JP6660008B2 - Display device - Google Patents

Description

  The present invention relates to a display device having a light guide plate.

2. Description of the Related Art Conventionally, a head-mounted display device that allows an observer to observe image light displayed by an image source such as an LCD (Liquid Crystal Display) through an optical system has been proposed (for example, see Patent Document 1). .
This head-mounted display device guides image light displayed by an image source to a position corresponding to an observer's eye by a light guide plate and reflects the light toward the observer. Thereby, the observer can observe the image formed by the image light at the end of the light guide plate (the position corresponding to the eye).
In the head-mounted display device described above, it is required to further improve the image quality of the displayed image.

JP 2011-509417 A

  It is an object of the present invention to provide a display device in which the quality of a displayed video is further improved.

The present invention solves the above problem by the following means. In addition, in order to make it easy to understand, description is given with reference numerals corresponding to the embodiment of the present invention, but the present invention is not limited to this.
The first invention is an image source (10) that projects image light, and a first light guide layer (201) on which a first total reflection surface (121) that totally reflects image light in a light guide direction is formed. A second total reflection surface (122) that is provided at a position facing the first total reflection surface and totally reflects image light in the light guide direction, and an image light projected from the image source is applied to the first total reflection surface. A light guide plate (20) having a second light guide layer (202) on which an incident surface (120) to be made incident is formed, wherein the image source emits the image light. The incident surface is arranged to be incident at an angle θ1 that is equal to or greater than the critical angle with respect to the perpendicular to the first total reflection surface, and the inclination angle θ2 of the incident surface with respect to the first total reflection surface is less than (90 ° −θ1) The thickness of the first light guide layer is th1, the thickness of the second light guide layer is th2, and the thickness is in a direction perpendicular to the first total reflection surface. The kick width of the incident surface when is W, a display device characterized by satisfying W> tanθ1 × (2 × th1 + th2).
According to a second aspect, in the display device (1) according to the first aspect, the light guide plate (20) has a unit optical shape portion (30) having a first inclined surface (30a) and a second inclined surface (30b). ), A second optical shape layer (23) having a plurality of layers arranged thereon, a second optical shape layer (23) laminated on a surface of the first optical shape layer on which the unit optical shape portion is provided, and A display device, comprising: a reflective layer (25) formed on at least a part of the first inclined surface and reflecting a part of incident light and transmitting the other.

  According to the present invention, it is possible to provide a display device in which the quality of a displayed image is further improved.

It is a figure explaining head-mounted type display device 1 of an embodiment. It is a figure explaining the detail of light guide plate 20 of an embodiment. It is a figure explaining the manufacturing method of light guide plate 20 of an embodiment. It is a figure explaining the manufacturing method of light guide plate 20 of an embodiment. It is a figure explaining an optical path of image light in a light guide plate of a comparative example and an embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings and the like. In addition, each figure shown below including FIG. 1 is a figure which showed typically, and the magnitude | size and shape of each part are exaggerated suitably for easy understanding. For example, the light guide plate 20 shown in FIG. 1 and the light guide plate 20 shown in FIG. 5B are substantially the same, but the angles of the same portions are shown at different angles.
Numerical values such as dimensions of each member and material names and the like described in this specification are merely examples of the embodiment, and are not limited thereto, and may be appropriately selected and used.
In the present specification, terms that specify shapes and geometric conditions, for example, terms such as parallel and orthogonal are not only strictly meaningful, but also have a similar optical function and can be regarded as parallel or orthogonal. It also includes a state having an error of

FIG. 1 is a diagram illustrating a head-mounted display device 1 according to the present embodiment. FIG. 1 is a diagram of the display device 1 in use as viewed from above in a vertical direction.
In the following description, in order to facilitate understanding, the vertical direction when the observer wears the display device 1 on the head is defined as the Z direction, and the horizontal direction is defined as the X direction and the Y direction. In this horizontal direction, the light guide direction of the image light entering the light guide plate 20 (the left-right direction of the light guide plate 20) is defined as the X direction, and the direction perpendicular to the direction (the thickness direction of the light guide plate 20) is defined as the Y direction. I do. In the Y direction, the −Y side is the observer side, and the + Y side is the back side.

The display device 1 is a so-called head-mounted display that the observer wears on the head and displays an image in front of the observer's eyes. The display device 1 of the present embodiment is disposed inside, for example, an eyeglass frame (not shown).
The display device 1 includes an image source 10 and a light guide plate 20. The display device 1 allows the observer to visually recognize the image displayed on the image source 10 via the light guide plate 20 when the observer wears the glasses frame on the head. Specifically, the display device 1 causes the image light formed by the image source 10 to enter the light guide plate 20 and guides the image light in the + X direction in the light guide plate 20. Then, the display device 1 reflects an image in the −Y direction orthogonal to the light guide direction, and displays an image in front of the eyes E of the observer who has the display device 1 mounted on the head.
In addition, the display device 1 has a so-called see-through function in which a part of the light from the outside that has entered the light guide plate 20 is transmitted to the observer side, and the image and the outside light are superimposed and viewed.

The image source 10 includes a display 11 and a projection optical system 12.
The display 11 is a microdisplay that displays image light, and for example, a transmission type liquid crystal display device, a reflection type liquid crystal display device, an organic EL, or the like is used. Specifically, for example, a microdisplay having a diagonal of 1 inch or less is used as the display 11.
The projection optical system 12 is an optical system including a plurality of lens groups that project image light emitted from the image source 10 toward the light guide plate 20. In FIG. 1, a plurality of lens groups constituting the projection optical system 12 are schematically illustrated as one lens.

The image source 10 is arranged such that the projected image light L is incident on a perpendicular PH of a first total reflection surface 121 (described later) at an angle θ1 equal to or larger than the critical angle. Here, the angle θ1 that is equal to or larger than the critical angle with respect to the perpendicular to the first total reflection surface 121 is an angle at which the image light L incident on the first total reflection surface 121 is totally reflected in the light guide direction (X direction). is there. As shown in FIG. 1, the image light L projected from the image source 10 is incident on a perpendicular line PH of the first total reflection surface 121 at an incident angle refracted at a boundary surface between an incident surface 120 (described later) and air. The angle θ1 is equal to or larger than the critical angle.
Although FIG. 1 illustrates the image light L entering from the image source 10 as one light beam, the image light L is projected as an image having a predetermined size in the vertical and horizontal directions. In the following description, the image lights L1 and L2 (described later) are also collectively referred to as image light L.

  The light guide plate 20 is a substantially flat transparent optical member that guides light. The light guide plate 20 of the present embodiment has a substantially trapezoidal shape when viewed from the vertical direction (Z direction). The light guide plate 20 includes a first light guide layer 201 and a second light guide layer 202. The first light guide layer 201 is a layer on which the first total reflection surface 121 is formed. The second light guide layer 202 is a layer on which the incident surface 120 and the second total reflection surface 122 are formed. Hereinafter, the incident surface 120, the first total reflection surface 121, and the second total reflection surface 122 will be described in this order.

  The incident surface 120 is a surface on which the image light L is incident on the first total reflection surface 121 side. The incident surface 120 is inclined at an angle θ2 with respect to the first total reflection surface 121 at the end on the −X side of the light guide plate 20. The angle θ2 is set so as to be less than (90 ° −θ1) at the angle θ1 at which the image light L is equal to or greater than the critical angle with respect to the perpendicular PH of the first total reflection surface 121. The incident surface 120 has a thickness of the first light guide layer 201 of th1, a thickness of the second light guide layer 202 of th2, and a width of the incident surface 120 in the direction perpendicular to the first total reflection surface 121 of W (W). When W2) described later is set, W is set so as to satisfy W> tan θ1 × (2 × th1 + th2). The operation when the angle θ2 and the width W of the incident surface 120 are set as described above will be described later.

The first total reflection surface 121 is a surface parallel to the XZ plane and located on the back side (+ Y side) among the surfaces forming the light guide plate 20. The first total reflection surface 121 totally reflects the image light L incident from the incident surface 120 toward the second total reflection surface 122.
The second total reflection surface 122 is a surface that is parallel to the XZ plane and located on the observer side (−Y side) among the surfaces forming the light guide plate 20. The second total reflection surface 122 and the first total reflection surface 121 are formed in parallel in the thickness direction (Y direction) of the light guide plate 20. The second total reflection surface 122 totally reflects the image light L totally reflected on the first total reflection surface 121 toward the first total reflection surface 121. The second total reflection surface 122 has an end on the + X side and a light-emitting surface for outputting the image light L reflected by the unit optical shape unit 30 and the light-emitting side unit optical shape unit 31 (described later) to the outside of the light guide plate 20. Become.

  In the above configuration, the image light L projected from the image source 10 and incident on the incident surface 120 is guided at an angle θ <b> 1 that is totally reflected by the first total reflection surface 121. Since the first total reflection surface 121 and the second total reflection surface 122 are parallel in the thickness direction (Y direction) of the light guide plate 20, the image light L passes through the first total reflection surface 121 and the second total reflection surface 122. The light is guided in the + X direction (light guide direction) in the light guide plate 20 while repeating total reflection between them. The optical path of the image light L having entered the light guide plate 20 will be described later.

Next, the layer configuration of the light guide plate 20 will be described.
FIG. 2 is a diagram illustrating details of the light guide plate 20 of the present embodiment. FIG. 2 shows details of the part a in FIG.
As shown in FIG. 2, the light guide plate 20 includes a base member 26, a bonding layer 24, a second optical shape layer 23, a first optical shape layer 22, and a base member 21 in order from the observer side (−Y side). Are laminated.

The base member 21 and the base member 26 are flat members serving as a basis of the light guide plate 20, and include, for example, acrylic resin, styrene resin, acrylic styrene resin, polycarbonate resin, and alicyclic polyolefin resin having high light transmittance. And so on.
The base portion 21 is a layer provided on the rearmost side of the light guide plate 20, and the surface on the rear side (+ Y side) is the first total reflection surface 121. The base member 21 is a base member serving as a basis of the first optical shape layer 22, and its thickness s1 is in a range of 10 μm ≦ s1 ≦ 100 μm in accordance with depths d1 and d2 of the unit optical shape portion 30 described later. It is desirable to be formed with. The rear surface of the base member 21 is desirably formed to be smooth (for example, 90 or more at a gloss of 60 degrees) from the viewpoint of suppressing diffusion of incident light.

  The base member 26 is a layer provided closest to the observer of the light guide plate 20, and the surface on the observer side (−Y side) becomes the second total reflection surface 122. The base member 26 is bonded to the back side of the second optical shape layer 23 via the bonding layer 24. The base member 26 is a base member that adjusts the overall thickness of the light guide plate 20 and gives the light guide plate 20 a predetermined rigidity. In addition, an incident surface 120 (see FIG. 1) is formed at an end on the −X side of the base 26.

It is preferable that the thickness s2 of the base member 26 be formed in the range of 2 mm ≦ s2 ≦ 3 mm. If the thickness s2 is less than 2 mm, the rigidity of the light guide plate 20 is reduced, and the screen displayed on the light exit surface of the light guide plate 20 is too small, which is not desirable. Further, when the thickness s2 exceeds 3 mm, the weight of the light guide plate 20 increases, which is not desirable because it becomes a load on an observer wearing the display device 1.
The surface of the base member 26 on the viewer side is desirably formed smooth (for example, 90 or more with a gloss of 60 degrees) from the viewpoint of suppressing light diffusion.

  The first optical shape layer 22 is a layer provided on the observer side (−Y side) of the base 21. As the first optical shape layer 22, an ultraviolet curable resin such as urethane acrylate, polyester acrylate, epoxy acrylate, polyether acrylate, polythiol, or butadiene acrylate having high light transmittance is used. The refractive index of the first optical shape layer 22 is desirably the same as the refractive index of the base member 21 and the base member 26 described above. In the present embodiment, an ultraviolet curable resin is described as an example of the resin forming the light guide plate 20, but the resin is not limited to this. The resin forming the light guide plate 20 may be, for example, an electron beam curing resin.

As shown in FIGS. 1 and 2, the first optical shape layer 22 is provided with a plurality of unit optical shape portions 30 on the observer side (−Y side) and near the end on the + X side. ing.
The unit optical shape portions 30 extend in the vertical direction (Z direction), and are arranged in a plurality in the light guide direction of the image light L (X direction). The unit optical shape part 30 is parallel to the direction in which the image light L is emitted (the thickness direction of the light guide plate 20, the Y direction), and is parallel to the arrangement direction (X direction) of the unit optical shape parts 30 (XY direction). Surface) is formed in a triangular shape (prism shape). The unit optical shape part 30 includes a first inclined surface 30a and a second inclined surface 30b.

The first inclined surface 30a is a surface on which the image light L totally reflected by the second total reflection surface 122 is directly incident. The first inclined surface 30a is inclined with respect to the light exit surface (the second total reflection surface 122, the surface of the second optical shape layer 23 on the observer side), and the + X side end thereof is on the −X side. It is located closer to the observer (light emission) side (−Y side) than the end.
Further, the reflection layer 25 is formed on the entire surface on the first inclined surface 30a, that is, on the entire area between the first inclined surface 30a and the third inclined surface 31a (described later).

  The second inclined surface 30b is a surface on which the image light L totally reflected by the second total reflection surface 122 does not directly enter. The second inclined surface 30b is provided on the side (+ X side) where the image light L travels more than the first inclined surface 30a, facing the first inclined surface 30a. The second inclined surface 30b is inclined with respect to the light exit surface (the second total reflection surface 122, the surface of the second optical shape layer 23 on the observer side), and the + X side end thereof is on the −X side. It is located on the back side (+ Y side) from the end.

  The second optical shape layer 23 is a layer provided on the surface of the first optical shape layer 22 on the unit optical shape portion 30 side (observer side). The second optical shape layer 23 is provided to flatten the surface of the first optical shape layer 22 on the observer side (−Y side). As the second optical shape layer 23, the same ultraviolet curable resin as the first optical shape layer 22 described above is used. It is desirable that the refractive index of the second optical shape layer 23 is equal to that of the first optical shape layer 22.

The observer-side surface of the second optical shape layer 23 is a surface that is bonded to the base 26 via the bonding layer 24. In addition, this surface is a light emission surface for light passing from the second optical shape layer 23 to the base member 26. The light exit surface of the second optical shape layer 23 is parallel to the second total reflection surface 122 (light exit surface, XZ plane) of the light guide plate 20.
The second optical shape layer 23 has a light emitting side unit optical shape portion 31 having a shape corresponding to the above-described unit optical shape portion 30 formed on a surface (back surface, + Y side surface) facing the first optical shape layer 22. I have.

The light-emitting-side unit optical shape portions 31 extend in the vertical direction (Z direction), and are arranged in a plurality along the light guide direction of the image light L (X direction). The light emitting side unit optical shape part 31 is a cross section parallel to the direction in which the image light L is emitted (the thickness direction of the light guide plate 20, the Y direction) and parallel to the arrangement direction (X direction) of the light emitting side unit optical shape part 31. The shape in the (XY plane) is formed in a triangular shape (prism shape). The light-emitting-side unit optical shape portion 31 includes a third inclined surface 31a and a fourth inclined surface 31b.
In the present embodiment, the light-emitting-side unit optical shape portions 31 and the unit optical shape portions 30 are formed in the same shape in the cross section.

  The third inclined surface 31a is a surface on which the image light L totally reflected by the second total reflection surface 122 is directly incident. The third inclined surface 31a is inclined with respect to the light exit surface (the second total reflection surface 122, the surface of the second optical shape layer 23 on the observer side), and the + X side end thereof is on the −X side. It is located closer to the observer (light emission) side (−Y side) than the end. The third inclined surface 31a is opposed to the first inclined surface 30a of the unit optical shape portion 30, and is a surface parallel to the first inclined surface 30a. As described above, the reflection layer 25 is provided between the third inclined surface 31a and the first inclined surface 30a.

  The fourth inclined surface 31b is a surface on which the image light L totally reflected by the second total reflection surface 122 does not directly enter. The fourth inclined surface 31b is provided on the image source side (−X side) with respect to the third inclined surface 31a, facing the third inclined surface. The fourth inclined surface 31b is inclined with respect to the light exit surface (the second total reflection surface 122, the surface of the second optical shape layer 23 on the observer side), and the + X side end thereof is on the −X side. It is located on the back side (+ Y side) from the end. The fourth inclined surface 31b is opposed to the second inclined surface 30b of the unit optical shape portion 30, and is a surface parallel to the second inclined surface 30b. The fourth inclined surface 31b is in close contact with the above-described second inclined surface 30b.

  Here, the angle at which the first inclined surface 30a and the third inclined surface 31a intersect with a plane (XZ plane) parallel to the first total reflection surface 121 (light emitting surface) is α. The angle at which the second inclined surface 30b and the fourth inclined surface 31b intersect with a plane (XZ plane) parallel to the second total reflection surface 122 (light emitting surface) is β. The arrangement pitch of the unit optical shape portions 30 and the light emitting side unit optical shape portions 31 is P. The height of the unit optical shape portion 30 (the dimension from the top t1 of the unit optical shape portion 30 to the valley v1 between the unit optical shape portions 30 in the thickness direction (Y direction) of the light guide plate 20) is h1. The height of the light emitting side unit optical shape portion 31 (the dimension from the top t2 of the light emitting side unit optical shape portion 31 to the valley v2 between the light emitting side unit optical shape portions 31 in the thickness direction (Y direction) of the light guide plate 20) is , H2. In the present embodiment, h1 = h2.

  In the present embodiment, an example in which the arrangement pitch P is equal to the width dimension of the first inclined surface 30a and the third inclined surface 31a in the arrangement direction (X direction) will be described. May be made larger than the width dimension.

  In the unit optical shape unit 30 and the light-emitting side unit optical shape unit 31 of the present embodiment, the arrangement pitch P and the like are constant, and the angle α gradually increases toward the traveling side (+ X side) of the image light L, and An example in which the heights h1 and h2 increase accordingly will be described, but the invention is not limited to this. For example, the arrangement pitch P, the angle α, the angle β, and the heights h1 and h2 may be formed to be constant.

  The bonding layer 24 is an adhesive that bonds the base member 26 and the second optical shape layer 23. The bonding layer 24 is preferably made of a material such that the image light L transmitted between the base 26 and the second optical shape layer 23 is not refracted. Therefore, it is formed of a material having a refractive index equivalent to that of the above-described layer, for example, a urethane acrylate resin, an epoxy acrylate resin, an acrylic adhesive, a silicon adhesive, or the like having high light transmittance.

  The reflective layer 25 is a semi-transmissive reflective layer that reflects a part of the incident light and transmits the other, that is, a so-called half mirror. The ratio between the reflectance and the transmittance of the reflective layer 25 can be set as appropriate. From the viewpoint of good reflection of the image light L and good transmission of external light, the transmittance is in the range of 40 to 60%. Desirably. The reflection layer 25 of the present embodiment is formed in a half mirror shape having a reflectance and a transmittance of 50%.

The reflection layer 25 is formed on the surface of the first inclined surface 30a, that is, between the first inclined surface 30a and the third inclined surface 31a, with a metal having high light reflectivity, for example, aluminum, silver, nickel, or the like. In the present embodiment, the reflection layer 25 is formed by evaporating aluminum. The reflective layer 25 is not limited thereto, and may be formed by sputtering a metal having high light reflectivity, transferring a metal foil, applying a paint containing a metal thin film, or the like. Further, as the reflective layer 25, a dielectric multilayer film in which a plurality of titanium oxide, silicon oxide, niobium, tantalum, magnesium fluoride, and the like are stacked may be formed. The dielectric multilayer film is a film in which dielectric films having a high refractive index and dielectric films having a low refractive index are alternately laminated.
The reflection layer 25 of the present embodiment is formed to a thickness of about 100 ° by vapor deposition of aluminum. However, if the reflectance and the transmittance of light can be set in the preferable ranges described above, the thickness can be freely set according to the material and the like. Can be set to

Here, parameters for efficiently reflecting the image light L and outputting the light from the light guide plate 20 in the unit optical shape unit 30 and the light exit side unit optical shape unit 31 will be exemplified.
In the unit optical shape part 30, the angle α between the first inclined surface 30a and the third inclined surface 31a is desirably formed in a range of 25 ° ≦ α ≦ 40 °.
In the light-emitting-side unit optical shape portion 31, the angle β between the second inclined surface 30b and the fourth inclined surface 31b is desirably formed in a range of 80 ° ≦ β ≦ 90 °.
The height h1 of the unit optical shape part 30 and the height h2 of the light-emitting side unit optical shape part 31 are desirably formed in the ranges of 20 μm ≦ h1 ≦ 700 μm and 20 μm ≦ h2 ≦ 700 μm, respectively.
The arrangement pitch P of the unit optical shape portions 30 is desirably formed in a range of 50 μm ≦ P ≦ 1000 μm.

Next, the optical paths of the image light L and the external light G emitted from the light guide plate 20 of the present embodiment will be described.
As shown in FIG. 1, the image light L projected from the image source 10 enters the incident surface 120 of the light guide plate 20 via the projection optical system 12. The image light L having entered the incident surface 120 is refracted at the boundary between the incident surface 120 and the air, and enters the first total reflection surface 121. The image light L enters the first total reflection surface 121 and is totally reflected toward the second total reflection surface 122, and then enters the second total reflection surface 122 and is totally reflected toward the unit optical shape portion 30. As described above, the image light L is guided from the −X side to the + X side of the light guide plate 20 by repeating total reflection between the first total reflection surface 121 and the second total reflection surface 122. Then, the image light L is incident on the reflection layer 25 provided between the first optical shape layer 22 and the second optical shape layer 23 in the unit optical shape portion 30.

  FIG. 1 shows an example in which the image light L is totally reflected once on each of the first total reflection surface 121 and the second total reflection surface 122 for ease of explanation. The configuration is not limited to this, and a configuration in which the image light L repeats total reflection more on each surface may be used.

  As shown in FIG. 2, a part of the image light L among the image light incident on the reflection layer 25 is reflected on the reflection layer 25 in a direction substantially perpendicular to the first total reflection surface 121 (−Y direction). Then, light is emitted from the second total reflection surface 122 toward the eye E of the observer. Further, other image light passes through the reflective layer 25 and enters the first optical shape layer 22, but most of the light exits from the back side of the light guide plate 20.

  The external light G enters the light guide plate 20 from the first total reflection surface 121 on the back side (+ Y side) of the light guide plate 20, as shown in FIG. Part of the external light G that has entered the light guide plate 20 enters the reflective layer 25. As shown in FIG. 2, a part of the light G <b> 1 passes through the reflection layer 25 and exits from the second total reflection surface 122 (light emission surface) toward the eye E of the observer. Further, other light is reflected to the back side (+ Y side) at the interface between the reflection layer 25 and the first optical shape layer 22.

Next, a method for manufacturing the light guide plate 20 of the present embodiment will be described.
3 and 4 are views for explaining a method of manufacturing the light guide plate 20 of the present embodiment. 3A to 3E are diagrams illustrating a process of manufacturing the first optical shape layer 22 bonded to the base 21. FIGS. 4F to 4H are diagrams illustrating a process of manufacturing the light guide plate 20 based on the first optical shape layer 22 bonded to the base 21. 3 and 4, hatching indicating the cross section of the member is omitted as appropriate.

First, as shown in FIG. 3A, a molding die 100 having a shaping surface 100a corresponding to the shape of the first optical shape layer 22 of the light guide plate 20 to be manufactured is prepared. (Top side of the direction). Mold 100 may be a mold or a resin mold.
Next, as shown in FIG. 3B, an ultraviolet curable resin 22a is uniformly formed on the shaping surface 100a. Here, for example, the ultraviolet curable resin 22a is applied in a dot or line shape along one side on the shaping surface 100a, and is stretched by a roller or the like (not shown) to be uniformly formed on the shaping surface 100a. can do.

Next, as shown in FIG. 3C, the base member 21 is attached on the ultraviolet curing resin 22a applied on the shaping surface 100a.
Next, as shown in FIG. 3D, an ultraviolet ray is applied to the uncured ultraviolet curable resin 22a from an ultraviolet ray irradiator (not shown). Thereby, the ultraviolet curable resin 22a is cured to form the first optical shape layer 22. In the present embodiment, the ultraviolet ray UV is applied to the ultraviolet curable resin 22 a via the base 21.
After the ultraviolet curable resin 22a is cured, as shown in FIG. 3E, the first optical shape layer 22 bonded to the base 21 is peeled off from the mold 100 by peeling the first optical shape layer 22 from the mold 100. Obtainable.

  Next, as shown in FIG. 4F, a vapor deposition metal is adhered to the surface of the unit optical shape portion 30 to form the reflection layer 25. In this step, the unit optical shape portion 30 of the first optical shape layer 22 is arranged so as to face downward, and a vapor deposition metal is attached to the surface of the unit optical shape portion 30.

  In FIG. 4F, the reflection layer 25 is formed in all the regions of the first optical shape layer 22. However, the reflection layer 25 is formed only in the region on the light emission side of the image light, and Is not formed in the region where light is guided. The region where the reflective layer 25 is not formed is directly bonded to the second optical shape layer 23 (described later). In order to form the reflection layer 25 only in the region on the light emission side of the image light, a stencil mask (not shown) having the same size as the region where the reflection layer 25 is formed covers the first optical shape layer 22. The metal may be deposited by masking deposition.

  Next, as shown in FIG. 4G, a second optical shape layer 23 is formed on the surface of the first optical shape layer 22 on the side where the unit optical shape portion 30 is provided. Here, for example, an ultraviolet curable resin can be uniformly formed by applying a point-like or linear shape along one side of the first optical shape layer 22 and stretching it with a roller or the like (not shown). Although not shown, the ultraviolet curable resin formed on the first optical shape layer 22 is irradiated with ultraviolet rays to cure the ultraviolet curable resin to form the second optical shape layer 23.

Next, as shown in FIG. 4H, the bonding layer 24 is formed on the surface on the second optical shape layer 23 side, and the base member 26 is attached.
Then, a corner on the observer side (−Y side) on the −X side (the side opposite to the side on which the unit optical shape part 30 is formed) of the laminate on which the base material part 26 is adhered via the bonding layer 24. Is processed to form the incident surface 120. Through the above steps, the light guide plate 20 is completed.

Next, the light guide plate 20 of the present embodiment and the light guide plate 20C of the comparative example will be described.
FIG. 5 is a diagram illustrating an optical path of image light in the light guide plates of the comparative example and the embodiment. FIG. 5A is a diagram illustrating an optical path of image light in the light guide plate 20C of the comparative example. FIG. 5B is a diagram illustrating an optical path of image light in the light guide plate 20 of the present embodiment. In FIG. 5A, the same components as those in the above-described embodiment (FIG. 1) are denoted by the same reference numerals, and "c" is added following the reference numerals. In addition, in each of the drawings shown in FIG. 5, reference numerals are given only to parts necessary for description.

  The light guide plate 20C of the comparative example shown in FIG. 5A shows the configuration of a conventional general light guide plate. In the light guide plate 20C of the comparative example, the angle θ2 ′ of the incident surface 120c with respect to the first total reflection surface 121c is the angle θ1 ′ at which the image light L is equal to or larger than the critical angle with respect to the perpendicular PH of the first total reflection surface 121c. (90 ° −θ1 ′) or more. The angle θ1 ′ is perpendicular to the first total reflection surface 121c at an incident angle at which the image light L (L1, L2) projected from the image source 10 (not shown) is refracted at the boundary between the incident surface 120c and the air. It is an angle that is greater than or equal to the critical angle with respect to PH. Here, the angle θ1 ′ = θ1 in order to make the same conditions as the light guide plate 20 of the embodiment. That is, the image source 10 in the comparative example is arranged such that the image light L refracted on the incident surface 120c (the angle θ2 ′) is incident on the perpendicular line PH of the first total reflection surface 121c at an angle θ1 ′ equal to or greater than the critical angle. Have been.

In the light guide plate 20C of the comparative example, the incident surface 120c has a thickness of the first light guide layer 201c of th1, a thickness of the second light guide layer 202c of th2, and a perpendicular PH direction of the first total reflection surface 121c. When the width of the incident surface 120c is W1, the setting is such that W1> tan θ1 ′ × (2 × th1 + th2).
In FIG. 5A, in the X direction (light guide direction) of the first total reflection surface 121c and the second total reflection surface 122c, a range where the image light L exists is defined as a region E1, and a range where the image light L is not defined is defined as a region E1. Each is represented by E2.
In the light guide plate 20C of the comparative example, the image light L1 that enters from the most -X side and the image light L2 that enters from the most + X side are totally between the first total reflection surface 121c and the second total reflection surface 122c. The light is guided in the + X direction (light guide direction) in the light guide plate 20C while repeating reflection.

  As shown in FIG. 5A, a comparative example in which the angle θ2 ′ of the incident surface 120c is equal to or more than (90 ° −θ1 ′), and the width W1 of the incident surface 120c is W1> tan θ1 ′ × (2 × th1 + th2). In the light guide plate 20C, the image light L1 entering the incident surface 120c from the most -X side is incident on a position away from the most -X side end of the second total reflection surface 122c to the + X side. Therefore, in the light guide plate 20C of the comparative example, a region E2 where the image light L does not enter is formed between the most-X-side end of the second total reflection surface 122c and the position where the image light L1 enters. The region E2 is alternately formed on the first total reflection surface 121c and the second total reflection surface 122c along the light guide direction of the image lights L1 and L2. Then, the image light L including the regions E1 and E2 is reflected on the −Y side by the reflection layer 25 formed on the first optical shape layer 22, and is emitted toward the eye E of the observer (see FIG. 2). . At this time, the region E2 is observed by the observer as a dark line extending in the vertical direction (Z direction) in the video. Such a dark line causes a reduction in image quality of an image.

  On the other hand, as shown in FIG. 5B, the angle θ2 of the incident surface 120 is set to be less than (90 ° −θ1), and the width W2 (the aforementioned W) of the incident surface 120 is set to W2> tan θ1 × (2 × th1 + th2). In the light guide plate 20 of the embodiment described above, the image light L <b> 1 entering the incident surface 120 from the most -X side is incident on the most -X-side end of the second total reflection surface 122. Therefore, in the light guide plate 20 of the embodiment, the region E2 where the image light L does not enter is not formed. That is, in all of the first total reflection surface 121c and the second total reflection surface 122c, the region E1 where the image light L exists is formed. Therefore, when the image light L1 is reflected to the −Y side by the reflection layer 25 formed on the first optical shape layer 22 and emitted toward the eye E of the observer, a dark line due to the region E2 occurs in the image. Nothing. Therefore, the image to be displayed on the light guide plate 20 of the present embodiment in which the angle θ2 of the incident surface 120 is less than (90 ° −θ1) and the width W2 of the incident surface 120 is W2> tan θ1 × (2 × th1 + th2). Image quality can be further improved.

  As described above, the embodiments of the present invention have been described. However, the present invention is not limited to the above-described embodiments, and various modifications and changes can be made as in the modifications described below. Within technical scope. Further, the effects described in the embodiments merely enumerate the most preferable effects resulting from the present invention, and the effects according to the present invention are not limited to those described in the embodiments. The above-described embodiment and the modified examples described below can be used in appropriate combinations, but detailed description is omitted.

(Modified form)
(1) In the above-described embodiment, an example in which the cross section in the thickness direction of the unit optical shape portion 30 is formed in a triangular shape (prism shape) is described, but the present invention is not limited to this. The cross section in the thickness direction of the unit optical shape portion 30 may be a prism shape such as a polygon, a hemisphere, a lens, or the like. Further, the prism shape may have a cross section extending in the depth direction, or may have a dimple shape, a pyramid shape (a triangular pyramid, a quadrangular pyramid, or the like).

(2) In the above-described embodiment, an example is described in which the reflective layer 25 is provided on the entire surface on the first inclined surface 30a, that is, on the entire region between the first inclined surface 30a and the third inclined surface 31a. Not done. The reflection layer 25 may be provided on a part of the first inclined surface 30a. For example, the reflective layer 25 may be provided only in the region on the + X side of the first inclined surface 30a, that is, in the region that contributes to the reflection of the image light.

(3) In the above-described embodiment, one or both of the back surface of the light guide plate 20 (the back surface of the base member 21) and the observer side surface of the light guide plate 20 (the observer side surface of the base member portion 26). May be subjected to a hard coat treatment for the purpose of preventing damage. As this hard coat treatment, for example, an ultraviolet curable resin (for example, urethane acrylate) having a hard coat function is applied to one or both of the back surface and the observer side surface of the light guide plate 20 to form a hard coat layer. May be formed.

(4) In the above-described embodiment, the configuration has been described in which the first total reflection surface 121 and the light emission surface from which the image light is emitted are formed as different surfaces in the light guide plate 20, but the invention is not limited thereto. In the light guide plate 20, the first total reflection surface 121 and the surface from which the image light is emitted may be formed in the same plane.

Reference Signs List 1 display device 10 image source 20 light guide plate 22 first optical shape layer 23 second optical shape layer 25 reflective layer 30 unit optical shape portion 30a first inclined surface 30b second inclined surface 120 incident surface 121 first total reflection surface 122 first 2 Total reflection surface 201 First light guide layer 202 Second light guide layer

Claims (2)

An image source for projecting image light,
A first light guide layer provided with a first total reflection surface that totally reflects the image light in the light guide direction, and a first light guide layer that is provided at a position facing the first total reflection surface and totally reflects the image light in the light guide direction. (2) a light guide plate having a second light guide layer formed with a total reflection surface and an incident surface for causing image light projected from the image source to enter the first total reflection surface;
A display device comprising:
The image source is arranged such that the projected image light is incident on the perpendicular to the first total reflection surface at an angle θ1 that is equal to or greater than the critical angle,
An inclination angle θ2 of the incident surface with respect to the first total reflection surface is less than (90 ° −θ1);
When the thickness of the first light guide layer is th1, the thickness of the second light guide layer is th2, and the width of the incident surface projected onto the first total reflection surface is W, W > Tan θ1 × (2 × th1 + th2)
A display device characterized by the above-mentioned. The display device according to claim 1,
The first light guide layer of the light guide plate includes:
A first optical shape layer in which a plurality of unit optical shape portions each having a first inclined surface and a second inclined surface are arranged,
A second optical shape layer laminated on a surface of the first optical shape layer on which the unit optical shape portion is provided;
A reflecting layer that is formed on at least a part of the first inclined surface, reflects a part of incident light, and transmits the other;
A display device comprising:

Images