Coating element for display device

Abstract

The utility model provides a coating element for a display device, which comprises at least one support member made of transparent thermoplastic material and comprising a support member inner surface rotating towards the display device and a support member outer surface opposite to the support member inner surface; and a coating layer comprising a coating layer inner surface extending opposite the support outer surface of the support and a coating layer outer surface opposite the coating layer inner surface, said coating layer being made of a transparent polymeric material, the coating layer outer surface comprising a sub-wavelength structure arranged to disperse light of a wavelength in the visible range. The coating element also includes a decorative layer extending between the support outer surface of the support and a coating layer inner surface of the coating layer.

Description

Technical Field

[0001] The utility model relates to a coating element for a display device, the coating element of this type comprises: at least one support made of a transparent thermoplastic material, the support comprising an inner surface intended to rotate toward a display device and an outer surface opposite to the inner surface; a coating layer comprising an inner surface extending relative to the outer surface of the support and an outer surface opposite to the inner surface, the coating layer is made of a transparent polymer material, the outer surface comprises a sub-wavelength structure, and the sub-wavelength structure is arranged to disperse light of wavelengths within a visible range. Background Art

[0002] It is known to coat the screen of a display device with a coating element formed by a transparent glass or a lens through which the image of the display device is displayed. Such a lens thus forms an element for protecting the display surface of the display device.

[0003] The coating element must further have certain characteristics that improve the quality of the display or make it possible to prevent the display from degrading over time. Therefore, anti-reflection and anti-glare treatments are usually provided to improve the quality of the display. In addition, a treatment to prevent finger marks and another treatment to facilitate cleaning of the display surface may be provided to maintain the quality of the display.

[0004] In order to perform all these functions, the coating element generally comprises several layers applied to a transparent support forming the lens, each layer being arranged to perform one or more of the functions provided. Thus, for example, it is known to provide a layer shaped to have a so-called sub-wavelength structure arranged to scatter or destroy light of wavelengths in the visible range in order to perform anti-reflection and anti-glare functions.

[0005] The accumulation of layers makes the arrangement of the coating element complex, increases its cost and complicates its production. Moreover, such an arrangement of thin layers generally does not allow the light reflected in the entire spectrum of the visible range to be disrupted. Thus, one or more wavelengths of light can be reflected by the coating element, which leads to changes in the color tone of the surface of the coating element and degrades the appearance of the display device. Utility Model Content

[0006] One of the objects of the present invention is to overcome these drawbacks by proposing a coating element for a display device which makes it possible to perform several comfort functions while having a simple arrangement.

[0007] To this end, the utility model relates to a coating element of the aforementioned type, wherein the material of the coating layer further comprises at least one fluorinated additive or a silicone additive.

[0008] By providing a structured coating made of a transparent polymer material including a fluorinated additive or a silicone additive, the coating element can perform the functions of preventing reflections, glare and finger marks and promoting cleaning in a single layer. In fact, the addition of a fluorinated additive or a silicone additive in the coating layer allows the surface tension on the outer surface of the coating layer to be reduced, and thus a beading effect is produced on the outer surface, which is conducive to the cleaning of the outer surface and makes the marks left thereon (such as finger marks) less visible. The number of layers of the coating element can therefore be reduced, which reduces the cost of the coating element and is conducive to its production. In addition, the coating element does not require additional processing steps when leaving the molding tool.

[0009] The coating element according to the present invention may further include one or more of the following features considered individually or in any technically feasible combination:

[0010] - the transparent polymer material of the coating layer exhibits a glass transition temperature less than or equal to 60°C;

[0011] - the transparent polymer material of the coating layer is polyurethane;

[0012] - the outer surface of the coating exhibits a contact angle with dispersed liquids greater than 60° and a contact angle with polar liquids greater than 100°;

[0013] - the amount of fluorinated additive or silicone additive in the transparent polymer material of the coating layer is between 0.1% and 1.0% by weight;

[0014] - fluorinated additives include fluorinated oligomers consisting of fluorinated chains of six to ten elements; and

[0015] The decorative layer extends between the outer surface of the support and the inner surface of the coating layer.

[0016] According to another aspect, the utility model relates to a method for producing a coated element as described above, comprising the following steps:

[0017] - production of supports made of transparent thermoplastic material,

[0018] - placing a support in a molding tool comprising a structured molding surface, the outer surface of the support defining together with the molding surface a molding cavity having the shape of the coating, the molding surface having a structure complementary to the sub-wavelength structure of the outer surface of the coating,

[0019] - Injecting a transparent polymer material comprising at least one fluorinated additive or silicone additive into said moulding cavity.

[0020] The production method according to the utility model may further include one or more of the following features considered individually or in any technically feasible combination:

[0021] - The support is made by injecting a transparent thermoplastic material into a moulding cavity having the shape of said support, said moulding cavity being defined by a moulding surface of at least one first mould part having the shape of an inner surface of the support and a moulding surface of a second mould part having the shape of an outer surface of the support.

[0022] The structured moulding surface is defined by a third mould part, the first mould part being separated from the second mould part after the support has been made and being moved together with the support relative to the third mould part to form a moulding cavity having the shape of the outer layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Other aspects and advantages of the invention will emerge on reading the following description given by way of example and made with reference to the accompanying drawings, in which:

[0024] Figure 1 is a schematic cross-sectional view of a coating element according to an embodiment of the present invention, and

[0025] Figure 2 is a schematic cross-sectional view of a molding tool during the production of a coating element according to the invention. DETAILED DESCRIPTION

[0026] refer to Figure 1 , a coating element 1 for a display device is described, comprising at least one support 2 and a coating layer 4. Figure 1 In the embodiment shown in FIG. 4 , the coated element 1 further comprises a decorative layer 6 disposed between the support 2 and the coating layer 4 .

[0027] Such a coating element 1 forms, for example, a lens extending over a screen of a display device (not shown) in order to protect the screen and improve its display quality. The display device may be of any type, such as a screen of a mobile device, a touch-sensitive surface and / or a motor vehicle display device.

[0028] The support 2 is made of a transparent thermoplastic material and extends between an inner support surface 8 and an outer support surface 10 .

[0029] Thermoplastic materials are, for example, materials having a glass transition temperature greater than or equal to 140° C., such as polycarbonate. Such materials impart mechanical characteristics to the support 2 , in particular in terms of rigidity, temperature resistance and impact strength, allowing protection of the screen of the display device.

[0030] The inner surface 8 of the support is intended to be applied to the screen of the display device, while the outer surface 10 of the support faces the outside of the display device. In other words, the light emitted by the display device passes from the inner surface 8 of the support through the support 2 to the outer surface 10 of the support. The thickness of the support 2 corresponds to the distance extending between the inner surface 8 of the support and the outer surface 10 of the support, and is, for example, between 1 mm and 5 mm, for example substantially equal to 2.5 mm. Figure 1 In the figure, the support inner surface 8 and the support outer surface 10 are shown as planar surfaces. However, it should be understood that these surfaces can be non-planar and can, for example, have a radius of curvature to form a curved support 2 based on the properties of the display device receiving the coated element 1.

[0031] The coating layer 4 is made of a functionalized transparent polymer material and extends between a coating layer inner surface 12 and a coating layer outer surface 14. The coating layer 4 has, for example, a thickness substantially comprised between 0.2 mm and 5 mm, for example substantially equal to 0.5 mm.

[0032] The coating inner surface 12 extends opposite to the support outer surface 10 of the support 2. According to one embodiment, the coating inner surface 12 is applied directly to the support outer surface 10 of the support 2, that is to say, there is no intermediate layer between the support 2 and the coating 4. As a variant, Figure 1 As shown in FIG. 4 , at least one decorative layer 6 extends between the support 2 and the coating layer 4 , to which the coating layer inner surface 12 is then applied.

[0033] This decorative layer 6 is formed, for example, by a film (for example, based on polyurethane) comprising one or more layers of ink. The layer of ink extends between two layers of heat-activatable adhesive, allowing the decorative layer 6 to adhere to the support on the one hand and to the coating layer 4 on the other hand. The decorative layer 6 is, for example, arranged to modify the appearance of the display device, in particular when the display device is not turned on, so that it has a satisfactory appearance when no image is displayed. Therefore, the decorative layer 6 is, for example, a colored film. The decorative layer 6 comprises an inner surface 16 and an outer surface 18, the inner surface being, for example, formed by a layer of heat-activatable adhesive applied to the outer surface 10 of the support 2, and the outer surface being, for example, formed by a layer of heat-activatable adhesive, on which the coating layer inner surface 12 of the coating layer 4 is applied. The decorative layer 6 is arranged to allow light emitted by the display device and passing through the support 2 to pass. It should be noted that the appearance of the display device can also be changed by means of the support 2 and / or the coating layer 4, for example, by giving these elements a smoky appearance.

[0034] Before it is used for coating the element, the decorative layer 6 is for example formed on a peelable support film, thereby allowing the ink layer to be deposited. As will be described later, this support film is removed during the production of the coating element.

[0035] The coating outer surface 14 of the coating 4 forms the outer surface of the cover element 1 , ie the surface extending outermost to the display device and which the user touches if he applies his finger on the coating 1 .

[0036] The coating outer surface 14 is structured, that is, given a specific shape so that incident light below the coating outer surface 14 is not reflected by the outer surface. Figure 1 The shapes shown in the figure are not shown to scale and are only schematically shown by way of example to clarify the meaning of the structured surface. In fact, according to the utility model and as will now be described, the coating outer surface 14 has a nanoscale structure that is invisible to the naked eye. In other words, the coating outer surface 14 is not smooth, but is smooth to the naked eye and touch.

[0037] More specifically, the shape of the coating outer surface 14 is such that the coating outer surface 14 includes a subwavelength structure 20, which is arranged to disperse wavelength light in the visible range and prevent the wavelength light from being reflected toward the outside of the display device by the coating outer surface 14. In other words, the subwavelength structure 20 prevents visible light incident on the coating outer surface 14 and visible light from the outside of the display device from returning toward the outside, thereby avoiding reflection on the coating outer surface 14.

[0038] This sub-wavelength structure 20 includes a plurality of nano-scale protruding elements 22 extending in the direction of the thickness of the coating layer 4, thereby forming protrusions 24 and recesses 26 on the coating layer outer surface 14. The protruding elements 22 have, for example, Figure 1 The pitch of the subwavelength structures 20, i.e. the distance separating two adjacent protruding elements, is, for example, between 150 nm and 250 nm. The height / pitch ratio of the protruding elements is, for example, substantially between 2 and 0.5, preferably substantially equal to 1, such a ratio making it possible to have a satisfactory compromise between the optical properties of the subwavelength structure 20 and its demoulding properties (i.e. its ability to be removed from the molding surface without degradation). The protruding elements 22 are arranged at Figure 1 , all having the same shape and the same size. However, it should be understood that the subwavelength structure 20 can be irregular, with protruding elements 22 of different heights and variable spacing, as long as the height / pitch ratio remains constant. The subwavelength structure 20 further allows a 50% drop in reflectivity with less than 20% difference in the visible spectrum, that is, it has little effect on the color of the image emitted by the display device.

[0039] The subwavelength structure 20 acts as a light trap that redirects incident light to the interior of the subwavelength structure and / or multiplies reflections between the protruding elements 22 forming the subwavelength structure 20, as shown by Figure 1The incident light ray r in FIG. 2 is schematically shown. The sub-wavelength structure 20 works according to the principle of Rayleigh scattering and / or "moth eye".

[0040] The sub-wavelength structure 20 extends, for example, over the entire coating outer surface 14 of the coating 4. Alternatively, for example when the coating element 1 has a larger surface area than the surface area of ​​the screen of the display device, the sub-wavelength structure 20 forms only a part of the coating outer surface 14. In this case, the sub-wavelength structure 20 has, for example, a surface that is substantially equal to or slightly larger than the surface of the screen and extends opposite thereto.

[0041] The sub-wavelength structure 20 allows the coating element 1 to perform anti-reflection and anti-glare functions, thereby improving the display quality on the outer surface 14 of the coating layer.

[0042] The functionalized polymer material forming the coating 4 has, for example, a glass transition temperature less than or equal to 60° C. According to one embodiment, the material of the coating 4 has a glass transition temperature less than or equal to 40° C. More particularly, the polymer material is, for example, polyurethane. Such a material allows to impart mechanical characteristics to the coating 4, in particular in terms of elasticity, which makes it possible to obtain an anti-scratch treatment of the outer surface 14 of the coating. In fact, the coating 4 made of such a polymer material has a certain shape memory that allows it to return to its initial shape after a stress, such as an action tending to scratch the outer surface 14 of the coating.

[0043] The polymer material is functionalized by adding at least one fluorinated additive or silicone additive to the polymer material. Such additives are obtained, for example, by adding fluorinated oligomers to the polymer material forming the coating layer 4. Such oligomers are composed, for example, of fluorinated chains of six to ten elements. Fluorinated additives are selected, for example, from fluorine-alkyurethanes or fluorinated polymers. The amount of additive in the polymer material is, for example, substantially between 0.1% and 2.0% by weight, for example, substantially equal to 0.5%. As a variation, in the case of silicone additives, the additive is formed by polysiloxane. According to another variation, a mixture of fluorinated additives and silicone additives is added to the polymer material forming the coating layer 4. One or more such additives allow the coating layer 4 to be easier to clean and are less likely to retain finger marks, etc. after the user has contacted the coating layer outer surface 14. In fact, the additive allows the surface tension of the coating layer outer surface 14 to be reduced, which imparts a beading effect on the coating layer outer surface 14 of the coating layer 4, whereby the liquid on the coating layer outer surface 14 tends to form droplets on the coating layer outer surface 14 and therefore does not stagnate on the coating layer outer surface 14. The surface tension of the coating outer surface 14 of the coating 4 is characterized by a contact angle of the coating outer surface 14 with a dispersed liquid (such as oil, for example) greater than 60°, and a contact angle of the coating outer surface 14 with a polar liquid (such as distilled water, for example) greater than 100°. This surface tension also corresponds to a surface energy level of less than 20 mN.m-1.

[0044] Thus, a single coating layer 4 as described above makes it possible to perform several functions that are usually performed by different stacked layers. More particularly, the coating layer 4 makes it possible to perform the functions of anti-reflection, anti-glare, anti-scratch, anti-fingerprint and easy cleaning. These functions, combined with the protective function provided by the support 2, make the coating element 1 particularly effective for protecting display devices with a simple and inexpensive arrangement. Moreover, the coating element 1 is particularly simple to produce and does not require finishing steps when leaving the molding tool, as will now be described with reference to the Figure 2 as described.

[0045] The production method comprises at least the following steps:

[0046] - producing a support 2 made of transparent material,

[0047] - placing the support 2 in a molding tool 28 comprising a molding surface 30 , the support outer surface 10 of the support 2 defining together with the molding surface 30 a molding cavity 32 having the shape of the coating 4 ,

[0048] A transparent polymer material 34 comprising at least one fluorinated additive or silicone additive is injected into the mold cavity 32 to form the coating layer 4 .

[0049] According to a particularly advantageous embodiment, the support 2 is also produced by injection into a molding cavity 36 having the shape of the support 2, wherein a transparent thermoplastic material 38 is injected. The molding cavity 36 is delimited by a first molding surface having the shape of at least the support inner surface 8 of the support 2 and a second molding surface having the shape of at least the support outer surface 10 of the support 2. The wall connecting the support inner surface 8 to the support outer surface 10 is defined by one or two molding surfaces. The first molding surface is formed by a first molding part 40 of the molding tool 28, and the second molding surface is formed by a second molding part 42 of the molding tool, which parts are movable relative to each other between a closed position and a separated position, in which the first and second parts define the molding cavity 36, and in which the first and second parts are spaced apart from each other. A first injection device 44 leading into the molding cavity 36 extends into one of the parts of the molding tool 28 and allows the injection of the transparent thermoplastic material 38.

[0050] When the first and second parts 40, 42 are in the closed position, once the support 2 has been made in the molding cavity 36, the first part 40 made with the support 2 is separated from the second part 42 and placed opposite to the third mold part of the molding tool 28, thereby defining the molding surface 30, and wherein the second injection device 46 is extended to inject the transparent polymer material 34. The first part 40 is brought closer to the third part, so that the support 2 forms together with the molding surface 30 the molding cavity 32 having the shape of the coating layer 4, and wherein the second injection device 46 is exposed. Thus, the coating layer 4 is overmolded on the support 2 using the same first part 40 in the molding tool 28 to produce the support 2 and the coating layer 4.

[0051] Advantageously, the second portion 42 and the third portion of the molding tool 28 are combined, that is, the same portion 42 of the molding tool 28 comprises a second molding surface defining a portion of the molding cavity 36 of the support 2 and a molding surface 30 defining a portion of the molding cavity 32 of the coating 4. The first portion 40 is, for example, movable in rotation relative to the second portion 42 to alternately define the molding cavity 36 of the support and the molding cavity 32 of the coating 4, as Figure 2 As shown by the arrow R in .

[0052] Particularly advantageously, the first portion 40 comprises two first molding surfaces so as to define simultaneously the molding cavity 36 of the support and the molding cavity 32 of the coating when the first and second portions 40, 42 are in the closed position, as shown in FIG. Figure 2As shown in . Thus, it is possible to produce a new support 2 while overmolding a previously produced support 2 by means of the coating layer 4, which makes it possible to obtain a particularly high production efficiency of the coated element 1. When the first and second parts 40, 42 are brought into the open position, the finished coated element can be removed from the molding tool 28, and the rotation of the first part 40 allows the first molding surface (from which the finished coated element has been removed) to be positioned opposite the second molding surface, and allows the first molding surface on which the support 3 is present to be positioned opposite the molding surface 30 of the molding cavity of the coating layer, as from Figure 2 Understandable.

[0053] The shape of the molding surface 30 is complementary to the shape of the coating layer outer surface 14 of the coating element 4 to be produced. Therefore, the molding surface 30 is configured to have a shape complementary to the sub-wavelength structure 20 formed by the coating layer outer surface 14. In other words, the molding surface 30 includes a nanoscale structure that allows the sub-wavelength structure 20 to be produced during the molding of the coating layer 4 in the molding cavity 32.

[0054] When the coating element 1 comprises a decorative layer 6, the decorative layer can be placed on the support 2 when the first and second parts 40, 42 of the molding tool 28 are in the open position. Alternatively, the decorative layer 6 is placed against the second molding surface before the support 2 is made so that the support 2 is overmolded on the decorative layer 6. In all cases, when the decorative layer 6 is formed on a support film, the support film is removed before the decorative layer 6 is attached to the coating layer 4.

[0055] As described above, the coated element 1 produced in the molding tool 28 requires no additional finishing steps once it has been removed from the molding tool 28 .

Claims

1. A coating element (1) for a display device, comprising: at least one support (2), the at least one support being made of a transparent thermoplastic material (38), the support (2) comprising a support inner surface (8) intended to rotate toward the display device and a support outer surface (10) opposite to the support inner surface (8); a coating layer (4), the coating layer comprising a coating layer inner surface (12) extending relative to the support outer surface (10) of the support (2) and a coating layer outer surface (14) opposite to the coating layer inner surface (12), the coating layer (4) being made of a transparent polymer material (34), the coating layer outer surface (14) comprising a sub-wavelength structure (20) arranged to disperse light of wavelengths in the visible range, It is characterized in that the coating element further comprises a decorative layer (6), which extends between the support member outer surface (10) of the support member (2) and the coating layer inner surface (12) of the coating layer (4).

2. The coating element according to claim 1, characterized in that The transparent polymer material (34) of the coating layer (4) exhibits a glass transition temperature less than or equal to 60°C.

3. The coating element according to claim 1 or 2, characterized in that The transparent polymer material (34) of the coating layer (4) is polyurethane.

4. The coating element according to claim 1 or 2, characterized in that The coating layer outer surface (14) of the coating layer (4) exhibits a contact angle with a dispersed liquid greater than 60° and a contact angle with a polar liquid greater than 100°.

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