JP2012015104A - Surface light-emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light-emitting device in which the direction of light can be changed greatly while suppressing the loss, and strength deterioration of a light guide does not occur.SOLUTION: The surface light-emitting device 1A is provided which is equipped with a light source 2 and a plate shaped light guide body 3 into which the light from the light source 2 is introduced. The light guide body 3 has a main light guide part 4 and one or more branched light guide parts 5 which are branched from the main light guide part 4 at a branching part 4a of the main light guide part 4. In the branching part 4a, a direction conversion part 6 which directs light in the main light guide part toward the branched light guide part 5 is formed. The direction conversion part 6 has a light guide passage structure 10 in which a plurality of direction conversion slits 7 are prepared that are formed mutually in parallel with a spacing as clad parts 8 and the spacings between mutually neighboring direction conversion slits 7 are prepared as the core parts 9.

Description

  The present invention relates to a planar light emitting device suitably used for a mobile phone, a personal digital assistant (PDA), an operation button of a personal computer, a key button, and the like.

Conventionally, as a planar light emitting device, there is one using a plate-shaped (or sheet-shaped) light guide (see Patent Documents 1 to 3).
FIG. 22 shows an illuminating light guide disclosed in Patent Document 1, and this illuminating light guide 21 connects the illuminating portions 22a to 22d extending in parallel with each other between these end portions. The light guide path part 23, the spectroscopic parts 25a to 25d formed in the light guide path part 23, and the LED 26 are provided.
When light from the LED 26 is incident on the light guide section 23 from the light incident section 24, the light is reflected by the spectroscopic sections 25a to 25d and guided to the illumination sections 22a to 22d, respectively.

  FIG. 23 is a surface-emitting illuminating device disclosed in Patent Document 3. This surface-emitting illuminating device 31 includes a light guide plate 32 and a light source 33 provided on the light guide plate 32, and emits light from the light source 33. A linear slit 35 is formed to reflect on the display area 34 side.

Japanese Utility Model Publication No. 6-035203 Utility Model Registration No. 2527183 Japanese Patent No. 3028465

Since the light guide 21 for illumination shown in FIG. 22 has a structure in which the amount of light branched to each of the illumination parts 22a to 22d is determined by the shape of the light guide part 23 (the spectroscopic parts 25a to 25d formed in the light guide part 23). The shape is limited by the branching ratio. On the contrary, when there is a restriction on the outer shape, the branching ratio is limited.
In addition, in order to realize a predetermined branching ratio, a portion where the width of the light guide path portion 23 is extremely narrow is required, so that the durability of the light guide 21 is lowered or the spectroscopic portions 25a to 25d are secured large. In some cases, the light guide 21 has a structure in which stress is easily concentrated and is easily damaged. In particular, damage was likely to occur when the molded light guide 21 was taken out of the mold.

In the light guide having the above structure, it is difficult to branch light in a direction that greatly changes the light guide direction, for example, includes a component in the return direction.
For example, as shown in FIG. 24, when the angle θ of the branch light guide unit 5 with respect to the main light unit 4 that propagates the light from the light source 2 is smaller than 90 degrees, the light may be directed to the branch light guide unit 5. As shown in FIG. 25, the amount of light obtained by the branch light guide 5 is reduced.

In addition, according to the structure shown in FIG. 23, the direction of light can be changed by reflecting light at the slit. However, if the required change in angle is large, the reflectance at the slit is reduced, so that reflected light is reflected. The amount of light decreases.
For example, as shown in FIG. 26, when the linear slit 41 is formed at the branch portion of the branch light guide 5 with respect to the main light portion 4, the smaller the angle θ, the smaller the incident angle of the light L1 with respect to the slit 41. The amount of transmitted light L2 increases, and as a result, the amount of branched light that is reflected light L3 decreases. R1 in FIG. 26 is an example of an incident angle range in which total reflection does not occur at the slit 41.

Moreover, not only in the case of illuminating not only the light guide structure extending in a predetermined direction (see FIG. 24) but also a planar light guide having no such light guide structure, the cost and the number of parts can be reduced. In consideration, the number of light sources (LEDs) that supply light to the light guide body may be reduced, and a spot that becomes a blind spot of light distribution occurs, and the brightness of the spot may be lowered. This tendency is remarkable in a light guide having a wide illumination area such as a light guide for a qwerty keyboard.
In the key switch with illumination function, there is a demand to make the luminance as uniform as possible. Therefore, when such a low-luminance light emitting area occurs, it is necessary to reduce the luminance of other areas, and the entire key switch As a result, there is a problem that the light utilization efficiency is lowered.

  The present invention has been made in view of the above circumstances, and provides a planar light emitting device that can greatly change the direction of light while suppressing loss and that does not cause a decrease in strength of the light guide. With the goal.

The planar light-emitting device of the present invention includes a light source and a sheet-like or plate-like light guide into which light from the light source is introduced. The light guide includes a leading light unit and a leading light unit. One or more branch light guides branching in a direction intersecting the main light part at the branch part, and the direction change part for directing light in the main light part toward the branch light guide part in the branch part The direction changing portion is a planar shape having a light guide structure in which a plurality of direction changing slits formed in parallel with each other at intervals are used as a cladding portion, and a core portion is provided between the adjacent direction changing slits. A light emitting device.
It is preferable that the direction change slit has a curved portion that extends from the main light portion to the branch light guide portion.
It is preferable that the direction changing slit has a straight portion extending along the branch light guide from the end of the curved portion on the side of the branch light guide.
The direction in which the branched light guide part is formed with respect to the main light part may be a direction including a return direction component with respect to the light guide direction in the main light part.
A clad agent having a lower refractive index than that of the core portion can be introduced on the side surface facing the core portion in the direction changing slit.
The clad agent is preferably filled in the direction change slit, and a black paint layer is preferably formed on at least one surface of the clad agent.
On at least one surface of the light guide, a light extraction portion for leaking a part of the light in the light guide to the outside can be formed.
The present invention includes a light source and a sheet-like or plate-like light guide into which light from the light source is introduced, and the light guide includes a direction conversion unit that converts the direction of light from the light source. The direction changer is a planar light emitting device having a light guide structure in which a plurality of direction change slits formed in parallel at intervals are used as a clad part and a core part is provided between adjacent direction change slits. Providing equipment.

According to the present invention, since the direction changing part having the light guide path structure composed of a plurality of direction changing slits is formed, light is introduced into the core part between the direction changing slits and guided to the branch light guiding part while being reflected on the side surface. Thus, the direction of light can be greatly changed while suppressing loss.
For this reason, light can be efficiently branched irrespective of the direction of the branch light guide part with respect to the main light part.
For example, even when the formation direction of the branch light guide part is a direction including a return direction component with respect to the light guide direction, the branched light quantity can be increased.
Moreover, since the direction change part is comprised by the several direction change slit parallel, it can restrict | limit so that the direction of light may not remove | deviate greatly from the target direction.
Therefore, the settable range of the light branching direction and the branching ratio can be widened, and the degree of freedom in design can be increased.
Furthermore, since the direction change part is comprised by the narrow direction change slit, the part where intensity | strength becomes low is not formed in a light guide, but durability of a light guide can be improved.

It is a top view which shows 1st Embodiment of the planar light-emitting device of this invention. It is the top view to which the principal part of the planar light-emitting device of 1st Embodiment was expanded. It is sectional drawing of the principal part of the planar light-emitting device of 1st Embodiment. It is sectional drawing of the principal part of the modification of a planar light-emitting device. It is sectional drawing of the principal part of the modification of a planar light-emitting device. It is a top view which shows 2nd Embodiment of the planar light-emitting device of this invention. It is a graph which shows a test result. It is a graph which shows a test result. It is a top view which shows the planar light-emitting device used in the Example. It is a top view which shows the planar light-emitting device used in the Example. 1 is a structural diagram schematically showing a key switch module using an example of a planar light emitting device of the present invention. It is a top view which shows a part of example of a planar light-emitting device. It is a top view which shows the luminance distribution of the planar light-emitting device shown to a previous figure. It is a top view which shows a part of example of the planar light-emitting device used in the Example. It is a top view which shows the luminance distribution of the planar light-emitting device shown to a previous figure. It is a top view which shows a part of example of a planar light-emitting device. It is a top view which shows the luminance distribution of the planar light-emitting device shown to a previous figure. It is a graph which shows a test result. It is a schematic diagram which shows the key switch module using the other example of the planar light-emitting device of this invention. It is a schematic diagram which shows the key switch module using the other example of the planar light-emitting device of this invention. It is a schematic diagram which shows the key switch module using the other example of the planar light-emitting device of this invention. It is a top view which shows the example of the conventional planar light-emitting device. It is a top view which shows the other example of the conventional planar light-emitting device. It is explanatory drawing explaining the structure of the light guide which has a branch light guide part. It is a graph which shows a test result. It is explanatory drawing explaining the structure of the light guide in which the slit was formed.

Hereinafter, embodiments of the planar light emitting device of the present invention will be described.
FIG. 1 is a plan view (top view) of a planar light emitting device 1A that is a first embodiment of the planar light emitting device of the present invention, and FIG. 2 is an enlarged view of a main part of the planar light emitting device 1A. These are sectional drawings of the principal part of planar light emitting device 1A.

As shown in FIG. 1, the planar light emitting device 1 </ b> A includes a light source 2 and a light guide 3 into which light from the light source 2 is introduced.
The light guide 3 can be formed in a plate shape (or a sheet shape).
The light guide 3 is made of a transparent material such as a light transmissive resin or glass.
As the light transmissive resin, urethane resin, acrylic resin, polycarbonate resin, silicone resin, polystyrene resin, polyimide resin, polymethyl methacrylate (PMMA) elastomer, urethane acrylate, or the like can be used.
The thickness of the light guide 3 can be 0.1-10 mm (preferably 0.1-1 mm), for example.

The light guide 3 includes a main light unit 4 and a branch light guide unit 5 that branches off at a branch unit 4 a of the main light unit 4.
The main light guide 4 is preferably formed in a straight line. In FIG. 1, the main light portion 4 has a linear shape extending in the vertical direction. It is preferable that the main light guide 4 has a constant width.

The branch light guide unit 5 is formed in a direction intersecting the main light unit 4. The branch light guide 5 is preferably formed in a straight line.
The angle θ of the branched light guide 5 with respect to the main light guide 4 is not particularly limited, and can be set in a range of more than 0 degrees and less than 180 degrees.
The formation direction of the branched light guide 5 can be a direction including a return direction component with respect to the light traveling direction in the main light unit 4 (hereinafter, the light guide direction X1).

The return direction is a direction opposite to the light guide direction X1, and the “direction including the return direction component with respect to the light guide direction X1” is a direction in which the angle θ is less than 90 degrees. In the illustrated example, the angle θ is smaller than 90 degrees.
In addition, the main light part 4 and the branch light guide part 5 may be formed not only in linear form but in curvilinear form.
The light guide direction X1 in the main light guide unit 4 coincides with the extending direction of the main light unit 4.

As the light source 2, a light emitting diode (hereinafter referred to as LED) (light emitting element) can be used.
The light source 2 can be provided at one end portion (base end portion 4 b) in the extending direction of the main light portion 4.
The light source 2 is installed so that light can be incident on the light guide 3 from the end face of the base end portion 4b.
In addition, the light emitting element used as the light source 2 is not limited to the LED but may be a cold cathode tube.

On the upper surface side of the branch part 4a, a direction changing part 6 for directing the light in the main light part 4 toward the branch light guide part 5 is formed.
The direction changing section 6 is composed of a plurality of direction changing slits 7 formed in parallel at intervals. The direction changing unit 6 includes a light guide structure 10 having the direction changing slit 7 as a cladding portion 8 and a core portion 9 between adjacent direction changing slits 7 (a portion between adjacent direction changing slits 7).
In the illustrated example, five direction changing slits 7 are formed. These five direction change slits 7 are respectively indicated by reference numerals 7A to 7E from the inner peripheral side in FIG. 2, and the core portion 9 is indicated by reference numerals 9A to 9D from the inner peripheral side, respectively.

As shown in FIG. 3, the direction changing slit 7 is for directing light in the main light portion 4 toward the branch light guide portion 5, and is a groove having a predetermined depth formed on the upper surface 3 a of the light guide 3. is there.
The direction changing slit 7 in this example has a rectangular cross section. The side surface 7 a facing the core portion 9 of the direction changing slit 7 is preferably perpendicular to the upper surface 3 a of the light guide 3. The side surface 7a serves as an interface between the air in the direction changing slit 7 and the light guide 3 having a higher refractive index.
In addition, the cross-sectional shape of the direction conversion slit 7 is not particularly limited, and may be, for example, a V-shaped cross section, a U-shaped cross section, or the like.

As shown in FIG. 2, the direction changing slit 7 includes a straight portion 11 along the light guide direction X <b> 1, a curved portion 12 extending from the end portion 11 a of the straight portion 11 in the light guide direction X <b> 1, and an extension of the curved portion 12. And a straight line portion 13 extending along the branch light guide 5 from the extended end 12b.
The straight line portions 11 are formed at intervals in the width direction of the main light portion 4 (direction orthogonal to the light guide direction X1). In the illustrated example, the five linear portions 11 are formed in parallel with each other at regular intervals in the width direction.

The bending portion 12 can have an arc shape with a central angle θ. The curved portion 12 is preferably designed so that light propagates while being totally reflected by the side surface 12c in the core portion 9 described later.
In the illustrated example, the five curved portions 12 have a concentric arc shape, and are formed at intervals in the radial direction of the arc. The interval between the adjacent curved portions 12 can be made substantially constant in the length direction.
Note that the bending portion 12 may have another shape, for example, an elliptical arc shape, a parabolic shape, or the like as long as light can propagate efficiently in the core portion 9.

The straight line portions 13 are formed at intervals in the width direction of the branch light guide portion 5. In the illustrated example, the five linear portions 13 are formed in parallel with each other at regular intervals in the width direction.
In the illustrated example, the forming directions of the straight portions 11 and 13 are the base end portion 12a (end portion on the main light portion 4 side) and the extended end portion 12b (end portion on the branch light guide portion 5 side) of the bending portion 12, respectively. It corresponds to the tangential direction at.

As shown in FIG. 2, the light L <b> 1 in the main light portion 4 enters between the direction changing slits 7 (core portion 9) and is reflected (preferably by the side surface 7 a (interface between the core portion 9 and the clad portion 8)). Is totally reflected), reaches the straight portion 13 through the straight portion 11 and the curved portion 12, and is introduced into the branch light guide portion 5 as light L2.
For example, the light L1 travels in the core portion 9 while being repeatedly reflected by the one side surface 7a and the other side surface 7a of the core portion 9. In the illustrated example, the light L1 is incident on the core portion 9C, reflected on the side surface 7a of the direction changing slit 7D (side surface 12c of the bending portion 12), and then again the side surface 7a of the direction changing slit 7D (side surface 12c of the bending portion 12). ) And then reflected on the side surface 7a of the direction changing slit 7C (straight line portion 13) and introduced into the branched light guide portion 5 as light L2.

Since the bending portion 12 has a curved shape (arc shape), the incident angle of light with respect to the direction changing slit 7 can be increased, and total reflection tends to occur.
Since the straight line portion 13 is formed along the branch light guide portion 5, the direction of the light L <b> 2 that has passed through the curved portion 12 can be limited to be close to the direction of the branch light guide portion 5.

Since a plurality of direction conversion slits 7 are formed, even if a part of the light L1 passes through one direction conversion slit 7 (7D), the light L3 (transmitted light) is transmitted to another direction conversion slit 7 (7E). ) Part of the light is reflected (light L4) and travels toward the branch light guide 5 (see FIG. 2).
For this reason, the light L1 in the main light part 4 is introduced into the branch light guide part 5 with high efficiency (light L5). In addition, L5 is the light introduced into the branch light guide 5, and includes light L2 and L4.
The light L6 that has passed through the direction changing slit 7B travels directly through the main light portion 4 in the light guide direction X1.

The direction changing slit 7 in the illustrated example is a groove formed on the upper surface 3a of the light guide 3 (see FIG. 3), and penetrates from the upper surface 3a to the lower surface 3b of the light guide 3 as shown in FIG. It may be a through hole.
The groove-type direction changing slit 7 is advantageous in the shape stability of the light guide 3 and has an advantage that no leakage of a clad agent (described later) occurs.
On the other hand, the through-hole type direction changing slit 7 has an advantage that it is easy to prevent light from traveling in a direction other than the intended direction.
The form (groove type and through-hole type) of the direction changing slit 7 can be properly used according to the purpose.

  The direction changing slit 7 can be formed by a known method, for example, laser processing. It can also be formed by punching with a big die or the like, or molding by pressing an indenter (so-called imprint). Moreover, the shaping | molding using the type | mold which formed the convex part of the shape according to the direction change slit 7 in the inner surface is also possible.

As shown in FIG. 5, the clad agent 14 can be introduced into the direction changing slit 7.
Examples of the clad agent 14 include materials having a lower refractive index than the material of the core portion 9 (the constituent material of the light guide 3), such as a fluororesin and a silicon resin, and a fluororesin is particularly preferable.
The clad agent 14 is introduced into at least a partial region of the side surface 7 a of the direction changing slit 7. The clad agent 14 may be applied to the side surface 7a to form a layer on the side surface 7a, or may fill the entire direction changing slit 7. In FIG. 5, the clad agent 14 is filled in the entire direction changing slit 7.

A black paint layer 15 made of a black paint capable of absorbing visible light can be formed on the upper surface 14 a (one face) of the clad agent 14.
By forming the black paint layer 15, it is possible to prevent light (visible light) that has entered the direction changing slit 7 from leaking outside from the direction changing slit 7.
When the direction changing slit 7 is a through-hole type (see FIG. 4), the black paint layer 15 may be formed on both upper and lower surfaces of the clad agent 14.

At any position of the light guide 3, for example, the branched light guide 5, a light extraction part (not shown) for leaking a part of the light in the light guide 3 to the outside can be formed.
The light extraction part may be a dot-like print pattern formed on the surface of the light guide 3 or an uneven part formed by laser processing.
Due to light leakage at the light extraction section, the operation buttons and key buttons of the device can be displayed brightly.

In the planar light emitting device 1 </ b> A, since the direction changing part 6 having the light guide structure 10 including the plurality of direction changing slits 7 is formed in the branching part 4 a, light is introduced into the core part 9 between the direction changing slits 7. Then, by guiding the light to the branch light guide unit 5 while reflecting the light to the side surface 7a, the direction of light can be greatly changed while suppressing loss.
For this reason, light can be efficiently branched regardless of the direction of the branch light guide part 5 with respect to the main light part 4.
For example, even when the formation direction of the branched light guide unit 5 is a direction including a return direction component with respect to the light guide direction X1 (that is, a direction in which the angle θ with respect to the main light guide unit 4 is less than 90 degrees), the amount of branched light is increased. be able to.
Moreover, since the direction change part 6 is comprised by the several direction change slit 7 paralleled, it can restrict | limit so that the direction of light may not remove | deviate largely from the target direction.
Therefore, the settable range of the light branching direction and the branching ratio can be widened, and the degree of freedom in design can be increased.

  Moreover, since the direction change part 6 is comprised by the narrow direction change slit 7, the part where intensity | strength becomes low is not formed in the light guide 3, but durability of the light guide 3 can be improved. it can.

Next, a second embodiment of the planar light emitting device of the present invention will be described.
FIG. 6 is a plan view (top view) of the planar light emitting device 1B of the second embodiment. In the following description, the same components as those described above may be denoted by the same reference numerals and description thereof may be omitted.
In the planar light emitting device 1 </ b> B, the light guide 3 includes the main light unit 4, the first branch light guide unit 5 branched by the first branch unit 4 a of the main light unit 4, and the first end of the branch light guide unit 5. It has the 2nd and 3rd branch light guide parts 16 and 17 branched by the 2 branch part 5a.

  The second branch light guide unit 16 extends from the second branch unit 5a in the light guide direction X1, and the third branch light guide unit 17 extends from the second branch unit 5a in the direction opposite to the light guide direction X1. ing.

The second branching unit 5 a includes a second direction conversion unit 18 that directs a part of the light in the branch light guide unit 5 to the second branch light guide unit 16, and the other part of the light in the branch light guide unit 5. A third direction conversion unit 19 facing the three-branch light guide unit 17 is formed.
The second and third direction changing portions 18 and 19 have a configuration in which a plurality of direction changing slits 7 are formed in parallel, similarly to the direction changing portion 6. In the illustrated example, the second direction conversion unit 18 includes three direction conversion slits 7, and the third direction conversion unit 19 includes two direction conversion slits 7.
The light L5 in the branch light guide 5 is branched into light L7 and L8 by the second and third direction converters 18 and 19.

Even in the planar light emitting device 1B, the direction changing units 6, 18, and 19 can greatly change the direction of light while suppressing loss.
Therefore, light can be efficiently branched regardless of the direction in which the branch light guides 5, 16, 17 are formed.

In the planar light emitting device 1B of the second embodiment, the two branch light guides 16 and 17 are formed in the second branch part 5a with respect to the branch light guide part 5, but the branch in one branch part is formed. The number of light guides (number of branches) is not particularly limited, and may be 1 or any number of 2 or more.
For example, it may be a bifurcated shape, a trifurcated shape, a four-forked shape, a five-forked shape, or a larger number of branches.

FIG. 11 is a structural diagram schematically showing a key switch module (key switch module with illumination function) using the planar light emitting device 1C which is the third embodiment of the planar light emitting device of the present invention.
The key switch module 80A includes a sheet switch module 50 and a key mat 60 provided on the upper surface side (the upper surface 3a side of the light guide 3).
The sheet switch module 50 includes a planar light emitting device 1C and a sheet switch 70 provided on the lower surface side of the planar light emitting device 1C.
The sheet switch 70 includes a plurality of central contact portions 72, an annular contact portion 73 that surrounds each central contact portion 72, and a dome-shaped metal plate that covers the contact portions 72 and 73 on the upper surface 71 a (one surface) of the substrate 71. 74 (movable contact portion).

As the board 71, a printed wiring board such as an FPC (Flexible Printed Circuit) or a PCB (Printed Circuit Board) can be used.
The center part of the metal plate 74 is deformed downward by pressing by the operator and comes into contact with the center contact part 72, so that the center contact part 72 and the annular contact part 73 can be conducted. When the metal plate 74 is released, the metal plate 74 is restored to its original shape by elasticity, and the central contact portion 72 and the annular contact portion 73 are in a non-conductive state.
The central contact portion 72, the annular contact portion 73 surrounding the central contact portion 72, and the metal plate 74 constitute a pressure-sensitive switch element 75. Reference numeral 76 denotes a sheet body that covers the switch element 75.
An operation key 62 is formed at a predetermined position of the mat base 61 of the key mat 60.

  The planar light emitting device 1 </ b> C includes a light source 2 and a light guide 3 into which light from the light source 2 is introduced. The operation key 62 can be displayed brightly by forming the above-described light extraction portion 63 on the upper surface or the lower surface of any position of the light guide 3, for example, the position corresponding to the operation key 62 of the key mat 60.

  The light guide 3 is formed with a direction changing portion 6 including a plurality of direction changing slits 7. Although only one direction changing slit 7 is shown in FIG. 11, the direction changing portion 6 is composed of a plurality of direction changing slits 7 formed in parallel at intervals. The direction changing slit 7 in this example penetrates the light guide 3 in the thickness direction.

FIG. 12 is a plan view showing a part of the planar light emitting device 1C shown in FIG.
In the planar light emitting device 1C, the planar shape of the light guide 3 is not particularly limited, and a light guide structure (leading light portion, branched light guide) extending in a predetermined direction as in the planar light emitting device 1A shown in FIG. Part) is not necessary. The planar shape of the light guide 3 may be a polygon such as a rectangle, a circle, an indeterminate shape, or any other shape.
The light source 2 (2A) is installed at the center of the upper edge 3c of the light guide 3, and the light sources 2 (2B1, 2B2) are installed at the left and right of the lower edge 3d at intervals. Yes.

As shown in FIG. 12A, in the planar light emitting device 1 </ b> C, two direction changing portions 6 (6 </ b> A, 6 </ b> B) are formed in the vicinity of the lower edge portion 3 d of the light guide 3 and spaced from each other. ing.
As shown in FIG. 12B, the first direction changing section 6A includes a plurality (three in the illustrated example) of direction changing slits 7 arranged in parallel. 6 A of 1st direction change parts have the light guide structure 10 which makes the direction change slit 7 the clad part 8, and makes the core part 9 between adjacent direction change slits 7 (part between adjacent direction change slits 7). Since the core 9 has a higher refractive index than the surroundings (inside the slit 7 (air or the like) or outside air), it becomes a light guide.

Each direction conversion slit 7 has a straight portion 11A whose end portion faces the light source 2B1, an arc-shaped curved portion 12A, and a straight portion 13A whose end portion faces the right direction. The position of the first direction conversion unit 6A in the left-right direction is slightly leftward from the center.
A part of the light from the light source 2B1 is introduced between the direction conversion slits 7 of the first direction conversion unit 6A. The portion between the direction changing slits 7 is a core portion 9 having a higher refractive index than the inside of the slit 7 (air or the like), and the light is changed in the right direction while being reflected by the side surfaces of the slit 7 and the upper and lower surfaces of the light guide 3. And led to the area A1.
In addition, although the brightness improvement effect to some extent is acquired even if one direction change slit 7 is taken into consideration, the light guide efficiency, the deformation prevention at the time of manufacture, etc. are considered to be 2 or more.

As shown in FIG. 12 (c), the second direction changing section 6B is composed of a plurality (five in the illustrated example) of direction changing slits 7 arranged in parallel. The second direction conversion section 6B has a light guide structure 10 having the direction conversion slit 7 as a cladding section 8 and a core section 9 between adjacent direction conversion slits 7 (part between adjacent direction conversion slits 7).
Each direction conversion slit 7 has an arcuate curved portion 12B having one end portion facing upward (in the direction of the light source 2A) and the other end portion facing leftward. The position in the left-right direction of the second direction conversion unit 6B is approximately the center position.
A part of the light from the light source 2A undergoes a direction change to the left through the direction change slits 7 (core portion 9) of the second direction change portion 6B and is guided to the region A2.

FIG. 16 is a plan view illustrating a part of the planar light emitting device 91 in which the direction changing unit 6 is not formed. When the direction changing unit 6 is not provided as in the planar light emitting device 91, the areas A1, A2, and A3 near the lower edge 3d of the light guide 3 are likely to have low luminance, as shown in FIG. .
On the other hand, as shown in FIG. 13, in the planar light emitting device 1 </ b> C, the light from the light source 2 </ b> B <b> 1 is guided to the area A <b> 1 by the first direction conversion unit 6 </ b> A and the light from the light source 2 </ b> A is transmitted by the second direction conversion unit 6 </ b> B. Since it can be led to the area A2, the brightness of the areas A1 and A2 that tend to be low brightness can be increased.

FIG. 14 is a plan view showing a part of a planar light emitting device 1D which is the fourth embodiment of the planar light emitting device of the present invention.
As illustrated in FIG. 14A, the planar light emitting device 1 </ b> D is different from the planar light emitting device 1 </ b> C illustrated in FIG. 12 in that the second direction conversion unit 6 </ b> C is formed in the light guide 3.
As shown in FIG. 14B, the second direction conversion portion 6C includes direction conversion slits 7F to 7M.
Each of the direction conversion slits 7F, 7G, and 7H has arcuate curved portions 12C1, 12C2, and 12C3 having one end portion facing upward (in the direction of the light source 2A) and the other end portion facing left.
The direction conversion slit 7I has an arcuate curved portion 12C4 whose one end directed upward (in the direction of the light source 2A) is common to the direction conversion slit 7H and whose other end is directed rightward.
The direction conversion slits 7J and 7K respectively have arc-shaped curved portions 12C5 and 12C6 having one end portion facing upward (in the direction of the light source 2A) and the other end portion facing left.
The direction changing slits 7L and 7M are adjacent to the lower sides of the direction changing slits 7H and 7I, respectively, and have arcuate curved portions 12C7 and 12C8, respectively.
Since the second direction conversion unit 6C includes the direction conversion slits 7I, 7J, 7K, and 7M having curved portions that are curved to the right from one end to the other end, a part of the light from the light source 2A is directed to the right. Can also lead.

  As shown in FIG. 15, in the planar light emitting device 1D, the first direction conversion unit 6A guides the light from the light source 2B1 to the region A1, and the second direction conversion unit 6C guides the light from the light source 2A to the region A2 and the region. Since it can guide to A3, the luminance of the regions A1 to A3 that tend to be low luminance can be increased.

  In a key switch module having a wide illumination area such as a light guide for a qwerty type keyboard, a low luminance area is likely to be generated due to the area of the illumination area. However, the planar light emitting devices 1C and 1D have a low luminance area. Since it can be prevented from occurring, it is particularly useful for a key switch module having a wide illumination area.

In the key switch module 80A shown in FIG. 11, the direction changing slit 7 is formed so as to penetrate the light guide 3. However, as shown in FIGS. 19 to 21, the form of the direction changing slit is not limited to this. The groove shape formed in one or both of the upper surface 3a and the lower surface 3b of the light guide 3 may be used.
The key switch module 80B shown in FIG. 19 is different from the key switch module 80A shown in FIG. 11 in that the direction changing portion 86B is composed of a groove-like direction changing slit 87B formed on the upper surface 3a of the light guide 3.
In the key switch module 80 </ b> C illustrated in FIG. 20, the direction conversion unit 86 </ b> C includes a groove-shaped direction conversion slit 87 </ b> C formed on the lower surface 3 b of the light guide 3.
In the key switch module 80D shown in FIG. 21, the direction changing portion 86D includes groove-shaped direction changing slits 87D1 and 87D2 formed on both the upper surface 3a and the lower surface 3b of the light guide 3, respectively.

In the key switch module 80 </ b> A shown in FIG. 11, since the direction changing slit 7 is formed through the light guide 3, it is possible to reflect light over the entire thickness direction of the light guide 3. Excellent in terms of light reflection characteristics. Therefore, light can be directed in a predetermined direction with high efficiency.
In the key switch modules 80B and 80C shown in FIG. 19 and FIG. 20, since the groove-shaped direction changing slit is formed on the upper surface 3a or the lower surface 3b of the light guide 3, it is easier to process than the penetrating structure. Become. For example, when the direction changing slit is formed by laser processing, processing can be performed with low output. In addition, the light guide 3 is unlikely to turn up as compared with the case where the direction changing slit has a penetrating structure.
In the key switch module 80D shown in FIG. 21, since groove-shaped direction changing slits are formed on both the upper surface 3a and the lower surface 3b of the light guide 3, light is transmitted over the entire thickness direction of the light guide 3. Since it can be reflected, it is excellent in terms of light reflection characteristics.
Further, since the direction changing slit can be formed by low-power laser processing, processing is easy. In addition, the light guide 3 is unlikely to turn up as compared with the case where the direction changing slit has a penetrating structure.

Example 1
In the planar light emitting device 1A shown in FIG. 1, the ratio of the light L5 introduced into the branch light guide 5 to the light L1 introduced from the light source 2 into the main light 4 was measured.
The thickness of the light guide 3 was 0.2 mm, and the widths of the main light guide 4 and the branch light guide 5 were 10 mm.
The radius of the arcuate curved portion 12 of the outermost direction change slit 7 (7E) was 8 mm, the width of the direction change slit 7 was 0.3 mm, and the pitch of the direction change slit 7 was 1.5 mm.
A sheet material made of acrylic resin having a refractive index of 1.49 was used for the light guide 3, and processing of the entire outer shape and processing of the direction changing slit 7 were performed by laser processing.
The angle θ of the branched light guide 5 with respect to the main light guide 4 is 45 to 90 degrees. The results are shown in FIG.

(Example 2)
A planar light emitting device 1A similar to that of Example 1 was prepared and the same measurement was performed except that the slits 7B and 7D among the five direction conversion slits 7A to 7E were not formed. The results are shown in FIG.

(Example 3)
A planar light emitting device 1A similar to that of Example 1 was prepared and the same measurement was performed except that the slits 7D and 7E were not formed among the five direction conversion slits 7A to 7E. The results are shown in FIG.

(Comparative Example 1)
A planar light emitting device having the same configuration as that of Example 1 except that the direction changing portion 6 was not formed was manufactured, and the same measurement was performed.
The results are shown in FIG.

  From FIG. 7, in Comparative Example 1 without the direction changing unit 6, when the formation angle θ of the branch light guide unit 5 is small, the arrival rate of light to the branch light guide unit 5 becomes very low, whereas the direction change unit In Examples 1 to 3 where 6 is provided, it can be seen that the light arrival rate can be significantly increased (for example, about 10 to 20 times) compared to Comparative Example 1.

Example 4
In the planar light emitting device 1A shown in FIG. 1, the amount of transmitted light (the amount of light L6 in FIG. 1) with respect to the total length of the direction changing slit 7 (the length in the direction orthogonal to the light guide direction X1) was examined. The results are shown in FIG.
FIG. 8 shows that the amount of transmitted light can be reduced as the total length in the width direction of the main light portion 4 of the direction changing slit 7 increases.
From this result, it can be seen that the branching ratio can be adjusted by increasing or decreasing the number of direction changing slits 7 and adjusting the shape of the bending portion 12.

(Example 5)
In the planar light emitting device 1A shown in FIG. 9, the amount of transmitted light (light L6) and the amount of branched light (light L5) were measured.
The thickness of the light guide 3 was 0.2 mm, and the widths of the main light guide 4 and the branch light guide 5 were 10 mm.
The angle θ of the branched light guide 5 with respect to the main light guide 4 is 60 degrees.
The direction changing slit 7 includes an arc-shaped curved portion 12 and a straight portion 13, and the curved portion 12 has an arc shape with a central angle of about 90 degrees.
The radius of the arcuate curved portion 12 of the outermost direction change slit 7 (7E) was 8 mm, the width of the direction change slit 7 was 0.3 mm, and the pitch of the direction change slit 7 was 1.5 mm.
A sheet material made of acrylic resin having a refractive index of 1.49 was used for the light guide 3, and processing of the entire outer shape and processing of the direction changing slit 7 were performed by laser processing.
An LED was used as the light source 2 to emit light with a luminous flux of 0.5 (lm). The clearance between the light source 2 and the base end portion 4b of the main light portion 4 was 0.3 mm.
The results are shown in Table 1.

(Comparative Example 2)
A planar light emitting device having the same configuration as that of Example 1 except that the direction changing portion 6 was not formed was manufactured, and the same measurement was performed.
The results are shown in Table 1.

  From Table 1, it can be seen that in Example 5 in which the direction changing unit 6 was formed, the amount of branched light could be increased.

(Example 6)
As shown in FIG. 10, in the planar light emitting device 1A having the same configuration as in Example 5 except that the curved portion 12 has an arc shape with a central angle of about 30 degrees, the transmitted light amount (light L6) and the branched light amount (light L5) was measured.
As a result of the test, the amount of transmitted light was about twice that of Example 5, and the amount of branched light was about one half.
From this result, it was found that the branched light quantity can be increased by forming the curved portion 12 longer.

(Example 7)
In the planar light emitting device 1 </ b> C shown in FIG. 12, the luminance of the areas A <b> 1 to A <b> 3 was measured. The results are shown in Table 2 and FIG.

(Example 8)
In the planar light emitting device 1D shown in FIG. 14, the luminance of the regions A1 to A3 was measured. The results are shown in Table 2 and FIG.

(Comparative Example 3)
In the planar light emitting device 91 shown in FIG. 16, the brightness of the areas A1 to A3 was measured. The results are shown in Table 2 and FIG.

From Table 2 and FIG. 18, in Example 7, the first direction conversion unit 6A guides the light from the light source 2B1 to the region A1, and the second direction conversion unit 6B guides the light from the light source 2A to the region A2. Therefore, the brightness of the areas A1 and A2 that tend to be low brightness can be increased. The brightness of the areas A1 and A2 in Example 7 was about 2 to 3 times that in Comparative Example 3 in which the direction changing units 6A and 6B were not provided.
In the eighth embodiment, the light from the light source 2B1 can be guided to the region A1 by the first direction conversion unit 6A, and the light from the light source 2A can be guided to the regions A2 and A3 by the second direction conversion unit 6C. In addition to the areas A1 and A2, the brightness could be increased not only in the area A3. The brightness of the region A3 in Example 8 was about 50% higher than that in Comparative Example 3.

DESCRIPTION OF SYMBOLS 1A, 1B, 1C, 1D ... Planar light-emitting device, 2 ... Light source, 3 ... Light guide, 3a ... Upper surface (one surface), 4a ... Branch part, 5a ... -2nd branch part, 4 ... led light part, 5 ... branch light guide part, 6, 6A, 6B, 86B, 86C, 86D ... direction change part, 7, 87B, 87C, 87D1, 87D2 ... direction changing slit, 7a ... side face, 8 ... clad part, 9 ... core part, 10 ... light guide structure, 12, 12A, 12B, 12C1-12C8 ... curved part, 13, 13 </ b> A... Linear portion, 12 b .. extended end portion, 14... Clad agent, 14 a.

Claims (8)

A light source (2), and a sheet-like or plate-like light guide (3) into which light from the light source is introduced,
The light guide includes a main light section (4) and one or more branch light guide sections (5) that branch in a direction intersecting the main light section at a branch section (4a) of the main light section. And
The branching unit is formed with a direction changing unit (6) for directing the light in the leading light unit toward the branching light guide unit,
The direction changer has a plurality of direction change slits (7) formed in parallel with a distance from each other as a clad part (8), and a core part (9) between adjacent direction change slits. A planar light emitting device (1A) having the structure (10).   The planar light-emitting device according to claim 1, wherein the direction changing slit has a curved portion (12) extending from the main light portion to a branch light guide portion.   The said direction change slit has a linear part (13) extended along the said branch light guide part from the edge part (12b) by the side of the branch light guide part of the said curved part, The Claim 3 characterized by the above-mentioned. Planar light emitting device.   The formation direction of the branch light guide part with respect to the main light part includes a return direction component with respect to the light guide direction (X1) in the main light part. Planar light emitting device.   The clad agent (14) having a lower refractive index than that of the core part is introduced into a side surface (7a) facing the core part in the direction changing slit. The planar light emitting device according to item. The clad agent is filled in the direction changing slit,
6. A planar light emitting device according to claim 5, wherein a black paint layer (15) is formed on at least one surface (14a) of the clad agent.   The light extraction part which leaks a part of light in the said light guide body outside is formed in the at least one surface (3a) of the said light guide body, The any one of Claims 1-6 characterized by the above-mentioned. 2. A planar light emitting device according to item 1. A light source (2), and a sheet-like or plate-like light guide (3) into which light from the light source is introduced,
The light guide is formed with a direction changing portion (6) for changing the direction of light from the light source,
The direction changer has a plurality of direction change slits (7) formed in parallel with a distance from each other as a clad part (8), and a core part (9) between adjacent direction change slits. A planar light emitting device (1C) having the structure (10).