JP2014035440A - Optical sheet, display device and production method of optical sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease visibility of moire that generates when an optical sheet for controlling a propagation direction of light depending on a polarization state of the light is used.SOLUTION: An optical sheet 40 is used in a display device that can display, as switchable, a two-dimensional image and a three-dimensional image visible by naked eyes. The optical sheet 40 includes an optically anisotropic first layer 51 and a second layer 52 stacked on the first layer. An optical interface 55 that changes propagation directions of light having one polarization component is formed between the first layer 51 and the second layer 52. The optical interface includes a plurality of unit optical interfaces 56 arrayed in one direction; and each unit optical interface extends in a direction not parallel to the one direction. When observed in the normal direction of the optical sheet, each side edge 57 of the unit optical interface is wavy.

Description

  The present invention relates to a display device that displays a planar image and a stereoscopic image that can be viewed with the naked eye in a switchable manner, and an optical sheet and an optical that are used in the display device and control the traveling direction of the light according to the polarization state of the light. The present invention relates to a sheet manufacturing method.

  For example, as disclosed in Patent Document 1, a display device that displays a stereoscopic image that can be observed with the naked eye has been developed. In such a display device, it is possible to switch between the display of a planar image formed on the display surface and the display of a stereoscopic image that has a sense of depth and is also visually recognized at a position shifted from the display surface. ing.

  In the display device disclosed in Patent Document 1, a planar image is formed with one linearly polarized component, and a stereoscopic image is formed with the other linearly polarized component. The display device has a birefringent lens that exhibits a lens function only with respect to the light of the other linearly polarized light component forming the stereoscopic image. The light of the other linearly polarized light component emitted from the pixel that forms the image for the left eye is collected by the birefringent lens, collected at the position of the left eye of the observer, and similarly, the pixel that forms the image for the right eye The light of the other linearly polarized light component emitted from is condensed by a birefringent lens and collected at the position of the right eye of the observer. As a result, the observer can observe the image for the left eye with the left eye and simultaneously observe the image for the right eye with the right eye, whereby the stereoscopic image can be visually recognized.

  The birefringent lens has an optically anisotropic layer and an optically isotropic layer disposed adjacent to each other. The refractive indexes of the optically anisotropic layer and the optically isotropic layer are the same in the vibration direction of one linearly polarized light component and are different in the vibration direction of the other linearly polarized light component. As a result, only the light of the other polarization component changes the traveling direction at the interface between the optically anisotropic layer and the optically isotropic layer.

JP-T-2004-538529

  Incidentally, the birefringent lens has unit lenses arranged in one direction. Then, due to the regularity of the arrangement of unit lenses and the regularity of the pixel arrangement of the image display unit that forms an image, a striped pattern, so-called moire, may be visually recognized on the display surface. When moiré is observed, the image quality of the displayed image is significantly deteriorated. From the viewpoint of simply making the moire invisible, it is considered effective to incline the arrangement direction of the unit lenses of the birefringence lens with respect to the arrangement direction of the pixels and to adjust the arrangement pitch of the unit lenses. .

  However, in a display device that displays a stereoscopic image that can be observed with the naked eye, the unit lens of the birefringent lens exhibits a lens function for image light from a specific pixel of the image display unit, and the image light is transmitted to a specific position. Designed to collect on. For this reason, each unit lens of the birefringent lens is arranged at a position facing the target pixel. That is, since the arrangement of the unit lenses of the birefringent lens cannot be determined regardless of the pixel arrangement, the conventional method of adjusting the arrangement direction or adjusting the arrangement pitch cannot always be adopted.

  The present invention has been made in consideration of such points, and an object of the present invention is to make the moire generated when using an optical sheet that controls the traveling direction of light according to the polarization state of the light inconspicuous. And

The optical sheet according to the present invention is
An optical sheet that is used in a display device that displays a planar image and a stereoscopic image that can be viewed with the naked eye in a switchable manner, and that controls the traveling direction of the light according to the polarization state of the light,
A first layer of optical anisotropy;
A second layer that is stacked on the first layer and forms an optical interface between the first layer and the optical layer that changes the traveling direction of light of one polarization component;
The optical interface has a plurality of unit optical interfaces arranged in one direction, and each unit optical interface extends in a direction non-parallel to the one direction,
When observed from the normal direction of the optical sheet, each side edge of the unit optical interface is wavy.

  In the optical sheet according to the present invention, the amount of variation along the one direction of the side edge within a range corresponding to one period of waviness of the side edge along the direction in which the unit optical interface extends may be 1 μm or more. Good.

  In the optical sheet according to the present invention, the amount of variation along the one direction of the side edge of the unit optical interface may be 2 μm or more.

  In the optical sheet according to the present invention, a length corresponding to one period of undulation of the side edge along a direction in which the unit optical interface extends may be 500 μm or less.

  In the optical sheet according to the present invention, the first layer may include a thermoplastic resin.

  In the optical sheet according to the present invention, the thermoplastic resin may be a polyethylene naphthalate resin.

  In the optical sheet according to the present invention, a glass transition temperature of the material forming the first layer may be 100 ° or more.

  In the optical sheet according to the present invention, the dimensional stability of the optical sheet measured at 30 ° C. for 30 minutes and measured according to JIS C2151 may be 2% or less.

  In the optical sheet according to the present invention, the in-plane birefringence Δn of the first layer may be 0.13 or more.

  In the optical sheet according to the present invention, the light of the other polarization component traveling in the normal direction to the optical sheet is transmitted through the optical sheet and then forms an angle of 2 ° or less with respect to the normal direction to the optical sheet. You may make it go to.

  In the optical sheet according to the present invention, the second layer may be optically isotropic.

A display device according to the present invention comprises:
A display device that displays a planar image and a stereoscopic image that can be viewed with the naked eye in a switchable manner,
Any of the optical sheets according to the invention described above;
An image display unit disposed to face the optical sheet, and emits light of one polarization component for displaying the stereoscopic image and light of the other polarization component for displaying the planar image Image display unit.

In the display device according to the present invention,
The pixel display unit includes partition walls that define pixels arranged in a direction parallel to the one direction of the optical sheet,
The amount of fluctuation along the one direction of the side edge within a range corresponding to one period of waviness of the side edge along the direction in which the unit optical interface extends is along the one direction of the partition of the pixel display unit. It may be smaller than the width.

In the display device according to the present invention,
The pixel display unit includes partition walls that define pixels arranged in a direction parallel to the one direction of the optical sheet,
The amount of variation along the one direction of the side edge of the unit optical interface may be smaller than the width of the partition of the pixel display unit along the one direction.

In the display device according to the present invention,
The pixel display unit includes partition walls that define pixels arranged in a direction parallel to the one direction of the optical sheet,
In the observation from the normal direction of the optical sheet, the side edge of the unit optical interface may be located only on the partition wall of the pixel display unit.

The method for producing the first optical sheet according to the present invention comprises:
A method for producing any of the optical sheets according to the present invention described above,
A step of producing a first layer of optical anisotropy by stretching a resin film formed by molding a thermoplastic resin;
Forming or laminating a second layer on the first layer.

The method for producing the second optical sheet according to the present invention comprises:
A method for producing any of the optical sheets according to the present invention described above,
Including a step of stretching the first layer and the second layer in a state where a second resin film formed by molding a thermoplastic resin is laminated on a first resin film formed by molding a thermoplastic resin,
The magnitude of the electric dipole moment of the first resin film is larger than the magnitude of the electric dipole moment of the second resin film.

  ADVANTAGE OF THE INVENTION According to this invention, the moire which arises when using the optical sheet which controls the advancing direction of the said light according to the polarization state of light can be made not conspicuous.

FIG. 1 is a perspective view schematically illustrating a display device for explaining an embodiment of the present invention. 2 is a view for explaining an optical path of light forming an image when a stereoscopic image is displayed on the display device of FIG. 1, and is a longitudinal sectional view of the display device of FIG. FIG. 3 is a view for explaining an optical path of light forming an image when a planar image is displayed on the display device of FIG. 1, and is a longitudinal sectional view of the display device of FIG. FIG. 4 is a plan view showing the optical sheet from the direction normal to the sheet surface of the optical sheet. FIG. 5 is a partially enlarged view of FIG. FIG. 6 is a perspective view showing refractive index ellipsoids of the first layer and the second layer of the optical sheet incorporated in the display device of FIG. 1. FIG. 7 is a view showing a modification of the refractive index distribution in the planes of the first layer and the second layer. FIG. 8 is a diagram showing another modification of the refractive index distribution in the plane of the first layer and the second layer. FIG. 9 is a diagram showing still another modification of the refractive index distribution in the plane of the first layer and the second layer. FIG. 10 is a diagram showing still another modified example of the refractive index distribution in the planes of the first layer and the second layer. FIG. 11 is a diagram for explaining an example of a method for manufacturing an optical sheet. FIG. 12 is a diagram for explaining another example of a method for manufacturing an optical sheet.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings attached to the present specification, for the sake of illustration and ease of understanding, the scale, the vertical / horizontal dimension ratio, and the like are appropriately changed and exaggerated from those of the actual product.

  1 to 6 are diagrams for explaining an embodiment of the present invention. Among these, FIG. 1 is a perspective view showing a display device. 2 and 3 are diagrams for explaining the operation of the display device when displaying a stereoscopic image or a planar image, respectively. 4 and 5 are plan views showing the optical sheet. FIG. 6 is a perspective view showing refractive index ellipsoids of the first layer and the second layer of the optical sheet.

  Display device 10 in the present embodiment can switchably display a planar image and a stereoscopic image that can be viewed with the naked eye. As illustrated in FIG. 1, the display device 10 includes an image display unit 15 and an optical sheet 40 disposed to face the image display unit 15. The image display unit 15 is configured to emit one linearly polarized light component for displaying a stereoscopic image and the other linearly polarized light component for displaying a planar image. The optical sheet 40 controls the traveling direction of the light according to the polarization state of the light. More specifically, the optical sheet 40 controls the traveling direction of light of one linearly polarized component for displaying a stereoscopic image, and the other straight line that vibrates in a direction orthogonal to the vibration direction of the one linearly polarized component. The traveling direction of the light of the polarization component is maintained.

  Here, the planar image is an image that is observed two-dimensionally on the display surface 10a, while the three-dimensional image is an image that has a depth that is also observed at a position different from the display surface 10a. . And in the display apparatus 10 demonstrated here, a stereo image can be displayed using a binocular parallax and a motion parallax. As shown in FIG. 2, when a stereoscopic image is displayed, each pixel 21 of the image forming apparatus 20 of the image display unit 15 is allocated to a plurality of positions assumed to be where the left eye or right eye of the observer is located. . A plurality of pixels 21 allocated at the same position forms an image to be observed at the allocated position. On the other hand, the optical sheet 40 is directed so that the light emitted from each pixel 21 is directed to the position where the pixel 21 is allocated among a plurality of positions where the left eye or the right eye of the observer is supposed to be located. Control the optical path. As a result, different images are observed in the right eye and left eye of the observer, and the observer recognizes the image three-dimensionally. Further, when the observation direction is changed, a stereoscopic image corresponding to the observation position can be observed.

  Hereinafter, each component will be further described in detail. In the following description, one linearly polarized light component that forms a stereoscopic image is a first polarized light component that vibrates in the x-axis direction (see FIG. 1) parallel to the sheet surface of the optical sheet 40. The other linearly polarized light component that forms the planar image is a second polarized light component that vibrates in the y-axis direction (see FIG. 1) perpendicular to the x-axis direction and parallel to the sheet surface of the optical sheet 40.

  In the present specification, the terms “sheet”, “film”, and “plate” are not distinguished from each other only based on the difference in names. For example, “film” is a concept that includes members that can be referred to as sheets and plates. Therefore, “optical sheet” is distinguished only from the members that are referred to as “optical films” and “optical plates”. I don't get it.

  The “sheet surface (film surface, plate surface, panel surface)” is a target when the target sheet-like (film shape, plate shape, panel shape) member is viewed as a whole and globally. It refers to the surface that matches the planar direction of the sheet-like member (film-like member, plate-like member, panel-like member). In the present embodiment, the image forming surface 20a of the image forming device 20, the panel surface of the liquid crystal display panel 25, the panel surface of the polarization control device 30, the sheet surface of the optical sheet 40, and the display surface 10a of the display device 10 are as follows. It is parallel. Further, the front direction refers to the normal direction to the sheet surface of the optical sheet 40.

  Furthermore, terms specifying the shape and geometric conditions used in the present specification, for example, terms such as “parallel” and “orthogonal” can be expected to have the same optical function without being bound to a strict meaning. Interpretation will be made including a margin of error.

  First, the image display unit 15 includes an image forming apparatus 20 and a polarization controller 30 that transmits light from the image forming apparatus 20. The polarization controller 30 is disposed between the image forming apparatus 20 and the optical sheet 40. Hereinafter, an example in which the image forming apparatus 20 forms an image with light of the first polarization component will be described. In this example, the polarization control device 30 maintains the polarization state of the light projected from the image forming device 20 as the first polarization component when displaying a stereoscopic image, and the second polarization state when displaying a planar image. Convert to However, the present invention is not limited to this example, and when the image forming apparatus 20 emits light of the second polarization component and the polarization control apparatus 30 displays a stereoscopic image, the polarization state of the light projected from the image forming apparatus 20 is changed to the first. When converting to one polarization component and displaying a planar image, the second polarization state may be maintained.

  As shown in FIG. 1 and FIG. 4, the image forming apparatus 20 includes a partition wall 22 configured to define a large number of opening regions forming the pixel 21. The partition wall 22 is formed in a plane parallel to the image forming surface 20a, and a large number of pixels 21 are arranged in a plane parallel to the image forming surface 20a. In the illustrated example, the partition walls 22 are configured in a matrix, and the pixels 21 are arranged in a square lattice. As well shown in FIG. 4, the pixels 21 are arranged at a constant pitch in the x-axis direction and at a constant pitch in the y-axis direction.

  In the illustrated example, the image forming apparatus 20 is formed as a liquid crystal display device. That is, the image forming apparatus 20 includes a liquid crystal display panel 25 and a backlight 24 disposed on the back surface of the liquid crystal display panel 25. The backlight 24 may be formed using a known configuration such as an edge light type or a direct type.

  On the other hand, the liquid crystal display panel 25 includes a pair of polarizing plates 26 and 28 and a liquid crystal cell 27 disposed between the pair of polarizing plates 26 and 28. The polarizing plates 26 and 28 have a function of decomposing incident light into two orthogonal polarization components, transmitting the polarization component in one direction, and absorbing the polarization component in the other direction orthogonal to the one direction. It has a polarizer. In one specific example described here, the lower polarizing plate 26 disposed on the backlight 24 side transmits light of the second polarization component, and the upper polarizing plate 28 disposed on the polarization control device 30 side includes the first polarizing plate 26. The light of the polarization component is transmitted.

  The liquid crystal cell 27 has a pair of support plates and liquid crystal molecules (liquid crystal material) disposed between the pair of support plates. The liquid crystal cell 27 can be applied with an electric field for each region where one pixel is formed. Then, the orientation of the liquid crystal in the liquid crystal cell 27 applied with an electric field changes. As an example, when the light of the second polarization component transmitted through the lower polarizing plate 26 passes through a liquid crystal cell 27 to which an electric field is not applied, its vibration direction is rotated by 90 ° and passes through the liquid crystal cell 27 to which an electric field is applied. The polarization state is maintained. For this reason, depending on whether or not an electric field is applied to the liquid crystal cell 27, whether the light of the second polarization component transmitted through the lower polarizing plate 26 further passes through the upper polarizing plate 28 disposed on the light output side of the lower polarizing plate 26, Alternatively, it is possible to control whether the light is absorbed and blocked by the upper polarizing plate 28. In this manner, an image is formed by the light of the first polarization component from each pixel 21 selectively transmitted through the upper polarizing plate 28.

  The liquid crystal cell 27 includes a color filter 27 a having a partition wall 22. That is, in the liquid crystal cell 27, the pixel 21 is defined by the color filter 27a. The pixel 21 defined by the color filter 27a includes a red pixel 21r, a green pixel 21g, and a blue pixel 21b as sub-pixels. In the illustrated example, the pixels 21 are arranged in a stripe arrangement, and the red pixel 21r, the green pixel 21g, and the blue pixel 21b are successively arranged in the y-axis direction. On the other hand, the red pixel 21r, the green pixel 21g, and the blue pixel 21b are sequentially arranged in the x-axis direction. As shown in FIG. 4, one pixel 21 is configured by the red pixel 21r, the green pixel 21g, and the blue pixel 21b arranged in the x-axis direction. On the other hand, the partition wall 22 is preferably blackened so as to prevent reflection of unnecessary light such as outside light and stray light and avoid a decrease in contrast. For example, the partition wall 22 is preferably configured as a so-called black matrix.

  Next, the polarization controller 30 will be described. As a basic configuration, the polarization controller 30 includes a first electrode 34 and a second electrode 36, and a medium layer 35 disposed on the first electrode 34 and the second electrode 36. The medium layer 35 generates anisotropy of the refractive index when a voltage is applied between the pair of electrodes 34 and 36. In the illustrated example, the first electrode 34, the liquid crystal layer 35, and the second electrode 36 are disposed between the first support film 33 and the second support film 37. The first electrode 34, the medium layer 35, and the second electrode 36 are supported and protected by a pair of support films 33 and 37. Hereinafter, an example in which the medium layer is configured as the liquid crystal layer 35 will be described.

  The pair of electrodes 34 and 36 and the liquid crystal layer 35 are wide enough to face the entire region of the image forming surface 20 a of the image forming apparatus 20. As shown in FIGS. 2 and 3, the liquid crystal layer 35 is configured as a layer including liquid crystal molecules 31. The pair of electrodes 34 and 36 are electrically connected to a voltage applying means (not shown). The pair of electrodes 34 and 36 is kept at a predetermined interval by a spacer (not shown) or the like.

  When the liquid crystal molecules 31 included in the liquid crystal layer 35 are TN type liquid crystal molecules as a typical example, when a voltage is applied between the pair of electrodes 34 and 36, the liquid crystal molecules 31 are aligned as shown in FIG. . In this case, the polarization state of the light from the image forming apparatus 20 is maintained as the first polarization component. On the other hand, when no voltage is applied between the pair of electrodes 34 and 36, as shown in FIG. 3, the liquid crystal molecules 31 rotate 90 ° in a twisted manner. In this case, the polarization state of the light from the image forming apparatus 20 is converted from the vibration direction from the x-axis direction to the y-axis direction, that is, from the first polarization component to the second polarization component.

  However, the description of the image display unit 15, the image forming apparatus 20, and the polarization control apparatus 30 described above is merely a specific example, and known means can be used.

  Next, the optical sheet 40 will be described. As shown in FIG. 1, the optical sheet 40 includes a first layer 51 and a second layer 52 provided adjacent to the first layer 51. In the illustrated example, the optical sheet 40 further includes a film layer 43 provided on the second layer 52.

  The film layer 43 is formed as a single layer or a plurality of stacked layers. The film layer 43 is a layer expected to exhibit a specific function, and forms the outermost light emitting side surface of the display device 10, that is, the display surface 10 a of the display device 10. As an example, the film layer 43 includes an antireflection layer (AR layer) having an antireflection function, an antiglare layer (AG layer) having an antiglare function, a hard coat layer (HC layer) having scratch resistance, It may be configured to include one or more antistatic layers (AS layers) having an antistatic function.

  The boundary surface between the first layer 51 and the second layer 52 is formed as an uneven surface. This boundary surface forms an optical interface 55 that changes the traveling direction of light of at least the first polarization component. In the illustrated example, the optical interface 55 that forms the boundary between the first layer 51 and the second layer 52 is configured as a surface including a plurality of unit optical interfaces 56. As will be described later, the optical interface 55 functions as a birefringent lens, and each unit optical interface 56 functions as a unit lens.

  As shown in FIG. 1, the unit optical interfaces 56 are arranged along a certain arrangement direction. Each unit optical interface 56 extends in a direction not parallel to the arrangement direction. In particular, in the illustrated example, the unit optical interfaces 56 are arranged without gaps in the x-axis direction, and each unit optical interface 56 extends linearly in the y-axis direction.

  As described above, the unit optical interface 56 is appropriately designed so that light emitted from each pixel 21 is directed to a predetermined position. In the illustrated example, the unit optical interface 56 has a convex lens-like contour in a cross section parallel to both the front direction and the arrangement direction of the unit optical interfaces 56, and the divergent light beam LF1 (FIG. 2) from each pixel 21 is obtained. The light is condensed at a preset position. The optical interface 55 as an aggregate of a plurality of unit optical interfaces 56 forms a lenticular lens.

  By the way, as shown in FIG. 4, when observed from the normal direction of the optical sheet 40, the side edge 57 of the unit optical interface 56 extending in the y-axis direction is wavy. In other words, the side edge 57 of the unit optical interface 56 extends while undulating in the y-axis direction which is the longitudinal direction thereof. Furthermore, in other words, the position of the side edge 57 of the unit optical interface 56 in the x-axis direction is not constant, and the side edge 57 of the unit optical interface 56 depends on the position in the y-axis direction, which is the longitudinal direction, in the x-axis direction. The position in is changed. As shown in FIG. 4, the side edges 57 of the unit optical interface 56 are irregularly undulated, and in this respect, one unit optical interface 56 has a shape at each position along the y-axis direction. And the plurality of unit optical interfaces 56 have different configurations.

  However, the unit optical interface 56 is expected to function as a lens having a focal point when the light traveling direction of the first polarization component is bent, and thus is not greatly undulated. When the optical interface 55 is observed globally to such an extent that the waviness of the side edge 57 can be ignored, each unit optical interface 56 extends linearly in the y-axis direction. One unit optical interface 56 has the same shape at each position along the y-axis direction, and the plurality of unit optical interfaces 56 are configured identically.

  Such waviness of the side edge 57 of the unit optical interface 56 is provided in order to make moiré that may occur due to the regularity of the arrangement of the unit optical interface 56 and the regularity of the arrangement of the pixels 21 invisible. Yes. From this point of view, in the combination with the pixel arrangement of the currently sold display device, the direction in which the unit optical interface 56 extends (that is, the longitudinal direction of the unit optical interface 56, and in the illustrated example, the y axis The fluctuation amount of the side edge 57 along the arrangement direction (in the illustrated example, the x-axis direction) of the unit optical interfaces 56 within the range of one period of waviness of the side edge 57 along the direction (sa) is 1 μm. The above is preferable. Moreover, it is preferable that the length of one swell of the side edge 57 along the direction in which the unit optical interface 56 extends is equal to or less than 500 μm. Furthermore, when the present inventor has conducted earnest experiments, it is more preferable that the variation amount of the side edge 57 in the arrangement direction of the unit optical interfaces 56 over the entire length of the unit optical interfaces 56 is 2 μm or more.

  Here, “one period of undulation” and “amount of fluctuation of the side edge” will be described. As shown in FIGS. 4 and 5, in a plan view of the optical sheet 40, in other words, when viewed from the normal direction to the sheet surface of the optical sheet 40, the side edge 57 of the unit optical interface 56 is unit optical. Convex portions (extreme values in the function) pa1, pb1, and pa2 projecting to the respective sides in the arrangement direction of the interfaces 56 (in the illustrated example, the x-axis direction) are included. The term “for one period of undulation” refers to the direction in which the unit optical interface 56 extends (shown in the drawing) to one side in the arrangement direction of the unit optical interfaces 56 (in the illustrated example, the right side in the x-axis direction in FIG. 5). In the example shown, it indicates the section sa between the two convex portions pa1 and pa2 located adjacent to each other in the y-axis direction). On the other hand, the “amount of fluctuation of the side edge” means, for example, within a range corresponding to one period of waviness of the side edge 57 along the direction in which the unit optical interface 56 extends in the target section or the total length of the unit optical interface 56. The size along the arrangement direction of the unit optical interfaces 56 in the range where the side edge 57 is located is meant.

  However, the illustrated unit optical interface 56 and optical interface 55 are merely examples, and various modifications are possible. For example, the cross-sectional contour of the unit optical interface 56 can be changed as appropriate. The plurality of unit optical interfaces 56 may have different shapes. As an example, the optical interface 55 may constitute a Fresnel lens.

Next, the refractive indexes of the first layer 51 and the second layer 52 will be described. The first layer 51 is optically anisotropic and has at least in-plane birefringence. That is, the refractive index n _1x of the first layer 51 in the x-axis direction is different from the refractive index n _{1y of} the first layer 51 in the y-axis direction. In addition, the optical sheet 40 will be described herein, the refractive index in the x-axis direction of the first layer 51 _{n 1x,} the refractive index in the x-axis direction of the second layer 52 _{n 2x,} y-axis direction of the first layer 51 refractive index _{n 1y} in, and the refractive index of the y-axis direction of the second layer 52 _{n 2y} satisfies the following relationship.
| N _1x −n _2x | ≠ | n _1y −n _2y |
Accordingly, the optical sheet 40 exhibits different optical functions for the light of the first polarization component that vibrates in the x-axis direction and the light of the second polarization component that vibrates in the y-axis direction. More specifically, when the light of the first polarization component and the light of the second polarization component traveling in the same direction pass through the optical interface 55 of the optical sheet 40, the light travels in different directions.

In particular, in the example described here, the following relationship is satisfied.
| N _1x −n _2x |> | n _1y −n _2y | = 0
In this case, the optical interface 55 of the optical sheet 40 no longer forms an optical interface having a refractive index difference with respect to the light of the second polarization component that vibrates in the y-axis direction. Accordingly, the light of the first polarization component is subjected to an optical function (for example, a lens function) from the optical interface 55 of the optical sheet 40, but the light of the second polarization component passes through the optical interface 55 of the optical sheet 40. The direction of travel is not changed. In this specification, the value of the refractive index is handled as a numerical value up to the second decimal place by rounding off the third decimal place.

However, in application to a display device that displays a planar image and a stereoscopic image that can be viewed with the naked eye in a switchable manner, setting | n _1y −n _2y | = 0 is not an essential condition for practical use. It is sufficient that _1x −n _2x |> | n _1y −n _2y | and | n _1y −n _2y | ≦ 0.02. In this case, the traveling direction of the light of the second polarization component is not changed at the optical interface 55 of the optical sheet 40 to such an extent that troubles such as ghost and crosstalk occur.

Further, in application to a display device that displays a planar image and a stereoscopic image that can be viewed with the naked eye in a switchable manner, the degree of optical action exerted on the light of the second polarization component is as large as | n _1y −n _2y |. Not only this, but also other configurations such as the shape of the optical interface 55 of the optical sheet 40 which will be described in detail later are affected. From such a viewpoint, after the light of the polarization component (second polarization component) oscillating in the y-axis direction traveling in the direction orthogonal to the sheet surface of the optical sheet 40 (ie, the front direction) is transmitted through the optical sheet 40, The optical sheet 40 may be configured to proceed in a direction that forms an angle of 2 ° or less with respect to the front direction. In this case, it is effective that an optical action that may cause defects, for example, image quality deterioration due to generation of a ghost when displaying a planar image, is exerted on the light of the second polarization component transmitted through the optical sheet 40. Can be prevented.

FIG. 6 shows an example of a refractive index ellipsoid showing a refractive index distribution in each direction of the first layer 51 and the second layer 52. In this example,
(N _1x −n _2x )> | n _1y −n _2y | = 0
The relationship is satisfied. The refractive index n _1x of the first layer 51 in the x-axis direction is larger than the refractive index n _{1y of} the first layer 51 in the y-axis direction. In the example shown in FIG. 6, the second layer 52 is formed as an optically isotropic layer. That is, the refractive index n _2x of the second layer 52 in the x-axis direction is equal to the refractive index n _{2y of} the second layer 52 in the y-axis direction. Accordingly, the refractive index n _1x of the first layer 51 in the x-axis direction is larger than the refractive index n _{2x of} the second layer 51 in the x-axis direction. As a result, the optical interface 55 shown in FIG. 1 can exhibit the same lens function as a convex lens.

In the example shown in FIG. 1, the slow axis direction in which the refractive index is maximum in the plane of the first layer 51 coincides with the x-axis direction, and the refractive index is in the plane of the first layer 51. The fast axis direction in which the minimum value is the same as the y-axis direction. In addition, the refractive index n _2x in the y-axis direction (fast axis direction) in the plane of the first layer 51 and the refractive index n _2y in the y-axis direction in the plane of the second layer 52 are configured to coincide with each other. Therefore, the refractive index difference between the first layer 51 and the second layer 52 in the x-axis direction is set to 0 while the refractive index difference between the first layer 51 and the second layer 52 in the y-axis direction is set to zero. Can be set large. In addition, in application to a home display device, the birefringence index Δn (= n _1x −n _1y ) of the first layer 51 is set on condition that the optical interface 55 is manufactured in a shape that can be easily manufactured. It is preferable that it is 0.13 or more. On the other hand, when the optical anisotropy of the first layer 51 is imparted by stretching as will be described later, the birefringence Δn of the first layer 51 is set to 0. 0 in consideration of the in-plane uniformity in the stretching step. It is preferable to make it 22 or less.

  The refractive index of the first layer 51 and the second layer 52 is “KOBRA-WR” manufactured by Oji Scientific Instruments, “Ellipsometer M150” manufactured by JASCO Corporation, or Abbe refractometer (NAR- manufactured by Atago Co., Ltd.). 4T) can be used as the measured value.

  Such an optical sheet 40 can be manufactured as follows. First, as shown in FIG. 11, the resin film 71 is produced using a thermoplastic resin. Thereafter, the resin film 71 is stretched to produce the first layer 51 made of the stretched resin film 71. Then, the optical sheet 40 is obtained by forming the second layer 52 on the first layer 51.

  The resin film 71 can be produced by molding a resin material containing a thermoplastic resin as a main component, or the thermoplastic resin itself. As the molding process, injection molding or melt extrusion molding can be employed. According to these molding processes, the resin film 71 having the unevenness forming the optical interface 55 can be produced.

  For the molding of the resin film 71, a mold having a mold surface or a mold formed of a resin can be used. In particular, when using a mold made of resin, compared to using a metal mold surface, when applying a heated thermoplastic resin, suppresses rapid heat absorption from the thermoplastic resin to the mold surface. be able to. Thereby, the heated thermoplastic resin can extend and spread sufficiently on the mold surface, and the molding rate can be improved. Moreover, since the release property from the mold surface of the produced resin film 71 is good, it is possible to prevent defects during release. As the mold whose mold surface is made of resin, a long film mold can be used.

  The stretching of the resin film 71 is a process for imparting optical anisotropy to the resin film 71, and therefore, it is preferable to perform uniaxial stretching. When the resin film 71 is made of a polyester resin, the stretching direction (stretching axis) coincides with the slow axis. Therefore, in such a case, as shown in FIG. 11, the resin film 71 is stretched in a direction parallel to the arrangement direction of the convex portions of the resin film 71 that forms the unit optical interface 56 of the optical interface 55. become.

  The stretching of the resin film 71 is performed in a state where the resin film 71 is heated to a temperature equal to or higher than the glass transition temperature of the thermoplastic resin forming the resin film 71. When the resin film 71 is produced by melt extrusion molding, the high-temperature resin film 71 just after extrusion may be stretched. That is, it is not necessary to separately provide a heat treatment for the resin film 71 for stretching. In addition, as shown in FIG. 11, the resin film 71 changes a shape by extending | stretching and comes to form the 1st layer 51. FIG. Therefore, in the molding process of the resin film 71 described above, the resin film 71 is manufactured in a shape that allows for deformation due to stretching.

  By the way, in the optical sheet 40 described here, the side edge 57 of the unit optical interface 56 forming the optical interface 55 extends in the longitudinal direction while undulating. Such waviness at the side edge 57 can be created in advance when the resin film 71 is formed.

  On the other hand, when the present inventors have made extensive studies, it is confirmed that by stretching the resin film 71, the side edge 57 of the unit optical interface 56 composed of convex portions or concave portions can be undulated. It was done. That is, it is confirmed that the convex portions or concave portions formed linearly at the time of molding of the resin film 71 can swell the side edges of the convex portions or concave portions by stretching the resin film 71. It was. According to such a method, it is possible to impart undulation effective for invisibility of moire to the optical sheet 40 very easily as will be described later, while forming the resin film 71 at a low cost.

  According to the present inventors' research, the amount of undulation of the side edge 57 of the unit optical interface 56 to be produced is not only the stretch amount of the resin film 71 but also the processing conditions during stretching, such as temperature conditions, stretching speed, Adjustment was also possible by the method of gripping the resin film 71 and the like. That is, separately from the birefringence of the first layer 51, the amount of undulation of the side edge 57 could be adjusted.

Next, a second layer 52 is formed on the first layer 51 by applying a resin on the manufactured first layer 51 and curing the resin on the first layer 51. The second layer 52 formed on the first layer 51 has an unevenness corresponding to the unevenness of the first layer 51 as a surface facing the first layer 51, in other words, an unevenness complementary to the unevenness of the first layer 51. Will have. As another method, a separately formed second layer 52 may be laminated on the first layer 51. The resin that forms the second layer 52 may be a thermoplastic resin having no birefringence, that is, a refractive index isotropic (n _2x = n _2y ), a thermosetting resin, or an ionizing radiation curing. Mold resin may be used. The optical sheet 40 is obtained as described above. These resins such as thermoplastic resins having no birefringence constituting the second layer are usually solidified in an unstretched state.

  As another method, the optical sheet 40 can also be manufactured by the manufacturing method shown in FIG.

  In the manufacturing method shown in FIG. 12, first, the resin film 71 having the unevenness described above (see FIG. 11) and the unevenness corresponding to the unevenness of the resin film 71, in other words, complementary to the unevenness of the resin film 71. A second resin film 72 having irregularities is prepared. Next, the resin film 71 and the second resin film 72 are laminated through, for example, an adhesive or a pressure-sensitive adhesive so that the unevenness of each other meshes. Thereafter, the laminated resin film 71 and the second resin film 72 are stretched to obtain the optical sheet 40 having the first layer 51 made of the resin film 71 and the second layer 52 made of the second resin film 72. .

  Also in the manufacturing method shown in FIG. 12, the resin film 71 and the second resin film 72 can be manufactured by molding using a thermoplastic resin in the same manner as the above-described manufacturing method shown in FIG. Also in the manufacturing method shown in FIG. 12, in-plane birefringence is imparted to the resin film 71 by stretching the resin film 71. As described above, the side edge of the concave portion or convex portion that forms the unit optical interface 56 can be undulated by this stretching process.

  The second resin film 72 is also stretched together with the resin film 71, but it is not necessary to positively impart optical anisotropy to the second resin film 72. Therefore, in order to prevent in-plane birefringence from occurring in the second resin film 72, it is preferable that the magnitude of the electric dipole moment of the molecules constituting the second resin film 72 is small. In particular, the magnitude of the electric dipole moment of the molecules constituting the second resin film 72 is preferably smaller than at least the magnitude of the electric dipole moment of the molecules constituting the resin film 71. The electric dipole moment is measured by first measuring the dielectric constant using a test fixture HP16451B electrode of a precision LCR meter HP4284A manufactured by Yokogawa-Hewlett-Packard Co., and then using the measured dielectric constant. This can be done by specifying the electric dipole moment.

By selecting the magnitude of the electric dipole moment of the constituent molecules for the resin film 71 and the second resin film 72 as described above, the resin film 71 and the second resin film 72 are stretched in an equal amount, even molecular orientation occurs, the degree of birefringence is expressed in each film (refractive index anisotropy) is dependent on the size of the electric dipole moments of the constituent molecules, the birefringence index of the resin film 71 delta _n1 > When expressed in the refractive index in the x and y-axis direction of the birefringent index delta _n2 or both film of the second resin film _72, and _{n 1x -n 1y> n 2x -n} 2y ( ideally → 0) I meet.

  As described above, the optically anisotropic first layer 51 containing the thermoplastic resin, and the optical interface 55 that is laminated on the first layer 51 and changes the traveling direction of the light of the first polarization component are combined with the first layer 51. The optical sheet 40 having the second layer 52 formed therebetween can be manufactured.

  Note that polycarbonate resin, cycloolefin polymer resin, acrylic resin, polyester resin, or the like can be used as the thermoplastic resin included in the first layer 51. Of these, polyester resins are advantageous in terms of cost and mechanical strength. Specific examples of the polyester resin include polyethylene naphthalate, polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, poly (1,4-cyclohexylenedimethylene terephthalate), and polyethylene-2,6-naphthalate. Further, the polyester resin forming the first layer 50 may be a copolymer of these polyester resins, and the polyester is the main component (for example, a component of 80 mol% or more), and a small proportion (for example, 20 mol% or less). It may be blended with other types of resins. As the polyester resin, polyethylene naphthalate is preferable in that a large birefringence can be secured. As the polyester resin, polyethylene terephthalate or polyethylene-2,6-naphthalate is preferable in terms of a good balance between mechanical properties and optical properties. In addition, from the viewpoint of the stability of the optical sheet 40, the glass transition temperature of the material forming the first layer 51 is preferably 100 ° C. or higher.

  The display device 10 including such an optical sheet 40 can display a planar image and a stereoscopic image that can be observed with the naked eye as follows. First, a case where a planar image is displayed will be described with reference mainly to FIG.

  The backlight 24 illuminates the liquid crystal display panel 25 in a planar shape from the back side. The liquid crystal display panel 25 selectively transmits the light from the backlight 24 for each pixel 21. The planar image lights L31 to L36 thus formed become the first polarization component that can pass through the lower polarizing plate 28 of the image forming apparatus 20 in a state where the planar image lights L31 to L36 are emitted from the image forming surface 20a of the image forming apparatus 20. Yes. Thereafter, the planar image lights L31 to L36 enter the polarization controller 30. When displaying a planar image, no voltage is applied between the pair of electrodes 34 and 36 of the polarization controller 30. For this reason, as shown in FIG. 3, the liquid crystal molecules 31 are turned 90 °. As a result, the planar image lights L31 to L36 that pass through the polarization control device 30 change their polarization states. Accordingly, the planar image lights L31 to L36 are the second polarization component in the state where they are emitted from the image display unit 15.

The planar image lights L31 to L36 emitted from the image display unit 15 enter the optical sheet 40. The optical sheet 40 has an optical interface 55 formed as an uneven surface. The optical interface 55 is configured as a boundary surface between the optically anisotropic first layer 51 and the second layer 52. However, the refractive index n _1y of the first layer 51 in the y-axis direction, which is the vibration direction of the second polarization component forming the planar image light L31 to L36, is the same as the refractive index n _2y of the second layer 52 in the y-axis direction. Is set to Accordingly, the planar image lights L31 to L36 travel without being bent in the traveling direction at the optical interface 55 of the optical sheet 40. In this way, the lights L31 to L36 forming a planar image are emitted from the display surface 10a of the display device 10. As a result, the observer can observe the planar image.

  The light from the backlight 24 that illuminates the liquid crystal display panel 25 has an optical axis in the front direction (that is, has a brightness peak in the front direction) and a certain angle around the front direction. Proceed in the direction of the region. Therefore, the light that has passed through each pixel 21 is emitted from the display surface 10a of the display device 10 as divergent light toward a certain angle range. As a result, as shown in FIG. 3, the observer can observe the same planar image formed on the display surface 10a from a certain angle range.

  Next, a case where a stereoscopic image that is stereoscopically observed with the naked eye is displayed will be described. In the case of displaying a stereoscopic image, the stereoscopic image lights L11 to L16 and Lr1 to Lr6 are emitted from the image forming apparatus 20 as in the case of displaying a planar image. The stereoscopic image lights L11 to L16 and Lr1 to Lr6 then enter the polarization control device 30. However, in the case of displaying a stereoscopic image, each pixel 21 of the image forming apparatus 20 of the image display unit 15 is one of a plurality of positions that are assumed to have the left eye or right eye of the observer positioned. Assigned to a location. The image display unit 15 transmits and blocks light for each pixel 21 so that one image that can be observed from the allocated position is formed by the light from the plurality of pixels 21 allocated to the same position. To control.

  As shown in FIG. 2, when displaying a stereoscopic image, a voltage is applied between the pair of electrodes 34 and 36 of the polarization control device 30. For this reason, the three-dimensional image lights L11 to L16 and Lr1 to Lr6 are transmitted through the polarization control device 30 while maintaining the polarization state in the first state.

The stereoscopic image lights L11 to L16 and Lr1 to Lr6 emitted from the image display unit 15 enter the optical sheet 40. Then, the refractive index n _1x of the first layer 51 in the x-axis direction, which is the vibration direction of the first polarization component forming the stereoscopic image light L11 to L16, Lr1 to Lr6, is the refractive index n of the second layer 52 in the x-axis direction. _The value is larger than _2xy . Thereby, the optical interface 55 of the optical sheet 40 controls the traveling direction of the stereoscopic image light L11 to L16 and Lr1 to Lr6 from each pixel 21.

  As described above, the light from each pixel 21 forms a divergent light beam and enters the optical sheet 40. The unit optical interface 56 of the optical interface 55 exhibits a lens function, and converges light from each pixel 21 to a focal position in the lens function. Specifically, the unit optical interface 56 allows the divergent light beam (for example, the light beam LF1 in FIG. 2) from the pixel 21 at the facing position to pass through the position where the pixel 21 is allocated, that is, the left eye or right eye of the observer. Converge toward one of the positions assumed to be located. In this way, the three-dimensional image lights L11 to L16 and Lr1 to Lr6 from the respective pixels 21 proceed to the predetermined positions, respectively.

  When the observer observes the display device 10 from a position assumed in advance, an image to be viewed from the position of the right eye is observed by the observer's right eye, and is viewed from the position of the left eye by the observer's left eye. A power image can be observed. As a result, the observer can visually recognize a stereoscopic image with the naked eye by binocular parallax. In addition, as shown in FIG. 2, when an observer observes the display device 10 from another position assumed in advance, an image to be observed from the position can be viewed stereoscopically with the naked eye. That is, when the observation direction is changed, the observer can observe with a naked eye different images to be observed according to the observation direction. That is, the observer can visually recognize the image with more stereoscopic effect by the motion parallax.

  By the way, as a general problem, when a lens surface (lens sheet) having regularly arranged unit lenses is superimposed on an image forming apparatus including regularly arranged pixels, a striped pattern called moire is formed. It is known to become visible. As a countermeasure against such moire, conventionally, the unit lens array direction is inclined with respect to the pixel array direction, and the unit lens array pitch is adjusted with respect to the pixel array pitch. However, as described above, in the display device 10 that displays a planar image and a stereoscopic image that can be viewed with the naked eye in a switchable manner, an image that allows each pixel 21 to be observed from a predetermined position assigned in advance is formed. Each unit optical interface 56 constituting the optical interface 55 of the optical sheet 40 functions as a lens that collects light from each pixel toward the predetermined position. For this reason, the arrangement of the unit optical interfaces 56 constituting the optical interface 55 is designed corresponding to the arrangement of the pixels 21 in the image forming apparatus 20. That is, the arrangement of the unit optical interface 56 with respect to the pixel 21 cannot be determined unconditionally, and therefore the conventional moiré countermeasure cannot be applied to the optical sheet 40 functioning as a birefringent lens as it is.

  On the other hand, according to the present embodiment, when observed from the normal direction of the optical sheet 40, each side edge 57 of the unit optical interface 56 is wavy. According to such an optical sheet 40, moire can be effectively made inconspicuous in combination with the image forming apparatus 20 (image display unit 15) including the regularly arranged pixels 21. Such moire invisibility phenomenon makes it possible to eliminate the regularity of the arrangement of the unit optical interface 56 that causes the moire extremely effectively by undulating the side edge 57 of the unit optical interface 56. This is presumed to be the main factor.

  In addition, as described above, when the present inventors have made intensive studies, the arrangement direction of the unit optical interfaces 56 within the range of one period of waviness of the side edge 57 along the longitudinal direction of the unit optical interfaces 56 is sa. When the fluctuation amount wa of the side edge 57 along the line is 1 μm or more, moire can be effectively made inconspicuous. Further, the length of the swell of one side sa of the side edge 57 along the longitudinal direction of the unit optical interface 56 is 500 μm or less, which is effective in effectively making the moire inconspicuous. In addition, it was confirmed that moire can be made invisible very effectively when the amount of variation of the side edge 57 along the arrangement direction of the unit optical interfaces 56 is 2 μm or more.

  On the other hand, according to the research results of the inventors of the present invention, increasing the degree of undulation is effective for invisibility of moire, but if the degree of undulation is increased too much, the lens function of the unit optical interface 56 is sufficient. It has been confirmed that there may be a problem that the position of each side edge 57 that does not appear on the display device 10 is visually recognized on the display surface 10a of the display device 10. From the viewpoint of avoiding such a problem, the side edges 57 of the side edges 57 along the arrangement direction of the unit optical interfaces 56 within the range of one period waviness of the side edges 57 along the longitudinal direction of the unit optical interfaces 56. It is effective to set the fluctuation amount wa to 5 μm or less, and it is also effective to set the length of the sag of one side edge 57 along the longitudinal direction of the unit optical interface 56 to 100 μm or more. It was. Furthermore, from the viewpoint of avoiding such a problem, it was confirmed that it is effective that the fluctuation amount of the side edge 57 along the arrangement direction of the unit optical interfaces 56 is 10 μm or less.

  In addition, in the display device 10 that displays a planar image and a stereoscopic image that can be viewed with the naked eye in a switchable manner, from the viewpoint of performing a lens function with respect to the stereoscopic image light from the corresponding pixel 21, It is preferable that all of the image light is incident on one unit optical interface 56. In other words, it is preferable that the side edge 57 of the unit optical interface 56 does not cross the pixel 21 in a plan view of the optical sheet 40, that is, in an observation from the normal direction to the sheet surface of the optical sheet 40. In other words, in the display device 10 that displays a planar image and a stereoscopic image that can be viewed with the naked eye in a switchable manner, the side edge 57 of the unit optical interface 56 in the planar view of the optical sheet 40 is the image forming device 20 (image display unit). It is preferable that the image forming apparatus 20 and the optical sheet 40 are positioned so as to be positioned on the partition wall 15).

  According to such a display device 10, all of the light from one pixel 21 intended to form a part of an image that can be observed from a predetermined position is arranged at a position facing the pixel 21. The light can enter one unit optical interface 56. As a result, the stereoscopic image light from each pixel 21 is collected at an intended predetermined position by effectively exhibiting the lens function of the unit optical interface 56. In addition, a crosstalk phenomenon in which light from a specific pixel 21 enters the unintended unit optical interface 56 and proceeds in an unintended direction is effectively prevented, and a clear stereoscopic image can be displayed. In addition, since the side edge 57 of the unit optical interface 56 is positioned on the partition wall 22 through which image light does not pass, the outline of the side edge 57 rises on the display surface 10a of the display device 10 to deteriorate the image quality. Can be effectively prevented.

  From the viewpoint of arranging the side edge 57 of the unit optical interface 56 on the partition wall 22 of the image forming apparatus 20 and making the side edge 57 inconspicuous, the unit optical interface 56 has a structure as shown in FIGS. The fluctuation amount wa of the side edge 57 along the arrangement direction of the unit optical interfaces 56 within the range of the waviness of the side edge 57 along the extending direction for one period sa is an image along the arrangement direction of the unit optical interfaces 56. The width is preferably smaller than the width wb of the partition wall 22 of the forming apparatus 20 (image display unit 15). Further, the fluctuation amount of the side edge 57 in the arrangement direction of the unit optical interface 56 over the entire length of the unit optical interface 56 is such that the fluctuation amount of the image forming apparatus 20 (image display unit 15) along the arrangement direction of the unit optical interface 56. More preferably, it is smaller than the width wb of the partition wall 22. As a result of extensive research by the present inventors, adjusting the amount of fluctuation of the side edge 57 to the width wb of the partition wall 22 in this way means that the side edge 57 is strictly located only on the partition wall 22. Even if it is not, it is very effective in achieving an effective lens function from the unit optical interface 56 with respect to the stereoscopic image light, preventing the occurrence of crosstalk, and making the side edge 57 invisible.

  Further, according to the present embodiment, the first layer 51 having the in-plane birefringence of the optical sheet 40 exhibits optical anisotropy by the stretched thermoplastic resin. Therefore, the first layer 51 can sufficiently have a glass transition temperature of 100 ° or more. For this reason, the optical sheet 40 according to the present embodiment and the display device 10 including the optical sheet 40 exhibit excellent stability. As an example, the optical sheet 40 according to the present embodiment can be remarkably improved in dimensional stability measured in accordance with JIS C2151 by heating at 150 ° C. for 30 minutes. Specifically, according to the present embodiment, the dimensional stability of the optical sheet 40 measured at 30 ° C. for 30 minutes and measured according to JIS C2151 can be suppressed to 2% or less. As a result, the optical sheet 40 according to the present embodiment can be used without significant restrictions in a usage environment within the range of general applications such as a home television receiver, and according to the present embodiment. The optical sheet 40 can express the expected optical function.

  Note that various modifications can be made to the above-described embodiment. Hereinafter, an example of modification will be described with reference to the drawings. In the following description and the drawings used in the following description, the same reference numerals as those used for the corresponding parts in the above embodiment are used for the parts that can be configured in the same manner as in the above embodiment. A duplicate description is omitted.

  The optical sheet 40 is merely an example and can be changed as appropriate. First, the film layer 43 is not an essential layer and can be omitted from the optical sheet 40. In addition, a film layer that is expected to exhibit some function may be provided closer to the polarization control device 30 than the first layer 51 and the second layer 52. Furthermore, as described above, the configurations of the optical interface 55 and the unit optical interface 56 can be appropriately changed according to the expected optical function. Furthermore, the first layer 51 having optical anisotropy may be disposed closer to the observation side than the second layer 52.

In the above-described embodiment, the refractive index n _1x of the first layer 51 in the x-axis direction, the refractive index n _{1y of} the first layer 51 in the y-axis direction, and the refractive index n _{2x of} the second layer 52 in the x-axis direction. Although the relationship between the refractive index n _{2y in} the y-axis direction of the second layer 51 has been described, the above-described relationship between the refractive indexes n _1x , n _1y , n _2x , and n _2y is merely an example.

For example, in the above-described embodiment, the example in which the refractive index n _{1x in} the x-axis direction of the first layer 51 is larger than the refractive index n _{2x in} the x-axis direction of the second layer 52 is shown, but the present invention is not limited thereto. Instead, the refractive index n _{1x of} the first layer 51 in the x-axis direction may be smaller than the refractive index n _{2x of} the second layer 52 in the x-axis direction. In the example shown in FIG. 7 as an example, the following relationship is satisfied:
(N _2x −n _1x )> | n _1y −n _2y | = 0
When the relationship of FIG. 7 is established, for example, by configuring the unit optical interface 56 of the optical interface 55 as a concave lens, it is possible to obtain an optical function substantially similar to that of the optical sheet 40 of the above-described embodiment. As already described, the following two conditions may be satisfied instead of the refractive index relationship shown in FIG.
(N _2x −n _1x )> | n _1y −n _2y |
| N _1y −n _2y | ≦ 0.02
Further, (n _2x −n _1x )> | n _1y −n _2y | is satisfied, and light of the second polarization component traveling in the front direction is transmitted through the optical sheet 40 and then 2 ° or less with respect to the front direction. The optical sheet 40 may be configured to proceed in a direction that forms an angle of.

In the embodiment described above, the magnitude of the refractive index difference (| n _1x −n _2x |) between the first layer 51 and the second layer 52 in the x-axis direction is the first in the y-axis direction. Although an example in which the magnitude of the refractive index difference (| n _1y −n _2y |) between the layer 51 and the second layer 52 is larger is shown, the example in the x-axis direction is used instead of the above-described example. The difference in refractive index between the first layer 51 and the second layer 52 is smaller than the difference in refractive index between the first layer 51 and the second layer 52 in the y-axis direction. Also good.

As an example, the following relationship may be satisfied.
| N _1y −n _2y |> | n _1x −n _2x | = 0
In this case, the traveling direction of the light of the second polarization component that vibrates in the y-axis direction is controlled by the optical interface 55. On the other hand, the light of the first polarization component that vibrates in the x-axis direction passes through the optical interface 55 while maintaining the traveling direction. In this example, the image display unit 15 emits light for displaying a stereoscopic image as light of the second polarization component by switching the polarization control device 30, for example, and the light for displaying a planar image is the first polarization. The light may be emitted as component light. Also by such an example, the same effect as embodiment mentioned above can be anticipated. In this example, as shown in FIG. 8, the refractive index n _{1y in} the y-axis direction of the first layer 51 is larger than the refractive index n _{2y in} the y-axis direction of the second layer 52, and the following relationship is satisfied. You may be made to do.
(N _1y −n _2y )> | n _1x −n _2x | = 0
Alternatively, as shown in FIG. 9, the refractive index n _{1y in} the y-axis direction of the first layer 51 is smaller than the refractive index n _{2y in} the y-axis direction of the second layer 52 so that the following relationship is satisfied. Also good.
(N _2y −n _1y )> | n _1x −n _2x | = 0

As described above, the following two conditions may be satisfied instead of the refractive index relationship shown in FIG.
(N _1y −n _2y )> | n _1x −n _2x |
| N _1x −n _2x | ≦ 0.02
Further, (n _1y −n _2y )> | n _1x −n _2x | is satisfied, and the polarization component (first order) that vibrates in the x-axis direction that proceeds in the direction orthogonal to the sheet surface of the optical sheet 40 (ie, the front direction). The optical sheet 40 may be configured so that light of one polarization component) travels in a direction that forms an angle of 2 ° or less with respect to the front direction after passing through the optical sheet 40.

Similarly, the following two conditions may be satisfied instead of the relationship of the refractive index shown in FIG.
(N _2y −n _1y )> | n _1x −n _2x |
| N _1x −n _2x | ≦ 0.02
Further, (n _2y −n _1y )> | n _1x −n _2x | is satisfied, and after the light of the first polarization component traveling in the front direction is transmitted through the optical sheet 40, it is 2 ° or less with respect to the front direction. The optical sheet 40 may be configured so as to proceed in a direction that forms the angle.

Furthermore, in the above-described embodiment, an example in which only the first layer 51 is optically anisotropic and the second layer 51 is optically isotropic has been described, but both the first layer 51 and the second layer 52 are described. Both may be optically anisotropic. In the example shown in FIG. 10 as an example, the refractive index n _1x of the first layer 51 in the x-axis direction, the refractive index n _{1y of} the first layer 51 in the y-axis direction, and the refraction of the second layer 52 in the x-axis direction. The index n _2x and the refractive index n _{2y in} the y-axis direction of the second layer 51 satisfy the following relationship.
(N _1x −n _2x )> | n _1y −n _2y | = 0
n _1x > n _1y
n _2x <n _2y
According to the example shown in FIG. 10, the first refractive index difference between the first layer 51 and the second layer 52 in the y-axis direction is small and typically kept at 0, while the first index in the x-axis direction is maintained. The difference in refractive index between the layer 51 and the second layer 52 can be increased. Thereby, the optical interface 55 of the optical sheet 40 can exhibit a strong optical function only with respect to the light of the polarization component that vibrates in the x-axis direction. In addition, the example shown by FIG. 10 can be produced by the manufacturing method demonstrated referring FIG. 12 as an example. At this time, a resin film 71 is produced using a material (for example, polyethylene naphthalate resin) in which the stretching direction and the slow axis direction coincide with each other, and the stretching direction and the fast axis direction coincide with each other. For example, the second resin film 72 may be manufactured using (styrene resin).

As already described, the following four conditions may be satisfied instead of the refractive index relationship shown in FIG.
(N _1x −n _2x )> | n _1y −n _2y |
| N _1y −n _2y | ≦ 0.02
n _1x > n _1y
n _2x <n _2y
Further, (n _1x −n _2x )> | n _1y −n _2y |, n _1x > n _1y and n _2x <n _2y are satisfied, and the direction orthogonal to the sheet surface of the optical sheet 40 (ie, the front direction). The light of the polarization component (second polarization component) oscillating in the y-axis direction that travels to the optical sheet 40 passes through the optical sheet 40 and then travels in a direction that forms an angle of 2 ° or less with respect to the front direction. It may be configured.

  Furthermore, in the above-described embodiment, the example in which the difference in refractive index between the first layer 51 and the second layer 52 in any one of the x-axis direction and the y-axis direction has been described. However, the refractive index difference between the first layer 51 and the second layer 52 may not be zero in both the x-axis direction and the y-axis direction. Also in this example, by appropriately designing the configuration of the optical interface 55 and the unit optical interface 56, it is possible to obtain the same effects as those of the above-described embodiment.

Further, in the above-described embodiment, the main axis (slow axis and fast axis) in the plane of the first layer 51 coincides with the vibration direction of the light forming the stereoscopic image and the light forming the planar image. Although an example is shown, it does not need to match. Also in this example, the effects similar to those of the above-described embodiment can be obtained by appropriately adjusting the sizes of the refractive indexes n _1x , n _1y , n _2x , and n _2y .

  Further, in the above-described embodiment, the optical sheet made of the resin film 71 is formed by stretching the resin film 71 along the arrangement direction of the unit optical interfaces 56 to be manufactured (see FIGS. 11 and 12). Although the example which gives in-plane birefringence to 40 1st layers 51 was shown, it is not restricted to this. For example, in-plane birefringence is imparted to the first layer 51 of the optical sheet 40 made of the resin film 71 by stretching the resin film 71 along the longitudinal direction of the unit optical interface 56 to be manufactured. You may do it. As a result of extensive research conducted by the present inventors, from the viewpoint of causing the side edge 57 extending in the longitudinal direction of the unit optical interface 56 to swell in the above-described preferred range, the unit optical interface 56 is to be manufactured along the longitudinal direction. Thus, it was confirmed that it was effective to stretch the resin film 71.

  Furthermore, in the above-described embodiment and its modifications, by stretching a resin film containing a thermoplastic resin, the first layer 51 and the second layer 52 of the optical sheet 40 have optical anisotropy, in other words, in-plane. An example of imparting birefringence was shown. However, the first layer 51 and the second layer 52 of the optical sheet 40 are formed as layers containing liquid crystal (liquid crystal molecules, liquid crystal material), and are provided with optical anisotropy by the light distribution of the liquid crystal. Also good. The first layer 51 or the second layer 52 of the optical sheet 40 is typically an ultraviolet curable type containing liquid crystal (liquid crystal molecules, liquid crystal material) on a base material that has been subjected to alignment treatment such as rubbing. It can be made by curing the resin. In such a modification, when forming the first layer 51 or the second layer 52, it is possible to form a concave or convex portion that forms the unit optical interface 56, and in this case, as described above. The same effect as the embodiment can be obtained.

  In addition, although the some modification with respect to embodiment mentioned above was demonstrated above, naturally, it is also possible to apply combining several modifications suitably.

DESCRIPTION OF SYMBOLS 10 Display apparatus 10a Display surface 15 Image display unit 20 Image forming apparatus 20a Image forming surface 21 Pixel 22 Partition 24 Backlight 25 Liquid crystal display panel 26 Polarizing plate, lower polarizing plate 27 Liquid crystal cell 27a Color filter 28 Polarizing plate, Upper polarizing plate 30 Polarization controller 31 Liquid crystal molecule, liquid crystal material, liquid crystal 33 first support film 34 first electrode 35 liquid crystal layer 36 second electrode 37 second support film 40 optical sheet 43 film layer 51 first layer 52 second layer 55 optical interface, Birefringent interface, lens surface 56 Unit optical interface, unit lens 57 Side edge

Claims (17)

An optical sheet that is used in a display device that displays a planar image and a stereoscopic image that can be viewed with the naked eye in a switchable manner, and that controls the traveling direction of the light according to the polarization state of the light,
A first layer of optical anisotropy;
A second layer that is stacked on the first layer and forms an optical interface between the first layer and the optical layer that changes the traveling direction of light of one polarization component;
The optical interface has a plurality of unit optical interfaces arranged in one direction, and each unit optical interface extends in a direction non-parallel to the one direction,
When observed from the normal direction of the optical sheet, each side edge of the unit optical interface is wavy.   2. The optical sheet according to claim 1, wherein an amount of variation along the one direction of the side edge within a range corresponding to one period of waviness of the side edge along a direction in which the unit optical interface extends is 1 μm or more. .   The optical sheet according to claim 1, wherein the amount of variation along the one direction of the side edge of the unit optical interface is 2 μm or more.   The optical sheet according to claim 1, wherein a length corresponding to one period of waviness of the side edge along a direction in which the unit optical interface extends is 500 μm or less.   The optical sheet according to any one of claims 1 to 4, wherein the first layer includes a thermoplastic resin.   The optical sheet according to claim 5, wherein the thermoplastic resin is a polyethylene naphthalate resin.   The optical sheet according to claim 5 or 6, wherein a glass transition temperature of the material forming the first layer is 100 ° or more.   The optical sheet according to any one of claims 5 to 7, wherein the optical sheet has a dimensional stability of 2% or less measured at 150 ° C for 30 minutes and measured according to JIS C2151.   The optical sheet according to any one of claims 1 to 8, wherein an in-plane birefringence Δn of the first layer is 0.13 or more.   The light of the other polarization component that travels in the normal direction to the optical sheet passes through the optical sheet and then travels in a direction that forms an angle of 2 ° or less with respect to the normal direction to the optical sheet. The optical sheet according to any one of 9.   The optical sheet according to claim 1, wherein the second layer is optically isotropic. A display device that displays a planar image and a stereoscopic image that can be viewed with the naked eye in a switchable manner,
The optical sheet according to any one of claims 1 to 11,
An image display unit disposed to face the optical sheet, and emits light of one polarization component for displaying the stereoscopic image and light of the other polarization component for displaying the planar image An image display unit. The pixel display unit includes partition walls that define pixels arranged in a direction parallel to the one direction of the optical sheet,
The amount of fluctuation along the one direction of the side edge within a range corresponding to one period of waviness of the side edge along the direction in which the unit optical interface extends is along the one direction of the partition of the pixel display unit. The display device according to claim 12, wherein the display device is smaller than the width. The pixel display unit includes partition walls that define pixels arranged in a direction parallel to the one direction of the optical sheet,
The display device according to claim 12, wherein an amount of variation along the one direction of the side edge of the unit optical interface is smaller than a width along the one direction of the partition wall of the pixel display unit. The pixel display unit includes partition walls that define pixels arranged in a direction parallel to the one direction of the optical sheet,
The observation from the normal line direction of the optical sheet WHEREIN: The said side edge of the said unit optical interface is located only on the said partition of the said pixel display unit, As described in any one of Claims 12-14. Display device. It is a manufacturing method of the optical sheet according to any one of claims 1 to 11,
A step of producing a first layer of optical anisotropy by stretching a resin film formed by molding a thermoplastic resin;
A method of producing or laminating a second layer on the first layer. It is a manufacturing method of the optical sheet according to any one of claims 1 to 11,
Including a step of stretching the first layer and the second layer in a state where a second resin film formed by molding a thermoplastic resin is laminated on a first resin film formed by molding a thermoplastic resin,
The magnitude | size of the electric dipole moment of the said 1st resin film is a manufacturing method of an optical sheet larger than the magnitude | size of the electric dipole moment of the said 2nd resin film.

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