Film confined to a frame having relative anisotropic expansion characteristics

• US 6,160,663 A
• Filed: 10/01/1998
• Issued: 12/12/2000
• Est. Priority Date: 10/01/1998
• Status: Expired due to Term

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Harvey, John C., Mills, Michael W., Langlois, Reney R., Peebles, Rosalind E., Merrill, William W., Roska, Fred J.
• Primary Examiner(s): Spyrou, Cassandra
• Assistant Examiner(s): Juba, Jr., John
• Application Number:
  US09/164,841
• Time in Patent Office: 803 Days
• Field of Search: 349/9, 349/58, 349/FOR 125, 40/701, 40/710, 359/500, 359/892, 359/820, 359/896, 359/483, 359/492, 359/494, 359/501, 359/900, 362/19, 353/20
• US Class Current: 359/242
• CPC Class Codes: G02F 1/133308 Support structures for LCD panels, e.g. frames or bezels
• CPC Class Codes: G02F 2201/54 Arrangements for reducing warping-twist
• CPC Class Codes: G02F 2203/60 Temperature independent

Abstract

An assembly comprising a film bounded by a frame, the film having a first thermal expansion coefficient along a first direction parallel to the film and a second thermal expansion coefficient along a second direction parallel to the film, wherein thermal expansion of the film compared to that of the frame is greater along the first direction than along the second direction, and wherein the film has a shape at an ambient reference temperature different from that of the frame, the shape of the film being selected to reduce clearance while allowing sufficient room between the film and the frame for thermal expansion in the first direction for temperatures up to a predetermined elevated reference temperature.

Claims

1. An assembly comprising:

a frame having an internal bounding edge enclosing a substantially rectangular internal area; and

a substantially planar anisotropic film contained within the bounding edge of the frame, the film having a first thermal expansion direction in the plane of the film and a second thermal expansion direction in the plane of the film, the second expansion direction having a lower coefficient of thermal expansion than the first expansion direction,

wherein the film has at least two principal edges joining at a non-right angle, the non-right angle being selected to reduce clearance along the second expansion direction while allowing sufficient room between the film and the frame for thermal expansion in the first expansion direction.

2. The assembly of claim 1, wherein the film forms a parallelogram at the ambient reference temperature.

3. The assembly of claim 1, wherein the film is a light management film.

4. The assembly of claim 3, wherein the film is a uniaxially oriented reflective polarizer.

5. An assembly comprising:

a frame having an internal bounding edge enclosing an internal area, the bounding edge having a shape defined by a set of boundary edge vertices in an x-y plane; and

a film contained within the frame, the film having a first coefficient of thermal expansion positioned along a first expansion axis in the x-y plane and a second coefficient of thermal expansion positioned along a second expansion axis in the x-y plane, the first coefficient of expansion being greater than the second coefficient of expansion,

wherein at an ambient reference temperature the film has a shape different from the shape of the bounding edge of the frame, the film shape being selected to reduce clearance along the second expansion axis and to allow sufficient room for expansion of the film along the first expansion axis for temperatures up to a predetermined elevated reference temperature.

6. The assembly of claim 5, wherein at the ambient reference temperature the film is no larger than a set of maximum film edge vertices in the x-y plane determined according to

7. The assembly of claim 6, wherein the frame further comprises tabs, tab cavities, pins, or slots whose positions are defined by vertices in the x-y plane, the vertices included in the set of boundary edge vertices of the frame.

8. The assembly of claim 5, further comprising a liquid crystal light modulator oriented in the x-y plane aligned with and positioned proximate to the frame.

9. The assembly of claim 5, wherein the film is a uniaxially oriented reflective polarizer.

10. A method for sizing an anisotropic film to fit in a frame comprising the steps of:

(a) determining a set of vertices in an x-y plane defining an area enclosed by a frame;

(b) providing a substantially planar film having a first coefficient of thermal expansion along a first expansion axis in the plane of the film and a second, different, coefficient of thermal expansion along a second, different, expansion axis in the plane of the film;

(c) calculating a set of maximum film edge vertices in the x-y plane given an ambient reference temperature and an elevated reference temperature higher than the ambient reference temperature using the formula

space="preserve" listing-type="equation">R.sub.S.sup.0 =O.sub.S.sup.0 +(Q.sub.S.sup.+ ·

D.sub.S.sup.+).sup.-1 ·

(-O.sub.S.sup.0 -Tr.sub.S.sup.+)+(Q.sub.S.sup.+ ·

D.sub.S.sup.+).sup.-1 ·

D.sub.B.sup.+ 19 R.sub.B.sup.0

wherein R_S⁰ is the set of maximum film edge vertices at the ambient reference temperature, R_B⁰ is the set of boundary edge vertices at the ambient reference temperature, D_S⁺ is an expansion displacement ratio tensor for the film, D_B⁺ is an expansion displacement ratio tensor for the frame, O_S⁰ is a center of rotation of the film, Tr_S⁺ is a solid body translation of O_S⁰, and Q_S⁺ is a solid body rotation tensor for the film; and

(d) cutting the film to have a size and an orientation at the ambient reference temperature selected to reduce clearance, the size being no larger than an area defined by the set of maximum film edge vertices calculated in the calculating step.

11. An assembly comprising

a frame having an internal bounding edge enclosing an internal area;

an anisotropic film having principal edges contained with the internal area of the frame; and

a positioning system comprising at least one positioning element of the film and at least one positioning element of the frame,

each positioning element of the film being at least one of a protrusion from a principal edge of the film or an indention in a principal edge of the film, and

each positioning element of the frame being one of an indention or protrusion at the bounding edge of the frame complementing the position, shape, and size of a corresponding positioning element of the film,

wherein the positioning system fixes at least one point of the film from moving relative to the frame in at least one direction parallel to the film due to thermal expansion of the film for temperatures ranging between a predetermined ambient reference temperature and a predetermined elevated reference temperature.