METHOD OF FABRICATING A LIQUID CRYSTAL DISPLAY DEVICE AND A LIQUID CRYSTAL DISPLAY DEVICE
20220197084 · 2022-06-23
Assignee
Inventors
Cpc classification
International classification
G02F1/1335
PHYSICS
Abstract
A method of fabricating a liquid crystal display device including a reflective or transflective liquid crystal cell whose liquid crystal molecules are aligned in a planar or vertical manner, this liquid crystal cell being formed of a transparent front substrate located on the side of an observer, and a rear substrate, also transparent, which extends beneath the front substrate, parallel to and at a distance from the latter, these two front and rear substrates being joined to each other with a sealing frame which defines a sealed enclosure in which a liquid crystal composition is confined, the front and rear substrates being coated on their opposite faces with electrically conductive transparent electrodes and counter-electrodes, the optical properties of the liquid crystal composition being modified by application of an electric field at the point of intersection between an electrode and a corresponding counter-electrode.
Claims
1. A method of fabricating a liquid crystal display device comprising a reflective or transflective liquid crystal cell whose liquid crystal molecules are aligned in a planar or vertical manner, said liquid crystal cell being formed of a transparent front substrate located on the side of an observer, and a rear substrate, also transparent, which extends beneath the front substrate, parallel to and at a distance from the latter, these two front and rear substrates being joined to each other with a sealing frame which defines a sealed enclosure in which a liquid crystal composition is confined, the front and rear substrates being coated on their opposite faces with electrically conductive transparent electrodes and counter-electrodes, the optical properties of the liquid crystal composition being modified by application of an electric field at the point of intersection between an electrode and a corresponding counter-electrode, the liquid crystal display device being provided with a reflective polarizing film arranged to absorb a first component of light which enters the liquid crystal cell through the front substrate, and to reflect a second component of light polarized in a direction orthogonal to that of the first component, the method including the step which consists in embossing the reflective polarizing film to impart thereto a decorative and/or functional shape visible to the observer through the front substrate of the liquid crystal cell, and then securing this reflective polarizing film to an underside of the rear substrate.
2. The fabrication method according to claim 1, wherein the reflective polarizing film is embossed by being pressed against a mould having relief shapes which correspond to the shapes which it is desired to imprint on said reflective polarizing film.
3. The fabrication method according to claim 2, wherein the reflective polarizing film is pressed against the relief mould by creating an air vacuum.
4. The fabrication method according to claim 2, wherein, during the time that the reflective polarizing film is pressed against the relief mould, said reflective polarizing film is heated.
5. The fabrication method according to claim 3, wherein, during the time that the reflective polarizing film is pressed against the relief mould, said reflective polarizing film is heated.
6. The fabrication method according to claim 1, wherein the reflective polarizing film is embossed by insert injection moulding.
7. The fabrication method according to claim 2, wherein once the reflective polarizing film is embossed, there are successively deposited on an upper face of the reflective polarizing film a transparent levelling layer and an adhesive layer by means of with which the reflective polarizing film is secured to the liquid crystal cell.
8. The fabrication method according to claim 3, wherein once the reflective polarizing film is embossed, there are successively deposited on an upper face of the reflective polarizing film a transparent levelling layer and an adhesive layer with which the reflective polarizing film is secured to the liquid crystal cell.
9. The fabrication method according to claim 4, wherein once the reflective polarizing film is embossed, there are successively deposited on an upper face of the reflective polarizing film a transparent levelling layer and an adhesive layer with which the reflective polarizing film is secured to the liquid crystal cell.
10. The fabrication method according to claim 5, wherein once the reflective polarizing film is embossed, there are successively deposited on an upper face of the reflective polarizing film a transparent levelling layer and an adhesive layer with which the reflective polarizing film is secured to the liquid crystal cell.
11. The fabrication method according to claim 7, wherein immediately after the reflective polarizing film is embossed and the transparent levelling layer is deposited, the liquid crystal cell is applied to the transparent levelling layer and the transparent levelling layer is solidified.
12. The fabrication method according to claim 7, wherein the adhesive layer is formed of an optically transparent adhesive also known as Optically Clear Adhesive or ‘OCA’ which takes the form of a pressure sensitive film which is laminated to the transparent levelling layer or which is dispensed as a layer of liquid adhesive on said transparent levelling layer.
13. The fabrication method according to claim 12, wherein the optically clear adhesive is partially diffusive.
14. The fabrication method according to claim 7, wherein a transparent levelling layer is deposited on the back of the reflective polarizing film.
15. The fabrication method according to claim 7, wherein the transparent levelling layer deposited on the upper face of the reflective polarizing film and, where appropriate, the transparent levelling layer deposited on the back of the reflective polarizing film, are obtained with a photopolymerizable resin.
16. The fabrication method according to claim 15, wherein the transparent levelling layer deposited on the upper face of the reflective polarizing film and, where appropriate, the transparent levelling layer deposited on the back of the reflective polarizing film are polymerized by ultraviolet radiation.
17. The fabrication method according to claim 1, wherein, before being embossed, an upper face of the reflective polarizing film is provided with a diffusion layer in order to create an at least partially diffuse reflection.
18. The fabrication method according to claim 1, wherein the reflective polarizing film comprises a reflective polarizer combined with an at least partially absorbent background layer arranged on the back of the reflective polarizer.
19. The fabrication method according to claim 18, wherein the at least partially absorbent background layer is black or coloured.
20. The fabrication method according to claim 19, wherein the black or coloured background layer is an ink layer or a laminated film applied to the back of the reflective polarizer, either before the shaping of said reflective polarizer, so that said black or coloured background layer is shaped at the same time as the reflective polarizer, or after the shaping of the reflective polarizer.
21. The fabrication method according to claim 18, wherein, when the background layer is partially absorbent, a backlight device is arranged underneath said background layer.
22. The fabrication method according to claim 19, wherein, when the background layer is partially absorbent, a backlight device is arranged underneath said background layer.
23. The fabrication method according to claim 20, wherein, when the background layer is partially absorbent, a backlight device is arranged underneath said background layer.
24. The fabrication method according to claim 1, wherein the reflective polarizing film comprises a reflective polarizer combined with an absorbent polarizer which is bonded to the back of the reflective polarizer, the assembly of the two reflective and absorbent polarizers being embossed simultaneously.
25. The fabrication method according to claim 1, wherein the reflective polarizing film comprises an absorbent polarizer combined with an at least partially reflective reflector arranged underneath the absorbent polarizer.
26. The fabrication method according to claim 24, wherein the reflector is metallic.
27. The fabrication method according to claim 24, wherein, when the reflector is partially reflective, a backlight device is arranged underneath the reflective polarizing film.
28. The fabrication method according to claim 25, wherein, when the reflector is partially reflective, a backlight device is arranged underneath the reflective polarizing film.
29. A liquid crystal display device comprising a reflective or transflective liquid crystal cell whose liquid crystal molecules are aligned in a planar or vertical manner, said liquid crystal cell being formed of a transparent front substrate located on the side of an observer, and a rear substrate, also transparent, which extends beneath the front substrate, parallel to and at a distance from the latter, said two front and rear substrates being joined to each other with a sealing frame which defines a sealed enclosure wherein a liquid crystal composition is confined, the front and rear substrates being coated on their opposite faces with electrically conductive transparent electrodes and counter-electrodes, the optical properties of the liquid crystal composition being modified by application of an electric field at the point of intersection between an electrode and a corresponding counter-electrode, the liquid crystal display device being provided with a reflective polarizing film to absorb a first component of light which enters the liquid crystal cell through the front substrate, and to reflect a second component of light polarized in a direction orthogonal to that of the first component, the reflective polarizing film having decorative and/or functional relief portions visible to an observer through the front substrate of the liquid crystal cell, the reflective polarizing film being secured to an underside of the rear substrate.
30. The liquid crystal display device according to claim 29, wherein the reflective polarizing film comprises a reflective polarizer combined with an at least partially absorbent background layer arranged on the back of the reflective polarizer.
31. The liquid crystal display device according to claim 29, wherein the at least partially absorbent background layer is black or coloured.
32. The liquid crystal display device according to claim 30, wherein the black or coloured background layer is an ink layer or a laminated film applied to the back of the reflective polarizer.
33. The liquid crystal display device according to claim 29, wherein the reflective polarizing film comprises a reflective polarizer combined with an absorbent polarizer which is bonded to the back of the reflective polarizer, the assembly of the two reflective and absorbent polarizers being embossed.
34. The liquid crystal display device according to claim 29, wherein the reflective polarizing film comprises an absorbent polarizer combined with an at least partially reflective reflector arranged underneath the absorbent polarizer.
35. A display device according to claim 33, wherein the reflector is metallic.
36. The display device according to claim 33, wherein, when the reflector is partially reflective, a backlight device is arranged underneath said reflector.
37. The display device according to claim 34, wherein, when the reflector is partially reflective, a backlight device is arranged underneath said reflector.
38. A timepiece comprising a display device according to claim 29.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0050] Other features and advantages of the present invention will appear more clearly from the following detailed description of an implementation mode of the method according to the invention, this example being given purely by way of non-limiting illustration with reference to the annexed drawing, in which:
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DETAILED DESCRIPTION OF THE INVENTION
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[0066] Liquid crystal cell 2 illustrated in
[0067] Reflective polarizer 24 is bonded to underside 22 of rear substrate 8 by means of an adhesive layer 25 formed of an optically transparent adhesive also called Optically Clear Adhesive or ‘OCA’. Likewise, background layer 26 is bonded underneath reflective polarizer 24 by means of an adhesive layer 27. Finally, liquid crystal cell 2 also comprises an absorbent polarizer 29 bonded to upper face 31 of front substrate 4 by means of an adhesive layer 33.
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[0069] Like the liquid crystal cell 2 described with reference to
[0070] The following description will be made with reference to a liquid crystal cell provided with a reflective polarizing film 18 comprising a reflective polarizer 24 combined with an at least partially absorbent black or coloured background layer 26. It goes without saying that this example is given purely by way of illustration and that the same method can be applied to a liquid crystal cell provided with a reflective polarizing film 34 which is composed of an absorbent polarizer 36 and an at least partially reflective reflector 38.
[0071] It is sought to imprint on reflective polarizing film 18 relief shapes which will be visible to the naked eye of observer 6 when said observer looks at useful display surface 40 of liquid crystal cell 2. Consequently, when liquid crystal cell 2 is mounted, for example, in a wristwatch, reflective polarizing film 18 can be embossed to give it a texture imitating the look of conventional watch dials: ‘Clous de Paris’, ‘Côtes de Genève’, woven effect, sun-brushed, engine-turned or ‘guillochage’ dials, etc. It is also possible to imprint reflective polarizing film 18 with figurative or technical shapes such as plant patterns, or patterns inspired by cameos, coin faces, sculptures or even bas-reliefs.
[0072] To achieve this result, reflective polarizer 24 is embossed by pressing it against a mould having relief shapes which correspond to the shapes which it is desired to imprint on reflective polarizer 24. Preferably, reflective polarizer 24 is pressed against the relief mould by creating an air vacuum and, even more preferably, reflective polarizer 24 is heated, for example by radiation, during the time that it is pressed against the relief mould. Consequently, reflective polarizer 24 faithfully conforms to even the smallest relief details of the mould and sets in this position on cooling. After cooling, a transparent levelling layer 42 (
[0073] Black or coloured background layer 26 is an ink layer or a laminated film applied to back 46 of reflective polarizer 24, either before the shaping of reflective polarizer 24, so that black or coloured background layer 26 is shaped at the same time as reflective polarizer 24, or after the shaping of reflective polarizer 24.
[0074] It is therefore understood that it is possible either first to shape reflective polarizer 24 and then coat it with black or coloured background layer 26, or immediately to shape reflective polarizing film 18 formed of a reflective polarizer 24 and its black or coloured background layer 26. For ease of reading and comprehension, it will be assumed in the following description that we are dealing with a complete reflective polarizing film 18.
[0075] According to a particular embodiment, complete reflective polarizing film 18 is embossed by being pressed against the relief mould by air vacuum, without applying heat. A transparent levelling layer 42, formed of a photopolymerizable adhesive, for example sensitive to ultraviolet radiation, is then deposited in the hollows of reflective polarizing film 18. Before or after polymerization of transparent levelling layer 42, optically clear adhesive layer 44 is deposited on transparent levelling layer 42.
[0076] According to a particular embodiment illustrated in
[0077] According to a variant that is not represented in the drawing, reflective polarizing film 18 is embossed by a method known as Insert-Injection Moulding. This method consists in arranging reflective polarizing film 18 between a mould having relief shapes that correspond to the shapes desired to be imprinted on reflective polarizer 24 and a flat counter-mould. A transparent material, such as an epoxy material, a thermoplastic polymer or a silicone material is then injected between the counter-mould and reflective polarizing film 18. This transparent material will form the transparent levelling layer when the mould is removed. Heated directly or by the injected transparent material, reflective polarizing film 18 is forced to conform to the contours of the mould under the effect of the injection pressure. An adhesive layer can be inserted between the counter-mould and the transparent material, or be applied to the flat face of the transparent levelling material once the mould is removed.
[0078] In order for the information displayed by liquid crystal cell 2 in the form of alphabetic or numerical characters or icons to stand out on a homogeneous diffusing background layer, it is possible to use at least partially diffusive optically clear adhesive. It is also possible, before embossing reflective polarizing film 18, to provide upper face 48 of the latter with a diffusion layer 50 in order to create an at least partially diffuse reflection (
[0079] Likewise, after the embossing of reflective polarizing film 18 comprising a reflective polarizer 24 combined with a black or coloured background layer 26 and deposition of transparent levelling layer 42 in the hollows of reflective polarizing film 18, reflective polarizing film 18 can be fixed to underside 22 of rear substrate 8 of liquid crystal cell 2 by means of an optically diffusive adhesive layer 52 (
[0080] As seen in
[0081] Likewise, as shown in
[0082] The following part of the description referring to
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[0084] It goes without saying that the present invention is not limited to the embodiments of a reflective or transflective liquid crystal display device that have just been described and that various modifications and simple variants can be envisaged by those skilled in the art without departing from the scope of the invention defined by the annexed claims. It will be recalled in particular that a ‘reflective polarizer’ means a polarizer that reflects one direction of polarization of light and transmits the orthogonal direction of polarization of light. Likewise, an absorbent polarizer means a polarizer which absorbs one component of light and which transmits the other component of light which is orthogonal to the component of absorbed light. It will also be noted that the present invention applies to reflective or transmissive liquid crystal cells whose liquid crystal molecules are aligned in a planar manner, i.e. with their major axis extending parallel to the liquid crystal cell substrates, or whose liquid crystal molecules are vertically aligned, i.e. with their major axis extending perpendicularly to the liquid crystal cell substrates. Examples of such liquid crystal cells include twisted nematic, super twisted nematic, guest host or vertically aligned or electrically controlled birefringence liquid crystal cells.
NOMENCLATURE
[0085] 1. Liquid crystal display device [0086] 2. Liquid crystal cell [0087] 4. Front substrate [0088] 6. Observer [0089] 8. Rear substrate [0090] 10. Sealing frame [0091] 12. Sealed enclosure [0092] 14. Electrodes [0093] 16. Counter-electrodes [0094] 18. Reflective polarizing film [0095] 20. Light [0096] 22. Underside [0097] 24. Reflective polarizer [0098] 25. Adhesive layer [0099] 26. Background layer [0100] 27. Adhesive layer [0101] 28. Backlight device [0102] 29. Absorbent polarizer [0103] 30. Liquid crystal display device [0104] 31. Upper face [0105] 32. Liquid crystal cell [0106] 33. Adhesive layer [0107] 34. Reflective polarizing film [0108] 36. Absorbent polarizer [0109] 38. Reflector [0110] 40. Useful display surface [0111] 42. Transparent levelling layer [0112] 44. Adhesive layer [0113] 46. Back [0114] 48. Upper face [0115] 50. Diffusion layer [0116] 52. Adhesive layer [0117] 54. Absorbent polarizer [0118] 56. Transparent levelling layer [0119] 58. Absorbent polarizer [0120] 60. Wristwatch [0121] 62. Figurative image [0122] 64. Useful information