JPH10227917A - Light transmission member of surface-emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance brightness by obtaining a matrix having matrix recessed parts formed to have the high density approximately proportional to the distances from light sources and injection molding a light transmission member formed with numerous post-completion recessed parts by injection molding from a light transparent resin material by using the metal mold obtd. from this matrix. SOLUTION: The matrix M having the matrix recessed parts 102 formed to have the high density approximately proportional to the distance from the light source is obtd. The metal mold 101 having the projecting parts 103 for molding the post- completion recessed parts 6 is obtd. by transfer with a transfer method including an electroforming method from this matrix M. The light transmission member 1 innumerably molded with the post-completion recessed parts 6 by injection molding is injection molded from the light transparent resin maternal by using the metal mold 101. At this time, the mold member 101 is so transferred with mold projecting parts 103 and a smooth surface 106 forming a rear surface constitutes a mirror finished surface by the electroforming. The light sources are arranged on both sides of the light transmission plate 1. The mold recessed parts are worked successively from the sections furthest from the central part of a cavity C when both flanks are provided with an incident surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a light guide member of a surface light emitting device used for illuminating a CD (liquid crystal display device) or the like from behind.

[0002]

2. Description of the Related Art When illuminating an LCD or the like having a predetermined area from the back, the first point to be considered is that light generated from a light source is made uniform over all portions of the LCD having a predetermined area. It is mentioned.

[0003] Therefore, conventionally, a light source is arranged on the side of a light guide member formed of a material having high light transmittance, and the light from the light source is guided in the surface direction of the light guide member to form a light guide member. When configured to scatter light emitted from the light emitting surface of the light guide member for the light emitting member arranged in parallel to the light emitting surface,
A large number of projections are formed on the side opposite to the light emitting surface of the light guide member, and while these projections reflect light from the light source, more projections are formed in a portion far from the light source. Many surface light emitting devices in which the brightness of the light emitting surface is uniform have been put to practical use.

According to the surface light emitting device thus configured, the light guide member is mass-produced by injection molding using, for example, an acrylic resin material having high light transmittance. The mold having the cavity is mainly processed by chemical etching.

FIG. 8 is an enlarged sectional view (a) of the conventional light guide plate 10 and an enlarged sectional view (b) of an injection mold 201 used for injection-processing the light guide plate 10.

First, in FIG. 8B, when a mold recess 202 for forming the projection 16 of the light guide plate 10 is formed by chemical etching using an injection mold 201, the bottom surface of the cavity of the mold is formed. A resist film 20 in which portions are provided with opening holes 203a having a predetermined pitch and a predetermined opening area.
3 and then introduce an etchant to open the opening 20.
After the surface contacting via 3a is formed by excavating by erosion, the cavity of the injection mold 201 is formed by removing the resist film 203.

[0007] The injection molding die 2 thus processed and formed.
01 and the thickness H as illustrated in FIG.
The light guide plate 10 having a large number of protrusions 16 formed by injection molding is used to form the light guide plate 10 as described above.
In (a), the light from the light source is reflected, and the projections 16 are formed more in a portion far from the light source so that the brightness on the light emitting surface is uniform.

However, when the mold cavity is machined by the chemical etching process as described above, it is known that the opening hole portion 203a has a hemispherical shape when it is a small-diameter dot, and has a pot-like shape when it is a large-diameter dot. ing.

If so-called over-etching occurs during the chemical etching step, an over-etched portion 202a as shown in FIG. 8B is formed. The diameter d of the protrusion 16b is, for example, Φ0.3.
mm or less and the arrangement pitch is 0.6
mm or less, the communication portion 202b may be formed. Therefore, the protrusion 16 of the light guide plate 10 injection-molded using such a mold has a defective portion 16 as shown in the figure.
a and 16b are formed.

As a result, the light L from the light source cannot be diffusely reflected at the defective portion 16a of the projection 16, or cannot be directed toward the light emitting surface 10a after being reflected by the projection 16, so that light can be efficiently emitted. In addition, it is not possible to select a shape that normally guides the light guide plate away from the light source, so that desired performance cannot be obtained.

Furthermore, in the chemical etching process, it is particularly difficult to control the concentration of the chemical solution, the temperature, and the like. In the case where the density of the projections is provided steplessly, it is very difficult to prevent the occurrence of variation depending on the location. It was difficult. For this,
It is necessary to increase the interval between the adjacent protrusions 16,
The arrangement density of the projections could not be increased, and there was naturally a limit. There was naturally a limit in increasing the amount of light emitted to the outside of the light guide plate to increase the luminance.

[0012]

Therefore, injection molding is performed from a light-transmitting acrylic resin or polycarbonate resin material using an ultra-precision injection molding die that is formed by processing other than the above-mentioned etching, and the above-mentioned projections are formed. The light guide plate is formed with a concave portion having an inclined surface of a suitable shape so that incident light incident at a critical angle β or more determined from the resin material can be reflected on the inclined surface of the concave portion, and the light emitting surface is formed. It is conceivable to increase the brightness by turning the light to.

Accordingly, the present invention has been made in view of the above-mentioned circumstances, and has a concave portion of a light guide plate having a triangular pyramid, a quadrangular pyramid, a polygonal shape other than a conical shape so as to have a high density substantially proportional to a distance from a light source. An object of the present invention is to provide a light-guiding member of a surface-emitting device that can increase luminance by processing it into an arbitrary shape such as a pyramid or a roof.

[0014]

Means for Solving the Problems The above-mentioned problems are solved,
In order to achieve the object, according to the present invention, a light source is disposed on at least one side of a light-transmitting plate-shaped light guide member,
In order to guide the light from the light source from the side light incident surface to the inside of the light guide member and scatter the light in a diffusion member arranged in parallel with the light emitting surface of the light guide member to perform illumination. A light-guiding member of a surface-emitting device in which a predetermined number of concave portions after completion of a predetermined shape are formed on the back surface of the light-emitting surface, wherein a matrix concave portion having a high density substantially proportional to the distance from the light source is provided. And a transfer step of obtaining a molding die having a convex portion for forming the concave portion after completion by transferring from the matrix by a transfer method including an electroforming method. ,
A molding step of injection molding the light guide member having the infinite number of concave portions formed after the completion by injection molding from a light transmitting resin material using the molding die.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1A is a cross-sectional view showing a main part of a surface light emitting device used for, for example, a liquid crystal backlight having no self-luminous ability. FIG. 1 (b)
FIG. 2 is an enlarged sectional view showing a main part of the light guide plate 1. FIG. 2 is a sectional view taken along the line XX of FIG.

In FIGS. 1 and 2, the light source unit 4 is formed by bonding a high-intensity light emitting diode (LED) on a substrate 5 and then sealing it with a silicon resin or an epoxy resin. As described above, the electrode section of the substrate 5 is exposed to the outside, and the electrode section is connected to a power supply section (not shown) so that the substrate 5 can be turned on, thereby enabling independent production and supply.

On the other hand, the light guide plate 1 formed in a flat shape as shown in the drawing has substantially the same shape and area as the flat display surface 15 of the liquid crystal. Is formed by injection molding using a transparent acrylic resin, polycarbonate (PC) resin, or the like as the material. The back surface 1b of the light guide plate 1 is formed of a mirror surface, while the inclined surface of the concave portion 6 is made to be a mirror surface or a rough surface so that incident light having a critical angle β or more is totally reflected or irregularly reflected.

The light emitting surface 1a of the light guide plate 1, the left and right side surfaces 1d, 1e and the opposite surface 1c and the back surface 1b are injection-molded so as to be mirror surfaces, respectively. Is formed. As shown in FIG. 2, the arrangement of these recesses 6 is such that the horizontal pitch Pw and the vertical pitch Pd are sparsely arranged in a portion close to the light source 4, while the distance from the light source 4 increases. The horizontal pitch Pw and the vertical pitch Pd gradually become denser.

Further, by arranging the concave portions 6 so as to be staggered as shown in the figure, the simulation analysis using a computer can be performed so that the light from the light source 4 can reach the distant adjacent concave portions 6 without fail. The concave portion 6 is provided based on this.

On the other hand, the reflection frame 3 formed in a substantially box shape as shown in the figure is formed in a box shape having a size for accommodating the light guide plate 1 with substantially no gap. Also, this reflection frame 3
Is formed by, for example, injection molding from a white resin or by electroless plating, so that reflection inner surfaces 3a, 3b, 3c, and 3d as reflection surfaces are formed on the inner side, and the light is reflected by each reflection inner surface. The emitted light is directed to the diffusion plate 2.

The above is the schematic configuration of the surface emitting device.
The dimensions are appropriately determined according to the size of the liquid crystal. When the liquid crystal size is large, a fluorescent lamp serving as a line light source is appropriately used as the light source 4. When the backlight is horizontally long, the devices shown in FIGS. 1 and 2 are symmetrically provided so that a pair of the devices face each other, and the concave portions 6 are disposed so as to be dense at the central portion. Will be.

Next, FIG. 3A is a schematic view showing a state of reflection of light L entering the light guide plate 1, and FIG.
FIG. 3B is a cross-sectional view of a main part illustrating a state of reflection of light L in the concave portion 6.

First, in FIG. 3A, light L emitted from the light source 4 and shown by a broken line in the figure is a critical angle β due to the refractive index n = 1.49 of the acrylic resin. 4
2.16 °, and the light is totally reflected when incident on each surface at an incident angle of 42.16 ° or more. That is, light entering the light guide plate 1 at an angle α formed with a perpendicular from the light guide plate 1 is refracted at the critical angle β, but the refractive index n = s
In the relational expression of inα / sinβ, when α is 90 °,
42. The critical angle β from sinβ = sin (90 °) / n
16 ° will be obtained.

Similarly, in the case of PC resin, since n = 1.59, the critical angle is 38.97 °, and the incident angle 38.97 ° on each surface.
When the light is incident at 97 ° or more, the light is totally reflected.

Therefore, the light L incident from the light incident side surface 1f of the light guide plate 1 formed of an acrylic resin is converted into the left and right side surfaces 1d, 1d at an angle of 47.84 ° or more, which is more than the critical angle.
e, the light is incident on portions other than the concave portions 6 of the light emitting surface 1a and the back surface 1b, and all are totally reflected. Similarly, in the case of PC resin, all light incident from the light incident side surface 1f is totally reflected.

The light that reaches the opposite surface 1c while repeating total reflection as described above is emitted from the light guide plate 1 to the outside, is reflected by the reflection inner surface 3b of the reflection frame 3, and then is returned to the light guide plate 1 again. Will be incident.

Next, the most characteristic concave portion 6 of the present invention is:
It is formed on the back surface 1b as shown in FIG. 3B, and is formed so as to be totally reflected as shown by a broken line if the incident angle of the concave portion 6 with respect to the reflection surface 6a is equal to or larger than the critical angle β. . When the reflection surfaces 6a and 6b are roughened, the light is partially diffused on the reflection surface 6 and travels as indicated by a broken line.

When the incident angle on the light emitting surface 1a is equal to or smaller than the critical angle β, the light is not reflected on the light emitting surface 1a and the light guide plate 1 is not reflected.
Refracted and emitted to the outside, reaches the diffusion plate 2, and diffuses there. In addition, incident light having an incident angle equal to or greater than the critical angle β on the light emitting surface 1a is totally reflected and guided to the far side in the light guide plate.

On the other hand, although not shown, light that has entered the back surface 1b at a critical angle β or less exits from the back surface 1b, is directed to the reflecting surface 3a of the reflecting frame 3, and is reflected by the reflecting surface 3a. After that, the light is again incident on the light guide plate 1 and directed to the light emitting surface 1a.

The light diffused by the diffusion plate 2 as described above forms a surface light source, and in the case of a liquid crystal backlight, passes through the LCD transmission pattern 15 shown in FIG. Will be done.

The concave portion 6 is formed so as to protrude conically from the back surface 1b of the light guide plate 1 toward the light emitting side surface 1a as shown in the figure. The angle θ is formed to be 130 ° or less. By forming the recesses 6 in this manner, the back surface 1b
Incident on the reflection surface 6 of the concave portion 6, which is light incident at a critical angle β or more with respect to
The light is emitted from the light emitting surface 1a so that the light is totally reflected at the light emitting surface a.

The concave portion 6 formed as described above is gradually shifted to the horizontal pitch Pw as the distance from the light source 4 is increased as described above.
And the vertical pitch Pd is arranged in a dense state, and furthermore, arranged so as to be staggered as much as possible, so that light from the light source 4 can surely reach the opposite surface 1c.

Various experiments were conducted on the apex angle θ of the protrusion, and it was confirmed that the efficiency was the best around 80 ° to 130 °, and the height h of the recess 6 was 0.05 mm and the diameter d was 0.2
At 5 mm, the horizontal pitch Pw and the vertical pitch Pd at the portion where the concave portions 6 are provided at the highest density and near the opposite surface 1c shown in FIG. 1 can be reduced to 0.3 mm, which is quite good as described later. The result was able to be obtained.

Next, after obtaining the base material M having the mold concave portion 102, the base material M is removed, and the process proceeds to an electroforming step (electroforming). Since the electroforming is a well-known technique, its details are omitted, but will be briefly described below.

In the schematic diagram of FIG. 4A, after a plating layer 110 of nickel or the like is formed on the outer peripheral surface of the matrix M to a predetermined thickness, the matrix M is peeled off and removed. As a result, the shape of the mold projection 1 completely inverted from the shape of the mold recess 102 is obtained.
03 is formed on the plating layer 110 side.

Thus, a mold member 101 having a cavity C is obtained by integrally forming the mold member 101 with the mold member 101. In FIG. The light guide plate 1 is obtained by injection molding using a material or the like under predetermined conditions. At this time, the mold member 101 is transferred by electroforming so that the mold convex portion 103 and the smooth portion 106 for molding the back surface are mirror-finished. Note that light sources 4 are provided on both sides of the light guide plate 1,
When f is provided on both side surfaces, it is needless to say that the mold concave portions are processed in order from the portion farthest from the center of the cavity C.

FIGS. 5 and 6 are tables showing that the concave portion 6 can be formed in an arbitrary shape. In both figures (a) to (m), external perspective views showing the shape of the light guide plate which is injection molded as the concave portion 6 and the state of reflecting light incident at a critical angle or more are shown.

First, in FIG. 5A, the concave portion has a conical shape having an apex angle of 80 to 130 degrees, and is injection molded as a conical concave portion as shown in the figure on the light guide plate. As a result, as described with reference to FIG. 3, light incident at a critical angle β or more can be reflected in the direction of the arrow.

In FIG. 5B, the concave portion is injection-molded in the light guide plate as a conical concave portion as shown in the drawing, so that the spherical portion can be made inconspicuous. As a result, as shown in FIG. Light entering at a critical angle β or more is reflected in the direction of the arrow, and the configuration can be such that the spherical portion is not conspicuous.

In FIG. 5 (c), the light guide plate is injection-molded as a conical concave portion as shown in the drawing, and by appropriately setting the area of the flat portion, the critical angle β as described in FIG. As described above, it becomes possible to control the amount of light when the incoming light is reflected in the direction of the arrow.

In FIG. 5D, the light guide plate is injection-molded as a triangular pyramid concave portion as shown in the figure, and light enters the inclined surface at 180 ° intervals from the three sides at a critical angle β or more. Light can be reflected in the direction of the arrow.

Further, in FIG. 5 (e), the light guide plate is injection-molded as a quadrangular pyramid recess as shown in FIG. The light thus emitted can be reflected in the direction of the arrow. Therefore, for example, by arranging the light sources on all four side surfaces, it is possible to significantly increase the luminance. Further, it is also possible to arrange so that light sources of different colors are arranged on the four side surfaces so as to be additively mixed in the concave portion to obtain various colors.

In FIG. 5 (f), a quadrangular pyramid is formed at the tip end as shown in the figure, and further, the vertex is spherical. For this reason, as in the case of FIG. 5B, the spherical portion can be configured so as not to be conspicuous. As a result, the light incident at the critical angle β or more is reflected in the arrow direction as described in FIG. It can be configured such that the spherical portion does not stand out.

In FIG. 5 (g), as shown, a quadrangular pyramid is formed at the tip to form a flat portion. For this reason, the light amount can be controlled in substantially the same manner as in FIG.

Next, FIG. 6 (h) shows a gable roof as shown in the figure, and as shown in the external perspective view, the light enters at a critical angle β or more as shown in FIG. The reflected light can be reflected in the direction of the arrow.

In FIG. 6 (i), the roof-like apex portion of FIG. 6 (h) is formed in a round shape, and in this portion, the structure is made inconspicuous.

Further, FIG. 6 (j) shows a roof-like structure of a ridge as shown in the figure, and as shown in the external perspective view, light incident at a critical angle β or more from the left, right, front and rear directions is reflected in the direction of the arrow. You can do it.

FIG. 6 (k) shows an oval-shaped body at the bottom, which is a roof-like portion of a deformed building as shown in the figure. Light incident at a critical angle β or more can be reflected in the direction of the arrow.

In FIG. 6 (l), the bottom surface is an oval shape, and as shown in the figure, a roof-like shaped portion of a deformed building having an arc surface and a flat surface is formed at the tip. In this case,
As shown in the external perspective view, light that has entered from the front, rear, left, and right directions at a critical angle β or more can be reflected in the direction of the arrow.

Finally, in FIG. 6 (m), the bottom surface is oval, and a trapezoidal long conical shape is formed at the tip as shown. In this case, as shown in the external perspective view, light that has entered from the front, rear, left, and right directions at a critical angle β or more is reflected in the arrow direction.

In FIG. 6 (o), the bottom surface is square, and the inclined surface facing the light source side is formed gently as shown. In this case, as shown in the external perspective view, only light that has entered from the right at a critical angle β or more can be reflected in the direction of the arrow.

FIG. 7 is an optical characteristic diagram obtained by measuring the optical characteristics of a light guide plate having a conical concave portion. As shown in FIG. 7A, a light source is provided on the side of the light guide plate. Place,
FIG. 9 is a characteristic diagram obtained by measuring the luminance diffused from the surface of the light guide plate by inclining the luminance form by an angle θ.

In this characteristic diagram, the cosine luminance is shown on the vertical axis, and the angle θ is shown on the horizontal axis. When the angle θ is zero,
The luminance meter is perpendicular to the diffuser surface, and when the angle is positive, the luminance meter is tilted away from the light source, and when the angle is negative, the luminance meter is tilted closer to the light source. It was measured as described above.

In the table, K1 indicates the characteristic in which the surface of the concave portion is roughened and the apex angle is 65 degrees, and K2 indicates the characteristic in which the surface of the concave portion is roughened and the apex angle is 65 degrees. Show, K3
Indicates that the surface of the concave portion is roughened and the apex angle is 80 degrees, and K4 is that the surface of the concave portion is a glossy surface and the apex angle is 100 degrees.
K5 has roughened surface of the concave part,
The characteristics are shown with the apex angle set to 100 degrees, and K6 in the table shows the characteristics when the surface of the concave portion is roughened and the apex angle is set to 55 degrees.

As can be seen from this chart, it is possible to arbitrarily control the luminance characteristics obtained by observing the light guide plate from an oblique direction. As shown, it is possible to set arbitrarily such as greatly improving the brightness increase in the vertical direction.

As described above, when the light guide plate 1 is formed, the shape and size of the concave portion 6 can be freely set.
It was confirmed that the arrangement interval of the concave portions 6 could be narrowed, and the amount of light emitted from the light guide plate could be increased, so that the brightness was increased about 1.5 times that of the conventional chemical etching. .

The light guide plate 1 is used for a liquid crystal backlight for a portable telephone, a notebook personal computer or a car navigation device having a larger display screen, and the power consumption of a fluorescent lamp as a light source thereof. Extremely good performance for liquid crystal backlights, which is used when the minimum is desired. Furthermore, the above-mentioned light guide plate can be applied in various other ways, and a light source and a reflection frame are appropriately designed according to the purpose of use of the surface light emitting device using the light guide plate.

[0059]

As described above, according to the present invention,
Increase the brightness by processing the concave portion of the light guide plate into a triangular pyramid, square pyramid, polygonal pyramid, rooftop, or any other shape other than a cone so that the density becomes high in proportion to the distance from the light source The light guide member of the surface light emitting device which can be provided can be provided.

[0060]

[Brief description of the drawings]

FIG. 1A is a cross-sectional view of a surface light emitting device, and FIG.
It is the elements on larger scale sectional view.

FIG. 2 is a sectional view taken along line XX of FIG.

FIG. 3A is a schematic diagram illustrating a state of reflection of light L entering a light guide plate 1; (B) is the light L in the recess 6
FIG. 5 is a cross-sectional view of a main part showing a state of reflection of the light.

FIG. 4 is a process drawing of electroforming.

FIG. 5 is a list showing that the recess can be forged into an arbitrary shape.

FIG. 6 is a list showing that the recess can be forged into an arbitrary shape.

FIG. 7 is an optical characteristic diagram of the light guide plate.

FIG. 8A is an enlarged sectional view of a conventional light guide plate 10,
FIG. 2B is an enlarged cross-sectional view of an injection mold 201 used for performing injection processing on the light guide plate 10.

[Explanation of symbols]

 Reference Signs List 1 light guide plate, 2 diffuser plate, 3 reflection frame, 4 light source, 5 substrate 6 concave portion, 101 type member 102 type concave portion M master mold 110 plating layer β critical angle

Claims (5)

[Claims] 1. A light source is disposed on at least one side of a light-transmitting plate-shaped light guide member, and light from the light source is guided from the side light incident surface into the light guide member. In order to illuminate by scattering light in a diffusion member arranged in parallel to the light emitting surface of the light guide member, the surface of the surface light emitting device has an infinite number of concaves formed after completion of a predetermined shape on the back surface of the light emitting surface. A light guide member, a mold manufacturing process for obtaining a mold having a mold recess having a high density substantially proportional to the distance from the light source; and a transfer method including an electroforming method from the mold. A transfer step of obtaining a molding die having a convex portion for molding a concave portion after completion of the above-mentioned completion, and an injection molding from a light-transmitting resin material using the molding die, and And a molding step of injection molding the light guide member having innumerable concave portions. A light guide member of a surface light emitting device. 2. The predetermined shape is set so that incident light incident at a critical angle β or more determined from the resin material is reflected on the inclined surface of the completed concave portion with respect to the light emitting surface. The light guide member of the surface light emitting device according to claim 1, wherein is a mirror surface. 3. A conical surface or a triangular, square, polygonal surface, trapezoidal long cone, gable, or the like having an apex angle in the range of 130 to 80 degrees to form the inclined surface of the recess after completion.
The light guide member of the surface light emitting device according to claim 2, wherein the light guide member has an arbitrary shape in which each surface of the ridge roof is formed. 4. The light guide member of a surface light emitting device according to claim 3, wherein the concave portion has an arbitrary shape in which a spherical portion or a flat portion is formed at a tip portion of the concave portion after completion. 5. The light guide member of a surface light emitting device according to claim 3, wherein the inclined surface of the concave portion after completion has an arbitrary shape formed only at a portion facing the light source.