JP2010102188A - Light-emitting display board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-emitting display board in which high front luminance is obtained by utilizing efficiently limited luminous flux of a LED and which has peculiar luster feeling by reflection of a mirror surface of a minute prism. <P>SOLUTION: In the display board having a light guide plate and a LED light source arranged at its end plane, many minute prisms forming continuous ridge-line are formed at the back face opposing to the surface of the light guide plate according to a display part, a reflecting plane which converges incident light in the vertical direction to an input light side is formed at a light input part of the light transmitter. The display board can obtain the display surface having high front (normal line direction) luminance by convergence at the reflection plane. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to an electric display panel, an electric signboard, a sign, an illumination, and an amusement electric decoration for displaying a specific character or design on a plane.

When unevenness is formed on a part of either the front or back surface (generally the back surface) of a highly transparent light guide plate such as an acrylic resin, a light source is placed on the end surface and light is incident on the light guide plate. Since only the formed part diffuses and reflects light (diffuse reflection), it looks shining. Light-emitting display boards that use these principles to emit symbols and characters have already been used in various fields such as signs, guide boards, signs, and illumination.
Laser beam machining, sand blasting, chemical etching, printing, or the like is used as a method for forming the unevenness. As a method for efficiently reflecting light, Patent Document 1 proposes a method for generating a fine crack, which has already been put into practical use. (Patent Document 1)

Further, Patent Document 2 proposes a light-emitting display panel that uses a diffuse reflection by an empty gun by generating vacuoles inside a light guide plate by laser beam irradiation, and has been put to practical use as such illumination. .

JP-A-10-105092 JP 2004-246260 A

There are various methods as described above, and these all diffuse and reflect light in the light guide plate. Although the light is emitted in all directions, it has the advantage that it appears to shine from any angle, but it is not suitable for applications where it is desired to collect emitted light in the front direction to obtain high front luminance.
As a light source to be used, there are a fluorescent discharge tube, an LED, and the like. When an LED is used, the light flux from one LED is limited. In particular, when a large-area display panel is intended to emit light with high luminance, it is necessary to arrange a large number of LEDs, which is disadvantageous in terms of power saving and also increases the device cost. Moreover, the light emission by diffuse reflection is an image that is calm to the eye, and is not suitable for giving a novel and strong impression.

The present invention provides a light-emitting display panel that can obtain a high front luminance by efficiently using a limited luminous flux of an LED and has a specific glossiness due to specular reflection of a fine prism.

The light emitting display panel of the present invention is a display panel having a light guide plate and an LED light source disposed on an end surface thereof, and a large number of fine prisms forming continuous ridge lines are displayed on the back surface facing the display surface of the light guide plate. The light-emitting display panel is characterized in that a light-reflecting surface is formed on the light incident portion of the light guide so as to collect incident light in a direction perpendicular to the light incident side. is there.

According to the present invention, the light condensed in the front direction can be emitted from the display portion by the condensing function of the reflecting surface formed in the light incident part and the specular reflecting function of the fine prism.

Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view for explaining the characteristics of a light emitting display panel according to the present invention. Two LED light sources 1 are arranged close to each other on an end surface that is a light incident side of a light incident portion to the light guide plate 2. Here, three letters XYZ are shown as an example of a display pattern.
On the back surface of the light guide plate, a fine prism 5 having a linear ridge line in a direction parallel to the light incident side (Y direction) is formed in the pattern portion 3. The prism is specularly reflective, and is shaped to reflect so that the emission angle becomes stronger near the normal direction. A reflection surface 4 that reflects incident light is formed in the light incident portion.

The light emission principle of the light guide plate of the present invention will be described with reference to the side view 2. The light incident on the inside of the light guide plate 2 is propagated by repeating internal reflection at the air interface between the front surface and the back surface. If both the front and back surfaces of the light guide plate are perfectly smooth, no light is emitted because all the light is internally reflected. The fine prisms 5 are arrayed and formed at a fine pitch (P) on the back surface of the pattern portion 3 of the light guide plate, and the light hitting the reflecting surface is reflected and emitted to the light emitting surface (display surface) side.

3 and 4 are side views showing a cross section of one fine prism and an optical path there.
As a cross-sectional shape of the fine prism for giving a peak in the normal direction, when the LEDs are arranged on two opposite sides, the shape having the prism reflecting surface 6 on both sides as shown in FIG. It is preferable that the angle γ formed with the normal line is approximately 30 degrees. Since the cross-sectional shape of the prism is symmetric, the light traveling from both sides is emitted in a distribution having a peak near the normal line. Assuming that the prism cross-sectional width is E and the height is D, the ratio of E / D is too small or too large, the output light rate is lowered. The proper range of E / D is approximately 3 to 8.

On the other hand, when the LEDs are arranged on only one side, the cross-sectional shape of the fine prism may be symmetrical as shown in FIG. 3, but the first reflecting surface 7 and the second reflecting surface as shown in FIG. More preferably, the angle δ formed with the normal line of the first reflecting surface is 75 to 85 degrees, and the angle ε formed with the second reflecting surface is 35 to 45 degrees.

The fine prisms having such a cross-sectional shape are arranged on the back surface of the symbol portion to be emitted at an appropriate interval in the X-axis direction. At this time, since the light flux density in the light guide plate decreases as the distance from the light incident portion increases, at least one of decreasing the X-direction formation pitch (P) of the fine prisms or increasing the height (D) is sequentially performed. It is also preferable in some cases to change the brightness to balance.

Next, the function of the reflecting surface of the light incident part, which is a feature of the present invention, will be described.
When the light sources are simply arranged in the incident side as shown in FIGS. 5 and 6, the reflection by the prism is specular reflection. Therefore, when viewed from the front, the light source is straight in the X direction as shown in FIG. 5. Only the hatched area in the extended line will appear shining. When observed from an inclined angle, as shown in FIG. 6, only the hatched area in the line that moves with the observation angle appears to shine. Such light emission is not desirable for a light-emitting display panel.

On the other hand, in the present invention, as shown in FIG. 7, a reflection surface 4 for reflecting light is provided in the light incident portion. By combining the light reflected by the reflecting surface and the light that travels directly, the entire design portion appears to shine. In addition, even if the observation angle is tilted, if the angle is within a certain range, the entire symbol appears to emit light.

8 and 9 show an optical path incident on the light guide plate.
The light emission of a general surface-mounted LED has an angular distribution close to Lambertian diffusion, and the light taken into the light guide is incident with a spread of about 40 degrees in both the Y direction and the Z direction (half angle). Become. If attention is paid to the spread in the Y direction, when the light is reflected by the prism 5 having a linear ridge line, as shown in the front view of FIG. 8, the emitted light further spreads in the Y direction. Strong light emission cannot be obtained in the front direction. (Here, for the sake of simplification, the light beam when the divergence angle in the Z direction is 0 degree is shown. However, even if there is a distribution in the Z direction, the spread in the Y direction is further expanded by reflection on the prism. On the other hand, in the case where a slope is formed in the light incident portion, the slope becomes the reflection surface 4 as shown in FIG. Are collected into the distribution indicated by the angle β. Correspondingly, the emitted light from the symbol part is also condensed in the front direction, and strong light emission can be obtained in the front direction.

When the reflecting surface is a flat surface, the angle α formed by the reflecting surface and the incident side is preferably in the range of 60 degrees to 85 degrees. If the angle α is too large or too small, the distribution of the spread angle is not narrowed, and a range of 75 degrees to 80 degrees is particularly preferable for narrowing the distribution.

5, 6, 7, and 9 show examples in which two LEDs are arranged, but in the present invention, the number of LEDs is not particularly limited, and may be one as shown in FIG. 10. Moreover, what is necessary is just to take the form where the same light-incidence part shape was repeated according to the number of LED, also when there are three or more LEDs. Furthermore, the direction in which the LED light source is arranged is not limited to one side, and it can be selected according to the situation to arrange the LED light source on two opposite sides.

In the case where it is desired to emit light in a relatively large area in the dimension in the Y direction with respect to the size of one LED light source, the merit of forming the curved reflecting surface 4 as shown in FIG. By forming a curved reflecting surface, it is possible to suitably emit light having a width that is four times or more the LED light emitting unit size in the Y direction. As an example of the curved shape, it is preferable that the curve when viewed from the front draws an ellipse or a parabola.

The ridgeline of the fine prism is typically a straight line, but it may be a gentle curve that is substantially parallel to the incident side, and the light output angle changes depending on the direction of the ridgeline, so the optimal visual effect You can choose to get.

The light guide plate can be mass-produced at low cost by preparing a mold and performing injection molding. The fine prism shape can be processed on the mold with high smoothness and high precision by cutting in the Y-axis direction using the corresponding tip-shaped cutting tool (bite). The inverted shape is transferred.

If the arrangement pitch of micro prisms is too large, each micro prism will be visually recognized as a line, so it is desirable that the pitch be as fine as possible to create a high-definition feeling. Since the accurate shape is sometimes difficult to transfer, the range of approximately 0.1 mm to 1 mm is preferable.

As a material of the light guide plate, a material having a high transmittance at the emission wavelength of the LED to be used is desirable, and an acrylic resin, a polycarbonate resin, a cycloolefin resin, or the like is preferably used.

As described above, in the light guide plate used in the present invention, firstly, the light distribution in the XY plane is condensed in the X direction by the action of the light incident part reflecting surface, and secondly, the action of specular reflection of the fine prism. Thus, the light distribution in the XZ plane is condensed and reflected in the Z (front) direction and emitted. By combining both actions, light is emitted with an angular distribution having a peak in the front (normal) direction. Therefore, it emits light with a front brightness several times higher than that of a conventional light emitting display panel using diffuse reflection. In addition, light emission having a rough feeling, a glossy feeling peculiar to specular reflection, and a high precision feeling can be obtained.

Not all of the light that reaches the micro prism is reflected and emitted to the front surface, but there is also light that is refracted and emitted to the rear surface side. Efficiency can be further increased.

In addition, multiple light guide plates are arranged in multiple layers, LEDs are arranged on the end faces of each light guide plate, and each layer is turned on and off to display different patterns and produce multicolored light emission in multiple layers It is also possible to do.

When two or more LEDs are arranged as shown in FIG. 7, it is possible to produce effects in which the LEDs are individually turned on and off. In the general system using diffuse reflection, light emitted from adjacent LEDs is mixed, whereas the light emitting display panel of the present invention corresponds to the width of each LED and the light incident portion reflecting surface. The linearly extending line shape mainly emits light. For this reason, the effect by turning on / off each LED arranged on the same light guide plate can be effectively performed.

The perspective view which shows the structure of the light emission display board of this invention. Light guide plate side view explaining the light emission principle Side view of light guide showing cross-sectional shape and emission direction of fine prism Side view of light guide showing cross-sectional shape and emission direction of fine prism Front view explaining the light emission state A perspective view explaining a light emission state Front view explaining the light emission state Front view explaining prism ridgeline and light emission direction Front view explaining the condensing action of the reflecting surface Front view showing an embodiment using a single LED Front view showing an embodiment provided with a curved reflecting surface

Explanation of symbols

1 LED (light emitting diode)
2 Light guide plate 3 Pattern 4 Light incident part reflection surface 5 Fine prism 6 Reflection surface of fine prism 7 First reflection surface of fine prism 8 Second reflection surface of fine prism

Claims (2)

A display panel having a light guide plate and an LED light source disposed on an end surface thereof, and a large number of fine prisms forming continuous ridge lines are formed on the back surface of the light guide plate facing the display surface to match the display portion. A light emitting display panel, wherein a light incident portion of a light guide is formed with a reflection surface for collecting incident light in a direction perpendicular to the light incident side. 2. The light emitting display panel according to claim 1, wherein the ridgeline of the fine prism on the back surface of the light guide plate is a straight line substantially parallel to the light incident side of the light incident portion.

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