CA2059157A1 - Sunlight readable display structure - Google Patents

Sunlight readable display structure

Info

Publication number
CA2059157A1
CA2059157A1 CA002059157A CA2059157A CA2059157A1 CA 2059157 A1 CA2059157 A1 CA 2059157A1 CA 002059157 A CA002059157 A CA 002059157A CA 2059157 A CA2059157 A CA 2059157A CA 2059157 A1 CA2059157 A1 CA 2059157A1
Authority
CA
Canada
Prior art keywords
colored filter
legend plate
display structure
light
liquid crystal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
CA002059157A
Other languages
French (fr)
Inventor
Lawrence E. Tannas, Jr.
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Illinois Tool Works Inc
Original Assignee
Illinois Tool Works Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Illinois Tool Works Inc filed Critical Illinois Tool Works Inc
Publication of CA2059157A1 publication Critical patent/CA2059157A1/en
Abandoned legal-status Critical Current

Links

Classifications

    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09FDISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
    • G09F13/00Illuminated signs; Luminous advertising
    • G09F13/04Signs, boards or panels, illuminated from behind the insignia
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09FDISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
    • G09F9/00Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements
    • G09F9/30Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements
    • G09F9/33Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements being semiconductor devices, e.g. diodes
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09FDISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
    • G09F13/00Illuminated signs; Luminous advertising
    • G09F13/04Signs, boards or panels, illuminated from behind the insignia
    • G09F13/0418Constructional details
    • G09F13/0472Traffic signs
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09FDISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
    • G09F13/00Illuminated signs; Luminous advertising
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09FDISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
    • G09F13/00Illuminated signs; Luminous advertising
    • G09F13/04Signs, boards or panels, illuminated from behind the insignia
    • G09F13/0418Constructional details
    • G09F2013/05Constructional details indicating exit way or orientation

Abstract

SUNLIGHT READABLE DISPLAY STRUCTURE
ABSTRACT OF THE DISCLOSURE
Sunlight readable display structure includes a layered structure formed of a reflective element, an LED
light source, a colored filter, a legend plate, and a liquid crystal shutter. The reflective element is positioned behind the LED light source. The light source is formed of an LED array having a diffusion medium disposed in front of the LED array for scattering light when energized. The liquid crystal shutter permits displayable information on the legend plate to be viewed only when the LED array and the liquid crystal shutter are energized. The reflective element and the diffusion medium reflect and scatter incident sunlight which is passed through the liquid crystal shutter, legend plate and colored filter back through the colored filter and legend plate and out the liquid crystal shutter. The colored filter is preferably selected to have certain spectral transmission characteristics. As a result, the contrast of the displayable information on the legend plate is enhanced and is unaffected by washout to a viewer located in the area of incident sunlight.

Description

r `- 20$91~7 , SUNLIGHT READABLE DISPLAY STRUCTURE : .
.

BACKGROUND OF THE INVENTION

l. Field of the Invention:

This invention relates generally to visual display device and more particularly, it relates to an improved display structure which is readable even in direct sunlight. The present invention has particular appli-cations for use in instrument panels in aircraft cockpits, automobiles, and other vehicles wherein the display can be readable even in direct sunlight and is unaffected by the phenomenon known as "washout."

: ,' ::'''.' 2. Description of the Prior Art~
c-There are well-known in the art various traditional display devices which utilize a white-light lamp (inàandescent or fluorescent) as an illuminating light souroe which is transmitted through the backside of a legend plate 80 as to illuminate the same. In order to ~-improve the readability of the legend plate under direct ~ . .
sunlight, it was generally required to increase the in- ~;
tensity of the liqht source so as to correct for dimness due to the washout phenomenon. However, this approach .

........ ,. ,, ._........... ,_.. _.. _. _.. __ '- ~

. -2- 20~57 suffers from the disadvantages of requiring a large operating voltage and a corresponding increase in power consumption and heat dissipation.

While there is also generally known of various display devices which use light-emitting diodes (LED) as a light source so as to reduce power consumption, such display devices have not been utilizes to any large extent due to the fact that they still have the drawback of being "washed out" in direct sunlight. In order to enhance the brightness of the LED light source, there is ~: typically needed a separate light transmissive/reflective component to be formed in front of the LED light source so as to allow the light generated by the LED light source to pass therethrough but reflect incoming sunlight .~15 back out.
.

A prior art search directed to the subject matter of this application in the U.S. Patent and Trademark Office revealed the following U.S.-Letters Patent:
3,881,809 4,772,885 4,182,553 4,791,418 4,3i5,258 4,799,050 4,603,973 4,915,486 20591~7 In U.S. Patent No. 3,881,809 to James L. Fergason et al., issued on May 6, 1975, there is disclosed a liquid crystal display which includes a layer of liquid crystal material disposed between first and second transparent parallel plates to provide a sandwich structure through which light can pass. A third transparent plate of a glass/plastic material has a diffuse surface on its forward face and a metal layer disposed on its other side having high reflectivity characteristics. Ambient light which has passed through the liquid crystal material is reflected from the metal layer and is passed back through the liquid crystal material so as to increase the contrast.

In U.S. Patent No. 4,315,258 to William H. McKnight et al., issued on February 9, 1982, there is taught a visual display which includes a twisted nematic liquid crystal sandwiched between a pair of linear polarizers having their polarization axes either parallel or mutually orthogonally disposed so that the crystal will present bright or dark areas in response to applied potentials. A partially transmissive mirror is inter-posed between the 6andwiched liquid crystal and a radiating light source so that in ambient light the image contrast is enhanced.

` ':

`~ 20~91~7 In U.S. Patent No. 4,791,418 to Hideo Kawahara et al., issued on December 13, 198~, there is disclosed a traffic signal light which is comprised of a light source and a liquid crystal means. A transparent colored plate is positioned in front of the light source and is coated with a transparent light-scattering paint to enhance contrast in sunlight. A control circuit applies an electric field to both the liquid crystal means and the 11ght source so that they are energized or de-energized simultaneously. Further, a light transparent layer having a light-reflecting film is disposed between the transparent colored plate and the light source so as to increase the visual distinguishability of the colored plate under direct sunlight.

15In U.S. Patent No. 4,799,050 to John C. Prince et ; al., there is disclosed a light valve for use in a full color liquid crystal display in which a layer of liquid crystal material is controlled by a transparent electrode matrix that is fixed to one surface of a fiber optic plate 6tructure. A matrix of phosphors, each being in alignment with a corresponding element in the transparent electrode matrix, is fixed to the opposed surface of the plate structure. A light source of ultraviolet radiation :;:, ., -` 20~91~7 iQ used to excite the phosphors. A dichroic filter is located behind the fiber optic plate structure t~ reflect visible light, both ambient and that emitted from the phosphors.

The remaining patents uncovered from the search but not specifically discussed are cited to merely show the state-of-the-art relating to visual display assemblies and thus are considered to be only of general interest.

It has now been discovered by the inventors that the light transmissivejreflective component between the light source and legend can be eliminated by utilizing a diffu-sion medium in fr~nt of the LED light source and a re~
flector behlnd the LED. The reflector functions to reflect incoming sunlight back through a filter and a legend. The diffusion medium and the reflector cause the reflected light to be lambertion and the LED light to ~e lambertion. None of the known display device techniques makes use of the reflective properties behind the light 'source (LED array) ~o as to reflect incident ~unlight back out. The elimination of the reflective surface or partially reflective surface from the front of the LED
-6- 2~91~7 allows more of the LED light to exit out the front and makes the display more efficient.

` Further, the inventors have found that the read-ability of the display structurle can be enhanced through the inclusion of a reflective ~lement positioned behind the LED light source. This element may also scatter light to improve viewing angle and uniformity. Also, the rear side of the legend plate can be provided with a reflective material in the opaic regions so as to reflect light striking the rear of the legend plate back into the interior of the display structure fvr reflection out the transparent region of the legend. This further conserves light energy. In addition, the filter has been selected to provide a desired transmittance dependent upon the emission spectral characteristics of both the LED light source and the ambient sunlight. This is done so as to prevent "washout," thus the output color having the desired chromaticity will be observed by the viewer. In this manner, there i5 achieved an improved display structure which is compact, has high reliability and is formed of fewer components compared to the various known and proposed display devices.

, .. . . . .. .

20~91~7 ; -7-SUMMARY OF THE INVENTION

Accordingly, it is a general object of the present invention to provide an improved display structure which is readable in the dark and in direct sunlight without color shift when ON and is unaffected by "washout."
Further, the legend and the legend color is completely unreadable in any ambient illumination including direct sunlight when it is intended to be OFF.

It is an object of the present invention to provide an improved display structure which is compact, light-weight, power efficient, has high reliability, and is formed of fewer components than those traditionally available.

~ .

It is still another object of the present invention to provide a sunlight readable display structure which includes a layered structure formed of a reflector, an LED light source, a diffusion medium, a colored filter, a legend plate and a liquid crystal shutter.

, ~ " ., ~

fJ~

`- 20591~7 It is yet still another object of the present in-vention to provide a method of enhancing the readability of a display structure even in direct sunlight by pre-venting the color of the legend image from shifting or becoming desaturated.

In accordance with these aims and objectives, the prcsent invention is concerned with the provision of a display structure whlch is readable even in direct sunlight. The display structure includes a layered structure formed of a reflective and light-scattering element, an LED array, a diffusion medium, a colored filter, a legend plate and a liquid crystal shutter. The reflective and light-scattering element is positioned behind the LED array. The LED light source is formed of the LED array and the diffusion medium disposed on its front portion for scattering light when energized~ ~he colored filter is arranged in front of the diffusion medium for transm1tting therethrough the radiated light from the LED array. The legend plate is disposed in front of the colored filter and has displayable informa-tion in the form of a transparent image surrounded by an opaic background, or vice versa.

9 2~91~7 The liquid crystal shutter is disposed in front of the legend plate for permitting the displayable informa-tion on the legend plate to be viewed only when the LED
array and the liquid crystal shutter are energized. Con-versely, the liquid crystal ~hutter is p~sitioned infront o~ the legend plate to prevent the image from being read when the LED array and liquid crystal shutter are not energized. The reflective and light-scattering ele-ment and the diffusion medium reflect and scatter inci-dent sunlight which has passed through the liquid crystalshutter, legend plate, and colored filter back through the colored filter and legend plate and out the liquid crystal shutter. The colored filter is preferably selected to have certain spectral transmission character-istics. As a result, the contrast of the displayableinformation on the legend plate is enhanced and is un-affected by washout to a viewer located in an area of the incident sunlight.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and advantages of the present invention will become more fully apparent from the following detailed description when read in conjunction with the accompanying drawings with like ,-,.,~ ....

: ~ , -lO- 20~ 7 reference numerals indicating corresponding parts throughout, wherein:

Figure 1 is an enlarged perspective view, partly in section, of a sunlight readable display structure, constructed in accordance with the principles of the present invention;

Figure 2 is a cross-sectional view, taken along the lines 2-2 of Figure l;

Figure 3 is a front plan view of the display ~txucture, illustrating a "dead face" when the liquid : crystal material and the LED light source are de-energized; and Figure 4 is a schematic representation of the display structure, illustrating the readability of the 15 legend plate even in direct sunlight when the liquid crystal material and the LED source are both energized.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now in detail to the drawings, there is ~hown in Figures 1 and 2 an improved sunlight readable - 20~91~7 display structure 10 constructed in accordance wlth the principles of the present invention. The display structure lo is comprised of a layered structure which includes an electro-optic shutter 12, a legend plate 14, S a ~olored filter 16, a low-powered light source 18, and a back reflector 42, all contained within a housing or casing 20.

The electro-optic shutter 12 is preferably formed of a layer of liquid crystal material which is of the phase change guest-host typeO This type of liquid crystal made is referred to in the literature as the Taylor and White made in honor of the inventors. In the energized condition, a power supply (not shown) is applied across electrical leads 22, 24 (Figure 2) 60 as to cause the molecules to become aligned and thus permit the passage of light. The electro-optic shutter 12 is similar to the type 103-9 which is manufactured and sold by Hercules.

The legend plate 14 is disposed adjacent and behind the inner surface of the layer of liquid crystal material 12. The legend plate 14 is formed with, or has deposited thereon, a transparen~ area image of the alphanumeric or graphic information, designated generally as displayable ... ..

~ ~ .
,,. .
:

~ -12- 20~91~7 information represented in Figure 4 by a message "IMAGE."
The part of the legend plate that is not transpar~nt must be made opaic. This will give a bright image on a dark background. The transparent and opaic areas can be reversed so as to provide a dark image on a bright background. The bright area is made bright by the light from the LED and, if present, the ambient illumination.
The back side ~r rear surface of the legend plate that is in the opaic area may be coated with a transparent light-reflecting film material 14a, which absorbs little light.As a result, any light striking the back side of the legend plate opaic area will not be absorbed but will be reflected back into the interior of the display structure and then subsequently further reflected and scattered 1~ back through the filter 16 and the legend plate 14. This serves to conserve the light energy from the LED and helps prevent the display from becoming hot to touch or overheated.

The filter 16 is arranged behind the inner surface of the legend plate 14 and is fabricated of selected characteristics such that the alphanumeric or graphic information depicted in Figure 4 as IMAGE will appear illuminated as a desired transmission color to the viewer. In orcler to obtain this desired color output of -13- 2~91~7 chromaticity without a color shift even under varying ambient (sunlight) intensity conditions, the colored filter must be designed to have certain spectral transmission characteristics ~transmissivity).

However, presently insufficient LED colors exist to achieve the desired color and it would be very costly to manufacture such a unique colored filter. Alternatively, the color filter can be selected from commercially available filters to match available LED colors to achieve acceptable usable colors, based upon conditions and criteria, as discussed below. These filters may be of the industrial grade, in production such as manu-~actured and sold by Hoya, such as red type R-60. The filter is selected to match available LED colors such as Hewlett-Packard type HLCP-HL100. The advantage to this latter approach is its low cost due to the use of the existing production filters at production thicknesses, and the disadvantage is that there may be a slight color shift due to the limited available filters when the ambient illumination (sunlight) increases in intensity and the color selection i6 somewhat limited by the avail-able LED colors.

:: . i 2~9157 Initiallyl a first color output of chromaticity co-ordinates xl and yl must be measured when the LED light source is activated and no sunlight exists. Next, a second color output of chromaticity coordinates x2 and y2 ~ust be measured in the presene of ambient illumination and the LED light source is inactivated. Then, the transmittance of the colored filter can be determined when the following factors are known: (1) emission spectral characteristics of the LED light source; (2) emission spectral characteristics of the ambient illumination; and (3) the desired output color with chromaticity coordinates x3 and y3. From a practical standpoint, it is necessary that the emission spectrum of the LED light source overlap the chromaticity coordinates of the desired output color. Further, it is helpful if the ambient illumination has a broad bandwidth such as exist with sunlight.

The filter transmittance is designed such that xl = x2 = x3 and yl = y2 = y3. As a consequence, the desired output color with chromaticity coordinates x3 and y3 will remain substantially the 6ame for any combination of the.LED light source and the ambient illumination. -~

"'~

`2~91~7 The filter transmittance can be computed using optical design computer programs by one skilled in the art. Due to the cost of the filters and the limited availability of LED colors as suggested above, the design was achieved as follows:

(1) Select an LED color as close to the desired color as possible, ~ (2) Select from available filters a filter : with high transmittance for the LED and such that xl = x2 and yl = y2 using the same computer program or engineering hand calculations, and (3) Measure the resulting filter and LED
performance.

.

' ~ 15 In this manner, the chromaticity of the LED light ; source and the reflected light of the LED light source passin~ through the colored filter 16 and the legend plate 14 and out the electro-optic shutter 12 will be substantially the 6ame as the chromaticity of the ambient illumination sunlight) passing through the electro-optic shutter 12, the legend plate 14 and colored filter 16 and -`` 20~91~7 reflected back again thr~ugh the colored filter, legend plate and out the electro-optic shutter. Consequently, the colored filter selected based upon this afore-mentioned technique will be optimized 50 that the light ha~ing the desired output color of chromaticity will be transmitted, thereby insuring image (or contrast) en-hancement of display structure even in the presence of sunlight.

In order to increase the readability of the display-able information or symbol on the legend plate 14, a first seal 36 functioning as an optical coupling is interposed between the inner surface of the layer 12 of liquid crystal material and the legend plate 14. A
second seal 38 functioning as an optical coupling is interposed between the inner surface of the legend plate 14 and the colored filter 16. Further, a third seal 40 functioning as an optical coupling is interposed between the inner surface of the colored filter 16 and the LED
media 28 of the light source. The edges and the bottom of the assembly are painted ~ith a white reflective paint to prevent any light loss and reflect inward all light so that it will exit the image area. The assembly of the layer of liquid crystal material, legend plate, colored filter and light source is installed snugly against :;'" ~;

r~

` 20591~7 ad~acent sur~aces in the rasing 20 so as to eliminate un-wanted reflection of incident sunlight along the edges of the casing which might decrease the image contrast.

.

Moreover, the readability of the displayable infor-S mation or symbol has been increased by the inclusion of the reflective and light-scattering element 42 positioned behind the LED light source 18. The light-scattering element may be preferably formed of a layer of light-scattering paint, glass, plastic or some other diffusive material. The light-scatterins material is suitably applied by coating the inner back surface of the casing , 20 directly behind the LED light source 18. Alterna-tively, a light-scattering material may be applied to the entire inside wall surfaces of the casing 20 so as to provide a diffusive condition.

The low-powered light source 18 is preferably formed of a light-emit~ing diode (LED) array 26 having the diffusion medium 28 disposed on its front portion. The . j , medium 28 1s transparent plastic and has scattering optical characteristics to diffuse the light coming from the points of each diode in the array 26 into a uniform film of light emitting from the source 18. It is to be -18- 20~9~ ~7 noted that the inventive concept described herein requires the reflector 42 to be behind the light source 18 for the best results as opposed to a transmissive/
reflective component (transflector) placed in front of the light source 18 as found in prior art patent Nos.
4,315,258; 4,791,418; and 4,799,050. This reflector 42 : ~ serves to eliminate the necessity of a separate light transmissive/reflective component between the light source and the filter which causes a reduction in the efficiency of the 1ED array Z6. The light source 18 with back reflector 42 and electrical leads 30 and 32 is of the type similar to HLCP H100 and HLMP-2685 which are commercially available from Hewlett Packard. The Hewlett Packard components HLCP H100 and HLMP-2685 are manu~
:~: 15 factured with the medium 28, the LED array 26, and back reflector 42 with power leads 30 and 32 all in one I assembly. .

The light source lB further includes electrical : ` leads 30, 32 for receiving power from the power BUpply.
When the power supply is turned off, the LED array 26 ~s . . .
de-energized and the layer of liquid crystal material ie ;`
in the~OFF condition. As a result, the displayable information defined by the symbol IMAGE on the legend plate 14 will not be visually observable by the viewer in 20~9~7 front of the display structure 10, as shown in Figure 3.
In particular, it can be seen that the front of the display structure lo presents a so-called "dead-face."

-'`

Referring now in particular to Figures 2 and 4, when5 the power supply is turned on, the LED array 26 is energized and the layer of liquid crystal material is in the ON condition. Consequently, the viewer will be able to see an image contrast attributed simultaneously by the internally reflected ambient sunlight 34 and by the transmitted radiating light from the LED array 26.

In other words, the ambient sunlight 34 from the viewer's side of the display structure lo will be passed through the layer 12 of liquid crystal material which is in the ON condition. After subsequently passing through the legend plate 14, the colored filter 16, and the medium 28, then reflected back from the element 42, this will cause the ambient 6unlight to be disbursed and reflected back through the medium 2~, colored filter 16, legend plate 14, and the layer 12 of li~uid cry~tal material and towards the viewer. Simultaneously, the light generated by the LED array 26 and the LED light as reflected by the light-scattering element 42 will pass ., ~ ' ' '.

-20- 2~9157 through the medium 28, colored filter 16, legend plate 14, and the layer 12 of liquid crystal material towards the viewer.

Since the coloxed filter 16 has been chosen to have a desired transmittance dependent upon both the emission ~pectrum of the LED light source 18 and the emission spectrum of the ambient sunli~ht 34 rather than being matched only to the emissivity of the LED light source, the final transmission of the visible light from the colored filter 16 will be at the chromaticity of the desired output color. There*ore, the displayable infor~
mation represented by the message IMAGE being visible through the layer 12 of liquid crystal material is en~
hanced rather than being "washed out" and appears to the viewer with the desired transmission color and at a higher luminescence in proportion to the ambient illumination.

From the foregoing detailed description, it can thus ~ be seen that the present invention provides an improved display structure readable even in direct sunlight, which includes an LED array with a front diffusion medium and a back reflective layer. The reflection/diffusion media ~ 20~9~7 reflects and scatters incident sunlight which i5 passed throuyh a layer of liquid crystal material, legend plate, and coloxed filter back thrvugh the colored filter, . legend plate and out the layer of liquid crystal material by using the reflective characteristics of the layer 42 so as to enhance rather than washout the contrast of the displayable information on the legend plate. In order to further increase the readability of the displày structure, the colored filter is selected to have lo certain spectral transmission characteristics dependent upon the emission spectrum of the LED light source, the emission spectrum of the ambient sunlight, and the de-sired transmission color.

~.
While there has been illustrated and described what is at present considered to be a preferred embodiment of the present inventlon, it will be understood by those skilled in the art that various changes and modifications may be made, and equivalents may be substituted for elements thereof without departing from the true scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the central scope thereof. Therefore, it is intended that this invention not be limited to the particular embodi-20591~7 ment disclosed as the best mode contemplated for carrying out the invention, but that the invention will include al~ embodiments falling within the scope of the appended cl~ims.

-: -, . . , ~ , ..... ~ : . :: .. ~

Claims (18)

1. A display structure which is readable even in direct sunlight, comprising:

reflector means;
light source means disposed in front of said reflector means and including an LED
array having a diffusion medium disposed on its front portion for radiating a light when energized;

a colored filter arranged in front of the media of said LED array for transmitting therethrough the radiated light from said LED
array;

a legend plate disposed in front of said colored filter and having a transparent image of displayable information against an opaic background or vice versa deposited thereon;

electro-optic shutter means disposed in front of said legend plate for permitting the displayable information on said legend plate to be viewed only when said LED array and said shutter means are energized; and said reflector means and said diffusion medium reflecting incident sunlight which has passed through said shutter means, legend plate, and colored filter back through said colored filter and legend plate and out said shutter means, whereby the contrast of said displayable information on said legend plate is enhanced rather than being washed out to a viewer located in an area of the incident sunlight.
2. A display structure as claimed in Claim 1, wherein said electro-optic shutter means is comprised of a layer of liquid crystal material.
3. A display structure as claimed in Claim 2, wherein the layer of liquid crystal material is of a phase change guest-host type.
4. A display structure as claimed in Claim 3, further comprising first optical coupling means inter-posed between said layer of liquid crystal material and said legend plate for facilitating the readability of said displayable information.
5. A display structure as claimed in Claim 4, wherein said first optical coupling means comprises a first seal.
6. A display structure as claimed in Claim 5, further comprising second optical coupling means interposed between said legend plate and said colored filter for facilitating the readability of said displayable information.
7. A display structure as claimed in Claim 6, wherein said second optical coupling means comprises a second seal.
8. A display structure as claimed in Claim 7, further comprising third optical coupling means inter-posed between said colored filter and said reflection/
diffusion media of said light source for facilitating the readability of said displayable information.
9. A display structure as claimed in Claim 8, wherein said third optical coupling means comprises a third seal.
10. A display structure as claimed in Claim l, wherein said light means, colored filter, legend plate and shutter means are disposed as a layered structure within a casing.
11. A display structure as claimed in Claim 10, wherein said reflector means is comprised of a reflective light-scattering paint which is coated to the inner back surface of said casing directly behind said LED array.
12. A display structure as claimed in Claim 1, wherein said colored filter is selected to have certain spectral transmission characteristics dependent upon the emission spectrum of the LED light source, the emission spectrum of the ambient sunlight, and the desired trans-mission color.
13. A display structure as claimed in Claim 1, wherein the back side of the non-transparent area of said legend plate is coated with a light-reflecting film material.
14. A display structure as claimed in Claim 11, wherein the entire inside wall surfaces of said casing is coated with said reflective light-scattering paint to provide a diffusive condition.
15. A method of enhancing the readability of a display structure even in direct sunlight comprising the steps of:

providing a reflective element;

radiating in front of the reflective element a light from an LED array having in front of it a diffusion medium with light scattering characteristics;

transmitting the radiated light through a colored filter by using the diffusion charac-teristics of the media;

providing a legend plate having display-able information deposited thereon;

activating a layer of liquid crystal material to permit the displayable information on the legend plate to be viewed when the LED

array is energized; and reflecting incident sunlight which is passed through the layer of liquid crystal material, legend plate, and colored filter back through the colored filter, legend plate and out the layer of liquid crystal material by using the reflective element and the diffusion medium so as to enhance rather than wash out the contrast of the displayable information on the legend plate.
16. A method as claimed in Claim 15, further comprising the step of selecting the colored filter to have certain spectral transmission characteristics dependent upon the emission spectrum of the LED array, the emission spectrum of the incident sunlight, and the desired transmission color.
17. A display structure which is readable even in direct sunlight, comprising:

reflective means for reflecting light;

light source means disposed in front of said reflective means for radiating a light when energized;

a colored filter arranged in front of said light source means for transmitting therethrough the radiated light;

said colored filter being selected to have certain spectral transmission character-istics dependent upon the emission spectrum of said light source means, the emission spectrum of the ambient sunlight, and a desired transmission color;

a legend plate disposed in front of said colored filter and having displayable informa-tion deposited thereon; and said reflective means reflecting incident sunlight which has passed through said legend plate and colored filter back through said colored filter and legend plate to provide a final transmission of visible light with the chromaticity of the desired output color, whereby the contrast of said displayable information on said legend plate is enhanced rather than being washed out to a viewer located in an area of the incident sunlight.
18. A display structure as claimed in Claim 17, further comprising electro-optic shutter means disposed in front of said legend plate for permitting the display-able information on said legend plate to be viewed only when said LED array and said shutter means are energized.
CA002059157A 1991-01-15 1992-01-10 Sunlight readable display structure Abandoned CA2059157A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US64118491A 1991-01-15 1991-01-15
US641,184 1991-01-15

Publications (1)

Publication Number Publication Date
CA2059157A1 true CA2059157A1 (en) 1992-07-16

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JP (1) JPH07302053A (en)
KR (1) KR950004717B1 (en)
CA (1) CA2059157A1 (en)

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Publication number Priority date Publication date Assignee Title
FR2711827A1 (en) * 1993-10-22 1995-05-05 Guigan Franck Display system
JP2018522263A (en) * 2015-05-11 2018-08-09 コーニング インコーポレイテッド Surface display unit with opaque screen

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JPS5146000U (en) * 1974-10-04 1976-04-05
JPS5492229A (en) * 1977-12-28 1979-07-21 Minolta Camera Co Ltd Flashing display device
DE2931327A1 (en) * 1979-08-02 1981-02-19 Rau Swf Autozubehoer DISPLAY SYSTEM, ESPECIALLY FOR MOTOR VEHICLES
US4791418A (en) * 1986-04-30 1988-12-13 Taliq Corporation Signal light
DE3710551A1 (en) * 1987-03-30 1988-10-13 Miditec Mikroelektronik Displa Display unit for variable display

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EP0495616A2 (en) 1992-07-22
KR950004717B1 (en) 1995-05-04
EP0495616A3 (en) 1993-02-03
JPH07302053A (en) 1995-11-14
KR920015148A (en) 1992-08-26

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