Optical laminate, display device, and head-mounted display

Abstract

The present invention provides an optical laminate capable of securing the optical path length from a display element to an eye of a user and reducing the necessity of highly precise management of the position of the display element. This optical laminate (10) has a reflective polarizing plate (31), a wavelength plate (32), and an optical element (33) having circular polarization selectivity that reflects one of right circularly polarized light and left circularly polarized light and transmits other circularly polarized light. The polarizing plate (31), the wavelength plate (32), and the optical element (33) are arranged side by side in this order in the direction in which the display element (De) emits light.

Description

Optical laminate, display device, and head-mounted display

[0001] The present invention relates to an optical laminate, a display device, and a head-mounted display.

[0002] Display devices are used to provide users with images displayed on display elements such as liquid crystal panels and organic electroluminescence (EL) panels. Patent Document 1 discloses a head-mounted display as an example of such a display device. To reduce the size of this type of display device, it is desirable to minimize the distance between the display element and the user's face.

[0003] Therefore, Patent Document 2 proposes a display device having a polarizing plate, a λ / 4 wavelength plate, a color filter layer, and a reflective layer between a display element and a lens placed in front of the user's eyes. The reflective layer has a light-transmitting region formed at the position of the pixel electrode (the region that emits light) and a reflective region between two adjacent light-transmitting regions. Image light emitted from the display element reaches the user's eyes after being reflected multiple times between the reflective layer and the polarizing plate. This structure makes it possible to shorten the actual distance between the display element and the lens while maintaining an optical distance between the display element and the lens that corresponds to the focal length of the lens.

[0004] JP 2017-223825 A International Publication No. 2020-026586

[0005] In the display device of Patent Document 2, the light-transmitting region of the reflective layer is located at the pixel electrode (light-emitting region that emits light) provided in each pixel, and the reflective region must be located between two adjacent pixel electrodes. However, it is not always easy to align the positions of the reflective layer and the pixel electrodes.

[0006] The optical laminate proposed in the present disclosure is an optical laminate for attachment to a display element that emits light in a first direction, and includes a reflective polarizing plate, a wave plate, and an optical element having circular polarization selectivity that reflects one of right-handed and left-handed circularly polarized light and transmits the other. The polarizing plate, the wave plate, and the optical element are arranged in this order in the first direction. This structure ensures a sufficient optical path length and reduces the need for high-precision management of the relative positions of the polarizing plate, the wave plate, and the optical element relative to the display element.

[0007] The display device proposed in the present disclosure includes the display element and the optical laminate.

[0008] The head-mounted display proposed in the present disclosure includes the display element and the optical laminate.

[0009] Fig. 1 is a diagram showing an example of an optical laminate proposed in the present disclosure; Fig. 2 is a diagram showing another example of an optical laminate proposed in the present disclosure; Fig. 3 is a diagram showing yet another example of an optical laminate; Fig. 4 is a perspective view showing a head-mounted display, which is an example of a display device having the optical laminate proposed in the present disclosure.

[0010] The optical laminate proposed in this disclosure will be described below. FIG. 1 is a diagram showing an optical laminate 10, which is an example of an optical laminate. The optical laminate 10, a display element De, and a lens shown in FIG. 1 constitute a display device. The display device is, for example, a head-mounted display (HMD). In the following description, Z1 and Z2 in FIG. 1 will be referred to as the upper and lower directions, respectively, and the X1-X2 direction will be referred to as the horizontal direction.

[0011] [Display Element] First, the display element De to which the optical laminate 10 is attached will be described. The display element is a panel that forms moving images according to moving image data supplied from an external device, and an example of such a panel is a liquid crystal panel. The display element may be an organic EL panel or a micro OLED (organic light emitting diode) panel.

[0012] As shown in FIG. 1, the display element De has a plurality of pixels Px. For example, the plurality of pixels Px include red pixels, green pixels, and blue pixels. The types of pixels are not limited to three colors, and may be four colors. The pixels Px are arranged, for example, in the horizontal direction (X1-X2 direction) and the vertical direction (direction perpendicular to the X1-X2 direction and the Z1-Z2 direction). The pixels Px may also be arranged diagonally.

[0013] As shown in FIG. 1 , each pixel Px has a light emission region R1. In this specification, the light emission region R1 refers to a region that emits light toward the user's eyes or a region through which light passes toward the user's eyes. When the display element De is a liquid crystal panel, the light emission region R1 is a region through which light from the backlight device 16 passes toward the user's eyes. When the display element De is a self-luminous element such as an organic EL panel or a micro OLED panel, the light emission region R1 is a region in which the light-emitting layer receives current and emits light. In the example shown in FIG. 1 , the display device has a lens S, and light from the display element De passes through the lens S to reach the user's eyes.

[0014] As shown in Fig. 1, the display element De has a non-light-emitting region R2 between adjacent light-emitting regions R1. The non-light-emitting region R2 is a region that does not emit light or transmit light. In other words, the non-light-emitting region R2 is a region other than the plurality of light-emitting regions R1. The display element De has, in this region R2, for example, electrical wires made of an opaque material (e.g., electrical wires through which signals or currents corresponding to the gradation values ​​of each pixel Px flow) and elements made of semiconductors (e.g., transistors).

[0015] As described above, the display element De is, for example, a liquid crystal panel. In this case, as shown in FIG. 1 , the display element De includes a substrate 11 made of glass or resin, a circuit layer 12 formed on the substrate 11, and a liquid crystal layer 14. The circuit layer 12 includes pixel electrodes 12a located in each light-emitting region R1 and driving the liquid crystal, and thin-film transistors (TFTs, not shown) that set the potential of the pixel electrodes 12a to a value corresponding to the gradation value. The display element De also includes a common electrode 13 formed across the multiple light-emitting regions R1. Light distribution films (not shown) are formed between the circuit layer 12 and the liquid crystal layer 14 and between the common electrode 13 and the liquid crystal layer 14. The display element De also includes a backlight device 16 that irradiates light onto the display element De, and a polarizing plate 15 formed between the display element De and the backlight device 16.

[0016] The display element De also has a counter substrate 21 and a color filter layer 22 formed on the counter substrate 21. The color filter layer 22 has colored portions 22b corresponding to the colors of the pixels Px. The color filter layer 22 also has a black matrix 22a formed between adjacent light emission regions R1 and partitioning the colored portions 22b.

[0017] [Lens] As shown in FIG. 1 , an example of a display device may include a lens S. The lens S is, for example, a lens having a positive refractive power that refracts light emitted from the display element De toward the optical axis. The lens S may be composed of one lens element or multiple lens elements. Each lens element may be a spherical lens or an aspherical lens. Each lens element may also have a Fresnel structure.

[0018] In addition to the lens S, or instead of the lens S, the polarizing plate 31 and / or the optical element 33 described below may have a lens function. In this case, the polarizing plate 31 and / or the optical element 33 may be an aspherical lens.

[0019] [Optical Path Extension Structure] The optical laminate 10 is disposed between the display element De and the lens S. The optical laminate 10 constitutes the optical path extension structure E1. The optical path extension structure E1 ensures an optical path length between the display element De and the lens S according to the focal length of the lens S by utilizing light reflection. As shown in FIG. 1 , the optical path extension structure E1 has a polarizing plate 31, a wave plate 32, and an optical element 33. The polarizing plate 31, the wave plate 32, and the optical element 33 are arranged in this order from the display element De toward the lens S. In FIG. 1 , the lens S is located above the display element De, and the polarizing plate 31, the wave plate 32, and the optical element 33 are arranged in this order toward the upper side.

[0020] The polarizing plate 31 transmits polarized light components vibrating in a direction along the transmission axis of the polarizing plate 31. The polarizing plate 31 is a reflective polarizing plate and reflects polarized light components vibrating in a direction perpendicular to the transmission axis. When the display element De is a liquid crystal panel, the polarizing plate 31 is disposed so that its transmission axis is perpendicular to the transmission axis of the polarizing plate 15 constituting the display element De. The polarizing plate 31 is disposed, for example, so that its transmission axis is along the horizontal direction (X1-X2 direction). Alternatively, the polarizing plate 31 may be disposed so that its transmission axis is along the vertical direction (a direction perpendicular to the Z1-Z2 direction and the X1-X2 direction). In this case, the polarizing plate 15 may have a transmission axis along the horizontal direction.

[0021] The wave plate 32 is, for example, a quarter-wave plate. That is, the wave plate 32 adds a phase difference (retardation) of π / 4 (90 degrees) to light passing through the wave plate 32. Linearly polarized light incident on the wave plate 32 is converted into circularly polarized light, and circularly polarized light incident on the wave plate 32 is converted into linearly polarized light. The orientation of the optical axes (slow axis and fast axis) of the wave plate 32 may be changed according to the orientation of the transmission axis of the polarizing plate 31. The wave plate 32 may be substantially a quarter-wave plate by stacking a plurality of wave plates.

[0022] The optical element 33 is an optical element having selectivity for circularly polarized light, that is, reflecting one of right-handed and left-handed circularly polarized light (first circularly polarized light) and transmitting the other circularly polarized light (second circularly polarized light). The optical element 33 includes, for example, a cholesteric liquid crystal film. In a cholesteric liquid crystal film, a liquid crystal polymer has a twisted structure with a central axis of rotation along the normal direction of the film, and reflects only selected wavelengths. Note that the optical element 33 is not necessarily limited to a cholesteric liquid crystal film, as long as it is an optical element having the above-mentioned selectivity for circularly polarized light.

[0023] The optical element 33 may have multiple layers. Specifically, the multiple layers correspond to multiple colors (e.g., red, green, and blue) of the multiple pixels Px, respectively. For example, as shown in FIG. 1 , the optical element 33 may have a first layer 33 a, a second layer 33 b, and a third layer 33 c. The first layer 33 a, for example, reflects first circularly polarized light (e.g., right-handed circularly polarized light) of a red wavelength and transmits second circularly polarized light (e.g., left-handed circularly polarized light) of a red wavelength. The first layer 33 a also transmits light of wavelengths of colors other than red.

[0024] The second layer 33b reflects, for example, a first circularly polarized light (for example, right-handed circularly polarized light) of a green wavelength and transmits a second circularly polarized light (for example, left-handed circularly polarized light) of a green wavelength. The second layer 33b transmits light of wavelengths of colors other than green. Furthermore, the third layer 33c reflects, for example, a first circularly polarized light (for example, right-handed circularly polarized light) of a blue wavelength and transmits a second circularly polarized light (for example, left-handed circularly polarized light) of a blue wavelength. The third layer 33c transmits light of wavelengths of colors other than blue.

[0025] Unlike the example shown in Fig. 1, the optical element 33 does not necessarily have to have three layers. For example, the optical element 33 may be composed of only one or two of the three layers 33a, 33b, and 33c described above. In the example shown in Fig. 1, the first layer 33a, the second layer 33b, and the third layer 33c are arranged in this order, but the order is not limited to this.

[0026] [Optical Path] An example of the optical path of light emitted from the display element De will be described with reference to FIG. 1 . In the following description, the first circularly polarized light corresponds to "right-handed circularly polarized light" and the second circularly polarized light corresponds to "left-handed circularly polarized light," but this correspondence may be reversed. That is, the first circularly polarized light may correspond to left-handed circularly polarized light and the second circularly polarized light may correspond to right-handed circularly polarized light. Furthermore, the first linearly polarized light corresponds to "horizontal linearly polarized light" and the second linearly polarized light corresponds to "vertical linearly polarized light," but this correspondence may also be reversed. That is, the first linearly polarized light may correspond to "vertical linearly polarized light" and the second linearly polarized light may correspond to "horizontal linearly polarized light."

[0027] When an on-voltage is applied to the pixel electrode 12 a , light from the backlight device 16 passes through the polarizer 15 , the liquid crystal layer 14 , the colored portion 22 b of the color filter layer 22 , and the polarizer 31 .

[0028] The light passing through the polarizing plate 31 becomes first linearly polarized light (for example, horizontally linearly polarized light) having a vibration component along the transmission axis (for example, the axis in the X1-X2 direction) of the polarizing plate 31. The phase difference of the light transmitted through the polarizing plate 31 is, for example, 0 degrees.

[0029] The linearly polarized light that has passed through the polarizing plate 31 passes through the wave plate 32. The phase difference of the light that has passed through the wave plate 32 becomes 90 degrees (π / 4), as shown in FIG. 1, and the linearly polarized light is converted into a first circularly polarized light (for example, right-handed circularly polarized light).

[0030] 1, the first circularly polarized light (e.g., right-handed circularly polarized light) that has passed through the wave plate 32 is reflected by the optical element 33. The phase difference of the reflected light is 90 degrees (π / 4), and the direction of rotation of the circularly polarized light is opposite to that of the light incident on the optical element 33. For example, if the light incident on the optical element 33 from the wave plate 32 is right-handed circularly polarized light, the reflected light becomes left-handed circularly polarized light (second circularly polarized light).

[0031] The phase difference of the light that is reflected by the optical element 33 and then transmitted from the top to the bottom of the wave plate 32 is 180 degrees (π / 2), as shown in FIG. 1 . That is, if the light that initially transmitted through the polarizing plate 31 from the bottom to the top is a first linearly polarized light (phase difference of 0 degrees, for example, horizontally linearly polarized light), the light that is reflected by the optical element 33 and then transmitted through the wave plate 32 becomes a second linearly polarized light (phase difference of 180 degrees, for example, vertically linearly polarized light). As a result, the vibration direction of the light becomes perpendicular to the direction of the transmission axis of the polarizing plate 31, and this light is reflected by the polarizing plate 31. The phase difference of the light reflected by the polarizing plate 31 is 180 degrees (π).

[0032] The linearly polarized light reflected by the polarizing plate 31 passes through the wave plate 32 and becomes circularly polarized light with a phase difference of 270 degrees (3π / 2). The direction of rotation of this circularly polarized light is opposite to that of the first circularly polarized light (e.g., right-handed circularly polarized light) that initially passed through the wave plate 32 from bottom to top, and becomes second circularly polarized light (e.g., left-handed circularly polarized light).

[0033] As described above, the optical element 33 reflects one of the right-handed and left-handed circularly polarized light (first circularly polarized light) and transmits the other circularly polarized light (second circularly polarized light). Therefore, the second circularly polarized light (e.g., left-handed circularly polarized light) that has passed through the wave plate 32 passes through the optical element 33, passes through the lens S, and reaches the user's eye.

[0034] According to such an optical stack 10 (optical path extension structure E1), light is reflected by the optical element 33, making it easy to ensure an optical path length between the display element De and the lens S that corresponds to the focal length of the lens S. Furthermore, the need for high-precision management of the relative positions of the optical path extension structure E1 and the light output region R1 of the display element De can be reduced, making it easier to manufacture a display device that includes the optical stack 10.

[0035] The polarizing plate 31 and other components of the optical path extension structure E1 satisfy the following conditions. Condition 1: The polarizing plate 31 transmits light with a phase difference of θ and reflects light with a phase difference of "θ+π(2n-1)". Condition 2: The wave plate 32 satisfies "φ1+φ2=π(2n-1)". Condition 3: The optical element 33 reflects light with a phase difference of "θ+φ1" and transmits light with a phase difference of "θ+φ1+π(2n-1)".

[0036] In these conditions 1 to 3, each letter represents the following value: φ1: phase difference that the wave plate 32 generates in light that transmits from the bottom (display element De side) to the top (lens S side); φ2: phase difference that the wave plate 32 generates in light that transmits from the top (lens S side) to the bottom (display element De side); n: natural number

[0037] In the example described with reference to FIG. 1 , θ is 0 degrees, and φ1 and φ2 are both 90 degrees (π / 4). In the optical path extension structure E1, the polarizing plate 31 reflects light with a phase difference of 180 degrees, thereby satisfying condition 1. Furthermore, since "φ1 + φ2" of the wave plate 32 is 180 degrees, condition 2 is satisfied. Furthermore, the optical element 33 reflects circularly polarized light with a phase difference of 90 degrees (first circularly polarized light) and transmits circularly polarized light with a phase difference of 270 degrees (second circularly polarized light), thereby satisfying condition 3.

[0038] The structure of the optical path extension structure E1 is not limited to the above example as long as it satisfies conditions 1 to 3. For example, although it has been described that the phase difference of light passing through the polarizing plate 31 is 0 degrees, the phase difference of this light does not have to be 0 degrees.

[0039] No material that generates a substantial phase difference is disposed between the wave plate 32 and the polarizing plate 31. Similarly, no material that generates a substantial phase difference is disposed between the wave plate 32 and the optical element 33. As shown in FIG. 1 , gaps (air layers) may be provided between the polarizing plate 31 and the wave plate 32, and between the wave plate 32 and the optical element 33. In other words, the polarizing plate 31 and the wave plate 32 may be spaced apart from each other. Similarly, the wave plate 32 and the optical element 33 may also be spaced apart from each other. This makes it easier to ensure an optical path length between the display element De and the lens S that corresponds to the focal length of the lens S.

[0040] A material that does not substantially cause a phase difference may be filled in the gap between the polarizing plate 31 and the wave plate 32. Similarly, a material that does not substantially cause a phase difference may also be filled in the gap between the polarizing plate 31 and the wave plate 32. Even in this case, it becomes easier to ensure an optical path length between the display element De and the lens S that corresponds to the focal length of the lens S.

[0041] 1 , a gap (air layer or material that does not generate a phase difference) may be provided only between the polarizing plate 31 and the wave plate 32, or a gap (air layer or material that does not generate a phase difference) may be provided only between the wave plate 32 and the optical element 33. That is, a gap may be provided between the polarizing plate 31 and the wave plate 32, and the wave plate 32 and the optical element 33 may be in contact with each other. Conversely, the polarizing plate 31 and the wave plate 32 may be in contact with each other, and a gap may be provided between the wave plate 32 and the optical element 33.

[0042] [Two-Stage Optical Path Extension Structure] When the polarizing plate 31, the wave plate 32, and the optical element 33 described above are defined as a first optical path extension structure E1, the optical stack 10 may have a second optical path extension structure E2 in addition to the first optical path extension structure E1. The first optical path extension structure E1 and the second optical path extension structure E2 may be aligned in the direction (upward) in which the display element De emits light. The second optical path extension structure E2 may have the same structure as the first optical path extension structure or may have a different structure from the first optical path extension structure E1.

[0043] 2 is a diagram showing an optical laminate according to such a modified example. The optical laminate 10A shown in the figure has a first optical path extension structure E1 and a second optical path extension structure E2. The second optical path extension structure E2 is formed between the first optical path extension structure E1 and the display element De.

[0044] As shown in Figure 2, the second optical path extension structure E2 includes, for example, a polarizing plate 41, a wavelength plate 42, a reflective layer 43, and a wavelength plate 44, which are arranged in this order from the display element De in the direction in which the display element De emits light (the direction from the display element De toward the lens S).

[0045] Hereinafter, the polarizing plate 31 and the wave plate 32 of the first optical path extension structure E1 will be referred to as the first polarizing plate 31 and the first wave plate 32, respectively. The polarizing plate 41, the wave plate 42, and the wave plate 44 of the second optical path extension structure E2 will be referred to as the second polarizing plate 41, the second wave plate 42, and the third wave plate 44, respectively.

[0046] Like the first polarizer 31, the second polarizer 41 transmits polarized light components vibrating in a direction along the transmission axis of the polarizer 41. The second polarizer 41 and the polarizer 15 of the display element De are arranged so that their transmission axes are perpendicular to each other. The second polarizer 41 and the first polarizer 31 are also arranged so that their transmission axes are substantially parallel to each other. For example, the first polarizer 31 and the second polarizer 41 are arranged so that their transmission axes are aligned along the horizontal direction (X1-X2 direction), and the polarizer 15 is arranged so that its transmission axis is aligned along the vertical direction (direction perpendicular to the X1-X2 direction and the Z1-Z2 direction). The second polarizer 41 may be a reflective polarizer or an absorptive polarizer.

[0047] 2, the reflective layer 43 has a reflective region F1 and a light-transmitting region F2. The reflective region F1 corresponds to the position of the non-light-emitting region R2 of the display element De and reflects light. The light-transmitting region F2 corresponds to the positions of the multiple light-emitting regions R1 of the display element De and transmits light. The positions of the light-transmitting region F2 and the light-emitting region R1 correspond one-to-one. The reflective region F1 corresponds to the position of the black matrix 22a of the color filter layer 22.

[0048] The reflective region F1 is formed with a reflective material that reflects light. For example, the reflective region F1 is formed of a metal (e.g., aluminum) with high light reflectivity. On the other hand, the light-transmitting region F2 is a region where such a reflective material is not formed. The reflective layer 43 has a transparent substrate formed of, for example, glass or resin. The reflective material is formed on the upper surface of the transparent substrate to form the reflective region F1. The light-transmitting region F2 is a region (opening) on ​​the upper surface of the transparent substrate where such a reflective region F1 is not formed. Therefore, the light-transmitting region F2 allows the transmission of visible light of substantially all frequencies. On the other hand, the reflective region F1 reflects visible light of substantially all frequencies.

[0049] The reflective material that constitutes the reflective region F1 is formed on the upper surface of the transparent substrate, for example, by vapor deposition. In this case, a mask with an opening corresponding to the reflective region F1 is used. Depending on the type of reflective material, the reflective material may be formed on the transparent substrate, for example, by printing. Alternatively, the optical stack 10 may not have a transparent substrate, and the reflective material may be formed on the second wave plate 42 to constitute the reflective region F1.

[0050] The second wave plate 42 and the third wave plate 44 are, for example, quarter-wave plates, similar to the wave plate 32. That is, the wave plates 42 and 44 impart a phase difference of 90 degrees (π / 4) to the light passing through the wave plates 42 and 44. The wave plates 42 and 45 convert linearly polarized light incident thereon into circularly polarized light and output the circularly polarized light, and convert circularly polarized light incident thereon into linearly polarized light and output the linearly polarized light. Each of the wave plates 42 and 43 may be substantially realized as a quarter-wave plate by stacking multiple wave plates.

[0051] [Optical Path] An example of the optical path of light emitted from the display element De will be described with reference to FIG. 2 . In the following description, the first circularly polarized light corresponds to "right-handed circularly polarized light" and the second circularly polarized light corresponds to "left-handed circularly polarized light," but this correspondence may be reversed. That is, the first circularly polarized light may correspond to left-handed circularly polarized light and the second circularly polarized light may correspond to right-handed circularly polarized light. Furthermore, the first linearly polarized light corresponds to "horizontal linearly polarized light" and the second linearly polarized light corresponds to "vertical linearly polarized light," but this correspondence may also be reversed. That is, the first linearly polarized light may correspond to "vertical linearly polarized light" and the second linearly polarized light may correspond to "horizontal linearly polarized light."

[0052] When an on-voltage is applied to the pixel electrode 12a, light from the backlight device 16 passes through the polarizer 15, the liquid crystal layer 14, the colored portion 22b of the color filter layer 22, and the second polarizer 41. The phase difference of the light passing through the second polarizer 41 is 0 degrees, and this light is the first linearly polarized light (for example, linearly polarized light in the horizontal direction (X1-X2 direction)).

[0053] This linearly polarized light is incident on the second wave plate 42. The second wave plate 42 adds a phase difference of 90 degrees (π / 2) to this light. This light becomes first circularly polarized light (for example, right-handed circularly polarized light). This circularly polarized light passes through the light-transmitting region F2 of the reflective layer 43 and enters the third wave plate 44. The third wave plate 44 adds another phase difference of 90 degrees (π / 2) to this circularly polarized light. As a result, the phase difference of the light transmitted through the third wave plate 44 becomes 180 degrees (π). This becomes second linearly polarized light (for example, vertically linearly polarized light).

[0054] As described above, the transmission axes of the first polarizing plate 31 and the second polarizing plate 41 are substantially parallel. In the example shown in the figure, the first polarizing plate 31 allows horizontally linearly polarized light to pass through and reflects vertically linearly polarized light. Therefore, vertically linearly polarized light (second linearly polarized light) that has passed through the third wave plate 44 is reflected by the first polarizing plate 31 and then passes through the third wave plate 44 again.

[0055] The third wave plate 44 adds a phase difference of 90 degrees (π / 2) to this light. As a result, the phase difference of the light transmitted through the third wave plate 44 toward the display element De is 270 degrees (3π / 2). This light becomes first circularly polarized light (e.g., right-handed circularly polarized light when viewed in the direction of light propagation). When this circularly polarized light is reflected by the reflective region F1 of the reflective layer 43, it becomes second circularly polarized light (e.g., left-handed circularly polarized light when viewed in the direction of light propagation) while maintaining the phase difference, and then re-enters the third wave plate 44. The third wave plate 44 adds a phase difference of 90 degrees (π / 2) to this circularly polarized light. As a result, the phase difference of the light transmitted through the third wave plate 44 toward the user's eye (toward the lens S) is 0 degrees, and it becomes first linearly polarized light (e.g., horizontally linearly polarized light).

[0056] The first linearly polarized light (e.g., horizontally linearly polarized light) that has passed through the third wave plate 44 passes through the first polarizing plate 31, and then passes through the above-mentioned first optical path extension structure E1 (and lens S) to reach the user's eye. The optical path in the first optical path extension structure E1 is the same as that in FIG. 1, so a description thereof will be omitted here.

[0057] In this way, the optical laminate 10A has two optical path extension structures E1 and E2, which further increases the optical path length from the display element De to the user's eye. As a result, a lens with low lens power can be used while maintaining the distance between the lens and the virtual image (the distance at which the user perceives an image). Using such a lens reduces aberrations. Furthermore, this reduces the need for highly accurate management of the relative position between the first optical path extension structure E1 and the light output region R1 of the display element De, thereby facilitating the manufacture of the display device.

[0058] In the example of the optical laminate 10A, gaps may be formed between the reflective layer 43 and the third wave plate 44, and between the third wave plate 44 and the first polarizing plate 31. This makes it easier to ensure the optical path length according to the focal length of the lens. Unlike the example shown in the figure, although a gap is formed between the reflective layer 43 and the third wave plate 44, the third wave plate 44 and the first polarizing plate 31 may be in contact. Conversely, although the reflective layer 43 and the third wave plate 44 are in contact, a gap may be secured between the third wave plate 44 and the first polarizing plate 31.

[0059] [Configuration using half mirror] Note that the plurality of optical path extension structures utilizing light reflection are not limited to the examples shown in Figs. 1 and 2. Fig. 3 is a diagram showing an optical laminate 10B according to a modified example. The optical laminate 10B has the second optical path extension structure E2 described above. Furthermore, the optical laminate 10B has a third optical path extension structure E3 instead of the first optical path extension structure E1. The second optical path extension structure E2 and the third optical path extension structure E3 are aligned in the direction in which the display element De emits light. The second optical path extension structure E2 is formed between the third optical path extension structure E3 and the display element De.

[0060] 3, the third optical path extension structure E3 has a polarizing plate 51, a wave plate 52, a half mirror 53, a wave plate 54, and a polarizing plate 55. Hereinafter, the polarizing plate 51, the wave plate 52, the wave plate 54, and the polarizing plate 55 will be referred to as the third polarizing plate 51, the fourth wave plate 52, the fifth wave plate 54, and the fourth polarizing plate 55 in order to distinguish them from the polarizing plate 31 and the like described so far.

[0061] 3, the polarizing plate 51 and / or the half mirror 53 may have a lens function in addition to or instead of the lens S. In this case, the polarizing plate 51 and / or the half mirror 53 may be an aspherical lens.

[0062] The fourth polarizer 55, the third polarizer 51, and the second polarizer 41 are arranged so that their transmission axes are substantially parallel. The transmission axes of the fourth polarizer 55, the third polarizer 51, and the second polarizer 41 are substantially perpendicular to the transmission axis of the polarizer 15 of the display element De. For example, the fourth polarizer 55, the third polarizer 51, and the second polarizer 41 are arranged so that their transmission axes are along the horizontal direction (X1-X2 direction). The third polarizer 51 is a reflective polarizer. The fourth polarizer 55 may be a reflective polarizer or an absorptive polarizer.

[0063] The fourth wave plate 52 and the fifth wave plate 54 are, for example, quarter-wave plates. That is, the wave plates 52 and 54 impart a phase difference of 90 degrees (π / 4) to the light passing through the wave plates 52 and 54. The wave plates 42 and 45 convert linearly polarized light incident thereon into circularly polarized light and output the circularly polarized light, and convert circularly polarized light incident thereon into linearly polarized light and output the circularly polarized light.

[0064] The half mirror 53 transmits, for example, substantially half of the light and reflects the remaining light.

[0065] [Optical Path] An example of the optical path of light emitted from the display element De will be described with reference to FIG. 3 . In the following description, the first circularly polarized light corresponds to "right-handed circularly polarized light" and the second circularly polarized light corresponds to "left-handed circularly polarized light," but this correspondence may be reversed. That is, the first circularly polarized light may correspond to left-handed circularly polarized light and the second circularly polarized light may correspond to right-handed circularly polarized light. Furthermore, the first linearly polarized light corresponds to "horizontal linearly polarized light" and the second linearly polarized light corresponds to "vertical linearly polarized light," but this correspondence may also be reversed. That is, the first linearly polarized light may correspond to "vertical linearly polarized light" and the second linearly polarized light may correspond to "horizontal linearly polarized light."

[0066] The optical path in the second optical path extension structure E2 is the same as that described with reference to Fig. 2. Therefore, the first linearly polarized light (for example, horizontally linearly polarized light) that has passed through the third wave plate 44 of the second optical path extension structure E2 passes through the third polarizing plate 51 with a phase difference of 0 degrees.

[0067] 3, the linearly polarized light that has passed through the third polarizing plate 51 passes through the fourth wave plate 52. A phase difference of 90 degrees (π / 2) is applied to the linearly polarized light that has passed through the fourth wave plate 52, and as a result, the linearly polarized light is converted into first circularly polarized light (for example, right-handed circularly polarized light). A portion of the circularly polarized light is reflected by the half mirror 53, and the remainder passes through the half mirror 53.

[0068] As shown in FIG. 3 , the light reflected by the half mirror 53 is transmitted again through the fourth wave plate 52. The fourth wave plate 52 imparts a phase difference of 90 degrees (π / 2) to this light. As a result, the phase difference of the light transmitted through the fourth wave plate 52 toward the display element De is 180 degrees (π). This light becomes second linearly polarized light (e.g., vertically linearly polarized light). The third polarizer 51 is a reflective polarizer, and its transmission axis is substantially parallel to the transmission axis of the second polarizer 41 (the horizontal transmission axis in the illustrated example). Therefore, the second linearly polarized light transmitted through the fourth wave plate 52 is reflected by the third polarizer 51.

[0069] The light reflected by the third polarizing plate 51 passes through the fourth wave plate 52 again while maintaining its phase difference, and the phase difference becomes 270 degrees (3π / 2). This light is the second circularly polarized light (e.g., left-handed circularly polarized light). A portion of this light passes through the half mirror 53 and then the fifth wave plate 54. The phase difference of the light that passes through the fifth wave plate 54 becomes 0 degrees, and the light becomes the first linearly polarized light (e.g., horizontally linearly polarized light). Therefore, the vibration direction becomes substantially parallel to the transmission axis of the fourth polarizing plate 55, and the light that passes through the fifth wave plate 54 passes through the fourth polarizing plate 55 (and the lens S) and reaches the user's eye.

[0070] In this way, the optical laminate 10B has two optical path extension structures E2 and E3, which further increases the optical path length from the display element De to the user's eye. As a result, a lens with low lens power can be used while maintaining the distance to the virtual image (the distance at which the user perceives the image). Furthermore, the use of such a lens can reduce aberrations.

[0071] In addition, in the optical laminate 10B, there is polarized light (e.g., right-handed circularly polarized light) that passes through the third polarizing plate 51 and the fourth wave plate 52 and is transmitted through the half mirror 53 without being reflected by the half mirror 53. This light passes through the fifth wave plate 54. The light that passes through the fifth wave plate 54 has a phase difference of 180 degrees (π) and is converted into second linearly polarized light (e.g., vertically linearly polarized light). As described above, the fourth polarizing plate 55 and the third polarizing plate 51 are arranged so that their transmission axes are substantially parallel. Therefore, the linearly polarized light that passes through the fifth wave plate 54 does not pass through the fourth polarizing plate 55. In this way, light with a short optical path length (light not reflected by the half mirror 53) can be prevented from reaching the user's eyes.

[0072] [Display Device] The optical laminates 10, 10A, and 10B, the display element De, and the lens constitute a display device. Fig. 4 is a diagram showing a head-mounted display (HMD) 100, which is an example of the display device.

[0073] The HMD 100 has a main body housing 3 placed in front of the user's eyes. A display device main body 100a including a display element De, a lens S, and optical stacks 10, 10A, and 10B is placed in the main body housing 3. The HMD 100 has a band mechanism 2 extending from the main body housing 3 and fixed to the user's head. Note that the display device proposed in this disclosure may be applied to a display device other than an HMD (for example, an in-vehicle display device).

[0074] [Summary] (1) As described above, the optical laminate 10 / 10A includes a reflective polarizing plate 31, a wavelength plate 32, and an optical element 33 having circular polarization selectivity that reflects one of right-handed and left-handed circularly polarized light and transmits the other. The polarizing plate 31, wavelength plate 32, and optical element 33 are arranged in this order in the direction in which the display element De emits light. This structure makes it easy to ensure a sufficient optical path length (e.g., an optical path length corresponding to the focal length of the lens S) between the display element De and the user's eye. Furthermore, it reduces the need for high-precision management of the relative positions of the display element De, the optical path extension structure E1 composed of the polarizing plate 31, wavelength plate 32, and optical element 33, and the display element De.

[0075] (2) In the structure of (1), the optical element 33 includes a first layer 33a having circular polarization selectivity for light of a first color (e.g., red) and a second layer 33b having circular polarization selectivity for light of a second color (e.g., green). This structure can increase the range of applications of the display device.

[0076] (3) In the structure of (1) or (2), the optical element 33 includes a cholesteric liquid crystal film.

[0077] (4) In any of the structures (1) to (3), the first linearly polarized light that passes through the polarizing plate 31 passes through the wave plate 32 and becomes the first circularly polarized light, the first circularly polarized light is reflected by the optical element 33, passes through the wave plate 32 and becomes the second linearly polarized light, the second linearly polarized light is reflected by the polarizing plate 31, passes through the wave plate 32 and becomes the second circularly polarized light, and the second circularly polarized light passes through the optical element 33.

[0078] (5) In any of the structures (1) to (4), a gap is provided between the polarizing plate 31 and the wave plate 32 and / or between the wave plate 32 and the optical element 33. This makes it easier to ensure a sufficient optical path length (e.g., an optical path length corresponding to the focal length of the lens S) between the display element De and the user's eye.

[0079] (6) In any of the structures (1) to (4), the optical laminate 10A includes a first optical path extension structure E1 including a polarizing plate 31, a wavelength plate 32, and an optical element 33, and a second optical path extension structure E2 in which the first optical path extension structure E1 and the display element De are aligned in the light emission direction. This structure allows the optical path length between the display element De and the user's eye to be further extended without increasing the actual distance between the display element De and the user's eye. Furthermore, a lens with low lens power can be used while maintaining the distance between the lens and the virtual image (the distance at which the user perceives the image to be displayed). Using such a lens can reduce aberrations.

[0080] (7) In the structure of (6), the display element De has a plurality of pixels Px, each of which has a light-emitting region R1 that transmits or emits light, and a non-light-emitting region R2 between adjacent light-emitting regions R1. The second light path extension structure E2 is disposed between the display element De and the first light path extension structure E2. The second light path extension structure E2 has a second polarizing plate 41, a wave plate 42, a reflective layer 43, and a third wave plate 44. The second polarizing plate 41, the second wave plate 42, the reflective layer 43, and the third wave plate 44 are arranged in this order in the direction in which the display element De emits light. The reflective layer 43 has a reflective region F1 that corresponds to the position of the non-light-emitting region R2 and reflects light, and a light-transmitting region F2 that corresponds to the position of the light-emitting region R1 and transmits light.

[0081] It should be noted that the structure of the optical laminate proposed in the present disclosure is not limited to the examples shown in Figures 1 to 3. For example, the optical laminate may have two optical path extension structures having the same structure (the same optical element).

Claims

1. An optical laminate for attachment to a display element that emits light in a first direction, comprising: a reflective polarizing plate; a wavelength plate; and an optical element having circular polarization selectivity that reflects one of right-handed and left-handed circularly polarized light and transmits the other circularly polarized light, wherein the polarizing plate, the wavelength plate, and the optical element are arranged in this order in the first direction.

2. The optical laminate according to claim 1, wherein the optical element comprises a first layer having the circular polarization selectivity for light of a first color, and a second layer having the circular polarization selectivity for light of a second color.

3. The optical laminate according to claim 1, wherein the optical element comprises a cholesteric liquid crystal film.

4. The optical laminate described in claim 1, wherein a first linearly polarized light that is linearly polarized light that has passed through the polarizing plate passes through the wave plate to become the one circularly polarized light, the one circularly polarized light is reflected by the optical element and passes through the wave plate to become the second linearly polarized light, the second linearly polarized light is reflected by the polarizing plate and passes through the wave plate to become the other circularly polarized light, and the other circularly polarized light passes through the optical element.

5. The optical laminate according to claim 1, wherein a gap is provided between the polarizing plate and the wave plate, and / or between the wave plate and the optical element.

6. The optical laminate according to claim 1, comprising: a first optical path extension structure including the polarizing plate, the wave plate, and the optical element; and a second optical path extension structure aligned with the first optical path extension structure in the first direction.

7. The optical laminate according to claim 6, wherein the display element has a plurality of pixels, each of the plurality of pixels having a light emission region which is a region through which light passes or a region that emits light, and a non-light emission region between adjacent light emission regions; the second optical path extension structure is disposed between the display element and the first optical path extension structure, and has a second polarizing plate, a second wave plate, a reflective layer, and a third wave plate, the second polarizing plate, the second wave plate, the reflective layer, and the third wave plate are arranged in this order in the first direction, and the reflective layer has a reflective region which corresponds to the position of the non-light emission region and reflects light, and a light transmitting region which corresponds to the position of the light emission region and transmits light.

8. A display device comprising the display element and the optical laminate according to claim 1.

9. A head mounted display comprising the display element and the optical laminate according to claim 1.

Images