Flexible Controllable Optical Surface and Method of Making the Same

1. Field of the Invention

This invention relates generally to flexible optical surfaces usable as filters, refractors, reflectors and the like, and more particularly to an improved controllable surface for optical applications with a flat state that is not influenced by repeatedly rolling and unrolling into a coiled state, and to a method for making the controllable surface.

2. Description of the Prior Art

An optical surface, film and laminate has optical applications in articles of manufacture ranging from a projector screen to a solar film. Various other optical applications include use in a television screen, highway reflector, sign or the like. For a desired application, the optical surface can be formed from a single substrate or from a wide variety of layered constructions. Some optical surfaces can be adapted with a precise optical characteristic or function to modulate incident light energy in accordance with the various laws of optics such as, for example, diffraction, diffusion, dispersion, refraction or reflection. The present invention provides both a controllable surface when unrolled, and permits the use of precision optical characteristics or functions. Furthermore, by forming the controllable surface using flexible, coilable spring-like materials having superior lay-flat characteristics, the present invention can be applied to many articles of manufacture that today use a rigid or non-rigid support substrate.

Some current designs of controllable surfaces use a rigid support substrate. The rigid support substrate is relatively stiff and thus can easily provide a predictable and usable planar surface area to define the controllable surface needed for optical applications. A spherically-curved rigid support substrate can be used to make the controllable surface more orthogonal to the incident light energy generated from a point source as is illustrated in U.S. Pat. No. 3,408,132 to Chandler et al., and thus can increase and control the light reflected to an audience viewing zone. The controllable surface formed using rigid support substrates can eliminate the problem of hot spotting as occurs with flat surfaces when the dynamic brightness range exceeds the tolerance of photopic vision. For example, in certain applications an optical pattern can be imprinted in or secured to the controllable surface to modulate incident light energy. The optical pattern can have the precision optical characteristic such as a differential refraction pattern to increase the dynamic range or gain of the optical surface. Patterns using multiple precision optical characteristics can also modulate incident light energy to a greater or lesser degree according to particular areas or zones of the optical surface. However, disadvantages of the rigid support substrate include storage problems where the rigid support substrate cannot be rolled-up and effectively transported. Other disadvantages include the optical surface being permanently secured to the rigid support substrate, being relatively bulky and unmovable, and requiring costly manufacture or installation.

Alternatively, known optical surfaces formed using a flexible or non-rigid support substrate cannot provide the controllable surface for optical applications requiring a pattern of precision optical characteristics because a non-uniform surface such as undulations, edge-curl or other surface deformations can negate the beneficial effects of the pattern. Most known non-rigid support substrates are manufactured from conventional polymeric materials such as nylons, vinyl, acetals, polyolefins, or other fiber reinforced materials with a modulus of elasticity of about 15,000 p.s.i. The resulting flexible optical surface can be rolled-up but does not have a controllable surface when unrolled. This feature of known non-rigid support substrates precludes the use of precise optical functions, particularly if the above-identified materials contain a plasticizer. For this reason, most applications for these optical surfaces using conventional non-rigid support substrates have not included precision optical characteristics or have reduced performance with restricted gains of 2 gains or less.

Projection screens are increasingly more diverse and sophisticated using precision optical characteristics, various combinations of optical patterns and a wide variety of layered constructions. An example of a projection screen is illustrated in U.S. Pat. No. 4,191,451, by the same inventor as the present application, and is hereby incorporated by reference. The patent relates to optical surfaces, and in particular to the forming of the optical layer for a multi-layered optical surface and method for manufacturing the same. The optical layer is formed with a pattern of light affecting elements to control the optical characteristics of the projection screen. The optical layer is secured to either a rigid or flexible support substrate made from conventional materials. However, the present invention overcomes the many disadvantages of known rigid and non-rigid support substrates made from conventional materials to provide a high gain, controllable surface using a non-rigid support substrate and precision optical characteristics.

Optical surfaces have applications in solar films. Solar films are mostly used to change the amplitude, magnitude or direction of incident light energy depending upon the application desired such as to reflect light energy in the summer or absorb light energy in the winter, or both. Known solar films are thin and flimsy requiring these to be permanently secured to a rigid support substrate such as glass in buildings, automobiles, etc. It would be advantageous if an all weather, relocatable roll-up solar film could be formed to function as a window shade and further to have precision optical characteristics incorporated thereon.

Accordingly, there is a need for a flexible optical surface, film or laminate with the advantages of the controllable surface with precision optical characteristics for such applications as roll-up projection screens. There is also a need for a simple, efficient and inexpensive method of producing these flexible optical surfaces to varied specifications. Such a method should be capable of producing high quality, superior controllable surfaces with optics at a reduced cost of manufacture.

It is an object of the present invention to provide a optical surface that overcomes many of the disadvantages of known flexible optical surfaces.

It is an object of the present invention to provide an optical surface using a support substrate made from flexible, stable material with an elasticity modulus between 300,000 and 600,000 p.s.i., and a thickness between 0.0015 and 0.018 inch thereby defining a planar or controllable surface. A feature of the flexible controllable surface provides good lay-flat properties which remain after repeatedly rolling into a coil and unrolling into the defined flat plane. An advantage of the present invention is increased applications in articles of manufacture requiring the flexible controllable surface and providing an effective means of transporting and storing the same.

Another feature of the flexible controllable surface as used in a roll-up projection screen having precision optical characteristics.

Another feature of the present invention is that the roll-up projection screen can have precise optical characteristics to control the dynamic range, gain or other optical characteristics to modulate efficiently incident light energy. An advantage of the present invention is the improved performance in a roll-up projection screen using precision optical characteristics and optical patterns. Another advantage of the roll-up projection screen is to increase the dynamic range and to vary the audience viewing zone of the screen by using a pattern having precision optical characteristics. Still yet another advantage is to make the roll-up projection screen with improved performance portable and thus easily relocatable.

Yet another object of the present invention is to provide an efficient solar film using varying transmissive properties of the support substrate and precision optical characteristics that can be rolled-up into a coil and unrolled to a flat state. It is a feature of the transmissive support substrate to be manufactured using dyes to absorb incident light energy and radiate heat. It is a feature of the solar film to use precision optical characteristics for affecting the amplitude, magnitude and direction of incident light energy. Another feature is that the solar film can be easily relocated for indoor or outdoor use. An advantage of the roll-up solar film is in having the portability and flexibility to move the solar film from room-to-room following high intensity light energy such as for seasonal changes. Another advantage of the roll-up solar film is the use as a window shade.

Still yet another object of the present invention is to provide a flexible optical surface having various combinations of predetermined precise optical characteristics to control and balance the optical properties of the optical surface. It is a feature of the present invention to use the optical pattern of precise optical characteristics in conjunction with the controllable surface such as dispersion optics or a differential optical pattern for modulating the brightness of on-axis incident light energy to a greater percentage than the brightness of off-axis incident light energy.

In brief, the present invention is directed to a flexible optical surface, film or laminate and method for making the same using a support substrate with both a sufficiently high modulus of elasticity to define accurately a controllable surface and a sufficiently low modulus of elasticity to permit the controllable surface to be repeatedly rolled into a coil and unrolled. An optical layer with precision optical characteristics can be extrusion cast or otherwise secured to the support substrate. The support substrate can have a modulus of elasticity from 300,000 p.s.i. to 600,000 p.s.i. and a thickness from 0.0015 to 0.018 inch. A reflective layer can be interposed between the support substrate and the optical layer. The optical layer can have precision optical characteristics or patterns such as to reflect, refract or otherwise modulate incident light energy. The support substrate can be formed by determining a required thickness for the support substrate and dividing the required thickness to form two segments of the support substrate. One segment is secured to the other segment by placing a side of the one segment having an inward curl to another side of the other segment also having an inward curl, where the inward curl of each segment is oriented in an opposite direction so as to place the inward curl of the one side opposite the inward curl of the other side, and thus negating the inward curl of each segment thereby forming the support substrate.

These and other objects and advantages of the present invention will become readily apparent upon consideration of the following detailed description and attached drawings, wherein:

FIGS. 1a and 1b are schematic illustrations of an image projection system using a projection screen according to the present invention; and FIG. 1c is a schematic illustration of a solar film according to the present invention;

FIG. 2 is a cross-sectional view of one embodiment of the present invention illustrating the support substrate and an optical layer;

FIG. 3 is a cross-sectional view, similar to FIG. 2, illustrating another embodiment of the present invention;

FIG. 4 is a cross-sectional view of a reflector-type of optical laminate according to the present invention;

FIGS. 5a, 5b, 5c, 5d, 5e, 5f and 5g are enlarged schematic cross-sectional views illustrating an upper layer using a differential gain layer according to an embodiment of the present invention;

FIGS. 6a, 6b, 6c and 6d are reduced schematic front plan views illustrating the upper layer using a differential gain layer according to an embodiment of the present invention; and

FIG. 7 is a cross-sectional view of another embodiment of the present invention illustrating a process of manufacturing the support substrate.

In accordance with the present invention, a flexible optical surface, film or laminate using a nonrigid support substrate and various optical layers is provided to affect incident light energy by means of an optical pattern with a precision optical characteristic or function. The flexible optical surface can be rolled into a coiled state and uncoiled returning to a flat state defining a planar or controllable surface. This controllable surface lacks a memory of the coiled state. In accordance with an important feature of the present invention, the support substrate is chosen to have a modulus of elasticity in the range from 300,000 p.s.i. to 600,000 p.s.i. and a thickness in the range from 0.0015 inch to 0.018 inch to provide the controllable surface with a sufficient usable surface area. Once the controllable surface is established, then subsequent optical layers can be secured thereto as needed for a particular application. The optical layer can include an optical pattern for establishing a precision optical characteristic as predetermined to modulate incident light energy in accordance with a designated application. The various features of the present invention will be described in both environments of a flexible projection screen and solar film but the present invention is not restricted solely to such as there are many articles of manufacture now using rigid and non-rigid support substrates which can benefit from the optical surface of the present invention.

One application for optical surfaces and films has been with image projection systems, for example, as roll-up front or rear projection screens illustrated in FIGS. 1a and 1b, respectively. The performance of such projection screens can be controlled by techniques such as increasing the dynamic range, restricting the audience viewing zone, and balancing the intensity of light energy across the projection screen as viewed by the audience member such as by using a gain optical layer. As above, conventional materials forming non-rigid support substrates heretofore could not be used to make high performance roll-up projection screens using a pattern with precision optical characteristics because the beneficial affects of the pattern to improve the dynamic gain and the projected image are negated by surface nonuniformities causing undesirable effects such as specularity, a shadowy image, hot spotting or light and dark zones. The disadvantage of surface non-uniformity results in roll-up projection screens that are restricted generally to a low optical gain such as of two gains or less. Other disadvantages restricting potential applications of conventional non-rigid support substrates as roll-up projection screens include the undesirable mechanical characteristics of a particular material such as the effects of temperature, instability, fragility, and hygroscopicity on the optical surface.

Referring now to FIG. 2-4, the optical surfaces shown generally as 20, 30 and 40 can be used for affecting incident light energy such as used in a refractive roll-up projection screen (FIGS. 1b, 2 and 3) and reflective roll-up projection screen (FIG. 1a and 4). The optical surfaces 20 includes a support substrate 22 and an optical layer 24. The materials used to form the support substrate 22 can have optical qualities such as being translucent, semi-translucent or opaque. The materials used to form the optical layer 24 can have similar optical qualities such as being translucent or semi-translucent. The support substrate 22 can be made from polymeric materials of a different chemical family or composition and elasticity modulus than the materials forming the optical layer 24. Each of the optical surfaces 20, 30 and 40 are now described in more detail.

Referring to FIG. 2, the optical surface 20 includes the support substrate 22 and the optical layer 24. The optical surface 20 can be used as a roll-up projection screen in FIGS. 1a and 1b. The support substrate 22 is formed from any polymeric material using an elasticity modulus between 300,000 and 600,000 p.s.i. and a substrate thickness 28 range between 0.0015 and 0.018 inch to provide a controllable surface with sufficient usable surface area that is flexible yet may be rolled into a coil. The optical layers 24 can be secured subsequently to the support substrate 22 to form an optical surface 20 with an overall thickness 29. In addition, the optical layer 24 can have a precision optical characteristic 26 as predetermined and formed from various optical patterns to modulate incident light energy. For example, as shown in FIGS. 5a and 6a, the precision optical characteristic 26 has optical properties to modulate light energy according to a differential dispersion function. Various patterns with precision optical characteristics 26 for the optical layer 24 are possible, as illustrated in FIGS. 5a through 5g and 6a through 6d, such as according to the law of diffraction, diffusion and dispersion as well as using other known techniques that are not shown.

In the preferred embodiment for a refractive roll-up projection screen functionally similar to the roll-up projection screen as shown in FIG. 1b, the flexible optical surface 20 uses the support substrate 22 with an elasticity modulus between 300,000 and 600,000 p.s.i.; a thickness between 0.0015 and 0.018 inch thus providing the controllable surface with sufficient usable surface area. Unlike a majority of known roll-up projection screens with elasticity modulus of approximately 15,000 p.s.i., suitable materials that exceed 200,000 p.s.i. cannot be readily embossed and thus the optical layers 24 must be separately applied to the support substrate 22, for example, as taught by my U.S. Pat. No. 4,191,451. Here, the optical layer 24 can be formed from thermally deformable plastics such as polyethylene. The optical layer 24 can be secured to the support substrate 22 using an extrusion casting technique. The extrusion casting technique can also be used to impart various patterns for the precision optical characteristics 26 using a casting cylinder.

An important feature of the present invention is to form the support substrate 22 with the controllable surface using a polymeric material within the specific elasticity modulus range. The modulus of elasticity of a particular material is measurable and expressed in pounds per square inch (p.s.i.). At a minimum, the support substrate 22 should have the modulus of elasticity of not less than 300,000 p.s.i. and thickness of not less than 0.0015 inch. For comparison, float gum rubber has high flexibility with a modulus of elasticity of 5000 p.s.i., whereas, glass has low flexibility with a modulus of elasticity of 8,000,000 p.s.i. Suitable polymeric films for forming the support substrate 22 are the polyethylenes, for example, polyethylene terephthalate (PET). Known suppliers for PET are the E.I. duPont deNemours and Company sold under the trade name Mylar; and the Kodak Corporation sold under the trade name Tetlar. In essence, the flexible optical surface 20 can be made from any number of combinations of polymeric materials with different thickness and elasticity modulus within the identified parameters.

Another parameter used as a consideration in designing the support substrate 22 of the present invention is the stiffness of a particular material. In general, as between discrete films, stiffness increases with the cube of the thickness. The overall stiffness of the support substrate 22 and subsequent memory or the spring-like quality of returning to the flat state defining the controllable surface is more a function of the elasticity modulus of a specific polymeric material. Furthermore, as the modulus of elasticity of a particular material increases, corresponding improvements occur in such properties as strain relief, thermal expansion, hygroscopic expansion and creep. Stiffness can be measured using a deflectometer constructed to measure grams of resistance to deflect a one square inch substrate sample a distance of 0.010 inch. Any reasonable optical flatness needed to form the controllable surface is achieved with not less than 800 grams of resistance. For example, the deflectometer measures approximately 800 grams of resistance for the substrate thickness 28 of 0.007 inch, 3200 grams of resistance for 0.01 inch thickness, and 8300 grams of resistance for a 0.014 inch thickness keeping a constant elasticity modulus of 500,000 p.s.i. As a design consideration, depending on the ultimate number of optical layers and desired application, the support substrate 22 should be dimensionally thicker than the optical layer 24 so as to assume the mechanical characteristics of the support substrate 22. Also, dependent upon the precision optical characteristic 26 as designated by a particular application, different substrate thickness 28 and elasticity modulus for the support substrate 22 can be used to form the roll-up projection screen. For each improvement of the above-identified properties, the particular material becomes more suitable for certain applications such as outdoor use.

For example, to illustrate these features, if the polymeric material used for the support substrate 22 has a modulus of elasticity of about 500,000 p.s.i., then flexibility can be maintained up to a thickness of about 0.018 inch, beyond which the support substrate 22 becomes excessively rigid. As a modulus of elasticity decreases, a corresponding increase in thickness is needed to maintain the desired stiffness. Similarly, a minimum thickness of about 0.0015 inch and elasticity modulus of about 500,000 p.s.i., the support substrate 22 has a stiffness value sufficient to provide the controllable optical surface of about 30 square inches. Increasing the thickness to about 0.008 inch also increases the useful controllable optical surface to more than 120 square inches. For optical surfaces intended for applications involving optical coatings, it is recommended that the non-rigid support substrate have a minimum thickness of 0.0075 inch for any area. Finally, in most roll-up applications it is recommended that the support substrate have a maximum thickness of 0.018 inch. Thus the roll-up projection screen of the present invention can overcome numerous disadvantages of known flexible support substrates, for example, undulations or warping caused by retaining undesirable nonuniformities introduced by rolling and unrolling the support substrate and by their inherent flexibility.

Referring now to FIG. 3, wherein similar elements will be designated using the same numerals, the optical layers 24 and 24a can be applied to both of the exposed upper and lower surfaces of the support substrate 22 to form the optical surface 30. In the optical surface 30, the support substrate 22 can take many forms such as being translucent or being semi-translucent as to have dyes dispersed within the polymeric material of the support substrate 22 or can further have dispersion fillers disposed within the support substrate 22 as are known in the art. By applying an additional support substrate 24a, the optical surfaces 30 or 40 can be protected from external contaminates and degrading factors such as dust, microorganisms or the adverse effects of extreme weather conditions for increased longevity and durability.

Referring now to FIG. 4, wherein similar elements will be designated using the same numerals, a reflective optical surface 40 can be used to form the reflective projection screen shown in FIG. 1a. The reflective optical surface 40 has the support substrate 22 and optical layer 24 with precision optical characteristics 26, and additionally includes a reflective layer 42. In the reflective screen of FIG. 1a, the support substrate 22 can be selected to have a modulus of elasticity within the range from 300,000 p.s.i. to 600,000 p.s.i.; and a thickness 44 from 0.0015 to 0.018 inch. The reflective layer 42 with a thickness dimension of less than 0.0005 inch can be formed of metal such as a thin reflective foil, for example, pack-rolled aluminum foil with an exposed matte surface, a deposited metal layer or by using other methods and known techniques. The reflective layer 42 using the thin pack-rolled reflective foil with a matte surface has particular advantages in that the matte surface has microscopic ridges causing dispersion that can be used to control specularity with a gain ratio of 2:1. An example of a reflective layer 42 formed from a thin aluminum foil with a matte surface for use in the projection screen is illustrated in U.S. Pat. No. 3,408,132 to Chandler et al. The matte surface has a random pattern of elongated irregularities forming an accurate surface pattern. The reflective layer 42 can be secured to the support substrate 22 using known techniques such as by adhesives. The thin reflective layer 42 will assume the mechanical characteristics of the support substrate 22. The optical layer 24 with a thickness dimension of greater than 0.002 inch can be secured to the now one layer comprised of the reflective layer 42 and support substrate 22 using extrusion casting or other techniques known in the art. The matte surface as well as other known techniques are used to improve the performance of the projection screen. However, as used in the present invention, the non-rigid support substrate 22 forms a controllable surface allowing for the use of precision optical characteristics that were once reserved for rigid support substrates.

Referring now to FIGS. 2-4, solar films using the support substrate 22 of the present invention will now be described. A solar film can be made using the same techniques and construction described for the optical surfaces 20, 30 and 40. In a preferred construction, the solar film forms an optical surface with a total modulus of elasticity of 500,000 p.s.i. to provide sufficient support, durability, strength and other beneficial features for indoor and outdoor applications. Furthermore, the thickness of the solar film can be between 0.003 and 0.018 inch which can include the support substrate 22 and subsequent layers such as the optical layer 24 and any reflective layers 42. The solar film can have a support substrate 22 and optical layer 24 of a combined thickness between 0.0015 and 0.006 inch. The optical layer 24 can be formed to control the transmissive value of incident light energy by absorbing energy and radiating heat such as by using a dye dispersed therein, differential gain layer or partially reflective layer. The solar film is not limited to one support substrate 22 and additional support substrates 24a can be used to provide a seal for the optical layers 24 and thus to provide protection from external contaminates. As shown in FIG. 1c, the relocatable solar film could be relocated at will, for example, put on the outside or inside of the window or selectively moved to different areas of high sunlight. Alternatively, the relocatable solar film could be rolled up such as on a cloudy day or lowered for increased privacy.

The support substrate 22 can also have a precision optical characteristic 26, for example, a specific transmissive value can be used. The transmissive value of the support substrate 22 allows more or less light energy to pass through optical surface. The transmission value can be controlled by using a dye introduced into the support substrate 22 at the time of manufacture or by other methods as are known in the art. The reflective layer 42 can also vary the transmission value and can be made partially reflective using reflective particles deposited on or dispersed in the support substrate 22, such as according to the principle of a half-silvered mirror. A partially-reflective reflective layer 24 can provide the appropriate optical characteristic for various applications. The reflective layer 42 can be protected by an additional support substrate 22 as well, or by using an optical layer 24 wherein the thickness and modulus of elasticity falls within the above-identified range.

Referring now to FIGS. 5a through 5g, various patterns for the optical layer 24 showing patterns with precision optical characteristics 26 can be formed such as with a differential refraction, reflection or dispersion optical patterns. As shown in FIGS. 5a and 5b, a dispersion pattern can be formed in the optical layer 24. The dispersion pattern can reduce problems of hot spotting and redistribute incident light energy in either refractive or reflective projection screens or solar films. As applied in solar films, the redistribution of light energy such as ultra-violet or infrared light energy can change the amplitude, magnitude or direction of incident light energy. Other pattern with precision optical characteristics 26 designs are illustrated in FIGS. 5c, 5d, 5e, 5f and 5g. The optical layer 24 can have additional patterns possible for a desired application as are known in the art.

As illustrated in FIGS. 6a, 6b, 6c and 6d, various plan views of the layers 24 for the optical surfaces 20, 30 and 40 are shown. The patterns shown in FIGS. 6a and 6b can be used to redirect incident light energy such as to control an audience viewing zone or to uniformly redistribute sunlight incident on a solar film. The patterns shown in FIGS. 6a and 6b can also be used to redirect incident light energy such as by a fresnel lens. The patterns shown in FIGS. 6c and 6d can be used for various applications to redistribute light according to a precision optical characteristic 26 such as a diffraction grating.

Referring to FIG. 7, a method of forming the optical surfaces 20, 30 or 40 is provided to neutralize inherent edge-curls and other surface non-uniformities. Typically, manufacturers of high elasticity modulus polymeric films for forming the support substrate 22 deliver these films on master rolls in various dimensions and thickness. When the master roll is unrolled and cut to a desired size, these high elasticity modulus films have an inherent manufactured tendency to curl toward an inward surface of the master roll. One method to eliminate the curl is to halve substrate thickness 60 forming thickness 62 and 64. Each half thickness 62 and 64 forming support substrate 22 are bonded together using a counter-balancing technique where each inward surface is bonded to another inward surface in opposite directions such as, for example, having the inward surface of each half thickness placed face-to-face or back-to-back. By using this process, the optical surface 20, 30 or 40 can have increased usable controllable surface area and achieve flatness while reducing inherent curl.

Obviously, many modifications and variations of the present invention are possible in light of the above teachings. Thus, it is to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described above.