Method for manufacturing a display device

Abstract

Method for manufacturing a display device The invention relates to a method for manufacturing a display device (1), the method comprising the following steps: providing a curved cover plate (10), this cover plate (10) being in particular made of glass or transparent PC, the curvature of this cover plate (10) being obtained in particular beforehand by thermoforming; providing a generally flat display structure (20), this display structure (20) being in particular of the TFT type; providing a retaining member (30) having a curved shape substantially conforming to that of the cover plate (10); placing the generally flat display structure (20) between the cover plate (10) and the retaining member (30);apply pressure to the stack thus formed, to deform the display structure (20) so that it conforms to the shape of the cover plate (10) and the retaining member (30), the application of pressure being carried out in particular while cold; remove the stack leaving the retaining member (30) permanently attached to the display structure (20). Figure for the abbreviation: Figure 1;

Description

Title of the invention: Method for manufacturing a display device

[0001] The present invention relates in particular to a method of manufacturing a display device, in particular intended to be mounted on board a vehicle.

[0002] The vehicle may be of land, sea or air type.

[0003] Currently, display devices, particularly TFT displays, use a curved protective lens / glass covering the TFT structure. When the radius of curvature falls below a certain limit, the liquid crystals of the TFT screen are subjected to stress due to the tension exerted by the screen glass, which is not stable in terms of curvature. This induces what is known as the Mura effect, as explained below.

[0004] The invention aims in particular to overcome this problem.

[0005] The invention thus relates to a method for manufacturing a display device, the method comprising the following steps: - provide a curved cover plate, this cover plate being in particular made of glass or transparent PC, the curvature of this cover plate being obtained in particular beforehand by thermoforming; - provide a globally flat display structure, this display structure being in particular of the TFT type; - provide a retaining element with a curved shape closely following that of the cover plate; - place the display structure generally flat between the cover plate and the retaining device; - apply pressure to the stack thus formed, to deform the display structure so that it conforms to the shape of the cover plate and the retaining device, the application of pressure being carried out in particular when cold; - remove the stack while leaving the retaining device attached to the display structure in place.

[0006] According to one aspect of the invention, the cover plate is first put into a curved shape, preferably by thermoforming, with the addition of heat.

[0007] Thus, in the invention, the cover plate and the retaining member are initially curved in shape, while the display structure is initially generally flat. The shaping of the display structure is thus achieved by undergoing a cold pressure, by being sandwiched between the cover plate and the retaining element.

[0008] As the cover plate is shaped into a curved form by hot thermoforming, the shape of the cover plate is stable.

[0009] On the contrary, the display structure undergoes cold forming, which results in an instability. The display structure is subject to internal stresses due to its curvature. The display structure is not hot formed because this would require a complex and costly process.

[0010] In the absence of the retaining element, internal stresses can impact layers that make up the display structure. In the case where the display structure is of the TFT type with different layers including a liquid crystal layer, some of these layers may, under the effect of internal stresses due to curvature, detach from each other, which generates areas of non-uniformity within the display structure accompanied by undesirable Mura effects.

[0011] It is recalled that the Mura effect is manifested in particular by defects of homogeneity in the display structure of the TFT screen type.

[0012] It has been found, surprisingly, that thanks to the support organ, it is possible to suppress or reduce the Mura effect.

[0013] It has been observed that, thanks to the invention and the presence of the retaining element, it is possible to balance the force exerted by the cover plate on the display structure. This imbalance of stresses on the display structure arises from the fact that the cover plate was deformed stably (while hot) whereas the display structure was deformed while cold. Some of the layers of the display structure tend to return to their flat shape after the pressure that caused the deformation is released.

[0014] In summary, it has been found that the invention makes it possible to preserve the balance of constraints within the display structure, which makes it possible to eliminate or reduce the Mura effect.

[0015] According to one aspect of the invention, the deformation of the display structure is achieved using a press tool configured to press on the stack which rests on a press base.

[0016] According to one aspect of the invention, this deformation is carried out cold, without the addition of heat.

[0017] According to one aspect of the invention, the press tool has a support surface with a shape that follows the curved shape of the cover plate.

[0018] According to one aspect of the invention, an optically transparent adhesive (OCA) is deposited between the display structure and the cover plate.

[0019] According to one aspect of the invention, the optically transparent adhesive (OCA) is deposited between the display structure and the retaining member.

[0020] According to one aspect of the invention, the display structure comprises a base substrate, in particular made of glass, which carries active layers, in particular with electrodes and liquid crystals interacting with the electrodes to enable display.

[0021] According to one aspect of the invention, the display structure is in particular of the TFT type

[0022] According to one aspect of the invention, the cover plate is a plate made of optically transparent material, made of a material capable of being hot-formed.

[0023] According to one aspect of the invention, the display structure comprises, in addition to the base substrate, in particular made of glass, a top plate, in particular made of glass, which is intended to be positioned opposite the cover plate.

[0024] Thus the display structure can have a multilayer structure, with, on one side, the base substrate and, on the other side, the top plate, in particular made of glass.

[0025] When earlier in the description, internal constraints within the display structure are mentioned, it can be said that it is the base substrate and the top plate of the display structure that tend to be separated from each other at the edges due to these internal constraints.

[0026] Indeed, the upper plate of the display structure is glued to the cover plate which is stable in its shape, while the base substrate, in the absence of a retaining element according to the invention, would be subjected to stresses which would cause it to detach from the upper plate.

[0027] Thanks to the retaining element according to the invention, the basic substrate of the display structure remains retained with the curved shape.

[0028] According to one aspect of the invention, the retaining member is presented as an additional part which is an integral part of the display device and is not a part used only at the time of manufacture.

[0029] According to one aspect of the invention, the retaining member has a main face intended to face the display structure.

[0030] According to one aspect of the invention, the main face of the retaining member has a curved shape.

[0031] According to one aspect of the invention, the retaining member has an edge which serves to stiffen the retaining member.

[0032] According to one aspect of the invention, the stiffening edge extends around the entire perimeter of the main face of the retaining member.

[0033] According to one aspect of the invention, the stiffening edge extends in the opposite direction of the display structure.

[0034] According to one aspect of the invention, the stiffening edge is made in one piece with the main face of the retaining member.

[0035] According to one aspect of the invention, the main face of the retaining member is solid. This means that this main face is not perforated.

[0036] In this case, the main face of the retaining member is optically transparent.

[0037] Alternatively, the main face of the retaining member is perforated.

[0038] For example, the openwork retaining element runs along a perimeter band of the display structure, and forms a frame.

[0039] According to one aspect of the invention, the frame formed by the retaining member may be sufficient to keep the display structure stable with respect to the internal stresses caused by the curvature.

[0040] According to one aspect of the invention, the retaining member can be made of a transparent or translucent material, in particular glass or transparent PC (polycarbonate).

[0041] According to one aspect of the invention, the retaining member can be made entirely of optically transparent material.

[0042] According to one aspect of the invention, the retaining member can be produced by injection molding.

[0043] According to one aspect of the invention, the retaining member can form a retaining plate which is in particular similar to the cover plate, being in particular transparent.

[0044] According to one aspect of the invention, the retaining plate and the cover plate may have similar shapes, in particular identical surfaces.

[0045] According to one aspect of the invention, the thickness of the retaining plate can be variable.

[0046] According to one aspect of the invention, the variation in thickness can be chosen according to the radius of curvature taken by the retaining plate.

[0047] According to one aspect of the invention, the thickness of the retaining plate and the thickness of the cover plate can be identical.

[0048] Thus it is possible to distribute the thickness of the retaining plate and that of the cover plate on either side of the display structure.

[0049] According to one aspect of the invention, the display device thus comprises a retaining plate and a cover plate between which is fixed the display structure which has taken a curved shape.

[0050] According to one aspect of the invention, the retaining plate, like the cover plate, has a curved shape obtained beforehand by hot forming.

[0051] The presence of the retaining plate in addition to the cover plate makes it possible in particular to improve compliance with regard to energy absorption in the event of an impact.

[0052] In the case where the retaining member has a stiffening edge, this stiffening edge can be made of optically opaque material while the main face is made of optically transparent material.

[0053] According to one aspect of the invention, the retaining member is configured to encapsulate elements of a backlighting unit.

[0054] According to one aspect of the invention, the backlighting module comprises a housing in which are placed a light source support, in particular of the LED type, a light guide above the light source support, and above this light guide, a stack of optical sheets.

[0055] According to one aspect of the invention, the retaining member is configured to close the housing of the backlight unit.

[0056] According to one aspect of the invention, the display device is placed on the housing of the backlight unit.

[0057] According to one aspect of the invention, the retaining element of the lighting device closes this housing of the backlighting unit.

[0058] According to one aspect of the invention, the retaining element of the lighting device thus serves as a housing cover for the module of the backlighting unit, preferably being made of optically transparent or translucent material.

[0059] The invention also relates to a display device obtained by the above process.

[0060] The invention also relates to a display device comprising successively, in a stack: - a curved cover plate, this cover plate being in particular made of glass or transparent PC; - a curved display structure, this display structure being in particular of the TFT type, the curved shape of the display structure resulting from cold forming; - a retaining element having a curved shape closely following that of the cover plate, and configured to retain display structure with the curved shape obtained from cold forming.

[0061] According to one aspect of the invention, the cover plate is curved at least in a peripheral area of ​​the cover plate, namely an area which is adjacent to the periphery of the cover plate.

[0062] According to one aspect of the invention, the cover plate is curved over its entire surface.

[0063] In this case, the cover plate does not include any flat parcel.

[0064] Other features and advantages of the invention will become more apparent upon reading the following description, given by way of illustrative and non-limiting example, and the accompanying drawing on which:

[0065] - Fig. 1 illustrates, schematically and partially, steps in a process of... construction according to an example of an embodiment of the invention;

[0066] - Figure 2 illustrates, schematically and partially, the display device obtained by the method of [Fig.1], in exploded view;

[0067] - Figure 3 illustrates, schematically and partially, steps in a manufacturing process brication according to another example of an embodiment of the invention;

[0068] - Figure 4 illustrates, schematically and partially, in cross-section, a device display according to another example of an embodiment of the invention;

[0069] - Figure 5 illustrates, schematically and partially, in cross-section, an organ of maintenance of a display device according to an example of an embodiment of the invention.

[0070] Figure 1 shows steps in a manufacturing process for a display device 1 according to an example of an embodiment of the invention, comprising the following steps: - provide a curved cover plate 10, this cover plate 10 being made of glass or transparent PC, the curvature of this cover plate being obtained beforehand by thermoforming; - provide a globally flat display structure 20, this display structure being of the TFT type (for "Thin-film transistor" in English or Thin-film transistor); - provide a retaining element 30 having a curved shape closely following that of the cover plate 10; - place the display structure 20 generally flat between the cover plate 10 and the retaining element 30 (step IA); - apply pressure to the stack 50 thus formed, to deform the display structure 20 so that it conforms to the shape of the cover plate 10 and the retaining member 30, the application of pressure being carried out cold (step IB); - remove the stack 50 leaving the retaining element 30 fixed to the display structure 20 (step IC).

[0071] The cover plate 10 is previously shaped into a curved form by thermoforming, with the addition of heat.

[0072] Thus, in the invention, the cover plate 10 and the retaining member 30 are initially curved, while the display structure 20 is initially generally flat. The shaping of the display structure 20 is thus achieved by subjected to cold pressure, being sandwiched between the cover plate 10 and the retaining member 30.

[0073] As the cover plate 10 is shaped into a curved form by hot thermoforming, the shape of the cover plate 10 is stable.

[0074] On the contrary, the display structure 20 undergoes cold forming, which results in the display structure 20 not being stable. Thus, the display structure 20 is subject to internal stresses due to the curvature it assumes. The display structure 20 is not hot formed because this would require a complex and costly process.

[0075] In the absence of the retaining element 30, internal stresses can have an impact on layers that make up the display structure 20. In the case where the display structure is of the TFT type with different layers including a liquid crystal layer, some of these layers can, under the effect of internal stresses due to curvature, detach from each other, which generates areas of non-uniformity within the display structure accompanied by undesirable Mura effect.

[0076] It is recalled that the Mura effect is manifested in particular by defects in homogeneity in the display structure of the TFT screen type.

[0077] It has been found, surprisingly, that thanks to the support organ 30, it is possible to suppress or reduce the Mura effect.

[0078] It has been observed that, thanks to the invention and the presence of the retaining element 30, it is possible to balance the force exerted by the cover plate 10 on the display structure. This imbalance of stresses on the display structure 20 arises from the fact that the cover plate 10 was deformed stably (while hot) whereas the display structure was deformed while cold. Some of the layers of the display structure tend to return to their flat shape after the pressure that caused the deformation is released.

[0079] In summary, it has been found that the invention makes it possible to preserve the balance of stresses within the display structure 20, which makes it possible to eliminate or reduce the Mura effect.

[0080] The deformation of the display structure 20 is achieved using a press tool 60 configured to press on the stack which rests on a press base 61.

[0081] This deformation is carried out cold, without the addition of heat.

[0082] The press tool 60 has a bearing surface with a shape that follows the curved shape of the cover plate 10.

[0083] A layer of optically transparent adhesive 25 (in English “Optical Clear Adhesive” or OCA) is deposited between the display structure 20 and the cover plate 10.

[0084] Another layer of optically transparent glue 25 is deposited between the structure display 20 and the holding element 30.

[0085] The cover plate 10 is a plate made of optically transparent material, made of a material capable of being hot-formed.

[0086] The display structure 20 comprises a basic substrate 22, made of glass, which carries active layers, with electrodes and liquid crystals interacting with the electrodes to enable display.

[0087] The display structure 20 comprises, in addition to the base substrate 22, a top plate 24, made of glass, which is intended to come opposite the cover plate 10, as illustrated in [Fig.2].

[0088] Thus the display structure 20 can have a multilayer structure, with, on one side, the base substrate 22 and, on the other side, the top plate 24.

[0089] The retaining member 30 is presented as an additional part which is an integral part of the display device 1 and is not a part used only at the time of manufacture.

[0090] The retaining member 30 has a main face 31 intended to face the display structure 20.

[0091] The main face 31 of the retaining member 30 has a curved shape.

[0092] The retaining member 30 has an edge 32 which serves to stiffen the retaining member 30.

[0093] The stiffening edge 32 extends around the entire perimeter of the main face of the retaining member 30, where the internal stresses of the display structure 20 can be most damaging.

[0094] The stiffening edge 32 extends opposite the display structure 20.

[0095] The stiffening edge 32 is made in one piece with the main face 31 of the holding organ 30.

[0096] The main face 31 of the retaining member 30 is solid. This means that this main face is not perforated.

[0097] In this case, the main face 31 of the retaining member 30 is optically transparent, and the stiffening edge 32 can be optically opaque, as illustrated in [Fig.5].

[0098] Alternatively, the main face 31 of the retaining member 30 is perforated.

[0099] For example, the openwork retaining member 30 runs along a perimeter band of the display structure 20, and forms a frame.

[0100] The frame formed by the retaining member 30 may be sufficient to keep the display structure stable with respect to the internal stresses caused by the curvature.

[0101] The retaining member 30 can be made of a transparent or translucent material, in particular glass or transparent PVC.

[0102] In one variant, the retaining member 30 can be made entirely of optically transparent material.

[0103] The retaining member 30 can be produced by injection molding.

[0104] In the embodiment example of [Fig.3] (which also shows the three steps 3A, 3B and 3C as in the example of [Fig.1]), the retaining member 30 can form a retaining plate 35 which is similar, or even identical, to the cover plate 10, being transparent.

[0105] The retaining plate and the cover plate 10 may have similar shapes, in particular identical surfaces.

[0106] The thickness of the retaining plate 35 can be variable.

[0107] The variation in thickness can be chosen according to the radius of curvature taken by the retaining plate 35.

[0108] The thickness of the retaining plate 35 and the thickness of the cover plate 10 can be identical.

[0109] Thus it is possible to distribute the thickness of the retaining plate 35 and that of the cover plate 10 on either side of the display structure.

[0110] The display device thus comprises a retaining plate 35 and a cover plate 10 between which is fixed the display structure 20 which has taken a curved shape.

[0111] The retaining plate 35, as well as the cover plate 10, have a curved shape obtained previously by hot forming.

[0112] In the embodiment example of [Fig.4], the retaining member 30 is configured to encapsulate elements of a backlight unit 70.

[0113] The backlight module 70 comprises a housing 71 in which are placed an electronic board 72 with LED light sources 73, a light guide 74 above the electronic board 72, and above this light guide, a stack of optical sheets 75.

[0114] The retaining member 30 is configured to close the housing 71 of the backlight unit 70.

[0115] The display device 1 is placed on the housing 71 of the backlight unit.

[0116] The retaining member 30 of the lighting device closes this housing 71 of the backlighting unit 70.

[0117] The retaining member 30 of the lighting device thus serves as a housing cover 71 of the backlighting unit module, being made of optically transparent or translucent material.

[0118] In general, the invention makes it possible to obtain a display device comprising successively, in a stack: - a curved cover plate 10, this cover plate 10 being notably glass-based or transparent PC-based; - a curved display structure 20, this display structure 20 being in particular of the TFT type, the curved shape of the display structure 20 resulting from a cold forming; - a retaining element 30 having a curved shape closely following that of the cover plate 10, and configured to retain display structure 20 with the curved shape obtained from cold forming.

[0119] The cover plate 10 is curved at least in a peripheral area of ​​the cover plate 10, namely an area which is adjacent to the periphery of the cover plate 10.

[0120] The cover plate 10 is preferably curved over its entire surface.

[0121] In this case, the cover plate 10 does not include any flat parcel.

[0122] The curvature of the cover plate 10 can be chosen according to requirements, particularly in terms of shape.

[0123] The retaining element can be made by injection molding of one or two materials in the same mold. In the case of two materials, the molding operation is designated as a 2K molding. The materials can be different.

Claims

Demands

1. Method for manufacturing a display device (1), the method comprising the following steps: - providing a curved cover plate (10), this cover plate (10) being in particular made of glass or transparent PC, the curvature of this cover plate (10) being obtained in particular beforehand by thermoforming; - providing a generally flat display structure (20), this display structure (20) being in particular of the TFT type; - providing a retaining member (30) having a curved shape substantially conforming to that of the cover plate (10); - placing the generally flat display structure (20) between the cover plate (10) and the retaining member (30);- apply pressure to the stack thus formed, to deform the display structure (20) so that it conforms to the shape of the cover plate (10) and the retaining member (30), the application of pressure being carried out in particular when cold; - remove the stack leaving the retaining member (30) permanently attached to the display structure (20).

2. Method according to the preceding claim, wherein the cover plate (10) is first curved, preferably by thermoforming, with the addition of heat.

3. A method according to any one of the preceding claims, wherein the deformation of the display structure (20) is carried out using a press tool configured to press on the stack which rests on a press base, this deformation being preferably carried out cold, without the addition of heat.

4. A method according to any one of the preceding claims, wherein an optically transparent adhesive (OCA) is deposited between the display structure (20) and the cover plate (10), in particular an optically transparent adhesive (OCA) is deposited between the display structure (20) and the retaining member (30).

5. A method according to any one of the preceding claims, wherein the display structure (20) comprises a base substrate, in particular made of glass, which carries active layers, in particular with electrodes and liquid crystals interacting with the electrodes to enable display.

6. A method according to any one of the preceding claims, wherein the cover plate (10) is a plate made of optically transparent material, made of a material capable of being hot-formed.

7. A method according to any one of the preceding claims, wherein the display structure (20) comprises, in addition to a base substrate in particular made of glass, a top plate in particular made of glass, which is intended to be positioned opposite the cover plate (10).

8. A method according to any one of the preceding claims, wherein the retaining member (30) is an additional part that forms an integral part of the display device.

9. A method according to any one of the preceding claims, wherein the retaining member (30) has a main face intended to face the display structure, and the main face of the retaining member (30) has a curved shape.

10. A method according to any one of the preceding claims, wherein the retaining member (30) has an edge which serves as stiffening to the retaining member (30), and the stiffening edge extends in particular over the entire perimeter of the main face of the retaining member (30).

11. A method according to any one of the preceding claims, wherein the retaining member (30) is configured to encapsulate elements of a backlighting unit, and the backlighting module comprises a housing in which are placed a support with light sources in particular of the LED type, a light guide above the support with light sources, and above this light guide, a stack of optical sheets.

12. A display device (1) comprising successively, in a stack: - a curved cover plate (10), this cover plate (10) being in particular made of glass or transparent PC; - a curved display structure (20), this display structure (20) being in particular of the TFT type, the shape curve of the display structure (20) resulting from cold forming; a retaining member (30) having a curved shape substantially conforming to that of the cover plate (10), and configured to retain display structure (20) with the curved shape obtained from cold forming.

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