Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.

Patents

  1. Advanced Patent Search
Publication numberUS3746853 A
Publication typeGrant
Publication dateJul 17, 1973
Filing dateMar 10, 1972
Priority dateMar 10, 1972
Publication numberUS 3746853 A, US 3746853A, US-A-3746853, US3746853 A, US3746853A
InventorsD Effer, K Kosman, L Boivin
Original AssigneeBell Canada Northern Electric
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Light emitting devices
US 3746853 A
Abstract
Light emitting arrays in which the light source is positioned between two opposed reflector surfaces. The light from the source is reflected back past the source by a first reflector and then re-reflected by a second reflector back past the light source to the first reflector. A very thin assembly is obtained. The arrangement is particularly suitable for light emitting diodes and can be used for character displays.
Images(3)
Previous page
Next page
Description  (OCR text may contain errors)

United States Patent [191 K'osman et al.

[111 3,746,853 [451 July 17, 1973 1 LIGHT EMITTING DEVICES [75] Inventors: Karel Jan Williams Kosman;

Louis-Philippe Boivin; Dennis Effer, all of Ottawa, Ontario, Canada [73] Assignee: Bell Canada-Northern Electric Research Limited, Ottawa, Ontario, Canada [22] Filed: Mar. 10, 1972 [21] Appl. No.2 233,674

[52] US. Cl. 240/4l.35 D, 313/108 D [51] Int. Cl. F2lv 7/00 [58] Field of Search 240/41.35, 46.55, 240/41.35 D, 46.01, 46.33, 46.45; 313/117, 108 D [56] References Cited UNITED STATES PATENTS 1,647,613 11/1927 Fredette 240/46.55 1,954,978 4/1934 Aldrich 240/46.55

1,877,978 9/1932 Sarver 240/46.55 3,518,418 6/1970 Dubois 313/108 D X 1,205,361 11/1916 Lakin 240/4l.35 B 3,676,668 7/1972 Collins et al.... 313/108 D 3,593,055 7/1971 Geusic 313/108 D 3,308,452 3/1967 Michel et al 313/108 D X Primary Examiner-Samuel S. Matthews Assistant Examiner-Richard M. Sheer Attorney-Sidney T. Jelly [57] ABSTRACT Light emitting arrays in which the light source is positioned between two opposed reflector surfaces. The light from the source is reflected back past the source by a first reflector and then re-reflected by a second reflector back past the light source to the flrst reflector. A very thin assembly is obtained. The arrangement is particularly suitable for light emitting diodes and can be used for character displays.

3 Claims, 5 Drawing Figures Patented July 17, 1973 3 Sheets-Sheet 1 Patented July 17, 1973 3 Sheets-Sheet 2 Fig. 4

Patented July 17, 1973 3 Sheets-Sheet m 6 om o O Q Q Q Q a Q a Q a Q a a U m U Q U 0 U 0 U U Q U a D a U Q U Q a u LIGHT EMITTING DEVICES This invention relates to light emitting devices, and in particular though not exclusively to light emitting devices as integers of a display, for example for displaying numerals, letters and symbols, and also to such displays.

Various forms of devices are used for the display of numerals, letters and symbols in the so-called matchstick" style or code. It has been proposed to use a small filament lamp for such a device. The light from a lamp is directed to a parabolic reflector, which reflects the light back past the lamp to issue from a viewing face. Because of the shape of the reflector and other requirements such as a device is relatively large, being of a substantial thickness in the direction of light emission from the size of the display. There is also the associated disadvantage of the relatively high power consumption of a filament lamp. Light emitting diodes have also been used, either with a plurality of the diodes extending for the form of the segment, for example side by side, or with a diode mounted at the focus point of a parabolic reflector. The use of a plurality of diodes not only negates the low power consumption of individual diodes but may increase the power consumption above that of a filament lamp. Using a diode with a parabolic reflector means that the device has substantial thickness.

The present invention provides a device which is thin, has a very low power consumption and permits a reduction in the number of light sources. In the broadest aspect the invention provides a light emitting device comprising a semiconductor light emitting element or diode having a reflector on a first side and a reflective surface on a second side, light from the element being reflected by the reflector to the reflective surface and then reflected back past the element and reflector by the reflective surface. Particularly there is provided a light emitting device having a substrate onto which is positioned a reflective layer. The reflective layer may be diffusing, and is substantially flat. The light emitting element is mounted on the reflective layer and a reflector positioned over the element such that light from the element first passes to the reflector, the reflector reflecting the light back to the reflecting layer. A light transmitting encapsulating material encapsulates the element and the reflective surface and the light is further reflected by the reflective layer through the encapsulating material to issue from a viewing surface thereof.

For a segment of a display array, the reflector is arranged symmetrical to the element and has two portions arranged to reflect the light from the element back past the element, on either side of the element. The reflective layer is flat and again reflects the light back past the element to form a lighted segment on either side of the element. Conveniently the device is encapsulated with a black or non-light transmitting outer portion or frame and the light transmitting material within the frame. The reflector can be mounted on the encapsulating material.

A display array is composed of a plurality of devices arranged in a predetermined pattern to meet the display requirements. The shape of individual devices can be varied to provide for effective assembly of the array.

The invention will be readily understood by the following description of certain embodiments, by way of 2 example, in conjunction with the accompanying drawings, in which:

FIG. 1 is a plan view of a device;

FIG. 2 is a cross-section on the line II-lI of FIG. 1;

FIG. 3 is a plan view of a display using devices in accordance with the invention;

FIG. 4 illustrates the conductor pattern and circuit for the arrangement of FIG. 3; and

FIG. 5 illustrates one form of multi-digit display using devices in accordance with the present invention.

As seen in FIGS. 1 and 2 a light emitting device 10 comprises a substrate 11 having a conducting layer or pattern 12 on which is mounted a semiconductor light emitting diode 13, hereinafter referred to as an LED, for example a gallium phosphide chip providing a p-n junction in the known manner. In addition to acting as a conductor the layer 12 serves as a reflective layer as will be described. The LED 13 is encapsulated in a light transmitting plastic material 14. The encapsulating material is formed to provide sloping sides 15, the sides inclined upwardly and inwardly relative to the substrate 11 and the LED 13. Immediately over the LED 13 the encapsulating material is shaped as a trough 16 having sides 17 which incline upwards and outwards relative to the LED 13, being on either side of the axis of the LED. A flat top surface 18 acts as the surface through which light is emitted.

A layer of reflecting material 19 is formed on each of the sides 15 and 17 so that a reflector is formed entirely around the periphery of the encapsulating material. On energization of the LED 13 light is emitted from the top 20 of the LED and from the sides 21. The light emitted from the top is reflected downwardly and outwardly to the layer 12. Layer 12, which conveniently is slightly diffusing, reflects the light upwards and light will issue through the surface 18 on either side of the trough 16. Some light will be reflected by the layer 12 upwardly and outwardly for further reflection by the reflecting layer 19. Also light emitted from the sides 21 will be reflected by the layer 19, in this instance downwards toward the reflective layer 12, and then upwards. The angles of the various sides 15 and 17 are chosen so that the distribution of the light emission from the surface 18 is approximately even to provide an appearance of uniform illumination at differing viewing angles. A typical value for angle 0, the inclination of the sides 15 is approximately 74, and for angle dz, the inclination of the sides 17 of the trough 16, is approximately 32. Any light emitted from the LED 13 is reflected repeatedly until it issues through the surface I8. The encapsulating material 14 is usually of clear plastic material, which can be coloured and can also contain a small addition of a light diffusing filler. Paths of rays are indicated by lines 22.

The reflecting layer 12, as previously stated, is conveniently part of the conducting layer or pattern for the LED 13 and, for example, is of gold.

FIGS. 1 and 2 illustrate a single light emitting device which can be used whenever a lighted device is required. Although shown as having the LED 13 mounted centrally with light issuing through two areas, one on each side of the central trough 16, the LED can be mounted at one end of a device to present one lighted area. Further, the particular shape of the device and particularly the shape or shapes of the area or areas through which light issues can be varied to suit requirements.

FIG. 3 illustrates an array or display using light emitting devices in accordance with the present invention, the array being one which can be arranged to produce characters, in the present example figures. As shown, a plurality of devices 30 are arranged in the form of a rectangle with a central transverse bar. The positions of the LEDs are indicated by the dotted circles 31 while the surfaces through which light issues are indicated at 32. A decimal point is produced by a device 33 which is single ended, that is, the LED indicated by the dotted circle 34 is at one end of the device, the light issuing surface indicated at 35. By suitable energization of particular LEDs it will be seen that figures and letters can be produced.

An array, as for example illustrated in FIG. 3, is made as a complete unit. For example the individual devices 30 are themselves encapsulated in a black plastic material. Either the black material can be moulded having cavities formed for the eventual filling with the light transmitting plastic encapsulating the LEDs or, alternatively, the LEDs are first encapsulated in the light transmitting plastic to form the individual devices and the devices are positioned in a mould and the black plastic material moulded around the devices. If the black material is first moulded, the reflecting layers 19 are formed by deposition by any suitable process on the related surfaces before the light transmitting plastic material is moulded into the black moulding. When the individual devices are first moulded the reflecting layers 19 are then deposited on the related surfaces prior to encapulsation into the black material. Other colours than black can be used, the main intention being to provide contrast.

The array for a character is generally mounted on a common substrate, which can be of ceramic for exam ple. The substrate will then usually form the substrate 11 as in FIG. I. A plan view of such a substrate showing the conductor circuitry is illustrated in FIG. 4. In this figure the devices are not shown, for clarity, but the positions of the surfaces through which light issues are indicated at 32, as in FIG. 3. Similarly the positions of the LEDs are indicated at 31 and 34 as in FIG. 3.

As seen in FIG. 4 the ceramic substrate is at 40. A layer of conducting material, for example gold, is deposited at 41. The LEDs 31 and 34 are mounted directly onto the gold layer. The conducting material 41 is deposited in such a pattern that conductors 42 are formed, separated from the main layer 41 by spaces 43. Connections are made to the LEDs from the conductor pattern 42 by leads 44. An MOS decoder/driver 45 is also mounted on the gold layer 41 and is connected to the conductor pattern 42.by leads 46.

A multiple array is shown in FIG. 5, comprising five character arrays 50 and a positive, negative and overflow array 51. A fixed decimal point is provided at 52 but it will be appreciated that a device for a decimal point can be provided at each character array, fora movable decimal point.

In the arrays described and illustrated, seven devices are used for each array. For a larger character size a larger number of devices can be used, for example nine. Also differing arrangements ofthe devices can be used to provide arrays capable of differing or more complex characters.

Although devices in accordance with the invention have been described in use for the production of character arrays, other uses exist for such devices, either used singly or in multiplicity. Devices can be mounted on a printed circuit board instead of a ceramic substrate, and can be a component ofa printed circuit device.

The devices in accordance with the invention are very thin. A character array as in FIGS. 3 and 4 can be produced with overall dimensions of approximately 0.25 ins. X 0.20 ins. and with a thickness from the substrate of approximately 0.020 ins. Individual devices have overall dimensions of approximately 0.120 ins. X 0.050 ins. by 0.020 ins. thick. These devices in accordance with the invention are thinner than conventional devices. The use of LEDs reduces the power requirements as compared with conventional devices, using other forms of light source. What Is claimed is:

l. A light emitting device for producing widely dif fused light comprising:

a substantially planar substrate having a reflecting surface thereon;

a semiconductor light emitting element mounted on the reflecting surface of said substrate, said light emitting element emitting light laterally in a direc tion parallel to said substrate and forwardly in a direction normal to said substrate;

a body of encapsulating material enclosing said light emitting element, said body of encapsulating material having a front surface and at least one side surface, said side surface being tapered inwardly from said substrate to said front surface;

a layer of reflecting material on the side surface of said body of encapsulating material for reflecting the laterally emitted light from said light emitting device downwardly onto the reflecting surface of said substrate;

a layer of reflecting material on a portion of the front surface of said body of encapsulating material, said layer of reflecting material on said portion of said front surface being substantially in alignment with said light emitting element and being tapered inwardly from said front surface toward the reflecting surface of said substrate to reflect the forwardly directed light downwardly onto the reflecting surface of said substrate;

the remaining portion of the front surface of said body of encapsulating material being light emitting to allow emission of the light reflected by the re fleeting surface of said substrate.

2. A light emitting device claimed in claim 1, said inwardly tapered layer of reflecting material on said portion of said front surface comprising two intersecting reflecting surfaces.

3. A light emitting device as claimed in claim I including an electrical conductor pattern on said substrate, the reflecting surface of said substrate comprising part of said electrical conductor pattern.

i i 1 4 l

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US1205361 *Feb 19, 1916Nov 21, 1916Harry W LakinNon-glaring headlight.
US1647613 *Dec 30, 1926Nov 1, 1927Frank H FredetteHeadlight antiglare shield
US1877978 *Jan 20, 1932Sep 20, 1932Bessie W StunzAutomobile headlamp
US1954978 *Feb 28, 1931Apr 17, 1934Carl G AldrichHeadlight
US3308452 *Dec 24, 1962Mar 7, 1967IbmHigh speed electro-optical semiconductor display apparatus
US3518418 *Dec 20, 1967Jun 30, 1970Philips CorpElectro-luminescent diode and radiation projector
US3593055 *Apr 16, 1969Jul 13, 1971Bell Telephone Labor IncElectro-luminescent device
US3676668 *Dec 29, 1969Jul 11, 1972Gen ElectricSolid state lamp assembly
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3869637 *Apr 24, 1973Mar 4, 1975Sony CorpAlpha-numeric display device utilizing light emitting diodes
US3876900 *May 14, 1973Apr 8, 1975Matsushita Electronics CorpElectric light-emitting apparatus
US4218165 *Nov 24, 1978Aug 19, 1980Riddersholm Viggo MQuick action collet lock
US4712163 *Aug 28, 1981Dec 8, 1987Oxley Robert FIndicator lamps
US6238076Mar 29, 1999May 29, 2001Primetech Electronics, Inc.Compact light mixing and diffusing apparatus
US6491412 *Jun 30, 2000Dec 10, 2002Everbrite, Inc.LED display
US6622372 *May 29, 2001Sep 23, 2003Honeywell International Inc.Method for setting electrical characteristics of sensors after assembly
US6674096 *Jun 8, 2001Jan 6, 2004Gelcore LlcLight-emitting diode (LED) package and packaging method for shaping the external light intensity distribution
US6851839 *Mar 12, 2002Feb 8, 2005Meridian Automotive Systems, Inc.Vehicular lamp assembly with a simplified structure and CHMSL and tail lamp incorporating the same
US7390109 *Sep 12, 2005Jun 24, 2008Lite-On Technology Corp.Light-emitting diode component having a light direction-changing unit and related light direction-changing unit and module
US7481563Sep 21, 2006Jan 27, 20093M Innovative Properties CompanyLED backlight
US7520641 *May 12, 2008Apr 21, 2009Light Prescription Innovators, LlcEtendue-squeezing illumination optics
US7798675Feb 11, 2009Sep 21, 2010Light Prescriptions Innovators, LlcLED luminance-enhancement and color-mixing by rotationally multiplexed beam-combining
US7806547Jan 14, 2009Oct 5, 2010Light Prescriptions Innovators, LlcBrightness-enhancing film
US7950831 *Apr 28, 2005May 31, 2011Lg Display Co., Ltd.Recessed LED lamp unit
US8152338Mar 15, 2010Apr 10, 2012Lg Display Co., Ltd.LED lamp unit
US8393777Jul 28, 2006Mar 12, 2013Light Prescriptions Innovators, LlcEtendue-conserving illumination-optics for backlights and frontlights
US8399904 *Aug 9, 2011Mar 19, 2013Lg Innotek Co., Ltd.Light emitting device and lighting system having the same
US8419232Jul 28, 2006Apr 16, 2013Light Prescriptions Innovators, LlcFree-form lenticular optical elements and their application to condensers and headlamps
US8631787Sep 8, 2008Jan 21, 2014Light Prescriptions Innovators, LlcMulti-junction solar cells with a homogenizer system and coupled non-imaging light concentrator
US20110309405 *Aug 9, 2011Dec 22, 2011Lg Innotek Co. Ltd.Light emitting device and lighting system having the same
DE3320953A1 *Jun 10, 1983Dec 13, 1984Telefunken Electronic GmbhOptoelectronic component
WO2001024146A1 *Sep 29, 2000Apr 5, 2001Everbrite IncLed display
WO2002101842A1 *Jun 10, 2002Dec 19, 2002Gelcore LlcLight- emitting diode (led) package and packaging method for shaping the external light intensity distribution.
Classifications
U.S. Classification362/301, 362/812, 362/800
International ClassificationG09F9/33
Cooperative ClassificationG09F9/33, Y10S362/812, Y10S362/80
European ClassificationG09F9/33