Display device

Abstract

Display device (10) with an uneven structure (11) with an uneven surface (11s) which serves as an incident surface onto which light is incident, wherein the uneven surface (11s) comprises a section in which raised surfaces (11a) and depression surfaces (11b) alternate in one arrangement direction, each raised surface (11a) has the form of a strip extending in a direction of extension perpendicular to the arrangement direction, Each raised surface (11a) tapers towards an uppermost section (11c) in a thickness direction of the uneven structure (11), each depression surface (11b) has the form of a strip extending in the direction of expansion, Each depression surface (11b) tapers towards a bottom section (11d) in the thickness direction of the uneven structure (11), the raised surfaces (11a) and the depression surfaces (11b) are arranged with a period that limits the reflection of light incident on the uneven surface (11s) in a front view direction of the uneven surface (11s), and diffractes the incident light to emit diffracted light in an oblique view direction of the uneven surface (11s), and the uneven structure (11) has an absorption property for light incident on the uneven structure (11), wherein a side from which light falls onto the uneven surface (11s) is a viewing side, a point at a predetermined position on the observation side is a first fixed point (OB1), a point at a position different from the first fixed point on the observation side is a second fixed point (OB2), the arrangement direction is a first arrangement direction, the direction of expansion is a first direction of expansion, the survey surfaces are the first survey surfaces (31a), the depression surfaces are the first depression surfaces (31b), a direction that intersects the first arrangement direction, is a second arrangement direction, the uneven surface (11s) is divided into a multitude of image elements (30), the image elements comprise (30): Image elements with a first arrangement (31) comprising the first raised surfaces (31a) and the first recessed surfaces (31b) alternating in the first arrangement direction, and emitting diffracted light in the direction of the first fixed point (OB1), and Image elements with a second arrangement (33) comprising second raised surfaces (33a) and second recessed surfaces (33b) alternating in the second arrangement direction, and emitting diffracted light in the direction of the second fixed point (OB2), every second elevation surface (33a) has the form of a strip extending in the second direction of extension, which is perpendicular to the second direction of arrangement, every second elevation surface (33a) tapers towards an uppermost section (33c) in the thickness direction of the uneven structure (11), every second depression surface (33b) has the form of a strip which extends in the second direction of extension perpendicular to the second arrangement direction, every second depression surface (33b) tapers towards a bottom section (33d) in the thickness direction of the uneven structure (11), and the second raised surfaces (33a) and the second recessed surfaces (33b) are arranged with a period that limits the reflection of light incident on the image elements with the second arrangement (33) in a front view direction of the image elements with the second arrangement (33), and diffractes the light incident on the image elements with the second arrangement (33) to emit diffracted light in an oblique view direction of the image elements with the second arrangement (33), wherein the uneven surface (11) includes a first area (11s1) that includes more than one of the image elements (30), and a second area (11s2) that includes more than one of the image elements (30), of the image elements with the first arrangement (31) and the image elements with the second arrangement (33), the first area (11s1) includes at least one or more of the image elements with the first arrangement (31), of the image elements with the first arrangement (31) and the image elements with the second arrangement (33), the second area (11s2) includes at least one or more of the image elements with the second arrangement (33), a ratio of a sum of areas of the image elements with the first arrangement (31) to an area of ​​the first region (11s1) differs from a ratio of a sum of areas of the image elements with the first arrangement (31) to an area of ​​the second region (11s2), and a ratio of a sum of areas of the image elements with the second arrangement (33) to the area of ​​the first region (11s1) differs from a ratio of a sum of areas of the image elements with the second arrangement (33) to the area of ​​the second region (11s2), characterized in that the uneven surface (11s) is arranged such that the brightness of an image displayed by the first area (11s1) in the front view direction and the brightness of an image displayed by the second area (11s2) in the front view direction are essentially the same.

Description

TECHNICAL AREA

[0001] The present invention relates to a display device that can be used to prevent the counterfeiting of an item. STATE OF THE ART

[0002] Securities such as gift certificates and checks, cards such as credit cards, bank cards and identity cards, as well as identification documents such as passports and driving licenses, include, in order to prevent counterfeiting of these items, display devices that produce visual effects different from those presented by a printed object formed by ink.

[0003] Such a display device can comprise a multitude of microstructures of protrusions and depressions arranged at regular intervals in a first direction and a second direction perpendicular to the first direction. These intervals are less than or equal to the shortest wavelength of visible light. The microstructures prevent reflection of the light incident on the display device, allowing the display device to show a black color when viewed from the front. Additionally, the periodic microstructures exhibit an iridescent color created by diffracted light when viewed from an oblique angle (see, for example, patent documents 1 and 2). DOCUMENTS OF THE STATE OF TECHNOLOGY Patent documents Patent document 1: Printed document JP 4 420 138 B2 Patent document 2: Publication JP 4 315 334 B2

[0004] Furthermore, publication EP 2 264 488 A1 discloses a marking material and a marked lot, publication US 2010 / 0 085 642 A1 discloses a bending device, and publication JP 5 740 811 B2 discloses a display body that can achieve a better anti-counterfeiting effect. INVENTION SUMMARY Problem statement of the invention

[0005] The display of a black color is possible in a front view of the display device, even if the amount of light incident on the display device is low. In contrast, the display of an iridescent color is less likely to be perceived in an oblique view of the display device if the amount of light incident on the display device is low. In the display device described above, to further enhance the counterfeit prevention effect, it is preferred that the display in the front view differs significantly from the display in an oblique direction, even if only a small amount of light incident on the display device. This requires a higher brightness of the diffracted light.

[0006] Furthermore, since the microstructures are arranged at regular intervals in the first and second directions, they are essentially arranged at regular intervals in other directions, including directions at angles of approximately 27° and 45° to the first direction. As a result, the diffracted light emitted by the display device is visually perceived over a wide range of angles. To distinguish the display device, for example, from a printed object formed with ink, the display device must exhibit higher directivity in the direction in which the diffracted light is emitted.

[0007] Such a requirement applies not only to a display device used to limit the counterfeiting of objects, but also to a display device used to decorate an object and to a display device considered on account of its own quality.

[0008] It is an object of the present invention to provide a display device that increases the brightness of diffracted light while increasing the directivity in the direction in which the diffracted light is emitted. Solution to the technical problem

[0009] To solve the aforementioned problem, a display device according to claim 1 is provided according to a first embodiment. According to a further embodiment, a display device according to claim 2 is provided.

[0010] In the display device, the raised and recessed surfaces alternate in the arrangement direction and extend in the dimension direction. This allows the uneven surface to emit diffracted light in the plane extending in both the arrangement and thickness directions of the uneven structure, thereby increasing the directivity of the diffracted light in the emission direction. Since the surfaces for emitting the diffracted light are continuous in the dimension direction, the brightness of the diffracted light emitted in the plane extending in both the arrangement and thickness directions of the uneven structure is correspondingly increased compared to a structure where the raised surfaces are arranged at regular intervals in both the dimension and arrangement directions. EFFECTS OF THE INVENTION

[0011] The present invention increases the luminance of diffracted light while increasing the directivity in the direction in which the diffracted light is emitted. BRIEF DESCRIPTION OF THE DRAWING Fig. Figure 1 shows a partially perspective view showing part of the structure of the uneven surface of a display device of a first embodiment. Fig. Figure 2 shows a partial sectional view, showing part of the cross-sectional structure of the display device in the YZ plane. Fig. Figure 3 shows a schematic view of the state in which a diffraction grating with a period larger than the shortest wavelength of visible light emits diffracted first-order light. Fig. Figure 4 is a schematic view of the state in which diffraction gratings with a smaller period than the shortest wavelength of visible light emit first-order diffracted light. Fig. Figure 5 is a representation to illustrate the function of the uneven surface in an oblique view. Fig. Figure 6 is a representation illustrating the function of the uneven surface in a front view. Fig. Figure 7 is a perspective view showing the structure of a conventional display device. Fig. Figure 8 is a top view showing the planar structure of a display device of a second embodiment. Fig. Figure 9 is an enlarged top view showing part of the planar structure of a first area in an uneven surface. Fig. Figure 10 is an enlarged top view showing part of the planar structure of a second area in the uneven surface. Fig. Figure 11 is a partially perspectival view showing part of the structure of the first uneven surface of a first image element. Fig. Figure 12 is a partially perspectival view showing part of the structure of the second uneven surface of a second image element. Fig. Figure 13 is a partially perspectival view showing part of the structure of the third uneven surface of a third image element. Fig. Figure 14 is a partially perspectival view showing part of the structure of the fourth uneven surface of a fourth image element. Fig. Figure 15 is a representation illustrating the function of the display device in a voluntarily modified description page for review in the national phase (fair copy) of an oblique view. Fig. Figure 16 is a representation illustrating the function of the display device in an oblique view. Fig. Figure 17 is a representation illustrating the function of the display device in a front view. Fig. Figure 18 is a cross-sectional view showing the cross-sectional structure of an example of a display body. Fig. Figure 19 is a section view showing the cross-sectional structure of an example of a display body. Fig. Figure 20 is a representation showing the relationship between the dose of electron beams applied to polymethyl acrylate and the amount of resolution of polymethyl acrylate. Fig. Figure 21 is a partial sectional view showing part of the cross-sectional structure of an original plate formed by a first method and measured using an atomic force microscope. Fig. Figure 22 is a partial sectional view showing part of the cross-sectional structure of an original plate formed by a second process and measured using an atomic force microscope. Fig. Figure 23 is a top view showing the planar structure of an example of an object with a display body. Fig. 24 is a sectional view showing the cross-sectional structure of the object along a line II in Fig. 23 shows. Fig. Figure 25 is a top view showing the planar structure of a display body of a third embodiment. Fig. Figure 26 is an enlarged top view showing part of the planar structure of a first area in an uneven surface. Fig. Figure 27 is an enlarged top view showing part of the planar structure of a second area in the uneven surface. Fig. Figure 28 is an enlarged top view showing part of the planar structure of a third area in the uneven surface. Fig. Figure 29 is an enlarged top view showing part of the planar structure of a fourth area in the uneven surface. Fig. Figure 30 is a representation showing the function of the display device in oblique view. Fig. Figure 31 is a representation illustrating the function of the display device in oblique view. Fig. Figure 32 is a representation illustrating the function of the display device in a top view. DESCRIPTION OF THE EXAMPLES [First example]

[0012] A first embodiment of a display device according to the invention is described with reference to the Fig. 1 to 7 are described below. The structure of the display device is described below, followed by its function. [Structure of the display device]

[0013] The structure of the display device is described below with reference to Fig. 1 described.

[0014] According to Fig. 1 comprises a display device 10 and an uneven structure 11 with an uneven surface 11s, which serves as an incident surface onto which light falls. The uneven surface 11s comprises raised surfaces 11a and recessed surfaces 11b, which alternate in a Y-direction, which is a direction and an example of an arrangement direction.

[0015] Each raised surface 11a has the form of a strip extending in the X-direction, which is perpendicular to the Y-direction and serves as an example of a direction of extension. The raised surface 11a tapers towards the uppermost section 11c in the Z-direction, which is perpendicular to both the X- and Y-directions and extends in the thickness direction of the uneven structure 11. The length of each raised surface 11a in the X-direction is considerably greater than its length in the Y-direction. Each raised surface 11a has a shape substantially identical to the other raised surfaces 11a.

[0016] Each depression surface 11b has the form of a strip extending in the X-direction. The depression surface 11b tapers towards the lowest section 11d in the Z-direction. The length of each depression surface 11b in the X-direction is considerably longer than the length in the Y-direction. The distance in the Z-direction between the uppermost sections 11c of the raised surface 11a and the lowest sections 11d of the depression surfaces 11b is a height H of the uneven surface 11s.

[0017] The uppermost sections 11c are arranged with a predetermined spacing P in the Y-direction. That is, the spacing P is the distance between two uppermost sections 11c that are adjacent to each other in the Y-direction. A raised surface 11a and two recessed surfaces 11b, located on opposite sides of the raised surface 11a in the Y-direction, form a structure with a maximum width W, which is the maximum value of the width in the Y-direction. The maximum width W is equal to the spacing P.

[0018] In the uneven surface 11s, the length of a repeating unit consisting of a raised surface 11a and a depression surface 11b in the Y-direction is called a period d. In the uneven surface 11s, the period d is equal to the distance measure P. However, the period d need not be equal to the distance measure P. For example, the uneven surface 11s can have distance measures P with a first distance measure and a second distance measure that differs from the first, and the first and second distance measures can alternate in the Y-direction. In this case, a raised surface 11a and a depression surface 11b that are adjacent to each other in the Y-direction form a set of uneven surfaces, and a repeating unit is formed by two sets of uneven surfaces that are adjacent to each other in the Y-direction. The period d is then the sum of the first distance measure and the second distance measure.

[0019] In another example of the uneven surface 11s, uneven surfaces with a first height equal to the distance between the uppermost sections 11c and the lowermost sections 11d can alternate with uneven surfaces with a second height other than the first height equal to the distance between the uppermost sections 11c and the lowermost sections 11d in the Y-direction, while the uppermost sections 11c are arranged with a predetermined spacing P. In this structure, the repeating unit is formed by two sets of uneven surfaces adjacent to each other in the Y-direction, and the period d is twice as long as the spacing P.

[0020] The uneven surface 11s is configured such that it limits the reflection of the light incident on the uneven surface 11s in a front-view direction, which is the direction from which the uneven surface 11s is viewed from the front. Additionally, the uneven surface 11s is configured such that the light incident on the uneven surface 11s is emitted as diffracted light in the oblique-view direction of the uneven surface 11s.

[0021] This means that in the uneven surface 11s, the raised surfaces 11a and the depression surfaces 11b are arranged with a period that limits the reflection of light incident on the uneven surface 11s in the frontal direction (the direction in which the uneven surface 11s is viewed from the front) and diffractes the incident light to emit diffracted light in the oblique direction of the uneven surface 11s. The uneven structure 11 has the property of absorbing incident light.

[0022] The spacing P of the uppermost sections 11c of the raised surfaces 11a is between 200 nm and 500 nm inclusive, and is preferably less than or equal to the shortest wavelength of visible light, for example 400 nm or less. The raised surfaces 11a are arranged regularly in the Y-direction such that the distance between adjacent uppermost sections 11c is the spacing P. The spacing P of the lowermost sections 11d of the recessed surfaces 11b is between 200 nm and 500 nm inclusive, and is preferably less than or equal to the shortest wavelength of visible light, for example 400 nm or less. The recessed surfaces 11b are arranged regularly in the Y-direction such that the distance between adjacent lowermost sections 11d is the spacing P.In the uneven surface 11s, the raised surfaces 11a, which have an essentially identical shape, and the depression surfaces 11b, which have an essentially identical shape, are arranged regularly, allowing the uneven surface 11s to act as a diffraction grating.

[0023] The height H of the uneven surface 11s is preferably greater than or equal to half the distance P between the raised surfaces 11a. If the height H of the uneven surface 11s is greater than or equal to half the distance P, the uneven surface 11s is able to limit the reflection of light incident in the front view direction of the display device 10, that is, light incident in the Z direction. Additionally, the height H of the uneven surface 11s is preferably greater than the distance P, since such a structure limits reflection more effectively than a structure where the height H of the uneven surface 11s is less than or equal to the distance P. In other words, the height H of the uneven surface 11s is preferably greater than or equal to 200 nm, and even more preferably greater than or equal to 500 nm.

[0024] Furthermore, the height H of the uneven surface 11s is preferably less than or equal to 750 nm in order to form the uneven surface 11s with a precision that enables the uneven surface 11s to act suitable for limiting reflection and emission of diffracted light.

[0025] Each raised surface 11a is a tapered surface that tapers towards the uppermost section 11c, and each depression surface 11b is a tapered surface that tapers towards the lowermost section 11d. The cross-sectional shape in the YZ plane of the structure formed by the uneven surface 11s comprises a variety of triangular shapes. The vertices of the triangles exhibit curvature, and the cross-sectional shape in the YZ plane is uniform in the X direction.

[0026] Each of the shapes defined in the cross-section along the YZ-plane of the structure formed by the uneven surface 11s can be the cross-sectional shape of a plane passing through the axis of one of the shapes listed below, and the cross-sectional shape in the YZ-plane is uniform in the X-direction. That is, each shape in the cross-sectional shape in the YZ-plane can be the cross-sectional shape of a plane passing through the axis of a half-spindle shape, a conical shape, a pyramidal shape, a truncated conical shape, or a truncated pyramidal shape. Furthermore, in the structure formed by the uneven surface 11s, the cross-sectional shape in the YZ-plane is uniform in the X-direction. Each of the raised surfaces 11a and the depression surfaces 11b can have a stepped surface with steps in the Z-direction.

[0027] According to Fig. 2. In the uneven surface 11s, the curvature of the uppermost sections 11c of the raised surfaces 11a is equal to the curvature of the lowermost sections 11d of the depression surfaces 11b. Additionally, the curvature of the uppermost sections 11c and the curvature of the lowermost sections 11d are greater than the curvatures of any other sections in the uneven surface 11s besides the uppermost sections 11c and the lowermost sections 11d.

[0028] In the cross-section of the raised surfaces 11a along the YZ plane, the tangents to the uppermost sections 11c form an angle of inclination θ with the tangents to sections other than the uppermost sections 11c. The angle of inclination θ is preferably between 50° and inclusive of 80° to limit reflection of light in the Z direction.

[0029] The gradient S in the Z-direction of the surfaces, which connects the uppermost sections 11c with the lowermost sections 11d in the uneven surface 11s, is defined by the following expression (1). S=|log10(Wb / Wt)|−1

[0030] In expression (1), the base width Wb is the width of the structure formed by two depression surfaces 11b adjacent to each other in the Y-direction and the raised surface 11a connected to the two depression surfaces 11b. The base width Wb is measured at a position that is 0.1 x H closer to the uppermost sections 11c than the lowermost sections 11d in the Z-direction. The uppermost width Wt is the width of the structure measured at a position that is 0.9 x H closer to the uppermost section 11c than the lowermost sections 11d in the Z-direction. The gradient S is preferably less than 25.The uneven surface 11s with a gradient S of less than 25 allows the flat surfaces forming the uppermost sections 11c of the raised surfaces 11a and the flat surfaces forming the lowermost sections 11d of the depression surfaces 11b to be suitable for limiting the reflection of light on the uneven surface 11s. [Function of the display device]

[0031] With reference to the Fig. The function of the display device 10 is described below in sections 3 to 7 according to the descriptions of the diffraction grating. [Diffraction grating]

[0032] The diffraction grating emits diffracted light with a high luminance in a predetermined direction with respect to the direction of propagation of the incident light. The emission angle β of the diffracted m-order light (m = 0, ±1, ±2, ...) is given by the following expression (2) if the light propagates in the plane orthogonal to the longitudinal direction of the trenches of the diffraction grating. d=mλ / (sinα−sinβ)

[0033] In expression (2), d is the period of the diffraction grating, m is the diffraction order, and λ is the wavelength of the incident and diffracted light. Additionally, α is the emission angle of the transmitted light or of regular reflected light, which is zero-order diffracted light. That is, the absolute value of α is equal to the angle of incidence of the illumination light. If the diffraction grating is a reflective grating, the angle of incidence of the illumination light and the emission direction of the regular reflected light are symmetrical with respect to the front view direction, which is the direction from which the diffraction grating is viewed from the front.

[0034] If the diffraction grating is a reflective grating, the angle α is greater than or equal to 0° and less than 90°. If the angle of the front view direction, which is 0°, is the limiting value, and the illumination light is oblique to the diffraction grating, the angular range encompassing the emission direction of the regular reflected light is the positive angular range, while the angular range encompassing the incident direction of the illumination light is the negative angular range. If the emission direction of the diffracted light and the emission direction of the regular reflected light are within the same angular range, that is, within the positive angular range, then the angle β is a positive value. If the emission direction of the diffracted light and the incident direction of the illumination light are within the same angular range, that is, within the negative angular range, then the angle β is a negative value.

[0035] If the observer views the diffraction grating in the frontal direction of the diffracted light emitted by the grating, only the diffracted light with an emission angle of 0° forms an image perceptible to the observer. If the period d is greater than the wavelength λ, there exist wavelengths λ and angles of incidence α that satisfy expression (2). Consequently, an observer perceives the diffracted light that has the wavelengths λ satisfying expression (2).

[0036] If, on the other hand, the period d is smaller than the wavelength λ, there is no angle of incidence α that satisfies expression (2), so that the observer who sees the diffraction grating in the front view direction cannot perceive diffracted light.

[0037] This means that a diffraction grating with a small period d, that is, a diffraction grating with a period d smaller than the wavelength λ, emits no diffracted light in the front direction. A diffraction grating with a period d approximately the same as the wavelength λ emits diffracted light that is barely perceptible in the front direction.

[0038] Regarding the Fig. 3 and Fig. Section 4 below describes the diffraction grating in detail. Fig. Figure 3 shows a diffraction grating with a period d that is larger than the shortest wavelength of visible light, and Fig. Figure 4 shows a diffraction grating with a period d that is smaller than the shortest wavelength of visible light. For the purpose of a simpler description and representation, we show... Fig. 3 and Fig. 4 only red diffracted light, green diffracted light and blue diffracted light as first order diffracted light emitted by the diffraction gratings.

[0039] According to Fig. 3. The diffraction grating DG has a period d that is greater than the shortest wavelength of visible light, for example, 400 nm. An illumination light IL, emitted by a light source LS, is white light consisting of light rays of different wavelengths. If the illumination light IL strikes the diffraction grating DG obliquely, the diffraction grating DG emits an emission light RL, which is a regular reflected light or zero-order diffracted light.

[0040] The diffraction grating DG also emits red diffracted light DLr, green diffracted light DLg, and blue diffracted light DLb as first-order diffracted light, which is created by scattering the illumination light IL. The emission angle βr of the red diffracted light DLr, the emission angle βg of the green diffracted light DLg, and the emission angle βb of the blue diffracted light DLb are positive values ​​in the positive angular range with respect to the front view direction DLV.

[0041] The diffraction grating DG according to Fig. 4 has a period d that is greater than half the shortest wavelength of visible light and less than the shortest wavelength of visible light, that is, greater than 200 nm and less than 400 nm.

[0042] If the illumination light IL falls obliquely on the diffraction grating DG, the diffraction grating DG emits in a similar way to the diffraction grating DG according to Fig. Three diffracted light types are red (DLr), green (DLg), and blue (DLb). However, the emission angle βr of red (DLr), the emission angle βg of green (DLg), and the emission angle βb of blue (DLb) are negative values.

[0043] For example, if the angle of incidence α of the illumination light IL is 50°, and the period d is 330 nm, the diffraction grating DG diffracts the illumination light IL and emits green light with a wavelength of 540 nm as green diffracted light DLg, which is a first-order diffracted light, at an emission angle βg of -60°. [Display device]

[0044] The function of the display device 10 is described below with reference to the Fig. 5 to 7 described.

[0045] According to Fig. In the uneven surface 11s of the display device 10, a plurality of top sections 11c with a predetermined period d in the Y-direction are arranged, that is, with a predetermined spacing P, and the period d is between 200 nm and inclusive of 500 nm. Each of the raised surfaces 11a and the recessed surfaces 11b has the form of a strip extending in the X-direction.

[0046] If white illumination IL, emitted by the light source LS, is obliquely incident on the uneven surface 11s, the uneven surface 11s emits a diffracted light DL in the YZ plane YZ, which encompasses the front view direction DLV. The diffracted light DL is emitted in the direction of the side of the YZ plane YZ that is opposite the emission light RL with respect to the front view direction DLV. Alternatively, a diffracted light DL is emitted to a barely perceptible extent in the direction of the YZ plane YZ RL that is the same as the emission light with respect to the front view direction DLV, while a diffracted light DL is emitted to a readily perceptible extent in the direction opposite the emission light RL with respect to the front view direction DLV.

[0047] The period d of the uneven surface 11s is preferably between 200 nm and inclusive of 400 nm, such that a reflection of the diffracted light DL in the direction of the side YZ-plane YZ is limited, which is the same as the emission light RL with respect to the front view direction DLV.

[0048] The display device 10 with the uneven surface 11s thus emits diffracted light DL in the YZ plane YZ, which is perpendicular to the direction in which the raised surfaces 11a extend. This increases the directivity of the diffracted light DL emitted by the display device 10. Additionally, the diffracted light DL is emitted through the uneven surface 11s formed by the raised surfaces 11a and the recessed surfaces 11b, which extend in the X direction. This increases the intensity of the diffracted light in the emission direction compared to a structure where the surfaces are arranged separately for diffracted light emission in the X direction.

[0049] If an observer observes an object, in particular a light-absorbing object, which emits reflected light or scattered light of low luminance, the observer usually adjusts the positional relationship between the object and the light source with respect to the observer's viewpoint in such a way that the regular reflected light emitted by the object is perceptible.

[0050] As described above, the display device 10 emits diffracted light to the side opposite the emission light RL, which includes the regular reflected light with respect to the front view direction DLV. An observer who does not know the direction in which the diffracted light DL is emitted is therefore unlikely to perceive the diffracted light emitted by the display device 10 when viewing the display device 10. As such, it is unlikely that the observer would recognize that the display device 10 has a diffracted light emission function.

[0051] With a display device that emits diffracted light to the same side as the regular reflected light with respect to the front view direction, it is likely that the observer of this display device will perceive the diffracted light emitted by the display device, even if the observer does not know that the display device has the effect of emitting diffracted light.

[0052] According to Fig. In the uneven surface 11s, the raised surfaces 11a taper towards the uppermost sections 11c, and the recessed surfaces 11b taper towards the lowermost sections 11d. The uppermost sections 11c and the lowermost sections 11d are arranged at a spacing P between 200 nm and 500 nm inclusive. Therefore, if the display device 10 is viewed from the side from which the light is incident on the uneven surface 11s of the display device 10, the reflectivity of the regular reflected light emitted by the display device 10 is low, regardless of the viewing angle, according to the principle described below.

[0053] Light is reflected at the interface where the refractive index varies continuously. If the areas of flat surfaces in the uppermost sections 11c of the raised surfaces 11a and the lowermost sections 11d of the depression surfaces 11b are small, these sections reflect small amounts of light.

[0054] If the distance P of the raised surface 11a is approximately less than or equal to the resolution limit wavelength, the refractive index at a horizontal plane perpendicular to the depth direction of the raised surfaces 11a or the direction of incidence of light is determined by the ratio between the uneven structure 11 and the air surrounding the uneven structure 11 in the horizontal plane. Since the distances between the raised and recessed areas are smaller than the resolution limit, the refractive index is considered to be uniform in the horizontal direction.

[0055] If the shape of the raised surfaces 11a changes substantially continuously in the depth direction of the raised surfaces 11a, the refractive index at the horizontal plane changes uniformly and continuously in accordance with the depth of the raised surfaces 11a. This reduces the influence of the interface between the refractive indices, thereby causing reflection of light in the inclined sections.

[0056] The uneven structure 11 has the property of absorbing incident light. That is, the uneven structure 11 includes a section that absorbs light transmitted through the uneven surface 11s, which is the incident surface and is located on the side of the uneven surface 11s opposite the incident side. Additionally, the uneven structure has a transmittance that transmits light to the absorption section. In other words, the uneven structure 11 includes a section that converts the light transmitted through the uneven surface 11s into thermal energy within the uneven structure 11, and a transmittance that transmits light to the section that converts light into thermal energy.

[0057] The light-absorbing section of the uneven structure 11 can exhibit the effect of reflecting light, as long as the uneven structure 11 absorbs the light incident on the absorption section through a multiple reflection effect.

[0058] According to the above description, the display device 10 emits diffracted light to an extent easily perceptible to the observer on the side opposite the regular reflected light with respect to the front view direction DLV, wherein the display device 10 essentially emits no diffracted light in the front view direction.

[0059] Accordingly, the display device 10 shows an image in, for example, black or gray when viewed from the front. A black image is displayed if white light is emitted in the front direction and the reflectivity of all wavelengths of light from 400 nm to 700 nm is less than or equal to 10%. The reflectivity is determined by measuring the intensity of the regular reflected light. A gray image is displayed if white light is emitted in the front direction and the reflectivity of all wavelengths of light from 200 nm to 700 nm is greater than 10% and less than 25%. The reflectivity is determined by measuring the intensity of the regular reflected light.

[0060] In order for the display device 10 to show an image in black, the uneven surface 11s preferably has a greater height H, which reduces the rate of change of the refractive index in the Z-direction in the uneven surface 11s. A smaller height H of the uneven surface 11s increases the reflectivity of the uneven surface 11s, and thus the brightness of the image displayed by the display device 10. As a result, the display device 10 shows an image in gray.

[0061] For example, if the distance P is 500 nm and the height H of the uneven surface is greater than or equal to 250 nm, the display device 10 shows an image in gray. A greater height H of the uneven surface 11s reduces the brightness of the image displayed by the display device 10. If the height H of the uneven surface 11s is greater than or equal to 500 nm, the display device shows an image that is essentially black.

[0062] On the other hand, if the height H of the uneven surface 11s exceeds 750 nm, that is, if the aspect ratio of the uneven surface 11s is greater than 1.5, any further increase in the height H of the uneven surface 11s hardly changes the brightness of the image displayed by the display device 10. Furthermore, if the aspect ratio exceeds 1.5, the uneven structure 11 is more difficult to manufacture with high precision than an uneven structure with an aspect ratio of less than or equal to 1.5.

[0063] For this reason, the height H of the uneven surface 11s is preferably between 200 nm and inclusive of 750 nm.

[0064] Fig. Figure 7 shows a conventional display device 20 with an uneven structure 21, which has an uneven surface 21s that serves as a light-incidence surface of the uneven structure 21. The uneven surface 21s comprises a plurality of raised surfaces 21a that are regularly arranged in the X and Y directions.

[0065] The regular arrangement of the raised surfaces 21a in the X and Y directions enables the display device 20 to emit diffracted light. However, the raised surfaces 21a are arranged separately in the X and Y directions. Compared to a structure like the display device 10 with raised surfaces 11a extending in the X direction, the surface area available for emitting diffracted light in the YZ plane is therefore small, which reduces the luminance of the diffracted light emitted in the YZ plane.

[0066] Furthermore, since the raised surfaces 21a are regularly arranged in the X and Y directions, they are also essentially regularly arranged in other directions, such as a direction at approximately 27° to the X direction and a direction at approximately 45° to the Y direction. As a result, diffracted light emitted by the display device 20 can be perceived over a larger angular range than that for the display device 10.

[0067] The display device of the first embodiment has the following advantage.

[0068] (1) The raised surfaces 11a and the depression surfaces 11b alternate in the Y-direction and extend in the X-direction. This allows the uneven surface 11s to emit diffracted light in the YZ-plane. The directivity of the emission direction of the diffracted light is thus increased. The raised surfaces 11a and the depression surfaces 11b in the uneven surface 11s extend in the X-direction. Since the surfaces for the emission of the diffracted light are continuous in the X-direction, the luminance of the diffracted light emitted in the YZ-plane is correspondingly increased compared to a structure in which the raised surfaces are arranged at regular intervals in the X- and Y-directions. [Variations of the first embodiment]

[0069] The first embodiment described above can be modified as follows.

[0070] The uppermost sections 11c and the lowermost sections 11d can be flat surfaces. In the first embodiment, the uppermost sections 11c and the lowermost sections 11d are curved surfaces. As such, the distance P between the uppermost sections 11c is equal to the maximum width W. However, if the uppermost sections 11c and the lowermost sections 11d are flat surfaces, the distance P between the uppermost sections 11c is greater than the maximum width W.

[0071] The heights H of the uneven surface 11s can have different values. If, as described above, the uneven surface 11s comprises a section with a first height and a section with a second height different from the first, these sections differ from each other in their effect of limiting the reflection of incident light. In order for the entire uneven surface 11s to produce the same degree of reflection limitation of the incident light, that is, to limit a deviation in the brightness of the image displayed by the display device 10 in the front-view direction of the display device 10, it is preferred that the height of the uneven surface 11s be substantially uniform over the entire uneven surface 11s. [Second embodiment]

[0072] A second embodiment of a display device according to the invention is described below with reference to the Fig. Sections 8 to 24 describe the display device of the second embodiment. It comprises components equivalent to those of the display device of the first embodiment. The same reference numerals are assigned to components that are identical to the corresponding components of the first embodiment. Such components are not described in detail. The second embodiment is an example where the distance measure and the period of the uneven surface are the same value.

[0073] The following description outlines the structure of the display device, the function of the display device, the method for manufacturing the display device, and the structure of an object that uses the display device, in that order. [Structure of the display device]

[0074] With reference to Fig. The structure of the display device is described below in sections 8 to 14.

[0075] According to Fig. 8 comprises a display device 10 and an uneven surface 11s, which is a light-incidence surface. The uneven surface 11s comprises a first region 11s1 and a second region 11s2. The first region 11s1 and the second region 11s2 each comprise a plurality of raised surfaces and a plurality of depressed surfaces.

[0076] The side from which light falls on the uneven surface 11s is the observation side, and a point at a predetermined position on the observation side is a fixed point. The luminance of the diffracted light emitted from the first region 11s1 towards the fixed point differs from the luminance of the diffracted light emitted from the second region 11s2 towards the fixed point, such that the uneven surface 11s is arranged such that the image shown by the first region 11s1 is visually distinguishable from the image shown by the second region 11s2 towards the fixed point. The luminance of the diffracted light is a first property, and the first property is one of the properties of the diffracted light.

[0077] The display device 10 projects an image to the viewer, who observes the display device 10 from the fixed point on the observation side. The image is formed by the difference between the luminance of the diffracted light emitted by the first region 11s1 and the luminance of the diffracted light emitted by the second region 11s2. In contrast to a structure where one type of diffracted light is emitted from the entire uneven surface 11s, the image displayed in the oblique viewing direction of the uneven surface 11s, which is one of the images displayed by the uneven surface 11s, is therefore complex.

[0078] The uneven surface 11s of the display device 10 is arranged such that the brightness of the image displayed by the first area 11s1 in the front view direction and the brightness of the image displayed by the second area 11s2 in the front view direction are essentially the same in the front view direction of the display device 10.

[0079] The image displayed by the display device 10 in the front view direction of the display device 10 is perceived as one image, and the difference between the luminance of the light diffracted by the first area 11s1 and the luminance of the light diffracted by the second area 11s2 is hidden from the observer who views the display device 10 in the front view direction of the display device 10.

[0080] According to Fig. In section 9, the first area 11s1 is subdivided into a multitude of image elements 30. Each image element 30 is square when viewed in the Z direction. The image elements 30 are arranged in the X and Y directions. In other words, the image elements 30 are arranged in a square grid.

[0081] When viewed from the Z-direction, the length of one side of each image element 30 has a maximum width Wp, which is between 3 µm and inclusive of 300 µm. A maximum width Wp less than or equal to 300 µm prevents the observer from seeing the image elements 30 with the naked eye when viewing the display device 10. A maximum width Wp greater than or equal to 3 µm allows the density of the arranged raised and recessed surfaces in the uneven surface of the image elements 30, as well as the precision of the shapes of the uneven surfaces, to be increased such that the image elements 30 act suitablely as a diffraction grating and limit the reflection of light.

[0082] When viewed from the Z-direction, each image element 30 can have a round shape, a polygonal shape other than a square shape such as a triangular shape, or a tetragonal shape other than a square shape. Even if the image elements 30 have such shapes, the maximum width of the image elements 30, which is the length of the longest of the sides defining each image element 30, is still preferably between 3 µm and inclusive of 300 µm.

[0083] Each image element 30 is part of the uneven surface 11s and comprises a multitude of raised surfaces. That is, each image element 30 also comprises a multitude of depressed surfaces. The raised and depressed surfaces alternate within the image elements 30.

[0084] The image elements 30 that form the first area 11s1 comprise first image elements 31, second image elements 32, and third image elements 33. A first image element 31, a second image element 32, and a third image element 33 differ from each other in the direction in which the raised and depression surfaces extend, and / or in the period d. The period d is the length of the repeating unit that forms the uneven surface in the direction in which the raised and depression surfaces alternate.

[0085] The image elements 30 that form the first area 11s1 comprise first image elements 31, second image elements 32 and third image elements 33 in the ratio defined by the following expression (3). [First image element]:[Second image element]:[Third image element]=2:1:1

[0086] The entirety of each image element 30 is an uneven surface in which raised and recessed surfaces alternate. However, a part of each image element 30 can be a flat surface as long as the ratio of the sum of the areas of the uneven surfaces in the first image elements 31, the sum of the areas of the uneven surfaces in the second image elements 32, and the sum of the areas of the uneven surfaces in the third image elements 33 satisfies expression (3).

[0087] According to Fig. The second region 11s2 is subdivided into a multitude of image elements 30 in the same way as the first region 11s1. Each image element 30 is square when viewed from the Z-direction. The image elements 30 are arranged in the X-direction and the Y-direction. In other words, the image elements 30 are arranged in a square grid.

[0088] When viewed from the Z-direction, the maximum width Wp of each of the image elements 30 is between 3 µm and inclusive of 300 µm, as is the case for the first region 11s1. When viewed in the Z-direction, each image element 30 can have a round shape or a polygonal shape other than a square shape, as is the case for the first region 11s1.

[0089] Each image element 30 is part of the uneven surface 11s and comprises a multitude of raised surfaces. That is, each image element 30 also comprises a multitude of depressed surfaces. The raised and depressed surfaces alternate within the image element 30.

[0090] The image elements 30 that form the second region 11s2 comprise first image elements 31, third image elements 33, and fourth image elements 34. The first image elements 31 are structurally identical to the first image elements 31 of the first region 11s1, and the third image elements 33 are structurally identical to the third image elements 33 of the first region 11s1.

[0091] The fourth image elements 34 differ from the first image elements 31, the second image elements 32 and the third image elements 33 in the direction in which the raised surfaces and the depression surfaces extend, and / or in the period d.

[0092] The image elements 30, which form the second area 11s2, comprise first image elements 31, third image elements 33 and fourth image elements 34 in the ratio defined by the following expression (4). [First image element]:[Third image element]:[Fourth image element]=1:2:1

[0093] Each entire image element 30 is an uneven surface in which raised and recessed surfaces alternate. However, a portion of each image element can be a flat surface. A portion of each image element can be a flat surface as long as the ratio of the sum of the areas of the uneven surfaces in the first image elements 31, the sum of the areas of the uneven surfaces in the third image elements 33, and the sum of the areas of the uneven surface in the fourth image elements 34 satisfies expression (4).

[0094] According to Fig. 11 comprises a first image element 31, which is an example of an image element with a first arrangement and also an example of an image element with a first period, and a first uneven surface 31s, which forms part of the uneven surface 11s. The first uneven surface 31s comprises first raised surfaces 31a and first indented surfaces 31b, which alternate in the Y-direction, which is an example of a first arrangement direction. The first raised surfaces 31a extend in the X-direction, which is an example of a first extension direction, and the first indented surfaces 31b also extend in the X-direction.

[0095] Each first raised surface 31a comprises a first top section 31c, and the first top sections 31c are arranged with a first spacing P1 in the Y-direction. In the first uneven surface 31s, a first raised surface 31a and a first depression surface 31b, adjacent to each other in the Y-direction, form a repeating unit, and the length of the repeating unit in the Y-direction is a first period d1. In the first uneven surface 31s, the maximum width described above is the first maximum width W1, which is equal to the first period d1. As is the case with the period d described above, the first period d1 is a predetermined value between 200 nm and 500 nm inclusive, and preferably less than or equal to 400 nm.In the first uneven surface 31s, the distance between the uppermost sections 31c of the first raised surfaces 31a and the first lowest sections 31d of the first depression surface 31b is a first height H1.

[0096] In each first image element 31, the first raised surfaces 31a and the first recessed surfaces 31b extend in the X-direction such that the first image element 31 emits diffracted light towards a first fixed point in the YZ-plane. The first fixed point is located at a predetermined position on the observation side. The diffracted light emitted by the first image element 31 towards the first fixed point has a wavelength determined by the first period d1.

[0097] According to Fig. 12 comprises a second image element 32, which is an example of an image element with a first arrangement and also an example of an image element with a second period, a second uneven surface 32s that forms part of the uneven surface 11s. The second uneven surface 32s comprises second raised surfaces 32a and second indented surfaces 32b that alternate in the Y direction. The second raised surfaces 32a and the second indented surfaces 32b extend in the X direction.

[0098] Every second raised surface 32a has the form of a strip extending in the X direction and tapering in the Z direction towards the second uppermost section 32c. Every second depression surface 32b has the form of a strip extending in the X direction and tapering in the Z direction towards the second lowermost section 32b.

[0099] In a similar manner to the first image element 31, the second raised surfaces 32a and the second recessed surfaces 32b of the second image element 32 are arranged with a period that limits the reflection of the light incident on the second image element 32 in the front view direction of the second image element 32, and allows the second image element 32 to diffract the light incident on the second image element 32 and emit diffracted light in the oblique view direction of the second image element 32.

[0100] Every second raised surface 32a comprises a second top section 32c, and the second top sections 32c are arranged with a second spacing P2 in the Y-direction. In the second uneven surface 32s, a second raised surface 32a and a second depression surface 32b, adjacent to each other in the Y-direction, form a repeating unit, and the length of the repeating unit in the Y-direction is a second period d2. The maximum width of the second uneven surface 32s is a second maximum width W2, which is equal to the second period d2. The second period d2 is smaller than the first period d1 and is a predetermined value between 200 nm and 500 nm inclusive, and preferably less than or equal to 400 nm.

[0101] In the second uneven surface 32s, the distance between the second uppermost sections 32c of the second raised surface 32a and the second lowest sections 32d of the second depression surfaces 32b is a second height H2, which is equal to the first height H1.

[0102] The second elevation surfaces 32a of the second image elements 32 extend in the X-direction, such that the second image elements 32 emit diffracted light towards the first fixed point in the same way as the first image elements 31. However, the second period d2 of the second image elements 32 differs from the first period d1 of the first image elements 31, so that the wavelength of the diffracted light, in other words, the color of the diffracted light emitted by the second image element 32 towards the first fixed point, differs from the wavelength of the diffracted light or the color of the diffracted light emitted by the first image element 31 towards the first fixed point.

[0103] According to Fig. 13 comprises a third image element 33, which is an example of an image element with a second arrangement and also an example of an image element with a first period, a third uneven surface 33s that forms part of the uneven surface 11s. The third uneven surface 33s comprises third raised surfaces 33a and third indented surfaces 33b that alternate in the X-direction, which is an example of a second arrangement direction. The third raised surfaces 33a extend in the Y-direction, which is an example of a second extension direction, and the third indented surfaces 33b also extend in the Y-direction.

[0104] Every third surface 33a has the shape of a strip extending in the Y direction and tapering in the Z direction towards the third uppermost section 33c. Every third depression surface 33b has the shape of a strip extending in the Y direction and tapering in the Z direction towards the third lowermost section 33d.

[0105] In the same way as the first image element 31, the third raised surfaces 33a and the third recessed surfaces 33b of the third image element 33 are arranged with a period that limits the reflection of the light incident on the third image element 33 in the front view direction of the third image element 33, and allows the third image element to diffract the light incident on the third image element 33 and emit diffracted light in the oblique view direction of the third image element 33.

[0106] Every third raised surface 33a includes a third top section 33c, and the third top sections 33c are spaced a third distance apart P3 in the X-direction. In the third uneven surface 33s, a third raised surface 33a and a third depression surface 33b, adjacent to each other in the X-direction, form a repeating unit, and the length of the repeating unit in the X-direction is a third period d3. The maximum width in the third uneven surface 33s is a third maximum width W3, which is equal to the third period d3. The third period d3 is equal to the first period d1.

[0107] In the third uneven surface 33s, the distance between the third uppermost sections 33c of the third raised surfaces 33a and the third lowest sections 33d of the third depression surfaces 33b is a third height H3, which is equal to the first height H1.

[0108] In the third image element 33, the third elevation surfaces 33a extend in the Y-direction such that, unlike the first image element 31 and the second image element 32, the third image element 33 emits diffracted light towards a second fixed point in an XZ-plane, which differs from the first fixed point in its position on the observation side. Furthermore, the third period d3 of the third image element 33 is equal to the first period d1.

[0109] If the third image element 33 is viewed from the second fixed point, the relative position of the third image element 33 to the second fixed point is a third image element position, and the relative position of the light source to the second fixed point is a third light source position. If the first image element 31 is viewed from the first fixed point, the relative position of the first image element 31 to the first fixed point is a first image element position, and the relative position of the light source to the first fixed point is a first light source position.If the third image element position is the same as the first image element position, and the third light source position is the same as the first light source position, the third image element 33 emits the diffracted light in the direction of the second fixed point, which has the same wavelength and therefore the same color as the diffracted light emitted by the first image element 31 in the direction of the first fixed point.

[0110] According to Fig. 14 comprises a fourth image element 34, which is an example of an image element with a second arrangement and also an example of an image element with a second period, a fourth uneven surface 34s, which forms part of the uneven surface 11s. The fourth uneven surface 34s comprises fourth raised surfaces 34a and fourth indented surfaces 34b, which alternate in the X direction. The fourth raised surfaces 34a and the fourth indented surfaces 34b extend in the Y direction.

[0111] Every fourth raised surface 34a, like the third raised surfaces 33a, has the form of a strip extending in the Y-direction and tapering in the Z-direction towards the fourth uppermost section 34c. Similarly, like the third depression surfaces 33b, every fourth depression surface 34b has the form of a strip extending in the Y-direction and tapering in the Z-direction towards the fourth lowermost sections 34d.

[0112] As with the first image element 31, the fourth raised surfaces 34a and the fourth recessed surfaces 34b of the fourth image element 34 are arranged with the period that limits the reflection of the light incident on the fourth image element 34 in the front view direction of the fourth image element 34, and allows the fourth image element 34 to diffract the light incident on the fourth image element 34 and emit diffracted light in the oblique view direction of the fourth image element 34.

[0113] Every fourth raised surface 34a comprises a fourth top section 34c, and the fourth top sections 34c are spaced a fourth distance apart P4 in the X-direction. In the fourth uneven surface 34s, a fourth raised surface 34a and a fourth depression surface 34b, adjacent to each other in the X-direction, form a repeating unit, and the length of the repeating unit in the X-direction is a fourth period d4. The maximum width in the fourth uneven surface 34s is a fourth maximum width W4, which is equal to the fourth period d4. The fourth period d4 is equal to the second period d2.

[0114] In the fourth uneven surface 34s, the distance between the fourth uppermost sections 34c of the fourth raised surface 34a and the fourth lowest sections 34d of the fourth depression surface 34b is a fourth height H4, which is equal to the first height H1.

[0115] The fourth elevation surfaces 34a of the fourth image element 34 extend in the Y direction, such that the fourth image element 34 emits diffracted light towards the second fixed point in a similar manner to the third image element 33. On the other hand, the fourth period d4 of the fourth image element 34 is equal to the second period d2.

[0116] If the fourth image element 34 is viewed from the second fixed point, the relative position of the fourth image element 34 to the second fixed point is a fourth image element position, and the relative position of the light source to the second fixed point is a fourth light source position. If the second image element 32 is viewed from the first fixed point, the relative position of the second image element 32 to the first fixed point is a second image element position, and the relative position of the light source to the first fixed point is a second light source position.If the fourth image element position is the same as the second image element position, and the fourth light source position is the same as the second light source position, the fourth image element 34 emits the diffracted light in the direction of the second fixed point, which has the same wavelength and thus the same color as the diffracted light emitted by the second image element 32 in the direction of the first fixed point. [Function of the display device]

[0117] The function of the display device 10 is described below with reference to the Fig. Described in sections 15 to 17. Fig. Figure 15 schematically shows an image formed by the diffracted light emitted by the display device 10 in the direction of the first fixed point. Fig. Figure 16 schematically shows an image formed by the diffracted light emitted by the display device 10 in the direction of the second fixed point. Fig. Figure 17 schematically shows an image displayed by the display device 10 in the front view direction.

[0118] According to Fig. 15 A light source LS can emit an illumination light IL from a predetermined surface in the YZ plane YZ towards the display device 10 in an oblique direction, and an observer can view the display device 10 from a first fixed point OB1, which is a point in the YZ plane YZ on the side opposite the emission light RL with respect to the front view direction DLV of the display device 10.

[0119] Here, only the first image elements 31 and the second image elements 32 are the image elements 30 that emit a diffracted light DL in the direction of the first fixed point OB1.

[0120] According to the above description, the first region 11s1 comprises first image elements 31 and second image elements 32, which are image elements 30 with raised surfaces extending in the X-direction, and third image elements 33, which are image elements 30 with raised surfaces extending in the Y-direction. The ratio between the image elements 30 with raised surfaces extending in the X-direction and the image elements 30 with raised surfaces extending in the Y-direction is 3:1 in the first region 11s1.

[0121] The second region 11s2 comprises first image elements 31, which are image elements 30 with raised surfaces extending in the X-direction, and third image elements 33 and fourth image elements 34, which are image elements 30 with raised surfaces extending in the Y-direction. The ratio between the image elements 30 with raised surfaces extending in the X-direction and the image elements 30 with raised surfaces extending in the Y-direction is 1:3 in the second region 11s2.

[0122] That is, the first area 11s1 differs from the second area 11s2 in the ratio of the sum of the areas of the image elements with the first arrangement to the area of ​​the area, as well as in the ratio of the sum of the areas of the image elements with the second arrangement to the area of ​​the area.

[0123] The luminance of the diffracted light DL emitted from the first region 11s1 towards the first fixed point OB1 is therefore higher than the luminance of the diffracted light DL emitted from the second region 11s2 towards the first fixed point OB1.

[0124] Additionally, the first region 11s1 comprises the image elements 30, which emit diffracted light DL towards the first fixed point OB1, as well as the first image elements 31 and the second image elements 32, while the second region 11s2 comprises only the first image elements 31. That is, the first region 11s1 differs from the second region 11s2 in the ratio between the sum of the areas of the first image elements 31 and the sum of the areas of the second image elements 32.

[0125] As such, the diffracted light DL emitted from the first area 11s1 towards the first fixed point OB1 comprises two types of diffracted light DL with different wavelengths, so that the image displayed by the first area 11s1 is perceived as an image of a first color in which two different colors are mixed.

[0126] In contrast, the diffracted light DL emitted from the second region 11s2 towards the first fixed point OB1 has the same wavelength as one of the two types of diffracted light DL emitted from the first region 11s1 towards the first fixed point OB1. As such, the image displayed by the second region 11s2 is perceived as an image of a second color, different from the color of the image displayed by the first region 11s1.

[0127] This means that the uneven surface 11s1 is configured such that the color of the diffracted light DL emitted from the first region 11s1 towards the first fixed point OB1 differs from the color of the diffracted light DL emitted from the second region 11s2 towards the first fixed point OB1. The color of the diffracted light DL is a second property, and this second property is one of the properties of the diffracted light DL.

[0128] The first region 11s1 and the second region 11s2 differ from each other in luminance and in the color of the displayed image towards the first fixed point OB1, so that the image displayed by the first region 11s1 is visually distinguishable from the image displayed by the second region 11s2 at the first fixed point OB1. The color of the light emitted by the first region 11s1 differs from the color of the light emitted by the second region 11s2. This allows for a clear demarcation between the first region 11s1 and the second region 11s2 compared to a structure where the two regions differ only in the luminance of the emitted light.

[0129] According to Fig. 16 The light source LS can emit an illumination light IL from a predetermined surface in the XZ-plane XZ towards the display device 10 in an oblique direction, and the observer can view the display device 10 from a second fixed point OB2, which is a point in the XZ-plane XZ on the side opposite the emission light RL with respect to the front view direction DLV of the display device 10.

[0130] In this process, of the image elements 30, only the third image elements 33 and the fourth image elements 34 emit a diffracted light DL in the direction of the second fixed point OB2.

[0131] As a result, the luminance of the diffracted light DL emitted from the second region 11s2 towards the second fixed point OB2 is higher than the luminance of the diffracted light DL emitted from the first region 11s1 towards the second fixed point OB2.

[0132] Additionally, the first region 11s1, as the image elements 30 that emit diffracted light DL towards the second fixed point OB2, comprises only the third image elements 33, while the second region 11s2 comprises the third image elements 33 and the fourth image elements 34. That is, the first region 11s1 differs from the second region 11s2 in the ratio between the sum of the areas of the third image elements 33 and the sum of the areas of the fourth image elements 34.

[0133] As such, the diffracted light DE emitted from the second region 11s2 towards the second fixed point OB2 comprises two types of diffracted light DL with different wavelengths, so that the image displayed by the second region 11s2 is perceived as a color image in which two different colors are mixed. The color of the image displayed by the second region 11s2 is the first color, and is the same as the color of the image displayed by the first region 11s1 if the first region 11s1 is viewed from the first fixed point OB1.

[0134] In contrast, the diffracted light DL emitted from the first region 11s1 towards the second fixed point OB2 has the same wavelength as one of the two types of diffracted light DL emitted from the second region 11s2 towards the second fixed point OB2. As such, the image displayed by the first region 11s1 is perceived as an image of a color different from the color of the image displayed by the second region 11s2. The color of the image displayed by the first region 11s1 is the second color, and when viewing the second region 11s2 from the first fixed point OB1, it is the same color as the image displayed by the second region 11s2.

[0135] The first area 11s1 and the second area 11s2 differ from each other in the luminance and in the color of the image displayed towards the second fixed point OB2, so that the image displayed by the first area 11s1 can be visually distinguished from the image displayed by the second area 11s2 at the second fixed point OB2.

[0136] The display device 10 enables the area emitting diffracted light DL with a higher luminance to switch between the first area 11s1 and the second area 11s2 when the viewing point of the display device 10 is switched between the first fixed point OB1 and the second fixed point OB2. In other words, the display device 10 is capable of displaying an image towards the second fixed point OB2 in which the ratio between the luminance of the first area 11s1 and the luminance of the second area 11s2 is inverted from the image displayed towards the first fixed point OB1.

[0137] Furthermore, the display device 10 enables the colors of the diffracted light emitted by the first area 11s1 and the second area 11s2 to be switched between the first color and the second color if the viewing point of the display device 10 is switched between the first fixed point OB1 and the second fixed point OB2.

[0138] According to Fig. 17 The display device 10 shows an image with reduced brightness, such as an image in black, in the direction of a third fixed point OB3, which is located in the front view direction DLV.

[0139] The first height H1 of the first uneven surface 31s, the second height H2 of the second uneven surface 32s, the third height H3 of the third uneven surface 33s, and the fourth height H4 of the fourth uneven surface 34s are all the same. This limits a variance in the brightness of the image displayed by the picture elements 30 in the front view direction DLV, which would otherwise occur if the heights of the uneven surfaces of the picture elements 30 differed.

[0140] According to the above description, in the first region 11s1 the ratio between the image elements 30, whose period d of the uneven surface is the first period d1 or the third period d3, and the image elements 30, whose period d of the uneven surface is the second period d2, is 3:1.

[0141] The ratio between the image elements 30, whose period d of the uneven surface is the first period d1 or the third period d3, and the image elements 30, whose period d of the uneven surface is the fourth period d4, is in the second region 11s2 3:1.

[0142] Each pixel 30 is so small that the pixels 30 are indistinguishable from one another when the display device 10 is viewed with the naked eye. Thus, in both the first area 11s1 and the second area 11s2, the average brightness of the pixels 30 in each area is perceived as the brightness of the area.

[0143] Additionally, the first region 11s1 and the second region 11s2 have the same ratio between the image elements 30 whose period d is the first period d1 or the third period d3, and the image elements 30 whose period d is the second period d2 or the fourth period d4. Consequently, the brightness of the image displayed by the first region 11s1 is equal to the brightness of the image displayed by the second region 11s2.

[0144] If the display device 10 is viewed from the third fixed point OB3, this structure allows the image displayed by the display device 10 to be perceived as a single image. If the display device 10 is viewed along the front view direction DLV, the image of the display device 10 formed by the first area 11s1 and the second area 11s2 is hidden from the viewer.

[0145] The following is with reference to the Fig. 18 and Fig. 19 describes a structure that can be used as the display devices 10 described above, that is, the display devices 10 of the first embodiment and the second embodiment. In the Fig. 18 and Fig. For illustrative purposes, 19 the same reference numerals are assigned to those components which are the same as the corresponding components of the first embodiment.

[0146] According to Fig. Figure 18 comprises an example of the display device 10 comprising an uneven structural layer 41, which is an example of an uneven structure, and a metal layer 42, which covers an uneven surface 11s of the uneven structural layer 41. That is, the composite of the uneven structural layer 41 and the metal layer 42 forms an example of an uneven structure. Of the surfaces of the uneven structural layer 41 of the display device 10, the surface opposite the surface in contact with the metal layer 42 is a flat surface, which is the front surface of the display device 10. The surface of the metal layer 42 opposite the surface in contact with the uneven structural layer 41 is the back surface of the display device 10.

[0147] In the display device 10 thus configured, the surface of the metal layer 42, which is in contact with the uneven surface 11s, which is an example of an uneven surface of a transmission side, is also an example of an uneven surface 42s serving as a light incidence surface. In the uneven surface 42s of the metal layer 42, the sections that are in contact with the raised surfaces 11a of the uneven structural layer 41 are raised surfaces 42 of the metal layer 42, and the sections that are in contact with the recessed surfaces 11b of the uneven structural layer 41 are the recessed surfaces 42b of the metal layer 42.In the uneven structure 42s of the metal layer 42, the sections that are in contact with the uppermost sections 11c of the uneven structure layer 41 are the uppermost sections 42c of the metal layer 42, and the sections that are in contact with the lowermost sections 11d of the uneven structure layer 41 are the lowermost sections 42d of the metal layer 42.

[0148] The interface between the uneven structural layer 41 and the metal layer 42, that is, both the uneven structural layer 41 and the metal layer 42, comprises the uneven structures in which raised and recessed surfaces are arranged with a period that limits the reflection of light. Accordingly, if light falls on the front of the display device 10, it is unlikely that the light will be reflected at the interface, so the light is transmitted to the metal layer 42. The light penetrating the metal layer 42 is absorbed by the metal layer 42, that is, converted into thermal energy within the metal layer 42.

[0149] Furthermore, the interface between the uneven structural layer 41 and the metal layer 42—that is, both the uneven structural layer 41 and the metal layer 42—comprises the uneven structures in which the raised surfaces 42a and the depression surfaces 42b are arranged with a period that emits diffracted light in a direction oblique to the body 10. Additionally, the uneven surface 11s of the uneven structural layer 41 is in contact with the metal layer 42. This increases the light reflectivity of the uneven surface 11s, thereby facilitating the emission of diffracted light from the uneven surface 11s.

[0150] If the display device 10 comprises the uneven structural layer 41 and the metal layer 42, the uneven surface 11s of the uneven structural layer 41 is not exposed to the exterior of the display device 10, thereby reducing damage to the uneven surface 11s compared to a structure without the metal layer 42. This allows the display device 10 to display an image with higher visibility.

[0151] The uneven structural layer 41 is a light-transmitting layer and can be formed from any transparent material. For example, the uneven structural layer 41 is formed by a step of applying resin to a flat component to form a coating, and a step of curing the resin, which forms the coating, while the coating is pressed with a die. Alternatively, the uneven structural layer 41 can be formed by a step of applying resin to a plate with depressions to form the uneven structural layer 41, and a step of curing the applied resin. The uneven structural layer 41 can be formed from, for example, thermoplastic resin, thermosetting resin, or light-curing resin.

[0152] The metal layer 42 can be made of aluminum, silver, gold, and alloys of these metals. The metal layer 42 can be formed to cover the uneven surface 11s by gas-phase deposition, such as vacuum deposition or sputtering. The metal layer 42 exhibits absorption properties for light incident on the uneven structure.

[0153] For example, in the formation of the display device 10, the uneven structural layer 41 is formed first, and subsequently the metal layer 42 is formed to cover the uneven surface 11s of the uneven structural layer 41.

[0154] Alternatively, the following method for forming the display device 10 can be used if the metal layer 42 comprises an uneven surface that serves as a surface with protrusions for forming the uneven structural layer 41, and has a flat surface on the opposite side of the uneven surface. That is, the display device 10 can be produced by forming a metal layer 42 by physical or chemical etching of a metal layer formed by the vapor deposition described above and by applying a resin to form the uneven structural layer 41 on the uneven surface 42s of the metal layer 42.

[0155] Of the surfaces of the uneven structural layer 41 of the display device 10, the surface opposite the surface in contact with the metal layer 42 can be the back surface of the display device 10, and the surface of the metal layer 42 opposite the surface in contact with the uneven structural layer 41 can be the front surface of the display device 10. In this case, the uneven surface serving as a light-incident surface of the display device 10 is the surface of the metal layer 42 opposite the surface in contact with the uneven structural layer 41, and the metal layer 42 and the uneven structural layer 41 form an example of an uneven structure.

[0156] That is, the display device 10 comprises the uneven structure, which in turn comprises the uneven structural layer 41 and the metal layer 42. The uneven structural layer 41 comprises the uneven surface 11s, which is an example of an uneven surface of a transmission side. The metal layer 42 covers the uneven surface 11s and comprises the surface that is in contact with the uneven surface 11s and the surface that is opposite the surface in contact with the uneven surface 11s. One of the two surfaces is the uneven surface that serves as a light-incidence surface.

[0157] Each raised surface has the form of a strip extending in the direction of extension perpendicular to the arrangement direction, and each raised surface tapers towards the uppermost section in the thickness direction of the uneven structure. Each depression surface has the form of a strip extending in the direction of extension, and each depression surface tapers towards the lowermost section in the thickness direction of the uneven structure. In the uneven surface, the raised and depression surfaces are arranged with a period that limits the reflection of light incident on the uneven surface in a frontal view direction and diffractes the incident light to emit diffracted light in the oblique view direction of the uneven surface.

[0158] According to Fig. Figure 19 is an example of a display device 10, a laminate consisting of a light-transmitting layer 40 and a metal layer 42. The surface of the light-transmitting layer 40 opposite the surface in contact with the metal layer 42 is the front of the display device 10, and the surface of the metal layer 42 opposite the light-transmitting layer 40 is the back surface of the display device 10.

[0159] The light-transmitting layer 40 is a laminate consisting of a support layer 43 and an uneven structural layer 41, and the uneven structural layer 41 is embedded between the support layer 43 and the metal layer 42. The surface of the uneven structural layer 41, which is in contact with the metal layer 42, is an uneven surface 11s that serves as a light-incidence surface.

[0160] That is, the laminate of the uneven structural layer 41 and the metal layer 42 is an example of an uneven structure. In the same way as above with reference to Fig. The display device 10 described in 18 is the surface of the metal layer 42 which is in contact with the uneven surface 11s, as well as an example of an uneven surface 42s serving as a light incidence surface. In the uneven surface 42s of the metal layer 42, the sections that are in contact with the raised surfaces 11a of the uneven structural layer 41 are raised surfaces 42a of the metal layer 42, and the sections that are in contact with the depression surfaces 11b of the uneven structural layer 41 are depression surfaces 42b of the metal layer 42. In the uneven surface 42s of the metal layer 42, the sections that are in contact with the uppermost sections 11c of the uneven structural layer 41 are uppermost sections 42c of the metal layer 42, and the sections that are in contact with the lowermost sections 11d of the uneven structural layer 41 are lowermost sections 42d of the metal layer 42.

[0161] The light-transmitting layer 40 can have a multilayer structure consisting of three or more layers, including the support layer 43, the uneven structure layer 41, and one or more additional layers. In this case, the additional layer can be located between the support layer 43 and the uneven structure layer 41, or on the surface of the support layer 43 opposite the uneven structure layer 41.

[0162] The support layer 43 is a thin film or a layer that can be handled independently. The support layer 43 can be made of a light-transmitting resin such as polycarbonate or polyester.

[0163] The uneven structural layer 41 is formed, for example, by an application step of resin onto the support layer 43 to form a coating, and a curing step of the resin to form the coating while the coating is pressed with a die. The uneven structural layer 41 can, for example, be made of a thermoplastic resin, a thermosetting resin, or a light-curing resin in the same manner as described above with reference to Fig. The uneven structural layer 41 described in 18 must be formed.

[0164] The metal layer 42 is formed on the entire uneven surface 11s of the uneven structural layer 41. However, the metal layer 42 can also be formed on a portion of the uneven surface 11s of the uneven structural layer 41. This also occurs in the above with reference to Fig. 18 described structure application.

[0165] The metal layer 42 can be made of one of the metals and alloys described above. The uneven surface 11s of the uneven structural layer 41 is in contact with the metal layer 42. This increases the light reflectivity of the uneven surface 11s, thereby facilitating the emission of diffracted light from the uneven surface 11s.

[0166] The metal layer 42 can be formed by gas-phase deposition, such as vacuum deposition or sputtering. If the metal layer 42 is formed on a portion of the uneven surface 11s, the metal layer 42 is formed by the following method.

[0167] This means that the metal layer 42 is formed by a formation step of a metal layer over the entire uneven surface 11s of the uneven structural layer 41 using vapor deposition and by a structuring step of the layer. The structuring step of the layer can employ a method for dissolving part of the layer with an alkaline or acidic chemical agent, or a method for detaching part of the layer using an adhesive that adheres to the layer with an adhesive force greater than the cohesion between the layer and the uneven structural layer 41. The metal layer 42, which covers part of the uneven surface 11s, can also be formed by vapor deposition using a mask.

[0168] The surface of the light-transmitting layer 40, which is opposite the surface in contact with the metal layer 42, can be the back surface, and the surface of the metal layer 42, which is opposite the surface in contact with the uneven structural layer 41, can be the front surface. In this case, the uneven surface, which serves as a light-incidence surface of the display device 10, is the surface of the metal layer 42 opposite the surface in contact with the uneven structural layer 41, and the metal layer 42 and the uneven structural layer 41 form an example of an uneven structure.

[0169] In addition to the light-transmitting layer 40 and the metal layer 42, the display device 10 may also include other layers such as an adhesion layer, a cohesion layer and a plastic layer.

[0170] If the display device 10 comprises an adhesive layer and / or a cohesive layer, the adhesive layer and the cohesive layer can be the layer covering the surface of the metal layer 42 opposite the uneven structural layer 41 and forming the back surface of the display device 10. In the display device 10, which comprises the light-transmitting layer 40 and the metal layer 42, the shape of the back surface formed by the metal layer 42 is usually substantially the same as the shape of the boundary layer between the uneven structural layer 41 and the metal layer 42. If the back surface of the display device 10 is an adhesive layer and / or a cohesive layer, the surface of the metal layer 42 is not exposed to the outside of the display device 10.

[0171] The shape of the back surface of the display device 10, which is a surface of the adhesion layer and / or cohesion layer, is smoother than the shape of the surface of the metal layer 42 and is therefore different from the shape of the surface of the metal layer 42. This increases the difficulty of counterfeiting the display device 10.

[0172] If the surface of the light-transmitting layer 40 opposite the metal layer 42 is the back surface, and the surface of the metal layer 42 opposite the light-transmitting layer 40 is the front surface, an adhesion layer and / or a cohesive layer may be formed on the surface of the light-transmitting layer 40 in the display device 10, which is opposite the surface in contact with the metal layer 42. Furthermore, if the surface of the metal layer 42 opposite the light-transmitting layer 40 is the front surface and is also an uneven surface serving as an incidence surface, a light-blocking layer may be located on the back surface of the metal layer 42 of the display device 10, in addition to or instead of the light-transmitting layer 40.

[0173] The display device 10 can include a plastic layer, which, for example, is positioned on the front side of the laminate consisting of the light-transmitting layer 40 and the metal layer 42 to form the front side of the display device 10. If, for example, the metal layer 42 is arranged facing the front side of the light-transmitting layer 40, the plastic layer covers and protects the metal layer 42 from damage. Additionally, the plastic layer covering the metal layer 42 increases the difficulty of counterfeiting the metal layer 42.

[0174] Examples of the plastic layer include a hard coating layer to limit scratching of the front of the display device 10, an anti-growth layer to prevent contamination of the display device 10, an anti-reflective layer to prevent reflection of light on the front of the display device 10, and an anti-static layer to prevent static electrical charge on the display device 10.

[0175] The display device 10 can further comprise a printing layer located on the side of the metal layer 42 that is closer to the light-transmitting layer 40. That is, the printing layer can be located on the side of the support layer 43 that is opposite the surface in contact with the uneven structural layer 41, can be located between the support layer 43 and the uneven structural layer 41, or can be located between the uneven structural layer 41 and the metal layer 42.

[0176] If the display device 10 includes a printing layer, the printing layer enables the display device 10 to display additional information, thereby increasing the complexity of the image displayed by the display device 10. The printing layer displays additional information on the display device 10 more easily than a structure where the uneven structure displays additional information on the display device 10. [Manufacturing method of a display device]

[0177] With reference to the Fig. Sections 20 to 22 below describe a manufacturing process for the display device 10. This manufacturing process describes a method for producing an original plate to form the uneven surface 11s of the display device 10.

[0178] As examples of a manufacturing process for an original plate, two methods are described below that form uneven surfaces 11s, where the distance between the uppermost and lowermost sections in the uneven surfaces 11s is 450 nm, and the spacing of the uppermost sections is 400 nm. To produce an original plate, a plastic layer formed from polymethyl acrylate, which is a positive photoresist, is prepared, and the plastic layer is irradiated with electron beams. In the plastic layer formed from a positive photoresist, the resolution in the electron-irradiated section is greater than the resolution in the non-irradiated section. After the plastic layer has been developed, the electron-irradiated section of the plastic layer is correspondingly deeper than the non-irradiated section.

[0179] Fig. Figure 20 shows the relationship between the electron beam dose (µC / cm²). 2 ), which is applied to polymethyl acrylate, the material used to form the original plate, and the dissolution rate of the polymethyl acrylate. The weight-average molecular weight of polymethyl acrylate is 495,000, and the dissolution rate of polymethyl acrylate is the amount measured after immersion of the irradiated polymethyl acrylate in 4-methyl-2-pentanone, a developer solution, for 12 minutes.

[0180] If according to Fig. 20 Polymethyl acrylate was not irradiated with electron beams, that is, if the dose of the electron beam was 0 µC / cm² 2 The dissolution rate of polymethyl acrylate is 100 nm.

[0181] To thus set the distance between the uppermost and lowermost sections to 450 nm, the electron beam dose is set to the value that allows a resolution of the plastic layer in the thickness direction of 550 nm, namely 35 µC / cm². 2 The plastic layer has an irradiation surface, which is a surface. Electron beams are directed onto the irradiation surface of the plastic layer.

[0182] In the first method, the irradiated surface of the plastic layer is divided into irradiated and non-irradiated sections that alternate in a specific direction. Each irradiated section has a width of 100 nm, and each non-irradiated section has a width of 300 nm.

[0183] If the irradiated plastic layer is immersed in a developer solution and developed, the polymethyl acrylate forming the irradiated surface and its surroundings within the plastic layer are exposed to the developer solution from the start of development. Thus, each irradiated section of the surface, along with two areas located on opposite sides of the irradiated section, are resolved in the specified direction. These two areas each have a width of 100 nm. As a result, the resolved sections of the irradiated surface of the plastic layer each have a width of approximately 300 nm.

[0184] In the two regions located on opposite sides of the irradiation section in the specified direction, the parts furthest from the illumination surface in the thickness direction of the plastic layer are exposed to the developer solution for a shorter time. The sections of the plastic layer to be dissolved comprise the deepest parts, those furthest from the irradiation surface in the thickness direction of the plastic layer. These deepest parts are exposed to the developer solution for only a very short time, just before the end of the plastic layer development. Therefore, in each deepest part, the width in the specified direction of the region where polymethyl acrylate is dissolved is approximately 100 nm, which is essentially the same as the width in the specified direction of each irradiation section.

[0185] Fig. Figure 21 shows part of a cross-sectional structure of an original plate formed by the first method and measured using an atomic force microscope.

[0186] The measurement conditions of the atomic force microscope include a leaf spring constant of 40,000 N / m, a torsional spring constant of 100.0 N / m, a resonance frequency of 300.00 kHz, a leaf spring length of 140.0 µm, and a probe height of 10.00 µm. The atomic force microscope uses the beam deflection method. The oscillation voltage is 0.018 V, the resonance frequency is 268.215 kHz, and the measurement frequency is 268.010 kHz. The oscillation constants include an oscillation damping ratio of -0.279, a Q-curve gain of 1.50, and a Q-factor of 463.608.

[0187] According to Fig. 21 comprises an original plate 51 with an uneven surface 51s. The uneven surface 51s has raised surfaces 51a, which correspond to the raised surfaces 11a of the uneven structural layer 41 according to Fig. 18 correspond to, and depression surfaces 51b correspond to the depression surfaces 11b of the uneven structural layer 41. In the uneven surface 51s, the raised surfaces 51a and the depression surfaces 51b alternate in one direction. According to Fig. Figure 21 shows the measurement result obtained using the atomic force microscope, which shows that the uneven surface 51s has essentially the same shape as described above, that is, the spacing of the top sections 51c is approximately 400 nm, and the distance between the top sections 51c and the bottom sections 51d is approximately 450 nm.

[0188] The second method differs from the first in that the second method irradiates each treatment area twice with electron beams. The second method also differs in the electron beam dose per irradiation on each treatment area. That is, during the first electron beam irradiation, the entire treatment area is irradiated with electron beams at a dose of 20 µC / cm². 2 irradiated.

[0189] For the second electron beam irradiation, a partial irradiation section is first defined within each irradiation section. Each partial irradiation section has a width of 20 nm in a specific direction and extends along the thickness of the plastic layer. The center of the irradiation section and the center of the partial irradiation section are aligned in this direction. During the second electron beam irradiation, the partial irradiation section is treated with electron beams at a dose of 20 µC / cm². 2 irradiated.

[0190] Fig. Figure 22 shows part of the cross-sectional structure of an original plate formed by the second method and measured using an atomic force microscope.

[0191] According to Fig. 22 An original plate 52 comprises an uneven surface 52s. The uneven surface 52s has raised surfaces 52a, which correspond to the raised surfaces 11a of the uneven structural layer 41 according to Fig. 18 correspond to, and depression surfaces 52b correspond to the depression surfaces 11b of the uneven structural layer 41. In the uneven surface 52s, the raised surfaces 52a and the depression surfaces 52b alternate in a specific direction. In the same way as in the original plate 51 formed by the first method, the uppermost sections 52c are arranged at a spacing of 400 nm, and the distance between the uppermost sections 52c and the lowermost sections 52d in the uneven surface 52s is approximately 450 nm. On the other hand, in the original plate 52 formed by the second method, the section where the radiation section and the partial irradiation section overlap receives a larger electron beam dose than the other section in the irradiation section.

[0192] In accordance with the width in the specified direction of the partial irradiation section, the width in the specified direction of the uppermost section 52c of each raised surface 52a is approximately 20 nm.

[0193] As described above, on an uneven surface, the smaller the areas of the flat surfaces forming the bottom and top sections become, the lower the reflectivity of light from these sections. Therefore, the display device 10, formed using the original plate 52 produced by the second method, displays an image with lower brightness in the front view direction of the display device 10 compared to the original plate 51 produced by the first method.

[0194] The uneven surface of the original plate, produced by the first or second process, can be subjected to a nickel electroplating process to form a die onto which the uneven surface is transferred. Subsequently, an uneven plastic structure can be transferred from the die to the plastic layer. Since the raised and recessed surfaces forming the uneven surface of the die are tapered, the uneven structure can be easily removed from the die, thereby increasing the productivity of the display device 10.

[0195] The second method allows the uppermost sections to have smaller areas than those produced by the first method, thus facilitating the integration of the uneven surface of the matrix, formed by transferring the original plate, into the plastic layer. This improves the forming of the uneven structural layer. The improved forming increases the forming speed, thereby improving the productivity of the display device. Furthermore, the improved forming allows for an increase in the aspect ratio of the uneven surface. Thus, the second method is also effective in reducing the brightness of the image displayed in the front-view direction of the display device 10.

[0196] The material used to form the original plate is not limited to polymethyl acrylate and can be an acrylic resin other than polymethyl acrylate or a photoresist material such as novolac resin and hydroxystyrene. Furthermore, the developer solution is not limited to 4-methyl-2-pentanone and can consist of alkyl acetates, ketones, aromatic compounds, or mixtures thereof. The aromatic compound could be, for example, xylene, anisole, or chlorobenzene.

[0197] If the original plate is made of a photoresist material such as a novolac resin and polyhydroxystyrene, the developer solution can be an ammonium salt such as tetramethylammonium hydroxide and a hydroxide such as potassium hydroxide.

[0198] The development process for the polymer layer, the development time for the polymer layer, and the width of the irradiation sections treated with electron beams can be freely modified, as long as an original plate with an uneven surface can be produced. The second method irradiates the partial irradiation sections with electron beams after the irradiation of the irradiation sections themselves. However, the partial irradiation sections can also be irradiated with electron beams before the irradiation of the irradiation sections themselves. The second method irradiates each irradiation section twice with electron beams. However, each irradiation section can be irradiated with electron beams three times or more.In this case, a multitude of partial irradiation segments are defined within each irradiation segment, and the partial irradiation segments are positioned such that their centers in the latitude direction align with the center in the latitude direction of the irradiation segment. Additionally, the partial irradiation segments are defined with different widths in one direction. [Structure of an object]

[0199] The display device 10 described above can be used with an object to prevent counterfeiting of the object. The uneven surface 11s of the display device 10 enables the display device 10 to limit the reflection of light in the frontal viewing direction of the display device 10 and to emit diffracted light in the oblique viewing direction of the display device 10.

[0200] As such, it is difficult to counterfeit the display device by replicating the shape of the uneven surface 11s of the display device 10. Accordingly, the display device 10 increases the difficulty of counterfeiting the object to which the display device 10 is attached.

[0201] By verifying whether the display device 10 is able to limit the reflection of light in the front view direction of the display device 10 and to emit diffracted light in the oblique view direction of the display device 10, the display device 10 and thus the object can be authenticated.

[0202] With reference to the Fig. 23 and Fig. 24 The structure of an IC card is described below as an example of an item with a display device 10.

[0203] According to Fig. 23 comprises a card with an integrated circuit (IC card) 60, a planar base 61 which may be made of plastic, a printing layer 62 on which an image is printed, an IC chip 63 and a display device 10.

[0204] According to Fig. 24 The printing layer 62 is formed on a surface of the base 61. The display device 10 described above is attached, for example, by means of an adhesive layer to the surface of the printing layer 62, which is opposite the surface that is in contact with the base 61. The display device 10 is prepared, for example, as a transfer film or as a sticker with an adhesive layer and attached to the printing layer 62.

[0205] The base 61 includes a recess 61a extending from a portion of the surface in contact with the printed layer 62 towards the surface opposite the surface in contact with the printed layer 62. The printed layer 62 includes a through-hole 62a at the position aligned with the recess 61a when viewed in the thickness direction of the IC card 60. The IC chip 63 is fitted into the recess 61a and the through-hole 62a. The IC chip 63 has a front face surrounded by the printed layer 62 and featuring a plurality of electrodes. Information is written to / read from the IC chip 63 via the electrodes.

[0206] The IC card 60 is difficult to counterfeit because it features the display device 10, which is difficult to counterfeit. Furthermore, in addition to the display device 10, the IC card 60 also features the IC chip 63 and the print layer 62. The IC chip 63 and the print layer 62 help prevent counterfeiting.

[0207] The display device of the second embodiment has the following advantages in addition to the advantage of the display device of the first embodiment.

[0208] (2) For an observer viewing the display device 10 from a fixed point on the observation side, the display device 10 shows an image formed by the difference between the luminance of the diffracted light emitted by the first area 11s1 and the luminance of the diffracted light emitted by the second area 11s2. Compared to a structure in which one type of diffracted light is emitted from the entire uneven surface 11s, the image emitted in the oblique viewing direction of the uneven surface 11s, which is one of the images displayed by the uneven surface 11s, is more complex.

[0209] (3) The difference between the luminance of the first area 11s1 and the luminance of the second area 11s2 enables the display device 10 to produce an image displayed in the direction of the first fixed point OB1 and an image displayed in the direction of the second fixed point OB2. Furthermore, the display device 10 is able to display an image in the direction of the second fixed point OB2 in which the ratio between the luminance of the first area 11s1 and the luminance of the second area 11s2 is inversely that of the image displayed in the direction of the first fixed point 1.

[0210] (4) In the image displayed by the display device 10 in the direction of a fixed point, the color of the first area 11s1 differs from the color of the second area 11s2. This allows a clear demarcation between the first area 11s1 and the second area 11s2 compared to a structure in which the two areas differ from each other only in luminance.

[0211] (5) The image displayed by the display device 10 in the front-view direction of the display device 10 is visually perceived as a single image. The image formed by the difference between a property of the diffracted light from the first area 11s1 and a property of the diffracted light from the second area 11s2 is thus hidden from the observer in the front-view direction of the display device 10. [Variations of the second embodiment]

[0212] The second embodiment described above can be modified as follows.

[0213] The second arrangement direction can intersect the first arrangement direction in such a way that they form an angle other than a right angle. Such a structure still allows image elements with a first arrangement in which the raised and recessed surfaces alternate in the first arrangement direction, and image elements with a second arrangement in which raised and recessed surfaces alternate in the second arrangement direction, to emit diffracted light in different directions.

[0214] The image elements 30 forming the uneven surface 11s comprise the first image elements 31, the second image elements 32, the third image elements 33, and the fourth image elements 34. Additionally, the uneven surface 11s need not be subdivided into the first region 11s1 and the second region 11s2. Such a display device is still capable of emitting light of a color mixed by two colors in the direction of both the first fixed point and the second fixed point.

[0215] The display device can be configured such that only the first area 11s1 emits diffracted light towards the first fixed point OB1, and only a second area 11s2 emits diffracted light towards the second fixed point OB2. With such a configuration, the difference between the luminances of the diffracted lights allows the image displayed by the first area 11s1 and the image displayed by the second area 11s2 to be visually distinguished from one another when the display device 10 is viewed from the first fixed point OB1, and likewise when viewed from the second fixed point OB2.

[0216] This means that the first area 11s1 can consist of the image elements 30, which include at least one of the first image elements 31 and the second image elements 32, while the second area 11s2 can consist of the image elements 30, which include at least one of the third image elements 33 and the fourth image elements 34.

[0217] The luminance of the diffracted light emitted from the first region 11s1 towards the first fixed point OB1 can be higher than the luminance of the diffracted light emitted from the second region 11s2 towards the first fixed point OB1, and the luminance of the diffracted light emitted from the first region 11s1 towards the second fixed point OB2 can be higher than the luminance of the diffracted light emitted from the second region 11s2 towards the second fixed point OB2. Such a structure still allows the image displayed by the first region 11s1 and the image displayed by the second region 11s2 to be visually distinguishable from each other when the display device 10 is viewed from the first fixed point OB1, and likewise when viewed from the second fixed point OB2.

[0218] For example, the ratio of the sums of the areas of the third image elements 33 and the areas of the fourth image elements 34 to the area of ​​the first region 11s1 can be greater than the ratio of the sum of the areas of the third image elements 33 and the areas of the fourth image elements 34 to the area of ​​the second region 11s2.

[0219] The luminance of the diffracted light emitted by the first region 11s1 towards a fixed point can be smaller than the luminance of the diffracted light emitted by the second region 11s2 towards the fixed point.

[0220] This means that the display device can have any structure, provided that: of the image elements with a first arrangement and the image elements with a second arrangement, the first region 11s1 includes at least the image elements with the first arrangement, while the second region 11s2 includes at least the image elements with the second arrangement; the ratio of the sum of the areas of the image elements with the first arrangement to the area of ​​the first region 11s1 differs from the ratio of the sum of the areas of the image elements with the first arrangement to the area of ​​the second region 11s2; and the ratio of the sum of the areas of the image elements with the second arrangement to the area of ​​the first region 11s1 differs from the ratio of the sum of the areas of the image elements with the second arrangement to the area of ​​the second region 11s2. Such a structure has the following advantage.

[0221] (6) In both the image displayed in the direction of the first fixed point OB1 and the image displayed in the direction of the second fixed point OB2 by the display device 10, the luminance of the image displayed by the first area 11s1 differs from the luminance of the image displayed by the second area 11s2. The luminance difference between the two images enables the display device 10 to display an image in which the section displayed by the first area 11s1 is visually distinguishable from the section displayed by the second area 11s2.

[0222] As long as the image elements 30 that form the uneven surface 11s include the image elements with the first arrangement and the image elements with the second arrangement, the uneven surface 11s does not need to be subdivided into the first area 11s1 and the second area 11s2.

[0223] Such a structure still has the following advantage. (7) The uneven surface 11s comprises the image elements with the first arrangement, which emit diffracted light in the direction of the first fixed point OB1, and the image elements with the second arrangement, which emit diffracted light in the direction of the second fixed point OB2. This enables the display device 10 to display an image in the direction of the first fixed point OB1, which is formed by the diffracted light emitted by the image elements that are different from the image elements emitting the diffracted light that forms the image displayed in the direction of the second fixed point OB2.

[0224] The color of the diffracted light emitted from the first region 11s1 towards a fixed point differs from the color of the diffracted light emitted from the second region 11s2 towards the fixed point. However, the luminance of the diffracted light emitted from the first region 11s1 towards the fixed point can be equal to the luminance of the diffracted light emitted from the second region 11s2 towards the fixed point. Such a structure still allows the image displayed by the first region 11s1 and the image displayed by the second region 11s2 to be visually distinguishable.

[0225] For example, the first area 11s1 can comprise one of a group of first image elements 31 and a group of second image elements 32, as well as one of a group of third image elements 33 and a group of fourth image elements 34 in a ratio of 1:1; the second area 11s2 can comprise the other of a group of first image elements 31 and a group of second image elements 32, as well as the other of a group of third image elements 33 and a group of fourth image elements 34 in a ratio of 1:1.

[0226] The structure of the image elements 30 in the first region 11s1 and the structure of the image elements 30 in the second region 11s2 may differ from the structures in the second embodiment, as long as the color of the diffracted light emitted from the first region 11s1 in the direction of the first fixed point OB1 differs from the color of the diffracted light emitted from the second region 11s2 in the direction of the first fixed point OB1.

[0227] For example, the period d of all image elements 30 located in the first region 11s1 and emitting diffracted light towards the first fixed point OB1 can be the first period, and the period d of all image elements 30 located in the second region 11s2 and emitting diffracted light towards the first fixed point OB1 can be the second period, which differs from the first period. This structure allows the color of the diffracted light emitted by the first region 11s1 towards the first fixed point OB1 to be different from the color of the diffracted light emitted by the second region 11s2 towards the first fixed point OB1.

[0228] Furthermore, the periods d of the image elements 30 located in the first region 11s1, which emit diffracted light towards the first fixed point OB1, can comprise three or more different values. Additionally, the periods of the image elements 30 located in the second region 11s2, which also emit light towards the first fixed point OB1, can comprise three or more different values. This structure still allows the color of the diffracted light emitted by the first region 11s1 towards the first fixed point OB1 to be different from the color of the diffracted light emitted by the second region 11s2 towards the first fixed point OB1.

[0229] The structure described above is also applicable to the structure that allows the color of the diffracted light emitted from the first region 11s1 towards the second fixed point OB2 to be different from the color of the diffracted light emitted from the second region 11s2 towards the second fixed point OB2.

[0230] As long as the color of the diffracted light emitted from the first region 11s1 differs from the color of the diffracted light emitted from the second region 11s2, diffracted light of the same color can be emitted from the first region 11s1 towards all fixed points, and diffracted light of the same color can be emitted from the second region 11s2 towards all fixed points.

[0231] For example, the first area 11s1 can consist of first image elements 31 and third image elements 33, and the second area 11s2 can consist of second image elements 32 and fourth image elements 34.

[0232] The color of the diffracted light emitted from the first region 11s1 towards the first fixed point OB1 can be the same as the color of the diffracted light emitted from the second region 11s2 towards the first fixed point OB1. This structure has an advantage equivalent to the advantage (2) described above, as long as the luminance of the diffracted light emitted from the first region 11s2 towards the first fixed point OB1 differs from the luminance of the diffracted light emitted from the second region 11s2 towards the first fixed point OB1.

[0233] For example, if the first region 11s1 includes the first image elements 31 instead of the second image elements 32, the color of the diffracted light emitted by the first region 11s1 towards the first fixed point OB1 will be the same as the color of the diffracted light emitted by the second region 11s2 towards the first fixed point OB1.

[0234] In this structure, the color of the diffracted light emitted from the first region 11s1 towards the second fixed point OB2 can be identical to or different from the color of the diffracted light emitted from the second region 11s2 towards the second fixed point OB2.

[0235] For example, in order that the diffracted light emitted from the first region 11s1 towards the second fixed point OB2 and the diffracted light emitted from the second region 11s2 towards the second fixed point OB2 have the same color, the second region 11s2 includes third image elements 33 instead of fourth image elements 34.

[0236] The first area 11s1 and the second area 11s2 can display images in the direction of only one fixed point, and the image displayed by the first area 11s1 can differ in color from the image displayed by the second area 11s2.

[0237] That is, the image elements 30 that form the uneven surface 11s comprise image elements with a first period, in which first raised surfaces and first depression surfaces are arranged with a first period in the arrangement direction, and image elements with a second period, in which second raised surfaces and second depression surfaces are arranged with a second period that differs from the first period in the arrangement direction. Of the image elements with the first period and the image elements with the second period, the first region 11s1 comprises at least the image elements with the first period, and the second region 11s2 comprises at least the image elements with the second period.The ratio in the first area 11s1 between the sum of the areas of the image elements with the first period and the sum of the areas of the image elements with the second period differs from the ratio in the second area 11s2 between the sum of the areas of the image elements with the first period and the sum of the areas of the image elements with the second period.

[0238] The structures described above have the following advantage.

[0239] (8) The color of the light emitted from the first area 11s1 towards a fixed point differs from the color of the light emitted from the second area 11s2 towards the fixed point. This allows a clear visual distinction between the image displayed by the first area 11s1 and the image displayed by the second area 11s2, in contrast to a structure in which the two areas differ only in luminance.

[0240] As long as the image elements 30 that form the uneven surface 11s include the image elements with the first period and the image elements with the second period, the uneven surface 11s does not need to be subdivided into the first region 11s1 and the second region 11s2.

[0241] Such a structure still has the following advantage. (9) The display device 10 is able to display an image formed by diffracted light emitted by the first-period image elements and by diffracted light emitted by the second-period image elements, and which differs in color from the diffracted light emitted by the first-period image elements.

[0242] The brightness of the image displayed by the first area 11s1 in the front-view direction of the display device 10 can differ from the brightness of the image displayed by the second area 11s2 in the front-view direction of the display device 10. Such a structure makes it possible for an image to be formed by the first area 11s1 and the second area 11s2, which is displayed both in the front-view direction of the display device 10 and in the oblique view direction of the display device 10.

[0243] For example, if the height H in the first area 11s1 differs from the height H in the second area 11s2 on the uneven surface 11s, the brightness of the image displayed by the first area 11s1 differs from the brightness of the image displayed by the second area 11s2.

[0244] The uneven structure 11 can comprise a light-absorbing layer other than the metal layer 42, such as a black layer containing plastic and black paint or pigment. The uneven structure 11 can include such a light-absorbing layer as long as the light-absorbing layer is located on the side of the light-incident uneven surface that is opposite the side onto which the light is incident. To facilitate reflection of the diffracted light, the display device 10 preferably includes the metal layer 42 as the light-absorbing layer.

[0245] In addition to the uneven surface 11s, the light-incidence surface of the display device 10 can include a diffraction part for diffracting light, a light-scattering part for scattering light, and a light-collecting part for collecting light.

[0246] The diffraction part can be the diffraction grating DG, which was described above with reference to Fig. 3 is described, and has a period d that is greater than or equal to the shortest wavelength of visible light.

[0247] The light-diffusing section comprises raised or recessed surfaces that are irregularly arranged and differ from one another in size, shape, and / or height in the Z-direction. The light-diffusing section diffusely reflects the light incident on the light section, so that an observer viewing the display device from the side from which light falls on the light-diffusing section perceives an image in a white or murky color.

[0248] In the light-scattering section, the raised surfaces have a width of 3 µm or more in the X or Y direction and a height of 1 µm or more in the Z direction, or the depression surfaces have a width of 3 µm or more in the X or Y direction and a depth of 1 µm or more in the Z direction. The width and height of the raised surfaces or the width and depth of the depression surfaces in the light-scattering section are greater than the width and height of the diffraction grating of the diffraction section as well as the width and height of the uneven surface 11s described above. If features of the light-scattering section, such as the shape of the raised and depression surfaces and the direction in which the raised and depression surfaces are arranged, exhibit regularity, the scattered light will be directional.

[0249] The light-collecting element can include a lens such as a microlens or a Fresnel lens. Such a lens allows light incident on the surface of the display device 10 to appear as if it is collected either on the side of the surface from which the light is incident or on the back side of the surface. This enables the display device 10 to produce a visual effect specific to the lens.

[0250] The display device 10, which includes the diffraction part, the light scattering part and the light collecting part, is more difficult to counterfeit.

[0251] The original plate for manufacturing the display device 10 may be formed by a method other than those described above. For example, an original plate with an uneven surface may be produced by wet etching or dry etching on the surface of a base for forming an original plate, and the base may, for example, be made of silicon or metal.

[0252] The object to which the display device 10 is attached is not limited to an IC card and can be another type of card, such as a magnetic stripe card, a wireless card, or an identification card (ID card). Alternatively, the object can be a security, such as a gift certificate or a share certificate, or a label to be affixed to an object to be authenticated, such as a luxury product like a work of art. Furthermore, the object can be packaging that encloses an object to be authenticated or be part of packaging.

[0253] If the base supporting the display device 10 is made of paper, the display device 10 may be embedded in the paper forming the base, and an opening may be formed in the section of the base flush with the display device 10, where a surface of the base is viewed in a direction facing the surface, so that the display device 10 is exposed to the outside of the base. If the base is made of a light-transmitting material, the display device 10 may be embedded in the base or may be attached to the back of the base opposite the display side, which includes information other than the display device 10.

[0254] The purpose of the display device 10 is not limited to preventing counterfeiting. The display device can be used to decorate an object. The display device 10 can be used for objects such as toys or learning materials. In this case, the display device itself is the object of observation. [Third embodiment]

[0255] With reference to the Fig. Sections 25 to 32 below describe a third embodiment of a display device according to the invention. The display device of the third embodiment differs from the display device of the second embodiment in the number of areas that form the uneven surface. Therefore, the following description focuses on this difference. The same reference numerals are assigned to those components that are identical to the corresponding components of the second embodiment. Such components are not described in detail below. As is the case with the second embodiment, the third embodiment is an example in which the distance dimension and the period of the uneven surface have the same value. The structure of the display device is described below, followed by a description of its function. [Structure of the display device]

[0256] With reference to the Fig. The structure of the display device is described below in sections 25 to 29. Fig. 25 Some parts of the uneven surface are shaded with dots to clearly distinguish between the areas in the uneven surface.

[0257] According to Fig. 25 comprises a display device 10 and an uneven surface 11s, which is a light-incidence surface. The uneven surface 11s comprises a first region 71, a second region 72, a third region 73, and a fourth region 74.

[0258] In a top view facing the uneven surface 11s, the first area 71 and the second area 72 are in contact with each other in the Y direction and represent the letter A. In other words, the first area 71 and the second area 72 are areas that represent part of the letter A.

[0259] The first area 71 and the third area 73 are in contact with each other in the X-direction when viewed from above on the uneven surface 11s, and represent the letter B. In other words, the first area 71 and the third area 73 are areas that each represent a part of the letter B.

[0260] The fourth area 74 is the area of ​​uneven surface 11s, which surrounds the first area 71, the second area 72 and the third area 73, and forms the outer edge of the uneven surface 11s.

[0261] According to Fig. 26 The first region 71 consists of a plurality of first image elements 31 and a plurality of third image elements 33. Each first image element 31 is located side by side with a third image element 33 in the X-direction, and these two image elements 30 form a set of a first image element group 71g. The first region 71 comprises a plurality of first image element groups 71g arranged in the X-direction and the Y-direction. The first period d1 of the first image elements 31 and the third period d3 of the third image elements 33 are the same value and can, for example, be 400 nm.

[0262] According to Fig. 27 The second region 72 consists of a plurality of first image elements 31 and a plurality of fourth image elements 34. Each first image element 31 is located side by side with a fourth image element 34 in the X-direction, and these two image elements 30 form a set of a second image element group 72g. The second region 72 comprises a plurality of second image element groups 72g arranged in the X-direction and the Y-direction. The fourth period d4 of the fourth image elements 34 is, for example, 300 nm.

[0263] According to Fig. 28 The third region consists of a plurality of second image elements 32 and a plurality of third image elements 33. Every second image element 32 is located side by side with a third image element 33 in the X direction, and these two image elements 30 form a set of a third image element group 73g. The third region 73 comprises a plurality of third image element groups 73g arranged in the X and Y directions. The second period d2 of the second image elements 32 and the fourth period d4 of the fourth image elements 34 are the same value and can, for example, be 300 nm.

[0264] According to Fig. 29 The fourth region 74 consists of a plurality of second image elements 32 and a plurality of fourth image elements 34. Every second image element 32 is located side by side with a fourth image element 34 in the X direction, and these two image elements form a set of a fourth image element group 74g. The fourth region 74 comprises a plurality of fourth image element groups 74g arranged in the X and Y directions.

[0265] The first area 71 and the second area 72, each representing a part of the letter A, comprise first image elements 31 as common image elements 30. The first area 71 and the third area 73, each representing a part of the letter B, comprise third image elements 33 as common image elements 30. The fourth area 74, which represents neither the letter A nor the letter B, comprises neither first image elements 31 nor third image elements 33, but it does comprise other image elements 30, namely second image elements 32 and fourth image elements 34. [Effect of the display device]

[0266] With reference to the Fig. The effect of the display device 10 is described below in sections 30 to 32.

[0267] According to Fig. In this case, a light source LS can emit an illumination light IL from a predetermined surface in the YZ plane YZ towards the display device 10 in an oblique direction, and an observer can view the display device 10 from a first fixed point OB1, which is a first point in the YZ plane YZ on the side opposite the emission light RL with respect to the front view direction DLV of the display device 10. Only the image elements 30, comprising raised and recessed surfaces extending in the X direction, namely the first image elements 31 and the second image elements 32, emit diffracted light DL towards the first fixed point OB1.

[0268] Since the first period D1 of the first image elements 31 differs from the second period d2 of the second image elements 32, the color of the diffracted light DL emitted by the first image elements 31 in the direction of the first fixed point OB1 differs from the color of the diffracted light DL emitted by the second image elements 32 in the direction of the first fixed point OB1.

[0269] Thus, if the display device 10 is viewed from the first fixed point OB1, the first region 71 and the second region 72 emit diffracted light DL of the same color in the direction of the first fixed point OB1. On the other hand, the third region 73 and the fourth region 74 emit diffracted light DL of the same color in the direction of the first fixed point OB1, but this color is different from the color of the diffracted light DL emitted by the first region 71 and the second region 72. As such, the display device 10 shows an image in the direction of the first fixed point OB1, which is formed by the image representing the letter A and the image representing the background of the letter A.

[0270] For example, the angle enclosed by the front view direction DLV and the illumination direction of the illumination light IL is -40°, and the angle enclosed by the front view direction DLV and the observer's viewing direction at the first fixed point OB1 is -60°. As defined by expression (2), the first region 71 and the second region 72 emit orange diffracted light DL in the direction of the first fixed point OB1, while the third region 73 and the fourth region 74 emit blue diffracted light DL in the direction of the first fixed point OB1.

[0271] According to Fig. 31 A light source LS can emit an illumination light IL from a predetermined surface in the XZ-plane XZ towards the display device 10 in an oblique direction, and the observer can view the display device 10 from a second fixed point OB2, which is a point in the XZ-plane XZ on the side opposite the emission light RL with respect to the front view direction DLV of the display device 10. Only the image elements 30, comprising the raised and recessed surfaces extending in the Y-direction, namely the third image elements 33 and the fourth image elements 34, emit diffracted light DL towards the second fixed point OB2.

[0272] Since the third period d3 of the third image elements 33 differs from the fourth period D4 of the fourth image elements 34, the color of the diffracted light DL emitted by the third image elements in the direction of the second fixed point OB2 differs from the color of the diffracted light DL emitted by the fourth image elements 34 in the direction of the second fixed point OB2.

[0273] Thus, if the display device 10 is viewed from the second fixed point OB2, the first region 71 and the third region 73 emit diffracted light DL of the same color towards the second fixed point OB2. On the other hand, the second region 72 and the fourth region 74 emit diffracted light DL of the same color towards the second fixed point OB2, but this color is different from the color of the diffracted light emitted by the first region 71 and the third region 73. As such, the display device 10 shows an image towards the second fixed point OB2 formed by the image representing the letter B and the image representing the background of the letter B.

[0274] In the XZ plane XZ, the angle enclosed by the front view direction DLV and the illumination direction of the illumination light IL is -40°, and the angle enclosed by the front view direction DLV and the view direction of the observer at the second fixed point OB2 is -60°. As defined in expression (2), the first region 71 and the third region 73 thus emit orange diffracted light DL in the direction of the second fixed point OB2, while the second region 72 and the fourth region 74 emit blue diffracted light DL in the direction of the second fixed point OB2.

[0275] According to Fig.32 further displays an image with reduced brightness, such as a black image, in the direction of the third fixed point OB3, which is located in the front view direction DLV. The images displayed by the first area 71, the second area 72, the third area 73, and the fourth area 74 in the front view direction DLV have essentially the same brightness.

[0276] Accordingly, if the display device 10 is viewed from the third fixed point OB3, the images displayed by the display device 10 are perceived as a single image. Therefore, if the display device 10 is viewed in the frontal view direction DLV, the image formed by the display device 10 with the first area 71 and the second area 72, and the image formed by the display device 10 with the first area 71 and the third area 73, are hidden from the viewer.

[0277] The third embodiment of the display device has the following advantage in conjunction with advantages (1), (4) and (5).

[0278] (10) The image displayed by the display device 10 in the direction of the first fixed point OB1 differs from the image displayed in the direction of the second fixed point OB2. Compared to a structure in which the image displayed in the direction of the first fixed point OB1 is identical to the image displayed in the direction of the second fixed point OB2, except for color and brightness, the visual effect produced by the display device 10 on the viewer is enhanced, and the display device 10 is more difficult to counterfeit. [Variations of the third embodiment]

[0279] The third embodiment described above can be modified as described below.

[0280] The uneven surface 11s can comprise at least the first region, the second region, and the third region. Such a structure has the following advantage, provided that the first region consists of the first image elements 31 and the third image elements 33, the second region consists of the first image elements 31 and the fourth image elements 34, and the third region consists of the second image elements 32 and the third image elements 33.

[0281] That is, the first and second regions display images of the same color in the direction of the first fixed point OB1, and the first and third regions display images of the same color in the direction of the second fixed point OB2. Thus, different regions of the display device show 10 images of the same color in the direction of the first fixed point OB1 and the second fixed point OB2.

[0282] In each of the first to fourth regions 71 to 74, two types of image elements 30, which form the region, can alternate in the X direction and the Y direction.

[0283] The first to fourth regions 71 to 74 can each, as the image elements that emit diffracted light towards the first fixed point OB1, comprise two or more types of image elements that differ from each other in the period of the repetition unit. The first to fourth regions 71 to 74 can each, as the image elements that emit diffracted light DL towards the second fixed point OB2, comprise two or more types of image elements that differ from each other in the period of the repetition unit. Such a structure allows a single region to emit light with a color mixed from different colors towards both the first fixed point OB1 and the second fixed point OB2.

[0284] A technical idea that can be obtained from the above-presented embodiments and variations is described below as a solution to the technical problem.

[0285] [1] Display device with: an uneven structure with a light-transmitting uneven structural layer comprising a transmission-side uneven surface, and a metal layer covering the transmission-side uneven surface, and comprising an uneven surface serving as an incident surface onto which light is incident, and which is either a surface in contact with the transmission-side uneven surface, or a surface opposite the surface in contact with the transmission-side uneven surface, wherein the uneven surface includes a section in which raised surfaces and depression surfaces alternate in one direction of arrangement, Each raised surface has the form of a strip extending in a direction of expansion perpendicular to the arrangement direction, Each raised surface tapers towards a top section in a thickness direction of the uneven structure, Each depression surface has the form of a strip extending in the direction of expansion, Each depression surface tapers towards a bottom section in the thickness direction of the uneven structure, and the raised surfaces and the depression surfaces are arranged with a period that limits the reflection of light incident on the uneven surface in a front view direction of the uneven surface, and diffractes the light incident on the uneven surface to emit diffracted light in an oblique view direction of the uneven surface.

Claims

[1] Display device (10) with an uneven structure (11) with an uneven surface (11s) which serves as an incident surface onto which light is incident, wherein the uneven surface (11s) comprises a section in which raised surfaces (11a) and depression surfaces (11b) alternate in one arrangement direction, each raised surface (11a) has the form of a strip extending in a direction of extension perpendicular to the arrangement direction, Each raised surface (11a) tapers towards an uppermost section (11c) in a thickness direction of the uneven structure (11), each depression surface (11b) has the form of a strip extending in the direction of expansion, Each depression surface (11b) tapers towards a bottom section (11d) in the thickness direction of the uneven structure (11), the raised surfaces (11a) and the depression surfaces (11b) are arranged with a period that limits the reflection of light incident on the uneven surface (11s) in a front view direction of the uneven surface (11s), and diffractes the incident light to emit diffracted light in an oblique view direction of the uneven surface (11s), and the uneven structure (11) has an absorption property for light incident on the uneven structure (11), wherein a side from which light falls onto the uneven surface (11s) is a viewing side, a point at a predetermined position on the observation side is a first fixed point (OB1), a point at a position different from the first fixed point on the observation side is a second fixed point (OB2), the arrangement direction is a first arrangement direction, the direction of expansion is a first direction of expansion, the survey surfaces are the first survey surfaces (31a), the depression surfaces are the first depression surfaces (31b), a direction that intersects the first arrangement direction, is a second arrangement direction, the uneven surface (11s) is divided into a multitude of image elements (30), the image elements comprise (30): Image elements with a first arrangement (31) comprising the first raised surfaces (31a) and the first recessed surfaces (31b) alternating in the first arrangement direction, and emitting diffracted light in the direction of the first fixed point (OB1), and Image elements with a second arrangement (33) comprising second raised surfaces (33a) and second recessed surfaces (33b) alternating in the second arrangement direction, and emitting diffracted light in the direction of the second fixed point (OB2), every second elevation surface (33a) has the form of a strip extending in the second direction of extension, which is perpendicular to the second direction of arrangement, every second elevation surface (33a) tapers towards an uppermost section (33c) in the thickness direction of the uneven structure (11), every second depression surface (33b) has the form of a strip which extends in the second direction of extension perpendicular to the second arrangement direction, every second depression surface (33b) tapers towards a bottom section (33d) in the thickness direction of the uneven structure (11), and the second raised surfaces (33a) and the second recessed surfaces (33b) are arranged with a period that limits the reflection of light incident on the image elements with the second arrangement (33) in a front view direction of the image elements with the second arrangement (33), and diffractes the light incident on the image elements with the second arrangement (33) to emit diffracted light in an oblique view direction of the image elements with the second arrangement (33), wherein the uneven surface (11) includes a first area (11s1) that includes more than one of the image elements (30), and a second area (11s2) that includes more than one of the image elements (30), of the image elements with the first arrangement (31) and the image elements with the second arrangement (33), the first area (11s1) includes at least one or more of the image elements with the first arrangement (31), of the image elements with the first arrangement (31) and the image elements with the second arrangement (33), the second area (11s2) includes at least one or more of the image elements with the second arrangement (33), a ratio of a sum of areas of the image elements with the first arrangement (31) to an area of ​​the first region (11s1) differs from a ratio of a sum of areas of the image elements with the first arrangement (31) to an area of ​​the second region (11s2), and a ratio of a sum of areas of the image elements with the second arrangement (33) to the area of ​​the first region (11s1) differs from a ratio of a sum of areas of the image elements with the second arrangement (33) to the area of ​​the second region (11s2), characterized by, that the uneven surface (11s) is arranged such that the brightness of an image displayed by the first area (11s1) in the front view direction and the brightness of an image displayed by the second area (11s2) in the front view direction are substantially equal to each other. [2] Display device (10) with an uneven structure (11) with an uneven surface (11s) which serves as an incident surface onto which light is incident, wherein the uneven surface (11s) comprises a section in which raised surfaces (11a) and depression surfaces (11b) alternate in one arrangement direction, each raised surface (11a) has the form of a strip extending in a direction of extension perpendicular to the arrangement direction, Each raised surface (11a) tapers towards an uppermost section (11c) in a thickness direction of the uneven structure (11), each depression surface (11b) has the form of a strip extending in the direction of expansion, Each depression surface (11b) tapers towards a bottom section (11d) in the thickness direction of the uneven structure (11), the raised surfaces (11a) and the depression surfaces (11b) are arranged with a period that limits the reflection of light incident on the uneven surface (11s) in a front view direction of the uneven surface (11s), and diffractes the incident light to emit diffracted light in an oblique view direction of the uneven surface (11s), and the uneven structure (11) has an absorption property for light incident on the uneven structure (11), wherein the period is a first period (d1), the survey surfaces are the first survey surfaces (31a), the depression surfaces are the first depression surfaces (31b), the uneven surface (11s) is subdivided into a multitude of image elements (30), the image elements (30) include: Image elements with a first period (31) comprising the first raised surfaces (31a) and the first indented surfaces (31b) arranged with the first period (d1) in the arrangement direction, and Image elements with a second period (32), comprising second raised surfaces (32a) and second indented surfaces (32b), arranged in the arrangement direction with a second period (d2) that is different from the first period (d1), every second elevation surface (32a) has the form of a strip extending in the direction of expansion, every second elevation surface (32a) tapers towards an uppermost section (32c) in the thickness direction of the uneven structure (11), every second depression surface (32b) has the form of a strip extending in the direction of expansion, every second depression surface (32b) tapers towards a bottom section (32d) in the thickness direction of the uneven structure (11), and the second raised surfaces (32a) and the second recessed surfaces (32b) are arranged with a second period (d2) which limits the reflection of light incident on the image elements with the second period (32) in a front view direction of the image elements with the second period (32), and diffractes the light incident on the image elements with the second period (32) in order to emit diffracted light in an oblique view direction of the image elements with the second period (32), wherein the uneven surface (11s) includes a first area (11s1) that includes more than one of the image elements (30), and a second area (11s2) that includes more than one of the image elements (30), of the image elements with the first period (31) and the image elements with the second period (32), the first area (11s1) includes at least one or more of the image elements with the first period (31), of the image elements with the first period (31) and the image elements with the second period (32), the second area (11s2) includes at least one or more of the image elements with the second period (32), and a ratio of a sum of areas of the image elements with the first period (31) in the first region (11s1) to a sum of areas of the image elements with the second period (32) in the first region (11s1) differs from a ratio of a sum of areas of the image elements with the first period (31) in the second region (11s2) to a sum of areas of the image elements with the second period (32) in the second region (11s2), characterized by , that the uneven surface (11s) is arranged such that the brightness of an image displayed by the first area (11s1) in the front view direction and the brightness of an image displayed by the second area (11s2) in the front view direction are essentially the same.

Images