Display device

Abstract

To provide a display device equipped with a liquid crystal panel having a polymer dispersed liquid crystal layer capable of obtaining high luminance even when the area of a display screen is made large.SOLUTION: A liquid crystal panel including a pair of substrates and a polymer dispersed liquid crystal layer sandwiched between the pair of substrates, the liquid crystal panel being curved such that a center of the liquid crystal panel in a curve direction along a surface of the liquid crystal panel protrudes toward a front side of the liquid crystal panel more than both ends of the liquid crystal panel in the curve direction, the light sources are disposed along at least one of both end portions of the liquid-crystal panel extending along a direction orthogonal to the curved direction in a plan view, and when a length of the liquid-crystal panel along the curved direction is W1 (unit: cm), a radius of curvature of the liquid-crystal panel is 1 / (W1 * 40) or more and 1 / (W1 * 1.25) or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The following disclosure relates to display devices. [Background technology]

[0002] A liquid crystal display device is a display device that uses a liquid crystal composition for display, and a typical display method thereof is to apply a voltage to a liquid crystal composition sealed between a pair of substrates, and to control the amount of light transmission by changing the alignment state of the liquid crystal component in the liquid crystal composition in response to the applied voltage. Such liquid crystal display devices are used in a wide range of fields, taking advantage of their features such as thinness, light weight, and low power consumption.

[0003] In recent years, see-through displays, which allow the backside of a liquid crystal display device to be seen through, have been attracting attention. Liquid crystal display devices using polymer-dispersed liquid crystal (PDLC) have been developed as see-through displays. PDLC has a liquid crystal component dispersed in a polymer network, and by changing the orientation of the liquid crystal component through the application of a voltage, the difference in refractive index between the liquid crystal component and the polymer network can be utilized to switch between a transparent state and a scattering state.

[0004] For example, Patent Document 1 discloses a display device including a display panel having a first substrate, a second substrate opposite the first substrate, and a polymer dispersed liquid crystal layer held between the first substrate and the second substrate and containing a polymer and liquid crystal molecules; a light guiding layer having a light emitting element, a first surface opposite the display panel, and an end portion opposite the light emitting element; and a first optical layer located between the display panel and the light guiding layer, wherein the refractive index of the first optical layer is lower than the refractive index of the light guiding layer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-032411 Summary of the Invention [Problem to be solved by the invention]

[0006] An example of a light source for a see-through display is an edge-lit backlight. By using an edge-lit backlight, the liquid crystal display device can be made thinner. An example of an edge-lit backlight is a light-guiding backlight using a light guide plate. In the light-guiding backlight using the light guide plate, a light source is disposed on a side surface of the light guide plate, and light incident from the light source on the side surface of the light guide plate is repeatedly reflected within the light guide plate and emitted to the front surface.

[0007] However, some of the light reflected by the light guide plate is diffracted and lost by components such as thin film transistors (TFTs) in the liquid crystal panel, so the further away from the light source the greater the light loss, which can result in a decrease in frontal characteristics such as brightness at the center of the display screen.

[0008] This deterioration in front-facing characteristics at the center of the display screen becomes more pronounced as the display screen becomes larger. Furthermore, some of the transmitted light is lost due to scattering when passing through PDLC. For this reason, it has been difficult to achieve both a large display screen area and good front-facing characteristics in a thin see-through display.

[0009] An object of the present invention is to provide a display device equipped with a liquid crystal panel having a polymer dispersed liquid crystal layer that can provide high brightness even when the display screen is enlarged. [Means for solving the problem]

[0010] (1) One embodiment of the present invention is a display device comprising a pair of substrates, a liquid crystal panel having a polymer dispersed liquid crystal layer sandwiched between the pair of substrates, and a light source arranged on the rear side of the liquid crystal panel at a distance from the liquid crystal panel, wherein the liquid crystal panel is curved so that the center of the curvature direction along the surface of the liquid crystal panel protrudes toward the front side of the liquid crystal panel more than both ends in the curvature direction, and the light source is arranged along at least one of the both ends of the liquid crystal panel extending in a direction perpendicular to the curvature direction in a planar view, and where W1 (unit: cm) is the length of the liquid crystal panel along the curvature direction, the curvature of the liquid crystal panel is 1 / (W1 x 40) or more and 1 / (W1 x 1.25) or less.

[0011] (2) Another embodiment of the present invention is a display device comprising a pair of substrates, a liquid crystal panel having a polymer dispersed liquid crystal layer sandwiched between the pair of substrates, and a light source arranged on the rear side of the liquid crystal panel at a distance from the liquid crystal panel, wherein the liquid crystal panel is curved so that the center of the curvature direction along the surface of the liquid crystal panel protrudes toward the rear side of the liquid crystal panel more than both ends in the curvature direction, and the light source is arranged along at least one of the both ends of the liquid crystal panel extending in a direction perpendicular to the curvature direction in a planar view, and where W1 (unit: cm) is the length of the liquid crystal panel along the curvature direction, the curvature of the liquid crystal panel is 1 / (W1 x 40) or more and 1 / (W1 x 1.25) or less.

[0012] (3) Furthermore, in addition to the configuration of (1) or (2), an embodiment of the present invention is a display device in which the light source irradiates light obliquely onto the surface of the liquid crystal panel.

[0013] (4) Furthermore, one embodiment of the present invention is a display device having any of the configurations (1) to (3) above, wherein the projection angle of light incident from the light source onto the center of the liquid crystal panel is 54.0° or more and 76.0° or less.

[0014] (5) Furthermore, in addition to the configuration of (4), one embodiment of the present invention is a display device in which the curvature of the liquid crystal panel is 1 / (W1×25) or more and 1 / (W1×1.25) or less.

[0015] (6) Furthermore, one embodiment of the present invention is a display device in which, in addition to the configuration of (2) or (3) above, the projection angle of light incident from the light source onto the center of the liquid crystal panel is 60.0° or more and 70.0° or less.

[0016] (7) Furthermore, one embodiment of the present invention is a display device having any of the configurations (1) to (3) above, wherein the curvature of the liquid crystal panel is 1 / (W1×13.75) or more and 1 / (W1×1.25) or less, and the projection angle of light incident from the light source on the center of the liquid crystal panel is 54.0° or more and 75.0° or less.

[0017] (8) Furthermore, one embodiment of the present invention is a display device having any of the configurations (1) to (3) above, wherein the curvature of the liquid crystal panel is 1 / (W1×5) or more and 1 / (W1×1.25) or less, and the projection angle of light incident from the light source on the center of the liquid crystal panel is 54.0° or more and 73.5° or less.

[0018] (9) Furthermore, one embodiment of the present invention is a display device having any of the configurations (1) to (3) above, wherein the curvature of the liquid crystal panel is 1 / (W1×2.5) or more and 1 / (W1×1.25) or less, and the projection angle of light incident from the light source to the center of the liquid crystal panel is 54.0° or more and 71.0° or less.

[0019] (10) Furthermore, one embodiment of the present invention is a display device having any of the configurations (1) to (3) above, wherein the curvature of the liquid crystal panel is 1 / (W1×2) or more and 1 / (W1×1.25) or less, and the projection angle of light incident from the light source on the center of the liquid crystal panel is 54.0° or more and 70.0° or less.

[0020] (11) Furthermore, one embodiment of the present invention is a display device having any of the configurations (1) to (3) above, wherein, when the distance from the light source to the liquid crystal panel is d1, the d1 is 1 / 10 or more and 1 / 3 or less of the W1.

[0021] (12) Furthermore, one embodiment of the present invention is a display device having the configuration of any one of (1) to (11) above, further comprising a display panel on the rear side of the liquid crystal panel.

[0022] (13) Furthermore, in addition to the configuration of (12), another embodiment of the present invention is a display device in which the display panel is curved so as to protrude toward the liquid crystal panel.

[0023] (14) Furthermore, in addition to the configuration of (12), an embodiment of the present invention is a display device in which the display panel is curved so as to protrude toward the side opposite to the liquid crystal panel side. [Effects of the Invention]

[0024] According to the present invention, it is possible to provide a display device that is thin and includes a liquid crystal panel having a polymer dispersed liquid crystal layer that can provide high brightness even when the display screen is enlarged. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a cross-sectional view schematically illustrating an example of a display device according to a first embodiment. [Figure 2] FIG. 2 is a schematic plan view of the display device shown in FIG. [Figure 3] 10A and 10B are schematic cross-sectional views of a liquid crystal panel illustrating a method for measuring a projection angle. [Figure 4] 10 is a cross-sectional view illustrating the projection angle from the edge of the liquid crystal panel to a predetermined point in the first embodiment in which the liquid crystal panel is bent toward the front side. FIG. [Figure 5] 1 is a cross-sectional view illustrating a transparent state of a polymer-dispersed liquid crystal layer. FIG. [Figure 6] 1A and 1B are cross-sectional schematic diagrams illustrating the scattering state of a polymer-dispersed liquid crystal layer. [Figure 7] 10 is a graph showing the angle dependence of a polymer dispersed liquid crystal layer. [Figure 8] 1 is a cross-sectional view showing an example of a display device according to Embodiment 1, which includes a display panel on the rear side of a liquid crystal panel. [Figure 9] 10 is a cross-sectional view schematically illustrating another example of the display device according to Embodiment 1, which includes a display panel on the rear side of the liquid crystal panel. FIG. [Figure 10] 10 is a cross-sectional view schematically illustrating an example of a display device according to a second embodiment. FIG. [Figure 11] FIG. 11 is a schematic plan view of the display device shown in FIG. [Figure 12] 10 is a cross-sectional view illustrating the projection angle from the edge of the liquid crystal panel to a predetermined point in the second embodiment in which the liquid crystal panel is bent toward the rear side. FIG. [Figure 13] 10 is a graph showing the angle dependence of the polymer dispersed liquid crystal layer used in the examples and comparative examples. [Figure 14] 10 is a cross-sectional view illustrating the projection angle at the center of the liquid crystal panel in Comparative Example 1. FIG. [Figure 15] 10 is a cross-sectional view illustrating the projection angle from an end of a liquid crystal panel to a predetermined point in Comparative Example 1. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0026] The present invention will be described in more detail below with reference to the drawings and with reference to the following embodiments, but the present invention is not limited to these embodiments.

[0027] <Embodiment 1> The display device of embodiment 1 comprises a pair of substrates, a liquid crystal panel having a polymer dispersed liquid crystal layer sandwiched between the pair of substrates, and a light source arranged on the back side of the liquid crystal panel at a distance from the liquid crystal panel, wherein the liquid crystal panel is curved so that the center of the curvature direction along the surface of the liquid crystal panel protrudes toward the front side of the liquid crystal panel more than both ends in the curvature direction, and the light source is arranged along at least one of the both ends of the liquid crystal panel extending along a direction perpendicular to the curvature direction in a planar view, and when the length of the liquid crystal panel along the curvature direction is W1 (unit: cm), the curvature of the liquid crystal panel is 1 / (W1 x 40) or more and 1 / (W1 x 1.25) or less.

[0028] FIG. 1 is a cross-sectional view schematically illustrating an example of a display device according to embodiment 1. FIG. 2 is a plan view schematically illustrating the display device shown in FIG. 1. FIG. 1 is a cross-sectional view taken along the curved direction along line X1-X2 in FIG. 2. As shown in FIG. 1, a display device 200A according to embodiment 1 includes a liquid crystal panel 100A and a light source 2 disposed on the rear side of the liquid crystal panel 100A. The light source 2 may be fixed to a housing (not shown), for example. In this specification, the term "front side" refers to the side closer to a viewer positioned in front of the display screen of the display device, and refers to the side closer to the display screen within the display device. The term "rear side" refers to the side farther from the viewer, and refers to the side farther from the display screen within the display device, opposite the front side.

[0029] The light source 2 is disposed on the rear side of the liquid crystal panel 100A with a gap between them. In other words, the light source 2 is disposed on the rear side of the liquid crystal panel 100A with an air gap between them. Conventional display devices have used edge-type backlights with a light guide plate, or have used transparent optical sheets (OCA) to bond the liquid crystal panel and the light guide plate. Light irradiated horizontally onto the side surface of the light guide plate is reflected inside the light guide plate and emitted toward the liquid crystal panel. However, light reflections inside the light guide plate and light loss when passing through the OCA can result in low brightness of the display device. In the display device 200A, the light source 2 is disposed on the rear side of the liquid crystal panel 100A with a gap between them with an air gap between them, eliminating the reflections inside the conventional light guide plate and the light loss when passing through the OCA, thereby increasing brightness.

[0030] If W1 is the length of the liquid crystal panel 100A along the curvature direction (described later) and d1 is the distance from the light source 2 to the liquid crystal panel 100A, then d1 is preferably 1 / 10 to 1 / 3 of W1. By setting the value in this range, the difference in brightness between the center and edges of the liquid crystal panel can be reduced. The distance d1 is the distance from a perpendicular line drawn toward the light source 2 from a line connecting both ends of the rear substrate of the liquid crystal panel 100A along the curvature direction.

[0031] The above d1 is appropriately selected depending on the size and use of the display device, but is, for example, 1 cm or more and 15 cm or less. When the display device 200A is used in an amusement device, the above d1 is preferably 5 cm or more and 10 cm or less. In order to ensure the brightness of the display device when driven by FSC, which will be described later, the above d1 is preferably 5 cm or more.

[0032] The light source 2 is arranged along at least one of the ends of the liquid crystal panel 100A extending in a direction perpendicular to the curvature direction of the liquid crystal panel 100A in a planar view. The light source 2 is preferably arranged so that the extension direction of the light source 2 is parallel to at least one of the ends of the liquid crystal panel 100A in a planar view. For example, when the light source 2 includes a plurality of point light sources such as LEDs, the arrangement direction of the plurality of light sources is preferably parallel to at least one of the ends of the liquid crystal panel 100A. When the light source 2 is a rod-shaped light source such as a linear fluorescent lamp, the light source is preferably arranged so that the longitudinal direction of the light source is parallel to at least one of the ends of the liquid crystal panel 100A. The light source 2 may be arranged along at least one of the ends of the liquid crystal panel 100A extending in a direction perpendicular to the curvature direction, but may include a first light source 2A arranged along one of the opposing ends and a second light source 2B arranged along the other. 1 and 2 show an example in which the liquid crystal panel 100A is a rectangular curved panel curved along the long side direction of the liquid crystal panel 100A, and the first light source 2A and the second light source 2B are arranged along the opposing short sides of the liquid crystal panel 100A. In this specification, when there is no need to particularly distinguish between the first light source 2A and the second light source 2B, they will simply be referred to as light source 2.

[0033] The light source 2 is disposed on the rear side of the liquid crystal panel 100A at a distance from the liquid crystal panel 100A and along at least one of the ends of the liquid crystal panel 100A extending in a direction perpendicular to the curvature direction in a plan view. This allows light emitted from the light source 2 to be irradiated obliquely toward the liquid crystal panel 100A. Irradiating light obliquely toward the liquid crystal panel 100A means that the light irradiated from the light source 2 is not parallel to the surface of the liquid crystal panel 100A. Irradiating light from the light source 2 obliquely toward the liquid crystal panel 100A can reduce light attenuation and increase brightness near the center of the liquid crystal panel compared to conventional edge-light systems where light is incident from the side of the light guide plate. The light source 2 preferably irradiates light obliquely toward the surface of the liquid crystal panel 100A, and more preferably irradiates light toward the center of the curvature direction of the liquid crystal panel 100A. The light source 2 can be positioned and oriented so that the center of its illumination range coincides with the center of the curvature direction of the liquid crystal panel 100A.

[0034] The light source 2 may be monochromatic or may include light-emitting elements of multiple colors. Examples of the light-emitting elements include light-emitting diodes (LEDs). The light-emitting elements preferably emit light in the same direction. The light-emitting elements of multiple colors may include, for example, a red light-emitting element R, a green light-emitting element G, and a blue light-emitting element B.

[0035] The liquid crystal panel 100A is a curved panel. In the first embodiment, a case will be described in which the liquid crystal panel 100A is curved so that the center of the curved surface of the panel protrudes further toward the front surface of the liquid crystal panel 100A than both ends of the curved surface. By curving the liquid crystal panel 100A, the angle of incidence of light incident on the liquid crystal panel 100A from the light source 2 can be reduced. As a result, the reflectance on the surface of the liquid crystal panel 100A can be reduced, and the brightness of the display device 200A can be improved.

[0036] The inventors' research has revealed that, for a flat, uncurved liquid crystal panel, arranging a light source behind the liquid crystal panel at a distance from the panel and along the edge of the panel in a planar view suppresses light attenuation within the panel, but increases the surface reflectivity near the center of the liquid crystal panel, resulting in reduced brightness of the display device. For example, the reflectivity of the glass substrate (flat synthetic quartz (refractive index: 1.458)) increases as the angle of incidence increases. That is, for a flat, uncurved liquid crystal panel, when light is emitted from a light source arranged behind the liquid crystal panel at a distance from the panel and along the edge of the panel in a planar view, the angle of incidence near the center of the liquid crystal panel is larger than the angle of incidence near the edge of the liquid crystal panel, resulting in increased surface reflectivity near the center of the liquid crystal panel. As a result, the brightness and contrast of the display device decrease. In contrast, the present invention uses a curved panel to reduce the reflectivity of the panel surface. Furthermore, in the first embodiment, by increasing the curvature of the liquid crystal panel 100A, the difference in brightness between the center and the edges of the liquid crystal panel can be reduced, and the brightness and contrast of the entire liquid crystal panel can be improved.

[0037] If the length of the liquid crystal panel 100A along the curvature direction of the liquid crystal panel 100A is W1 (unit: cm), the curvature of the liquid crystal panel is 1 / (W1×40) or more and 1 / (W1×1.25) or less. W1 is the length (unit: cm) of the front surface of the liquid crystal panel 100A along the curvature direction of the liquid crystal panel 100A. By setting the curvature of the liquid crystal panel to 1 / (W1×40) or more, the surface reflectance at the center of the liquid crystal panel 100A can be reduced, thereby improving the brightness of the display device. Furthermore, by setting the curvature of the liquid crystal panel to 1 / (W1×1.25) or less, deterioration of the panel appearance due to excessive curvature can be suppressed. If the curvature of the liquid crystal panel is less than 1 / (W1×40), the surface reflection of the liquid crystal panel 100A cannot be sufficiently reduced. The curvature of the liquid crystal panel 100A may be 1 / (W1×25) or more and 1 / (W1×1.25) or less.

[0038] The length W1 of the liquid crystal panel may be 15 cm or more and 150 cm or less, for example, 40 cm for a 19-inch liquid crystal panel.

[0039] The projection angle of light incident from the light source 2 onto the center of the liquid crystal panel 100A may be 54.0° or more and 76.0° or less. This configuration effectively increases the brightness at the center of the panel. Hereinafter, the projection angle of light incident from the light source 2 onto the center of the liquid crystal panel 100A will also be referred to as the "projection angle from the light source 2 to the center of the liquid crystal panel 100A."

[0040] Fig. 3 is a cross-sectional schematic diagram of a liquid crystal panel illustrating a method for measuring the projection angle. As shown in Fig. 3, if the direction toward the light source 2 that is perpendicular to the tangent β at an arbitrary point α on the surface of the rear side of the liquid crystal panel 100A in a cross section along the curvature direction is defined as the 0° direction, and the angle θx formed between the 0° direction and light irradiated from the light source 2 onto the rear side of the liquid crystal panel 100A is defined as the θx, then the θx is the projection angle of light incident from the light source to the arbitrary point α of the liquid crystal panel 100A (the projection angle from the light source to point α). Note that for ease of explanation, a flat panel is shown in Fig. 3, but in this embodiment, the substrates 10 and 20 are curved.

[0041] In a cross section taken along the curvature direction, when the arbitrary point α is the center point of the liquid crystal panel 100A in the curvature direction, if the direction toward the light source 2 that is perpendicular to the tangent β at point α is defined as the 0° direction, the projection angle of light incident from the light source 2 to the center of the liquid crystal panel 100A is the angle between the light emitted from the light source 2 and the 0° direction. The direction of the light incident from the light source 2 to the center of the liquid crystal panel 100A may be parallel to the curvature direction of the liquid crystal panel 100A in a plan view.

[0042] When the light source 2 includes a first light source 2A and a second light source 2B, the projection angle of the light irradiated from the first light source 2A to an arbitrary point α is defined as θ1, and the projection angle of the light irradiated from the second light source 2B to an arbitrary point α is defined as θ2, as shown in FIG. 、The projection angle θ2 of the light incident from the second light source 2B to the center of the liquid crystal panel is equal. Therefore, the projection angle of the light incident from the first light source 2A to the center of the liquid crystal panel 100A (the projection angle from the first light source 2A to the center of the liquid crystal panel 100A) and the projection angle of the light incident from the second light source 2B to the center of the liquid crystal panel 100A (the projection angle from the second light source 2B to the center of the liquid crystal panel 100A) may both be 54.0° or more and 76.0° or less.

[0043] The curvature of the liquid crystal panel 100A may be 1 / (W1×13.75) or more and 1 / (W1×1.25) or less. In this case, the projection angle at the center of the liquid crystal panel 100A may be 54.0° or more and 75.0° or less. When the light source 2 includes a first light source 2A and a second light source 2B, the projection angle from the first light source 2A to the center of the liquid crystal panel 100A and the projection angle from the second light source 2B to the center of the liquid crystal panel 100A may both be 54.0° or more and 75.0° or less.

[0044] The curvature of the liquid crystal panel 100A may be 1 / (W1×5) or more and 1 / (W1×1.25) or less. In this case, the projection angle at the center of the liquid crystal panel 100A may be 54.0° or more and 73.5° or less. When the light source 2 includes a first light source 2A and a second light source 2B, the projection angle from the first light source 2A to the center of the liquid crystal panel 100A and the projection angle from the second light source 2B to the center of the liquid crystal panel 100A may both be 54.0° or more and 73.5° or less.

[0045] The curvature of the liquid crystal panel 100A may be 1 / (W1×2.5) or more and 1 / (W1×1.25) or less. In this case, the projection angle at the center of the liquid crystal panel 100A may be 54.0° or more and 71.0° or less. When the light source 2 includes a first light source 2A and a second light source 2B, the projection angle from the first light source 2A to the center of the liquid crystal panel 100A and the projection angle from the second light source 2B to the center of the liquid crystal panel 100A may both be 54.0° or more and 71.0° or less.

[0046] The curvature of the liquid crystal panel 100A may be 1 / (W1×2) or more and 1 / (W1×1.25) or less. In this case, the projection angle at the center of the liquid crystal panel 100A may be 54.0° or more and 70.0° or less. When the light source 2 includes a first light source 2A and a second light source 2B, the projection angle from the first light source 2A to the center of the liquid crystal panel 100A and the projection angle from the second light source 2B to the center of the liquid crystal panel 100A may both be 54.0° or more and 70.0° or less.

[0047] FIG. 4 is a cross-sectional schematic diagram illustrating the projection angle of a predetermined point from the edge of the liquid crystal panel in the first embodiment, in which the liquid crystal panel is bent toward the front side. An arbitrary point α on the rear surface of the liquid crystal panel 100A in a cross section along the curvature direction is defined as the predetermined point from the edge of the liquid crystal panel, and the direction toward the light source 2 that is perpendicular to the tangent line β at point α is defined as the 0° direction. When the first light source 2A and the second light source 2B are disposed at both ends of the liquid crystal panel 100A, the projection angle refers to either θ1 or θ2, whichever is closer to the light source. Because the light source 2 is disposed at a distance from the liquid crystal panel 100A on the rear side of the liquid crystal panel 100A, both θ1 and θ2 are greater than 0° and less than 90°.

[0048] The projection angle at a point 1 / 4 of the way from the edge of the liquid crystal panel 100A may be 45° or more and 65° or less. The projection angle at a point 1 / 4 of the way from the edge of the liquid crystal panel 100A is the projection angle at a point 1 / 4 of the length W1 of the liquid crystal panel from the edge of the liquid crystal panel 100A along the curvature direction toward the center of the liquid crystal panel 100A.

[0049] The projection angle at a point 1 / 8 of the way from the edge of the liquid crystal panel 100A in the cross section along the curvature direction may be 27° or more and 55° or less. The projection angle at a point 1 / 8 of the way from the edge of the liquid crystal panel 100A is the projection angle at a point 1 / 8 of the length W1 of the liquid crystal panel from the edge of the liquid crystal panel 100A along the curvature direction toward the center of the liquid crystal panel 100A.

[0050] The width W2 of the liquid crystal panel 100A may be equal to or greater than W1 × 0.95 cm and less than W1 × 1 cm. The width W2 is the width of the liquid crystal panel 100A when projected onto a tangent plane at the center of its surface, and is not the actual width of the liquid crystal panel 100A, but rather the apparent panel width taking curvature into consideration. The width W2 is smaller than the width W1.

[0051] The height H of the liquid crystal panel 100A may be 15 cm or more and 150 cm or less. The height H is the width of the liquid crystal panel 100A in a direction perpendicular to the curvature direction in a plan view.

[0052] The depth d2 of the liquid crystal panel 100A may be 1 / 320 or more and 1 / 10 or less of the length W1 of the liquid crystal panel along the curvature direction. The depth d2 is the distance from both ends of the liquid crystal panel 100A along the curvature direction to the tangent plane at the center of the front surface of the liquid crystal panel 100A. The depth d2 of the liquid crystal panel 100A may be 0.1 cm or more and W1 × 0.1 cm or less.

[0053] 1, the liquid crystal panel 100A has a pair of substrates 10 and 20 and a polymer dispersed liquid crystal layer 30. The polymer dispersed liquid crystal layer 30 is sandwiched between the pair of substrates 10 and 20. The edges of the substrates 10 and 20 are sealed with a sealant 1, and the polymer dispersed liquid crystal layer 30 is surrounded by the sealant 1 in a plan view.

[0054] The polymer-dispersed liquid crystal (PDLC) layer 30 includes a polymer network 31 and a liquid crystal component 32 dispersed in the polymer network 31. The polymer-dispersed liquid crystal layer 30 is controlled so that it is transparent when no voltage is applied, allowing the background to be seen through, and is controlled so that it is scattered when voltage is applied, scattering light incident from the light source. The display mode in which the layer is transparent when no voltage is applied and scattered when voltage is applied is also called reverse mode. The display mode in which the layer is scattered when no voltage is applied and transparent when voltage is applied is also called normal mode. The "no voltage application" refers to when the voltage applied to the polymer-dispersed liquid crystal layer 30 is less than the threshold voltage of the liquid crystal component (including when no voltage is applied), and the "voltage application" refers to when the voltage applied to the polymer-dispersed liquid crystal layer 30 is equal to or greater than the threshold voltage of the liquid crystal component.

[0055] The alignment states of the liquid crystal component in the transparent state and the scattering state will be described below with reference to FIGS. 5 and 6. FIG. 5 is a cross-sectional view illustrating the transparent state of the polymer-dispersed liquid crystal layer. FIG. 6 is a cross-sectional view illustrating the scattering state of the polymer-dispersed liquid crystal layer. As shown in FIGS. 5 and 6, the substrates 10 and 20 preferably have electrodes for applying a voltage to the polymer-dispersed liquid crystal layer 30. The electrode arrangement is not particularly limited, but for example, the substrate 10 may have a base material 11, an electrode 12, and an alignment film 13 in this order, and the substrate 20 may have a base material 21, an electrode 22, and an alignment film 23 in this order.

[0056] Examples of the substrates 11 and 21 include transparent substrates such as glass substrates and plastic substrates. A transparent substrate refers to a substrate having a total light transmittance of 90% or more. In this specification, the total light transmittance is measured by a method conforming to JIS K 7361-1. The total light transmittance can be measured using, for example, a turbidity meter such as the "HazeMeter NDH2000" manufactured by Nippon Denshoku Industries Co., Ltd.

[0057] It is preferable that electrodes 12 and 22 are connected to different power sources and supplied with different potentials. In the case of Fig. 5, when a voltage is applied to polymer dispersed liquid crystal layer 30, a vertical electric field is formed between electrode 12 and electrode 22 along the thickness direction of polymer dispersed liquid crystal layer 30. Examples of materials for electrodes 12 and 22 include transparent conductive materials such as indium tin oxide (ITO) and indium zinc oxide (IZO).

[0058] The alignment films 13 and 23 are preferably disposed on the side of the substrate 10 facing the polymer-dispersed liquid crystal layer 30 and the side of the substrate 20 facing the polymer-dispersed liquid crystal layer 30, respectively, and are in contact with the polymer-dispersed liquid crystal layer 30. The alignment films 13 and 23 control the alignment direction of the liquid crystal component 32 dispersed in the polymer network 31 when no voltage is applied to the polymer-dispersed liquid crystal layer 30. The alignment films 13 and 23 are preferably subjected to a parallel alignment treatment so that when no voltage is applied, the long axis direction of the liquid crystal component is homogeneously aligned in parallel to the surfaces of the substrates 10 and 20. The material of the alignment films 13 and 23 is not particularly limited, and materials commonly used in the field of liquid crystal displays, such as rubbing alignment film materials and photo-alignment film materials, can be used.

[0059] As shown in Figure 5, when no voltage is applied, it is preferable that the orientation directions of the polymer network 31 and the liquid crystal component 32 are approximately the same. Figure 5 illustrates an example in which the polymer network 31 and the liquid crystal component 32 are both homogeneously oriented with respect to the surfaces of substrates 10 and 20. When no voltage is applied, there is almost no difference in the refractive index between the extraordinary refractive index n e of the liquid crystal component 32 and the polymer network 31, and almost no difference in the refractive index between the ordinary refractive index n e of the liquid crystal component 32 and the polymer network 31, in any direction including the thickness direction of the polymer dispersed liquid crystal layer 30. Therefore, light irradiated from the light source passes through the polymer dispersed liquid crystal layer 30, resulting in a transparent state.

[0060] The transparent state is a state in which the polymer dispersed liquid crystal layer 30 is transparent to light. The transmittance of the polymer dispersed liquid crystal layer 30 in the transparent state may be 80% or more, or may be 90% or more. The upper limit of the transmittance of the polymer dispersed liquid crystal layer 30 in the transparent state is, for example, 100%. In this specification, the transmittance of the polymer dispersed liquid crystal layer in the transparent state and the scattering state refers to the parallel light transmittance. The parallel light transmittance can be measured using an LCD5200 (photal) manufactured by Otsuka Electronics.

[0061] As shown in Figure 6, when a voltage is applied, the polymer network 31 remains aligned horizontally relative to the surfaces of substrates 10 and 20, while the liquid crystal component 32 is aligned vertically. When a voltage is applied, the alignment direction of the liquid crystal component 32 changes due to the electric field formed in the polymer-dispersed liquid crystal layer 30, while the polymer network 31 is not affected by the electric field. Therefore, the refractive index difference between the extraordinary refractive index n e of the liquid crystal component 32 and the polymer network 31 and the refractive index difference between the ordinary refractive index n e of the liquid crystal component 32 and the polymer network 31 become large in all directions, including the thickness direction of the polymer-dispersed liquid crystal layer 30. When unpolarized light enters the polymer-dispersed liquid crystal layer 30, the light is scattered regardless of polarization, and the polymer-dispersed liquid crystal layer 30 enters a scattering state.

[0062] The scattering state is a state in which light is scattered, and has an appearance similar to that of frosted glass. The transmittance of the polymer-dispersed liquid crystal layer 30 in the scattering state may be 10% or less, or may be 8% or less. The lower limit of the transmittance of the polymer-dispersed liquid crystal layer 30 in the scattering state is, for example, 0%. The haze, which indicates the light scattering rate of the polymer-dispersed liquid crystal layer 30 in the scattering state, varies depending on the applied voltage and may be, for example, 80% or more, or 90% or more. The upper limit of the haze, which indicates the light scattering rate of the polymer-dispersed liquid crystal layer 30 in the scattering state, is, for example, 100%. In this specification, the haze is measured using a method conforming to JIS K 7136. The haze is measured using, for example, a turbidity meter such as the HazeMeter NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd. The light may be visible light.

[0063] The display device 200A adjusts the amount of light passing through the liquid crystal panel 100A by changing the refractive index difference between ne and no between the liquid crystal component 32 and the polymer network 31 in the polymer dispersed liquid crystal layer 30, and therefore does not require a polarizing plate, which is required in general liquid crystal panels.

[0064] The polymer-dispersed liquid crystal layer 30 may have angle dependence. The angle dependence refers to the property that, in the scattering state, the transmittance of light emitted from the front surface of the polymer-dispersed liquid crystal layer changes depending on the angle of light incident from the back surface of the polymer-dispersed liquid crystal layer. The "transmittance of light emitted from the front surface of the polymer-dispersed liquid crystal layer" refers to the parallel light transmittance measured at a light-receiving angle of approximately 3°, and is hereinafter also referred to as the "front transmittance." A higher front transmittance indicates stronger scattering when the liquid crystal panel 100A is viewed from the front (observer side), and indicates higher brightness of the liquid crystal panel 100A in the scattering state. The front transmittance was measured using an "LCD5200" manufactured by Otsuka Electronics Co., Ltd. The transmittance was calculated by setting the transmittance when no sample was placed and the light source was off to 0% and the transmittance when no sample was placed and the light source was on to 100%.

[0065] (Study on the angle dependence of polymer dispersed liquid crystal layer) The angle dependency of the polymer dispersed liquid crystal layer will be explained below with reference to Fig. 7. Fig. 7 is a graph showing the angle dependency of the polymer dispersed liquid crystal layer.

[0066] The inventors fabricated a liquid crystal cell composed of only one type of polymer-dispersed liquid crystal layer with a specific angle dependence and investigated the angle dependence of the polymer-dispersed liquid crystal layer. For this investigation, a flat, uncurved liquid crystal cell was used. As shown in Figure 3, the liquid crystal cell used for this investigation had a polymer-dispersed liquid crystal layer 30 containing a polymer network 31 and liquid crystal components 32, and a pair of substrates 10 and 20 sandwiching the polymer-dispersed liquid crystal layer 30. Each of the pair of substrates 10 and 20 had planar electrodes 12 and 22 and alignment films 13 and 23 on the side facing the polymer-dispersed liquid crystal layer 30.

[0067] 3 is also a cross-sectional schematic diagram illustrating a method for measuring the front transmittance of a polymer-dispersed liquid crystal layer. Light L1 was irradiated from the rear of the liquid crystal cell at a projection angle θx, and light L2 emitted from the front side of the liquid crystal cell was measured to obtain the front transmittance. When the liquid crystal component 32 is in a scattering state and aligned in the thickness direction of the polymer-dispersed liquid crystal layer 30, i.e., perpendicular to the surfaces of the substrates 10 and 20, the projection angle θx is also the angle between the alignment direction of the liquid crystal component 32 and the direction of light irradiation.

[0068] Liquid crystal cells were prepared in the following Reference Examples 1 to 4, and the front transmittance of each was measured using the method described above to examine the relationship between the projection angle and the front transmittance. A scattering state was established by applying a voltage of 7 V to the polymer-dispersed liquid crystal layer. Table 1 summarizes the presence or absence of a chiral agent in Reference Examples 1 to 4, and the refractive index anisotropy Δn of the liquid crystal component.

[0069] The polymer-dispersed liquid crystal layer of Reference Example 1 contains a liquid crystal component, 9 wt % of a polymerizable liquid crystal compound relative to the weight of the liquid crystal component, 5 wt % of a polymerization initiator relative to the weight of the polymerizable liquid crystal compound, and 2 wt % of a chiral agent relative to the combined weight of the liquid crystal component, the polymerizable liquid crystal compound, and the polymerization initiator.The polymer-dispersed liquid crystal layers of Reference Examples 2 to 4 contain a liquid crystal component, 9 wt % of a polymerizable liquid crystal compound relative to the weight of the liquid crystal component, and 5 wt % of a polymerization initiator relative to the weight of the polymerizable liquid crystal compound.

[0070] [Table 1]

[0071] As shown in Figure 7, we found that by changing the Δn of the liquid crystal component, it is possible to adjust the scattering characteristics (front scattering characteristics) when the liquid crystal panel is observed from the front in the scattering state. Note that the front scattering characteristics in the transparent state do not depend on the type of polymer-dispersed liquid crystal layer and do not change much regardless of the angle at which light is incident, so brightness can be improved by changing the Δn of the liquid crystal component.

[0072] The liquid crystal component 32 may have a positive or negative dielectric anisotropy (Δε) defined by the following formula, but preferably has a positive dielectric anisotropy. The dielectric anisotropy of the liquid crystal component 32 is more preferably greater than 0 and less than or equal to 20. The long axis direction of the liquid crystal component is the direction of the slow axis. Δε = (dielectric constant in the long axis direction) - (dielectric constant in the short axis direction)

[0073] The refractive index anisotropy Δn of the liquid crystal component 32 is preferably 0.14 or more. The upper limit of Δn is, for example, 0.28. A larger Δn of the liquid crystal is preferable, as this can increase the refractive index difference between the extraordinary refractive index n e of the liquid crystal component 32 and the polymer network 31, and the refractive index difference between the ordinary refractive index n e of the liquid crystal component 32 and the polymer network 31. Δn is preferably 0.16 or more, and more preferably 0.18 or more. Δn is particularly preferably 0.18 or more and 0.22 or less.

[0074] The rotational viscosity γ of the liquid crystal component 32 is preferably 100 mPa·s or more and 400 mPa·s or less. By setting γ in this range, the response speed of the liquid crystal component 32 can be increased, and color mixing can be suppressed when the light source 2 is driven in FSC mode, as described below. The above γ is more preferably 150 mPa·s or more and 350 mPa·s or less.

[0075] For example, a tolan-based liquid crystal material (a liquid crystal material having a -C≡C- (carbon-carbon triple bond) as a linking group) can be used as the liquid crystal component 32. Specific examples of tolan-based liquid crystal materials include liquid crystal materials having a structure represented by the following general formula (L1):

[0076] [ka] (In the above formula, Q1 and Q2 each independently represent an aromatic ring group, X represents a fluorine group or a cyano group, and n1 and n2 each independently represent 0 or 1.)

[0077] In the above general formula (L1), n1 and n2 cannot simultaneously be 0. That is, the sum of n1 and n2 is 1 or 2.

[0078] The aromatic ring group in the above general formula (L1) may have a substituent.

[0079] In the above general formula (L1), Q1 and Q2 each preferably independently represent any one of the structures of the following general formulae (L2-1) to (L2-7).

[0080] [ka]

[0081] Specific examples of the liquid crystal material having the structure represented by the above general formula (L1) include the following structures.

[0082] [ka]

[0083] The polymer network 31 is preferably a cured product of a polymerizable liquid crystal compound. The polymer network 31 may be, for example, a three-dimensionally continuous matrix of the fibrous cured product. The liquid crystal component 32 is preferably present in the polymer network 31 in a phase-separated dispersed state.

[0084] From the viewpoint of improving the transparency of the polymer-dispersed liquid crystal layer 30 in the transparent state, it is preferable that the polymerizable liquid crystal compound constituting the polymer network and the liquid crystal component have approximately the same extraordinary refractive index n e and ordinary refractive index n o when no voltage is applied. For example, it is preferable that the difference in the extraordinary refractive index n e and the ordinary refractive index n o between the polymerizable liquid crystal compound and the liquid crystal component be Δn o, Δn o ≦ 0.02. More preferably, Δn o, Δn o ≦ 0.01.

[0085] The polymerizable liquid crystal compound preferably exhibits a liquid crystal phase at room temperature, is compatible with the liquid crystal component, and phase-separates from the liquid crystal component after being cured to form a polymer network. The polymerizable liquid crystal compound may be a photopolymerizable liquid crystal compound that is cured by irradiation with ultraviolet light.

[0086] Examples of the photopolymerizable liquid crystal compound include substituents (hereinafter also referred to as mesogenic groups) such as biphenyl, terphenyl, naphthalene, phenylbenzoate, azobenzene, and derivatives thereof; photoreactive groups such as cinnamoyl, chalcone, cinnamylidene, β-(2-phenyl)acryloyl, and derivatives thereof; and monomers having a polymerizable group such as acrylate, methacrylate, maleimide, N-phenylmaleimide, and siloxane. The polymerizable group is preferably an acrylate. The number of polymerizable groups per molecule of the photopolymerizable liquid crystal compound is not particularly limited, but is preferably one or two. The liquid crystal component does not necessarily have to have a polymerizable group such as acrylate, methacrylate, maleimide, N-phenylmaleimide, or siloxane.

[0087] The content of the polymerizable liquid crystal compound in the polymer dispersed liquid crystal layer 30 is preferably 5% by weight or more and 10% by weight or less with respect to the weight of the liquid crystal component.

[0088] The polymer dispersed liquid crystal layer 30 may contain a polymerization initiator. The content of the polymerization initiator in the polymer dispersed liquid crystal layer 30 is preferably 5% by weight or more and 10% by weight or less with respect to the weight of the polymerizable liquid crystal compound.

[0089] The polymerization initiator is not particularly limited, and a conventionally known initiator can be used. For example, Omnirad184 (registered trademark) (manufactured by IGM Resins. BV) represented by the following chemical formula (IN1), OXE03 (manufactured by BASF) represented by the following chemical formula (IN2), etc. can be used.

[0090] [ka]

[0091] [ka]

[0092] The polymer-dispersed liquid crystal layer 30 may contain a chiral agent. The content of the chiral agent in the polymer-dispersed liquid crystal layer 30 is preferably 0.5% by weight or more and 4% by weight or less with respect to the total weight of the liquid crystal component, the polymerizable liquid crystal compound, and the polymerization initiator.

[0093] The chiral agent is not particularly limited, and conventionally known ones can be used. Examples of the chiral agent include CM-51L (manufactured by JNC Corporation) and S-811 (manufactured by Merck) represented by the following chemical formula (C1).

[0094] [ka]

[0095] The thickness of the polymer dispersed liquid crystal layer 30 is preferably 3 μm or more and 10 μm or less.

[0096] The liquid crystal panel 100A may have a plurality of pixels arranged in a matrix in a planar view. In this case, the display device 200A may be an active-matrix drive display device. Either electrode 12 or electrode 22 may include a plurality of pixel electrodes arranged for each pixel, and the on / off of each pixel electrode may be controlled by a switching element such as a TFT arranged for each pixel. The other electrode may be, for example, a solid electrode formed in a planar shape and a common electrode to which a common potential is supplied. Alternatively, both electrode 12 and electrode 22 may be solid electrodes formed in a planar shape, and the transmittance of the entire surface of the liquid crystal panel 100A may be controlled uniformly without dividing it into pixels. In this case, the display device 200A may be used as a light control panel, a lighting fixture, etc.

[0097] In the display device 200A, the light source 2 includes light-emitting elements of multiple colors, which may be driven by a field sequential (FSC) method (hereinafter also referred to as FSC drive) in which the light-emitting elements of multiple colors are turned on in a time-division manner. FSC drive enables color display by sequentially turning on light-emitting elements of multiple colors at different times. Displaying colors using FSC drive eliminates the need for color filters, allowing the display device to be made thinner. Furthermore, the use of a PDLC panel eliminates the need for polarizing plates, and also eliminates the need for color filters and black matrices to separate the color filters, allowing the display device to have higher brightness than a liquid crystal display device with a general flat backlight.

[0098] The display device 200A may further include a display panel on the rear side of the liquid crystal panel 100A. Fig. 8 is a cross-sectional view showing an example of the display device according to embodiment 1, which includes a display panel on the rear side of the liquid crystal panel. Fig. 9 is a cross-sectional view showing another example of the display device according to embodiment 1, which includes a display panel on the rear side of the liquid crystal panel.

[0099] The display panel 110 may be curved so that its center protrudes toward the liquid crystal panel 100A side. Alternatively, the display panel 110 may be curved so that its center protrudes toward the opposite side from the liquid crystal panel 100A side.

[0100] The display panel 110 may be a display panel that displays an image. Since the liquid crystal panel 100A is a see-through display, a variety of images can be expressed by displaying an image on the liquid crystal panel 100A while displaying another image on the display panel disposed on the rear side, superimposed on the image.

[0101] The display panel 110 may be, for example, a liquid crystal panel including a pair of substrates and a liquid crystal layer sandwiched between the pair of substrates. When the display panel 110 is a liquid crystal panel, a backlight may be further provided on the rear side. Alternatively, the display panel 110 may be a self-luminous panel such as an LED (light-emitting diode) panel.

[0102] The display device 200A can be used as, for example, a television, an electronic advertisement, a show window, a lighting fixture, a light control panel, an amusement device, a guide board, a mobile terminal, and the like.

[0103] <Embodiment 2> In the second embodiment, a case will be described in which the liquid crystal panel 100B is curved so that its center protrudes toward the light source 2. Since the second embodiment is the same as the first embodiment except for the direction in which the liquid crystal panel is curved, a description of the overlapping members will be omitted.

[0104] The display device of embodiment 2 comprises a pair of substrates, a liquid crystal panel having a polymer dispersed liquid crystal layer sandwiched between the pair of substrates, and a light source arranged on the rear side of the liquid crystal panel at a distance from the liquid crystal panel, wherein the liquid crystal panel is curved so that the center of the curvature direction along the surface of the liquid crystal panel protrudes toward the rear side of the liquid crystal panel more than both ends in the curvature direction, and the light source is arranged along at least one of both ends of the liquid crystal panel extending in a direction perpendicular to the curvature direction in a planar view, and when the length of the liquid crystal panel along the curvature direction is W1 (unit: cm), the curvature of the liquid crystal panel is 1 / (W1 x 40) or more and 1 / (W1 x 1.25) or less.

[0105] FIG. 10 is a cross-sectional view showing an example of a display device according to embodiment 2. FIG. 11 is a plan view showing the display device shown in FIG. 10. FIG. 10 is a cross-sectional view taken along the curved line X3-X4 in FIG. 11. In embodiment 2, too, by setting the curvature of the liquid crystal panel to be 1 / (W1×40) or more and 1 / (W1×1.25) or less, the surface reflectance at the center of the liquid crystal panel 100B can be reduced, thereby improving the brightness of the display device. The curvature of the liquid crystal panel 100B may be in the same range as the curvature of the liquid crystal panel 100A described in embodiment 1. Furthermore, the projection angle of light incident from the light source 2 on the center of the liquid crystal panel 100B may be in the same range as the projection angle of light incident from the light source 2 on the center of the liquid crystal panel 100A described in embodiment 1.

[0106] FIG. 12 is a cross-sectional schematic diagram illustrating the projection angle of a predetermined point from the edge of the liquid crystal panel in the second embodiment, in which the liquid crystal panel is bent toward the rear side. An arbitrary point α on the surface of the rear side of the liquid crystal panel 100B in a cross section along the curvature direction is defined as the predetermined point from the edge of the liquid crystal panel, and the direction toward the light source 2 that is perpendicular to the tangent line β at point α is defined as the 0° direction. When the first light source 2A and the second light source 2B are disposed at both ends of the liquid crystal panel 100B, the projection angle refers to either θ1 or θ2, whichever is closer to the light source. Because the light source 2 is disposed at a distance from the liquid crystal panel 100B on the rear side of the liquid crystal panel 100B, both θ1 and θ2 are greater than 0° and less than 90°.

[0107] The projection angles at 1 / 4 and 1 / 8 points from the edge of the liquid crystal panel 100B may be in the same range as the projection angles at 1 / 4 and 1 / 8 points from the edge of the liquid crystal panel 100A described in the first embodiment.

[0108] In the second embodiment, the projection angle of the light emitted from the light source 2 and incident on the center of the liquid crystal panel 100B is preferably 60.0° or more and 70.0° or less.

[0109] The length W1 of the liquid crystal panel 100B along the curvature direction, the width W2 of the liquid crystal panel 100B, and the height H of the liquid crystal panel 100B may each be in the same range as the liquid crystal panel 100A described in the first embodiment.

[0110] The distance d3 from the light source 2 to the liquid crystal panel 100B is preferably 1 / 20 to 1 / 5 times the length W1 of the liquid crystal panel 100B. By setting the distance within this range, the difference in brightness between the center and the edges of the liquid crystal panel can be reduced. The distance d3 is the distance from the tangent to the rear surface of the liquid crystal panel 100B that protrudes most toward the rear side to the perpendicular line drawn toward the light source 2.

[0111] The above d3 is appropriately selected depending on the size and use of the display device, but is, for example, 1 cm or more and 15 cm or less. When the display device 200B is used in an amusement device, the above d3 is preferably 5 cm or more and 10 cm or less. In order to ensure the brightness of the display device when driven by FSC, which will be described later, the above d3 is preferably 5 cm or more.

[0112] The depth d4 of the liquid crystal panel 100B may be 1 / 320 or more and 1 / 10 or less of the length W1 of the liquid crystal panel along the curvature direction. d4 is the longest distance between a line connecting both ends of the liquid crystal panel 100B perpendicular to the curvature direction and a perpendicular line drawn toward the rear surface of the liquid crystal panel 100A. The depth d4 of the liquid crystal panel 100B may be 0.1 cm or more and W2 × 0.1 cm or less.

[0113] The display device 200B according to the second embodiment can also be driven by FSC. As in the first embodiment, a further display panel may be provided on the rear side of the liquid crystal panel 100B. [Example]

[0114] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0115] The display devices according to the examples and comparative examples are reverse mode display devices that have a liquid crystal panel (hereinafter referred to as a PDLC panel) with a polymer dispersed liquid crystal layer and a light source, and perform color display using FSC driving. The light sources are red, green, and blue LEDs, which are arranged along each of the two opposing short sides of the liquid crystal panel.

[0116] Figure 13 is a graph showing the angle dependence of the polymer-dispersed liquid crystal layer used in the examples and comparative examples. The polymer-dispersed liquid crystal (PDLC) material used in the polymer-dispersed liquid crystal layer does not contain a chiral agent, but contains a liquid crystal component, a polymerizable liquid crystal compound, and a polymerization initiator. The liquid crystal component used in the study had a refractive index anisotropy Δn of 0.18, a dielectric anisotropy Δε of 20, and a rotational viscosity γ of 170 mPa·s (liquid crystal A), and another had a refractive index anisotropy Δn of 0.22, a dielectric anisotropy Δε of 20, and a rotational viscosity γ of 350 mPa·s (liquid crystal B). A photopolymerizable liquid crystal compound that hardens upon exposure to ultraviolet light was used as the polymerizable liquid crystal compound, and was added at 9 wt % of the liquid crystal component. When liquid crystal A was used as the liquid crystal component, the polymerization initiator was added at 10 wt % of the polymerizable liquid crystal compound. When liquid crystal B was used as the liquid crystal component, the polymerization initiator was added in an amount of 7% by weight relative to the weight of the polymerizable liquid crystal compound.

[0117] (Comparative Examples 1 to 3) The liquid crystal panels used in Comparative Examples 1 to 3 were non-curved 19-inch PDLC panels. The length W1 of the liquid crystal panel was 40 cm, and the distance d1 between the liquid crystal panel and the light source was 10 cm. FIG. 14 is a cross-sectional view illustrating the projection angle at the center of the liquid crystal panel for Comparative Example 1. In Comparative Examples 1 to 3, the light sources were positioned so that the projection angles (θ1 = θ2) at the center of the liquid crystal panel were 63.4°, 76.0°, and 68.2°, respectively. FIG. 15 is a cross-sectional view illustrating the projection angle at a predetermined point from the edge of the liquid crystal panel for Comparative Example 1.

[0118] Comparative Example 4 The display device of Comparative Example 4 used a PDLC panel as a liquid crystal panel that was curved so that the center of the curve along the surface of the liquid crystal panel protruded more toward the front side of the liquid crystal panel than both ends in the curve direction. The PDLC panel used in Comparative Example 4 had the same light source angle as Comparative Example 1, and the curvature of the PDLC panel was changed as shown in Table 2.

[0119] Examples 1 to 9 The display devices according to Examples 1 to 9 are specific examples of Embodiment 1, and used PDLC panels curved so that the center of the curve along the surface of the liquid crystal panel protruded more toward the front side of the liquid crystal panel than both ends in the curve. The length W1 of the liquid crystal panel was 40 cm, and the distance d1 between the liquid crystal panel and the light source was 10 cm. The PDLC panels used in Examples 1 to 9 had the same light source angle as Comparative Example 1, and the curvature of the PDLC panel was changed as shown in Table 2. For example, in Example 1, the depth d2 of the liquid crystal panel was 2 cm, and the width W2 of the liquid crystal panel was 39.7 cm.

[0120] (Examples 10 to 18) The display devices of Examples 10 to 18 are specific examples of Embodiment 1, and used PDLC panels curved so that the center of the curve along the surface of the liquid crystal panel protruded more toward the front side of the liquid crystal panel than both ends in the curved direction. The length W1 of the liquid crystal panel was 40 cm, and the distance d1 between the liquid crystal panel and the light source was 5 cm. The PDLC panels used in Examples 10 to 18 had the same light source angle as Comparative Example 2, and the curvature of the PDLC panel was changed as shown in Table 3.

[0121] (Examples 19 to 24) The display devices of Examples 19 to 24 are specific examples of Embodiment 1, and used PDLC panels curved so that the center of the curve along the surface of the liquid crystal panel protruded more toward the front side of the liquid crystal panel than both ends in the curved direction. The length W1 of the liquid crystal panel was 15 cm, and the distance d1 between the liquid crystal panel and the light source was 3 cm. The PDLC panels used in Examples 19 to 24 had the same light source angle as Comparative Example 3, and the curvature of the PDLC panel was changed as shown in Table 4.

[0122] Examples 25 to 32 The display devices of Examples 25 to 32 are specific examples of Embodiment 2, and used PDLC panels curved so that the center of the curve along the surface of the liquid crystal panel protruded more toward the rear side of the liquid crystal panel than both ends in the curved direction. The length W1 of the liquid crystal panel was 40 cm, and the distance d1 between the liquid crystal panel and the light source was 10 cm. The PDLC panels used in Examples 25 to 32 had the same light source angle as Comparative Example 1, and the curvature of the PDLC panel was changed as shown in Table 5.

[0123] Examples 33 to 38 The display devices of Examples 33 to 38 are specific examples of Embodiment 2, and used PDLC panels curved so that the center of the curve along the surface of the liquid crystal panel protruded toward the rear side of the liquid crystal panel more than both ends in the curved direction. The length W1 of the liquid crystal panel was 15 cm, and the distance d1 between the liquid crystal panel and the light source was 3 cm. The PDLC panels used in Examples 33 to 38 had the same light source angle as Comparative Example 3, and the curvature of the PDLC panel was changed as shown in Table 6.

[0124] <Consideration of the rate of increase in brightness> For Examples 1 to 38 and Comparative Examples 1 to 4, the brightness of the liquid crystal panels when displaying white was calculated based on the graph shown in FIG. 13. The brightness was measured and calculated using an "LCD5200" manufactured by Otsuka Electronics Co., Ltd. Note that "white display" refers to the state when a voltage of, for example, 7.0 V is applied to the polymer-dispersed liquid crystal layer. The results are shown in Tables 2 to 6 below. Regarding the "brightness increase rate" in each table, in Tables 2 to 4, the brightness of the liquid crystal panels of Comparative Examples 1, 2, and 3 was set to 1.00, respectively; in Table 5, the brightness of the liquid crystal panel of Comparative Example 1 was set to 1.00; and in Table 6, the brightness of the liquid crystal panel of Comparative Example 3 was set to 1.00.

[0125] In Examples 25 to 38 using a liquid crystal panel protruding toward the rear side, the projection angle θ1 at the 1 / 4 point from the edge of the liquid crystal panel on the side where the first light source 2A is arranged, as shown in Fig. 12, is shown in Tables 5 and 6. The increase rates of brightness shown in Tables 5 and 6 are values ​​calculated using only the light from the light source (first light source 2A) closer to the 1 / 4 point.

[0126] [Table 2]

[0127] [Table 3]

[0128] [Table 4]

[0129] [Table 5]

[0130] [Table 6]

[0131] As shown in Table 2, in Example 5, in which the curvature of the liquid crystal panel was 1 / 200, the front transmittance of the liquid crystal panel was 1.27 times higher for liquid crystal A and 1.15 times higher for liquid crystal B than in Comparative Example 1, in which the liquid crystal panel was not curved. Also, in Example 7, in which the curvature of the liquid crystal panel was 1 / 100, the front transmittance of the liquid crystal panel was 1.53 times higher for liquid crystal A and 1.36 times higher for liquid crystal B than in Comparative Example 1. Also, in Example 7, the projection angle was reduced by 4.6° per LED at the center of the panel, and by an average of 3.5° in a section 10 cm from the edge of the panel.

[0132] As shown in Tables 3 to 6, even when the projection angle at the center of the liquid crystal panel was changed, the greater the curvature of the liquid crystal panel, the higher the front transmittance of the liquid crystal panel compared to the comparative examples for both Liquid Crystal A and Liquid Crystal B. Specifically, by setting the curvature of the liquid crystal panel to 1 / (W1×13.75) or more and 1 / (W1×1.25) or less, and setting the projection angle at the center of the liquid crystal panel to 54.0° or more and 75.0° or less, the brightness at the center of the liquid crystal panel could be increased by 10% or more for Liquid Crystal A and by 5% or more for Liquid Crystal B.

[0133] As shown in Tables 3 to 6, by setting the curvature of the LCD panel to 1 / (W1×5) or more and 1 / (W1×1.25) or less, and by setting the projection angle at the center of the LCD panel to 54.0° or more and 73.5° or less, the brightness at the center of the LCD panel could be increased by 15% or more for both LCD A and LCD B. In particular, with LCD A in Tables 2 to 4, the brightness at the center of the LCD panel could be increased by 27% or more.

[0134] As shown in Tables 3 to 6, by setting the curvature of the LCD panel to 1 / (W1×2.5) or more and 1 / (W1×1.25) or less, and by setting the projection angle at the center of the LCD panel to 54.0° or more and 71.0° or less, the brightness at the center of the LCD panel can be increased by more than 20% for both LCD A and LCD B. In particular, with LCD A in Tables 2 to 4, the brightness at the center of the LCD panel could be increased by more than 53%.

[0135] As shown in Tables 3 to 6, by setting the curvature of the LCD panel to 1 / (W1×2) or more and 1 / (W1×1.25) or less, and by setting the projection angle at the center of the LCD panel to 54.0° or more and 70.0° or less, the brightness at the center of the LCD panel could be increased by more than 30% for both LCD A and LCD B. In particular, with LCD A in Tables 2 to 4, the brightness at the center of the LCD panel could be increased by more than 67%.

[0136] <Study of brightness unevenness on LCD panels> For Examples 1 to 9 and Comparative Examples 1 and 4, when Liquid Crystal A was used, the luminance at the center of the liquid crystal panel relative to the luminance at a point 1 / 8 from the edge of the panel was calculated, and the results are summarized in Table 7. The point 1 / 8 from the edge of the left side of the liquid crystal panel where the first light source 2A is arranged was defined as the point 1 / 8 from the edge of the liquid crystal panel. In Table 7, θ1 and θ2 are the projection angles of light emitted from the first light source 2A and the second light source 2B to the point 1 / 8 from the edge of the liquid crystal panel, respectively.

[0137] [Table 7]

[0138] As shown in Table 7, the ratio of the brightness at the center of the liquid crystal panel to the brightness at a point 1 / 8 from the edge of the liquid crystal panel was 12.5 times in Comparative Example 1, where the liquid crystal panel was not curved, 7.0 times in Example 5, where the curvature of the liquid crystal panel was 1 / 200, and 4.6 times in Example 7, where the curvature of the liquid crystal panel was 1 / 100. It was confirmed that by increasing the curvature of the liquid crystal panel, the brightness unevenness of the entire liquid crystal panel was improved.

[0139] For Comparative Example 1 and Examples 1 and 5, the projection angle θ1 of the first light source 2A, which is irradiated at points 1 / 8, 1 / 4, 1 / 2, 3 / 4, and 7 / 8 from the left end of the liquid crystal panel on which the first light source 2A is arranged, the projection angle θ2 of the second light source 2B arranged at the left end of the liquid crystal panel, and the average of θ1 and θ2 are summarized in Table 8 below.

[0140] [Table 8]

[0141] As shown in Table 8, the greater the curvature of the LCD panel, the smaller the difference in projection angle (average values ​​of θ1 and θ2) between the center and the 1 / 8 point from the edge of the LCD panel. Reducing the difference in average values ​​of θ1 and θ2 between the center and edge of the LCD panel also reduces the difference in brightness between the center and edge of the LCD panel. [Explanation of symbols]

[0142] 1: Sealing material 2:Light source 2A: First light source 2B: Second Light Source 10, 20: Substrate 11, 21: Base material 12, 22: Electrode 13, 23: Alignment film 30: Polymer dispersed liquid crystal layer 31: Polymer network 32: Liquid crystal component 100A, 100B, 1100: LCD panel 110: Display panel 200A, 200B, 1200: Display device

Claims

1. a liquid crystal panel having a pair of substrates and a polymer dispersed liquid crystal layer sandwiched between the pair of substrates; a light source disposed on the rear side of the liquid crystal panel at a distance from the liquid crystal panel; the liquid crystal panel is curved such that a center in a curved direction along a surface of the liquid crystal panel protrudes toward a front surface side of the liquid crystal panel more than both end portions in the curved direction, the light source is arranged along at least one of the two end portions of the liquid crystal panel extending in a direction perpendicular to the curvature direction in a plan view, The length of the liquid crystal panel along the curved direction is W １ (unit: cm), the curvature of the liquid crystal panel is 1 / (W １ ×40) or more, 1 / (W １ 2. A display device characterized in that:

2. a liquid crystal panel having a pair of substrates and a polymer dispersed liquid crystal layer sandwiched between the pair of substrates; a light source disposed on the rear side of the liquid crystal panel at a distance from the liquid crystal panel; the liquid crystal panel is curved such that a center in a curved direction along a surface of the liquid crystal panel protrudes toward a rear surface side of the liquid crystal panel more than both end portions in the curved direction, the light source is arranged along at least one of the two end portions of the liquid crystal panel extending in a direction perpendicular to the curvature direction in a plan view, The length of the liquid crystal panel along the curved direction is W １ (unit: cm), the curvature of the liquid crystal panel is 1 / (W １ ×40) or more, 1 / (W １ 2. A display device characterized in that:

3. 3. The display device according to claim 1, wherein the light source irradiates the surface of the liquid crystal panel with light in an oblique direction.

4. 3. The display device according to claim 1, wherein a projection angle of light incident on the center of the liquid crystal panel from the light source is equal to or greater than 54.0° and equal to or less than 76.0°.

5. The curvature of the liquid crystal panel is 1 / (W １ ×25) or more, 1 / (W １ 5. The display device according to claim 4, wherein the value of the surface roughness is equal to or less than 1.

25.

6. 3. The display device according to claim 2, wherein a projection angle of the light incident on the center of the liquid crystal panel from the light source is equal to or greater than 60.0° and equal to or less than 70.0°.

7. The curvature of the liquid crystal panel is 1 / (W １ × 13.75) or more, 1 / (W １ × 1.25) or less, 3. The display device according to claim 1, wherein a projection angle of light incident on the center of the liquid crystal panel from the light source is equal to or greater than 54.0° and equal to or less than 75.0°.

8. The curvature of the liquid crystal panel is 1 / (W １ ×5) or more, 1 / (W １ × 1.25) or less, 3. The display device according to claim 1, wherein a projection angle of light incident on the center of the liquid crystal panel from the light source is equal to or greater than 54.0 degrees and equal to or less than 73.5 degrees.

9. The curvature of the liquid crystal panel is 1 / (W １ × 2.5) or more, 1 / (W １ × 1.25) or less, 3. The display device according to claim 1, wherein a projection angle of light incident on the center of the liquid crystal panel from the light source is equal to or greater than 54.0° and equal to or less than 71.0°.

10. The curvature of the liquid crystal panel is 1 / (W １ ×2) or more, 1 / (W １ × 1.25) or less, 3. The display device according to claim 1, wherein a projection angle of light incident on the center of the liquid crystal panel from the light source is equal to or greater than 54.0° and equal to or less than 70.0°.

11. The distance from the light source to the liquid crystal panel is d １ Then, the above d １ is the W １ 3. The display device according to claim 1, wherein the display area is 1 / 10 to 1 / 3 of the above.

12. 3. The display device according to claim 1, further comprising a display panel on the rear side of the liquid crystal panel.

13. 13. The display device according to claim 12, wherein the display panel is curved so as to protrude toward the liquid crystal panel.

14. 13. The display device according to claim 12, wherein the display panel is curved so as to protrude toward the side opposite to the liquid crystal panel.

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