JP2008235137A - Key lighting system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin key lighting system having excellent light uniformity appropriate for lighting keys of a mobile terminal such as a cellular phone and a PDA, and achieving low electric consumption and low cost without loosing a clicking feeling on operating the keys. <P>SOLUTION: A dome switch 2 composed of an elastically-deformable electrically-conductive material is mounted to a circuit board 1 and the operation keys 3 on which a character and a figure are printed are arranged on its upper surface. A light guiding plate 4 composed of a transparent resin substrate of acrylic and the like is provided between the circuit board 1 and the operation keys 3 and an LED as a light source is provided at its end. A through hole 6 is formed at the light guiding plate 4. This through hole 6 and the dome switch 2 are formed to be stored by each longitudinal row. A light dispersion part 7 for guiding light emitted from the LED 5 to the operation keys 3 is formed on the side surface of the light guiding plate 4 corresponding to a position of the dome switch 2. A light dispersion part 7 has a cylindrical shape piercing through the light guiding plate 4 in its thickness direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is an operation key illumination device used as an input device for a mobile phone or the like, and is particularly thin, low power consumption without impairing the visibility of the key in a dark place and the click feeling during key operation. The present invention relates to a key illumination device that can reduce costs.

A conventional key illumination device will be described. FIG. 9 is a cross-sectional view of a key illumination device using an LED multipoint arrangement method disclosed in Japanese Patent Laid-Open No. 7-58815. As shown in FIG. 9, a key illumination device 60 according to a conventional LED multi-point arrangement system includes a circuit board 61, a dome switch 62, a silicon rubber 63 provided with a protrusion 63a for pressing the dome switch 62, a transparent operation. The key 64 is configured. Between the operation keys 64 on the circuit board 61, a large number of LEDs 65 serving as light sources are arranged. In the dark place, the light emission of the many LEDs 65 arranged is diffused by the silicon rubber 63, and the operation keys 64 are moved from the inside. Illuminated. In the key illumination device 60 by this LED multi-point arrangement method, since a large number of LEDs 65 for illuminating the operation key 64 are arranged in the vicinity of the operation key 64, the power consumption increases and the battery life is affected. There is a problem that leads to up.
FIG. 10 is a cross-sectional view of a key illumination device according to the LED end arrangement method disclosed in Japanese Patent Laid-Open No. 2001-167655. As shown in FIG. 10, a key illumination device 70 according to a conventional LED end arrangement method has a flexible light guide plate 74 interposed between a dome switch 72 and an operation key 73 provided on a circuit board 71. An LED 75 serving as a light source is disposed at the end. The light of the LED 75 arranged at the end is incident from the side surface of the light guide plate 74, is diffracted by the hologram layer 74a provided in the portion corresponding to the operation key 73, and illuminates the operation key 73 from the inside. In the key illumination device 70 according to this LED end arrangement method, the LEDs 75 are arranged at the end of the light guide plate 74. Therefore, the number of LEDs 75 can be reduced, and power consumption and cost can be reduced. However, since the light guide plate 74 used in the key illumination device 70 has a low elastic modulus and high hardness, the click feeling is lost when the operation key 73 is pressed. Further, it is difficult to reduce the thickness of the light guide plate 74 by the thickness. In addition, there is a problem that the hologram layer 74a provided on the light guide plate 74 is deformed due to repeated operation for a long time and the reflection luminance is lowered.
11 (a) and 11 (b) are a cross-sectional view of a key illumination device according to another LED end arrangement method disclosed in Japanese Patent Laid-Open No. 2004-356028 and a plan view of a state excluding operation keys. is there. As shown in FIGS. 11A and 11B, another conventional key illumination device 80 has a light guide plate 84 interposed between a dome switch 82 and an operation key 83 provided on a circuit board 81, and ends thereof. An LED 85 serving as a light source is arranged in the part. Further, the light guide plate 84 is formed with a hollow portion 86, and a light emitting portion 87 subjected to a satin finish is formed on the side surface thereof, so that the light of the LED 85 is incident from the side surface of the light guide plate 84, and the light emission portion. The operation key 83 is illuminated from the inside. The key illumination device 80 using this LED end arrangement method has a hollow portion 86 at a position corresponding to the operation key 83 of the light guide plate 84, so that the click feeling can be improved when the operation key 83 is pressed, and the thickness is reduced. Suitable for.
JP 7-58815 A JP 2001-167655 A Japanese Patent Laid-Open No. 2004-356028

However, the key illumination device 80 using the other conventional LED end face arrangement method described above has the following problems.
As shown in FIG. 11B, the light of the LED 85 arranged at the end portion of the light guide plate 84 enters from the side surface of the light guide plate 84, proceeds while repeating reflection inside, exits from the light emitting portion 87, and operates with the operation key 83. Illuminate from the inside. At this time, the light reaching the side surface of the hollow portion 86 from the LED 85 is emitted as leakage light not only from the light emitting portion 87 but also from the entire side surface portions 84a to 84d. When this leakage light is present, the operation key 83a near the LED 85 is brightly illuminated, but the operation key 83b far from the LED 85 is dark. As described above, when variations in brightness occur in the plurality of operation keys 83 a and 83 b, a serious problem occurs in the quality of the key illumination device 80. In order to reduce this variation in brightness, for example, it is conceivable to adjust the area of the light emitting portion 87 or to arrange the LEDs 85 on both sides of the light guide plate 84. It is necessary to change the number of manufacturing steps, and the number of LEDs 85 increases. Both of these lead to increased product costs.
The present invention has been conceived to solve the above problems, and has excellent light uniformity suitable for key illumination, does not impair the click feeling during key operation, and achieves thinness, low power consumption, and low cost. An object of the present invention is to provide a key illumination device that can be used.

In order to achieve the above object, a key illumination device according to claim 1 of the present invention includes an operation key for inputting information, a circuit board on which a switch element that operates when the operation key is pressed, and the operation key. A light guide plate disposed between the light guide plate and the light source plate, and a light source disposed at an end of the light guide plate. It is a continuous long hole shape that accommodates at least two or more switch elements in the optical path direction of the light source. According to this configuration, undesired leakage light on the side surface of the light guide plate can be reduced, and light uniformity can be improved. Furthermore, since there are no inclusions between the operation key and the switch element, it is possible to improve the click feeling and reduce the thickness when operating the key.
The key illumination device according to claim 2 is the key illumination device according to claim 1, wherein a light diffusing portion for guiding light emitted from the light source to the operation key is provided on a side surface of the through hole. It is characterized by being. According to this configuration, light can be efficiently guided to the position corresponding to the operation key.

  The key illumination device according to claim 3 is the key illumination device according to claim 2, wherein the light diffusion portion has a size of 5% to 70% of the switch element diameter. According to this configuration, since the size of the light diffusing unit is optimized, light can be guided more efficiently to the position corresponding to the operation key.

  The key illumination device according to claim 4 is the key illumination device according to claim 2 or 3, wherein the light diffusing unit changes the number according to the distance from the light source. According to this configuration, the uniformity of light can be further improved.

  According to a fifth aspect of the present invention, there is provided the key illumination device according to the second or third aspect, wherein the light diffusing unit changes the size according to the distance from the light source. This configuration can further improve the uniformity of light.

The key illumination device according to claim 6 is the key illumination device according to claim 2 or 3, wherein the light diffusing section changes the depth of the light guide plate in the thickness direction according to the distance from the light source. Features. This configuration can further improve the uniformity of light.
The key illumination device according to claim 7 is the key illumination device according to any one of claims 2 to 6, wherein the light diffusing portion is configured by a part of at least one side surface of a cylinder, a cone, a polygonal column, and a polygonal pyramid. It is characterized by. According to this configuration, the light can be efficiently guided to the position corresponding to the operation key by appropriately selecting the shape of the light diffusion portion.
The key illumination device according to claim 8 is the key illumination device according to any one of claims 2 to 7, wherein a reflection pattern including at least one of printing, scratching, unevenness, and prism is formed around the light diffusion portion. It is characterized by. According to this configuration, the light diffusion area can be increased.

  The key illumination device according to claim 9 is the key illumination device according to any one of claims 1 to 7, wherein the light guide plate has front and back surfaces and ends of the light guide plate except for a light source incident end and a light diffusion portion emission end. A total reflection mirror is formed. According to this configuration, the light from the light source can be totally reflected within the light guide plate and efficiently guided to the light diffusion portion.

  Since the key illumination device of the present invention is configured as described above, a plurality of operation keys can be illuminated with uniform brightness. Further, since there are no inclusions between the operation key and the switch element, the click feeling is not impaired, and the thickness space is not increased. In addition, the number of light sources used can be reduced, and an inexpensive key illumination device with low power consumption can be provided.

Hereinafter, a preferred embodiment of a key illumination device of the present invention will be described with reference to the drawings.
FIG. 1A is a cross-sectional view of a key illumination device according to a first embodiment of the present invention, and FIG. 1B is a plan view of a state in which an operation key is removed from FIG.
As shown in FIG. 1A, in the key illumination device 10 of the first embodiment, a dome switch 2 made of an elastically deformable metal material is mounted on a circuit board 1, and characters and figures are printed on the upper surface thereof. The operation keys 3 are arranged. A light guide plate 4 made of a transparent resin substrate such as acrylic whose front and back surfaces are mirror-finished is provided between the circuit board 1 and the operation key 3, and an LED 5 serving as a light source is disposed at an end portion thereof. . A through hole 6 is formed in the light guide plate 4. As shown in FIG. 1B, the through-hole 6 is configured to accommodate the dome switches 2 in each vertical row. Further, a light diffusion portion 7 for guiding light emitted from the LED 5 to the operation key 3 is formed on the side surface portion of the light guide plate 4 corresponding to the position of the dome switch 2. The light diffusion portion 7 has a cylindrical shape that penetrates the light guide plate 4 in the thickness direction.
One of the features of the present embodiment is that the through-hole 6 formed in the light guide plate 4 has a continuous long hole shape that accommodates the dome switch 2 in each vertical row. For this reason, the side surface parts 84a and 84c in the light guide plate 84 of FIG. These side portions 84a and 84c are side portions perpendicular to the optical path direction of the LED 85, and since there are many components of light whose incident angle is smaller than the critical angle, larger leakage light is emitted compared to the horizontal side portions 84b and 84d. The Therefore, in this embodiment, the leakage light can be greatly reduced by eliminating the side surface perpendicular to the optical path direction of the LED 5, and the light of the LED 5 can be used effectively.

Furthermore, another feature of the present embodiment is that a light diffusion portion 7 for guiding light emitted from the LED 5 to the operation key 3 is formed on the side surface of the light guide plate 4 corresponding to the position of the dome switch 2. It is that you are. The size of the light diffusing unit 7 is greatly related to the luminance.
This will be described with reference to the drawings. 2A is an enlarged view of the light diffusion portion, FIG. 2B is a graph showing the relationship between the size of the light diffusion portion and the luminance ratio, and FIG. 3 is a luminance distribution diagram of the light guide plate examined by simulation. is there.
The width of the through hole 6 shown in FIG. 2A is D ₁ , the width of the light diffusion portion 7 is D ₂ , and the relationship with the luminance at the center of the through hole 6 was examined. Note that the luminance is the luminous intensity per unit area emitted by the surface of the light diffusing unit 7 facing the LED 5 as the main light diffusing surface 8. FIG. 2B is a graph showing the results, where the horizontal axis is D ₂ / D ₁ and the vertical axis is the luminance ratio (measured luminance / maximum luminance). Note that the measurement is constant D ₁ = 5 mm (corresponding to the dome switch diameter), D ₂ = 0.1 mm to 4 mm (D ₂ / D ₁ = 0.02 to 0.8), and the arrangement range of the light diffusion part 7 = 7. 5 mm (1.5 times the dome switch diameter, equidistant arrangement).
As shown in the figure, it can be seen that the desired luminance can be obtained when D ₂ / D ₁ is 0.05 or more. When D ₂ / D ₁ is less than 0.05, the light diffusing surface 8 becomes small and the luminance ratio decreases. In addition, it becomes difficult to form the through holes 6 and the light diffusion portions 7 at the same time, which causes a problem in manufacturing. Further, when D ₂ / D ₁ exceeds 0.7, the luminance ratio starts to decrease. This is because the number of the light diffusing surfaces 8 is reduced, and the luminance unevenness becomes large, which causes a quality problem. Accordingly, it can be seen that the range of D ₂ / D ₁ for obtaining the desired luminance may be selected from 0.05 to 0.7.
Based on the above measurement results, D ₁ = 5 mm, D ₂ = 0.5 mm (D ₂ / D ₁ = 0.1), and the light diffusion state from the light diffusion unit 7 at that time is subjected to light analysis by the Monte Carlo method. FIG. 3 shows the result of simulation based on the above. (A) is when the LED is not lit, and (b) is when the LED is lit. From the same figure, it can be seen that a portion where the light diffusing portion 7 is present shines brighter than other portions. Also, there is no difference in brightness depending on the location. In addition, although the center of the through-hole 6 is dark, this is because the simulation is a result of the light guide plate 4 alone. In the actual key illumination device 10, since the light diffused from the light diffusing unit 7 is reflected by the dome switch 2 made of a metal material, the entire operation key 3 can be illuminated brightly.
As mentioned above, according to this invention, since the through-hole 6 of the light-guide plate 4 was made into the elongate hole shape which continued vertically, leak light can be decreased. In addition, since the light diffusion portion 7 is formed on the side surface of the light guide plate 4 and the size thereof is optimized, the plurality of operation keys 3 can be illuminated uniformly and brightly. Further, the number of LEDs 5 can be reduced, and power consumption can be reduced. Moreover, since the dome switch 2 is accommodated in the through hole 6 of the light guide plate 4, a good click feeling can be obtained.
Further, the light diffusion portion 7 differs from the conventional μm-order satin structure in the range of 0. Since it has a size on the order of several mm to several mm, the through-hole 6 and the light diffusing portion 7 can be simultaneously formed by a method such as injection, punching press, NC processing, and the manufacturing cost can be greatly reduced.
Next, a key illumination device according to a second embodiment of the present invention will be described with reference to the drawings. 4A is a graph showing the relationship between the number of light diffusing sections and the luminance ratio, FIG. 4B is a plan view of the key illumination device according to the second embodiment with the operation keys removed, and FIG. (C) is the enlarged view of the A-D part of FIG.4 (b).

In the first embodiment, it was explained that D ₂ / D ₁ is preferably in the range of 0.05 to 0.7. Therefore, as shown in FIG. 4A, the relationship between the number of light diffusion portions and the luminance ratio when D ₁ = 5 mm and D ₂ = 0.5 mm (D ₂ / D ₁ = 0.1) is examined. It was. As shown in the figure, it was found that the luminance ratio increases as the number of light diffusion portions increases. Based on this result, as shown in FIGS. 4B and 4C, the number was gradually increased from the light diffusing portion 17a in the region A close to the LED 5 to the light diffusing portion 17d in the far region D.
According to the present embodiment, since the number of the light diffusion portions 17a to 17d is adjusted according to the distance from the LED 5, a plurality of operation keys can be illuminated more uniformly and brightly. The number of the light diffusion portions 17a to 17d is not limited to the example shown in FIGS. 4B and 4C, but the area of the operation key to be illuminated, the brightness of the LED 5, the light guide plate 14 and the through hole 16 It can adjust suitably according to the area etc. of this.
Next, a key illumination device according to a third embodiment of the present invention will be described with reference to the drawings. 5A is a graph showing the relationship between the size of the light diffusing portion and the luminance ratio, FIG. 5B is a plan view of the key illumination device according to the third embodiment with the operation key removed, and FIG. (C) is an enlarged view of the A-D part of FIG.5 (b).

As shown in FIG. 5A, D ₁ = 5 mm, D ₂ = 0.25 mm to 3.5 mm (D ₂ / D ₁ = 0.05 to 0.7), and the number M of light diffusing portions is one. The relationship between the size of the light diffusion part and the luminance ratio was investigated. As shown in the figure, it has been found that the luminance ratio increases as the width of the light diffusion portion increases. Based on this result, as shown in FIGS. 5B and 5C, the width was gradually increased from the light diffusing portion 27 a in the region A close to the LED 5 to the light diffusing portion 27 d in the far region D.
According to the present embodiment, since the sizes of the light diffusion portions 27a to 27d are adjusted according to the distance from the LED 5, a plurality of operation keys can be illuminated more uniformly and brightly. The sizes of the light diffusing portions 27a to 27d are not limited to the examples shown in FIGS. 5B and 5C, but the area of the operation keys to be illuminated, the brightness of the LEDs 5, the light guide plate 24 and the through holes. It can be appropriately adjusted according to the area of 26.
Next, a key illumination device according to a fourth embodiment of the present invention will be described with reference to the drawings. FIG. 6A is a graph showing the relationship between the depth of the light diffusing portion and the luminance ratio, FIG. 6B is a plan view of a state in which the operation key is removed from the key illumination device of the fourth embodiment, and FIG. (C) is an enlarged view of the AD part of FIG.6 (b).

As shown in FIG. 6 (a), the depth and the luminance ratio of the light diffusion part when D ₁ = 5 mm, D ₂ = 0.5 mm (D ₂ / D ₁ = 0.1), and M = 3 I investigated the relationship. As shown in the figure, it has been found that the luminance ratio increases as the depth of the light diffusion portion increases. Based on this result, as shown in FIGS. 6B and 6C, the depth was gradually increased from the light diffusing portion 37 a in the region A close to the LED 5 to the light diffusing portion 37 d in the far region D.
According to the present embodiment, the depths of the light diffusion portions 37a to 37d are adjusted according to the distance from the LED 5, so that the plurality of operation keys can be illuminated more uniformly and brightly. The depths of the light diffusion portions 37a to 37d are not limited to the examples shown in FIGS. 6B and 6C, but the area of the operation key to be illuminated, the brightness of the LED 5, the light guide plate 34 and the through hole It can be appropriately adjusted according to the 36 area and the like.
As mentioned above, in each Example mentioned above, although the shape of the light-diffusion parts 7, 17a-17d, 27a-27d, 37a-37d was made into the column shape penetrating the light-guide plates 4, 14, 24, 34 in the thickness direction, For example, as shown in FIG. 7, any shape of (b) cone 47b, (c) triangular prism 47c, and (d) square pillar 47d may be used, as shown in FIG. Further, light can be diffused efficiently even in a shape such as a triangular pyramid or a quadrangular pyramid.
Note that the key illumination device of the present invention can obtain a desired luminance only by the light diffusing unit, but a reflection pattern may be provided as an auxiliary. For example, as shown in FIG. 8, on the bottom surface surrounding the light diffusing unit 7, (a) a reflection pattern 58a by white pigment dot printing, (b) a reflection pattern 58b by sandblasting, and (c) a reflection pattern 58c by etching. (D) It is possible to form a reflection pattern 58d by a prism. Since these reflection patterns 58a-58d have the effect | action which guides light upwards, the whole operation key can be illuminated more widely and uniformly.
Further, total reflection mirrors (not shown) are provided on the front and rear surfaces of the light guide plates 4, 14, 24, and 34, and on the LED 5 incident end and the end portions other than the light diffusion portions 7, 17a to 17d, 27a to 27d, and 37a to 37d. ) May be provided. For this total reflection mirror, a thin film of aluminum, silver, chromium or the like by a sputtering method or a vapor deposition method, or a white pigment by a printing method can be used. Since the total reflection mirror has a function of totally reflecting light, it is possible to efficiently guide the light from the LED 5 to the light diffusing sections 7, 17a to 17d, 27a to 27d, and 37a to 37d.

  The present invention can be applied to a portable terminal such as a cellular phone or a PDA having a light source that illuminates an operation key.

Sectional drawing of the key illuminating device of 1st Example of this invention, and the top view of the state except the operation key The enlarged view of the light-diffusion part of this invention, and the graph which shows the relationship between the magnitude | size of a light-diffusion part, and a luminance ratio Luminance distribution diagram of light guide plate investigated by simulation The graph which shows the relationship between the number of light-diffusion parts and a luminance ratio, the top view of the state which excluded the operation key from the key illumination apparatus of 2nd Example of this invention, and the enlarged view of A-D part The graph which shows the relationship between the magnitude | size of a light-diffusion part, and a luminance ratio, the top view of the state which removed the operation key from the key illumination apparatus of 3rd Example of this invention, and the enlarged view of AD part The graph which shows the relationship between the depth of a light-diffusion part, and a luminance ratio, the top view of the state which remove | excluded the operation key from the key illumination apparatus of 4th Example of this invention, and the enlarged view of AD part Cross-sectional perspective view showing the shape of the light diffusion portion Sectional drawing which shows the reflection pattern provided in the bottom face part of a light-diffusion part Sectional view of a conventional key illumination device using LED multi-point arrangement Sectional drawing of the key illumination device by the conventional LED edge part arrangement system Sectional drawing of the key illumination device by other conventional LED edge part arrangement | positioning systems, and the top view of the state except an operation key

Explanation of symbols

1 Circuit board 2 Dome switch 3 Operation key 4 Light guide plate 5 LED
6 Through-hole 7 Light diffusing portion 8 Light diffusing surface 10 Key illuminating device 14 according to the first embodiment of the present invention Light guide plate 16 Through-holes 17a to 17d Light diffusing portion 20 Key illuminating device 24 according to the second embodiment of the present invention 26 Through-holes 27a to 27d Light diffusing portion 30 Key illumination device 34 according to the third embodiment of the present invention Light guide plate 36 Through-holes 37a to 37d Light diffusing portion 40 Key illumination devices 44a to 44d according to the fourth embodiment of the present invention 47a to 47d Light diffusing parts 58a to 58d Reflective pattern 60 Key LED lighting device 61 by conventional LED multi-point arrangement method Circuit board 62 Dome switch 63 Silicon rubber 63a Projection 64 Operation key 65 LED
70 Key illumination device 71 by conventional LED edge arrangement method Circuit board 72 Dome switch 73 Operation key 74 Light guide plate 74a Hologram layer 75 LED
80 Key illumination device 81 based on other conventional LED end arrangement system Circuit board 82 Dome switches 83, 83a, 83b Operation keys 84 Light guide plates 84a to 84d Side surface 85 LED
86 Cavity 87 Light emission part

Claims (9)

  An operation key for inputting information, a circuit board on which a switch element that operates when the operation key is pressed, a light guide plate disposed between the operation key and the circuit board, and an end of the light guide plate In the key illumination device having the light source disposed in the light guide plate, a through hole is provided in the light guide plate, and the through hole has a continuous long hole shape that accommodates at least two switch elements in the optical path direction of the light source. There is a key illumination device.   The key illumination device according to claim 1, wherein a light diffusing portion for guiding light emitted from the light source to the operation key is provided on a side surface of the through hole.   The key illumination device according to claim 2, wherein the light diffusion portion has a size of 5% to 70% of the diameter of the switch element.   4. The key illumination device according to claim 2, wherein the light diffusing unit changes the number according to a distance from the light source.   4. The key illumination device according to claim 2, wherein the light diffusing unit changes the size according to a distance from the light source. 5.   4. The key illumination device according to claim 2, wherein the light diffusing unit changes a depth of the light guide plate in a thickness direction according to a distance from the light source.   The key illuminating device according to claim 2, wherein the light diffusing unit is configured by a part of at least one side surface of a cylinder, a cone, a polygonal column, and a polygonal pyramid.   The key illumination device according to claim 2, wherein a reflection pattern made of at least one of printing, scratching, unevenness, and prism is formed around the light diffusion portion.   The key illumination device according to claim 1, wherein total reflection mirrors are formed on the front and back surfaces of the light guide plate and on the end portions of the light guide plate excluding the light source incident end and the light diffusion portion emission end.