WO2017098718A1 - Backlight unit - Google Patents

Backlight unit Download PDF

Info

Publication number
WO2017098718A1
WO2017098718A1 PCT/JP2016/005059 JP2016005059W WO2017098718A1 WO 2017098718 A1 WO2017098718 A1 WO 2017098718A1 JP 2016005059 W JP2016005059 W JP 2016005059W WO 2017098718 A1 WO2017098718 A1 WO 2017098718A1
Authority
WO
WIPO (PCT)
Prior art keywords
light
plate
guide plate
light guide
backlight unit
Prior art date
Application number
PCT/JP2016/005059
Other languages
French (fr)
Japanese (ja)
Inventor
浩太郎 保田
齊藤　之人
Original Assignee
富士フイルム株式会社
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 富士フイルム株式会社 filed Critical 富士フイルム株式会社
Publication of WO2017098718A1 publication Critical patent/WO2017098718A1/en

Links

Images

Classifications

    • 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
    • F21V9/00—Elements for modifying spectral properties, polarisation or intensity of the light emitted, e.g. filters
    • F21V9/14—Elements for modifying spectral properties, polarisation or intensity of the light emitted, e.g. filters for producing polarised light
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/08—Mirrors
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof

Definitions

  • the present invention relates to a backlight unit used in a liquid crystal display device.
  • Liquid crystal display devices consume less power and are increasingly used year by year as space-saving image display devices.
  • the liquid crystal display device has a configuration in which a backlight unit, a backlight side polarizing plate, a liquid crystal panel, a viewing side polarizing plate, and the like are provided in this order.
  • a so-called edge light type backlight unit having a light guide plate that propagates light incident from the end surface and emits the light from the main surface, and a light source that enters light to the end surface of the light guide plate, and one surface
  • a so-called direct-type backlight unit comprising a diffuser that diffuses light incident from the diffuser and emits the light from the other surface, and a light source that is disposed on one side (directly below) of the diffuser and that is incident on one surface of the diffuser It has been known.
  • the backlight unit greatly affects the performance of the LCD, such as image brightness and visibility.
  • various proposals have been made to improve the luminance of light (backlight) emitted from the backlight unit.
  • a reflective polarizing plate As a brightness enhancement film.
  • the reflective polarizing plate transmits predetermined polarized light and reflects other polarized light.
  • a reflective polarizing plate only linearly polarized light corresponding to the backlight-side polarizing plate is transmitted and incident on the backlight-side polarizing plate, and other polarized light is reflected to repeat retroreflection in the backlight unit. Then, it can be reused by being incident on the reflective polarizing plate again.
  • Patent Document 1 in a direct type backlight unit, a reflective polarizer is provided on the exit surface side of the diffuser plate, and a reflective plate is disposed on the side opposite to the diffuser plate of the light source.
  • luminance is proposed by reflecting the light reflected by (1) by the reflecting plate again to a reflection type polarizer.
  • Patent Document 2 discloses that an edge light type backlight unit is guided to a surface facing the light exit surface of the light guide plate. A light reflecting portion for reflecting the light propagating in the light plate to be emitted from the light emitting surface; the light reflecting portion is located inside the light guide plate; and on the light source side of the light reflecting portion A backlight unit (surface light source device) having a directivity conversion unit that improves the directivity of light incident on the reflection unit is described. Since the backlight unit described in Patent Document 2 has such a configuration, the directivity of light emitted from the backlight unit can be improved, and the luminance of light incident on the liquid crystal panel can be improved.
  • JP-A 63-168626 JP 2005-268201 A Japanese Patent Laying-Open No. 2015-173066
  • a reflective polarizing plate that transmits polarized light in a predetermined state and reflects other polarized light, and described in Patent Documents 2 and 3
  • the light use efficiency can be improved and the luminance of the light incident on the liquid crystal panel can be improved.
  • the present invention has been made in view of the above circumstances, and is a backlight unit used in an LCD or the like, which further improves light utilization efficiency and can emit high-luminance light (backlight).
  • An object is to provide a light unit.
  • the first backlight unit of the present invention includes a light source, The light emitted from the light source is incident from the end face, propagates the light incident from the end face, and exits from one main surface.
  • the degree of depolarization Dg is 40% or less, and the propagating light is the one main surface.
  • a ⁇ / 4 plate disposed between the reflective linearly polarized light separating plate and the reflective plate.
  • the second backlight unit of the present invention includes a light source, The light emitted from the light source is incident from the end face, propagates the light incident from the end face, and exits from one main surface.
  • the degree of depolarization Dg is 40% or less, and the propagating light is transmitted to one main surface.
  • the ⁇ / 4 plate may be disposed between the reflective linearly polarized light separating plate and the light guide plate, or between the light guide plate and the reflective plate. preferable.
  • the total depolarization degree Da of the optical members excluding the reflective linearly polarized light separating plate and the ⁇ / 4 plate is 50% or less.
  • the reflecting plate is preferably a specular reflecting plate.
  • the mirror surface of the mirror reflector is a metal deposition surface.
  • the phase difference of the light guide plate is It is preferable that it is 100 nm or less.
  • the ⁇ / 4 plate also serves as the light guide plate.
  • the directivity imparting mechanism of the light guide plate is preferably at least one of a plurality of concave portions and a plurality of convex portions formed on the other main surface.
  • the area ratio of the flat surface perpendicular to the arrangement direction of the reflecting plate, the light guide plate and the reflective linearly polarized light separating plate on the other main surface is preferably 30 to 98%.
  • the directivity imparting mechanism of the light guide plate is composed of a plurality of through holes penetrating from one main surface to the other main surface, and the through holes include the reflector, the light guide plate, and the reflective linearly polarized light. It may have an inclination with respect to the arrangement direction of the separation plates.
  • the light guide plate may be a film having a thickness of 200 ⁇ m or less.
  • a diffusion plate may be provided between the light guide plate and the reflective linearly polarized light separating plate.
  • a wavelength conversion layer may be provided between one main surface of the light guide plate and the reflective linearly polarized light separating plate.
  • the backlight unit of the present invention it is possible to improve the light utilization efficiency and emit high-luminance light.
  • FIG. 10 is a perspective view showing a part of the light guide film 1 used in Example 21.
  • FIG. 12 is a plan view showing a part of the light guide film 2 used in Example 22.
  • a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
  • (meth) acrylate is used to mean “one or both of acrylate and methacrylate”.
  • “same” includes an error range generally allowed in the technical field.
  • “all”, “any” or “entire surface” it includes an error range generally allowed in the technical field in addition to the case of 100%, for example, 99% or more, The case of 95% or more, or 90% or more is included.
  • Visible light is light having a wavelength visible to the human eye among electromagnetic waves, and indicates light having a wavelength range of 380 nm to 780 nm.
  • light in the wavelength region of 420 nm to 495 nm is blue light (B light)
  • light in the wavelength region of more than 495 nm to 570 nm is green light ( G light)
  • light in the wavelength range of 620 nm to 750 nm is red light (R light).
  • the backlight unit of the present invention is mainly used in an LCD (Liquid Crystal Display), and in the LCD, light (backlight) for displaying an image is arranged in a liquid crystal cell (pixel by liquid crystal). It is for emitting to the liquid crystal panel.
  • the backlight unit of the present invention is a so-called edge light type (also referred to as a side light type or a light guide plate type) backlight unit.
  • FIG. 1 is a diagram schematically showing an overall configuration of a backlight unit according to the first embodiment of the present invention. This embodiment is an aspect of the first backlight unit of the present invention.
  • the backlight unit 10 of the present embodiment shown in FIG. 1 has a light source 12 and light L emitted from the light source 12 incident from the end surface 14b, propagates the light L incident from the end surface 14b, and is transmitted from one main surface 14a.
  • the light guide plate 14 for emitting, a reflector 16 disposed on the other main surface 14c side opposite to the main surface thereof 14a, disposed on the main surface 14a side of the light guide plate 14, a first linearly polarized light L 1
  • a reflective linearly polarized light separating plate 24 that transmits and reflects the second linearly polarized light L 2 orthogonal to the first linearly polarized light L 1, and is disposed between the reflective linearly polarized light separating plate 24 and the light guide plate 14.
  • a ⁇ / 4 plate 20 In the backlight unit of the present invention, the light guide plate has a degree of depolarization Dg of 40% or less and a directivity imparting mechanism that directs propagating light to the main surface.
  • the reflection plate has a depolarization degree Dm of 30% or less.
  • Reference numeral 26 indicated by a broken line in FIG. 1 is a backlight-side polarizing plate 26 that is usually provided in the LCD and converts light incident on the liquid crystal panel into predetermined linearly polarized light.
  • the other main surface 14c opposite to the exit surface 14a of the light guide plate 14 is also referred to as a “back surface 14c”.
  • the emission surface 14a is a surface that emits light to which directivity is imparted by the directivity imparting mechanism.
  • the optical members are arranged such that the exit surface 14a of the light guide plate 14 is on the reflective linearly polarized light separating plate 24 side, and the back surface 14c is on the reflective plate 16 side.
  • the backlight unit 10 uses a reflective linearly polarized light separating plate 24 that transmits linearly polarized light in a predetermined direction and reflects linearly polarized light orthogonal to the first direction (second direction), and further, the degree of depolarization.
  • a reflective linearly polarized light separating plate 24 that transmits linearly polarized light in a predetermined direction and reflects linearly polarized light orthogonal to the first direction (second direction), and further, the degree of depolarization.
  • the light source 12 emits light L for displaying the LCD, and enters the end surface 14 b that is a light incident surface to the light guide plate 14.
  • the light source 12 is an edge light type backlight unit such as a light source or a fluorescent lamp in which point light sources such as LEDs (Light Emitting Diodes) are arranged in a line along the end surface 14 b of the light guide plate 14.
  • Various known light sources used can be used.
  • the light guide plate 14 is a plate-shaped (sheet-shaped) member, and as described above, the light L incident from the light source 12 propagates in the surface direction, and the light exit surface 14a which is one main surface (maximum surface). It is emitted from. Since the light guide plate 14 has a directivity imparting mechanism, the directivity of light emitted from the backlight unit 10 can be improved, and the front luminance of the backlight unit 10 can be improved.
  • the luminance of light incident on the backlight side polarizing plate from the backlight unit is also referred to as “front luminance”. Further, the front luminance of the light emitted from the backlight unit is also referred to as “front luminance of the backlight unit”.
  • the light guide plate 14 of the present embodiment has a concave portion 15c formed on the other main surface 14c facing the emission surface 14a as a directivity imparting mechanism.
  • the recess 15c is a right triangle whose cross section in the light propagation direction is formed by a surface 15a orthogonal to the flat surface of the back surface 14c and an inclined surface 15b intersecting the orthogonal surface 15a at an angle ⁇ . Shape.
  • the inclined surface 15b is formed so as to go in a direction away from the light source 12 as it approaches the emission surface 14a.
  • the light incident from the end face 14b is guided in the light guide plate 14, enters the inclined surface 15b at a critical angle or more and is totally reflected, and thereby directivity toward the exit surface 14a is given.
  • the recesses 15c may be formed by interspersing island-like (dot-like) objects, or, as shown in FIG. 4 to be described later, the long recesses 15c are arranged in a direction perpendicular to the longitudinal direction. May be provided. When the island-shaped concave portions 15c are scattered, the concave portions 15c may be arranged regularly or irregularly. Moreover, the long recessed part 15c may be divided in the longitudinal direction.
  • the reflective linearly polarized light separating plate 24 transmits the first linearly polarized light L 1 that is linearly polarized light in a predetermined direction and reflects the second linearly polarized light L 2 that is orthogonal to the first linearly polarized light L 1. If it is a thing, a well-known thing can be used suitably.
  • the ⁇ / 4 plate 20 is not particularly limited, and a known ⁇ / 4 plate can be used.
  • the ⁇ / 4 plate 20 is generally composed of a support and a ⁇ / 4 layer formed on the support, but after the ⁇ / 4 layer is formed on the support by coating. You may be comprised only from (lambda) / 4 layer which removed the support body.
  • the light guide plate 14 or the reflective linearly polarized light separating plate 24 may be directly applied.
  • the ⁇ / 4 layer ( ⁇ / 4 plate) to the light guide plate 14 or the reflective linearly polarized light separating plate 24, the thickness of the entire backlight unit can be reduced.
  • the ⁇ / 4 plate and the light guide plate can also be used.
  • the light L emitted from the light source 12 enters the light guide plate 14 from the end face 14 b of the light guide plate 14.
  • the incident light is guided by repeating total reflection in the light guide plate 14, and the traveling direction is changed by the inclined surface of the recess 15 c and is emitted from the exit surface 14 a of the light guide plate 14.
  • FIG. 2 schematically shows main paths of light after exiting from the exit surface 14 a of the light guide plate 14.
  • the light L emitted from the emission surface 14 a of the light guide plate 14 enters the reflective linearly polarized light separating plate 24 via the ⁇ / 4 plate 20.
  • the first linearly polarized light L 1 passes through the reflective linearly polarized light separating plate 24 and enters the backlight side polarizing plate 26, and the second linearly polarized light L 2 is reflected by the reflective linearly polarized light separating plate 24. It is reflected by.
  • the second linearly polarized light L 2 reflected by the reflective linearly polarized light separating plate 24 passes through the ⁇ / 4 plate 20 and becomes circularly polarized light (for example, left circularly polarized light here) L1.
  • the left circularly polarized light L1 reenters the light guide plate 14 from the emission surface 14a, passes through the light guide plate 14, and is reflected by the reflection plate 16. Since the polarization direction is reversed when the circularly polarized light is reflected by the reflector, the left circularly polarized light Ll becomes the right circularly polarized light Lr.
  • the right circularly polarized light Lr reenters the light guide plate 14, passes through the light guide plate 14, and enters the ⁇ / 4 plate 20 again to become the first linearly polarized light L 1 .
  • the light passes through and enters the backlight-side polarizing plate 26, passes through, and enters the liquid crystal panel disposed on the backlight-side polarizing plate 26.
  • the reflective linearly polarized light separating plate and the ⁇ / 4 plate theoretically, all the linearly polarized light can be used as light incident on the backlight side polarizing plate 26.
  • reflected light also exists at the interface between the members or the air. Further, when passing through each member, not all polarized light is maintained as it is, and partial depolarization also occurs. These light eliminating reflected light or polarized light can repeat the same optical path as the original light L, incident on the backlight side polarizing plate 26 finally as the first linearly polarized light L 1 through the multiple reflections, transparent Then, the light enters the liquid crystal panel arranged on the backlight side polarizing plate 26.
  • the polarized light may be broken by being reflected by the reflecting plate. Also, when propagating through the light guide plate, the polarization may be lost due to a mechanism or the like that directs light to the exit surface.
  • the left circularly polarized light Ll that is reflected by the reflective linear polarization separation plate and passes through the ⁇ / 4 plate to become circularly polarized light is transmitted through the light guide plate. Therefore, many components of circularly polarized light are eliminated, and many components of circularly polarized light are eliminated by reflection by the reflector.
  • the left circularly polarized light L1 is free from many components of circularly polarized light and reaches the reflective linearly polarized light separating plate as non-polarized light.
  • the reflective linearly polarized separated plate is again polarization splitting, resulting in reflected again unable linearly polarized light L 2 is transmitted corresponding to half the amount.
  • the reflected light is gradually absorbed or becomes stray light.
  • the luminance improvement rate by using the ⁇ / 4 plate and the reflective linearly polarized light separating plate is only about 1.3 times.
  • the backlight unit of the present invention uses the light guide plate 14 having a depolarization degree Dg of 40% or less and the reflection plate 16 having a depolarization degree Dm of 30% or less. Since the reflected linearly polarized light or the circularly polarized light that has passed through the ⁇ / 4 plate is transmitted through the light guide plate and reflected by the reflecting plate, it is possible to prevent the polarization from being eliminated. As a linearly polarized light that passes through a reflective linearly polarized light separating plate that is orthogonal to the linearly polarized light that has been reflected, the reflected linearly polarized light separating plate can be returned to the reflective linearly polarized light separating plate.
  • the advantages of using the light guide plate having a mechanism for directing light to the exit surface, the reflective linearly polarized light separating plate and the ⁇ / 4 plate are sufficiently expressed, Light having high front luminance can be incident on the backlight side polarizing plate 26 (liquid crystal panel).
  • the depolarization degree Dg of the light guide plate 14 being 40% or less is caused by the light guide plate 14 out of the circularly polarized light incident from the output surface 14a of the light guide plate 14 and output from the output surface 14a of the light guide plate 14. This indicates that the amount of light from which circularly polarized light is eliminated is 40% or less. That is, more than 60% of the circularly polarized light that is incident from the light exit surface 14 a of the light guide plate 14 and is emitted from the light exit surface 14 a of the light guide plate 14 maintains the circularly polarized light inside the light guide plate 14.
  • a method for measuring the degree of depolarization Dg and the degree of depolarization Dg of the light guide plate 14 will be described in detail later.
  • the degree of depolarization Dg of the light guide plate 14 is 30% or less.
  • the area occupied by the directivity imparting mechanism that directs the light provided on the light guide plate 14 toward the emission surface 14a and the phase difference of the light guide plate 14 are important. That is, the light guide plate 14 having a depolarization degree Dg of 40% or less can be obtained by appropriately setting the occupation area ratio of the directivity imparting mechanism and / or the phase difference of the light guide plate 14.
  • the occupation area ratio of the directivity imparting mechanism is the ratio of the area occupied by the directivity imparting mechanism to the entire area of the main surface 14c where the directivity imparting mechanism of the light guide plate 14 is provided.
  • the area occupied by the directivity imparting mechanism is an area ratio occupied by the directivity imparting mechanism with respect to the entire area of the exit surface 14a of the light guide plate 14 when the light guide plate 14 is viewed from a direction perpendicular to the exit surface 14a. is there.
  • FIG. 4 schematically shows a side view A and a bottom view B of the light guide plate 14.
  • a long concave portion 15c having a width a whose cross-sectional shape in the light propagation direction is a right-angled triangle having a surface perpendicular to the back surface 14c side and an inclined surface, is elongated at the same interval b as the width a.
  • the light guide plate 14 is arranged in the direction orthogonal to the direction and formed so that the number of the concave portions 15c and the non-formed portions of the concave portions 15c are the same, the occupation of the concave portion 15c on the emission surface 14a where the concave portions 15c are formed The area is 50%. At this time, the area occupied by the flat surface, which is a non-formed portion where the concave portion 15c is not formed, is 50%.
  • the occupied area of the recess 15c is preferably 2% or more, and more preferably 5% or more. That is, the occupied area of the plane portion is preferably 98% or less, and more preferably 95% or less.
  • the occupied area ratio of the recess 15c is preferably 70% or less, and more preferably 50% or less. That is, in the present invention, the occupation area ratio of the directivity imparting mechanism is preferably 2 to 70%, more preferably 5 to 70%, and further preferably 5 to 50%. Further, the area occupied by the directivity imparting mechanism is particularly preferably 10 to 50%. That is, the occupation area of the flat surface is preferably 30 to 98%, more preferably 30 to 95%, further preferably 50 to 95%, and particularly preferably 50 to 90%.
  • the degree of depolarization Dg of the light guide plate 14 increases.
  • the light guide plate 14 is made of a material having a phase difference of several thousand to several tens of thousands such as polyethylene terephthalate, the light incident on the light guide plate is largely depolarized, and the degree of depolarization Dg of the light guide plate 14 is increased. End up. Therefore, in a mode in which the light guide plate does not serve as a ⁇ / 4 plate, the light guide plate 14 is preferably made of a material having a small phase difference, and the phase difference is preferably 100 nm or less.
  • both Re (550) and Rth (550) are preferably 100 nm or less, more preferably 50 nm or less, and particularly preferably 30 nm or less.
  • Re ( ⁇ ) and Rth ( ⁇ ) represent in-plane retardation at wavelength ⁇ and retardation in the thickness direction, respectively.
  • the phase difference of the light guide plate is preferably 100 nm or more and less than 200 nm.
  • Re ( ⁇ ) is measured by making light of wavelength ⁇ nm incident in the normal direction of the light guide plate 14 in KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments). In selecting the measurement wavelength ⁇ nm, the wavelength selection filter can be exchanged manually, or the measurement value can be converted by a program or the like.
  • Rth ( ⁇ ) is calculated by the following method.
  • Rth ( ⁇ ) is Re ( ⁇ ) with the in-plane slow axis (determined by KOBRA 21ADH or WR) as the tilt axis (rotary axis) (if there is no slow axis, film
  • the light of wavelength ⁇ nm is incident from the inclined direction in steps of 10 degrees from the normal direction to 50 degrees on one side with respect to the normal direction of the light guide plate 14 (with an arbitrary direction in the plane as the rotation axis).
  • KOBRA 21ADH or WR is calculated based on the measured retardation value, the assumed average refractive index, and the input film thickness value.
  • the retardation value when the in-plane slow axis is the axis of rotation from the normal direction and the retardation value is zero at a certain inclination angle, the retardation value at an inclination angle larger than that inclination angle.
  • KOBRA 21ADH or WR calculates.
  • the retardation value is measured from two inclined directions with the slow axis as the tilt axis (rotation axis) (if there is no slow axis, the arbitrary direction in the film plane is the rotation axis).
  • Rth can also be calculated from the following formula (A) and formula (B) based on the value, the assumed value of the average refractive index, and the input film thickness value.
  • Re ( ⁇ ) represents a retardation value in a direction inclined by an angle ⁇ from the normal direction.
  • nx represents the refractive index in the slow axis direction in the plane
  • ny represents the refractive index in the direction orthogonal to nx in the plane
  • nz is the direction orthogonal to nx and ny.
  • d is the film thickness.
  • Rth ( ⁇ ) is calculated by the following method. Is done. That is, Rth ( ⁇ ) is Re ( ⁇ ), and the in-plane slow axis (determined by KOBRA 21ADH or WR) is the tilt axis (rotation axis) with respect to the normal direction of the light guide plate 14.
  • the average refractive index values of main optical films are exemplified below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), Polystyrene (1.59).
  • KOBRA 21ADH or WR calculates nx, ny, and nz.
  • Nz (nx ⁇ nz) / (nx ⁇ ny) is further calculated from the calculated nx, ny, and nz.
  • the occupation ratio of the flat surface on the main surface on which the directivity imparting mechanism is formed is 2 to 70% and the light guide plate does not function as a ⁇ / 4 plate, the position of the light guide plate 14 is reduced.
  • the phase difference is 100 nm or less, the light guide plate 14 having a depolarization degree Dg of 40% or less can be suitably obtained.
  • the material for forming the light guide plate 14 is polypropylene, polycarbonate, polymethyl (meth) acrylate, benzyl (meth) acrylate, MS resin, cycloolefin polymer, cycloolefin copolymer
  • the light guide plate 14 preferably has a small phase difference.
  • the light guide plate 14 is formed of a material having a small phase difference such as an acrylic material such as polymethyl (meth) acrylate or benzyl (meth) acrylate, a cycloolefin polymer, or a cycloolefin copolymer. Is preferred.
  • the light guide plate 14 when the light guide plate also serves as a ⁇ / 4 plate, the light guide plate 14 having a depolarization degree Dg of 40% or less can be suitably obtained by setting the phase difference of the light guide plate to 100 nm or more and less than 200 nm.
  • a material for forming the light guide plate when the light guide plate also serves as a ⁇ / 4 plate it is preferable to use a highly transparent resin such as polycarbonate, cycloolefin polymer, and cycloolefin copolymer.
  • the light guide plate 14 in order to reduce the degree of depolarization Dg, the light guide plate 14 preferably has a small phase difference.
  • the light guide plate 14 is formed of a material having a small phase difference such as an acrylic material such as polymethyl (meth) acrylate or benzyl (meth) acrylate, a cycloolefin polymer, or a cycloolefin copolymer. Is preferred.
  • the thickness of the light guide plate is not particularly limited, but it may be formed in a film shape of 200 ⁇ m or less from the viewpoint of thinning and flexibility.
  • a light guide plate having a thickness of 200 ⁇ m or less may be referred to as a light guide film.
  • production by roll-to-roll and direct application of ⁇ / 4 layer associated therewith are possible, which is advantageous in production.
  • the directivity imparting mechanism is a recess
  • a method of cutting or punching a sheet-like material that becomes the light guide plate 14 and a method of embossing (embossing) the sheet-like material that becomes the light guide plate 14 are exemplified. Is done.
  • the mechanism for directing light toward the light exit surface 14a is a convex portion
  • a method for nanoimprinting the convex portion on the sheet-like material that becomes the light guide plate 14, or the convex portion on the sheet-like material that becomes the light guide plate 14 The method of transferring the structure to become is illustrated.
  • this reflector preferably has a depolarization degree Dm of 30% or less.
  • the reflecting plate 16 propagates the light transmitted through the light guide plate 14 and emitted from the back surface 14c, or the left circularly polarized light Ll reflected by the reflective linearly polarized light separating plate 24 and re-entered the light guide plate 14 from the emitting surface 14a and transmitted. (Refer FIG. 2), it reflects toward the light-guide plate 14. FIG. By having such a reflecting plate 16, the light utilization efficiency can be improved.
  • the reflection plate 16 has a depolarization degree Dm of 30% or less. Specifically, the degree of depolarization Dm of the polarized light incident on and reflected by the reflecting plate 16 is 30% or less. Therefore, more than 70% of the polarized light that is incident and reflected by the reflecting plate 16 maintains the polarization state at the time of incidence, and reenters the light guide plate 14.
  • the depolarization degree Dm of the reflecting plate 16 is preferably 25% or less, and more preferably 20% or less.
  • Various reflectors can be used as the reflector 16 as long as the degree of depolarization Dm is 30% or less.
  • the reflection plate having a depolarization degree Dm of 30% or less for example, the reflection plates described in Japanese Patent Nos. 3416302, 3363565, 4091978, and 348656 can be used. is there.
  • a specular reflector is preferable in that light can be regularly reflected while maintaining a polarization state, and a reflector 16 having a depolarization degree Dm of 30% or less can be easily obtained.
  • a single-layer mirror reflector more easily obtains a lower degree of depolarization than a multilayer reflector made of different materials, and in particular, a single-layer metal such as silver, aluminum, tin, etc. is deposited.
  • a layered specular reflector is preferred.
  • a specular reflector formed by vapor-depositing silver is particularly preferable.
  • the single-layer film includes a film in which a plurality of films made of the same material are stacked.
  • the degree of depolarization of the light guide plate 14 and the reflection plate 16 is measured as follows.
  • the light guide plate 14 and the reflection plate 16 are arranged in the same manner as the backlight unit 10.
  • the recessed part of the light-guide plate 14 is abbreviate
  • the linearly polarizing plate 46 and the ⁇ / 4 plate 48 are arranged on the light guide plate 14 so as not to cover the entire surface. In this state, parallel light is incident on the linearly polarizing plate 46 at an angle of 5 degrees with respect to the normal line of the exit surface 14 a of the light guide plate 14, and then transmitted through the ⁇ / 4 plate 48.
  • the ⁇ / 4 plate 50 and the linearly polarizing plate 52 and the color luminance at a position symmetrical to the parallel light with respect to the normal line and at a position where the reflected light does not pass through the linearly polarizing plate 46 and the ⁇ / 4 plate 48.
  • a total 54 is placed and the luminance is measured. This luminance measurement is performed by appropriately rotating the ⁇ / 4 plate 50 and the linearly polarizing plate 52, and an angle between the minimum luminance (Y min ) and the maximum luminance (Y max ) is detected. Using the measured minimum luminance (Y min ) and maximum luminance (Y max ), the degree of depolarization is calculated by the following equation.
  • Depolarization degree 100 ⁇ (1 ⁇ (Y max ⁇ Y min ) / (Y max + Y min ))
  • the slow axis of the ⁇ / 4 plate 48 is set to ⁇ 45 degrees with respect to the absorption axis of the linear polarizing plate 46 so that the right circularly polarized light or the left circularly polarized light is guided to the light guide plate 14 (reflecting plate 16).
  • the slow axis of the ⁇ / 4 plate 50 is set to ⁇ 45 degrees with respect to the absorption axis of the linearly polarizing plate 52, whereby the maximum luminance ( Y max ) and minimum luminance (Y min ) can be measured.
  • This degree of depolarization is the total degree of depolarization of the optical member in the backlight unit 10 excluding the ⁇ / 4 plate and the reflective linearly polarized light separating plate. In the following description, this degree of depolarization is also referred to as the total degree of depolarization Da. In the present invention, the total depolarization degree Da is preferably 50% or less. Thereby, the backlight unit 10 with higher front luminance can be obtained.
  • the measurement of the degree of depolarization is performed by removing the light guide plate 14. Thereby, the depolarization degree Dm of the reflecting plate 16 can be measured.
  • the depolarization degree Dg of the light guide plate of 40% or less indicates that the depolarization degree Dg of the light guide plate measured by this measurement method is 40% or less.
  • the depolarization degree Dm of the reflecting plate being 30% or less indicates that the depolarization degree Dm of the reflecting plate measured by this measurement method is 30% or less.
  • the backlight unit 10 may include a diffusion plate between the light guide plate and the reflective linearly polarized light separating plate.
  • the diffusing plate By providing the diffusing plate, the uniformity of the surface direction of the light guide plate 14 of the light emitted from the backlight unit 10 can be improved.
  • Various diffuser plates that are used in known backlight units used in LCDs can be used.
  • the diffusion plate it is preferable that the diffusion plate also has a small degree of depolarization.
  • the depolarization degree of the diffusion plate is the total depolarization degree of the optical member excluding the ⁇ / 4 plate and the reflective linearly polarized light separating plate, and the depolarization degree Da of the entire backlight unit described above is It is preferable that the degree of depolarization is 50% or less.
  • the entire degree of depolarization Da is obtained when the diffusion plate is disposed so as to cover the entire light guide plate 14 between the ⁇ / 4 plate 20 and the light guide plate 14. It can be measured by measuring the degree of depolarization in the same manner as described above. Further, the degree of depolarization of the diffusion plate alone can be measured according to the degree of depolarization of the light guide plate 14.
  • the directivity imparting mechanism for directing the light propagating inside the light guide plate 14 toward the emission surface 14a is not limited to the concave portion 15c having a right triangle shape as shown in FIGS.
  • Various shapes and configurations that can direct light propagating through the light exit surface 14a can be used.
  • a shape having a curved slope that is convex toward the inside of the light guide plate 14 such as a recess 15d shown in FIG. 3A, or a curved surface that is concave toward the inside of the light guide plate 14 like a recess 15e shown in FIG. 3B.
  • the shape which has a shape-like slope may be sufficient.
  • it may have an arcuate shape (bow shape) or a semicircular cross-sectional shape like a recess 15f shown in FIG. 3C.
  • the directivity imparting mechanism may be a convex portion provided on the back surface 14c of the light guide plate 14 instead of the concave portion.
  • the convex part 15g which has the circular-arc shaped cross section provided in the back surface 14c of the light-guide plate 14 as shown to FIG. 3D is illustrated.
  • such a convex portion may be a (substantially) triangular convex portion as shown in FIG.
  • the directivity imparting mechanism is the convex portion 15g provided on the back surface 14c of the light guide plate 14
  • the light guide plate 14 and the convex portion 15g may be integrally formed, and the convex portion is formed on the back surface 14c of the light guide plate 14.
  • the structure which added 15g may be sufficient.
  • the mechanism for directing the light propagating inside the light guide plate 14 toward the emission surface 14a may be dotted in an island shape, or a long object may be arranged. These directivity imparting mechanisms may be used in combination.
  • the surface roughness of the concave and convex portions serving as the directivity imparting mechanism for directing light toward the light exit surface 14a is large, the degree of depolarization Dg of the light guide plate 14 increases. Therefore, it is preferable that the surface of these concave and convex portions is smooth.
  • the directivity imparting mechanism may be formed not only on the other main surface 14 c but also on both main surfaces 14 a and 14 c of the light guide plate 14. Further, the directivity imparting mechanism may include a through-hole penetrating from one main surface 14a of the light guide plate 14 to the other main surface 14c. When penetrating, the area of one mechanism with respect to the cross-sectional area of the light incident on the light guide plate is large, so that the light can be directed to the exit surface more efficiently.
  • FIG. 6 shows a schematic configuration of the backlight unit 11 of the design change example of the first embodiment.
  • the backlight unit 11 has a reflecting plate 16 disposed on the light exit surface 14a side of the light guide plate 14, and a ⁇ / 4 plate on the other main surface 14c side where a concave portion 15c serving as a directivity imparting mechanism of the light guide plate 14 is formed. 20 and a reflective linearly polarized light separating plate 24 are arranged.
  • This configuration contemplates the second backlight unit aspect of the present invention.
  • the light L emitted from the light source 12 enters the light guide plate 14 from the end surface 14 b of the light guide plate 14.
  • the incident light is guided by repeating total reflection in the light guide plate 14, and the traveling direction is changed by the inclined surface of the recess 15 c and is emitted from the exit surface 14 a of the light guide plate 14.
  • the light L emitted from the emission surface 14a of the light guide plate 14 is incident on the reflection plate 16, is reflected, enters the light guide plate 14 again, passes through the light guide plate 14, and passes through the ⁇ / 4 plate 20.
  • the subsequent light path is the same as that of the backlight unit 10 of the first embodiment, and the effects to be achieved are also the same.
  • FIG. 7 shows a schematic configuration of the backlight unit 60 according to the second embodiment of the present invention.
  • the backlight unit 60 of the present embodiment is illustrated in that the ⁇ / 4 plate 20 is provided not between the light guide plate 14 and the reflective linearly polarized light separating plate 24 but between the light guide plate 14 and the reflective plate 16. 1 is different from the backlight unit 10 of the first embodiment shown in FIG.
  • the second linearly polarized light L 2 reflected by the reflective linearly polarized light separating plate 24 passes through the light guide plate 14 and then enters the ⁇ / 4 plate 20, and is circularly polarized within the ⁇ / 4 plate 20.
  • left circularly polarized light L1 here
  • the light enters the reflector 16 as the left circularly polarized light Ll, and the direction of rotation is reversed on the reflector 16 to be reflected as the right circularly polarized light Lr.
  • the right circularly polarized light Lr becomes the first linearly polarized light in the ⁇ / 4 plate 20 and is incident on the light guide plate 14 again.
  • the first linearly polarized light transmitted through the light guide plate 14 is transmitted through the reflective linearly polarized light separating plate 24 and is incident on the backlight side polarizing plate 26 of the liquid crystal cell.
  • the linearly polarized light reflected by the reflective linearly polarized light separating plate 24 passes through the ⁇ / 4 plate and is re-incident on the light guide plate 14 while being circularly polarized.
  • the linearly polarized light reflected by the reflective linearly polarized light separating plate 24 reenters the light guide plate 14 as it is.
  • the light guide plate 14 and the reflection plate 16 are the same as those in the first embodiment, and those having a small degree of depolarization are used. The same effect as the light unit 10 can be obtained.
  • the ⁇ / 4 plate may be a ⁇ / 4 layer that is directly applied and formed on the surface of the reflecting plate 16.
  • FIG. 8 shows a schematic configuration of a backlight unit 70 according to the third embodiment of the present invention.
  • the backlight unit 70 of the present embodiment is different from the backlight unit 10 of the first embodiment shown in FIG. 1 in that a light guide plate 34 having a through hole 35 is provided as a directivity providing mechanism instead of the light guide plate 14. Different.
  • FIG. 9 is a cross-sectional view (A) and a bottom view (B) showing a part of the light guide plate 34 provided in the backlight unit 70 of the present embodiment.
  • the light guide plate 34 is provided with a plurality of oblique columnar through holes 35 penetrating the front and back surfaces (from one main surface to the other main surface).
  • the through hole 35 is formed with an inclination with respect to the normal line (direction perpendicular to the main surface) Z of the main surface.
  • the normal line of the main surface is parallel to the arrangement direction of the reflecting plate 16, the light guide plate 34, and the reflective linearly polarized light separating plate 24.
  • the inclination of the through-hole 35 is defined as the inclination of a straight line connecting the center of the opening of one main surface to the center of the opening of the other main surface, and the inclination of the through-hole 35 with respect to the direction Z perpendicular to the main surface.
  • the center of the opening is the center of gravity of the opening shape.
  • the angle ⁇ formed by Z and the through hole 35 is preferably 30 ° to 80 °.
  • the occupied area ratio of the flat surface on one main surface is directed from a concave portion.
  • it is preferably 30 to 98%, more preferably 30 to 95%, and even more preferably 50 to 95% in order to satisfy the degree of depolarization of 40% or less and to have a directivity imparting function.
  • 50 to 90% is particularly preferable.
  • the opening shape in the main surface of the through hole 35 is not limited to a circle, and may be an ellipse, an arc, a polygon, or the like. Moreover, although it is preferable that the shape of the cross section parallel to the main surface corresponds to the opening shape, the through hole 35 may have a partially different cross sectional shape.
  • the directivity provision mechanism in the light guide plate is a through-hole as in this embodiment, the light guide is more light compared to the case where the directivity provision mechanism including a concave portion or a convex portion is provided only on one main surface. Since it becomes easy to give directivity to the light guided in the wave path, the light guide plate itself can be made thin, and a film having a thickness of 200 ⁇ m or less can be easily realized.
  • FIG. 10 shows a schematic configuration of a backlight unit 80 according to the fourth embodiment of the present invention.
  • the backlight unit 80 of the present embodiment includes a wavelength conversion member 40 that is excited by incident light and generates fluorescence via an adhesive layer 45 on the exit surface side of the light guide plate 14, and includes an excitation wavelength as a light source. It differs from the backlight unit 10 of 1st Embodiment shown in FIG. 1 by the point provided with the light source 13 which inject
  • the wavelength conversion member 40 includes a first substrate 41, a second substrate 42, and a wavelength conversion layer 44, and the wavelength conversion layer 44 is sandwiched between the first substrate 41 and the second substrate 42 as shown in FIG. .
  • the wavelength conversion layer 44 converts the wavelength of incident light into a relatively long wavelength.
  • the wavelength conversion layer 44 can include phosphors, quantum dots, or combinations thereof.
  • the phosphor may be a general organic phosphor or an inorganic phosphor.
  • the phosphor may be a yellow phosphor.
  • Such a yellow phosphor may be, but is not limited to, a YAG phosphor, a silicate phosphor, an oxynitride phosphor, or a combination thereof.
  • Quantum dots have core-shell structure semiconductor nanoparticles with a size of several nanometers to several tens of nanometers.
  • the quantum confinement effect (Quantum Quantfinement Effect) has a characteristic that emitted light varies depending on the size of the particles. It means having. More specifically, quantum dots generate strong light in a narrow wavelength band, and light emitted by quantum dots is generated when electrons in the excited state transition from a conduction band to a valence band. To do. At this time, the quantum dot has a property of generating light having a shorter wavelength as the particle is smaller and generating light having a longer wavelength as the particle is larger. Therefore, when the size of the quantum dot is adjusted, all light in the visible light region having a desired wavelength can be emitted.
  • the quantum dot may be any one of Si-based nanocrystals, II-VI group compound semiconductor nanocrystals, III-V group compound semiconductor nanocrystals, IV-VI group compound semiconductor nanocrystals, and mixtures thereof. Can be included.
  • II-VI group compound semiconductor nanocrystals are CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, HgS, HgSe, HgTe, CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeC, HgSTeS, HgSTeS.
  • CdZnTe CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HggZnTe, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSeTe, HgZnSe, and HgZnSe.
  • the group III-V compound semiconductor nanocrystal is composed of GaPAs, AlNP, AlNAs, AlPAs, InNP, InNAs, InPAs, GaAlNP, GaAlNAs, GaAlPAs, GaInNP, GaInNAs, GaInPAs, InAlNP, InAlNAs, and InAlPAs.
  • the group IV-VI compound semiconductor nanocrystal may be SbTe.
  • the wavelength conversion layer 44 can include one type of quantum dot.
  • the wavelength conversion layer 44 may include yellow quantum dots that convert the wavelength of incident light into the wavelength of yellow light.
  • the present invention is not limited to this, and the wavelength conversion layer 44 may include two or more types of quantum dots.
  • the wavelength conversion layer 44 may include a red quantum dot that converts the wavelength of incident light into a wavelength of red light and a green quantum dot that converts the wavelength of incident light into a wavelength of green light.
  • the wavelength conversion layer 44 may further include a dispersion medium that disperses the wavelength conversion substance in addition to the wavelength conversion substance such as the phosphor and the quantum dots. That is, the phosphor or quantum dots can be dispersed in a form that is naturally coordinated in a dispersion medium such as an organic solvent or a polymer resin. As such a dispersion medium, any medium can be used as long as it does not affect the wavelength conversion performance of the phosphor or the quantum dot, does not reflect light, and does not cause light absorption.
  • a dispersion medium any medium can be used as long as it does not affect the wavelength conversion performance of the phosphor or the quantum dot, does not reflect light, and does not cause light absorption.
  • the organic solvent may include at least one of toluene, chloroform, and ethanol
  • the polymer resin may include, for example, epoxy, silicon, polystyrene, and polystyrene. At least one of acrylates may be included.
  • the wavelength conversion layer 44 may further include a UV initiator, a thermosetting additive, a crosslinking agent, a diffusing agent, and combinations thereof. As described above, the wavelength conversion layer 44 is formed by being applied and cured on the first substrate 41 in a state where the wavelength conversion substance and the additive are mixed.
  • the first substrate 41 and the second substrate 42 are made of a substance capable of blocking moisture and oxygen.
  • it may include silicon oxide (SiOx), silicon nitride (SiNx), or combinations thereof.
  • it may be a plastic film such as polyethylene terephthalate (PET) and polycarbonate (Polycarbonate, PC). It may be made of a glass material.
  • substrate 42 may consist of the same substance, and may differ.
  • a sealing member such as a sealant is disposed between the first substrate 41 and the second substrate 42 along the edges of the first substrate 41 and the second substrate 42. And the second substrate 42 can be bonded together and sealed.
  • the wavelength conversion member 40 forms the wavelength conversion layer 44 on the first substrate 41, and the second substrate on the wavelength conversion layer 44. It is formed by the process of attaching 42.
  • the wavelength conversion member 40 can be formed by a laminating process.
  • the light emitted from the light source 13 and passed through the wavelength conversion member 40 is generally uniform.
  • White color When the light source 13 emits blue light and the wavelength conversion layer 44 converts the color of the light emitted from the light source 13 to white, the light emitted from the light source 13 and passed through the wavelength conversion member 40 is generally uniform. White color.
  • a blue LED is provided as the light source 13, quantum dots that are excited by blue light and emit green light, and quantum dots that are excited by blue light and emit red light; Can be provided with a wavelength conversion layer 44 dispersed in a matrix.
  • ⁇ Production of light guide films 1 and 2> Using a commercially available cycloolefin polymer film (Zeonor ZF14, manufactured by Nippon Zeon Co., Ltd., thickness 100 ⁇ m), as shown in FIG. 11, the polar angle is 40 ° in the same direction as the incident light direction.
  • a plurality of through holes 50 (diameter of 50 ⁇ m, elliptical cylindrical body having a major axis of 60 ⁇ m) 37 having a diameter of 50 ⁇ m penetrating the film 36 were formed as the light guide film 1.
  • the plurality of through holes 37 were randomly arranged so that the area of the flat surface (portion other than the through hole opening) with respect to the area of the one main surface 36a of the film was 80%.
  • the degree of depolarization of the light guide film 1 was 10%.
  • through holes were provided so that the major axis of the ellipse was orthogonal to the side surface 36 b that is a light incident surface to the light guide film 1.
  • the opening shape of the through hole 39 of the film 36 is an arc shape as shown in FIG. 12, and the oblique columnar through hole 39 having the bottom surface of the arc shape has a period as shown in FIG.
  • the light guide film 2 was formed in the same manner except for the arrangement.
  • the through-hole 39 was formed so that a perpendicular line (string) connecting both ends of the arc was perpendicular to a side surface that is a light incident surface to the light guide film 2.
  • the degree of depolarization of the light guide film 2 was 10%.
  • ⁇ Preparation of light guide film 3> A laser was used for a commercially available polycarbonate film (Pure Ace WR-W, manufactured by Teijin Ltd.), and a through hole 39 was formed in the same manner as the light guide film 2 to obtain a light guide film 3. Since the degree of depolarization of the light guide film 3 is 10% and the planar phase difference is 150 nm, it also functions as a ⁇ / 4 plate.
  • the reflector 1 was MIRO-SILVER 2 manufactured by ALANOD.
  • This reflecting plate is a specular reflecting plate having a reflecting surface made of deposited silver. The degree of depolarization of this reflector was 3%.
  • the reflector used in iPad Air (registered trademark) manufactured by Apple Inc. was designated as reflector 2.
  • This reflecting plate has a reflecting surface made of an organic laminated film.
  • the degree of depolarization of the produced light guide plates 1 and 2, light guide films 1 and 2, and reflectors 1 and 2 was measured by the method shown in FIG. 5 described above.
  • the color luminance meter used was BM-5A manufactured by Topcon Technohouse.
  • a linearly polarizing plate and a ⁇ / 4 plate produced in the same manner as described later were disposed in order to make circularly polarized light incident on the member to be measured.
  • a cellulose ester support T1 for a ⁇ / 4 plate was prepared.
  • cellulose ester solution A-1 The following composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose ester solution A-1.
  • the cast dope film was dried on the drum by applying a drying air of 34 ° C. at 150 m 3 / min, and peeled off from the drum with a residual solvent of 150%. During peeling, 15% stretching was performed in the transport direction (longitudinal direction). Thereafter, the film is conveyed while being held by a pin tenter (pin tenter described in FIG. 3 of JP-A-4-1009) at both ends in the width direction (direction perpendicular to the casting direction) and stretched in the width direction. No processing was performed. Furthermore, it dried further by conveying between the rolls of the heat processing apparatus, and manufactured the cellulose-ester support body T1. The produced long cellulose ester support T1 had a residual solvent amount of 0.2%, a thickness of 60 ⁇ m, and Re and Rth at a wavelength of 550 nm of 0.8 nm and 40 nm, respectively.
  • the solvent was kept at 85 ° C. for 2 minutes to evaporate the solvent, and then heat-aged at 100 ° C. for 4 minutes to obtain a uniform alignment state.
  • the discotic compound was aligned perpendicular to the support plane.
  • this coating film was kept at 80 ° C. and irradiated with ultraviolet rays using a high-pressure mercury lamp in a nitrogen atmosphere to produce a ⁇ / 4 plate.
  • ⁇ Production of wavelength conversion member> (Preparation of barrier film) An organic layer and an inorganic layer were sequentially formed on one side of a commercially available cellulose acetate film (ZRD40SL, manufactured by FUJIFILM Corporation) by the following procedure. Prepare trimethylolpropane triacrylate (TMCTA manufactured by Daicel Cytec Co., Ltd.) and photopolymerization initiator (Lamberti Co., Ltd., ESACURE KTO46). It was dissolved in toluene to obtain a coating solution having a solid concentration of 15%. This coating solution was applied onto the cellulose acetate film film by roll-to-roll using a die coater, and passed through a drying zone at 50 ° C. for 3 minutes.
  • TMCTA trimethylolpropane triacrylate
  • ESACURE KTO46 photopolymerization initiator
  • the sample was irradiated with ultraviolet rays (integrated irradiation amount: about 600 mJ / cm 2 ) in a nitrogen atmosphere, cured by ultraviolet curing, and wound up.
  • the thickness of the first organic layer formed on the support was 1 ⁇ m.
  • an inorganic layer (silicon nitride layer) was formed on the surface of the first organic layer using a roll-to-roll CVD (Chemical Vapor Deposition) apparatus.
  • Silane gas (flow rate 160 sccm), ammonia gas (flow rate 370 sccm), hydrogen gas (flow rate 590 sccm), and nitrogen gas (flow rate 240 sccm) were used as source gases.
  • a high frequency power supply having a frequency of 13.56 MHz was used as the power supply.
  • the film forming pressure was 40 Pa, and the reached film thickness was 50 nm.
  • stacked on the surface of the 1st organic layer was produced.
  • phosphor-containing polymerizable composition for forming wavelength conversion layer
  • the following phosphor dispersion was prepared as a phosphor-containing polymerizable composition for forming a wavelength conversion layer, filtered through a polypropylene filter having a pore size of 0.2 ⁇ m, and then dried under reduced pressure for 30 minutes to be used as a coating solution.
  • the quantum dot concentration in the following toluene dispersion was 1% by mass.
  • quantum dots 1 and 2 nanocrystals having the following core-shell structure (InP / ZnS) were used.
  • Quantum dot 1 INP530-10 (manufactured by NN-labs): fluorescence half width of 65 nm
  • Quantum dot 2 INP620-10 (manufactured by NN-labs): fluorescence half width 70 nm
  • the viscosity of the phosphor dispersion was 50 mPa ⁇ s.
  • Two barrier films prepared by the above-described procedure are used, one of which is the first film, and the phosphor dispersion liquid is applied on the surface of the inorganic layer with a die coater, with a tension of 1 m / min and 60 N / m.
  • a coating film having a thickness of 50 ⁇ m was formed while continuously conveying.
  • the barrier film on which the coating film is formed is wound around a backup roller, and laminated as a second film on the coating film so that the inorganic layer surface of the other barrier film is in contact with the coating film.
  • the film was wound around a backup roller while the coating film was sandwiched between the barrier films (first and second films) and irradiated with ultraviolet rays while being continuously conveyed.
  • the diameter of the backup roller was ⁇ 300 mm, and the temperature of the backup roller was 50 ° C.
  • the irradiation amount of ultraviolet rays was 2000 mJ / cm 2 .
  • the coating film was cured by irradiation with the ultraviolet rays to form a cured layer (wavelength conversion layer), and a wavelength conversion member was produced.
  • the thickness of the cured layer of the wavelength conversion member was about 50 ⁇ m.
  • SK Dyne 2057 25 ⁇ m
  • Soken Chemical Soken Chemical
  • the reflector, the light guide plate, the ⁇ / 4 plate, and the reflective linearly polarized light separating plate were all used at 10 ⁇ 10 cm.
  • Example 1 The reflective linearly polarized light separating plate, the ⁇ / 4 plate, the light guide plate 1 and the reflective plate 1 were arranged in this order. Furthermore, a white LED was provided as a light source on one side of the light guide plate 1 to produce a backlight unit as shown in FIG.
  • Example 2 The ⁇ / 4 plate and the light guide plate were bonded using SK Dyne 2057 (25 ⁇ m) manufactured by Soken Chemical. That is, a backlight unit was obtained in the same manner as in Example 1 except that an adhesive layer was provided between the ⁇ / 4 plate and the light guide plate.
  • Example 3 A backlight unit as shown in FIG. 7 was produced in the same manner as in Example 1 except that the ⁇ / 4 plate was disposed between the reflecting plate 1 and the light guide plate 1.
  • Example 1 a backlight unit having a configuration not including the reflective linearly polarized light separating plate and the ⁇ / 4 plate was produced.
  • Comparative Example 5 A backlight unit of Comparative Example 5 was obtained in the same manner as in Example 1 except that a prism sheet pair was disposed between the reflective linearly polarized light separating plate and the ⁇ / 4 plate.
  • Reference Example 1 The backlight unit of Reference Example 11 was configured in the same manner except that the reflective linearly polarized light separating plate was not provided in Example 1.
  • Table 1 summarizes the backlight unit configurations of Examples 1 to 3, Comparative Examples 1 to 5 and Reference Example 1 and evaluation results based on the evaluation described below.
  • the polarizing plate located on the light exit side of the reflective linearly polarized light separating plate described in the examples and comparative examples in Table 1 is a backlight type polarizing plate of a liquid crystal cell, and is used when measuring the total luminous flux described later. , It shows that the measurement was performed in a state of being arranged at this position. The same applies to the following tables.
  • Example 11 The reflective linearly polarized light separating plate, the ⁇ / 4 plate, the wavelength converting member, the light guide plate 1 and the reflecting plate 1 were arranged in this order. Further, a blue LED was provided as a light source on one side surface of the light guide plate 1 to constitute a backlight unit of Example 11 as shown in FIG. In addition, the wavelength conversion member and the light-guide plate 1 were bonded together using the SK dyne 2057 (25 micrometers) by Soken Chemical. That is, an adhesive layer is provided between the wavelength conversion member and the light guide plate 1.
  • Example 11 the backlight unit of Reference Example 11 was configured in the same manner except that the reflective linearly polarized light separating plate was not provided.
  • Table 2 summarizes the backlight unit configurations of Example 11 and Reference Example 1 and the evaluation results based on the evaluation described below.
  • Example 21 In the same manner as in Example 1 except that the light guide film 1 was used instead of the light guide plate 1, a backlight unit of Example 21 as shown in FIG. 8 was configured.
  • Example 22 The backlight unit of Example 22 was configured in the same manner except that the light guide film 2 was used instead of the light guide film 1 in Example 21.
  • Example 23 In Example 21, the light guide film 3 is used instead of the light guide film 1, and the ⁇ / 4 plate is not used (the light guide film 3 also serves as the ⁇ / 4 plate). A light unit was constructed.
  • Example 21 the backlight unit of Reference Example 21 was configured in the same manner except that the reflective linearly polarized light separating plate was not provided.
  • Table 3 summarizes the backlight unit configurations of Examples 21, 22, and 23 and Reference Example 21 and the evaluation results based on the evaluation described below.
  • the backlight side polarizing plate of the liquid crystal cell is arranged on the emission surface side of the backlight unit, is transmitted through the reflective linearly polarized light separation plate of the backlight unit, and is emitted as backlight unit light.
  • the light transmitted through the polarizer is set to a luminance [cd / m 2 ] at polar angles of -80 to 80 degrees every 10 degrees and every azimuth angle every 15 degrees. Measurement was performed, and all measurement points were added for each solid angle to obtain a total luminous flux.
  • the backlight side polarized light is used. No light was provided, that is, light emitted as backlight unit light from the backlight unit was directly detected without passing through the backlight side polarizing plate.
  • the ratio of the total luminous flux in each example and comparative example was evaluated as the total luminous flux ratio. The closer this value is to 100%, the better the performance.
  • the backlight unit of the example using the light guide plate and the reflection plate having a small degree of depolarization and including the ⁇ / 4 plate and the reflection type linearly polarized light separation plate as in the present invention is a comparative example.
  • the ratio of the total luminous flux transmitted through the backlight side polarizing plate was large and the effect of improving the luminance was high.
  • good luminance improvement could be achieved by the configuration of the present invention.
  • a very thin light guide film was used as the light guide plate as in Examples 21 and 22, a very good total luminous flux ratio could be obtained.
  • Example 21 and 22 since the light guide film is very thin as 100 ⁇ m, the thickness of the entire backlight unit can be very small. Except for Comparative Example 5 provided with a prism sheet, no visible moire occurred. Obviously, it is effective not to have a prism sheet in order to suppress moire. And in the Example of this invention which does not need to provide a prism sheet, it is clear that the thickness as the whole backlight unit can be suppressed compared with the case where a prism sheet is provided.

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • General Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Planar Illumination Modules (AREA)
  • Liquid Crystal (AREA)

Abstract

[Problem] To provide a backlight unit with which it is possible to cause light emitted by a light source to enter a liquid crystal panel at a high efficiency. [Solution] A configuration having: a light source (12); a light guide plate (14) into which light emitted by the light source (12) enters through an end surface (14b), through which the light L entering through the end surface (14b) propagates, and out of which the light L is emitted through one main surface (14a), the light guide plate (14) having a depolarization degree Dg of 40% or below and having a directionality-imparting mechanism (15c) for directing the propagating light towards the one main surface (14a); a reflecting plate (16) having a depolarization degree (Dm) of 30% or below, the reflecting plate (16) being disposed on the side of the other main surface (14c) opposite the one main surface (14a) of the light guide plate (14); a reflection-type linearly polarized light separation plate (24) disposed on the one main surface (14a) side of the light guide plate (14), the reflection-type linearly polarized light separation plate (24) transmitting first linearly polarized light (L1) and reflecting second linearly polarized light (L2) orthogonal to the first linearly polarized light (L1); and a λ/4 plate (20) disposed between the reflection-type linearly polarized light separation plate (24) and the light guide plate (14) or between the light guide plate (14) and the reflecting plate (16).

Description

バックライトユニットBacklight unit
　本発明は、液晶表示装置に用いられるバックライトユニットに関する。 The present invention relates to a backlight unit used in a liquid crystal display device.
　液晶表示装置（以下、ＬＣＤとも言う）は、消費電力が小さく、省スペースの画像表示装置として年々その用途が広がっている。液晶表示装置は、一例として、バックライトユニット、バックライト側偏光板、液晶パネル、視認側偏光板などを、この順で設けられた構成となっている。 Liquid crystal display devices (hereinafter also referred to as LCDs) consume less power and are increasingly used year by year as space-saving image display devices. As an example, the liquid crystal display device has a configuration in which a backlight unit, a backlight side polarizing plate, a liquid crystal panel, a viewing side polarizing plate, and the like are provided in this order.
　バックライトユニットとしては、端面から入射した光を伝搬して主面から出射させる導光板と、導光板の端面に光を入射する光源とを有する、いわゆるエッジライトタイプのバックライトユニット、および、一面から入射した光を拡散させて他面から出射させる拡散板と、拡散板の一面側（直下）に配置されて拡散板の一面に光を入射する光源とからなる、いわゆる直下型のバックライトユニットが知られている。 As the backlight unit, a so-called edge light type backlight unit having a light guide plate that propagates light incident from the end surface and emits the light from the main surface, and a light source that enters light to the end surface of the light guide plate, and one surface A so-called direct-type backlight unit comprising a diffuser that diffuses light incident from the diffuser and emits the light from the other surface, and a light source that is disposed on one side (directly below) of the diffuser and that is incident on one surface of the diffuser It has been known.
　バックライトユニットは、画像の輝度や視認性など、ＬＣＤの性能に大きな影響を与える。これに対応して、バックライトユニットが出射する光（バックライト）の輝度を向上するため、各種の提案が行われている。 The backlight unit greatly affects the performance of the LCD, such as image brightness and visibility. In response to this, various proposals have been made to improve the luminance of light (backlight) emitted from the backlight unit.
　例えば、輝度向上フィルムとして反射型偏光板を用いることも提案されている。反射型偏光板は、所定の偏光を透過し、それ以外の偏光を反射するものである。反射型偏光板を用いることにより、バックライト側偏光板に対応する直線偏光のみを透過してバックライト側偏光板に入射し、それ以外の偏光を反射してバックライトユニット内で再帰反射を繰り返して、再度、反射型偏光板に入射させて再利用することができる。 For example, it has been proposed to use a reflective polarizing plate as a brightness enhancement film. The reflective polarizing plate transmits predetermined polarized light and reflects other polarized light. By using a reflective polarizing plate, only linearly polarized light corresponding to the backlight-side polarizing plate is transmitted and incident on the backlight-side polarizing plate, and other polarized light is reflected to repeat retroreflection in the backlight unit. Then, it can be reused by being incident on the reflective polarizing plate again.
　また、特許文献１には、直下型のバックライトユニットにおいて、拡散板の出射面側に反射型偏光子を備え、光源の拡散板とは逆側に反射板を配置して、反射型偏光子により反射された光を反射板により再度反射型偏光子へと反射させることにより、輝度向上を図る構成が提案されている。 Further, in Patent Document 1, in a direct type backlight unit, a reflective polarizer is provided on the exit surface side of the diffuser plate, and a reflective plate is disposed on the side opposite to the diffuser plate of the light source. The structure which improves a brightness | luminance is proposed by reflecting the light reflected by (1) by the reflecting plate again to a reflection type polarizer.
　一方、光の指向性を高めることにより輝度向上を図る方策も検討されており、例えば、特許文献２には、エッジライトタイプのバックライトユニットにおいて、導光板の出射面に対向する面に、導光板内で伝搬される光を反射して出射面から出射させるための光反射部を有し、この光反射部が、導光板の内部に位置し、かつ、光反射部の光源側に、光反射部に入射する光の指向性を向上させる指向性変換部を有するバックライトユニット（面光源装置）が記載されている。
　特許文献２に記載されるバックライトユニットは、このような構成を有することにより、バックライトユニットから出射する光の指向性を向上して、液晶パネルに入射する光の輝度を向上できる。 On the other hand, a measure for improving the luminance by increasing the directivity of light has been studied. For example, Patent Document 2 discloses that an edge light type backlight unit is guided to a surface facing the light exit surface of the light guide plate. A light reflecting portion for reflecting the light propagating in the light plate to be emitted from the light emitting surface; the light reflecting portion is located inside the light guide plate; and on the light source side of the light reflecting portion A backlight unit (surface light source device) having a directivity conversion unit that improves the directivity of light incident on the reflection unit is described.
Since the backlight unit described in Patent Document 2 has such a configuration, the directivity of light emitted from the backlight unit can be improved, and the luminance of light incident on the liquid crystal panel can be improved.
　また、平板状の導光板からの出射光の指向性を、プリズムシートにより出射面の正面方向に補正して液晶表示パネルに供給する構成も提案されている。特許文献３では、プリズムシートを導光板側に凸となるように配置することにより、単純な断面三角形状の凸状が隣接して繰り返されてなるプリズムシートを用いて、より好ましい指向性を得ることができる構成が提案されている。 Also proposed is a configuration in which the directivity of the emitted light from the flat light guide plate is corrected by the prism sheet in the front direction of the emission surface and supplied to the liquid crystal display panel. In Patent Document 3, by arranging the prism sheet so as to be convex toward the light guide plate, a more preferable directivity can be obtained by using a prism sheet in which convex shapes having a simple cross-sectional triangular shape are repeated adjacent to each other. A possible configuration is proposed.
特開昭６３－１６８６２６号公報JP-A 63-168626 特開２００５－２６８２０１号公報JP 2005-268201 A 特開２０１５－１７３０６６号公報Japanese Patent Laying-Open No. 2015-173066
　ＬＣＤに用いられるバックライトユニットにおいて、特許文献１に記載されるような、所定の状態の偏光を透過し、それ以外の偏光を反射する反射型偏光板や、特許文献２、３に記載されるような、出射する光の指向性を制御する導光板あるいはプリズムシートを用いることにより、光の利用効率を向上し、液晶パネルに入射する光の輝度を向上することができる。 In a backlight unit used in an LCD, as described in Patent Document 1, a reflective polarizing plate that transmits polarized light in a predetermined state and reflects other polarized light, and described in Patent Documents 2 and 3 By using such a light guide plate or prism sheet that controls the directivity of the emitted light, the light use efficiency can be improved and the luminance of the light incident on the liquid crystal panel can be improved.
　しかしながら、近年では、例えばＬＣＤの高精細化による画素の開口率低下に起因する表示画像輝度の低下など、様々な理由によって、液晶パネルに入射する光の輝度の向上が要求されている。そのため、バックライトユニットは、さらに光の利用効率を向上する必要がある。また、指向性付与のために特許文献３のような多数のプリズムが互いに隣接して配列されてなるプリズムシートを用いるとモアレが生じるという問題点があった。また、プリズムシートを備えることによりユニット全体の厚みが厚くなるという問題もあった。 However, in recent years, there has been a demand for an improvement in the luminance of light incident on a liquid crystal panel for various reasons, such as a decrease in display image luminance due to a decrease in pixel aperture ratio due to high definition of LCD, for example. Therefore, the backlight unit needs to further improve the light utilization efficiency. Further, when a prism sheet in which a large number of prisms as in Patent Document 3 are arranged adjacent to each other for providing directivity is used, there is a problem that moire occurs. Moreover, there also existed a problem that the thickness of the whole unit became thick by providing a prism sheet.
　本発明は、上記事情に鑑みてなされたものであって、ＬＣＤ等に用いられるバックライトユニットであって、光の利用効率をより向上させて、高輝度な光（バックライト）を出射できるバックライトユニットを提供することを目的とする。 The present invention has been made in view of the above circumstances, and is a backlight unit used in an LCD or the like, which further improves light utilization efficiency and can emit high-luminance light (backlight). An object is to provide a light unit.
　本発明の第１のバックライトユニットは、光源と、
　光源が出射する光を端面から入射され、端面から入射された光を伝搬して一方の主面から出射する、偏光解消度Ｄｇが４０％以下で、かつ、伝搬する光を前記一方の主面に向ける指向性付与機構を有する導光板と、
　導光板の一方の主面と対向する他方の主面側に配置された、偏光解消度Ｄｍが３０％以下の反射板と、
　導光板の一方の主面側に配置された、第１の直線偏光を透過して、第１の直線偏光と直交する第２の直線偏光を反射する反射型直線偏光分離板と、
　反射型直線偏光分離板と反射板との間に配置されたλ／４板とを有することを特徴とする。 The first backlight unit of the present invention includes a light source,
The light emitted from the light source is incident from the end face, propagates the light incident from the end face, and exits from one main surface. The degree of depolarization Dg is 40% or less, and the propagating light is the one main surface. A light guide plate having a directivity imparting mechanism directed toward
A reflector having a depolarization degree Dm of 30% or less, disposed on the other principal surface side opposite to one principal surface of the light guide plate;
A reflective linearly polarized light separating plate that is disposed on one main surface side of the light guide plate and transmits the first linearly polarized light and reflects the second linearly polarized light orthogonal to the first linearly polarized light;
And a λ / 4 plate disposed between the reflective linearly polarized light separating plate and the reflective plate.
　また、本発明の第２のバックライトユニットは、光源と、
　光源が出射する光を端面から入射され、端面から入射された光を伝搬して一方の主面から出射する、偏光解消度Ｄｇが４０％以下で、かつ、伝搬する光を一方の主面に向ける指向性付与機構を有する導光板と、
　導光板の一方の主面側に配置された、偏光解消度Ｄｍが３０％以下の反射板と、
　導光板の一方の主面と対向する他方の主面側に配置された、第１の直線偏光を透過して、第１の直線偏光と直交する第２の直線偏光を反射する反射型直線偏光分離板と、
　反射型直線偏光分離板と反射板との間に配置されたλ／４板とを有することを特徴とする。 The second backlight unit of the present invention includes a light source,
The light emitted from the light source is incident from the end face, propagates the light incident from the end face, and exits from one main surface. The degree of depolarization Dg is 40% or less, and the propagating light is transmitted to one main surface. A light guide plate having a directivity imparting mechanism to be directed;
A reflector having a depolarization degree Dm of 30% or less, disposed on one main surface side of the light guide plate;
Reflective linearly polarized light that is disposed on the other principal surface opposite to one principal surface of the light guide plate and transmits the first linearly polarized light and reflects the second linearly polarized light orthogonal to the first linearly polarized light A separating plate,
And a λ / 4 plate disposed between the reflective linearly polarized light separating plate and the reflective plate.
　本発明の第１および第２のバックライトユニットにおいては、λ／４板が、反射型直線偏光分離板と導光板との間、もしくは導光板と反射板との間に配置されていることが好ましい。 In the first and second backlight units of the present invention, the λ / 4 plate may be disposed between the reflective linearly polarized light separating plate and the light guide plate, or between the light guide plate and the reflective plate. preferable.
　このような本発明のバックライトユニットにおいて、反射型直線偏光分離板およびλ／４板を除く光学部材の合計の偏光解消度Ｄａが５０％以下であることが好ましい。 In such a backlight unit of the present invention, it is preferable that the total depolarization degree Da of the optical members excluding the reflective linearly polarized light separating plate and the λ / 4 plate is 50% or less.
　本発明のバックライトユニットにおいては、反射板が鏡面反射板であることが好ましい。特に、鏡面反射板の鏡面が金属の蒸着面からなることが好ましい。 In the backlight unit of the present invention, the reflecting plate is preferably a specular reflecting plate. In particular, it is preferable that the mirror surface of the mirror reflector is a metal deposition surface.
　本発明のバックライトユニットにおいては、λ／４板が、反射型直線偏光分離板と導光板との間、もしくは導光板と反射板との間に配置されている場合、導光板の位相差が１００ｎｍ以下であることが好ましい。 In the backlight unit of the present invention, when the λ / 4 plate is disposed between the reflective linearly polarized light separating plate and the light guide plate, or between the light guide plate and the reflective plate, the phase difference of the light guide plate is It is preferable that it is 100 nm or less.
　本発明のバックライトユニットにおいては、λ／４板が導光板を兼ねることも好ましい。 In the backlight unit of the present invention, it is preferable that the λ / 4 plate also serves as the light guide plate.
　本発明のバックライトユニットにおいては、導光板の指向性付与機構が、上記他方の主面に形成された複数の凹部および複数の凸部の少なくとも一方であることが好ましい。 In the backlight unit of the present invention, the directivity imparting mechanism of the light guide plate is preferably at least one of a plurality of concave portions and a plurality of convex portions formed on the other main surface.
　本発明のバックライトユニットにおいては、上記他方の主面における、反射板、導光板および反射型直線偏光分離板の並び方向に垂直な平坦面の面積率が３０～９８％であることが好ましい。 In the backlight unit of the present invention, the area ratio of the flat surface perpendicular to the arrangement direction of the reflecting plate, the light guide plate and the reflective linearly polarized light separating plate on the other main surface is preferably 30 to 98%.
　本発明のバックライトユニットにおいては、導光板の指向性付与機構は、一方の主面から他方の主面を貫く複数の貫通孔からなり、貫通孔は、反射板、導光板および反射型直線偏光分離板の並び方向に対して傾きを有するものであってもよい。 In the backlight unit of the present invention, the directivity imparting mechanism of the light guide plate is composed of a plurality of through holes penetrating from one main surface to the other main surface, and the through holes include the reflector, the light guide plate, and the reflective linearly polarized light. It may have an inclination with respect to the arrangement direction of the separation plates.
　本発明のバックライトユニットにおいては、導光板は厚み２００μｍ以下のフィルム状のものであってもよい。 In the backlight unit of the present invention, the light guide plate may be a film having a thickness of 200 μm or less.
　本発明のバックライトユニットにおいては、導光板と反射型直線偏光分離板との間に拡散板を備えていてもよい。 In the backlight unit of the present invention, a diffusion plate may be provided between the light guide plate and the reflective linearly polarized light separating plate.
　本発明のバックライトユニットにおいては、導光板の一方の主面と反射型直線偏光分離板との間に波長変換層を備えていてもよい。 In the backlight unit of the present invention, a wavelength conversion layer may be provided between one main surface of the light guide plate and the reflective linearly polarized light separating plate.
　本発明のバックライトユニットによれば、光の利用効率を向上して、高輝度な光を出射することができる。 According to the backlight unit of the present invention, it is possible to improve the light utilization efficiency and emit high-luminance light.
本発明の第１の実施形態のバックライトユニットの全体構成を示す模式図である。It is a schematic diagram which shows the whole structure of the backlight unit of the 1st Embodiment of this invention. 図１の部分拡大図である。It is the elements on larger scale of FIG. 導光板の別の例を示す導光板部分拡大図である。It is a light-guide plate partial enlarged view which shows another example of a light-guide plate. 導光板の別の例を示す導光板部分拡大図である。It is a light-guide plate partial enlarged view which shows another example of a light-guide plate. 導光板の別の例を示す導光板部分拡大図である。It is a light-guide plate partial enlarged view which shows another example of a light-guide plate. 導光板の別の例を示す導光板部分拡大図である。It is a light-guide plate partial enlarged view which shows another example of a light-guide plate. 本発明のバックライトユニットの導光板の例を説明するための概念図である。It is a conceptual diagram for demonstrating the example of the light-guide plate of the backlight unit of this invention. 偏光解消率の測定方法を説明するための概念図である。It is a conceptual diagram for demonstrating the measuring method of a depolarization rate. 第１の実施形態のバックライトユニットの設計変更例を概念的に示す図である。It is a figure which shows notionally the example of a design change of the backlight unit of 1st Embodiment. 本発明の第２の実施形態のバックライトユニットの全体構成を示す模式図である。It is a schematic diagram which shows the whole structure of the backlight unit of the 2nd Embodiment of this invention. 本発明の第３の実施形態のバックライトユニットの全体構成を示す模式図である。It is a schematic diagram which shows the whole structure of the backlight unit of the 3rd Embodiment of this invention. 図８の導光板の断面および他方の面を示す図である。It is a figure which shows the cross section and other surface of the light-guide plate of FIG. 本発明の第４の実施形態のバックライトユニットの全体構成を示す模式図である。It is a schematic diagram which shows the whole structure of the backlight unit of the 4th Embodiment of this invention. 実施例２１に用いた導光フィルム１の一部を示す斜視図である。10 is a perspective view showing a part of the light guide film 1 used in Example 21. FIG. 実施例２２に用いた導光フィルム２の一部を示す平面図である。12 is a plan view showing a part of the light guide film 2 used in Example 22. FIG.
　以下、図面を参照して、本発明のバックライトユニットの実施形態を詳細に説明する。 Hereinafter, embodiments of the backlight unit of the present invention will be described in detail with reference to the drawings.
　なお、本明細書において「～」を用いて表される数値範囲は、「～」の前後に記載される数値を下限値および上限値として含む範囲を意味する。
　本明細書において、「（メタ）アクリレート」は、「アクリレートおよびメタクリレートのいずれか一方または双方」の意味で使用される。
　本明細書において、「同一」は、技術分野で一般的に許容される誤差範囲を含むものとする。また、本明細書において、「全部」、「いずれも」または「全面」などというとき、１００％である場合のほか、技術分野で一般的に許容される誤差範囲を含み、例えば９９％以上、９５％以上、または９０％以上である場合を含むものとする。
　可視光は、電磁波のうち、ヒトの目で見える波長の光であり、３８０ｎｍ～７８０ｎｍの波長域の光を示す。また、これに限定されるものではないが、可視光のうち、４２０ｎｍ～４９５ｎｍの波長域の光は、青色光（Ｂ光）であり、４９５ｎｍ超～５７０ｎｍの波長域の光は、緑色光（Ｇ光）であり、６２０ｎｍ～７５０ｎｍの波長域の光は、赤色光（Ｒ光）である。 In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
In this specification, “(meth) acrylate” is used to mean “one or both of acrylate and methacrylate”.
In this specification, “same” includes an error range generally allowed in the technical field. In addition, in the present specification, when “all”, “any” or “entire surface” is used, it includes an error range generally allowed in the technical field in addition to the case of 100%, for example, 99% or more, The case of 95% or more, or 90% or more is included.
Visible light is light having a wavelength visible to the human eye among electromagnetic waves, and indicates light having a wavelength range of 380 nm to 780 nm. Although not limited to this, among visible light, light in the wavelength region of 420 nm to 495 nm is blue light (B light), and light in the wavelength region of more than 495 nm to 570 nm is green light ( G light) and light in the wavelength range of 620 nm to 750 nm is red light (R light).
　本発明のバックライトユニットは、主にＬＣＤ（液晶表示装置）に用いられるもので、ＬＣＤにおいて、画像を表示するための光（バックライト）を、液晶セル（液晶による画素）を配列してなる液晶パネルに出射するためのものである。また、本発明のバックライトユニットは、いわゆるエッジライト型（サイドライト型、あるいは導光板方式ともいう。）のバックライトユニットである。 The backlight unit of the present invention is mainly used in an LCD (Liquid Crystal Display), and in the LCD, light (backlight) for displaying an image is arranged in a liquid crystal cell (pixel by liquid crystal). It is for emitting to the liquid crystal panel. The backlight unit of the present invention is a so-called edge light type (also referred to as a side light type or a light guide plate type) backlight unit.
　図１は、本発明の第１の実施形態のバックライトユニットの全体構成を模式的に示す図である。本実施形態は本発明の第１のバックライトユニットの態様である。
　図１に示す本実施形態のバックライトユニット１０は、光源１２と、光源１２が出射する光Ｌを端面１４ｂから入射され、端面１４ｂから入射された光Ｌを伝搬して一方の主面１４ａから出射する導光板１４と、その主面１４ａと対向する他方の主面１４ｃ側に配置された反射板１６と、導光板１４の主面１４ａ側に配置された、第１の直線偏光Ｌ１を透過して、第１の直線偏光Ｌ１と直交する第２の直線偏光Ｌ２を反射する反射型直線偏光分離板２４と、反射型直線偏光分離板２４と導光板１４との間に配置されたλ／４板２０とを有する。
　本発明のバックライトユニットにおいては、導光板は、偏光解消度Ｄｇが４０％以下であり、かつ、伝搬する光を主面に向ける指向性付与機構を有する。また、反射板は、偏光解消度Ｄｍが３０％以下である。
　図１中に破線で示す符号２６は、ＬＣＤに通常設けられる、液晶パネルに入射する光を所定の直線偏光にするためのバックライト側偏光板２６である。
　以下の説明では、導光板１４の出射面１４ａと逆側の他方の主面１４ｃを、『裏面１４ｃ』とも言う。ここでいう出射面１４ａは、指向性付与機構による指向性が付与された光を出射する面である。本実施形態においては、導光板１４の出射面１４ａが反射型直線偏光分離板２４側、裏面１４ｃが反射板１６側となるように各光学部材が配置されている。 FIG. 1 is a diagram schematically showing an overall configuration of a backlight unit according to the first embodiment of the present invention. This embodiment is an aspect of the first backlight unit of the present invention.
The backlight unit 10 of the present embodiment shown in FIG. 1 has a light source 12 and light L emitted from the light source 12 incident from the end surface 14b, propagates the light L incident from the end surface 14b, and is transmitted from one main surface 14a. a light guide plate 14 for emitting, a reflector 16 disposed on the other main surface 14c side opposite to the main surface thereof 14a, disposed on the main surface 14a side of the light guide plate 14, a first linearly polarized light L 1 A reflective linearly polarized light separating plate 24 that transmits and reflects the second linearly polarized light L 2 orthogonal to the first linearly polarized light L 1, and is disposed between the reflective linearly polarized light separating plate 24 and the light guide plate 14. And a λ / 4 plate 20.
In the backlight unit of the present invention, the light guide plate has a degree of depolarization Dg of 40% or less and a directivity imparting mechanism that directs propagating light to the main surface. Further, the reflection plate has a depolarization degree Dm of 30% or less.
Reference numeral 26 indicated by a broken line in FIG. 1 is a backlight-side polarizing plate 26 that is usually provided in the LCD and converts light incident on the liquid crystal panel into predetermined linearly polarized light.
In the following description, the other main surface 14c opposite to the exit surface 14a of the light guide plate 14 is also referred to as a “back surface 14c”. Here, the emission surface 14a is a surface that emits light to which directivity is imparted by the directivity imparting mechanism. In the present embodiment, the optical members are arranged such that the exit surface 14a of the light guide plate 14 is on the reflective linearly polarized light separating plate 24 side, and the back surface 14c is on the reflective plate 16 side.
　本バックライトユニット１０は所定方向の直線偏光を透過してその第１の方向と直交する（第２の方向）の直線偏光を反射する反射型直線偏光分離板２４を用い、さらに、偏光解消度Ｄｇが４０％以下であり、かつ、伝搬する光を出射面１４ａに向ける機構を有する導光板１４、および、偏光解消度Ｄｍが３０％以下である反射板１６を用いることによって、高輝度な光をバックライト側偏光板２６（液晶パネル）に入射することを可能にしている。
　この点に関しては、後に詳述する。 The backlight unit 10 uses a reflective linearly polarized light separating plate 24 that transmits linearly polarized light in a predetermined direction and reflects linearly polarized light orthogonal to the first direction (second direction), and further, the degree of depolarization. By using the light guide plate 14 having a mechanism for directing propagating light to the exit surface 14a and the reflecting plate 16 having a depolarization degree Dm of 30% or less, Dg is 40% or less and high-intensity light Is allowed to enter the backlight side polarizing plate 26 (liquid crystal panel).
This will be described in detail later.
　光源１２は、ＬＣＤを表示するための光Ｌを射出して、導光板１４への光入射面である端面１４ｂに入射するものである。
　バックライトユニット１０において、光源１２としては、ＬＥＤ(Light Emitting Diode)等の点光源を導光板１４の端面１４ｂに沿ってライン状に配列した光源や蛍光灯など、エッジライト型のバックライトユニットで用いられている公知の光源が、各種、利用可能である。 The light source 12 emits light L for displaying the LCD, and enters the end surface 14 b that is a light incident surface to the light guide plate 14.
In the backlight unit 10, the light source 12 is an edge light type backlight unit such as a light source or a fluorescent lamp in which point light sources such as LEDs (Light Emitting Diodes) are arranged in a line along the end surface 14 b of the light guide plate 14. Various known light sources used can be used.
　導光板１４は、板状（シート状）の部材であり、既述の通り、光源１２から入射された光Ｌを面方向に伝搬して、一方の主面（最大面）である出射面１４ａから出射するものである。導光板１４は、指向性付与機構を有することにより、バックライトユニット１０が出射する光の指向性を向上して、バックライトユニット１０の正面輝度を向上できる。ここでは、バックライトユニットからバックライト側偏光板に入射する光の輝度を、『正面輝度』とも言う。また、バックライトユニットが出射する光の正面輝度を、『バックライトユニットの正面輝度』とも言う。 The light guide plate 14 is a plate-shaped (sheet-shaped) member, and as described above, the light L incident from the light source 12 propagates in the surface direction, and the light exit surface 14a which is one main surface (maximum surface). It is emitted from. Since the light guide plate 14 has a directivity imparting mechanism, the directivity of light emitted from the backlight unit 10 can be improved, and the front luminance of the backlight unit 10 can be improved. Here, the luminance of light incident on the backlight side polarizing plate from the backlight unit is also referred to as “front luminance”. Further, the front luminance of the light emitted from the backlight unit is also referred to as “front luminance of the backlight unit”.
　本実施形態の導光板１４は、指向性付与機構として、出射面１４ａと対向する他方の主面１４ｃに形成された凹部１５ｃを有する。凹部１５ｃは、裏面１４ｃの平坦面と直交する面１５ａと、その直交する面１５ａと角度θで交差する傾斜面１５ｂとから構成される、光伝搬方向の断面が、頂角θを有する直角三角形状である。傾斜面１５ｂは、出射面１４ａに近づくにつれ、光源１２から離間する方向に向かうように形成されている。端面１４ｂから入射した光は導光板１４内を導波して傾斜面１５ｂに臨界角以上で入射して全反射されることにより、出射面１４ａに向かう指向性が付与される。 The light guide plate 14 of the present embodiment has a concave portion 15c formed on the other main surface 14c facing the emission surface 14a as a directivity imparting mechanism. The recess 15c is a right triangle whose cross section in the light propagation direction is formed by a surface 15a orthogonal to the flat surface of the back surface 14c and an inclined surface 15b intersecting the orthogonal surface 15a at an angle θ. Shape. The inclined surface 15b is formed so as to go in a direction away from the light source 12 as it approaches the emission surface 14a. The light incident from the end face 14b is guided in the light guide plate 14, enters the inclined surface 15b at a critical angle or more and is totally reflected, and thereby directivity toward the exit surface 14a is given.
　凹部１５ｃは、島状（ドット状）の物を点在して形成してもよく、あるいは、後述する図４に示すように、長尺な凹部１５ｃを、その長手方向と直交する方向に配列して設けてもよい。
　島状の凹部１５ｃを点在させる場合には、凹部１５ｃは、規則的に配列しても、不規則に配列してもよい。また、長尺な凹部１５ｃは、長手方向に分割されたものでもよい。 The recesses 15c may be formed by interspersing island-like (dot-like) objects, or, as shown in FIG. 4 to be described later, the long recesses 15c are arranged in a direction perpendicular to the longitudinal direction. May be provided.
When the island-shaped concave portions 15c are scattered, the concave portions 15c may be arranged regularly or irregularly. Moreover, the long recessed part 15c may be divided in the longitudinal direction.
　反射型直線偏光分離板２４としては、所定の方向の直線偏光である第１の直線偏光Ｌ１を透過して、第１の直線偏光Ｌ１と直交する第２の直線偏光Ｌ２を反射するものであれば、公知のものを適宜使用することができる。
　同様に、λ／４板２０としては、特に制限なく、公知のλ／４板を用いることができる。なお、λ／４板２０は、支持体と支持体上に形成されたλ／４層とから構成されるのが一般的であるが、支持体上にλ／４層を塗布により形成した後に支持体を取り外したλ／４層のみから構成されていてもよい。また、導光板１４もしくは反射型直線偏光分離板２４に直接塗布により形成されていてもよい。λ／４層（λ／４板）を導光板１４もしくは反射型直線偏光分離板２４に直接塗布することにより、バックライトユニット全体としての厚みを薄型化することができる。
　上記と異なる形態としては、導光板自体の位相差を１００ｎｍより大きく２００ｎｍ未満とすることで、λ／４板と導光板を兼ねることもできる。 The reflective linearly polarized light separating plate 24 transmits the first linearly polarized light L 1 that is linearly polarized light in a predetermined direction and reflects the second linearly polarized light L 2 that is orthogonal to the first linearly polarized light L 1. If it is a thing, a well-known thing can be used suitably.
Similarly, the λ / 4 plate 20 is not particularly limited, and a known λ / 4 plate can be used. The λ / 4 plate 20 is generally composed of a support and a λ / 4 layer formed on the support, but after the λ / 4 layer is formed on the support by coating. You may be comprised only from (lambda) / 4 layer which removed the support body. Alternatively, the light guide plate 14 or the reflective linearly polarized light separating plate 24 may be directly applied. By directly applying the λ / 4 layer (λ / 4 plate) to the light guide plate 14 or the reflective linearly polarized light separating plate 24, the thickness of the entire backlight unit can be reduced.
As a form different from the above, by setting the phase difference of the light guide plate itself to be greater than 100 nm and less than 200 nm, the λ / 4 plate and the light guide plate can also be used.
　光源１２から出射した光Ｌは、導光板１４の端面１４ｂから導光板１４内に入射する。この入射光は導光板１４内で全反射を繰り返して導波されつつ、凹部１５ｃの斜面で進行方向が転換されて導光板１４の出射面１４ａから出射される。 The light L emitted from the light source 12 enters the light guide plate 14 from the end face 14 b of the light guide plate 14. The incident light is guided by repeating total reflection in the light guide plate 14, and the traveling direction is changed by the inclined surface of the recess 15 c and is emitted from the exit surface 14 a of the light guide plate 14.
　図２に導光板１４の出射面１４ａから出射した後の光の主な経路を模式的に示している。図２に示すように、導光板１４の出射面１４ａから出射した光Ｌは、λ／４板２０を介して反射型直線偏光分離板２４に入射する。光Ｌのうち第１の直線偏光Ｌ１のみが反射型直線偏光分離板２４を透過して、バックライト側偏光板２６に入射し、第２の直線偏光Ｌ２は反射型直線偏光分離板２４により反射される。反射型直線偏光分離板２４により反射された第２の直線偏光Ｌ２は、λ／４板２０を通過することにより円偏光（例えば、ここでは左円偏光）Ｌlとなる。この左円偏光Ｌｌは、出射面１４ａから導光板１４に再入射し、導光板１４を透過して反射板１６により反射される。円偏光は反射板で反射される際に偏光方向が反転するため、この左円偏光Ｌｌは、右円偏光Ｌｒとなる。この右円偏光Ｌｒは、導光板１４に再々入射し、導光板１４を透過して再度λ／４板２０に入射することにより第１の直線偏光Ｌ１となり、反射型直線偏光分離板２４を透過してバックライト側偏光板２６に入射、透過して、バックライト側偏光板２６の上に配置される液晶パネルに入射する。 FIG. 2 schematically shows main paths of light after exiting from the exit surface 14 a of the light guide plate 14. As shown in FIG. 2, the light L emitted from the emission surface 14 a of the light guide plate 14 enters the reflective linearly polarized light separating plate 24 via the λ / 4 plate 20. Of the light L, only the first linearly polarized light L 1 passes through the reflective linearly polarized light separating plate 24 and enters the backlight side polarizing plate 26, and the second linearly polarized light L 2 is reflected by the reflective linearly polarized light separating plate 24. It is reflected by. The second linearly polarized light L 2 reflected by the reflective linearly polarized light separating plate 24 passes through the λ / 4 plate 20 and becomes circularly polarized light (for example, left circularly polarized light here) L1. The left circularly polarized light L1 reenters the light guide plate 14 from the emission surface 14a, passes through the light guide plate 14, and is reflected by the reflection plate 16. Since the polarization direction is reversed when the circularly polarized light is reflected by the reflector, the left circularly polarized light Ll becomes the right circularly polarized light Lr. The right circularly polarized light Lr reenters the light guide plate 14, passes through the light guide plate 14, and enters the λ / 4 plate 20 again to become the first linearly polarized light L 1 . The light passes through and enters the backlight-side polarizing plate 26, passes through, and enters the liquid crystal panel disposed on the backlight-side polarizing plate 26.
　従って、反射型直線偏光分離板とλ／４板とを用いることにより、理論的には全ての直線偏光をバックライト側偏光板２６に入射する光として利用することができ、理論的には、バックライトユニットが出射する光の正面輝度を、２倍に向上できる。そのため、光を出射面に向ける機構を有する導光板１４と、λ／４板２０および反射型直線偏光分離板２４とを用いることにより、正面輝度が高いバックライトユニットが期待できる。 Therefore, by using the reflective linearly polarized light separating plate and the λ / 4 plate, theoretically, all the linearly polarized light can be used as light incident on the backlight side polarizing plate 26. Theoretically, The front luminance of the light emitted from the backlight unit can be improved by a factor of two. Therefore, a backlight unit with high front luminance can be expected by using the light guide plate 14 having a mechanism for directing light toward the exit surface, the λ / 4 plate 20 and the reflective linearly polarized light separating plate 24.
　なお、各部材同士あるいは空気との界面においては、実際には反射光も存在する。また、各部材を透過する際には、全ての偏光がそのまま維持されているわけではなく、一部偏光解消も生じる。これらの反射光や偏光解消した光は、元の光Ｌと同様の光経路を繰り返し、複数回の反射を経て最終的に第１の直線偏光Ｌ１としてバックライト側偏光板２６に入射、透過して、バックライト側偏光板２６の上に配置される液晶パネルに入射する。 In fact, reflected light also exists at the interface between the members or the air. Further, when passing through each member, not all polarized light is maintained as it is, and partial depolarization also occurs. These light eliminating reflected light or polarized light can repeat the same optical path as the original light L, incident on the backlight side polarizing plate 26 finally as the first linearly polarized light L 1 through the multiple reflections, transparent Then, the light enters the liquid crystal panel arranged on the backlight side polarizing plate 26.
　ここで、導光板１４と反射板１６の偏光解消度が小さければ、小さいほど、反射型直線偏光分離板で反射された直線偏光を直交する直線偏光に変換して再度反射型直線偏光分離板に入射させることができ、輝度向上の効果が高い。 Here, the smaller the degree of depolarization of the light guide plate 14 and the reflection plate 16, the more the linearly polarized light reflected by the reflective linearly polarized light separating plate is converted into orthogonal linearly polarized light, and again converted into a reflective linearly polarized light separating plate. It can be made incident, and the effect of improving luminance is high.
　偏光は、反射板によって反射されることによって偏光が崩れる場合が有る。また、導光板で伝搬される際にも、光を出射面に向ける機構等に起因して、偏光が崩れる場合が有る。
　ここで、偏光解消度が大きい反射板や導光板を用いた場合、反射型直線偏光分離板によって反射され、λ／４板透過して円偏光となった左円偏光Ｌｌは、導光板を透過して多くの成分の円偏光が解消され、また、反射板による反射で、多くの成分の円偏光が解消される。そのため、この左円偏光Ｌｌは、多くの成分の円偏光が解消され、無偏光として反射型直線偏光分離板に到達する。
　このように、無偏光が増えた状態で、反射型直線偏光分離板に到達した光は、再び偏光分離され、その半分量に相当する直線偏光Ｌ２が透過できずに再び反射してしまう。これを繰り返すことによって、反射された光は、徐々に吸収されたり、迷光となったりする。その結果、λ／４板および反射型直線偏光分離板を用いることによる輝度向上率は、実質１.３倍程度にしかならない。 The polarized light may be broken by being reflected by the reflecting plate. Also, when propagating through the light guide plate, the polarization may be lost due to a mechanism or the like that directs light to the exit surface.
Here, when a reflection plate or a light guide plate having a large degree of depolarization is used, the left circularly polarized light Ll that is reflected by the reflective linear polarization separation plate and passes through the λ / 4 plate to become circularly polarized light is transmitted through the light guide plate. Therefore, many components of circularly polarized light are eliminated, and many components of circularly polarized light are eliminated by reflection by the reflector. For this reason, the left circularly polarized light L1 is free from many components of circularly polarized light and reaches the reflective linearly polarized light separating plate as non-polarized light.
Thus, in a state where non-polarized light increases with the light reaching the reflective linearly polarized separated plate is again polarization splitting, resulting in reflected again unable linearly polarized light L 2 is transmitted corresponding to half the amount. By repeating this, the reflected light is gradually absorbed or becomes stray light. As a result, the luminance improvement rate by using the λ / 4 plate and the reflective linearly polarized light separating plate is only about 1.3 times.
　これに対し、本発明のバックライトユニットは、偏光解消度Ｄｇが４０％以下の導光板１４と、偏光解消度Ｄｍが３０％以下の反射板１６を用いるので、反射型直線偏光分離板２４により反射された直線偏光あるいは、その直線偏光がλ／４板を経た円偏光として、導光板を透過し、反射板で反射した際に偏光が解消されるのを抑制することができるため、より多くの光を反射した直線偏光と直交する反射型直線偏光分離板を透過する直線偏光として反射型直線偏光分離板に再帰させることができ、輝度向上を図ることができる。
　そのため、本発明のバックライトユニット１０によれば、光を出射面に向ける機構を有する導光板と、反射型直線偏光分離板およびλ／４板とを用いることの利点を十分に発現して、正面輝度が高い光を、バックライト側偏光板２６（液晶パネル）に入射できる。 On the other hand, the backlight unit of the present invention uses the light guide plate 14 having a depolarization degree Dg of 40% or less and the reflection plate 16 having a depolarization degree Dm of 30% or less. Since the reflected linearly polarized light or the circularly polarized light that has passed through the λ / 4 plate is transmitted through the light guide plate and reflected by the reflecting plate, it is possible to prevent the polarization from being eliminated. As a linearly polarized light that passes through a reflective linearly polarized light separating plate that is orthogonal to the linearly polarized light that has been reflected, the reflected linearly polarized light separating plate can be returned to the reflective linearly polarized light separating plate.
Therefore, according to the backlight unit 10 of the present invention, the advantages of using the light guide plate having a mechanism for directing light to the exit surface, the reflective linearly polarized light separating plate and the λ / 4 plate are sufficiently expressed, Light having high front luminance can be incident on the backlight side polarizing plate 26 (liquid crystal panel).
　導光板１４の偏光解消度Ｄｇが４０％以下であるとは、導光板１４の出射面１４ａから入射して、導光板１４の出射面１４ａから出射した円偏光のうち、導光板１４に起因して円偏光が解消される光の量が４０％以下であることを示す。すなわち、導光板１４の出射面１４ａから入射して、導光板１４の出射面１４ａから出射した円偏光は、導光板１４の内部で６０％超が円偏光を維持する。
　導光板１４の偏光解消度Ｄｇおよび偏光解消度Ｄｇの測定方法は、後に詳述する。 The depolarization degree Dg of the light guide plate 14 being 40% or less is caused by the light guide plate 14 out of the circularly polarized light incident from the output surface 14a of the light guide plate 14 and output from the output surface 14a of the light guide plate 14. This indicates that the amount of light from which circularly polarized light is eliminated is 40% or less. That is, more than 60% of the circularly polarized light that is incident from the light exit surface 14 a of the light guide plate 14 and is emitted from the light exit surface 14 a of the light guide plate 14 maintains the circularly polarized light inside the light guide plate 14.
A method for measuring the degree of depolarization Dg and the degree of depolarization Dg of the light guide plate 14 will be described in detail later.
　既述のとおり、導光板１４の偏光解消度Ｄｇが低い程、バックライトユニット１０が出射する光の正面輝度を向上できる。この点を考慮すると、導光板１４の偏光解消度Ｄｇが３０％以下であるのが好ましい。 As described above, the lower the degree of depolarization Dg of the light guide plate 14, the higher the front luminance of the light emitted from the backlight unit 10. Considering this point, it is preferable that the degree of depolarization Dg of the light guide plate 14 is 30% or less.
　本発明のバックライトユニット１０においては、導光板１４に設けられる光を出射面１４ａに向ける指向性付与機構の占有面積、および、導光板１４の位相差が重要である。
　すなわち、指向性付与機構の占有面積率、および／または、導光板１４の位相差を、適正に設定することにより、偏光解消度Ｄｇが４０％以下の導光板１４を得ることができる。 In the backlight unit 10 of the present invention, the area occupied by the directivity imparting mechanism that directs the light provided on the light guide plate 14 toward the emission surface 14a and the phase difference of the light guide plate 14 are important.
That is, the light guide plate 14 having a depolarization degree Dg of 40% or less can be obtained by appropriately setting the occupation area ratio of the directivity imparting mechanism and / or the phase difference of the light guide plate 14.
　指向性付与機構の占有面積率とは、導光板１４の指向性付与機構が設けられている主面１４ｃの全面積に対する指向性付与機構が占める面積の割合である。言い換えると、指向性付与機構の占有面積とは、導光板１４を出射面１４ａに垂直な方向から見た際に、導光板１４の出射面１４ａの全面積に対する指向性付与機構が占める面積率である。 The occupation area ratio of the directivity imparting mechanism is the ratio of the area occupied by the directivity imparting mechanism to the entire area of the main surface 14c where the directivity imparting mechanism of the light guide plate 14 is provided. In other words, the area occupied by the directivity imparting mechanism is an area ratio occupied by the directivity imparting mechanism with respect to the entire area of the exit surface 14a of the light guide plate 14 when the light guide plate 14 is viewed from a direction perpendicular to the exit surface 14a. is there.
　図４に導光板１４の側面図Ａおよび底面図Ｂを模式的に示す。図４に示すように、光伝搬方向の断面形状が裏面１４ｃ側に垂直な面と傾斜面を有する直角三角形である、幅ａの長尺な凹部１５ｃを、幅ａと同じ間隔ｂでその長手方向に直交する方向に配列して、凹部１５ｃと凹部１５ｃの非形成部とが同数になるように形成した導光板１４であれば、凹部１５ｃが形成されている出射面１４ａにおける凹部１５ｃの占有面積は５０％となる。このとき、凹部１５ｃが形成されていない非形成部である平坦面の占有面積は５０％となる。 FIG. 4 schematically shows a side view A and a bottom view B of the light guide plate 14. As shown in FIG. 4, a long concave portion 15c having a width a, whose cross-sectional shape in the light propagation direction is a right-angled triangle having a surface perpendicular to the back surface 14c side and an inclined surface, is elongated at the same interval b as the width a. If the light guide plate 14 is arranged in the direction orthogonal to the direction and formed so that the number of the concave portions 15c and the non-formed portions of the concave portions 15c are the same, the occupation of the concave portion 15c on the emission surface 14a where the concave portions 15c are formed The area is 50%. At this time, the area occupied by the flat surface, which is a non-formed portion where the concave portion 15c is not formed, is 50%.
　凹部１５ｃすなわち指向性付与機構は、多いほど、導光板１４内を伝搬する光を出射面に向ける効率が高くなる。従って、凹部１５ｃの占有面積が大きいほど、バックライトユニット１０が出射する光の指向性を高くして、正面輝度を高くできる。
　この点を考慮すると、凹部１５ｃの占有面積は２％以上が好ましく、５％以上であるのがより好ましい。つまり、平面部の占有面積は９８％以下が好ましく、９５％以下であるのがより好ましい。 The more concave portions 15c, that is, the directivity imparting mechanisms, the higher the efficiency of directing the light propagating in the light guide plate 14 toward the exit surface. Therefore, the larger the area occupied by the recess 15c, the higher the directivity of the light emitted from the backlight unit 10, and the higher the front luminance.
Considering this point, the occupied area of the recess 15c is preferably 2% or more, and more preferably 5% or more. That is, the occupied area of the plane portion is preferably 98% or less, and more preferably 95% or less.
　その反面、凹部１５ｃが多いと、偏光が崩れやすくなる。すなわち、凹部１５ｃが多過ぎると、導光板１４の偏光解消度Ｄｇが高くなってしまう。導光板１４の偏光解消度Ｄｇが高くなると、バックライトユニット１０の正面輝度が低くなる。
　この点を考慮すると、凹部１５ｃの占有面積率は７０％以下が好ましく、５０％以下がより好ましい。
　すなわち、本発明において、指向性付与機構の占有面積率は２～７０％が好ましく、５～７０％がより好ましく、５～５０％がさらに好ましい。さらに、指向性付与機構の占有面積率は１０～５０％が特に好ましい。つまり、平坦面の占有面積は３０～９８％が好ましく、３０～９５％がより好ましく、５０～９５％がさらに好ましく、５０～９０％が特に好ましい。 On the other hand, if there are many concave portions 15c, the polarization is easily broken. That is, if there are too many recesses 15c, the degree of depolarization Dg of the light guide plate 14 will increase. When the degree of depolarization Dg of the light guide plate 14 increases, the front luminance of the backlight unit 10 decreases.
Considering this point, the occupied area ratio of the recess 15c is preferably 70% or less, and more preferably 50% or less.
That is, in the present invention, the occupation area ratio of the directivity imparting mechanism is preferably 2 to 70%, more preferably 5 to 70%, and further preferably 5 to 50%. Further, the area occupied by the directivity imparting mechanism is particularly preferably 10 to 50%. That is, the occupation area of the flat surface is preferably 30 to 98%, more preferably 30 to 95%, further preferably 50 to 95%, and particularly preferably 50 to 90%.
　また、導光板１４の位相差が２００ｎｍより大きいと、導光板１４の偏光解消度Ｄｇが大きくなる。例えば、ポリエチレンテレフタレートのように、位相差が数千～数万の材料で導光板１４を作製すると、導光板に入射した光は偏光が大きく崩れ、導光板１４の偏光解消度Ｄｇが大きくなってしまう。
　そのため、導光板がλ／４板を兼ねない態様においては、導光板１４は、位相差が小さい材料からなることが好ましく、位相差が１００ｎｍ以下であるのが好ましい。具体的には、導光板１４は、Ｒｅ（５５０）およびＲｔｈ（５５０）が、共に、１００ｎｍ以下であるのが好ましく、５０ｎｍ以下であるのがより好ましく、３０ｎｍ以下であるのが特に好ましい。なお、Ｒｅ（λ）、Ｒｔｈ（λ）は、各々、波長λにおける面内のレターデーション、および、厚さ方向のレターデーションを表す。
　一方、導光板がλ／４板を兼ねる態様においては、導光板の位相差は１００ｎｍ以上２００ｎｍ未満であることが好ましい。 If the phase difference of the light guide plate 14 is larger than 200 nm, the degree of depolarization Dg of the light guide plate 14 increases. For example, when the light guide plate 14 is made of a material having a phase difference of several thousand to several tens of thousands such as polyethylene terephthalate, the light incident on the light guide plate is largely depolarized, and the degree of depolarization Dg of the light guide plate 14 is increased. End up.
Therefore, in a mode in which the light guide plate does not serve as a λ / 4 plate, the light guide plate 14 is preferably made of a material having a small phase difference, and the phase difference is preferably 100 nm or less. Specifically, in the light guide plate 14, both Re (550) and Rth (550) are preferably 100 nm or less, more preferably 50 nm or less, and particularly preferably 30 nm or less. Re (λ) and Rth (λ) represent in-plane retardation at wavelength λ and retardation in the thickness direction, respectively.
On the other hand, in a mode in which the light guide plate also serves as the λ / 4 plate, the phase difference of the light guide plate is preferably 100 nm or more and less than 200 nm.
　Ｒｅ（λ）はＫＯＢＲＡ　２１ＡＤＨ、またはＷＲ（王子計測機器社製）において、波長λｎｍの光を導光板１４の法線方向に入射させて測定される。測定波長λｎｍの選択にあたっては、波長選択フィルターをマニュアルで交換するか、または測定値をプログラム等で変換して測定することができる。導光板１４が、１軸または２軸の屈折率楕円体で表されるものである場合には、以下の方法によりＲｔｈ（λ）が算出される。
　Ｒｔｈ（λ）は、先のＲｅ（λ）を、面内の遅相軸（ＫＯＢＲＡ　２１ＡＤＨ、またはＷＲにより判断される）を傾斜軸（回転軸）として（遅相軸がない場合には、フィルム面内の任意の方向を回転軸とする）の導光板１４の法線方向に対して法線方向から片側５０度まで１０度ステップで各々その傾斜した方向から波長λｎｍの光を入射させて全部で６点測定し、その測定されたレターデーション値と平均屈折率の仮定値および入力された膜厚値を基にＫＯＢＲＡ　２１ＡＤＨまたはＷＲが算出する。
　この方法において、法線方向から面内の遅相軸を回転軸として、ある傾斜角度にレターデーションの値がゼロとなる方向を持つ場合には、その傾斜角度より大きい傾斜角度でのレターデーション値はその符号を負に変更した後、ＫＯＢＲＡ　２１ＡＤＨ、またはＷＲが算出する。なお、遅相軸を傾斜軸（回転軸）として（遅相軸がない場合には、フィルム面内の任意の方向を回転軸とする）、任意の傾斜した２方向からレターデーション値を測定し、その値と平均屈折率の仮定値、および入力された膜厚値を基に、以下の式（Ａ）、および式（Ｂ）よりＲｔｈを算出することもできる。 Re (λ) is measured by making light of wavelength λnm incident in the normal direction of the light guide plate 14 in KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments). In selecting the measurement wavelength λnm, the wavelength selection filter can be exchanged manually, or the measurement value can be converted by a program or the like. When the light guide plate 14 is represented by a uniaxial or biaxial refractive index ellipsoid, Rth (λ) is calculated by the following method.
Rth (λ) is Re (λ) with the in-plane slow axis (determined by KOBRA 21ADH or WR) as the tilt axis (rotary axis) (if there is no slow axis, film The light of wavelength λ nm is incident from the inclined direction in steps of 10 degrees from the normal direction to 50 degrees on one side with respect to the normal direction of the light guide plate 14 (with an arbitrary direction in the plane as the rotation axis). Then, KOBRA 21ADH or WR is calculated based on the measured retardation value, the assumed average refractive index, and the input film thickness value.
In this method, when the in-plane slow axis is the axis of rotation from the normal direction and the retardation value is zero at a certain inclination angle, the retardation value at an inclination angle larger than that inclination angle. After changing its sign to negative, KOBRA 21ADH or WR calculates. The retardation value is measured from two inclined directions with the slow axis as the tilt axis (rotation axis) (if there is no slow axis, the arbitrary direction in the film plane is the rotation axis). Rth can also be calculated from the following formula (A) and formula (B) based on the value, the assumed value of the average refractive index, and the input film thickness value.
Figure JPOXMLDOC01-appb-M000001
 　なお、上記のＲｅ（θ）は法線方向から角度θ傾斜した方向におけるレターデーション値を表す。また、式（Ａ）におけるｎｘは、面内における遅相軸方向の屈折率を表し、ｎｙは、面内においてｎｘに直交する方向の屈折率を表し、ｎｚは、ｎｘおよびｎｙに直交する方向の屈折率を表す。ｄは膜厚である。
Ｒｔｈ＝（（ｎｘ＋ｎｙ）／２－ｎｚ）×ｄ　　　　　　　式（Ｂ）
Figure JPOXMLDOC01-appb-M000001
 Note that Re (θ) represents a retardation value in a direction inclined by an angle θ from the normal direction. In the formula (A), nx represents the refractive index in the slow axis direction in the plane, ny represents the refractive index in the direction orthogonal to nx in the plane, and nz is the direction orthogonal to nx and ny. Represents the refractive index. d is the film thickness.
Rth = ((nx + ny) / 2−nz) × d Formula (B)
　測定される導光板１４が、１軸や２軸の屈折率楕円体で表現できないもの、いわゆる光学軸（ｏｐｔｉｃ　ａｘｉｓ）がない物である場合には、以下の方法により、Ｒｔｈ（λ）は算出される。
　すなわち、Ｒｔｈ（λ）は、Ｒｅ（λ）を、面内の遅相軸（ＫＯＢＲＡ　２１ＡＤＨ、またはＷＲにより判断される）を傾斜軸（回転軸）として、導光板１４の法線方向に対して－５０°から＋５０°まで１０°ステップで各々その傾斜した方向から波長λｎｍの光を入射させて１１点測定し、その測定されたレターデーション値と平均屈折率の仮定値および入力された膜厚値を基にＫＯＢＲＡ　２１ＡＤＨまたはＷＲが算出する。また、この測定において、平均屈折率の仮定値は、ポリマーハンドブック（ＪＯＨＮ　ＷＩＬＥＹ＆ＳＯＮＳ，ＩＮＣ）、各種光学フィルムのカタログの値を使用することができる。平均屈折率の値が既知でないものについては、アッベ屈折計で測定することができる。主な光学フィルムの平均屈折率の値を以下に例示する：セルロースアシレート（１．４８）、シクロオレフィンポリマー（１．５２）、ポリカーボネート（１．５９）、ポリメチルメタクリレート（１．４９）、ポリスチレン（１．５９）である。これら平均屈折率の仮定値と膜厚を入力することで、ＫＯＢＲＡ　２１ＡＤＨまたはＷＲはｎｘ、ｎｙ、ｎｚを算出する。この算出されたｎｘ、ｎｙ、ｎｚよりＮｚ＝（ｎｘ－ｎｚ）／（ｎｘ－ｎｙ）が更に算出される。 When the light guide plate 14 to be measured is a material that cannot be expressed by a uniaxial or biaxial refractive index ellipsoid, that is, a material that does not have a so-called optical axis, Rth (λ) is calculated by the following method. Is done.
That is, Rth (λ) is Re (λ), and the in-plane slow axis (determined by KOBRA 21ADH or WR) is the tilt axis (rotation axis) with respect to the normal direction of the light guide plate 14. Measured at 11 points with light having a wavelength of λ nm incident in 10 ° steps from −50 ° to + 50 °, respectively, and the measured retardation value, assumed average refractive index, and input film thickness KOBRA 21ADH or WR is calculated based on the value. In this measurement, as the assumed value of the average refractive index, values in the polymer handbook (John Wiley & Sons, Inc.) and catalogs of various optical films can be used. If the average refractive index is not known, it can be measured with an Abbe refractometer. The average refractive index values of main optical films are exemplified below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), Polystyrene (1.59). By inputting these assumed values of average refractive index and film thickness, KOBRA 21ADH or WR calculates nx, ny, and nz. Nz = (nx−nz) / (nx−ny) is further calculated from the calculated nx, ny, and nz.
　このように、指向性付与機構が形成された主面における平坦面の占有面積率を２～７０％とし、かつ、導光板がλ／４板の機能を兼ねない場合には導光板１４の位相差を１００ｎｍ以下とすることにより、好適に、偏光解消度Ｄｇが４０％以下の導光板１４を得ることができる。 Thus, when the occupation ratio of the flat surface on the main surface on which the directivity imparting mechanism is formed is 2 to 70% and the light guide plate does not function as a λ / 4 plate, the position of the light guide plate 14 is reduced. By setting the phase difference to 100 nm or less, the light guide plate 14 having a depolarization degree Dg of 40% or less can be suitably obtained.
　導光板１４の形成材料は、導光板がλ／４板の機能を兼ねない場合には、ポリプロピレン、ポリカーボネート、ポリメチル（メタ）アクリレート、ベンジル（メタ）アクリレート、ＭＳ樹脂、シクロオレフィンポリマー、シクロオレフィンコポリマー等の透明性が高い樹脂からなる、公知のエッジライト型のバックライトユニットに用いられるものが、各種、利用可能である。
　なお、前述のように、偏光解消度Ｄｇを小さくするためには導光板１４は位相差が小さい方が好ましい。この点を考慮すると、導光板１４の形成材料は、ポリメチル（メタ）アクリレートやベンジル（メタ）アクリレート等のアクリル系の材料、シクロオレフィンポリマー、シクロオレフィンコポリマー等の位相差が小さい材料で形成するのが好ましい。 When the light guide plate does not function as a λ / 4 plate, the material for forming the light guide plate 14 is polypropylene, polycarbonate, polymethyl (meth) acrylate, benzyl (meth) acrylate, MS resin, cycloolefin polymer, cycloolefin copolymer Various kinds of known edge light type backlight units made of a highly transparent resin such as the above can be used.
As described above, in order to reduce the degree of depolarization Dg, the light guide plate 14 preferably has a small phase difference. In consideration of this point, the light guide plate 14 is formed of a material having a small phase difference such as an acrylic material such as polymethyl (meth) acrylate or benzyl (meth) acrylate, a cycloolefin polymer, or a cycloolefin copolymer. Is preferred.
　一方、導光板がλ／４板を兼ねる場合は、導光板の位相差を１００ｎｍ以上２００ｎｍ未満とすることにより、好適に、偏光解消度Ｄｇが４０％以下の導光板１４を得ることができる。
　導光板がλ／４板を兼ねる場合の導光板の形成材料としては、ポリカーボネート、シクロオレフィンポリマー、シクロオレフィンコポリマー等の透明性が高い樹脂を用いることが好ましい。
　なお、前述のように、偏光解消度Ｄｇを小さくするためには導光板１４は位相差が小さい方が好ましい。この点を考慮すると、導光板１４の形成材料は、ポリメチル（メタ）アクリレートやベンジル（メタ）アクリレート等のアクリル系の材料、シクロオレフィンポリマー、シクロオレフィンコポリマー等の位相差が小さい材料で形成するのが好ましい。 On the other hand, when the light guide plate also serves as a λ / 4 plate, the light guide plate 14 having a depolarization degree Dg of 40% or less can be suitably obtained by setting the phase difference of the light guide plate to 100 nm or more and less than 200 nm.
As a material for forming the light guide plate when the light guide plate also serves as a λ / 4 plate, it is preferable to use a highly transparent resin such as polycarbonate, cycloolefin polymer, and cycloolefin copolymer.
As described above, in order to reduce the degree of depolarization Dg, the light guide plate 14 preferably has a small phase difference. In consideration of this point, the light guide plate 14 is formed of a material having a small phase difference such as an acrylic material such as polymethyl (meth) acrylate or benzyl (meth) acrylate, a cycloolefin polymer, or a cycloolefin copolymer. Is preferred.
　導光板の厚みに特に制限はないが、薄膜化やフレキシビリティ付与の観点から、２００μｍ以下のフィルム状に作製してもよい。２００μｍ以下の厚みの導光板は導光フィルムと称する場合がある。フィルム状である場合、ロールトゥロールによる作製や、それに伴うλ／４層の直塗布が可能になり、製造上有利である。 The thickness of the light guide plate is not particularly limited, but it may be formed in a film shape of 200 μm or less from the viewpoint of thinning and flexibility. A light guide plate having a thickness of 200 μm or less may be referred to as a light guide film. In the case of a film, production by roll-to-roll and direct application of λ / 4 layer associated therewith are possible, which is advantageous in production.
　導光板１４の形成方法も、公知の方法が、各種、利用可能である。
　指向性付与機構が凹部である場合には、導光板１４となるシート状物を切削加工や穿孔加工する方法や、導光板１４となるシート状物を型押し加工（エンボス加工）する方法が例示される。
　他方、光を出射面１４ａに向ける機構が凸部である場合には、導光板１４となるシート状物に凸部となる物をナノインプリントする方法や、導光板１４となるシート状物に凸部となる構造物を転写する方法が例示される。 Various known methods can be used for forming the light guide plate 14.
When the directivity imparting mechanism is a recess, a method of cutting or punching a sheet-like material that becomes the light guide plate 14 and a method of embossing (embossing) the sheet-like material that becomes the light guide plate 14 are exemplified. Is done.
On the other hand, when the mechanism for directing light toward the light exit surface 14a is a convex portion, a method for nanoimprinting the convex portion on the sheet-like material that becomes the light guide plate 14, or the convex portion on the sheet-like material that becomes the light guide plate 14 The method of transferring the structure to become is illustrated.
　なお、導光板１４の入射面である端面１４ｂと対向する端面には、この端面から出射しようとする光Ｌを反射して、導光板１４内に戻すための、反射板を設けるのが好ましい。あるいは、導光板１４の入射面１４ｂを除く全ての端面に、導光板１４の端面から出射しようとする光Ｌを反射して、導光板１４内に戻すための、反射板を設けるのがより好ましい。
　また、この反射板も、反射板１６と同様、偏光解消度Ｄｍが３０％以下であることが好ましい。 In addition, it is preferable to provide a reflecting plate for reflecting the light L to be emitted from this end surface and returning it to the inside of the light guide plate 14 on the end surface facing the end surface 14 b that is the incident surface of the light guide plate 14. Alternatively, it is more preferable to provide a reflecting plate for reflecting the light L to be emitted from the end surface of the light guide plate 14 and returning it to the inside of the light guide plate 14 on all end surfaces except the incident surface 14 b of the light guide plate 14. .
In addition, like the reflector 16, this reflector preferably has a depolarization degree Dm of 30% or less.
　反射板１６は、導光板１４を伝搬されて裏面１４ｃから出射した光や、反射型直線偏光分離板２４によって反射され、出射面１４ａから導光板１４に再入射して透過した左円偏光Ｌｌを（図２参照）、導光板１４に向かって反射するものである。このような反射板１６を有することにより、光の利用効率を向上できる。 The reflecting plate 16 propagates the light transmitted through the light guide plate 14 and emitted from the back surface 14c, or the left circularly polarized light Ll reflected by the reflective linearly polarized light separating plate 24 and re-entered the light guide plate 14 from the emitting surface 14a and transmitted. (Refer FIG. 2), it reflects toward the light-guide plate 14. FIG. By having such a reflecting plate 16, the light utilization efficiency can be improved.
　既述の通り、本発明のバックライトユニットにおいて、反射板１６は、偏光解消度Ｄｍが３０％以下である。具体的には、反射板１６に入射して、反射される偏光の偏光解消度Ｄｍが３０％以下である。従って、反射板１６に入射して反射された偏光は、７０％超が入射時の偏光状態を維持して、導光板１４に再入射する。 As described above, in the backlight unit of the present invention, the reflection plate 16 has a depolarization degree Dm of 30% or less. Specifically, the degree of depolarization Dm of the polarized light incident on and reflected by the reflecting plate 16 is 30% or less. Therefore, more than 70% of the polarized light that is incident and reflected by the reflecting plate 16 maintains the polarization state at the time of incidence, and reenters the light guide plate 14.
　また、導光板１４と同様、反射板１６の偏光解消度Ｄｍが低いほど、バックライトユニット１０の正面輝度を向上できる。したがって、反射板１６の偏光解消度Ｄｍは２５％以下が好ましく、２０％以下がより好ましい。 Further, similarly to the light guide plate 14, the lower the depolarization degree Dm of the reflection plate 16, the better the front luminance of the backlight unit 10. Therefore, the depolarization degree Dm of the reflecting plate 16 is preferably 25% or less, and more preferably 20% or less.
　反射板１６は、偏光解消度Ｄｍが３０％以下のものであれば、公知のものが、各種、利用可能である。
　偏光解消度Ｄｍが３０％以下の反射板としては、例えば、特許第３４１６３０２号、同第３３６３５６５号、同４０９１９７８号、および、同３４８６５６号の各公報に記載されている反射板が、利用可能である。
　中でも、偏光状態を維持したまま光を正反射でき、偏光解消度Ｄｍが３０％以下の反射板１６が得やすい等の点で、鏡面反射板が好ましい。また、異なる材料を積層した多層膜の鏡面反射板よりも、単層膜の鏡面反射板の方が低い偏光解消度を得やすく、中でも、銀、アルミニウム、スズ等の金属を蒸着してなる単層膜の鏡面反射板が好ましい。その中でも、銀を蒸着してなる鏡面反射板が特に好ましい。なお、単層膜には、同じ材料からなる膜を複数層積層した膜も含む。 Various reflectors can be used as the reflector 16 as long as the degree of depolarization Dm is 30% or less.
As the reflection plate having a depolarization degree Dm of 30% or less, for example, the reflection plates described in Japanese Patent Nos. 3416302, 3363565, 4091978, and 348656 can be used. is there.
Among these, a specular reflector is preferable in that light can be regularly reflected while maintaining a polarization state, and a reflector 16 having a depolarization degree Dm of 30% or less can be easily obtained. In addition, a single-layer mirror reflector more easily obtains a lower degree of depolarization than a multilayer reflector made of different materials, and in particular, a single-layer metal such as silver, aluminum, tin, etc. is deposited. A layered specular reflector is preferred. Among these, a specular reflector formed by vapor-depositing silver is particularly preferable. Note that the single-layer film includes a film in which a plurality of films made of the same material are stacked.
　導光板１４および反射板１６の偏光解消度は、以下のように測定する。 The degree of depolarization of the light guide plate 14 and the reflection plate 16 is measured as follows.
　図５に概念的に示すように、導光板１４および反射板１６を、バックライトユニット１０と同様に配置する。なお、図５においては、導光板１４の凹部は図示を省略している。また、導光板１４の上に、全面を覆わないように、直線偏光板４６およびλ／４板４８を配置する。
　この状態で、導光板１４の出射面１４ａの法線に対して５度の角度で、平行光を直線偏光板４６に入射させ、次いで、λ／４板４８を透過させる。さらに、法線に対して平行光と対称の位置で、かつ、反射光が直線偏光板４６およびλ／４板４８を透過しない位置に、λ／４板５０および直線偏光板５２、ならびに色彩輝度計５４を配置し、輝度を測定する。
　この輝度測定を、λ／４板５０および直線偏光板５２を適宜回転させて行い、最小輝度（Ｙｍｉｎ）と最大輝度（Ｙｍａｘ）となる角度を検出する。測定した最小輝度（Ｙｍｉｎ）と最大輝度（Ｙｍａｘ）を用いて、下記式によって偏光解消度を算出する。
　　偏光解消度＝１００×（１－（Ｙｍａｘ－Ｙｍｉｎ）／（Ｙｍａｘ＋Ｙｍｉｎ））
　平行光の入射側は、直線偏光板４６の吸収軸に対してλ／４板４８の遅相軸を±４５度にすることにより、右円偏光または左円偏光を導光板１４（反射板１６）に入射できる。また、出射側（測定側）は、円偏光が維持されていれば、直線偏光板５２の吸収軸に対してλ／４板５０の遅相軸を±４５度にすることにより、最大輝度（Ｙｍａｘ）および最小輝度（Ｙｍｉｎ）を測定することが可能である。
　この偏光解消度は、バックライトユニット１０において、λ／４板および反射型直線偏光分離板を除いた光学部材の合計の偏光解消度である。以下の説明では、この偏光解消度を、全体の偏光解消度Ｄａとも言う。
　なお、本発明においては、この全体の偏光解消度Ｄａが５０％以下であるのが好ましい。これにより、より正面輝度が高いバックライトユニット１０を得ることができる。 As conceptually shown in FIG. 5, the light guide plate 14 and the reflection plate 16 are arranged in the same manner as the backlight unit 10. In addition, in FIG. 5, the recessed part of the light-guide plate 14 is abbreviate | omitting illustration. Further, the linearly polarizing plate 46 and the λ / 4 plate 48 are arranged on the light guide plate 14 so as not to cover the entire surface.
In this state, parallel light is incident on the linearly polarizing plate 46 at an angle of 5 degrees with respect to the normal line of the exit surface 14 a of the light guide plate 14, and then transmitted through the λ / 4 plate 48. Further, the λ / 4 plate 50 and the linearly polarizing plate 52, and the color luminance at a position symmetrical to the parallel light with respect to the normal line and at a position where the reflected light does not pass through the linearly polarizing plate 46 and the λ / 4 plate 48. A total 54 is placed and the luminance is measured.
This luminance measurement is performed by appropriately rotating the λ / 4 plate 50 and the linearly polarizing plate 52, and an angle between the minimum luminance (Y min ) and the maximum luminance (Y max ) is detected. Using the measured minimum luminance (Y min ) and maximum luminance (Y max ), the degree of depolarization is calculated by the following equation.
Depolarization degree = 100 × (1− (Y max −Y min ) / (Y max + Y min ))
On the incident side of the parallel light, the slow axis of the λ / 4 plate 48 is set to ± 45 degrees with respect to the absorption axis of the linear polarizing plate 46 so that the right circularly polarized light or the left circularly polarized light is guided to the light guide plate 14 (reflecting plate 16). ). Further, on the emission side (measurement side), if circularly polarized light is maintained, the slow axis of the λ / 4 plate 50 is set to ± 45 degrees with respect to the absorption axis of the linearly polarizing plate 52, whereby the maximum luminance ( Y max ) and minimum luminance (Y min ) can be measured.
This degree of depolarization is the total degree of depolarization of the optical member in the backlight unit 10 excluding the λ / 4 plate and the reflective linearly polarized light separating plate. In the following description, this degree of depolarization is also referred to as the total degree of depolarization Da.
In the present invention, the total depolarization degree Da is preferably 50% or less. Thereby, the backlight unit 10 with higher front luminance can be obtained.
　次いで、同様の偏光解消度の測定を、導光板１４を取り除いて行う。これにより、反射板１６の偏光解消度Ｄｍが測定できる。 Next, the measurement of the degree of depolarization is performed by removing the light guide plate 14. Thereby, the depolarization degree Dm of the reflecting plate 16 can be measured.
　測定した全体の偏光解消度Ｄａおよび反射板１６の偏光解消度Ｄｍから、下記式によって導光板１４の偏光解消度Ｄｇを算出できる。
　導光板１４の偏光解消度Ｄｇ＝１００×（１－（１００－Ｄａ）／（１００－Ｄｍ）） From the measured total depolarization degree Da and the depolarization degree Dm of the reflecting plate 16, the depolarization degree Dg of the light guide plate 14 can be calculated by the following equation.
Depolarization degree Dg = 100 × (1− (100−Da) / (100−Dm)) of the light guide plate 14
　本発明のバックライトユニットにおいて、導光板の偏光解消度Ｄｇが４０％以下とは、この測定方法で測定される導光板の偏光解消度Ｄｇが４０％以下であることを示す。
　同様に、反射板の偏光解消度Ｄｍが３０％以下とは、この測定方法で測定される反射板の偏光解消度Ｄｍが３０％以下であることを示す。 In the backlight unit of the present invention, the depolarization degree Dg of the light guide plate of 40% or less indicates that the depolarization degree Dg of the light guide plate measured by this measurement method is 40% or less.
Similarly, the depolarization degree Dm of the reflecting plate being 30% or less indicates that the depolarization degree Dm of the reflecting plate measured by this measurement method is 30% or less.
　なお、バックライトユニット１０には、導光板と反射型直線偏光分離板との間に拡散板を備えてもよい。拡散板を設けることにより、バックライトユニット１０が出射する光の導光板１４の面方向の均一性を向上できる。拡散板は、ＬＣＤに用いられる公知のバックライトユニットで用いられているものが、各種、利用可能である。
　拡散板を備える場合には、拡散板も偏光解消度が小さいのが好ましい。具体的には、拡散板の偏光解消度は、λ／４板および反射型直線偏光分離板を除いた光学部材の合計の偏光解消度である、前述のバックライトユニット全体の偏光解消度Ｄａが５０％以下となるような偏光解消度であるのが好ましい。
　なお、拡散板を用いる構成において、全体の偏光解消度Ｄａは、λ／４板２０と導光板１４との間に、導光板１４を全面的に覆うように拡散板を配置した状態で、先と同様にして偏光解消度を計ることで、測定できる。
　また、拡散板単体の偏光解消度は、導光板１４の偏光解消度に準じて測定できる。 Note that the backlight unit 10 may include a diffusion plate between the light guide plate and the reflective linearly polarized light separating plate. By providing the diffusing plate, the uniformity of the surface direction of the light guide plate 14 of the light emitted from the backlight unit 10 can be improved. Various diffuser plates that are used in known backlight units used in LCDs can be used.
When the diffusion plate is provided, it is preferable that the diffusion plate also has a small degree of depolarization. Specifically, the depolarization degree of the diffusion plate is the total depolarization degree of the optical member excluding the λ / 4 plate and the reflective linearly polarized light separating plate, and the depolarization degree Da of the entire backlight unit described above is It is preferable that the degree of depolarization is 50% or less.
In the configuration using the diffusion plate, the entire degree of depolarization Da is obtained when the diffusion plate is disposed so as to cover the entire light guide plate 14 between the λ / 4 plate 20 and the light guide plate 14. It can be measured by measuring the degree of depolarization in the same manner as described above.
Further, the degree of depolarization of the diffusion plate alone can be measured according to the degree of depolarization of the light guide plate 14.
　本発明において、導光板１４の内部を伝搬する光を出射面１４ａに向ける指向性付与機構は、図１および図２に示すような断面が直角三角形状の凹部１５ｃに限定はされず、導光板１４が伝搬する光を出射面１４ａに向けることができる形状や構成が、各種、利用可能である。
　例えば、図３Ａに示す凹部１５ｄのように、導光板１４内に向かって凸の曲面状の斜面を有する形状や、図３Ｂに示す凹部１５ｅのように、導光板１４内に向かって凹の曲面状の斜面を有する形状でもよい。
　あるいは、図３Ｃに示す凹部１５ｆのように、円弧状（弓形）や半円状の断面形状を有するものであってもよい。 In the present invention, the directivity imparting mechanism for directing the light propagating inside the light guide plate 14 toward the emission surface 14a is not limited to the concave portion 15c having a right triangle shape as shown in FIGS. Various shapes and configurations that can direct light propagating through the light exit surface 14a can be used.
For example, a shape having a curved slope that is convex toward the inside of the light guide plate 14 such as a recess 15d shown in FIG. 3A, or a curved surface that is concave toward the inside of the light guide plate 14 like a recess 15e shown in FIG. 3B. The shape which has a shape-like slope may be sufficient.
Alternatively, it may have an arcuate shape (bow shape) or a semicircular cross-sectional shape like a recess 15f shown in FIG. 3C.
　さらに、指向性付与機構は、凹部ではなく、導光板１４の裏面１４ｃに設けた凸部でもよい。
　一例として、図３Ｄに示すような、導光板１４の裏面１４ｃに設けた円弧状の断面を有する凸部１５ｇが例示される。また、このような凸部は、図２等に示すような（略）三角形状の凸部であってもよい。
　指向性付与機構を、導光板１４の裏面１４ｃに設けた凸部１５ｇとする場合には、導光板１４と凸部１５ｇとを一体で形成してもよく、導光板１４の裏面１４ｃに凸部１５ｇを付加した構成でもよい。 Furthermore, the directivity imparting mechanism may be a convex portion provided on the back surface 14c of the light guide plate 14 instead of the concave portion.
As an example, the convex part 15g which has the circular-arc shaped cross section provided in the back surface 14c of the light-guide plate 14 as shown to FIG. 3D is illustrated. Further, such a convex portion may be a (substantially) triangular convex portion as shown in FIG.
When the directivity imparting mechanism is the convex portion 15g provided on the back surface 14c of the light guide plate 14, the light guide plate 14 and the convex portion 15g may be integrally formed, and the convex portion is formed on the back surface 14c of the light guide plate 14. The structure which added 15g may be sufficient.
　以上の構成においても、導光板１４の内部を伝搬する光を出射面１４ａに向ける機構は、島状に点在しても、長尺な物を配列してもよい。
　また、これらの指向性付与機構は、複数種を併用してもよい。 Also in the above configuration, the mechanism for directing the light propagating inside the light guide plate 14 toward the emission surface 14a may be dotted in an island shape, or a long object may be arranged.
These directivity imparting mechanisms may be used in combination.
　光を出射面１４ａに向ける指向性付与機構としての凹部および凸部は、表面粗さが大きいと、導光板１４の偏光解消度Ｄｇが大きくなってしまう。従って、これらの凹部および凸部は、表面が滑らかであるのが好ましい。 If the surface roughness of the concave and convex portions serving as the directivity imparting mechanism for directing light toward the light exit surface 14a is large, the degree of depolarization Dg of the light guide plate 14 increases. Therefore, it is preferable that the surface of these concave and convex portions is smooth.
　また、指向性付与機構は他方の主面１４ｃのみならず、導光板１４の両方の主面１４aおよび１４ｃに形成されていてもよい。また、指向性付与機構は導光板１４の一方の主面１４ａから他方の主面１４ｃに貫通する貫通孔から構成されていてもよい。貫通している場合は、導光板に入射する光の断面積に対する機構１個の面積が大きいため、より効率よく出射面に光を向けることが可能である。 Further, the directivity imparting mechanism may be formed not only on the other main surface 14 c but also on both main surfaces 14 a and 14 c of the light guide plate 14. Further, the directivity imparting mechanism may include a through-hole penetrating from one main surface 14a of the light guide plate 14 to the other main surface 14c. When penetrating, the area of one mechanism with respect to the cross-sectional area of the light incident on the light guide plate is large, so that the light can be directed to the exit surface more efficiently.
　特許文献３に記載のように、従来、導光板から出射する光を視認側へ向けるため、厚み１５０～３００μｍのプリズムシートを用いる方法が一般に採用されていた。しかし本発明では、導光板が指向性付与機構を備えているため、プリズムシートを備える必要なくなり（厚み０μｍ）、バッテリー容量の増加や、ＢＬシステムの薄膜化が可能という利点がある。また、本発明のように反射型直線偏光分離板とλ／４板とを組み合わせて使用する系では、既述の通り、バックライト部材による偏光解消が小さい方が再帰光利用効率増加に有利であるが、プリズムシートは位相差だけでなくその構造によっても偏光解消度が高くなるので、プリズムシートの使用は好ましくない。 As described in Patent Document 3, conventionally, a method using a prism sheet having a thickness of 150 to 300 μm has been generally employed in order to direct light emitted from the light guide plate to the viewing side. However, according to the present invention, since the light guide plate has a directivity imparting mechanism, there is no need to provide a prism sheet (thickness: 0 μm), and there is an advantage that the battery capacity can be increased and the BL system can be made thinner. In addition, in the system using a combination of the reflective linearly polarized light separating plate and the λ / 4 plate as in the present invention, as described above, the smaller the depolarization by the backlight member, the more advantageous for increasing the efficiency of using the recursive light. However, since the degree of depolarization is increased not only by the phase difference but also by the structure of the prism sheet, the use of the prism sheet is not preferable.
＜設計変更例＞
　第１の実施形態の設計変更例のバックライトユニット１１の概略構成を図６に示す。図６おいて、図１に示した第１の実施形態のバックライトユニット１０と同一の要素については同一の符号を付し詳細な説明を省略する。以下において同様とする。
　本バックライトユニット１１は、導光板１４の出射面１４ａ側に反射板１６が配置され、導光板１４の指向性付与機構である凹部１５ｃが形成された他方の主面１４ｃ側にλ／４板２０および反射型直線偏光分離板２４が配置されている。本構成は、本発明の第２のバックライトユニットの態様に想到する。 <Design change example>
FIG. 6 shows a schematic configuration of the backlight unit 11 of the design change example of the first embodiment. In FIG. 6, the same components as those of the backlight unit 10 of the first embodiment shown in FIG. The same shall apply hereinafter.
The backlight unit 11 has a reflecting plate 16 disposed on the light exit surface 14a side of the light guide plate 14, and a λ / 4 plate on the other main surface 14c side where a concave portion 15c serving as a directivity imparting mechanism of the light guide plate 14 is formed. 20 and a reflective linearly polarized light separating plate 24 are arranged. This configuration contemplates the second backlight unit aspect of the present invention.
　本バックライトユニット１１においても、光源１２から出射した光Ｌは、導光板１４の端面１４ｂから導光板１４内に入射する。この入射光は導光板１４内で全反射を繰り返して導波されつつ、凹部１５ｃの斜面で進行方向が転換されて導光板１４の出射面１４ａから出射される。本例においては、導光板１４の出射面１４ａから出射した光Ｌは、反射板１６に入射して、反射されて再度導光板１４に入射し、導光板１４を透過し、λ／４板２０を介して反射型直線偏光分離板２４に入射する。その後の光経路は第１の実施形態のバックライトユニット１０と同様であり、奏する効果も同様である。 Also in the backlight unit 11, the light L emitted from the light source 12 enters the light guide plate 14 from the end surface 14 b of the light guide plate 14. The incident light is guided by repeating total reflection in the light guide plate 14, and the traveling direction is changed by the inclined surface of the recess 15 c and is emitted from the exit surface 14 a of the light guide plate 14. In this example, the light L emitted from the emission surface 14a of the light guide plate 14 is incident on the reflection plate 16, is reflected, enters the light guide plate 14 again, passes through the light guide plate 14, and passes through the λ / 4 plate 20. Through the reflection type linearly polarized light separating plate 24. The subsequent light path is the same as that of the backlight unit 10 of the first embodiment, and the effects to be achieved are also the same.
　本発明の第２の実施形態に係るバックライトユニット６０の概略構成を図７に示す FIG. 7 shows a schematic configuration of the backlight unit 60 according to the second embodiment of the present invention.
　本実施形態のバックライトユニット６０は、λ／４板２０を、導光板１４と反射型直線偏光分離板２４との間ではなく、導光板１４と反射板１６との間に備えた点で図１に示す第１の実施形態のバックライトユニット１０と異なる。 The backlight unit 60 of the present embodiment is illustrated in that the λ / 4 plate 20 is provided not between the light guide plate 14 and the reflective linearly polarized light separating plate 24 but between the light guide plate 14 and the reflective plate 16. 1 is different from the backlight unit 10 of the first embodiment shown in FIG.
　この場合、反射型直線偏光分離板２４において反射された第２の直線偏光Ｌ2は、導光板１４を通過した後、λ／４板２０に入射され、このλ／４板２０内において円偏光（例えば、ここでは左円偏光Ｌｌ）に変換される。そして、左円偏光Ｌｌとして反射板１６に入射し、この反射板１６において、回転方向が反転し、右円偏光Ｌｒとして反射される。この右円偏光Ｌｒはλ／４板２０内において第１の直線偏光となり、再度導光板１４に入射される。その後、導光板１４を透過した第１の直線偏光は反射型直線偏光分離板２４を透過して液晶セルのバックライト側偏光板２６に入射する。 In this case, the second linearly polarized light L 2 reflected by the reflective linearly polarized light separating plate 24 passes through the light guide plate 14 and then enters the λ / 4 plate 20, and is circularly polarized within the λ / 4 plate 20. (For example, left circularly polarized light L1 here). Then, the light enters the reflector 16 as the left circularly polarized light Ll, and the direction of rotation is reversed on the reflector 16 to be reflected as the right circularly polarized light Lr. The right circularly polarized light Lr becomes the first linearly polarized light in the λ / 4 plate 20 and is incident on the light guide plate 14 again. Thereafter, the first linearly polarized light transmitted through the light guide plate 14 is transmitted through the reflective linearly polarized light separating plate 24 and is incident on the backlight side polarizing plate 26 of the liquid crystal cell.
　第１の実施形態のバックライトユニット１０では、反射型直線偏光分離板２４で反射された直線偏光がλ／４板を透過して円偏光になった状態で導光板１４に再入射したが、本実施形態では、反射型直線偏光分離板２４で反射された直線偏光がそのまま導光板１４に再入射する。
　本実施形態のバックライトユニット６０においても、導光板１４および反射板１６は第１の実施形態の場合と同様であり、偏光解消度が小さいものを用いているので、第１の実施形態のバックライトユニット１０と同様の効果を得ることができる。 In the backlight unit 10 of the first embodiment, the linearly polarized light reflected by the reflective linearly polarized light separating plate 24 passes through the λ / 4 plate and is re-incident on the light guide plate 14 while being circularly polarized. In the present embodiment, the linearly polarized light reflected by the reflective linearly polarized light separating plate 24 reenters the light guide plate 14 as it is.
Also in the backlight unit 60 of this embodiment, the light guide plate 14 and the reflection plate 16 are the same as those in the first embodiment, and those having a small degree of depolarization are used. The same effect as the light unit 10 can be obtained.
　なお、本実施形態の構成の場合、λ／４板は反射板１６の表面に直接塗布形成されたλ／４層であってもよい。 In the case of the configuration of the present embodiment, the λ / 4 plate may be a λ / 4 layer that is directly applied and formed on the surface of the reflecting plate 16.
　本発明の第３の実施形態に係るバックライトユニット７０の概略構成を図８に示す。 FIG. 8 shows a schematic configuration of a backlight unit 70 according to the third embodiment of the present invention.
　本実施形態のバックライトユニット７０は、導光板１４に代えて、指向性付与機構として貫通孔３５を有する導光板３４を備えた点で図１に示す第１の実施形態のバックライトユニット１０と異なる。 The backlight unit 70 of the present embodiment is different from the backlight unit 10 of the first embodiment shown in FIG. 1 in that a light guide plate 34 having a through hole 35 is provided as a directivity providing mechanism instead of the light guide plate 14. Different.
　図９は、本実施形態のバックライトユニット７０に備えられた導光板３４の一部を示す断面図（Ａ）および底面図（Ｂ）である。
　導光板３４は、表裏面（一方の主面から他方の主面）に貫通する斜柱状の複数の貫通孔３５が設けられてなる。貫通孔３５は、主面の法線（主面に対して直交する方向）Ｚに対して傾きを持って形成されている。ここで、主面の法線は、反射板１６、導光板３４および反射型直線偏光分離板２４の並び方向に平行である。貫通孔３５の傾きは一方の主面の開口の中心から他方の主面の開口の中心を結ぶ直線の、貫通孔３５は主面に対して直交する方向Ｚに対する傾きで定義する。開口の中心は、開口形状の重心位置とする。Ｚと貫通孔３５がなす角度φは３０°～８０°であることが好ましい。 FIG. 9 is a cross-sectional view (A) and a bottom view (B) showing a part of the light guide plate 34 provided in the backlight unit 70 of the present embodiment.
The light guide plate 34 is provided with a plurality of oblique columnar through holes 35 penetrating the front and back surfaces (from one main surface to the other main surface). The through hole 35 is formed with an inclination with respect to the normal line (direction perpendicular to the main surface) Z of the main surface. Here, the normal line of the main surface is parallel to the arrangement direction of the reflecting plate 16, the light guide plate 34, and the reflective linearly polarized light separating plate 24. The inclination of the through-hole 35 is defined as the inclination of a straight line connecting the center of the opening of one main surface to the center of the opening of the other main surface, and the inclination of the through-hole 35 with respect to the direction Z perpendicular to the main surface. The center of the opening is the center of gravity of the opening shape. The angle φ formed by Z and the through hole 35 is preferably 30 ° to 80 °.
　本実施形態のように貫通孔３５を指向性付与機構として備えた導光板においても、一主面（一方の主面および他方の主面のそれぞれ）における平坦面の占有面積率は凹部からなる指向性付与機構を備えた場合と同様に、偏光解消度４０％以下を満たし、かつ指向性付与機能を有するために３０～９８％が好ましく、３０～９５％がより好ましく、５０～９５％がさらに好ましく、５０～９０％が特に好ましい。 Also in the light guide plate provided with the through-hole 35 as a directivity imparting mechanism as in the present embodiment, the occupied area ratio of the flat surface on one main surface (each of the one main surface and the other main surface) is directed from a concave portion. As in the case of providing a property imparting mechanism, it is preferably 30 to 98%, more preferably 30 to 95%, and even more preferably 50 to 95% in order to satisfy the degree of depolarization of 40% or less and to have a directivity imparting function. Preferably, 50 to 90% is particularly preferable.
　貫通孔３５の主面における開口形状は、円形に限らず、楕円、弧状、多角形などであってもよい。また、貫通孔３５は、主面に平行な断面の形状が開口形状と一致することが好ましいが、一部異なる断面形状を有していても構わない。 The opening shape in the main surface of the through hole 35 is not limited to a circle, and may be an ellipse, an arc, a polygon, or the like. Moreover, although it is preferable that the shape of the cross section parallel to the main surface corresponds to the opening shape, the through hole 35 may have a partially different cross sectional shape.
　なお、本実施形態のように、導光板における指向性付与機構が貫通孔であれば、片方の主面にのみ凹部や凸部からなる指向性付与機構を備えた場合と比較して、より光導波経路内において導波する光に指向性を与えやすくなるため、導光板自体を薄くすることができ、厚み２００μｍ以下のフィルム状を容易に実現することが可能となる。 In addition, if the directivity provision mechanism in the light guide plate is a through-hole as in this embodiment, the light guide is more light compared to the case where the directivity provision mechanism including a concave portion or a convex portion is provided only on one main surface. Since it becomes easy to give directivity to the light guided in the wave path, the light guide plate itself can be made thin, and a film having a thickness of 200 μm or less can be easily realized.
　本発明の第４の実施形態に係るバックライトユニット８０の概略構成を図１０に示す。 FIG. 10 shows a schematic configuration of a backlight unit 80 according to the fourth embodiment of the present invention.
　本実施形態のバックライトユニット８０は、導光板１４の出射面側に、入射光により励起されて、蛍光を生じる波長変換部材４０を粘着剤層４５を介して備え、光源として、励起波長を含む入射光を射出する光源１３を備えた点で図１に示す第１の実施形態のバックライトユニット１０と異なる。これらの点以外はバックライトユニット１０と同様であり、同様の効果を奏する。 The backlight unit 80 of the present embodiment includes a wavelength conversion member 40 that is excited by incident light and generates fluorescence via an adhesive layer 45 on the exit surface side of the light guide plate 14, and includes an excitation wavelength as a light source. It differs from the backlight unit 10 of 1st Embodiment shown in FIG. 1 by the point provided with the light source 13 which inject | emits incident light. Except for these points, it is the same as the backlight unit 10 and has the same effects.
　波長変換部材４０の詳細について説明する。
　波長変換部材４０は、第１基板４１、第２基板４２および波長変換層４４を備えており、図９に示す通り、波長変換層４４が第１基板４１と第２基板４２によって挟持されている。 Details of the wavelength conversion member 40 will be described.
The wavelength conversion member 40 includes a first substrate 41, a second substrate 42, and a wavelength conversion layer 44, and the wavelength conversion layer 44 is sandwiched between the first substrate 41 and the second substrate 42 as shown in FIG. .
　波長変換層４４は入射する光の波長を相対的に長い波長へと変換する。波長変換層４４は蛍光体、量子ドット、またはこれらの組合せを含み得る。 The wavelength conversion layer 44 converts the wavelength of incident light into a relatively long wavelength. The wavelength conversion layer 44 can include phosphors, quantum dots, or combinations thereof.
　蛍光体は一般的な有機蛍光体または無機蛍光体であり得る。例示的な実施形態で、蛍光体は黄色蛍光体であり得る。このような黄色蛍光体はＹＡＧ系蛍光物質、シリケート系蛍光物質、酸窒化物蛍光物質、またはこれらの組合せであり得るが、これに限定されない。 The phosphor may be a general organic phosphor or an inorganic phosphor. In an exemplary embodiment, the phosphor may be a yellow phosphor. Such a yellow phosphor may be, but is not limited to, a YAG phosphor, a silicate phosphor, an oxynitride phosphor, or a combination thereof.
　量子ドットは、コアシェル（Ｃｏｒｅ－Ｓｈｅｌｌ）構造の半導体ナノ粒子としてサイズが数ｎｍないし数十ｎｍサイズを有し、量子閉じ込め効果（Ｑｕａｎｔｕｍ　Ｑｕａｎｆｉｎｅｍｅｎｔ　Ｅｆｆｅｃｔ）によって粒子のサイズによって発光光が異なって出る特性を有することを意味する。より詳細には、量子ドットは狭い波長帯で強い光を発生し、量子ドットが発散する光は伝導帯（Ｃｏｎｄｕｃｔｉｏｎ　ｂａｎｄ）から励起状態の電子が価電子帯（ｖａｌｅｎｃｅ　ｂａｎｄ）に遷移する際に発生する。このとき、量子ドットはその粒子が小さいほど短い波長の光が発生して粒子が大きいほど長い波長の光を発生する性質がある。したがって、量子ドットのサイズを調節すると所望する波長の可視光線領域の光をすべて出すことができる。 Quantum dots have core-shell structure semiconductor nanoparticles with a size of several nanometers to several tens of nanometers. The quantum confinement effect (Quantum Quantfinement Effect) has a characteristic that emitted light varies depending on the size of the particles. It means having. More specifically, quantum dots generate strong light in a narrow wavelength band, and light emitted by quantum dots is generated when electrons in the excited state transition from a conduction band to a valence band. To do. At this time, the quantum dot has a property of generating light having a shorter wavelength as the particle is smaller and generating light having a longer wavelength as the particle is larger. Therefore, when the size of the quantum dot is adjusted, all light in the visible light region having a desired wavelength can be emitted.
　量子ドットは、Ｓｉ系ナノ結晶、ＩＩ－ＶＩ族系化合物半導体ナノ結晶、ＩＩＩ－Ｖ族系化合物半導体ナノ結晶、ＩＶ－ＶＩ族系化合物半導体ナノ結晶及びこれらの混合物のうち何れか一つのナノ結晶を含み得る。 The quantum dot may be any one of Si-based nanocrystals, II-VI group compound semiconductor nanocrystals, III-V group compound semiconductor nanocrystals, IV-VI group compound semiconductor nanocrystals, and mixtures thereof. Can be included.
　ＩＩ－ＶＩ族系化合物半導体ナノ結晶は、ＣｄＳ、ＣｄＳｅ、ＣｄＴｅ、ＺｎＳ、ＺｎＳｅ、ＺｎＴｅ、ＨｇＳ、ＨｇＳｅ、ＨｇＴｅ、ＣｄＳｅＳ、ＣｄＳｅＴｅ、ＣｄＳＴｅ、ＺｎＳｅＳ、ＺｎＳｅＴｅ、ＺｎＳＴｅ、ＨｇＳｅＳ、ＨｇＳｅＴｅ、ＨｇＳＴｅ、ＣｄＺｎＳ、ＣｄＺｎＳｅ、ＣｄＺｎＴｅ、ＣｄＨｇＳ、ＣｄＨｇＳｅ、ＣｄＨｇＴｅ、ＨｇＺｎＳ、ＨｇＺｎＳｅ、ＨｇｇＺｎＴｅ、ＣｄＺｎＳｅＳ、ＣｄＺｎＳｅＴｅ、ＣｄＺｎＳＴｅ、ＣｄＨｇＳｅＳ、ＣｄＨｇＳｅＴｅ、ＣｄＨｇＳＴｅ、ＨｇＺｎＳｅＳ、ＨｇＺｎＳｅＴｅ及びＨｇＺｎＳＴｅで構成された群から選択された何れか一つであり得る。 II-VI group compound semiconductor nanocrystals are CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, HgS, HgSe, HgTe, CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeC, HgSTeS, HgSTeS. CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HggZnTe, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSeTe, HgZnSe, and HgZnSe.
　また、ＩＩＩ－Ｖ族系化合物半導体ナノ結晶は、ＧａＰＡｓ、ＡｌＮＰ、ＡｌＮＡｓ、ＡｌＰＡｓ、ＩｎＮＰ、ＩｎＮＡｓ、ＩｎＰＡｓ、ＧａＡｌＮＰ、ＧａＡｌＮＡｓ、ＧａＡｌＰＡｓ、ＧａＩｎＮＰ、ＧａＩｎＮＡｓ、ＧａＩｎＰＡｓ、ＩｎＡｌＮＰ、ＩｎＡｌＮＡｓ、及びＩｎＡｌＰＡｓで構成された群から選択された何れか一つであり得、ＩＶ－ＶＩ族系化合物半導体ナノ結晶はＳｂＴｅであり得る。 In addition, the group III-V compound semiconductor nanocrystal is composed of GaPAs, AlNP, AlNAs, AlPAs, InNP, InNAs, InPAs, GaAlNP, GaAlNAs, GaAlPAs, GaInNP, GaInNAs, GaInPAs, InAlNP, InAlNAs, and InAlPAs. The group IV-VI compound semiconductor nanocrystal may be SbTe.
　波長変換層４４は一種類の量子ドットを含み得る。例えば、波長変換層４４は入射する光の波長を黄色光の波長に変換する黄色量子ドットを含み得る。しかし、これに限定されず、波長変換層４４は二つの種類以上の量子ドットを含んでいてもよい。例えば、波長変換層４４は入射する光の波長を赤色光の波長に変換する赤色量子ドット及び入射する光の波長を緑色光の波長に変換する緑色量子ドットを含み得る。 The wavelength conversion layer 44 can include one type of quantum dot. For example, the wavelength conversion layer 44 may include yellow quantum dots that convert the wavelength of incident light into the wavelength of yellow light. However, the present invention is not limited to this, and the wavelength conversion layer 44 may include two or more types of quantum dots. For example, the wavelength conversion layer 44 may include a red quantum dot that converts the wavelength of incident light into a wavelength of red light and a green quantum dot that converts the wavelength of incident light into a wavelength of green light.
　波長変換層４４は蛍光体及び量子ドットのような波長変換物質の他に波長変換物質を分散させる分散媒質をさらに含み得る。すなわち、蛍光体または量子ドットは有機溶媒または高分子樹脂のような分散媒質に自然に配位した形態に分散され得る。このような分散媒質としては、蛍光体または量子ドットの波長変換性能に影響を及ぼさず、かつ光を反射させず、光吸収を起こさない範囲で透明な媒質であれば、いかなるものでも使用できる。 The wavelength conversion layer 44 may further include a dispersion medium that disperses the wavelength conversion substance in addition to the wavelength conversion substance such as the phosphor and the quantum dots. That is, the phosphor or quantum dots can be dispersed in a form that is naturally coordinated in a dispersion medium such as an organic solvent or a polymer resin. As such a dispersion medium, any medium can be used as long as it does not affect the wavelength conversion performance of the phosphor or the quantum dot, does not reflect light, and does not cause light absorption.
　有機溶媒は、例えば、トルエン（ｔｏｌｕｅｎｅ）、クロロホルム（ｃｈｌｏｒｏｆｏｒｍ）及びエタノール（ｅｔｈａｎｏｌ）のうち少なくとも一つを含み得、高分子樹脂は例えば、エポキシ（ｅｐｏｘｙ）、シリコン（ｓｉｌｉｃｏｎｅ）、ポリスチレン（ｐｏｌｙｓｔｙｒｅｎｅ）及びアクリレート（ａｃｒｙｌａｔｅ）のうち少なくとも一つを含み得る。 The organic solvent may include at least one of toluene, chloroform, and ethanol, and the polymer resin may include, for example, epoxy, silicon, polystyrene, and polystyrene. At least one of acrylates may be included.
　また、波長変換層４４は分散媒質の他にＵＶ開始剤、熱硬化添加剤、架橋剤、拡散剤、及びこれらの組合せをさらに含み得る。このように、波長変換層４４は波長変換物質と添加剤が混合された状態で第１基板４１上に塗布硬化されて形成される。 In addition to the dispersion medium, the wavelength conversion layer 44 may further include a UV initiator, a thermosetting additive, a crosslinking agent, a diffusing agent, and combinations thereof. As described above, the wavelength conversion layer 44 is formed by being applied and cured on the first substrate 41 in a state where the wavelength conversion substance and the additive are mixed.
　第１基板４１および第２基板４２は水分及び酸素を遮断できる物質からなる。例えば、酸化ケイ素（ＳｉＯｘ）、窒化ケイ素（ＳｉＮｘ）、またはこれらの組合せを含み得る。また、ポリエチレンテレフタレート（Ｐｏｌｙｅｔｈｙｌｅｎｅ　ｐｈｔｈａｌａｔｅ、ＰＥＴ）及びポリカーボネート（Ｐｏｌｙｃａｒｂｏｎａｔｅ、ＰＣ）のようなプラスチックフィルムであってもよい。ガラス材質からなるものであってもよい。なお、第１基板４１と第２基板４２とは、同一物質からなるものであってもよいし、異なるものであってもよい。 The first substrate 41 and the second substrate 42 are made of a substance capable of blocking moisture and oxygen. For example, it may include silicon oxide (SiOx), silicon nitride (SiNx), or combinations thereof. Further, it may be a plastic film such as polyethylene terephthalate (PET) and polycarbonate (Polycarbonate, PC). It may be made of a glass material. In addition, the 1st board | substrate 41 and the 2nd board | substrate 42 may consist of the same substance, and may differ.
　図面に示していないが、第１基板４１と第２基板４２との間にはシーラントなどのようなシーリング部材が第１基板４１及び第２基板４２の縁に沿って配置され、第１基板４１と第２基板４２を相互合着して密封することができる。 Although not shown in the drawings, a sealing member such as a sealant is disposed between the first substrate 41 and the second substrate 42 along the edges of the first substrate 41 and the second substrate 42. And the second substrate 42 can be bonded together and sealed.
　第１基板４１と第２基板４２が剛性（Ｒｉｇｉｄ）のガラス材質からなる場合、波長変換部材４０は第１基板４１上に、波長変換層４４を形成し、波長変換層４４上に第２基板４２を合着する工程により形成される。また、第１基板４１と第２基板４２がフレキシブル（Ｆｌｅｘｉｂｌｅ）のフィルム材質からなる場合、波長変換部材４０はラミネート（Ｌａｍｉｎａｔｉｏｎ）工程により形成され得る。 When the first substrate 41 and the second substrate 42 are made of rigid glass material, the wavelength conversion member 40 forms the wavelength conversion layer 44 on the first substrate 41, and the second substrate on the wavelength conversion layer 44. It is formed by the process of attaching 42. In addition, when the first substrate 41 and the second substrate 42 are made of a flexible film material, the wavelength conversion member 40 can be formed by a laminating process.
　光源１３が青色の光を放出し、波長変換層４４が光源１３から放出された光の色を白色に変換する場合、光源１３から放出されて波長変換部材４０を通過した光は全体的に均一な白色を有し得る。 When the light source 13 emits blue light and the wavelength conversion layer 44 converts the color of the light emitted from the light source 13 to white, the light emitted from the light source 13 and passed through the wavelength conversion member 40 is generally uniform. White color.
　本実施形態のバックライトユニット８０においては、例えば、光源１３として青色ＬＥＤを備え、青色光により励起されて緑色光を発光する量子ドットと、青色光により励起されて赤色光を発光する量子ドットとがマトリックス中に分散されてなる波長変換層４４を備えることができる。 In the backlight unit 80 of the present embodiment, for example, a blue LED is provided as the light source 13, quantum dots that are excited by blue light and emit green light, and quantum dots that are excited by blue light and emit red light; Can be provided with a wavelength conversion layer 44 dispersed in a matrix.
　以上、本発明のバックライトユニットについて詳細に説明したが、本発明は上述の例に限定はされず、本発明の要旨を逸脱しない範囲において、各種の改良や変更を行ってもよいのは、もちろんである。 As described above, the backlight unit of the present invention has been described in detail, but the present invention is not limited to the above-described examples, and various modifications and changes may be made without departing from the scope of the present invention. Of course.
　以下に実施例を挙げて本発明の特徴をさらに具体的に説明する。以下の実施例に示す材料、試薬、使用量、物質量、割合、処理内容、処理手順等は、本発明の趣旨を逸脱しない限り適宜変更することができる。したがって、本発明の範囲は以下に示す具体例により限定的に解釈されるべきものではない。 Hereinafter, the features of the present invention will be described more specifically with reference to examples. The materials, reagents, used amounts, substance amounts, ratios, processing details, processing procedures, and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.
　まず、各実施例および比較例に用いた各部材について説明する。 First, each member used in each example and comparative example will be described.
　＜導光板１、２の作製＞
　厚さ２ｍｍのアクリル板（スミホリデー、光社製）を用意した。
　このアクリル板の一面に、凹部として、底辺ａが１０μｍで、頂角θが４５度である、長尺な直角三角形の溝を、溝の延在方向と直交する方向に配列して形成した（図２および図４参照）。
　この際において、溝の間隔ｂを変更することにより、凹部の占有面積率が１０％の導光板１、および、凹部の占有面積率が１００％の導光板２（間隔ｂ＝０μｍ）を作製した。
　導光板１の偏光解消度は１０％、導光板２の偏光解消度は９０％であった。 <Production of light guide plates 1 and 2>
An acrylic plate (Sumi Holiday, manufactured by Kogyo Co., Ltd.) having a thickness of 2 mm was prepared.
On one surface of this acrylic plate, as a recess, long right triangular grooves having a base a of 10 μm and an apex angle θ of 45 degrees were arranged in a direction orthogonal to the extending direction of the grooves ( 2 and 4).
At this time, the light guide plate 1 having a recess occupation area ratio of 10% and the light guide plate 2 having a recess occupation area ratio of 100% (interval b = 0 μm) were produced by changing the groove spacing b. .
The degree of depolarization of the light guide plate 1 was 10%, and the degree of depolarization of the light guide plate 2 was 90%.
　＜導光フィルム１、２の作製＞
　市販のシクロオレフィンポリマーフィルム（ゼオノアZF１４、日本ゼオン社製、厚み１００μｍ）に、レーザーを利用し、図１１に示すように、入射光の方位と同じ方位で、極角４０°となるように、フィルム３６を貫通する、直径５０μｍの貫通孔（短径５０μｍ、長径６０μｍの楕円斜柱体状の貫通孔）３７を複数開け、導光フィルム１とした。その際、複数の貫通孔３７はランダムに配置し、フィルムの一方の主面３６ａの面積に対する平坦面（貫通孔開口以外の部分）の面積が８０％となるようにした。本導光フィルム１の偏光解消度は１０％であった。なお、この導光フィルム１においては、楕円の長径が導光フィルム１への光入射面である側面３６ｂに対して直交するように貫通孔を設けた。 <Production of light guide films 1 and 2>
Using a commercially available cycloolefin polymer film (Zeonor ZF14, manufactured by Nippon Zeon Co., Ltd., thickness 100 μm), as shown in FIG. 11, the polar angle is 40 ° in the same direction as the incident light direction. A plurality of through holes 50 (diameter of 50 μm, elliptical cylindrical body having a major axis of 60 μm) 37 having a diameter of 50 μm penetrating the film 36 were formed as the light guide film 1. At that time, the plurality of through holes 37 were randomly arranged so that the area of the flat surface (portion other than the through hole opening) with respect to the area of the one main surface 36a of the film was 80%. The degree of depolarization of the light guide film 1 was 10%. In this light guide film 1, through holes were provided so that the major axis of the ellipse was orthogonal to the side surface 36 b that is a light incident surface to the light guide film 1.
　また、導光フィルム１において、フィルム３６の貫通孔３９の開口形状を図１２に示すような弧形状とし、この弧形状の底面を有する斜柱状の貫通孔３９を、図１２に示すように周期的に配置した以外は同様にして導光フィルム２とした。なお、導光フィルム２においては、弧の両端を結ぶ直線（弦）の垂線が、導光フィルム２への光入射面である側面に対して垂直となるように貫通孔３９を形成した。
　本導光フィルム２の偏光解消度は１０％であった。 Further, in the light guide film 1, the opening shape of the through hole 39 of the film 36 is an arc shape as shown in FIG. 12, and the oblique columnar through hole 39 having the bottom surface of the arc shape has a period as shown in FIG. The light guide film 2 was formed in the same manner except for the arrangement. In the light guide film 2, the through-hole 39 was formed so that a perpendicular line (string) connecting both ends of the arc was perpendicular to a side surface that is a light incident surface to the light guide film 2.
The degree of depolarization of the light guide film 2 was 10%.
＜導光フィルム３の作製＞
　市販のポリカーボネートフイルム（ピュアエースＷＲ―Ｗ、帝人株式会社製）にレーザーを使用し、導光フィルム２と同様に貫通孔３９を形成し、導光フィルム３とした。
　本導光フィルム３の偏光解消度は１０％であり、平面位相差が１５０ｎｍなのでλ／４板としても機能するものである。 <Preparation of light guide film 3>
A laser was used for a commercially available polycarbonate film (Pure Ace WR-W, manufactured by Teijin Ltd.), and a through hole 39 was formed in the same manner as the light guide film 2 to obtain a light guide film 3.
Since the degree of depolarization of the light guide film 3 is 10% and the planar phase difference is 150 nm, it also functions as a λ / 4 plate.
　＜反射板１、２の作製＞
　ＡＬＡＮＯＤ社製のＭＩＲＯ－ＳＩＬＶＥＲ ２を、反射板１とした。この反射板は、蒸着された銀からなる反射面を有する鏡面反射板である。この反射板の偏光解消度は３％であった。
　アップル社製のｉＰａｄ Ａｉｒ（登録商標）に使用されている反射板を、反射板２とした。この反射板は、有機物の積層膜からなる反射面を有するものである。 <Production of reflectors 1 and 2>
The reflector 1 was MIRO-SILVER 2 manufactured by ALANOD. This reflecting plate is a specular reflecting plate having a reflecting surface made of deposited silver. The degree of depolarization of this reflector was 3%.
The reflector used in iPad Air (registered trademark) manufactured by Apple Inc. was designated as reflector 2. This reflecting plate has a reflecting surface made of an organic laminated film.
　＜偏光解消度の測定＞
　作製した導光板１，２、導光フィルム１，２、および反射板１，２の偏光解消度は、前述の図５に示した方法で測定した。色彩輝度計は、トプコンテクノハウス社製のＢＭ－５Ａを用いた。
　また、測定する部材に円偏光を入射するため、直線偏光板と、後述する方法と同様に作製したλ／４板とを配置した。 <Measurement of degree of depolarization>
The degree of depolarization of the produced light guide plates 1 and 2, light guide films 1 and 2, and reflectors 1 and 2 was measured by the method shown in FIG. 5 described above. The color luminance meter used was BM-5A manufactured by Topcon Technohouse.
In addition, a linearly polarizing plate and a λ / 4 plate produced in the same manner as described later were disposed in order to make circularly polarized light incident on the member to be measured.
　＜λ／４板の作製＞
　まず、λ／４板のためのセルロースエステル支持体Ｔ１を作製した。
（セルロースエステル溶液Ａ－１の調製）
　下記の組成物をミキシングタンクに投入し、加熱しながら攪拌して、各成分を溶解し、セルロースエステル溶液Ａ－１を調製した。
Figure JPOXMLDOC01-appb-I000001
<Production of λ / 4 plate>
First, a cellulose ester support T1 for a λ / 4 plate was prepared.
(Preparation of cellulose ester solution A-1)
The following composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose ester solution A-1.
Figure JPOXMLDOC01-appb-I000001
（マット剤分散液Ｂ－１の調製）
　下記の組成物を分散機に投入し、攪拌して各成分を溶解し、マット剤分散液Ｂ－１を調製した。
Figure JPOXMLDOC01-appb-I000002
(Preparation of matting agent dispersion B-1)
The following composition was charged into a disperser and stirred to dissolve each component to prepare a matting agent dispersion B-1.
Figure JPOXMLDOC01-appb-I000002
　（紫外線吸収剤溶液Ｃ－１の調製）
　下記の組成物を別のミキシングタンクに投入し、加熱しながら攪拌して、各成分を溶解し、紫外線吸収剤溶液Ｃ－１を調製した。
Figure JPOXMLDOC01-appb-I000003
(Preparation of UV absorber solution C-1)
The following composition was put into another mixing tank and stirred while heating to dissolve each component to prepare an ultraviolet absorber solution C-1.
Figure JPOXMLDOC01-appb-I000003
Figure JPOXMLDOC01-appb-C000001
Figure JPOXMLDOC01-appb-C000001
（セルロースエステル支持体Ｔ１の作製）
　セルロースエステル溶液Ａ－１を９４．６質量部、マット剤分散液Ｂ－１を１．３質量部とした混合物に、セルロースエステル１００質量部当たり、紫外線吸収剤（ＵＶ－１）および紫外線吸収剤（ＵＶ－２）がそれぞれ１．０質量部となるように、紫外線吸収剤溶液Ｃ－１を加え、加熱しながら充分に攪拌して各成分を溶解し、ドープを調製した。得られたドープを３０℃に加温し、流延ギーサーを通して直径３ｍのドラムである鏡面ステンレス支持体上に流延した。支持体の表面温度は－５℃に設定し、塗布幅は１４７０ｍｍとした。流延したドープ膜をドラム上で３４℃の乾燥風を１５０ｍ3／分で当てることにより乾燥させ、残留溶剤が１５０％の状態でドラムより剥離した。剥離の際、搬送方向（長手方向）に１５％の延伸を行った。その後、フィルムの幅方向（流延方向に対して直交する方向）の両端をピンテンター（特開平４－１００９号公報の図３に記載のピンテンター）で把持しながら搬送し、幅手方向には延伸処理を行わなかった。さらに、熱処理装置のロール間を搬送することによりさらに乾燥し、セルロースエステル支持体Ｔ１を製造した。作製した長尺状のセルロースエステル支持体Ｔ１の残留溶剤量は０．２％で、厚みは６０μｍで、波長５５０ｎｍにおけるＲｅとＲｔｈはそれぞれ０．８ｎｍ、４０ｎｍであった。 (Preparation of cellulose ester support T1)
Ultraviolet absorber (UV-1) and ultraviolet absorber per 100 parts by mass of cellulose ester in a mixture comprising 94.6 parts by mass of cellulose ester solution A-1 and 1.3 parts by mass of matting agent dispersion B-1 An ultraviolet absorbent solution C-1 was added so that (UV-2) would be 1.0 part by mass, and each component was dissolved by stirring thoroughly while heating to prepare a dope. The obtained dope was heated to 30 ° C., and cast on a mirror surface stainless steel support, which was a drum having a diameter of 3 m, through a casting Giuser. The surface temperature of the support was set to −5 ° C., and the coating width was 1470 mm. The cast dope film was dried on the drum by applying a drying air of 34 ° C. at 150 m 3 / min, and peeled off from the drum with a residual solvent of 150%. During peeling, 15% stretching was performed in the transport direction (longitudinal direction). Thereafter, the film is conveyed while being held by a pin tenter (pin tenter described in FIG. 3 of JP-A-4-1009) at both ends in the width direction (direction perpendicular to the casting direction) and stretched in the width direction. No processing was performed. Furthermore, it dried further by conveying between the rolls of the heat processing apparatus, and manufactured the cellulose-ester support body T1. The produced long cellulose ester support T1 had a residual solvent amount of 0.2%, a thickness of 60 μm, and Re and Rth at a wavelength of 550 nm of 0.8 nm and 40 nm, respectively.
（λ／４板の液晶層の作製）
　クラレ社製ポバールＰＶＡ－１０３を純水に溶解した。溶液の濃度および塗布量を、乾燥膜厚が０．５μｍになるように調整し、上記で作製したセルロースエステル支持体Ｔ１上にバー塗布した。その後、塗布膜を１００℃で５分間加熱した。さらにこの表面をラビング処理して配向層を得た。
　続いて下記の組成の溶質を、ＭＥＫ（メチルエチルケトン）に溶解し、塗布液を調製した。この塗布液を濃度および塗布量が乾燥膜厚が１μｍになるように調整して、上記の配向層上にバー塗布した。その後、溶媒を８５℃、２分間保持して溶媒を気化させた後に１００℃で４分間加熱熟成を行って、均一な配向状態を得た。なお、円盤状化合物は支持体平面に対して垂直配向していた。
　その後この塗布膜を８０℃に保持し、これに窒素雰囲気下で高圧水銀灯を用いて紫外線照射してλ／４板を作製した。 (Production of liquid crystal layer of λ / 4 plate)
POVAL PVA-103 manufactured by Kuraray Co., Ltd. was dissolved in pure water. The concentration of the solution and the coating amount were adjusted so that the dry film thickness was 0.5 μm, and bar coating was performed on the cellulose ester support T1 produced above. Thereafter, the coating film was heated at 100 ° C. for 5 minutes. Further, this surface was rubbed to obtain an alignment layer.
Subsequently, a solute having the following composition was dissolved in MEK (methyl ethyl ketone) to prepare a coating solution. This coating solution was adjusted so that the concentration and the coating amount were 1 μm in dry film thickness, and bar-coated on the alignment layer. Thereafter, the solvent was kept at 85 ° C. for 2 minutes to evaporate the solvent, and then heat-aged at 100 ° C. for 4 minutes to obtain a uniform alignment state. The discotic compound was aligned perpendicular to the support plane.
Thereafter, this coating film was kept at 80 ° C. and irradiated with ultraviolet rays using a high-pressure mercury lamp in a nitrogen atmosphere to produce a λ / 4 plate.
（液晶層作製用の塗布液の溶質組成）
下記円盤状液晶化合物１　　　　　　　３５質量部
下記円盤状液晶化合物２　　　　　　　３５質量部
配向助剤（下記化合物３）　　　　　　　１質量部
配向助剤（下記化合物４）　　　　　　　１質量部
重合開始剤（下記化合物５）　　　　　　３質量部 (Solute composition of coating solution for liquid crystal layer production)
The following discotic liquid crystal compound 1 35 parts by mass The following discotic liquid crystal compound 2 35 parts by mass alignment aid (the following compound 3) 1 part by mass alignment aid (the following compound 4) 1 part by mass polymerization initiator (the following compound 5) 3 masses Part
Figure JPOXMLDOC01-appb-C000002
Figure JPOXMLDOC01-appb-C000002
Figure JPOXMLDOC01-appb-C000003
Figure JPOXMLDOC01-appb-C000003
Figure JPOXMLDOC01-appb-C000004
Figure JPOXMLDOC01-appb-C000004
＜波長変換部材の作製＞
（バリアフィルムの作製）
　市販のセルロースアセテートフィルム（ＺＲＤ４０ＳＬ、富士フイルム社製）の片面側に以下の手順で有機層および無機層を順次形成した。
　トリメチロールプロパントリアクリレート（ダイセルサイテック社製ＴＭＰＴＡ）および光重合開始剤（ランベルティ社製、ＥＳＡＣＵＲＥ　ＫＴＯ４６）を用意し、質量比率として、前者：後者＝９５：５となるように秤量し、これらをトルエンに溶解させ、固形分濃度１５％の塗布液とした。この塗布液を、ダイコーターを用いてロールトウロールにて上記セルロースアセテートフイルムフィルム上に塗布し、５０℃の乾燥ゾーンを３分間通過させた。その後、窒素雰囲気下で紫外線を照射（積算照射量約６００ｍＪ／ｃｍ２）し、紫外線硬化にて硬化させ、巻き取った。支持体上に形成された第一有機層の厚さは、１μｍであった。 <Production of wavelength conversion member>
(Preparation of barrier film)
An organic layer and an inorganic layer were sequentially formed on one side of a commercially available cellulose acetate film (ZRD40SL, manufactured by FUJIFILM Corporation) by the following procedure.
Prepare trimethylolpropane triacrylate (TMCTA manufactured by Daicel Cytec Co., Ltd.) and photopolymerization initiator (Lamberti Co., Ltd., ESACURE KTO46). It was dissolved in toluene to obtain a coating solution having a solid concentration of 15%. This coating solution was applied onto the cellulose acetate film film by roll-to-roll using a die coater, and passed through a drying zone at 50 ° C. for 3 minutes. Thereafter, the sample was irradiated with ultraviolet rays (integrated irradiation amount: about 600 mJ / cm 2 ) in a nitrogen atmosphere, cured by ultraviolet curing, and wound up. The thickness of the first organic layer formed on the support was 1 μm.
　次に、ロールトウロールのＣＶＤ（Chemical Vapor Deposition）装置を用いて、第一有機層の表面に無機層（窒化ケイ素層）を形成した。原料ガスとして、シランガス（流量１６０ｓｃｃｍ）、アンモニアガス（流量３７０ｓｃｃｍ）、水素ガス（流量５９０ｓｃｃｍ）、および窒素ガス（流量２４０ｓｃｃｍ）を用いた。電源として、周波数１３．５６ＭＨｚの高周波電源を用いた。製膜圧力は４０Ｐａ、到達膜厚は５０ｎｍであった。このようにして第一有機層の表面に無機層が積層されたバリアフィルムを作製した。 Next, an inorganic layer (silicon nitride layer) was formed on the surface of the first organic layer using a roll-to-roll CVD (Chemical Vapor Deposition) apparatus. Silane gas (flow rate 160 sccm), ammonia gas (flow rate 370 sccm), hydrogen gas (flow rate 590 sccm), and nitrogen gas (flow rate 240 sccm) were used as source gases. A high frequency power supply having a frequency of 13.56 MHz was used as the power supply. The film forming pressure was 40 Pa, and the reached film thickness was 50 nm. Thus, the barrier film by which the inorganic layer was laminated | stacked on the surface of the 1st organic layer was produced.
（波長変換層形成用蛍光体含有重合性組成物（蛍光体分散液）の調製）
　波長変換層形成用蛍光体含有重合性組成物として、下記の蛍光体分散液を調製し、孔径０．２μｍのポリプロピレン製フィルターでろ過した後、３０分間減圧乾燥して塗布液として用いた。以下のトルエン分散液中の量子ドット濃度は、１質量％であった。
Figure JPOXMLDOC01-appb-I000004
　量子ドット１、２としては、下記のコア‐シェル構造（ＩｎＰ／ＺｎＳ）を有するナノ結晶を用いた。
量子ドット１：ＩＮＰ５３０―１０（ＮＮ-ｌａｂｓ社製)：蛍光半値幅６５ｎｍ
量子ドット２：ＩＮＰ６２０－１０（ＮＮ-ｌａｂｓ社製)：蛍光半値幅７０ｎｍ
　蛍光体分散液の粘度は５０ｍＰａ・ｓであった。 (Preparation of phosphor-containing polymerizable composition (phosphor dispersion) for forming wavelength conversion layer)
The following phosphor dispersion was prepared as a phosphor-containing polymerizable composition for forming a wavelength conversion layer, filtered through a polypropylene filter having a pore size of 0.2 μm, and then dried under reduced pressure for 30 minutes to be used as a coating solution. The quantum dot concentration in the following toluene dispersion was 1% by mass.
Figure JPOXMLDOC01-appb-I000004
As the quantum dots 1 and 2, nanocrystals having the following core-shell structure (InP / ZnS) were used.
Quantum dot 1: INP530-10 (manufactured by NN-labs): fluorescence half width of 65 nm
Quantum dot 2: INP620-10 (manufactured by NN-labs): fluorescence half width 70 nm
The viscosity of the phosphor dispersion was 50 mPa · s.
（波長変換部材の作製）
　上述した手順で作製したバリアフィルムを２枚使用し、うち１枚を第一のフィルムとして、無機層面上に蛍光体分散液をダイコーターにて塗布し、１ｍ／分、６０Ｎ／ｍの張力で連続搬送しながら、５０μｍの厚さの塗膜を形成した。次いで、塗膜の形成されたバリアフィルムをバックアップローラに巻きかけ、塗膜の上に第二のフィルムとして、もう１枚のバリアフィルムの無機層面が塗膜に接する向きでラミネートし、その後、２枚のバリアフィルム（第一、第二のフィルム）で塗膜を挟持した状態でバックアップローラに巻きかけ、連続搬送しながら紫外線を照射した。バックアップローラの直径はφ３００ｍｍであり、バックアップローラの温度は５０℃であった。紫外線の照射量は２０００ｍＪ／ｃｍ２であった。上記紫外線の照射により塗膜を硬化させて硬化層（波長変換層）を形成し、波長変換部材を作製した。波長変換部材の硬化層の厚みは約５０μｍであった。 (Production of wavelength conversion member)
Two barrier films prepared by the above-described procedure are used, one of which is the first film, and the phosphor dispersion liquid is applied on the surface of the inorganic layer with a die coater, with a tension of 1 m / min and 60 N / m. A coating film having a thickness of 50 μm was formed while continuously conveying. Next, the barrier film on which the coating film is formed is wound around a backup roller, and laminated as a second film on the coating film so that the inorganic layer surface of the other barrier film is in contact with the coating film. The film was wound around a backup roller while the coating film was sandwiched between the barrier films (first and second films) and irradiated with ultraviolet rays while being continuously conveyed. The diameter of the backup roller was φ300 mm, and the temperature of the backup roller was 50 ° C. The irradiation amount of ultraviolet rays was 2000 mJ / cm 2 . The coating film was cured by irradiation with the ultraviolet rays to form a cured layer (wavelength conversion layer), and a wavelength conversion member was produced. The thickness of the cured layer of the wavelength conversion member was about 50 μm.
　＜反射型直線偏光分離板の作製＞
　アップル社製のiPad Air（登録商標）に使用されている反射型直線偏光分離板を剥がして、実施例および比較例における反射型直線偏光分離板として用いた。 <Preparation of reflective linearly polarized light separation plate>
The reflective linearly polarized light separating plate used in Apple Air iPad Air (registered trademark) was peeled off and used as a reflective linearly polarized light separating plate in Examples and Comparative Examples.
　＜粘着層＞
　粘着層としては綜研化学製ＳＫダイン２０５７（２５μｍ）を用いた。 <Adhesive layer>
As the adhesive layer, SK Dyne 2057 (25 μm) manufactured by Soken Chemical was used.
　以下の実施例および比較例において、反射板、導光板、λ／４板および反射型直線偏光分離板は、全て、１０×１０ｃｍにして使用した。 In the following examples and comparative examples, the reflector, the light guide plate, the λ / 4 plate, and the reflective linearly polarized light separating plate were all used at 10 × 10 cm.
　［実施例１］
　反射型直線偏光分離板、λ／４板、導光板１、反射板１の順に配置した。さらに、導光板１の一方の側面に光源として白色のＬＥＤを設けて、図１に示すようなバックライトユニットを作製した。 [Example 1]
The reflective linearly polarized light separating plate, the λ / 4 plate, the light guide plate 1 and the reflective plate 1 were arranged in this order. Furthermore, a white LED was provided as a light source on one side of the light guide plate 1 to produce a backlight unit as shown in FIG.
　［実施例２］
　λ／４板と導光板とを綜研化学製ＳＫダイン２０５７（２５μｍ）を用いて貼合した。すなわち、λ／４板と導光板との間に粘着層を備えた以外は、実施例１と同様にバックライトユニットとした。 [Example 2]
The λ / 4 plate and the light guide plate were bonded using SK Dyne 2057 (25 μm) manufactured by Soken Chemical. That is, a backlight unit was obtained in the same manner as in Example 1 except that an adhesive layer was provided between the λ / 4 plate and the light guide plate.
　［実施例３］
　λ／４板を反射板１と導光板１との間に配置した以外は実施例１と同様にして、図７に示すようなバックライトユニットを作製した。 [Example 3]
A backlight unit as shown in FIG. 7 was produced in the same manner as in Example 1 except that the λ / 4 plate was disposed between the reflecting plate 1 and the light guide plate 1.
　［比較例１］
　実施例１において、反射型直線偏光分離板とλ／４板を備えていない構成のバックライトユニットを作製した。 [Comparative Example 1]
In Example 1, a backlight unit having a configuration not including the reflective linearly polarized light separating plate and the λ / 4 plate was produced.
　[比較例２]
　λ／４板を備えていない点以外は実施例１と同様にバックライトユニットを作製した。 [Comparative Example 2]
A backlight unit was produced in the same manner as in Example 1 except that the λ / 4 plate was not provided.
　[比較例３]
　導光板１に変えて、導光板２を用いた以外は、実施例１と同様にバックライトユニットを作製した。 [Comparative Example 3]
A backlight unit was produced in the same manner as in Example 1 except that the light guide plate 2 was used instead of the light guide plate 1.
　[比較例４]
　反射板１に代えて、反射板２を用いた以外は、実施例１と同様にバックライトユニットを作製した。 [Comparative Example 4]
A backlight unit was produced in the same manner as in Example 1 except that the reflector 2 was used instead of the reflector 1.
　[比較例５]
　反射型直線偏光分離板とλ／４板との間にプリズムシート対を配置した以外は、実施例１と同様として、比較例５のバックライトユニットを得た。 [Comparative Example 5]
A backlight unit of Comparative Example 5 was obtained in the same manner as in Example 1 except that a prism sheet pair was disposed between the reflective linearly polarized light separating plate and the λ / 4 plate.
　[参考例１]
　実施例１において反射型直線偏光分離板を備えない以外は同様として参考例１１のバックライトユニットを構成した。 [Reference Example 1]
The backlight unit of Reference Example 11 was configured in the same manner except that the reflective linearly polarized light separating plate was not provided in Example 1.
　実施例１～３、および比較例１～５並びに参考例１のバックライトユニット構成および後述の評価による評価結果を纏めて表１に示す。なお、表１中の実施例および比較例において記載されている反射型直線偏光分離板の光出射側に位置する偏光板は、液晶セルのバックライト型偏光板であり、後述の全光束測定時に、この位置に配置された状態で測定したことを示している。以下の表においても同様とする。 Table 1 summarizes the backlight unit configurations of Examples 1 to 3, Comparative Examples 1 to 5 and Reference Example 1 and evaluation results based on the evaluation described below. Note that the polarizing plate located on the light exit side of the reflective linearly polarized light separating plate described in the examples and comparative examples in Table 1 is a backlight type polarizing plate of a liquid crystal cell, and is used when measuring the total luminous flux described later. , It shows that the measurement was performed in a state of being arranged at this position. The same applies to the following tables.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　[実施例１１]
　反射型直線偏光分離板、λ／４板、波長変換部材、導光板１、反射板１の順に配置した。さらに、導光板１の一方の側面に光源として青色のＬＥＤを設けて、図１０に示すような、実施例１１のバックライトユニットを構成した。なお、波長変換部材と導光板１を綜研化学製ＳＫダイン２０５７（２５μｍ）を用いて貼合した。すなわち、波長変換部材と導光板１との間に粘着層を備えている。 [Example 11]
The reflective linearly polarized light separating plate, the λ / 4 plate, the wavelength converting member, the light guide plate 1 and the reflecting plate 1 were arranged in this order. Further, a blue LED was provided as a light source on one side surface of the light guide plate 1 to constitute a backlight unit of Example 11 as shown in FIG. In addition, the wavelength conversion member and the light-guide plate 1 were bonded together using the SK dyne 2057 (25 micrometers) by Soken Chemical. That is, an adhesive layer is provided between the wavelength conversion member and the light guide plate 1.
　[参考例１１]
　実施例１１において、反射型直線偏光分離板を備えない以外は同様として参考例１１のバックライトユニットを構成した。 [Reference Example 11]
In Example 11, the backlight unit of Reference Example 11 was configured in the same manner except that the reflective linearly polarized light separating plate was not provided.
　実施例１１および参考例１のバックライトユニット構成および後述の評価による評価結果を纏めて表２に示す。 Table 2 summarizes the backlight unit configurations of Example 11 and Reference Example 1 and the evaluation results based on the evaluation described below.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　[実施例２１]
　実施例１において導光板１に代えて導光フィルム１を用いた以外は同様として、図８に示すような、実施例２１のバックライトユニットを構成した。 [Example 21]
In the same manner as in Example 1 except that the light guide film 1 was used instead of the light guide plate 1, a backlight unit of Example 21 as shown in FIG. 8 was configured.
　[実施例２２]
　実施例２１において導光フィルム１に代えて導光フィルム２を用いた以外は同様として実施例２２のバックライトユニットを構成した。 [Example 22]
The backlight unit of Example 22 was configured in the same manner except that the light guide film 2 was used instead of the light guide film 1 in Example 21.
　[実施例２３]
　実施例２１において導光フィルム１に代えて導光フィルム３を用い、λ／４板を使用しない（導光フィルム３がλ／４板の役割を兼ねる）こと以外は同様として実施例２３のバックライトユニットを構成した。 [Example 23]
In Example 21, the light guide film 3 is used instead of the light guide film 1, and the λ / 4 plate is not used (the light guide film 3 also serves as the λ / 4 plate). A light unit was constructed.
　[参考例２１]
　実施例２１において、反射型直線偏光分離板を備えない以外は同様として参考例２１のバックライトユニットを構成した。 [Reference Example 21]
In Example 21, the backlight unit of Reference Example 21 was configured in the same manner except that the reflective linearly polarized light separating plate was not provided.
　実施例２１，２２、２３および参考例２１のバックライトユニット構成および後述の評価による評価結果を纏めて表３に示す。 Table 3 summarizes the backlight unit configurations of Examples 21, 22, and 23 and Reference Example 21 and the evaluation results based on the evaluation described below.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
「評価方法」
　＜全光束比＞
　作製した各バックライトユニットについて、液晶セルのバックライト側偏光板をバックライトユニットの出射面側に配置し、バックライトユニットの反射型直線偏光分離板を透過してバックライトユニット光として出射し、偏光子を透過した光を、輝度計（ＢＭ－５、トプコン社製）を用いて、極角－８０～８０度まで１０度おき、全方位角１５度おきに輝度［ｃｄ／ｍ2］を測定し、全測定点を立体角ごとに足し合わせ、全光束とした。
　また、本発明では、導光板から取り出した光がどれだけ効率良くバックライト側偏光板を通過するかが重要であるため、参考例１、参考例１１、参考例２１においては、バックライト側偏光板を備えない、すなわち、バックライト側偏光板を介さずバックライトユニットからバックライトユニット光として出射した光を直接検出した。この時の全光束を１００％とした時の、各実施例、比較例の全光束の割合を全光束比として評価した。この値は、１００％に近いほどより性能良となる。 "Evaluation methods"
<Total luminous flux ratio>
For each manufactured backlight unit, the backlight side polarizing plate of the liquid crystal cell is arranged on the emission surface side of the backlight unit, is transmitted through the reflective linearly polarized light separation plate of the backlight unit, and is emitted as backlight unit light. Using a luminance meter (BM-5, manufactured by Topcon Corp.), the light transmitted through the polarizer is set to a luminance [cd / m 2 ] at polar angles of -80 to 80 degrees every 10 degrees and every azimuth angle every 15 degrees. Measurement was performed, and all measurement points were added for each solid angle to obtain a total luminous flux.
Further, in the present invention, since it is important how efficiently the light extracted from the light guide plate passes through the backlight side polarizing plate, in Reference Example 1, Reference Example 11, and Reference Example 21, the backlight side polarized light is used. No light was provided, that is, light emitted as backlight unit light from the backlight unit was directly detected without passing through the backlight side polarizing plate. When the total luminous flux at this time was 100%, the ratio of the total luminous flux in each example and comparative example was evaluated as the total luminous flux ratio. The closer this value is to 100%, the better the performance.
＜モアレ確認方法＞
　各実施例、比較例を目視にて確認し、モアレの有無を確認した。視認された場合を「有」、視認されなかった場合を「無」として表１～表３中に示した。 <Moire confirmation method>
Each Example and Comparative Example was confirmed visually to check for the presence of moire. Tables 1 to 3 show “Yes” when the image was visually recognized and “No” when the image was not visually recognized.
「評価結果」
　表１に示した通り、本発明のように、偏光解消度の小さい導光板および反射板を用い、λ／４板と反射型直線偏光分離板を備えた実施例のバックライトユニットは、比較例と比較してバックライト側偏光板を透過した全光束比が大きく、輝度向上効果が高いという結果が得られた。
　表２に示す通り、実施例１１のように波長変換部材を備えた構成においても、本発明の構成により良好な輝度向上を達成することができた。
　さらに、実施例２１、２２のように、導光板として非常に薄い導光フィルムを用いた場合にも、非常に良好な全光束比を得ることができた。なお、実施例２１、２２では、導光フィルムが１００μｍと非常に薄いため、バックライトユニット全体としての厚みを非常に小さくすることができる。
　プリズムシートを備えた比較例５以外では、視認できるモアレは生じなかった。モアレを抑制するためには、プリズムシートを備えないことが有効であることは明らかである。そして、プリズムシートを備える必要がない本発明の実施例においては、プリズムシートを備えた場合と比較してバックライトユニット全体としての厚みを抑制することができることは、明らかである。 "Evaluation results"
As shown in Table 1, the backlight unit of the example using the light guide plate and the reflection plate having a small degree of depolarization and including the λ / 4 plate and the reflection type linearly polarized light separation plate as in the present invention is a comparative example. As a result, the ratio of the total luminous flux transmitted through the backlight side polarizing plate was large and the effect of improving the luminance was high.
As shown in Table 2, even in the configuration provided with the wavelength conversion member as in Example 11, good luminance improvement could be achieved by the configuration of the present invention.
Further, even when a very thin light guide film was used as the light guide plate as in Examples 21 and 22, a very good total luminous flux ratio could be obtained. In Examples 21 and 22, since the light guide film is very thin as 100 μm, the thickness of the entire backlight unit can be very small.
Except for Comparative Example 5 provided with a prism sheet, no visible moire occurred. Obviously, it is effective not to have a prism sheet in order to suppress moire. And in the Example of this invention which does not need to provide a prism sheet, it is clear that the thickness as the whole backlight unit can be suppressed compared with the case where a prism sheet is provided.
　１０，６０，７０，８０　バックライトユニット
　１２，１３　光源
　１４，３４　導光板
　１４ａ　一方の主面（出射面）
　１４ｂ　端面（入射面）
　１４ｃ　他方の主面（裏面）
　１５ｃ，１５ｄ，１５ｅ，１５ｆ　凹部（指向性付与機構）
　１５ｇ　凸部（指向性付与機構）
　１６　反射板
　２０，４８，５０　λ／４板
　２４　反射型直線偏光分離板
　２６　バックライト側偏光板
　３５，３７，３９　貫通孔（指向性付与機構）
　４６，５２　直線偏光板
　５４　色彩輝度計 10, 60, 70, 80 Backlight unit 12, 13 Light source 14, 34 Light guide plate 14a One main surface (outgoing surface)
14b End face (incident surface)
14c The other main surface (back surface)
15c, 15d, 15e, 15f Recess (Direction imparting mechanism)
15g Convex part (directivity imparting mechanism)
16 Reflecting plate 20, 48, 50 λ / 4 plate 24 Reflective linearly polarized light separating plate 26 Backlight side polarizing plate 35, 37, 39 Through hole (directivity providing mechanism)
46,52 Linear polarizing plate 54 Color luminance meter

Claims (14)

  1. 　光源と、
    　前記光源が出射する光が端面から入射され、前記端面から入射された光を伝搬して一方の主面から出射する、偏光解消度Ｄｇが４０％以下で、かつ、伝搬する光を前記一方の主面に向ける指向性付与機構を有する導光板と、
    　前記導光板の前記一方の主面と対向する他方の主面側に配置された、偏光解消度Ｄｍが３０％以下の反射板と、
    　前記導光板の前記一方の主面側に配置された、第１の直線偏光を透過して、該第１の直線偏光と直交する第２の直線偏光を反射する反射型直線偏光分離板と、
    　前記反射型直線偏光分離板と前記反射板との間に配置されたλ／４板とを有することを特徴とするバックライトユニット。     A light source;
    The light emitted from the light source is incident from the end face, propagates the light incident from the end face, and exits from one main surface. The degree of depolarization Dg is 40% or less and the propagating light is A light guide plate having a directivity imparting mechanism directed toward the main surface;
    A reflector having a depolarization degree Dm of 30% or less, disposed on the other principal surface side facing the one principal surface of the light guide plate;
    A reflective linearly polarized light separating plate that is disposed on the one main surface side of the light guide plate and transmits the first linearly polarized light and reflects the second linearly polarized light orthogonal to the first linearly polarized light;
    A backlight unit comprising: the reflective linearly polarized light separating plate and a λ / 4 plate disposed between the reflective plate.
  2. 　光源と、
    　前記光源が出射する光が端面から入射され、前記端面から入射された光を伝搬して一方の主面から出射する、偏光解消度Ｄｇが４０％以下で、かつ、伝搬する光を前記一方の主面に向ける指向性付与機構を有する導光板と、
    　前記導光板の前記一方の主面側に配置された、偏光解消度Ｄｍが３０％以下の反射板と、
    　前記導光板の前記一方の主面と対向する他方の主面側に配置された、第１の直線偏光を透過して、該第１の直線偏光と直交する第２の直線偏光を反射する反射型直線偏光分離板と、
    　前記反射型直線偏光分離板と前記反射板との間に配置されたλ／４板とを有することを特徴とするバックライトユニット。     A light source;
    The light emitted from the light source is incident from the end face, propagates the light incident from the end face, and exits from one main surface. The degree of depolarization Dg is 40% or less and the propagating light is A light guide plate having a directivity imparting mechanism directed toward the main surface;
    A reflector having a depolarization degree Dm of 30% or less, disposed on the one main surface side of the light guide plate;
    Reflection that transmits the first linearly polarized light and that reflects the second linearly polarized light that is orthogonal to the first linearly polarized light, disposed on the other principal surface opposite to the one principal surface of the light guide plate. Mold linear polarization separator,
    A backlight unit comprising: the reflective linearly polarized light separating plate and a λ / 4 plate disposed between the reflective plate.
  3. 　前記λ／４板が、前記反射型直線偏光分離板と前記導光板との間、もしくは該導光板と前記反射板との間に配置されている、請求項１または２に記載のバックライトユニット。 The backlight unit according to claim 1, wherein the λ / 4 plate is disposed between the reflective linearly polarized light separating plate and the light guide plate, or between the light guide plate and the reflective plate. .
  4. 　前記導光板の位相差が１００ｎｍ以下である請求項３記載のバックライトユニット。 The backlight unit according to claim 3, wherein a phase difference of the light guide plate is 100 nm or less.
  5. 　前記反射型直線偏光分離板および前記λ／４板を除く光学部材の合計の偏光解消度Ｄａが５０％以下である請求項１から４いずれか１項記載のバックライトユニット。 The backlight unit according to any one of claims 1 to 4, wherein a total depolarization degree Da of the optical members excluding the reflective linearly polarized light separating plate and the λ / 4 plate is 50% or less.
  6. 　前記λ／４板が前記導光板を兼ねる請求項１または２記載のバックライトユニット。 The backlight unit according to claim 1 or 2, wherein the λ / 4 plate also serves as the light guide plate.
  7. 　前記反射板が鏡面反射板である請求項１から６いずれか１項記載のバックライトユニット。 The backlight unit according to any one of claims 1 to 6, wherein the reflector is a specular reflector.
  8. 　前記鏡面反射板の鏡面が金属の蒸着面からなる請求項７に記載のバックライトユニット。 The backlight unit according to claim 7, wherein the mirror surface of the mirror reflector is a metal deposition surface.
  9. 　前記導光板の前記指向性付与機構が、前記他方の主面に形成された複数の凹部および複数の凸部の少なくとも一方である請求項１から８いずれか１項記載のバックライトユニット。 The backlight unit according to any one of claims 1 to 8, wherein the directivity imparting mechanism of the light guide plate is at least one of a plurality of concave portions and a plurality of convex portions formed on the other main surface.
  10. 　前記他方の主面における、前記反射板、前記導光板および前記反射型直線偏光分離板の並び方向に垂直な平坦面の面積率が３０～９８％である請求項９記載のバックライトユニット。 10. The backlight unit according to claim 9, wherein an area ratio of a flat surface perpendicular to an arrangement direction of the reflecting plate, the light guide plate, and the reflective linearly polarized light separating plate on the other main surface is 30 to 98%.
  11. 　前記導光板の前記指向性付与機構は、前記一方の主面から前記他方の主面を貫く複数の貫通孔からなり、該貫通孔は、前記反射板、前記導光板および前記反射型直線偏光分離板の並び方向に対して傾きを有するものである請求項１から１０いずれか１項記載のバックライトユニット。 The directivity imparting mechanism of the light guide plate includes a plurality of through holes penetrating from the one main surface to the other main surface, and the through holes include the reflection plate, the light guide plate, and the reflective linearly polarized light separation. The backlight unit according to claim 1, wherein the backlight unit has an inclination with respect to a direction in which the plates are arranged.
  12. 　前記導光板が、厚み２００μｍ以下である請求項１１記載のバックライトユニット。 The backlight unit according to claim 11, wherein the light guide plate has a thickness of 200 μm or less.
  13. 　前記導光板と前記反射型直線偏光分離板との間に拡散板を備えた請求項１から１２いずれか１項記載のバックライトユニット。 The backlight unit according to any one of claims 1 to 12, further comprising a diffusion plate between the light guide plate and the reflective linearly polarized light separating plate.
  14. 　前記導光板の前記一方の主面と前記反射型直線偏光分離板との間に波長変換層を備えた請求項１から１３いずれか１項記載のバックライトユニット。 The backlight unit according to any one of claims 1 to 13, further comprising a wavelength conversion layer between the one main surface of the light guide plate and the reflective linearly polarized light separating plate.
PCT/JP2016/005059 2015-12-07 2016-12-05 Backlight unit WO2017098718A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2015-238524 2015-12-07
JP2015238524 2015-12-07

Publications (1)

Publication Number Publication Date
WO2017098718A1 true WO2017098718A1 (en) 2017-06-15

Family

ID=59013846

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2016/005059 WO2017098718A1 (en) 2015-12-07 2016-12-05 Backlight unit

Country Status (1)

Country Link
WO (1) WO2017098718A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20220308393A1 (en) * 2020-04-17 2022-09-29 Boe Technology Group Co., Ltd. Back Light Unit Structure, Display Panel and Display Apparatus
EP4071526A1 (en) * 2021-03-26 2022-10-12 Alps Alpine Co., Ltd. Display device

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH10142407A (en) * 1996-11-08 1998-05-29 Nitto Denko Corp Reflection plate, surface light source apparatus and liquid crystal display device
JPH11218760A (en) * 1998-02-02 1999-08-10 Nitto Denko Corp Polarization plane light source device and liquid crystal display device
JP2002015612A (en) * 2000-04-12 2002-01-18 Semiconductor Energy Lab Co Ltd Illumination device
CN1828385A (en) * 2005-03-05 2006-09-06 群康科技(深圳)有限公司 Light-guiding plate
WO2011083809A1 (en) * 2010-01-08 2011-07-14 アルプス電気株式会社 Tac base for cycloolefin polymer bonding, tac bonding member, and liquid crystal display device
JP2012141394A (en) * 2010-12-28 2012-07-26 Nippon Zeon Co Ltd Liquid crystal display device
JP2014164133A (en) * 2013-02-25 2014-09-08 Keiwa Inc Light guide film, ultra-slim liquid crystal backlight unit, and portable computer
JP2015060794A (en) * 2013-09-20 2015-03-30 大日本印刷株式会社 Light guide plate, surface light source device, and transmission display device

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH10142407A (en) * 1996-11-08 1998-05-29 Nitto Denko Corp Reflection plate, surface light source apparatus and liquid crystal display device
JPH11218760A (en) * 1998-02-02 1999-08-10 Nitto Denko Corp Polarization plane light source device and liquid crystal display device
JP2002015612A (en) * 2000-04-12 2002-01-18 Semiconductor Energy Lab Co Ltd Illumination device
CN1828385A (en) * 2005-03-05 2006-09-06 群康科技(深圳)有限公司 Light-guiding plate
WO2011083809A1 (en) * 2010-01-08 2011-07-14 アルプス電気株式会社 Tac base for cycloolefin polymer bonding, tac bonding member, and liquid crystal display device
JP2012141394A (en) * 2010-12-28 2012-07-26 Nippon Zeon Co Ltd Liquid crystal display device
JP2014164133A (en) * 2013-02-25 2014-09-08 Keiwa Inc Light guide film, ultra-slim liquid crystal backlight unit, and portable computer
JP2015060794A (en) * 2013-09-20 2015-03-30 大日本印刷株式会社 Light guide plate, surface light source device, and transmission display device

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20220308393A1 (en) * 2020-04-17 2022-09-29 Boe Technology Group Co., Ltd. Back Light Unit Structure, Display Panel and Display Apparatus
EP4071526A1 (en) * 2021-03-26 2022-10-12 Alps Alpine Co., Ltd. Display device

Similar Documents

Publication Publication Date Title
CN108474524B (en) Edge-lit backlight unit
CN108474522B (en) Direct type backlight unit
US10268077B2 (en) Polarized light source device
US8212966B2 (en) Diffuser for light from light source array and displays incorporating same
US8591052B2 (en) Semispecular hollow backlight with gradient extraction
US10670229B2 (en) Emitting film with improved light-out coupling
JP2016194996A (en) Backlight device and display device
WO2017098718A1 (en) Backlight unit
JP6454969B2 (en) Backlight device, liquid crystal display device
JP2016008998A (en) Liquid crystal display, and light source set and wavelength cut element used in the liquid crystal display
US11874560B2 (en) Backlight for uniform illumination
JP2001166116A (en) Prism sheet, surface light source and liquid crystal display device
WO2007018079A1 (en) Liquid crystal display device and mobile electronic device using the same
JP2016194561A (en) Quantum dot sheet, backlight device, and display
JP7188666B1 (en) Optical member, surface light source device and display device
US11125934B2 (en) Optical member and light guide system
WO2022265068A1 (en) Optical member, planar light source device, and display device
JP2023081197A (en) Optical member, plane light source device, display device and wavelength conversion sheet

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: 16872620

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 16872620

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: JP