JP5194428B2 - Reflective encoder - Google Patents

Description

The present invention relates to a reflective encoder.

  As a sealing structure of a light emitting diode, a light emitting diode element is accommodated in a cavity of a ceramic or synthetic resin container, and a synthetic resin such as a translucent epoxy resin or silicone resin is poured into the cavity to emit the light emitting diode element. There is known one that seals.

  However, when a light emitting diode employing the above sealing structure is mounted on a wiring board, there is a problem that it is difficult to reduce the size.

  Therefore, it has been proposed to mount the light emitting diode element directly on the wiring board (see, for example, Patent Document 1).

JP 2003-304003 A

  However, the light emitted from the light emitting part of the light emitting diode element and reflected from the light emitting diode element is reflected by other members, returned to the light emitting diode element side, and repeatedly reflected on the surface of the light emitting diode element. There is a problem that light is emitted from the location.

An object of the present invention is to provide a reflective encoder in which light is not emitted from a portion other than a light emitting unit.

According to the first aspect of the present invention, a light emitting diode element including a mesa portion and a light emitting portion that emits light, a reflecting plate having a reflecting portion that reflects the light, and the light reflected by the reflecting portion. A light-receiving element that receives light, and a sealing layer that is covered with the light-emitting diode element of the light-emitting diode element and the light-receiving element and has an absorption characteristic that absorbs the light reflected by the reflector , A reflective encoder is provided in which the sealing layer includes a resin containing an absorbent that absorbs the light .

  For example, the absorption characteristics may be provided by the molecular structure itself of the synthetic resin constituting the sealing layer. In some cases, for example, an organic or inorganic compound having an absorption band of light in the wavelength range of light emission may be added to the synthetic resin constituting the sealing layer to provide absorption characteristics.

In the reflective encoder, the sealing layer is covered with the mesa portion and the light emitting portion of the light emitting diode element.

In the reflective encoder, the sealing layer includes a resin containing an absorbent that absorbs the light.

  Examples of the absorbent include organic and inorganic compounds having an absorption band that absorbs light in the wavelength range of light emission.

In the reflective encoder, the resin is dropped on the light emitting diode element to form the sealing layer.
In the reflective encoder, the light emitting diode element has a light emitting window through which the light is transmitted, and the light emitting window has a transparent protective film.
The reflective encoder includes a pair of the light receiving elements, and the light emitting diode element and the pair of light receiving elements are mounted on the substrate in parallel so that the pair of light receiving elements are located on both sides of the light emitting diode element. Has been.

According to the second aspect of the present invention, the sealing layer having an absorption characteristic for absorbing the reflected light reflected by the reflection plate of the reflective encoder on which the light in the wavelength region emitted from the light emitting diode element is incident is formed. A first step of dropping a sealing agent on the light emitting diode element; and the step of dropping the sealing agent in the first step so as to form the sealing layer having a substantially uniform film thickness on the entire surface of the light emitting diode element. And a second step of covering the entire surface of the light emitting diode element with a sealing agent. A method for coating a light emitting diode for a reflective encoder is provided.

  The sealant is, for example, an uncured synthetic resin, and has a viscosity that can flow on the surface of the light-emitting diode element due to the surface tension of the resin being blown by blowing the gas.

The method for coating a light emitting diode for a reflective encoder includes a third step of curing the sealant.
In the above-described method for coating a light emitting diode for a reflective encoder, the second step includes spraying a gas onto the sealing agent dropped in the first step.
In the method for coating a light emitting diode for a reflective encoder, in the first step, the uncured sealing agent is dropped onto the light emitting diode element.

  According to the present invention, since it is covered with the sealing layer having an absorption characteristic that absorbs light in the wavelength region emitted from the light emitting portion, no light is emitted from a portion other than the light emitting portion.

  Hereinafter, an embodiment of a light-emitting diode, an encoder equipped with the light-emitting diode, and a method of covering the light-emitting diode according to the present invention will be described with reference to FIGS.

  FIG. 1A is a plan view showing an embodiment of a light emitting diode of the present invention, FIG. 1B is a perspective view thereof, and FIG. 2 is a perspective view of a state in which the light emitting diode of FIG. 3 is a flow chart showing an embodiment of the light emitting diode coating method of the present invention, FIG. 4 is a schematic perspective view showing an embodiment of the encoder of the present invention equipped with the light emitting diode of FIG. 1, and FIG. 5 is shown in FIG. It is a partial expanded side view of an encoder.

  As shown in FIGS. 1A and 1B, the light-emitting diode 10 of the present embodiment includes an LED chip 14 as a light-emitting diode element on a cathode electrode 11 with a conductive adhesive (silver paste) 12 interposed therebetween. Constructed by bonding.

  An electrode 13 is provided on the surface of the LED chip 14 opposite to the side fixed to the cathode electrode 11, and this electrode 13 is connected to the anode electrode 16 via a lead wire 15.

  The light emitting unit 17 of the LED chip 14 emits light having a predetermined wavelength by applying a voltage between the cathode electrode 11 and the anode electrode 16. The light emitting unit 17 emits light through a light emitting window 18 formed on the surface portion on the side where the electrode 13 is provided. The light emitting window 18 is provided with a transparent protective film (not shown), and the light emitting portion 17 is protected by this protective film.

  The entire surface of the LED chip 14 including the light emitting portion 17 and the mesa portion 19 of the LED chip 14 is coated with a sealing layer 20 made of a synthetic resin. Therefore, the light-emitting portion 17 and the mesa portion 19 that are at a high risk of being corroded by the external environment are protected from being cut off from the external environment, and the LED chip 14 is accommodated in the container cavity without any lighting failure. Thus, reliability can be ensured as in the case of resin sealing. In addition, the sealing layer 20 is not too thick and covers the entire surface of the LED chip 14 with a substantially uniform thickness, so that the sealing layer 20 is contained in a cavity of a container and is resin-sealed. And small and thin. In other words, it is possible to ensure the reliability by preventing the corrosion due to the external environment without changing so much from the size of the LED chip 14 itself.

  The sealing layer 20 has an absorption (absorption) characteristic that absorbs (absorbs) light in the wavelength region emitted from the light emitting unit 17, for example, an absorbent (absorbing agent) having an absorption band of the light wavelength of the light emitting unit 17. Added epoxy resin is used. An absorbent is added to the epoxy resin, but a filler (filler) that causes scattering and dispersion of light from the light emitting portion 17 is not added.

  As the absorber (light absorber), for example, an organic or indefinite compound such as a colorant having an absorption band of the light wavelength of the light emitting portion 17 is used. Further, among the various additives added to the epoxy resin, when there is an additive having an absorption band of light wavelength of the light emitting portion 17 (having absorption characteristics), the absorbent is not added. Further, the absorbent is not added even when the synthetic resin constituting the sealing layer 20 has an absorption band in the light wavelength region of the light emitting portion 17.

  The absorption rate of the sealing layer 20 is set to about 5%, for example. If the absorptance is about 5%, the ratio of the light emitted from the light emitting unit 17 to be absorbed and lost before exiting the sealing layer 20 is small, and approximately 95% of the light emitted from the light emitting unit 17. Since the light passes through the sealing layer 20 and is emitted, there is no possibility that the emission intensity is greatly reduced.

  In addition, as shown in FIG. 2, the light L from the light emitting unit 17 is reflected by another member such as a rotary reflection disk 27 (see FIGS. 4 and 5 described later) and returns to the LED chip 14. (The light intensity is smaller than the light H emitted from the light emitting portion 17) is absorbed by the sealing layer 20, and the returned light h is formed on the surface portion of the LED chip 14 (the electrode 13 made of gold plating is formed). The surface is easy to reflect) and there is no risk of repeated reflection. That is, the sealing layer 20 can prevent light from being emitted from a place other than the light emitting portion 17.

  Next, an embodiment of the coating method of the present invention will be described with reference to the flowchart of FIG.

  In step S100, the light emitting diode 10 including the cathode electrode 11 shown in FIGS. 1A and 1B and the LED chip 14 and the anode electrode 16 on the cathode electrode 11 is mounted on the wiring board 22 (see FIG. 2).

  In step S101, an uncured epoxy resin as a sealant for forming the sealing layer 20 (see FIGS. 1A and 1B) is dropped on the surface of the LED chip 14 on the side where the electrodes 13 are formed. . The dropped epoxy resin is raised on the surface portion of the LED chip 14 due to its surface tension. The epoxy resin is added with an absorbent having an absorption band that absorbs light in the wavelength region emitted from the light emitting portion 17 of the LED chip 14.

  When air is blown onto the epoxy resin raised on the LED chip 14 due to surface tension in step S102, the surface tension is broken and the epoxy resin flows along the surface of the LED chip 14, and includes the light emitting part 17 and the mesa part 19. The entire surface of the LED chip 14 is covered with a substantially uniform thickness.

  In step S103, the LED chip 14 is placed in an oven together with the wiring board 22, and the epoxy resin is heated and cured.

  Thereby, an epoxy resin hardens | cures and the whole surface of LED chip 14 is coat | covered with the substantially uniform thickness by the sealing layer 20 which consists of an epoxy resin. Further, the surface portion on the side where the light emitting portion 17 of the LED chip 14 to which air is directly blown in step S102 is disposed is covered with the sealing layer 20 with an appropriate thickness without the sealing layer 20 being too thick. It will be.

  Thus, by covering the LED chip 14 with the sealing agent made of an epoxy resin to which an absorbent is added, it becomes possible to provide the light emitting diode 10 having the above-described effects at low cost.

  Next, the rotary encoder 25 using the light emitting diode 10 described above with reference to FIGS. 4 and 5 will be described.

  The rotary encoder 25 is a reflection type light emitting diode 10 (cathode electrode 11, LED chip 14 and anode electrode 16) as a light emitting element, a pair of photodiodes 26 as light receiving elements, and the pair of photodiodes 26, respectively. The rotating reflecting disc 27 is provided with the reflecting portions 27a and 27a facing each other at appropriate intervals along the circumferential direction.

  The light emitting diode 10 and the pair of photodiodes 26 are mounted in parallel on the same wiring board 22 so that the photodiodes 26 are located on both sides of the light emitting diode 10.

  The rotary reflection disk 27 has reflection portions 27a and 27a formed on the outer peripheral portion of one surface thereof, and the wiring board is configured to reflect the light from the light emitting diode 10 to the photodiode 26 side by the reflection portion 27a. The light emitting diode 10 and the photodiode 26 mounted on 22 are arranged to face each other.

  According to the rotary encoder 25, the light reflected by the rotary reflection disk 27 is covered with the surface of the LED chip 14 before it is repeatedly reflected on the surface of the LED chip 14 (the surface on which the electrode 13 made of gold plating is easily formed). Since only light that has been absorbed by the stop layer 20 and emitted from the light emitting portion 17 of the LED chip 14 and reflected by the reflecting portion 27a is incident on the photodiode 26, the output of the photodiode 26 has little noise and is high. Accuracy can be measured.

  Further, since the light emitting diode 10 is configured such that the LED chip 14 is accommodated in the cavity of the container and is not sealed with the synthetic resin, but directly mounted on the wiring substrate 22, the rotary encoder 25 can be reduced in size and thickness. I can do it.

  The present invention is not limited to the above embodiment.

  For example, the case where the sealing layer 20 is made of an epoxy resin is shown, but an absorbent (light absorber) having an absorption band (light absorption band) of the light wavelength of the light emitting portion 17 is added to a transparent silicone resin. May be.

  Further, the light emitting diode 10 of the present invention can be used in addition to the rotary encoder 25, and is effective particularly when it is required to be small and thin when mounted directly on the wiring board 22.

  Further, in the method for coating a light emitting diode of the present invention, the heat curing step may be omitted, the synthetic resin may be dropped, air may be blown, and then left at room temperature to cure the synthetic resin.

FIG. 1A is a plan view and FIG. 1B is a perspective view showing an embodiment of a light-emitting diode according to the present invention. It is a perspective view of the state which mounted the light emitting diode of FIG. 1 on the wiring board. It is a flowchart which shows one Embodiment of the coating method of the light emitting diode of this invention. FIG. 2 is a schematic perspective view showing an embodiment of an encoder of the present invention equipped with the light emitting diode of FIG. 1. FIG. 5 is a partially enlarged side view of the encoder shown in FIG. 4.

Explanation of symbols

10 LED 14 LED chip (LED element)
17 Light emitting part 19 Mesa part 20 Sealing layer 25 Rotary encoder 26 Photodiode (light receiving element)
27 Rotating Reflection Disc (Reflector)
27a Reflector

Claims (5)

A light-emitting diode element including a mesa portion and a light-emitting portion that emits light;
A reflector having a reflecting portion for reflecting the light;
A light receiving element that receives the light reflected by the reflecting portion;
A sealing layer that is covered with the light emitting diode element out of the light emitting diode element and the light receiving element and has an absorption characteristic that absorbs the light reflected by the reflector;
Equipped with a,
The reflective encoder , wherein the sealing layer includes a resin containing an absorbent that absorbs the light . The reflective encoder according to claim 1, wherein
The reflective encoder, wherein the sealing layer is covered with the mesa portion and the light emitting portion of the light emitting diode element. The reflective encoder according to claim 1 or 2 ,
A reflective encoder, wherein the resin is dropped onto the light emitting diode element to constitute the sealing layer. In the reflective encoder according to any one of claims 1 to 3 ,
The light emitting diode element has a light emitting window through which the light is transmitted,
The light emitting window has a transparent protective film,
A reflective encoder characterized by that. In the reflective encoder according to any one of claims 1 to 4 ,
A pair of the light receiving elements,
The reflective encoder, wherein the light emitting diode element and the pair of light receiving elements are mounted on a substrate in parallel so that the pair of light receiving elements are positioned on both sides of the light emitting diode element.

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