GB1602881A

GB1602881A - Reflecting surface manufacturing process

Info

Publication number: GB1602881A
Application number: GB11214/78A
Authority: GB
Original assignee: Schudel C R
Current assignee: Schudel C R
Priority date: 1977-03-21
Filing date: 1978-03-21
Publication date: 1981-11-18
Also published as: FR2384608B3; JPS53118458A; FR2384608A1; DE2805960A1

Description

(54) REFLECTING SURFACE MANUFACTURING PROCESS (71) I, CONRAD R. SCHUDEL, a citizen of Canada, of 6973 Consolidated Way, San Diego, California, United States of America, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to a method of manufacturing a theatre viewing screen having compound curvature and to a reflective surface so formed.

Viewing screens such as that disclosed in U.S. Patent No. 3408132 have been developed which have relatively high gain. Such screens are used in large screen televisions and in small projection theatre devices in which the high gain of the screen is necessary. The reflective element of such screens comprises the dull side of compression rolled aluminium foil. The aluminium foil has irregular grooves in the highly reflective aluminium surface which accounts for the high gain of the screen, and the screen must be curved in both directions, i.e., it must have compound curvature, to properly focus the reflected image and to minimize hot spots or bright spots in the viewed image.

Such screens are generally formed by first clamping compression rolled aluminium foil in a circular hoop-shaped clamp. The clamped foil is then pulled over a tool having a doubly curved forming surface. A hoopshaped clamp must be used in order that the aluminium foil does not tear while it is being stretched and the foil must be in a fully annealed, soft condition to allow proper stretching. While the aluminium is stretched over the tool, a backing is laminated to the stretched aluminium foil to give rigidity to the foil. The bond between the backing and the aluminium foil is then allowed to cure while the foil remains stretched over the tool, which takes approximately 2 to 3 hours. Thereafter, the foil with the backing bonded thereto is removed from the tool and is trimmed from its circular configuration into a rectangular configuration to provide a viewing screen.

High gain viewing screens have more recently been developed in which a metallized film, usually aluminized Mylar (RTM), is used as the reflective element rather than aluminium foil. Such a screen is illustrated in patent specification No. 1580722. This type of screen surface has certain advantages over the compression rolled aluminium foil surface. However, there are difficulties in shaping the metallized film so that it has the desired compound curvature and attaching it to the backing so that a smooth reflective surface is provided having the desired high gain.

Accordingly the present invention provides a method of constructing a theatre viewing screen having compound curvature comprising bonding a reflective element to a backing material having a thermoformable temperature characteristic to form a continuous laminated sheet comprising the blank for the screen forming process, heating the laminated sheet to at least the forming temperature range of the thermoformable backing material, locating the heated laminated sheet proximate a tool having a forming surface corresponding to the desired shape and compound curvature of the screen, shaping the heated laminated sheet by pressing the heated sheet against the forming surface of the tool, and allowing the heated laminated sheet to at least partially cool in contact with the forming surface of the tool to provide a screen having the desired compound curvature.

The present invention provides a method of constructing a viewing screen having compound curvature. In a preferred embodiment, a metallized film is bonded to a thermoformable backing material to form a laminated sheet which includes both the film and the backing material. The laminated sheet is heated to the forming temperature range of the thermoformable backing. The heating sheet is located proximate a tool having a forming surface corresponding to the desired compound curvature of the reflecting surface.

The heated laminated sheet is shaped by pressing the heated sheet against the forming surface of the tool. The sheet is allowed to cool in contact with the forming surface of the tool to provide a reflecting surface having the desired compound curvature.

As described in patent specification No.

1580722, it is possible to form a projection screen surface with the metallized surface of the film as either the front or back surface with reference to the projector. In the present invention, if the reflective surface of the film comprises the front surface, the back surface of the film may be metallized as well. The back surface of the 51m is bonded to the backing material using the adhesive, and if the back surface is metalized, the adherance of the film to the backing material is increased.

The laminated sheet formed from the metallized film and backing material can be shaped using either a convex or a concave forming tool. If a convex tool is used, the laminated sheet is stretched over the tool with the metallized film disposed on the side of the laminated sheet toward the tool. The convex surface of the tool should be cleaned, and a resilient coating may be applied to the tool, to minimize imperfections in the viewing screen formed in this manner. If the tool has a concave forming surface, a pressure differential is applied to the lamiated sheet to press it against the concave surface of the tool with the metallized film disposed on the side of the laminated sheet away from the tool. If this embodiment of the present invention is used, the thickness of the backing material must be relatively uniform so that the compound curvature of the reflective surface of the viewing screen is smooth and even.

The present invention provides an extremely smooth (in a microscopic sense) and even viewing surface in which the high gain properties of the film are distributed equally throughout its entire reflective surface.

The reflective properties of the material are fully retained because it does not have to be heated until soft for forming. The viewing screen can be formed from a laminated sheet whose outer periphery closely matches the dimensions of the periphery of the end product viewing screen, and the viewing screen can be formed without substantial waste of the material used to construct the screen.

Since the metallized film is bonded to the backing before the film, together with the backing, is shaped to the appropriate concurvature, there is no need to wait for the bond between the backing and the metallized film to cure before removing the article from the tool. Using the method of the present invention, the entire forming cycle, including both heating and cooling, typically takes approximately 10 minutes or less if advanced heating and cooling techniques are employed. For a given tool, viewing screens can be constructed at a rate of at least 6 screens per hour. This is in contrast to known methods in which a single tool can only be used to produce a screen every 2 to 3 hours. Thus, the number of screens which can be produced using a given tool are substantially increased using the method of the present invention, correspondingly reducing the cost of constructing the screens.

The invention is further illustrated in the accompanying drawings wherein: Figure 1 is a perspective schematic view of the bonding of the metallized film to the backing material to form a laminated sheet; Figure 2A is a greatly enlarged sectional schematic view taken along lines 2-2 of Figure 1 illustrating one possible construction of the laminated sheet formed as illustrated in Figure 1; Figure 2B is a view similar to that of Figure 2A illustrating an alternate construction of the laminated sheet; Figures 3A and 3B are sequential schematic sectional elevation views of the formation of a viewing screen according to the present invention using a convex tool; Figures 4A and 4B are sequential schematic elevational sectional views of the formation of a viewing screen according to the present invention using a concave tool.

As shown in Figure 1, a laminated sheet 10 is formed by bonding a metallized film 12 to a backing material 14. Film 12 is ordinarily flexible and is typically supplied on a roll 16 as illustrated or in the form of large sheets.

Backing material 14 is typically rigid at room temperatures and is provided in sheet form.

Film 12 is bonded to backing 14 by means of an adhesive which is supplied from a container 18. After laminated sheet 10 has been formed using film 12 and backing material 14, it is cut into rectangular sheets having dimensions somewhat larger than the dimensions of the desired viewing screen.

One form of laminated sheet 10 is illustrated in Figure 2A. Film 12 is typically Mylar (RTM). Film 12 has a metallized surface 20, usually deposited aluminium, on the side of the film disposed toward backing material 14. Metallized surface 20 of film 12 is bonded to backing material 14 with a layer of adhesive 24.

In the laminated sheet 10 shown in Figure 2A, film 12 must be translucent so that light can pass through the film. The light passing through the film is reflected by metallized surface 20 which thereby provides the reflective surface of the screen formed from laminated sheet 10.

An alternative laminated sheet 101, is illustrated in Figure 2B. In Figure 2B, film 121 is metallized both on its exposed surface 25 and its underside surface 26.

Film 121 may again be Mylar (RTM), and metallized surfaces 25, 26 are ordinarily formed by using deposited aluminium, although other suitable metals may be used as well. In laminated sheet 101, the outer metallized surface 25 of the film 121 forms the reflective surface of the viewing screen eventually formed using the laminated sheet.

The inner surface 26 of film 121 may be metallized so that it can be more readily bonded to backing material 141 using adhesive 24l.

Backing material 14 or 141 comprises a material which is generally rigid at room temperature, but is thermoformable, i.e., it can be formed when heated to its forming temperature range and retains its new shape when it later cools. High impact styrene or other thermoformable materials can be used. However, the forming temperature range of the backing material should be sufficiently low so that the metalized surfaces of film 12 are not excessively oxidized when the laminated sheet 10 is heated. The thickness of backing material 14 is much greater than that of film 12, Figs. 2A and 2B being distorted for clarity.

One method by which laminated sheet 10 can be formed into a viewing screen according to the present invention is illustrated in Figs. 3A and 3B in sequence. As illustrated in Fig. 3A, a section of laminated sheet 10, generally rectangular, is positioned using clamping members 28, 29. Sheet 10 is located beneath a heater 30, and is heated so that the temperature of the backing material of sheet 10 is raised to the forming temperature range of that material.

A tool 32 is provided having a convex forming surface 34 having compound curvature corresponding to the shape of the screen to be manufactured. A resilient surface coating 36 may be provided on forming surface 34, or a nonstatic air source 38 used to clean the forming surface of tool 32 as sheet 10 is being heated. While sheet 10 is being heated, it may be disposed directly over the forming surface 34 of tool 32, or the heating may take place at a site remote from the tool.

After laminated sheet 10 is heated, it is stretched over the forming surface 34 of tool 32 as illustrated in Fig. 3B. The metallized film 12 is disposed on the side of lam- inated sheet 10 toward the forming surface of the tool so that the reflective surface of the film 12 takes on the desired compound concave curvature of the viewing screen.

Cleaning of tool 32 is advisable to minimize imperfections in the reflective surface. Laminated sheet 10 is allowed to cool in contact with the forming surface 34 of tool 32 until the backing material is sufficiently set so that handling is possible. Laminated sheet 10 is then removed from tool 32 and trimmed to provide the desired viewing screen.

Typicllly, the heating of laminated sheet 10 takes 3 minutes to raise the temperature of the backing material to its forming temperature range, using the setap of Figs. 3A and 3B. However, the time necessary for the heating step can be significantly reduced by sandwiching the laminated sheet 10 between a pair of heating elements.

Approximately 3 minutes or less are ordinarily required for laminated sheet 10 to cool so that it can be handled after it has been shaped as depicted in Fig. 3B. The time required for this step can be reduced by actively cooling the sheet on the tool. How ever, care must be taken in any cooling operation to ensure that the sheet is cooled uniformly so that drill marks or distortions are not formed in the viewing screen.

A second embodiment of the forming operation of the present invention is illustrated in Figs. 4A and 4B. In Figs. 4A and 4B, a tool 40 is used which has a concave forming surface 42. Forming surface 42 has compound curvature corresponding to the compound curvature of the desired viewing screen. The forming surface 42 of tool 40 is porous and communicates with a vacuum pump 44.

Referring to Fig. 4A, laminated sheet 10 is heated by heater 30 until the backing material reaches its forming temperature range. After sheet 10 is so heated, it is pressed against the forming surface 42 of tool 40 as illustrated in Fig. 4B by creating a pressure difference between the two sides of laminated sheet 10. The desired pressure difference is achieved by operating vacuum pump 44 or by communicating a blower 46 to an enclosed chamber 48 overlying forming surface 42, or by a combination of the two techniques. In any event, laminated sheet 10 is located so that the metallized film 12 on one side thereof is disposed away from forming surface 42 so that the metallized film takes on the desired compound curvature of the viewing screen. The thickness of backing material 14 must be uniform so that the contour of film 12 corresponds with that of the forming surface of the tool.

After the backing material of laminated sheet 10 has set, sheet 10 is removed from tool 40 and trimmed to provide the desired viewing screen having the appropriate compound curvature.

In operation, laminated sheet 10 is formed by bonding a metallized film 12 to a suitable backing material 14 before the film is shaped to any desired contour. Thereafter, the laminated sheet is heated and shaped so that it takes on the desired compound curvature of the viewing screen, using either a convex or a concave forming surface. After the viewing screen has been formed, it is trimmed and may be placed in a frame or suitable support for use as a viewing screen.

Claims

WHAT I CLAIM IS:

1. A method of constructing a theatre viewing screen having compound curvature comprising bonding a reflective element to a backing material having a thermoformable temperature characteristic to form a continuous laminated sheet comprising the blank for the screenforming process, heating the laminated sheet to at least the forming temperature range of the thermoformable backing material, locating the heated laminated sheet proximate a tool having a forming surface corresponding to the desired shape and compound curvature of the screen, shaping the heated laminated sheet by pressing the heated sheet against the forming surface of the tool, and allowing the heated laminated sheet to at least partially cool in contact with the forming surface of the tool to provide a screen having the desired compound curvature.

2. A method according to Claim 1, wherein the locating step includes providing a tool having a convex forming surface, and wherein the shaping step includes stretching the heated laminated sheet over the convex forming surface of the tool with the reflective element disposed on the side of the laminated sheet toward the tool.

3. A method according to Claim 2 additionally comprising the step of cleaning the convex surface of the tool prior to stretching the heated laminated sheet over the forming surface thereof to minimize the formation of imperfections in the relative element.

4. A method according to Claim 1, wherein the locating step includes providing a tool having a concave forming surface corresponding to the desired compound curvature of the reflector, and wherein the shaping step includes drawing a vacuum between the heated laminated sheet and the concave surface of the tool with the reflective element disposed on the side of the laminated sheet away from the tool.

5. A method according to any of Claims 1 to 4, wherein the reflective element comprises a translucent film having a reflective surface formed on one side surface only, and wherein the reflective surface is bonded to the backing material using an adhesive.

6. A method according to any of Claims 1 to 4, wherein the reflective element has two reflective surfaces.

7. A method according to any preceding claim wherein the reflective element has one or both surfaces metallised.

8. A method as claimed in Claim 1 substantially as herein described with reference to the accompanying drawings.

9. A theatre viewing screen whenever constructed by a method as claimed in any of Claims 1 to 8.