JP2518817Y2 - Light guide plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a backlight for a liquid crystal display, a backlight for advertising billboards, or a light guide plate used as a lighting fixture.

(Prior Art) A conventional light guide plate has a transparent plastic plate such as the light guide plate shown by I in FIG. 4 in order to increase the amount of light incident from the light source and to have a high-luminance light emitting surface. There are those in which a plurality of laminated sheets 3 are used and the number of laminated sheets is increased, and one in which the thickness of one transparent plastic plate 3 is increased like the light guide plate indicated by II in FIG.

For example, if the plastic plate 3 is doubled or the thickness is doubled, the brightness of the light guide plate is exactly 2
It can be said that the area of the light entrance surface and the luminance are in a proportional relationship.

(Problems to be solved by the invention) However, when a plurality of plastic plates are stacked and used like the light guide plate or used with a large thickness, the capacity and weight of the entire light guide plate are significantly increased. However, it is not possible to meet the demand for lighter and thinner light guide plates used in displays and the like.

In view of the above problems, it is an object of the present invention to provide a light guide plate that is thin and light, while improving the efficiency and brightness of light emission.

(Means for Solving the Problems) The present invention takes the following technical means in order to achieve the above object.

That is, the diffusion film 2, the transparent plastic plate 3, and the reflective film 4 are sequentially laminated, the light of the light source 8 is incident from the side end surface of the transparent plastic plate 3, and the incident light is reflected on the reflective film 2 side, In the light guide plate configured to emit light from the diffusion film 2 side, a short condensing piece 11 is provided so as to overlap with the side end of the transparent plastic plate 3 on the light source 8 side. On the opposite side, the inclined surface 10 is inclined so as to gradually approach the transparent plastic plate 3 as the distance from the light source 8 increases.
Is provided, where the length A of the condensing piece 11 is l / 20 to l / 5 (l: the length of the plastic plate 3), and the inclination angle θ is 10 ° to 45 °, The thickness B is characterized by being less than 2t (t: thickness of the plastic plate 3).

(Operation) As shown in FIGS. 1 and 2, the central portion 9 of the transparent plastic plate 3 is formed on a part of the upper surface of the light incident portion 6 adjacent to the light source 8.
Since a short and small light condensing piece 11 having an inclined surface 10 is provided toward, when light emitted from the light source 8 enters the transparent plastic plate 3 from the light entrance portion 6 as shown by the arrow in FIG. At the same time, the light enters the condensing piece 11, the light is refracted by the inclined surface 10 and enters the transparent plastic plate 3. Then, the light that has directly entered the plastic plate 3 merges, is emitted from the diffusion film 2 while being reflected and transmitted, and emits light.

Therefore, the luminance in the portion H actually used as the light emitting surface is increased by the amount of light emitted from the light condensing piece 11 which enters the transparent plastic plate 3.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

1 and 2 are schematic views showing an embodiment of the present invention, FIG. 1 is a front view, and FIG. 2 is a sectional view.

FIG. 3 is an explanatory view showing the shape patterns of various condensing pieces,
FIG. 4 is an explanatory view showing a conventional example. 3 and 4 only show the transparent plastic plate 3 and the light condensing piece 11 in a schematic form.

Reference numeral 1 is a light guide plate main body, and a diffusion film 2, a transparent plastic plate 3, and a reflective film 4 are sequentially laminated from the top. At this time, printing ink, scratches, etc. are formed on the mating surface of the transparent plastic plate 3 and the reflective film 4. A screen-printed surface 5 that is diffused and patterned is provided.

The light guide plate main body 1 has a light incident portion 6 on one side and a light shielding portion 7 on the other side shielded by an edge tape or the like.

A light source 8 is attached along the light incident portion 6, and the light emitted from the light source 8 enters the transparent plastic plate 3 from the light incident portion 6, is reflected by the reflection film 4 and the light shielding portion 7, and is a diffusion film. 2 is configured to emit and emit light.

As the transparent plastic plate 3, an acrylic plate is generally used, but any plastic plate can be used as long as it has transparency and weldability such as polypropylene, polyethylene, polyethylene terephthalate.

As the diffusion film 2, for example, a polycarbonate film or the like is used, and as the reflection film 4, a white polyethylene film or the like is used to prevent light leakage.

As the light source 8, a hot cathode discharge tube or the like is used when importance is attached to brightness, and a cold cathode discharge tube or the like is used when importance is attached to thinness. The length is preferably slightly longer than the light emitting surface H of the light guide plate body 1 used, and the thickness is most preferably about twice the thickness of the light guide plate body 1.

The present invention is an improvement of the light guide plate configured as described above so as to increase the light incident area from the light source 8 as shown in FIGS.

That is, the transparent plastic plate 3 is directly made of the same material as the transparent plastic plate 3 on the upper surface of the transparent plastic plate 3 on the light entrance portion 6 side,
A short light condensing piece 11 having an inclined surface 10 toward the central portion 9 of the plastic plate 3 is attached with a transparent adhesive 12 having a refractive index similar to that of the plastic plate 3. The condensing piece 11 may be a separate body from the transparent plastic plate 3 as described above, but may be integrally molded.

When the length of the condensing piece 11 is A, the inclination angle is θ, and the thickness is B, light guide plates having various patterns are exemplified as shown in b to i of FIG. is not.

Table 1 below shows the results of measuring the average luminance on the light emitting surface of the light guide plate shown in FIGS. 3 and 4.

In the table, a to i are patterns of various light guide plates shown in FIG. 3, and I and II are conventional examples shown in FIG.

The size of the light guide plate body 1 used for the measurement is the length l
= 20 cm and 30 cm, and thickness t = 2 mm and 3 mm, and shows the average measured by four kinds of light guide plates by these combinations.

In addition, the measurement method is to measure the luminance at a certain number of points in a portion H actually used as a light emitting surface of a backlight or the like, calculate an average value thereof, and make relative comparison.

At this time, the average measured value of the light guide plate a made of one transparent plastic plate 3 to which the light condensing piece 11 is not attached is converted to 100.

From the above table, the shape of the condensing piece 11 is such that the longer its length A is (but shorter than 1), the higher the luminance, and the smaller the inclination angle θ, the higher the luminance. It can be said that the thicker the thickness B, the higher the brightness.

(Effect of the Invention) According to the light guide plate of the present invention, since the light condensing piece 11 is provided on a part of the upper surface of the one side light incident part 6 of the transparent plastic plate 3, the light is incident from the light condensing piece 11. The amount of light that enters the transparent plastic plate 3 and is reflected / transmitted to emit light improves the brightness. Further, since various brightnesses can be obtained depending on the difference in the length A, the inclination angle θ, and the thickness B of the light condensing piece 11, a brightness suitable for the purpose can be appropriately used.

Further, since only the light incident area is increased and the portion H actually used as the light emitting surface does not include the portion provided with the condensing piece 11, the light guide plate can be an ultra-thin and light guide plate.

[Brief description of drawings]

FIG. 1 is a front view showing an embodiment of the present invention, and FIG. 2 is a sectional view of the same. FIGS. 3a to 3i are explanatory views showing patterns of various light guide plates used for luminance measurement, FIG. 4 is an explanatory view of the same conventional example, I is a laminate of two plastic plates, and II is a plastic. The doubled plate thickness is shown. Incidentally, in FIGS. 3 and 4, the diffusion film, the reflection film and the like are omitted, and only the plastic plate and the light condensing piece are shown. 1 ... Light guide plate body, 3 ... Transparent plastic plate, 8 ...
Light source, 11 ... Focusing piece, H ... Used part.

Claims (4)

(57) [Scope of utility model registration request] 1. A diffusion film (2), a transparent plastic plate (3), and a reflective film (4) are sequentially laminated, and light from a light source (8) is incident from a side end surface of the transparent plastic plate (3).
A light guide plate in which the incident light is reflected on the reflection film (2) side so that the diffusion film (2) side emits light, wherein the transparent plastic plate (3) has a side end portion on the light source (8) side. A short condensing piece (11) is provided so as to overlap, and the condensing piece (11) approaches the transparent plastic plate (3) gradually away from the light source (8) on the side opposite to the light source (8). A light guide plate, which is provided with an inclined surface (10) inclined as described above. 2. The length of the transparent plastic plate (3) is l
The light guide plate according to claim 1, wherein the length (A) of the condensing piece (11) is 1/20 to 1/5. 3. The inclination angle (θ) of the light collecting piece (11) is 10 ° to
The light guide plate according to claim 1, wherein the light guide plate has an angle of 45 °. 4. The thickness of the transparent plastic plate (3) is t
The light guide plate according to any one of claims (1), (2), and (3), wherein the thickness (B) of the condensing piece (11) is less than 2t.