Process of producing polarizing optical devices and product thereof

United States Patent H9]

Laliberte

Hi] 3,970,362 [45] July 20, 1976

[54] PROCESS OF PRODUCING POLARIZING OPTICAL DEVICES AND PRODUCT THEREOF

[75] Inventor: Norman U. Laliberte, Woodstock, Conn.

[73] Assignee: American Optical Corporation,

Southbridge, Mass.

[22] Filed: July 3, 1974 [21] Appl. No.: 485,398

Related U.S. Application Data

[60] Continuation of Ser. No. 219,847, Jan. 21, 1972, abandoned, which is a division of Ser. No. 35,132, May 6, 1970, Pat. No. 3,674,587.

[52] U.S. CI 350/155; 351/163;

425/110; 428/174; 428/213; 428/412;

428/68

[51] Int. CI.2 G02B 1/08; G02B 1/04;

G02C 7/12

[58] Field of Search 350/155; 264/1, 2, 328,

264/329, 331, 273, 275; 161/1, 5, 183, 408; 156/245; 428/174, 213, 332, 339, 412, 68;

425/110

[56] References Cited

UNITED STATES PATENTS

2,263,249 11/1941 Rogers 350/155

2,320,375 6/1943 Moulton ..350/155

2,387,308 10/1945 Styll 264/2

2,397,231 3/1946 Barnes 264/2

3,171,869 3/1965 Weinberg 264/1

3,208,902 9/1965 Arond et al ..161/183

3,211,811 10/1965 Lanman 264/1

3,560,076 2/1971 Ceppi 350/155

3,673,055 6/1972 Sheld 264/1

3,711,417 1/1973 Schiller 351/163

3,833,289 9/1974 Schuler 264/2

Primary Examiner—Marion E. McCamish
Assistant Examiner—Charles E. Lipsey
Attorney, Agent, or Firm—Kenway & Jenney

[57] ABSTRACT
A laminated optical element is produced by preposi-
tioning a polarizing sheet, which has been coated on
both sides with adhesive compatible with the encasing
material, in a mold so as to accurately space the polar-
izing sheet from the inner mold surfaces, injecting a
monomer of allyl diglycol carbonate into the mold so
as to completely encase the polarizing sheet, and then
curing the laminate. The process includes producing
stress free castings capable of being subjected to sub-
sequent color accepting treatment and various finish-
ing processes. The laminated product provides a fully
encased polarizing sheet with a thin layer of uniform
thickness of the polymer on the front side of the polar-
izing sheet which may be readily finished for optical
devices.

6 Claims, 14 Drawing Figures

1

PROCESS OF PRODUCING POLARIZING OPTICAL DEVICES AND PRODUCT THEREOF This is a continuation of application Ser. No. 219,847, filed Jan. 21, 1972, now abandoned, which is 5 a division of Ser. No. 35,132, filed May 6, 1970 now U.S. Pat. No. 3,674,587.

Various types of laminated polarizing optics have been proposed in the prior art, these, however, were normally formed of three individual sheets, usually with 10 two optical sheets sandwiched over a polarizing sheet. In other instances, only two sheets were used with a polarizing sheet cemented to an optically clear sheet which leaves the polarizing sheet exposed. A very common type of laminate utilized two sheets of glass lami- 15 nated with a polarizing sheet therebetween. The polarizing sheet is a polymer such as oriented polyvinylene in molecularly oriented polyvinyl alcohol or polyvinyl butyral, or oriented polyvinyl alcohol dyed or stained with a solution to form in the sheet an oriented dichroic 20 complex. A difficult problem of adhesion of the polarizing sheet to the covering optical sheets is produced by the attempted lamination. One major problem with previous laminates is separation if the optical device is further processed as by being immersed in a hot solvent 25 for an extended period of time for surface dyeing the optical device to reduce visual transmittance, as is desirable in certain types of sunglasses. The prepared laminated polarizing optics are usually fabricated at a central plant, and are therefore subject to storage and 30 shipment to points of use. The optics may, also, be subjected to further treatment, such as grinding, polishing, mounting, etc., all of which may result in defects in the laminates particularly separation, some fragmentation and sheet split. Storage conditions, also, have 35 caused defects which may include chemical changes and deterioration of the polymer or adhesives.

A principle object of the invention is to provide a process for producing a cast, light polarizer wherein a polarizing sheet is embedded in a polymer. 40

Another object of the invention is to provide an improved light polarizer which comprises a sheet of light polarizing material bonded to and embedded in a cast polymer.

Another object of the invention is to provide an im- 45 proved process for embedding a polarizing sheet in a cast polymer which is cured in situ around said polarizing sheet, and providing good adhesion between the polymer and the polarizing sheet.

An additional object of the invention is to provide a 50 process for accurately locating a polarizing sheet in a cast polymer, with the polarizing sheet in close proximity to the front of a cast optical element, but remaining completely embedded within the casting.

Another object of the invention is to provide a pro- 55 cess and apparatus for accurately positioning a polarizing sheet in a cast polymer, so that the polarizing sheet is accurately positioned in the cast polymer without distortion.

A still further object of the invention is to provide an 60 improved process for producing a polarizing sheet in a cast polymer which includes accurately positioning a polarizing sheet in a mold, filling the mold with a liquid monomer which flows on the front and the back of the polarizing sheet, and then curing the monomer to pro- 65 duce a laminated polarizing optic.

Yet another object of the invention is to provide a polarizing sheet in a cast optical element in which the

monomer embedding a polarizing sheet adheres both to the convex and concave mold surfaces throughout the curing cycle, but releases when the curing cycle is completed.

These and other objects and advantages of the invention may be readily ascertained by referring to the following description and appended illustrations in which:

FIG. 1 is a side elevation, in cross-section, of a mold for forming a polarizing optical element according to the present invention;

FIG. 2 is a top plan of one form of a polarizing sheet arranged for placement in a mold for embedding in a polymer;

FIG. 3 is a side elevational view of the polarizing sheet in FIG. 2;

FIG. 4 is side elevational view of a slightly modified polarizing sheet according to the invention, illustrating a means for adjusting the position of the polarizing sheet in a mold;

FIG. 5 is a side elevation, in cross-section, of a mold showing a modified polarizing sheet holding means;

FIG. 6 is a top plan view of a form of a polarizing sheet for use in the mold of FIG. 5;

FIGS. 7-12 inclusive, illustrate various means for orienting a polarizing sheet in a mold and providing communication between the front and rear of a polarizing sheet mounted in a mold, permitting liquid monomer to completely encase the polarizing sheet and permit the exhaust of air bubbles from both sides of the polarizing sheet;

FIG. 13 is a top plan view of a modified form of polarizing sheet for positioning the same in a mold; and

FIG. 14 is a side elevational view of the polarizing sheet of FIG. 13.

According to the present invention there is provided a polarizing element which consists of a cast lens element having embedded therein a polarizing sheet positioned near the front of the lens and coated on the front of the sheet with a uniform thickness of the resultant polymer. The polarizing sheet is initially coated with a substance which provides good adhesion between the resultant case polymer and the polarizing sheet. In a preferred form, a polymer called CR-39 formed from a liquid monomer (diethylene glycol bis (allyl carbonate)) or allyl diglycol carbonate, is cast around a polarizing sheet which has been coated with an adhesive, preferably polyvinyl butyral or other composition which provides good adhesion between the polarizing sheet and the resultant polymer. The polarizing sheet must be positioned near the front of the resultant cast polymer, but the polarizing sheet must be covered by at least a film of the polymer which prevents chemical attack or physical abuse of the polarizing sheet. The positioning of the sheet in the laminate must, however, be accurately controlled since if the polarizing sheet is not close to the front surface of the polymer, a problem develops which destroys or partly destroys the polarizing effect of the sheet. This is because the polymer, under stress, becomes birefringent, and if sufficient material thickness is in front of the polarizing sheet the axis of the polarization is rotated. The extent to which it is rotated depends on the thickness of the polymer and the amount of stress.

Another problem overcome by the present process is to hold the polarizing sheet or film so that it is accurately held but not distorted. Since the polarizing sheet must cover the major part of the lens, the polarizing