JP2012028085A - Light guide plate, key module, electronic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light guide plate capable of efficiently utilizing the light made incident into the light guide plate, realizing improvement of both of luminance and luminance evenness of the light guide plate, and realizing excellent click feeling, and provide a key module equipped with the light guide plate and an electronic equipment having the key module.SOLUTION: In the light guide plate 20, the light made incident into a plate thickness is guided inside the plate thickness and emitted out of the plate thickness at a prescribed position. The light guide plate is provided with a folded part R which turns back the light guiding direction in the midway and thus has an upper and lower layers.

Description

  The present invention relates to a light guide plate, a key module including the light guide plate, and an electronic device including the key module.

In electronic devices such as mobile phones, a light guide plate is used for uniform illumination. Polycarbonate and polyurethane are often used for the light guide plate, and the thickness is generally 0.1 mm to 0.2 mm.
In addition, since the light guide plate has a structure in which light from a light source such as a light emitting diode (LED) is incident from the end face, the illumination brightness by the light guide plate increases the amount of light taken in as the thickness of the light guide plate increases. The illumination brightness tends to increase.
In such a light guide plate, technical development for efficiently capturing more light has been an issue.
For example, the following Patent Documents 1 and 2 are known as conventional techniques capable of improving the illumination brightness by increasing the amount of light taken in.

Japanese Patent No. 3760658 Japanese Patent No. 4080271

Patent Document 1 is an invention related to a light guide, a display device, and an optical communication device. The light guide sheets 24 are laminated and integrated while the base end portions of a plurality of light guide sheets 24 are stacked and integrated by adhesion. The structure which arrange | positions the one light emitting module 23 in the end surface of is disclosed.
With such a configuration, there is an advantage that light can be introduced into a plurality of light guide sheets 24 by one light emitting module 23.
Patent Document 2 is an invention relating to a light guide sheet and a key switch incorporating the light guide sheet. The light receiving surface 24 is formed by thickening a part of the side surface of the light guide main body 22 facing the LED 26, and the light is guided from the light receiving surface 24. The structure which provides the light-receiving part 23 integrally formed with the taper-shaped light guide part 25 which inclines toward the main-body part 22 is disclosed.
With such a configuration, there is an advantage that light emitted from the light source can be taken in without leakage and can be efficiently guided to the light guide main body.
However, the above Patent Documents 1 and 2 both have a structure in which light is incident from one end face of the light guide sheet (so-called edge light system) and a structure that increases the amount of light incident from one end face, so that the vicinity of the light source There is a problem that non-uniform brightness is likely to occur between the light source vicinity side and the light source far side because the light amount on the side is large and the light amount on the far side of the light source is small.
Further, Patent Documents 1 and 2 are configured to include a diffusion pattern 26 and a light scattering portion 71, which are dots for so-called light scattering analysis, in order to efficiently emit incident light.
When arranging dots for so-called light scattering analysis on the so-called edge light type light guide plate, it is common to make the dot density rough on the side near the light source with a large amount of light. In the case of the configuration including the configuration in which the light amount in the vicinity of the light source is increased as in 1 and 2, there is a problem that the dots arranged in the vicinity of the light source become conspicuous, so-called dot visualization is likely to occur.
Moreover, since the said patent documents 1 and 2 are the structures which make light inject from one side end surface, the angle of the light which injects into a light guide sheet from a light source is limited, and the area | region where light does not reach easily occurs near the light source. There was a problem.

  Therefore, the present invention solves the above-mentioned conventional problems, makes it possible to efficiently use the light incident on the light guide plate, and to improve the brightness of the light guide plate and to make the brightness uniform, and to provide a good click feeling. It is an object of the present invention to provide a light guide plate capable of realizing the above, a key module including the light guide plate, and an electronic device including the key module.

  The light guide plate of the present invention is a light guide plate that guides light incident within the plate thickness while guiding the light through the thickness, and emits the light outside the plate thickness at a predetermined position. The first feature is that a folding portion that is folded back is provided in the middle to form an upper and lower two layers.

  According to the first feature of the present invention, the light guide plate guides the light incident within the thickness while guiding the light within the thickness and emits the light outside the thickness at a predetermined position. And since the folding | turning part which folds the direction which guide | induces light in the middle is provided and it has two upper and lower layers, the light which injects into the plate | board thickness and guides in the thickness can be folded | folded by a folding | turning part. Therefore, the light incident on the plate thickness can be efficiently used and emitted outside the plate thickness at a predetermined position.

  In addition to the first feature of the present invention described above, the light guide plate of the present invention has the folded portion provided on the end side facing the incident side, and the incident light in the light guide plate having the upper and lower layers. The second feature is that the overlapping end surface on the side is a light incident end surface that allows light to enter the plate thickness.

  According to the second feature of the present invention, in addition to the function and effect of the first feature of the present invention, the folded portion is provided on the end side facing the incident side, and the upper and lower layers are formed. In the light guide plate, the overlapping end surface on the incident side is used as a light incident end surface for allowing light to be incident within the plate thickness, so that the light incident end surfaces can be provided in two upper and lower layers. Therefore, the amount of light incident on the light guide plate can be increased, and the luminance can be improved. Further, since the light guided to the terminal side can be returned to the incident side, the luminance on the terminal side can be improved efficiently, and the luminance of the light guide plate can be made uniform.

  In addition to the first or second feature of the present invention, the light guide plate of the present invention includes an input key for inputting a predetermined command, and a switch driven by the operation of the input key. A third feature is that it is used as a part of a key module including a dome-shaped dome switch that is turned on and off, and is provided with a hollow portion for receiving the dome switch.

According to the third feature of the present invention, in addition to the operational effects of the first or second feature of the present invention, the light guide plate includes an input key for inputting a predetermined command, and the input key. It is used as a part of a key module including a dome-shaped dome switch that is switched on and off in accordance with the operation of the above, and a hollow portion for receiving the dome switch is provided. The dome switch can be received through the penetration.
Therefore, a good click feeling can be obtained. Moreover, it can suppress that the thickness of a key module increases.

  In addition to the third feature of the present invention, the light guide plate of the present invention has a fourth feature that a light-shielding paint is applied to the side cross section of the cut-through portion.

  According to the fourth feature of the present invention, in addition to the function and effect of the third feature of the present invention, a light-shielding paint is applied to the side cross section of the cut-through portion. It is possible to suppress the luminance from becoming non-uniform due to leakage light from the side cross section.

  In addition to the fourth feature of the present invention, the light guide plate of the present invention has a fifth feature that the light-shielding paint has a property of absorbing light.

  According to the fifth aspect of the present invention, in addition to the function and effect of the fourth aspect of the present invention, the light-shielding paint has a property of absorbing light. It is possible to efficiently prevent the luminance from becoming non-uniform due to the leaked light.

  In addition to the fourth feature of the present invention, the light guide plate of the present invention has a sixth feature that the light-shielding paint has a property of reflecting light.

  According to the sixth aspect of the present invention, in addition to the function and effect of the fourth aspect of the present invention, the shading paint has a characteristic of reflecting light, so It is possible to efficiently suppress uneven brightness due to light leaked from the cross section and to effectively use light.

  Further, the light guide plate of the present invention, in addition to any one of the first to sixth features of the present invention described above, the light incident on the upper light guide plate in the upper and lower light guide plates is externally provided. The seventh feature is that a light emitting structure for emitting light is provided.

  According to the seventh feature of the present invention, in addition to the function and effect of any one of the first to sixth features of the present invention, the upper light guide plate in the upper and lower light guide plates has two layers. Since the light emitting structure for emitting the incident light to the outside is provided, the illumination brightness can be improved efficiently.

  In addition to the first feature of the present invention, the light guide plate of the present invention has an eighth feature that the folded portion is provided on the side shoulder on the incident side.

  According to the eighth aspect of the present invention, in addition to the function and effect of the first aspect of the present invention, the folded portion is provided on the side shoulder on the incident side. Brightness can be improved.

  A key module according to the present invention includes a light guide plate according to any one of claims 1 to 8, an input key that is positioned above the light guide plate and inputs a predetermined command, and the light guide plate. A circuit board having a light source for making light incident thereon and a movable contact sheet positioned below the light guide plate and having a dome-shaped switch operator that switches on and off according to the operation of the input key This is the ninth feature.

  According to the ninth aspect of the present invention, a key module is located above the light guide plate according to any one of claims 1 to 8 and for inputting a predetermined command. A movable contact sheet having an input key, a light source that makes light incident on the light guide plate, and a dome-shaped switch operator that is positioned below the light guide plate and that is switched on and off according to the operation of the input key Therefore, the light incident on the thickness of the plate can be efficiently used and emitted outside the thickness at a predetermined position. Further, it is possible to improve the luminance and make the luminance uniform. Also, a good click feeling can be realized. In addition, it is possible to efficiently suppress non-uniform brightness due to light leaked from the side cross section of the cut-through portion. In addition, the luminance near the light source can be improved.

  According to a tenth aspect of the present invention, there is provided an electronic apparatus including the key module according to the ninth aspect.

  According to the tenth aspect of the present invention, since the electronic apparatus includes the key module described in the ninth aspect, it can exhibit a sufficiently uniform illumination function. Also, a good click feeling can be realized.

  According to the light guide plate of the present invention, the key module including the light guide plate, and the electronic device including the key module, the light guide plate can exhibit a sufficiently uniform illumination function and can realize a good click feeling. An optical plate, a key module including the light guide plate, and an electronic device including the key module can be provided.

1 is a perspective view showing a mobile phone as an electronic apparatus according to a first embodiment of the present invention. It is a top view which shows the key module of the mobile telephone as an electronic device which concerns on the 1st Embodiment of this invention. FIGS. 3A and 3B are diagrams showing a main part of the key module shown in FIG. 2, wherein FIG. 3A is a diagram showing a main part of a cross-sectional view in the direction of line AA in FIG. 2, and FIG. . It is a figure which shows the principal part of the conventional key module, (a) is a figure which shows the principal part of sectional drawing of the conventional key module, (b) is a top view of the principal part of the conventional key module. It is a top view which shows the principal part of the modification of the light-guide plate in the key module which concerns on the 1st Embodiment of this invention. It is a figure which shows the principal part of the key module which concerns on the 2nd Embodiment of this invention, (a) is a top view of the principal part of a key module, (b) simplifies the advancing direction of the light which injected into the light-guide plate. (C) is a right side view of (a), and (d) is a diagram showing a simplified traveling direction of light incident on a conventional light guide plate not provided with a folded portion.

  With reference to the following drawings, a mobile phone will be described as an example of an electronic apparatus according to the present invention to help understand the present invention. However, the following description does not limit the invention described in the claims of the present invention.

First, a mobile phone 1 according to a first embodiment of the present invention will be described with reference to FIGS.
Referring to FIG. 1, a mobile phone 1 includes an input unit 1a and a display unit 1b. The display unit 1b is openable and closable with respect to the input unit 1a via a hinge unit 1c.

  2 and 3, the input unit 1a includes a key module 2 as an input module in a case 1d. The key module 2 includes an input key 10, a light guide plate 20, a movable contact sheet 30, a light source 40, and a circuit board 50.

  The input key 10 is located above the light guide plate 20 and is used to input a predetermined command. The input key 10 includes an input key group 11 to an input key group 13 exposed to the input unit 1a. Here, as shown in FIG. 2, the input key group 11 to the input key group 13 input the input key group arranged on the side closest to the light source 40 in the input key 10 arranged in a grid pattern. The key group 11 is the input key group 13 and the input key group arranged on the farthest side is the input key group 13.

The input key 10 is formed of a transparent hard resin, and is provided with a specific shape such as numerals, alphabets, and symbols so that it can be visually recognized. A method for forming a specific shape such as numerals, alphabets, and symbols may be any of marking a specific shape with a light-shielding material and marking a non-specific shape with a light-shielding material.
Note that the shape, number, arrangement position, and the like of the input keys 10 are not limited to those of the present embodiment, and can be changed as appropriate.

As shown in FIG. 3A, the light guide plate 20 is used as a part of the key module 2 including the input key 10 and a dome switch 31 to be described later. The layer of the input key 10 and the circuit board 50 are used. The light input from the light source 40 into the wall thickness (plate thickness) is emitted to the outside at a predetermined position while being guided, and the input key 10 is illuminated.
More specifically, as shown in FIG. 3A, the light guide plate 20 causes light emitted from the illumination end surface 41 of the light source 40 to enter from the light incident end surface 21 of the light guide plate 20, and The light is guided while being totally reflected within the thickness, and is emitted toward the input key 10, thereby illuminating the input key 10.

In the present embodiment, as shown in FIG. 3A, a folded portion R that folds the light guide plate 20 toward the incident side is provided, and the light guide plate 20 has two upper and lower layers. Further, in the light guide plate 20 provided with the folded portion R on the end side facing the incident side and having two upper and lower layers, two end surfaces overlapping the upper and lower two layers on the incident side are used as the light incident end surfaces 21.
With such a configuration, two light incident end surfaces 21 can be provided on one light guide plate 20, and the number of light incident ports can be increased. Therefore, the amount of light incident on the light guide plate 20 can be increased, and the luminance of the entire light guide plate 20 can be improved efficiently.

In addition, since the folded portion R is provided on the terminal side facing the incident side, the light guided to the terminal side can be returned to the incident side, and the luminance on the terminal side can be improved efficiently.
More specifically, as shown by the phantom line (one-dot chain line) in FIG. 3A, the light guide plate 20 is made to be incident on the lower light guide plate 20 among the upper and lower layers, and within the thickness. The light reaching the end side can be guided to the upper light guide plate 20 by the folded portion R. Therefore, the luminance on the terminal side of the light guide plate 20 can be improved, and the light for illuminating the input key group 13 arranged on the terminal side of the light guide plate 20 can be effectively increased.
That is, the light guide plate 20 can be a light guide plate that can emit light by effectively using incident light, and has a structure in which light is incident only from one light incident end face with a single light guide plate. In such a case, a light guide plate that can efficiently deliver light to a distant part of the light source where it was difficult to sufficiently reach the light can be obtained. Accordingly, it is possible to improve the luminance of the light guide plate 20 and make the luminance uniform.

In this embodiment, as shown in part in FIG. 3A, light that has passed through the light guide plate 20 is input to the upper light guide plate 20 of the two upper and lower light guide plates 20 as an input key. A plurality of light emitting structures 22 made of convex dots that are scattered and diffracted in 10 directions to be emitted are provided.
With such a configuration, the light guided through the light guide plate 20 can be reliably scattered at the position of the physical convex pattern and emitted toward the input key 10. Therefore, the illumination brightness of the input key 10 can be improved more efficiently.

In particular, as described above, in the present embodiment, by providing the turn-up portion R, light in the lower light guide plate 20 is guided, and light that reaches the end side (light source far side) is transmitted to the upper light guide plate. Since the light emitting structure 22 is provided on the distal end side (the light source far side) of the upper light guide plate 20, the luminance on the distal end side of the light guide plate 20 can be further improved more efficiently. And uniform luminance can be realized more efficiently.
Therefore, as shown in FIG. 3B, the dot density on the light emitting structure 22 provided on the upper light guide plate 20 near the light source (incident side of the light guide plate 20) and on the far side of the light source (end side of the light guide plate 20). Can be reduced. Therefore, it is possible to effectively prevent the dots of the light emitting structure 22 provided on the incident side from being visualized.
FIG. 3B shows only the upper light guide plate 20 in the light guide plate 20 having two upper and lower layers for convenience of explanation.

That is, as shown in FIG. 4A, a configuration in which one light guide plate 200 is used as a key module used in a cellular phone or the like and light from the light source 400 is incident from one light incident end surface 210 (so-called edge light method). However, the conventional key module 3 has a problem that the light intensity is likely to be uneven between the light source vicinity side and the light source distant side because the light quantity near the light source is large and the light amount is small on the far side of the light source. It was.
Therefore, as shown in FIG. 4B, when the light emitting structure 220 is formed in such a key module 3, the dot density is roughened near the light source near the light source (incident side of the light guide plate 200), On the far side of the light source with a small amount of light (the end side of the light guide plate 200), the dot density is generally high. Therefore, there is a problem that the dots arranged near the light source become conspicuous, so-called dot visualization is likely to occur.
Of the light that enters the light guide plate 200 and guides the light within the thickness, the light that reaches the end side without contributing to the illumination of the input key 100 exits from the end face on the end side. There is a problem that the light incident in the 200 cannot be used effectively.
In the conventional key module 3 shown in FIG. 4, the same members and the same functions as those of the key module 2 according to the embodiment of the present invention are given the same reference numerals in the first two digits, and detailed description thereof is omitted. Shall.

  Therefore, with the configuration of the present embodiment, the light incident on the light guide plate 20 can be used efficiently, and the light guide plate 20 can be improved in luminance and uniform in brightness, and the light output structure portion. The light guide plate 20 and the key module 2 can prevent the 22 dots from being visualized.

  The light emitting structure portion 22 formed of the convex dots can be formed by a printing pattern using ink containing a light scattering agent, for example.

The light emitting structure 22 is not necessarily limited to the configuration formed by the convex dots, but may be configured by the concave dots, or may be formed by hot stamping, injection molding, microblasting, or other methods. Is possible.
Further, the arrangement position, shape, size, number, and distance between adjacent light emitting structure portions 22 of the light emitting structure portion 22 are not limited to those of the present embodiment, and can be changed as appropriate.
Moreover, although the structure which does not provide the light emission structure part 22 may be sufficient, it is desirable to set it as the structure provided.

Furthermore, in this embodiment, as shown in FIG. 3A, each dome switch 31 is received at a position corresponding to a dome switch 31 to be described later on the lower light guide plate 20 which is made up of two layers. A cut-through portion 23 is provided.
With such a configuration, the dome switch 31 can be received by the cut-out portion 23. Therefore, even when the light guide plate 20 has two upper and lower layers, the same click feeling as when the light guide plate 20 is a single-layer light guide plate can be obtained. Further, the thickness of the lower light guide plate 20 does not affect the thickness of the entire key module 2, and the thickness of the entire key module 2 can be prevented from becoming thick.
Therefore, the mobile phone 1 can exhibit a sufficiently uniform illumination function and can realize a good click feeling.
In addition, by forming the cut-out portion 23 only in the lower light guide plate 20, light is emitted to a position corresponding to a dome switch 31 described later on the upper light guide plate 20, that is, in the vicinity of the input key 10. An emission structure 22 can be provided. Therefore, the input key 10 can be illuminated more efficiently. Therefore, the light guide plate 20 and the key module 2 that can simultaneously realize the efficiency of the illumination function and a good click feeling can be obtained.
The cut-through portion 23 can be formed by punching or the like.

Although not shown in FIG. 3A, a light-shielding paint having a property of reflecting light is applied to the side cross section of the cut-through portion 23.
By adopting such a configuration, even in the configuration in which the cutout portion 23 is provided, it is possible to efficiently suppress uneven brightness due to light leaking from the side cross section of the cutout portion 23 (leakage light). In addition, light can be used effectively.
In addition, as the light-shielding paint having a property of reflecting light, a light-shielding paint having excellent reflection characteristics such as silver can be used.
The light-shielding paint may be configured to use a light-shielding paint having a characteristic of absorbing light such as black, but it is desirable to use a light-shielding paint having a characteristic of reflecting light.

The light guide plate 20 can be formed of a resin that can sufficiently transmit light in the visible light region, such as polycarbonate, polyurethane, or polymethyl methacrylate resin.
The thickness of the light guide plate 20 is desirably 20 μm to 300 μm.

The movable contact sheet 30 is positioned below the light guide plate 20 and forms a dome switch layer. As shown in FIG. 3A, the movable contact sheet 30 has a dome-shaped dome switch 31 made of a conductive metal called a metal dome below the input key 10 and covers the upper surface portion of the circuit board 50. It is arranged to do. The dome-shaped dome switch 31 is driven by the operation of the input key 10 and is brought into contact with or not in contact with the circuit board 50, whereby the key module 2 is switched on and off.
Although not shown in detail in FIG. 3A, the surface of the movable contact sheet 30 on the light guide plate 20 side is colored white. With such a configuration, light leaking downward from the light guide plate 20 can be efficiently reflected upward.

The movable contact sheet 30 can be formed of a soft resin sheet such as polyethylene terephthalate. The thickness of the movable contact sheet 30 is desirably 20 μm to 300 μm.
In addition, the colorant for coloring the surface of the movable contact sheet 30 on the light guide plate 20 side to white is any colorant that is normally used as a colorant for coloring the resin sheet, such as a colorant containing titanium oxide. May be.

The light source 40 is for making light incident on the light guide plate 20, and may be composed of, for example, an LED. As shown in FIG. 3A, the light source 40 is installed at a position on the circuit board 50 that faces the light incident end face 21 of the light guide plate 20.
Note that the number, shape, arrangement position, and the like of the light sources 40 are not limited to those of the present embodiment, and can be changed as appropriate.

  As shown in FIG. 3, the circuit board 50 includes a printed wiring layer 51 and a resin layer 52.

  The printed wiring layer 51 includes a circuit portion that is a conductive layer that serves as a switch contact, and is configured by forming a pattern of copper foil on the resin layer 52.

Next, a modification of the light guide plate 20 in the key module 2 according to the first embodiment of the present invention will be described with reference to FIG.
This modification is obtained by changing the configuration of the cut-through portion 23 provided in the light guide plate 20 with respect to the first embodiment of the present invention described above. Other configurations are the same as those of the first embodiment of the present invention. The same member and the same function are given the same number, and the following description is omitted.
In FIG. 5, only the lower light guide plate 20 of the light guide plate 20 folded in two upper and lower layers is shown for convenience of explanation.

As shown in FIG. 5, in this modified example, the input keys 10 from the input key group 11 to the input key group 13 arranged in the light traveling direction indicated by the phantom line (one-dot chain line) can be received collectively. The cut-out part 23 is provided in the shape which can be performed.
With such a configuration, it is possible to facilitate the formation of the cut-through portion 23 and to facilitate the application of the light-shielding paint.

Next, with reference to FIG. 6, the key module 4 which concerns on the 2nd Embodiment of this invention is demonstrated.
The key module 4 according to the second embodiment of the present invention is different from the key module 2 according to the first embodiment of the present invention described above in the configuration of the input key 10 and the configuration of the folded portion R provided in the light guide plate 20. Is a change. Other configurations are the same as those of the first embodiment of the present invention. The same member and the same function are given the same number, and the following description is omitted.

As shown in FIGS. 6A to 6C, in the key module 4 according to the second embodiment of the present invention, a large number of input keys 10 are provided particularly on the incident side, and the folded portion R is provided. The light guide plate 20 is provided on the side shoulder on the incident side. More specifically, the light guide plate 20 on the side shoulder on the incident side is extended in the short side direction of the light guide plate 20 as viewed in a plan view. The folded portion R is provided by folding back and the side shoulders on the incident side are divided into two upper and lower layers.
Here, the “side shoulder portions” refer to both end portions of the light guide plate 20 in a direction orthogonal to the light traveling direction.
Furthermore, as shown to Fig.6 (a), the front-end | tip part of the lower side light-guide plate 20 in the folding | turning part R is made into the curve shape. More specifically, as shown in FIG. 6B, when light is incident from the light source 40 to the lower light guide plate 20, the light traveling direction can be guided to the side of the light guide plate 20. Such a curved shape.

With such a configuration, the light incident on the lower light guide plate 20 from the light source 40 can be first guided to the side of the light guide plate 20, and further, the upper light guide plate via the folded portion R. 20 can be guided. Therefore, the light quantity which illuminates the light source vicinity side (especially side shoulder part) of the light-guide plate 20 can be increased effectively.
Therefore, in the so-called edge light type light guide plate, the directivity angle of the light source 40 is often a half-value angle of about 60 degrees, and the angle becomes small when light enters the light guide plate having a high refractive index from the air. Therefore, the angle of light incident on the light guide plate 20 from the light source 40, which is indicated by the phantom line (one-dot chain line) in FIG. 6D, is limited, and the region where light does not easily reach the light source vicinity side (FIG. 6D ), The brightness of the light source vicinity side (particularly the side shoulder portion) can be improved by providing the folded portion R on the side shoulder portion on the incident side of the light guide plate 20. .
Such a configuration is particularly effective in a key module in which a large number of input keys 10 are arranged near the light source of the light guide plate 20 as shown in FIG.

  In the second embodiment of the present invention, the traveling direction of the light incident on the lower light guide plate 20 is changed to a curved shape at the tip of the lower light guide plate 20 in the folded portion R. The light guide plate 20 can be guided to the side of the light guide plate 20, but is not necessarily limited to such a configuration, and the traveling direction of light incident on the lower light guide plate 20 from the light source 40 can be determined by the light guide plate 20. Any shape and configuration may be used as long as they can be guided to the side.

  In the embodiment of the present invention, the key modules 2 and 4 are applied to the mobile phone. However, the present invention is not necessarily limited to such a configuration, and may be applied to other electronic devices. For example, the present invention can be applied to a PDA, a mobile type PC (personal computer), a portable game machine, and the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to this Example.

A polycarbonate light guide plate 20 having a thickness of 0.1 mm is prepared. In order to affix to the slightly adhesive carrier film and remove the outer shape and the portion that cushions with the dome switch 31 by the pinnacle blade, the light guide plate 20 is cut so as to reach half the thickness of the carrier film.
Next, a silver reflective material is applied by screen printing so as to flow into the cut surface portion of the lower portion, and dried.
Next, a white pigment is applied by screen printing so as to be appropriately arranged with a diameter of 100 μm for the dots of the light emitting structure 22.
Next, a double-sided tape is affixed along the cutting periphery.
Thereafter, the light guide plate 20 is folded back to the incident side at the folded portion R, and is attached to the circuit board 50 (on which the electronic components such as LEDs serving as the light source 40 are mounted and the upper surface is covered with the movable contact sheet 30 including the dome switch 31).
Further, the input key 10 is covered with a housing.
Thus, the key module 2 is formed.
In such a key module 2, the light incident on the light guide plate 20 can be efficiently used, the luminance of the light guide plate 20 can be improved and the luminance can be made uniform, and the light emitting structure 22 can be realized. Dot visualization can be prevented.

  The present invention can be used as an electronic device such as a mobile phone, a key module used in the electronic device, and a light guide plate constituting the key module.

DESCRIPTION OF SYMBOLS 1 Mobile phone 1a Input part 1b Display part 1c Hinge part 1d Case 2 Key module 3 Key module 3d Case 4 Key module 10 Input key 11 Input key group 12 Input key group 13 Input key group 20 Light guide plate 21 Light incident end face 22 Light emission Structure 23 Cut-through 30 Movable contact sheet 31 Dome switch 40 Light source 41 Illumination end face 50 Circuit board 51 Printed wiring layer 52 Resin layer 100 Input key 110 Input key group 120 Input key group 130 Input key group 200 Light guide plate 210 Light incident end face 220 light emitting structure 300 movable contact sheet 310 dome switch 400 light source 410 illumination end face 500 circuit board 510 printed wiring layer 520 resin layer R folded portion

Claims (10)

  A light guide plate that guides light incident on the thickness of the plate while guiding the inside of the thickness and emits the light outside the plate thickness at a predetermined position, and is provided with a folding portion that turns back the light guiding direction in the middle. A light guide plate characterized by having two upper and lower layers.   The folded portion is provided on the terminal side facing the incident side, and the overlapping end surface on the incident side of the light guide plate having the two upper and lower layers is used as a light incident end surface for allowing light to enter within the plate thickness. The light guide plate according to claim 1.   The light guide plate is used as part of a key module including an input key for inputting a predetermined command and a dome-shaped dome switch that is switched on and off in accordance with the operation of the input key. The light guide plate according to claim 1, further comprising a cut-through portion for receiving the dome switch.   The light guide plate according to claim 3, wherein a light-shielding paint is applied to a side cross section of the cut-through portion.   The light guide plate according to claim 4, wherein the light-shielding paint has a property of absorbing light.   The light guide plate according to claim 4, wherein the light shielding paint has a property of reflecting light.   7. The light emitting structure according to claim 1, wherein a light emitting structure for emitting incident light to the outside is provided on an upper light guiding plate of the upper and lower light guiding plates. 8. The light guide plate described.   The light guide plate according to claim 1, wherein the folded portion is provided on a side shoulder on the incident side.   The light guide plate according to any one of claims 1 to 8, an input key that is located above the light guide plate for inputting a predetermined command, a light source that makes light incident on the light guide plate, and A key module comprising a circuit board provided with a movable contact sheet having a dome-shaped dome switch which is positioned below a light guide plate and which is switched on and off according to the operation of the input key. .   An electronic apparatus comprising the key module according to claim 9.

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