Elastomer Display

The present invention relates to an elastomer display and, more particularly, to a display system which utilizes a deformation effect of an elastomer under a predetermined electric field.

An elastomer display system is well known in the art, wherein a light beam applied to an elastomer is modulated through the use of deformation of the elastomer caused by a voltage signal applied thereto. The elastomer display system has a great advantage because of its low power drive characteristics.

However, the conventional elastomer display systems do not provide sufficient legibility because the elastomer does not emit light by itself. Moreover, in the conventional elastomer display system, relief deformation of the elastomer is utilized for display purposes and, therefore, an additional optical system such as the phase control system and the double refraction system is required to complete the display system.

Accordingly, an object of the present invention is to provide an elastomer display system of high legibility.

Another object of the present invention is to provide a fluorescent elastomer display system.

Still another object of the present invention is to provide an elastomer display system, wherein the frost deformation is created in the elastomer.

Yet another object of the present invention is to provide an electrode for the elastomer display system for ensuring the stable frost deformation in the elastomer.

Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

To achieve the above objects, pursuant to an embodiment of the present invention, electrodes are formed on both of the major surfaces of a transparent elastomer to create the frost deformation in the elastomer. Fluorescent centers are disposed in the transparent elastomer to generate the luminescence when a light beam is applied to the transparent elastomer. A scattering section is formed at a position where the frost deformation is created, thereby displaying a desired pattern through the use of the fluorescence derived from the fluorescent centers and scattered at the scattering section.

In a preferred form, the electrodes are mesh shaped or comb shaped to form a nonuniform electric field across the transparent elastomer. The thus formed nonuniform electric field creates the frost deformation in the transparent elastomer.

The present invention will be better understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention and wherein:

FIG. 1 is a sectional view of an embodiment of an elastomer display system of the present invention;

FIGS. 2(A) and 2(B) are sectional views of the elastomer employed in the elastomer display system of FIG. 1, wherein FIG. 2(A) shows the off state, and FIG. 2(B) snows the on state;

FIG. 3 is a graph showing a contrast characteristic of the elastomer display system of FIG. 1;

FIG. 4 is a sectional view of another embodiment of an elastomer display system of the present invention;

FIG. 5 is a sectional view showing an operation mode of the elastomer display system of FIG. 4; FIGS. 6, 7 and 8 are plan views of embodiments of an electrode employed in the elastomer display system of FIG. 4;

FIG. 9 is a graph showing a contrast characteristic of the elastomer display system of FIG. 4; and

FIG. 10 is a sectional view of still another embodiment of an elastomer display system of the present invention.

FIG. 1 schematically shows an embodiment of an elastomer display system of the present invention.

The elastomer display system mainly comprises a transparent substrate 1, a transparent electrode 2 formed on the transparent substrate 1, a counter electrode 4, and a transparent elastomer 3 disposed between the transparent electrode 2 and the counter electrode 4. The transparent electrode 2 and the counter electrode 4 are connected to a power supply source 8 via a switch 7, thereby establishing an electric field across the transparent elastomer 3.

Fluorescent centers 5 are included in the transparent elastomer 3 through the use of solution techniques or dispersion techniques. The counter electrode 4 must be a transparent electrode when the elastomer display system is the transparent type, but the counter electrode 4 need not necessarily be a transparent electrode when the elastomer display system is the reflection type. A conductive elastomer or liquid can be used as the electrode.

A reflection film 6 is provided to surround the edges of the transparent substrate 1, the transparent electrode 2 and the transparent elastomer 3, thereby preventing the light from emitting through surfaces other than the display surface. An observer 9 recognizes the display information which is formed by the fluorescent pattern caused by an exciting light applied from a light source 10.

The transparent elastomer 3 preferably has a refractive index greater than that of the transparent substrate 1, wherein the fluorescence from the fluorescent centers 5 is retained within the transparent elastomer 3 due to the total reflection. If the transparent elastomer 3 has a refractive index smaller than or equal to that of the transparent substrate 1, a transparent layer 11 is interposed between the transparent substrate 1 and the transparent elastomer 3, the transparent layer 11 having the refractive index smaller than that of the transparent elastomer 3. The above-mentioned refractive index relationship must also be satisfied on the side of the counter electrode 4, if the counter electrode 4 is not made of the reflective material.

The transparent elastomer 3 is required to provide the frost deformation (not only the relief deformation) when a predetermined electric field is applied across the transparent elastomer 3 through the use of the transparent electrode 2 and the counter electrode 4. The thus formed frost deformation functions to scatter the light beam. An operation mode of the elastomer display system of FIG. 1 will be described with reference to FIGS. 2(A) and 2(B).

The fluorescent centers 5 emit fluorescence r.sub.2 when an exciting light r.sub.1 is applied thereto. The thus developed fluorescence r.sub.2 is transferred through the transparent elastomer 3 in a fashion similar to the optical fiber, and the majority of the fluorescence r.sub.2 is accumulated in the transparent elastomer 3 along the plane perpendicular to the thickness of the transparent elastomer 3.

When the transparent elastomer 3 is not activated by the electric field, only a part of the fluorescence r.sub.2 reaches the observer 9 and, therefore, he recognizes the "off" state (FIG. 2(A)). When a predetermined voltage is applied between the electrodes 2 and 4, the transparent elastomer 3 is activated and a frost deformation is created in the transparent elastomer 3. The thus created frost deformation functions as a scattering center. That is, the fluorescence r.sub.2 is scattered by the frost deformation and reaches the observer 9 and, therefore, he recognizes the "on" state (FIG. 2(B)).

The transparent substrate 1 is made of quartz glass, Pyrex glass, sodium glass, plexi glass (an acryl plate), or polyethylene. The material of the transparent substrate 1 is selected in accordance with the absorption spectrum and the fluorescent spectrum of the fluorescent centers 5. The transparent substrate 1 has the thickness 0.5 mm to 3 mm. The transparent electrode 2 is made of In.sub.2 O.sub.3 or SnO.sub.2. If required, the transparent electrode 2 is shaped in a desired configuration through the use of an etching method or a masked evaporation method.

The low refractive index transparent layer 11 is formed on the transparent electrode 2 through the use an evaporation method or a painting method. Preferred materials for the transparent layer 11 are as follows:

BaF.sub.2 (n=1.48)

CaF.sub.2 (n=1.43)

Na.sub.5 Al.sub.5 F.sub.14 (n=1.33)

LiF (n=1.36)

MgF.sub.2 (n=1.38)

SiO.sub.2 (n=1.46)

SrF.sub.2 (n=1.44)

The low refractive index transparent layer 11 has the thickness about 500 A to 5000 A.

The transparent elastomer 3 is preferably made of high refractive index silicon elastomer such as MP-011 (n=1.51) manufactured by Toray Silicone Co., Ltd. The silicon elastomer is painted on the transparent layer 11 to the thickness about 1 .mu.m to 15 .mu.m through the use of a spinner.

The counter electrode 4 comprises an elastic conductor including carbon grains distributed therein. An indium layer is formed on the elastic counductor to the thickness about 1000 A through the use of an evaporation method, the indium layer functioning as a reflection layer. The counter electrode 4 must have a characteristic to allow the occurrence of the frost deformation in a transparent elastomer 3 when the predetermined voltage is applied between the electrodes 2 and 4.

The fluorescent centers 5 can be organic fluorescent materials. Preferred materials are as follows:

anthracene

tetracene

pyrene

fluorescein

9.10-dimethylanthracene

9.10-diphenylanthracene

perylene

fluorene

p-quaterphenyl

rubrence

2.5-diphenylfuran

2.5-diphenyloxazole

samaron brilliant yellow H6GL

brilliant phosphine

primulin O

acridine yellow

thioflavine S

rhodamine 6G perchrorate

pyronin G

pyronin B

cumarin 7

cumarin 10

cumarin 138

cumarin 337

europium thenoyltrifluoroacetonate trihydrate tris[4.4.4-trifluoro (2-thienyl)-1.3-butanedione] europium

The power supply source 8 can be a DC voltage source, a DC pulse generator, or an AC pulse generator. Generally, the output level is below 100 V.

FIG. 3 shows the contrast characteristic of the elastomer display system of FIG. 1, wherein cumarin cumarin 7 manufactured by Eastman Kodok Co. is used for the fluorescent centers 5. The detection is conducted through the use of a light beam of the wavelength 550 nm. The response characteristic is about 10 msec to 100 msec, and the power consumption is about 0.01 .mu.W/cm.sup.2.

To ensure the creation of the frost deformation, it is necessary to establish a nonuniform electric field across the transparent elastomer 3.

FIG. 4 shows another embodiment of the elastomer display system of the present invention, wherein the fluorescent centers are not disposed in the transparent elastomer 3.

That is, only the light beam derived from the light source 10 is used for display purposes. Like elements corresponding to those of FIG. 1 are indicated by like numerals.

The counter electrode 4, which is mesh shaped, is made of Al, Ni, Co, Au, In.sub.2 O.sub.3, or SnO.sub.2. An insulator layer 12 is formed on the counter electrode 4 to cover the transparent elastomer 3. The insulator layer 12 is made of an evaporated layer of SiO.sub.2, Al.sub.2 O.sub.3, TiO.sub.2, Y.sub.2 O.sub.3, or Si.sub.3 N.sub.4, or a thin-film layer of an organic insulation material. A reflection layer 13 is formed on the insulator layer 12. The reflection layer 13 can be made of Al or Au, or a stacked layer of dielectric materials.

When a predetermined voltage is applied between the transparent electrode 2 and the mesh-shaped counter electrode 4, the frost deformation is created in the transparent elastomer 3 due to the nonuniform electric field formed by the mesh-shaped counter electrode 4 as shown in FIG. 5.

Of course, the fluorescent centers can be added to the transparent elastomer 3.

The transparent substrate 1 is a float glass plate of 3 mm thick. An In.sub.2 O.sub.3 layer of 500 A thick is formed on the transparent substrate 1 through the use of electron beam evaporation techniques. The thus formed In.sub.2 O.sub.3 layer is shaped in a desired pattern through the use of a photoetching method, thereby providing the transparent electrode 2. The transparent elastomer 3 comprises a silicon elastomer, such as MP-011 manufactured by Toray Silicone Co., Ltd., which is coated on the transparent electrode 2 to the thickness about 3 .mu.m to 15 .mu.m through the use of the spinner.

The counter electrode 4, made of Al, Au, Ni, In or Co, is formed on the transparent elastomer 3 through the use of an evaporation method or a spattering method to the thickness of about 1000 A to 1 .mu.m. Then, the counter electrode 4 is shaped in a desired pattern such as the mesh pattern through the use of the photoetching method.

FIGS. 6, 7 and 8 show examples of the pattern of the counter electrode 4. The electrode pattern is not limited to the patterns shown in FIGS. 6, 7 and 8, but must have the shape to ensure the generation of the nonuniform electric field suited for forming the frost deformation.

The insulator layer 12 is preferably about 1 .mu.m thick and made of CX52-003LTV manufactured by Toray Silicon Co., Ltd. As already discussed, the insulator layer 12 can be an inorganic layer made of SiO.sub.2, MgF.sub.2 or Al.sub.2 O.sub.3. The reflection layer 13 is made of Al, Au or In, and formed to the thickness around 1000 A through the use of the evaporation method.

FIG. 9 shows the contrast ratio characteristic of the elastomer display system of FIG. 4, wherein the applied voltage is shown along the abscissa axis, and the contrast ratio is shown along the ordinate axis. The detection is carried out under the temperature 25.degree. C., and the transparent elastomer 3 is about 5 .mu.m thick. The response characteristic is as follows.

rise time 7 msec

decay time 5 msec

where the applied voltage is 50 V.

The reflection layer 13 can be made of a desired material when the counter electrode 4 is the transparent electrode made of, for example, In.sub.2 O.sub.3 or SnO.sub.2. However, if the counter electrode 4 is made of metal, the reflection layer 13 is preferably made of a material which shows the reflection characteristic similar to that of the counter electrode 4 for achieving a clean display.

FIG. 10 shows still another embodiment of the elastomer display system of the present invention. Like elements corresponding to those of FIG. 4 are indicated by like numerals.

In the embodiment of FIG. 10, the transparent electrode 2 is omitted, and the electrode pair is formed on one major surface of the transparent elastomer 3 in the interdigital fashion. More specifically, electrodes 14 and 14' form a prularity of pairs of electrodes.

The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications are intended to be included within the scope of the following claims.