JP2004069751A - Light guide sheet and key switch with the same assembled therein - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light guide sheet capable of efficiently guiding light from a light source for back light without leaking it from the side surface side and mounted on the key switch of a cellular phone or a personal digital assistant or the like made thinner. <P>SOLUTION: In the light guide sheet 21 where a light receiving part 23 into which the light emitted by an LED 26 is guided is formed on the side surface of a sheet main body part 22 formed like a plate, the light receiving part 23 is equipped with a light receiving surface 24 formed to have nearly the same thickness as the light emitting surface 27 of the LED 26, and a tapered light guiding part 25 inclined from the light receiving surface 24 toward the main body part 22, whereby the light emitted by the LED 26 is efficiently guided into the sheet 21 and irradiates the entire sheet 21 brightly. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a light guide sheet for causing a key operation unit of a mobile phone, a portable information terminal, or the like to emit light from inside, and a key switch incorporating the light guide sheet.
[0002]
[Prior art]
Conventionally, a key switch 1 having a structure as shown in FIG. 9 has been employed for numeric keys and function keys provided in a mobile phone, a portable information terminal, and the like. The key switch 1 includes a circuit board 2 on which an electrode 3 and a wiring pattern are formed, a tact spring 4 provided on the electrode 3, a light guide plate 5 provided on the circuit board 2, and a light guide plate 5 includes a backlight light source (LED 6) that irradiates the side surface of the light guide 5, and a key top 7 that penetrates the light guide plate 5 and presses the tact spring 4. In the key switch 1 having such a structure, the LED 6 emits light to illuminate the light guide plate 5 uniformly, thereby illuminating the keytop 7 brightly. Therefore, the key switch 1 can be easily used at night or in a dark place. The key to be pressed can be confirmed and operated.
[0003]
10, a plurality of LEDs 16 are evenly arranged below the surface of a key panel 13 on which a plurality of key switches 12 are formed and arranged, and direct light from the LEDs 16 is arranged in the vicinity thereof. Some of them illuminate the key switch 12 provided.
[0004]
[Problems to be solved by the invention]
By the way, in the key switch 1 shown in FIG. 9, since the light is diffused by the light guide plate 5, the number of the LEDs 6 is small, but in order to guide the light from the LEDs 6 efficiently from the side without leakage. The light guide plate 5 must be formed to have a certain thickness or more. However, if the light guide plate 5 is made thicker, the thickness of the key switch 1 as a whole is also increased.
[0005]
On the other hand, in the key panel 13 of the mobile phone 11 shown in FIG. 10, in order to uniformly and brightly illuminate all the key switches 12, a large number of LEDs 16 must be used. For this reason, there is a problem that power consumption increases in addition to an increase in the number of parts.
[0006]
In the key switch 1 using the light guide plate 5, the light received from the LED 6 can be diffused throughout the light guide plate 5 to uniformly emit light. It was difficult to obtain a lighting effect such as increasing the lighting.
[0007]
Therefore, a first object of the present invention is to provide a light guide sheet that can efficiently guide light from a light source for a backlight from the side without leakage and can be mounted on a thin key switch of a mobile phone or a portable information terminal. It is to provide.
[0008]
Further, a second object of the present invention is to provide a light source which is easy to confirm and operate keys by causing light incident from a light source for a backlight to be scattered around a position where a key top is provided. A key switch incorporating an optical sheet is provided.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the light guide sheet according to claim 1 of the present invention has a light receiving unit that guides light into the light guide main body on a side surface of the light guide main body formed in a flat plate shape. A light-receiving surface of the light-receiving portion is formed to be larger than a thickness of a side surface of the light-guiding body.
[0010]
According to the light guide sheet of the present invention, the light receiving surface of the light receiving unit that receives light emitted from the light source for the backlight is formed large with respect to the light guide main body that uniformly diffuses the light. The light emitted from the light guide can be taken in without leakage, and can be efficiently guided to the light guide main body. Therefore, it is possible to make the light guide main body thinner without reducing the amount of light received, and it can be mounted on a key switch constituting a numeric keypad or a function key of a mobile phone or a portable information terminal, which is becoming smaller and thinner year by year. it can.
[0011]
Further, since the light guide portion for guiding the light received on the light receiving surface to the light guide main body portion is formed to be inclined in a tapered shape, the light taken in on the light receiving surface is smoothly guided to the light guide main body portion and diffused. Can be done.
[0012]
Further, by forming the light receiving surface according to the shape and size of the light emitting surface of the light source, light from the light source can be taken in without leakage. If the light source is a point-like light source such as an LED, the light-receiving surface is formed in a true circle or an elliptical shape, and if the light source is a rod-shaped fluorescent tube, the light source is formed in a wide rectangular shape. It can be formed in a light guide sheet provided with an optimal light receiving surface and a light guide section as appropriate.
[0013]
The key switch according to claim 4 of the present invention is a key switch, wherein a circuit board on which a plurality of electrodes are formed, a tact spring disposed on the electrodes, and the light guide body on a side surface of a flat light guide body. The light guide sheet includes a light receiving surface that is thicker than the side surface of the portion, and a key top disposed on the light guide sheet.
[0014]
According to the present invention, since the light receiving surface of the light guide sheet is formed with a certain thickness, the light emitted from the light source can be guided to the light guide main body without leakage. Therefore, the light diffusion efficiency does not decrease even if the light guide main body is made thinner, and the thickness of the entire key switch can be reduced when the light guide main body is inserted between the tact spring and the key top. it can.
[0015]
Further, when a light scattering portion having a plurality of concave and convex patterns is provided at a place where the key top of the light guide main body is placed, light can be scattered in multiple directions by the light scattering portion. By employing a light guide sheet having such a light scattering portion as a backlight of a key switch constituting a numeric keypad of a mobile phone or the like, the key switch can be made to emit light effectively. In addition, the light scattering portion can be easily formed by forming the light guide sheet surface in a streak shape or a ring shape or the like, and different light emitting effects can be obtained by setting the angle or depth of the recess. can get.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a light guide sheet according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a perspective view of a light guide sheet according to the present invention, and FIG. 2 is a side view of the light guide sheet.
[0017]
(Light guide sheet)
As shown in FIGS. 1 and 2, the light guide sheet 21 according to the first embodiment of the present invention includes a thin light guide main body (sheet main body 22) on one side and a light source (LED 26). The light receiving portion 23 having a large thickness for receiving light is integrally formed. The sheet main body 22 is formed of an acrylic resin having a thickness of about 0.1 mm. Further, the light receiving portion 23 includes a light receiving surface 24 that receives light from the LED, and a light guide portion 25 that is narrowed down from the light receiving surface 24 toward the middle of the front surface and the back surface of the sheet body 22. Are formed integrally. The thickness of the light receiving surface 23 is appropriately set according to the size of the LED 26. When the thickness of the sheet main body 22 is 0.1 mm, the thickness of the light receiving surface 24 is set to 0.3 mm or more. Is preferred.
[0018]
When the light guide sheet 21 is used as a light source for a backlight, as shown in FIG. 2, the light receiving surface 24 is placed so that the center of the light receiving surface 24 substantially matches the center of the light emitting surface 27 of the LED 26. The light emitted from the light emitting surface 27 of the LED 26 is applied to the light receiving surface 24, and is diffused into the sheet main body 22 via the light guide 25 narrowed down in a conical shape. Since the light receiving surface 24 having substantially the same surface area as the light emitting surface 27 of the LED 26 is provided on the side surface of the sheet main body 22 in this manner, the light emitted by the LED 26 can be incident without leakage. Can be made to emit light uniformly and brightly without reducing the amount of light even when it is formed thin.
[0019]
The light guide sheet 21 is a configuration example in which a single LED 26 is used. However, the light guide sheet 21 can take various forms according to the type, shape, or use form of a backlight light source. Hereinafter, a light guide sheet according to another embodiment will be described with reference to FIGS. 3 to 5. Here, (a) of each figure is an overall perspective view, and (b) is a side view as viewed from the light receiving surface. FIG. 3 shows a light guide sheet 31 of the second embodiment. As shown in the figure, the light receiving portion 33 of the light guide sheet 31 has the same shape of the light receiving surface 34 as the light receiving surface 24 of the light guide sheet 21, and separates the light guide 35 from the light receiving surface 34. It is formed toward the sheet body 32 so as to spread radially. When the light receiving portion 33 has such a shape, the thickness and the surface area of the light guiding portion 35 can be made larger than those of the light receiving portion 23 of the light guiding sheet 21. There is an advantage that the diffusion range toward the seat body 32 is widened. Further, since the bottom of the light guide 35 is parallel to the light receiving surface 34, the light incident on the light receiving surface 34 can be widely propagated toward the sheet main body 32.
[0020]
Further, the light receiving portion 43 of the light guide sheet 41 of the third embodiment shown in FIG. 4 has an elliptical shape in which the light receiving surface 44 is formed to be long in the lateral direction, and the light guiding portion 45 is formed radially from the light receiving surface 44. It is formed toward the seat body 42 so as to spread out. According to the light guide sheet 41, since the light receiving surface 44 is wide in the horizontal direction, even when a relatively large LED is provided, light can be effectively diffused to the sheet main body without leaking light. .
[0021]
The light receiving portion 53 of the light guide sheet 51 of the fourth embodiment shown in FIG. 5 has a light receiving surface 54 in a rectangular shape in which the entire side surface of the sheet body 52 is uniformly thickened. Are gently inclined so as to be narrowed down from the light receiving surface 54 to the thickness of the sheet body 52. As described above, since the light receiving surface 54 is formed over the entire side surface of the sheet main body 52, a plurality of LEDs are provided along the light receiving surface 54, or a rod-shaped fluorescent tube is provided instead of the LED. It is suitable for taking in a large amount of light. When the light enters the light receiving surface 54 uniformly and parallel using the plurality of LEDs or the rod-shaped fluorescent tubes, the light passes through the light guide 55 as it is and is diffused into the sheet main body 52. Therefore, the sheet body 52 can be evenly and uniformly illuminated.
[0022]
According to the light guide sheets 21, 31, 41, 51 having the above configuration, the light receiving units 23, 33, 33 having the wide light receiving surfaces 24, 34, 44, 54 on the side surfaces of the sheet main bodies 22, 32, 42, 52. Since the sheets 43 and 53 are integrally formed, light supplied from a light source such as an LED can be effectively taken in even when the sheet main bodies 22, 32, 42 and 52 are formed thin. Further, since the light receiving portions 23, 33, 43, 53 are integrally formed with the sheet main portions 22, 32, 42, 52, the incident light can be smoothly transmitted to the sheet main portion.
[0023]
The light guide sheets 21, 31, 41, and 51 are arranged such that the sheet main bodies 22, 32, 42, and 52 are disposed on the lower surface of a key switch or a liquid crystal panel, so that an operation unit such as a mobile phone or a portable information terminal is provided. And a thinner display unit.
[0024]
(Key switch incorporating light guide sheet)
Next, a key switch incorporating the light guide sheet 21 will be described with reference to FIGS. FIG. 6 shows a cross-sectional configuration of a key switch 61 mainly used in a numeric keypad portion of a mobile phone or the like. The key switch 61 is formed by placing a tact spring 64 on a circuit board 63 on which a plurality of electrode portions 62 are formed, and laminating the light guide sheet 21 and the key top 65 thereon in this order. The LED 26 is positioned and mounted on the circuit board 63 such that the light emitting surface 27 faces the light receiving surface 24 of the light guide sheet 21.
[0025]
The circuit board 63, which is a component of the key switch 61, is formed of glass epoxy, BT resin (Bismaleimide Triazine Resin), or the like, and has an electrode portion 62 for switching on the surface thereof. The tact spring 64 is formed of a conductive member having elasticity and is formed in a bowl shape, and is placed on the electrode portion 62 in a state where the bowl is closed. The light guide sheet 21 is placed with the sheet body 22 superimposed on the tact spring 64. The key top 65 is formed integrally with the touch part 66 and the leg part 67 using a transparent or translucent plastic member, and the tip of the leg part 67 is mounted on the tact spring 64 in a sheet body part. 22, and is supported in a state where the touch part 66 is exposed from a window part 69 formed on the surface of the case 68.
[0026]
(Light scattering part)
The sheet main body 22 is provided with a light scattering portion 71 that partially scatters light guided to a portion where the leg 67 of the key top 65 contacts. The light scattering portion 71 is formed, for example, by forming the surface of the sheet main body 22 finely in a streak shape. By providing the light scattering portion 71, the light guided to the sheet main body 22 is refracted and emitted in multiple directions, so that it emits light brighter than other surfaces, and also when viewed obliquely or from the side. A decrease in emission luminance can be suppressed.
[0027]
The light scattering portion 71 may be formed in a V-shaped groove 72 having a predetermined cutting angle on the surface of the sheet body portion 22 as shown in FIG. The V-shaped groove 72 is cut and formed along a circular or elliptical shape, and a point A is set such that a point B facing the point A has a maximum depth with respect to the point A on the surface of the sheet main body 22. From point B to point B while gradually increasing the cutting amount. By forming such a V-shaped groove 72, a light emitting effect of changing the refraction direction of light guided to the sheet main body 22 can be obtained. For example, when the V-shaped groove 72 is provided immediately below each touch part 66 of the key top 65 as shown in FIG. 6, the contour of each touch part 66 is made to stand out by the light refraction effect. The display can be brightly displayed.
As an example, when the backlight light source such as the LED 26 is irradiated from the right direction in the drawing of the sheet main body 22, the light amount gradually decreases from the point A to the point B, but the light amount gradually decreases toward the point B. Since the cut angle of the V-shaped groove 72 is set to be large, the light amount irradiating the upper surface of the sheet main body 22 by the light scattering effect at this cut angle becomes substantially the same as the point A. For this reason, it is possible to illuminate the outline of each touch portion 66 of the key top 65 with a uniform amount of light. Also, by appropriately setting the cut angle of the V-shaped groove 72, a light scattering effect corresponding to the amount of light of the backlight light source and the size or thickness of the sheet body 22 can be obtained. Note that the V-shaped groove 72 is formed in a circular or elliptical shape so as to conform to the circular touch portion 66, but if the touch portion 66 is square or polygonal, the V-shaped groove 72 is adapted to the shape. V-shaped grooves may be formed. Further, in the present embodiment, the light scattering portion 71 having the V-shaped groove 72 is provided on the front surface of the sheet main body 22, but the same light scattering effect can be obtained by providing the light scattering portion 71 on the back surface.
[0028]
The light scattering portion 71 can be formed by cutting the surface of the sheet main body portion 22 or by forming a concave-convex surface in a resin molding die in advance and simultaneously forming the light guide sheet. Note that the light scattering portion 71 is not limited to the above-described shape, and the decoration effect can be improved if it is formed in a lattice shape, a concentric ring shape, or a simple character.
[0029]
According to the key switch 61 having the above configuration, the light emitted from the LED 26 irradiates the light receiving surface 24 of the light receiving section 23 of the light guide sheet 21 without leakage. Then, the light is guided from the light receiving surface 24 to the inside of the sheet main body 22 through the light guide 25, and the key top 65 can be brightly illuminated from below. As described above, even when the thickness of the sheet main body 22 of the light guide sheet 21 is reduced to about 0.1 mm, which is 1/10 or less of the thickness of the light guide plate conventionally used, the light emitted from the LED 26 is not changed. It can be used effectively without leaking. Further, as the seat body 22 becomes thinner, the thickness of the key switch 61 as a whole is reduced, so that it becomes possible to cope with information devices and the like which are becoming smaller and thinner year by year.
[0030]
【The invention's effect】
As described above, according to the light guide sheet of the present invention, since the light receiving portion is formed thick, light emitted from the backlight light source can be effectively taken into the light guide main body without leakage. . By increasing the thickness of the light receiving section, the light receiving efficiency is not impaired, so that the light guide main body can be formed thin, and numeric keys and functions of mobile phones, portable information terminals, etc., which become thinner year by year. It can be mounted on key switches that constitute a key.
[0031]
In addition, by incorporating the light guide sheet as a backlight inside the key switch, it is possible to reduce the thickness of a key operation unit of a mobile phone or the like.
[0032]
Further, in the key switch, in the case where an uneven light scattering portion is formed at a predetermined position of the sheet body portion abutting directly below each key top, the light scattering portion partially transmits light in multiple directions. This makes it easy to confirm when operating, and a key switch with a high decorative effect can be formed.
[Brief description of the drawings]
FIG. 1 is a perspective view showing the overall shape of a light guide sheet according to a first embodiment of the present invention.
FIG. 2 is a side view of the light guide sheet of FIG. 1;
FIG. 3 is a perspective view of a light guide sheet according to a second embodiment of the present invention and a side view of a light receiving unit.
FIG. 4 is a perspective view of a light guide sheet according to a third embodiment of the present invention and a side view of a light receiving unit.
FIG. 5 is a perspective view of a light guide sheet according to a fourth embodiment of the present invention and a side view of a light receiving unit.
FIG. 6 is a sectional view of a key switch incorporating the light guide sheet of FIG. 1;
FIG. 7 is an exploded perspective view of the key switch.
8A and 8B are a cross-sectional view and a perspective view showing an example of forming a light scattering portion provided on a light guide sheet.
FIG. 9 is a cross-sectional view of a conventional key switch using a light guide plate as a backlight.
FIG. 10 is an explanatory diagram showing the internal structure of a conventional mobile phone that directly emits light from an LED and causes a key operation unit to emit light.
[Explanation of symbols]
21, 31, 41, 51 Light guide sheet 22, 32, 42, 52 Sheet body (light guide body)
23, 33, 43, 53 Light receiving parts 24, 34, 44, 54 Light receiving surfaces 25, 35, 45, 55 Light guide part 26 LED (backlight light source)
27 Light emitting surface 61 Key switch 62 Electrode 65 Key top 71 Light scattering part

Claims (6)

A light guide sheet in which a light receiving portion that guides light into the light guide main body portion is formed on a side surface of the light guide main body portion formed in a flat plate shape,
A light guide sheet, wherein a light receiving surface of the light receiving portion is formed to be thicker than a side surface of the light guide main body. The light guide sheet according to claim 1, wherein the light receiving unit includes the light receiving surface and a tapered light guide that is inclined from the light receiving surface toward the inside of the light guide body. The light guide sheet according to claim 1, wherein the light receiving surface is formed in a shape and a size corresponding to a light emitting surface of a light source. A circuit board on which a plurality of electrodes are formed; a tact spring disposed on the electrodes; A key switch having a sheet and a key top provided on the light guide sheet. The key switch according to claim 4, wherein the light guide body has a light scattering portion formed at a position where the key top is disposed. The key switch according to claim 5, wherein the light scattering portion is formed of a plurality of uneven patterns, and is formed corresponding to a size of an upper surface of the key top.

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