JP2014056042A - Optical sheet, surface light source device, transmissive display device, and production method of optical sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical sheet which suppresses occurrence of optical adhesion, can improve display failure and achieves bright and good illumination, and to provide a surface light source device and a transmissive display device including the optical sheet, and a production method of the optical sheet.SOLUTION: An optical sheet 14 to be disposed on a light-exiting side of a light guide plate 13 in a surface light source device 10 has a roughened surface having a fine rugged pattern on a light-entering surface thereof opposing to the light guide plate 13; and the film is configured to have an average interval Sm of 250 μm or more and 650 μm or less of a rugged pattern in at least a peripheral region of the light-entering surface. The optical sheet 14 is prepared by forming a roughened state of the light-entering surface and then roughening by polishing in a predetermined direction by use of a polishing tool.

Description

  The present invention relates to an optical sheet, a surface light source device including the optical sheet, a transmissive display device, and an optical sheet manufacturing method.

2. Description of the Related Art Conventionally, there is a remarkable spread of transmissive display devices that display images by illuminating a transmissive display unit such as an LCD panel from the back side with a surface light source device. As the surface light source device used for this transmissive display device, an edge light type, a direct type and the like are known.
The edge light type surface light source device is a form in which a light source is disposed at a position facing at least one end surface of the light guide plate, and compared to a direct type surface light source device in which a light source is disposed on the back side of various optical sheets, There is an advantage that the thickness of the surface light source device can be reduced. Therefore, a liquid crystal display device using an edge light type surface light source device is used for various purposes, and development relating to its optical characteristics and the like has been actively performed (for example, Patent Document 1).

JP 2012-113891 A

In such an edge-light type surface light source device, in order to further reduce the thickness, optical members such as a light guide plate and various optical sheets arranged on the light output side thereof are subjected to pressure in the thickness direction at the peripheral portion thereof. When the structure is held over the optical member, there is a problem that the optical members come into contact with each other and are in close contact (optical contact).
Such optical contact (also referred to as WET-OUT) is particularly likely to occur between a light guide plate having a smooth light exit surface and an optical sheet disposed on the light exit side, and the light guide plate of the optical sheet. This occurs remarkably when the side surface is a smooth surface. Also, this optical contact is likely to occur in the vicinity of the peripheral edge where pressure is applied, and the portion where the optical contact is generated is observed as a spot-like light / dark unevenness that is wet with indeterminate water, or a rainbow-like unevenness due to interference. Display defects such as color unevenness occur, which hinders visual recognition of good images.
Patent Document 1 does not disclose any measures against such optical contact and display failure caused by the optical contact.

  An object of the present invention is to provide an optical sheet that can suppress the occurrence of optical adhesion, improve display defects, and can perform bright and good illumination, a surface light source device including the optical sheet, a transmissive display device, and an optical sheet manufacturing method. It is to be.

The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected and demonstrated, it is not limited to this.
The invention according to claim 1 is an optical sheet disposed on the light output side of the light guide plate in the surface light source device, wherein the first surface (14a) facing the light guide plate is rough and has at least the first surface. The peripheral edge (A) of the surface of No. 1 is an optical sheet (14) characterized in that the average interval Sm between the irregularities is 250 μm or more and 650 μm or less.
According to a second aspect of the present invention, in the optical sheet according to the first aspect, a fine hairline shape is formed at least on the peripheral edge (A) of the first surface (14a), and the Sm value is It is an optical sheet (14) characterized by being a value in the direction orthogonal to the longitudinal direction of a fine hairline shape.
According to a third aspect of the present invention, in the optical sheet according to the first or second aspect, the second surface (14b) facing the first surface (14a) has a plurality of unit optical shapes (141). An optical sheet (14) characterized by being arranged.

The invention of claim 4 includes a light source part (12A, 12B) that emits light, a light incident surface (13a, 13b) on which light from the light source part is incident, and a light exit surface (13c) from which light is emitted. A surface light source device comprising: a light guide plate (13); and the optical sheet (14) according to any one of claims 1 to 3 disposed on a light output side of the light guide plate, The surface light source device (10) is characterized in that the light exit surface of the light guide plate is planar and substantially smooth.
According to a fifth aspect of the present invention, in the surface light source device according to the fourth aspect of the present invention, at least the optical sheet (14) and the light guide plate (13) are pressed and held by applying pressure in the thickness direction to the peripheral edge thereof. The surface light source device (10) characterized by the above.
The invention of claim 6 is a transmissive display comprising the surface light source device (10) according to claim 4 or 5, and a transmissive display unit (11) illuminated from the back side by the surface light source device. Device (1).

Invention of Claim 7 is a manufacturing method of the optical sheet (14) of any one of Claim 1 to Claim 3, Comprising: The said 1st surface (14a) which is rough surface shape is provided. A molding step for molding the optical sheet; and a roughening step for expressing the peripheral portion (A) of the first surface. In the roughening step, the peripheral portion is formed by a non-woven fabric for polishing (32). The optical sheet manufacturing method is characterized in that polishing is performed in a predetermined direction, and an average interval Sm between the irregularities of the peripheral portion is set to 250 μm or more and 650 μm or less.
The invention of claim 8 is the method for producing an optical sheet according to claim 7, wherein the count of the nonwoven fabric (32) is # 400 to # 600, and the first surface is applied in the roughening step. The load per unit area is 0.22 g / mm ² or more and 0.55 g / mm ² .

  According to the present invention, an optical sheet that can suppress the occurrence of optical adhesion, improve display defects, and can perform bright and favorable illumination, a surface light source device including the optical sheet, a transmissive display device, and an optical sheet manufacturing method are provided. can do.

It is a figure explaining the structure of the transmissive display apparatus 1 of embodiment. It is a figure explaining the unit lens 141 of the optical sheet 14 of embodiment. It is a figure explaining the light-incidence surface 14a of the optical sheet 14 of embodiment. It is a figure explaining an example of the manufacturing method of the optical sheet 14 of embodiment. It is a figure explaining the holding mechanism of the light-guide plate 13 grade | etc., And LCD panel 11 of the transmissive display apparatus 1 of embodiment.

Embodiments of the present invention will be described below with reference to the drawings. In addition, each figure shown below including FIG. 1 is the figure shown typically, and the magnitude | size and shape of each part are exaggerated suitably for easy understanding.
Further, in the following description, terms such as plate and sheet are used, but these are generally used in the order of thickness in the order of plate, sheet, and film as the general usage. It is used in the book as well. However, there is no technical meaning in such proper use, so these terms can be replaced as appropriate.
Furthermore, numerical values such as dimensions and material names of each member described in the present specification are examples of the embodiment, and the present invention is not limited thereto, and may be appropriately selected and used.
Furthermore, in the present specification, terms specifying shape and geometric conditions, for example, terms such as parallel and orthogonal, have the same optical function in addition to being strictly meant, and are parallel and orthogonal. It also includes a state having an error that can be regarded as an error.

(Embodiment)
FIG. 1 is a diagram illustrating the configuration of a transmissive display device 1 according to this embodiment.
The transmissive display device 1 includes an LCD (Liquid Crystal Display) panel 11 and a surface light source device 10. The transmissive display device 1 illuminates the LCD panel 11 with the surface light source device 10 from the back side, and displays the image information formed on the LCD panel 11 so as to be observable. The transmissive display device 1 is used as, for example, a liquid crystal television.
In addition, although description etc. are abbreviate | omitted, the transmission type | mold display apparatus 1 is equipped with the normal apparatus required in order to operate | move as a video display apparatus besides this.

In the following drawings including FIG. 1 and the following description, in order to facilitate understanding, the screen of the transmissive display device 1 (the surface on the most observer side of the LCD panel 11) in the usage state of the transmissive display device 1. The two directions parallel to and perpendicular to the display surface 11a) are the X direction (X1-X2 direction) and the Y direction (Y1-Y2 direction), and the direction orthogonal to the screen of the transmissive display device 1 is the Z direction. (Z1-Z2 direction). In the Z direction, the Z1 side is the back side, and the Z2 side is the observer side.
The “front direction” of the transmissive display device 1 of the present embodiment is the normal direction of the display surface 11a and is parallel to the Z direction. Further, this “front direction” is assumed to coincide with a normal direction to a sheet surface such as an optical sheet 14 to be described later or a plate surface (light exit surface 13 c) of the light guide plate 13.
The sheet surface (plate surface) indicates the surface in the planar direction of the sheet when viewed as the entire sheet (plate) in each sheet member (plate material). The same definition is used in the claims.

The LCD panel 11 is a transmissive display unit that is formed of a transmissive liquid crystal display element and forms video information on its display surface.
The LCD panel 11 of the present embodiment has a substantially flat plate shape, and the outer shape of the LCD panel 11 and the display surface 11a are rectangular when viewed from the Z direction. The LCD panel 11 has two opposite sides parallel to the X direction and two opposite sides parallel to the Y direction when viewed from the Z direction.

The surface light source device 10 is an edge light type surface light source device (backlight) including light source units 12A and 12B, a light guide plate 13, an optical sheet 14, a prism sheet 15, a polarization selective reflection sheet 16, a reflection sheet 17, and the like.
The light source units 12A and 12B are portions that emit light that illuminates the LCD panel 11. The light source unit 12A of the present embodiment is provided at a position facing the light incident surface 13a which is one end surface (Y1 side) in the Y direction of the light guide plate 13, and the light source unit 12B is the other of the light guide plate 13 in the Y direction. It is provided at a position facing the light incident surface 13b which is the end surface on the (Y2 side). Each of the light source units 12A and 12B is formed by arranging a plurality of point light sources 121 at a predetermined interval along the X direction.

The point light source 121 of this embodiment uses an LED (Light Emitting Diode) light source. The light source unit 12 is not limited to the above-described point light source, and may be a linear light source such as a cold cathode tube, or may have a form in which a light source is disposed on an end surface of a light guide extending in the X direction. Further, from the viewpoint of improving the utilization efficiency of light emitted from the light source unit 12, a not-shown reflecting plate or the like may be provided so as to cover the outside of the light source unit 12.
Moreover, in this embodiment, although the surface light source device 10 showed the form provided with light source part 12A, 12B, according to screen size, a light source type, etc., it is provided only with the light source part 12A, for example, The light source unit 12B may be a surface light source device that is not arranged (so-called single lamp type).

The light guide plate 13 is a substantially flat member that guides light.
The light guide plate 13 has light incident surfaces 13a and 13b, a light exit surface 13c, and a back surface 13d.
The light incident surfaces 13a and 13b are located at both ends in the Y direction (Y1 side, Y2 side) of the light guide plate 13 and extend in the X direction when viewed from the normal direction (Z direction) of the plate surface of the light guide plate 13. Exist. The light incident surfaces 13a and 13b are parallel to the X direction and the Z direction, and are orthogonal to the Y direction.
The light exit surface 13c is a surface from which light is emitted, and has a smooth surface shape (including a state that can be regarded as a substantially smooth surface shape).
The back surface 13d is a surface facing the light exit surface 13c in the Z direction. A dot-like diffusion pattern is appropriately formed on the back surface 13d by printing or the like.
The plate surface of the light guide plate 13 is parallel to the XY plane, and the light output surface 13c and the back surface 13d of the present embodiment are surfaces parallel to the plate surface.
The light guide plate 13 allows light from the light source portions 12A and 12B to be incident from the light incident surfaces 13a and 13b and totally reflected by the light exit surface 13c and the back surface 13d, while the light incident surfaces 13a and 13b face each other. The light is mainly guided in the Y direction and appropriately emitted from the light exit surface 13c to the optical sheet 14 side (Z2 side).

The light guide plate 13 of this embodiment can be formed by, for example, extrusion molding or injection molding of a thermoplastic resin.
Examples of the thermoplastic resin used for the light guide plate 13 include acrylic resins, PC (polycarbonate) resins, COP (cycloolefin polymer) resins, acrylonitrile resins, and polyolefin resins. In addition, not only the above-mentioned material but glass etc. may be used, for example.

FIG. 2 is a diagram illustrating the unit lens 141 of the optical sheet 14 according to the present embodiment. In FIG. 2, a part of a cross section parallel to the XZ plane of the optical sheet 14 is shown enlarged.
The optical sheet 14 is disposed on the light output side (Z2 side) of the light guide plate 13 and has an action of controlling the traveling direction of light emitted from the light output surface 13 c of the light guide plate 13.
As shown in FIGS. 1 and 2, the optical sheet 14 has a plurality of unit lenses 141 arranged on the light exit surface 14b on the LCD panel 11 side (light exit side, Z2 side). Further, on the light incident surface 14a of the optical sheet 14 on the light guide plate 13 side (light incident side, Z1 side), a fine uneven shape is formed to be a mat surface (rough surface).
As shown in FIGS. 1 and 2, the unit lens 141 has a columnar shape that is convex on the LCD panel 11 side (light emission side, Z2 side), and a plurality of unit lenses 141 are arranged in the X direction with the Y direction as the longitudinal direction (ridge line direction). Has been. The unit lens 141 is not limited to this, and the unit lens 141 may be arranged in the Y direction with the longitudinal direction being the X direction.

As shown in FIG. 2, the cross-sectional shape of the unit lens 141 in a cross section parallel to the arrangement direction of the unit lenses 141 and the thickness direction of the optical sheet 14 (cross section parallel to the XZ plane) is such that the major axis is the sheet surface of the optical sheet 14. It is a partial shape of an elliptical shape orthogonal to
The unit lens 141 is not limited to this, and the cross-sectional shape thereof may be a partial shape of a circle or the like, or a shape formed by combining a plurality of types of ellipses and circles. Further, the unit lens 141 may have an isosceles triangle shape in cross section, an isosceles triangle shape whose top is formed by a curved surface, or the like.

In the cross section shown in FIG. 2, the arrangement pitch of the unit lenses 141 is P1, and the lens height is H1 (dimension from the apex 141t of the unit lenses 141 in the thickness direction to the point 141v that is the valley bottom of the valley between the unit lenses 141). And
In the present embodiment, the unit lens 141 arrangement pitch P1 is equal to the lens width W1 in the arrangement direction. The thickness of the optical sheet 14 (dimension in the Z direction from the light incident surface 14a to the vertex 141t) is D1.

FIG. 3 is a diagram illustrating the light incident surface 14a of the optical sheet 14 of the present embodiment. In FIG. 3, the light incident surface 14a is viewed from the normal direction (Z1 side).
The light incident surface 14a of the optical sheet 14 is formed with a fine uneven shape or the like, and is a so-called mat surface (rough surface).
In addition to the fine uneven shape, the light incident surface 14a of the present embodiment has a fine hairline shape that is finer than the fine uneven shape in the region A (the portion of the width S1 from the outer peripheral edge) that is the peripheral portion. Is formed. This fine hairline shape has irregular intervals and lengths.
In the light incident surface 14a of the present embodiment, a region inside the region A is a region B. This region B does not have such a fine line shape, but has the mat surface (rough surface) as described above.

When the fine hairline shape is formed in the region A that becomes the peripheral portion of the light incident surface 14a as in the present embodiment, the longitudinal direction of the fine hairline is mainly as shown by the arrows in FIG. It is parallel to the direction of the side of the adjacent optical sheet 14.
Therefore, as shown in FIG. 3, the fine hairline shape is both ends of the light incident surface 14a in the X direction, and in the region A adjacent to the side parallel to the Y direction, the longitudinal direction is formed parallel to the Y direction. In the region A adjacent to the sides parallel to the X direction at both ends of the light incident surface 14a in the Y direction, the longitudinal direction is formed parallel to the X direction.

In these areas A and B, the value of the center line average roughness Ra (JIS B 0601-1982), which is an index of surface roughness (hereinafter referred to as Ra value), and the ten-point average roughness Rz (JIS B 0601-). 1982) (hereinafter referred to as Rz value) is substantially equivalent. However, the value of the average interval Sm (corresponding to ISO468-1982) (hereinafter referred to as the Sm value) of the unevenness is smaller in the region A. The Ra value, Rz value, and Sm value are measured in a direction orthogonal to the longitudinal direction of the fine hairline shape formed in the region A.
The Sm value of the region A is preferably 250 μm or more and 650 μm or less from the viewpoint of suppressing optical contact (WET-OUT) between the light exit surface 13 c of the light guide plate 13 and the light entrance surface 14 a of the optical sheet 14.
When the Sm value is less than 250 μm, the optical adhesion is improved, but the region A in which the fine hairline shape is formed looks whitish, which is not preferable. Moreover, when Sm value is larger than 650 micrometers, formation of a fine hairline shape is inadequate and optical contact | adherence tends to arise and it is unpreferable.
In the present embodiment, the light incident surface 14a of the optical sheet 14 has an example in which a fine hairline shape is formed in the peripheral region A, but the present invention is not limited to this, and the entire surface of the light incident surface 14a. A fine hairline shape may be formed.

The optical sheet 14 of this embodiment is formed by extruding PC resin.
The optical sheet 14 is not limited to the above example. For example, an acrylic resin, an MBS (methyl methacrylate / butadiene / styrene copolymer) resin, a PET (polyethylene terephthalate) resin, a COP resin, or a PS (polystyrene) resin. A thermoplastic resin having light permeability and heat resistance that can be used as an optical member such as the above may be formed by extrusion molding. Alternatively, the optical sheet 14 may be manufactured by forming the unit lens 141 with an ultraviolet curable resin on a sheet-like substrate made of PET resin or PC resin.

The optical sheet 14 is manufactured through the following manufacturing process.
FIG. 4 is a diagram illustrating an example of a method for manufacturing the optical sheet 14 of the present embodiment.
First, as shown in FIG. 4A, the unit lenses 141 are arranged on one surface (light exit surface 14b) and the other surface (light entrance surface 14a) is fine uneven by extruding PC resin or the like. The optical sheet 14 which is a rough surface having a shape is formed (molding step).
Here, the light incident surface 14a can be formed, for example, as a mat surface (rough surface) in which a fine concavo-convex shape is formed by pressing a molding die whose surface is blasted or embossed. However, the present invention is not limited to this. For example, after the optical sheet 14 is molded, predetermined masking is performed, and a mat surface (roughness) on which a rough surface is formed by performing blasting or the like directly on the light entrance surface 14a. Surface) may be formed.

Next, as shown in FIG. 4B, the polishing tool 30 is placed on the light incident surface 14a of the optical sheet 14 cut to a predetermined size and moved along the outer peripheral edge (four sides). A roughening step is performed for forming a portion (region A) and forming a fine hairline shape.
As illustrated in FIG. 4C, the polishing tool 30 includes a main body portion 31, a cross portion 32 attached to the lower surface of the main body portion 31, and a handle portion 33 provided on a side surface of the main body portion 31. ing.
The main body portion 31 of the present embodiment has a substantially rectangular parallelepiped shape, and the cross portion 32 is attached to the lower surface. The shape and material of the main body 31 are not limited, but it is preferable that the main body 31 has an appropriate load, has no bias in the load, and is substantially uniformly loaded on the lower surface.
The cross part 32 is a part that contacts the light incident surface 14a and polishes the light incident surface 14a. The cloth portion 32 is preferably a non-woven fabric made of a polishing resin, and a general-purpose polishing cloth can be used.
The handle portion 33 is a portion that is held by an operator when the polishing tool 30 placed on the light incident surface 14a is moved. The shape of the handle 33 and the position where it is formed are not particularly limited as long as it is a shape that can move the polishing tool 30 stably.

The polishing tool 30 is disposed such that the lower surface to which the cross portion 32 is attached is in contact with the light incident surface 14a. Then, the operator holds the handle portion 33 and moves it at a predetermined speed along the side of the optical sheet 14 in a direction illustrated in FIGS. 4D and 4E at a predetermined speed. At this time, due to the weight of the polishing tool 30, the light incident surface 14a is polished in a state where a predetermined load is applied, and a fine hairline shape is formed in the region A of the light incident surface 14a. The fine hairline shape may be formed by causing the polishing tool 30 to move at a predetermined speed by an apparatus (not shown) instead of an operator.
The speed at which the polishing tool 30 is moved is preferably 0.3 m / s to 0.9 m / s from the viewpoint of forming a good fine hairline shape. When the speed at which the polishing tool 30 is moved is greater than 0.9 m / s, there are problems such as an unprocessed portion at the end of the optical sheet and a fine hairline shape meandering. In addition, when the speed at which the polishing tool 30 is moved is less than 0.3 m / s, there is a problem that the unevenness of the fine hairline shape is so deep that it easily looks like a scratch, and a problem that the workability is deteriorated. is there. Therefore, the speed at which the polishing tool 30 is moved is preferably in the above range.

Moreover, it is preferable to move the polishing tool 30 without stopping on the way from the end of the side to the end in the region along one side of the optical sheet 14. If it stops in the middle, the portion may be deeply polished and look like scratches or appear to be rubbed white, which is not preferable.
By performing such a roughening step, as schematically shown in FIG. 4 (f), an optical sheet 14 in which fine hairline processing is formed in the region A in addition to the fine uneven shape is produced.

Here, the contact surface between the light incident surface 14a of the polishing tool 30, the load per unit area grinding tool 30 is given to the light incident surface 14a ^is a 0.22g / mm ² ~0.55g / mm 2 Preferably there is.
When the load per unit area given to the light incident surface 14a by the polishing tool 30 is less than 0.22 g / mm ² , the formation of a fine hairline shape on the light incident surface 14a becomes insufficient, and the effect of reducing optical adhesion is obtained. I can't get it.
Further, when the load per unit area applied to the light incident surface 14a by the polishing tool 30 is larger than 0.55 g / mm ² , the load is excessively applied, so that the unevenness of the fine hairline shape is deeply formed, and the light incident surface Since 14a is exposed too much, the portion where the fine hairline shape is formed by the polishing tool 30 is visually recognized as white, which is not preferable.
Therefore, it is preferable that the load per unit area given to the light incident surface 14a by the polishing tool 30 satisfies the above range.

Moreover, it is preferable to use the cross part 32 whose count is # 400 to # 600.
When the cross part 32 having a count greater than # 600 (such as # 1000) is used, the count is too fine, and the finer hairline shape is innumerable than desired. A) is visually recognized as white. Moreover, since the count is too fine, even if the load applied to the light incident surface 14a by the polishing tool 30 is increased, the load is applied to the surface instead of the fine hairline shape (linear shape), and the fine hairline shape is sufficiently obtained. It cannot be formed.
When the cross part 32 having a count smaller than # 400 (# 150 or the like) is used, the count is too rough, fine hairline-shaped irregularities are formed deeply, and a portion visually recognized as a streak is generated.
Therefore, it is preferable that the count of the cross portion 32 is # 400 to # 600.
In addition, it is preferable to use a non-woven fabric made of PE (polyester) resin for the cloth portion 32. In addition, for example, a non-woven fabric made of nylon, PP (polypropylene) resin, or aramid fiber may be used. Can do.

Next, returning to FIG. 1, the prism sheet 15 and the polarization selective reflection sheet 16 will be described.
The prism sheet 15 is disposed on the LCD panel 11 side (Z2 side) of the optical sheet 14. The prism sheet 15 has a plurality of unit prisms 151 arranged on its light output side (Z2 side) surface.
The unit prisms 151 of the present embodiment have an isosceles triangular prism shape, and a plurality of unit prisms 151 are arranged in the Y direction with the X direction as the longitudinal direction (ridge line direction). Note that the longitudinal direction and arrangement direction of the unit prisms 151 may be appropriately selected.
The polarization selective reflection sheet 16 is an optical member having a function of transmitting light in a specific polarization state and reflecting light in other polarization states. The polarization axis of polarized light transmitted through the polarization selective reflection sheet 16 is a polarizing plate (not shown) (not shown) located on the back side (Z1 side) of the LCD panel 11 when viewed from the normal direction (Z direction) of the sheet surface. It is preferable that it is parallel to the transmission axis of the polarizing plate from the viewpoint of increasing the light utilization efficiency and improving the luminance. As the polarization selective reflection sheet 16, for example, DBEF (manufactured by Sumitomo 3M Limited) can be used.

FIG. 5 is a diagram illustrating a holding mechanism for the light guide plate 13 and the like of the transmissive display device 1 and the LCD panel 11 of the present embodiment. In FIG. 5, a part of a cross section parallel to the XZ plane of the transmissive display device 1 is shown in an enlarged manner, and the optical sheet 14 and the prism sheet 15 are simplified by omitting the shapes of the unit lens 141 and the unit prism 151. Is shown.
The LCD panel 11, the light source units 12 </ b> A and 12 </ b> B, the light guide plate 13, the optical sheet 14, the prism sheet 15, and the polarization selective reflection sheet 16 of the present embodiment are held by a frame 18, a back plate 19, screws 20, and the like. A mold display device 1 is configured.

The frame 18 is a member that houses the LCD panel 11, the light guide plate 13, the optical sheet 14, the prism sheet 15, the polarization selective reflection sheet 16, and the like. On the side surface of the frame body 18, as needed, light source portions 12 </ b> A and 12 </ b> B are provided, and through holes (not shown) through which an electric cable (not shown) connected to the LCD panel 11 is passed are appropriately provided. .
An end of the frame 18 on the LCD panel 11 side (Z2 side) is a bezel portion 18 a that protrudes to the center side (inside) in the screen direction (XY plane) of the transmissive display device 1. The bezel portion 18a is provided on the entire periphery of the frame 18 on the LCD panel 11 side (Z2 side), and is configured to press the peripheral edge portion of the LCD panel 11.

The back side (Z1 side) of the frame 18 from the bezel portion 18a supports the back side of the LCD panel 11, and positions of the optical sheet 14, the prism sheet 15, and the polarization selective reflection sheet 16 in the XY plane direction. A supporting portion 18b for determining is provided. The support portion 18b protrudes in the center side (inner side) and the thickness direction (Z direction) of the screen direction (XY plane), and is provided on the entire periphery on the back side (Z1 side) of the bezel portion 18a of the frame 18. It has been.
The back plate 19 is a plate material that presses the back surface (the surface on the Z1 side) of the reflection sheet 17 toward the LCD panel 11 side (the Z2 side).
The frame 18 and the back plate 19 are made of metal, resin, or the like, and preferably have no light transmittance.

As shown in FIG. 5, the transmissive display device 1 is assembled with the LCD panel 11, the polarization selective reflection sheet 16, the prism sheet 15, the optical sheet 14, the light guide plate 13, the reflection in order from the Z2 side of the frame 18. The sheet 17 is incorporated, and the back plate 19 is further laminated on the Z1 side of the reflection sheet 17. And the screw 20 screws the flange-shaped collar part 19a provided in the peripheral part of the backplate 19 to the back side (Z1 side) of the frame 18, and couples the backplate 19 and the frame 18. A plurality of the above-mentioned screwing locations are provided so that the back plate 19 can press the reflective sheet 17 and the like in a balanced manner.
The frame 18, the back plate 19, and the screw 20 apply pressure in the thickness direction (Z direction) at the peripheral portions of the polarization selective reflection sheet 16, the prism sheet 15, the optical sheet 14, the light guide plate 13, and the reflection sheet 17. These are held under pressure.

In the case where the transmissive display device 1 (surface light source device 10) is configured as described above, the light-emitting surface 13c of the light guide plate 13 that is a smooth surface and the adjacent side (Z2) at the peripheral edge to which the pressure to be pressed and held is applied. And a light incident surface such as a lens sheet disposed on the side) is in contact with and in close contact with each other, so-called optical contact occurs.
When the light source units 12A and 12B are turned on and the screen is observed in a state in which the optical contact has occurred, a rainbow-like shape caused by interference such as a wet spot-like light and dark unevenness due to the optical contact on the periphery of the screen. Color unevenness occurs. In particular, when the light incident surface such as a lens sheet disposed on the Z2 side of the light guide plate 13 is a smooth surface (including a level that can be regarded as a substantially smooth surface), or an insufficiently fine convex shape is formed. In such a case, the optical contact as described above and display defects due to the optical contact are remarkably generated, which hinders good visual recognition.

However, according to the present embodiment, in addition to the fine concavo-convex shape, the region A serving as the peripheral portion of the light incident surface 14a of the optical sheet 14 facing the light exit surface 13c of the light guide plate 13 is further roughened. Since the fine hairline shape is formed and the Sm value is 250 μm or more and 650 μm or less, the optical contact between the light exit surface 13c of the light guide plate 13 and the light entrance surface 14a of the optical sheet 14 can be significantly suppressed, and the optical contact is improved. Display defects such as wet blot-like light and dark unevenness and rainbow-like color unevenness caused by the image can be greatly reduced.
In addition, according to the present embodiment, a good Sm value can be obtained in the region A serving as the peripheral portion only by placing the polishing tool 30 on the peripheral portion of the light incident surface 14a of the optical sheet 14 and moving it at a predetermined speed. Since a fine hairline shape satisfying the range can be formed, manufacturing is easy and production costs can be suppressed.

(Evaluation of Examples and Comparative Examples)
Optical sheets corresponding to the examples and comparative examples of the optical sheet 14 of the present embodiment are manufactured, and the optical performance (haze value and total light transmittance), and the optical adhesion and display failure when the transmission type display device 1 is used. The situation of occurrence was investigated.
The optical sheets of Examples 1 to 4 and Comparative Examples 1 to 4 are both formed by extruding PC resin, and the unit lens 141 is formed by arranging a plurality of unit lenses 141 on the light exit surface. However, the presence or absence of fine hairline shape formation in the area A of the light incident surface is different.
In the optical sheets of Examples 1 to 4 and Comparative Examples 1 to 4, the outer shape of the plane parallel to the XY plane is about 1550 × 880 mm (corresponding to a screen size diagonal of 70 inches), and the total thickness D1 is about 400 μm.
The unit lenses 141 formed on the light exit surfaces of the optical sheets of Examples 1 to 4 and Comparative Examples 1 to 4 have an elliptic cylinder shape whose major axis is orthogonal to the sheet surface, and the arrangement pitch P1 = 64 μm and the lens height. H1 = 27 μm.

On the light incident surfaces of the optical sheets of Examples 1 to 4 and Comparative Examples 1 to 4, the region A is a region having a width S1 from the outer edges of the four sides to the center side of about 70 mm when viewed from the Z1 side.
The optical sheets of Comparative Examples 1 and 2 do not have a fine hairline shape in the region A, and the light incident surface is a matte surface (rough surface) in which fine irregularities are formed on the entire surface.
In the optical sheets of Examples 1 to 4 and Comparative Examples 3 and 4, in the region B of the light incident surface, the same fine uneven shape as that of the light incident surface of the optical sheets of Comparative Examples 1 and 2 is formed. In addition to the fine uneven shape, a fine hairline shape by the polishing tool 30 is formed.

In the optical sheets of Examples 1 to 4 and Comparative Examples 3 and 4, the weight of the polishing tool 30 in the roughening process for forming the fine hairline shape in the region A is different (5000 g, 4000 g, 3000 g, 2000 g, 6000 g, 1000 g). ), The load per unit area on the lower surface of the polishing tool 30 is different. In the optical sheets of Examples 1 to 4 and Comparative Examples 3 and 4, the load per unit area given to the light incident surface by the polishing tool 30 is 0.55 g / mm ² , 0.44 g / mm ² , and 0, respectively. .33 g / mm ² , 0.22 g / mm ² , 0.66 g / mm ² , and 0.11 g / mm ² .
The size of the portion of the polishing tool 30 where the cross portion 32 is in contact with the light incident surface is 70 mm × 130 mm. The cloth part 32 is a non-woven fabric made of polyester of # 600 (Migaki cloth # 600 NA600-800 manufactured by Komeri Co., Ltd.).

In the optical sheets of Examples 1 to 4 and Comparative Examples 1 to 4, Ra value, Rz value, and Sm value indicating the surface roughness of the area A of the light incident surface were measured. At this time, it measured in the direction orthogonal to the longitudinal direction of the fine hairline shape formed in the area | region A in the optical sheet of Examples 1-4 and Comparative Examples 3 and 4. FIG.
These Ra value, Rz value, and Sm value are measured three times by changing the measurement location in the same sample with a surface roughness measuring instrument (Surfcom (E-RM-S18B) manufactured by Tokyo Seimitsu Co., Ltd.). It is an average value of the obtained values. The measurement conditions are cut-off: 0.8 mm, measurement speed: 0.3 mm / s, and measurement length: 10 mm.

The haze value is a haze value in the region A when light is irradiated from the light incident surface side of the optical sheets of Examples 1 to 4 and Comparative Examples 1 to 4. Moreover, a total light transmittance is a total light transmittance of the area | region A when light is irradiated from the light-incidence surface side of the optical sheet of Examples 1-4 and Comparative Examples 1-4.
The haze value and the total light transmittance are average values of values obtained by measuring three times with a haze meter (NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd.) while changing the measurement location.

Furthermore, using the optical sheets of Examples 1 to 4 and Comparative Examples 1 to 4, a transmissive display device including the frame body 18 as shown in FIG. 5 is manufactured, and the light source units 12A and 12B are actually installed. It was turned on and the occurrence of display defects due to optical contact was examined.
The light guide plate 13 used at this time is made of acrylic resin, the light exit surface 13c is substantially smooth, and the surface roughness is Ra = 0.0 μm, Rz = 0.2 μm (measurement conditions and the like are This is the same as the measurement of the light incident surface 14a of the optical sheet 14 described above. Since the light exit surface 13c is a substantially smooth surface, the Sm value cannot be measured. A dot-like pattern having a diffusing action is formed on the back surface 13d. The light guide plate 13 is a so-called printing light guide plate.
The prism sheet 15 is made of UV resin, the unit prism 151 has an isosceles triangular prism shape with an apex angle of 90 °, and the arrangement pitch is 50 μm. The total thickness of the prism sheet 15 is 295 μm.
The deflection selective reflection sheet is DBEF (DBEF-D3-340 manufactured by Sumitomo 3M Limited).

Table 1 below summarizes the measurement results such as Ra value, Rz value, Sm value, haze value, etc. in region A of the optical sheets of Examples 1 to 4 and Comparative Examples 1 to 4.
In addition, as for the measurement of these Ra value, Rz value, Sm value, the measurement of haze value, and total light transmittance, about the optical sheet of Examples 1-4 and Comparative Examples 3 and 4, all are fine hairline shape. A region A in which the longitudinal direction is mainly the X direction (region A near the end in the Y direction) and a region A in which the longitudinal direction of the fine hairline shape is mainly in the Y direction (region A near the end in the X direction) Measurements were taken for both. Moreover, also in the optical sheets of Comparative Examples 1 and 2, the same measurement points as those in the optical sheets of Examples 1 to 4 and Comparative Examples 3 and 4 described above (corresponding to the region A at the ends in the Y direction and the X direction). Area).

As shown in Table 1, in the optical sheets of Examples 1 to 4 and Comparative Examples 1 to 4, the Ra value and Rz value in region A are substantially the same or slightly different, but the presence or absence of a fine hairline shape The Sm value varies greatly depending on the factors.
In the optical sheets of Examples 1 to 4 in which the fine hairline shape was formed in the region A, the Sm values in the region A all satisfied the preferred range (250 μm or more and 650 μm or less). However, in the optical sheets of Comparative Examples 1 and 2 in which the fine hairline shape is not formed in the region A, the Sm value of the region A is larger than the preferable range.
Although fine hairline shape is formed in the region A, than the load is preferably in the range of per unit area of the polishing tool 30 in the roughening step (0.22 g / mm ² or more 0.55 g / mm ² or less) In the large optical sheet of Comparative Example 3, the Sm value in the region A was smaller than the preferred range. Furthermore, although the fine hairline shape is formed in the region A, in the optical sheet of Comparative Example 4 in which the load per unit area of the polishing tool 30 in the roughening process is smaller than the preferred range, the Sm value in the region A is It was larger than the preferred range.

  Next, the optical sheets of Comparative Examples 1 and 2 in which the fine hairline shape is not formed in the region A, and the optical sheets of Examples 1 to 4 and Comparative Examples 3 and 4 in which the fine hairline shape is formed in the region A. In comparison, although the haze value differs depending on the presence or absence of the fine hairline shape, the total light transmittance was substantially the same. That is, by forming a fine hairline shape, the degree of light diffusion was slightly increased, but the brightness was hardly reduced.

Next, display defects due to optical adhesion are as follows.
In the transmissive display devices using the optical sheets of Comparative Examples 1 and 2, display defects such as a wet light and dark unevenness such as wet due to optical adhesion occurred. Further, in the transmissive display device using the optical sheet of Comparative Example 3, no display defect due to optical adhesion occurs, but the load of the polishing tool 30 at the time of forming the region A is too large, and a fine hairline shape is formed. Region A was observed as white and cloudy. Furthermore, in the transmissive display device using the optical sheet of Comparative Example 4, the region A was not observed as being cloudy white, but the load of the polishing tool 30 at the time of forming the region A was insufficient, and the optical adhesion Display failure due to was observed.

On the other hand, in the transmissive display devices using the optical sheets of Examples 1 to 4, streak scratches, white cloudiness, display defects due to optical adhesion, and the like were not observed.
Further, the total light transmittance in the region A of the optical sheets of Examples 1 to 4 is substantially equal to the total light transmittance of the region A of the optical sheets of Comparative Examples 1 and 2 where the region A is not roughened. The brightness does not decrease due to the fine hairline shape, and the transmittance is sufficient as an optical member.
From the above, according to the optical sheets of Examples 1 to 4, the optical contact with the light guide plate 13 can be largely suppressed, display defects caused by the optical contact can be greatly improved, and a bright and good surface light source device and A transmissive display device can be obtained.

In addition, in Example 3 described above, Example 3-2 in which the roughening step of forming a fine hairline shape with the polishing tool 30 on the entire surface of the light incident surface 14a is performed in the same manner as in the region A. , 3-3 optical sheets were produced. In the optical sheet of Example 3-2, the polishing tool 30 is moved in the X direction, and in the optical sheet of Example 3-3, the polishing tool 30 is moved in the Y direction, so that the fine hairline shape is formed on the entire light incident surface. Formed.
Then, in the optical sheets of Examples 3-2 and 3-3 and Comparative Example 1, the luminance at the center of the screen was measured and compared. The luminance was measured under the following two conditions.
Condition 1 is that the light source units 12A and 12B, the light guide plate 13, the optical sheet of any of Examples 3-2 and 3-3 and Comparative Example 1, a polarizing plate (not shown) (corresponding to the lower polarizing plate of the LCD panel 11). It is the state of a surface light source device provided with.
Condition 2 is that the light source sections 12A and 12B, the light guide plate 13, the optical sheet of any of Examples 3-2 and 3-3, Comparative Example 1, the prism sheet 15, the polarization selective reflection sheet 16, and the polarizing plate (not shown) This is a state of a surface light source device including a lower polarizing plate of the LCD panel 11.
The light guide plate 13, the prism sheet 15 and the like are the same as those used for the evaluation of the presence or absence of display defects due to the above-described optical contact in the luminance measurement under any condition.
Also, in any condition, the brightness of the light source sections 12A and 12B is turned on under any dark condition, and the brightness of the center of the screen is measured from a position 1 m from the center of the screen in the normal line direction (manufactured by Topcon). BM-9).

As shown in Table 2, the brightness of the optical sheet of Example 3-2 was 99.1% in Condition 1 and Condition 2 when the brightness of the optical sheet of Comparative Example 1 was used as a reference (100%). 99.4%, and good brightness comparable to that of the conventional optical sheet of Comparative Example 1 was maintained.
The optical sheet of Example 3-3 had a luminance of 97.7% in condition 1 and 98.3% in condition 2 when the luminance of the optical sheet of comparative example 1 was used as a reference (100%). Although it was slightly lower than that of Example 3-2, it maintained good brightness comparable to that of the optical sheet of Comparative Example 1.

  Therefore, even when a fine hairline shape is formed on the entire light incident surface of the optical sheet 14 by a roughening process, sufficiently good brightness can be maintained, optical adhesion can be improved, and display defects can be reduced. Therefore, when it is difficult to form a fine hairline shape only in the peripheral edge (region A) in the manufacturing process, it may be formed on the entire surface as in Examples 3-2 and 3-3. Etc. can be expanded.

(Deformation)
The present invention is not limited to the embodiment described above, and various modifications and changes are possible, and these are also within the scope of the present invention.
(1) In the present embodiment, an example in which the prism sheet 15 and the polarization selective reflection sheet 16 are formed on the light output side (Z2 side) of the optical sheet 14 is not limited to this, but other optical actions and A member having an optical shape may be disposed.
For example, a microlens sheet in which a microlens array is formed, a lenticular lens sheet, a diffusion sheet coated with a diffusion material on the surface, a diffusion sheet containing a diffusion material, or the like may be disposed. The prism sheet 15 and the polarization selective reflection sheet 16 may be used in appropriate combination.
Various optical sheets used in combination with the light guide plate 13 as the surface light source device 10 can be appropriately selected and used in accordance with the usage environment of the surface light source device 10 and the transmissive display device 1 and desired optical performance.

(2) In the present embodiment, the light guide plate 13 has been described with reference to an example having a printed dot pattern having a diffusing action on the back surface. However, the present invention is not limited to this. It is good also as a form to contain, and it may have a prism shape, a lens shape, etc. in a back surface, and it is good also as a back surface having a planar shape.
In addition, the light guide plate 13 may have a shape in which the light incident surfaces 13a and 13b are thick and the central portion is thin in the light guide direction. Further, in the case of a configuration including only the light source portion 12A (so-called single-lamp type), the light guide plate 13 may be configured to become gradually thinner toward the surface 13b side where the light incident surface 13a side is thicker.

(3) In the present embodiment, the reflection sheet 17 has a sheet shape and is separate from the light guide plate 13. However, the present invention is not limited thereto, and for example, the back side (Z1 side) of the light guide plate 13. In addition, they may be integrally joined. Also, instead of the reflective sheet 17, a light-reflective coating or metal foil is applied to the surface of the back plate 19 located on the back side (Z1 side) of the light guide plate 13 on the side of the light guide plate 13 (Z2 side). Or you may form by transcription | transfer etc.

  In addition, although this embodiment and modification can also be used in combination as appropriate, detailed description is abbreviate | omitted. Further, the present invention is not limited by the above-described embodiments and the like.

DESCRIPTION OF SYMBOLS 1 Transmission type display apparatus 10 Surface light source device 11 LCD panel 12A, 12B Light source part 121 Point light source 13 Light guide plate 14 Optical sheet 15 Prism sheet 16 Polarization selective reflection sheet 17 Reflection sheet 18 Frame 19 Back plate 20 Screw 30 Polishing tool 31 Main body Part 32 Cross part 33 Handle part

Claims (8)

An optical sheet disposed on the light output side of the light guide plate in the surface light source device,
The first surface facing the light guide plate is rough,
At least the peripheral portion of the first surface has an average interval Sm value of 250 μm or more and 650 μm or less,
An optical sheet characterized by The optical sheet according to claim 1,
A fine hairline shape is formed at least on the peripheral edge of the first surface, and the Sm value is a value in a direction perpendicular to the longitudinal direction of the fine hairline shape,
An optical sheet characterized by In the optical sheet according to claim 1 or 2,
A plurality of unit optical shapes are arranged on the second surface facing the first surface;
An optical sheet characterized by A light source that emits light;
A light guide plate including a light incident surface on which light from the light source unit is incident and a light output surface from which light is emitted;
The optical sheet according to any one of claims 1 to 3, which is disposed on a light output side of the light guide plate;
A surface light source device comprising:
The light exit surface of the light guide plate is planar and substantially smooth;
A surface light source device. The surface light source device according to claim 4,
At least pressurizing and holding the optical sheet and the light guide plate by applying pressure in the thickness direction to the peripheral portion thereof;
A surface light source device. The surface light source device according to claim 4 or 5,
A transmissive display unit illuminated from the back side by the surface light source device;
A transmissive display device. It is a manufacturing method of the optical sheet according to any one of claims 1 to 3,
A molding step of molding the optical sheet including the first surface that is rough;
A roughening step that represents a peripheral edge of the first surface;
With
In the roughening step, the peripheral edge is polished in a predetermined direction with a non-woven fabric for polishing, and the average interval Sm of the unevenness of the peripheral edge is set to 250 μm or more and 650 μm or less,
An optical sheet manufacturing method characterized by the above. In the manufacturing method of the optical sheet according to claim 7,
The count of the nonwoven fabric is # 400 to # 600,
In the roughening step, a load per unit area applied to the first surface is 0.22 g / mm ² or more and 0.55 g / mm ² .
An optical sheet manufacturing method characterized by the above.

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