JP7112367B2 - capacitive touch switch - Google Patents

Description

The present invention relates to capacitive touch switches, and more particularly to capacitive touch switches with LED backlight.

2. Description of the Related Art In home appliances, AV equipment, PC/OA equipment, industrial machinery, and other electronic devices, a capacitive touch switch is used as one of input means to each equipment (see, for example, Patent Document 1). . In this capacitive touch switch, finger contact is determined based on a change in the capacitance of the sensor electrode.

An example of a conventional capacitive touch switch is shown in FIG. FIG. 4 is a side sectional view of the touch switch. The touch switch 21 includes a glass substrate 22 having a sensor portion 23 on the surface opposite to the touch surface, a design layer 24 formed with a switch design portion 24a, a diffusion layer 28 for diffusing light, and an LED 25. A circuit board 26 is laminated in order. The sensor section 23 is connected to the circuit board 26 by sensor wiring 30 and a flexible printed circuit board (FPC) 27 . A control unit (see the drawing) is mounted on the circuit board 26 .

In the touch switch 21 of FIG. 4, an LED 25 is mounted on the rear surface of the switch design portion 24a in order to more clearly indicate that the switch has been operated. An LED backlight (a so-called top-type backlight) is used to indicate the state of the switch, and the pictograms and characters are illuminated. The LED 25 is provided from the diffusion layer 28 via a spacer 29 having a thickness of about 3 mm to 6 mm. The diffusion layer 28 is formed, for example, by printing light diffusion ink, and provided adjacent to the design layer 24 .

In the touch switch configured as shown in FIG. 4, when the touch surface 22a of the glass substrate 22 is touched with a finger, electrostatic coupling occurs between the sensor electrode of the sensor section 23 and the finger, and the capacitance of the electrode changes. The control unit of the circuit board 26 quantifies the amount of change in capacitance, and determines that the finger has touched when the numerical value exceeds a predetermined threshold value. When the contact of the finger is determined, the LED 25 is turned on or off, and the user can recognize that the switch has been pressed.

JP 2013-65429 A

In recent years, the use of touch switches has expanded, and they have come to be used not only indoors but also outdoors. In outdoor use, sunlight entering the touch switch may make it difficult to see the state of the switch. For example, in the configuration of FIG. 4, when the switch design (pictogram or character) is irradiated with light from the outside, the light is reflected by the diffusion layer 28, making it difficult to distinguish whether the LED 25 is on or off. .

SUMMARY OF THE INVENTION It is an object of the present invention to provide a touch switch which has excellent visibility and can easily determine whether the light source is on or off even when light is irradiated from the outside. aim.

In the capacitive touch switch of the present invention, a glass substrate having a sensor portion on the side opposite to the touch surface, a design layer having a switch design portion formed thereon, and a circuit board having a light source mounted thereon are laminated in this order. In the capacitive touch switch, a light guide plate is provided between the design layer and the circuit board, and the light guide plate has an incident surface on which light from the light source is incident and crosses the incident surface. and a light emitting surface from which light is emitted toward the switch design portion, and the light guide plate has a white reflective layer on a surface opposite to the light emitting surface and facing the circuit board. characterized by

The sensor section is formed with a predetermined wiring pattern, and is arranged at a position overlapping the switch design section and the light guide plate in the stacking direction, and the surface of the light guide plate is formed with an uneven portion for diffusing light. characterized in that it is not

The light guide plate is characterized by having the white reflective layer at a position corresponding to the shape of the switch design portion in the stacking direction.

A surface of the circuit board facing the light guide plate is black.

A diffusion layer for diffusing light is not provided at a position in contact with the switch design portion.

The capacitive touch switch is characterized by being used in an outdoor display device.

The capacitive touch switch of the present invention has a structure in which a glass substrate on which a sensor portion is formed, a design layer on which a switch design portion is formed, and a circuit board on which a light source is mounted are laminated in this order. Since the light guide plate is provided between and the circuit board, even when light is irradiated from the outside, the light guide plate suppresses the reflection of the light, making it less susceptible to external light. As a result, it is possible to easily determine whether the switch is lit or not. In addition, since the light guide plate has a white reflective layer on the surface opposite to the light emitting surface and facing the circuit board, the reflectance of the light from the light source can be increased and uniform surface light emission can be realized. In addition, since it is difficult for light to pass through to the circuit board side, unevenness in brightness can be prevented without being affected by the pattern and through holes of the circuit board.

In the configuration where the sensor section formed with a predetermined wiring pattern is arranged so as to overlap the switch design section and the light guide plate in the stacking direction, the surface of the light guide plate is provided with uneven portions (slits, dots, etc.) for light diffusion. Then, the wiring pattern of the sensor section and the concave-convex pattern of the light guide plate may interfere with each other, causing moire. On the other hand, in the touch switch, since the surface of the light guide plate is not formed with an uneven portion for diffusing light, moiré can be prevented and the visibility can be improved. Also, there is no restriction in designing the wiring pattern of the sensor section.

Since the light guide plate has a white reflective layer at a position corresponding to the shape of the switch design part in the stacking direction, the reflective layer is provided only at the place where the switch design part such as pictograms and letters is desired to emit light, making it brighter. It becomes a light guide plate.

Since the surface of the circuit board facing the light guide plate is black, the contrast of the switch design can be improved. Moreover, even if the light incident on the light guide plate leaks from a portion other than the white reflective layer or passes through the white reflective layer, the diffusion of the light can be prevented.

Since a diffusion layer for diffusing light is not provided at a position in contact with the switch design portion, the light is reflected by the diffusion layer when external light is irradiated, and the adjacent switch design portion is irradiated to display the design. can be suppressed.

INDUSTRIAL APPLICABILITY The capacitive touch switch of the present invention is used in an outdoor display device, and even when sunlight is irradiated from the touch surface, the light guide plate suppresses the reflection of sunlight, and the state of the light source can be easily determined.

1 is a side sectional view showing an example of a capacitive switch panel of the present invention; FIG. 2A and 2B are an enlarged schematic cross-sectional view of the sensor part of FIG. 1 and the like; It is a photograph showing the visibility of the example and the comparative example when the LED is not lit. FIG. 10 is a side cross-sectional view showing an example of a conventional capacitive switch panel;

An example of the capacitive touch switch of the present invention will be described with reference to FIG. FIG. 1 is a side cross-sectional view of a capacitive touch switch. As shown in FIG. 1, the touch switch 1 includes a glass substrate 2, a design layer 4 on which a switch design portion 4a is formed, a light guide plate 8, and a circuit board 6 on which an LED 5 as a light source is mounted. Laminated. The glass substrate 2 has a sensor section 3 formed on the opposite surface 2b side of the touch surface 2a. The sensor section 3 is connected to the circuit board 6 by the sensor wiring 10 and the FPC 7 .

In the touch switch of the present invention, by providing the light guide plate 8 instead of the diffusion layer (see FIG. 4), even when light is irradiated from the outside, the light guide plate 8 suppresses the reflection of the light, thereby reducing the influence of the external light. hard to receive. In the touch switch 1, a diffusion layer for diffusing light is not provided at a position in contact with the switch design portion 4a. Further, the touch switch 1 employs a so-called side-type backlight in which the LEDs 5 emit light from the side surface of the light guide plate 8 . This eliminates the need for a spacer (see FIG. 4), making it possible to reduce the overall thickness of the touch switch and make it compact.

The glass substrate 2 is a translucent insulating substrate, and can be made of soda-lime glass, quartz glass, borosilicate glass, alkali-free glass containing no alkali component, or the like. It is preferable to use soda-lime glass because it has a high transmittance, is used for window glass of general building materials, and is very inexpensive. The thickness of each glass substrate 2 is approximately 0.5 to 5 mm, preferably approximately 1.8 to 3.0 mm. Also, a transparent member such as an acrylic plate may be arranged on the front surface of the glass substrate 2 .

FIG. 2(a) shows an enlarged schematic sectional view of the sensor section 3. As shown in FIG. In FIG. 2A, the thicknesses of the sensor electrodes and the like are exaggerated for the purpose of explanation. As shown in FIG. 2(a), the sensor section 3 has a sensor electrode 3a made of a conductive film. Examples of the conductive film include metal thin films, conductive inorganic thin films such as tin oxide and ITO, and conductive low-melting-point glasses mainly composed of vanadate, bismuth, or lead. The metal thin film includes a metal thin film produced by a thin film forming method, and a metal thin film made of metal foil such as copper foil and gold foil.

Metal thin films produced by thin film forming methods are formed by known thin film forming methods using materials such as aluminum (Al), Al alloys, niobium, molybdenum, gold, silver, and copper. Among these, it is preferable to employ an Al thin film because of its excellent environmental resistance and low cost. As a specific example, an Al thin film is formed by sputtering or vacuum deposition, which is a vacuum process, using an Al solid target (evaporation material). The film thickness of the Al thin film is suitably 500 nm to 5000 nm.

In FIG. 2( a ), an intermediate layer 3 b is formed between the sensor electrode 3 a and the glass substrate 2 . The intermediate layer 3b is a thin film containing (1) at least one metal selected from Cr, Mo and W. The intermediate layer 3b is a layer (black layer) that absorbs incident light by interference of visible light and looks black. From the touch surface 2a, the switch portion appears black, and reflection can be suppressed. The intermediate layer 3b can be formed by sputtering or the like in the same manner as the formation of the Al thin film described above. Further, intermediate layer 3b preferably contains a predetermined amount of at least one oxide selected from (2) oxides of Al (such as Al ₂ O ₃ ) and oxides of Ti (such as TiO ₂ ). By including a predetermined amount of these oxides, the reflectance can be further reduced. The intermediate layer 3b is more preferably a mixed layer of _Mo and _Al2O3 . The film thickness of the intermediate layer is suitably 5 nm to 500 nm, more preferably 50 nm to 200 nm. This film thickness is determined for each material according to the refractive index of the intermediate layer material.

FIG. 2B shows a partially enlarged view of the sensor section. The sensor part is formed with a predetermined wiring pattern, and in FIG. 2B, the sensor electrode 3a and the intermediate layer 3b are formed in a grid pattern. The space between the lattices is the opening 3c. The opening 3c here is an opening in the two-layer portion of the sensor electrode 3a and the intermediate layer 3b. This grid shape is a fine grid shape, and each switch-shaped portion (the above-mentioned two-layer portion) becomes a translucent portion that looks transparent to the naked eye at a glance. In the case of a lattice shape (a unit lattice is a square), the line width W is usually set to 3 μm to 100 μm, and the pitch width P is set to about 0.2 mm to 1 mm. In addition, as long as the shape uses continuous fine lines, any pattern such as a hexagon, a vertically long rectangular rhombus, or a trapezoid can be used.

Note that the sensor electrode 3a and the intermediate layer 3b may be formed in a half-mirror pattern. Specifically, the sensor electrode 3a and the intermediate layer 3b are provided in the inner region between the grids, and openings are provided in a grid pattern. In this structure, the internal regions between the lattices are electrically connected in order to secure the conduction paths of the sensor electrodes.

In FIG. 1, the design layer 4 is a layer on which a switch design portion is formed. The design layer 4 can be a layer in which the switch design is directly printed on (on the sensor portion of) the glass substrate 2, or a layer of a film substrate (a separate member from the glass substrate) on which the switch design is printed. The printing method is not particularly limited, and for example, screen printing, color printing, or decorative printing using paint containing glass beads can be employed. The switch design portion 4a is arranged at a position overlapping the sensor portion 3 in the stacking direction.

The switch design is appropriately selected depending on the usage and purpose of the touch switch, and for example, pictograms and characters can be used. The design layer 4 may be transparent or translucent as long as it has translucency. Synthetic resins and ceramics can be used as the material for the film. Examples of synthetic resins include polyethylene terephthalate resin, polycarbonate resin, and acrylic resin. When a film is used, the design layer 4 may be composed of one sheet of film, or may be composed of a laminate in which a plurality of films are laminated.

As shown in FIG. 1, a light guide plate 8 is provided between the design layer 4 and the circuit board 6 . The light guide plate 8 has an incident surface 8a on which light from the LEDs 5 is incident, and an output surface 8b that intersects with the incident surface 8a and emits the light toward the switch design portion 4a. The touch switch 1 is characterized in that the light guide plate 8 has a white reflective layer 9 on the surface 8c facing the circuit board 6 and opposite to the light emitting surface 8b. Here, the white color may be any color that has a high reflectance in the visible light region, and is a color including milky white. By forming the white reflective layer 9 on the facing surface 8c of the light guide plate 8, it is possible to suppress the absorption of the light incident from the LED 5 by the circuit board 6 or the like, thereby improving the light reflectance. . As a result, the light emitted from the LEDs 5 can be effectively used, and uniform surface light emission can be achieved without providing the diffusion layer 28 (see FIG. 4), separate diffusion sheet, and polarizing sheet as in the conventional configuration.

The light guide plate 8 is a substantially rectangular parallelepiped plate member made of translucent resin that allows light to pass therethrough. Examples of translucent resins include acrylic resins, styrene resins, carbonate resins, cyclic olefin resins, and polystyrene resins. The thickness of the light guide plate 8 in the stacking direction is, for example, 1 to 3 mm. Although it is conceivable that the light irradiated from the outside is reflected by the white reflective layer 9, the reflection of the external light can be prevented by securing a certain distance D from the end surface of the sensor section 3 to the white reflective surface 9. can be suppressed. For example, the distance D is 2-10 mm, preferably 2-5 mm.

In addition, in the configuration of FIG. 1, the sensor section 3 is arranged at a position overlapping the switch design section 4a and the light guide plate 8 in the stacking direction. Therefore, if the surface of the light guide plate 8 (particularly, the exit surface 8b) has uneven portions such as slits or dots for diffusing light, it may interfere with the wiring pattern of the sensor unit 3 and cause moiré on the display screen. There is In consideration of this, the surface of the light guide plate 8 (particularly, the exit surface 8b) is not formed with an uneven portion, so visibility can be improved.

The white reflective layer 9 is composed of, for example, a white coating film or a white resin sheet material. For example, a whitish coating film can be obtained by coating the surface of the facing surface 8c of the light guide plate 8 with a paint containing a pigment component exhibiting a whitish color. As the pigment component, titanium oxide, zinc oxide, magnesium oxide, barium sulfate, calcium carbonate, alumina powder and the like are used. These may be used singly or in combination. Among the above, it is preferable to use zinc oxide and titanium oxide. As the white resin sheet material, specifically, an acrylic material or the like can be used.

The thickness of the white reflective layer 9 is 5-300 μm, preferably 5-30 μm. If the thickness is less than 5 μm, the light reflectance may decrease. Also, the white reflective layer 9 can be provided on the entire facing surface 8c of the light guide plate 8, but as shown in FIG. preferable. Further, it is more preferable to provide the white reflective layer 9 only at a position corresponding to the shape of the switch design portion 4a, for example, the shape to transmit light. Specifically, when the switch design is formed of predetermined characters as in the embodiment described later, the white reflective layer 9 can be provided along the shape of the characters.

On the other hand, the surface of the circuit board 6 facing the light guide plate 8 is formed in white or black. Since the white reflective layer 9 of the light guide plate 8 is provided above the circuit board 6, the circuit pattern and through-holes of the circuit board 6 do not interfere with each other to cause uneven brightness. It is preferable that the circuit board 6 be black because the contrast of the switch design can be improved and the light leaking from the light guide plate 8 can be prevented from diffusing.

The circuit board 6 is mounted with an LED 5 and a control section (see illustration). When the user touches the touch surface 2a of the glass substrate 2 with a finger, electrostatic coupling occurs between the sensor electrode of the sensor section 3 and the finger, and the capacitance of the electrode changes. The control unit of the circuit board 6 quantifies the amount of change in the capacitance, and determines that the finger has touched when the numerical value exceeds a predetermined threshold value. When finger contact is determined, for example, the LED 5 is lit to display the switch design. This allows the user to recognize that the switch has been pressed (that the signal has been turned ON).

INDUSTRIAL APPLICABILITY The capacitive touch switch of the present invention is used as a touch switch for home appliances, AV equipment, PC/OA equipment, industrial machinery, and other electronic devices. In particular, it is preferably used as a touch switch for outdoor display devices. Examples of outdoor display devices include display devices for pedestrian crossing signals.

In the configuration shown in FIG. 1, a translucent glass substrate is used as the glass substrate 2, but a half-mirror type glass substrate may be used instead. This glass substrate is formed by vapor-depositing an Al thin film or the like over one side of the glass substrate. In this configuration, in the area where the switch design part is arranged, the switch design is displayed on the display surface (surface of the half-mirror type glass substrate) when the backlight is lit from the back, and normally (when the backlight is not lit) becomes a mirror surface. As a result, the display surface can be switched between a mirror surface and a design display surface, and the design can be improved.

Example A capacitive touch switch having the shape shown in FIG. 1 was produced. Specifically, an intermediate layer (thickness: 100 nm) was formed on a soda-lime glass substrate (thickness: 1.0 mm) by sputtering using a target of a mixture of Mo and Al ₂ O ₃ (containing 10% by weight of Al ₂ O ₃ ). ), and a 99% pure Al thin film (thickness: 1000 nm) was formed thereon by sputtering. After that, wet etching was performed to form a sensor part having a lattice-shaped sensor electrode and an intermediate layer. A character "please" was formed on this sensor portion by screen printing. An acrylic plate (thickness: 2 mm) was used as the light guide plate. A white reflective layer was obtained by screen printing on one surface of the acrylic plate. These were laminated together with an adhesive to obtain a capacitive touch switch in which each member was laminated.

FIG. 3(a) shows a photograph of the obtained capacitive touch switch under sunlight irradiation with the LED not lit.

Comparative Example A capacitive touch switch having the shape shown in FIG. 4 was produced. A glass substrate and a sensor portion having the same configuration as those in the example were used. Also, the diffusion layer was formed on the glass substrate by screen printing. FIG. 3(b) shows a photograph of the obtained capacitive touch switch under sunlight irradiation with the LED not lit.

As shown in FIG. 3, the characters "please" were hardly observed in the capacitive touch switch of the example (FIG. 3(a)). That is, the user can recognize that the LED is not lit. On the other hand, in the comparative example (FIG. 3(b)), the characters can be clearly recognized, and although the LED is not lit, it can be recognized as if the LED is lit. In this manner, the capacitive touch switch according to the present invention can easily determine whether the LED is off even when exposed to external light.

INDUSTRIAL APPLICABILITY The capacitive touch switch of the present invention has excellent visibility and can be widely used as a capacitive touch switch because the state of the light source can be easily determined even when light is irradiated from the outside. In particular, it is suitable for use outdoors where sunlight is irradiated.

1 touch switch (capacitive touch switch)
2 glass substrate 3 sensor part 4 design layer 4a switch design part 5 LED (light source)
6 circuit board 7 FPC
8 light guide plate 8a entrance surface 8b exit surface 8c opposing surface 9 reflective layer 10 sensor wiring

Claims (6)

A capacitive touch switch in which a glass substrate having a sensor portion on the side opposite to the touch surface, a design layer in which a switch design portion is formed, and a circuit board on which a light source is mounted are laminated in this order,
A light guide plate is provided between the design layer and the circuit board, and the light guide plate has an incident surface on which light from the light source is incident, intersects the incident surface, and directs light toward the switch design section. It has an exit surface from which light exits,
The light guide plate has a white reflective layer on a surface opposite to the output surface and facing the circuit board ,
The capacitive touch switch , wherein the sensor section is formed with a predetermined wiring pattern, and is arranged at a position overlapping with the switch design section and the light guide plate in a stacking direction . 2. The capacitive touch switch according to claim 1, wherein the surface of said light guide plate is not formed with an uneven portion for diffusing light. 3. The capacitive touch switch according to claim 1, wherein the light guide plate has the white reflective layer at a position corresponding to the shape of the switch design portion in the stacking direction. 4. The capacitive touch switch according to any one of claims 1 to 3, wherein the surface of the circuit board facing the light guide plate is black. 5. The capacitive touch switch according to any one of claims 1 to 4, wherein no diffusion layer for diffusing light is provided at a position in contact with the switch design portion. The capacitive touch switch according to any one of claims 1 to 5, wherein the capacitive touch switch is used for an outdoor display device.

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