TW201706630A - Optical thin sheet, surface light source device and display device comprising a substrate layer, a roughness layer, and a prism layer comprising first photodiffusion particles, second photodiffusion particles, and a binder resin - Google Patents

Abstract

An optical thin sheet (60) comprises: a substrate layer (65), a roughness layer (70), and a prism layer (80). the prism layer (80) comprises: first photodiffusion particles (71), second photodiffusion particles (72), and a binder resin (73). The refractive index n2 of the second photodiffusion particles is different from refractive index nb of the binder resin and the refractive index n1 of the first photodiffusion particles. The average grain size d1 of the first photodiffusion particles, the average grain size d2 of second photodiffusion particles, and the thickness tb of roughness layer at the position not across the first photodiffusion particles and second photodiffusion particles satisfy the following relationship: d2<tb<d1.

Description

Optical sheet, surface light source device and display device

The present invention relates to an optical sheet having a rough layer and a tantalum layer, and more particularly to an optical sheet which can effectively prevent glare from occurring. Further, the present invention relates to a surface light source device and a display device which can effectively prevent glare from occurring.

An optical sheet having a rough layer containing light-diffusing particles and a binder resin, and a tantalum layer containing linearly-arranged unit crucibles (for example, JP2000-338310A) is widely used in various industrial fields. For example, it can be used in a surface light source device that emits light in a planar manner. The surface light source device can be used as, for example, a backlight that illuminates the liquid crystal display panel on the back side. In such an optical sheet, the ruthenium layer functions to correct the optical axis direction of incident light. On the other hand, the rough layer functions to diffuse the emitted light from the optical sheet, to make the luminance angle distribution smooth, to give a wide viewing angle, and to hide defects such as bright spots or defects.

However, in a display device in which an optical sheet is disposed in a rough layer of an optical sheet and an image display panel having a pixel arrangement (hereinafter also simply referred to as a display panel), it is confirmed that a plurality of color components are generated. Most people think that the graininess is called the "glare". The inventors of the present invention confirmed that glare occurs in an optical sheet in which unit 稜鏡 is arranged at a high-definition arrangement pitch, and is particularly apparent in an optical sheet in which a unit 稜鏡 is arranged at a distribution pitch of 35 μm or less. Of course, the occurrence of glare causes the color reproducibility of the display image to be directly lowered, thereby deteriorating the display quality of the display device.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an optical sheet, a surface light source device, and a display device which can effectively prevent glare from occurring.

The optical sheet obtained by the present invention has a pair of optical sheets facing each other, and includes a sheet-like base material layer, and includes first light-diffusing particles, second light-diffusing particles, and a binder resin. a rough layer provided on one side of the base material layer; and a plurality of unit turns including a plurality of units arranged in a direction, and each of which is linearly extended in a direction intersecting the one direction In the enamel layer on the other side of the base material layer, one of the pair of surfaces is formed as a rough surface due to the rough layer, and the other of the pair of surfaces is formed by the rib In the surface of the mirror layer, the refractive index of the second light-diffusing particle is different from the refractive index of the binder resin and the refractive index of the first light-diffusing particle, and the first light-diffusing particle The average particle diameter d ₁ , the average particle diameter d _{2 of} the second light-diffusing particles, and the thickness t _{b of the} rough layer at a position not spanning the first light-diffusing particle and the second light-diffusing particle satisfy the following relationship : _{d 2 <t b <d 1} .

In the optical sheet obtained by the present invention, the average particle diameter d ₁ of the first light-diffusing particles, the average particle diameter d _{2 of} the second light-diffusing particles, and the rough layer may not spread across the first light. The thickness t _b of the position of the particles and the second light-diffusing particles and the arrangement pitch P of the complex unit 沿着 along the one direction satisfy the following relationship: d ₂ [ μ m] < t _b [ μ m ] < d ₁ [ μ m] < P / 2 [ μ m].

In the optical sheet obtained by the present invention, each unit may include: a first surface facing one side in the one direction and a second surface facing the other side in the one direction, and the first light diffusion The average particle diameter d _{1 of the} particles, the average particle diameter d _{2 of} the second light-diffusing particles, the thickness t _{b of the} rough layer at a position not spanning the first light-diffusing particles and the second light-diffusing particles, and the foregoing The length Wb _{2 of} the second surface along the aforementioned direction satisfies the following relationship: d ₂ [ μ m ] < t _b [ μ m ] < d ₁ [ μ m] < Wb ₂ [ μ m].

In the optical sheet obtained by the present invention, each unit may include a first surface facing one side of the one direction and a second surface facing the other side of the one direction, and the second surface may be The main cut surface of the optical sheet parallel to both the one direction and the normal direction of the base material layer includes an inclination angle with respect to the one direction to be the unit unit which is most separated from the base material layer. a side of the front end portion, a plurality of element faces arranged to gradually increase toward a side closer to a base end portion of the unit substrate of the base material layer, an average particle diameter d _{2 of} the second light diffusion particles, and one unit The minimum value Wb _2pmin among the lengths of the plurality of element faces included in the above-described one direction satisfies the following relationship: d ₂ [ μ m] < Wb _2pmin [ μ m].

In the optical sheet obtained by the present invention, the refractive index n ₁ of the first light-diffusing particles, the refractive index n _{2 of} the second light-diffusing particles, and the refractive index n _{b of the} binder resin may satisfy the following relationship: n ₁ ≦n _b <n ₂ .

In the optical sheet obtained by the present invention, the number N ₁ of the first light-diffusing particles contained in the rough layer and the number N _{2 of} the second light-diffusing particles contained in the rough layer may satisfy the following Relationship: 50 ≦ (N ₂ /N ₁ ) ≦ 200.

In the optical sheet obtained by the present invention, the haze value may be 90% or more.

In the optical sheet obtained by the present invention, the optical sheet may be used in an overlapping manner with the display panel. The rough layer is located on the side of the display panel of the substrate layer.

The surface light source device obtained by the present invention is provided with: a light guide plate; a light source disposed on a side of the light guide plate; and the optical sheet obtained by the present invention disposed so as to face the surface of the light guide plate.

The display device obtained by the present invention includes: any one of the surface light source devices obtained by the present invention; and a display panel disposed to face the surface light source device.

With the present invention, glare can be effectively prevented from occurring.

10‧‧‧ display device

11‧‧‧ Display surface

12‧‧‧Liquid layer unit

13‧‧‧Upper polarizer

14‧‧‧Lower polarizer

15‧‧‧LCD panel

20‧‧‧ surface light source device

21‧‧‧Lighting surface

24‧‧‧Light source

25‧‧‧Lights

28‧‧‧Reflecting sheets

30‧‧‧Light guide

31‧‧‧Glossy

32‧‧‧Back

33‧‧‧Into the glossy surface

34‧‧‧ opposite side

35, 36‧‧‧Fold

35a, 36a‧‧‧ first side

35b, 36b‧‧‧2nd inclined surface

37, 37a, 37b‧‧‧ sloped surface

38‧‧‧Development

39‧‧‧ Connection surface

40‧‧‧ base

41‧‧‧One side of the base 40

42‧‧‧Face on the other side of the base 40

50‧‧‧Unit optical elements

51‧‧‧Outer contour

52a‧‧‧ front end

52b‧‧‧ base end

60‧‧‧ optical sheets

65‧‧‧Substrate layer

66‧‧‧Resin film

70‧‧‧Rough layer

70a‧‧‧Rough surface

71‧‧‧1st light diffusing particle

72‧‧‧2nd light diffusing particles

73‧‧‧Binder resin

74‧‧‧Resin materials

80‧‧‧稜鏡

80a‧‧‧稜鏡

81‧‧‧ Land Department

83‧‧‧Materials

85‧‧‧Units

86‧‧‧1st

87‧‧‧2nd

87a‧‧‧Part 1 (1st element)

87b‧‧‧Part 2 (Part 2)

87c‧‧‧Part 3 (3rd Elemental)

88a‧‧‧ front end

88b‧‧‧ base end

150‧‧‧稜鏡layer forming device

152‧‧‧Molding mold

152a‧‧‧

154‧‧‧Material supply device

156‧‧‧hardening device

158‧‧‧Roller

160‧‧‧Rough layer forming device

162‧‧‧ Coating device

164‧‧‧ Hardening device

CA‧‧‧ central axis

d ₁ ‧‧‧1st direction (light guiding direction)

d ₂ ‧‧‧2nd direction

Ha‧‧‧High height

Hb‧‧‧ Height

L21, L22, L51, L52, L72, L72‧‧‧ light

Nd‧‧‧ normal direction

P‧‧‧ arrangement spacing

t _b ‧‧‧thickness

Wa‧‧‧ wide format

Wb‧‧‧ wide format

Wb ₂ ‧‧‧ length

Wb _2pa , Wb _2pb , Wb _2pc ‧‧‧ length

θa‧‧‧Gloss angle

Θb‧‧‧reflecting surface angle

Θc‧‧‧ angle

θk‧‧‧Out angle

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view showing a schematic configuration of a display device and a surface light source device, showing an embodiment of the present invention.

Fig. 2 is a view for explaining the action of the surface light source device of Fig. 1.

Fig. 3 is a perspective view showing the light guide plate incorporated in the surface light source device of Fig. 1 from the side of the light-emitting surface.

Fig. 4 is a perspective view showing the light guide plate incorporated in the surface light source device of Fig. 1 from the side of the back surface.

Fig. 5 is a view for explaining the action of the light guide plate, and a view of the light guide plate is shown in a cross section taken along line V-V of Fig. 3.

Figure 6 is a perspective view showing an optical sheet incorporated in the surface light source device of Figure 1.

Figure 7 is a partial cross-sectional view showing the optical sheet of Figure 6 on its main cut surface.

Figure 8 is an enlarged cross-sectional view showing a rough layer of the optical sheet of Figure 6.

Figure 9 is a partial cross-sectional view showing the optical sheet of Figure 6 on its main cut surface.

Fig. 10 is a partial cross-sectional view showing a modification of one of the optical sheets on the main cut surface.

Fig. 11 is a view for explaining an example of a method of manufacturing an optical sheet.

Fig. 12 is a view for explaining an example of a method of manufacturing an optical sheet.

Fig. 13 is a graph showing an angular distribution of luminance on a light-emitting surface of a surface light source device for explaining the influence on the angular distribution of luminance by the reflection characteristics of the reflective sheet.

Fig. 14 is a view corresponding to Fig. 1 for explaining a modification of a surface light source device.

Fig. 15 is a view corresponding to Fig. 1 for explaining another modification of the surface light source device.

Fig. 16 is a view showing a cross-sectional shape of a unit 稜鏡 on a main cut surface of an optical sheet.

Fig. 17 is a view showing a cross-sectional shape of a unit 稜鏡 of a main cut surface of an optical sheet produced as a sample.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings of the present specification, for convenience of illustration and ease of understanding, the appropriate scale and the aspect ratio of the aspect and the like are exaggerated and displayed by the physical objects.

1 to 13 are diagrams for explaining one of the objects obtained by the present invention. A diagram of an embodiment. 1 is a perspective view showing a schematic configuration of a liquid crystal display device and a surface light source device, and FIG. 2 is a cross-sectional view for explaining the action of the surface light source device. 3 and 4 are perspective views showing a light guide plate included in the surface light source device, and FIG. 5 is a cross-sectional view showing the light guide plate on the main cut surface of the light guide plate. Fig. 6 is a perspective view showing an optical sheet included in the surface light source device, and Fig. 7 is a cross-sectional view showing the optical sheet on the main cut surface. 11 and 12 are views for explaining an example of a method of manufacturing an optical sheet. Fig. 13 is a graph showing an angular distribution of luminance measured on the light-emitting surface of the surface light source device of Fig. 1.

As shown in FIG. 1 , the display device 10 includes a liquid crystal display panel 15 and a surface light source device 20 that is disposed on the back side of the liquid crystal display panel 15 and that illuminates the liquid crystal display panel 15 in a planar manner from the back side. The display device 10 has a display surface 11 on which an image is displayed. The liquid crystal display panel 15 functions as a shutter for controlling the transmission or blocking of light from the surface light source device 20 for each pixel, and is configured to display the image on the display surface 11.

The liquid crystal display panel 15 shown in the figure includes an upper polarizing plate 13 disposed on the light emitting side, a lower polarizing plate 14 disposed on the light incident side, and a liquid crystal disposed between the upper polarizing plate 13 and the lower polarizing plate 14. Layer unit 12. The polarizing plates 14 and 13 are decomposed into two polarized components (P wave and S wave) in which incident light is orthogonal, and have linear polarized components that vibrate in one of the directions (direction parallel to the transmission axis) (for example, P wave) transmits and absorbs a linearly polarized component that vibrates in the other direction orthogonal to the one direction (the direction parallel to the absorption axis) The function of (for example, S wave).

In the liquid crystal layer 12, electric field application can be performed for each of the regions forming one pixel. Next, the alignment direction of the liquid crystal molecules in the liquid crystal layer 12 changes depending on the application of no electric field. For example, the polarizing component that passes through the specific direction of the lower polarizing plate 14 disposed on the light incident side is rotated by 90° when the liquid crystal layer 12 is applied by the electric field, and When the liquid crystal layer 12 is applied by an electric field, its polarization direction is maintained. In this case, depending on whether or not the electric field is applied to the liquid crystal layer 12, it is possible to control that the polarized component that has passed through the lower polarizing plate 14 and vibrated in a specific direction is more transmitted through the upper polarizing plate 13 disposed on the light outgoing side of the lower polarizing plate 14, or The polarizing plate 13 is absorbed and blocked.

As described above, in the liquid crystal panel (liquid crystal display unit) 15, the transmission or blocking of light from the surface light source device 20 can be controlled for each pixel. In addition, the details of the liquid crystal display panel 15 have been described in various well-known documents (for example, "Industrial Survey of the Flat Panel Display Dictionary (Uchida Ryuo, Neichi Hiroki)", which is omitted here. Detailed explanation.

Next, the surface light source device 20 will be described. The surface light source device 20 has a light-emitting surface 21 that emits light in a planar shape. In the present embodiment, the surface light source device 20 is used as a device for illuminating the liquid crystal display panel 15 from the back side.

As shown in FIG. 1, the surface light source device 20 is configured as an edge illumination type surface light source device, and includes a light guide plate 30 and a side light source disposed on one side (the left side in FIG. 1) of one of the light guide plates 30. 24, and optical sheets (稜鏡 sheets) 60 respectively disposed opposite to the light guide plate 30 And a reflective sheet 28. In the illustrated example, the optical sheet 60 is disposed facing the liquid crystal display panel 15. Next, the light-emitting surface 21 is defined by the light-emitting surface of the optical sheet 60.

In the illustrated example, the light-emitting surface 31 of the light guide plate 30 is similar to the light-emitting surface 21 of the liquid crystal display device 10 and the light-emitting surface 21 of the surface light source device 20, and has a plan view shape (in FIG. The shape obtained is formed into a quadrangular shape. As a result, the entire light guide plate 30 is configured to have a pair of main surfaces (the light-emitting surface 31 and the back surface 32) which are opposite to each other in the thickness direction, and a side surface defined between the pair of main surfaces The system contains four faces. Similarly, the optical sheet 60 and the reflective sheet 28 are all formed in a rectangular parallelepiped shape with the side in the upper thickness direction being smaller than the other sides.

The light guide plate 30 has a light-emitting surface 31 formed by one of the main surfaces of the liquid crystal display panel 15 side, a back surface 32 formed by the other main surface facing the light-emitting surface 31, and a light-emitting surface 31 and a back surface. The side that extends between 32. Among the side faces, one of the two faces facing in the first direction d ₁ forms a light incident surface 33. As shown in FIG. 1, a light source 24 is provided on the surface opposite to the light incident surface 33. The light incident on the light guide plate 30 by the light incident surface 33 is directed toward the opposite surface 34 facing the light incident surface 33 along the first direction (light guiding direction) d ₁ , approximately along the first direction (light guiding direction). D ₁ is guided inside the light guide plate 30. As shown in FIGS. 1 and 2, the optical sheet 60 is disposed opposite to the light-emitting surface 31 of the light guide plate 30, and the reflective sheet 28 is disposed opposite to the back surface 32 of the light guide plate 30.

The light source may be a fluorescent lamp such as a linear cold cathode tube, It is composed of various patterns such as a dotted LED (light emitting diode) or an incandescent light bulb. In the present embodiment, the light source 24 is arranged in a plurality of dot-like light rays arranged in the longitudinal direction of the light-incident surface 33 (the direction perpendicular to the paper surface in FIG. 1, that is, the front and back directions of the paper surface). The body 25 is specifically composed of a plurality of light-emitting diodes (LEDs). Here, the light guide plate 30 shown in FIGS. 3 and 4 presents the arrangement position of the plurality of dot-shaped light-emitting bodies 25 forming the light source 24.

The reflective sheet 28 is for reflecting light leaked from the back surface 32 of the light guide plate 30 and causing it to enter the member inside the light guide plate 30 again. The reflective sheet 28 can be composed of a white diffuse reflection sheet, a sheet made of a material having high reflectance such as metal, and a film (for example, a metal film) made of a material having high reflectance as a surface layer. Sheets, etc. The reflection of the reflective sheet 28 may be a regular reflection (specular reflection) or a diffuse reflection. If the reflection of the reflective sheet 28 is diffuse reflection, the diffusion reflection may be an isotropic diffusion reflection or an anisotropic diffusion reflection.

However, in the present specification, the "light-emitting side" means that the light source 24, the light guide plate 30, the optical sheet 60, the liquid crystal display panel 15, and the components of the display device 10 are not moved forward, and the display device 10 is moved forward. The downstream side (the observer side, for example, the upper side of the paper surface in FIG. 1) in the traveling direction of the light that is emitted toward the observer, and the "light incident side" means that the light source 24, the light guide plate 30, the optical sheet 60, The components of the liquid crystal display panel 15 and the display device 10 are moved forward, and are emitted by the display device 10 toward the upstream side in the traveling direction of the light of the observer.

Further, in the present specification, terms such as "slice", "film", and "plate" are not distinguished from each other only by the difference in the name. Thus, for example, "sheet" also encompasses the concept of a component that may also be referred to as a film or sheet.

In the present specification, the "sheet surface (sheet surface, film surface)" refers to a surface that coincides with the planar direction of the target sheet-like member when the sheet-like member to be the object is viewed in a whole manner. . In the present embodiment, the sheet surface of the light guide plate 30 and the light guide plate 30, the sheet surface (plate surface) of the base portion 40, the sheet surface of the optical sheet 60, the sheet surface of the reflective sheet 28, and the panel of the liquid crystal display panel will be described later. The surface, the display surface 11 of the display device 10, and the light-emitting surface 21 of the surface light source device 20 are parallel to each other. In the present specification, the "front direction" refers to the normal direction of the light-emitting surface 21 of the surface light source device 20. In the present embodiment, the optical direction of the surface of the light guide plate 30 is also oriented in the normal direction. The normal direction of the sheet surface of the sheet 60 is aligned with the normal direction of the display surface 11 of the display device 10 (see, for example, FIG. 2).

Next, the light guide plate 30 will be further described in detail with reference mainly to FIGS. 2 to 5 . As shown in FIG. 2 to FIG. 5, the light guide plate 30 has a base portion 40 formed in a plate shape, and a plurality of unit opticals formed on a surface (a side facing the viewer side and a light emitting side surface) 41 on one side of the base portion 40. Element 50. The base portion 40 is configured as a flat member having a pair of parallel main faces. Next, the back surface 32 of the light guide plate 30 is constituted by the surface 42 on the other side of the base portion 40 on the side opposite to the reflective sheet 28.

Among them, the "unit" and "unit" in this manual The shape element, the "unit optical element", and the "unit lens" are elements that have an optical effect of refracting or reflecting light, and have a function of changing the traveling direction of the light, and are not mutually different depending on the name. Make a distinction.

As shown in detail in Fig. 4, the other side surface 42 of the base portion 40 on which the back surface 32 of the light guide plate 30 is formed is formed as an uneven surface. In a specific configuration, the back surface 32 has an inclined surface 37, a step surface 38 extending in the normal direction nd of the light guide plate 30, and a plate surface direction of the light guide plate 30 by the unevenness of the other side surface 42 of the base portion 40. Extended connecting surface 39. The light guiding in the light guide plate 30 depends on the total reflection of the pair of main faces 31, 32 of the light guide plate 30. On the other hand, the inclined surface 37 is inclined with respect to the plate surface of the light guide plate 30 so as to be closer to the light-emitting surface 31 toward the opposite surface 34 side from the light-incident surface 33 side. Therefore, the incident angle when the light reflected on the inclined surface 37 is incident on the pair of main faces 31 and 32 is small. By reflecting on the inclined surface 37, if the incident angle to the pair of main faces 31, 32 does not reach the total reflection critical angle, the light system is emitted by the light guide plate 30. In other words, the inclined surface 37 functions as an element for extracting light from the light guide plate 30.

By adjusting the distribution of the inclined surface 37 in the first direction d ₁ in the light guiding direction in the back surface 32, the distribution of the amount of light emitted from the light guide plate 30 along the first direction d ₁ can be adjusted. In the example shown in FIGS. 2 to 5, as the incident surface 33 approaches the opposite surface 34 along the light guiding direction, the proportion of the inclined surface 37 in the back surface 32 becomes high. With the configuration as described above, the emission of light from the light guide plate 30 in the region separated by the incident surface 33 along the light guiding direction is promoted, and it is possible to effectively prevent the amount of emitted light from being lowered as being separated by the incident surface 33. .

Next, the unit optical element 50 provided on the surface 41 on one side of the base 40 will be described. FIG 34 shown in detail, a plurality of unit optical elements 50 based at D ₁ crossing the first direction and the side of the base 40 of the surface 41 is in the array direction parallel (FIG. 3 is a left direction), is arranging the base 40 On one side of the face 41. Each unit optical elements 50 based on the side surface 41 of the base portion 40, to its ligand was linearly extending in a column direction intersecting the direction (d ₁ direction).

Especially in the present embodiment, as shown in FIG. 3, a plurality of unit optical elements 50 based on the side surface 41 of the base portion 40, the first direction and the d ₁₁ was perpendicular to the second direction (arranging direction) d ₂ Arrange the rows without gaps. Therefore, the light-emitting surface 31 of the light guide plate 30 is configured as inclined surfaces 35 and 36 which are formed by the surface of the unit optical element 50. Further, each unit optical element 50 extends linearly in the first direction d ₁ orthogonal to the arrangement direction. Further, each unit optical element 50 is formed in a columnar shape and has the same cross-sectional shape along the longitudinal direction thereof. Further, in the present embodiment, the plurality of unit optical elements 50 are configured to be identical to each other. As a result, the light guide plate 30 based on the present embodiment, respective positions along _a first direction D 1, having a certain cross-sectional shape.

Next, the cross section shown in FIG. 5, that is, the direction in which the unit optical elements are arranged (the second direction) and the normal direction nd toward the one side surface 41 of the base portion 40 (the plate surface of the light guide plate 30) are parallel to each other. The cross-sectional shape of each unit optical element 50 in the cross section (hereinafter also referred to simply as "main cut surface"). As shown in FIG. 5, in the illustrated example, the light guide plate The cross-sectional shape of each unit optical element 50 in the main cut surface is formed to be thinner toward the light-emitting side tip. That is, in the main cut surface of the light guide plate, the width of the unit optical element 50 which is parallel to the plate surface of the light guide plate 30 is smaller as the base portion 40 is separated as it goes along the normal direction nd of the light guide plate 30. .

Further, in the present embodiment, the outer contour 51 (corresponding to the light-emitting side surface 31) 51 of the main cut surface of the unit optical element 50 is such that the outer contour is at an angle with respect to one side surface 41 of the base portion 40, that is, the light-emitting surface. The angle θa is changed such that the distal end portion 52a of the outer contour 51 of the unit optical element 50, which is most separated from the base portion 40, becomes larger toward the proximal end portion 52b of the outer contour 51 of the unit optical element 50 closest to the base portion 40. . Regarding the light-emitting surface angle θa, a disclosure as disclosed in Japanese Laid-Open Patent Publication No. 2013-51149 can be set.

Here, the light-emitting surface angle θa referred to herein means that the light-emitting side surface (outer contour) 51 of the unit optical element 50 is formed on one side surface 41 of the base portion 40 in the main cut surface of the light guide plate 30 as described above. angle. In the example shown in FIG. 5, the outer contour (light-emitting side surface) 51 of the main cut surface of the unit optical element 50 is formed in a zigzag line shape, and is formed between each straight line portion constituting the fold line and one side surface 41 of the base portion 40. The angle (strictly speaking, the smaller of the two angles formed (the angle of the sharp corner)) becomes the exit surface angle θa. On the other hand, if the outer contour (light-emitting side surface) 51 in the main cut surface of the unit optical element 50 is constituted by a curved surface, the angle formed between the tangent to the outer contour and one side surface 41 of the base portion 40 is specified ( Strictly speaking, the smaller of the two angles formed (sharp angle Angle)) is the exit surface angle θa.

The unit optical element 50 shown in FIG. 5 as a specific example is formed in the main cut surface of the light guide plate 30, and is formed on one side surface 41 of the base portion 40, and the front end portion 52a on both sides of the outer contour 41 is formed. A pentagonal shape with each of the base end portions 52b or a shape obtained by chamfering one or more corners of the pentagon shape. Further, in the illustrated example, the main optical element 50 is cut for the purpose of effectively increasing the luminance in the front direction and imparting symmetry to the angular distribution of the luminance in the plane along the second direction d ₂ . The cross-sectional shape in the cross section is symmetrical with respect to the front direction nd. That is, as shown in detail in FIG. 5, the light-emitting side surface 51 of each unit optical element 50 is constituted by a pair of folded surfaces 35 and 36 which are formed symmetrically around the front direction. The pair of folded faces 35, 36 are interconnected to define a front end portion 52a. Each of the folded surfaces 35 and 36 has a first surface 35a and 36a defining a front end portion 52a, and second surfaces 35b and 36b connected to the first surfaces 35a and 36a from the side of the base portion 40. The pair of first inclined faces 35a and 36a have a symmetrical structure centering on the front direction nd, and the pair of second inclined faces 35b and 36b have a symmetrical structure centering on the front direction nd.

In the overall configuration of the unit optical element 50, the protruding height Ha of the unit optical element 50 from the base portion 40 along the front direction in the main cut surface of the light guide plate 30 is relative to the unit optical element in the main cut surface of the light guide plate 30. The ratio (Ha/Wa) of the wide Wa in the direction of the arrangement of 50 is preferably 0.3 or more and 0.45 or less. With the unit optical element 50 as shown above, the relative light along the unit light is refracted and reflected on the light exit side 51 The component of the light in the arrangement direction (second direction) of the element 50 exhibits an excellent condensing function and can effectively suppress the occurrence of sidelobe.

Here, the "pentagon shape" in the present specification does not mean only a pentagonal shape under strict meaning, but also includes a substantially pentagonal shape including a limit in the manufacturing technique or an error in molding. In addition, the terms used in the specific other shapes or geometric conditions used in the present specification, such as "parallel", "orthogonal" and "symmetric", are not limited to rigorous meanings, including the expectation of the same. An error in the degree of optical function is explained.

Here, the size of the light guide plate 30 can be set as an example as shown below. First, in a specific example of the unit optical element 50, the wide Wa (see FIG. 5) can be formed to be 10 μm or more and 500 μm or less. On the other hand, the thickness of the base portion 40 can be formed to be 0.3 mm to 6 mm.

The light guide plate 30 formed by the above-described configuration can be produced by forming the unit optical element 50 on a substrate or by extrusion molding. Various materials can be used for forming the base 40 of the light guide plate 30 and the material of the unit optical element 50. However, a material which is widely used as an optical sheet to be incorporated in a display device, and which has excellent mechanical properties, optical properties, stability, workability, and the like, and which can be obtained at low cost, for example, an acrylic resin, Reactivity of a transparent resin containing at least one of polystyrene, polycarbonate, polyethylene terephthalate, polyacrylonitrile, or the like, or epoxy acrylate or urethane acrylate Resin (ionizing radiation curable resin, etc.). Further, a diffusing component having a function of diffusing light may be added to the light guide plate 30 as needed. As the diffusion component, particles made of a transparent material such as vermiculite (cerium oxide), alumina (alumina), acrylic resin, polycarbonate resin, or oxime resin having an average particle diameter of about 0.5 to 100 μm can be used. An example.

When the light guide plate 30 is formed by hardening the ionizing radiation-curable resin on the substrate, a flaky land between the unit optical element 50 and the substrate may be formed on the substrate together with the unit optical element 50. unit. At this time, the base portion 40 is formed of a base material and a land portion formed of an ionizing radiation-curable resin. Further, a plate material made of a resin material which is extrusion-molded together with the light-diffusing particles may be used as the substrate. On the other hand, in the light guide plate 30 which is formed by extrusion molding, the base 40 and the plurality of unit optical elements 50 on one side surface 41 of the base 40 can be integrally formed.

Next, the optical sheet (稜鏡 sheet) 60 will be described in more detail with reference mainly to FIGS. 2 and 6 to 10. The optical sheet 60 has a function of changing the traveling direction of transmitted light, and corrects the direction of the optical axis of the light incident on the light guide plate 30.

The optical sheet 60 shown in Fig. 6 and Fig. 7 has a sheet-like base material layer 65, a rough layer 70 laminated on the base layer 65 from one side thereof, and a laminate layer on the other side. The layer 80 of the layer 65. The base material layer 65 is formed of a resin film such as polyethylene terephthalate, and functions as a layer supporting the rough layer 70 and the ruthenium layer 80. The layer 80 includes a plurality of units 85 arranged in a single direction. Each unit 稜鏡85 extends in a line shape in a direction crossing the aforementioned one direction. The optical sheet 60 has a pair of opposing major faces. One of the main faces of the optical sheet 60 is formed as a rough surface 70a due to the rough layer 70. The other main surface of the optical sheet 60 is formed as a top surface 80a due to the enamel layer 80. As shown in FIGS. 1 and 2, the optical sheet 60 is disposed such that the rough surface 70a faces the side of the liquid crystal display panel 15 and the pupil surface 80a faces the side of the light guide plate 30. Further, the arrangement direction of the unit turns 85 is formed to be parallel to the first direction d _{1 which} is the light guiding direction obtained by the light guide plate 30.

The rough layer 70 includes first light diffusion particles 71, second light diffusion particles 72, and a binder resin 73. The first light-diffusing particles 71 and the second light-diffusing particles 72 function to change the direction in which the light travels in the rough layer 70 by reflection or refraction. The first light-diffusing particles 71 and the second light-diffusing particles 72 are made of different materials. Next, the refractive index n ₁ of the first light-diffusing particle 71 is different from the refractive index n ₂ of the second light-diffusing particle 72. Further, the first light-diffusing particles 71 and the second light-diffusing particles 72 have different particle diameters. 7, the first light diffusion average particle size D 71 of the _first and second light diffusing particles 72 of average particle diameter d 70 across the first light diffusion without particles 71 and the second light _2, and a roughened layer The thickness t _b of the position of the diffusion particles 72 satisfies the following relationship (a): d ₂ <t _b <d ₁ ‧‧‧(a). The specific particle diameter d _{1 of the} first light-diffusing particles 71 can be 3.5 μm or more and 8.0 μm or less, and the average particle diameter d _{2 of} the second light-diffusing particles 72 can be 0.8 μm or more. The thickness t _{b of the} rough layer 70 at a position that does not straddle the first light-diffusing particles 71 and the second light-diffusing particles 72 can be 0.8 μm or more and 7.5 μm or less.

The average particle diameters d ₁ and d _{2 of the} light-diffusing particles 71 and 72 and the thickness t _b of the rough layer 70 satisfy the above relationship. As shown in detail in FIG. 7, the rough surface 70a of the rough layer 70 is formed to have a resin larger than the binder. The position where the first light-diffusing particles 71 having the particle diameter d ₁ of the thickness t _b of 73 is present is formed with the uneven surface of the convex portion corresponding to the first light-diffusing particles 71. The rough surface 70a formed as the uneven surface as described above is a function of bending the traveling direction of light at the interface with the adjacent air layer. In other words, the first light-diffusing particles 71 can mainly exhibit unevenness by imparting irregularities to the rough surface 70a.

On the other hand, as shown in detail in FIG. 7, the second light-diffusing particles 72 having a particle diameter d ₂ smaller than the thickness t _b of the rough layer 70 are buried in the binder resin 73. Therefore, the second light-diffusing particles 72 are slightly unevenly formed due to the difference in the shrinkage ratio of the binder resin 73. However, as in the first light-diffusing particles 71, there is no active formation of a light-diffusing function. The situation of the uneven surface. However, the refractive index n ₂ of the second light-diffusing particles 72 has a value different from the refractive index n _b of the binder resin 73. That is, formed as: n ₂ >n _b n ₂ <n _b , the second light-diffusing particles 72 form an interface having a refractive index difference with the binder resin 73, whereby the light diffusion function can be exhibited.

In the first light-diffusing particle 71, as described later, when the optical sheet 60 is provided with an uneven surface and the optical sheet 60 is overlapped with another member, for example, interference fringes and liquid infiltration are caused. The appearance of defects such as the observed dip pattern (also referred to as "wet out") is not obvious for the purpose. Next, from the viewpoint that the glare is effectively made inconspicuous, it is preferable that the first light-diffusing particles 71 do not exhibit a strong light diffusing function. Therefore, the light diffusing function in the rough layer 70 is mainly responsible for the interface between the second light diffusing particles 72 and the binder resin 73 in the rough layer. The second light-diffusing particle 72 is used to diffuse the first light, and the second light-diffusing particle 71 suppresses the occurrence of glare, and the first light is diffused. The volume ratio of the particles 71 to the second light-diffusing particles 72 is preferably 1:1 to 1:10, and more preferably 1:3 to 1:10. In addition, the second light-diffusing particle 72 is inconspicuous in glare, and the concealing function to be described later and the second light-diffusing particle 71 suppress the occurrence of glare, and the appearance defect is not conspicuous. The number of particles of the light-diffusing particles 71 (the number of primary particles) is N ₁ , and the number of particles of the first light-diffusing particles 72 (the number of primary particles) is N ₂ , which satisfies the following relationship: 50 ≦ ( N ₂ /N ₁ )≦200.

Further, in the present invention, since the first light-diffusing particles 71 are not designed to have a strong light diffusing function, the refractive index n ₁ of the first light-diffusing particles 71 can be combined with the binder resin 73. The refractive index n _b is different, but may be the same. That is, it can also be formed as: n ₁ ≧ n _b or n ₁ ≦ n _b . Further, the refractive index of the first light diffusing particles 71 is n ₁ and the second light diffusing particle refractive index n ₂ of the system 72 to form a good different values: n _1> n ₂ or n ₁ <n _2. Further, as shown in FIG. 8, the rough surface 70a of the rough layer 70 is formed as an uneven surface in which the convex portion is formed corresponding to the first light-diffusing particles 71. The light diffusing function of the convex surface on the convex surface as described above is referred to as FIG. 9 and FIG. 10, and as will be described later, a lens effect which can be formed as a cause of glare can be exhibited. Therefore, in order to reduce the light diffusing function of the rough surface 70a at the convex portion, it is preferable that the refractive index n _b of the binder resin 73 which forms the interface with the air layer is close to 1 in such a manner as to reduce the refractive index difference from the air layer. . Further, as shown in FIG. 8, in the convex portion of the rough surface 70a, the first light-diffusing particles 71 may be exposed by the binder resin 73. Therefore, the refractive index n _{1 of the} first light-diffusing particle 71 is preferably similar to the refractive index n _{b of the} binder resin 73 so as to be close to 1 so as to reduce the difference in refractive index from the air layer.

From the above viewpoints, the appearance of the visibility reduction effect of the appearance defect, and the ease of obtaining the material, it is preferable to form n ₁ ≦n _b <n ₂ . Generally, when considering the range of materials that can be easily obtained, the refractive indices n ₁ , n ₂ , and n _b of each material are formed as follows: n ₁ = 1.43 to 1.60

n ₂ =1.38~2.20

It is preferable that n _b = 1.43 to 1.60 is selected so as to satisfy the relationship between the respective refractive indexes within the range. For example, a value rounded to the second decimal place can be formed as n ₁ = 1.49, n ₂ = 1.59, and n _b = 1.51.

The particle diameters of the light-diffusing particles 71 and 72 are the primary particle diameters of the light-diffusing particles 71 and 72, and the diameters of the light-diffusing particles 71 and 72 when they are determined as spherical particles. The average particle diameter of the light-diffusing particles 71 and 72 can be measured by, for example, a laser diffraction type particle size distribution measuring method using a precise particle size distribution measuring apparatus "COULTER Multisizer". In addition, the average particle diameter of the light-diffusing particles 71 and 72 dispersed in the rough layer 70 can be formed as a value measured by a cross-sectional electron microscope, using an image processing software or the like.

The first light-diffusing particles 71 and the second light-diffusing particles 72 of the rough layer 70 can be used: an organic polymer such as an acrylic resin, a silicon resin, a fluororesin, a polyester, a polycarbonate, or a polystyrene. Particles composed of metal compounds or inorganic substances, such as particles, alumina, vermiculite, calcium carbonate, fluorite, cryolite, magnesium fluoride, tin oxide, indium oxide, zirconium oxide, titanium oxide, tungsten oxide, etc. Various known particles such as porous physical particles. Further, the shapes of the light-diffusing particles 71 and the second light-diffusing particles 72 do not need to be spherical as in the case shown in FIG. 7, and may have, for example, a spheroid shape or a cube, a cuboid, a rhombohedron, and a positive 8-face. Various shapes such as a polyhedral shape such as a body, a hexagonal column, and a 12-faced body. In addition, as the binder resin 73, a resin such as an acrylic resin, a polyester resin, a urethane resin, or an epoxy resin may be used as the resin material, and a thermosetting type or Ionizing radiation hardening type (the hardened resin is also called thermosetting resin or ionizing radiation hardening resin), or solvent drying hardened by thermoplastic resin Various resin materials known in the form of a hardened form such as a heat-melting-cooling-curing type are used as a hardened form.

Next, the ruthenium layer 80 of the optical sheet 60 will be described. As shown in FIGS. 6 and 7, the enamel layer 80 has a sheet-like land portion 81 formed on the base material layer 65 and a plurality of unit dams 85 arranged on the land portion 81. The land portion 81 is formed by a manufacturing method described later, and is integrally formed of the same resin material as the unit 稜鏡85. The thickness of the land portion 81 is usually about 1 to 10 μm. However, the land portion 81 is not essential, and may be formed in a form in which the land portion 81 is not provided (the thickness of the land portion is 0). However, it is preferable to form the land portion 81 having a thickness of 2 to 8 μm from the viewpoint of improving the adhesion between the ruthenium layer 80 and the base material layer 65, and the relaxation of the deformation at the time of curing and shrinkage of the ruthenium layer 80.

The surface 80a of the surface on the other side of the optical sheet 60 is formed by the surface of the unit crucible 85, that is, the crucible surface. As shown in FIG. 6, the unit 稜鏡85 is arranged along an arrangement direction parallel to the sheet surface of the optical sheet 60. In the illustrated form, the arrangement direction of the unit turns 85 is formed to be parallel to the first direction d ₁ described above. Each unit 稜鏡85 is linearly extended in a direction intersecting the arrangement direction. In particular, in the illustrated example, each unit 稜鏡85 is linearly extended in a direction orthogonal to the arrangement direction. In the illustrated form, each unit Prism 85 along lines d 1 d of the first direction as a second direction perpendicular to the straight line ₁₂ extends. Further, each unit 稜鏡85 is formed in a columnar shape and has the same cross-sectional shape along the longitudinal direction thereof. Further, the plurality of units 85 are configured to be identical to each other, and are arranged on the land portion 81 without a gap. Therefore, in the illustrated optical sheet 60, the relief surface 80a is formed only by the surfaces 86, 87 of the unit crucible 85.

Shown in detail in FIG. 7, the unit 85 based Prism arranging direction Prism unit 85, i.e., the first direction D _1, having a sheet-section in a direction parallel to the optical sheet 60 to the first mutually arranged Face 86 and second face 87. The first surface 86 of each unit 稜鏡85 is located on one side in the first direction d ₁ (the left side in the paper surface of FIGS. 1 and 2 ), and the second surface 87 is located on the other side in the first direction d ₁ . (The right side of the paper in Figures 1 and 2). More detail, each unit Prism surface 86 of the first line 85 located on the side of the direction d ₁ of the light source 24, each unit 87 based Prism second surface 85 of the light source located in the first direction d ₁ 24 separated sides. Then, the first surface 86 is mainly introduced into the light guide plate 30 by the light source 24 disposed on one side in the first direction d ₁ , and then the light emitted from the light guide plate 30 is used as an incident surface when incident on the optical sheet 60 . Features. On the other hand, the second surface 87 has a function of reflecting light incident on the optical sheet 60 and correcting the optical path of the light.

As shown in detail in Fig. 7, the first surface 86 and the second surface 87 are respectively extended by the land portion 81 and connected to each other. The base end portion 88b of the unit crucible 85 is defined at a position where the first surface 86 and the second surface 87 are connected to the land portion 81, respectively. Further, at a position where the first surface 86 and the second surface 87 are connected to each other, a front end portion (which is a top portion and a ridge line) 88a of the unit crucible 85 which protrudes most toward the light-incident side of the base material layer 65 is defined.

Next, a cross section shown in FIG. 7 , that is, a cross section parallel to the normal direction nd of the optical sheet 60 (base material layer 65) and the arrangement direction (first direction d ₁ ) of the unit 稜鏡 85 will be described. Hereinafter, the cross-sectional shape of each unit 稜鏡85 in the "main cut surface of the optical sheet" is also referred to below. As shown in FIG. 6 and FIG. 7 , in the illustrated example, the cross-sectional shape of each unit 稜鏡 85 in the main cut surface of the optical sheet is formed so that the tip side is tapered toward the light incident side (the side of the light guide plate). shape. That is, in the main cut surface, the width of the unit 稜鏡 85 which is parallel to the sheet surface of the optical sheet 60 is smaller as it is separated from the base layer 65 along the normal direction nd of the optical sheet 60. .

In the illustrated example, a second surface 87 (a second surface 87 forming a part of the relief surface 80a) of a part of the outline of the unit 稜鏡85 is formed on the main cut surface of the optical sheet, and the opposite optical sheet 60 is to be formed. The angle formed by the sheet surface is the reflection surface angle θb, and the reflection surface angle θb of the unit 稜鏡85 is not formed constant in the second surface 87. As shown in FIG. 7, the reflection surface angle θb is in the second surface 87, and the unit 稜鏡60 closest to the base material layer 65 is oriented toward the front end portion 88a of the unit yoke 85 which is most separated from the base material layer 65. The manner in which the base end portion 88b becomes larger changes. As shown in FIG. 7, by the unit 稜鏡60 as shown above, the erected light L71 is mainly incident on the direction in which the inclination angle with respect to the front direction nd of the second surface 87 is smaller than the smaller one. The area on the side of the base end portion 88b and the direction in which the inclination angle toward the front direction nd is extremely large is larger than the area on the side of the tip end portion 88a on which the horizontal light L72 mainly enters, thereby ensuring excellent light collecting function. .

With a specific configuration, in the present embodiment shown in the drawing, the outline of the second surface 87 of the unit 稜鏡 85 is on the main cut surface of the optical sheet. Among them, there is a shape in which straight portions are connected, or straight portions are connected, and the connected portions are chamfered. In other words, the outer contour of the second surface 87 of the unit cymbal 85 is formed in a shape of a broken line or a chamfered corner portion of the fold line. More specifically, the second surface 87 has a first portion (first element surface) 87a that defines the distal end portion 88a, and a second portion that is adjacent to the first portion 87a from the side of the base material layer 65 ( The second element surface) 87b. Next, the reflection surface angle θb of the second portion 87b is larger than the reflection surface angle θb of the first portion 87a.

Further, in another example, in the example shown in FIG. 10, the second surface 87 has a first portion (first element surface) 87a defining the distal end portion 88a, and a side of the base material layer 65 and The second portion (second element surface) 87b adjacent to the one portion 87a and the third portion (third element surface) 87c adjacent to the second portion 87b from the side of the base material layer 65. Next, the reflection surface angle θb of the third portion 87c is larger than the reflection surface angle θb of the second portion 87b, and the reflection surface angle θb of the second portion 87b is larger than the reflection surface angle θb of the first portion 87a.

However, the second surface 87 is not limited to the examples shown in FIGS. 9 and 10, and may have four or more element surfaces.

Here, the reflection surface angle θb is as described above, and the second surface 87 of the unit crucible 60 is formed on the sheet surface of the optical sheet 60 (the sheet surface of the base material layer 65) on the main cut surface of the optical sheet. angle. In the example shown in Fig. 7, when the second surface 87 of the main cut surface of the unit 稜鏡85 is formed in a zigzag line, the angle formed between each straight line portion constituting the fold line and the sheet surface of the optical sheet (strictly In terms of the smaller of the two corners formed The angle (angle of the sharp corner) is the reflection surface angle θb. On the other hand, if the second surface 87 of the main cut surface of the unit 稜鏡85 is formed by a curved surface, the angle formed between the tangent to the outer contour and the sheet surface of the optical sheet (strictly, The smaller angle (angle of the sharp angle) among the two angles formed is specified as the reflection surface angle θb.

In the optical sheet 60 having the configuration shown above, the height Hb of the unit 稜鏡85 along the normal direction nd of the optical sheet in the main cut surface of the optical sheet is along the main cut surface of the optical sheet. Prism unit than the d 85 direction of arranging the bottom surface 85 of the unit ₁ of the Prism width Wb (FIG. 7) (Hb / Wb) can affect the size and dispersion of the converging optical sheet 60. The ratio (Hb/Wb) of the height Hb of the unit 稜鏡85 to the width Wb of the second surface 87 of the unit 稜鏡85 is preferably 0.55 or more and 0.90 or less, and is preferably 0.75 or more and 0.85 or less. Better. In addition, the reflection surface angle θb of the first portion 87a of the second surface 87 can be 45° or more and 60° or less, and the reflection surface angle θb of the second portion 87b of the second surface 87 can be 50. Above °, below 70 °. Further, an angle θc (see FIG. 7) of the apex angle of the unit 稜鏡85 with respect to one side of the unit 稜鏡85 is formed at an acute angle in the main cut surface of the optical sheet 60, and is typically formed at 60°. Above, below 80°.

The width Wb of the bottom surface is as shown in FIG. 7 and is arranged between the adjacent unit cymbals 85 without passing through the gap portion, and is aligned with the arrangement pitch P of the unit 稜鏡 (see FIG. 17).

In addition, other dimensions of the optical sheet 60 can be set as follows As an example. First, in the specific example of the unit 稜鏡85 formed by the above-described configuration, the arrangement pitch P of the unit 稜鏡85 (in the illustrated example, corresponds to the width of the unit 稜鏡85) Wb) is formed to be 10 μm or more and 200 μm or less. Further, the protruding height Hb of the unit 稜鏡85 from the land portion 81 along the normal direction nd of the sheet surface facing the optical sheet 60 can be formed to be 5.5 μm or more and 180 μm or less. However, recently, the high definition of the arrangement of the unit 稜鏡85 has progressed rapidly, and it is preferable to form the arrangement pitch P of the unit 稜鏡85 to be 10 μm or more and 35 μm or less.

Further, the glare effectively make obvious the viewpoint, the first light diffusing particle average particle diameter d 71 of the _second light diffusing average particle diameter d 72 of ₂ lines 85 relative units Prism arranging pitch P, Adjust to the appropriate range. In terms of specific conditions, it is preferable to satisfy the following relationship (s1) to satisfy the relationship (s2) or the relationship (s3). In the relationship (s3), Wb ₂ is a length of the second surface 87 along the arrangement direction d ₁ of the unit ,, in other words, a direction orthogonal to the arrangement direction d ₁ of the unit ( (in the drawing In the example, the length of the second surface 87 projected in the front direction nd is referred to (see FIG. 7).

d ₂ <t _b <d ₁ <P/2‧‧‧(s1)

d ₂ <t _b <d ₁ <P/3‧‧‧(s2)

_{d 2 <t b <d 1} <Wb 2 ‧‧‧ (s3) In addition, if the unit 85 Prism arranging pitch P of 10μm or more, 35 m or less, in order to take into account the following relation (S4) and the relationship (S5) are preferred. If both the relationship (s4) and the relationship (s5) are satisfied, the optical sheet 60 that satisfies the conditions (s1) to (s3) can be secured without causing the above-described other problems.

t _b +1[ μ m]≦d ₁ [ μ m]≦10[ μ m]‧‧‧(s4)

0.78[ μ m]≦d ₂ [ μ m]‧‧‧(s5)

However, as a result of intensive study by the inventors of the present invention, it is confirmed that the following conditions are satisfied in relation to the surface hardness of the optical sheet 60 described above. When the following conditions (d) to (f) are satisfied, in the optical sheet 60 having the enamel layer 80 and the rough layer 70 applied to the display device 10, it is possible to effectively prevent the occurrence of defects on the dam surface 80a or the rough surface 70a.

Hp<Hm‧‧‧(d)

HB≦Hm≦2H‧‧‧(e)

B≦Hp≦HB‧‧‧(f) Here, Hp is based on the pencil hardness Hp of the face 80a measured by JIS K5600-5-4 (1999) (load 750g, speed 1mm/s), Hm basis The pencil hardness of the rough surface 70a measured by JIS K5600-5-4 (1999) (load weight 750 g, speed 1 mm/s).

Here, the magnitude relationship of the pencil hardness is defined as the case where the hardness is high. That is, it becomes "B<HB<F<H<2H".

The optical sheet 60 is subjected to storage or transportation in a state of being laminated or wound before being attached to a final device such as a surface light source device. That is, the optical sheet 60 is processed in a state where the top surface 80a thereof is in contact with the rough surface 70a of the other optical sheet 60 or the rough surface 70a of the other portion of the same optical sheet 60. Next, in this process, there is a possibility that the kneading surface 80a and the rough surface 70a are worn. Wear is the cause of defects such as bright spots or defects. In particular, regarding the micro unit 稜鏡85 that is applied to a small display device The optical sheet 60 was confirmed to be more likely to become more conspicuous.

In the method of disposing the wear formed before assembly, a protective film is interposed between the facing surface 80a and the rough surface 70a. However, the protective film directly increases the manufacturing cost of the optical sheet 60. Further, not only the labor for inserting the protective film into the package of the optical sheet 60 is increased, but also when the optical sheet 60 is used, the work such as disposal of the protective film is forced.

On the other hand, as a result of the intensive study by the inventors of the present invention, if the above conditions satisfy (d), (e), and (f), in the optical sheet 60 having the fine unit 稜鏡 85 applied to the small display device, Also in the process before the assembly of the optical sheet 60, damage to the kneading surface 80a or the rough surface 70a can be effectively prevented.

In the condition (d), the pencil hardness Hm of the rough layer 70 is formed such that the pencil hardness Hp of the enamel layer 80 is based on the viewpoint that the rough surface 70a of the rough layer 70 is prevented from being damaged by the apex angle of the unit 稜鏡85. The reason. If the pencil hardness Hm of the rough surface 70a does not reach the pencil hardness Hp of the kneading surface 80a, it is likely to be damaged on the rough surface 70a as compared with the kneading surface 80a. On the other hand, if the condition (d) is satisfied, the kneading surface 80a is deformed when an external force is applied, and when it is released by the external force, it becomes soft as it is, and the kneading surface 80a can be prevented from being damaged.

Further, although it is irrelevant to the damage occurring before assembly, the rough surface 70a is used to maintain the function of sufficiently diffusing the rough layer 70, or to avoid optical density of other members adjacent thereto. From the point of view, it is better to deform the terrain. Further, the convex portion of the uneven surface in the rough surface 70a is formed as a dot-like protruding portion by the light-diffusing particles 71. In particular, in the optical sheet 60 described above, the first light-diffusing particles 71 having a large particle diameter and the second light-diffusing particles 72 having a small particle diameter are dispersed in the binder resin 73b, and the main first light-diffusing particles 71 are mainly dispersed. The convex portion of the rough surface 70a is discretely formed. Therefore, the portion where the first light-diffusing particles 71 are disposed in the rough layer 70 is more likely to cause stress concentration than the ridge line of the unit cymbal 85 forming the relief surface 80a. In order to withstand the stress concentration, it is preferable that the pencil hardness Hm of the rough layer 70 is equal to or higher than the pencil hardness Hp of the enamel layer 80 in the condition (d).

Further, if the pencil hardness Hp of the kneading surface 80a is higher than "HB", when one optical sheet 60 (sheet 11) is wound, or when a plurality of optical sheets 60 are laminated, there is a rough damage of the kneading surface 80a. The possibility of face 70a. Similarly, if the pencil hardness Hm on the rough surface 70a is higher than "2H", when one optical sheet 60 (sheet 11) is wound, or when the plurality of optical sheets 60 are laminated, the rough surface 70a is damaged. The possibility of face 80a.

Further, when the pencil hardness Hp of the kneading surface 80a is lower than "B", when one optical sheet 60 (sheet 11) is wound or a plurality of optical sheets 60 are laminated, it is necessary to provide a protective film. That is, the condition (f) must be satisfied from the viewpoint of eliminating the protective film. Similarly, when the pencil hardness Hm on the rough surface 70a is lower than "HB", when one optical sheet 60 (sheet 11) is wound or a plurality of optical sheets 60 are laminated, it is necessary to provide a protective film.

Based on the above, it is preferable to satisfy the conditions (d) to (f) in the optical sheet 60.

Next, an example of a method of manufacturing the optical sheet 60 formed by the above configuration will be described.

The method for producing an optical sheet described below includes a process of forming the rough layer 70 on the resin film 66 on which the base material layer 65 is formed, and a process of forming the ruthenium layer 80 on the resin film 66. The following describes each project together with the devices used in each project.

First, the process of forming the rough layer 70 on the resin film 66 will be described mainly with reference to Fig. 11 .

In this project, the rough layer forming device 160 shown in Fig. 11 is used. The rough layer forming apparatus 160 includes a coating device 162 that applies a resin material 74 including the first light-diffusing particles 71 and the second light-diffusing particles 72 to the resin film 66, and is coated on the resin film. The hardening device 164 of the resin material 74 on 66 is hardened. In the coating apparatus 162, in FIG. 11, a coater in the form of a liquid resin material is discharged from a T-die type nozzle, but other notch coater and roll coater may be used. Various known coaters such as a gravure roll coater and a bar coater. Further, the curing device 164 can be appropriately configured in accordance with the hardening characteristics of the resin material 74 applied by the coating device 162.

When the resin film 66 extending in a strip shape is supplied to the rough layer forming apparatus 160, the coating material 162 of the rough layer forming apparatus 160 is coated with the resin material 74 including the first and second light diffusing particles 71 and 72. The cloth is placed on one of the faces of the resin film 66 (in FIG. 11 Upper side). The applied resin material 74 is stretched over the resin film 66. The resin film 66 is a substrate layer 65 in which the optical sheet 60 is finally formed, and can be formed into mechanical properties (strength, etc.), chemical properties (stability, etc.), and optical properties (light permeability, etc.) as an example. And a biaxially stretched polyethylene terephthalate film having a thickness of 30 to 250 μm which can be obtained at low cost.

The resin material 74 supplied from the coating device 162 forms the binder resin 73 of the rough layer 70. As the resin material 74, various known resin materials of a thermosetting type or an ionizing radiation curing type can be used. Further, as described above, the first and second light-diffusing particles 71 and 72 dispersed in the resin material 74 can be formed of various known materials and have various known shapes. In the example shown below, an example in which the ionizing radiation-curable resin is supplied from the coating device 162 will be described. In the ionizing radiation-curable resin, for example, a UV-curable resin which is cured by irradiation with ultraviolet rays (UV) or an EB-curable resin which is cured by irradiation with an electron beam (EB) can be selected.

The resin film 66 coated with the ionizing radiation-curable resin material 74 in which the first and second light-diffusing particles 71 and 72 are dispersed is placed at a position facing the curing device 164. At this time, the ionizing radiation corresponding to the hardening characteristics of the ionizing radiation-curable resin material 74 is emitted by the curing device 164. Therefore, the ionizing radiation-curable resin material 74 coated on the resin film 66 is irradiated with ionizing radiation and hardened. As a result, a resin resin 73 composed of the hardened ionizing radiation-curable resin material 74 is formed on the resin film 66, and is dispersed in electricity. The rough layer 70 of the first and second light-diffusing particles 71 and 72 in the radiation-curable resin material 74 is separated.

Next, the process of forming the ruthenium layer 80 on the side opposite to the side on which the rough layer 70 of the resin film 66 is formed will be mainly described with reference to FIG. In this project, the ruthenium layer forming device 150 shown in Fig. 12 is used.

The ruthenium layer forming device 150 will be initially described. As shown in FIG. 12, the ruthenium layer forming apparatus 150 has a molding die 152 having a substantially cylindrical outer contour. A cylindrical mold surface (concave surface) 152a is formed in a portion corresponding to the outer peripheral surface (side surface) of the cylinder of the molding die 152. The molding die 152 formed of a cylindrical shape has a central axis CA passing through the center of the outer peripheral surface of the cylinder, in other words, a central axis CA passing through the center of the cross section of the cylinder. A concave portion (not shown) corresponding to the unit 稜鏡 85 of the optical sheet 60 is formed on the mold surface 152a. In other words, the molding die 152 is configured as a drum mold that molds the ruthenium layer 80 while rotating the central axis CA as a rotation axis.

As shown in FIG. 12, the ruthenium layer forming apparatus 150 further includes a material supply device 154 that supplies a fluid resin material 83 between the supplied strip-shaped resin film 66 and the mold surface 152a of the molding die 152. And a curing device 156 that cures the material 83 between the resin film 66 and the uneven surface 152a of the molding die 152. The curing device 156 can be suitably configured in accordance with the hardening characteristics of the material 83 to be cured.

Next, the use of the ruthenium layer forming device 150 will be described. The mirror layer 80 is formed by a method. First, the resin film 66 in which the rough layer 70 is formed to extend in a strip shape is supplied to the ruthenium layer forming device 150 by the rough layer forming device 160. As shown in FIG. 12, the supplied resin film 66 is fed to the molding die 152 from the left side, and is held by the molding die 152 and the pair of rollers 158 so as to face the uneven surface 152a of the die 152. Among them, the side of the resin film 66 in which the rough layer 70 is not formed is opposed to the mold 152.

Further, as shown in FIG. 12, a resin material 83 having fluidity is supplied from the material supply device 154 between the resin film 66 and the mold surface 152a of the molding die 152 with the supply of the resin film 66. This material 83 forms a unit 稜鏡85 and a land portion 81. Here, "having fluidity" means that the material 83 supplied to the mold surface 152a of the molding die 152 has fluidity that can enter the concave portion (not shown) of the mold surface 152a.

As the material 83 to be supplied, various known materials which can be used in molding can be used. In the example shown below, an example in which an acrylic-based ionizing radiation-curable resin is supplied from the material supply device 154 will be described. In the ionizing radiation-curable resin, for example, a UV-curable resin which is cured by irradiation with ultraviolet rays (UV) or an EB-curable resin which is cured by irradiation with an electron beam (EB) can be selected.

After that, the resin film 66 as a base material for molding passes through the position facing the curing device 156 in a state where the ionizing radiation-curable resin is filled between the mold surface 152a of the mold 152. At this time, the curing device 156 is irradiated as a resin material. The ionizing radiation of the curing property of the ionizing radiation-curable resin 83 is irradiated onto the ionizing radiation-curable resin 83 through the rough layer 70 and the resin film 66. When the ionizing radiation curable resin 83 is an ultraviolet curable resin, the curing device 156 is formed as an ultraviolet irradiation device such as a high pressure mercury lamp. As a result, the ionizing radiation-curable resin 83 which is filled between the mold surface 152a and the resin film 66 is cured, and is formed of the hardened ionizing radiation-curable resin 83 and includes the unit 稜鏡85 and the land portion 81. The layer 80 is formed on the resin film 66.

Thereafter, as shown in FIG. 12, the resin film 66 is separated by the mold 152, and the unit 稜鏡 85 molded in the concave portion of the mold surface 152a is accompanied by the land portion 81 located between the mold 152 and the resin film 66. The position of the roller 158 on the right in Fig. 12 is pulled apart by the mold 152. Among them, in the molding method as described above, since the land portion 81 is present, it is possible to effectively prevent the molded unit crucible 85 from remaining partially in the concave portion of the mold 152 at the time of demolding.

As described above, while the molding die 152 which is a drum mold is rotated about the central axis CA, the mold surface 152a of the mold 152 is sequentially formed: the resin material 83 having fluidity is formed. The enamel layer 80 is formed by a process of supplying the inside of the mold 152, a process of curing the resin material 83 supplied into the mold 152 in the mold 152, and a process of extracting the cured resin material 83 from the mold 152.

As described above, the base material layer 65 made of the resin film 66 and the side formed on one side of the base material layer 65 are produced. The rough layer 70 and the optical sheet 60 of the enamel layer 80 formed on the other side of the base material layer 65. Further, unlike the above example, the enamel layer 80 may be formed on the resin film 66, and then the rough layer 70 may be formed on the resin film 66.

Next, the operation of the display device 10 formed by the configuration shown above will be described.

First, as shown in FIGS. 1 and 2, the light emitted from the illuminator 25 forming the light source 24 passes through the light incident surface 33 and enters the light guide plate 30. As shown in FIG. 2, the light beams L21 and L22 incident on the light guide plate 30 are on the light-emitting surface 31 and the back surface 32 of the light guide plate 30, and are repeatedly reflected by the difference in refractive index between the material and the air forming the light guide plate 30 due to reflection. The reflection advances in the first direction (light guiding direction) d ₁ that connects the light incident surface 33 of the light guide plate 30 to the opposite surface 34.

The back surface 32 of the light guide plate 30 has an inclined surface 37 that is inclined so as to approach the light-emitting surface 31 as the light-incident surface 33 faces the opposite surface 34. The inclined surface 37 is connected to the stepped surface 38 and the connecting surface 39. The step surface 38 extends in the normal direction _n d of the plate surface of the light guide plate 30. Therefore, most of the light traveling in the light guide plate 30 from the side of the light incident surface 30c toward the side of the opposing surface 30d is in the back surface 32, and is not incident on the step surface 38, but on the inclined surface 37 or the joint surface 39 Make a reflection. Next, when the back surface 32 is reflected on the inclined surface 37, the traveling direction of the light in the cross section shown in FIG. 2 is such that the inclination angle with respect to the plate surface of the light guide plate 30 is increased. That is, when the back surface 32 is reflected by the inclined surface 37, the incident angle of the light toward the light-emitting surface 31 and the back surface 32 becomes small. Therefore, the incident angle of the light traveling in the light guide plate 30 to the light-emitting surface 31 and the back surface 32 is gradually reduced by one or more reflections on the inclined surface 37 in the back surface 32, and is formed so as not to reach the total reflection critical angle. At this time, the light system can be emitted from the light-emitting surface 31 and the back surface 32 of the light guide plate 30. The light beams L21 and L22 emitted from the light-emitting surface 31 are directed toward the optical sheet 60 disposed on the light-emitting side of the light guide plate 30. On the other hand, the light emitted from the rear surface 32 is reflected by the reflection sheet 28 disposed on the back surface of the light guide plate 30, and enters the light guide plate 30 again to advance in the light guide plate 30.

In particular, in the illustrated example, as the incident surface 33 approaches the opposite surface 34 along the light guiding direction, the proportion of the inclined surface 37 in the back surface 32 becomes higher. By this, the amount of light emitted from the light-emitting surface 31 of the light guide plate 30 can be sufficiently ensured in a region separated by the light-incident surface 33 where the amount of emitted light is reduced, and the amount of light emitted along the light-guiding direction can be made uniform.

However, the light-emitting surface 31 of the light guide plate 30 shown in the drawing is constituted by a plurality of unit optical elements 50, and the cross-sectional shape of the main cut surface of each unit optical element 50 is formed symmetrically around the front direction. A pentagonal shape or a shape obtained by chamfering one or more of the pentagon shapes. More specifically, as described above, the light-emitting surface 31 of the light guide plate 30 is formed so as to be inclined with respect to the back surface 32 of the light guide plate 30 (see FIG. 5). The folded surface is formed as inclined surfaces 35 and 36 which are inclined to the opposite sides from each other with respect to the normal direction nd of the light-emitting side surface 41 of the base portion 40. Then, the light that is totally reflected by the inclined surfaces 35 and 36 and travels in the light guide plate 30 and the light that is emitted from the light guide plate 30 through the inclined surfaces 35 and 36 are formed by the inclined surfaces 35 and 36, and the following description is achieved. effect. first First, the action achieved by the light that is totally reflected by the inclined faces 35 and 36 and advanced in the light guide plate 30 will be described.

In FIG. 5, in the main cut surface of the light guide plate, the light paths of the lights L51 and L52 that advance in the light guide plate 30 while being totally reflected on the light-emitting surface 31 and the back surface 32 are present. As described above, the inclined surfaces 35 and 36 that form the light-emitting surface 31 of the light guide plate 30 include two types of surfaces that are inclined to the opposite sides from each other across the normal direction nd of the light-emitting side surface 41 of the base portion 40. Further, the two types of inclined faces 35 and 36 which are inclined to each other on the opposite side are alternately arranged along the second direction d ₂ . Next, as shown in FIG. 5, the light L51 and L52 which are advanced toward the light-emitting surface 31 in the light guide plate 30 and incident on the light-emitting surface 31 are incident on the inclined surfaces 35 and 36 of the two types in most cases. The main cut surface of the light guide plate is inclined on the opposite side to the traveling direction of the light with respect to the normal direction nd of the light exit side surface 41 of the base portion 40.

As a result, as shown in FIG. 5, when the light beams L51 and L52 advancing in the light guide plate 30 are mostly the total reflection of the inclined surfaces 35 and 36 of the light-emitting surface 31, the components along the second direction d ₂ are The reduction is even caused by the main cutting surface, and the traveling direction is directed to the opposite side centering on the front direction nd. As described above, by forming the inclined surfaces 35 and 36 of the light-emitting surface 31 of the light guide plate 30, it is possible to restrict the light that radiates radially at a certain light-emitting point from continuing to expand in the second direction d ₂ as it is. That is, the d 25 direction relative to the first luminous body ₁ has a light source 24 is largely inclined direction and is incident to the light emission within the light guide plate 30 while also limiting movement toward the second direction d _2, toward the first side of the main Direction d ₁ advances. Thereby, the light amount distribution along the second direction d ₂ of the light emitted from the light-emitting surface 31 of the light guide plate 30 can be adjusted by the configuration of the light source 24 (for example, the arrangement of the light-emitting bodies 25) or the output of the light-emitting body 25. .

Next, the action achieved by the light emitted from the light guide plate 30 through the light exit surface 31 will be described. As shown in FIG. 5, the light L51 and L52 emitted from the light guide plate 30 through the light-emitting surface 31 are refracted on the light-emitting side surface of the unit optical element 50 on which the light-emitting surface 31 of the light guide plate 30 is formed. By the refraction, the traveling direction (emission direction) of the lights L51 and L52 which are advanced in the direction in which the front direction nd is inclined on the main cut surface is mainly compared with the traveling direction of the light when passing through the light guide plate 30. It is curved in such a manner that the angle formed by the front direction nd becomes smaller. By the action as described above, the unit optical element 50 is configured to limit the traveling direction of the transmitted light to the front direction nd side with respect to the component of the light in the second direction d ₂ orthogonal to the light guiding direction. In other words, the unit optical element 50 exhibits a condensing action on a component of light in the second direction d ₂ that is orthogonal to the light guiding direction. As described above, the emission angle of the light emitted from the light guide plate 30 is in a plane parallel to the direction in which the unit optical elements 50 of the light guide plate 30 are arranged, and is limited to a narrow angle range centering on the front direction.

As described above, the emission angle of the light emitted from the light guide plate 30 is parallel to the arrangement direction of the unit optical element 50 of the light guide plate 30, and is limited to a narrow angle range centering on the front direction. On the other hand, the emission angle of the light emitted from the light guide plate 30 is advanced in the first direction d ₁ mainly in the light guide plate 30 at this time, as shown in FIG. 2, in the first direction (light guiding direction). The d ₁ is a parallel surface, and is formed as a relatively large exit angle θk from which the phase in the front direction nd is relatively large. Specifically, the emission angle of the first direction component d ₁ of the light emitted from the light guide plate 30 (the angle θk between the first direction component of the emitted light and the normal direction nd of the plate surface of the light guide plate 30 (refer to FIG. 2 ) )) There is a tendency to be within a narrow angle range which is a relatively large angle. For example, as described above, the light guide plate 30 formed by the above-described shape and size can be 65° or more and 80° or less (or even 65° or more in the normal direction nd of the plate surface facing the light guide plate 30. Set the peak brightness in the range of 75° or less.

The light emitted from the light guide plate 30 is incident on the optical sheet 60 thereafter. As described above, the optical sheet 60 has a unit meander 85 that protrudes toward the side of the light guide plate 30 and protrudes from the front end portion 88a. Shown in detail in FIG. 2, the longitudinal direction of the unit 85 Prism system and by the light guiding direction (first direction) as a direction intersecting the D _1, in particular light system in the present embodiment, the guide plate 30 due to the The second direction d ₂ in which the directions are orthogonal is parallel.

As a result, in order to be arranged in the first direction d ₁ of the light source side (the left side of the paper surface in FIG. 2) and 24 of the light emitting through the light guide plate 30 toward the optical sheet 30, L21, L22 based on interconnected through Among the one surface 86 and the second surface 87, the first surface 86 located on one side of the light source 24 side in the first direction d ₁ is incident on the unit 稜鏡 85. 2, the light L21, L22 system located after the _light source form the second surface side opposite to the other side (right side of the paper surface in FIG. 2) in the first direction 1 d 87 for the total reflection Its direction of travel changes.

Next, by the total reflection on the second surface 87 of the unit 稜鏡 85, the main cut surface (the cross section parallel to the first direction (light guiding direction) d ₁ and the front direction nd in the first direction (the cross direction)) The light beams L21 and L22 which are advanced in the direction in which the front direction nd is inclined are curved such that the angle of travel thereof becomes smaller with respect to the front direction nd. As shown by the action of, for the line unit 85 Prism light component d ₁ along a first direction (a light guiding direction), it may be defined in the front direction side nd traveling direction of light transmission. That is, the optical sheet 60 causes a condensing action on the components of the light along the first direction d ₁ .

Here, as described above, the light whose traveling direction is largely changed by the unit 稜鏡 85 of the optical sheet 60 is mainly a component which advances in the first direction d ₁ which is the arrangement direction of the unit 稜鏡 85, and the light guide plate The inclined surfaces 35 and 36 of the unit optical element 50 of 30 are different in composition in which the condensed light advances in the second direction. Therefore, by the optical action of the unit unit 85 of the optical sheet 60, the brightness in the front direction by the unit optical element 50 of the light guide plate 30 is not impaired, and the brightness in the front direction can be improved.

The light system incident on the optical sheet 60 by the light guide plate 30 is diffused in the rough layer 70 to be emitted from the optical sheet 60. By being diffused in the rough layer 70, the defects occurring in the optical sheet 60 or the light guide plate 30 can be made less concealed and concealed. For example, even if a bright spot or a defect occurs due to damage or depression generated in the manufacture of the optical sheet 60 or the light guide plate 30, the defect can be made invisible by the diffusion energy of the rough layer 70. The allowable range for the defects of the reflective sheet 28, the light guide plate 30 or the rough layer 70 can be made by the light diffusing function in the rough layer 70 as shown above. Zooming in, as a result, the yield of the reflective sheet 28, the light guide plate 30, the rough layer 70, and the like can be improved. In addition, the diffusion function of the rough layer 70 can make the angular distribution of the brightness measured on the light-emitting surface 21 of the surface light source device 20 smooth, and the observer can effectively avoid the change of the large brightness when the observation angle is changed. Provide an angular range (viewing angle) that allows proper image observation. Among them, from the viewpoint of imparting an effective concealing effect to the optical sheet, the haze value of the entire optical sheet 60 including the rough layer 70 and the enamel layer 80 is preferably 90% or more and 100% or less, and more preferably 95% or more. More than 100% is better. The haze value is formed into a value measured in accordance with JIS K 7105.

The light emitted from the optical sheet 60 is incident on the lower polarizing plate 14 of the liquid crystal display panel 15. The lower polarizing plate 14 transmits one of the polarized components (P wave in the present embodiment) among the incident light, and absorbs the other polarized component (in the present embodiment, the S wave). The light transmitted through the lower polarizing plate 14 is selectively transmitted through the upper polarizing plate 13 in accordance with the state of application of the electric field to each pixel. As described above, the light from the surface light source device 20 is selectively transmitted by the liquid crystal display panel 15 for each pixel, whereby the observer of the liquid crystal display device 10 can observe the image.

Here, FIG. 13 is an angular distribution of luminance measured on the light-emitting surface 21 of the surface light source device 20. This luminance distribution actually investigates the luminance in each direction in a plane parallel to the two directions of the first direction d ₁ and the front direction nd. The experimental result 1 shown in Fig. 13 is the result of an experiment using a white PET sheet having a diffuse reflection function as the reflective sheet 28. The experimental result 2 shown in Fig. 13 is the result of an experiment using a PET sheet having a silver vapor-deposited film having a specular reflection function (positive reflection function) as the reflective sheet 28. As shown in FIG. 13, even by changing the reflection characteristics of the reflective sheet 28, the luminance characteristics on the light-emitting surface 21 can be adjusted.

However, as already mentioned in the paragraphs of the prior art, when a surface light source device having an optical sheet having a rough layer and a tantalum layer is used as a backlight, when a display panel having a pixel arrangement is illuminated by the back side, it is confirmed that occurrence occurs. A multi-color component is considered to be a granule-like phenomenon called "glare". According to the study by the inventors of the present invention, if the arrangement of the unit 稜鏡 contained in the ruthenium layer is high-definition, that is, if the arrangement pitch of the unit 稜鏡 is narrowed to 10 μm or more and 35 μm or less, the above-described disadvantages are caused. It became more obvious.

On the other hand, in the optical sheet 60 described above, the rough layer 70 includes the second light-diffusing particles 72 and the binder resin 73, and satisfies the following conditions (x) and (related to the second light-diffusing particles 72 and the binder resin 73). y).

(x): the refractive index n ₂ of the second light-diffusing particle 72 of the rough layer 70 is different from the refractive index n _b of the binder resin 73, (y): the average particle diameter d _{2 of} the second light-diffusing particle 72, and The thickness t _{b of the} rough layer 70 at a position that does not straddle the first light diffusion particle 71 and the second light diffusion particle 72 satisfies the following condition (a').

d ₂ <t _b ‧‧‧(a') Next, by satisfying the optical sheets 60 of the conditions (x) and (y), the glare can be effectively made inconspicuous.

By using optics that satisfy the above conditions (x) and (y) Although the detailed reason why the sheet 60 can effectively make the glare inconspicuous is unknown, it is estimated as one of the reasons why the glare is not noticeable. However, the present invention is not limited to the following presumers.

That is, the layer forming the uneven surface generally called a rough layer uses light-diffusing particles having a particle diameter larger than the thickness of the binder resin. Therefore, the light-diffusing particles are in the rough layer and protrude into a convex lens shape.

On the other hand, the unit 稜鏡 of the 稜鏡 layer located on the light incident side of the roughening layer is located on the inclined surface (the first surface 86) on the side closer to the light source in the arrangement direction, and functions as a light incident surface in the arrangement direction. The inclined surface (the second surface 87) on the side away from the light source functions as a reflecting surface. As described above, since the surface on the light source side of the unit 稜鏡 included in the 稜鏡 layer functions differently from the surface on the opposite side, the light-emitting side of the ruthenium layer is estimated as shown in FIG. 9 and FIG. The difference in brightness between the arrangement pitch of the unit 稜鏡 is generated.

Then, by a specific combination of the arrangement pitch of the unit 稜鏡 and the particle diameter of the light-diffusing particles, the unevenness of the light and dark is enlarged to match the pixel by the lens effect due to the convex lenticular portion of the rough layer. The spacing is the same. At this time, granular unevenness is prevented from occurring in the transmission of a specific sub-pixel, and in particular, in color display, coloring of a specific color component can be hindered. The phenomenon as described above is presumed to be apparently formed as a "glare" in which a color component different from the originally intended color is visually recognized as a plurality of particles.

On the other hand, most of the second light-diffusing particles 72 are buried in the binder resin 73 by the above condition (x). In addition, by condition (y) The second light-diffusing particles 72 buried in the binder resin 73 change the traveling direction of light at the interface with the binder resin 73. That is, the rough layer 70 has internal diffusion energy. In the rough layer 70, the second light-diffusing particles 72 are also arranged in the thickness direction, and the surface of the rough layer 70 facing the second light-diffusing particles 72 is gentle due to shrinkage during curing of the binder resin 73. However, it is formed as an uneven surface. Therefore, compared with the conventional rough layer mainly composed of surface diffusion due to the uneven surface, the rough layer 70 described herein is superposed in light diffusion at different positions in the thickness direction, and is particularly homogenized. Light diffusion function. Thereby, the unevenness of the light and dark is reduced, and the glare estimated to be caused by the lens effect is effectively inconspicuous, and even glare can be prevented from occurring.

However, in the rough layer 70 satisfying only the conditions (x) and (y), there is a possibility that the unevenness of the rough surface 70a is too gentle. At this time, a problem that occurs when the optical sheet 60 is overlapped with other members, such as interference fringes, or an infiltrated pattern observed as if liquid is infiltrated, may occur. In order to avoid the occurrence of the above-described problem, the rough layer 70 of the optical sheet 60 described above additionally has the first light-diffusing particles 71 made of a material different from the second light-diffusing particles 72, and satisfies The following condition (z) related to the first light-diffusing particle 71.

(z): the average particle diameter d _{1 of the} first light-diffusing particles 71 and the thickness t _b at a position where the rough layer 70 does not straddle the first light-diffusing particles 71 and the second light-diffusing particles 72 satisfy the following condition (a) ).

t _b <d ₁ ‧‧‧(a")

If the condition (z) is satisfied, shown in detail in FIG. 7, a rough surface 70a roughened layer 70 based position of the first light-diffusing particles 71 is greater than a layer thickness t _b 70 roughened the diameter D ₁ in the present form of An uneven surface of the convex portion is formed corresponding to the first light-diffusing particle 71. With the convex portion, it is possible to effectively solve the problem that occurs when the optical sheet 60 is overlapped with other members.

Further, according to the first light diffusion unit average particle diameter D 71 of _1, the second light diffusing particles 72 of average particle diameter D _2, and D ₁ along a direction 85 Prism arranging pitch P of the relationship, glare The effect of preventing the invisibility and the occurrence of the occurrence of the problem when the optical sheet 60 is overlapped with other members are changed. Therefore, these factors are set such that the glare is not visualized and the problem of disambiguation when overlapping with other members is optimized. That is, the unit 85 Prism arranging pitch P corresponding to the selected first light diffusion average particle size d 71 of the _second light-diffusing particles 72 of average particle diameter D _2, whereby the unit can accompanying Prism The glare which is a problem of high definition of the arrangement pitch P of 85 and which is a problem is effectively not noticeable. Specifically, it is preferable that the above-described condition (s1) is satisfied, and the condition (s2) is satisfied to be more preferable. Further, it was found that satisfying the following condition (s3) is also extremely effective in visualizing glare.

d ₂ <t _b <d ₁ <P/2‧‧‧(s1)

d ₂ <t _b <d ₁ <P/3‧‧‧(s2)

d ₂ <t _b <d ₁ <W _b2 ‧‧‧(s3)

As shown in the description of FIG. 2, when the light source 24 is disposed only on one of the side faces 33 of the light guide plate 30, the traveling directions of the lights L21 and L22 emitted from the light exit surface 31 of the light guide plate 30 are greatly increased from the front direction nd. tilt. As a result, the unit Prism 85 lines in its arranging direction d of the first surface in _a close-source-side 24 of the 86 functions as a light incident surface, located in the array direction d ₁ of the second surface remote from the side of the light source 24 of the 87 as the reflection Face function. Next, the second surface 87 totally reflects the light source lights L21 and L22 and directs the traveling directions of the lights L21 and L22 toward the substantially front direction nd. That is, a region in which the second surface 87 is projected in the front direction nd is observed as a bright portion. On the other hand, with respect to the first surface 86, the amount of light emitted from the region facing the front direction nd is greatly reduced. That is, a region in which the first surface 86 is projected in the front direction nd is observed as a dark portion. As a result, as shown in FIG. 9 and FIG. 10, the light-emitting side of the enamel layer 80 is estimated to be uneven in brightness at the arrangement pitch P of the unit 稜鏡85. Then, as a result of careful study by the inventors of the present invention, if one light diffusing particle is disposed so as to cover the entire area of the region in which the second surface 87 is projected in the front direction nd, the lens effect of the light diffusing particle is remarkable. Occurred, it was estimated that glare occurred. In this estimation, it is assumed that light from one bright portion is easily observed by the lens effect of one light-diffusing particle.

On the other hand, when the above condition (s1) is satisfied, the first light-diffusing particles 71 are disposed so as to cover the entire area of the region in which the first surface 87 is projected in the front direction, in other words, it is possible to effectively avoid the use of one The light diffusing particles 71 adjust the optical path of all of the light collected on one second inclined surface. When the above condition (s2) is satisfied, it is possible to substantially prevent the first light-diffusing particles 71 from being disposed so as to cover the entire area of the region in which the first surface 87 is projected in the front direction. Further, when the above condition (s3) is satisfied, it is possible to prevent the first light-diffusing particles 71 from being disposed so as to cover the entire area of the region in which the first surface 87 is projected in the front direction. As a result, glare can be extremely effectively avoided. That is, the case based inventors discovered Prism unit 85 corresponding to the arranging pitch P, to adjust the average particle diameter of the first light diffusion average particle size d 71 of the _second light-diffusing particles 72 is D _2, in that the glare Effectively unobvious aspects are extremely effective.

In addition, when the arrangement pitch P of the unit 稜鏡85 is high-definition to 10 μm or more and 35 μm or less, both of the following relationship (s4) and the relationship (s5) are satisfied, and the optical sheet 60 can effectively make the glare ineffective. The quality required in the liquid crystal display device 10 is sufficiently ensured.

t _b +1[ μ m]≦d ₁ [ μ m]≦10[ μ m]‧‧‧(s4)

0.78[ μ m]≦d ₂ [ μ m]‧‧‧(s5)

Further, in the example shown in FIGS. 9 and 10, the second surface 87 on which the bright portion is formed is formed as a folded surface. The second surface 87 includes portions (element surfaces) 87a, 87b, and 87c having mutually different reflecting surface angles θb. Regarding the enamel layer 80 having the unit 稜鏡85 as described above, depending on the light-emitting characteristics of the light-emitting surface 31 from the light guide plate 30, any one of the portions (element surfaces) 87a, 87b, and 87c that form the folded surface is used. There is the possibility of forming a brighter brighter part. That is, if the light emitted from the light-emitting surface 31 of the light guide plate 30 is directed in a specific direction, the light that is supposed to be reflected by any of the portions 87a, 87b, and 87c is brightly observed in the front direction. Then, the reflected light of each of the portions (element surfaces) 87a, 87b, and 87c may be clearly observed brightly due to the lens effect of the second light-diffusing particles 72. In order to avoid the undesirable situation as shown above, it is preferable to satisfy the following condition (s6). In the condition (s6), Wb _2pmin forms the length Wb _2pa of each portion (each element surface) 87a, 87b, 87c of one surface included in the folded surface of the second surface 87 along the arrangement direction d ₁ of the unit 稜鏡. The minimum value among Wb _2pb and Wb _2pc , in other words, is projected in the direction orthogonal to the arrangement direction d ₁ of the unit ( (in the illustrated example, the front direction nd) to form the second surface 87 The minimum value among the lengths Wb _2pa , Wb _{2pb , and} Wb _2pc of the respective portions (each element surface) 87a, 87b, and 87c included in the folded surface.

After _{d 2 <Wb 2pmin ‧‧‧ (s6} ) If the condition (S6) is satisfied, the second light diffusion particles are prevented from 72 to cover the surface of any element off of the surface of the second surface 87 included in the front direction to be projected The global way of the zone is configured. The inventor of the present invention confirmed that the condition (s6) is satisfied, and it is confirmed that glare can be extremely effectively prevented.

As described above, according to the present embodiment, the rough layer 70 of the optical sheet 60 includes the first light-diffusing particles 71, the second light-diffusing particles 72, and the binder resin 73. 2 refractive index n ₂ of the light diffusing particles 73 and the resin binder _B and the second refractive index n 1 the refractive index of the light-diffusing particles 71 is different from the refractive index n is _1. Subsequently, the first light diffusion average particle diameter D 71 of _1, the second light diffusing particles 72 of average particle diameter D _2, and the roughened layer 70 does not cross the first light diffusing particles 71 and the second light diffusion particle 72 The thickness t _{b of the} position satisfies the following relationship.

d ₂ <t _b <d ₁ can effectively make the glare inconspicuous by the optical sheet 60 as shown above.

However, various modifications can be made to the above embodiment. Take Next, an example of the deformation will be described with reference to the drawings. In the following description, the same reference numerals are used for the same parts as those of the above-described embodiment, and the same reference numerals are used for the parts corresponding to the above-described embodiments, and the overlapping description will be omitted.

First, in the above embodiment, an example of the unit 稜鏡 85 of the optical sheet 60 will be described. However, the present invention is not limited to this example, and various modifications are possible. For example, the plurality of units 85 included in the layer 80 may have mutually different configurations. Further, the cross-sectional shape of the main cut surface of the unit cymbal 85 is not limited to the specific example shown in FIG. 7, and may be, for example, a triangular shape, a pentagon shape, or a hexagonal shape.

Further, in the above-described embodiment, an example of the unit optical element 50 of the light guide plate 30 will be described, but the present invention is not limited to this example, and various modifications are possible. For example, the plurality of unit optical elements 50 included in the light guide plate 30 may have mutually different configurations. Further, the cross-sectional shape of the main cut surface of the unit optical element 50 is not limited to the specific example shown in FIG. 5, and may be, for example, a triangular shape or a semicircular shape.

Further, in the above-described embodiment, the configuration is such that the light incident on the light guide plate 30 is emitted from the light guide plate 30, and the back surface 32 of the light guide plate 30 has an inclined surface 37. However, instead of or in addition to the inclined surface 37, the light guide plate 30 may be formed to be emitted from the light guide plate 30 to have another configuration (other light extraction configuration). In the configuration in which the light-diffusing component is dispersed in the light guide plate 30, at least one of the light-emitting surface 31 and the back surface 30b is formed into a rough surface, and a white scattering layer is provided on the back surface 32. The composition of the pattern, etc.

Further, in the above embodiment, only one of the side faces of the light guide plate 30 is formed to constitute the light incident surface 33, but the invention is not limited thereto. For example, in the modification shown in FIG. 14, the light source 24 is also disposed on the opposite surface 34 of the light guide plate 30, and the opposite surface 34 is also formed as a light incident surface. In the modification shown in FIG. 14, the edge illumination type surface light source device in which the light source 24 is disposed on both surfaces of the opposite surfaces 33 and 34 of the light guide plate is symmetrically represented by the normal direction nd. The inclined faces 37a and 37b of the two types of inclined are formed with the back surface 32 of the light guide plate 30. Further, in this modification, the unit 稜鏡 85 of the optical sheet 60 is a main cut surface that is orthogonal to the longitudinal direction thereof, and has a symmetrical eccentric equilateral triangle shape. Alternatively, although not shown in the drawings, the shape of the main cut surface of the optical sheet 60 may be formed into a pentagon shape in which both slopes have the first surface and the second surface.

Further, in the above embodiment, the light from the light source 24 is incident on the optical sheet 60 via the light guide plate 30, but the invention is not limited thereto. As shown in FIG. 15, the light source 24 can also project light incident directly onto the optical sheet 60.

Further, although not shown, the surface light source device 20 may be disposed between the light-emitting surface of the optical sheet 60 (the light-emitting surface 21 of the surface light source device in FIG. 1) and the lower polarizing plate 14 of the liquid crystal display panel 15. A reflective polarizer (also known as a polarizing separation film). In this form, among the light emitted from the optical sheet 60, only the specific polarizing component is transmitted, and the polarizing component orthogonal to the specific polarizing component is not absorbed and reflected. The polarized component reflected by the reflective polarizer is reflected by the rough layer 70, the reflective sheet 28, and the like, and the polarized light is removed (including a specific polarizing component and a polarizing component orthogonal to the specific polarizing component). After the state), it is incident on the reflective polarizer again. Therefore, the polarization component converted into the specific polarization component among the light incident again is transmitted through the reflection type polarization, and the polarization component orthogonal to the specific polarization component is reflected again. In the following, by repeating the same process, 70 to 80% of the light emitted from the optical sheet 60 is formed to be light source light that is the specific polarization component, and is emitted. Therefore, by emitting the polarization direction of the specific polarization component (transmission axis component) of the reflective type polarizer and the transmission axis direction of the lower polarizing plate 14 of the liquid crystal display panel 15, the emitted light system from the surface light source device 20 can be entirely The liquid crystal display panel 15 is formed in an image. Therefore, even if the light energy input by the light source 24 is the same, the image formation with higher brightness can be performed as compared with the case where the reflection type polarizer is not disposed, and the energy utilization efficiency of the light source 24 (even its power source) is also Upgrade.

The form of the surface light source device using such a reflective type of polarizer is known from the Japanese Patent Publication No. Hei 9-506985, Japanese Patent No. 3,347,701, and the like. However, as a result of careful study by the inventors of the present invention, when the optical sheet 60 of the present invention is applied to the surface light source device of this type, it is found that the brightness of the front direction of the polarized light obtained by the light-emitting surface 21 of the surface light source device depends on the unit rib. The shape of the mirror 85 was found to maximize the front luminance of the polarized light obtained by optimizing the shape.

The following description will be mainly made with reference to Fig. 16 (for the drawing of the sample 1 to be described later). Regarding the shape of the main cut surface of the unit 稜鏡85, The factor which influences the shape of the brightness of the front direction of the polarized ray obtained by the light-emitting surface 21 of the surface light source device is the following three.

(1) The ratio of the height (Hb/Wb) of the height Hb to the width Wb of the base (in the form shown in Figs. 7, 16, and 17 coincides with the pitch P).

(2) The ratio (z/Wb) of the displacement amount z of the vertical bisector of the bottom edge of the position of the front end portion 88a to the width Wb of the base. Here, as shown in FIG. 16, the displacement amount z is measured in a direction parallel to the bottom side AC, and the front end portion 88a (which coincides with the vertex B in the same figure) and the vertical 2 bisector of the bottom side AC are measured. The value after the distance between. Here, in the figure, M is the midpoint of the bottom side.

(3) The ratio of the full circumference C _ABDC (refer to FIG. 17 ) of the unit DC 85 in the main cut surface to the full circumference C _ABC of the inscribed triangle ABC (C _ABDC /C _ABC ) and the unit rib The ratio of the full circumference C _ABDC of the shape ABDC of the mirror 85 to the width Wb of the bottom side (C _ABDC /Wb).

Next, in order to maximize the luminance in the front direction of the polarized light obtained by the light-emitting surface 21 of the light source device, it is found that it is preferable to form the factor of the above three shapes into the following range: 0.7≦Hb/Wb≦0.9

| z/Wb |≦0.06

1.06≦C _ABDC /C _ABC ≦1.21

2.70≦C _ABDC /Wb≦3.00.

In the above, a few modifications of the above-described embodiment are described above, but it is needless to say that a plurality of modifications can be appropriately combined.

[Examples]

The present invention will be described in more detail below by way of examples, but the invention is not limited thereto.

The optical sheets of the samples 1 to 4 were produced as described below.

<sample 1>

Sample 1 was formed into an optical sheet having a base layer, a rough layer, and a ruthenium layer. The rough layer and the ruthenium layer were formed on the base material layer by the method described with reference to Figs. 11 and 12 .

[Substrate layer]

For the base material layer, a PET film (A4300 manufactured by Toyobo Co., Ltd.) having a thickness of 125 μm was used.

[稜鏡层]

On one of the base material layers, an ultraviolet curable resin (DIC Co., Ltd. RC25-750) was used to form a tantalum layer having a plurality of unit turns having a cross-sectional shape in the main cut surface and having the shape shown in FIG. . The arrangement pitch P of the unit ( (the case of this sample is the same as the width Wb of the bottom side) is formed to be 18 μm.

[rough layer]

The rough layer is formed to have a layer of a binder resin, first light-diffusing particles, and second light-diffusing particles. The rough layer is produced using the composition of the following. The average particle diameter of the light-diffusing particles was determined by a COULTER Multisizer. The thickness t _b of the rough layer at a position that does not straddle the first light-diffusing particles and the second light-diffusing particles is 3 μm.

(composition)

First and second light-diffusing particles/translucent resin (mass ratio): 7/100

First light diffusing particle / second light diffusing particle (mass ratio): 1.5/8.5

Translucent resin: pentaerythritol triacrylate (refractive index 1.51)

First light-diffusing particle: made of acrylic resin, having an average particle diameter of 5 μm (refractive index of 1.49)

Second light-diffusing particle: made of styrene resin, average particle diameter 2 μm (refractive index 1.59)

<sample 2>

Sample 2 was formed into an optical sheet having a base material layer, a rough layer, and a ruthenium layer in the same manner as Sample 1. The rough layer and the ruthenium layer were produced on the base material layer in the same manner as the sample 1 by the method described with reference to Figs. 11 and 12 .

[Substrate layer]

The substrate layer was the same as the sample 1, and a PET having a thickness of 125 μm was used. Film (A4300, manufactured by Toyobo Co., Ltd.).

[稜鏡层]

The ruthenium layer was produced in the same manner as in Sample 1.

[rough layer]

The rough layer is formed to have a layer of a binder resin and a second light-diffusing particle. On the other hand, the rough layer does not include the first light-diffusing particles. The rough layer is produced using the composition of the following. The average particle diameter of the light-diffusing particles was determined by a COULTER Multisizer. The thickness t _b of the rough layer at a position that does not straddle the first light-diffusing particles is 3 μm.

(composition)

Second light-diffusing particle / light-transmitting resin (mass ratio): 7/100

Translucent resin: pentaerythritol triacrylate (refractive index 1.51)

Second light-diffusing particle: made of styrene resin, average particle diameter 2 μm (refractive index 1.59)

<sample 3>

Sample 3 was formed into an optical sheet having a base material layer, a rough layer, and a ruthenium layer in the same manner as Sample 1. The rough layer and the ruthenium layer were produced in the same manner as the sample 1 by the method described with reference to FIGS. 11 and 12 . On the substrate layer.

[Substrate layer]

In the same manner as in Sample 1, a PET film (A4300 manufactured by Toyobo Co., Ltd.) having a thickness of 125 μm was used.

[稜鏡层]

The ruthenium layer was produced in the same manner as in Sample 1.

[rough layer]

The rough layer is formed to have a layer of a binder resin and first light-diffusing particles. On the other hand, the rough layer does not include the second light-diffusing particles. The rough layer is produced using the composition of the following. The average particle diameter of the light-diffusing particles is determined by a laser diffraction type particle size distribution measurement method. The thickness t _b of the rough layer at a position that does not straddle the first light-diffusing particles is 3 μm.

(composition)

First light-diffusing particle / light-transmitting resin (mass ratio): 10/100

Translucent resin: pentaerythritol triacrylate (refractive index 1.51)

First light-diffusing particle: made of acrylic resin, having an average particle diameter of 5 μm (refractive index of 1.49)

<sample 4>

The sample 4 was formed into an optical sheet having a base material layer and a ruthenium layer. On the other hand, the optical sheet of Sample 4 did not contain a rough layer. The ruthenium layer was produced on the base material layer in the same manner as the sample 1 by the method described with reference to FIG.

[Substrate layer]

In the same manner as in Sample 1, a PET film (A4300 manufactured by Toyobo Co., Ltd.) having a thickness of 125 μm was used.

[稜鏡层]

The ruthenium layer was produced in the same manner as in Sample 1.

<evaluation>

In the optical sheets of the samples 1 to 4, the display device having the configuration shown in Fig. 1 was produced, and the presence or absence of glare, the appearance of the pattern due to overlap with the display panel, and the like, and the concealability were confirmed. The components other than the optical sheet of the display device are incorporated in a commercially available display device. The confirmation results are shown in Table 1. In the "glare" field in Table 1, "○" is attached to the sample in which glare is not observed, and "x" is attached to the sample in which glare is observed. In the field of "sticking" in Table 1, "○" is attached to a sample in which a defect such as a pattern that overlaps with the display panel does not occur, and a defect such as a pattern overlapping with the display panel occurs. situation The sample is marked with "X". In the "concealment" field in Table 1, "○" is attached to a sample in which no bright spots or defects are observed, and "X" is marked on a sample in which a bright spot or a defect is observed.

60‧‧‧ optical sheets

65‧‧‧Substrate layer

70‧‧‧Rough layer

70a‧‧‧Rough surface

71‧‧‧1st light diffusing particle

72‧‧‧2nd light diffusing particles

73‧‧‧Binder resin

80‧‧‧稜鏡

80a‧‧‧稜鏡

81‧‧‧ Land Department

85‧‧‧Units

86‧‧‧1st

87‧‧‧2nd

87a‧‧‧Part 1 (1st element)

87b‧‧‧Part 2 (Part 2)

88a‧‧‧ front end

88b‧‧‧ base end

d ₁ ‧‧‧1st direction (light guiding direction)

Hb‧‧‧ Height

L72, L72‧‧‧ light

t _b ‧‧‧thickness

Wb‧‧‧ wide format

Wb ₂ ‧‧‧ length

Θb‧‧‧reflecting surface angle

Θc‧‧‧ angle

Claims (10)

An optical sheet comprising a pair of optical sheets facing each other, comprising: a sheet-like base material layer; comprising first light-diffusing particles, second light-diffusing particles, and a binder resin; a rough layer on one side of the base material layer; and a plurality of unit turns including a plurality of units arranged in a direction, and each of the plurality of unit turns extending in a line intersecting the one direction is provided in the foregoing One of the pair of surfaces on the other side of the base material layer is formed as a rough surface due to the rough layer, and the other one of the pair of surfaces is formed by the above-mentioned layer In the surface of the second light-diffusing particle, the refractive index of the second light-diffusing particle is different from the refractive index of the binder resin and the refractive index of the first light-diffusing particle, and the average of the first light-diffusing particles The particle diameter d ₁ , the average particle diameter d _{2 of} the second light-diffusing particle, and the thickness t _{b of the} rough layer at a position not spanning the first light-diffusing particle and the second light-diffusing particle satisfy the following relationship: d ₂ <t _b <d ₁ . The optical sheet of claim 1, wherein the average particle diameter d ₁ of the first light-diffusing particles, the average particle diameter d _{2 of} the second light-diffusing particles, and the rough layer do not straddle the first light The thickness t _b of the position of the diffusion particle and the second light-diffusing particle, and the arrangement pitch P of the complex unit 沿着 along the one direction satisfy the following relationship: d ₂ [ μ m] < t _b [ μ m] < d ₁ [ μ m] < P / 2 [ μ m]. The optical sheet of claim 1, wherein each unit includes: a first surface facing one side of the one direction and a second surface facing the other side of the one direction, the first light The average particle diameter d _{1 of the} diffusing particles, the average particle diameter d _{2 of} the second light diffusing particles, and the thickness t _{b of the} rough layer at a position that does not straddle the first light diffusing particles and the second light diffusing particles, and The length Wb _{2 of} the second surface along the one direction satisfies the following relationship: d ₂ [ μ m ] < t _b [ μ m ] < d ₁ [ μ m] < Wb ₂ [ μ m]. The optical sheet of claim 1, wherein each unit includes: a first surface facing one side of the one direction and a second surface facing the other side of the one direction, the second surface The main cut surface of the optical sheet parallel to both the one direction and the normal direction of the base material layer includes an inclination angle of the one direction to be the most separated unit from the base material layer. The side of the front end portion, the plurality of element faces disposed so as to gradually increase toward the side of the base end portion of the unit crucible of the base material layer, and the average particle diameter d _{2 of} the second light diffusing particles and one The minimum value Wb _2pmin among the lengths of the plurality of element faces included in the unit direction in the one direction satisfies the following relationship: d ₂ [ μ m] < Wb _2pmin [ μ m]. The optical sheet of the first aspect of the invention, wherein the refractive index n ₁ of the first light-diffusing particle, the refractive index n _{2 of} the second light-diffusing particle, and the refractive index n _{b of the} binder resin satisfy the following relationship :n ₁ ≦n _b <n ₂ . The optical sheet of the first aspect of the invention, wherein the number N ₁ of the first light-diffusing particles and the number N _{2 of} the second light-diffusing particles contained in the rough layer are satisfied. The following relationship: 50 ≦ (N ₂ /N ₁ ) ≦ 200. The optical sheet of claim 1, wherein the haze value is 90% or more. The optical sheet of claim 1, wherein the optical sheet is used in combination with a display panel, and the rough layer is located on the display panel side of the base material layer. A surface light source device comprising: a light guide plate; a light source disposed on a side of the light guide plate; and the first layer of the patent layer is disposed to face the surface of the light guide plate The optical sheet of any of item 8. A display device comprising: the surface light source device according to claim 9; and a display panel disposed to face the surface light source device.