JP2002225068A - Molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molding which is improved in visibility by improving brightness by increasing the amount of light transmitted from an included emitter to the outside and has improved durability. SOLUTION: A thermoplastic resin 11 which forms the whole or part of the molding 10 has a light transmission property and seals the included emitter 22 directly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molded product suitable for application to a proximity sensor or the like.

[0002]

2. Description of the Related Art Many proximity switches and photoelectric switches serving as detection switches are provided with a light-emitting element, for example, an LED for recognizing an operation state. In order to make the LED of the chip or the unit disposed inside the housing visible from the outside, a part of the housing may be made of a light-transmitting component that transmits light emitted from the LED, or FIG.
As shown in (1), it is necessary to house the LED 2 in the housing 1 formed of a translucent resin. In particular, in an environment where a liquid such as water is used, or in a manufacturing line or the like, water resistance, environmental resistance, and the like are required.

[0003]

In a structure in which a part of the housing is formed of a light-transmitting component, it is necessary to use a material having both light-transmitting properties and mechanical strength for the light-transmitting component.
For a thermosetting resin, it is desirable to use a thermoplastic resin because the molding time is short, an ordinary injection molding machine can be used, and there are many resin options and a resin can be selected according to product specifications. However, in general, a thermoplastic resin (amorphous resin) having a good translucency tends to have a low mechanical strength, so that the type of resin that can be selected as a material for the translucent component is limited, and thus a product is not produced. There is a problem that the degree of freedom in design is small. In addition, since the number of components of the housing increases, there is a problem that component costs and assembling costs are high, or it is not possible to meet the demand for further downsizing. Also, particularly for applications requiring environmental resistance, it is possible to prevent foreign substances (water, gas, etc.) from entering the inside of the housing from the boundary between the components forming the majority of the housing and the light-transmitting components fitted therein. It is difficult to seal to prevent over a period, and there is a problem that even if it is possible, the cost is high.

[0004] Further, a structure in which the entire housing is formed of a light-transmitting resin as shown in Fig. 8 can be envisaged. However, as described above, generally, a thermoplastic resin (amorphous resin) having a good light-transmitting property is used. Has a problem that the degree of freedom in product design is small with respect to the mechanical strength and durability of the housing. Furthermore, when at least a part of the housing is formed of a light-transmitting component as described above, there is a problem that the amount of light emitted from the light-emitting body (LED, miniature light bulb, etc.) emitted from the housing to the outside is reduced.
For example, the LED 2 is obtained by sealing a light emitting element made of a semiconductor with a sealing body made of a transparent epoxy resin (hereinafter, also referred to as “sealing body 2”). Light emitted from the light emitting element is emitted to the outside using the sealing body 2 as a medium. At this time, since the medium around the sealing body 2 is air, the first time at the interface due to the difference in the refractive index between these mediums. Reflection occurs, and the amount of light L transmitted to the outside decreases. When light L emitted from the light emitting surface 2a reaches the inner surface 1a of the housing 1, air and the housing 1
The second reflection occurs at the interface due to the difference in the refractive index between the first and second surfaces, and when the light reaches the outer surface 1b of the housing 1, the third reflection occurs at the interface due to the difference in the refractive index between the housing 1 and the outside air. The amount of light decreases. As described above, the amount of the light La that has reached the outside is reduced due to these three reflections. In addition, most of the light (for example, Lb shown in FIG. 8) that has returned inward due to these reflections is repeatedly reflected and attenuated without leaving the housing 1. For this reason, there is a problem that the LED 2 viewed from the outside of the housing 1 has low luminance and poor visibility.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and improves visibility by increasing the amount of light transmitted from a built-in luminous body to the outside world, thereby improving visibility, and further improving durability. It is an object of the present invention to provide a molded article that achieves the following.

[0006]

According to a first aspect of the present invention, there is provided a molded article, wherein a thermoplastic resin forming the whole or a part of the molded article has a light-transmitting property and a built-in light emitting body. Is directly sealed. According to a second aspect of the present invention, in the first aspect, the whole or a part of the light emitting portion of the light emitting body is in close contact with the thermoplastic resin.

A third aspect of the present invention is the molded article according to the first or second aspect, wherein the thermoplastic resin is an elastomer. According to a fourth aspect of the present invention, there is provided a molded article according to the third aspect, wherein a part of the surface of the elastomer is covered with a material having a larger elastic coefficient than the elastomer. According to such a configuration of the present invention, by directly sealing the luminous body, a package having excellent environmental resistance is possible, and the refractive index of the luminous body and the thermoplastic resin that directly seals the luminous body are reduced. Since the difference is smaller than the difference between the refractive indices of the luminous body and air, light passing through the interface is hardly attenuated. Furthermore, a light medium (a translucent material,
Since the total number of interfaces between (air) can be reduced, light passing therethrough is hardly attenuated. Therefore, the amount of light transmitted from the light emitter increases, and visibility from the outside is improved.
In addition, when an elastomer is used as the thermoplastic resin, the fluidity can be maintained at a low melting temperature, so that it is difficult to exert a bad thermal and mechanical influence on the light emitting body as an insert part during molding. In addition, since the elastic modulus is relatively small even at room temperature, the stress generated inside the molded body during cooling after molding is small, and it is unlikely to exert a mechanical adverse effect on the light emitting body as an insert part. Further, when a part of the surface of the elastomer is covered with a material having a large elastic modulus, it can be applied to an application requiring mechanical strength.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a perspective view of a proximity sensor showing an embodiment of a molded body according to the present invention, FIG. 2 is a perspective view of a primary molded body of the proximity sensor shown in FIG. 1, and FIG. 3 is primary molding of the proximity sensor shown in FIG. It is a perspective view of the secondary molded object which covers a body. The secondary molded body shown in FIG. 3 shows a state in which the primary molded body shown in FIG. 2 has been removed from the proximity sensor shown in FIG. 1 in order to easily understand the shape.

As shown in FIGS. 1 to 3, a proximity sensor (molded body) 10 is a primary molded body 1 as a proximity sensor body.
1, a secondary molded body 12 as an outer shell that covers the primary molded body 11 and an electric wire 13. The primary molded body 11 is intended to seal an insert part having a luminous body and transmit light from the luminous body to the outside world, that is, to have visibility, and the secondary molded body 12 is provided with a proximity sensor. For the purpose of housing 10, a molding resin satisfying the specifications required for the sensor housing is selected, and by molding twice, sealing and housing of the sensor are realized without damaging the insert part. It has a solid integrated molding structure. In addition, it is a matter of course to select a resin that can provide adhesion between the primary molding resin and the secondary molding resin.

As shown in FIG. 4, a primary molded body 11 is a core 2 on which a detection coil as an electric component or an electronic component is wound.
1. A circuit board 20 on which a light emitting element (for example, LED) 22 as a light emitting body and other circuit elements 24 and the like are mounted is inserted. In the electric wire 13, the terminals of the core wires 15 to 17 drawn out from the terminals 14 a of the covering material 14 are connected to the circuit board 20 (FIG. 6).

The circuit board 20 and the terminal of the electric wire 13 are housed in a primary molding die (not shown), and a portion 14 b of the electric wire 13 near the terminal of the coating 14 is caulked and narrowed, and the primary molding resin 25 is removed. Will be filled. This primary molding resin 25
Is filled in a gap between the circuit board 20, the core 21, the light emitting element 22, and the circuit element 24, and is filled at a melting temperature lower than the heat resistant temperature when reaching the vicinity of these built-in components. You. For example, when a molten resin of 250 degrees Celsius is injected into a mold, the skin layer of the molten resin is cooled in the flow path and the core layer flows to the vicinity of the component while being kept at a high temperature. The skin layer is 90 degrees Celsius
Degree, and this skin layer has a heat-resistant temperature of 10 degrees Celsius.
There is no problem even if it comes into contact with the 0 degree part. Also, at this time, since the skin layer exerts a heat insulating effect, heat from the core layer kept at a high temperature does not reach the components directly and has no adverse effect. In particular, polyester-based thermoplastic elastomers have translucency and good fluidity even in a relatively low-temperature molten state, and can be injected at a relatively low pressure. Molding can be performed integrally without causing damage or displacement of the built-in components. The light emitting surface 22a of the light emitting element 22 is in direct contact with the primary molding resin 25, and there is no air layer between them.

Further, the primary molding resin 25 enters the inside from the terminal 14a where the covering material 14 opens, and is prevented from intruding into the inside from the part 14b because the part 14b near the terminal is swaged. The portion 14b is spread out in a substantially trumpet shape that expands toward the terminal 14a. Of course, the primary molding resin 25 also enters between the core wires 15 to 17 at the terminal 14a. Thereby, the electric wire 1
3, the pull-out strength (tensile strength) from the primary molded body 11 is greatly improved, and the sealing property of the insert part is ensured. Thus, the primary molded body 11 is molded.

As shown in FIG. 2 and FIG.
Has a substantially rectangular parallelepiped shape, and has an upper surface 1 behind the circuit board 20.
A screw mounting hole (step hole) 11c is provided to penetrate the rear surface 1a and the rear lower surface 11b '. Further, in order to improve the adhesion to the secondary molded body 12 and prevent deformation of the circuit board 20, etc. A plurality of tapered holes 11d are provided from the upper surface 11a to the circuit board 20, and grooves 11e and 11f are provided before and after both side surfaces, respectively.
However, a groove 11g is provided at the center of the front surface. The lower end of the groove 11g is connected to the front lower surface 11b.

A central portion of the top surface 11a of the primary molded body 11 projects upward from the light emitting element 22 to form a convex portion 11h. Accordingly, the light emitting element 22 is molded in close contact with the primary molded body 25 over the entire surface in front, above, and in the left-right direction of the light emitting surface 22a, and light emitted from the light emitting surface 22a is directly transmitted to the outside through the primary molded resin 25. That is, it is possible to go outside from the primary molded body 11.

As shown in FIG. 4, the front lower surface 11b of the primary molded body 11 is flush with the end surface (detection surface) 21a of the core 21 fixed to the circuit board 20.
The rear lower surface 11b 'connected to 1b is set at a predetermined height t from the front lower surface 11b. This front lower surface 11b
Is a reference plane (hereinafter referred to as “reference plane 11b”).
Cylindrical protrusions 1 on the left and right sides near the front end of reference surface 11b
1i and 11i are protruded, and the height thereof is
The predetermined height t is set from 1b.

The primary molded body 25 is molded of a resin having a light transmitting property. As the resin having a light-transmitting property, the above-mentioned polyester-based thermoplastic elastomer is an alloy material of an amorphous resin and a crystalline resin, has a translucent milky white color, has a light-transmitting property, and has an elasticity. Since the modulus is small (for example, the modulus of longitudinal elasticity is 45 to 460 MPa) and the crack resistance is excellent, it is most suitable for implementing the present invention.

Further, since this resin has a small modulus of longitudinal elasticity (Young's modulus), it absorbs a difference in linear expansion coefficient between an insert part and a secondary molding resin of a secondary molding 12 described later,
Decrease in adhesion between primary and secondary molding resin due to temperature change,
Generation of cracks and the like can be suppressed. Further, since the glass transition point is equal to or lower than the room temperature, the absolute value of the thermal stress applied to the insert part itself can be reduced.

In addition to these, various thermoplastic elastomers are suitable as the transparent resin material, and engineering plastics such as polyarylate (PAR) and polycarbonate (PC) are also applicable depending on the conditions of the insert part. When a translucent material is used, light from the illuminant is diffused, and the entire molded article appears to emit light relatively uniformly. When a transparent material is used, the luminous body is directly observed, and depending on the viewing position, reflected light on each surface (the interface between the transparent resin and air) is also observed.

Next, the primary molded body 11 is housed in a mold (not shown) for secondary molding, and two gates 11a, 11f on both sides and a gate 11g provided on the front face are provided. The secondary molding 12 is molded by injecting the molten molding resin 26 for the next molding under pressure. As the secondary molding resin 26, a hard resin is used to secure strength as an outer shell for protecting the primary molded body 11 and to obtain dimensional accuracy.

The primary molding resin used for the primary molded body 11 has a small longitudinal elasticity coefficient but a large linear expansion coefficient, so that the secondary molded body 12 covers the entire outer peripheral surface of the primary molded body 11 in the sensor package. When a constrained sealing structure is adopted, all the strains generated due to a change in ambient temperature become internal stresses in the primary molded body 11, which gives a large stress to the insert part.

Therefore, in the present invention, the secondary molded body 12 has a stress relief structure that restricts only to a portion requiring mechanical strength and dimensional accuracy. That is, by opening a predetermined area with respect to the primary molded body 11 and allowing the primary molded body to expand and contract in accordance with a change in the ambient temperature in that part, an occurrence occurs in the insert part of the primary molded body 11. It has a structure that can radiate thermal stress to the outside. Representative secondary molding resins include PBT, ABS, and PC. The secondary molding resin 26 has a larger longitudinal elastic modulus than the primary molding resin 25 (for example, 2000 to 6000MP).
a).

As shown in FIGS. 3, 5, and 6, the secondary molded body 12 is formed between the upper plate 12a for protecting the upper surface 11a of the primary molded body 11, the reference surface 11b, and the end surface of each projection 11i. The lower plate 12b that fills the space that has been filled to protect the end surface 21a of the core 21, the screw mounting reinforcing portion 12c that covers the inner peripheral surface of the screw mounting hole 11c and the stepped surface that comes into contact with the screw head, and each hole 11d of the upper surface 11a. 12d to prevent deformation such as warpage of the circuit board 20 and to fill the grooves 11e on both sides to connect the upper plate 12a and the lower plate 12b and to reinforce a part of the front side. A continuous part 12e also serving as a part, a reinforcing part 12f filled in the grooves 11f on both sides to protect a part of the rear part, a reinforcing part 12g filled in the grooves 11e on the front and protecting a part of the front, And a portion 14b near the end of the covering material 14 of the electric wire 13 And a protective section 12j and the like to cover.

The lower plate 12b of the secondary molded body 12 is formed in close contact with the reference surface 11b of the primary molded body 11, and the left and right protrusions 1 are formed.
The plate thickness is accurately formed to a predetermined height t by 1i and 11i, and the lower surface is flush with the rear lower surface 11b '. Each projection 11i prevents deformation due to resin filled in the front portion of the upper surface 11a and maintains the space between the front lower surface 11b and the mold at a predetermined interval t. Thereby, the distance from the end surface (detection surface) 21a of the core 21 to the lower surface of the lower plate 12b is accurately set to the predetermined height t (FIG. 5), and the variation in the operating distance of the proximity sensor 10 is suppressed. Further, the lower plate 12b is tightly formed on the reference surface 11b to ensure sealing performance, and the end surface 21a of the core 21 is liquid-tightly sealed.

As shown in FIGS. 5 and 6, the inner peripheral surface and the step surface of the screw mounting hole 11c are connected to the reinforcing portion 1 of the secondary molded body 12.
By covering with 2c, the strength is secured, and when attached with a screw, deformation or breakage of the proximity sensor 10 due to the lower surface contact portion of the screw head and the penetrating screw shaft portion are prevented,
The core wires 15 to 17 of the electric wire 13 are protected, and the sealing property is also ensured.

As described above, the proximity sensor 10 is formed by the primary molded body 11 and the secondary molded body 12 into a structure that satisfies the sealing, strength, and light-transmitting functions required for sensor sealing. I have. By adopting such a structure,
The size of the proximity sensor 10 is further reduced. As shown in FIG. 7, the light L emitted from the light emitting surface 22a of the light emitting element 22 directly passes through the primary molding resin 25 and exits the primary molded body 11 as transmitted light La, and a part of the light L is transmitted to the outside (air). And is returned to the resin 25 (the primary molded body 11) as reflected light Lb at the boundary surface 11s. However, when the light L emitted from the light emitting surface 22a proceeds directly from the resin 25 to the air (outside world),
The reflectance at the boundary surface is greatly different from the case where the resin 25 passes through the air, and the reflectance at the boundary surface 11 s is larger than the reflectance at the inner surface 1 a of the resin (housing 1) in the conventional structure shown in FIG. And very small. Therefore, most of the light L emitted from the light emitting surface 22a travels to the outside world as transmitted light La, and the reflected light Lb is small.

Further, most of the reflected light Lb is again transmitted light L
The light travels to the outside as c, and the reflected light Ld becomes very small.
Therefore, most of the light L emitted from the light emitting surface 22a of the light emitting element 22 comes out of the primary molded body 11, so that the amount of transmitted light increases and the luminance increases. In addition, the brightness of a wide range over the front surface, the convex portion 11h, and the front side surfaces of the primary molded body 11 surrounding the light emitting surface 22a increases. This allows the light-emitting element 22 to visually recognize the proximity sensor 10 in a wide range.

In addition, since the brightness of the primary molded body 11 is increased over a wide range, the degree of freedom of arrangement of the light emitting elements 22 is increased, setting is easy, and the size of the sensor can be reduced.
Further, a sensor package capable of improving water resistance and environmental resistance can be provided.

[0028]

As described above, according to the structure of the present invention, a package excellent in productivity and environmental resistance can be obtained by directly sealing a luminous body with a thermoplastic resin. The transmitted light amount of the emitted light is increased, and the visibility from the outside is improved. Also, when a thermoplastic elastomer is used as the thermoplastic resin, it is difficult to exert a bad thermal and mechanical influence on the light emitting body which is an insert part at the time of molding,
Since the stress generated inside the molded body at the time of cooling after molding is small, it is difficult to exert a mechanical adverse effect on the light emitting body which is an insert part. Further, if a part of the surface of the thermoplastic elastomer is covered with a material having a large elastic modulus, it can be applied to uses requiring mechanical strength.

[Brief description of the drawings]

FIG. 1 shows a first embodiment of a molded article according to the present invention,
It is a perspective view of a proximity sensor.

FIG. 2 is a perspective view of a primary molded body of the proximity sensor shown in FIG.

FIG. 3 is a perspective view of a secondary molded body covering the primary molded body of the proximity sensor shown in FIG. 2;
2 shows a state where the primary molded body shown in FIG.

4 is a cross-sectional view of the primary molded body shown in FIG. 2, taken along the line IV-IV.

5 is a cross-sectional view of the proximity sensor shown in FIG. 1 taken along the line VV.

6 is a cross-sectional view of the proximity sensor shown in FIG. 5, taken along the line VI-VI.

FIG. 7 is an explanatory diagram of an optical path of light emitted from a light emitting element of the proximity sensor shown in FIG.

FIG. 8 is an explanatory diagram of an optical path of light emitted from a light emitting body housed in a housing of a conventional detection switch.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Proximity sensor (molded body) 11 Primary molded body 12 Secondary molded body 13 Electric wire 20 Circuit board 21 Core 22 Light emitting element (Light emitting body) 24 Circuit element 25 Primary molded resin 26 Secondary molded resin

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Koji Seki 2-12-19, Shibuya, Shibuya-ku, Tokyo F-term 4F206 AA45 AH33 JB11

Claims (4)

[Claims] 1. A molded article characterized in that a thermoplastic resin forming the whole or a part of the molded article has a light-transmitting property, and a built-in luminous body is directly sealed. 2. The molded article according to claim 1, wherein the whole or a part of the light emitting portion of the light emitting body is in close contact with the thermoplastic resin. 3. The molded article according to claim 1, wherein the thermoplastic resin is an elastomer. 4. The molded article according to claim 3, wherein a part of the surface of the elastomer is covered with a material having a larger elastic coefficient than the elastomer.