Method for manufacturing display device

Abstract

The invention relates to a method for producing a display device (1), comprising the following steps:-providing a cover plate (10) in a curved shape, in particular made of glass or of transparent PC, the curvature of which is obtained in advance, in particular by thermoforming; -providing a generally planar display structure (20), in particular of the TFT type; providing a retaining member (30) having a curved shape substantially matching the curved shape of the cover plate (10); -positioning a substantially planar display structure (20) between the cover plate (10) and the holding member (30); applying pressure to the stack thus formed, in order to deform the display structure (20) such that the display structure (20) matches the shape of the cover plate (10) and of the retaining member (30), the pressure being applied, in particular in the cold state; -removing the stack leaving a retaining member (30) permanently attached to the display structure (20).

Description

Technical Field

[0001] The present invention relates in particular to a method for manufacturing a display device, which is specifically designed for installation on a vehicle. Background Technology

[0002] The means of transportation can be land vehicles, ships, or aircraft.

[0003] Currently, TFT-type display devices, in particular, employ curved protective lenses / glass covering the TFT structure. When the radius of curvature falls below a certain limit, the liquid crystal in the TFT screen experiences stress due to the tension applied by the screen glass, and the curvature of the screen glass is unstable. This leads to the so-called Mura effect, as described below. Summary of the Invention

[0004] This invention is specifically designed to solve this problem.

[0005] Therefore, the present invention relates to a method for manufacturing a display device, the method comprising the following steps:

[0006] - Provides curved covers, which are made of glass or transparent PC, and whose curvature is obtained in advance by thermoforming;

[0007] - Provides a planar display structure, particularly of the TFT type;

[0008] - Provide a retaining member having a bending shape that substantially matches the bending shape of the cover plate;

[0009] - Position the overall planar display structure between the cover plate and the retaining member;

[0010] - Apply pressure to the resulting stack to deform the display structure so that it matches the shape of the cover plate and retaining members, especially when applying pressure in a cold state;

[0011] - Remove the stack, leaving the retaining member permanently attached to the display structure.

[0012] According to one aspect of the invention, the cover plate is pre-formed into a curved shape, preferably by thermoforming, utilizing heat input.

[0013] Therefore, in this invention, the cover plate and retaining member initially have curved shapes, while the display structure is initially generally planar. Thus, the display structure is shaped by subjecting it to pressure in a cold state, by being clamped between the cover plate and the retaining member.

[0014] Because the cover plate is given its curved shape through hot thermoforming, the shape of the cover plate is stable.

[0015] In contrast, display structures undergo cold forming, resulting in instability. Consequently, the display structure experiences internal stresses due to its curvature. Display structures are not thermoformed because this would require a complex and expensive process.

[0016] Without retaining components, internal stresses can affect the layers that make up the display structure. If the display structure is a TFT type with different layers including a liquid crystal layer, some of these layers may separate from each other under the influence of internal stresses caused by curvature, creating non-uniform regions within the display structure accompanied by the undesirable Mura effect.

[0017] As will be recalled, the Mura effect is particularly evident in the uniformity defects of TFT screen-type display structures.

[0018] It has been surprisingly discovered that retaining components make it possible to eliminate or reduce the Mura effect.

[0019] It has been discovered that by maintaining the presence of the components, the present invention allows for the balancing of the forces exerted on the display structure by the cover plate. This stress imbalance in the display structure stems from the fact that the cover plate has already undergone stable deformation (in a hot state), while the display structure has already deformed in a cold state. After the pressure used to induce deformation is released, some layers of the display structure tend to return to a planar shape.

[0020] In summary, it has been found that the present invention allows stress within the structure to remain balanced, thereby eliminating or reducing the Mura effect.

[0021] According to one aspect of the invention, a display structure is deformed by using a stack of pressing tools configured to press against a pressing base plate.

[0022] According to one aspect of the invention, this deformation is achieved in a cold state without any heat input.

[0023] According to one aspect of the invention, the pressing tool has a supporting surface having a shape that matches the curved shape of the cover plate.

[0024] According to one aspect of the invention, an optically clear adhesive (OCA) is deposited between the display structure and the cover plate.

[0025] According to one aspect of the invention, an optically transparent adhesive (OCA) is deposited between the display structure and the retaining member.

[0026] According to one aspect of the invention, the display structure includes a substrate made particularly of glass, which supports an active layer, and in particular has electrodes and a liquid crystal that interacts with the electrodes to achieve the display.

[0027] According to one aspect of the invention, the display structure is particularly of the TFT type.

[0028] According to one aspect of the invention, the cover plate is a plate made of an optically transparent material, or a material that can be thermoformed.

[0029] According to one aspect of the invention, in addition to a base substrate made of glass, the display structure also includes an upper plate made of glass, which is intended to be adjacent to the cover plate.

[0030] Therefore, the display structure can have a multi-layer structure, with a base plate on one side and a top plate, specifically made of glass, on the other side.

[0031] When the internal stresses within the display structure are mentioned in the above description, it can be said that, due to these internal stresses, the base plate and the top plate of the display structure tend to separate from each other at the edges.

[0032] This is because the upper plate of the display structure is adhesively bonded to the cover plate which has a stable shape, whereas without the retaining member according to the invention, the substrate would be subjected to stress that would cause the upper plate to separate.

[0033] Due to the retaining member according to the invention, the base plate of the display structure retains its curved shape.

[0034] According to one aspect of the invention, the retaining member is provided as an additional component that forms an integral part of the display device and is not a component used only during manufacturing.

[0035] According to one aspect of the invention, the retaining member has a main surface intended to face the display structure.

[0036] According to one aspect of the invention, the main surface of the component is kept to have a curved shape.

[0037] According to one aspect of the invention, the retaining member has edges for reinforcing the retaining member.

[0038] According to one aspect of the invention, the reinforcing edge extends around the entire periphery of the main surface of the retaining member.

[0039] According to one aspect of the invention, the reinforced edge extends away from the display structure.

[0040] According to one aspect of the invention, the reinforcing edge and the main surface of the retaining member are integrally formed.

[0041] According to one aspect of the invention, the main surface of the component is solid. This means that the main surface is not perforated.

[0042] In this case, the main surface of the component remains optically transparent.

[0043] In one variation, the main surface of the component is kept open.

[0044] For example, the retaining members with openings surround the peripheral strip of the display structure and form a frame.

[0045] According to one aspect of the invention, the frame formed by the retaining member can be sufficient to keep the display structure stable relative to the internal stress caused by bending.

[0046] According to one aspect of the invention, the retaining member may be made of a transparent or translucent material, particularly of glass or transparent PC (polycarbonate).

[0047] According to one aspect of the invention, the retaining member can be made entirely of an optically transparent material.

[0048] According to one aspect of the invention, the retaining member can be manufactured by injection molding.

[0049] According to one aspect of the invention, the retaining member can be formed as a retaining plate, which is particularly similar to a cover plate, especially transparent.

[0050] According to one aspect of the invention, the retaining plate and the cover plate may have similar shapes, and in particular, the same surface area.

[0051] According to one aspect of the invention, the thickness of the retaining plate can be variable.

[0052] According to one aspect of the invention, the thickness variation can be selected based on the radius of curvature adopted by the retaining plate.

[0053] According to one aspect of the invention, the thickness of the retaining plate and the thickness of the cover plate can be the same.

[0054] This allows the thickness of the retaining plate and the cover plate to be distributed on either side of the display structure.

[0055] According to one aspect of the invention, the display device thus includes a retaining plate and a cover plate, with a display structure in a curved shape attached between the retaining plate and the cover plate.

[0056] According to one aspect of the invention, the retaining plate, like the cover plate, has a curved shape pre-obtained by thermoforming.

[0057] In addition to the cover plate, the presence of the retaining plate makes it possible to improve the consistency of energy absorption in the event of an impact.

[0058] If the retaining component has a reinforcing edge, the reinforcing edge can be made of an optically opaque material, while the main surface is made of an optically transparent material.

[0059] According to one aspect of the invention, the retaining member is configured as an element for encapsulating the backlight unit.

[0060] According to one aspect of the invention, the backlight module includes a housing comprising a support for a light source, particularly of the LED type, a light guide above the support for the light source, and an optical sheet stack above the light guide.

[0061] According to one aspect of the invention, the retaining member is configured to enclose the housing of the backlight unit.

[0062] According to one aspect of the invention, the display device is placed on the housing of the backlight unit.

[0063] According to one aspect of the invention, the housing of the backlight unit is sealed by the holding member of the display device.

[0064] According to one aspect of the invention, the holding member of the display device thus serves as a cover for the housing of the module for the backlight unit, and is preferably made of an optically transparent or translucent material.

[0065] The present invention also relates to a display device obtained by the above method.

[0066] The present invention also relates to a display device comprising the following components stacked one after another:

[0067] - A curved cover, specifically made of glass or transparent PC;

[0068] - A curved display structure, particularly of the TFT type, wherein the curved shape of the display structure is produced by cold forming;

[0069] - A retaining member having a curved shape substantially matching the curved shape of the cover plate, and configured to retain the display structure in the curved shape obtained from cold forming.

[0070] According to one aspect of the invention, the cover plate is curved at least in the peripheral region of the cover plate (i.e., the region adjacent to the periphery of the cover plate).

[0071] According to one aspect of the invention, the cover plate is curved over its entire surface area.

[0072] In this case, the cover plate has no flat portion. Attached Figure Description

[0073] Other features and advantages of the invention will become clearer from the following description, given by way of illustrative and non-limiting examples, and in conjunction with the accompanying drawings, in which:

[0074] Figure 1The steps of a manufacturing method according to an exemplary embodiment of the present invention are illustrated schematically and in part.

[0075] Figure 2 The schematic and partial illustration shows the passage through Figure 1 Exploded view of the display device obtained by the method described above;

[0076] Figure 3 The steps of a manufacturing method according to another exemplary embodiment of the present invention are illustrated schematically and in part.

[0077] Figure 4 A cross-sectional view of a display device according to another exemplary embodiment of the present invention is shown schematically and in part.

[0078] Figure 5 A cross-sectional view of a holding member of a display device according to another exemplary embodiment of the present invention is shown schematically and in part. Detailed Implementation

[0079] Figure 1 The steps of a method for manufacturing a display device 1 according to an exemplary embodiment of the present invention are shown, including the following steps:

[0080] - A curved cover plate 10 is provided, which is made of glass or transparent PC, and the curvature of the cover plate is obtained in advance by thermoforming;

[0081] - Provides a planar display structure 20, which is of the TFT (for "thin-film transistor") type;

[0082] - A retaining member 30 is provided, which has a bending shape that substantially matches the bending shape of the cover plate 10;

[0083] - Position the overall planar display structure 20 between the cover plate 10 and the retaining member 30 (step 1A);

[0084] - Pressure is applied to the resulting stack 50 to deform the display structure 20 so that it matches the shape of the cover plate 10 and the retaining member 30, the pressure being applied in a cold state (step 1B).

[0085] - Remove the stack 50, leaving the retaining member 30 permanently attached to the display structure 20 (step 1C).

[0086] The cover plate 10 is pre-formed into a curved shape by heat input through thermoforming.

[0087] Therefore, in this invention, the cover plate 10 and the retaining member 30 initially have curved shapes, while the display structure 20 is initially generally planar. Thus, the display structure 20 is shaped by subjecting it to pressure in a cold state, by being sandwiched between the cover plate 10 and the retaining member 30.

[0088] Since the cover plate 10 is given a curved shape through hot thermoforming, the shape of the cover plate 10 is stable.

[0089] In contrast, display structure 20 undergoes cold forming, resulting in instability. Therefore, display structure 20 experiences internal stress due to its curvature. Display structure 20 is not thermoformed because this would require a complex and expensive process.

[0090] Without retaining member 30, internal stress may affect the layers constituting display structure 20. If the display structure is a TFT type with different layers including liquid crystal layers, some of these layers may become separated from each other under the action of internal stress caused by curvature, and this creates non-uniform regions within the display structure, accompanied by the undesirable Mura effect.

[0091] As will be recalled, the Mura effect is particularly evident in the uniformity defects of TFT screen-type display structures.

[0092] It has been surprisingly discovered that retaining component 30 makes it possible to eliminate or reduce the Mura effect.

[0093] It has been found that by maintaining the presence of member 30, the present invention makes it possible to balance the forces exerted on the display structure by cover plate 10. This stress imbalance on display structure 20 stems from the fact that cover plate 10 has been stably deformed (in a hot state), while the display structure has been deformed in a cold state. After the pressure that caused the deformation is released, some layers of the display structure tend to return to a planar shape.

[0094] In summary, it has been found that the present invention allows the stress within the display structure 20 to remain balanced, thereby making it possible to eliminate or reduce the Mura effect.

[0095] The display structure 20 is deformed by using a stack of pressing tools 60 configured to press and rest on a pressing base plate 61.

[0096] This deformation is achieved in a cold state without any heat input.

[0097] The pressing tool 60 has a bearing surface that has a shape that matches the curved shape of the cover plate 10.

[0098] A layer of optically clear adhesive 25 (OCA) is deposited between the display structure 20 and the cover plate 10.

[0099] Another layer of optically transparent adhesive 25 is deposited between the display structure 20 and the retaining member 30.

[0100] The cover plate 10 is a plate made of an optically transparent material, which is made of a thermoforming material.

[0101] The display structure 20 includes a substrate 22 made of glass, which supports an active layer, specifically having electrodes and liquid crystals that interact with the electrodes to achieve a display.

[0102] In addition to the substrate 22, the display structure 20 also includes a glass upper plate 24, which is intended to be adjacent to the cover plate 10, such as Figure 2 As shown.

[0103] Therefore, the display structure 20 can have a multi-layer structure, wherein the base substrate 22 is on one side and the top plate 24 is on the other side.

[0104] The retaining component 30 is provided as an additional part, which forms an integral part of the display device 1, and is not a part used only during manufacturing.

[0105] The retaining member 30 has a main surface 31 that is intended to face the display structure 20.

[0106] The main surface 31 of the retaining member 30 has a curved shape.

[0107] The retaining member 30 has an edge 32 for reinforcing the retaining member 30.

[0108] The reinforcing edge 32 extends around the entire periphery of the main surface of the retaining member 30, where the internal stress of the structure 20 may be the most destructive.

[0109] Strengthen the edge 32 away from the display structure 20 extension.

[0110] The reinforcing edge 32 is integrally formed with the main surface 31 of the retaining member 30.

[0111] Main surface 31 of component 30 is solid. This means that the main surface is not perforated.

[0112] In this case, the main surface 31 of the retaining member 30 is optically transparent, and the reinforcing edge 32 can be optically opaque, such as... Figure 5 As shown.

[0113] In one variation, the main surface 31 of retaining member 30 is open.

[0114] For example, the retaining member 30 with the opening surrounds the peripheral strip of the display structure 20 and forms a frame.

[0115] The frame formed by the retaining member 30 is sufficient to keep the display structure stable relative to the internal stress caused by curvature.

[0116] The retaining member 30 can be made of transparent or translucent materials, particularly glass or transparent PVC.

[0117] In one variation, the retaining member 30 can be made entirely of an optically transparent material.

[0118] The retaining component 30 can be manufactured by injection molding.

[0119] exist Figure 3 In an exemplary embodiment (which also shows the same as...), Figure 1 In the example of three steps 3A, 3B and 3C, the retaining member 30 can form a retaining plate 35, which is similar to or even the same as the cover plate 10 and is transparent.

[0120] The retaining plate and cover plate 10 can have similar shapes, and in particular, the same surface area.

[0121] The thickness of the retaining plate 35 can be variable.

[0122] The thickness variation can be selected based on the radius of curvature adopted by the retaining plate 35.

[0123] The thickness of the retaining plate 35 and the cover plate 10 can be the same.

[0124] This allows the thickness of the retaining plate 35 and the cover plate 10 to be distributed on either side of the display structure.

[0125] Therefore, the display device includes a retaining plate 35 and a cover plate 10, with a display structure 20 in a curved shape attached between the retaining plate 35 and the cover plate 10.

[0126] Like the cover plate 10, the retaining plate 35 has a curved shape pre-obtained through thermoforming.

[0127] exist Figure 4 In an exemplary embodiment, the retaining member 30 is configured to encapsulate the elements of the backlight unit 70.

[0128] The backlight module 70 includes a housing 71 which contains an electronic circuit board 72 having an LED-type light source 73, a light guide 74 above the electronic circuit board 72, and an optical sheet 75 stacked above the light guide.

[0129] The retaining member 30 is configured to enclose the housing 71 of the backlight unit 70.

[0130] The display device 1 is placed on the housing 71 of the backlight unit.

[0131] The housing 71 of the display device, which is enclosed by the retaining member 30, encloses the backlight unit 70.

[0132] Therefore, the holding member 30 of the display device serves as a cover for the housing 71 of the module for the backlight unit and is made of an optically transparent or translucent material.

[0133] Typically, the present invention enables the provision of a display device comprising the following components stacked one after another:

[0134] - A curved cover plate 10, which is specifically made of glass or transparent PC;

[0135] - A curved display structure 20, particularly of the TFT type, wherein the curved shape of the display structure 20 is produced by cold forming;

[0136] - Retaining member 30, which has a curved shape substantially matching the curved shape of cover plate 10, and configured to retain display structure 20 in the curved shape obtained from cold forming.

[0137] The cover plate 10 is curved at least in the peripheral region of the cover plate 10 (i.e., the region adjacent to the periphery of the cover plate 10).

[0138] The cover plate 10 is preferably curved over its entire surface area.

[0139] In this case, the cover plate 10 does not have any flat portion.

[0140] The curvature of the cover plate 10 can be selected as needed, especially in terms of shape.

[0141] Retaining components can be made by injection molding from one or two materials in a single mold. In the case of two materials, the injection molding operation is called 2K or two-shot injection molding. The materials can be different.

Claims

1. A method for manufacturing a display device (1), the method comprising the steps of: - providing a cover plate (10) of curved shape, in particular made of glass or made of transparent PC, the curvature of the cover plate (10) being in particular pre-obtained by thermoforming; - providing a display structure (20) of overall planar shape, in particular of TFT type; - providing a retaining member (30) having a curved shape substantially matching the curved shape of the cover plate (10); - positioning the display structure (20) of overall planar shape between the cover plate (10) and the retaining 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 of the retaining member (30), the pressure being in particular applied in cold state; - removing the stack, leaving the retaining member (30) permanently attached to the display structure (20).

2. The method of the preceding claim, wherein, The cover plate (10) is pre-endowed with a curved shape, preferably by thermoforming, with heat input.

3. The method of any of the preceding claims, wherein, The display structure (20) is deformed using a pressing tool configured to press the stack resting on a pressing floor, the deformation being preferably achieved in the cold state, without heat input.

4. The method of 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 between the display structure (20) and the retaining member (30).

5. The method of any one of the preceding claims, wherein, The display structure (20) comprises a base substrate made in particular of glass, which supports an active layer, in particular having electrodes and liquid crystals interacting with the electrodes to enable display.

6. The method of any one of the preceding claims, wherein, The cover plate (10) is a plate made of an optically transparent substance, made of a material capable of thermoforming.

7. The method of any one of the preceding claims, wherein, The display structure (20) comprises, in addition to the base substrate made in particular of glass, an upper plate made in particular of glass, intended to be adjacent to the cover plate (10).

8. The method of any one of the preceding claims, wherein, The retaining member (30) is provided as an additional component forming an integral part of the display device.

9. The method of 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. The method of any one of the preceding claims, wherein, The retaining member (30) has an edge for stiffening the retaining member (30), and the stiffening edge extends in particular around the entire periphery of the main face of the retaining member (30).

11. The method of any one of the preceding claims, wherein, The retaining member (30) is configured to encapsulate the elements of a backlight unit, and the backlight module comprises a housing containing a support having light sources, in particular of LED type, a light guide above the support having light sources, and a stack of optical sheets above the light guide.

12. A display device (1) comprising the following components stacked one after the other: - a cover plate (10) of curved shape, in particular made of glass or made of transparent PC; - a display structure (20) of curved shape, in particular of TFT type, the curved shape of the display structure (20) resulting from cold forming; - a retaining member (30) having a curved shape substantially matching the curved shape of the cover plate (10); - a retaining member (30) having a curved shape substantially matching the curved shape of the cover plate (10) and configured to retain the display structure (20) in the curved shape obtained from cold forming.

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