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 when 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 of manufacturing a display device

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

[0002] The vehicle can be land, sea or air.

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

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

[0005] The invention thus relates to a method of 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 in particular obtained beforehand by thermoforming; - provide a generally flat display structure, this display structure being in particular of the TFT type; - provide a holding member having a curved shape substantially matching that of the cover plate; - place the generally flat display structure between the cover plate and the holding member; - applying pressure to the stack thus formed, to deform the display structure so that it matches the shape of the cover plate and the holding member, the application of the pressure being carried out in particular cold; - remove the stack, leaving the retaining member fixed to the display structure.

[0006] According to one aspect of the invention, the cover plate is previously shaped into a curve, preferably by thermoforming, with the addition of heat.

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

[0008] Since the cover plate is formed into a curved shape by hot thermoforming, the shape of the cover plate is stable.

[0009] On the contrary, the display structure undergoes cold forming with the consequence that the display structure is not stable. Thus, the display structure undergoes internal stresses due to the curvature that the display structure takes. The display structure is not hot formed because this would require a complex and expensive process.

[0010] In the absence of the holding member, the internal stresses can have an impact on 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 can, under the effect of internal stresses due to the curvature, detach from one another, which generates areas of non-uniformity within the display structure accompanied by an undesirable Mura effect.

[0011] It is recalled that the Mura effect manifests itself 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 holding member, it is possible to eliminate or reduce the Mura effect.

[0013] It has been found that, thanks to the invention and the presence of the holding member, it is possible to balance the force exerted by the cover plate on the display structure. This imbalance of stresses on the display structure comes from the fact that the cover plate has been deformed in a stable manner (when hot) while the display structure has been deformed when cold. Some of the layers of the display structure tend to return to the flat shape after releasing the pressure which was used to produce the deformation.

[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 carried out 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 bearing surface with a shape which matches 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 holding 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 the 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, an upper plate, in particular made of glass, which is intended to come opposite the cover plate.

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

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

[0026] In fact, the upper plate of the display structure is glued to the cover plate which is stable in terms of its shape while the base substrate, in the absence of a holding member according to the invention, would be subject to stresses resulting in it becoming detached from the upper plate.

[0027] Thanks to the holding member according to the invention, the base substrate of the display structure remains held with the curved shape.

[0028] According to one aspect of the invention, the holding 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 holding member has a main face intended to come opposite the display structure.

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

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

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

[0033] According to one aspect of the invention, the stiffening edge extends opposite 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 holding member.

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

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

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

[0038] For example, the openwork holding member runs along a peripheral strip of the display structure, and forms a frame.

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

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

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

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

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

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

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

[0046] According to one aspect of the invention, the variation in thickness can be chosen as a function of the radius of curvature taken by the holding plate.

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

[0048] Thus it is possible to distribute the thickness of the holding 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 holding plate and a cover plate between which the display structure which has taken a curved shape is fixed.

[0050] According to one aspect of the invention, the holding 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 impact.

[0052] In the case where the holding 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 holding member is configured to encapsulate elements of a backlight 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 holding 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 holding member of the lighting device closes this housing of the backlighting unit.

[0058] According to one aspect of the invention, the holding member 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 method.

[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 holding member having a curved shape substantially matching that of the cover plate, and configured to hold the 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 zone 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 area.

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

[0064] Other characteristics and advantages of the invention will appear more clearly on reading the following description, given by way of illustrative and non-limiting example, and the appended drawing in which:

[0065] - [Fig.l] illustrates, schematically and partially, steps of a method of fa construction according to an exemplary embodiment of the invention;

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

[0067] - [Fig.3] illustrates, schematically and partially, steps of a method of fa construction according to another exemplary embodiment of the invention;

[0068] - [Fig.4] illustrates, schematically and partially, in section, a device display according to another exemplary embodiment of the invention;

[0069] - [Fig.5] illustrates, schematically and partially, in section, a member of maintaining a display device according to an exemplary embodiment of the invention.

[0070] [Fig. 1] shows steps of a method for manufacturing a display device 1 according to an exemplary embodiment of the invention, comprising the following steps: - providing 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; - providing a generally planar display structure 20, this display structure being of the TFT type (for “Thin-film transistor” in English or Thin-film transistor); - provide a holding member 30 having a curved shape substantially matching that of the cover plate 10; - placing the generally flat display structure 20 between the cover plate 10 and the holding member 30 (step 1A); - applying pressure to the stack 50 thus formed, to deform the display structure 20 so that it matches the shape of the cover plate 10 and the holding member 30, the application of the pressure being carried out cold (step IB); - remove the stack 50 while leaving the holding member 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 holding member 30 are initially curved in shape while the display structure 20 is initially generally flat. The shaping of the display structure 20 is thus done in undergoing cold pressure, being sandwiched between the cover plate 10 and the holding member 30.

[0073] Since the cover plate 10 is formed into a curved shape by hot thermoforming, the shape of the cover plate 10 is stable.

[0074] On the contrary, the display structure 20 undergoes cold forming with the consequence that the display structure 20 is not stable. Thus, the display structure 20 undergoes internal stresses due to the curvature that the display structure takes. The display structure 20 is not hot formed because this would require a complex and expensive process.

[0075] In the absence of the holding member 30, the internal stresses can have an impact on layers which 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 the curvature, detach from one another, which generates zones of non-uniformity within the display structure accompanied by an undesirable Mura effect.

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

[0077] It has been found, surprisingly, that thanks to the holding member 30, it is possible to eliminate or reduce the Mura effect.

[0078] It has been found that, thanks to the invention and the presence of the holding member 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 comes from the fact that the cover plate 10 has been deformed in a stable manner (when hot) while the display structure has been deformed when cold. Some of the layers of the display structure have a tendency to return to the flat shape after releasing the pressure which was used to produce the deformation.

[0079] In summary, it has been found that the invention makes it possible to preserve the balance of constraints 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 carried out 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 matches 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 member 30.

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

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

[0087] The display structure 20 comprises, in addition to the base substrate 22, an upper 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 multi-layer structure, with, on one side, the base substrate 22 and, on the other side, the upper plate 24.

[0089] The holding 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 holding member 30 has a main face 31 intended to come opposite the display structure 20.

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

[0092] The holding member 30 comprises an edge 32 which serves to stiffen the holding member 30.

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

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

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

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

[0099] For example, the openwork holding member 30 runs along a peripheral strip of the display structure 20, and forms a frame.

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

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

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

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

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

[0105] The holding plate and the cover plate 10 may have similar shapes, in particular identical surface areas.

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

[0107] The variation in thickness can be chosen as a function of the radius of curvature taken by the holding plate 35.

[0108] The thickness of the holding plate 35 and the thickness of the cover plate 10 may be identical.

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

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

[0111] The holding plate 35, like the cover plate 10, has a curved shape obtained beforehand by hot forming.

[0112] In the exemplary embodiment of [Fig.4], the holding 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 card 72 with LED type light sources 73, a light guide 74 above the electronic card 72, and above this light guide, a stack of optical sheets 75.

[0114] The holding 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 holding member 30 of the lighting device closes this housing 71 of the backlighting unit 70.

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

[0118] Generally speaking, 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 in particular glass-based or transparent PC-based; - a display structure 20 of curved shape, this display structure 20 being in particular of the TFT type, the curved shape of the display structure 20 resulting from cold forming; - a holding member 30 having a curved shape substantially matching that of the cover plate 10, and configured to hold the display structure 20 with the curved shape obtained from the 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 area.

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

[0122] The curvature of the cover plate 10 can be chosen according to the needs, especially in shape.

[0123] The holding member may be made by injection molding one material or two materials in a single mold. In the case of two materials, the molding operation is referred to as 2K molding. The materials may be different.

Claims

Claims

1. Method for manufacturing a display device (1), the method comprising the following steps: - providing a cover plate (10) of curved shape, this cover plate (10) being in particular based on glass or based on transparent PC, the curvature of this cover plate (10) being in particular obtained beforehand by thermoforming; - providing a display structure (20) which is generally planar, this display structure (20) being in particular of the TFT type; - providing a holding member (30) having a curved shape substantially matching that of the cover plate (10); - placing the display structure (20) which is generally planar between the cover plate (10) and the holding member (30);- applying pressure to the stack thus formed, to deform the display structure (20) so that it matches the shape of the cover plate (10) and the holding member (30), the application of the pressure being carried out in particular cold; - removing the stack while leaving the holding member (30) fixed to the display structure (20).;

2. Method according to the preceding claim, in which the cover plate (10) is previously shaped into a curve, preferably by thermoforming, with the addition of heat.

3. Method according to one of the preceding claims, in which 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 preferably being carried out cold, without the addition of heat.

4. Method according to one of the preceding claims, in which 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 holding member (30).

5. Method according to one of the preceding claims, in which 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 the display.

6. Method according to one of the preceding claims, in which the cover plate (10) is a plate of optically transparent material, made of a material capable of being hot formed.

7. Method according to one of the preceding claims, in which the display structure (20) comprises, in addition to a base substrate, in particular made of glass, an upper plate, in particular made of glass, which is intended to come opposite the cover plate (10).

8. Method according to one of the preceding claims, in which the holding member (30) is presented as an additional part which is an integral part of the display device.

9. Method according to one of the preceding claims, in which the holding member (30) has a main face intended to come opposite the display structure, and the main face of the holding member (30) has a curved shape.

10. Method according to one of the preceding claims, in which the holding member (30) comprises an edge which serves to stiffen the holding member (30), and the stiffening edge extends in particular around the entire periphery of the main face of the holding member (30).

11. Method according to one of the preceding claims, in which the holding 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. Display device (1) comprising successively, in a stack: - a cover plate (10) of curved shape, this cover plate (10) being in particular based on glass or based on transparent PC; - a display structure (20) of curved shape, this display structure (20) being in particular of the TFT type, the shape curve of the display structure (20) resulting from cold forming; a holding member (30) having a curved shape substantially matching that of the cover plate (10), and configured to hold the display structure (20) with the curved shape obtained from the cold forming.

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