reflector, milky white light diffusion / transmission extruded acrylic light diffusion / transmission plate approximately 1.4 times (ii) uneven brightness : Light irradiation surface brightness maximum point brightness / Light irradiation brightness minimum point brightness: 2.4
… Improving degree of 30% compared to the conventional i configuration of (i) above: Invisible… The conventional configuration of (i) above is visible As described above from the concrete examples of (1) and (2) According to the surface light source device configuration of the present invention, it is possible to obtain a highly efficient (high brightness) surface light source device that is thin and has less uneven brightness.

As a result, even if a cold cathode fluorescent tube having a smaller luminous efficiency than that of the hot cathode fluorescent tube is used as the fluorescent lamp of the surface light source device, a surface using a straight tube type or a U-shaped hot cathode fluorescent tube with the same power is used. It is possible to obtain a light irradiation surface brightness higher than that of the light source device. The cold cathode fluorescent tube is generally inferior in luminous efficiency to the hot cathode fluorescent tube, but has a long life and can be thinned, and is useful in extending the life of the surface light source device and making it thinner. is there.

FIG. 6 is a front perspective view of the fourth embodiment of the present invention. 4th
The difference between the first embodiment and the first embodiment is the W-shaped fluorescent tube 2 '.
The light reflectors 9-1, 9-2, 9-3 are partially formed on the curved portions a ₁ ′, a ₂ ′, a ₃ ′ and the surface in the vicinity thereof. From this configuration, light beam 'relatively fluorescent tube 2 in' the light irradiation surface 1 is concentrated, the curved portion a ₁ prone to high luminance ', a _2',
The brightness of the portion directly above a ₃ ′ is reduced, and the corner portion 1′-3,
It is possible to increase the brightness of the 1'-15, peripheral parts 1'-6, 1'-7, 1'-9, 1'-12, and as a result, the brightness distribution of the light irradiation surface 1'is made more uniform. You can also do it. The curved part
a ₁ ′, a ₂ ′, a ₃ ′ and light reflecting objects 9-1,9-
When forming 2,9-3, the reflectors 9-1,9-2,9-3 are formed more on the inner diameter side than on the outer diameter side of the curved portions a ₁ ′, a ₂ ′, a ₃ ′. The effect of uniforming the uneven brightness is greater.

FIG. 7 is a side sectional view of an embodiment of a transmissive liquid crystal display device to which the first embodiment of the surface light source device of the present invention is applied. As shown in the embodiment of FIG. 7, when the surface light source device of the present invention is used, high brightness,
It is possible to realize a thin transmission type liquid crystal display device with high image quality.

〔The invention's effect〕

As described above, according to the surface light source device of the present invention, by setting the shape of the W-shaped fluorescent tube capable of reducing the unevenness of the surface light source light irradiation surface brightness, even if the surface light source device is made sufficiently thin, the light irradiation can be performed. It is possible to reduce the brightness unevenness of the surface, and the tube shadow is not visible on the light irradiation surface. Further, by forming the light reflection image material of the surface light source device with a white titanium oxide-containing PBT resin and the light diffusion / transmission plate with a milky white light diffusion / transmission stretched acrylic plate, the light guide efficiency from the fluorescent tube to the irradiation surface is improved. 70% or more (more than 1.4 times the light guide efficiency of conventional surface light source devices)
Therefore, a surface light source device with low power consumption and high brightness can be obtained.

[Brief description of the drawings]

FIG. 1 is a first embodiment of the surface light source device of the present invention. FIG. 1 (a) is a front perspective view thereof, FIG. 1 (b) is a side sectional view thereof, and FIG. FIG. 3 is a longitudinal luminance distribution diagram of FIG. 3, FIG. 3 is a second embodiment of the surface light source device of the present invention, FIG. 3 (a) is its lateral sectional view, FIG. 3 (b) is its longitudinal sectional view, FIG. 4 is a diagram showing the surface light source device irradiation surface luminance of the present invention, the light reflection surface of the uneven brightness, and the fluorescent tube interval dependence. FIG. 5 is a longitudinal sectional view of the third embodiment of the surface light source device of the present invention. FIG. 7 is a side sectional view of an embodiment of a transmissive liquid crystal display device using the light source device of the present invention. 1,1 ′ …… Light irradiation surface 2,2 ′ …… W-shaped fluorescent tube 3 …… Light diffusion transmission plate 4,4 ′ …… Light reflection plate 5,6 …… Light ray 7 …… Average brightness 8 …… Brightness Mura 9-1, 9-2, 9-3 ...... Light reflector L …… Light irradiation surface width H …… Light irradiation surface width l ₁ , 1, ₂ …… W-shaped fluorescent tube width h …… W-shaped fluorescence Tube vertical width F …… Outside diameter of W-shaped fluorescent tube a ₁ , a ₂ , a ₃ , a ₁ ′, a ₂ ′, a ₃ ′ …… W-shaped fluorescent tube curved portion D …… Light reflecting surface depth S ₁ , S ₂ , S ₃ , S ₄ …… Straight part of W-shaped fluorescent tube 10 …… Transmissive liquid crystal panel

Claims (5)

(57) [Claims] 1. A light diffusion / transmission plate is disposed above a light reflection surface,
In a surface light source device in which a W-shaped fluorescent tube is arranged between the light-reflecting surface and the light diffusion / transmission number, the arrangement state of the W-shaped fluorescent tube is as follows (1), (2), (3). A surface light source device characterized by being set as follows. (1) Of the three fluorescent tube curved portions having the W-shaped fluorescent tube, the convex portions of the fluorescent tube curved portions a ₁ and a ₂ located at the first and third positions from the end of the W-shaped fluorescent tube A length l ₁ that joins the substantially central point of the points of the tip and the tip of the convex portion of the second fluorescent-tube curved portion a ₃ and a length L of the light irradiation surface viewed in the direction of the length l ₁ To 0.7 ≦ l ₁ / L ≦ 1, and (2) the length H of the light irradiation surface as viewed in a direction perpendicular to the direction of the length L and the W-shape as viewed in the length H direction. The relationship with the length h of the fluorescent tube is set to 0.6 ≦ h / H ≦ 0.75. (3) The approximate center point of the tip of the convex portion of the fluorescent tube curved portions a ₁ and a ₂ and the fluorescent tube curved portion a ₃ A straight line that intersects with the tip of the convex portion is the axis of the W-shaped fluorescent tube, and the straight-line portions of S ₁ and S ₂ , which are the linear portions of the W-shaped fluorescent tube, are substantially symmetrical with respect to the axis. Set S ₃ and S ₄ to be arranged. 2. The distance d between the W-shaped fluorescent tube and the light diffusion / transmission plate.
2. The surface light source device according to claim 1, wherein the relationship between the fluorescent lamp and the tube diameter F of the fluorescent tube is set to be 0.6 ≦ d / F ≦ 1.4. 3. A surface light source device in which a W-shaped fluorescent tube is arranged above a light reflecting surface and a light diffusion / transmission plate is arranged above the W-shaped fluorescent tube. A surface light source device characterized in that a reflective material is formed. 4. A surface light source device in which a W-shaped fluorescent tube is arranged above a light reflecting surface and a light diffusing and transmitting plate is arranged above the light reflecting surface, and the light diffusing and transmitting plate and the light reflecting surface are in contact with each other. A surface light source device characterized in that the distance between the light diffusion / transmission plate and the light reflecting surface in the non-contact portion of the fluorescent tube is larger than the distance between the portions. 5. A transmission type liquid crystal display device using the surface light source device according to any one of claims 1 to 4.