Display device with decorative sheet, design method of decorative sheet and design method of display device

Abstract

To make a display surface with a difference in brightness hard to be observed by a decorative sheet.SOLUTION: A display device 1 with a decorative sheet comprises a display device 10 and a decorative sheet 20. The display device 10 has a display surface 11 for displaying an image. The decorative sheet 20 is arranged so as to be opposite to the display surface 11. The decorative sheet 20 displays a design and transmits visible light. For a visible light transmittance T[%] of the decorative sheet 20, a value L of brightness L* in L*a*b* color system of the design displayed by the decorative sheet 20, and a ratio C of the maximum reflection luminance to the minimum reflection luminance of the display surface 11 in an image non-display state, the following relational expression (i) is satisfied when L is equal to or more than 20, and the following relational expression (ii) is satisfied when L is less than 20, (i) C≤(0.0003×L-0.0022)×(T-30)2+1, (ii) C≤(0.0007×L-0.0010)×(T-30)2+1.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a display device and a display device with a decorative sheet, and also to a method for designing a decorative sheet and a display device. [Background technology]

[0002] Display devices that display images are widely used. When no image is displayed on such display devices, the non-emitting display surface is directly observed. On the other hand, design is considered very important for surface components of automobiles, furniture, housing construction materials, etc. Currently, display devices applied to such fields are expected not only to simply display images on the display device, but also to have a design that blends in with the surrounding environment.

[0003] In order to impart design features to display devices, decorative sheets have been proposed, as shown in Patent Document 1, for example. The decorative sheet is provided in a position facing the display surface of the display device. The decorative sheet has a design portion that forms a design. When the decorative sheet is provided in a position facing the display surface of the display device, the surface of the decorative sheet becomes the surface of the display device with the decorative sheet. The decorative sheet displays the design created by the design portion on its surface. This gives the display device with the decorative sheet design. The imparted design allows the display device with the decorative sheet to blend in with the surrounding environment. Furthermore, the decorative sheet is provided with a transparent portion that transmits, for example, visible light, so that image light from the display device can pass through the decorative sheet. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-331132 Summary of the Invention [Problem to be solved by the invention]

[0005] On the display surface of a display device, even when an image is not displayed, there may be a difference in appearance between the portion displaying the image and the portion not displaying the image. More specifically, there may be a large difference in brightness between the portion displaying the image and the portion not displaying the image when the image is not displayed. Even if a decorative sheet is provided on the display device, the difference in brightness of the display surface may be observed through the decorative sheet. In such cases, the design imparted to the display device with the decorative sheet is impaired.

[0006] The inventors of the present invention have found that by devising a design displayed by a decorative sheet, it is possible to make differences in brightness on the display surface less noticeable. The present invention has been made in consideration of this point, and aims to make it possible to make display surfaces with differences in brightness less noticeable by using a decorative sheet. [Means for solving the problem]

[0007] The display device with a decorative sheet of the present invention comprises: a display device having a display surface for displaying an image; a decorative sheet disposed opposite the display surface, the decorative sheet displays a design and transmits visible light; The visible light transmittance T [%] of the decorative sheet, L of the design displayed by the decorative sheet * a * b * Lightness L in the color system * Regarding the value L and the ratio C of the maximum reflection luminance to the minimum reflection luminance of the display surface in the image non-display state, when L is 20 or more, the following relational expression (i) is satisfied, and when L is less than 20, the following relational expression (ii) is satisfied. C≦(0.0003×L-0.0022)×(T-30) 2 +1 (i) C≦(0.0007×L-0.0010)×(T-30) 2 +1 (ii)

[0008] In the display device with a decorative sheet of the present invention, the decorative sheet may have a visible light transmittance T of 30% or less.

[0009] In the display device with a decorative sheet of the present invention, a ratio C of maximum reflection luminance to minimum reflection luminance of the display surface in a non-display state may be 3 or more.

[0010] In the display device with a decorative sheet of the present invention, the L of the design displayed by the decorative sheet * a * b * Lightness L in the color system * The value L may be 30 or greater.

[0011] In the display device with a decorative sheet of the present invention, the visible light transmittance T [%] of the decorative sheet, the L of the design displayed by the decorative sheet, * a * b * Lightness L in the color system * Regarding the value L of T and the ratio C of the maximum reflection luminance to the minimum reflection luminance of the display surface in an image non-display state, when T is 10% or less, the following relational expression (iii) may be satisfied if L is 20 or more, and the following relational expression (iv) may be satisfied if L is less than 20. C≧(0.0003×L-0.0022)×(T-10) 2 +1 (iii) C≧(0.0007×L-0.0010)×(T-10) 2 +1 (iv)

[0012] A first method for designing a decorative sheet of the present invention is a method for designing a decorative sheet to be placed opposite a display surface that displays an image on a display device, the decorative sheet displays a design and transmits visible light; The visible light transmittance T [%] of the decorative sheet is the L of the design displayed by the decorative sheet. * a * b * Lightness L in the color system *and the ratio C of the maximum reflection luminance to the minimum reflection luminance of the display surface in the non-image display state.

[0013] A second method for designing a decorative sheet of the present invention is a method for designing a decorative sheet to be placed opposite a display surface that displays an image on a display device, the decorative sheet displays a design and transmits visible light; L of the design displayed by the decorative sheet * a * b * Lightness L in the color system * The value L is determined based on the visible light transmittance T [%] of the decorative sheet and the ratio C of the maximum reflection luminance to the minimum reflection luminance of the display surface in the image non-display state.

[0014] A method for designing a display device of the present invention is a method for designing a display device having a display surface for displaying an image, comprising the steps of: A decorative sheet is disposed facing the display surface, the decorative sheet displays a design and transmits visible light; The ratio C of the maximum reflection brightness to the minimum reflection brightness of the display surface in the image non-display state is determined by the visible light transmittance T [%] of the decorative sheet and the L of the design displayed by the decorative sheet. * a * b * Lightness L in the color system * is determined based on the value of L. [Effects of the Invention]

[0015] According to the present invention, the decorative sheet can make it difficult to observe a display surface having different brightness levels. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is an exploded perspective view that schematically shows a display device with a decorative sheet. [Figure 2] FIG. 2 is a cross-sectional view of a display device with a decorative sheet. [Figure 3]FIG. 3 is a front view of the display device. [Figure 4] FIG. 4 is a front view of the decorative sheet. [Figure 5] FIG. 5 is a front view of the display device with a decorative sheet, showing a state in which the display device is not displaying an image. [Figure 6] FIG. 6 is a front view of the display device with a decorative sheet, showing a state in which the display device is displaying an image. [Figure 7] FIG. 7 is a graph showing the relationship between the visible light transmittance and the contrast of the display surface of a display device for examples and comparative examples of decorative sheets that display a whitish color design. [Figure 8] FIG. 8 is a graph showing the relationship between the visible light transmittance and the contrast of the display surface of the display device for examples and comparative examples of decorative sheets that display designs in grayish colors. [Figure 9] FIG. 9 is a graph showing the relationship between the visible light transmittance and the contrast of the display surface of the display device for examples and comparative examples of decorative sheets that display brownish designs. [Figure 10] FIG. 10 is a graph showing the relationship between the visible light transmittance and the contrast of the display surface of the display device for examples and comparative examples of decorative sheets that display designs in black-based colors. DETAILED DESCRIPTION OF THE INVENTION

[0017] An embodiment of the present invention will now be described with reference to the drawings. In the drawings accompanying this specification, the scale and aspect ratios have been appropriately changed and exaggerated from those of the actual objects for the sake of ease of illustration and understanding.

[0018] In addition, in this specification, the terms "layer," "sheet," and "film" are not distinguished from one another solely based on differences in name. For example, the term "sheet" is a concept that includes a member that can be called a layer or a film.

[0019] Furthermore, terms used in this specification that specify shapes, geometric conditions, and their degrees, such as "parallel," "orthogonal," and "identical," as well as values ​​of lengths and angles, are intended to be interpreted without being bound by strict meanings, but to include a range within which similar functions can be expected.

[0020] FIG. 1 is an exploded perspective view schematically illustrating a display device 1 with a decorative sheet according to an embodiment of the present invention. As shown in FIG. 1, the display device 1 with a decorative sheet includes a display device 10 and a decorative sheet 20. The display device 10 has a display surface 11 that displays an image. The decorative sheet 20 is disposed facing the display surface 11 of the display device 10. FIG. 2 also illustrates a cross-sectional view of the display device 1 with a decorative sheet. As shown in FIG. 2, in the display device 1 with a decorative sheet, the decorative sheet 20 is disposed such that the side on which a light-shielding portion 25 is provided faces the display device 10 relative to a design portion 23 (described later). Note that, although the display device 1 with a decorative sheet is shown as a flat plate in the illustrated example, the display device 1 with a decorative sheet may be curved by curving each component of the display device 1 with a decorative sheet. For example, only the decorative sheet 20 may be curved, or both the display surface 11 of the display device 10 and the decorative sheet 20 may be curved.

[0021] The display device 1 with a decorative sheet can be in an image non-display state and an image display state. In the image non-display state, the display device 1 with a decorative sheet displays the design formed by the decorative sheet 20. In the image display state, the display device 1 with a decorative sheet displays the image displayed by the display device 10. Each component of the display device 1 with a decorative sheet will be described below.

[0022] First, we will explain the display device 10. The display device 10 can display an image on a display surface 11. The display device 10 can emit image light from the display surface 11. The display device 10 can be in a state where an image is displayed on the display surface 11, and a state where an image is not displayed on the display surface 11.

[0023] 2, the display device 10 has a surface light source device 13 and a shading sheet 15. Such a display device 10 can display an image using light and dark by blocking part of the light from the surface light source device 13 with the shading sheet 15. The display surface 11 of the display device 10 is formed by the shading sheet 15.

[0024] The surface light source device 13 is a device that emits light in a planar manner. The surface light source device 13 has a light-emitting surface 13a that emits light. The surface light source device 13 emits light with uniform intensity from the light-emitting surface 13a. The surface light source device 13 is not particularly limited, and various types of devices, such as edge-light type and direct type devices, can be used. The surface light source device 13 may emit white light or may emit light of a color such as red.

[0025] The shading sheet 15 is disposed on the light-emitting surface 13a of the surface light source device 13. The shading sheet 15 is planarly divided into transmissive regions 15a that transmit light from the surface light source device 13 and shading regions 15b that absorb light, corresponding to the pattern of the image to be displayed. FIG. 3 shows a front view of the shading sheet 15 of the display device 10. In this embodiment, as shown in FIG. 3, the transmissive regions 15a and shading regions 15b are provided so that the letter "A" is displayed by the transmitted light, as an example. That is, the transmissive regions 15a are provided in a portion corresponding to the shape of the letter "A," and the shading regions 15b are provided so as to surround the transmissive regions 15a. The transmissive regions 15a may be apertures or may be transparent or colored transparent films. The shading regions 15b may be made of a resin material containing a black pigment or the like. The shading sheet 15 functions as a shading mask that transmits light in a desired pattern. By changing the light-shielding sheet 15, that is, by using a different light-shielding sheet 15, various images can be displayed inside the outer contour of the light-emitting surface 13a.

[0026] As used herein, "transparent" means that the visible light transmittance, specified as the average value of the transmittance at each wavelength, measured using a spectrophotometer (Shimadzu Corporation's "UV-3100PC," compliant with JIS K 0115) within a wavelength range of 380 nm to 780 nm, is 50% or more, preferably 80% or more. "Colored transparent" means that the transmittance of light in a specific wavelength range is intentionally reduced, but the visible light transmittance, specified as the average value of the transmittance at each wavelength, measured using a spectrophotometer within a wavelength range of 380 nm to 780 nm, is 50% or more, preferably 80% or more.

[0027] In the image non-display state, i.e., when the light-emitting surface 13a of the surface light source device 13 is not emitting light, the reflective luminance of the transmissive region 15a is greater than the reflective luminance of the shading region 15b. Therefore, the reflective luminance of the transmissive region 15a is the maximum reflective luminance of the display surface 11, and the reflective luminance of the shading region 15b is the minimum reflective luminance of the display surface 11. In this embodiment, the contrast of the display surface 11, in other words, the ratio C of the maximum reflective luminance to the minimum reflective luminance of the display surface 11 in the image non-display state, may be any value, but can be particularly high. Specifically, the ratio C of the maximum reflective luminance to the minimum reflective luminance of the display surface 11 in the image non-display state can be 1 or more, and even 3 or more. That is, in the image non-display state, there is a difference in appearance between the transmissive region 15a and the shading region 15b of the shading sheet 15. The ratio C of the maximum reflective luminance to the minimum reflective luminance of the display surface 11 in the image non-display state is preferably 15 or less, more preferably 13 or less.

[0028] The display device 10 is not limited to the example shown in Fig. 2, and any display device such as a liquid crystal display, a plasma display, or an organic electroluminescence (EL) display may be used. The display surface 11 of such a display device 10 includes a peripheral region where an image is not displayed and a central region where an image can be displayed. In such a display device 10, for example, the reflective luminance of the peripheral region becomes the minimum reflective luminance of the display surface 11, and the reflective luminance of the central region becomes the maximum reflective luminance of the display surface 11. When the display device 10 is a liquid crystal display or the like, these luminances can be used to define the ratio C of the maximum reflective luminance to the minimum reflective luminance of the display surface 11 in an image-nondisplay state.

[0029] Next, the decorative sheet 20 will be described. The decorative sheet 20 is disposed facing the display surface 11 of the display device 10, and covers at least the entire display surface 11 so that the display surface 11 cannot be directly observed from the outside. In the example shown in Fig. 1, the decorative sheet 20 is a flat plate-shaped member that extends overall in the same direction as the display surface 11 of the display device 10. The thickness of the decorative sheet 20 is, for example, 20 µm or more and 550 µm or less.

[0030] The decorative sheet 20 displays a design and imparts design to the display device 1 with the decorative sheet. As shown in FIG. 2, the decorative sheet 20 has a base portion 21, a plurality of design portions 23, a light-shielding portion 25, and a light-transmitting portion 27. The design portions 23 are laminated on the base portion 21. The light-shielding portion 25 is laminated on the design portions 23. The light-transmitting portion 27 is a portion where the design portions 23 and the light-shielding portion 25 are not formed. Note that, not limited to the example shown in the figure, the light-shielding portion 25 may be omitted.

[0031] The substrate 21 appropriately supports the design portion 23 and the light-shielding portion 25. The substrate 21 is a transparent film-like member. Any material may be used for the substrate 21 as long as it is transparent and can appropriately support the design portion 23 and the light-shielding portion 25. Examples of such materials include polymethyl methacrylate, polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polystyrene, cyclic polyolefin, and ABS (acrylonitrile butadiene styrene copolymer). In addition, in consideration of transparency and appropriate support for the design portion 23 and the light-shielding portion 25, the substrate 21 preferably has a thickness of 10 μm or more and 500 μm or less.

[0032] The design portion 23 forms the design displayed by the decorative sheet 20. More specifically, one design is formed by a plurality of design portions 23. The design portion 23 can form a design such as a figure, pattern, design, color, picture, photograph, character, mark, pictogram, letter, or number. For example, the design portion 23 may form a wood-grain or marble-like design or a geometric pattern as a design that can harmonize with the surrounding environment in which the display device 1 with the decorative sheet is installed.

[0033] The thickness of the design portion 23 is preferably 1 μm or more and 20 μm or less. By making the design portion 23 sufficiently thick, the pattern formed by the design portion 23 can be made thick and clear. Here, the thickness of the design portion 23 refers to the length of the design portion 23 along the normal direction of the base portion 21 that supports the design portion 23. Note that in a cross section perpendicular to the sheet surface of the decorative sheet 20 as shown in FIG. 2, the cross-sectional shape of the design portion 23 is rectangular, but it is not limited to this and may be trapezoidal, for example.

[0034] The light-shielding portion 25 is provided to cover the design portion 23 from the side facing the display device 10. The light-shielding portion 25 has a light-absorbing function to prevent image light from the display device 10 from entering the design portion 23. The light-shielding portion 25 may contain, for example, light-absorbing particles in a binder resin. Examples of light-absorbing particles include black pigments such as carbon black and titanium black. Preferably, the light-shielding portion 25 is provided only in a position facing the design portion 23 so that the light-shielding portion 25 does not prevent the image light emitted from the display device 10 from passing through the transmission portion 27. Furthermore, if the light-shielding portion 25 is sufficiently thick to cover the design portion 23, the image formed by the design portion 23 can be made dark and clear. As a specific example, the thickness of the light-shielding portion 25 is 1 μm or more and 20 μm or less.

[0035] The transmissive portions 27 are provided to transmit image light from the display device 10 to the decorative sheet 20. FIG. 4 shows an enlarged portion of a front view of the decorative sheet 20. As shown in FIGS. 2 and 4, the transmissive portions 27 are portions where the design portions 23 and the light-shielding portions 25 are not formed when the decorative sheet 20 is observed from the front. In order to sufficiently transmit the image light from the display device 10, the ratio of the area occupied by the transmissive portions 27 in the decorative sheet 20 (also referred to as the aperture ratio) is preferably 5% or more, and more preferably 10% or more. In other words, the visible light transmittance T of the decorative sheet 20 is preferably 5% or more, and more preferably 10% or more. On the other hand, in order to make the design displayed by the decorative sheet 20 easier to observe, the ratio of the area occupied by the transmissive portions 27 in the decorative sheet 20 is preferably 30% or less. In other words, the visible light transmittance T of the decorative sheet 20 is preferably 30% or less.

[0036] In the example shown in FIG. 4 , multiple transmissive portions 27 are spaced apart from one another. Design portions 23 are formed between each of the transmissive portions 27. In the illustrated example, each transmissive portion 27 is circular in front view, and the multiple transmissive portions 27 are arranged in a square lattice pattern. When each transmissive portion 27 is circular, diffusion of image light passing through the transmissive portions 27 can be suppressed. Furthermore, when the transmissive portions 27 are arranged in a lattice pattern, particularly a square lattice pattern, the image light from the display device 10 can be uniformly transmitted, making it less likely for unevenness to occur in the image light. However, the transmissive portions 27 are not limited to the illustrated example and may have any shape or be arranged in any position. The diameter of each transmissive portion 27 is, for example, 30 μm or more and 150 μm or less.

[0037] The transmissive portion 27 may be a void such as a hole, as in the example shown in FIG. 2, or may be formed of, for example, a transparent resin. Such a transparent resin can effectively prevent foreign matter such as dust from entering the transmissive portion 27. Furthermore, the transparent resin may be formed so as to cover not only the transmissive portion 27 but also the design portion 23 and the light-shielding portion 25 from the side opposite to the side on which the base portion 21 is provided. Such a transparent resin can form the transmissive portion 27 and also function as a transparent protective film that protects the design portion 23 and the light-shielding portion 25.

[0038] The transparent portion 27 can be formed, for example, by irradiating a laser onto the design portion 23 and the light-shielding portion 25 provided on the entire surface of the base material portion 21 at the position where the transparent portion 27 is to be formed, and removing the design portion 23 and the light-shielding portion 25 at the position irradiated with the laser.

[0039] The decorative sheet 20 is not limited to the illustrated example, and may be a plate-like member having a translucent design as a whole. That is, the decorative sheet 20 may be one that can semi-transmit light at each position and display the design formed at each position.

[0040] It is preferable that the design displayed by the decorative sheet 20 has high brightness. Such a design can provide the display device 1 with a decorative sheet with excellent design. Specifically, the L of the design displayed by the decorative sheet 20 * a * b * Lightness L in the color system * The value L is preferably 30 or more, and more preferably 40 or more.

[0041] Here, the L of the design displayed by the decorative sheet 20 * a * b * Lightness L in the color system * A method for determining the value L of the brightness is explained below. First, a black plate is placed on the back side of the decorative sheet 20, in other words, on the side opposite to the side of the decorative sheet 20 that is observed, that is, on the side where the light-shielding portion 25 is provided relative to the design portion 23. In this state, light is irradiated from the side of the decorative sheet 20 that is observed, and the light reflected by the decorative sheet 20 is measured with, for example, a spectrophotometer ("CM-700d" manufactured by Konica Minolta). This determines the brightness L of the decorative sheet 20 with the black plate placed on the back side. * The value L1 of the black board can be measured under the same conditions. * In other words, the lightness L measured without the decorative sheet in place * The lightness value L of the design displayed by the decorative sheet 20 can be calculated from the measured lightness L1 and the visible light transmittance T of the decorative sheet 20. Specifically, L can be calculated using the following formula: L=L1×100 / (100+T) L<20 L=L1×100 / (100-T) L≧20 According to this method, it is possible to determine the lightness value L of the design displayed by the decorative sheet 20 before the transparent portions 27 are provided on the decorative sheet 20, which is independent of the visible light transmittance T of the decorative sheet 20. Note that if the lightness value varies at each position on the decorative sheet 20 depending on the design displayed by the decorative sheet 20, the lightness value L of the design displayed by the decorative sheet 20 can be determined by, for example, averaging the lightness values ​​determined at 20 randomly selected positions on the decorative sheet 20.

[0042] In order to make the display surface 11 of the display device 10 less observable by the decorative sheet 20, the higher the ratio C of the maximum reflection luminance to the minimum reflection luminance of the display surface 11 in the image non-display state, the lower the visible light transmittance T [%] of the decorative sheet 20 and the L of the design displayed by the decorative sheet 20. * a * b * Lightness L in the color system * Specifically, C, T, and L satisfy the following relational expression (i) when L is 20 or more, and satisfy the following relational expression (ii) when L is less than 20. C≦(0.0003×L-0.0022)×(T-30) 2 +1 (i) C≦(0.0007×L-0.0010)×(T-30) 2 +1 (ii)

[0043] When the design of the decorative sheet 20 has been determined, that is, when the visible light transmittance of the decorative sheet 20 and the design to be displayed by the decorative sheet 20 have been determined, the display device 10 is designed to correspond to the decorative sheet 20. Specifically, the visible light transmittance T [%] of the decorative sheet 20 disposed opposite the display surface 11 and the L of the design to be displayed by the decorative sheet 20 are determined. * a * b * Lightness L in the color system *Based on the value L, a ratio C of the maximum reflection luminance to the minimum reflection luminance of the display surface 11 in the image non-display state is determined. The display device 10 designed in this manner satisfies the above-mentioned relational expression (i) for the decorative sheet 20 displaying the desired design when L is 20 or more, and satisfies the above-mentioned relational expression (ii) for L is less than 20. Therefore, according to this design method, the decorative sheet 20 can make the display surface 11 of the display device 10 less observable.

[0044] When the design to be displayed by the decorative sheet 20 and the design of the display surface 11 of the display device 10 are determined, the visible light transmittance of the decorative sheet 20 is designed in accordance with the design to be displayed by the decorative sheet 20 and the display surface 11 of the display device 10. Specifically, the L of the design to be displayed by the decorative sheet 20 is * a * b * Lightness L in the color system * The visible light transmittance T [%] of the decorative sheet 20 is designed based on the value L of the maximum reflected luminance of the display surface 11 in the image non-display state and the ratio C of the maximum reflected luminance to the minimum reflected luminance of the display surface 11. The decorative sheet 20 designed in this way satisfies the above-mentioned relational expression (i) with respect to the display surface 11 of the display device 10 when L is 20 or more, and satisfies the above-mentioned relational expression (ii) when L is less than 20. Therefore, according to this design method, the decorative sheet 20 can make the display surface 11 of the display device 10 less observable.

[0045] When the visible light transmittance of the decorative sheet 20 and the design of the display surface 11 of the display device 10 are determined, the design displayed by the decorative sheet 20 is designed in accordance with the visible light transmittance of the decorative sheet 20 and the display surface 11 of the display device 10. Specifically, the L of the design displayed by the decorative sheet 20 is determined based on the visible light transmittance T [%] of the decorative sheet 20 and the ratio C of the maximum reflection brightness to the minimum reflection brightness of the display surface 11 in the image non-display state. * a * b * Lightness L in the color system *The value L is designed. The decorative sheet 20 designed in this way satisfies the above-mentioned relational expression (i) with respect to the display surface 11 of the display device 10 when L is 20 or more, and satisfies the above-mentioned relational expression (ii) when L is less than 20. Therefore, according to this design method, the decorative sheet 20 can make the display surface 11 of the display device 10 less observable.

[0046] Furthermore, when the visible light transmittance T of the decorative sheet 20 is low, it is preferable that the lightness value L of the design displayed by the decorative sheet 20 is high so as to impart particularly excellent design to the display device 1 with the decorative sheet. Specifically, when T is 10% or less, it is preferable that C, T, and L satisfy the following relational formula (iii) when L is 20 or more, and satisfy the following relational formula (iv) when L is less than 20, and it is more preferable that when T is 15% or less, satisfy the following relational formula (v) when L is 20 or more, and satisfy the following relational formula (vi) when L is less than 20. C≧(0.0003×L-0.0022)×(T-10) 2 +1 (iii) C≧(0.0007×L-0.0010)×(T-10) 2 +1 (iv) C≧(0.0003×L-0.0022)×(T-15) 2 +1 (v) C≧(0.0007×L-0.0010)×(T-15) 2 +1 (vi)

[0047] Next, the operation of the display device 1 with the decorative sheet of this embodiment will be described.

[0048] When no image is displayed on the display surface 11 of the display device 10, the display device 1 with decorative sheet displays a design formed by the design portion 23 of the decorative sheet 20, as shown in FIG. 5. That is, the display device 1 with decorative sheet can display a design that is intended to be observed. The displayed design prevents the display surface 11 of the display device 10 from being observed by an external observer, allowing the display device 1 with decorative sheet to blend in with the surrounding environment in terms of design. In particular, when the shading portion 25 is provided only in a position facing the design portion 23, the shading portion 25 cannot be observed by an observer, and the shading portion 25 can be prevented from impairing the design of the decorative sheet 20.

[0049] On the other hand, when the display device 10 displays an image on the display surface 11, the image light passes through the base material portion 21 and the transmissive portion 27 of the decorative sheet 20, as shown in FIG. 6. This allows the observer to observe the image displayed on the display surface 11. In the example shown in FIG. 6, the letter "A" is observed as an image on the design displayed by the decorative sheet 20. In this way, the display device 1 with the decorative sheet can display the image that is intended to be observed, and an external observer can observe the image.

[0050] Furthermore, the design portion 23 is covered from the side of the display device 10 by the light-shielding portion 25. Therefore, the light-shielding portion 25 prevents image light from entering the design portion 23. This prevents the image light from passing through the design portion 23 and the design represented by the design portion 23 from being mixed with the image light and observed. In other words, it is possible to effectively prevent degradation of the color reproducibility of the image caused by the absorption of visible light in a specific wavelength range by the design portion 23. Furthermore, when the light-shielding portion 25 is provided only in the area facing the design portion 23, the light-shielding portion 25 prevents the image light from being blocked from passing through the transmission portion 27. In other words, the image light can be efficiently used to display a bright image.

[0051] However, even if a decorative sheet is placed facing the display surface of a display device, the presence of the display surface may be recognized through the decorative sheet even when an image is not displayed. The inventors of the present invention have found that if there are areas on the display surface where the brightness differs significantly, the display surface will be observed. The difference in brightness on the display surface is expressed by the ratio of the maximum reflected luminance to the minimum reflected luminance of the display surface 11 when an image is not displayed. In other words, if the ratio of the maximum reflected luminance to the minimum reflected luminance of the display surface 11 when an image is not displayed is large, the display surface will be observed even if a decorative sheet is placed facing the display surface of the display device.

[0052] In this embodiment, the visible light transmittance T [%] of the decorative sheet 20 and the L of the design displayed by the decorative sheet 20 are * a * b * Lightness L in the color system * Regarding the value L and the ratio C of the maximum reflection brightness to the minimum reflection brightness of the display surface 11 in the image non-display state, when L is 20 or more, the following relational expression (i) is satisfied, and when L is less than 20, the following relational expression (ii) is satisfied. C≦(0.0003×L-0.0022)×(T-30) 2 +1 (i) C≦(0.0007×L-0.0010)×(T-30) 2 +1 (ii) As a result of the study by the present inventors, it has been found that by satisfying the above-mentioned relational expressions (i) and (ii), the display surface can be effectively made difficult to observe. That is, even if there is a difference in brightness of the display surface 11, in other words, even if the ratio C of the maximum reflection luminance to the minimum reflection luminance of the display surface 11 in the image non-display state is large, the visible light transmittance T [%] of the decorative sheet 20 and the L of the design displayed by the decorative sheet 20 can be effectively made difficult to observe. * a * b * Lightness L in the color system * By increasing the value L, the display surface 11 can be made less observable through the decorative sheet 20.

[0053] The visible light transmittance T of the decorative sheet 20 is 30% or less. Since the visible light transmittance T of the decorative sheet 20 is sufficiently low, the design displayed by the decorative sheet 20 is easily observed. In addition, the display surface 11 of the display device 10 is prevented from being observed through the decorative sheet 20.

[0054] For example, in a display device 10 having transmissive regions 15a colored in multiple colors, the ratio C of the maximum reflection luminance to the minimum reflection luminance of the display surface 11 in the image non-display state is 3 or more. Such a display surface 11 can display images with excellent design. However, even if a conventional decorative sheet is placed facing a display surface having a ratio of the maximum reflection luminance to the minimum reflection luminance of 3 or more, the display surface can be observed. On the other hand, according to the display device 1 with a decorative sheet of the present embodiment, by satisfying the above-mentioned relational expressions (i) and (ii), the display surface 11 can be made difficult to observe by the decorative sheet 20, even if the ratio C of the maximum reflection luminance to the minimum reflection luminance of the display surface 11 in the image non-display state is 3 or more. In other words, the display surface 11 can be made difficult to observe by the decorative sheet 20, while still allowing the display of images with excellent design.

[0055] L of the design displayed by the decorative sheet 20 * a * b * Lightness L in the color system * The value L of the design is 30 or more. Such a design can provide an excellent design to the display device 1 with the decorative sheet. However, the L of the design to be displayed * a * b * Lightness L in the color system * Even if a conventional decorative sheet having a value L of 5 or more is placed facing the display surface, the display surface will be observed. On the other hand, according to the display device 1 with a decorative sheet of the present embodiment, the above-mentioned relational expressions (i) and (ii) are satisfied, and therefore the L of the displayed design can be * a * b * Lightness L in the color system *Even if the value L is 5 or more, the display surface 11 can be made difficult to observe by the decorative sheet 20. In other words, the display surface 11 can be made difficult to observe by the decorative sheet 20, while providing the display device 1 with the decorative sheet with excellent design properties.

[0056] In addition, the visible light transmittance T [%] of the decorative sheet 20 and the L of the design displayed by the decorative sheet 20 are * a * b * Lightness L in the color system * Regarding the value L and the ratio C of the maximum reflected brightness to the minimum reflected brightness of the display surface 11 in the image non-display state, when T is 10% or less, the following relational expression (iii) is satisfied when L is 20 or more, and the following relational expression (iv) is satisfied when L is less than 20. C≧(0.0003×L-0.0022)×(T-10) 2 +1 (iii) C≧(0.0007×L-0.0010)×(T-10) 2 +1 (iv) When the visible light transmittance T of the decorative sheet 20 is low, the design displayed by the decorative sheet 20 is easily observed and particularly prominent. When the brightness of the design displayed by the decorative sheet 20 is high, the design is easily observed, and the display device 1 with the decorative sheet can be given particularly excellent design. Specifically, when the visible light transmittance T of the decorative sheet 20 is low, satisfying these relational expressions (iii) and (iv) can give the display device 1 with the decorative sheet particularly excellent design.

[0057] As described above, the display device 1 with a decorative sheet of this embodiment includes the display device 10 having the display surface 11 for displaying an image, and the decorative sheet 20 arranged opposite the display surface 11. The decorative sheet 20 displays a design and transmits visible light, and has a visible light transmittance T [%] of the decorative sheet 20 and a light transmittance L [%] of the design displayed by the decorative sheet 20. * a * b * Lightness L in the color system *Regarding the value L and the ratio C of the maximum reflected luminance to the minimum reflected luminance of the display surface 11 in the image non-display state, when L is 20 or more, the following relational expression (i) is satisfied, and when L is less than 20, the following relational expression (ii) is satisfied. C≦(0.0003×L-0.0022)×(T-30) 2 +1 (i) C≦(0.0007×L-0.0010)×(T-30) 2 +1 (ii) According to such a display device 1 with a decorative sheet, even if the ratio C of the maximum reflection luminance to the minimum reflection luminance of the display surface 11 in the image non-display state is large, the visible light transmittance T [%] of the decorative sheet 20 and the L of the design displayed by the decorative sheet 20 can be * a * b * Lightness L in the color system * By increasing the value L, the display surface 11 can be made difficult to observe through the decorative sheet 20. In other words, even if there is a difference in brightness on the display surface 11, the display surface 11 can be made difficult to observe through the decorative sheet.

[0058] Although one embodiment of the present invention has been described, the aspects of the present invention are not limited to the above-described embodiment. The present invention also includes various modifications to the above-described embodiment that a person skilled in the art can conceive, and various additions, modifications, partial deletions, etc. are possible within the scope of the conceptual idea and intent of the present invention. [Example]

[0059] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0060] As examples and comparative examples, display devices with decorative sheets were prepared, each combining a decorative sheet with different visible light transmittances T (%) and brightness values ​​L of the displayed design with a display device with different ratios C of the maximum reflected brightness to the minimum reflected brightness of the display surface when no image is displayed. The visible light transmittance T (%) of the decorative sheet can be appropriately set, for example, by changing the proportion of the transparent portions provided in the decorative sheet. The brightness value L of the displayed design can be appropriately set, for example, by changing the brightness of the pattern in the design portion of the decorative sheet or the thickness of the design portion. As examples and comparative examples, decorative sheets displaying white designs, gray designs, brown designs, and black designs were prepared. The ratio C of the maximum reflected brightness to the minimum reflected brightness of the display surface of the display device can be appropriately set, for example, by changing the color of a colored transparent film provided in the transparent region of the light-shielding sheet of the display device.

[0061] The display devices with the decorative sheet of each example and each comparative example were visually inspected to see if the display surface was observable. Those in which the display surface was not observable were evaluated as A, and those in which the display surface was observable were evaluated as B.

[0062] For each example and comparative example, the values ​​of T, L, and C and the evaluation results of whether the display surface was observable are shown in Table 1.

[0063] [Table 1]

[0064] From Table 1, it can be seen that the higher the lightness value L of the design displayed by the decorative sheet, the more difficult it is to observe a display surface with a high ratio C of the maximum reflected brightness to the minimum reflected brightness of the display surface in the image-displaying state, even if the visible light transmittance T of the decorative sheet is high.

[0065] Fig. 7 is a graph showing the relationship between the visible light transmittance T of a decorative sheet displaying a white design, specifically when the lightness value L of the design displayed by the decorative sheet is 54.3, and the ratio C of the maximum reflected luminance to the minimum reflected luminance of the display surface in an image-non-display state. In the graph of Fig. 7, black circles indicate cases where the display surface was not observed, and white circles indicate cases where the display surface was observed. Furthermore, since L is 20 or more, C = (0.0003 × L - 0.0022) × (T - 30) 2 +1 As can be seen from Fig. 7, when L is 54.3, the following relational expression (i) is satisfied, and therefore the display surface can be made difficult to observe by the decorative sheet. C≦(0.0003×L-0.0022)×(T-30) 2 +1 (i)

[0066] Fig. 8 is a graph showing the relationship between the visible light transmittance T of a decorative sheet displaying a grayish design, specifically when the lightness value L of the design displayed by the decorative sheet is 33.2, and the ratio C of the maximum reflected luminance to the minimum reflected luminance of the display surface in an image-non-display state. In the graph of Fig. 8, black circles indicate cases where the display surface was not observed, and white circles indicate cases where the display surface was observed. Furthermore, since L is 20 or more, C = (0.0003 × L - 0.0022) × (T - 30) 2 +1 As can be seen from Fig. 8, when L is 33.2, the following relational expression (i) is satisfied, and therefore the display surface can be made difficult to observe by the decorative sheet. C≦(0.0003×L-0.0022)×(T-30) 2 +1 (i)

[0067] Fig. 9 is a graph showing the relationship between the visible light transmittance T of a decorative sheet displaying a brownish design, specifically when the lightness value L of the design displayed by the decorative sheet is 20.8, and the ratio C of the maximum reflected luminance to the minimum reflected luminance of the display surface in an image-non-display state. In the graph of Fig. 9, black circles indicate cases where the display surface was not observed, and white circles indicate cases where the display surface was observed. Furthermore, since L is 20 or more, C = (0.0003 × L - 0.0022) × (T - 30) 2 +1 9, when L is 20.8, the following relational expression (i) is satisfied, and therefore the display surface can be made difficult to observe by the decorative sheet. C≦(0.0003×L-0.0022)×(T-30) 2 +1 (i)

[0068] Fig. 10 is a graph showing the relationship between the visible light transmittance T of a decorative sheet displaying a black design, specifically when the lightness value L of the design displayed by the decorative sheet is 15.1, and the ratio C of the maximum reflected luminance of the display surface to the minimum reflected luminance of the display surface when no image is displayed. In the graph of Fig. 10, black circles indicate cases where the display surface was not observed, and white circles indicate cases where the display surface was observed. Furthermore, since L is less than 20, C = (0.0007 × L - 0.0010) × (T - 30) 2 +1 As can be seen from Fig. 10, when L is 15.1, the following relational expression (ii) is satisfied, and therefore the display surface can be made difficult to observe by the decorative sheet. C≦(0.0007×L-0.0010)×(T-30) 2 +1 (ii)

[0069] From the examples and comparative examples described above, the visible light transmittance T [%] of the decorative sheet and the L of the design displayed by the decorative sheet can be * a * b* Lightness L in the color system * Regarding the value L and the ratio C of the maximum reflected brightness to the minimum reflected brightness of the display surface in the image non-display state, it is understood that when L is 20 or more, the relational expression (i) is satisfied, and when L is less than 20, the relational expression (ii) is satisfied, so that even if there is a difference in brightness on the display surface, the display surface can be made difficult to observe by the decorative sheet. [Explanation of symbols]

[0070] 1 Display device with decorative sheet 10 Display device 11 Display surface 13 Surface light source device 13a Light-emitting surface 15 Blackout sheet 15a Transparent area 15b Shading area 20 Decorative sheet 21 Base material part 23 Design Department 25 Light blocking section 27 Transparent part

Claims

1. a display device having a display surface for displaying an image; a decorative sheet disposed facing the display surface so as to cover the entire display surface; the decorative sheet displays a design and transmits visible light; The visible light transmittance T of the decorative sheet is 22% or less, the value L of lightness L* in the L*a*b* color system of the design displayed by the decorative sheet is less than 20; a ratio C of a maximum reflection luminance to a minimum reflection luminance of the display surface in an image non-display state is 2.5 or less; The visible light transmittance T [%] of the decorative sheet, the L of the design displayed by the decorative sheet ＊ a ＊ b ＊ Lightness L in the color system ＊ and a ratio C of the maximum reflection luminance to the minimum reflection luminance of the display surface in an image non-display state, satisfying the following relational expression (ii): ≦(). ２ ・・・( ) )

2. A method for designing a decorative sheet to be placed facing a display surface on a display device so as to cover the entire display surface on which an image is displayed, comprising: the decorative sheet displays a design and transmits visible light; the value L of lightness L* in the L*a*b* color system of the design displayed by the decorative sheet is less than 20; a ratio C of a maximum reflection luminance to a minimum reflection luminance of the display surface in an image non-display state is 2.5 or less; A method for designing a decorative sheet, wherein the visible light transmittance T [%] of the decorative sheet is determined to be 22% or less and to satisfy the following relational expression (ii), which includes the value L of the lightness L* in the L*a*b* color system of the design displayed by the decorative sheet and the ratio C of the maximum reflected brightness to the minimum reflected brightness of the display surface in an image-non-display state. C≦(0.0007×L-0.0010)×(T-30) 2 +1...(ii)

3. A method for designing a decorative sheet that is disposed facing a display surface on a display device so as to cover the entire display surface on which an image is displayed, comprising: the decorative sheet displays a design and transmits visible light; The visible light transmittance T of the decorative sheet is 22% or less, a ratio C of a maximum reflection luminance to a minimum reflection luminance of the display surface in an image non-display state is 2.5 or less; A method for designing a decorative sheet, wherein the value L of lightness L* in the L*a*b* color system of the design displayed by the decorative sheet is determined to be less than 20 and to satisfy the following relational expression (ii) including the visible light transmittance T [%] of the decorative sheet and the ratio C of the maximum reflected brightness to the minimum reflected brightness of the display surface in an image-nondisplay state. C≦(0.0007×L-0.0010)×(T-30) 2 +1...(ii)

4. A method for designing a display device having a display surface for displaying an image, comprising: a decorative sheet is disposed facing the display surface so as to cover the entire display surface; the decorative sheet displays a design and transmits visible light; the value L of lightness L* in the L*a*b* color system of the design displayed by the decorative sheet is less than 20; The visible light transmittance T of the decorative sheet is 22% or less, A method for designing a display device, wherein the ratio C of the maximum reflection brightness to the minimum reflection brightness of the display surface in an image non-display state is determined to be 2.5 or less, and to satisfy the following relational expression (ii) including the visible light transmittance T [%] of the decorative sheet and the value L of the lightness L* in the L*a*b* color system of the design displayed by the decorative sheet. C≦(0.0007×L-0.0010)×(T-30) 2 +1...(ii)

Images