EP1505560B1 - Light guide member for multisegment displays - Google Patents

Abstract

The light conducting component has a mask into which a light conductor (3) per segment is fed with a cross-section with the shape of the segment and that is manufactured using 2k injection molding technology. A continuous air gap (20) is formed between the mask and the light conductor. The dimension of the air gap is in the micrometer range. Independent claims are also included for the following: (a) an optical assembly with an inventive device (b) a domestic machine with an inventive optical assembly (c) and a method of manufacturing an inventive light conducting component.

Description

The present invention relates to a light guide member having a light entrance side and a light exit side for multi-segment optical displays, comprising a mask in which for each segment a light guide is guided in the form of the segment, and which is manufactured in 2K injection molding technology, and a corresponding optical assembly, which is set up for a multi-segment display, a household appliance with such an optical assembly and a method for manufacturing the optical fiber component in 2K injection molding.

It is known to use 7-segment displays with LED display for number displays in household appliances. These LED displays are available with different digit heights, display colors and number of digits with and without decimal point. The LED displays have on their underside connection pins, which are inserted for electrical connection of the LED display in connection holes of a printed circuit board and soldered there. For household appliances, the 7-segment displays are generally positioned behind a window in a panel of the household appliance. A disadvantage is that the fixed height of the LED displays determines the installation depth of the circuit board behind the panel. Due to requirements of the diaphragm design or the mechanical structure of the diaphragm, it may be necessary to change the installation depth of the circuit board behind the panel. Increasing the overall height of the LED displays is only possible to a limited extent by extending the connection pins or an additional display base, so that the display quality deteriorates with larger installation depths. A reduction in the height is usually not possible.

Out DE 101 12 640 C1 is a display device for household appliances with display segments known in which juxtaposed light guide in the form of light fingers through guide channels in guide bodies through. The display device is composed along the Lichtleitweges of several guide bodies, wherein the juxtaposed light fingers are manufacturing reasons connected to each other by a photoconductive plate. This has the disadvantage that light is coupled into adjacent segments via this connection, as a result of which light disturbances occur in the individual segments, which deteriorate the display quality. Therefore, it is necessary to cover the display area with a contour shutter to cover the light disturbances and thus achieve sharper contours.

From the control of a washing machine from AEG a light guide component for optical multi-segment displays is known, which is made of two plastic components (2K) in 2K injection molding. In this case, a mask is first made from a first plastic component, into which then a second plastic component is injected as a light guide. The choice of materials is subject to the condition that the mask must not deform significantly during the injection of the optical waveguide material in order not to impair the light-guiding property of the optical waveguide. The known optical fiber component has a mask made of high glass fiber-filled polyamide and a light guide of polymethyl methacrylate. A disadvantage of this combination of materials, that the optical fiber with the mask at least partially connects adhesively, whereby the light transmission property of the optical fiber and thus the display quality is reduced. Moreover, due to the processing characteristics of the high glass fiber filled polyamide, the fine patterning and the length of the optical fiber device are severely limited. Accordingly, and also due to the relatively high light losses in the optical fiber component only a short Lichtleitlänge is possible and thus limits the installation depth of the circuit board behind the aperture.

The invention has for its object to provide a cost-effective optical fiber component for optical multi-segment displays available, with which the installation depth of the circuit board behind a display surface with high display quality can be made variable.

This object is achieved in a light guide component of the type mentioned in that between the mask and the light guide is continuously formed an air gap, in particular in the micrometer range. Through this air gap, light propagating in the light guide is totally reflected at the interface with the air gap, whereby the light is guided further in the light guide and is not absorbed by the mask material. In this way, it is possible to keep the light losses low for optical fibers of great length, so that a high luminance and thus a high display quality is achieved on the display surface.

According to a preferred embodiment, it is provided that the mask material is a light-tight, easily flowing material with a low volume shrinkage during the cooling process. In particular, the mask material is a liquid crystalline polymer (LCP), such as Vectra®. Due to the processing properties of this mask material a production of long and filigree masks is possible. This has the advantage that optical fiber components can be manufactured with a large length, so that at large installation depths of the circuit board behind a display surface, the light can be guided by means of the optical fiber component to the display surface, whereby a high display quality is achieved. Furthermore, in spite of the large length of the mask and thus of the optical waveguide component, a small width of the individual segments can be realized in this mask material and, in addition to an improved visual appearance of the multisegment display, also a high display quality can be achieved.

According to a preferred embodiment, it is provided that the optical waveguide material is a transparent amorphous plastic, in particular polymethylmethacrylate (PMMA). This light guide material has the advantage that it does not form a bond with the mask material LCP and shrinks strongly on cooling. Thus, during the cooling process of the ready-sprayed optical fiber component, a continuous air gap can form between the optical fiber and the mask. That The air gap is formed by a higher volume shrinkage of the optical waveguide material compared to the mask material during the cooling process and is therefore largely independent of the manufacturing process, which leads to a high process reliability.

Furthermore, PMMA has the advantage that it has a much lower melting point than the mask material LCP. Thus, in the process of fabricating the optical fiber device in 2K injection molding, the manufacturing parameters may be adjusted to the melting temperature of the mask material such that fusing of the mask material upon injection of the optical fiber material into the forming mask is minimized. This has the advantage that the light guide is formed exactly in the light guide geometry predetermined by the mask, since the light guide material does not melt the mask material during the production process and thus deforms, whereby a high quality of the light guide and thus a high display quality can be achieved.

Advantageously, in the method for manufacturing the optical waveguide component in 2K injection molding technique, the optical waveguide material is injected into the mask via a mass cushion on the light exit side. In this way it is possible to fill closely adjacent segments with optical fiber material. In addition, this has indirect injection of the optical fiber material in the segment of the mask has the advantage that the light guide streaks and bubbles produced and thus a high quality of the light guide can be achieved. As a result of this ground cushion, the light-conducting material on the light exit side of the light-conducting component forms a light-conducting plate to which, in particular, the light guide of each segment is connected. This has the advantage that the light guide of each segment is fixed by the plate. In particular, the photoconductive plate can be made such that it has a rough and / or a structured surface. The rough surface scatters the emerging light, making the light distribution of each segment uniform. The structured surface highlights the structure of the individual segments, which makes the display easy to see from oblique angles.

Preferably, at least one injection point of the optical waveguide material is arranged between the segments. In this way, the light-guiding material can be injected uniformly into the individual segments. Another advantage is that the injection point does not interfere with the light emission from the individual segments, whereby a homogeneous light distribution for each segment can be achieved.

According to a preferred embodiment, it is provided that the photoconductive plate protrudes laterally beyond the mask. In particular, it is provided that the shape of the plate is adapted to a panel. This has the advantage that the optical fiber component mounted in a form-fitting manner in the diaphragm and thus can be dispensed with a glass cover. Advantageously, latching elements for fastening the optical waveguide component to a housing part and / or to a diaphragm part are formed on the plate, so that an optical assembly, which is set up with the optical waveguide component for a multi-segment display, by means of these locking elements of the optical waveguide component on the housing or on the diaphragm, for example a household appliance can be locked. In this way, a mounting of the optical fiber component and thus the optical assembly in a particularly simple manner possible.

Preferably, the optical fiber is polished at the light entrance side. In this way, a scattering of the incoming light can be reduced, whereby more light enters the light guide. This has the advantage that even with long light guides a display with high luminance can be achieved.

In a preferred embodiment, it is provided that the optical waveguide component has on the light entry side for each segment a recess for enclosing a light-emitting component, in particular for enclosing an SMD LED. In this way, in an optical assembly containing SMD LEDs and in which such a fiber optic device is used, on the one hand get a lot of light in the respective light guide, on the other hand overcoupling of the light can be avoided in the light guide of another segment. This has the advantage that for each segment only the light of the associated light-emitting component passes into the light guide, whereby a particularly good optical separation of the individual segments is achieved from each other. A particularly good coupling of the light from the SMD LED into the light guide can be achieved by filling the recess of the light guide component, which contains the SMD LED, with a transparent potting compound and / or with diffuser material. In this way, the number of optical transitions is reduced, thus minimizing the loss of light. When using diffuser material, the light of the light source can be coupled particularly evenly distributed in the light guide of the respective segment due to the scattering in the diffuser material.

Advantageously, the mask is cuboid and has latching elements for fastening the optical fiber component to a printed circuit board and / or on a housing part, in particular on the light entry side. In this way, the optical fiber device can be easily mounted on the circuit board. In particular, in the case of the optical assembly, the optical waveguide component can be latched on the light entry side with an electronic circuit board on which the SMD LEDs are arranged. Advantageously, at two diagonally opposite corners of one of the light entrance side associated square surface per locking element is arranged so that it is directed freely movable from one to the associated, parallel to the optical waveguide square edge on the circuit board, and the two remaining, to the light guides parallel edges each have a line-shaped, formed in a negative mold to the locking element recess which is positively connected with the latching element of an adjacent light guide component. This has the advantage that a plurality of optical waveguide components can be mounted in a form-fitting manner next to one another on the printed circuit board, and thus multi-digit displays can be realized with a plurality of the same optical waveguide components.

Preferably, the optical fiber material and / or the mask material is colored in itself. In particular, it is provided that, for the use of the optical waveguide component in a domestic appliance, the optical waveguide and / or the mask is colored in accordance with the housing or the diaphragm. This has the advantage that the optical waveguide component and thus the optical subassembly with the optical waveguide component can be optically adapted to the housing or the diaphragm such that only the display is visible on the display surface.

The optical fiber component is preferably used in optical assemblies that are set up for multi-segment displays, in particular for 7-segment displays. Advantageously, such assemblies are used as display devices in the housing or the bezel of household appliances, since in this way modifications of the housing or bezel design can be performed without the circuit board or the electronics must be changed.

The invention and its developments are explained in more detail below with reference to drawings:

Fig.1

eine schematische perspektivische Ansicht auf die Lichtaustrittseite eines Lichtleiterbauteils für eine optische 7-Segmentanzeige mit Dezimalpunkt,

Fig.2

eine schematische perspektivische Ansicht auf die Lichteintrittseite des Lichtleiterbauteils gemäß Figur 1,

Fig.3

einen Längsschnitt entlang einem Lichtleiter durch eine optische Baugruppe, die für eine optische 7-Segmentanzeige eingerichtet ist, und

Fig.4

einen Längsschnitt entlang einem Lichtleiter einer optischen Baugruppe für eine optische Mehrsegmentanzeige mit einem Blendenteil an der Lichtaustrittseite.

Show it

Fig.1

a schematic perspective view of the light exit side of a light guide device for a 7-segment optical display with decimal point,

Fig.2

a schematic perspective view of the light entry side of the optical fiber device according to FIG. 1 .

Figure 3

a longitudinal section along an optical fiber through an optical assembly, which is adapted for a 7-segment optical display, and

Figure 4

a longitudinal section along an optical fiber of an optical assembly for a multi-segment optical display with a shutter member on the light exit side.

According to FIG. 1 and FIG. 2 As an exemplary embodiment, a light guide component 1 for a 7-segment optical display with a decimal point is shown schematically. The optical waveguide component 1 consists of a cuboid main body 2 which forms a mask M with parallel channels K, the mask M corresponding in cross section to a 7-segment display with a decimal point. In the channels K of the main body 2, a light guide 3 with a segmental cross-sectional area and for the decimal point a light guide 4 is guided with a circular cross-sectional area from a light entrance side 5 to one of the light entrance side 5 opposite light exit side 6 for each of the seven segments of the 7-segment display , At the light exit side 6, the light guides 3, 4 open into a light-conducting plate 7, which is arranged on the base body 2 and has a planar surface 8. The light guides 3, 4 are in FIG. 1 shown by dashed lines, since they are below the photoconductive plate 7. Each of the segment-shaped light guides 3 has a width B and the circular light guide 4 has a diameter D, both of which are in particular less than or equal to one millimeter. The individual segmental light guides 3 are separated from one another by webs S of the mask M continuously from the light entrance side 5 to the light exit side 6. At the light entrance side 5, the light guide component 1 in the region of each of the light guides 3, 4 recesses 9 for receiving light-emitting components. These recesses 9 are far enough away from each other that the webs S of the mask M are in between.

On the main body 2, which is in particular cuboid, is arranged at two diagonally opposite corners of the Lichteintrittseite 5 associated rectangular surface each locking element 11 so that it starting from one of the associated, parallel to the optical fibers 3, 4 cuboid edge 10th protrudes beyond the light entry side 5 of the optical fiber component 1 and is freely movable. At the two remaining, parallel to the light guides 3, 4 edges 12, the base body 2 each have a line-shaped recess 13 which is formed form-fitting manner to the locking elements 11. The curvature 14 of the locking elements 11 corresponds in its negative shape of the curvature 15 of the recesses 13. In addition to the light guide 1, another identical optical fiber component 1 can be arranged without gaps (not shown), since the locking element 11 fits into the recess 13 in a form-fitting manner.

In FIG. 3 is a section along the light guides 3, 4 shown by an optical assembly 16, which is adapted for the optical 7-segment display. The optical assembly 16 includes the optical fiber device 1 and a printed circuit board 17 with SMD LEDs 18 as light-emitting components. The light guide component 1 is latched with its locking elements 11 in holes 19 of the circuit board 17. The SMD LEDs 18 are encompassed by the recesses 9 of the optical waveguide component 1, so that light emitted by the SMD LEDs can propagate along the optical waveguides 3, 4 only in the direction marked by arrows. Overcoupling of light of the SMD LED in adjacent light guides 3, 4 is avoided in that on the light entrance side 5, the light guide component 1 between the recesses 9 positively closes with the circuit board 17. These recesses 9 can be filled in particular with the use of SMD LED chips 18 without LED housing with a transparent potting compound, on the one hand protects the SMD LED chips 18 from damage and on the other hand, the light coupling of the emitted light in the light guide. 3 , 4, since the number of optical transitions is reduced and the transparent potting compound can be selected such that its optical refractive index is matched to that of the optical waveguide 3, 4. The recesses 9 can also be filled with diffuser material, by which light emitted by the SMD LEDs is scattered, so that the light enters the light guides 3, 4 with a uniform distribution. In general, other light-emitting components can be used, such as LEDs or incandescent lamps, the dimensions of the optical fiber component can be adjusted accordingly.

Between each of the light guides 3, 4 and the main body 2, an air gap 20 is formed in the channels K throughout the entire length L of the light guide 3, 4 from the light entrance side 5 to the light exit side 6, which is in particular of the order of microns. Through this air gap, the light emitted by the SMD LED 18 and coupled on the light entrance side 5 in the light guide 3, 4 light that propagates in the light guide 3, 4 and which meets the air gap 20 in the light guide 3, 4 reflected back , In this way, the light is guided in the light guide 3, 4 and not absorbed by the base body 2. Thus, it is possible with optical fibers 3, 4 with a long length L to keep the light losses low. At the light exit side 6, the photoconductive plate 7 in FIG. 3 a structured surface 21 in which the individual segments 22 of the 7-segment display are highlighted. The light thus leaves the individual segments 22 on the light exit side 6 also at different angles to the longitudinal direction of the light guides 3, 4, as a result of which it is also clearly visible at these angles.

In FIG. 4 schematically shows a section along the light guide 3 through a shutter member 23 with an optical assembly 16 which is adapted according to a further embodiment of the invention for a multi-segment optical display. The light-conducting plate 7 extends in its planar extension beyond the base body 2 and has a curved shape, which is adapted to the curvature of the diaphragm part 23. The outer contour may, as shown, have a rectangular shape or any other desired shape. Furthermore, 7 latching elements 24 are integrally formed on the photoconductive plate 7, which are bounded on the light exit side 6 of the plate 7 and parallel to the light guide component 1 to the light entrance side 5 point. On the panel part 23 counter-locking elements 25 are formed, with which the latching elements 25 are latched for mounting the optical assembly 16 on the panel part 23.

The optical fiber component 1 is manufactured in 2K injection molding technology from two plastic components (2K). First, the base body 2 with the mask M is made from an opaque, easily flowing material with a low volume shrinkage during the cooling process, which according to the invention is a liquid-crystalline polymer (LCP), such as Vectra®. Due to the processing properties of this liquid-crystalline polymer, the production of long and filigree masks M is possible. In this mask M then the light guide 3, 4 are injected from a second translucent plastic, which does not connect to the plastic of the mask M and according to the invention is a transparent amorphous plastic, in particular polymethylmethacrylate (PMMA). The PMMA has a lower melting point than LCP, so that the temperature of the PMMA melt during the manufacturing process can be chosen so that the mask M does not melt when injecting the PMMA as possible. The PMMA is injected via a ground pad P at the light exit side 6 in the mask M, which forms the photoconductive plate 7. In FIG. 1 are centrally shown between the individual light guides 3 two injection points A in dotted lines through which the ground pad P is filled with PMMA. Starting from this mass cushion P, the PMMA is pressed into channels K of the mask M. During the cooling process of the finished sprayed optical fiber component 1, a volume shrinkage occurs. This is very low for an LCP, such as Vectra®, while the volume shrinkage of PMMA is in the order of 0.6%. Thus, the volume shrinkage of the optical waveguide material compared to the mask material during the cooling process is significantly higher, resulting in a over the entire length L of the optical fibers 3, 4 continuous air gap 20 between optical fibers 3, 4 and mask M is formed. On In this way, the formation of the air gap 20 largely independent of the manufacturing process, resulting in a high process reliability for the production of the optical fiber components 1.

According to the invention, the optical waveguide component 1 can be manufactured with a ratio of length L to width B or diameter D of the optical waveguides 3, 4 which is greater than 13 or on the order of 30. In particular, the width B or the diameter D of the light guides 3, 4 may be less than or equal to 1 millimeter and the length L of the light guides 35 millimeters. In particular, a digit height of the 7-segment display of 10 millimeters can be realized with a segment width of 1 millimeter and an optical fiber length of 35 millimeters. However, other dimensions of the optical waveguide component 1 are also possible.

According to the invention, the plastic for forming the light guides 3, 4 or the light-guiding plate 7 and / or the plastic for forming the main body 2 may be colored in itself. In particular, the light guides 3, 4 and the photoconductive plate 7 may be adapted in color to the panel part 23 or to a housing part such that segments of the multi-segment display are visible only when illuminated. In particular, the light-emitting components can be chosen such that they emit colored light, so that there is a color contrast between illuminated and unlit segments of the multi-segment display.

Claims (36)

1. Optical waveguide component with a light entry side (5) and a light exit side (6) for optical multi-segment displays, which comprises a mask (M) in which for each segment an optical waveguide (3, 4) with a cross-section in the form of the segment is guided, and which is produced by two-component injection-moulding, characterised in that an air gap (20) is formed continuously between the mask (M) and the optical waveguide (3, 4).
2. Optical waveguide component according to claim 1, characterised in that the air gap (20) has a size in the micron range.
3. Optical waveguide component according to claim 1 or 2, characterised in that the air gap (20) is formed by a higher volume shrinkage of the optical waveguide material by comparison with the mask material during the cooling-down process.
4. Optical waveguide component according to any one of claims 1 to 3, characterised in that the mask material and the optical waveguide material are not connected together during the production process.
5. Optical waveguide component according to any one of the preceding claims, characterised in that the optical waveguide material does not fuse the mask material during the production process.
6. Optical waveguide component according to any one of the preceding claims, characterised in that the mask material is a light-tight easy-flowing material with a small volume shrinkage during the cooling-down process.
7. Optical waveguide component according to any one of the preceding claims, characterised in that the mask material is a liquid-crystalline polymer.
8. Optical waveguide component according to any one of the preceding claims, characterised in that the optical waveguide material is a transparent amorphous plastics material.
9. Optical waveguide component according to claim 8, characterised in that the optical waveguide material is a polymethylmethacrylate.
10. Optical waveguide component according to any one of the preceding claims, characterised in that the ratio of length (L) to width (B) or diameter (D) of the optical waveguide (3, 4) is greater than 13 or lies in the order of magnitude of 30.
11. Optical waveguide component according to any one of the preceding claims, characterised in that the width (B) or the diameter (D) of the optical waveguide (3, 4) is at most 1 millimetre and/or the length (L) of the optical waveguide (3, 4) is 35 millimetres.
12. Optical waveguide component according to any one of the preceding claims, characterised in that the optical waveguide material forms an optically conductive plate (7) on the light exit side (6).
13. Optical waveguide component according to claim 12, characterised in that the optical waveguide (3, 4) of each segment is connected with the plate (7).
14. Optical waveguide component according to claim 12 or 13, characterised in that the plate (7) has a rough and/or a structured surface (8, 21).
15. Optical waveguide component according to any one of the claims 12 to 14, characterised in that the plate (7) protrudes laterally beyond the mask (2, M).
16. Optical waveguide component according to any one of claims 12 to 15, characterised in that the plate (7) is cylindrically or spherically curved.
17. Optical waveguide component according to claim 16, characterised in that the shape of the plate (7) is matched to an aperture (23).
18. Optical waveguide component according to any one of claims 12 to 17, characterised in that detent elements (24) for fastening the optical waveguide component (1) to a housing part and/or an aperture part (23) are formed at the plate (7).
19. Optical waveguide component according to any one of the preceding claims, characterised in that the optical waveguide (3, 4) is polished at the light exit side (5).
20. Optical waveguide component according to any one of the preceding claims, characterised in that the optical waveguide component (1) has at the light exit side (5) for each segment a cut-out (9) for framing a light-emitting component (18).
21. Optical waveguide component according to claim 20, characterised in that the cut-out (9) is constructed for framing an SMD light-emitting diode (18).
22. Optical waveguide component according to any one of the preceding claims, characterised in that the mask (2, M) is block-shaped and comprises detent elements (11) for fastening the optical waveguide component (1) to a circuitboard (17) and/or to a housing part.
23. Optical waveguide component according to claim 22, characterised in that the detent elements (11) are arranged at the light exit side (5).
24. Optical waveguide component according to claim 22 or 23, characterised in that a respective detent element (11) is so arranged at each of two diagonally opposite corners of a block surface associated with the light exit side (5) that going out from an associated block edge (10) lying parallel to the optical waveguides (3, 4) it is oriented freely movably on the circuitboard (17), and that the two remaining edges (12) lying parallel to the optical waveguides (3, 4) each have a lineal cut-out (13) which is constructed in negative shape relative to the detent element (11) and which can be mechanically positively joined together with the detent element (11) of an adjacent optical waveguide component (1).
25. Optical waveguide component according to any one of the preceding claims, characterised in that the optical waveguide material and/or the mask material is or are intrinsically coloured.
26. Optical subassembly with an optical waveguide component according to any one of claims 1 to 25, which is arranged for a multi-segment display.
27. Optical subassembly according to claim 26, characterised in that the multi-segment display is a seven-segment display.
28. Optical subassembly according to claim 26 or 27, characterised in that it contains SMD light-emitting diodes (18).
29. Optical subassembly according to claim 28, characterised in that the cut-out (9) of the optical waveguide component (1), which comprises the SMD light-emitting diode (18), is filled with a transparent casting mass and/or with diffusor material.
30. Optical subassembly according to claim 28 or 29, characterised in that the optical waveguide component ('1) is detented at the light exit side (5) with a circuitboard (17) on which the SMD light-emitting diodes (18) are arranged.
31. Domestic appliance comprising a housing or an aperture (23) with an optical subassembly (16) according to any one of claims 26 to 30.
32. Domestic appliance according to claim 31, characterised in that the colouring of the optical waveguides (3, 4) and/or the mask (2, M) is matched to the housing or the aperture (23).
33. Domestic appliance according to claim 31 or 32, characterised in that the optical subassembly (16) is detented by means of detent elements (24) of the optical waveguide component (1) to the housing or to the aperture (23).
34. Method of producing an optical waveguide component according to any one of claims 1 to 25, by two-component injection moulding, characterised in that the production parameters are so adapted to the melt temperature of the mask material that melting of the mask material during injection of the optical waveguide material into the mask (M) is reduced to a minimum.
35. Method according to claim 34, characterised in that the optical waveguide material is injected into the mask (M) by way of a material cushion at the light exit side.
36. Method according to claim 35, characterised in that at least one injection point (A) of the optical waveguide material is arranged between the segments.

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