JP2011113756A - Light guide sheet and key sheet having light guide sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology of easily installing a light guide sheet in an electronic device, and hardly deteriorating light guiding efficiency to secure high light guiding efficiency, and a technology adapted to specifications of other electronic elements on a circuit board. <P>SOLUTION: The engagement of a housing frame 13 and an LED 4 can easily position the light guide sheet 11 and can easily install it in an electronic device 1. The engagement of the housing frame 13 and the LED 4 hardly causes the displacement of the light guide sheet 11 and the electronic device 1, so that high light guiding efficiency is maintained easily. The housing frame 13 forms a clearance between a base 12 and a circuit board 3 to secure a pressing stroke needed for a corned disc spring 5 on the circuit board 3. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention is mounted on an electronic device and used for illuminating a push button switch or an exterior part. Light emitted from an internal light source is received by a light receiving unit, guided by a light guiding unit, and scattered by the irradiation unit. The present invention relates to a light guide sheet and a key sheet including a light guide sheet used for a push button switch.

  A light guide sheet mounted for illumination of an electronic device is disposed on a circuit board, receives light emitted from an internal light source on the circuit board by a light receiving unit, guides the light to the irradiation unit by a light guiding unit, and Light is scattered by the irradiating unit and used to illuminate characters, symbols, designs, etc., such as pushbutton switches and exterior parts that are substantially opposed to the circuit board, from the inside of the electronic device.

  For example, Japanese Unexamined Patent Application Publication No. 2008-130506 (Patent Document 1) describes a key unit that is illuminated using a light guide film. Specifically, a key sheet provided with a light guide film is adhered to the top cover member, and light from a side-emitting LED (light source) provided on the circuit board is received by the side of the light guide film, The key top of the key sheet is illuminated.

  The key unit described in Patent Literature 1 can efficiently transmit light received by the light guide film to the key top. However, various electronic elements such as contact switches are attached to the circuit board, and a gap is formed between the circuit board and the key sheet in accordance with the specifications of these electronic elements. For example, when a pressing input type contact switch is provided on the circuit board, a gap for forming a pressing stroke is required between the circuit board and the key sheet. For this reason, it is difficult to align and fix the side surface of the light guide film on the optical axis of the LED while forming a gap between the circuit board and the key sheet, and it is difficult to increase the light introduction efficiency in the light guide film. . Furthermore, since the light guide film and the LED are fixed to separate members, a slight misalignment is likely to occur between them due to the press input operation, and if the misalignment occurs, the amount of light received by the light guide film is reduced and the key top There is a problem that illumination brightness is lowered and brightness unevenness of key tops occurs.

The following two techniques are known as a configuration that increases the efficiency of introducing light into the light guide member and makes it difficult for the light source and the light guide member to be misaligned.
One of them is, as described in, for example, Japanese Patent Application Laid-Open No. 2007-27115 (Patent Document 2), in which an LED and an optical waveguide are fixed to a circuit board to make it difficult to cause a positional shift between them. Then, the light receiving side end of the optical waveguide is bent to the circuit board side, and the light receiving side end of the optical waveguide is aligned with the optical axis of the LED on the circuit board to improve the light introduction efficiency in the optical waveguide, and the optical waveguide and circuit A gap is formed between the circuit board and the electronic device on the circuit board.
The other is, for example, as described in Japanese Patent Application Laid-Open No. 2006-324240 (Patent Document 3), a second board is prepared separately from a circuit board having contact switches and the like. The LED and the light guide plate are fixed to each other to make it difficult to cause a positional shift between them. And the side of the light guide plate is fixed so as to be aligned with the optical axis of the LED to increase the light introduction efficiency in the light guide plate, and the second substrate is separated from the circuit board to form a gap between the keypad and the circuit board. This corresponds to the specifications of the electronic elements on the circuit board.

JP 2008-130506 A JP 2007-27115 A JP 2006-324240 A

  By the way, in the structure described in patent document 2, although LED and an optical waveguide are made difficult to position-shift and the light introduction efficiency in an optical waveguide is raised, since the optical waveguide is bent, light leaks at the time of light guide. This is likely to occur, and the illumination brightness of the key top may be lowered. Further, even in the configuration described in Patent Document 3, the LED and the light guide plate are hardly misaligned to increase the light introduction efficiency in the light guide plate, but a new separate member called the second substrate is required, Assembling is troublesome and the cost may increase.

  The present invention has been made against the background of the prior art as described above. That is, an object of the present invention is to provide a technique that is easy to be incorporated into an electronic device, has a high light guide efficiency, and has a low light introduction efficiency. Furthermore, it is providing the technique which can respond also to the specification of the other electronic element on a circuit board.

In order to achieve the above object, the present invention is configured as follows.
That is, a light receiving unit that introduces light from an internal light source provided on a circuit board provided inside the electronic device, a light guide unit that guides the introduced light toward the irradiation unit, and light that is guided A light guide sheet including an irradiation part that scatters to an illumination member, and projects into a hollow frame shape from one side of the flat base serving as the light guide part on the side of the internal light source and opens at the tip The housing is provided with a housing frame that serves as a light receiving portion by allowing the internal light source to enter the hollow through the opening, and at least part of the outer surface of the housing frame has a thickness of the housing frame from the tip side toward the base side. Provided is a light guide sheet that is an inclined surface that is inclined so as to be thin and reflects incident light to a light guide section.

In the present invention, the housing frame that serves as the light receiving portion is provided by allowing the internal light source to enter the hollow space. For this reason, an internal light source can be covered with a storage frame, and it can suppress that light escapes outside and can improve light reception efficiency. Even if the internal light source has an optical axis, light can be received on the optical axis. Moreover, if this accommodation frame and an internal light source are engaged, it can position easily and can make a light guide sheet easy to incorporate in the inside of an electronic device. Further, the engagement between the housing frame and the internal light source can make it difficult for the two to be misaligned, and high light guiding efficiency can be easily maintained. Note that the housing frame that serves as the light receiving unit may receive light as a whole or may receive light partially. For example, if the internal light source emits light in the entire circumferential direction, the receiving frame can receive light on the entire inner surface to increase the light receiving efficiency. If the internal light source emits light with directivity, the housing frame can receive light at a part of the inner surface and efficiently illuminate the illumination member in a specific direction.
At least a part of the outer surface of the housing frame is an inclined surface that reflects incident light to the light guide. This inclined surface makes it easy to transmit light to the base serving as the light guide unit, and the light guide efficiency can be increased.
Since such an accommodation frame is provided on one surface of the base on the side of the internal light source, a gap can be formed between the base and the circuit board like a spacer provided between the base and the circuit board. It can correspond to the specifications of the electronic elements on the circuit board.
Since the base used as a light guide part is flat form, it can make it hard to produce light leakage and can exhibit high light guide efficiency.
In this way, the light receiving member efficiently increases the light receiving efficiency, and the light receiving efficiency increases the light guiding efficiency. The light irradiating member scatters the light toward the light irradiating member. It is possible to realize a light guide sheet that enhances the illumination brightness.

  The refractive index of the housing frame can be higher than the refractive index of the base. When light enters a medium having a high refractive index into a medium having a low refractive index, the refractive angle of the refracted light is larger than the incident angle of the incident light. Therefore, if the receiving frame has a higher refractive index than the base, the refraction angle of light incident on the base from the receiving frame can be made larger than the incident angle, and the refracted light of the base is directed toward the surface of the base. Can do. Therefore, light leakage at the base can be made difficult to occur, and the light guide efficiency can be increased.

The housing frame may have a bottomed frame shape having a bottom. If it is such a shape, the fixation area with respect to a light guide sheet can be increased compared with the storage frame without a bottom, and the fixation force of a light guide sheet and a storage frame can be raised. Therefore, when the housing frame is used for positioning the light guide sheet with respect to the circuit board, even if the housing frame is brought into contact with the internal light source, the housing frame is not easily peeled off from the light guide sheet, so that accurate positioning can be performed.
In addition, since the housing frame without a bottom is composed of only the side wall, when the height of the internal light source is smaller than the height of the housing frame, an extra space is formed between the internal light source and the light guide sheet. Sometimes. When there is such an extra space, light emitted from the internal light source and reflected by the side wall may enter the light guide sheet through the extra space and be scattered in a direction different from the light guide direction. However, if the bottomed frame shape is used as in the present invention, the space formed between the internal light source and the light guide sheet can be eliminated by adjusting the thickness of the bottom, and the bottom is the height of the internal light source. It can be a light receiving part in the direction. Therefore, the light guide efficiency and the light receiving efficiency can be increased.

  The front end surface of the housing frame can be a contact surface that contacts the circuit board on which the internal light source is mounted. In this way, the gap dimension between the base and the circuit board can be made the thickness dimension of the housing frame (projection dimension from the base), and the gap dimension between the base and the circuit board can be formed with high accuracy. .

  An extension that extends along one surface of the base can be provided at the base side end of the inclined surface. If it does in this way, the light which injected into the storage frame can be light-guided also by an extension part, light guide efficiency can be improved and the illumination brightness of an illumination member can be raised.

  A gap filler that fills the gap between the internal light source and the housing frame can be provided in the hollow of the housing frame. If it does in this way, a space | gap can be eliminated between an internal light source and a storage frame, and the light reception efficiency of a storage frame can be improved.

The gap filler can be a soft resin member that can be deformed at the operating temperature, or a low-melting resin member made of a resin having a melting point lower than the softening temperature of the base and the housing frame.
If the gap filling material is a soft resin member, when the internal light source is accommodated in the hollow of the accommodation frame, the gap between the two is filled by deformation of the soft resin member so that the light from the internal light source does not pass through the air layer. Light can be received by the light receiving unit, and the light receiving efficiency can be increased. Moreover, since the soft resin member is constrained and deformed in the hollow interior, it can be deformed so as to follow the outer shape of the internal light source, and the soft resin member can be securely adhered to the internal light source. it can. Furthermore, if the gap between the internal light source and the housing frame is filled with the soft resin member, the engagement retention between the two can be improved, and it is possible to make it difficult for the two to be displaced.
Further, if the gap filler is a low-melting resin member, when the internal light source is housed in the hollow of the housing frame, the low-melting resin member is deformed by low-temperature heating that does not deform the housing frame or the base. The low-melting resin member fills the gap between the two and allows the light from the internal light source to be received by the light receiving unit without passing through the air layer, and the light receiving efficiency can be increased. Also, since the low-melting resin member is constrained and deformed inside the hollow space, it can be deformed so as to follow the outer shape of the internal light source, and the low-melting resin member is securely attached to the internal light source. Can be made. Furthermore, if the gap between the internal light source and the housing frame is filled with the low-melting resin member, the low-melting resin member is solid at the operating temperature, so that it is possible to strengthen the engagement retention between the two, and it is difficult for the two to be displaced. can do. In the present invention, a resin having a melting point lower than the softening temperature of the base and the housing frame is referred to as “low melting resin”.

  A transparent resin layer having a refractive index different from that of the base can be provided on one side of the base. If it does in this way, the reflectance of the one surface side of the base which provided the transparent resin layer can be raised, and it can be made hard to leak light from the one surface side of a base. Therefore, the light guide efficiency can be increased, and the illumination brightness of the illumination member can be increased. A preferable difference in refractive index from the base in the transparent resin layer is 0.06 or more. Thus, if it is 0.06 or more, sufficient reflection efficiency can be obtained. Further, if the interface between the base and the transparent resin layer is a smooth surface, irregular reflection can be made difficult to occur, and the reflectance can be increased.

  In the present invention, any one of the light guide sheets according to the present invention, a pressing protrusion formed on one side of the light guiding sheet, and the other side of the light guiding sheet corresponding to the pressing protrusion are fixed. There is provided a key sheet including a key top as an illuminating member.

The key sheet of the present invention includes a light guide sheet having high light receiving efficiency and light guiding efficiency. For this reason, the illumination brightness of the key top can be increased. Moreover, if the accommodation frame and internal light source in a light guide sheet are engaged, it can position easily and can make a key sheet easy to incorporate in the inside of an electronic device. Furthermore, since it is difficult for the housing frame and the internal light source to be displaced, high light guide efficiency can be easily maintained.
Furthermore, a gap corresponding to the specifications of the electronic elements on the circuit board can be formed between the key sheet and the circuit board. For example, with respect to the contact switch on the circuit board, a pressing stroke can be formed between the circuit board and the key sheet, and a reliable input operation by the pressing protrusion can be performed.

According to the light guide sheet of the present invention, the internal light source can be covered with the housing frame, and light can be prevented from escaping to the outside, thereby improving the light receiving efficiency. In addition, since the internal light source is covered with the housing frame, even if the internal light source is displaced in the hollow of the housing frame, the light receiving efficiency due to it is difficult to decrease, and the allowable range of displacement between the housing frame and the internal light source is increased. be able to. Even if the internal light source has an optical axis, the light receiving portion can be formed on the optical axis.
Moreover, if this accommodation frame and an internal light source are engaged, it can position easily and can make a light guide sheet easy to incorporate in the inside of an electronic device. Furthermore, it is possible to make it difficult to cause a positional shift between the two, and it is possible to easily maintain high light guide efficiency.
Light can be easily transmitted to the base serving as the light guide portion by the inclined surface of the outer surface of the housing frame, and the light guide efficiency can be increased.
With such a housing frame, a gap can be formed between the base and the circuit board, and the specifications of the electronic elements on the circuit board can be met.
Since the base has a flat plate shape, light leakage can hardly occur and high light guiding efficiency can be exhibited.
Thus, the light guide sheet which can raise the illumination brightness of an illumination member is realizable by the accommodating frame and base which improved light guide efficiency, and an irradiation part.

According to the key sheet including the light guide sheet of the present invention, the illumination brightness of the key top can be increased. Furthermore, high light guide efficiency can be easily maintained.
Further, it is possible to easily incorporate the key sheet into the electronic device while forming a gap corresponding to the specification of the electronic element on the circuit board between the key sheet and the circuit board.

The top view which shows the light guide sheet of 1st Embodiment. The back view which shows the light guide sheet of 1st Embodiment. FIG. 3 is a sectional view taken along line SA-SA in FIG. 2. Partial expansion explanatory drawing at the time of incorporating a key sheet provided with the light guide sheet of 1st Embodiment in an electronic device. Partial expansion explanatory drawing at the time of incorporating a key sheet provided with the light guide sheet of 1st Embodiment in the electronic device. It is explanatory drawing which shows the 1st modification of the light guide sheet in 1st Embodiment, A part view (A) is a back view, A part view (B) is a SB-SB sectional view taken on the line (A), a part view (C) is the sectional view on the SC-SC line of a fraction (A). It is explanatory drawing which shows the 2nd modification of the light-guide sheet | seat in 1st Embodiment, A part view (A) is a back view, A part view (B) is SD-SD line sectional drawing of a part view (A), a part view (C) is a sectional view taken along the line SE-SE in FIG. It is explanatory drawing which shows the 3rd modification of the light-guide sheet | seat in 1st Embodiment, A part view (A) is a back view, A part view (B) is SF-SF line sectional drawing of a part view (A), a part view (C) is a sectional view taken along line SG-SG in the partial diagram (A). It is explanatory drawing which shows the 4th modification of the light guide sheet in 1st Embodiment, A part view (A) is a back view, A part view (B) is the SH-SH sectional view taken on the part view (A). The back view which shows the light guide sheet of 2nd Embodiment. FIG. 11 is a cross-sectional view taken along the line SI-SI in FIG. 10. Partial expansion explanatory drawing at the time of incorporating a key sheet provided with the light guide sheet of 2nd Embodiment in an electronic device. Partial expansion explanatory drawing at the time of incorporating a key sheet provided with the light guide sheet of 2nd Embodiment in the electronic device. FIG. 11 is a cross-sectional view corresponding to FIG. 11 showing a modification of the light guide sheet in the second embodiment. The back view which shows the light guide sheet of 3rd Embodiment. FIG. 16 is a sectional view taken along line SJ-SJ in FIG. 15. Partial expansion explanatory drawing at the time of incorporating a key sheet provided with the light guide sheet of 3rd Embodiment in an electronic device. Partial expansion explanatory drawing at the time of incorporating a key sheet provided with the light guide sheet of 3rd Embodiment in the electronic device. The top view which shows a key sheet provided with the light guide sheet of 4th Embodiment. The back view which shows a key sheet provided with the light guide sheet of 4th Embodiment. SK-SK sectional view taken on the line of FIG. Partial expansion explanatory drawing at the time of incorporating a key sheet provided with the light guide sheet of 4th Embodiment in an electronic device. Partial expansion explanatory drawing at the time of incorporating a key sheet provided with the light guide sheet of 4th Embodiment in the electronic device. FIG. 21 is a cross-sectional view corresponding to FIG. 21 illustrating a key sheet including a first modification of a key sheet including the light guide sheet of the fourth embodiment. FIG. 21 is a cross-sectional view corresponding to FIG. 21 illustrating a key sheet including a second modification of the key sheet including the light guide sheet of the fourth embodiment. FIG. 21 is a cross-sectional view corresponding to FIG. 21 illustrating a key sheet including a third modification of the key sheet including the light guide sheet of the fourth embodiment. FIG. 21 is a cross-sectional view corresponding to FIG. 21 illustrating a key sheet including a fourth modification of the key sheet including the light guide sheet according to the fourth embodiment. The top view which shows a key sheet provided with the light guide sheet of 5th Embodiment. The back view which shows a key sheet provided with the light guide sheet of 5th Embodiment. FIG. 30 is a sectional view taken along line SL-SL in FIG. 29. The SM-SM sectional view taken on the line of FIG. The top view which shows the light guide sheet of 6th Embodiment. Sectional drawing equivalent to FIG. 2 which shows the light-guide sheet | seat of 6th Embodiment. Partial expansion explanatory drawing at the time of incorporating a key sheet provided with the light guide sheet of 6th Embodiment in an electronic device. Partial expansion explanatory drawing at the time of incorporating a key sheet provided with the light guide sheet of 6th Embodiment in the electronic device. The partial expanded sectional view which shows the 1st modification common to the light guide sheet of each embodiment. Partial expansion explanatory drawing at the time of incorporating the key sheet provided with the 1st modification common to the light guide sheet of each embodiment in an electronic device. Partial expansion explanatory drawing at the time of incorporating the key sheet provided with the 1st modification common to the light guide sheet of each embodiment in the electronic device. The partial expanded sectional view which shows the 2nd modification common to the light guide sheet of each embodiment. The top view which shows the 3rd modification common to the light guide sheet of each embodiment. The back view which shows the 3rd modification common to the light guide sheet of each embodiment. FIG. 42 is a sectional view taken along line SN-SN in FIG. 41.

  The present invention will be described in more detail with reference to the drawings. In the present embodiment, a light guide sheet provided in a key sheet used for a push button switch of an electronic device will be described as an example. In addition, the same reference numerals are assigned to configurations common to the embodiments, and redundant description is omitted, and redundant descriptions of common materials, functions, effects, manufacturing methods, and the like are also omitted.

First Embodiment (FIGS. 1 to 5) :
The light guide sheet 11 of 1st Embodiment is shown in FIGS. 1-3, and the electronic device 1 incorporating the light guide sheet 11 is shown in FIG. 4, FIG. 1 is a plan view of the light guide sheet 11, FIG. 2 is a rear view of the light guide sheet 11, FIG. 3 is a sectional view taken along the line SA-SA of the light guide sheet 11, and FIG. FIG. 5 is a partially enlarged explanatory view of the electronic device 1 in which the light guide sheet 11 is incorporated. The light guide sheet 11 according to the present embodiment includes a base 12, an accommodation frame 13, and an irradiation unit 14.

  The base 12 is a base portion of the light guide sheet 11 and is a light guide portion that mainly guides light. And it is formed in rectangular flat plate shape with transparent resin. The surface of the base 12 is a flat smooth surface, and if it is such a smooth surface, light can hardly be leaked out of the base 12, and the light guide efficiency in the base 12 can be increased and the position far from the internal light source can be increased. This illumination member can also be illuminated brightly. Such a smooth surface looks transparent without any graining or the like. The thickness of the base 12 is preferably 30 μm to 500 μm. If it is less than 30 μm, since the base 12 is thin, the amount of light transmitted to the inside becomes small, and the illumination brightness is lowered. Even if the thickness exceeds 500 μm, the amount of light incident from the internal light source can hardly be increased, which is uneconomical, and since it has high rigidity, when used as a key sheet, the pressing load increases and the operability is deteriorated. For this reason, a resin film is used for the base 12 of the present embodiment.

  The housing frame 13 is a light receiving portion that allows an internal light source to enter and covers at least the light emitting portion of the internal light source. And it is formed with transparent resin. The housing frame 13 is provided on one surface of the base 12 on the side of the internal light source, protrudes from one surface by forming two rectangular hollows 13h, and has two openings 13b formed by the hollow 13h at the tip. Have. The front end surface of the housing frame 13 is a contact surface 13a that contacts the circuit board, and a bottom 13i is provided on the base 12 side of the hollow 13h. That is, the storage frame 13 has a bottomed frame shape. Then, the outer surface facing the light guide direction (indicated by the arrow in FIG. 3) of the light received by the storage frame 13 is inclined so that the thickness of the storage frame 13 decreases from the front end side toward the base 12 side. It becomes the surface 13c. The inclined surface 13c reflects incident light to the housing frame 13 to the base 12, and the outer surface that is not in the light guide direction is not an inclined surface. In addition, although described as a modified example later, the shape and position of the inclined surface are configured so as to exhibit appropriate functions and effects for realizing the specifications required for the light guide sheet.

  The hollow 13h of the housing frame 13 is formed to be slightly larger than the internal light source in plan view. Specifically, if the internal light source is formed so that a gap of about 0.2 mm can be formed, the internal light source can be easily entered with high positional accuracy. Note that this gap is not limited to 0.2 mm, and is set as appropriate in accordance with the process capability and the tolerance of misalignment when incorporated in an electronic device. If an internal light source is made to enter such a hollow 13h, when the light guide sheet 11 is incorporated into an electronic device, the positional deviation of the light guide sheet 11 can be made smaller than this gap. The depth of the hollow 13h is a depth at which the light emitting surface of the internal light source is buried. Specifically, if the thickness is equal to or deeper than the thickness of the internal light source, the light emitting surface of the internal light source can be reliably buried. Furthermore, since the light emitting surface of the internal light source is not the entire side surface, even if the depth is slightly shallower than the thickness of the internal light source, it can be sufficiently buried.

Both the resin forming the housing frame 13 and the resin forming the base 12 have high transparency, but the refractive indexes of both resins will be described.
It is preferable that the refractive index n1 of the resin forming the base 12 and the refractive index n2 of the resin forming the housing frame 13 satisfy the relationship of Formula 1.
n1 <n2 (Formula 1)
When light enters the base 12 having a low refractive index from the housing frame 13 having a high refractive index as described above, the refractive angle of the refracted light can be made larger than the incident angle of the incident light. The direction of the surface can be directed. However, contrary to this condition, if light enters the base 12 having a high refractive index from the housing frame 13 having a low refractive index, the refraction angle becomes smaller than the incident angle, and it is difficult to guide the light toward the surface of the base 12. .

  The inclined surface 13c preferably has an acute angle of 2 ° to 10 ° with respect to one surface of the base 12. Below 2 °, even if a relatively thin internal light source is used, it becomes a large inclined surface that extends to the long side of the base 12 and reaches the pressing operation part, and the pressing operation is inaccurate on the inclined surface. There is a risk. If the inclined surface is steeper than 10 °, the angle at which the light reflected by the inclined surface is incident on the base 12 becomes obtuse, and after entering the base 12, it is difficult to totally reflect inside the base 12. There is a risk that the amount of light leaking outside will increase and the illumination brightness at a position far from the internal light source will decrease. In order to increase the amount of light transmitted through the base 12, it is more preferably set to 2 ° to 5 °.

  The irradiation unit 14 is a part that changes the direction of light by changing the reflection direction of the light transmitted to the base 12 and scatters light toward the illumination member. It is formed of a resin coating film to which a high refractive index filler or a high light reflectance filler is added. The irradiation unit 14 of the present embodiment is formed in a dot-like manner in a substantially equivalent region overlapping the illumination member in plan view with respect to the other surface opposite to the one surface of the base 12. As for the thickness of this irradiation part 14, 5 micrometers-30 micrometers are preferable.

Next, the material of each member constituting the light guide sheet 11 will be described.
The base 12 is made of a highly transparent resin. In particular, a thermoplastic resin that can be easily formed into a film is preferable. For example, polyolefin resin, vinyl resin, acrylic resin, polyamide resin, polyester resin, polycarbonate resin, polyurethane resin, polyether resin, acetate resin, styrene thermoplastic elastomer, olefin thermoplastic elastomer, Examples thereof include urethane-based thermoplastic elastomers, ester-based thermoplastic elastomers, vinyl chloride-based thermoplastic elastomers, amide-based thermoplastic elastomers, and fluorine-based thermoplastic elastomers. Of these, highly transparent polycarbonate resin, acrylic resin, polyurethane resin, and urethane thermoplastic elastomer having no wavelength absorption region in the visible light region are preferable.

  As the material of the housing frame 13, a rubber-like elastic body or resin having high transparency is used. For example, examples of the rubber-like elastic body include acrylic rubber, silicone rubber, urethane rubber, ethylene propylene rubber, and butadiene rubber. Examples of resins include polyolefin resins, vinyl resins, acrylic resins, polyamide resins, polyester resins, polycarbonate resins, polyurethane resins, polyether resins, acetate resins, epoxy resins, silicone resins, and styrene resins. Examples thereof include thermoplastic elastomers, olefin-based thermoplastic elastomers, urethane-based thermoplastic elastomers, ester-based thermoplastic elastomers, vinyl chloride-based thermoplastic elastomers, amide-based thermoplastic elastomers, and fluorine-based thermoplastic elastomers. Among these resins, it is preferable to use an acrylic resin, an epoxy resin, a polyurethane resin, or a polyester resin that has a high adhesion to the base 12 described above. In order to easily maintain the gap between the base 12 and the circuit board with high accuracy, it is more preferable that the hardness conforming to JIS K 6253 is made of a resin having D70 or more.

  The material of the irradiation part 14 uses what added the filler with a high refractive index and the filler with a high light reflectance to the resin which can be printed on the base 12. For example, as the resin, polyolefin resin, vinyl resin, acrylic resin, polyamide resin, polyester resin, polycarbonate resin, polyurethane resin, polyether resin, acetate resin, epoxy resin, silicone resin, An alkyd resin etc. are mentioned. Among these resins, it is preferable to use vinyl resins, acrylic resins, polycarbonate resins, polyester resins, polyurethane resins, epoxy resins, silicone resins, and alkyd resins that can be easily converted into ink. Examples of the high refractive index filler and the high light reflectance filler added to the resin include titanium oxide.

Next, a method for manufacturing the light guide sheet 11 will be described.
First, the irradiation part 14 is formed on the other surface opposite to the one surface of the base 12 made of a resin film by printing.
Next, a mold for forming the housing frame 13 is prepared, and a liquid resin for forming the housing frame 13 is poured into the mold. Then, one side of the base 12 is set in a mold so as to be in contact with the liquid resin, the liquid resin is cured, and the housing frame 13 and the base 12 are integrated.
Finally, the mold is removed to obtain the light guide sheet 11.

The electronic apparatus 1 in which the key sheet 10 including such a light guide sheet 11 is incorporated will be described.
As shown in FIG. 4, the electronic device 1 includes a key sheet 10 including a light guide sheet 11 and a cover sheet 15 and a circuit board 3 inside the housing 2.
In the cover sheet 15, a key top 15b made of a transparent resin as an “illuminating member” is fixed to the surface of a base sheet 15a made of a thin resin film, and the back surface of the base sheet 15a corresponds to each key top 15b. A pressing protrusion 15c made of a resin or rubber-like elastic body is provided.
On the circuit board 3, an LED 4 as an “internal light source” and a disc spring 5 as a contact switch are arranged.
The casing 2 is formed with an operation opening 2a that exposes the key top 15b of the key sheet 10, and a pressing protrusion 2b that presses and fixes the key sheet 10 against the circuit board 3 is provided inside the casing 2. It has been.
As shown in FIG. 5, the key sheet 10 is pressed against the circuit board 2 by the pressing protrusion 2 b of the housing 2, the LED 4 is caused to enter the hollow 13 h of the housing frame 13, and the contact surface 13 a of the housing frame 13 is the circuit board 3. The key sheet 10 is fixed so that the key top 15 b corresponds to the disc spring 5. A gap necessary for the pressing stroke of the disc spring 5 is formed between the base 12 of the key sheet 10 and the circuit board 3 by the housing frame 13.

The operation and effect of the light guide sheet 11 will be described.
According to the light guide sheet 11, the LED 4 can be covered with the housing frame 13, and light can be prevented from escaping to the outside of the housing frame 13, thereby increasing the light receiving efficiency. Even if the LED 4 has an optical axis, light can be received on the optical axis. Moreover, if this accommodation frame 13 and LED4 are engaged, it can position easily and can make it easy to incorporate the light guide sheet 11 in the inside of the electronic device 1. FIG. Further, the engagement between the housing frame 13 and the LED 4 makes it difficult to cause a positional shift between the two, and it is possible to easily maintain high light guide efficiency.
Since the outer surface of the housing frame 13 in the light guiding direction is the inclined surface 13c, light can be easily reflected on the inclined surface 13c and transmitted to the base 12, and light guiding efficiency can be increased.
A gap can be formed between the base 21 and the circuit board 3 like a spacer provided between the base 12 and the circuit board 3, and the disc spring 5 on the circuit board 3 can be formed. Necessary pressing stroke can be ensured.
Since the base 12 has a flat plate shape, it is difficult to cause light leakage, and high light guide efficiency can be exhibited.
Light is efficiently guided by the housing frame 13 with improved light receiving efficiency and the housing frame 13 and the base 12 with improved light guiding efficiency, and the light is scattered toward the key top 15b by the irradiation unit 14. Therefore, the light guide sheet 11 that enhances the illumination brightness of the key top 15b can be realized.

  Since the refractive index of the storage frame 13 is higher than the refractive index of the base 12, the refraction angle of light incident on the base 12 from the storage frame 13 can be made larger than the incident angle, and the refracted light of the base 12 can be used as the surface of the base 12. Can be directed. Therefore, light leakage at the base 12 can be made difficult to occur, and the light guide efficiency can be increased.

Since the receiving frame 13 has a bottomed frame shape having a bottom 13i, the fixing area to the light guide sheet 11 can be increased as compared with a receiving frame without a bottom, and the fixing force between the light guiding sheet 11 and the receiving frame 13 is increased. be able to. Therefore, when positioning the housing frame 13 with respect to the circuit board 3, even if the housing frame 13 is brought into contact with the LED 4, the housing frame 13 can be hardly peeled off from the light guide sheet 11, and the key sheet 10 is accurately positioned. can do.
Also, the space between the LED 4 and the light guide sheet 11 can be substantially eliminated by adjusting the thickness of the bottom 13i, preventing light dissipation that tends to occur when there is space, and allowing light in the light guide direction. It can be made easier to communicate. Furthermore, the bottom 13i can be a light receiving portion in the height direction of the LED 4. Therefore, the light guide efficiency and the light receiving efficiency can be increased, and the illumination brightness of the key top 15b can be increased.

  Since the housing frame 13 is provided with the contact surface 13a, the gap dimension between the base 12 and the circuit board 3 can be set by the housing frame 13, and the gap dimension between the base 12 and the circuit board 3 can be formed with high accuracy. Can do.

According to the key sheet 10 including the light guide sheet 11, since the light guide sheet 11 having high light reception efficiency and high light guide efficiency is provided, the illumination brightness of the key top 15 b can be increased. Further, if the housing frame 13 and the LED 4 in the light guide sheet 11 are engaged, the key sheet 10 can be easily positioned, and the key sheet 10 can be easily incorporated into the electronic device 1. Furthermore, since it is difficult for the housing frame 13 and the LED 4 to be misaligned, high light guide efficiency can be easily maintained.
Further, a gap of a pressing stroke necessary for the disc spring 5 on the circuit board 3 can be formed between the key sheet 10 and the circuit board 3, and a reliable input operation by the pressing protrusion 15c can be performed.

  The following modifications of the light guide sheet 11 can be obtained by changing the configuration of the housing frame 13.

First Modification of Light Guide Sheet 11 [FIG. 6] :
The light guide sheet 11 has one housing frame 13 and is formed with two openings 13b and an inclined surface 13c on one side. The housing frame 131 of the light guide sheet 111 in the first modification is provided for each LED. Each of the housing frames 131 can be formed with a contact surface 131a and three inclined surfaces 131c facing different directions from the one opening 131b.
In this way, when the LED 4 having the optical axis in the surface direction of the base 12 is used, three directions can be set as the light guide direction, and light can be guided at a wide angle.

Second Modification of Light Guide Sheet 11 [FIG. 7] :
The light guide sheet 11 has one housing frame 13 and is formed with two openings 13b and a one-side inclined surface 13c. The light guide sheet 112 housing frame 132 in the second modification is provided for each LED. Each of the housing frames 132 can be formed with a contact surface 132a, one opening 132b, and an inclined surface 132c continuous in three directions.
In this way, when the LED 4 having the optical axis in the surface direction of the base 12 is used, three directions can be set as the light guide direction, and light can be guided at a wide angle. In the light guide sheet 111 of the first modified example, the reflected light may be biased at the corners formed by the inclined surfaces 131c, but in the light guide sheet 112 of the second modified example, the inclined surface 132c continues in three directions. Therefore, it is difficult for the reflected light to be biased, and uneven illumination can be reduced.

Third modification of light guide sheet 11 [FIG. 8] :
The light guide sheet 11 has one housing frame 13 and has two openings 13b and an inclined surface 13c on one side. The housing frame 133 of the light guide sheet 113 in the third modification is provided for each LED. Each of the housing frames 133 can be formed with one opening 133b and four inclined surfaces 133c facing different directions. Further, an intermediate beam 16a that connects between the storage frames 133 and an outer frame 16b that extends outward from each of the storage frames 133 are formed on a straight line, and protrudes in the same manner as the storage frame 133 on the intermediate beam 16a and the outer frame 16b. 16c can be provided, and the front end surfaces of these convex portions 16c can be formed as contact surfaces 16d.
In this way, since the contact surface 16d is formed in a portion other than the housing frame 133, the contact surface 16d is provided avoiding these electronic elements even if many electronic elements are placed on the circuit board. It is possible to install a large number of electronic elements on the circuit board while accurately maintaining the gap between the circuit board and the base 12.

Fourth Modified Example of Light Guide Sheet 11 [FIG. 9] :
The housing frame 13 of the light guide sheet 11 has an inner surface formed perpendicular to one surface of the base 12, but the housing frame 134 of the light guide sheet 114 in the fourth modification is on the inclined surface 134c side of the hollow 134h. The inner surface can be inclined so as to widen the opening 134b side. The other inner surface connected to the contact surface 134 a is formed perpendicular to one surface of the base 12.
If it does in this way, the opening 134b of the hollow 134h can be widened, and engagement with LED can be made easy. Further, since the inner side surface in the light guide direction of the hollow 134h is inclined so as to widen the opening 134b side, the light received by this inner side surface can be refracted to the base 12 side, and the incident angle and reflection with respect to the inclined surface 134c are reflected. The angle can be increased to facilitate the transmission of light to the base 12. If the incident angle with respect to the base 12 can be increased, the refraction angle of the base 12 can also be increased, and the light guide efficiency can be increased by directing the refracted light of the base 12 toward the surface of the base 12.

Second Embodiment [FIGS. 10 to 13] :
A light guide sheet 21 of the second embodiment is shown in FIGS. 10 and 11, and an electronic device 1 incorporating the light guide sheet 21 is shown in FIGS. 12 and 13. 10 is a rear view of the light guide sheet 21, FIG. 11 is a cross-sectional view taken along the line SI-SI of the light guide sheet 21, and FIG. 12 is a partially enlarged explanatory view of the electronic device 1 when the light guide sheet 21 is incorporated. These are the elements on larger scale of the electronic device 1 incorporating the light guide sheet 21. FIG. Unlike the light guide sheet 11 of the first embodiment, the light guide sheet 21 of the present embodiment includes a transparent resin layer 26. Other configurations are the same as those of the light guide sheet 11.

The transparent resin layer 26 increases the light guide efficiency of the base 12. The transparent resin layer 26 is formed of a transparent resin in a thin film shape, and the remaining portion where the end of the inclined surface 13 c of the housing frame 13 and the housing frame 13 on one side of the base 12 on the internal light source side are not fixed. The part of is covered. The thickness of the transparent resin layer 26 is preferably 1 μm or more, and more preferably 5 μm or more. If the thickness is less than 1 μm, a smooth surface may not be maintained due to penetration of the solvent when other layers are laminated. The upper limit of the thickness is not particularly limited, but a practical range is about 50 μm. Even if it is thicker than 50 μm, the light guide efficiency cannot be increased, and the thickness of the light guide sheet is increased.
In such a transparent resin layer 26, it is preferable that at least one of the interfaces with the base or the opposite surface is a smooth surface, and it is more preferable that both the interfaces are smooth surfaces. If the interface is smooth, it is difficult to cause irregular reflection and the light guide efficiency of the base can be increased.
Further, the difference in refractive index between the transparent resin layer 26 and the base 12 is preferably 0.06 or more. Thus, if the difference is 0.06 or more, the reflection efficiency of light transmitted through the base 12 can be increased. The relationship between the refractive index n3 of the transparent resin layer 26 and the refractive index n1 of the base 12 preferably satisfies Expression 2.
n3 <n1 (Formula 2)
When the relationship between the refractive indexes satisfies Expression 2, total reflection of light easily occurs at the interface between the two, and the light guide efficiency of the base can be increased. If the relationship of the refractive index n2 of the housing frame 13 is added here, it is preferable to satisfy Formula 3.
n3 <n1 <n2 (Formula 3)

  The material of the transparent resin layer 26 is formed of a non-erodible resin liquid so that it is highly transparent and easy to maintain smoothness. Specifically, a solvent-free cross-linked or curable resin is used, an active energy ray-curable ink such as a solvent-free ultraviolet curable type or an EB curable type, or a non-erodible type such as an aqueous or alcohol type. A two-component curable ink containing a solvent and a thermosetting ink are used. Examples of such resin inks include ultraviolet curable urethane acrylate inks and thermosetting urethane inks. If the transparent resin layer 26 is formed of a cross-linked or curable ink, it can be a layer that is hardly eroded by other members.

In the manufacturing method of the light guide sheet 21, first, the irradiation part 14 is printed and formed on the other surface of the base 12 made of a resin film.
Next, after the transparent resin layer 26 is printed on the exposed one surface of the base 12, the housing frame 13 is formed to obtain the light guide sheet 21.

As shown in FIG. 12, the electronic device 1 in which the key sheet 20 including the light guide sheet 21 is incorporated has a key sheet 20 including a light guide sheet 21 and a cover sheet 15 inside the housing 2. Circuit board 3.
As shown in FIG. 13, the key sheet 20 is pressed against the circuit board 2 by the pressing protrusion 2 b of the housing 2, and the LED 4 enters the hollow 13 h of the housing frame 13, and the contact surface 13 a of the housing frame 13 is the circuit board 3. The key sheet 20 is fixed so that the key top 15 b corresponds to the disc spring 5. A gap necessary for the pressing stroke of the disc spring 5 is formed between the base 12 of the key sheet 20 and the circuit board 3 by the housing frame 13.

  According to the key sheet 20 including the light guide sheet 21 and the light guide sheet 21, since the transparent resin layer 26 is provided on the one surface side of the base 12, the reflectance on the one surface side of the base 12 can be increased. It is possible to make it difficult for light to leak from the one surface side. Therefore, the light guide efficiency can be increased, and the illumination brightness of the key top 15b can be increased.

Modified example of light guide sheet 21 (FIG. 14) :
The transparent resin layer 26 of the light guide sheet 21 is formed on one surface of the base 12, but the light guide sheet 211 in the modification has the transparent resin layer 26 formed on the other surface opposite to the one surface of the base 12. Can do.
If it does in this way, the reflectance of the other surface side of base 12 can be raised, and it can be made hard to leak light from the other surface side of base 12 in which irradiation part 14 is not provided.
Further, if the transparent resin layer 26 is formed on both the one surface and the other surface of the base 12, the light guide efficiency can be further increased.

Third Embodiment (FIGS. 15 to 18) :
The light guide sheet 31 of 3rd Embodiment is shown in FIG.15, FIG.16, and the electronic device 1 incorporating the light guide sheet 31 is shown in FIG.17, FIG.18. 15 is a rear view of the light guide sheet 31, FIG. 16 is a sectional view taken along the line SJ-SJ of the light guide sheet 31, FIG. 17 is a partially enlarged explanatory view of the electronic device 1 when the light guide sheet 31 is incorporated, and FIG. These are the elements on larger scale of the electronic device 1 incorporating the light guide sheet 31. FIG. Unlike the light guide sheet 11 of the first embodiment, the light guide sheet 31 of the present embodiment includes an accommodation frame 33. Other configurations are the same as those of the light guide sheet 11.

  Similar to the housing frame 13, the housing frame 33 is a light receiving unit that allows an internal light source to enter and covers at least the light emitting unit of the internal light source. The housing frame 33 is fixed to one short side of one surface of the base 12 on the internal light source side, protrudes from one surface by forming two rectangular hollows 33h, and has a hollow 33h at its tip. Has two openings 33b. The front end surface of the housing frame 33 is a contact surface 33a that contacts the circuit board, and a bottom 33i is provided on the base 12 side of the hollow 33h. That is, the receiving frame 33 is also a bottomed frame shape. And the outer surface which faces the light guide direction (arrow direction of FIG. 16) in the storage frame 33 is inclined so that the thickness of the storage frame 33 becomes thinner from the tip side toward the base 12 side. It has become. The difference from the storage frame 13 is that the storage frame 33 has an extension 33d that extends along one surface of the base 12 from the end of the inclined surface 33c on the base 12 side. That is, the entire portion of one surface of the base 12 is covered with the extension 33 d of the housing frame 33. Further, a pressing projection 33e that presses the disc spring on the circuit board is provided on the surface of the extension 33d facing the circuit board.

In the manufacturing method of the light guide sheet 31, first, the irradiation part 14 is printed and formed on the other surface of the base 12 made of a resin film.
Next, a mold for forming the housing frame 33 is prepared, and a liquid resin for forming the housing frame 33 is injected into the mold, and the base 12 is set on the mold so that one surface of the base 12 is in contact with the liquid resin. The housing frame 33 and the base 12 are integrated by curing.
Finally, the mold is removed to obtain the light guide sheet 31.

As shown in FIG. 17, the electronic device 1 in which the key sheet 30 including such a light guide sheet 31 is incorporated includes a key sheet 30 including a light guide sheet 31 and a cover sheet 35 inside the housing 2. Circuit board 3.
In the cover sheet 35, a key top 35b made of a transparent resin as an “illuminating member” is fixed to the surface of a base sheet 35a made of a thin resin film.
As shown in FIG. 18, the key sheet 30 is pressed against the circuit board 2 by the pressing protrusion 2 b of the housing 2, and the LED 4 is caused to enter the hollow 33 h of the housing frame 33, and the contact surface 33 a of the housing frame 33 is the circuit board 3. The key sheet 30 is fixed so that the key top 35 b corresponds to the disc spring 5. A gap necessary for the pressing stroke of the disc spring 5 is formed between the pressing projection 33 e of the key sheet 30 and the circuit board 3 by the housing frame 33.

  According to the key sheet 30 including the light guide sheet 31 and the light guide sheet 31, since the housing frame 33 has the extension 33d, the light incident on the housing frame 33 can be guided by the base 12 and the extension 33d. The light guide efficiency can be increased and the illumination brightness of the key top 35b can be increased as compared with the case where the light is guided only by the base 12.

Fourth Embodiment (FIGS. 19 to 23) :
The light guide sheet 41 of the fourth embodiment is integrated with a transparent molded body 45 having a key top 45b, and a key sheet 40 including the light guide sheet 41 and the transparent molded body 45 is shown in FIGS. An electronic device 1 incorporating 40 is shown in FIGS. 19 is a plan view of the key sheet 40, FIG. 20 is a rear view of the key sheet 40, FIG. 21 is a sectional view taken along the line SK-SK of the key sheet 40, and FIG. FIG. 23 is a partially enlarged explanatory view of the electronic device 1 in which the key sheet 40 is incorporated. Unlike the light guide sheet 11 of the first embodiment, the light guide sheet 41 of the present embodiment is provided with a housing frame 33 on one surface side that is the internal light source side of the base 12, and on the other surface side opposite to the one surface side. A transparent resin layer 26 and a translucent printing layer 47 are sequentially provided. Other configurations are the same as those of the light guide sheet 11.

The translucent printing layer 47 is a layer serving as a background of the key top 45b.
The translucent print layer 47 is preferably formed from a non-erodible paint for the transparent resin layer 26. This is because if the surface of the transparent resin layer 26 is eroded by the erosion of the transparent resin layer 26, the interface between the transparent resin layer 26 and the translucent printing layer 47 is not a smooth surface, and the reflection efficiency is improved. This is because it becomes low. For example, if the transparent resin layer 26 is a strongly crosslinked type, there are few material restrictions, and if the transparent resin layer 26 is a coating layer of solvent-based ink, alcohol-based or water-soluble ink can be used. Note that erosion refers to the fact that the adherend member is melted when a solvent is applied, for example, and the surface of the adherend member is rough, but does not refer to a state that causes solvent cracks or resin deterioration. Further, when a coating liquid containing resin is applied, even if the solvent is dried, the resin covers the surface of the adherend member, so it is not apparent whether the surface of the adherend member is rough. In such a case, when the coating liquid is applied and wiped off from the adherend before drying, the surface of the adherend is melted or swollen, etc. Use an erodible coating solution. On the other hand, when the surface of the adherend member is kept smooth when the coating liquid is wiped off, the coating liquid is a non-erodible coating liquid.

The transparent molded body 45 is an exterior part of the key sheet 40. It is made of a transparent resin or rubber-like elastic body, and is formed so as to integrally connect a plurality of key tops 45b at their lower ends. A display print layer 45d representing a display element for each key top 45b and a light-blocking print layer 45e for preventing light leakage are provided between the key tops 45b.
As a material of the transparent molded body 45, a rubber-like elastic body having a hardness of A50 or more according to JIS K 6253 or a resin is used. For example, rubber-like elastic materials include acrylic rubber, silicone rubber, urethane rubber, ethylene propylene rubber, butadiene rubber, styrene thermoplastic elastomer, olefin thermoplastic elastomer, urethane thermoplastic elastomer, ester thermoplastic elastomer, chloride Examples thereof include vinyl-based thermoplastic elastomers, amide-based thermoplastic elastomers, and fluorine-based thermoplastic elastomers. Examples of resins include polyolefin resins, vinyl resins, acrylic resins, polyamide resins, polyester resins, polycarbonate resins, polyurethane resins, polyether resins, acetate resins, epoxy resins, silicone resins, alkyd resins. Etc.

In the method of manufacturing the key sheet 40, first, the irradiation part 14, the transparent resin layer 26, the translucent printing layer 47, the display printing layer 45d, and the light shielding printing layer 45e are sequentially printed on the other surface of the base 12 made of a resin film. After that, a mold for forming the transparent molded body 45 is prepared, a liquid resin for forming the transparent molded body 45 is injected into the mold, the other surface side of the base 12 is set in the mold, and the liquid resin is cured. The base 12 and the transparent molded body 45 are integrated.
Next, the housing frame 33 is integrated with one surface of the base 12.
Finally, the mold is removed to obtain the key sheet 40.
In addition, as another manufacturing method, the transparent molded body 45 which has the display printing layer 45d and the light-shielding printing layer 45e separately from the light guide sheet 41 is produced, and the transparent molded body 45 is translucent printing layer with an adhesive agent. It can also be laminated on 47.

The electronic device 1 in which the key sheet 40 including the light guide sheet 41 is incorporated includes the key sheet 40 and the circuit board 3 inside the housing 2 as shown in FIG.
As shown in FIG. 23, the key sheet 40 is pressed against the circuit board 2 by the pressing protrusion 2 b of the housing 2, the LED 4 is caused to enter the hollow 33 h of the housing frame 33, and the contact surface 33 a of the housing frame 33 is the circuit board 3. The key sheet 40 is fixed so that the key top 45 b corresponds to the disc spring 5. A gap necessary for the pressing stroke of the disc spring 5 is formed between the pressing projection 33 e of the key sheet 40 and the circuit board 3 by the housing frame 33.

According to the light guide sheet 41 and the key sheet 40 including the light guide sheet 41, since the key sheet 40 is an integrated object, it can be easily incorporated into the electronic apparatus 1.
Further, the light guide sheet 41 can increase the illumination brightness of the key top 45b, and can easily maintain a higher light guide efficiency.

First Modification of Key Sheet 40 (FIG. 24) :
The key sheet 401 of the first modified example is different from the key sheet 40 in that the irradiation unit 14 is formed on one side instead of the other side of the base 12 and the base 12 and the housing frame 33 are extended so as to cover the irradiation unit 14. The transparent resin layer 26 is newly formed between the portions 33d, and a blank character print layer 45f that represents other than the display elements is formed in place of the display print layer 45d and the light-shielding print layer 45e.
In this way, it is possible to realize the key sheet 401 in which the display element shines brightly.

Second Modification of Key Sheet 40 (FIG. 25) :
The key sheet 402 of the second modification is different from the key sheet 40 in that the irradiation unit 14 is formed in a display element shape on one side instead of the other side of the base 12 and is accommodated with the base 12 so as to cover the irradiation unit 14. A transparent resin layer 26 and a dark color print layer 48 are sequentially formed between the extension 33d of the frame 33, and the transparent resin layer 26 on the other side of the base 12, the translucent print layer 47, the display print layer 45d, and the light shielding print. The point is that the layer 45e is deleted.
In this way, since the number of layers to be stacked can be reduced, a thin key sheet 402 can be manufactured at a low cost. In addition, since the dark print layer 48 is formed through the transparent resin layer 26, the key top 45b side is adapted to suppress irregular reflection light that easily occurs on the side surface of the pressing protrusion 33e or irregular reflection light from the circuit board while suppressing a decrease in luminance. It is possible to easily prevent leakage.

Third Modification of Key Sheet 40 (FIG. 26) :
The key sheet 403 of the third modified example is different from the key sheet 40 in that a transparent resin layer 46 is provided by removing the pressing protrusion 33e formed on the surface of the housing frame 33 facing the circuit board of the extension 33d, and further transparent. The pressing protrusion 46a is formed on the surface of the resin layer 46 facing the circuit board.
As shown in the above-described Expression 3, a preferable relationship among the refractive index n1 of the base 12, the refractive index n2 of the housing frame 33, and the refractive index n3 of the transparent resin layers 26 and 46 is “n3 <n1 <n2.” Thus, if the extension part 33d of the base 12 and the storage frame part 33 is sandwiched between the transparent resin layers 26 and 46 having a low refractive index, the light transmitted through the base 12 and the extension part 33d can be easily subjected to total reflection, thereby improving the light guide efficiency. Can be increased. Therefore, the key top 45b can be illuminated brightly. Further, by increasing the reflection efficiency at the interface with the transparent resin layer 46 in the extension portion 33d, it is possible to reduce the incidence of light on the pusher and to reduce irregular reflection on the side surface of the pusher.

Fourth Modification of Key Sheet 40 (FIG. 27) :
The key sheet 404 of the fourth modified example is different from the key sheet 40 in that a transparent resin layer 26 is formed between the base 12 and the extension 33d of the housing frame 33.
If the base 12 is sandwiched between the transparent resin layers 26 having a low refractive index in this way, light transmitted through the base 12 can be easily subjected to total reflection, and the light guide efficiency can be increased. Therefore, the key top 45b can be illuminated brightly.

Fifth Embodiment (FIGS. 28 to 31) :
The light guide sheet 51 of the fifth embodiment is integral with the key top 55, and a key sheet 50 including the light guide sheet 51 and the key top 55 is shown in FIGS. 28 to 31. 28 is a plan view of the key sheet 50, FIG. 29 is a rear view of the key sheet 50, FIG. 30 is a sectional view taken along the line SL-SL of the key sheet 50, and FIG. FIG. Unlike the light guide sheet 11 of the first embodiment, the light guide sheet 51 of the present embodiment includes the irradiation unit 14 and the storage frame 53 on one surface side that is the internal light source side of the base 12, and is an extension of the storage frame 53. A transparent resin layer 26 and a dark print layer 48 are sequentially formed so as to cover the irradiation portion 14 between 53d and the base 12. Then, a soft resin film 56 is fixed to the other surface side opposite to the one surface side of the base 12 via a first adhesive layer 56a, and a key top 55 provided with a decorative print layer 55g on the surface of the soft resin film 56 is provided. It is fixed by the second adhesive layer 55h. Furthermore, a slit 59 is formed from the first adhesive layer 56 a on the other surface side of the base 12 in the light guide sheet 51 to the dark color print layer 48 on the one surface side of the base 12, and an upright portion 53 f of the housing frame 53 is formed in the slit 59. Buried.

  Similar to the housing frame 33, the housing frame 53 is a light receiving unit that covers the inner light source. The housing frame 53 is fixed to one short side of one surface of the base 12 on the internal light source side, protrudes from one surface by forming two rectangular hollows 53h, and has a hollow 53h at its tip. Have two openings 53b. The front end surface of the housing frame 53 is a contact surface 53a that contacts the circuit board, and a bottom 53i is provided on the base 12 side of the hollow 53h. That is, the storage frame 53 is also a bottomed frame shape. The outer surface of the storage frame 53 facing the light guide direction (the direction indicated by the arrow in FIG. 30) is inclined so that the thickness of the storage frame 53 decreases from the front end side toward the base 12 side. It has become. Furthermore, it has the extension part 53d which spreads along the one surface of the base 12 from the edge part by the side of the base 12 of the inclined surface 53c, and the disk spring on a circuit board is provided in the surface facing this circuit board in this extension part 53d. A pressing protrusion 53e for pressing is provided. The difference from the housing frame 33 is that the standing portion 53f that fills the slit 59 is formed as described above.

  The slit 59 is formed between the key tops 55 so as not to block the light guide of the base 12 and extends in the light guide direction (indicated by the arrow in the drawing).

The soft resin film 56 is a member that protects the base 12, is interposed between the key top 55 and the base 12, adjusts the light guide characteristics, and increases the fixing strength of the key top 55 to the light guide sheet 51. Adjustment of the light guide characteristics of the base 12 by the soft resin film 56 is, for example, increasing the light guide efficiency of the base 12 by increasing the difference between the refractive index of the soft resin film 56 and the refractive index of the base 12, The amount of light emitted to the key top 55 side can be increased by making the refractive index of 56 equal to the refractive index of the base 12.
The material of the soft resin film 56 is preferably a thin and flexible transparent resin. For example, vinyl resin, polyester resin, polyurethane resin, styrene thermoplastic elastomer, olefin thermoplastic elastomer, urethane thermoplastic elastomer, ester thermoplastic elastomer, vinyl chloride thermoplastic elastomer, amide thermoplastic elastomer And fluorine-based thermoplastic elastomers. Of these, polyurethane-based resins or urethane-based thermoplastic elastomers that are thin, flexible, hardly broken, and easy to select an adhesive are suitable. In the case of a thermoplastic resin, the adhesive layer may be omitted because it can be softened or melted by heating to be firmly fixed to other members.

The first adhesive layer 56a and the second adhesive layer 55h are layers that fix the soft resin film 56 to other members. The layer thickness is preferably about 5 μm to 30 μm, and if it is thinner than 5 μm, the adhesive strength may be reduced, and even if it exceeds 30 μm, the adhesive strength hardly changes.
Examples of the material of the first adhesive layer 56a and the second adhesive layer 55h include a hot-melt adhesive that is thermocompression-bonded and an ultraviolet curable adhesive.

  In the method of manufacturing the key sheet 50, first, the irradiation portion 14, the transparent resin layer 26, and the dark print layer 48 are sequentially printed on one surface of the base 12 made of a resin film, and then the slit 59 is formed with a punching die. Next, the soft resin film 56 is fixed to the other surface of the base 12 via the first adhesive 56a. Next, a mold for forming the housing frame 53 is prepared, a liquid resin for forming the housing frame 53 is injected into the mold, the other surface side of the base 12 to which the soft resin film 56 is fixed is set in the mold, and the slit The liquid resin is infiltrated into 59 and then the liquid resin is cured to integrate the housing frame 53. Finally, the key top 55 provided with the decorative printing layer 55g and the second adhesive layer 55h in this order is fixed onto the soft resin film 56 via the second adhesive 55h to obtain the key sheet 50.

  The key sheet 50 having such a light guide sheet 51 presses the key sheet 50 against the circuit board 2 with the pressing protrusion 2 b of the housing 2, and the housing recess 53 b of the housing frame 53 houses the LED 4. The electronic device 1 is fixed so that the contact surface 53a contacts the circuit board 3 and the key top 55 corresponds to the disc spring 5 (see FIG. 23). A gap necessary for the pressing stroke of the disc spring 5 is formed between the pressing projection 53 e of the key sheet 50 and the circuit board 3 by the housing frame 53.

  According to the light guide sheet 51 and the key sheet 50 including the light guide sheet 51, since the key sheet 50 is an integrated object, it can be easily incorporated into the electronic apparatus 1. Further, the light guide sheet 51 can increase the illumination brightness of the key top 55, and can easily maintain a higher light guide efficiency.

  Since the slit 59 is provided, the deformation stress of the light guide sheet 51 can be relaxed through the slit 59, and the pressing load can be reduced during the pressing operation.

  The key sheet 50 according to the fifth embodiment can be modified similarly to the key sheet 40 according to the fourth embodiment. For example, the irradiation unit 14 may be provided on the other surface of the base 12 and may be formed in the shape of a display element. A decorative print layer may be formed on the base 12.

  A modification common to the embodiments will be described. In addition, although demonstrated below as a modification of the light guide sheet 11, the light guide sheets 21, 31, 41, 51, 111-114, and 211 can be described similarly.

Sixth Embodiment [FIGS. 32 to 35]
The light guide sheet 61 of the sixth embodiment is shown in FIGS. 32 and 33, and the electronic device 1 incorporating the light guide sheet 61 is shown in FIGS. 32 is a plan view of the light guide sheet 61, FIG. 33 is a sectional view of the light guide sheet 61, FIG. 34 is a partially enlarged explanatory view of the electronic device 1 when the light guide sheet 61 is incorporated, and FIG. 1 is a partially enlarged explanatory view of an electronic device 1 incorporating 61. FIG. Unlike the light guide sheet 11 of the first embodiment, the light guide sheet 61 of this embodiment includes a base 62 and a housing frame 63. Other configurations are the same as those of the light guide sheet 11.

  Like the base 12, the base 62 is a base portion of the light guide sheet 61, and is a light guide portion that mainly guides light. And it is formed in rectangular flat plate shape with transparent resin, and the surface is a flat smooth surface. The difference from the base 12 is that it has two through holes 62a formed in a rectangular shape. A part of a storage frame 63 described later is inserted into the through hole 62a.

  Similar to the housing frame 13, the housing frame 63 is a light receiving unit that allows an internal light source to enter and covers at least the light emitting unit of the internal light source. And it is formed in bottomed frame shape with transparent resin. However, unlike the housing frame 13, the two hollows 63 h enter the through holes 62 a of the base 62, respectively, and the surface on the other surface side of the bottom 63 i forms the same surface as the other surface of the base 62. Further, the tip surface protruding from one surface of the base 62 is a contact surface 63a that contacts the circuit board, and an inclined surface 63c that is inclined from the tip side toward the base 62 is also formed. However, since the hollow 63h is also formed in the through hole 62a of the base 62, the projecting dimension of the contact surface 63a is smaller than the projecting dimension of the contact surface 13a, and the inclined surface 63c is also smaller than the inclined surface 13c.

In the method of manufacturing the light guide sheet 61, first, the through hole 62a is formed in the base 62 made of a resin film, and then the irradiation portion 14 is printed on the other surface of the base 62.
Next, the housing frame 63 is formed on the base 62 to obtain the light guide sheet 61.

As shown in FIG. 34, the electronic device 1 in which the key sheet 60 including the light guide sheet 61 is incorporated has a key sheet 60 composed of the light guide sheet 61 and the cover sheet 15 inside the casing 2, Circuit board 3.
As shown in FIG. 35, the key sheet 60 is pressed against the circuit board 2 by the pressing protrusion 2 b of the housing 2, and the LED 4 is caused to enter the hollow 63 h of the housing frame 63, and the contact surface 63 a of the housing frame 63 is the circuit board 3. The key sheet 60 is fixed so that the key top 15 b corresponds to the disc spring 5. A gap necessary for the pressing stroke of the disc spring 5 is formed between the base 62 of the key sheet 60 and the circuit board 3 by the housing frame 63.

  According to the light guide sheet 61 and the key sheet 60 including the light guide sheet 61, since the hollow 63h is also formed in the through hole 62a of the base 62, the projecting dimension of the contact surface 63a can be reduced. A gap between the base 62 and the circuit board 3 can be reduced. Therefore, the thin disc spring 5 can be mounted, and the electronic device 1 can be thinned. Furthermore, the inclined surface 63c can be reduced, and the key sheet 60 can be reduced.

  Since the hollow 63h of the housing frame 63 is in the through hole 62a of the base 62, the light of the LED 4 can be easily incident on the end face of the through hole 62a in the base 62, and the light guide efficiency of the base 62 is increased. Can do.

Modification 1 common to each embodiment (FIGS. 36 to 38) :
The light guide sheet 71 is a soft resin member 76 that is deformed so as to fill a gap between the LED 4 and the housing frame 13 in the hollow 13 h of the housing frame 13, or is soft at the operating temperature and softens the base 12 and the housing frame 13. A low-melting resin member 77 made of a resin having a melting point lower than the temperature can be provided.

The soft resin member 76 is a member that is in close contact with the light emitting surface of the LED 4 and receives the irradiation light of the LED 4 more efficiently. For this reason, first, it is more preferable to have transparency and higher transmittance. If the transmittance is high, the amount of light is less attenuated and light can be guided to the base 12.
The capacity of the soft resin member 76 may be provided so as to fill the hollow 13h, or the hollow 13h may not be completely filled. When the LED 4 is buried, it is preferable to have a capacity sufficient to receive the soft resin member 76 that is in close contact with the light emitting surface of the LED 4 and is pushed away by the LED 4.
When the light guide sheet 11 is pressed against the LED 4 and incorporated, the soft resin member 76 is restricted from being deformed by the housing frame 13 and closely contacts the LED 4. Therefore, the soft resin member 76 needs to be made of at least a softer resin or rubber-like elastic body than the housing frame 13. In order to easily follow the outer shape of the LED 4 flexibly and adhere to the light emitting surface of the LED 4 without an air layer when pressed and adhered, a rubber-like elastic body is preferable. . This is because if an air layer is interposed between the light emitting surface of the LED 4 and the soft resin member 76, a part of the irradiation light is reflected and the amount of light that can be guided to the base 12 is reduced. If the soft resin member 76 is a rubber-like elastic body, it can be easily deformed and attached to the light emitting surface of the LED 4 with a low load without passing through an air layer, so that it can be easily assembled and pressed with a high load. It is also possible to use a thin casing 2 that is difficult to perform.
Furthermore, since side view type chip LEDs that emit light from the side are often used recently, it is preferable that the LED can be brought into close contact with the light emitting surface on the side when pressed from the upper surface. In such a case, the material used for the soft resin member 76 is preferably a rubber-like elastic body having a rubber hardness of JIS K 6253 at an ordinary temperature of E0 or less, and the penetration of JIS K 2207 is 180 or more at an ordinary temperature. More preferably. If the soft resin member 76 is a rubber-like elastic body having a rubber hardness E0 or less, the soft resin member 76 is deformed by the stress from the upper surface and can be easily brought into close contact with the side surface of the LED 4. Further, if the soft resin member 76 has a penetration of 180 or more, the soft resin member 76 can be deformed with a weaker stress and can be easily brought into close contact with the side surface of the LED 4. Moreover, it is preferable that the soft resin member 76 has adhesiveness. This is because, if the adhesiveness is provided, the air layer can be adhered more reliably without passing through the air layer, and even if an impact or vibration is applied, the air layer is less likely to be formed.
Examples of the material of the soft resin member 76 include silicone rubber, urethane rubber, and acrylic rubber as rubber-like elastic bodies having a rubber hardness of E0 or less. Among these, silicone rubber having excellent transparency is used. It is preferable to use it. Furthermore, it is more preferable that the rubbery elastic body has a penetration of 180 or more by adjusting the crosslinking density or adding a plasticizer.

The housing frame 13 provided with the soft resin member 76 has a role of holding the soft resin member 76 and restricting deformation thereof, and therefore needs to be a material harder than at least the soft resin member 76. Furthermore, in order to securely hold the soft resin member 76 even when incorporated in the electronic apparatus 1, it is preferable that the rubber hardness is not less than A50. Examples of such materials include acrylic resins, polyurethane resins, epoxy resins, silicone resins, and the like.
Here, it is necessary to “hold” the soft resin member 76 because the soft resin member 76 is easily deformed or broken when the soft resin member 76 is particularly flexible.
“Regulating” means that the housing frame 13 prevents the flexible resin member 76 from being deformed to the outside when the flexible soft resin member 76 is pressed by the LED 4 and incorporated into the electronic device 1. It shows that it acts so that it may adhere more closely to LED4. When not restricting within the housing frame 13, when the soft resin member 76 is pressed against the LED 4, the soft resin member 76 is easily deformed so as to spread outward, and it is difficult to sufficiently adhere to the side surface of the LED 4.
The shape of the opening is larger than the LED 4 at least in a top view. Further, the distance between the light emitting surface of the LED 4 and the inner side surface of the housing frame 13 needs to include a space that allows the soft resin member 76 to be sufficiently deformed. For example, when the LED 4 has a height of 0.5 mm, the soft resin member 76 can be sufficiently deformed if the distance from the light emitting surface to the inner surface of the housing frame 13 is about 0.5 mm to 5 mm. . If this gap is less than 0.5 mm, the soft resin member 76 in the narrow gap may be excessively deformed and destroyed, or may be peeled off from the housing frame 13 due to the deformation. If this gap is larger by 5 mm, the effect of restricting the deformation of the soft resin member 76 may be reduced at the time of incorporation, and 0.5 mm to 2 mm is more preferable in order to reliably restrict the gap.
Further, in the housing frame 13 provided with the soft resin member 76, the gap between the base 12 and the circuit board 3 can be set by the soft resin member 76, so that the contact surface 13a can be omitted.
It is preferable that the refractive index n2 of the housing frame 13 and the refractive index n4 of the soft resin member 76 satisfy the relationship of Expression 4.
n2≈n3 (Formula 4)
The light emitted from the LED 4 has the largest light component incident substantially perpendicularly on the interface between the soft resin member 76 and the housing frame 13. At this time, if the relationship of Expression 4 is satisfied, the amount of light reflected at the interface can be minimized, so that more light can be guided to the base 12.

The low-melting resin member 77 is a member that is in close contact with the LED 4 like the soft resin member 76, and the appearance that is in close contact with the LED 4 is the same as the state in which the soft resin member 76 is in close contact, and has the same optical function. On the other hand, since the adhesion method between the low-melting resin member 77 and the LED 4 is different from the adhesion method between the soft resin member 76 and the LED 4, some characteristics such as thermal characteristics required for the low-melting resin member 77 are different.
The low-melting resin member 77 has transparency and is preferably as high as possible in the same manner as the soft resin member 76, but need not be soft at room temperature. Instead, it is necessary to use a resin having a melting point lower than the heat resistance temperature of each member constituting the base 12 and the housing frame 13 and other light guide sheets 61 provided as necessary. Here, the “heat-resistant temperature” is a temperature that does not cause deterioration or deformation particularly by a short-time heat treatment, and the deflection temperature under load of each material can be used as a guide. However, in the present invention, at least the low-melting resin member 77 is pressed and brought into close contact with the LED 4 so long as there is no problem such as deterioration or deformation of each material under a relatively small load. Therefore, it is defined in JIS K 7191. It may be slightly higher than the deflection temperature under which the load is deformed when a load of 1.82 MPa or 0.45 MPa is applied. For example, for a polycarbonate resin base, a resin having a melting point of 130 to 140 degrees can be used. On the other hand, the melting point needs to be a temperature that does not cause problems such as flowing out during actual use. From such a viewpoint, the melting point of the low-melting resin member 77 needs to be at least 60 degrees or more, preferably 85 degrees or more. Examples of such a resin include paraffin and caprolactone resin.
Further, since the low-melting resin member 77 only needs to be in a molten state in the step of closely contacting the LED 4, the low-melting resin member 77 contains a curing agent that starts reaction by heating or melting, and cures and melts the resin while closely contacting the LED 4. By making it difficult, the heat resistance of the light guide sheet 61 can be increased.
The adhesion between the low-melting resin member 77 and the LED 4 is performed in a heated state. That is, the low-melting resin member 77 is melted by heating at a temperature lower than the heat resistance temperature of the base 12 and the housing frame 13. At this time, it is preferable to partially heat the LED 4 in a state where the housing frame 13 is weakly pressed. The LED 4 enters the housing frame 13 and is covered with the low-melting resin member 77 simultaneously with heating and melting. By cooling as it is, the LED 4 is fixed in the housing frame 13 without an air layer. By doing so, the low-melting resin member 77 is deformed by being constrained by the housing frame 13, so that it can be deformed so as to follow the outer shape of the LED 4. Can be adhered to. Further, since the low-melting resin member 77 is solid in use, it is possible to strengthen the engagement retention between the low-melting resin member 77 and the LED 4, and to make it difficult to shift the positions of both.

Modification 2 common to the embodiments (FIG. 39) :
In the light guide sheet 81, the soft resin member 76 or the low-melting resin member 77 provided in the hollow 13h in the housing frame 13 can be biased more than the light guide method.
In this way, when the side emitting LED 4 is used, the light emitting surface of the LED 4 can be easily adhered to the soft resin member 76 or the low-melting resin member 77.

Modification 3 (FIGS. 40 to 42) common to the embodiments :
In the light guide sheet 91, U-shaped ribs 93 g are provided on the housing frame 93 in plan view along the outer edge of the base 12. The surface of the rib 93g facing the circuit board is also a part of the contact surface 93a that contacts the circuit board. That is, the housing frame 93 includes a frame-shaped contact surface 93a that contacts the circuit board, an opening 93b formed by two hollows 93h that stores the internal light source, and an inclined surface 93c that is inclined toward the base 12 in the light guiding direction. And have.
In this way, the base 12 can be supported by the outer edge of the base 12 with respect to the circuit board, and a gap can be reliably formed between the base 12 and the circuit board even if the base 12 is wide. it can. Further, since the housing frame 93 has a frame shape, the inside of the rib 93g in the housing frame 93 can be made to have a sealed structure, and a dustproof and waterproof effect can be expressed to increase the reliability of the electronic device. Further, the contact surface 93a may be made sticky, or an adhesive material may be applied. By doing so, it can be easily fixed to the circuit board without using other members, and the dustproof and waterproof effect can be enhanced.

Hereinafter, the present invention will be described in detail with reference to examples.
Test items were “positional displacement of internal light source and change in brightness of key sheet” and “refractive index of housing frame and brightness of key sheet”.

1. Production of sample: The light guide sheets of Sample 1 to Sample 3 were produced.

Sample 1 : First, white ink (SG740, manufactured by Seiko Advance) was applied to one side of a polycarbonate resin film (refractive index n1 = 1.59, Iupilon sheet, manufactured by Mitsubishi Gas Chemical) having a smooth surface and a thickness of 300 μm as a base. Screen printing was performed to form a dot-shaped irradiation part. Next, a mold for forming the housing frame is prepared, and ultraviolet curable resin (refractive index n2 = 1.49) is injected into the mold. Then, one surface of the base 12 is set in a mold so as to be in contact with the ultraviolet curable resin, and the ultraviolet curable resin is cured by irradiating the ultraviolet rays so that the base and the housing frame are integrated. Thus, the light guide sheet of Sample 1 was obtained as Example 1.

Sample 2 : After the light guide sheet was produced in the same manner as Sample 1, addition reaction type silicone was dropped into the inside of the housing recess and cured, and a soft resin member having a penetration of 230 and a rubber hardness of E0 or less (refractive index) 1.46) is provided. Thus, the light guide sheet of Sample 2 was obtained as Example 2.

Sample 3 : A light guide sheet of Sample 3 was obtained as Comparative Example 1 in which an irradiation part was formed on one surface of the base in the same manner as Sample 1 and no housing frame was provided.

Sample 4 : First, a white ink was screen-printed on one surface of a urethane resin film (refractive index n1 = 1.51) having a smooth surface and a thickness of 100 μm as a base to form a dot-shaped irradiated portion. Next, UV curable resin (refractive index 1.59) is cured as a housing frame on one surface of the base 12 to integrate the base and the housing frame. Thus, the light guide sheet of Sample 4 was obtained as Example 3.

Sample 5 : A white ink was screen-printed on one side of the same base as that of the sample 4 to form a dot-shaped irradiation portion. Next, an addition reaction type silicone resin (refractive index: 1.42) is cured on one surface of the base 12 as a housing frame to integrate the base and the housing frame. Thus, the light guide sheet of Sample 5 was obtained as Example 4.

2. Test method :

  “Position deviation of internal light source and luminance change of key sheet”; When light from two white LEDs (side-emitting LEDs, SWAK08, manufactured by Seol Semiconductor) is incident on the samples 1 to 3 from the light receiving surface, The luminance of the measurement part in the irradiation unit was measured with a luminance meter (LS-110, manufactured by Minolta), and the luminance ratio according to the gap size between the white LED and the light receiving surface was calculated. The results are shown in Table 1. Specifically, the gap size between the white LED and the light receiving surface is set to 0 mm, 0.2 mm, 0.4 mm, 0.6 mm, and 0.8 mm, and the ratio of the brightness of the other gap size to the gap size of 0 mm. Is represented by the average value of measurement points 1 to 4. Measurement point 1 to measurement point 4 are a position where measurement point 1 is 23 mm away from the light receiving surface, a measurement point 2 is 38 mm away from the light receiving surface, a measurement point 3 is 53 mm away from the light receiving surface, and a measurement point 4 receives light. The position was 66 mm away from the surface.

  “Refractive index of housing frame and luminance of key sheet”; Sample 4, Sample 5 and white LED were fixed, and the luminance of the measurement points 1 to 4 was measured with a luminance meter (LS-110, manufactured by Minolta). . The results are shown in Table 2.

3. Measurement results :

  Sample 1 and sample 2 had a lower luminance drop than sample 3 even when the gap between the white LED and the light-receiving surface widened.

The brightness of the sample 5 whose refractive index of the housing frame is lower than the refractive index of the base is drastically decreased as the distance from the light source is larger than that of the brightness near the light source. On the other hand, the sample 4 in which the refractive index of the housing frame is higher than the refractive index of the base is bright even away from the light source, and is brightly illuminated in a wide range with no difference in distance from the light source. This shows that the sample 4 is superior to the sample 5 in order to obtain more uniform illumination performance over a wide range.
Since the refractive index of the storage frame of Sample 4 is higher than the refractive index of the base, all the measurement points are brighter than Sample 5 whose refractive index of the storage frame is lower than the refractive index of the base.

DESCRIPTION OF SYMBOLS 1 Electronic device 2 Case 3 Circuit board 4 LED (Internal light source)
5 Disc spring 10 Key sheet (first embodiment)
11 Light guide sheet (first embodiment)
111 Light guide sheet (first modification of the first embodiment)
112 Light Guide Sheet (Second Modification of First Embodiment)
113 Light guide sheet (third modification of the first embodiment)
114 Light guide sheet (4th modification of 1st Embodiment)
12 Base 13 Housing frame 13a Contact surface 13b Opening 13c Inclined surface 13h Hollow 13i Bottom 131 Housing frame (first modification of the first embodiment)
131a Contact surface 131b Opening 131c Inclined surface 132 Housing frame (second modification of the first embodiment)
132a Contact surface 132b Opening 132c Inclined surface 133 Accommodating frame (third modification of the first embodiment)
133a Contact surface 133b Opening 133c Inclined surface 134 Accommodating frame (fourth modified example of the first embodiment)
134a Contact surface 134b Opening 134c Inclined surface 134h Hollow 14 Irradiation part 15 Cover sheet 15a Base sheet 15b Key top (lighting member)
15c Pressing projection 16a Intermediate bar 16b Outer bar 16c Protruding part 16d Contact surface 20 Key sheet (second embodiment)
21 Light guide sheet (second embodiment)
211 Light Guide Sheet (Modification of Second Embodiment)
26 transparent resin layer 30 key sheet (third embodiment)
31 Light guide sheet (third embodiment)
33 receiving frame 33a contact surface 33b opening 33c inclined surface 33d extension 33e pressing projection 33h hollow 33i bottom 35 cover sheet 35a base sheet 35b key top (lighting member)
40 Key sheet (fourth embodiment)
401 Key sheet (first modification of the fourth embodiment)
402 Key sheet (second modification of the fourth embodiment)
403 key sheet (third modification of the fourth embodiment)
404 key sheet (fourth modification of the fourth embodiment)
41 Light guide sheet (fourth embodiment)
45 Transparent molded body 45b Key top (lighting member)
45d Display printing layer 45e Light-shielding printing layer 45f Blank character printing layer 46 Transparent resin layer 46a Press projection 47 Translucent printing layer 48 Dark printing layer 50 Key sheet (fifth embodiment)
51 Light guide sheet (fifth embodiment)
53 Housing frame 53a Contact surface 53b Opening 53c Inclined surface 53d Extension part 53e Pressing protrusion 53f Standing part 53h Hollow 53i Bottom 55 Key top (Lighting member)
55g Decorative Print Layer 55h Second Adhesive Layer 56 Soft Resin Film 56a First Adhesive Layer 59 Slit 60 Key Sheet (Sixth Embodiment)
61 Light Guide Sheet (Sixth Embodiment)
62 Base 62a Through-hole 63 Housing frame 63a Abutting surface 63c Inclined surface 63h Hollow 63i Bottom 71 Light guide sheet (first modification common to each embodiment)
76 Soft resin member 77 Fusing resin member 81 Light guide sheet (second modification common to each embodiment)
91 Light guide sheet (third modification common to the embodiments)
93 Housing frame 93a Contact surface 93b Opening 93c Inclined surface 93g Rib 93h Hollow 93i Bottom

Claims (9)

A light receiving unit that introduces light from an internal light source provided on a circuit board provided inside the electronic device, a light guide unit that guides the introduced light toward the irradiation unit, and an illumination member that guides the guided light A light guide sheet comprising:
A flat base that serves as a light guide portion has a hollow frame shape projecting from the one surface on one side of the internal light source side, and has an opening at the tip. A storage frame is provided,
At least a part of the outer surface of the housing frame is an inclined surface that is inclined so as to reduce the thickness of the housing frame from the tip side toward the base side and reflects incident light to the light guide section. .   The light guide sheet according to claim 1, wherein the refractive index of the housing frame is higher than the refractive index of the base.   The light guide sheet according to claim 1, wherein the housing frame has a bottomed frame shape having a bottom.   The light guide sheet according to any one of claims 1 to 3, wherein the front end surface of the housing frame is a contact surface that contacts a circuit board on which the internal light source is mounted.   The light guide sheet according to any one of claims 1 to 4, wherein an extension portion extending along one surface of the base is provided at a base side end portion of the inclined surface.   The light guide sheet according to any one of claims 1 to 5, further comprising a gap filler that fills a gap between the internal light source and the housing frame in the hollow of the housing frame.   The light guide sheet according to claim 6, wherein the gap filler is a soft resin member that can be deformed at a use temperature, or a low-melting resin member made of a resin having a melting point lower than the softening temperature of the base and the housing frame.   The light guide sheet according to any one of claims 1 to 7, wherein a transparent resin layer having a refractive index different from that of the base is provided on one surface side of the base.   The light guide sheet according to any one of claims 1 to 8, a pressing protrusion formed on one side of the light guiding sheet, and fixed to the other side of the light guiding sheet corresponding to the pressing protrusion. And a key top as an illuminating member.

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