JP2015173130A - Light guide film, backlight unit, and portable terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light guide film capable of suppressing unevenness in brightness of a liquid crystal display surface and being made thin when being used in an edge light-type backlight unit.SOLUTION: A light guide film used in an edge light-type backlight unit and having flexibility includes sticking prevention means on its back surface, includes a plurality of recessed portions recessed to a front surface side, on its back surface, and further includes: a plurality of raised portions present around the plurality of recessed portions and projecting to a back surface side; and a plurality of projecting portions dispersedly disposed on a region where the raised portions are not present, as the sticking prevention means. An average thickness of the light guide film is preferably 100 μm or more than 600 μm or less. An average height (H3) from a back surface average interface of the projecting portions is preferably 2 μm or more and 7 μm or less.

Description

  The present invention relates to a light guide sheet, a backlight unit, and a portable terminal.

  In the liquid crystal display device, a backlight system in which a liquid crystal layer is illuminated from the back surface is widely used, and a backlight unit such as an edge light type or a direct type is provided on the lower surface side of the liquid crystal layer. Such an edge light type backlight unit 110 generally has a reflection sheet 115 disposed on the surface of the top plate 116 and a light guide disposed on the surface of the reflection sheet 115 as shown in FIG. A sheet 111, an optical sheet 112 disposed on the surface of the light guide sheet 111, and a light source 117 that irradiates light toward an end face of the light guide sheet 111 are provided (see Japanese Patent Application Laid-Open No. 2010-177130). In the edge light type backlight unit 110 of FIG. 7A, the light emitted from the light source 117 and incident on the light guide sheet 111 propagates in the light guide sheet 111. A part of the propagating light is emitted from the back surface of the light guide sheet 111, reflected by the reflection sheet 115, and incident on the light guide sheet 111 again.

  A liquid crystal display device having such a liquid crystal display unit is required to be thin and light in order to improve its portability and convenience, and accordingly, the liquid crystal display unit is also required to be thin. In particular, in an ultra-thin portable terminal with the thickest part of the casing being 21 mm or less, the thickness of the liquid crystal display part is desired to be about 4 mm to 5 mm, and the edge light incorporated in the liquid crystal display part The type backlight unit is required to be thinner.

  In the edge-light type backlight unit of such an ultra-thin portable terminal, in addition to the one having the reflection sheet 115 disposed on the back surface of the light guide sheet 111 as shown in FIG. As shown in FIG. 7 (b), there has been proposed one that is reduced in thickness by not using the reflection sheet 115 as shown in FIG. 7 (a). The edge light type backlight unit 210 shown in FIG. 7B includes a metal top plate 216, a light guide sheet 211 laminated on the surface of the top plate 216, and a laminate on the surface of the light guide sheet 211. The optical sheet 212 is provided, and a light source 217 that irradiates light toward the end face of the light guide sheet 211. The top plate 216 is polished to a mirror surface and has a function as a reflecting surface 216a. The light emitted from the light source 217 and incident on the light guide sheet 211 propagates in the light guide sheet 211, and a part of the propagated light is emitted from the back surface of the light guide sheet 211 and is on the surface of the top plate 216. The light is reflected by the reflecting surface 216a and enters the light guide sheet 211 again. As described above, in the edge light type backlight unit 210 shown in FIG. 7B, the surface of the top plate 216 is the reflective surface 216a, so that the reflective surface 216a replaces the reflective sheet 115 of FIG. 7A. It becomes. Therefore, such an edge light type backlight unit 210 is promoted to be thin because the reflection sheet 115 is not necessary. In addition, in the edge-light type backlight unit of such an ultra-thin portable terminal, a light guide sheet (light guide film) having an average thickness of 600 μm or less is used as the light guide sheet, thereby further reducing the thickness. There are some that are designed.

JP 2010-177130 A

  The present inventor has found that when such a liquid crystal display device is used, a defect (brightness unevenness) in which the luminance of the liquid crystal display surface becomes non-uniform occurs. As a result of intensive studies by the inventor on the cause of this defect, the back surface of the light guide sheet is in close contact (sticking) with the surface of the reflective sheet or the top plate disposed on the back surface side of the light guide sheet, It has been found that luminance unevenness is caused by the incidence of light.

  The present invention has been made in view of such circumstances, and an object of the present invention is to suppress the uneven brightness of the liquid crystal display surface and reduce the thickness when used in an edge light type backlight unit. It is to provide a light guide sheet. Another object of the present invention is to provide an edge light type backlight unit and a portable terminal in which unevenness in luminance is suppressed and the thickness is reduced.

  The light guide sheet according to the present invention, which has been made to solve the above problems, emits light incident from the end face substantially uniformly from the front surface, and includes an anti-sticking means on the back surface. And having a plurality of concave portions recessed on the front surface side on the back surface, and as the sticking prevention means, a plurality of annular ridge portions that exist around the plurality of concave portions and project to the back surface side, and these annular ridge portions And a plurality of convex portions arranged in a scattered manner in a region where no portion exists.

  Since the light guide sheet has a plurality of recesses recessed on the front surface side on the back surface, the light rays incident on these recesses can be scattered on the front surface side. Therefore, the light guide sheet can emit light from the surface side substantially uniformly by forming a plurality of concave portions at desired positions and scattering incident light by these concave portions. In addition, the light guide sheet is disposed around the plurality of concave portions as sticking prevention means, and a plurality of annular ridges projecting to the back surface side, and dispersedly disposed in an area where these annular ridge portions do not exist. The light guide sheet and the reflective sheet and the top plate disposed on the back side of the light guide sheet are scattered by the plurality of annular ridges and the plurality of protrusions. The back surface of the light guide sheet can be prevented from coming into close contact with the reflection sheet, the top plate, or the like. Therefore, the light guide sheet can prevent the occurrence of uneven brightness due to the incidence of light rays on such a close contact portion, and it is not necessary to provide a separate anti-sticking layer on the back surface. can do. Furthermore, the light guide sheet can accurately prevent the concave portion and the vicinity of the concave portion from being closely contacted by the presence of the annular raised portion around the concave portion. The uneven brightness can be suitably prevented.

  The light guide sheet may be used as a light guide film with an average thickness of 100 μm to 600 μm. Thereby, it can use suitably for the backlight unit of an ultra-thin portable terminal.

The average height from the back surface average surface of the convex portion as (H ₃₎ is preferably 2μm or more 7μm or less. As a result, it is possible to suitably prevent sticking with the reflective sheet or the top plate disposed on the back side, and the surface of the reflective sheet or the top plate is damaged due to contact with the convex portion. It can be suppressed from occurring.

The height ratio (H ₃ / D ₃ ) to the average diameter (D ₃ ) of the average height (H ₃ ) of the convex portion at the back average interface is preferably 0.05 or more and 0.5 or less. Thereby, it is possible to improve the anti-sticking property and the anti-scratching property to the reflection sheet and the top plate surface arranged on the back side.

The average height from the back surface average surface of the annular ridge as _{(H 2)} is preferably 0.1μm or more 6μm or less. Thereby, while being able to improve the sticking prevention property of a recessed part and the recessed part vicinity, the brightness nonuniformity resulting from the light ray scattered by the recessed part can be prevented exactly. Moreover, according to this structure, it can suppress that a damage | wound arises on the surface of a reflective sheet or a top plate resulting from contact | abutting with a cyclic | annular protruding part.

The average height of the annular ridge _{(H 2)} height ratio to the average width _{(W 2)} at the rear surface average surface as _{(H 2} / _W 2) is preferably 0.04 to 0.8. As a result, it is possible to improve the anti-sticking property and the anti-scratching property of the reflection sheet and the top plate disposed on the back surface side.

  The arrangement pattern of the convex portions is formed so that the density gradually increases from one end side to the other end side, and the arrangement pattern of the annular ridges is gradually decreased from one end side to the other end side. It is good to be formed. Thereby, a light ray can be suitably scattered by a recessed part and the surface uniformity of emitted light can be improved. Further, according to such a configuration, it becomes easy to suitably form the arrangement pattern of the convex portions corresponding to the arrangement pattern of the annular raised portions existing around the concave portion, and sticking can be prevented accurately. .

  A polycarbonate-based resin may be included as a main component. Since the polycarbonate-based resin is excellent in transparency and has a high refractive index, total reflection is likely to occur on the front and back surfaces of the light guide sheet, and light can be efficiently propagated. In addition, since the polycarbonate-based resin has heat resistance, deterioration due to heat generation of the light source hardly occurs. Furthermore, since the polycarbonate resin has less water absorption than the acrylic resin or the like, the dimensional stability is high. Therefore, aged deterioration can be suppressed by including a polycarbonate-based resin as a main component.

  An edge light type backlight unit according to the present invention made to solve the above-described problems includes the light guide sheet having the above-described configuration and a light source that irradiates light to an end surface of the light guide sheet.

  Since the backlight unit includes the light guide sheet, it is possible to scatter light incident on the plurality of concave portions formed on the back surface of the light guide sheet to the front surface side. Therefore, the backlight unit forms a plurality of recesses at desired positions on the back surface of the light guide sheet, and scatters incident light by these recesses, thereby emitting light from the surface side substantially uniformly. Can do. Further, the backlight unit includes a plurality of annular ridges that protrude around the back surface, and are scattered in an area where these annular ridges do not exist, as the light guide sheet is provided as a sticking prevention unit. Since the light guide sheet and the reflective sheet or the top plate disposed on the back surface side of the light guide sheet have a plurality of annular ridges and a plurality of protrusions. It is possible to prevent the back surface of the light guide sheet from coming into close contact with the reflective sheet, the top plate, and the like by being scattered at points. Therefore, the backlight unit can prevent light from being incident on such a close contact portion to cause uneven brightness, and it is not necessary to provide a separate anti-sticking layer on the back surface, thus facilitating thinning. can do. Furthermore, the backlight unit can accurately prevent the recesses and the vicinity of the recesses from being in close contact with each other because the annular ridge formed on the back surface of the light guide sheet exists around the recesses. In addition, it is possible to suitably prevent luminance unevenness due to the light beam scattered by the concave portion.

  A portable terminal according to the present invention made to solve the above problems includes the backlight unit having the above configuration in a liquid crystal display unit.

  Since the portable terminal includes the backlight unit having the light guide sheet, the portable terminal can emit light substantially uniformly from the surface of the light guide sheet, and the back surface of the light guide sheet and the light guide sheet. It is possible to prevent sticking with a reflection sheet, a top plate or the like disposed on the side. In addition, since the portable terminal includes the backlight unit including the light guide sheet, it can promote thinning.

  In the present invention, the “surface” in the light guide sheet means the direction in which the light guide sheet emits light, and means the display surface side of the liquid crystal display unit. Further, the “back surface” of the light guide sheet means a surface opposite to the front surface, and means a side opposite to the display surface of the liquid crystal display unit. The “average thickness” is an average value of values measured by the A-2 method of 5.1.2 defined in JIS-K-7130. The “diameter” means an intermediate value between the maximum width of the diameter and the width of the diameter in the direction orthogonal to the maximum width direction. The “width” of the annular ridge means the difference between the outer radius and the inner radius.

  As described above, when the light guide sheet according to the present invention is used in an edge light type backlight unit, luminance unevenness of the liquid crystal display surface is suppressed and a reduction in thickness is achieved. Therefore, the edge-light type backlight unit according to the present invention using the light guide sheet and the portable terminal according to the present invention including the backlight unit can suppress uneven luminance of the liquid crystal display unit and can be thinned. It is done.

1A and 1B are schematic perspective views of a portable terminal according to an embodiment of the present invention, in which FIG. 1A shows a state in which a liquid crystal display unit is opened, and FIG. 2B shows a state in which the liquid crystal display unit is closed. It is typical sectional drawing which shows the edge light type backlight unit of the portable terminal of FIG. It is a typical back view of the light guide sheet of the backlight unit of FIG. It is a typical enlarged view which shows the recessed part and cyclic | annular protruding part of the light guide sheet of FIG. 3, (a) is sectional drawing, (b) is a back view. It is a typical expanded sectional view which shows the convex part of the light-guide sheet | seat of FIG. It is a typical enlarged view which shows the planar view shape of the cyclic | annular protruding part which concerns on other embodiment of this invention. It is typical sectional drawing which shows the conventional edge light type backlight unit.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

[First embodiment]
<Portable terminal>
A portable terminal 1 in FIG. 1 includes an operation unit 2 and a liquid crystal display unit 3 connected to the operation unit 2 so as to be rotatable (openable and closable). In the portable terminal 1, the thickness of the casing (casing) that entirely accommodates the components of the portable terminal 1 (the thickest portion when the liquid crystal display unit 3 is closed) is 21 mm or less, and is extremely thin. It is a laptop computer (hereinafter sometimes referred to as “ultra-thin computer 1”).

  The liquid crystal display unit 3 of the ultra-thin computer 1 includes a liquid crystal panel 4 and an edge light type ultra-thin backlight unit that irradiates light toward the liquid crystal panel 4 from the back side. The liquid crystal panel 4 is held around the back surface, side surfaces, and front surface by a casing 5 for a liquid crystal display portion of the housing. Here, the casing 5 for the liquid crystal display unit includes a top plate 6 disposed on the back surface (and the back surface) of the liquid crystal panel 4, and a surface support member 7 disposed on the surface side around the surface of the liquid crystal panel 4. Have The casing of the ultra-thin computer 1 is provided with a casing 5 for the liquid crystal display section and the casing 5 for the liquid crystal display section so as to be pivotable via a hinge section 8, and a central processing unit (ultra-low voltage CPU). And the like.

  The average thickness of the liquid crystal display unit 3 is not particularly limited as long as the thickness of the housing is in a desired range, but the upper limit of the average thickness of the liquid crystal display unit 3 is preferably 7 mm, more preferably 6 mm, and further 5 mm. preferable. On the other hand, as a minimum of average thickness of liquid crystal display part 3, 2 mm is preferred, 3 mm is more preferred, and 4 mm is still more preferred. If the average thickness of the liquid crystal display unit 3 exceeds the upper limit, it may not be possible to meet the demand for thinning the ultra-thin computer 1. In addition, when the average thickness of the liquid crystal display unit 3 is less than the lower limit, there is a possibility that the strength of the liquid crystal display unit 3 is decreased, the luminance is decreased, or the like.

<Backlight unit>
The backlight unit 11 of FIG. 2 is provided in the liquid crystal display unit 3 of the ultra-thin computer 1. The backlight unit 11 includes a light guide sheet 12, a light source 13 that irradiates light to the end face of the light guide sheet 12, a reflection sheet 14 disposed on the back side of the light guide sheet 12, and the surface of the light guide sheet 12. This is configured as an edge light type backlight unit having an optical sheet 15 disposed on the side.

(Light guide sheet)
The light guide sheet 12 emits light incident from the end face thereof from the surface substantially uniformly. As shown in FIG. 3, the light guide sheet 12 has sticking prevention means on the back surface. Moreover, the light guide sheet 12 has a plurality of recesses 16 that are recessed toward the front surface side on the back surface. The light guide sheet 12 is present around the plurality of recesses 16 as the above-mentioned sticking prevention means, and a plurality of annular ridges 17 projecting to the back surface side, and the areas where these annular ridges 17 do not exist are scattered. And a plurality of convex portions 18 disposed. The light guide sheet 12 is formed in a substantially rectangular shape in plan view, and is formed in a plate shape (non-wedge shape) having a substantially uniform thickness.

  The upper limit of the average thickness of the light guide sheet 12 is preferably 600 μm, more preferably 580 μm, and even more preferably 550 μm. On the other hand, as a minimum of average thickness of light guide sheet 12, 100 micrometers is preferred, 150 micrometers is more preferred, and 200 micrometers is still more preferred. When the average thickness of the light guide sheet 12 exceeds the upper limit, the light guide sheet 12 cannot be used as a thin light guide film desired in an ultra-thin portable terminal, and may not meet the demand for thinning the backlight unit 11. Conversely, when the average thickness of the light guide sheet 12 is less than the above lower limit, the strength of the light guide sheet 12 may be insufficient, and the light from the light source 13 may be sufficiently incident on the light guide sheet 12. It may not be possible.

  The lower limit of the essential light guide distance from the end surface on the light source 13 side in the light guide sheet 12 is preferably 7 cm, more preferably 9 cm, and even more preferably 11 cm. On the other hand, the upper limit of the essential light guide distance from the end surface on the light source 13 side in the light guide sheet 12 is preferably 45 cm, more preferably 43 cm, and even more preferably 41 cm. When the essential light guide distance is less than the lower limit, there is a possibility that it cannot be used for a large terminal other than a small mobile terminal. On the contrary, when the essential light guide distance exceeds the above upper limit, when it is used as a thin light guide film having an average thickness of 600 μm or less, the light guide film is likely to be bent and the light guide property may not be sufficiently obtained. In addition, the essential light guide distance from the end surface of the light guide sheet 12 on the light source 13 side is a light beam emitted from the light source 13 and incident on the end surface of the light guide sheet 12 is propagated from the end surface toward the facing end surface. This is the distance that requires it. Specifically, the essential light guide distance from the end surface on the light source 13 side in the light guide sheet 12 is the distance from the end surface on the light source side of the light guide sheet to the opposite end surface, for example, for a one-side edge light type backlight unit. For the double-sided edge-light type backlight unit, the distance from the light source side end face of the light guide sheet to the central portion is referred to.

As a minimum of the surface area of light guide sheet 12, 150 cm ² is preferred, 180 cm ² is more preferred, and 200 cm ² is still more preferred. On the other hand, the upper limit of the surface area of the light guide sheet 12, preferably 1000 cm ^2, more preferably 950 cm ^2, more preferably 900 cm ^2. When the surface area of the light guide sheet 12 is less than the above lower limit, there is a possibility that it cannot be used for a large terminal other than a small mobile terminal. Conversely, when the surface area of the light guide sheet 12 exceeds the above upper limit, the light guide sheet 12 is likely to be bent when used as a thin light guide film having an average thickness of 600 μm or less, and sufficient light guide properties may not be obtained. .

  Since the light guide sheet 12 is required to transmit light, the light guide sheet 12 is formed mainly of a transparent, particularly colorless and transparent synthetic resin. As a main component of the light guide sheet 12, polycarbonate resin, acrylic resin, polyethylene terephthalate, polyethylene naphthalate, polystyrene, methyl (meth) acrylate-styrene copolymer, polyolefin, cycloolefin polymer, cycloolefin copolymer, cellulose Examples include acetate, weather resistant vinyl chloride, and active energy ray curable resin. Especially, as a main component of a light guide sheet, polycarbonate-type resin or acrylic resin is preferable. Since the polycarbonate resin is excellent in transparency and has a high refractive index, when the light guide sheet 12 contains the polycarbonate resin as a main component, total reflection is likely to occur on the front and back surfaces of the light guide sheet 12, and light rays are efficiently generated. Can be propagated. In addition, since the polycarbonate resin has heat resistance, the light source 13 is unlikely to deteriorate due to heat generation. Furthermore, since the polycarbonate resin has less water absorption than the acrylic resin or the like, the dimensional stability is high. Therefore, the light guide sheet 12 can suppress deterioration over time by including a polycarbonate-based resin as a main component. On the other hand, since acrylic resin has high transparency, it is possible to reduce light wear on the light guide sheet 12. The light guide sheet 12 preferably contains 80% by mass or more of the main component, more preferably 90% by mass or more, and still more preferably 98% or more.

  The polycarbonate resin is not particularly limited, and may be either a linear polycarbonate resin or a branched polycarbonate resin, and a polycarbonate resin including both a linear polycarbonate resin and a branched polycarbonate resin. It may be.

  As the linear polycarbonate-based resin, there is a linear aromatic polycarbonate-based resin produced by a known phosgene method or a melting method, and includes a carbonate component and a diphenol component. Examples of the precursor for introducing the carbonate component include phosgene and diphenyl carbonate. Examples of the diphenol include 2,2-bis (4-hydroxyphenyl) propane, 2,2-bis (3,5-dimethyl-4-hydroxyphenyl) propane, and 1,1-bis (4-hydroxyphenyl). ) Cyclohexane, 1,1-bis (3,5-dimesyl-4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) decane, 1,1-bis (4-hydroxyphenyl) cyclodecane, 1-bis (4-hydroxyphenyl) propane, 1,1-bis (3,5-dimethyl-4-hydroxyphenyl) cyclododecane, 4,4′-dihydroxydiphenyl ether, 4,4′-thiodiphenol, 4, Examples include 4′-dihydroxy-3,3-dichlorodiphenyl ether. These can be used alone or in combination of two or more.

  As the branched polycarbonate resin, there is a polycarbonate resin manufactured using a branching agent. Examples of the branching agent include phloroglucin, trimellitic acid, 1,1,1-tris (4-hydroxyphenyl) ethane, 1,1. , 2-tris (4-hydroxyphenyl) ethane, 1,1,2-tris (4-hydroxyphenyl) propane, 1,1,1-tris (4-hydroxyphenyl) methane, 1,1,1-tris ( 4-hydroxyphenyl) propane, 1,1,1-tris (2-methyl-4-hydroxyphenyl) methane, 1,1,1-tris (2-methyl-4-hydroxyphenyl) ethane, 1,1,1 -Tris (3-methyl-4-hydroxyphenyl) methane, 1,1,1-tris (3-methyl-4-hydroxyphenyl) ethane, 1, , 1-tris (3,5-dimethyl-4-hydroxyphenyl) methane, 1,1,1-tris (3,5-dimethyl-4-hydroxyphenyl) ethane, 1,1,1-tris (3-chloro -4-hydroxyphenyl) methane, 1,1,1-tris (3-chloro-4-hydroxyphenyl) ethane, 1,1,1-tris (3,5-dichloro-4-hydroxyphenyl) methane, 1,1-tris (3,5-dichloro-4-hydroxyphenyl) ethane, 1,1,1-tris (3-bromo-4-hydroxyphenyl) methane, 1,1,1-tris (3-bromo- 4-hydroxyphenyl) ethane, 1,1,1-tris (3,5-dibromo-4-hydroxyphenyl) methane, 1,1,1-tris (3,5-dibromo-4-hydroxyphenyl) ethane Emissions, 4,4'-dihydroxy-2,5-dihydroxydiphenyl ether, and the like.

  The acrylic resin is a resin having a skeleton derived from acrylic acid or methacrylic acid. Examples of acrylic resins include, but are not limited to, poly (meth) acrylic acid esters such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymers, and methyl methacrylate- (meth) acrylic acid esters. Copolymer, methyl methacrylate-acrylic ester- (meth) acrylic acid copolymer, (meth) methyl acrylate-styrene copolymer, polymer having an alicyclic hydrocarbon group (for example, methyl methacrylate- Cyclohexyl methacrylate copolymer, methyl methacrylate- (meth) acrylate norbornyl copolymer), and the like. Among these acrylic resins, poly (meth) acrylic acid C1-6 alkyl such as poly (meth) methyl acrylate is preferable, and methyl methacrylate resin is more preferable.

  Examples of the active energy ray curable resin include an active energy ray curable acrylic resin and an active energy ray curable epoxy resin. As said active energy ray hardening-type resin, what contains at least 1 sort (s) among a photopolymerizable prepolymer, an oligomer, and a monomer, a photopolymerizable initiator, etc. is used, for example.

  Examples of the prepolymer and oligomer in the active energy ray-curable acrylic resin include epoxy (meth) acrylate, urethane (meth) acrylate, polyester (meth) acrylate, and polyether (meth) acrylate.

  Examples of the monomer in the active energy ray-curable acrylic resin include methyl (meth) acrylate, lauryl (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, methoxytriethylene glycol (meth) acrylate, and phenoxyethyl (meth) ) Acrylate, tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxy (meth) acrylate, etc. Acrylate, neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, penta Rithritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) Multifunctional acrylates such as acrylate, tripentaerythritol tri (meth) acrylate, tripentaerythritol hexa (meth) triacrylate, trimethylolpropane (meth) acrylic acid benzoate, trimethylolpropane benzoate, glycerin di (meth) Urethanes such as acrylate hexamethylene diisocyanate, pentaerythritol tri (meth) acrylate, hexamethylene diisocyanate Relate and the like.

  Examples of the photopolymerizable initiator include acetophenone, 2,2-diethoxyacetophenone, p-dimethylacetophenone, p-dimethylaminopropiophenone, benzophenone, benzyl, 2-chlorobenzophenone, 4,4′-dichlorobenzophenone, 4,4′-bisdiethylaminobenzophenone, Michler's ketone, benzyl, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, methyl benzoylformate, p-isopropyl-α-hydroxyisobutylphenone, α-hydroxyisobutylphenone, 2, Carbonyl compounds such as 2-dimethoxy-2-phenylacetophenone and 1-hydroxycyclohexyl phenyl ketone, tetramethylthiuram monosulfide, teto And sulfur compounds such as lamethylthiuram disulfide, thioxanthone, 2-chlorothioxanthone, and 2-methylthioxanthone. These photopolymerization initiators may be used alone or in combination of two or more.

  The light guide sheet 12 is composed of an ultraviolet absorber, a flame retardant, a stabilizer, a lubricant, a processing aid, a plasticizer, an impact resistance aid, a phase difference reducing agent, a matting agent, an antibacterial agent, an antifungal agent, and an antioxidant. Further, optional components such as a release agent and an antistatic agent may be included.

  The concave portion 16 is configured as a light scattering portion that scatters incident light to the surface side. As shown in FIGS. 3 and 4, the recess 16 is formed in a substantially circular shape in plan view. Moreover, the recessed part 16 is formed so that it may reduce in diameter gradually toward the surface side. The three-dimensional shape of the recess 16 is not particularly limited, and may be a hemispherical shape, a substantially hemispherical shape, a conical shape, a truncated cone shape, a cylindrical shape, or the like. Among these, the three-dimensional shape of the recess 16 is preferably a hemisphere. When the three-dimensional shape of the recess 16 is hemispherical, the moldability of the recess 16 can be improved, and the light incident on the recess 16 can be suitably scattered. The arrangement pattern of the recesses 16 is formed so that the density gradually decreases from one end side to the other end side. In particular, the arrangement pattern of the recesses 16 is formed so that the density gradually decreases from the edge on the opposite side to the light source 13 side to the edge on the light source 13 side.

The upper limit of the average depth from the back surface average surface of the recess 16 _{(L 1),} 10μm are preferred, more preferably 9 .mu.m, more preferably 7 [mu] m. On the other hand, the lower limit of the average depth (L ₁ ) from the back surface average interface of the recess 16 is preferably 1 μm, more preferably 2 μm, and even more preferably 4 μm. When the average depth (L ₁ ) from the back surface average interface of the recess 16 exceeds the above upper limit, brightness unevenness may occur, and the light guide sheet 12 may be required to be thinned. On the contrary, when the average depth (L ₁ ) from the back surface average interface of the recess 16 is less than the lower limit, the light scattering effect may not be sufficiently obtained.

The upper limit of the average diameter (D ₁ ) of the recesses 16 at the back average interface is preferably 50 μm, more preferably 40 μm, and even more preferably 30 μm. On the other hand, the lower limit of the average diameter of the recess 16 on the back surface average surface _{(D 1),} 10 [mu] m are preferred, more preferably 12 [mu] m, more preferably 15 [mu] m. When the average diameter (D ₁ ) of the recesses 16 at the back average interface exceeds the above upper limit, uneven brightness may occur. Conversely, when the average diameter (D ₁ ) of the recesses 16 at the back average interface is less than the lower limit, the light scattering effect may not be sufficiently obtained.

  The annular raised portion 17 is integrally formed on the back surface of the light guide sheet 12. The annular raised portion 17 protrudes on the back surface side so as to extend from the lower end of the recessed portion 16. As shown in FIGS. 3 and 4, the annular ridge portion 17 is formed so as to surround the recess 16 in an annular shape in plan view. As a planar view shape of the cyclic | annular protruding part 17, it can prescribe | regulate corresponding to the outer peripheral shape of the recessed part 16, for example, and an annular | circular shape, a polygonal cyclic | annular form, etc. are possible. Moreover, as a planar view shape of the cyclic | annular protruding part 17, it is not necessary to surround the outer periphery of the recessed part 16 completely, for example, as shown in FIG. 6, you may surround the outer periphery of the recessed part 16 partially. . Especially, as a planar view shape of the cyclic | annular protruding part 17, an annular shape is preferable. The light guide sheet 12 can accurately prevent the concave portion 16 and the vicinity of the concave portion 16 from coming into close contact with the reflection sheet 14 and the like disposed on the back surface side by forming the annular raised portion 17 in an annular shape. It is possible to suitably prevent luminance unevenness due to the light beam scattered by the recess 16. Further, the annular ridge portion 17 has a shape with a rounded tip. The light guide sheet 12 can enhance the scratch resistance against the reflection sheet 14 and the like disposed on the back surface side by rounding the tip of the annular raised portion 17.

  The annular ridge 17 may be formed continuously with the recess 16. Specifically, it is preferable that the inner periphery of the annular ridge 17 and the periphery of the recess 16 substantially coincide. Further, it is preferable that the inner side surface of the annular ridge 17 and the inner surface of the recess 16 are smoothly continuous. By forming the annular raised portion 17 smoothly and continuously in the concave portion 16, it is possible to accurately prevent luminance unevenness of light scattered by the concave portion 16 and emitted from the surface of the light guide sheet 12. Here, “circumference” means a curve formed by a three-dimensional shape (recess 16 or annular ridge 17) intersecting the back average interface of the light guide sheet 12. The “inner circumference” refers to the circumference of the inner side surface of the annular ridge 17.

  The arrangement pattern of the annular ridges 17 is formed so that the density gradually decreases from one end side to the other end side. Particularly, the arrangement pattern of the annular ridges 17 is formed such that the density gradually decreases from the edge on the opposite side to the light source 13 side to the edge on the light source 13 side.

The upper limit of the average height (H ₂ ) from the back surface average interface of the annular ridge 17 is preferably 6 μm, more preferably 5 μm, and even more preferably 4 μm. On the other hand, the lower limit of the average height from the back surface average surface of the annular ridge 17 _{(H 2),} 0.1μm are preferred, more preferably 0.3 [mu] m, more preferably 0.6 .mu.m. When the average height (H ₂ ) from the back average interface of the annular ridge 17 exceeds the upper limit, the surface such as the reflection sheet 14 disposed on the back side due to the contact with the annular ridge 17 is formed. There is a risk of scratching. Conversely, if the average height (H ₂ ) from the back surface average interface of the annular ridge 17 is less than the lower limit, sticking may not be prevented accurately. On the other hand, when the average height (H ₂ ) from the back surface average interface of the annular ridge portion 17 is within the above range, the anti-sticking property and the anti-scratch property of the reflection sheet 14 or the like disposed on the back surface side. In particular, luminance unevenness caused by the light beam scattered by the recess 16 can be accurately prevented.

The upper limit of the average width (W ₂ ) of the annular ridges 17 at the back average interface is preferably 15 μm, more preferably 12 μm, and even more preferably 10 μm. On the other hand, the lower limit of the average width (W ₂ ) of the annular ridges 17 at the back average interface is preferably 1 μm, more preferably 3 μm, and even more preferably 5 μm. When the average width (W ₂ ) of the annular ridges 17 at the back average interface exceeds the above upper limit, the area where the annular ridges 17 are in contact with the reflection sheet 14 and the like is increased, which may cause uneven brightness. Conversely, when the average width (W ₂ ) of the annular ridges 17 at the back average interface is less than the lower limit, the surface of the reflective sheet 14 and the like disposed on the back side due to contact with the annular ridges 17. May be damaged.

The upper limit of the height ratio (H ₂ / W ₂ ) to the average width (W ₂ ) at the back side interface of the average height (H ₂ ) from the back side average interface of the annular ridge 17 is preferably 0.8, 0.6 is more preferable and 0.4 is more preferable. On the other hand, as a lower limit of the height ratio (H ₂ / W ₂ ) to the average width (W ₂ ) at the back side interface of the average height (H ₂ ) from the back side average interface of the annular ridge 17, 0.04 is set. Preferably, 0.06 is more preferable, and 0.08 is even more preferable. When the height ratio (H ₂ / W ₂ ) exceeds the upper limit, the surface of the reflection sheet 14 or the like disposed on the back surface may be damaged. Conversely, if the height ratio (H ₂ / W ₂ ) is less than the lower limit, sticking may not be prevented accurately.

The upper limit of the width ratio (W ₂ / D ₁ ) of the average width (W ₂ ) of the annular ridge 17 to the average diameter (D ₁ ) of the recess 16 is preferably 1, more preferably 0.8, 0.6 Is more preferable. On the other hand, the lower limit of the width ratio (W ₂ / D ₁ ) of the average width (W ₂ ) of the annular ridge 17 to the average diameter (D ₁ ) of the recess 16 is preferably 0.1 and more preferably 0.2. 0.3 is more preferable. When the width ratio (W ₂ / D ₁ ) exceeds the upper limit, the area where the annular raised portion 17 is in contact with the reflection sheet 14 and the like is increased, and there is a risk that luminance unevenness occurs. On the contrary, when the width ratio (W ₂ / D ₁ ) is less than the lower limit, the sticking prevention effect may not be sufficiently obtained.

  The convex portion 18 is integrally formed on the back surface of the light guide sheet 12. The convex portion 18 is formed in a substantially circular shape in plan view. Moreover, the convex part 18 is made into the shape where the front-end | tip was rounded, as shown in FIG. Although the three-dimensional shape of the convex part 18 is not specifically limited, A hemispherical shape is preferable. Since the three-dimensional shape of the convex portion 18 is hemispherical, the moldability of the convex portion 18 can be improved, and the scratch resistance to the reflection sheet 14 and the like disposed on the back surface side can be improved. . The arrangement pattern of the convex portions 18 is formed so that the density gradually increases from one end side to the other end side. In particular, the arrangement pattern of the protrusions 18 is formed such that the density gradually increases from the edge on the side opposite to the light source 13 to the edge on the light source 13 side.

The upper limit of the average height from the back surface average surface of the convex portion 18 _{(H 3),} 7μm are preferred, more preferably 6 [mu] m, more preferably 5 [mu] m. On the other hand, the lower limit of the average height from the back surface average surface of the convex portion 18 _{(H 3),} 2μm are preferred, more preferably 3 [mu] m, even more preferably 4 [mu] m. When the average height (H ₃ ) from the back surface average interface of the convex portion 18 exceeds the above upper limit, the surface of the reflective sheet 14 or the like disposed on the back surface is damaged due to contact with the convex portion 18. May occur. Conversely, if the average height (H ₃ ) from the back surface average interface of the convex portion 18 is less than the lower limit, sticking may not be prevented accurately.

The upper limit of the height ratio (H ₃ / D ₃ ) to the average diameter (D ₃ ) of the average height (H ₃ ) of the convex portion 18 at the back average interface is preferably 0.5, more preferably 0.3. 0.2 is more preferable. On the other hand, the lower limit of the height ratio (H ₃ / D ₃ ) to the average diameter (D ₃ ) of the average height (H ₃ ) of the convex portion 18 at the back surface average interface is preferably 0.05 and 0.07. More preferably, 0.1 is even more preferable. When the height ratio (H ₃ / D ₃ ) exceeds the upper limit, the surface of the reflection sheet 14 or the like disposed on the back surface may be damaged. Conversely, if the height ratio (H ₃ / D ₃ ) is less than the lower limit, sticking may not be prevented accurately.

The upper limit of the average height of the projections 18 _{(H 3)} height ratio average height of the annular ridge 17 for _{(H 2)} of _{(H 3 / H 2),} 7 , more preferably 5, 3 Is more preferable. On the other hand, the lower limit of the average height of the projections 18 _{(H 3)} height ratio average height of the annular ridge 17 for _{(H 2)} of _(H 3 / _{H 2),} is preferably 1/2, 2 / 3 is more preferable, and 1 is more preferable. If the height ratio _(H 3 / H ₂₎ is outside the above range, a difference of the average height of the projections 18 and _{(H 3)} the average height of the annular ridge 17 and the _{(H 2)} is increased, the whole There is a possibility that the anti-sticking property as a sufficient amount may not be obtained. On the other hand, when the height ratio (H ₃ / H ₂ ) is within the above range, the overall anti-sticking property is improved, and in particular, the anti-sticking property in the vicinity of the recess 16 and the recess 16 is improved. Therefore, uneven brightness can be effectively prevented.

The upper limit of the total the density of the annular ridge 17 and the convex portion 18 on the back surface of the light guide sheet 12 is preferably 500 / mm ^2, more preferably 400 / mm ^2, more preferably 300 pieces / mm ^2. On the other hand, the lower limit of the total the density of the annular ridge 17 and the convex portion 18 on the back surface of the light guide sheet 12, 40 / mm ^2, more preferably from 60 / mm ^2, further 80 pieces / mm ² preferable. When the total existence density of the annular ridges 17 and the protrusions 18 on the back surface of the light guide sheet 12 exceeds the upper limit, there is a high possibility that the surface of the reflection sheet 14 and the like disposed on the back surface will be damaged. On the other hand, when the total density of the annular ridges 17 and the protrusions 18 on the back surface of the light guide sheet 12 is less than the lower limit, the sticking prevention property may not be sufficiently obtained. In addition, the total density of the annular ridges 17 and the protrusions 18 is obtained by measuring the number of the annular ridges 17 and the protrusions 18 in the field of view that is magnified 1000 times with a laser microscope, and using the visual field area. The calculated value. In addition, when there are a plurality of annular ridges 17 surrounding one recess 16, these annular ridges 17 are calculated as one.

(Reflective sheet)
The reflection sheet 14 is disposed on the back surface side of the light guide sheet 12 so as to come into contact with the plurality of annular ridges 17 and the plurality of protrusions 18 formed on the back surface of the light guide sheet 12. The reflection sheet 14 reflects the light beam emitted from the back surface side of the light guide sheet 12 to the front surface side. The reflection sheet 14 is made by depositing a metal such as aluminum or silver on the surface of a white sheet in which a filler is dispersed in a base resin such as a polyester resin or a film formed from a polyester resin or the like. Examples thereof include a mirror surface sheet with improved reflectivity.

(light source)
The light source 13 is disposed such that the irradiation surface faces (or abuts) the end surface of the light guide sheet 12. Various light sources 13 can be used. For example, a light emitting diode (LED) can be used. Specifically, a light source 13 in which a plurality of light emitting diodes are disposed along the end surface of the light guide sheet 12 can be used.

(Optical sheet)
The optical sheet 15 has optical functions such as diffusion and refraction with respect to light rays incident from the back side. Examples of the optical sheet 15 include a light diffusion sheet having a light diffusion function and a prism sheet having a refraction function toward the normal direction.

<Method for producing light guide sheet>
As a manufacturing method of the light guide sheet 12, for example, (a) a plurality of recesses, a plurality of annular ridges around the recesses, and a region where these annular ridges do not exist are arranged in a scattered manner. An injection molding method in which a forming material for a molten light guide sheet is injected into a mold having a reversed shape of a plurality of convex portions,
(B) A method of re-heating a sheet body made of a material for forming a light guide sheet and sandwiching it between a mold having the inverted shape and a metal plate or a roll to transfer the shape,
(C) Forming a sheet body by supplying a forming material for a light guide sheet in a molten state to a T die and extruding the forming material from the extruder and the T die, and forming the sheet body with the above inverted shape A method using an extrusion molding method in which the shape is transferred by pressing between a metal plate or a roll, and
(D) A casting method (solution casting method) in which a solution (dope) in which a material for forming a light guide sheet is melted in a solvent and made fluid is poured into a mold having the above inverted shape, and then the solvent is evaporated.
(E) A method of filling an uncured active energy ray-curable resin into a mold having the above inverted shape and irradiating active energy rays such as ultraviolet rays,
(F) A plurality of recesses and annular ridges are formed by a method similar to the above (a) to (e), using a mold having only a plurality of recesses and a reverse shape of the plurality of annular ridges existing around the recesses. And forming a plurality of convex portions by a known printing method such as screen printing or ink jet printing in a region where the plurality of annular ridges on one surface of the sheet body do not exist. Method,
(G) A plurality of recesses and annular ridges are formed by a method similar to the above (a) to (e) using a molding die having only a plurality of recesses and a reverse shape of the plurality of annular ridges existing around the recesses. Forming a plurality of convex portions using a photolithography method and an etching method in a region where the plurality of annular ridges on one surface of the sheet body are not present,
(H) A plurality of concave portions and a plurality of annular ridges existing around the concave portions by cutting using one of a surface of a sheet body made of a light guide sheet forming material using a carbide tool, a diamond tool, an end mill, or the like. A method of forming a plurality of convex portions in a scattered manner using the above-described known printing method, photolithography method and etching method in a region where the plurality of annular ridges on one surface of the sheet body do not exist Etc.

<Molding mold>
As described above, as the mold, (i) a plurality of concave portions 16 arranged in a predetermined pattern, a plurality of annular ridges 17 around these concave portions 16 and the absence of these annular ridges 17 exist. A mold having a reverse shape of a plurality of convex portions 18 arranged in a scattered manner in the region, or (ii) a plurality of concave portions 16 arranged in a predetermined pattern, and present around these concave portions 16 A mold having only the inverted shape of the plurality of annular ridges 17 on the surface is used.

  Although it does not specifically limit as a forming material of the said shaping | molding die, For example, metals, such as nickel, gold | metal | money, silver, copper, and aluminum, are mentioned.

(Prototype manufacturing method)
The mold is manufactured using a prototype having a plurality of concave portions arranged in a predetermined pattern and a plurality of annular ridges around the plurality of concave portions on the surface.

As a method for producing the prototype, for example, (A) a method of simultaneously forming the plurality of recesses and a plurality of annular ridges by performing laser irradiation on the surface of the base material forming the prototype,
(B) A method of simultaneously forming the plurality of concave portions and the plurality of annular ridges by cutting the surface of the base material forming the prototype using a cemented carbide tool, a diamond tool, an end mill, or the like.

  Examples of the original forming material manufactured by the method (A) include metals such as SUS. On the other hand, examples of the original forming material manufactured by the method (B) include relatively hard synthetic resins such as polycarbonate resins and acrylic resins, in addition to metals such as SUS.

  When the laser irradiation is performed, the laser irradiation portion is melted. As a result, when the recess is formed, the molten material is deposited around the recess to form an annular ridge. On the other hand, when the above-described cutting is performed, the cut portion of the base material is deposited around the concave portion formed by the cutting to form an annular ridge. The depth and diameter of the recess, the height, width, shape, and the like of the annular raised portion are adjusted by laser irradiation, cutting strength, angle, diameter, and the like.

  Further, the laser irradiated to form a plurality of recesses and a plurality of annular ridges on the prototype surface is not particularly limited. For example, carbon dioxide laser, carbon monoxide laser, semiconductor laser, YAG (yttrium)・ Aluminum garnet) Laser etc. are mentioned. Among these, a carbon dioxide laser having a wavelength of 9.3 μm to 10.6 μm is suitable for forming a fine shape. Examples of the carbon dioxide laser include a lateral atmospheric pressure excitation (TEA) type, a continuous oscillation type, and a pulse oscillation type.

(Manufacturing method of mold)
As a method for manufacturing the mold of (ii) above, an inverted shape of the prototype is formed on the surface of the prototype having a plurality of recesses arranged in a predetermined pattern and a plurality of annular ridges present around the recesses. A step (S1) of forming a plating layer having a surface thereof by electroforming, and a step (S2) of peeling the plating layer from the prototype. In addition, as a method for manufacturing the mold of the above (i), a plurality of protrusions disposed on the surface of the plating layer peeled off from the original mold in a region where the plurality of annular ridges do not exist. A step (S3) of forming an inverted shape of the part.

  The plating layer forming step (S1) is performed, for example, by depositing metallic nickel as an anode and energizing the prototype as a cathode and depositing a plating layer on the surface of the prototype in a plating bath.

  The plating layer peeling step (S2) is performed by peeling the plating layer deposited on the surface of the original pattern in the plating layer forming step (S1) from the original pattern. In addition, as a plating layer peeling process (S2), in order to raise the intensity | strength of the plating layer peeled from the said original pattern, you may have further the process of reinforcing this plating layer with a reinforcement member.

  In the inversion shape forming step (S3) of the convex portion, the surface of the plating layer formed in the plating layer peeling step (S2) is irradiated with a laser to the region where the plurality of annular ridges do not exist, or a carbide tool, diamond It is performed by forming the inverted shape of a plurality of convex portions by cutting using a cutting tool, an end mill or the like. The plating layer is formed as a forming die by forming a plurality of inverted shapes of the convex portions on the surface of the plating layer in the reverse shape forming step (S3) of the convex portions. Note that a release treatment layer may be formed on the surface of the mold. As a method for forming such a release treatment layer, for example, a method of forming a film by depositing titanium nitride (TiN) on the surface of the mold by sputtering is exemplified. By having the mold release treatment layer on the surface of the molding die, it is possible to prevent the resin sheet material from coming into close contact with the molding die.

<Advantages>
Since the light guide sheet 12 has a plurality of concave portions 16 that are recessed toward the front surface side on the back surface, the light incident on the concave portions 16 can be scattered on the front surface side. Therefore, the light guide sheet 12 can emit light from the surface side substantially uniformly by forming a plurality of concave portions 16 at desired positions and scattering incident light by the concave portions 16. In addition, the light guide sheet 12 is present around the plurality of recesses 16 as sticking prevention means, and a plurality of annular ridges 17 projecting to the back side, and scattered points in areas where these annular ridges 17 do not exist. Since the light guide sheet 12 and the reflective sheet 14 provided on the back surface side of the light guide sheet 12 have a plurality of annular ridges 17 and a plurality of It is possible to prevent the back surface of the light guide sheet 12 and the reflection sheet 14 and the like from coming into close contact with each other by the convex portions 18. Therefore, the light guide sheet 12 can prevent the occurrence of uneven brightness due to the incidence of light rays on such a close contact portion, and it is not necessary to provide a separate anti-sticking layer on the back surface. Can be promoted. Further, since the light guide sheet 12 can prevent the concave portions 16 and the vicinity of the concave portions 16 from being closely contacted with each other due to the presence of the annular raised portions 17 around the concave portions 16, the light guide sheet 12 is scattered by the concave portions 16. It is possible to suitably prevent luminance unevenness caused by the light rays.

  The light guide sheet 12 is formed such that the arrangement pattern of the convex portions 18 gradually increases in density from one end side to the other end side, and the arrangement pattern of the annular ridges 17 gradually increases from one end side to the other end side. Therefore, it is possible to scatter the light beam suitably by the concave portion 16 to improve the surface uniformity of the emitted light, and to arrange the arrangement pattern of the convex portion 18 around the concave portion 16. It becomes easy to form suitably according to the arrangement pattern of the existing annular ridges 17, and sticking can be prevented accurately. In particular, the light guide sheet 12 is formed such that the arrangement pattern of the recesses 16 and the annular ridges 17 gradually decreases in density from the edge on the opposite side to the light source 13 side to the edge on the light source 13 side. Therefore, the light scattering rate in the vicinity of the light source 13 is suppressed, the light scattering rate is improved as the distance from the light source 13 increases, and uneven brightness due to scattered light is accurately prevented, and the surface uniformity of emitted light is effectively enhanced. be able to.

  Since the backlight unit 11 includes the light guide sheet 12, it can scatter light rays incident on the plurality of concave portions 16 formed on the back surface of the light guide sheet 12 to the front surface side. Therefore, the backlight unit 11 forms a plurality of recesses 16 at desired positions on the back surface of the light guide sheet 12, and scatters incident light by these recesses 16, so that light rays are substantially uniform from the front surface side. Can be emitted. Further, the backlight unit 11 includes a plurality of annular ridges 17 that are present around the plurality of recesses 16 and project to the back surface side as a means for preventing the sticking of the light guide sheet 12, and the annular ridges 17. Since the light guide sheet 12 and the reflective sheet 14 provided on the back surface side of the light guide sheet 12 have a plurality of annular shapes, the light guide sheet 12 has a plurality of convex portions 18 arranged in a scattered manner in a non-existing region. The raised portions 17 and the plurality of convex portions 18 are in contact in a scattered manner, and the back surface of the light guide sheet 12 and the reflection sheet 14 and the like can be prevented from coming into close contact with each other. Accordingly, the backlight unit 11 can prevent light from being incident on such a close contact portion to cause uneven brightness, and it is not necessary to provide a separate anti-sticking layer on the back surface of the light guide sheet 12. Therefore, reduction in thickness can be promoted. Further, the backlight unit 11 accurately prevents the concave portion 16 and the vicinity of the concave portion 16 from being in close contact with each other because the annular ridge portion 17 formed on the back surface of the light guide sheet 12 exists around the concave portion 16. Therefore, luminance unevenness due to the light scattered by the recess 16 can be suitably prevented.

  Since the portable terminal 1 includes the backlight unit 11 having the light guide sheet 12, the light can be emitted from the surface of the light guide sheet 12 substantially uniformly as described above. Sticking between the light sheet 12 and the reflective sheet 14 disposed on the back side of the light guide sheet 12 can be prevented. Moreover, since the said portable terminal 1 is provided with the said backlight unit 11 which has the said light guide sheet 12, it can accelerate | stimulate thickness reduction.

  The light guide sheet manufacturing method has a plurality of recesses 16 recessed on the front surface side on the back surface, and a plurality of annular ridges 17 that exist around the plurality of recesses 16 and protrude to the back surface side as sticking prevention means. And the said light guide sheet 12 which has the some convex part 18 arrange | positioned in a scattered manner in the area | region where these cyclic | annular protruding parts 17 do not exist can be manufactured easily and reliably.

  Since the molding die includes a plurality of concave portions arranged in a predetermined pattern and a reverse shape of a plurality of annular ridges existing around the concave portions on the surface, the molding die is a mold for manufacturing the light guide sheet 12. Preferably used.

  The mold manufacturing method can easily and surely manufacture a mold having a plurality of recesses arranged in a predetermined pattern and a plurality of annular ridges present around the recesses on the surface. it can.

  Since the prototype has a plurality of recesses arranged in a predetermined pattern and a plurality of annular ridges around the plurality of recesses on the surface, a predetermined shape is provided on the surface of a mold manufactured using the prototype. It is possible to easily and reliably form a plurality of concave portions arranged in a pattern and a plurality of annular ridges around the plurality of concave portions.

[Other Embodiments]
In addition, the light guide sheet, backlight unit, and portable terminal according to the present invention can be implemented in variously modified and improved modes in addition to the above mode. For example, the light guide sheet is not necessarily a single layer structure as long as the back surface side has a predetermined shape, and may be a multilayer structure having two or more layers. In addition, the light guide sheet may have a surface coated with a hard coat layer or the like. Furthermore, the light guide sheet may have a lenticular shape or the like on the surface so that the emitted light can be controlled. In addition, the light guide sheet has a plurality of notches such as a V shape and a trapezoidal shape formed continuously or at predetermined intervals on the end surface on the light source side in order to suppress luminance unevenness in the vicinity of the light source. You may have. The arrangement pattern of the convex portions and the annular raised portions is not particularly limited. For example, when the light guide sheet is used in a double-sided edge-light type backlight unit in which the light source is provided on both side edges facing each other, the plurality of convex parts are arranged on both sides. It may be arranged so that the density gradually decreases from the edge toward the center, and the plurality of annular ridges may be arranged so that the density gradually increases from both side edges toward the center.

  As a method for producing the light guide sheet, in addition to the method described above, for example, a method using a mold having only the inverted shapes of the plurality of recesses arranged in a predetermined pattern on the surface can be used. As a method of using such a mold, for example, a plurality of concave portions are formed on one surface of a sheet body made of a material for forming a light guide sheet using the mold, and the plurality of concave portions are formed by a photolithography method and an etching method. There is a method in which a plurality of annular ridges are formed around the recesses, and a plurality of convex portions are formed in a scattered manner in a region where these annular ridges do not exist by a known printing method. In addition, as a method of forming the inverted shape of the plurality of recesses in the molding die, for example, a prototype having a plurality of recesses on the surface is created by using, for example, a photolithography method and an etching method, and further, by electroforming using this prototype The method of manufacturing a shaping | molding die is mentioned.

  Further, the molding die is not necessarily produced by electroforming using a prototype, and may be produced directly using, for example, a photolithography method, an etching method, and the known printing method. In this case, a relatively hard synthetic resin such as a polycarbonate resin or an acrylic resin can also be used as a forming material of the mold.

  The light guide sheet is manufactured using an extrusion molding method in which a forming material of a molten light guide sheet is supplied to a T die and the forming material is extruded from the extruder and the T die to form a sheet body. One of the pair of pressing rolls sandwiching the extruded sheet body is scattered in a plurality of recesses, a plurality of annular ridges around the recesses, and a region where these annular ridges do not exist. You may use as a shaping | molding die which has the inversion shape of a some convex part. As a method of forming such a reverse shape on the surface of one pressing roll, for example, a plurality of recesses arranged in a predetermined pattern, a plurality of annular ridges existing around these recesses, and the annular ridges A method of laminating on the surface of the pressing roll a plating layer having a plurality of convex reversal shapes arranged on the surface in a scattered manner in a non-existing region, or using laser or cutting the above reversal shape on the surface of the pressing roll The method of forming is mentioned. In this case, for example, a lenticular shape may be formed on the surface of the light guide sheet by forming an inverted shape of the lenticular shape on the surface of the other pressing roll.

  The edge light type backlight unit does not necessarily have a reflective sheet disposed on the back side of the light guide sheet. For example, the surface of the top plate disposed on the back side of the light guide sheet It may be formed as a polished reflective surface, and this reflective surface may be used in place of the reflective sheet. In the edge light type backlight unit, the top plate surface is formed as the outermost back surface of the backlight unit in this way, so that the thinning can be promoted except for the reflection sheet.

  Examples of the portable terminal include various portable terminals such as a mobile phone terminal such as a smartphone and a portable information terminal such as a tablet terminal in addition to the laptop computer as described above. Further, the light guide sheet and the edge-light type backlight unit include various liquid crystal displays such as a laptop computer having a casing (casing) thickness of more than 21 mm, a desktop computer, and a thin TV, in addition to the portable terminal. It can be used in the device.

  As described above, the light guide sheet, the backlight unit, and the portable terminal of the present invention include the light guide sheet and the reflective sheet and the top plate that are disposed on the back side of the light guide sheet without providing a separate anti-sticking layer. Therefore, it is suitably used for a liquid crystal display device in which luminance unevenness is prevented and thinning is promoted.

DESCRIPTION OF SYMBOLS 1 Portable terminal, ultra-thin computer 2 Operation part 3 Liquid crystal display part 4 Liquid crystal panel 5 Casing for liquid crystal display part 6 Top plate 7 Surface support member 8 Hinge part 9 Casing for operation part 11 Backlight unit 12 Light guide sheet 13 Light source 14 Reflective sheet 15 Optical sheet 16 Concave portion 17 Ring-shaped raised portion 18 Convex portion 110 Edge light type backlight unit 111 Light guide sheet 112 Optical sheet 115 Reflective sheet 116 Top plate 117 Light source 210 Edge light type backlight unit 211 Light guide sheet 212 Optical Sheet 216 Top plate 217 Light source

Claims (10)

A light guide film that is used for an edge light type backlight unit and has flexibility,
Provided with anti-sticking means on the back
It has a plurality of recesses that sink into the front side on the back side,
As the sticking prevention means, there are a plurality of ridges that exist around the plurality of recesses and project to the back surface side, and a plurality of projections that are scattered in areas where these ridges do not exist. A light guide film comprising:   The light guide film according to claim 1, having an average thickness of 100 μm to 600 μm. The light guide film according to claim 1 or 2, wherein an average height (H ₃ ) from the back surface average interface of the convex portion is 2 µm or more and 7 µm or less. Claim 1 height ratio to the average diameter of the rear surface average surface of average height of the convex portions _{(H 3) (D 3)} (H 3 / D 3) is 0.05 to 0.5, claims The light guide film of Claim 2 or Claim 3. 5. The light guide film according to claim 1, wherein an average height (H ₂ ) from the back surface average interface of the raised portion is 0.1 μm or more and 6 μm or less. The height ratio (H ₂ / W ₂ ) to the average width (W ₂ ) of the average height (H ₂ ) of the raised portion at the back average interface is 0.04 or more and 0.8 or less. 6. The light guide film according to any one of 5 above.   The convex portion arrangement pattern is formed so that the density gradually increases from one end side to the other end side, and the raised portion arrangement pattern is formed so that the density gradually decreases from one end side to the other end side. The light guide film according to any one of claims 1 to 6.   The light guide film according to claim 1, comprising a polycarbonate-based resin as a main component. The light guide film according to any one of claims 1 to 8,
An edge light type backlight unit comprising: a light source for irradiating light on an end face of the light guide film. A portable terminal comprising the backlight unit according to claim 9 in a liquid crystal display unit.

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