JPH09147617A - Surface light emitting body and back light unit using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light emitting body and a back light unit using it of which the cost is reduced by automating its manufacturing process to simplify its assembling process. SOLUTION: This surface light emitting body 1 is formed by molding in two colors a light transmission body 2 formed of a transparent resin composition using a transparent resin as a base material and containing uniformly-dispersed transparent particles 5 and a reflecting part 3 formed of an opaque resin composition on the side of the light transmission body 2 and the rear of its light emitting surface. A light entering part 4 is formed by not forming the reflecting part 3 in at least one end part of the rear of the surface light emitting body 1, and a reflecting part 3' is formed in an overhang-like form from the side on the light emitting surface side corresponding to the light entering part 4. A light source is positioned upon the position capable of radiating light to the surface light emitting body l and the light entering part 4 of the surface light emitting part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface light emitter used for a liquid crystal panel backlight and the like, and a backlight unit using the surface light emitter.

[0002]

2. Description of the Related Art As a display device for a word processor, a laptop computer or the like, a thin liquid crystal display device having a backlight mechanism which is easy to see is widely used. Currently, as these backlights, ones in which a plurality of light emitters such as cold cathode tubes and a light diffusing plate are arranged immediately below the panel, or ones using an electroluminescence (EL) surface light emitter are used. However, in the former configuration, the entire display device is thick, and in the latter configuration, a thin one can be obtained, but the brightness is insufficient, the life is relatively short, and the cost is high. There is.

On the other hand, various light guide plate type (edge light type) backlights having a linear light source at a side end of a light-transmitting plate have been tried, but the light incident from the end face is flat as it is. Since it does not emit light, the light exit surface of the translucent plate or its back surface or both are roughened to a satin finish, or a dot pattern is formed on the back surface, and a light diffusion layer is provided on the light exit surface.
Etc. are being processed. In addition, it has been attempted to geometrically change the optical path of light by performing processing such as thinning the facing reflection layer on the light emitting surface according to the distance from the light source.

Generally, a reflective layer for reflecting a part of the light incident on the back surface of such a light guide is provided. However, in order to make the surface of the conventional light guide uniformly emit light, it is necessary to print a dot pattern on the back surface of the light guide or to apply a satin finish, and the reflective layer is formed after such a process. Further, in the edge light system, a linear light source is provided on the side end surface of the light guide plate, but it is necessary to provide a dedicated reflector called a lamp house, which complicates the assembly process.

On the other hand, with the recent widespread use of mobile phones and the like, there is an increasing demand for a small-sized light-emitting type liquid crystal panel whose display section can be visually recognized even at night. When forming such a small light emitting device, an LED lamp is used as a light source.
For mounting the LED lamp, there are a method of making a hole in the light guide and fitting it into the hole, and a method of attaching a thin LED to the side surface of the light guide. However, these mountings have problems such as the step of providing a reflector and the precise position control as described above, the manufacturing process is complicated, and automation is difficult.

Further, if dust enters between the light guide portion and the reflection portion, there is a problem that the portion is not reflected uniformly. Therefore, generally, in order to avoid such quality deterioration in the process from the manufacturing of the light guide part and the reflection part to the combination, it is necessary to wash each part and equipment such as a clean clean room. And increased capital investment.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a surface light emitter which can efficiently guide light to a light guide section. Further, the present invention provides a method for manufacturing the above-mentioned surface light emitting device, which automates the manufacturing process, simplifies the assembly process, and prevents adhesion of dust and the like in the manufacturing process.

[0008]

The present inventors have made extensive studies to solve the above problems, and as a result, arrived at the present invention.

That is, according to the present invention, a light guide formed of a transparent resin composition containing a transparent resin as a base material and uniformly dispersed transparent particles, and a side surface and a back surface of a light emitting surface of the light guide. A surface light-emitting body, which is formed by two-color molding, and a reflecting section formed of an opaque resin composition, wherein a light-entering section is formed without forming a reflecting section on at least one end of the back surface of the surface-emitting body. Further, the surface emitting body is characterized in that the reflecting portion is formed in an overhang shape from the side surface on the light emitting surface side corresponding to the light entering portion.

The present invention also relates to a backlight unit having the above-mentioned surface light emitter and a light source arranged at a position where light can be emitted to the light entrance portion of the surface light emitter.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, since the reflecting portion is integrally formed with the light guide body by the two-color molding, the assembling process is unnecessary, and the problem of dust adhesion is solved. It is simplified and the manufacturing equipment can be reduced.

The present invention will be described below with reference to the drawings.

FIG. 1 is a schematic sectional view for explaining an embodiment of the present invention. In the figure, 2 is a light guide for uniformly dispersing and holding transparent particles, and 3 is a reflection part made of an opaque resin composition. The reflecting portions are provided on the side surface of the surface light-emitting body 1 and on the back surface of the light emitting surface, and the light entering portions 4 are formed on both ends of the back surface without providing the reflecting portions 3. In the present invention, the light emitting surface side corresponding to the light incident portion 4 is continuously provided from the side surface with the reflecting portion 3 '.
Is characterized by being formed in an overhang shape. By thus providing the overhanging reflecting portion 3 ′, the light incident from the light incident portion is reflected by the reflecting portion 3 ′ and guided to the light guide 2. In the light guide section, light is repeatedly reflected between the light emitting surface interface of the light guide body 2 and the reflector 3, and during that time,
The light is emitted from the light emitting surface by being refracted by the transparent particles 5 in the light guide. Also, some light is emitted as it is without being reflected at the light emitting surface interface, but the amount of light emitted can be reduced by finishing the light emitting surface of the light guide body as a mirror surface, and more uniform light emission is obtained over the entire light emitting surface. be able to.

The tip of the overhanging reflecting portion 3'may be formed so as to be located inside the end of the reflecting portion on the back surface. Is preferably located within 5 mm or less from the end of the back reflector.

The shape of the overhanging reflecting portion 3'is rectangular in FIG. 1, but if the light incident from the incident portion into the light guide portion can be efficiently reflected and introduced, the shape shown in FIG.
Various shapes such as the arc shape shown in FIG. 2A and the inclined shape shown in FIG. 2B can be adopted.

Further, according to the present invention, the light entrance portion may be provided with a recess for mounting the light source. "Recess" here
For example, when a linear fluorescent tube is used as a light source, it is a groove having a width, depth, and length that can accommodate the fluorescent tube. When using a chip-type LED as a light source, The hole is a hole in which the chip can be fitted, and the shape thereof may be appropriately selected depending on the size of the surface light emitter itself, the size of the light source, the shape, and the like. Such recesses may be provided at the same time as molding, or may be formed by cutting or the like after obtaining a molded product.

By using the surface-emitting body provided with the concave portion as described above, the backlight unit can be completed simply by mounting the light source at a predetermined position on the substrate and then covering the surface-emitting body of the present invention from above. This backlight unit is also an object of the present invention.

The light guide section of the present invention comprises a transparent resin as a base material and transparent particles uniformly dispersed in the transparent resin. In particular, the present inventor first disclosed in JP-A-6-338206.
It is preferable to use the surface light-emitting device disclosed in Japanese Unexamined Patent Application Publication No. 2004-242242 because uniform light emission can be obtained over the entire light emitting surface.

Examples of the transparent resin used as the base material of the light guide section include conventionally known thermoplastic resins and thermosetting resins, preferably polycarbonate resin, polymethylmethacrylate resin, polystyrene resin and the like. To be The light guide portion is formed by uniformly dispersing transparent particles in this transparent resin.

When a polycarbonate resin is used, the molded product may be colored by melt mixing with transparent particles, especially glass particles. In that case, coloring can be prevented by adding an organic phosphorus compound. it can.

For the transparent particles used in the present invention, a material having a refractive index different from that of the above transparent resin is selected. Particularly preferred are transparent particles having a refractive index of 0.005 to 0.2 which is different from the refractive index of the transparent resin, and having an average major axis of 80 μm or less and an average minor axis of 1 μm or more. The shape is not particularly limited as long as this condition is satisfied, and may be, for example, spherical, rugby spherical, comet-shaped, cylindrical, polygonal, or the like. It is also possible to use a mixture of two or more kinds of transparent particles. In that case, the total refractive index of the transparent particles is determined by the sum of the products of the respective refractive indexes and the respective volume ratios. Thus, the difference between the transparent particles and the refractive index of the transparent resin used is 0.0
It must have a refractive index of 05 to 0.2. Further, it is preferable that the difference in refractive index is 0.01 to 0.1. When the difference in the refractive index is less than 0.005, the light refraction effect is reduced, so that sufficient light emission cannot be obtained to the light exit surface, and when it exceeds 0.2, the light dispersion effect is high. Therefore, uniform light emission cannot be obtained over the entire light emitting surface. It does not matter which of the transparent resin and the glass particles has a higher refractive index, and only the difference is important.

In the present invention, the major axis and minor axis of the transparent particles are defined by the longest diameter (major axis) and the shortest diameter (minor axis) of the projected image obtained by placing them on a horizontal plate.

The average major axis and the average minor axis can be determined by measuring the major axis and the minor axis of at least 100 transparent particles and calculating the average value of each. The average major axis and the average minor axis of the transparent particles are 80 μm or less and 1 μm or more, respectively, and it is particularly preferable that the average major axis is 40 μm or less and the average minor axis is 5 μm or more. Average minor axis is 1
If it is less than μm, not only is it inconvenient to handle, but it tends to cause poor dispersion in the molded product, and if the average major axis exceeds 80 μm, it is necessary to increase the volume ratio, and the resin composition has uneven flow during molding. Is not preferred because it tends to cause unevenness in optical and mechanical properties.

Glass particles are preferable as the transparent particles satisfying such conditions, but other particles can be used as long as the above conditions are satisfied.

Although such glass particles can be easily obtained from the market, non-alkali particles are particularly preferable.
Preferred specific examples include crushed aluminum-borosilicate glass (“E-glass”) and quartz glass, and beads.

The blending amount of the transparent particles needs to be within the range of less than 0.01 in the volume ratio of the transparent particles to the total volume of the transparent particles and the transparent resin. It is preferable that the content of the transparent particles be decreased as the shape of the surface light emitter to be formed becomes larger.

Further, the blending amount of the transparent particles needs to be such that the f value represented by the following equation is 10 or less.

[0028]

(Equation 1) [Here, t is the thickness (μm) of the surface light emitter, R is the average particle size of the transparent particles, VA is the volume part of the transparent resin, VB is the volume part of the transparent particles, and the average particle size R is R = ( The average major axis + the average minor axis) / 2. ]

In the present invention, a composition comprising a transparent resin and transparent particles is used as a material for the light guide body, and if desired, other additives such as other heat stabilizers and light stabilizers may be added to the material.
An ultraviolet absorber, a release agent, a dye or pigment may be added in an amount range that does not impair the effects of the present invention. Further, the transparent particles may be surface-treated with a coupling agent or the like.

In the present invention, as the base material of the opaque resin composition which becomes the reflective portion, a material having excellent adhesiveness to the transparent resin which becomes the base material of the transparent resin composition of the light guide portion is selected and used. It is sufficient to use the same material,
A white pigment is kneaded with this base material to obtain an opaque resin composition. When the emission is limited to light of a specific wavelength, a pigment that sufficiently reflects light of that wavelength may be used instead of the white pigment.

The white pigment that can be used in the present invention has sufficient heat resistance and chemical resistance that can impart sufficient hiding property and reflectivity to the reflective portion and does not deteriorate during kneading with a resin. In this case, any one may be used as long as it has sufficient light resistance, and for example, an inorganic pigment such as titanium oxide, zinc white, barium sulfate, calcium carbonate or the like is preferably used. The particle size of these white pigments varies depending on the type of pigment, but is 0.1
It can be appropriately selected and used from the range of about 50 μm. These white pigments are commercially available and are easily available.

Such a white pigment varies depending on the particle size of the pigment used and the hiding power, but it is 1 to the base resin.
30% by weight, preferably 2 to 20% by weight is used. If the amount of the pigment is too large, it becomes difficult to perform the two-color molding. On the contrary, if the amount of the pigment is too small, sufficient hiding property and reflectivity cannot be obtained.

If desired, other additives such as a heat stabilizer, a light stabilizer, a fluorescent whitening agent, and a release agent may be added to the opaque resin composition in an amount range that does not impair the effects of the present invention. Is also good.

The thickness of the reflecting portion depends on the type and amount of the added pigment and cannot be generally stated, but is at least 0.5 mm.
It would be fine if more. Although the upper limit is not particularly specified, it is not preferable because the effect cannot be expected to increase even if the thickness is too large, and the thickness of the surface light emitting device itself increases, so that the upper limit may be determined according to desired conditions. For example, when titanium oxide is used as the pigment, it may be molded with a thickness of about 0.5 to 0.8 mm.

Next, a method for manufacturing the surface light emitter of the present invention will be described.

The molded article of the present invention is manufactured by injection two-color molding. The design of the mold is important in manufacturing the surface light-emitting device of the present invention in terms of the adhesiveness between the light guide portion and the reflection portion, the stability of the shape, and the like.
It is possible to control by computer until C processing, and it is possible to manufacture a die having a desired shape. In the present invention,
It is preferable to use a variable mold in which primary molding and secondary molding can be performed continuously without taking out a molded product. An example of the structure of such a mold is shown in FIGS.

FIG. 3 is a schematic cross-sectional view of a die for performing the primary side molding and each part of a molding apparatus associated therewith. Here, the light guide is molded as the primary molding.

For example, a composition pellet obtained by previously melting and mixing a thermoplastic resin as a transparent resin and a glass particle as a transparent particle is put into a hopper for molding on the primary side, melted, and injected from an injection molding gate 8 into a mold cavity. To eject. After the injection, the mold is once cooled to cure the light guide section. At this time, the insert piece 7 in the lower part of the mold is in a state of being pushed up by the supporting jig 10, and as shown in a partially enlarged view of FIG. Has a step.

In the production of pellets, it is desirable that at least the transparent resin and the glass particles are separately charged into the extruder. For example, a method in which a transparent resin is put in a hopper and glass particles are continuously charged through a vent hole in accordance with the extrusion speed, or a method in which a transparent resin and glass particles are separately continuously charged into a hopper, etc. Can be used.

When a polycarbonate resin is used as the transparent resin, the method of adding the organic phosphorus compound is arbitrary,
It is convenient to use a method in which it is mixed with the volatile resin and added.

FIG. 4 is a view for explaining the secondary molding.
(B) is a partially enlarged view. Also in the secondary molding, the resin and the white pigment are kneaded in advance to form a pellet, which is put into the secondary molding hopper and similarly injected into the cavity. At this time, the insert piece 7 is lowered and the shaft 9 is raised to expand the cavity and perform injection. Although not shown in the drawing because the cross section is schematically shown, the side surface of the light guide 2 is formed with a reflection portion, and the overhang portion 3'is filled by wraparound from the side surface. Of course, the mold is extended in the front-back direction of the drawing. Further, in the secondary molding, in order to allow the resin to wrap around, it is a preferred embodiment to enhance the fluidity by increasing the melting temperature from the primary side.

The molded product thus obtained is taken out of the mold, burrs and the like are removed, and if necessary, the surface of the light guide, which becomes the light emitting surface, is polished to a mirror surface to obtain the surface light emitter of the present invention.

In order to form a backlight unit using this surface light emitter, it is necessary to provide a light source at a position where light can be irradiated onto the light entering portion of the surface light emitter. The light source that can be used in the present invention includes a linear fluorescent tube used in a conventional backlight unit and a small chip LE.
D etc. can be used. Such a light source is arranged at a position where the light entering portion of the surface light-emitting body can be irradiated with light from the light source. In the present invention, in particular, these light sources are combined in a recess provided in the light entering portion to form a backlight. Form a unit. For example, after mounting the light source at a predetermined position on the board for supplying power to the light source by soldering or the like, a surface light emitter having a concave portion is covered at a position where the light source can be fitted. In order to fix the surface light emitter to the substrate, it is possible to bond the surface light emitter with an adhesive, or to dispose a fixing jig such as a claw on the substrate side, or conversely to fix the surface light emitter side to the substrate at the time of molding. The backlight unit is manufactured by fixing it by providing means such as nails. In the backlight unit manufactured in this way, for example, when a linear light source is used, by replacing the conventionally required lamp house with an overhang-shaped reflecting portion of the surface light emitter, It can be simplified. Also, even when using a chip-type LED, by automating the mounting of the LED on the substrate,
The production yield is improved.

[0044]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1 A small type backlight unit (43.6 × 26 × 1.8 mm) using an LED as a light source was manufactured.

Polycarbonate 10 derived from 2,2-bis (4-hydroxyphenyl) propane as transparent resin
To 0.1 parts by weight of trimethyl phosphate per 0 parts by weight of polycarbonate powder having a refractive index of 1.58, 0.001 parts by weight of a refractive index of 1.56 and an average particle size of 30
Glass beads of μm were melt-kneaded to produce a pellet for a light guide section.

Titanium oxide (average particle size 21 μm, Ishihara Sangyo Co., Ltd.) as a white pigment on the same polycarbonate resin
12 wt% of the product name "CR60") was melt-kneaded to produce pellets for the reflection part.

A two-color injection molding machine "All Rounder 320M" manufactured by Arburg Co. having a mold as shown in FIGS.
The light guide section pellets were put in the hopper of the primary side injection unit, and the reflection section pellets were put in the hopper of the secondary side injection unit to perform two-color injection molding.

The conditions of injection molding are as follows. Primary side molding Injection pressure 800 bar Mold temperature 100 ° C Holding time 5 seconds Secondary side molding Injection pressure 1000 bar Mold temperature 100 ° C Holding time 5 seconds

The reflecting portions 3 on the back and side surfaces were formed to have a thickness of 0.6 mm, and the overhang portion 3'was formed to have a thickness of 0.5 mm. At the time of molding, two holes for mounting the LEDs were simultaneously provided on both short sides of the surface light emitter.

The thus-obtained surface light-emitting body was fixed on a substrate on which chip-type LEDs were automatically mounted by using an adhesive to complete a backlight unit. This backlight unit was able to uniformly radiate the light from the LED from the light emitting surface.

Example 2 In the same manner as in Example 1, a backlight unit used for a liquid crystal display such as a personal computer having a size of 256 × 194.75 × 5 mm was produced. Since a 2 mmφ L-shaped fluorescent tube is used as a light source, a groove of 4 × 4 mm is provided on two sides on the surface light emitter side. The obtained backlight unit was able to obtain a sufficient amount of light emission for liquid crystal display applications.

[0053]

As described above, according to the present invention, since the light guide portion and the reflection portion can be integrally formed by the two-color molding, dust or the like is not caught between the light guide portion and the reflection portion. A high-quality surface light emitter can be obtained. Further, since the molding is performed in the mold, no expensive auxiliary equipment such as a clean room is required, and the process is simplified, so that the manufacturing cost can be reduced.

[Brief description of the drawings]

1A and 1B are diagrams illustrating an embodiment of a surface light emitter according to the present invention, in which FIG. 1A is a schematic cross-sectional view and FIG.

FIG. 2 is a diagram illustrating another example of the overhang shape in the surface light emitter of the present invention.

FIG. 3 shows primary side molding in a manufacturing process of a surface light emitter of the present invention, (a) is a schematic sectional view of a mold,
(B) is a partially enlarged view thereof.

FIG. 4 shows secondary side molding in the manufacturing process of the surface light emitter of the present invention, (a) is a schematic sectional view of a mold,
(B) is a partially enlarged view thereof.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Surface light emitter 2 Light guide part 3 Reflection part 3'Overhang-like reflection part 4 Light entrance part 5 Transparent particles 6 Recesses 7 Mold insert 8 Injection molding gate 9 Shaft 10 Support jig

Claims (6)

[Claims] 1. A light guide formed of a transparent resin composition containing a transparent resin as a base material and uniformly dispersed transparent particles, and an opaque resin composition on a side surface of the light guide and a rear surface of a light emitting surface. Is a surface-emitting body formed by dichroic molding, and a light-entering section is formed on at least one end of the back surface of the surface-emitting body without forming a reflecting section. A surface light emitter, wherein a reflecting portion is formed in an overhang shape from a side surface on the light guide surface side corresponding to the light portion. 2. The surface-emitting body according to claim 1, wherein the light-entering portion has a recess for mounting a light source. 3. The transparent particles are those having a refractive index of 0.005 to 0.2, which is different from the refractive index of the transparent resin of the base material, and having an average major axis of 80 μm or less and an average minor axis of 1 μm or more. The surface light emitter according to claim 1, wherein the surface light emitter is present. 4. The surface light emitter according to claim 1, wherein the opaque resin composition is a resin of a base material to which a white pigment is added. 5. The surface light emitting device according to claim 4, wherein the transparent resin as a base material of the light guide and the resin as a base material of the reflecting portion are the same resin. 6. A backlight unit comprising the surface light emitter according to claim 1, and a light source arranged at a position where light can be emitted to a light entering portion of the surface light emitting portion.