Optical laminates and displays

Abstract

To provide an optical laminate capable of focusing light in a direction inclined with respect to the normal direction of the screen, and a display unit having said optical laminate. [Solution] An optical laminate is formed by stacking a prism member having a first surface on which a prism pattern composed of multiple prism units is formed, and a second surface facing the first surface on which no prism pattern is formed, and a light source member having a light source that emits light. Each prism unit has a first prism component surface and a second prism component surface that protrude from the first surface, and a top edge where the first prism component surface and the second prism component surface intersect. In a cross-section of the prism unit with a plane perpendicular to the top edge, when the acute angle made by the first prism component surface with respect to the first surface is defined as the first base angle, and the acute angle made by the second prism component surface with respect to the first surface is defined as the second base angle, the angles of the first base angle and the angles of the second base angle are different, and the light source member is located on the second surface side.

Description

Technical Field

[0001] The present invention relates to an optical laminate and a display.

Background Art

[0002] A display is a device that displays visual information such as characters and images on a screen. The display includes a light source for increasing the brightness of the screen so that an observer can clearly visually recognize the visual information.

[0003] Since the light emitted from the light source generally spreads isotropically, a brightness enhancement film may be used in the display in order to improve the visibility for an observer located in the normal direction of the screen. The brightness enhancement film is disposed between the light source and the observer, deflects the isotropically spreading light, condenses the light around the direction toward the observer (the normal direction of the screen), and increases the brightness of the screen.

[0004] As a brightness enhancement film, the one shown in FIG. 7 is known. The brightness enhancement film 100 shown in FIG. 7 has a plurality of prisms 102 formed on one surface of a flat substrate 101. The angle (apex angle) formed by the tops of the prisms 102 is 90°, and the angles (base angles) formed by the bottoms of the prisms 102 are 45° each. Since the prisms 102 have such a configuration, the light incident on the surface 105 of the substrate 101 on which the prisms 102 are not formed at various incident angles is refracted or reflected at the boundary surface of the prisms 102, and finally the ratio of the light traveling toward the vicinity of the normal direction of the brightness enhancement film 100 increases. As a result, the light from the light source is condensed in the normal direction.

[0005] As an example of such a brightness enhancement film, Patent Document 1 discloses a brightness adjustment film having a first surface having an array of repetitive chevron surface structures and a substantially flat second surface.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Special Publication No. 10-506500 [Overview of the project] [Problems that the invention aims to solve]

[0007] For information devices such as navigation systems installed in mobile vehicles, and for display devices used in digital signage installed outdoors or indoors, the primary observers (drivers, pedestrians, etc.) may view the screen not only from the normal direction but also from a direction tilted from the normal direction.

[0008] When a brightness-enhancing film that increases only the brightness in the direction of the screen's normal is applied to such a display device, a problem arises where the brightness of the screen in directions tilted from the normal direction drops sharply.

[0009] This invention has been made in view of the above circumstances and aims to provide an optical laminate capable of focusing light in a direction inclined with respect to the normal direction of the screen, and a display unit having said optical laminate. [Means for solving the problem]

[0010] The embodiments of the present invention are as follows.

[0011] [1] A prism member having a first surface on which a prism pattern composed of multiple prism units is formed, and a second surface opposite the first surface on which no prism pattern is formed, An optical laminate in which a light source member having a light source that emits light is stacked, A prism unit has a first prism-forming surface and a second prism-forming surface that protrude from a first surface, and a vertex where the first prism-forming surface and the second prism-forming surface intersect. In a prism-unit cross-section defined by a plane perpendicular to the apex, when the acute angle formed by the first prism-forming surface with respect to the first surface is defined as the first base angle, and the acute angle formed by the second prism-forming surface with respect to the first surface is defined as the second base angle, the angle of the first base angle and the angle of the second base angle are different. The light source component is an optical laminate positioned on the second surface side.

[0012] [2] The optical laminate described in [1], wherein the first base angle is 1° or more and 89° or less, and the second base angle is 1° or more and 89° or less.

[0013] [3] An optical laminate according to [1] or [2], wherein prism units are regularly arranged along any direction on a first plane.

[0014] [4] The prism unit is an optical laminate according to any one of [1] to [3], having a first prism unit and a second prism unit different from the first prism unit.

[0015] [5] An optical laminate according to any one of [1] to [4], further comprising a light diffusing member.

[0016] A display unit having an optical laminate as described in any of [6], [1] to [5], and a display unit. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide an optical laminate capable of focusing light in a direction inclined with respect to the normal direction of the screen, and a display unit having the optical laminate. [Brief explanation of the drawing]

[0018] [Figure 1A] Figure 1A is a schematic perspective view showing an example of an optical laminate according to this embodiment. [Figure 1B] Figure 1B is a schematic cross-sectional view along the IB-IB line shown in Figure 1A. [Figure 2] Figure 2 is a schematic exploded cross-sectional view of the optical laminate according to this embodiment. [Figure 3] FIG. 3 is a schematic plan view showing another example of the optical laminate according to the present embodiment. [Figure 4] FIG. 4 is a schematic cross-sectional view showing another example of the optical laminate according to the present embodiment. [Figure 5] FIG. 5 is a schematic cross-sectional view showing another example of the optical laminate according to the present embodiment. [Figure 6] FIG. 6 is a graph showing the relationship between the light intensity and the emission angle calculated by ray tracing for the optical laminates according to the examples and the comparative examples. [Figure 7] FIG. 7 is a schematic perspective view showing the configuration of a conventional brightness enhancement film.

BEST MODE FOR CARRYING OUT THE INVENTION

[0019] Hereinafter, the present invention will be described in detail based on specific embodiments.

[0020] (1. Optical laminate) The brightness enhancement film improves the brightness of the screen by finally condensing the light emitted from the light source near the normal direction of the screen. Therefore, the brightness enhancement film is used to improve the visibility of an observer located in the normal direction of the screen. However, in such a brightness enhancement film, the brightness of the screen rapidly decreases in a direction inclined at a predetermined angle with respect to the normal direction of the screen. As a result, the visibility rapidly decreases when the line of sight is moved from the normal direction.

[0021] In addition to the normal direction of the screen, examples of display bodies that may view the screen from a direction inclined from the normal direction include information devices such as navigation systems provided in moving bodies such as automobiles, and digital signage installed outdoors or indoors. Therefore, there has been a problem that a conventional brightness enhancement film cannot be applied to display bodies used in such applications.

[0022] In this embodiment, as described below, by using an optical laminate in which a prism member having a predetermined prism pattern and a light source member having a light source are stacked, light from the light source can be focused not only near the normal direction of the screen, but also in directions tilted from the normal direction. Therefore, by applying the optical laminate according to this embodiment to a display, the brightness of the screen is improved and visibility is enhanced even in directions tilted at a predetermined angle with respect to the normal direction of the screen.

[0023] As shown in Figure 1A, the optical laminate 1 according to this embodiment includes a prism member 10 and a light source member 30. In this embodiment, the prism member 10 is a plate-shaped member, and a plurality of prism units 20 are regularly arranged along the X-axis direction on a first surface 11 which is the main surface, forming a prism pattern. The second surface 12 of the prism member 10 is a main surface facing the first surface 11 and faces one of the main surfaces 31 of the light source member 30. No prism pattern is formed on the second surface 12, and in this embodiment, as shown in Figure 1A, the second surface 12 is a flat surface. The light source member 30 has a light source (not shown). Light from the light source is emitted from at least a portion of the main surface 31 that is in contact with the second surface 12 of the prism member 10 and incident on the second surface 12.

[0024] In Figure 1A, the X, Y, and Z axes are orthogonal to each other. The X and Y axes form an XY plane parallel to the main surfaces (first surface 11 and second surface 12) of the prism member 10, and the Z axis is parallel to the direction perpendicular to the main surfaces of the prism member 10 (the stacking direction of the prism member 10 and the light source member 30). On the Z axis, the direction from the second surface 12 toward the first surface 11 is defined as the positive Z-axis direction, and the direction from the first surface 11 toward the second surface 12 is defined as the negative Z-axis direction. The observer is positioned on the positive Z-axis side, and the positive Z-axis direction is the front direction. Furthermore, the normals to the main surfaces (first surface and second surface) of the prism member and the main surface of the light source member all coincide and are parallel to the Z-axis. The same applies to Figures 2 and onward.

[0025] (1.1. Prism component) In the prism member 10, the prism unit 20 has a first prism-forming surface 21 and a second prism-forming surface 22 that protrude from the first surface 11 (protruding in the positive Z-axis direction). The intersection of the first prism-forming surface 21 and the second prism-forming surface 22 forms a vertex 23 parallel to the Y-axis.

[0026] In this embodiment, the prism member is made of a transparent material, and the prism unit may be formed from the transparent material on a transparent substrate having a first surface and a second surface, or the substrate and the prism unit may be made of a transparent material that is integrated with it. Examples of transparent materials include glass and resin.

[0027] Prism components can be manufactured by known means. For example, a prism component may be manufactured by forming a curable resin on a transparent substrate made of glass, resin, etc., pressing a mold with a pattern corresponding to the prism pattern onto the resin to transfer the pattern from the mold to the resin, and then curing it. Alternatively, a prism component may be manufactured by cutting the surface of the transparent substrate with a cutting tool such as a cutting tool to form a prism pattern.

[0028] Figure 1B shows a cross-sectional view obtained by cutting the optical laminate along the IB-IB line (direction perpendicular to the top edge: X-axis direction) shown in Figure 1A. In Figure 1B, the cross-section of each prism unit 20 forms a triangle with the first surface 11 as the base. In the prism unit 20, the acute angle that the first prism constituent surface 21 makes with the first surface 11 is defined as the first base angle θ1, and the acute angle that the second prism constituent surface 22 makes with the first surface 11 is defined as the second base angle θ2.

[0029] In this embodiment, unlike the prism formed on the brightness-enhancing film shown in Figure 7, the first base angle θ1 and the second base angle θ2 of the prism unit are different. In other words, there is an angle difference between the first base angle θ1 and the second base angle θ2. As a result, the light incident on the prism unit is refracted or reflected at the interface of the prism unit and is ultimately focused in a direction inclined from the normal direction. Therefore, when such an optical laminate is used as a display, visibility is good even when viewing the screen from a direction inclined with respect to the normal direction of the screen.

[0030] Figure 2 is a schematic exploded cross-sectional view of the optical laminate shown in Figures 1A and 1B. Note that the prism member shown in Figure 2 is made of a single transparent material. Light from the light source is refracted or reflected at the interface with the second surface 12 depending on the angle of incidence. The reflected light travels in the negative Z-axis direction, is reflected by a reflective part provided on the light source member, for example, and travels in the positive Z-axis direction, reaching the interface with the second surface again.

[0031] On the other hand, the refracted light travels through the prism member in the positive Z-axis direction at a predetermined angle of refraction and is incident on the interface (the first prism surface or the second prism surface). Here, as shown in Figure 1B, the first base angle θ1 is smaller than the second base angle θ2. Consequently, even though the light travels through the prism member at the same angle of refraction, the incident angle θL1in of the light L1 incident on the first prism surface 21 is different from the incident angle θL2in of the light L2 incident on the second prism surface 22.

[0032] Since the critical angle at the first prism surface 21 and the critical angle at the second prism surface 22 are the same, light incident on the first prism surface 21 is more likely to exit from the first prism surface 21 in the positive Z-axis direction (front direction), and light incident on the second prism surface 22 is more likely to be reflected by the second prism surface 22. Much of the light reflected by the second prism surface 22 is incident on the first prism surface 21 and tends to exit in the positive Z-axis direction (front direction) at an angle tilted toward the first prism surface 21 from the normal direction. As a result, the amount of light exiting in the direction tilted toward the first prism surface 21 from the normal direction increases, and light is also focused in a direction tilted at a predetermined angle with respect to the normal direction (front direction) of the screen.

[0033] As mentioned above, the amount of light emitted from the prism surface with a smaller base angle tends to increase. Therefore, by controlling the angles of the first base angle θ1 and the second base angle θ2, the distribution of the emission angle of the focused light intensity can be adjusted.

[0034] In this embodiment, as long as the angle of the first base angle θ1 and the angle of the second base angle θ2 are different, the angle of the first base angle θ1 is preferably 1° to 89°, more preferably 10° to 80°, and even more preferably 30° to 60°. Also, as long as the angle of the first base angle θ1 and the angle of the second base angle θ2 are different, the angle of the second base angle θ2 is preferably 1° to 89°, more preferably 10° to 80°, and even more preferably 30° to 60°.

[0035] Furthermore, the absolute value of the angular difference between the first base angle θ1 and the second base angle θ2 may be between 1° and 88°, between 5° and 60°, or between 10° and 30°. By setting the angular difference within a predetermined range, it becomes easier to control the angular distribution of the focused light.

[0036] The vertex angle of prism unit 20 is the value obtained by subtracting the sum of the first base angle θ1 and the second base angle θ2 from 180°, but in this embodiment it may be between 5° and 175°, between 30° and 150°, or between 60° and 120°. As an example of the most preferred embodiment, the vertex angle may be 90°.

[0037] The length L of the bottom of the prism unit 20 may be 1 to 100,000 μm, 10 to 1,000 μm, or 50 to 150 μm. The height H of the prism unit 20 from the first surface 11 may be 1 to 30,000 μm, 3 to 300 μm, or 10 to 50 μm.

[0038] Furthermore, the thickness T of the prism member 10 (the distance from the second surface 12 to the first surface 11) may be 1 to 10,000 μm, 10 to 1,000 μm, or 50 to 150 μm.

[0039] The refractive index of the prism member 10 may be 1.3 or higher, 1.4 or higher, or 1.45 or higher. The upper limit of the refractive index is 2.7, considering the refractive index of the materials constituting the prism member.

[0040] By controlling the size of the prism components and prism units, it becomes easier to control the angular distribution of the focused light. The appropriate size of the prism components and prism units will vary depending on the overall image and pixel size, as well as the distance to the observer, but generally, the above values ​​will produce the desired effect.

[0041] In Figures 1A and 1B, the prism units 20 are arranged regularly (periodically) along the X-axis on the first surface 11, but the prism units may also be arranged regularly along any direction other than the X-axis. For example, as shown in Figure 3, the prism units 20 may be arranged regularly along a direction tilted 45° from the X-axis.

[0042] Furthermore, in Figures 1A and 1B, one prism unit 20 is repeatedly formed on the first surface 11, but a prism pattern may be formed by combining two or more prism units on the first surface. In Figure 4, on the first surface 11, a first prism unit 21 with a first base angle θA and a second base angle θB, and a second prism unit 22 with a first base angle θC and a second base angle θD are arranged alternately. In addition to the base angles, the apex angle, height, base length, refractive index, etc. of the prism units may differ between the first and second prism units.

[0043] Furthermore, at least one of the first prism surface and the second prism surface does not have to rise from the first surface. For example, as shown in Figure 5, the first prism surface 21 or the second prism surface 22 may rise from the first prism surface 21 or the second prism surface 22 of an adjacent prism unit 20, rather than rising from the first surface 11.

[0044] By controlling the configuration of the prism units, it becomes easier to control the angular distribution of the focused light. Furthermore, if the display unit is a display with pixel units, interference (moire) caused by the periodicity of the pixel units and prism units can be effectively avoided.

[0045] The optical laminates shown in Figures 1A and 1B have one prism member, but may have two or more prism members. When there are two prism members, it is preferable that they are laminated so that the top edge of the prism unit formed in one prism member and the top edge of the prism unit formed in the other prism member are perpendicular to each other.

[0046] (1.2. Light source components) The light source component may be an edge-lit backlight, a direct-lit backlight, a light source component incorporated into a self-emissive display such as an organic EL or micro-LED, or a light source component (backlight) incorporated into a liquid crystal display device.

[0047] (1.3. Light Diffusing Material) The optical laminate according to this embodiment may have components other than the prism member and the light source member. For example, in order to widen the viewing angle and make the display area uniformly bright, the optical laminate according to this embodiment may have a light diffusing member.

[0048] A light-diffusing member scatters light incident on it, causing it to emit light that spreads in the direction of propagation. Therefore, by having a light-diffusing member in an optical laminate, the intensity distribution of the emitted light is broadened, and uniform brightness can be obtained.

[0049] Examples of light diffusing members include light diffusing members with uneven surfaces formed by fine particles, light diffusing members with a smooth surface and fine particles inside, and light diffusing members in which multiple high refractive index regions and low refractive index regions alternate, with each region extending in the thickness direction. From the viewpoint of preventing surface scattering and backscattering of incident light, light diffusing members in which multiple high refractive index regions and low refractive index regions alternate, with each region extending in the thickness direction, are preferred.

[0050] Examples of light diffusing members having multiple alternating high-refractive-index and low-refractive-index regions, each extending in the thickness direction, include a light diffusing member having a structure in which plate-like regions of high refractive index and plate-like regions of low refractive index are alternately arranged in parallel in the plane direction of the light diffusing member, a so-called louver structure, and a light diffusing member having a structure in which multiple columnar objects with relatively high refractive index are lined up in a region with a relatively low refractive index along the thickness direction of the light diffusing member, a so-called column structure.

[0051] A light-diffusing member having a louver structure is a member that diffuses incident light from a point light source in a linear manner (anisotropic diffusion), for example, an anisotropic diffusion film (ADF). A light-diffusing member having a column structure is a member that diffuses incident light from a point light source in a circular manner (isotropic diffusion), for example, an isotropic diffusion film (IDF). Furthermore, light-diffusing members may have both louver and column structures. Light-diffusing members having louver structures, light-diffusing members having column structures, and light-diffusing members having both louver and column structures can be used depending on the application of the display.

[0052] The light diffusing member may be positioned on the first side of the prism member or on the second side.

[0053] (2.Display body) The display body according to this embodiment comprises the optical laminate described above and a display unit. The display unit may be a display unit that displays still images or a display unit that displays moving images. The configuration of the display unit may be a transmissive display or an image display device described above in which a light source member of the optical laminate and a display are combined. Examples of transmissive displays include those on which visual information is displayed on a transparent substrate such as a liquid crystal panel or an acrylic plate.

[0054] If the display unit is a transmissive display, the display unit is located on the prism member side of the optical laminate.

[0055] The display unit may have components other than those described above. Examples of such components include known components used in display units, such as polarizing films, color filters, and reflective films.

[0056] The display unit is obtained by laminating an optical laminate, a light source component, and other components as needed using a transparent adhesive, or by laminating them while leaving air interfaces.

[0057] Although embodiments of the present invention have been described above, the present invention is not limited in any way to the embodiments described above, and may be modified in various ways within the scope of the present invention. [Examples]

[0058] The invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0059] In this embodiment, the optical laminate was evaluated by ray tracing. Ray tracing is a simulation method that determines how light rays incident on an optical element are refracted or reflected at the interface and how they exit the optical element, assuming a given optical element.

[0060] The optical laminate of Example 1 had a prism member in which prism units were arranged, each having a first base angle θ1 of 35°, a second base angle θ2 of 55°, and a base length of 100 μm, with a distance (thickness) of 30 μm between the first and second surfaces. The refractive index of the prism member was 1.5, and the refractive index of air was 1. The light source member was positioned in contact with the second surface of the prism member and was configured to emit light in all directions from the entire contact surface.

[0061] The optical laminate of Example 2 had prism members that were the same as those of Example 1, except that the first base angle of the prism unit was 35° and the second base angle was 45°. The light source member was the same as that of Example 1.

[0062] The optical laminate of Comparative Example 1 had a prism member that was the same as the prism member of Example 1, except that the first and second base angles of the prism unit were both 45°. The light source member was the same as the light source member of Example 1.

[0063] Ray tracing was performed under the condition that all light that does not satisfy the total internal reflection condition at the interface is refracted, and all light that does satisfy the total internal reflection condition is reflected.

[0064] The angle of incidence and emission of light rays were defined with the normal direction of the optical stack (direction in front of the observer) set as 0°. The angle between a light ray incident or emitted from the positive X-axis side and the normal (the acute angle at the base when the light ray is represented as an arrow indicating the direction of propagation) was represented as + (plus), and the angle between a light ray incident or emitted from the negative X-axis side and the normal was represented as - (minus).

[0065] Ray tracing was performed on incident light with uniform brightness (strong front light intensity at cosθ and weak diffuse light distribution at oblique angles) at incident angles from -89° to +89° in 0.02° increments, when incident light was introduced from the second surface of the prism member. The light intensity of the emitted light from each prism unit was calculated in 1° increments. Figure 6 shows the angular distribution of the emitted light when the integrated amount of incident light is set to 100%. Table 1 shows the light intensity at 0° and at -44°.

[0066] Furthermore, the angle at which the light intensity exceeds 0.5% was used as the threshold, and the positive and negative threshold angles were calculated. The results are shown in Table 1.

[0067] The light intensity returning to the light source was calculated when the integrated amount of incident light was set to 100%. The results are shown in Table 1.

[0068] [Table 1]

[0069] From Figure 6 and Table 1, it was confirmed that in Comparative Example 1, the distribution of light intensity and the threshold angle were almost symmetrical with respect to the front direction (0°), and the light intensity at -44° was 0.

[0070] On the other hand, in Example 1, the light intensity distribution and threshold angle were shifted to the negative side compared to Comparative Example 1. As a result, while the light intensity at 0° was equivalent to that of Comparative Example 1, the light intensity at -44° was approximately 80% of that at 0°, confirming that good visibility could be obtained even at -44°.

[0071] In Example 2, the light intensity distribution and threshold angle were similar on the positive side and wider on the negative side compared to Comparative Example 1. Similar to Example 1, the light intensity at 0° was equivalent to that of Comparative Example 1, while good visibility was also confirmed at -44°. Furthermore, the light intensity returning to the light source was confirmed to be equivalent to that of Comparative Example 1.

[0072] From the above, it was confirmed that an optical laminate equipped with a prism member having the above-described configuration can provide a bright display not only in the front direction but also in the direction tilted from the front, thereby widening the viewing angle. [Industrial applicability]

[0073] The optical laminate of the present invention can be suitably used, for example, in information equipment such as navigation systems installed in mobile vehicles, or in display elements used in digital signage installed outdoors or indoors. [Explanation of symbols]

[0074] 1...Optical laminate 10…Prism component 11…First side 12…Second side 20...Prism units 21...First prism configuration surface 22...Second prism configuration surface 23...Top 30…Light source component

Claims

1. A prism member having a first surface on which a prism pattern composed of multiple prism units is formed, and a second surface opposite the first surface on which no prism pattern is formed, An optical laminate in which a light source member having a light source that emits light is stacked, The prism unit comprises a first prism-forming surface and a second prism-forming surface that protrude from the first surface, and the first prism-forming surface and the second prism The constituent surfaces intersect at the top edge, In the cross-section of the prism unit with respect to the aforementioned apex, when the acute angle formed by the first prism constituent surface with respect to the first surface is defined as the first base angle, and the acute angle formed by the second prism constituent surface with respect to the first surface is defined as the second base angle, the angle of the first base angle and the angle of the second base angle are different. The light source member is an optical laminate disposed on the second surface side.

2. The optical laminate according to claim 1, wherein the first base angle is 1° or more and 89° or less, and the second base angle is 1° or more and 89° or less.

3. The optical laminate according to claim 1 or 2, wherein the prism units are regularly arranged along any direction on the first surface.

4. The optical laminate according to claim 1 or 2, wherein the prism unit comprises a first prism unit and a second prism unit different from the first prism unit.

5. The optical laminate according to claim 1 or 2, further comprising a light diffusing member.

6. A display unit having an optical laminate according to claim 1 or 2 and a display unit.

Images