WO2021124639A1 - Light diffusing sheet and backlight unit for liquid crystal display device - Google Patents

Light diffusing sheet and backlight unit for liquid crystal display device Download PDF

Info

Publication number
WO2021124639A1
WO2021124639A1 PCT/JP2020/036991 JP2020036991W WO2021124639A1 WO 2021124639 A1 WO2021124639 A1 WO 2021124639A1 JP 2020036991 W JP2020036991 W JP 2020036991W WO 2021124639 A1 WO2021124639 A1 WO 2021124639A1
Authority
WO
WIPO (PCT)
Prior art keywords
light
protrusions
light guide
sheet
light diffusion
Prior art date
Application number
PCT/JP2020/036991
Other languages
French (fr)
Japanese (ja)
Inventor
忠仁 福田
Original Assignee
恵和株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 恵和株式会社 filed Critical 恵和株式会社
Priority to KR1020227022264A priority Critical patent/KR20220108127A/en
Priority to CN202080081743.XA priority patent/CN114746779B/en
Publication of WO2021124639A1 publication Critical patent/WO2021124639A1/en

Links

Images

Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0033—Means for improving the coupling-out of light from the light guide
    • G02B6/0035—Means for improving the coupling-out of light from the light guide provided on the surface of the light guide or in the bulk of it
    • G02B6/004—Scattering dots or dot-like elements, e.g. microbeads, scattering particles, nanoparticles
    • G02B6/0041—Scattering dots or dot-like elements, e.g. microbeads, scattering particles, nanoparticles provided in the bulk of the light guide
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21S—NON-PORTABLE LIGHTING DEVICES; SYSTEMS THEREOF; VEHICLE LIGHTING DEVICES SPECIALLY ADAPTED FOR VEHICLE EXTERIORS
    • F21S2/00—Systems of lighting devices, not provided for in main groups F21S4/00 - F21S10/00 or F21S19/00, e.g. of modular construction
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
    • F21V3/00—Globes; Bowls; Cover glasses
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/02—Diffusing elements; Afocal elements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/02—Diffusing elements; Afocal elements
    • G02B5/0205—Diffusing elements; Afocal elements characterised by the diffusing properties
    • G02B5/021—Diffusing elements; Afocal elements characterised by the diffusing properties the diffusion taking place at the element's surface, e.g. by means of surface roughening or microprismatic structures
    • G02B5/0221—Diffusing elements; Afocal elements characterised by the diffusing properties the diffusion taking place at the element's surface, e.g. by means of surface roughening or microprismatic structures the surface having an irregular structure
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/02—Diffusing elements; Afocal elements
    • G02B5/0205—Diffusing elements; Afocal elements characterised by the diffusing properties
    • G02B5/021—Diffusing elements; Afocal elements characterised by the diffusing properties the diffusion taking place at the element's surface, e.g. by means of surface roughening or microprismatic structures
    • G02B5/0226—Diffusing elements; Afocal elements characterised by the diffusing properties the diffusion taking place at the element's surface, e.g. by means of surface roughening or microprismatic structures having particles on the surface
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0033—Means for improving the coupling-out of light from the light guide
    • G02B6/0035—Means for improving the coupling-out of light from the light guide provided on the surface of the light guide or in the bulk of it
    • G02B6/004—Scattering dots or dot-like elements, e.g. microbeads, scattering particles, nanoparticles
    • G02B6/0043—Scattering dots or dot-like elements, e.g. microbeads, scattering particles, nanoparticles provided on the surface of the light guide
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/1336—Illuminating devices
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/1336—Illuminating devices
    • G02F1/133615—Edge-illuminating devices, i.e. illuminating from the side

Definitions

  • the present invention relates to a light diffusion sheet and a backlight unit for a liquid crystal display device.
  • a liquid crystal display device such as a flat panel display is arranged on, for example, a liquid crystal cell and a liquid crystal display panel having a pair of polarizing plates laminated on both side surfaces of the liquid crystal cell, and the back surface side of the liquid crystal display panel. It is equipped with a backlight unit that irradiates a light beam toward the panel.
  • the edge light type backlight unit includes a light guide plate or a light guide sheet that guides light rays incident from an end face toward the surface side, and one or a plurality of light sources arranged along the end face of the light guide plate or the light guide sheet. It has a light diffusing sheet arranged on the surface side of the light guide plate or the light guide sheet, and a prism sheet arranged on the surface side of the light diffusing sheet.
  • the back surface of the light diffusion sheet is in contact with the light guide plate or the light guide sheet. Therefore, in the edge light type backlight unit, the back surface of the light diffusion sheet may partially adhere to the light guide plate or the light guide sheet to cause sticking. Since it is difficult for the light to be sufficiently diffused in the portion where this sticking occurs, it causes uneven brightness in the light emitted from the backlight unit.
  • an anti-sticking layer in which beads are dispersed in a binder is provided (see JP-A-2004-252353).
  • the protruding height of the beads may be partially increased, and the load applied to this portion is increased, so that the surface of the light guide plate or the light guide sheet is more likely to be scratched.
  • the present invention has been made in view of such circumstances, and an object of the present invention is to provide a light diffusion sheet and a backlight unit for a liquid crystal display device, which have high scratch resistance and excellent sticking prevention.
  • the light diffusion sheet according to one aspect of the present invention made to solve the above problems is provided with a plurality of protrusions on the back surface in a scattered manner, and the average height of the plurality of protrusions is 3.0 ⁇ m or more and 20.0 ⁇ m or less. , The coefficient of variation of height is 0.30 or less.
  • the coefficient of variation of the heights of the plurality of protrusions of the light diffusion sheet is equal to or less than the upper limit, it is possible to suppress the bias of the load applied to the plurality of protrusions. Further, since the average height of the plurality of protrusions of the light diffusing sheet is within the above range, the plurality of light diffusing sheets suppress sticking with other optical members arranged on the back surface side of the light diffusing sheet. It is possible to prevent the surface of the optical member from being scratched due to the contact with the protrusion. Therefore, the light diffusion sheet has high scratch resistance and excellent sticking prevention.
  • the protrusion has a truncated cone-shaped body portion and a dome-shaped tip portion continuous to the tip end side of the trunk portion.
  • the protrusions have a truncated cone-shaped body portion and a dome-shaped tip portion continuous to the tip end side of the body portion, thereby increasing the strength of the plurality of protrusions while increasing the strength of these protrusions.
  • the contact area between the and the optical member can be reduced to suppress the occurrence of sticking. As a result, it is possible to display a sufficiently high-definition image even when it is used in a small mobile terminal such as a smartphone or a tablet terminal.
  • the occupied area ratio of the plurality of protrusions on the back surface is preferably 2% or more and 80% or less. As described above, when the occupied area ratio of the plurality of protrusions on the back surface is within the above range, scratch prevention and sticking prevention can be enhanced.
  • the backlight unit for a liquid crystal display device includes a light guide plate or a light guide sheet that guides light rays incident from an end surface toward the surface side, and the light guide plate or the light guide sheet. It includes one or a plurality of light sources arranged along the end face of the light guide sheet, and the light diffusing sheet arranged on the surface side of the light guide plate or the light guide sheet.
  • the backlight unit for the liquid crystal display device includes the light diffusion sheet, it has high scratch prevention and excellent sticking prevention.
  • the "front surface” refers to the surface on the viewer side when incorporated in the liquid crystal display device, and the “back surface” refers to the surface on the opposite side.
  • the "average height of a plurality of protrusions” means an average value of the heights of any 10 protrusions.
  • the “coefficient of variation of the heights of a plurality of protrusions” means a value obtained by dividing the standard deviation of the heights of any 10 protrusions by the average height.
  • the “light ray emitting area” refers to an area that overlaps with the display screen in a plan view.
  • the average radius of a circle containing three adjacent protrusions on the back surface means that any 10 protrusions are extracted, and for each of the extracted protrusions, this protrusion and the other two protrusions other than this protrusion are It is the average value of the values obtained by calculating the minimum radius of the circle on the back surface to be inserted and excluding the largest value and the smallest value among the obtained 10 radii.
  • the light diffusion sheet according to one aspect of the present invention and the backlight unit for a liquid crystal display device according to another aspect have high scratch prevention and excellent sticking prevention.
  • FIG. 1 is a schematic end view showing a backlight unit for a liquid crystal display device according to an embodiment of the present invention.
  • FIG. 2 is a schematic bottom view of the light diffusion sheet of the backlight unit for the liquid crystal display device of FIG.
  • FIG. 3 is a schematic side view showing the protrusions of the light diffusion sheet of FIG.
  • FIG. 4 is a schematic bottom view of the protrusion of FIG. 3 as viewed from the tip side.
  • FIG. 5 is a schematic partially enlarged bottom view showing the arrangement of the protrusions of the light diffusion sheet of FIG.
  • FIG. 6 is a schematic side view showing a protrusion according to an embodiment different from the protrusion of FIG.
  • FIG. 7 is a schematic bottom view of the protrusion of FIG. 6 as viewed from the tip side.
  • the backlight unit 1 for a liquid crystal display device (hereinafter, also simply referred to as “backlight unit 1”) of FIG. 1 is an edge light type backlight unit.
  • the backlight unit 1 includes a light guide sheet 2 that guides light rays incident from an end surface toward the surface side, one or a plurality of light sources 3 arranged along the end surface of the light guide sheet 2, and a light guide sheet 2.
  • the light diffusing sheet 4 is provided on the surface side of the above.
  • the light diffusion sheet 4 is laminated directly (without interposing other members) on the surface of the light guide sheet 2.
  • the light diffusion sheet 4 itself constitutes an aspect of the present invention.
  • the backlight unit 1 includes a prism sheet 5 arranged on the front surface side of the light diffusion sheet 4 and a reflection sheet 6 arranged on the back surface side of the light guide sheet 2.
  • another prism sheet may be arranged on the surface side of the prism sheet 5.
  • the light diffusion sheet 4 has a light incident surface facing the light guide sheet 2 and a light emitting surface on the opposite side of the light incident surface.
  • the light diffusion sheet 4 emits light rays incident from the light incident surface from the light emitting surface.
  • the light diffusion sheet 4 has flexibility as a whole.
  • the light diffusion sheet 4 is provided with a plurality of protrusions 11 on the back surface 4a in a scattered manner.
  • the light diffusion sheet 4 includes a base material layer 12 and a light diffusion layer 13 laminated on the front surface side of the base material layer 12, and a plurality of protrusions 11 are scattered on the back surface of the base material layer 12. It is formed.
  • the light diffusion layer 13 is directly laminated on the surface of the base material layer 12, and a plurality of protrusions 11 are directly formed on the back surface of the base material layer 12.
  • the light diffusion sheet 4 does not have any layers other than the base material layer 12, the light diffusion layer 13, and the plurality of protrusions 11, and the back surface of the base material layer 12 is the back surface 4a of the light diffusion sheet 4. Consists of.
  • the back surface of the base material layer 12 and the outer surfaces of the plurality of protrusions 11 form a light incident surface, and the surface of the light diffusion layer 13 constitutes a light emitting surface.
  • the light diffusing sheet 4 is arranged on the surface side of the light guide sheet 2 by partially contacting the surface of the light guide sheet 2 with a plurality of protrusions 11. The contact portion between the plurality of protrusions 11 and the light guide sheet 2 is not fixed by an adhesive or the like.
  • the base material layer 12 is transparent because it needs to transmit light rays.
  • the base material layer 12 has flexibility.
  • the base material layer 12 contains a synthetic resin as a main component.
  • the main component of the base material layer 12 is not particularly limited, and examples thereof include polyethylene terephthalate, polyethylene naphthalate, acrylic resin, polycarbonate, polystyrene, polyolefin, cellulose acetate, and weather-resistant vinyl chloride. Among them, polyethylene terephthalate having excellent transparency and high strength is preferable, and polyethylene terephthalate having improved bending performance is particularly preferable.
  • the "main component” refers to a component having the highest content in terms of mass, for example, a component having a content of 50% by mass or more.
  • the upper limit of the average thickness of the base material layer 12 is preferably 200 ⁇ m, more preferably 100 ⁇ m, and even more preferably 50 ⁇ m. If the average thickness does not reach the lower limit, the strength of the base material layer 12 becomes insufficient, and the back surface of the base material layer 12 may partially come into contact with the light guide sheet 2. On the contrary, when the average thickness exceeds the upper limit, the load applied to the plurality of protrusions 11 becomes large due to the possibility of violating the request for thinning of the light diffusion sheet 4 and the heaviness of the base material layer 12. There is a high possibility that the surface of the light guide sheet 2 will be scratched.
  • the plurality of protrusions 11 project from the back surface of the base material layer 12 to the incident side (light guide sheet 2 side) of the light beam.
  • the plurality of protrusions 11 are irregularly arranged on the back surface of the base material layer 12.
  • the average height H1 AVG of the plurality of protrusions 11 is 3.0 ⁇ m or more and 20.0 ⁇ m or less. Further, the coefficient of variation of the height H1 of the plurality of protrusions 11 is 0.30 or less.
  • the light diffusion sheet 4 has a plurality of protrusions 11 formed into a desired shape by forming the plurality of protrusions 11 by using a pressing roll having a plurality of recesses having an inverted shape of the plurality of protrusions 11 as described later. Can be formed.
  • the lower limit of the average height H1 AVG of the plurality of protrusions 11 is preferably 4.0 ⁇ m, more preferably 5.0 ⁇ m.
  • the upper limit of the average height H1 AVG is preferably 16.0 ⁇ m, more preferably 10.0 ⁇ m. If the average height H1 AVG does not reach the lower limit, sticking with the light guide sheet 2 may not be sufficiently suppressed. On the contrary, when the average height H1 AVG exceeds the upper limit, the surface of the light guide sheet 2 may be scratched due to the contact with the plurality of protrusions 11, or the protrusions 11 may be easily broken. is there.
  • the upper limit of the coefficient of variation of the height H1 of the plurality of protrusions 11 is preferably 0.20, more preferably 0.10, and even more preferably 0.05. If the coefficient of variation exceeds the upper limit, the heights of the plurality of protrusions 11 become non-uniform, the load is biased to the protrusions 11 having a large height, and the surface of the light guide sheet 2 may be scratched based on this. is there.
  • the lower limit of the coefficient of variation is not particularly limited and may be, for example, 0.
  • the lower limit of the average diameter D1 AVG of the bottom surfaces (boundary surface with the base material layer 12) of the plurality of protrusions 11 is preferably 10 ⁇ m, more preferably 15 ⁇ m.
  • the upper limit of the average diameter D1 AVG is preferably 40 ⁇ m, more preferably 30 ⁇ m. If the average diameter D1 AVG does not reach the lower limit, the strength of the plurality of protrusions 11 may be insufficient. On the contrary, when the average diameter D1 AVG exceeds the upper limit, the contact area between the plurality of protrusions 11 and the light guide sheet 2 becomes large, which may cause sticking.
  • the "diameter” means a diameter converted into a perfect circle with an equal area. Further, throughout the present specification, the "average diameter” means an average value of any 10 diameters.
  • the protrusion 11 has a truncated cone-shaped body portion 11a and a dome-shaped tip portion 11b continuous to the tip end side of the body portion 11a.
  • the body portion 11a has a reduced diameter from the base end side (base material layer 12 side) toward the tip end side.
  • the protrusion 11 comes into contact with the light guide sheet 2 on the tip side of the tip portion 11b. Since the protrusion 11 has the body portion 11a of the light diffusion sheet 4, the strength of the protrusion 11 can be sufficiently increased even when the size of the protrusion 11 is relatively small.
  • the light diffusion sheet 4 can reduce the contact area between the protrusion 11 and the light guide sheet 2 and suppress the occurrence of sticking. it can. As a result, the light diffusion sheet 4 can display a sufficiently high-definition image even when it is used in a small mobile terminal such as a smartphone or a tablet terminal.
  • the term "truncated cone" includes a cross section having a perfect circular shape or a substantially perfect circular shape in the direction perpendicular to the height direction, as well as an elliptical shape and the like.
  • the "dome shape” refers to a shape in which the outer edge on the tip side is curved in an arc shape (arc shape, elliptical arc shape, etc.) on the tip side in an arbitrary cross section that passes through the apex and is parallel to the height direction.
  • the ratio of the height H1 to the diameter D1 of the bottom surface of the protrusion 11 is smaller than 1. That is, it is preferable that the protrusion 11 has a flat shape having a height H1 smaller than that of the diameter D1. The strength of the protrusion 11 can be easily increased by reducing the ratio of the height H1 to the diameter D1. Further, since the protrusion 11 has a dome-shaped tip portion 11b on the tip end side of the truncated cone-shaped body portion 11a, the protrusion 11 and the light guide sheet 2 are in contact with each other even if the ratio of the height H1 to the diameter D1 is reduced. It is possible to prevent the contact area from becoming too large.
  • the outer surface of the tip portion 11b is formed continuously from the side surface of the body portion 11a.
  • the tip portion 11b may be configured such that the radius of curvature gradually and / or continuously increases from the base end side to the tip end side. Since the body 11a of the light diffusion sheet 4 has the above-mentioned truncated cone shape, contact between the body 11a and the light guide sheet 2 is prevented. Therefore, the light diffusing sheet 4 can keep the contact area between the protrusion 11 and the light guide sheet 2 small even if the radius of curvature on the tip side of the tip portion 11b is increased. As a result, the light diffusing sheet 4 can sufficiently suppress sticking with the light guide sheet 2 and sufficiently suppress scratches on the surface of the light guide sheet 2 due to contact with the plurality of protrusions 11. it can.
  • the lower limit of the occupied area ratio of the plurality of protrusions 11 on the back surface 4a of the light diffusion sheet 4 is preferably 2%.
  • the upper limit of the occupied area ratio is preferably 80%. If the occupied area ratio does not reach the lower limit, sticking with the light guide sheet 2 may not be sufficiently suppressed. On the contrary, when the occupied area ratio exceeds the upper limit, the plurality of protrusions 11 may be unnecessarily increased, and the surface of the light guide sheet 2 may be scratched.
  • the light diffusing sheet 4 has a light emitting region A corresponding to the liquid crystal display screen of the liquid crystal display panel in a state of being incorporated in the liquid crystal display device.
  • the light emitting region A has, for example, a rectangular shape, and is typically rectangular.
  • the size of the light emitting region A of the light diffusing sheet 4 is S [inch] and the occupied area ratio of the plurality of protrusions 11 on the back surface 4a of the light emitting region A is R [%]
  • R the occupied area ratio of the plurality of protrusions 11 on the back surface 4a of the light emitting region A
  • (1) When S ⁇ 7, 60 ⁇ R (2)
  • the light emitting region A is usually substantially equal to the plane area of the light diffusion sheet 4.
  • the light emitting region A When the light emitting region A is substantially equal to the plane area of the light diffusing sheet 4, the light emitting region A can be converted into the plane area of the light diffusing sheet. Further, 7 inches means a size having a diagonal length of 17.8 cm, and 15 inches means a size having a diagonal length of 38.1 cm.
  • the upper limit of R is more preferably 25.0 and even more preferably 20.0. If R does not reach the above lower limit, sticking with the light guide sheet 2 may not be sufficiently suppressed. On the contrary, if R exceeds the above upper limit, the surface of the light guide sheet 2 may be scratched.
  • the size of the light emitting region A is S [inch]
  • a circle (a circle tangent to the side edges of the three protrusions 11) containing the three adjacent protrusions 11 on the back surface 4a of the light emitting region A. )
  • Is r [ ⁇ m] it is preferable to satisfy the following conditions (1) or (2). (1) When S ⁇ 7, r ⁇ 40 (2) When 7 ⁇ S ⁇ 15, 40 ⁇ r ⁇ 400
  • the protrusion 11 does not contain particles such as resin beads.
  • the protrusion 11 contains, for example, an active energy ray-curable resin or a synthetic resin similar to the main component of the base material layer 12 as a main component.
  • Examples of the active energy ray-curable resin include an ultraviolet curable resin.
  • Examples of the ultraviolet curable resin include urethane acrylate and acrylic resin.
  • Examples of the acrylic resin include ultraviolet curable polyester acrylate, ultraviolet curable epoxy acrylate, and ultraviolet curable polyol acrylate.
  • the light diffusion layer 13 constitutes the outermost surface of the light diffusion sheet 4.
  • the light diffusing layer 13 has a plurality of light diffusing agents 13a and a binder 13b thereof.
  • the light diffusing agent 13a is surrounded by a binder 13b.
  • the light diffusing layer 13 disperses and contains a plurality of light diffusing agents 13a to diffuse light rays transmitted from the back surface side to the front surface side substantially uniformly.
  • fine irregularities are formed substantially uniformly on the surface by the plurality of light diffusing agents 13a, and each concave portion and convex portion of the fine irregularities are formed in a lens shape.
  • the light diffusing layer 13 exerts an excellent light diffusing function due to the lens-like action of such fine irregularities, and due to this light diffusing function, the refracting function for refracting the transmitted light rays in the normal direction and the normalizing the transmitted light rays. It has a condensing function that condenses light in the direction macroscopically.
  • the light diffusing agent 13a is fine particles having a property of diffusing light rays, and is typically resin beads.
  • the main component of the light diffusing agent 13a include acrylic resin, acrylonitrile resin, polyurethane, polyvinyl chloride, polystyrene, polyamide, polyacrylonitrile and the like. Of these, an acrylic resin having high transparency is preferable, and polymethylmethacrylate (PMMA) is particularly preferable.
  • the shape of the light diffusing agent 13a is not particularly limited, and examples thereof include a spherical shape, a cubic shape, a needle shape, a rod shape, a spindle shape, a plate shape, a scale shape, and a fibrous shape, and among them, a spherical shape having excellent light diffusing property. Is preferable.
  • the binder 13b is formed by curing (crosslinking or the like) a polymer composition containing a base polymer.
  • the light diffusing agent 13a is fixed to the entire surface of the base material layer 12 at a substantially equal density by the binder 13b.
  • the polymer composition for forming the binder 13b includes, for example, a microinorganic filler, a curing agent, a plasticizer, a dispersant, various leveling agents, an antistatic agent, an ultraviolet absorber, an antioxidant, and a viscosity modification. Agents, lubricants, light stabilizers and the like may be appropriately blended.
  • the light guide sheet 2 is formed in a substantially rectangular shape in a plan view, and is formed in a plate shape (non-wedge shape) having a substantially uniform thickness.
  • the lower limit of the average thickness of the light guide sheet 2 is preferably 100 ⁇ m, more preferably 150 ⁇ m, and even more preferably 200 ⁇ m.
  • the upper limit of the average thickness of the light guide sheet 2 is preferably 600 ⁇ m, more preferably 400 ⁇ m. If the average thickness of the light guide sheet 2 does not reach the above lower limit, the strength of the light guide sheet 2 may be insufficient, and it may be difficult for the light of the light source 3 to be sufficiently incident on the light guide sheet 2. is there. On the contrary, if the average thickness of the light guide sheet 2 exceeds the above upper limit, there is a possibility that the request for thinning the backlight unit 1 is violated.
  • the light guide sheet 2 Since the light guide sheet 2 needs to have translucency, it is formed mainly of a transparent resin, particularly a colorless and transparent resin.
  • the main component of the light guide sheet 2 is not particularly limited, and examples thereof include polycarbonate having excellent transparency and strength, and synthetic resins such as acrylic resin having excellent transparency and scratch resistance.
  • the light guide sheet 2 may have an uneven shape such as a lenticular or a prism row on the surface so that the emitted light can be controlled.
  • the light source 3 is arranged so that the irradiation surface faces (or abuts) the end surface of the light guide sheet 2.
  • various light sources can be used, and for example, a light emitting diode (LED) can be used.
  • a light emitting diode LED
  • the plurality of light sources 3 those in which a plurality of light emitting diodes are arranged along the end faces of the light guide sheet 2 can be used.
  • the prism sheet 5 has a base material layer 5a and a prism row 5b composed of a plurality of convex prism portions laminated on the surface of the base material layer 5a.
  • the base material layer 5a and the prism row 5b are transparent because they need to transmit light rays.
  • the base material layer 5a and the prism row 5b are formed mainly of a synthetic resin.
  • another prism sheet may be arranged on the surface side of the prism sheet 5, and in this case, the directions of the prism sheet 5 and the prism rows of the other prism sheet are preferably orthogonal to each other.
  • Reflective sheet As the reflective sheet 6, the specular reflectivity is enhanced by depositing a metal such as aluminum or silver on the surface of a white sheet in which a filler is dispersed and contained in a base resin such as polyester or a film formed of polyester or the like. Examples include the mirror-finished sheet.
  • the method for producing the light diffusion sheet includes a step of preparing the base material layer 12 (preparation step) and a step of forming a plurality of protrusions 11 on the back surface side of the base material layer 12 prepared in the preparation step (protrusion formation step). ) And a step of laminating the light diffusing layer 13 on the surface side of the base material layer 12 (light diffusing layer laminating step).
  • the protrusion forming step includes, for example, a step of applying the protrusion forming resin composition containing the above-mentioned ultraviolet curable resin to the back surface of the base material layer 12 (coating step), and a step of applying the coating liquid on the coating liquid applied by the coating step.
  • a step of pressing a pressing roll having a plurality of concave portions on the outer peripheral surface which is an inverted shape of the plurality of protrusions 11 pressing step
  • the plurality of protrusions 11 are transferred to the back surface of the base material layer 12.
  • the curing step is preferably performed with the pressing roll pressed against the back surface of the base material layer 12.
  • Examples of the method of forming a plurality of recesses on the outer peripheral surface of the pressing roll include a method of laser irradiation and a method of forming a copper plating layer on the outer peripheral surface of the pressing roll and then performing etching.
  • Light diffusion layer laminating process In the light diffusing layer laminating step, after the protrusion forming step, a coating liquid containing a plurality of light diffusing agents 13a and a binder composition is applied to the surface of the base material layer 12, and the applied coating liquid is dried and cured. ..
  • the coefficient of variation of the heights of the plurality of protrusions 11 of the light diffusion sheet 4 is equal to or less than the above upper limit, it is possible to suppress the bias of the load applied to the plurality of protrusions 11. Further, since the average height H1 AVG of the plurality of protrusions 11 of the light diffusion sheet 4 is within the above range, another optical member (light guide sheet 2) arranged on the back surface side of the light diffusion sheet 4 It is possible to prevent the surface of the optical member from being scratched due to contact with the plurality of protrusions 11 while suppressing sticking with the light. Therefore, the light diffusion sheet 4 has a high scratch prevention property and an excellent sticking prevention property.
  • the backlight unit 1 includes the light diffusion sheet 4, it has high scratch prevention and excellent sticking prevention.
  • the method for manufacturing the light diffusing sheet can easily and surely manufacture the light diffusing sheet 4 having excellent scratch prevention and sticking prevention properties.
  • the plurality of protrusions may not be directly formed on the back surface of the base material layer.
  • the light diffusion sheet may have a synthetic resin back layer laminated on the back surface side of the base material layer, and may have a plurality of protrusions on the back surface of the back layer.
  • the back surface of the back layer constitutes the back surface of the light diffusion sheet.
  • the specific configuration of the light diffusion layer is not limited to the configuration described in the above embodiment.
  • the light diffusion layer may have an uneven shape formed on the outer surface by embossing or the like.
  • the protrusion does not necessarily have to consist only of a truncated cone-shaped body and a dome-shaped tip continuous to the tip side of the body.
  • a modified example of the protrusion will be described with reference to FIGS. 6 and 7.
  • the protrusions 21 of FIGS. 6 and 7 include a truncated cone-shaped body portion 21a, a dome-shaped tip portion 21b continuous with the tip end side of the body portion 21a, and a skirt portion 21c continuous with the base end side of the body portion 21a.
  • the body portion 21a can have the same configuration as the body portion 11a of the protrusion 11 of the light diffusion sheet 4 of FIG.
  • the tip portion 21b can have the same configuration as the tip portion 11b of the protrusion 11 of the light diffusion sheet 4 shown in FIG.
  • the skirt portion 21c has a trumpet-shaped diameter increase from the tip end side to the base end side of the protrusion 21. According to this configuration, the light diffusing sheet can increase the adhesion between the back surface and the plurality of protrusions.
  • the protrusion preferably has a truncated cone-shaped body portion and a continuous dome-shaped tip portion on the tip end side of the trunk portion.
  • a specific shape of the protrusion for example, it is possible to have a configuration that does not have a truncated cone-shaped body.
  • the protrusion may have a body such as a columnar shape, a polygonal columnar shape, or a polygonal pyramid shape instead of the truncated cone shape.
  • the backlight unit may include, for example, a light guide plate having an average thickness of more than 600 ⁇ m instead of the light guide sheet. Further, the light guide plate may have a flat plate shape or a wedge shape in cross section.
  • the specific configuration of the backlight unit is not limited to the configuration described in the above embodiment.
  • the backlight unit may have another optical sheet such as a microlens sheet, or may have an upper light diffusing sheet having a relatively low diffusing function on the surface side of the prism sheet.
  • the backlight unit may be a direct type backlight unit.
  • the backlight unit is an edge light type backlight unit, it is a one-sided edge light type backlight unit in which one or more light sources are arranged only along one end surface of the light guide sheet or the light guide plate.
  • the backlight unit can be used for a relatively small mobile terminal such as a smartphone or a tablet terminal, a personal computer such as a notebook computer, or a relatively large display device such as an LCD TV.
  • Examples 1 to 3 A substrate layer having an average thickness of 50 ⁇ m containing polyethylene terephthalate as a main component was prepared. While feeding this base material layer between a pair of pressing rolls, an ultraviolet curable resin (projection formation) is formed on the back surface side (back surface side when incorporated in a liquid crystal display device) of the base material layer immediately before the pair of pressing rolls. Resin composition for use) was supplied. As the pressing roll on the side in contact with the ultraviolet curable resin, one having a plurality of recesses on the outer peripheral surface was used.
  • the ultraviolet curable resin and the base material layer are pressed by the pair of pressing rolls, and then the ultraviolet curable resin is cured by irradiating with ultraviolet rays, and a plurality of recesses are inverted on the back surface side of the base material layer. Multiple protrusions were transferred. Further, a coating liquid containing a plurality of beads and a binder composition is applied to the surface side of the base material layer, and the light diffusion layer is laminated on the surface side of the base material layer by drying and curing the coating liquid. , A light diffusing sheet was obtained. In Examples 1 to 3 and Comparative Examples 1 to 3, the average height of the plurality of protrusions was adjusted by changing the average depth of the recesses of the pressing roll. Table 1 shows the average height of a plurality of protrusions and the coefficient of variation of the height.
  • ⁇ Scratch prevention> The light diffusing sheets of Examples 1 to 3 and Comparative Examples 1 to 3 were punched into a rectangular shape of 10 cm ⁇ 20 cm, and three test pieces were prepared for each light diffusing sheet. For these test pieces, a prism sheet is attached to the lower part of the ASTM indenter using a planar friction resistance tester (Tribotester TYPE14 manufactured by Shinto Kagaku Co., Ltd.) having an ASTM planar indenter, and a plurality of protrusions face each other on the prism sheet.
  • a planar friction resistance tester Tribotester TYPE14 manufactured by Shinto Kagaku Co., Ltd.
  • test pieces were arranged so as to be used, and a scratch test was conducted with a moving speed of 50 mm / min, an indenter moving distance of 50 mm, and a load of 500 g, and the presence or absence of scratches on the test pieces was evaluated according to the following criteria.
  • the evaluation results are shown in Table 1.
  • An edge light type backlight having a plane dimension of 13 cm ⁇ 21 cm having an LED light source, a light guide sheet that guides the light emitted from the LED light source, and a reflective sheet arranged on the back surface side of the light guide sheet.
  • a polyethylene bag having an inner size of 20 cm ⁇ 25 cm.
  • a bag having an opening on one side and having such an opening portion hermetically sealed was used. With the laminate inserted, a hose for vacuum exhaust was inserted through the opening of the bag, and the opening was sealed.
  • Examples 4 to 7 The average diameter of the bottom surfaces of the plurality of protrusions was set as shown in Table 2, and a light diffusion sheet was manufactured by the same procedure as in Example 1. The average diameter of the protrusions was adjusted by changing the opening diameter of the recesses of the pressing roll. The average height of the plurality of protrusions in Examples 4 to 7 was 9.0 ⁇ m, and the coefficient of variation of the height was 0.15.
  • the light diffusing sheets of Examples 4 to 7 were punched into a rectangular shape of 10 cm ⁇ 10 cm, and three test pieces were prepared for each light diffusing sheet.
  • the above-mentioned test piece is stuck on it with an adhesive so that a plurality of protrusions face the wrenchular of the light guide plate, and then an ASTM indenter is attached at a moving speed of 50 mm / min, an indenter moving distance of 50 mm, and a load of 500 g. Was reciprocated to the center of the test piece.
  • This ASTM indenter first reciprocates 5 times in the direction parallel to the ridgeline of the lenticular, then peels off the light guide plate from the test table and rotates it 90 ° while still attached to the test piece, and then attaches the light guide plate to the test table again. After pasting with, it was reciprocated 5 times in the direction orthogonal to the ridgeline of the lenticular.
  • the test piece was peeled off from the light guide plate, the lenticular surface of the light guide plate was visually confirmed, and the strength of the protrusion was evaluated according to the following criteria.
  • the evaluation results are shown in Table 2.
  • an adhesive an adhesive spray manufactured by 3M Co., Ltd. is used so that when the test piece is peeled off from the light guide plate, the protrusions are not damaged or the protrusion fragments are not attached to the light guide plate due to the adhesive. "Spray glue 55" was used. A: The fragments of the protrusions are not visible B: The fragments of the protrusions are visible
  • Examples 4 and 5 in which the average diameter of the plurality of protrusions is 10 ⁇ m or more and 40 ⁇ m or less have high protrusion strength and excellent sticking prevention property.
  • Example 6 since the average diameter of the plurality of protrusions is small, the protrusion strength is low.
  • the contact area of the protrusions is large and the sticking prevention property is low.
  • Example 8 to 15 The average thickness of the base material layer is 38 ⁇ m, the size of the light emitting region and the occupied area ratio of the plurality of protrusions on the back surface of the base material layer are as shown in Table 3, and the light diffusion sheet is prepared in the same procedure as in Example 1. Manufactured. The occupied area ratio of the plurality of protrusions was adjusted by changing the density of the recesses of the pressing roll. The average height of the plurality of protrusions in Examples 8 to 15 was 10.0 ⁇ m, and the coefficient of variation of the height was 0.10.
  • the liquid crystal display panel (color filter / liquid crystal layer / TFT substrate) is arranged so that the TFT substrate faces the prism sheet, and a sphere made of nylon 66 having a diameter of 30 mm is placed 100 cm above the liquid crystal display panel. It was dropped, and the presence or absence of scratches on the light diffusion sheet was visually confirmed and evaluated according to the following criteria. The evaluation results are shown in Table 3. Note that light diffusion sheets having a small light emitting area are often used for smartphones, tablet terminals, etc., and it is important to evaluate the presence or absence of scratches due to dropping of the terminals. Is conducting a ball drop test. A: Scratches are not visible B: Scratches are visible
  • Example 14 since the ratio of the occupied area of the plurality of protrusions to the size of the light emitting region is small, the anti-sticking property is insufficient. Further, in Example 15, since the ratio of the occupied area of the plurality of protrusions to the size of the light emitting region is large, the scratch prevention property is insufficient, and in Example 11, the occupied area of the plurality of protrusions to the size of the light emitting region is insufficient. Since the rate is small, the cushioning function due to the plurality of protrusions against impact is insufficient, and the scratch prevention property by the ball drop test is insufficient.
  • Examples 16 to 23 The average thickness of the base material layer is 38 ⁇ m, the size of the light emitting region and the average radius of the circle containing the three adjacent protrusions on the back surface of the base material layer are as shown in Table 4, and the procedure is the same as in Example 1. , Manufactured a light diffusing sheet. The average radius of the circle containing the three adjacent protrusions on the back surface of the base material layer was adjusted by changing the arrangement of the recesses of the pressing roll. The average height of the plurality of protrusions in Examples 16 to 23 was 9.0 ⁇ m, and the coefficient of variation of the height was 0.15.
  • Examples 16 to 19 are scratched by the same ball drop test as in Examples 8 to 11, and Examples 20 to 23 are scratched by the same procedure and the same evaluation criteria as in Examples 1 to 3 and Comparative Examples 1 to 3. The anti-stickiness was evaluated. The evaluation results are shown in Table 4.
  • Examples 16, 17, 18, 20, and 21 are scratch-prevented by sufficiently adjusting the average radius of the circle containing the three adjacent protrusions with respect to the size of the light emitting region. It has excellent properties and anti-sticking properties.
  • Example 22 since the average radius of the circle containing the three adjacent protrusions is small with respect to the size of the light emitting region, the scratch prevention property is insufficient, and in Example 19, the size of the light emitting region is reduced. Since the average radius of the circle containing the three adjacent protrusions is large, the cushioning function of the plurality of protrusions against impact is insufficient, and the scratch prevention property by the ball drop test is insufficient. Further, in Examples 19 and 23, the sticking prevention property is insufficient because the average radius of the circle into which the three adjacent protrusions are inserted is large with respect to the size of the light emitting region.
  • the light diffusion sheet according to one aspect of the present invention has high scratch resistance and excellent sticking prevention properties, and is therefore suitably used for various liquid crystal display devices.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Nonlinear Science (AREA)
  • Mathematical Physics (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Planar Illumination Modules (AREA)
  • Optical Elements Other Than Lenses (AREA)
  • Liquid Crystal (AREA)

Abstract

The present invention addresses the problem of providing a light diffusing sheet that offers excellent scratch resistance and excellent anti-sticking properties. A light diffusing sheet according to an aspect of the present invention is provided with multiple protrusions on the rear surface in a scattered manner; the average height of the multiple protrusions is 3.0 μｍ - 20. 0 μｍ inclusive; and the variation coefficient of height is 0.30 or less. A backlight unit for a liquid crystal display device according to another aspect of the present invention is provided with: a light guide plate or a light guide sheet that guides a beam entering from the end surface toward the front surface side; one or more light sources placed along the end surface of the light guide plate or the light guide sheet; and the light diffusing sheet that is placed on the front surface side of the light guide plate or the light guide sheet.

Description

光拡散シート及び液晶表示装置用バックライトユニットBacklight unit for light diffusion sheet and liquid crystal display device
　本発明は、光拡散シート及び液晶表示装置用バックライトユニットに関する。 The present invention relates to a light diffusion sheet and a backlight unit for a liquid crystal display device.
　フラットパネルディスプレイ等の液晶表示装置は、例えば液晶セル及びこの液晶セルの両面側に積層される一対の偏光板を有する液晶表示パネルと、この液晶表示パネルの裏面側に配設され、この液晶表示パネルに向けて光線を照射するバックライトユニットとを備える。 A liquid crystal display device such as a flat panel display is arranged on, for example, a liquid crystal cell and a liquid crystal display panel having a pair of polarizing plates laminated on both side surfaces of the liquid crystal cell, and the back surface side of the liquid crystal display panel. It is equipped with a backlight unit that irradiates a light beam toward the panel.
　上記バックライトユニットの種類としては、エッジライト型（サイドライト型）、直下型等が存在している。上記エッジライト型バックライトユニットは、端面から入射された光線を表面側に導く導光板又は導光シートと、この導光板又は導光シートの端面に沿って配設される１又は複数の光源と、上記導光板又は導光シートの表面側に配設される光拡散シートと、この光拡散シートの表面側に配設されるプリズムシートとを有する。 As the type of the above backlight unit, there are an edge light type (side light type), a direct type, and the like. The edge light type backlight unit includes a light guide plate or a light guide sheet that guides light rays incident from an end face toward the surface side, and one or a plurality of light sources arranged along the end face of the light guide plate or the light guide sheet. It has a light diffusing sheet arranged on the surface side of the light guide plate or the light guide sheet, and a prism sheet arranged on the surface side of the light diffusing sheet.
　このエッジライト型バックライトユニットでは、上記光拡散シートの裏面は導光板又は導光シートと接触している。そのため、上記エッジライト型バックライトユニットでは、光拡散シートの裏面が導光板又は導光シートと部分的に密着してスティッキングを生じることがある。このスティッキングが生じた部分では光が十分に拡散し難いため、バックライトユニットからの出射光に輝度ムラを生じる原因となる。 In this edge light type backlight unit, the back surface of the light diffusion sheet is in contact with the light guide plate or the light guide sheet. Therefore, in the edge light type backlight unit, the back surface of the light diffusion sheet may partially adhere to the light guide plate or the light guide sheet to cause sticking. Since it is difficult for the light to be sufficiently diffused in the portion where this sticking occurs, it causes uneven brightness in the light emitted from the backlight unit.
　このような観点から、今日では、光拡散シートの最裏層として、バインダー中にビーズが分散したスティッキング防止層を設けることが行われている（特開２００４－２５２３５３号公報参照）。 From this point of view, today, as the innermost layer of the light diffusion sheet, an anti-sticking layer in which beads are dispersed in a binder is provided (see JP-A-2004-252353).
特開２００４－２５２３５３号公報Japanese Unexamined Patent Publication No. 2004-252353
　しかしながら、上記公報に記載の従来のスティッキング防止層によると、ビーズの突出高さを制御し難い。そのため、ビーズの突出高さが部分的に大きくなることがあり、この部分に加わる荷重が大きくなることで、導光板又は導光シートの表面に傷付きを生じるおそれが大きくなる。 However, according to the conventional anti-sticking layer described in the above publication, it is difficult to control the protruding height of the beads. Therefore, the protruding height of the beads may be partially increased, and the load applied to this portion is increased, so that the surface of the light guide plate or the light guide sheet is more likely to be scratched.
　本発明は、このような事情に鑑みてなされたものであり、傷付き防止性が高く、かつ優れたスティッキング防止性を有する光拡散シート及び液晶表示装置用バックライトユニットの提供を課題とする。 The present invention has been made in view of such circumstances, and an object of the present invention is to provide a light diffusion sheet and a backlight unit for a liquid crystal display device, which have high scratch resistance and excellent sticking prevention.
　上記課題を解決するためになされた本発明の一態様に係る光拡散シートは、裏面に複数の突起を散点的に備え、上記複数の突起の平均高さが３．０μｍ以上２０．０μｍ以下、高さの変動係数が０．３０以下である。 The light diffusion sheet according to one aspect of the present invention made to solve the above problems is provided with a plurality of protrusions on the back surface in a scattered manner, and the average height of the plurality of protrusions is 3.0 μm or more and 20.0 μm or less. , The coefficient of variation of height is 0.30 or less.
　当該光拡散シートは、上記複数の突起の高さの変動係数が上記上限以下であるので、上記複数の突起に加わる荷重の偏りを抑制することができる。また、当該光拡散シートは、上記複数の突起の平均高さが上記範囲内であるので、当該光拡散シートの裏面側に配設される他の光学部材とのスティッキングを抑制しつつ、上記複数の突起との当接に起因して上記光学部材表面に傷付きを生じるのを抑制することができる。従って、当該光拡散シートは、傷付き防止性が高く、かつ優れたスティッキング防止性を有する。 Since the coefficient of variation of the heights of the plurality of protrusions of the light diffusion sheet is equal to or less than the upper limit, it is possible to suppress the bias of the load applied to the plurality of protrusions. Further, since the average height of the plurality of protrusions of the light diffusing sheet is within the above range, the plurality of light diffusing sheets suppress sticking with other optical members arranged on the back surface side of the light diffusing sheet. It is possible to prevent the surface of the optical member from being scratched due to the contact with the protrusion. Therefore, the light diffusion sheet has high scratch resistance and excellent sticking prevention.
　上記突起が、円錐台状の胴部と、この胴部の先端側に連続するドーム状の先端部とを有するとよい。このように、上記突起が、円錐台状の胴部と、この胴部の先端側に連続するドーム状の先端部とを有することで、上記複数の突起の強度を大きくしつつ、これらの突起と上記光学部材との当接面積を小さくして、スティッキングの発生を抑制することができる。これにより、例えばスマートフォンやタブレット端末等の小型の携帯端末に用いられた場合でも十分に高精細な画像を表示することができる。 It is preferable that the protrusion has a truncated cone-shaped body portion and a dome-shaped tip portion continuous to the tip end side of the trunk portion. As described above, the protrusions have a truncated cone-shaped body portion and a dome-shaped tip portion continuous to the tip end side of the body portion, thereby increasing the strength of the plurality of protrusions while increasing the strength of these protrusions. The contact area between the and the optical member can be reduced to suppress the occurrence of sticking. As a result, it is possible to display a sufficiently high-definition image even when it is used in a small mobile terminal such as a smartphone or a tablet terminal.
　上記裏面における上記複数の突起の占有面積率としては２％以上８０％以下が好ましい。このように、上記裏面における上記複数の突起の占有面積率が上記範囲内であることによって、傷付き防止性及びスティッキング防止性を高めることができる。 The occupied area ratio of the plurality of protrusions on the back surface is preferably 2% or more and 80% or less. As described above, when the occupied area ratio of the plurality of protrusions on the back surface is within the above range, scratch prevention and sticking prevention can be enhanced.
　光線出射領域のサイズをＳ［インチ］、この光線出射領域の上記裏面における上記複数の突起の占有面積率をＲ［％］とした場合、以下の（１）又は（２）の条件を満たすとよい。
（１）Ｓ＜７の場合、６０≦Ｒ
（２）７≦Ｓ≦１５の場合、２．０≦Ｒ≦３０．０ When the size of the light emitting region is S [inch] and the occupied area ratio of the plurality of protrusions on the back surface of the light emitting region is R [%], the following conditions (1) or (2) are satisfied. Good.
(1) When S <7, 60 ≦ R
(2) When 7 ≦ S ≦ 15, 2.0 ≦ R ≦ 30.0
　これにより、傷付き防止性及びスティッキング防止性をより高めることができる。 This makes it possible to further improve scratch prevention and sticking prevention.
　光線出射領域のサイズをＳ［インチ］、この光線出射領域の上記裏面上において近接する３つの上記突起が入る円の平均半径をｒ［μｍ］とした場合、以下の（１）又は（２）の条件を満たすとよい。
（１）Ｓ＜７の場合、ｒ≦４０
（２）７≦Ｓ≦１５の場合、４０≦ｒ≦４００ When the size of the light emitting region is S [inch] and the average radius of the circle containing the three adjacent protrusions on the back surface of the light emitting region is r [μm], the following (1) or (2) It is good to satisfy the condition of.
(1) When S <7, r ≦ 40
(2) When 7 ≦ S ≦ 15, 40 ≦ r ≦ 400
　これにより、傷付き防止性及びスティッキング防止性をより高めることができる。 This makes it possible to further improve scratch prevention and sticking prevention.
　上記課題を解決するためになされた本発明の他の一態様に係る液晶表示装置用バックライトユニットは、端面から入射された光線を表面側に導く導光板又は導光シートと、上記導光板又は導光シートの上記端面に沿って配設される１又は複数の光源と、上記導光板又は導光シートの表面側に配設される当該光拡散シートとを備える。 The backlight unit for a liquid crystal display device according to another aspect of the present invention, which has been made to solve the above problems, includes a light guide plate or a light guide sheet that guides light rays incident from an end surface toward the surface side, and the light guide plate or the light guide sheet. It includes one or a plurality of light sources arranged along the end face of the light guide sheet, and the light diffusing sheet arranged on the surface side of the light guide plate or the light guide sheet.
　当該液晶表示装置用バックライトユニットは、当該光拡散シートを備えるので、傷付き防止性が高く、かつ優れたスティッキング防止性を有する。 Since the backlight unit for the liquid crystal display device includes the light diffusion sheet, it has high scratch prevention and excellent sticking prevention.
　なお、本発明において、「表面」とは、液晶表示装置に組み込まれた際の視認者側の面をいい、「裏面」とは、その反対側の面をいう。「複数の突起の平均高さ」とは、任意の１０個の突起の高さの平均値をいう。「複数の突起の高さの変動係数」とは、任意の１０個の突起の高さの標準偏差を平均高さで割った値をいう。「光線出射領域」とは、表示画面と平面視で重なり合う領域をいう。「裏面上において近接する３つの突起が入る円の平均半径」とは、任意の１０個の突起を抽出し、抽出した各突起について、この突起とこの突起以外の他の２個の突起とが入る裏面上の円の最小半径を求めたうえ、求められた１０個の半径のうち１番大きい値と１番小さい値とを除いた値の平均値をいう。 In the present invention, the "front surface" refers to the surface on the viewer side when incorporated in the liquid crystal display device, and the "back surface" refers to the surface on the opposite side. The "average height of a plurality of protrusions" means an average value of the heights of any 10 protrusions. The "coefficient of variation of the heights of a plurality of protrusions" means a value obtained by dividing the standard deviation of the heights of any 10 protrusions by the average height. The “light ray emitting area” refers to an area that overlaps with the display screen in a plan view. "The average radius of a circle containing three adjacent protrusions on the back surface" means that any 10 protrusions are extracted, and for each of the extracted protrusions, this protrusion and the other two protrusions other than this protrusion are It is the average value of the values obtained by calculating the minimum radius of the circle on the back surface to be inserted and excluding the largest value and the smallest value among the obtained 10 radii.
　以上説明したように、本発明の一態様に係る光拡散シート及び他の態様に係る液晶表示装置用バックライトユニットは、傷付き防止性が高く、かつ優れたスティッキング防止性を有する。 As described above, the light diffusion sheet according to one aspect of the present invention and the backlight unit for a liquid crystal display device according to another aspect have high scratch prevention and excellent sticking prevention.
図１は、本発明の一実施形態に係る液晶表示装置用バックライトユニットを示す模式的端面図である。FIG. 1 is a schematic end view showing a backlight unit for a liquid crystal display device according to an embodiment of the present invention. 図２は、図１の液晶表示装置用バックライトユニットの光拡散シートの模式的底面図である。FIG. 2 is a schematic bottom view of the light diffusion sheet of the backlight unit for the liquid crystal display device of FIG. 図３は、図２の光拡散シートの突起を示す模式的側面図である。FIG. 3 is a schematic side view showing the protrusions of the light diffusion sheet of FIG. 図４は、図３の突起を先端側から見た模式的底面図である。FIG. 4 is a schematic bottom view of the protrusion of FIG. 3 as viewed from the tip side. 図５は、図２の光拡散シートの突起の配置を示す模式的部分拡大底面図である。FIG. 5 is a schematic partially enlarged bottom view showing the arrangement of the protrusions of the light diffusion sheet of FIG. 図６は、図３の突起とは異なる実施形態に係る突起を示す模式的側面図である。FIG. 6 is a schematic side view showing a protrusion according to an embodiment different from the protrusion of FIG. 図７は、図６の突起を先端側から見た模式的底面図である。FIG. 7 is a schematic bottom view of the protrusion of FIG. 6 as viewed from the tip side.
　以下、適宜図面を参照しつつ、本発明の実施の形態を詳説する。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.
［第一実施形態］
＜光拡散シート＞
　図１の液晶表示装置用バックライトユニット１（以下、単に「バックライトユニット１」ともいう）は、エッジライト型バックライトユニットである。当該バックライトユニット１は、端面から入射された光線を表面側に導く導光シート２と、導光シート２の上記端面に沿って配設される１又は複数の光源３と、導光シート２の表面側に配設される光拡散シート４とを備える。光拡散シート４は、導光シート２の表面に直接（他の部材を介することなく）積層されている。光拡散シート４は、それ自体本発明の一態様を構成する。また、当該バックライトユニット１は、光拡散シート４の表面側に配設されるプリズムシート５と、導光シート２の裏面側に配設される反射シート６とを備える。なお、当該バックライトユニット１は、プリズムシート５の表面側に他のプリズムシートが配設されていてもよい。 [First Embodiment]
<Light diffusion sheet>
The backlight unit 1 for a liquid crystal display device (hereinafter, also simply referred to as “backlight unit 1”) of FIG. 1 is an edge light type backlight unit. The backlight unit 1 includes a light guide sheet 2 that guides light rays incident from an end surface toward the surface side, one or a plurality of light sources 3 arranged along the end surface of the light guide sheet 2, and a light guide sheet 2. The light diffusing sheet 4 is provided on the surface side of the above. The light diffusion sheet 4 is laminated directly (without interposing other members) on the surface of the light guide sheet 2. The light diffusion sheet 4 itself constitutes an aspect of the present invention. Further, the backlight unit 1 includes a prism sheet 5 arranged on the front surface side of the light diffusion sheet 4 and a reflection sheet 6 arranged on the back surface side of the light guide sheet 2. In the backlight unit 1, another prism sheet may be arranged on the surface side of the prism sheet 5.
（光拡散シート）
　当該光拡散シート４は、導光シート２に対向する光入射面と、この光入射面と反対側の光出射面とを有する。当該光拡散シート４は、上記光入射面から入射した光線を上記光出射面から出射する。当該光拡散シート４は、全体として可撓性を有する。 (Light diffusion sheet)
The light diffusion sheet 4 has a light incident surface facing the light guide sheet 2 and a light emitting surface on the opposite side of the light incident surface. The light diffusion sheet 4 emits light rays incident from the light incident surface from the light emitting surface. The light diffusion sheet 4 has flexibility as a whole.
　当該光拡散シート４は、裏面４ａに複数の突起１１を散点的に備える。当該光拡散シート４は、基材層１２と、基材層１２の表面側に積層される光拡散層１３とを備えており、基材層１２の裏面に複数の突起１１が散点的に形成されている。当該光拡散シート４は、基材層１２の表面に光拡散層１３が直接積層され、基材層１２の裏面に複数の突起１１が直接形成されている。つまり、当該光拡散シート４は、基材層１２、光拡散層１３及び複数の突起１１以外の他の層を有しておらず、基材層１２の裏面が当該光拡散シート４の裏面４ａを構成している。当該光拡散シート４は、基材層１２の裏面及び複数の突起１１の外面が光入射面を構成し、光拡散層１３の表面が光出射面を構成している。当該光拡散シート４は、複数の突起１１が導光シート２の表面に部分的に当接することで導光シート２の表面側に配置されている。複数の突起１１と導光シート２との当接部分は、接着剤等によって固定されていない。 The light diffusion sheet 4 is provided with a plurality of protrusions 11 on the back surface 4a in a scattered manner. The light diffusion sheet 4 includes a base material layer 12 and a light diffusion layer 13 laminated on the front surface side of the base material layer 12, and a plurality of protrusions 11 are scattered on the back surface of the base material layer 12. It is formed. In the light diffusion sheet 4, the light diffusion layer 13 is directly laminated on the surface of the base material layer 12, and a plurality of protrusions 11 are directly formed on the back surface of the base material layer 12. That is, the light diffusion sheet 4 does not have any layers other than the base material layer 12, the light diffusion layer 13, and the plurality of protrusions 11, and the back surface of the base material layer 12 is the back surface 4a of the light diffusion sheet 4. Consists of. In the light diffusion sheet 4, the back surface of the base material layer 12 and the outer surfaces of the plurality of protrusions 11 form a light incident surface, and the surface of the light diffusion layer 13 constitutes a light emitting surface. The light diffusing sheet 4 is arranged on the surface side of the light guide sheet 2 by partially contacting the surface of the light guide sheet 2 with a plurality of protrusions 11. The contact portion between the plurality of protrusions 11 and the light guide sheet 2 is not fixed by an adhesive or the like.
〔基材層〕
　基材層１２は、光線を透過させる必要があるので透明である。基材層１２は、可撓性を有する。基材層１２は、合成樹脂を主成分とする。基材層１２の主成分としては、特に限定されるものではなく、例えばポリエチレンテレフタレート、ポリエチレンナフタレート、アクリル樹脂、ポリカーボネート、ポリスチレン、ポリオレフィン、セルロースアセテート、耐候性塩化ビニル等が挙げられる。中でも、透明性に優れ、強度が高いポリエチレンテレフタレートが好ましく、撓み性能が改善されたポリエチレンテレフタレートが特に好ましい。なお、「主成分」とは、質量換算で最も含有量の多い成分をいい、例えば含有量が５０質量％以上の成分をいう。 [Base layer]
The base material layer 12 is transparent because it needs to transmit light rays. The base material layer 12 has flexibility. The base material layer 12 contains a synthetic resin as a main component. The main component of the base material layer 12 is not particularly limited, and examples thereof include polyethylene terephthalate, polyethylene naphthalate, acrylic resin, polycarbonate, polystyrene, polyolefin, cellulose acetate, and weather-resistant vinyl chloride. Among them, polyethylene terephthalate having excellent transparency and high strength is preferable, and polyethylene terephthalate having improved bending performance is particularly preferable. The "main component" refers to a component having the highest content in terms of mass, for example, a component having a content of 50% by mass or more.
　基材層１２の平均厚さの下限としては、１０μｍが好ましく、２０μｍがより好ましい。一方、基材層１２の平均厚さの上限としては、２００μｍが好ましく、１００μｍがより好ましく、５０μｍがさらに好ましい。上記平均厚さが上記下限に満たないと、基材層１２の強度が不十分となり、基材層１２の裏面が部分的に導光シート２に接触するおそれがある。逆に、上記平均厚さが上記上限を超えると、当該光拡散シート４の薄型化の要請に反するおそれや、基材層１２が重くなることで、複数の突起１１に加わる荷重が大きくなり、導光シート２の表面に傷付きを生じるおそれが高くなる。 As the lower limit of the average thickness of the base material layer 12, 10 μm is preferable, and 20 μm is more preferable. On the other hand, the upper limit of the average thickness of the base material layer 12 is preferably 200 μm, more preferably 100 μm, and even more preferably 50 μm. If the average thickness does not reach the lower limit, the strength of the base material layer 12 becomes insufficient, and the back surface of the base material layer 12 may partially come into contact with the light guide sheet 2. On the contrary, when the average thickness exceeds the upper limit, the load applied to the plurality of protrusions 11 becomes large due to the possibility of violating the request for thinning of the light diffusion sheet 4 and the heaviness of the base material layer 12. There is a high possibility that the surface of the light guide sheet 2 will be scratched.
〔突起〕
　図２～図４に示すように、複数の突起１１は、基材層１２の裏面から光線の入射側（導光シート２側）に突出している。複数の突起１１は、基材層１２の裏面上に不規則に配置されている。 [Protrusion]
As shown in FIGS. 2 to 4, the plurality of protrusions 11 project from the back surface of the base material layer 12 to the incident side (light guide sheet 2 side) of the light beam. The plurality of protrusions 11 are irregularly arranged on the back surface of the base material layer 12.
　複数の突起１１の平均高さＨ１ＡＶＧは３．０μｍ以上２０．０μｍ以下である。また、複数の突起１１の高さＨ１の変動係数は０．３０以下である。当該光拡散シート４は、例えば後述するように複数の突起１１の反転形状を有する複数の凹部を備える押圧ロールを用いて複数の突起１１を形成することで、これらの突起１１を所望の形状に形成することができる。 The average height H1 AVG of the plurality of protrusions 11 is 3.0 μm or more and 20.0 μm or less. Further, the coefficient of variation of the height H1 of the plurality of protrusions 11 is 0.30 or less. The light diffusion sheet 4 has a plurality of protrusions 11 formed into a desired shape by forming the plurality of protrusions 11 by using a pressing roll having a plurality of recesses having an inverted shape of the plurality of protrusions 11 as described later. Can be formed.
　複数の突起１１の平均高さＨ１ＡＶＧの下限としては、４．０μｍが好ましく、５．０μｍがより好ましい。一方、上記平均高さＨ１ＡＶＧの上限としては、１６．０μｍが好ましく、１０．０μｍがより好ましい。上記平均高さＨ１ＡＶＧが上記下限に満たないと、導光シート２とのスティッキングを十分に抑制することができないおそれがある。逆に、上記平均高さＨ１ＡＶＧが上記上限を超えると、複数の突起１１との当接に起因して導光シート２の表面に傷付きを生じるおそれや、突起１１が折れやすくなるおそれがある。 The lower limit of the average height H1 AVG of the plurality of protrusions 11 is preferably 4.0 μm, more preferably 5.0 μm. On the other hand, the upper limit of the average height H1 AVG is preferably 16.0 μm, more preferably 10.0 μm. If the average height H1 AVG does not reach the lower limit, sticking with the light guide sheet 2 may not be sufficiently suppressed. On the contrary, when the average height H1 AVG exceeds the upper limit, the surface of the light guide sheet 2 may be scratched due to the contact with the plurality of protrusions 11, or the protrusions 11 may be easily broken. is there.
　複数の突起１１の高さＨ１の変動係数の上限としては、０．２０が好ましく、０．１０がより好ましく、０．０５がさらに好ましい。上記変動係数が上記上限を超えると、複数の突起１１の高さが不均一となり、高さの大きい突起１１に荷重が偏り、これに基づいて導光シート２の表面に傷付きが生じるおそれがある。一方、上記変動係数の下限としては、特に限定されるものではなく、例えば０とすることができる。 The upper limit of the coefficient of variation of the height H1 of the plurality of protrusions 11 is preferably 0.20, more preferably 0.10, and even more preferably 0.05. If the coefficient of variation exceeds the upper limit, the heights of the plurality of protrusions 11 become non-uniform, the load is biased to the protrusions 11 having a large height, and the surface of the light guide sheet 2 may be scratched based on this. is there. On the other hand, the lower limit of the coefficient of variation is not particularly limited and may be, for example, 0.
　複数の突起１１の底面（基材層１２との境界面）の平均径Ｄ１ＡＶＧの下限としては、１０μｍが好ましく、１５μｍがより好ましい。一方、上記平均径Ｄ１ＡＶＧの上限としては、４０μｍが好ましく、３０μｍがより好ましい。上記平均径Ｄ１ＡＶＧが上記下限に満たないと、複数の突起１１の強度が不十分となるおそれがある。逆に、上記平均径Ｄ１ＡＶＧが上記上限を超えると、複数の突起１１と導光シート２との当接面積が大きくなり、スティッキングを生じるおそれがある。なお、「径」とは、等面積の真円に換算した径をいう。また、本明細書全体を通して「平均径」とは、任意の１０個の径の平均値をいう。 The lower limit of the average diameter D1 AVG of the bottom surfaces (boundary surface with the base material layer 12) of the plurality of protrusions 11 is preferably 10 μm, more preferably 15 μm. On the other hand, the upper limit of the average diameter D1 AVG is preferably 40 μm, more preferably 30 μm. If the average diameter D1 AVG does not reach the lower limit, the strength of the plurality of protrusions 11 may be insufficient. On the contrary, when the average diameter D1 AVG exceeds the upper limit, the contact area between the plurality of protrusions 11 and the light guide sheet 2 becomes large, which may cause sticking. The "diameter" means a diameter converted into a perfect circle with an equal area. Further, throughout the present specification, the "average diameter" means an average value of any 10 diameters.
　図３及び図４に示すように、突起１１は、円錐台状の胴部１１ａと、胴部１１ａの先端側に連続するドーム状の先端部１１ｂとを有する。胴部１１ａは、基端側（基材層１２側）から先端側に向けて縮径している。突起１１は、先端部１１ｂの先端側で導光シート２と当接する。当該光拡散シート４は、突起１１が胴部１１ａを有することで、突起１１のサイズを比較的小さくした場合でも、突起１１の強度を十分に大きくすることができる。当該光拡散シート４は、胴部１１ａの先端側にドーム状の先端部１１ｂを有することで、突起１１と導光シート２との当接面積を小さくして、スティッキングの発生を抑制することができる。これにより、当該光拡散シート４は、例えばスマートフォンやタブレット端末等の小型の携帯端末に用いられた場合でも十分に高精細な画像を表示することができる。なお、「円錐台状」とは、高さ方向と垂直な方向の断面が真円状又は略真円状のものの他、楕円状等のものを含む。また「ドーム状」とは、頂点を通り高さ方向に平行な任意の断面において先端側の外縁が先端側に凸な弓なり（円弧状、楕円弧状等）に湾曲した形状をいう。 As shown in FIGS. 3 and 4, the protrusion 11 has a truncated cone-shaped body portion 11a and a dome-shaped tip portion 11b continuous to the tip end side of the body portion 11a. The body portion 11a has a reduced diameter from the base end side (base material layer 12 side) toward the tip end side. The protrusion 11 comes into contact with the light guide sheet 2 on the tip side of the tip portion 11b. Since the protrusion 11 has the body portion 11a of the light diffusion sheet 4, the strength of the protrusion 11 can be sufficiently increased even when the size of the protrusion 11 is relatively small. By having the dome-shaped tip portion 11b on the tip end side of the body portion 11a, the light diffusion sheet 4 can reduce the contact area between the protrusion 11 and the light guide sheet 2 and suppress the occurrence of sticking. it can. As a result, the light diffusion sheet 4 can display a sufficiently high-definition image even when it is used in a small mobile terminal such as a smartphone or a tablet terminal. The term "truncated cone" includes a cross section having a perfect circular shape or a substantially perfect circular shape in the direction perpendicular to the height direction, as well as an elliptical shape and the like. Further, the "dome shape" refers to a shape in which the outer edge on the tip side is curved in an arc shape (arc shape, elliptical arc shape, etc.) on the tip side in an arbitrary cross section that passes through the apex and is parallel to the height direction.
　突起１１は、底面の径Ｄ１に対する高さＨ１の比が１より小さいことが好ましい。つまり、突起１１は、径Ｄ１に対して高さＨ１の小さい扁平状であることが好ましい。突起１１は、径Ｄ１に対する高さＨ１の比を小さくすることで強度を大きくしやすい。また、突起１１は、円錐台状の胴部１１ａの先端側にドーム状の先端部１１ｂを有するので、径Ｄ１に対する高さＨ１の比を小さくしても突起１１と導光シート２との当接面積が大きくなり過ぎることを抑制できる。 It is preferable that the ratio of the height H1 to the diameter D1 of the bottom surface of the protrusion 11 is smaller than 1. That is, it is preferable that the protrusion 11 has a flat shape having a height H1 smaller than that of the diameter D1. The strength of the protrusion 11 can be easily increased by reducing the ratio of the height H1 to the diameter D1. Further, since the protrusion 11 has a dome-shaped tip portion 11b on the tip end side of the truncated cone-shaped body portion 11a, the protrusion 11 and the light guide sheet 2 are in contact with each other even if the ratio of the height H1 to the diameter D1 is reduced. It is possible to prevent the contact area from becoming too large.
　先端部１１ｂの外面は胴部１１ａの側面から連続して形成されている。先端部１１ｂは、基端側から先端側に向けて曲率半径が段階的及び／又は連続的に漸増するよう構成されてもよい。当該光拡散シート４は、胴部１１ａが上述の円錐台状であることで胴部１１ａと導光シート２との接触が防止される。そのため、当該光拡散シート４は、先端部１１ｂの先端側の曲率半径を大きくしても、突起１１と導光シート２との当接面積を小さく抑えることができる。その結果、当該光拡散シート４は、導光シート２とのスティッキングを十分に抑制しつつ、複数の突起１１との当接に起因する導光シート２の表面の傷付きを十分に抑えることができる。 The outer surface of the tip portion 11b is formed continuously from the side surface of the body portion 11a. The tip portion 11b may be configured such that the radius of curvature gradually and / or continuously increases from the base end side to the tip end side. Since the body 11a of the light diffusion sheet 4 has the above-mentioned truncated cone shape, contact between the body 11a and the light guide sheet 2 is prevented. Therefore, the light diffusing sheet 4 can keep the contact area between the protrusion 11 and the light guide sheet 2 small even if the radius of curvature on the tip side of the tip portion 11b is increased. As a result, the light diffusing sheet 4 can sufficiently suppress sticking with the light guide sheet 2 and sufficiently suppress scratches on the surface of the light guide sheet 2 due to contact with the plurality of protrusions 11. it can.
　当該光拡散シート４の裏面４ａ（本実施形態では基材層１２の裏面）における複数の突起１１の占有面積率の下限としては２％が好ましい。一方、上記占有面積率の上限としては、８０％が好ましい。上記占有面積率が上記下限に満たないと、導光シート２とのスティッキングを十分に抑制できないおそれがある。逆に、上記占有面積率が上記上限を超えると、複数の突起１１が不必要に多くなり、導光シート２の表面に傷付きを生じるおそれがある。 The lower limit of the occupied area ratio of the plurality of protrusions 11 on the back surface 4a of the light diffusion sheet 4 (the back surface of the base material layer 12 in this embodiment) is preferably 2%. On the other hand, the upper limit of the occupied area ratio is preferably 80%. If the occupied area ratio does not reach the lower limit, sticking with the light guide sheet 2 may not be sufficiently suppressed. On the contrary, when the occupied area ratio exceeds the upper limit, the plurality of protrusions 11 may be unnecessarily increased, and the surface of the light guide sheet 2 may be scratched.
　図２に示すように、当該光拡散シート４は、液晶表示装置に組み込まれた状態で、液晶表示パネルの液晶表示画面に対応する光線出射領域Ａを有する。光出射領域Ａは、例えば矩形状であり、典型的には長方形状である。当該光拡散シート４は、光線出射領域ＡのサイズをＳ［インチ］、この光線出射領域Ａの裏面４ａにおける複数の突起１１の占有面積率をＲ［％］とした場合、以下の（１）又は（２）の条件を満たすことが好ましい。
（１）Ｓ＜７の場合、６０≦Ｒ
（２）７≦Ｓ≦１５の場合、２．０≦Ｒ≦３０．０
　なお、この光線出射領域Ａは、通常は当該光拡散シート４の平面面積と略等しい。光線出射領域Ａが当該光拡散シート４の平面面積と略等しい場合、この光線出射領域Ａは、当該光拡散シートの平面面積に換算することも可能である。また、７インチとは、対角線の長さが１７．８ｃｍであるサイズをいい、１５インチとは、対角線の長さが３８．１ｃｍであるサイズをいう。 As shown in FIG. 2, the light diffusing sheet 4 has a light emitting region A corresponding to the liquid crystal display screen of the liquid crystal display panel in a state of being incorporated in the liquid crystal display device. The light emitting region A has, for example, a rectangular shape, and is typically rectangular. When the size of the light emitting region A of the light diffusing sheet 4 is S [inch] and the occupied area ratio of the plurality of protrusions 11 on the back surface 4a of the light emitting region A is R [%], the following (1) Alternatively, it is preferable to satisfy the condition of (2).
(1) When S <7, 60 ≦ R
(2) When 7 ≦ S ≦ 15, 2.0 ≦ R ≦ 30.0
The light emitting region A is usually substantially equal to the plane area of the light diffusion sheet 4. When the light emitting region A is substantially equal to the plane area of the light diffusing sheet 4, the light emitting region A can be converted into the plane area of the light diffusing sheet. Further, 7 inches means a size having a diagonal length of 17.8 cm, and 15 inches means a size having a diagonal length of 38.1 cm.
　また、Ｓ＜７の場合、Ｒの下限としては、６５がより好ましい。Ｒが上記下限に満たないと、当該光拡散シート４を組み込んだ装置の落下等に起因して、当該光拡散シート４に傷付きを生じるおそれがある。一方、この場合のＲの上限としては、例えば９０が好ましく、８５がより好ましい。Ｒが上記上限を超える場合、スティッキング防止機能の向上効果が得られないおそれがある。 Further, when S <7, 65 is more preferable as the lower limit of R. If R does not reach the above lower limit, the light diffusing sheet 4 may be damaged due to dropping of the device incorporating the light diffusing sheet 4. On the other hand, as the upper limit of R in this case, for example, 90 is preferable, and 85 is more preferable. If R exceeds the above upper limit, the effect of improving the sticking prevention function may not be obtained.
　７≦Ｓ≦１５の場合、Ｒの下限としては、３．０がより好ましく、５．０がさらに好ましい。一方、この場合、Ｒの上限としては、２５．０がより好ましく、２０．０がさらに好ましい。Ｒが上記下限に満たないと、導光シート２とのスティッキングを十分に抑制することができないおそれがある。逆に、Ｒが上記上限を超えると、導光シート２の表面に傷付きを生じるおそれがある。 When 7 ≦ S ≦ 15, 3.0 is more preferable and 5.0 is more preferable as the lower limit of R. On the other hand, in this case, the upper limit of R is more preferably 25.0 and even more preferably 20.0. If R does not reach the above lower limit, sticking with the light guide sheet 2 may not be sufficiently suppressed. On the contrary, if R exceeds the above upper limit, the surface of the light guide sheet 2 may be scratched.
　図５に示すように、光線出射領域ＡのサイズをＳ［インチ］、この光線出射領域Ａの裏面４ａ上において近接する３つの上記突起１１が入る円（３つの突起１１の側縁に接する円）の平均半径をｒ［μｍ］とした場合、以下の（１）又は（２）の条件を満たすことが好ましい。
（１）Ｓ＜７の場合、ｒ≦４０
（２）７≦Ｓ≦１５の場合、４０≦ｒ≦４００ As shown in FIG. 5, the size of the light emitting region A is S [inch], and a circle (a circle tangent to the side edges of the three protrusions 11) containing the three adjacent protrusions 11 on the back surface 4a of the light emitting region A. ) Is r [μm], it is preferable to satisfy the following conditions (1) or (2).
(1) When S <7, r ≦ 40
(2) When 7 ≦ S ≦ 15, 40 ≦ r ≦ 400
　また、Ｓ＜７の場合、ｒの上限としては、３５がより好ましい。ｒが上記上限を超えると、当該光拡散シート４を組み込んだ装置の落下等に起因して、当該光拡散シート４に傷付きを生じるおそれがある。一方、この場合のｒの下限としては、例えば５が好ましく、１０がより好ましい。ｒが上記下限に満たない場合、スティッキング防止機能の向上効果が得られないおそれがある。 Further, when S <7, 35 is more preferable as the upper limit of r. If r exceeds the above upper limit, the light diffusing sheet 4 may be damaged due to dropping of the device incorporating the light diffusing sheet 4. On the other hand, as the lower limit of r in this case, for example, 5 is preferable, and 10 is more preferable. If r is less than the above lower limit, the effect of improving the sticking prevention function may not be obtained.
　７≦Ｓ≦１５の場合、ｒの下限としては、５０がより好ましい。また、この場合、ｒの上限としては、７０がより好ましく、６０がさらに好ましい。ｒが上記下限に満たないと、導光シート２の表面に傷付きを生じるおそれがある。逆に、ｒが上記上限を超えると、導光シート２とのスティッキングを十分に抑制することができないおそれがある。 When 7 ≦ S ≦ 15, 50 is more preferable as the lower limit of r. Further, in this case, as the upper limit of r, 70 is more preferable, and 60 is further preferable. If r is less than the above lower limit, the surface of the light guide sheet 2 may be scratched. On the contrary, if r exceeds the above upper limit, sticking with the light guide sheet 2 may not be sufficiently suppressed.
　突起１１は、樹脂ビーズ等の粒子を含有しない。突起１１は、例えば活性エネルギー線硬化型樹脂や、基材層１２の主成分と同様の合成樹脂を主成分とする。 The protrusion 11 does not contain particles such as resin beads. The protrusion 11 contains, for example, an active energy ray-curable resin or a synthetic resin similar to the main component of the base material layer 12 as a main component.
　上記活性エネルギー線硬化型樹脂としては、例えば紫外線硬化型樹脂が挙げられる。この紫外線硬化型樹脂としては、例えばウレタンアクリレート、アクリル樹脂等が挙げられる。上記アクリル樹脂としては、例えば紫外線硬化型ポリエステルアクリレート、紫外線硬化型エポキシアクリレート、紫外線硬化型ポリオールアクリレート等が挙げられる。 Examples of the active energy ray-curable resin include an ultraviolet curable resin. Examples of the ultraviolet curable resin include urethane acrylate and acrylic resin. Examples of the acrylic resin include ultraviolet curable polyester acrylate, ultraviolet curable epoxy acrylate, and ultraviolet curable polyol acrylate.
〔光拡散層〕
　光拡散層１３は、当該光拡散シート４の最表面を構成する。光拡散層１３は、複数の光拡散剤１３ａ及びそのバインダー１３ｂを有する。光拡散剤１３ａはバインダー１３ｂに囲まれている。光拡散層１３は、複数の光拡散剤１３ａを分散含有することによって、裏面側から表面側に透過する光線を略均一に拡散させる。また、光拡散層１３は、複数の光拡散剤１３ａによって表面に微細凹凸が略均一に形成され、この微細凹凸の各凹部及び凸部がレンズ状に形成されている。光拡散層１３は、かかる微細凹凸のレンズ的作用によって、優れた光拡散機能を発揮し、この光拡散機能に起因して透過光線を法線方向側へ屈折させる屈折機能及び透過光線を法線方向に巨視的に集光させる集光機能を有している。 [Light diffusion layer]
The light diffusion layer 13 constitutes the outermost surface of the light diffusion sheet 4. The light diffusing layer 13 has a plurality of light diffusing agents 13a and a binder 13b thereof. The light diffusing agent 13a is surrounded by a binder 13b. The light diffusing layer 13 disperses and contains a plurality of light diffusing agents 13a to diffuse light rays transmitted from the back surface side to the front surface side substantially uniformly. Further, in the light diffusing layer 13, fine irregularities are formed substantially uniformly on the surface by the plurality of light diffusing agents 13a, and each concave portion and convex portion of the fine irregularities are formed in a lens shape. The light diffusing layer 13 exerts an excellent light diffusing function due to the lens-like action of such fine irregularities, and due to this light diffusing function, the refracting function for refracting the transmitted light rays in the normal direction and the normalizing the transmitted light rays. It has a condensing function that condenses light in the direction macroscopically.
　光拡散剤１３ａは、光線を拡散させる性質を有する微粒子であり、典型的には樹脂ビーズである。光拡散剤１３ａの主成分としては、例えばアクリル樹脂、アクリロニトリル樹脂、ポリウレタン、ポリ塩化ビニル、ポリスチレン、ポリアミド、ポリアクリロニトリル等が挙げられる。中でも、透明性が高いアクリル樹脂が好ましく、ポリメチルメタクリレート（ＰＭＭＡ）が特に好ましい。 The light diffusing agent 13a is fine particles having a property of diffusing light rays, and is typically resin beads. Examples of the main component of the light diffusing agent 13a include acrylic resin, acrylonitrile resin, polyurethane, polyvinyl chloride, polystyrene, polyamide, polyacrylonitrile and the like. Of these, an acrylic resin having high transparency is preferable, and polymethylmethacrylate (PMMA) is particularly preferable.
　光拡散剤１３ａの形状は、特に限定されるものではなく、例えば球状、立方状、針状、棒状、紡錘形状、板状、鱗片状、繊維状などが挙げられ、中でも光拡散性に優れる球状が好ましい。 The shape of the light diffusing agent 13a is not particularly limited, and examples thereof include a spherical shape, a cubic shape, a needle shape, a rod shape, a spindle shape, a plate shape, a scale shape, and a fibrous shape, and among them, a spherical shape having excellent light diffusing property. Is preferable.
　バインダー１３ｂは、基材ポリマーを含むポリマー組成物を硬化（架橋等）させることで形成される。光拡散剤１３ａは、バインダー１３ｂによって、基材層１２の表面全面に略等密度で固定される。なお、バインダー１３ｂを形成するためのポリマー組成物は、その他に例えば微小無機充填剤、硬化剤、可塑剤、分散剤、各種レベリング剤、帯電防止剤、紫外線吸収剤、抗酸化剤、粘性改質剤、潤滑剤、光安定化剤等が適宜配合されていてもよい。 The binder 13b is formed by curing (crosslinking or the like) a polymer composition containing a base polymer. The light diffusing agent 13a is fixed to the entire surface of the base material layer 12 at a substantially equal density by the binder 13b. In addition, the polymer composition for forming the binder 13b includes, for example, a microinorganic filler, a curing agent, a plasticizer, a dispersant, various leveling agents, an antistatic agent, an ultraviolet absorber, an antioxidant, and a viscosity modification. Agents, lubricants, light stabilizers and the like may be appropriately blended.
（導光シート）
　導光シート２は、平面視略方形状に形成されており、厚さが略均一の板状（非楔形状）に形成されている。 (Light guide sheet)
The light guide sheet 2 is formed in a substantially rectangular shape in a plan view, and is formed in a plate shape (non-wedge shape) having a substantially uniform thickness.
　導光シート２の平均厚さの下限としては、１００μｍが好ましく、１５０μｍがより好ましく、２００μｍがさらに好ましい。一方、導光シート２の平均厚さの上限としては、６００μｍが好ましく、４００μｍがより好ましい。導光シート２の平均厚さが上記下限に満たないと、導光シート２の強度が不十分となるおそれがあり、また光源３の光を導光シート２に十分に入射させ難くなるおそれがある。逆に、導光シート２の平均厚さが上記上限を超えると、当該バックライトユニット１の薄型化の要請に反するおそれがある。 The lower limit of the average thickness of the light guide sheet 2 is preferably 100 μm, more preferably 150 μm, and even more preferably 200 μm. On the other hand, the upper limit of the average thickness of the light guide sheet 2 is preferably 600 μm, more preferably 400 μm. If the average thickness of the light guide sheet 2 does not reach the above lower limit, the strength of the light guide sheet 2 may be insufficient, and it may be difficult for the light of the light source 3 to be sufficiently incident on the light guide sheet 2. is there. On the contrary, if the average thickness of the light guide sheet 2 exceeds the above upper limit, there is a possibility that the request for thinning the backlight unit 1 is violated.
　導光シート２は、透光性を有する必要があるため透明、特に無色透明の樹脂を主成分として形成される。導光シート２の主成分としては、特に限定されるものではないが、透明性、強度等に優れるポリカーボネートや、透明性、耐擦傷性等に優れるアクリル樹脂等の合成樹脂が挙げられる。 Since the light guide sheet 2 needs to have translucency, it is formed mainly of a transparent resin, particularly a colorless and transparent resin. The main component of the light guide sheet 2 is not particularly limited, and examples thereof include polycarbonate having excellent transparency and strength, and synthetic resins such as acrylic resin having excellent transparency and scratch resistance.
　導光シート２は、出射光を制御できるよう、表面にレンチキュラー、プリズム列等の凹凸形状を有していてもよい。 The light guide sheet 2 may have an uneven shape such as a lenticular or a prism row on the surface so that the emitted light can be controlled.
（光源）
　光源３は、照射面が導光シート２の端面に対向（又は当接）するよう配設されている。光源３としては、種々のものを用いることが可能であり、例えば発光ダイオード（ＬＥＤ）を用いることが可能である。具体的には、複数の光源３として、複数の発光ダイオードが導光シート２の端面に沿って配設されたものを用いることができる。 (light source)
The light source 3 is arranged so that the irradiation surface faces (or abuts) the end surface of the light guide sheet 2. As the light source 3, various light sources can be used, and for example, a light emitting diode (LED) can be used. Specifically, as the plurality of light sources 3, those in which a plurality of light emitting diodes are arranged along the end faces of the light guide sheet 2 can be used.
（プリズムシート）
　プリズムシート５は、基材層５ａと、この基材層５ａの表面に積層される複数の凸条プリズム部からなるプリズム列５ｂとを有する。基材層５ａ及びプリズム列５ｂは光線を透過させる必要があるので透明である。基材層５ａ及びプリズム列５ｂは合成樹脂を主成分として形成される。当該バックライトユニット１は、プリズムシート５の表面側に他のプリズムシートが配設されてもよく、この場合、プリズムシート５及び上記他のプリズムシートのプリズム列の方向は直交することが好ましい。 (Prism sheet)
The prism sheet 5 has a base material layer 5a and a prism row 5b composed of a plurality of convex prism portions laminated on the surface of the base material layer 5a. The base material layer 5a and the prism row 5b are transparent because they need to transmit light rays. The base material layer 5a and the prism row 5b are formed mainly of a synthetic resin. In the backlight unit 1, another prism sheet may be arranged on the surface side of the prism sheet 5, and in this case, the directions of the prism sheet 5 and the prism rows of the other prism sheet are preferably orthogonal to each other.
（反射シート）
　反射シート６としては、ポリエステル等の基材樹脂にフィラーを分散含有させた白色シートや、ポリエステル等から形成されるフィルムの表面に、アルミニウム、銀等の金属を蒸着させることで正反射性が高められた鏡面シート等が挙げられる。 (Reflective sheet)
As the reflective sheet 6, the specular reflectivity is enhanced by depositing a metal such as aluminum or silver on the surface of a white sheet in which a filler is dispersed and contained in a base resin such as polyester or a film formed of polyester or the like. Examples include the mirror-finished sheet.
＜光拡散シートの製造方法＞
　当該光拡散シート４の製造方法の一例について説明する。以下では、複数の突起１１の主成分として紫外線硬化型樹脂を用いる場合について説明する。当該光拡散シートの製造方法は、基材層１２を用意する工程（用意工程）と、上記用意工程で用意された基材層１２の裏面側に複数の突起１１を形成する工程（突起形成工程）と、基材層１２の表面側に光拡散層１３を積層する工程（光拡散層積層工程）とを備える。 <Manufacturing method of light diffusion sheet>
An example of the manufacturing method of the light diffusion sheet 4 will be described. Hereinafter, a case where an ultraviolet curable resin is used as the main component of the plurality of protrusions 11 will be described. The method for producing the light diffusion sheet includes a step of preparing the base material layer 12 (preparation step) and a step of forming a plurality of protrusions 11 on the back surface side of the base material layer 12 prepared in the preparation step (protrusion formation step). ) And a step of laminating the light diffusing layer 13 on the surface side of the base material layer 12 (light diffusing layer laminating step).
（突起形成工程）
　上記突起形成工程は、例えば上述の紫外線硬化型樹脂を含有する突起形成用樹脂組成物を基材層１２の裏面に塗布する工程（塗布工程）と、上記塗布工程によって塗布した塗工液上に、複数の突起１１の反転形状である複数の凹部を外周面に有する押圧ロールを押圧する工程（押圧工程）と、上記押圧工程後に、紫外線照射によって上記突起形成用樹脂組成物を硬化させる工程（硬化工程）とを備える。上記押圧工程では、基材層１２の裏面に複数の突起１１を転写する。上記硬化工程は、基材層１２の裏面に上記押圧ロールを押圧した状態で行うことが好ましい。上記押圧ロールの外周面に複数の凹部を形成する方法としては、例えばレーザー照射による方法や、押圧ロールの外周面に銅めっき層を形成したうえでエッチングを施す方法が挙げられる。 (Protrusion formation process)
The protrusion forming step includes, for example, a step of applying the protrusion forming resin composition containing the above-mentioned ultraviolet curable resin to the back surface of the base material layer 12 (coating step), and a step of applying the coating liquid on the coating liquid applied by the coating step. A step of pressing a pressing roll having a plurality of concave portions on the outer peripheral surface which is an inverted shape of the plurality of protrusions 11 (pressing step), and a step of curing the resin composition for forming protrusions by ultraviolet irradiation after the pressing step (pressing step). It has a curing process). In the pressing step, the plurality of protrusions 11 are transferred to the back surface of the base material layer 12. The curing step is preferably performed with the pressing roll pressed against the back surface of the base material layer 12. Examples of the method of forming a plurality of recesses on the outer peripheral surface of the pressing roll include a method of laser irradiation and a method of forming a copper plating layer on the outer peripheral surface of the pressing roll and then performing etching.
（光拡散層積層工程）
　上記光拡散層積層工程では、上記突起形成工程後に、複数の光拡散剤１３ａ及びバインダー組成物を含む塗工液を基材層１２の表面に塗布し、塗布した塗工液を乾燥及び硬化させる。 (Light diffusion layer laminating process)
In the light diffusing layer laminating step, after the protrusion forming step, a coating liquid containing a plurality of light diffusing agents 13a and a binder composition is applied to the surface of the base material layer 12, and the applied coating liquid is dried and cured. ..
＜利点＞
　当該光拡散シート４は、複数の突起１１の高さの変動係数が上記上限以下であるので、複数の突起１１に加わる荷重の偏りを抑制することができる。また、当該光拡散シート４は、複数の突起１１の平均高さＨ１ＡＶＧが上記範囲内であるので、当該光拡散シート４の裏面側に配設される他の光学部材（導光シート２）とのスティッキングを抑制しつつ、複数の突起１１との当接に起因して上記光学部材表面に傷付きを生じるのを抑制することができる。従って、当該光拡散シート４は、傷付き防止性が高く、かつ優れたスティッキング防止性を有する。 <Advantage>
Since the coefficient of variation of the heights of the plurality of protrusions 11 of the light diffusion sheet 4 is equal to or less than the above upper limit, it is possible to suppress the bias of the load applied to the plurality of protrusions 11. Further, since the average height H1 AVG of the plurality of protrusions 11 of the light diffusion sheet 4 is within the above range, another optical member (light guide sheet 2) arranged on the back surface side of the light diffusion sheet 4 It is possible to prevent the surface of the optical member from being scratched due to contact with the plurality of protrusions 11 while suppressing sticking with the light. Therefore, the light diffusion sheet 4 has a high scratch prevention property and an excellent sticking prevention property.
　当該バックライトユニット１は、当該光拡散シート４を備えるので、傷付き防止性が高く、かつ優れたスティッキング防止性を有する。 Since the backlight unit 1 includes the light diffusion sheet 4, it has high scratch prevention and excellent sticking prevention.
　当該光拡散シートの製造方法は、傷付き防止性及びスティッキング防止性に優れる当該光拡散シート４を容易かつ確実に製造することができる。 The method for manufacturing the light diffusing sheet can easily and surely manufacture the light diffusing sheet 4 having excellent scratch prevention and sticking prevention properties.
［その他の実施形態］
　今回開示された実施の形態は全ての点で例示であって制限的なものではないと考えられるべきである。本発明の範囲は、上記実施形態の構成に限定されるものではなく、特許請求の範囲によって示され、特許請求の範囲と均等の意味及び範囲内での全ての変更が含まれることが意図される。 [Other Embodiments]
It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is not limited to the configuration of the above embodiment, but is indicated by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims. To.
　例えば上記複数の突起は、基材層の裏面に直接形成されたものでなくてもよい。例えば当該光拡散シートは、上記基材層の裏面側に積層される合成樹脂製の裏層を有し、この裏層の裏面に複数の突起を有していてもよい。なお、この場合、上記裏層の裏面が当該光拡散シートの裏面を構成する。 For example, the plurality of protrusions may not be directly formed on the back surface of the base material layer. For example, the light diffusion sheet may have a synthetic resin back layer laminated on the back surface side of the base material layer, and may have a plurality of protrusions on the back surface of the back layer. In this case, the back surface of the back layer constitutes the back surface of the light diffusion sheet.
　上記光拡散層の具体的構成は、上記実施形態に記載の構成に限定されるものではない。例えば上記光拡散層は、エンボス加工等によって外面に凹凸形状が形成されたものであってもよい。 The specific configuration of the light diffusion layer is not limited to the configuration described in the above embodiment. For example, the light diffusion layer may have an uneven shape formed on the outer surface by embossing or the like.
　上記突起は、必ずしも円錐台状の胴部及びこの胴部の先端側に連続するドーム状の先端部のみからなる必要はない。図６及び図７を参照して、上記突起の変形例について説明する。図６及び図７の突起２１は、円錐台状の胴部２１ａと、胴部２１ａの先端側に連続するドーム状の先端部２１ｂと、胴部２１ａの基端側に連続する裾野部２１ｃとを有する。胴部２１ａとしては、図１の光拡散シート４の突起１１の胴部１１ａと同様の構成とすることができる。先端部２１ｂとしては、図１の光拡散シート４の突起１１の先端部１１ｂと同様の構成とすることができる。裾野部２１ｃは、突起２１の先端側から基端側に向けてラッパ状に拡径している。この構成によると、当該光拡散シートは、裏面と複数の突起との密着力を大きくすることができる。 The protrusion does not necessarily have to consist only of a truncated cone-shaped body and a dome-shaped tip continuous to the tip side of the body. A modified example of the protrusion will be described with reference to FIGS. 6 and 7. The protrusions 21 of FIGS. 6 and 7 include a truncated cone-shaped body portion 21a, a dome-shaped tip portion 21b continuous with the tip end side of the body portion 21a, and a skirt portion 21c continuous with the base end side of the body portion 21a. Has. The body portion 21a can have the same configuration as the body portion 11a of the protrusion 11 of the light diffusion sheet 4 of FIG. The tip portion 21b can have the same configuration as the tip portion 11b of the protrusion 11 of the light diffusion sheet 4 shown in FIG. The skirt portion 21c has a trumpet-shaped diameter increase from the tip end side to the base end side of the protrusion 21. According to this configuration, the light diffusing sheet can increase the adhesion between the back surface and the plurality of protrusions.
　上記突起は、円錐台状の胴部及びこの胴部の先端側に連続するドーム状の先端部を有することが好ましい。しかしながら、上記突起の具体的形状としては、例えば円錐台状の胴部を有しない構成とすることも可能である。この場合、上記突起は、上記円錐台状の胴部に代えて、円柱状、多角柱状、多角錐台状等の胴部を有していてもよい。 The protrusion preferably has a truncated cone-shaped body portion and a continuous dome-shaped tip portion on the tip end side of the trunk portion. However, as a specific shape of the protrusion, for example, it is possible to have a configuration that does not have a truncated cone-shaped body. In this case, the protrusion may have a body such as a columnar shape, a polygonal columnar shape, or a polygonal pyramid shape instead of the truncated cone shape.
　当該バックライトユニットは、上記導光シートに代えて、例えば平均厚さが６００μｍ超の導光板を備えていてもよい。また、この導光板は、平板状であってもよく、断面楔形状であってもよい。 The backlight unit may include, for example, a light guide plate having an average thickness of more than 600 μm instead of the light guide sheet. Further, the light guide plate may have a flat plate shape or a wedge shape in cross section.
　当該バックライトユニットの具体的構成は、上記実施形態に記載の構成に限定されるものではない。当該バックライトユニットは、例えばマイクロレンズシート等の他の光学シートを有していてもよく、プリズムシートの表面側に比較的拡散機能の低い上用光拡散シートを有していてもよい。また、当該バックライトユニットは、直下型バックライトユニットであってもよい。さらに、当該バックライトユニットがエッジライト型バックライトユニットである場合でも、導光シート又は導光板の一の端面に沿ってのみ１又は複数の光源が配設された片側エッジライト型バックライトユニットである必要はなく、導光シート又は導光板の対向する一対の端面に沿って１又は複数の光源が配設された両側エッジライト型バックライトユニットや、導光シート又は導光板の各端面に沿って１又は複数の光源が配設された全周囲エッジライト型バックライトユニットであってもよい。 The specific configuration of the backlight unit is not limited to the configuration described in the above embodiment. The backlight unit may have another optical sheet such as a microlens sheet, or may have an upper light diffusing sheet having a relatively low diffusing function on the surface side of the prism sheet. Further, the backlight unit may be a direct type backlight unit. Further, even when the backlight unit is an edge light type backlight unit, it is a one-sided edge light type backlight unit in which one or more light sources are arranged only along one end surface of the light guide sheet or the light guide plate. It does not have to be, and it is necessary to have one or a plurality of light sources arranged along a pair of opposite end faces of the light guide sheet or the light guide plate, or along each end face of the light guide sheet or the light guide plate. It may be an omnidirectional edge light type backlight unit in which one or more light sources are arranged.
　当該バックライトユニットは、スマートフォンやタブレット端末等、比較的小型の携帯端末や、ノートパソコン等のパーソナルコンピュータや液晶テレビ等の比較的大型の表示装置に用いることが可能である。 The backlight unit can be used for a relatively small mobile terminal such as a smartphone or a tablet terminal, a personal computer such as a notebook computer, or a relatively large display device such as an LCD TV.
　以下、実施例によって本発明をさらに詳細に説明するが、本発明はこれらの実施例に限定されるものではない。 Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.
［実施例１～３、比較例１～３］
　ポリエチレンテレフタレートを主成分とする平均厚さ５０μｍの基材層を用意した。この基材層を一対の押圧ロール間に送りつつ、一対の押圧ロールの直前部分でこの基材層の裏面側（液晶表示装置に組み込まれた場合における裏面側）に紫外線硬化型樹脂（突起形成用樹脂組成物）を供給した。この紫外線硬化型樹脂に接する側の押圧ロールとしては、外周面に複数の凹部を有するものを用いた。この紫外線硬化型樹脂及び上記基材層を上記一対の押圧ロールで押圧したうえ、紫外線を照射することで上記紫外線硬化型樹脂を硬化させ、基材層の裏面側に、複数の凹部の反転形状である複数の突起を転写した。さらに、基材層の表面側に、複数のビーズ及びバインダー組成物を含む塗工液を塗布し、この塗工液を乾燥及び硬化させることで基材層の表面側に光拡散層を積層し、光拡散シートを得た。実施例１～３及び比較例１～３では、上記押圧ロールの凹部の平均深さを変えることで、複数の突起の平均高さを調整した。表１に、複数の突起の平均高さ及び高さの変動係数を示す。 [Examples 1 to 3, Comparative Examples 1 to 3]
A substrate layer having an average thickness of 50 μm containing polyethylene terephthalate as a main component was prepared. While feeding this base material layer between a pair of pressing rolls, an ultraviolet curable resin (projection formation) is formed on the back surface side (back surface side when incorporated in a liquid crystal display device) of the base material layer immediately before the pair of pressing rolls. Resin composition for use) was supplied. As the pressing roll on the side in contact with the ultraviolet curable resin, one having a plurality of recesses on the outer peripheral surface was used. The ultraviolet curable resin and the base material layer are pressed by the pair of pressing rolls, and then the ultraviolet curable resin is cured by irradiating with ultraviolet rays, and a plurality of recesses are inverted on the back surface side of the base material layer. Multiple protrusions were transferred. Further, a coating liquid containing a plurality of beads and a binder composition is applied to the surface side of the base material layer, and the light diffusion layer is laminated on the surface side of the base material layer by drying and curing the coating liquid. , A light diffusing sheet was obtained. In Examples 1 to 3 and Comparative Examples 1 to 3, the average height of the plurality of protrusions was adjusted by changing the average depth of the recesses of the pressing roll. Table 1 shows the average height of a plurality of protrusions and the coefficient of variation of the height.
＜傷付き防止性＞
　実施例１～３及び比較例１～３の光拡散シートを１０ｃｍ×２０ｃｍの長方形状に打ち抜き加工し、各光拡散シートについて３つの試験片を作成した。これらの試験片について、ＡＳＴＭ平面圧子を有する平面型摩擦抵抗試験機（新東科学社製のトライボテスター　ＴＹＰＥ１４）を用い、ＡＳＴＭ圧子下部にプリズムシートを貼り付け、このプリズムシートに複数の突起が対向するように試験片を配置し、移動速度５０ｍｍ／ｍｉｎで、圧子移動距離５０ｍｍ、負荷５００ｇとして傷付き試験を行い、試験片の傷付きの有無を以下の基準で評価した。この評価結果を表１に示す。
Ａ：２つ以上の試験片について目視にて全く傷付きが視認できない
Ｂ：２つ以上の試験片について目視にて傷付きが視認される <Scratch prevention>
The light diffusing sheets of Examples 1 to 3 and Comparative Examples 1 to 3 were punched into a rectangular shape of 10 cm × 20 cm, and three test pieces were prepared for each light diffusing sheet. For these test pieces, a prism sheet is attached to the lower part of the ASTM indenter using a planar friction resistance tester (Tribotester TYPE14 manufactured by Shinto Kagaku Co., Ltd.) having an ASTM planar indenter, and a plurality of protrusions face each other on the prism sheet. The test pieces were arranged so as to be used, and a scratch test was conducted with a moving speed of 50 mm / min, an indenter moving distance of 50 mm, and a load of 500 g, and the presence or absence of scratches on the test pieces was evaluated according to the following criteria. The evaluation results are shown in Table 1.
A: No scratches are visually visible on two or more test pieces B: Scratches are visually visible on two or more test pieces
＜スティッキング防止性＞
　実施例１～３及び比較例１～３の光拡散シートを気温４０℃、湿度９０％の環境下に４８時間放置した後、これらの光拡散シートのスティッキングの有無を以下の手順で測定した。 <Anti-sticking property>
After the light diffusion sheets of Examples 1 to 3 and Comparative Examples 1 to 3 were left to stand in an environment of a temperature of 40 ° C. and a humidity of 90% for 48 hours, the presence or absence of sticking of these light diffusion sheets was measured by the following procedure.
　ＬＥＤ光源と、このＬＥＤ光源から照射された光を導光する導光シートと、この導光シートの裏面側に配設される反射シートとを有する平面寸法が１３ｃｍ×２１ｃｍのエッジライト型バックライト上に光拡散シートを１３．５ｃｍ×２２ｃｍに切断した試験片を積層し、さらにこの試験片の表面に厚さ１００μｍで平面寸法が１３．５ｃｍ×２２ｃｍの透明なポリエチレンテレフタレートフィルムを積層した積層体を、内寸が２０ｃｍ×２５ｃｍのポリエチレン製の袋に入れた。この袋としては、その１辺が開口しており、この開口部分が密閉可能に構成されたものを用いた。上記積層体が入れられた状態で、上記袋の開口部分から真空排気用のホースを差し込んだうえで、この開口部分を密閉した。 An edge light type backlight having a plane dimension of 13 cm × 21 cm having an LED light source, a light guide sheet that guides the light emitted from the LED light source, and a reflective sheet arranged on the back surface side of the light guide sheet. A laminated body in which a test piece obtained by cutting a light diffusion sheet into a 13.5 cm × 22 cm layer is laminated on the test piece, and a transparent polyethylene terephthalate film having a thickness of 100 μm and a plane dimension of 13.5 cm × 22 cm is further laminated on the surface of the test piece. Was placed in a polyethylene bag having an inner size of 20 cm × 25 cm. As this bag, a bag having an opening on one side and having such an opening portion hermetically sealed was used. With the laminate inserted, a hose for vacuum exhaust was inserted through the opening of the bag, and the opening was sealed.
　試験片の表面から法線方向に５０ｃｍ離れた位置にトプコンテクノハウス社製の色彩輝度計「ＢＭ－７」を設置した状態で、ダイヤフラムポンプにて３０秒間袋内の空気を排気し、この排気を停止すると同時に上述の色彩輝度計で輝度を測定した。この測定の後、ダイヤフラムポンプにてさらに３０秒間袋内を排気し、輝度を測定した。最初の測定時における輝度をＬ１［ｃｄ／ｍ２］、最初の測定の後、３０秒間袋内を排気した後の輝度をＬ２［ｃｄ／ｍ２］とし、以下の基準にてスティッキングの有無を評価した。この評価結果を表１に示す。
Ａ（スティッキング無し）：（Ｌ２－Ｌ１）／Ｌ２＜０．１４
Ｂ（スティッキング有り）：（Ｌ２－Ｌ１）／Ｌ２≧０．１４ With the color luminance meter "BM-7" manufactured by Topcon Techno House Co., Ltd. installed at a position 50 cm away from the surface of the test piece in the normal direction, the air in the bag is exhausted for 30 seconds with a diaphragm pump, and this exhaust is performed. At the same time as stopping, the brightness was measured with the above-mentioned color luminance meter. After this measurement, the inside of the bag was exhausted with a diaphragm pump for another 30 seconds, and the brightness was measured. The brightness at the time of the first measurement is L1 [cd / m 2 ], the brightness after exhausting the inside of the bag for 30 seconds after the first measurement is L2 [cd / m 2 ], and the presence or absence of sticking is determined according to the following criteria. evaluated. The evaluation results are shown in Table 1.
A (without sticking): (L2-L1) / L2 <0.14
B (with sticking): (L2-L1) / L2 ≧ 0.14
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
＜評価結果＞
　表１に示すように、実施例１～３は、複数の突起の平均高さが３．０μｍ以上２０．０μｍ以下であり、かつ高さの変動係数が０．３０以下であるので、傷付き防止性及びスティッキング防止性がいずれも優れている。これに対し、比較例１は、複数の突起の平均高さが小さいため、スティッキングが不十分となっている。比較例２は、複数の突起の平均高さが大きいため、傷付き防止性が不十分となっている。比較例３は、突起の高さの変動係数が大きいため、傷付き防止性が不十分となっている。 <Evaluation result>
As shown in Table 1, in Examples 1 to 3, the average height of the plurality of protrusions is 3.0 μm or more and 20.0 μm or less, and the coefficient of variation of the height is 0.30 or less, so that they are scratched. Both the preventive property and the anti-sticking property are excellent. On the other hand, in Comparative Example 1, sticking is insufficient because the average height of the plurality of protrusions is small. In Comparative Example 2, since the average height of the plurality of protrusions is large, the scratch prevention property is insufficient. In Comparative Example 3, since the coefficient of variation of the height of the protrusion is large, the scratch prevention property is insufficient.
［実施例４～７］
　複数の突起の底面の平均径を表２の通りとし、実施例１と同様の手順で、光拡散シートを製造した。なお、突起の平均径は、上記押圧ロールの凹部の開口径を変えることで調整した。また、実施例４～７における複数の突起の平均高さは９．０μｍ、高さの変動係数は０．１５とした。 [Examples 4 to 7]
The average diameter of the bottom surfaces of the plurality of protrusions was set as shown in Table 2, and a light diffusion sheet was manufactured by the same procedure as in Example 1. The average diameter of the protrusions was adjusted by changing the opening diameter of the recesses of the pressing roll. The average height of the plurality of protrusions in Examples 4 to 7 was 9.0 μm, and the coefficient of variation of the height was 0.15.
＜突起強度＞
　実施例４～７の光拡散シートを１０ｃｍ×１０ｃｍの長方形状に打ち抜き加工し、各光拡散シートについて３つの試験片を作成した。ＡＳＴＭ圧子を有する平面型摩擦抵抗試験機（新東科学社製のトライボテスター　ＴＹＰＥ４０）を用意し、この平面型摩擦抵抗試験機の試験テーブルにレンチキュラーが上面に形成された導光板を接着剤にて貼り付け、さらにこの上に上述の試験片を複数の突起が導光板のレンチキュラーと対向するように接着剤にて貼り付けたうえ、移動速度５０ｍｍ／ｍｉｎ、圧子移動距離５０ｍｍ、負荷５００ｇでＡＳＴＭ圧子を試験片の中央部に往復させた。このＡＳＴＭ圧子は、まずレンチキュラーの稜線と平行な方向に５往復させ、その後試験片と貼り付けた状態のまま導光板を試験テーブルから剥がして９０°回転させ、再度導光板を試験テーブルに接着剤にて貼り付けたうえ、レンチキュラーの稜線と直交する方向に５往復させた。この往復試験の後、試験片を導光板から剥がし、導光板のレンチキュラー面を目視にて確認し、突起の強度を以下の基準で評価した。この評価結果を表２に示す。なお、接着剤としては、試験片を導光板から剥離した際等に、接着剤に起因して突起の破損や導光板への突起の破片の付着が生じないよう、３Ｍ社製の粘着剤スプレー「スプレーのり５５」を用いた。
Ａ：突起の破片が視認されない
Ｂ：突起の破片が視認される <Protrusion strength>
The light diffusing sheets of Examples 4 to 7 were punched into a rectangular shape of 10 cm × 10 cm, and three test pieces were prepared for each light diffusing sheet. Prepare a flat friction resistance tester with an ASTM indenter (Tribotester TYPE40 manufactured by Shinto Kagaku Co., Ltd.), and attach a light guide plate with a lenticular on the upper surface to the test table of this flat friction resistance tester with an adhesive. After sticking, the above-mentioned test piece is stuck on it with an adhesive so that a plurality of protrusions face the wrenchular of the light guide plate, and then an ASTM indenter is attached at a moving speed of 50 mm / min, an indenter moving distance of 50 mm, and a load of 500 g. Was reciprocated to the center of the test piece. This ASTM indenter first reciprocates 5 times in the direction parallel to the ridgeline of the lenticular, then peels off the light guide plate from the test table and rotates it 90 ° while still attached to the test piece, and then attaches the light guide plate to the test table again. After pasting with, it was reciprocated 5 times in the direction orthogonal to the ridgeline of the lenticular. After this reciprocating test, the test piece was peeled off from the light guide plate, the lenticular surface of the light guide plate was visually confirmed, and the strength of the protrusion was evaluated according to the following criteria. The evaluation results are shown in Table 2. As an adhesive, an adhesive spray manufactured by 3M Co., Ltd. is used so that when the test piece is peeled off from the light guide plate, the protrusions are not damaged or the protrusion fragments are not attached to the light guide plate due to the adhesive. "Spray glue 55" was used.
A: The fragments of the protrusions are not visible B: The fragments of the protrusions are visible
＜スティッキング防止性＞
　実施例１～３、比較例１～３と同様の手順及び同様の評価基準でスティッキング防止性を評価した。この評価結果を表２に示す。 <Anti-sticking property>
The anti-sticking property was evaluated by the same procedure and the same evaluation criteria as in Examples 1 to 3 and Comparative Examples 1 to 3. The evaluation results are shown in Table 2.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
＜評価結果＞
　表２に示すように、複数の突起の平均径が１０μｍ以上４０μｍ以下である実施例４、５は、突起強度が高く、かつスティッキング防止性にも優れている。これに対し、実施例６は、複数の突起の平均径が小さいため、突起強度が低くなっている。また、実施例７は、複数の突起の平均径が大きいため、突起の当接面積が大きくなり、スティッキング防止性が低くなっている。 <Evaluation result>
As shown in Table 2, Examples 4 and 5 in which the average diameter of the plurality of protrusions is 10 μm or more and 40 μm or less have high protrusion strength and excellent sticking prevention property. On the other hand, in Example 6, since the average diameter of the plurality of protrusions is small, the protrusion strength is low. Further, in the seventh embodiment, since the average diameter of the plurality of protrusions is large, the contact area of the protrusions is large and the sticking prevention property is low.
［実施例８～１５］
　基材層の平均厚さを３８μｍとし、光線出射領域のサイズ及び基材層の裏面における複数の突起の占有面積率を表３の通りとし、実施例１と同様の手順で、光拡散シートを製造した。なお、複数の突起の占有面積率は、上記押圧ロールの凹部の密度を変えることで調整した。また、実施例８～１５における複数の突起の平均高さは１０．０μｍ、高さの変動係数は０．１０とした。 [Examples 8 to 15]
The average thickness of the base material layer is 38 μm, the size of the light emitting region and the occupied area ratio of the plurality of protrusions on the back surface of the base material layer are as shown in Table 3, and the light diffusion sheet is prepared in the same procedure as in Example 1. Manufactured. The occupied area ratio of the plurality of protrusions was adjusted by changing the density of the recesses of the pressing roll. The average height of the plurality of protrusions in Examples 8 to 15 was 10.0 μm, and the coefficient of variation of the height was 0.10.
＜傷付き防止性＞
（ボールドロップ試験）
　実施例８～１１について、以下の手順でボールドロップ試験を行い、傷付き防止性について評価した。厚さ５ｍｍのステンレス板の表面に導光シートを模した厚さ４７５μｍのポリカーボネートフィルムを積層し、その上に実施例８～１１の光拡散シートを複数の突起が導光シートと当接するように積層した。さらに、この光拡散シート上にプリズム頂点が上方に突出する２枚のプリズムシートを互いの稜線方向が直交するように積層した。次に、液晶表示パネル（カラーフィルタ／液晶層／ＴＦＴ基板）をＴＦＴ基板がプリズムシートに対向するように配置したうえ、直径３０ｍｍのナイロン６６製の球体を液晶表示パネルの上方１００ｃｍの高さから落下させ、光拡散シートの傷付きの有無を目視にて確認し、以下の基準で評価した。この評価結果を表３に示す。なお、光線出射領域の小さい光拡散シートについては、スマートフォンやタブレット端末等に使用されることが多く、端末の落下による傷付きの有無を評価することが重要となるため、実施例８～１１についてはボールドロップ試験を行っている。
Ａ：傷が視認されない
Ｂ：傷が視認される <Scratch prevention>
(Ball drop test)
For Examples 8 to 11, a ball drop test was carried out according to the following procedure, and the scratch prevention property was evaluated. A polycarbonate film having a thickness of 475 μm imitating a light guide sheet is laminated on the surface of a stainless steel plate having a thickness of 5 mm, and the light diffusion sheets of Examples 8 to 11 are placed on the polycarbonate film so that a plurality of protrusions come into contact with the light guide sheet. Laminated. Further, two prism sheets having prism vertices protruding upward were laminated on the light diffusion sheet so that their ridges were orthogonal to each other. Next, the liquid crystal display panel (color filter / liquid crystal layer / TFT substrate) is arranged so that the TFT substrate faces the prism sheet, and a sphere made of nylon 66 having a diameter of 30 mm is placed 100 cm above the liquid crystal display panel. It was dropped, and the presence or absence of scratches on the light diffusion sheet was visually confirmed and evaluated according to the following criteria. The evaluation results are shown in Table 3. Note that light diffusion sheets having a small light emitting area are often used for smartphones, tablet terminals, etc., and it is important to evaluate the presence or absence of scratches due to dropping of the terminals. Is conducting a ball drop test.
A: Scratches are not visible B: Scratches are visible
　実施例１２～１５については、実施例１～３、比較例１～３と同様の手順及び同様の評価基準で傷付き防止性を評価した。この評価結果を表３に示す。 For Examples 12 to 15, the scratch prevention property was evaluated by the same procedure and the same evaluation criteria as in Examples 1 to 3 and Comparative Examples 1 to 3. The evaluation results are shown in Table 3.
＜スティッキング防止性＞
　実施例１～３、比較例１～３と同様の手順及び同様の評価基準でスティッキング防止性を評価した。この評価結果を表３に示す。 <Anti-sticking property>
The anti-sticking property was evaluated by the same procedure and the same evaluation criteria as in Examples 1 to 3 and Comparative Examples 1 to 3. The evaluation results are shown in Table 3.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
＜評価結果＞
　表３に示すように、実施例８、９、１０、１２、１３は、光線出射領域のサイズに対する複数の突起の占有面積率が十分に調整されていることで、傷付き防止性及びスティッキング防止性がいずれも優れている。これに対し、実施例１４は、光線出射領域のサイズに対する複数の突起の占有面積率が小さいため、スティッキング防止性が不十分となっている。また、実施例１５は、光線出射領域のサイズに対する複数の突起の占有面積率が大きいため、傷付き防止性が不十分となり、実施例１１は、光線出射領域のサイズに対する複数の突起の占有面積率が小さいため、衝撃に対する複数の突起による緩衝機能が不十分となり、ボールドロップ試験による傷付き防止性が不十分となっている。 <Evaluation result>
As shown in Table 3, in Examples 8, 9, 10, 12, and 13, the ratio of the occupied area of the plurality of protrusions to the size of the light emitting region is sufficiently adjusted to prevent scratches and sticking. Both are excellent in sex. On the other hand, in Example 14, since the ratio of the occupied area of the plurality of protrusions to the size of the light emitting region is small, the anti-sticking property is insufficient. Further, in Example 15, since the ratio of the occupied area of the plurality of protrusions to the size of the light emitting region is large, the scratch prevention property is insufficient, and in Example 11, the occupied area of the plurality of protrusions to the size of the light emitting region is insufficient. Since the rate is small, the cushioning function due to the plurality of protrusions against impact is insufficient, and the scratch prevention property by the ball drop test is insufficient.
［実施例１６～２３］
　基材層の平均厚さを３８μｍとし、光線出射領域のサイズ及び基材層の裏面上において近接する３つの突起が入る円の平均半径を表４の通りとし、実施例１と同様の手順で、光拡散シートを製造した。なお、基材層の裏面上において近接する３つの突起が入る円の平均半径は、上記押圧ロールの凹部の配置を変えること等で調整した。また、実施例１６～２３における複数の突起の平均高さは９．０μｍ、高さの変動係数は０．１５とした。 [Examples 16 to 23]
The average thickness of the base material layer is 38 μm, the size of the light emitting region and the average radius of the circle containing the three adjacent protrusions on the back surface of the base material layer are as shown in Table 4, and the procedure is the same as in Example 1. , Manufactured a light diffusing sheet. The average radius of the circle containing the three adjacent protrusions on the back surface of the base material layer was adjusted by changing the arrangement of the recesses of the pressing roll. The average height of the plurality of protrusions in Examples 16 to 23 was 9.0 μm, and the coefficient of variation of the height was 0.15.
＜傷付き防止性＞
　実施例１６～１９については実施例８～１１と同様のボールドロップ試験によって、また実施例２０～２３については実施例１～３、比較例１～３と同様の手順及び同様の評価基準によって傷付き防止性を評価した。この評価結果を表４に示す。 <Scratch prevention>
Examples 16 to 19 are scratched by the same ball drop test as in Examples 8 to 11, and Examples 20 to 23 are scratched by the same procedure and the same evaluation criteria as in Examples 1 to 3 and Comparative Examples 1 to 3. The anti-stickiness was evaluated. The evaluation results are shown in Table 4.
＜スティッキング防止性＞
　実施例１～３、比較例１～３と同様の手順及び同様の評価基準でスティッキング防止性を評価した。この評価結果を表４に示す。 <Anti-sticking property>
The anti-sticking property was evaluated by the same procedure and the same evaluation criteria as in Examples 1 to 3 and Comparative Examples 1 to 3. The evaluation results are shown in Table 4.
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000004
＜評価結果＞
　表４に示すように、実施例１６、１７、１８、２０、２１は、光線出射領域のサイズに対する近接する３つの突起が入る円の平均半径が十分に調整されていることで、傷付き防止性及びスティッキング防止性がいずれも優れている。これに対し、実施例２２は、光線出射領域のサイズに対する近接する３つの突起が入る円の平均半径が小さいため、傷付き防止性が不十分となり、実施例１９は、光線出射領域のサイズに対する近接する３つの突起が入る円の平均半径が大きいため、衝撃に対する複数の突起による緩衝機能が不十分となり、ボールドロップ試験による傷付き防止性が不十分となっている。また、実施例１９、２３は、光線出射領域のサイズに対する近接する３つの突起が入る円の平均半径が大きいため、スティッキング防止性が不十分となっている。 <Evaluation result>
As shown in Table 4, Examples 16, 17, 18, 20, and 21 are scratch-prevented by sufficiently adjusting the average radius of the circle containing the three adjacent protrusions with respect to the size of the light emitting region. It has excellent properties and anti-sticking properties. On the other hand, in Example 22, since the average radius of the circle containing the three adjacent protrusions is small with respect to the size of the light emitting region, the scratch prevention property is insufficient, and in Example 19, the size of the light emitting region is reduced. Since the average radius of the circle containing the three adjacent protrusions is large, the cushioning function of the plurality of protrusions against impact is insufficient, and the scratch prevention property by the ball drop test is insufficient. Further, in Examples 19 and 23, the sticking prevention property is insufficient because the average radius of the circle into which the three adjacent protrusions are inserted is large with respect to the size of the light emitting region.
　以上のように、本発明の一態様に係る光拡散シートは、傷付き防止性が高く、かつ優れたスティッキング防止性を有するので、種々の液晶表示装置に好適に用いられる。 As described above, the light diffusion sheet according to one aspect of the present invention has high scratch resistance and excellent sticking prevention properties, and is therefore suitably used for various liquid crystal display devices.
１　液晶表示装置用バックライトユニット（バックライトユニット）
２　導光シート
３　光源
４　光拡散シート
４ａ　裏面
５　プリズムシート
５ａ　基材層
５ｂ　プリズム列
６　反射シート
１１，２１　突起
１１ａ，２１ａ　胴部
１１ｂ，２１ｂ　先端部
１２　基材層
１３　光拡散層
１３ａ　光拡散剤
１３ｂ　バインダー
２１ｃ　裾野部
Ａ　光線出射領域
Ｄ１　突起の底面の径
Ｈ１　突起の高さ
ｒ　平均半径 1 Backlight unit for liquid crystal display device (backlight unit)
2 Light guide sheet 3 Light source 4 Light diffusion sheet 4a Back surface 5 Prism sheet 5a Base material layer 5b Prism row 6 Reflection sheets 11 and 21 Projections 11a, 21a Body 11b, 21b Tip 12 Base material layer 13 Light diffusion layer 13a Light diffusion Agent 13b Binder 21c Base A Light source area D1 Diameter of bottom surface of protrusion H1 Height of protrusion r Average radius

Claims (6)

  1. 　裏面に複数の突起を散点的に備え、
    　上記複数の突起の平均高さが３．０μｍ以上２０．０μｍ以下、高さの変動係数が０．３０以下である光拡散シート。     With multiple protrusions on the back side,
    A light diffusion sheet in which the average height of the plurality of protrusions is 3.0 μm or more and 20.0 μm or less, and the coefficient of variation of the height is 0.30 or less.
  2. 　上記突起が、円錐台状の胴部と、この胴部の先端側に連続するドーム状の先端部とを有する請求項１に記載の光拡散シート。 The light diffusion sheet according to claim 1, wherein the protrusion has a truncated cone-shaped body portion and a dome-shaped tip portion continuous to the tip end side of the body portion.
  3. 　上記裏面における上記複数の突起の占有面積率が２％以上８０％以下である請求項１又は請求項２に記載の光拡散シート。 The light diffusion sheet according to claim 1 or 2, wherein the occupied area ratio of the plurality of protrusions on the back surface is 2% or more and 80% or less.
  4. 　光線出射領域のサイズをＳ［インチ］、この光線出射領域の上記裏面における上記複数の突起の占有面積率をＲ［％］とした場合、以下の（１）又は（２）の条件を満たす請求項１、請求項２又は請求項３に記載の光拡散シート。
    （１）Ｓ＜７の場合、６０≦Ｒ
    （２）７≦Ｓ≦１５の場合、２．０≦Ｒ≦３０．０     When the size of the light emitting region is S [inch] and the occupied area ratio of the plurality of protrusions on the back surface of the light emitting region is R [%], the following (1) or (2) is satisfied. The light diffusion sheet according to claim 1, claim 2 or claim 3.
    (1) When S <7, 60 ≦ R
    (2) When 7 ≦ S ≦ 15, 2.0 ≦ R ≦ 30.0
  5. 　光線出射領域のサイズをＳ［インチ］、この光線出射領域の上記裏面上において近接する３つの上記突起が入る円の平均半径をｒ［μｍ］とした場合、以下の（１）又は（２）の条件を満たす請求項１から請求項３のいずれか１項に記載の光拡散シート。
    （１）Ｓ＜７の場合、ｒ≦４０
    （２）７≦Ｓ≦１５の場合、４０≦ｒ≦４００     When the size of the light emitting region is S [inch] and the average radius of the circle containing the three adjacent protrusions on the back surface of the light emitting region is r [μm], the following (1) or (2) The light diffusion sheet according to any one of claims 1 to 3, which satisfies the condition of.
    (1) When S <7, r ≦ 40
    (2) When 7 ≦ S ≦ 15, 40 ≦ r ≦ 400
  6. 　端面から入射された光線を表面側に導く導光板又は導光シートと、
    　上記導光板又は導光シートの上記端面に沿って配設される１又は複数の光源と、
    　上記導光板又は導光シートの表面側に配設される請求項１から請求項５のいずれか１項に記載の光拡散シートとを備える液晶表示装置用バックライトユニット。

          A light guide plate or a light guide sheet that guides light rays incident from the end face toward the surface side,
    With one or more light sources arranged along the end face of the light guide plate or the light guide sheet,
    A backlight unit for a liquid crystal display device including the light diffusing sheet according to any one of claims 1 to 5, which is arranged on the surface side of the light guide plate or the light guide sheet.
PCT/JP2020/036991 2019-12-16 2020-09-29 Light diffusing sheet and backlight unit for liquid crystal display device WO2021124639A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
KR1020227022264A KR20220108127A (en) 2019-12-16 2020-09-29 Light diffusing sheet and backlight unit for liquid crystal display
CN202080081743.XA CN114746779B (en) 2019-12-16 2020-09-29 Light diffusion sheet and backlight unit for liquid crystal display device

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2019-226736 2019-12-16
JP2019226736A JP7374748B2 (en) 2019-12-16 2019-12-16 Light diffusion sheets and backlight units for liquid crystal display devices

Publications (1)

Publication Number Publication Date
WO2021124639A1 true WO2021124639A1 (en) 2021-06-24

Family

ID=76431187

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2020/036991 WO2021124639A1 (en) 2019-12-16 2020-09-29 Light diffusing sheet and backlight unit for liquid crystal display device

Country Status (5)

Country Link
JP (1) JP7374748B2 (en)
KR (1) KR20220108127A (en)
CN (1) CN114746779B (en)
TW (1) TWI797516B (en)
WO (1) WO2021124639A1 (en)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2011133555A (en) * 2009-12-22 2011-07-07 Toppan Printing Co Ltd Optical sheet, backlight unit, and display device
JP2016028275A (en) * 2014-07-09 2016-02-25 恵和株式会社 Optical sheet, edge light-type backlight unit, and optical sheet manufacturing method
JP2016028272A (en) * 2014-07-09 2016-02-25 恵和株式会社 Optical sheet and edge light-type backlight unit
JP2017207736A (en) * 2016-05-16 2017-11-24 恵和株式会社 Optical sheet for liquid crystal display device, backlight unit for liquid crystal display device and production method of optical sheet for liquid crystal display device
JP2018109748A (en) * 2016-12-28 2018-07-12 恵和株式会社 Optical sheet for liquid crystal display device and backlight unit for liquid crystal display device

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004252353A (en) 2003-02-21 2004-09-09 Keiwa Inc Light diffusion sheet and back light unit using the same
US7924368B2 (en) * 2005-12-08 2011-04-12 3M Innovative Properties Company Diffuse multilayer optical assembly
TW200745680A (en) * 2006-04-19 2007-12-16 Omron Tateisi Electronics Co Diffuser plate and surface light source device
JP2009075539A (en) * 2007-08-28 2009-04-09 Nissan Motor Co Ltd Anti-reflective structure and anti-reflective molded body
CN201319075Y (en) * 2008-07-14 2009-09-30 上海赞高光学材料有限公司 Optical diffusion membrane and liquid crystal display device using same
JP2010026231A (en) * 2008-07-18 2010-02-04 Jiroo Corporate Plan:Kk Optical sheet and backlight unit using the same
JP2010096916A (en) * 2008-10-15 2010-04-30 Keiwa Inc Optical sheet and backlight unit using the same
JP5760566B2 (en) * 2011-03-23 2015-08-12 ソニー株式会社 Optical element, optical system, imaging device, optical apparatus, and master
JP6647761B2 (en) * 2015-12-07 2020-02-14 恵和株式会社 Top light diffusion sheet and backlight unit

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2011133555A (en) * 2009-12-22 2011-07-07 Toppan Printing Co Ltd Optical sheet, backlight unit, and display device
JP2016028275A (en) * 2014-07-09 2016-02-25 恵和株式会社 Optical sheet, edge light-type backlight unit, and optical sheet manufacturing method
JP2016028272A (en) * 2014-07-09 2016-02-25 恵和株式会社 Optical sheet and edge light-type backlight unit
JP2017207736A (en) * 2016-05-16 2017-11-24 恵和株式会社 Optical sheet for liquid crystal display device, backlight unit for liquid crystal display device and production method of optical sheet for liquid crystal display device
JP2018109748A (en) * 2016-12-28 2018-07-12 恵和株式会社 Optical sheet for liquid crystal display device and backlight unit for liquid crystal display device

Also Published As

Publication number Publication date
TWI797516B (en) 2023-04-01
KR20220108127A (en) 2022-08-02
JP7374748B2 (en) 2023-11-07
CN114746779B (en) 2024-08-20
CN114746779A (en) 2022-07-12
JP2021096335A (en) 2021-06-24
TW202125064A (en) 2021-07-01

Similar Documents

Publication Publication Date Title
JP6746282B2 (en) Optical sheet, edge light type backlight unit, and method for manufacturing optical sheet
US10386567B2 (en) Optical sheet for liquid crystal display device, backlight unit for liquid crystal display device and production method of optical sheet for liquid crystal display device
TWI684049B (en) Optical sheet for liquid crystal display device, and backlight unit for liquid crystal display device
TWI662300B (en) Light diffusing sheet and backlight device including the same
KR102105135B1 (en) A buffer sheet and a flat panel display
JP2017107193A (en) Upper light diffusion sheet and backlight unit
JP2010164657A (en) Optical sheet, back light unit and display device
TW201602644A (en) Optical sheet and edge-lit backlight unit
JP2010210882A (en) Optical sheet and display using the same
JP4970663B2 (en) Light diffusion sheet and backlight unit using the same
KR102049301B1 (en) Optical sheet for liquid crystal display apparatus, backlight unit for liquid crystal display apparatus, and method for manufacturing optical sheet for liquid crystal display apparatus
JP6974004B2 (en) Optical sheet for backlight unit and backlight unit
US20240231147A1 (en) Optical sheet, backlight unit, liquid crystal display apparatus, and information device
JP2010032739A (en) Lens film, and backlight unit for optical display equipped therewith
WO2021124639A1 (en) Light diffusing sheet and backlight unit for liquid crystal display device
WO2021014813A1 (en) Light-diffusing sheet
JP6744759B2 (en) Optical unit and method of manufacturing optical unit
KR20110082327A (en) Reflection sheet for back light unit
JP6288358B2 (en) Daylighting member
TW201910889A (en) Buffer sheet and flat panel display
JP6880521B2 (en) Light reflective film and edge light type backlight
JP2010176133A (en) Optical film, and backlight unit for optical display with the same
KR20100004537A (en) Composite optical sheet and back light unit comprising the same
JP2021184088A (en) Optical sheet, backlight unit, liquid crystal display device and information apparatus

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 20903892

Country of ref document: EP

Kind code of ref document: A1

ENP Entry into the national phase

Ref document number: 20227022264

Country of ref document: KR

Kind code of ref document: A

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 20903892

Country of ref document: EP

Kind code of ref document: A1