JP2014164133A - Light guide film, ultra-slim liquid crystal backlight unit, and portable computer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light guide film that suppresses luminance unevenness of a liquid crystal display surface and achieves reduction in thickness, when used for an ultra-slim liquid crystal backlight unit of an ultra-slim portable computer.SOLUTION: A light guide film 12 is a light guide film for an ultra-slim liquid crystal backlight unit substantially uniformly emitting light rays incident from an edge face from a front face. The light guide film comprises a light guide layer 19 whose main component is polycarbonate resin and a hard coat layer 22 formed on the surface side of the light guide layer 19, and has the average thickness of 600 μm or less. An absolute value (|n-n|) of the difference between a refractive index (n) of the light guide layer 19 and a refractive index (n) of the hard coat layer 22 is preferably 0.1 or less.

Description

  The present invention relates to a light guide film, an ultra-thin liquid crystal backlight unit, and a portable computer.

  In the liquid crystal display device, a backlight system in which a liquid crystal layer is illuminated from the back side 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. As shown in FIG. 9, the edge light type backlight unit 111 is generally placed on the inner surface side of the top plate 114 which is the casing on the rearmost surface of the liquid crystal display unit, and is arranged on the surface of the top plate 114. Reflection sheet 113, a light guide plate 112 disposed on the surface of the reflection sheet 113, and a light source 115 that irradiates light toward an end surface of the light guide plate 112 (Japanese Patent Laid-Open No. 2010-177130). See the official gazette). In the edge light type backlight unit 111, the light emitted from the light source 115 enters the end surface of the light guide plate 112, and the light incident on the light guide plate 112 propagates through the light guide plate 112, The light is emitted from the surface of the guide plate 112. The light beam emitted from the back surface of the light guide plate 112 is reflected by the reflection sheet 113 and is incident on the light guide plate 112 again to reduce the loss of the light beam.

  A portable computer 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 the ultra-thin laptop computer whose ultrathin laptop computer whose thickness is 21 mm or less, called Ultrabook (registered trademark), the thickness of the liquid crystal display unit is desired to be about 4 mm to 5 mm. The edge light type backlight unit incorporated in the liquid crystal display unit is required to be thinner.

  For this reason, the light guide film used in such an ultra-thin portable computer is also required to be thin in accordance with the thinning of the liquid crystal display portion. Specifically, such a light guide film is required. The thickness is preferably about 600 μm or less. As a material for forming such a light guide film, a polycarbonate resin having excellent light guiding properties and a certain strength is used.

JP 2010-177130 A

  However, when another optical sheet is laminated on the surface of the ultra-thin light guide film having an average thickness of 600 μm or less as described above, the light guide film is scratched by the sticking of the light guide film and the optical sheet. May occur. Such a scratch on the surface of the light guide film is likely to cause uneven brightness in the ultra-thin light guide film as compared with a relatively thick light guide plate. In other words, an ultra-thin light guide film has a higher number of reflections on the front and back surfaces of the light guide film during light guiding than a relatively thick light guide plate, so the light beam being guided enters the scratches. This is likely to cause uneven brightness.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide uneven luminance on a liquid crystal display surface when used in an ultra-thin liquid crystal backlight unit of an ultra-thin portable computer. An object of the present invention is to provide a light guide film that is suppressed and thinned. Another object of the present invention is to provide an ultra-thin liquid crystal backlight unit and a portable computer in which luminance unevenness is suppressed and the thickness can be reduced.

The light guide film according to the present invention made to solve the above problems is
A light guide film for an ultra-thin liquid crystal backlight unit that emits light incident from the end face substantially uniformly from the surface,
A light guide layer mainly composed of polycarbonate resin;
A hard coat layer formed on the surface side of the light guide layer,
The average thickness is 600 μm or less.

  The light guide film is prevented from being scratched on the surface of the light guide layer by the hard coat layer formed on the surface side of the light guide layer. Therefore, the light guide film is provided on the surface of the light guide layer even when another optical sheet such as a light diffusion sheet is disposed on the surface side and the back surface of the optical sheet and the surface of the light guide film are rubbed. The light guide film can be prevented from being scratched, whereby the light guide film is formed with an average thickness as thin as 600 μm or less, while obtaining a sufficient light guide by a light guide layer mainly composed of a polycarbonate-based resin, It is possible to prevent the occurrence of uneven brightness due to scratches on the surface side. In addition, since the light guide layer has a polycarbonate resin as a main component, the polycarbonate resin has less water absorption than an acrylic resin and the light guide film has high dimensional stability.

The light guide film may have a refractive index (n ₁ ) of the light guide layer larger than a refractive index (n ₂ ) of the hard coat layer, and the light guide layer has a wavy fine modulation structure on the surface. As described above, the refractive index (n ₁ ) of the light guide layer is larger than the refractive index (n ₂ ) of the hard coat layer, and the light guide layer has a wave-like fine modulation structure on the surface, thereby guiding light. Further, the diffusibility or the light exiting property is promoted, and even if the thickness is 600 μm or less, it is possible to suppress a decrease in luminance and uniformity of the light emitted from the surface of the light guide film. Specifically, when the ridge line direction and the light incident direction in the fine modulation structure of the light guide layer are installed substantially parallel, the transmitted light in the light guide layer is condensed on the ridge line direction side by the wavy fine modulation structure. Since the light beam emitted from the surface of the light guide layer is slightly diffused in the direction perpendicular to the ridge line direction due to refraction by the wavy fine modulation structure, Light diffusibility can be improved. On the other hand, when the ridge line direction and the incident direction of the light beam in the fine modulation structure of the light guide layer are set substantially perpendicular, the incident angle of the light beam on the surface of the light guide layer varies due to the wavy fine modulation structure. The light output from the surface of the light guide layer can be improved.

The light guide film has an absolute value (| n ₁ −n ₂ |) of a difference between the refractive index (n ₁ ) of the light guide layer and the refractive index (n ₂ ) of the hard coat layer of 0.1 or less. There should be. Thereby, emission from the light guide layer to the hard coat layer and emission from the hard coat layer to the surface side are suitably performed, and light can be suitably emitted from the light guide film surface.

The light guide film includes an aromatic polycarbonate resin in which the light guide layer is a main component and an antioxidant, and the content of the antioxidant is 0.000 parts by mass with respect to 100 parts by mass of the aromatic polycarbonate resin. The weight average molecular weight of the aromatic polycarbonate-based resin is 2.0 × 10 ⁴ or more and 5.0 × 10 ⁴ or less, and was measured by gel permeation chromatography. The ratio (Mw / Mn) of polystyrene-equivalent weight average molecular weight and number average molecular weight of the aromatic polycarbonate resin is preferably 1.0 or more and 2.5 or less. Thus, the viscosity average molecular weight of the aromatic polycarbonate resin and the ratio (Mw / Mn) of the polystyrene-converted weight average molecular weight and number average molecular weight of the aromatic polycarbonate resin measured by gel permeation chromatography are in the above range. By being inside, the light transmittance and mechanical strength after shaping | molding can be improved together, improving the extrusion moldability in the said light guide layer formation. Therefore, the light guide film has an average thickness in the above range and can cope with a large screen. Moreover, the light guide film can contain the antioxidant in the above proportion, thereby preventing yellowing during molding and preventing a decrease in luminance.

  The light guide film may further include a protective layer laminated on the surface of the light guide layer, the protective layer may be mainly composed of an acrylic resin, and the hard coat layer may be formed on the surface of the protective layer. . Thereby, the hardness of the surface side can be further increased and the scratch resistance can be improved.

The light guide film has an absolute value (| n ₁ −n ₃ |) of the difference between the refractive index (n ₁ ) of the light guide layer and the refractive index (n ₃ ) of the protective layer and the refraction of the hard coat layer. The absolute value (| n ₂ −n ₃ |) of the difference between the refractive index (n ₂ ) and the refractive index (n ₃ ) of the protective layer is preferably 0.1 or less. Thereby, the light emission from the light guide layer to the protective layer, the light emission from the protective layer to the hard coat layer, and the light emission from the hard coat layer to the surface side are each suitably performed, and the light is preferably emitted from the surface of the light guide film. be able to.

In the light guide film, the refractive index (n ₁ ) of the light guide layer, the refractive index (n ₂ ) of the hard coat layer, and the refractive index (n ₃ ) of the protective layer are n ₁ > n ₃ > it may meet the n _2. As a result, light rays incident on the protective layer from the light guide layer at a constant angle are totally reflected at the interface between the light guide layer and the protective layer and propagate in the light guide layer. Further, light rays incident on the hard coat layer from the protective layer at a certain angle are totally reflected at the interface between the protective layer and the hard coat layer and propagate in the light guide layer and the protective layer. Therefore, the light guide film can reduce the amount of light reaching the hard coat layer among the light propagating in the light guide film. Therefore, the light guide film can suitably emit light from the surface side, and even if the surface of the hard coat layer is scratched or dust is attached, It can suppress that light is irregularly reflected.

  In the light guide film, the light guide layer and the protective layer may be formed by a coextrusion molding method. Thereby, the said light guide film whose average thickness is the said range can be formed easily and reliably.

  The light guide film may have a diffusion pattern on the back surface of the light guide layer. Thereby, the light beam introduced from the light source can be efficiently diffused by the diffusion pattern and emitted from the surface side.

  The light guide film may be a plurality of light scattering portions in which the diffusion pattern is colored by laser irradiation. Thereby, a desired diffusion pattern can be formed easily and reliably. Moreover, when forming a diffusion pattern by such a method, thickness reduction of the light guide film can be promoted as compared with the case of forming a diffusion pattern by providing a convex portion or the like on the back surface of the light guide film.

  Further, an ultra-thin liquid crystal backlight unit according to the present invention made to solve the above-described problems is a reflection sheet, the light guide film having the above-described configuration laminated on the surface side of the reflection sheet, and the light guide film. The optical sheet laminated | stacked on the surface of this and the light source which irradiates light to the end surface of the said light guide film are provided.

  The ultra-thin liquid crystal backlight unit is prevented from being scratched on the surface side of the light guide film, so that the light guide layer having a polycarbonate resin as a main component obtains sufficient light guiding properties, and the light guide film It is possible to prevent uneven brightness due to scratches on the surface side. Moreover, since the ultrathin liquid crystal backlight unit has an average thickness of the light guide film of 600 μm or less, it is possible to promote thinning.

  Furthermore, a portable computer according to the present invention, which has been made to solve the above problems, includes the ultra-thin liquid crystal backlight unit having the above-described configuration in a liquid crystal display unit.

  Since the portable computer includes the ultra-thin liquid crystal backlight unit, it is possible to prevent uneven brightness from occurring due to scratches on the surface side of the light guide film. In the portable computer, since the average thickness of the light guide film is 600 μm or less, it is possible to promote thinning.

  The “front side” means the display surface side of the liquid crystal display unit. "Back side" means the top plate side and means the opposite side of the display surface of the liquid crystal display unit. When used as “refractive index”, it is used as a term meaning absolute refractive index. This refractive index is measured by light having a wavelength of 589.3 nm (sodium D-line). 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 “weight average molecular weight” (Mw) means a polystyrene equivalent value measured by gel permeation chromatography (GPC).

  As described above, when the light guide film of the present invention is used in an ultra-thin liquid crystal backlight unit of an ultra-thin portable computer, luminance unevenness on the liquid crystal display surface is suppressed and the thickness is reduced. . In addition, the ultra-thin liquid crystal backlight unit and the portable computer of the present invention can be reduced in thickness while suppressing unevenness in luminance of the liquid crystal display surface.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic perspective view of a laptop computer according to an embodiment of the present invention, where (A) shows a state in which a liquid crystal display unit is opened, and (B) shows a state in which the liquid crystal display unit is closed. It is typical sectional drawing which shows the ultra-thin liquid crystal backlight unit of the laptop computer of FIG. It is A1-A2 arrow sectional drawing (schematic sectional drawing) of the light guide film of the ultra-thin liquid crystal backlight unit of FIG. It is a typical partial enlarged view which shows the manufacturing apparatus of the light guide film of the ultra-thin liquid crystal backlight unit of FIG. It is typical sectional drawing which shows the light guide film which concerns on the form different from the light guide film of the ultra-thin liquid crystal backlight unit of FIG. FIG. 6 is a schematic partial enlarged view showing a light guide manufacturing apparatus of the ultra-thin liquid crystal backlight unit of FIG. 5. It is typical sectional drawing which shows the ultra-thin liquid crystal backlight unit light which concerns on a different form from the ultra-thin liquid crystal backlight unit of FIG. It is typical sectional drawing which shows the light guide film which concerns on the form different from the light guide film of the ultra-thin liquid crystal backlight unit of FIG. 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]
<Laptop computer>
The laptop computer 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). The laptop computer 1 has a casing thickness (the thickest part (when the liquid crystal display unit 3 is closed)) of 21 mm or less, and is called a so-called Ultrabook (registered trademark) (hereinafter 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 backlight unit 11 (hereinafter referred to as “backlight unit 11”) that emits light toward the liquid crystal panel 4 from the back side. There is). In the liquid crystal panel 4, the back surface, the side surface, and the periphery of the front surface are held by the casing 5 for the liquid crystal display unit of the housing. Here, the casing 5 for the liquid crystal display unit includes a top plate 14 disposed on the back surface (and the back surface) of the liquid crystal panel 4, and a surface support member 6 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 in the casing 5 for the liquid crystal display section and the casing 5 for the liquid crystal display section so as to be rotatable via a hinge section 7. An operation unit casing 8 in which a voltage CPU) and the like are incorporated is provided.

  The thickness of the liquid crystal display unit 3 is not particularly limited as long as the thickness of the casing is in a desired range, but the lower limit of the thickness of the liquid crystal display unit 3 is preferably 2 mm, more preferably 3 mm, and further 4 mm. preferable. On the other hand, the upper limit of the liquid crystal display unit 3 is preferably 7 mm, more preferably 6 mm, and even more preferably 5 mm. If the thickness of the liquid crystal display unit 3 exceeds the above upper limit, it may be difficult to meet the demand for thinning the ultra-thin computer 1. Further, when the 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 lowered, the luminance is lowered, or the like.

<Backlight unit>
As shown in FIG. 2, the backlight unit 11 includes a light guide film 12, a reflective sheet 13 laminated on the back surface of the light guide film 12, a light source 17 that irradiates light to the light guide film 12, and a light guide. And an optical sheet (not shown) laminated on the surface of the film 12. The light source 17 is disposed on the end face side substantially orthogonal to the ridge line direction in the fine modulation structure of the light guide film 12 described later.

(Light guide film)
The light guide film 12 emits light incident from the end surface thereof from the surface substantially uniformly. The light guide film 12 is formed as a two-layer structure of a light guide layer 19 and a hard coat layer 22 as shown in FIG. The light guide film 12 is formed in a substantially square shape in plan view, and is formed in a plate shape (non-wedge shape) having a substantially uniform thickness. The average thickness of the light guide film 12 is 600 μm or less. The lower limit of the average thickness of the light guide film 12 is preferably 100 μm, more preferably 150 μm, and even more preferably 200 μm. On the other hand, the upper limit of the average thickness of the light guide film 12 is more preferably 580 μm, and further preferably 550 μm. When the average thickness exceeds the upper limit, there is a possibility that the demand for thinning the backlight unit 11 desired in the ultra-thin computer 1 may not be met. Moreover, when the said average thickness is less than the said minimum, there exists a possibility that the intensity | strength of the light guide film 12 may become inadequate, and there exists a possibility that the light of the light source 17 cannot fully inject into the light guide film 12. FIG.

(Light guide layer)
Since the light guide layer 19 needs to transmit light, it is transparent, particularly colorless and transparent. The light guide layer 19 is formed with a polycarbonate resin as a main component. Since the light guide layer 19 is mainly composed of a polycarbonate-based resin, it can improve transparency and reduce light wear. In addition, since the polycarbonate-based resin has heat resistance, deterioration or the like hardly occurs due to heat generated by the light source 17. A diffusion pattern 23 is formed on the back surface of the light guide layer 19. Further, the polycarbonate resin has high dimensional stability because it has less water absorption than acrylic resin and the like.

  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 polycarbonate resin, an aromatic polycarbonate resin excellent in transparency, impact resistance, flame retardancy, dimensional stability and the like is preferable.

The aromatic polycarbonate resin is not particularly limited, and only one kind may be used, or two or more kinds may be used in combination. The aromatic polycarbonate-based resin has a general formula — (— O—X ¹ —O—C (═O) —) — (wherein X ¹ is generally a hydrocarbon, but imparts desired properties). Therefore, a polymer having a basic structure having a carbonic acid ester bond represented by a hetero atom or a hetero bond may be introduced. The aromatic polycarbonate resin refers to a polycarbonate resin in which the carbons directly bonded to the carbonate ester bond are aromatic carbons.

  As said aromatic polycarbonate-type resin, the aromatic polycarbonate polymer of the thermoplastic resin formed by making an aromatic dihydroxy compound and a carbonate precursor react is mentioned, for example. Moreover, in addition to the said dihydroxy compound and a carbonate precursor, you may make a polyhydroxy compound etc. react. Further, a method of using carbon dioxide as a carbonate precursor and reacting with a cyclic ether may be employed. The aromatic polycarbonate polymer may be a homopolymer consisting of only one type of repeating unit or a copolymer having two or more types of repeating units. Such a copolymer is not particularly limited, and is selected from various copolymerization forms such as a random copolymer and a block copolymer.

  Examples of the aromatic dihydroxy compound used as a raw material for the aromatic polycarbonate resin include dihydroxybenzenes such as 1,2-dihydroxybenzene, 1,3-dihydroxybenzene, and 1,4-dihydroxybenzene; -Bis (4-hydroxyphenyl) propane, bis (4-hydroxyphenyl) methane, 1,1-bis (4-hydroxyphenyl) ethane, 1,1-bis (4-hydroxy-t-butylphenyl) propane, 2 , 2-bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl) octane, 2,2-bis (4-hydroxyphenyl) phenylmethane, 2,2-bis (4-hydroxy-1) -Methylphenyl) propane, bis (4-hydroxyphenyl) naphthylmethane, 2,2 Bis (4-hydroxy-3-bromophenyl) propane, 2,2-bis (4-hydroxy-3,5-tetramethylphenyl) propane, 2,2-bis (4-hydroxy-3-chlorophenyl) propane, 2 Bis (hydroxyaryl) alkanes such as 1,2-bis (4-hydroxy-3,5-tetrachlorophenyl) propane and 2,2-bis (4-hydroxy-3,5-tetrabromophenyl) propane; -Bis (4-hydroxyphenyl) cyclopentane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -3,5,5-trimethylcyclohexane, 1,1-bis Bis (hydroxyaryl) cycloal such as (4-hydroxyphenyl) -3-tert-butyl-cyclohexane Dihydroxy aryl ethers such as 4,4′-dihydroxyphenyl ether and 4,4′-dihydroxy-3,3′-dimethylphenyl ether; 4,4′-dihydroxydiphenyl sulfide, 4,4′-dihydroxy- Dihydroxy diaryl sulfides such as 3,3′-dimethyldiphenyl sulfide; dihydroxy diaryl sulfoxides such as 4,4′-dihydroxydiphenyl sulfoxide, 4,4′-dihydroxy-3,3′-dimethyldiphenyl sulfoxide; -Dihydroxy diaryl sulfones such as dihydroxy diphenyl sulfone and 4,4'-dihydroxy-3,3'-dimethyl diphenyl sulfone; and dihydroxy diphenyls such as 4,4'-dihydroxydiphenyl.

  Of these, bis (hydroxyaryl) alkanes are preferred as the aromatic dihydroxy compound. Among the bis (hydroxyaryl) alkanes, bis (4-hydroxyphenyl) alkanes are preferable, and 2,2-bis (4-hydroxyphenyl) propane (bisphenol A) is particularly preferable. In addition, as said aromatic dihydroxy compound, only 1 type may be used independently and 2 or more types may be used in combination.

  Examples of the carbonate precursor used as a raw material for the aromatic polycarbonate resin include carbonyl halides and carbonate esters.

  Examples of the carbonyl halide include phosgene; haloformates such as a bischloroformate of a dihydroxy compound and a monochloroformate of a dihydroxy compound.

  Examples of the carbonate ester include diaryl carbonates such as diphenyl carbonate and ditolyl carbonate; dialkyl carbonates such as dimethyl carbonate and diethyl carbonate; dihydroxy compounds such as biscarbonates of dihydroxy compounds, monocarbonates of dihydroxy compounds, and cyclic carbonates. And the like.

  In addition, the said carbonate precursor may be used individually by 1 type, and may be used in combination of 2 or more type.

  The method for producing the aromatic polycarbonate resin is not particularly limited, and includes an interfacial polymerization method, a melt transesterification method, a pyridine method, a ring-opening polymerization method of a cyclic carbonate compound, a solid phase transesterification method of a prepolymer, and the like. A well-known method is mentioned.

  Moreover, about manufacture of the said aromatic polycarbonate-type resin, a branching agent may be used as needed. Examples of such branching agent include 1,1,1-tris (4-hydroxyphenyl) ethane; α, α ′, α ″ -tris (4-hydroxyphenyl) -1,3,5-triisopropylbenzene; [Α-methyl-α- (4′-hydroxyphenyl) ethyl] -4- [α ′, α′-bis (4 ″ -hydroxyphenyl) ethyl] benzene; phloroglysin, trimellitic acid, isatin bis (o-cresol) Etc.

  The branching rate of the aromatic polycarbonate resin is not particularly limited, but the lower limit of the branching rate of the aromatic polycarbonate resin is preferably 0.5 mol%, more preferably 0.7 mol%, and further 0.8 mol%. preferable. Moreover, as an upper limit of the branching rate of the said aromatic polycarbonate-type resin, 1.5 mol% is preferable, 1.3 mol% is more preferable, and 1.2 mol% is further more preferable. When the branching rate of the aromatic polycarbonate resin exceeds the above upper limit, impact resistance and transparency are lowered, and moldability may be lowered. On the other hand, when the branching rate of the aromatic polycarbonate resin is less than the lower limit, the melt tension may decrease and flame retardancy may decrease.

The weight average molecular weight (Mw) of the aromatic polycarbonate resin is not particularly limited, but the lower limit of the weight average molecular weight (Mw) of the aromatic polycarbonate resin is preferably 2.0 × 10 ⁴ , 2.2 × 10 ^4, more preferably, 2.4 × 10 ⁴ is more preferable. The upper limit of the weight average molecular weight of the aromatic polycarbonate resin (Mw), preferably from 5.0 × 10 ^4, more preferably 4.8 × 10 ^4, more preferably 4.6 × 10 ^4. If the weight average molecular weight (Mw) of the aromatic polycarbonate resin exceeds the upper limit, moldability may be reduced. On the other hand, when the weight average molecular weight (Mw) of the aromatic polycarbonate resin is less than the lower limit, the mechanical strength may decrease. The said weight average molecular weight (Mw) means the polystyrene conversion value measured by GPC.

  The ratio of the weight average molecular weight to the number average molecular weight (Mw / Mn) is not particularly limited, but the lower limit of the ratio of the weight average molecular weight to the number average molecular weight (Mw / Mn) is preferably 1.0. 3 is more preferable, and 1.5 is more preferable. The upper limit of the ratio (Mw / Mn) between the weight average molecular weight and the number average molecular weight is preferably 2.5, more preferably 2.3, and even more preferably 2.1. When the ratio (Mw / Mn) between the weight average molecular weight and the number average molecular weight exceeds the upper limit, the light transmittance may be reduced. On the contrary, when the ratio (Mw / Mn) of the weight average molecular weight to the number average molecular weight is less than the lower limit, the moldability may be lowered. The ratio of the weight average molecular weight to the number average molecular weight (Mw / Mn) can be measured using “PLGel 5μ MIXED-C” manufactured by Polymer Laboratories as a column and tetrahydrofuran as a solvent. The ratio of the weight average molecular weight to the number average molecular weight (Mw / Mn) can be adjusted by adjusting the molecular weight regulator usage fee, addition time, etc. during polymerization, or by polymerization conditions such as reaction time and reaction temperature. It is possible to adjust this.

The aromatic polycarbonate resin of the melt volume flow rate (300 ° C., 1.2 kg load) is not particularly limited, the lower limit is preferably 15cm ³ / ^10min, more preferably 17cm 3 / ^10min, more preferably 20 cm 3 / 10min . The upper limit of the melt volume flow rate is ^preferably from 80 cm 3 / ^10min, more preferably 75 cm 3 / ^10min, more preferably 70cm 3 / 10min. When the melt volume flow rate exceeds the above upper limit, the melting temperature becomes low, and the discharge amount in the case of melt extrusion molding may become unstable and formability may deteriorate. On the other hand, when the melt volume flow rate is less than the lower limit, the melting temperature becomes high, and when melt extrusion is performed, the filter installed between the extruder and the die is likely to be clogged. “Melt volume flow rate (300 ° C., 1.2 kg load)” is a value measured in accordance with ISO1133.

  The light guide layer 19 may include a polystyrene resin having a weight average molecular weight of 1000 or more and 10,000 or less. As a weight average molecular weight of the said polystyrene-type resin, 1500 or more and 8000 or less are more preferable, and 2000 or more and 5000 or less are more preferable. When the weight average molecular weight of the polystyrene resin exceeds the upper limit, the light transmittance may be reduced.

  Further, the content of the polystyrene resin is not particularly limited, but the lower limit of the content with respect to 100 parts by mass of the aromatic polycarbonate resin is preferably 0.1 parts by mass, and more preferably 0.2 parts by mass. 0.3 parts by mass is more preferable. The upper limit of the content of the polystyrene resin relative to 100 parts by mass of the aromatic polycarbonate resin is preferably 3 parts by mass, more preferably 2 parts by mass, and even more preferably 1 part by mass. When content of the said polystyrene-type resin exceeds the said upper limit, there exists a possibility that light transmittance may fall. On the contrary, when the content of the polystyrene resin is less than the lower limit, the effect of improving the light transmittance may not be obtained.

  The light guide layer 19 may include a thermoplastic polyacrylic resin. The thermoplastic polyacrylic resin is not particularly limited, and for example, polyacrylic acid, polymethyl methacrylate (PMMA), polyacrylonitrile, acrylic acid-n-butyl-acrylonitrile copolymer, ethyl acrylate-acrylic acid- Examples include 2-chloroethyl copolymer, acrylonitrile-butadiene copolymer, and acrylonitrile-butadiene-styrene copolymer. Of these, polymethyl methacrylate (PMMA) is particularly preferable.

  The content of the thermoplastic polyacrylic resin is not particularly limited, but the lower limit of the content of the thermoplastic polyacrylic resin with respect to 100 parts by mass of the aromatic polycarbonate resin is preferably 0.01 parts by mass, 0.03 mass part is more preferable, and 0.05 mass part is further more preferable. Moreover, as an upper limit of content of the said thermoplastic polyacrylic-type resin, 1 mass part is preferable, 0.7 mass part is more preferable, and 0.5 mass part is further more preferable. When content of the said thermoplastic polyacrylic-resin exceeds the said upper limit, there exists a possibility that the improvement effect of transparency may not be acquired so much and spectral light transmittance may not improve. Conversely, when the content of the thermoplastic polyacrylic resin is less than the lower limit, the transparency may be lowered.

  The molecular weight of the thermoplastic polyacrylic resin is not particularly limited, but the lower limit is preferably 5000, more preferably 10,000, and even more preferably 20,000. Further, the upper limit of the molecular weight of the thermoplastic polyacrylic resin is preferably 100,000, more preferably 80,000, and even more preferably 60,000. When the molecular weight of the thermoplastic polyacrylic resin is in the above range, phase separation during molding is suppressed, and transparency is suitably improved.

  The light guide layer 19 preferably contains an antioxidant. Although it does not specifically limit as said antioxidant, For example, a hindered phenol type compound and a thioether type compound are mentioned. Especially, as said antioxidant, a hindered phenol type compound is preferable, pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate is particularly preferred.

  The content of the antioxidant is not particularly limited, but the lower limit of the content of the antioxidant with respect to 100 parts by mass of the aromatic polycarbonate resin is preferably 0.01 parts by mass, and 0.03. A mass part is more preferable and 0.04 mass part is further more preferable. Moreover, as an upper limit of content of the said antioxidant, 0.1 mass part is preferable, 0.08 mass part is more preferable, and 0.07 mass part is further more preferable. When content of the said antioxidant exceeds the said upper limit, there exists a possibility that the effect of containing antioxidant may not be improved. On the other hand, when the content of the antioxidant is less than the lower limit, the effect due to the inclusion of the antioxidant may not be sufficiently obtained.

  The light guide layer 19 is an optional component such as an ultraviolet absorber, a flame retardant, a stabilizer, a lubricant, a processing aid, a plasticizer, an impact aid, a retardation reducing agent, a matting agent, an antibacterial agent, and an antifungal agent. May be included.

  The average thickness of the light guide layer 19 is not particularly limited, but the lower limit is preferably 100 μm, more preferably 150 μm, and even more preferably 200 μm. The upper limit of the average thickness of the light guide layer 19 is preferably 580 μm or less, more preferably 560 μm, and further preferably 540 μm. When the average thickness of the light guide layer 19 is less than the lower limit, the light guide film 12 may be thinned and the strength may not be sufficient, and the light from the light source 17 may be sufficiently incident on the light guide layer 19. You may not be able to. On the other hand, when the average thickness of the light guide layer 19 exceeds the above upper limit, the light guide film 12 becomes thick, which may not meet the demand for thinning the backlight unit 11 desired in the ultra-thin computer 1.

  The spectral light transmittance at a wavelength of 300 nm of the light guide layer 19 is not particularly limited, but the lower limit is preferably 65% or more, more preferably 70%, and even more preferably 73%. When the spectral light transmittance is in the above range, the light guide property of the light guide layer 19 can be improved and the luminance can be improved. In addition, the light guide film 12 is incident on a light beam having a wavelength in the visible light region from the end face of the light guide layer 19 and propagates in the light guide layer 19. In this respect, the spectral light transmittance at a wavelength of 300 nm does not directly represent the spectral light transmittance in the visible light region, but tends to reflect the spectral light transmittance in the visible light region. The “spectral light transmittance at a wavelength of 300 nm of the light guide layer” is in a visible-UV spectral spectrum measured at a thickness of 400 μm.

Refractive index of the light guide layer 19 _{(n 1)} is not particularly limited, but is preferably 1.56 or more 1.68 or less, more preferably 1.58 or more 1.66 or less.

  The surface of the light guide layer 19 (interface with the hard coat layer 22) has a wavy fine modulation structure. Further, the direction of the ridge line 20 in the wavy fine modulation structure and the end face on which the light beam enters are substantially orthogonal. Thereby, when the light beam propagating in the light guide layer 19 is reflected on the surface, the traveling direction of a part of the light beam approaches the ridge line 20 side, so that the light beam is easily collected on the ridge line direction side. In addition, since the light emitted from the surface is slightly diffused in the direction perpendicular to the ridge line by refraction by the wavy fine modulation structure, the diffusibility of the emitted light is improved.

  Although it does not specifically limit as the ridgeline space | interval p in the said fine modulation structure, 1 mm or more and 500 mm or less are preferable. The upper limit of the ridge line interval p is more preferably 100 mm, and further preferably 60 mm. On the other hand, the lower limit of the ridge line interval p is more preferably 10 mm, and even more preferably 20 mm. When the ridge line interval p is out of the above range, the light beam propagating in the light guide film 12 is not easily condensed on the ridge line direction side.

  In addition, the average height h of the ridge line 20 based on the approximate virtual plane through which the plurality of valley lines 21 in the modulation structure passes is not particularly limited, but is preferably 5 μm or more and 40 μm or less. The lower limit of the average height is more preferably 7 μm and even more preferably 9 μm. On the other hand, the upper limit of the average height is more preferably 20 μm and even more preferably 15 μm. When the average height h is out of the above range, the light beam propagating through the light guide film 12 is not easily collected on the ridge line side.

  The diffusion pattern 23 is composed of a plurality of recesses formed on the back surface of the light guide layer. The plurality of recesses are formed in a dotted pattern on the back surface of the light guide layer 19. The plurality of recesses are arranged so that uniform light can be emitted from the light guide film 12 to the surface side. Specifically, the plurality of recesses are formed such that the existence ratio at a position close to the light source 17 is small and the existence ratio increases as the distance from the light source 17 increases. The presence ratio of the plurality of recesses can be adjusted by adjusting the arrangement position or changing the size of each recess while keeping the size of each recess the same. However, from the viewpoint of improving the light guide property while promoting the thinning of the light guide film 12, it is preferable to adjust the arrangement position while keeping the size of each recess the same.

  The average diameter of the recess is not particularly limited, but the lower limit is preferably 0.5 μm, more preferably 1 μm, and still more preferably 5 μm. The upper limit of the average diameter of the recesses is preferably 50 μm or less, more preferably 40 μm, and even more preferably 30 μm. When the average diameter of the recess is less than the lower limit, the light scattering effect may not be sufficiently obtained. Conversely, when the average diameter of the recess exceeds the upper limit, brightness unevenness may occur, and the height of the recess may increase, making it difficult to promote thinning of the light guide film 12. The “diameter” means an intermediate value between the maximum width of the outer shape and the width of the outer shape in the direction orthogonal to the maximum width direction. Furthermore, the “average diameter” refers to the average value of the diameters of the plurality of recesses.

  The shape of the concave portion is not particularly limited, but may be a hemispherical shape, a conical shape, a cylindrical shape, a polygonal pyramid shape, a polygonal columnar shape, a hoof shape, or the like. Especially, it is preferable that the said recessed part is formed as a hemispherical recessed part. By making the said recessed part into a hemispherical recessed part, a moldability can be improved and it can prevent that an edge comes out, and thickness reduction is accelerated | stimulated.

(Hard coat layer)
The hard coat layer 22 is laminated on the surface of the light guide layer 19. The hard coat layer 22 contains a synthetic resin such as a thermosetting resin or an active energy ray curable resin as a main component. Especially, it is preferable that the hard-coat layer 22 contains the active energy ray curable resin hardened | cured with active energy rays, such as an ultraviolet-ray and an electron beam. In particular, as the main component of the hard coat layer 22, an active energy ray-curable acrylic resin is preferable from the viewpoint of reducing the refractive index of the hard coat layer 22.

  Examples of the active energy ray-curable acrylic resin include a composition in which a monomer or oligomer having a polymerizable functional group such as a (meth) acryloyl group or a (meth) acryloyloxy group is mixed. As this composition, it is preferable to use a polyfunctional monomer having three or more functional groups. Moreover, the said monomer or oligomer can be used individually or in mixture of multiple.

  The monomer is not particularly limited, and methyl (meth) acrylate, lauryl (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, methoxytriethylene glycol (meth) acrylate, phenoxyethyl (meth) acrylate, tetrahydrofur Monofunctional acrylates such as furyl (meth) acrylate, isobornyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxy (meth) acrylate, neopentyl glycol Di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate , Pentaerythritol tetra (meth) acrylate, dipentaerythritol tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, tripentaerythritol Multifunctional acrylates such as tri (meth) acrylate, tripentaerythritol hexa (meth) triacrylate, trimethylolpropane (meth) acrylic acid benzoate, trimethylolpropane benzoate, glycerin di (meth) acrylate hexamethylene diisocyanate, Examples thereof include urethane acrylates such as pentaerythritol tri (meth) acrylate and hexamethylene diisocyanate.

  The oligomer is not particularly limited, and polyester (meth) acrylate, polyurethane (meth) acrylate, epoxy (meth) acrylate, polyether (meth) acrylate, alkit (meth) acrylate, melamine (meth) acrylate, Examples include silicone (meth) acrylate.

  Although content of the said active energy ray-curable acrylic resin is not specifically limited, 50 mass% or more is preferable with respect to the solid content total amount of the hard-coat layer 22, 55 mass% or more is more preferable, 60 mass% The above is more preferable, and 70% by mass or more is particularly preferable.

  In order to initiate the polymerization of the monomer or oligomer, a photopolymerization initiator is preferably used. Such a photopolymerization initiator is not particularly limited, and 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- Carbonyl compounds such as hydroxyisobutylphenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexyl phenyl ketone, tetramethylthiura And sulfur compounds such as dimethyl monosulfide, tetramethylthiuram disulfide, thioxanthone, 2-chlorothioxanthone, and 2-methylthioxanthone. These photopolymerization initiators may be used alone or in combination of two or more.

  Although content of the said photoinitiator is not specifically limited, 0.1 mass% or more and 10 mass% or less are preferable with respect to the solid content total amount of the hard-coat layer 22, 0.5 mass% or more and 8 mass% or less are preferable. More preferred.

  The hard coat layer 22 has colloidal silica, colloidal aluminum oxide, colloidal calcium carbonate, smectite, mica, titanium oxide, zircon oxide, antimony oxide, for adjusting the refractive index and improving heat resistance and dimensional stability. Inorganic ultrafine particles such as zinc oxide, magnesium oxide, talc, alumina, barium sulfate, asbestos, tin oxide-doped indium oxide (ITO), and antimony-doped tin oxide (ATO) may be dispersed.

  Further, the hard coat layer 22 may contain an antioxidant, an ultraviolet absorber, a leveling agent, an antistatic agent, a lubricant, a colorant and the like.

  The average thickness of the hard coat layer 22 is not particularly limited, but the lower limit is preferably 2 μm, more preferably 7 μm, and even more preferably 10 μm. The upper limit of the average thickness of the hard coat layer 22 is preferably 20 μm, more preferably 18 μm, and further preferably 15 μm. When the average thickness of the hard coat layer 22 is less than the above lower limit, the light guide layer 19 may not be able to be accurately prevented from being damaged. On the other hand, when the average thickness of the hard coat layer 22 exceeds the above upper limit, the light guide film 12 may not meet the demand for thinning, and is caused by the difference in hardness between the light guide layer 19 and the hard coat layer 22. May cause curling.

  The pencil hardness of the hard coat layer 22 is preferably HB or higher, more preferably H or higher, and further preferably 2H or higher. By setting the pencil hardness of the hard coat layer 22 to be equal to or higher than the above lower limit, the hard coat layer 22 itself can be accurately prevented from being scratched, and light is inadvertently diffused due to scratches on the surface of the hard coat layer 22. Can be prevented accurately. In addition, the upper limit of the pencil hardness of the light guide film 12 is not specifically limited, For example, it is 4H. The “pencil hardness” refers to a value based on the pencil scratch value described in 8.4 of the test method defined in JIS K5400.

The refractive index (n ₂ ) of the hard coat layer 22 is not particularly limited, but is preferably 1.3 or more and 1.75 or less, more preferably 1.4 or more and 1.65 or less, and 1.5 or more and 1.56 or less. Further preferred. The refractive index (n ₂ ) of the hard coat layer 22 is preferably smaller than the refractive index (n ₁ ) of the light guide layer 19. That is, the refractive index of the light guide layer 19 and _{(n 1)} the refractive index of the hard coat layer and _{(n 2),} it is preferable to satisfy _n 1> n _2. The absolute value of the difference between the refractive index of the light guide layer 19 and _{(n 1)} the refractive index of the hard coat layer 22 and the _{(n 2) (| n 1} -n 2 |) is preferably 0.1 or less. The upper limit of the absolute value of the refractive index difference (| n ₁ −n ₂ |) is more preferably 0.08, and even more preferably 0.06. If the absolute value of the difference between the refractive index of the light guide layer 19 and the (n ₁₎ the refractive index of the hard coat layer 22 and the (n ₂₎ exceeds the upper limit, the hard coat layer rays propagating light guide layer 19. There is a possibility that the laser beam cannot be suitably emitted into the area 22. The lower limit of the absolute value (| n ₁ −n ₂ |) of the difference in refractive index is not particularly limited, and is 0 or 0.001.

(Reflective sheet)
The reflection sheet 13 reflects the light beam emitted from the back side of the light guide film 12 to the front side. The reflection sheet 13 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 17 is built in the casing 5 for the liquid crystal display unit, and is disposed so that the irradiation surface faces (or abuts) the end surface of the light guide layer 19 of the light guide film 12. Various light sources 17 can be used. For example, a light emitting diode (LED) can be used. Specifically, a light source 17 in which a plurality of light emitting diodes are disposed along the end face of the light guide layer 19 can be used.

  In the backlight unit 11, the one-side edge light system in which the light source 17 is disposed on the side of only one side edge of the light guide film 12, or the light source 17 is disposed on the side of the opposite side edge of the light guide film 12. It is possible to adopt a double-sided edge light method in which the light source film 17 is disposed, an all-around edge light method in which the light source 17 is disposed on the side of each side edge of the light guide film 12, or the like.

(Optical sheet)
The optical sheet is a sheet that is laminated on the surface of the light guide film 12 as described above, and has an optical function of diffusing and refracting the light emitted from the light guide 12. As this optical sheet, for example, a light diffusion sheet, a prism sheet or the like is used. This optical sheet preferably has an anti-sticking layer for preventing sticking with the light guide film 12 on the back surface. As the anti-sticking layer, for example, a layer formed by coating a coating liquid containing beads and having fine irregularities on the back surface can be adopted.

<Method for producing light guide film>
Next, although the manufacturing method of the said light guide film 12 is demonstrated below, the manufacturing method of the light guide film 12 of this invention is not limited to the manufacturing method described below.

  As a method for manufacturing the light guide film 12, a step of forming the light guide layer 19 having a wavy fine modulation structure on the surface (STEP 1), and a step of forming the diffusion pattern 17 on the back surface of the light guide layer 19 (STEP 2) And a step of forming a hard coat layer 22 on the surface of the light guide layer 19 (STEP 3). Although STEP 1 and STEP 2 can be performed in separate steps, in this embodiment, the extrusion sheet forming method is adopted in STEP 1, and in STEP 2, the pressing roll is a roll-like shape to which the diffusion pattern is transferred. By using the inversion type, STEP1 and STEP2 are performed simultaneously.

  STEP1 is implemented using the extrusion molding apparatus 24 of FIG. The extrusion molding device 24 includes an extruder and a T die 25, a pair of pressing rolls 26, a winding device (not shown), and the like. As the T die 25, for example, a well-known one such as a fish tail die, a manifold die, a coat hanger die, or the like can be used. The cross-sectional shape of the T die 25 is an inverted shape of the cross-sectional shape perpendicular to the ridgeline of the fine modulation structure. As a result, a light guide film having a fine modulation structure with a wavy surface is formed.

  The pair of pressing rolls 26 are disposed adjacent and in parallel. The extruder and the T die 25 are configured to be able to extrude the molten resin into a sheet shape at the nip between the pair of pressing rolls 26. The pair of pressing rolls 26 is provided with a temperature control means, and is configured to be able to control the surface temperature to a temperature optimum for extrusion molding. As the pressing roll 26, it is preferable to use a metal elastic roll comprising a metal roll and a flexible roll whose surface is covered with an elastic body.

  The pair of pressing rolls 26 includes a pressing roll 26a and a pressing roll 26b. Among these, the press roll 26a is formed as a reverse type in which the diffusion pattern is transferred to the surface.

  STEP 1 is performed by an extrusion sheet forming method in which a light guide layer forming material in a molten state is supplied to the T die 25, the forming material is extruded from the extruder and the T die 25, and then pressed by a pair of pressing rolls 26. The melting temperature of the light guide layer forming material extruded from the T die 25 is appropriately selected in consideration of the melting point of the resin used. The average thickness of the light guide layer formed in STEP 1 is less than 600 μm. The average thickness of the light guide layer 19 is adjusted by adjusting the arrangement interval of the pair of pressing rolls 26.

  In addition, the arrangement interval, the rotation speed, and the like of the pair of pressing rolls 26 are adjusted in consideration of the supply amount of the forming material of the sheet body extruded from the T die 25, the melted state, and the like.

  STEP2 is performed by transferring the diffusion pattern transferred to the surface of the pressing roll 26a before the forming material of the molten sheet body is cured. In STEP2, the forming material of the molten sheet main body is pressed by the pair of pressing rolls 26, whereby the diffusion pattern transferred to the surface of the pressing roll 26a is transferred to the back surface of the sheet main body. In STEP 2, a plurality of recesses are formed on the back surface of the sheet body by this transfer.

  STEP 3 is a step of forming the hard coat layer 22 by applying a material for forming the hard coat layer 22 on the surface of the light guide layer 19 on which the fine modulation structure is formed. Thus, the method for applying the material for forming the hard coat layer 22 is not particularly limited, and for example, spin coating, spraying, slide coating, dipping, bar coating, roll coater, screen printing, etc. Various methods can be used. In manufacturing the hard coat layer 22, surface modification treatment such as plasma treatment in an inert gas atmosphere such as argon gas or nitrogen gas may be performed as a pretreatment as necessary.

<advantage>
The light guide film 12 can prevent the surface of the light guide layer 19 from being scratched by the hard coat layer 22 formed on the surface of the light guide layer 19. For this reason, it is possible to accurately prevent the occurrence of uneven brightness due to inadvertent diffusion or the like of the light beam guided in the light guide layer 19 due to scratches on the surface of the light guide layer 19.

  Moreover, since the light guide film 12 has an average thickness of 600 μm or less, it is possible to promote a reduction in thickness. And since the light guide film 12 is thin in this way, the light beam guided through the light guide layer 19 is reflected more frequently on the front and back surfaces of the light guide layer 19 than the conventional light guide plate, but as described above, the hard coat film Since the layer 22 prevents the light guide layer 19 from being scratched, the occurrence of luminance unevenness can be effectively suppressed.

  Further, the light guide film 12 has a corrugated fine modulation structure in which the surface of the light guide layer 19 has a wave-like fine modulation structure by applying an inverted shape of the vertical cross-sectional shape to the ridge line of the fine modulation structure on the extrusion die by an extrusion sheet forming method. A light guide film can be formed easily and reliably.

  Further, since the light guide film 12 is arranged so that the direction of the ridge line 20 in the wavy fine modulation structure and the end surface on which the light beam enters are substantially orthogonal, the transmitted light beam in the light guide layer 19 is collected on the ridge line direction side. It is easy to be lighted. For this reason, the light guide property of the incident light beam can be improved. Further, the light beam emitted from the surface of the light guide layer 19 is slightly diffused in the direction perpendicular to the ridge line direction due to refraction by the wavy fine modulation structure, so that the diffusibility of the emitted light beam can be improved.

[Second Embodiment]
<Light guide film>
Next, the light guide film 33 shown in FIG. 5 is demonstrated as a light guide film of 2nd embodiment. In the description of the second embodiment, the description of the same configuration as that of the first embodiment may be omitted.

  The light guide film 33 includes a light guide layer 34 and a hard coat layer 22, and further includes a protective layer 38 laminated between the light guide layer 34 and the hard coat layer 22. A diffusion pattern 37 is formed on the back surface of the light guide layer 34.

  The protective layer 38 has an acrylic resin as a main component. Here, the protective layer 38 can be composed of only an acrylic resin, but it can also include other resins such as an aromatic polycarbonate resin as an auxiliary component. Thus, when a subcomponent is included, the protective layer 38 is good in it being a copolymer or polymer alloy of an acrylic resin and an aromatic polycarbonate resin. The aromatic polycarbonate resin may be contained in a proportion of 10 parts by weight or more and 50 parts by weight or less with respect to 100 parts by weight of the acrylic resin.

  Although it does not specifically limit as said acrylic resin, Poly (meth) acrylic acid ester, such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymer, methyl methacrylate- (meth) acrylic acid ester copolymer Polymer, methyl methacrylate-acrylic ester- (meth) acrylic acid copolymer, (meth) methyl acrylate-styrene copolymer, polymer having alicyclic hydrocarbon group (for example, methyl methacrylate-methacrylic acid) Acid cyclohexyl 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.

  The thickness ratio of the protective layer 38 to the light guide layer 34 is not particularly limited, but the lower limit of the thickness ratio is preferably 1/50, more preferably 1/25, and even more preferably 1/20. Moreover, as an upper limit of the said thickness ratio, 1/5 is preferable, 1/8 is more preferable, 1/10 is further more preferable. When the thickness ratio of the protective layer 38 to the light guide layer 34 exceeds the above upper limit, the thickness of the light guide layer 34 is reduced, and there is a high possibility that light incident from the light source cannot be accurately propagated in the light guide layer 34. On the contrary, when the thickness ratio of the protective layer 38 to the light guide layer 34 is less than the lower limit, the hardness on the surface side of the light guide film 33 may not be suitably increased.

Refractive index of the light guide layer 34 _{(n 1)} and the absolute value of the difference between the refractive index of the protective layer 38 and the _{(n 3) (| n 1} -n 3 |), and the refractive index of the hard coat layer 22 _(n 2) The absolute value (| n ₂ −n ₃ |) of the difference between the refractive index of the protective layer 38 and the refractive index (n ₃ ) of the protective layer 38 is preferably 0.1 or less. Refractive index of the light guide layer 34 _{(n 1)} and the absolute value of the difference between the refractive index of the protective layer 38 and the _{(n 3) (| n 1} -n 3 |), and the refractive index of the hard coat layer 22 _(n 2) The upper limit of the absolute value (| n ₂ −n ₃ |) of the difference between the refractive index of the protective layer 38 and the refractive index (n ₃ ) of the protective layer 38 is more preferably 0.08, and further preferably 0.06. The refractive index of the light guide layer 34 _{(n 1)} and the absolute value of the difference between the refractive index of the protective layer 38 and the _{(n 3) (| n 1} -n 3 |) when a exceeds the upper limit, the light guide layer 34 There is a possibility that the light beam propagating the light cannot be suitably emitted into the protective layer 38. If the absolute value (| n ₂ −n ₃ |) of the difference between the refractive index (n ₂ ) of the hard coat layer 22 and the refractive index (n ₃ ) of the protective layer 38 exceeds the above upper limit, There is a possibility that the light beam propagating through the film cannot be suitably emitted into the hard coat layer 22.

The refractive index of the light guide layer 34 and _{(n 1),} the refractive index of the hard coat layer 22 and the _{(n 2),} the refractive index of the protective layer 38 and the _{(n 3),} but the n _1> n 3> _{n 2} It is preferable to satisfy. As a result, light rays incident on the protective layer 38 from the light guide layer 34 at a certain angle or more are totally reflected at the interface between the light guide layer 34 and the protective layer 38 and propagate in the light guide layer 34. Further, light rays incident on the hard coat layer 22 from the protective layer 38 at a certain angle or more are totally reflected at the interface between the protective layer 38 and the hard coat layer 22 and propagate in the light guide layer 34 and the protective layer 38. Therefore, the light guide film 33 can reduce the amount of light reaching the hard coat layer 22 among the light propagating in the light guide film 33. Therefore, the light guide film 33 can suitably emit light from the surface side, and even if the surface of the hard coat layer 22 is scratched or dust is attached, It is possible to suppress the irregular reflection of light due to the like.

<Method for producing light guide film>
Next, although the manufacturing method of the said light guide film 33 is demonstrated below, the manufacturing method of the light guide film 33 of this invention is not limited to the manufacturing method described below.

  As a method for manufacturing the light guide film 33, a step of generating a sheet-like laminate including the light guide layer 34 and the protective layer 38 (STEP 1), and a step of forming a diffusion pattern 37 on the back surface of the light guide layer 34 (STEP 2). And a step of forming the hard coat layer 22 by applying a material for forming the hard coat layer 22 on the surface of the protective layer 38, drying and irradiating with active energy rays (STEP 3). The light guide film 33 is formed by a coextrusion molding method using the coextrusion machine 39 of FIG. STEP 3 is the same as that described in the first embodiment, and a description thereof will be omitted.

  The co-extruder 39 includes extruders 40 and 41, a distribution block 42, a multi-manifold die (T die) 43, and pressing rolls 44 and 45. The pressing roll 44 and the pressing roll 45 are adjacently arranged in parallel. The pressing roll 45 is formed as an inverted type in which the diffusion pattern 37 is transferred to the surface.

  In STEP 1, first, the forming material of the protective layer 38 is put into the extruder 40, and the forming material of the light guide layer 34 is put into the extruder 41. Next, the forming material of the protective layer 38 and the forming material of the light guide layer 34 are supplied to the distribution block 42 and distributed so as to have a desired thickness. Then, the forming material of the protective layer 38 and the forming material of the light guide layer 34 are distributed in a desired thickness, stacked in the multi-manifold die 43, and extruded from the tip of the multi-manifold die 43 into a film shape. The temperature settings of the extruders 40 and 41 and the multi-manifold die 43 are appropriately selected in consideration of the melting point of the resin used. The light guide film 33 is not necessarily manufactured by using a multi-manifold method using the distribution block 42 and the multi-manifold die 43, but using a dual slot die that is a feed block stacking method or an external die stacking method. May be.

  STEP 2 is performed by transferring the diffusion pattern transferred to the surface of the pressing roll 45 before the forming material of the molten sheet body is cured. In STEP 2, the material for forming the molten sheet main body is pressed by the pair of pressing rolls 44 and 45, so that the diffusion pattern transferred to the surface of the pressing roll 45 is transferred to the back surface of the sheet main body. In STEP 2, a plurality of recesses are formed on the back surface of the sheet body by this transfer.

  STEP 3 is a step of forming the hard coat layer 22 by applying a material for forming the hard coat layer 22 on the surface of the protective layer 38. Thus, the method for applying the material for forming the hard coat layer 22 is not particularly limited, and for example, spin coating, spraying, slide coating, dipping, bar coating, roll coater, screen printing, etc. Various methods can be used. In manufacturing the hard coat layer 22, surface modification treatment such as plasma treatment in an inert gas atmosphere such as argon gas or nitrogen gas may be performed as a pretreatment as necessary.

[Third embodiment]
<Backlight unit>
Next, the backlight unit 60 shown in FIG. 7 is demonstrated as a backlight unit of 3rd embodiment. In the description of the third embodiment, the description of the same configuration as that of the first embodiment may be omitted.

  The backlight unit 60 is laminated on the surface of the light guide film 61, the reflection sheet 62 laminated on the back surface of the light guide film 61, the light source 68 that irradiates light to the light guide film 61, and the surface of the light guide film 61. And an optical sheet (not shown). The light source 68 is disposed on the end face side substantially parallel to the ridge line direction in the fine modulation structure of the light guide film 61 described later.

  Similar to the first embodiment, the light guide film 61 includes a light guide layer 63 and a hard coat layer 64, and a diffusion pattern 65 is formed on the back surface of the light guide layer 63.

  The surface of the light guide layer 63 (interface with the hard coat layer 64) has a wavy fine modulation structure. In addition, the direction of the ridgeline 66 in the wavy fine modulation structure and the end face on which the light beam enters are located substantially in parallel. As a result, the direction of the ridgeline 66 of the fine modulation structure is positioned substantially perpendicular to the traveling direction of the light propagating in the light guide layer 63, so that the incident angle of the light ray on the surface varies due to the wavy fine modulation structure. For this reason, light rays are suitably emitted from the light guide layer 63 to the hard coat layer 64, thereby improving the light output from the surface of the light guide film 61.

  Although it does not specifically limit as a ridgeline space | interval in the said fine modulation structure, 1 mm or more and 500 mm or less are preferable. The upper limit of the ridge line interval is more preferably 100 mm, and further preferably 60 mm. On the other hand, the lower limit of the ridge line interval is more preferably 10 mm, and further preferably 20 mm. When the ridge line interval is less than the lower limit, light may be emitted from the light guide layer 63 to the hard coat layer 64 too much. On the other hand, when the ridge line spacing exceeds the above upper limit, the effect of improving the light output from the light guide layer 63 may be low. In addition, although it is preferable that all the ridge line intervals in the fine modulation structure are within the above range, some of the plurality of ridge line intervals in the fine modulation structure may be outside the above range. Of the ridge line intervals, 50% or more, preferably 70% of the ridge line intervals may be within the above range.

  Moreover, the average height of the ridgeline 66 on the basis of the approximate virtual plane through which the plurality of valley lines 67 in the fine modulation structure is based is not particularly limited, but is preferably 5 μm or more and 40 μm or less. The lower limit of the average height is more preferably 7 μm and even more preferably 9 μm. The upper limit of the average height h is more preferably 20 μm and even more preferably 15 μm. When the average height exceeds the upper limit, there is a possibility that light rays are emitted from the surface of the light guide film 61 too much. On the other hand, when the average height is less than the lower limit, the effect of improving the light output property of the light guide film 61 may be lowered.

[Fourth embodiment]
<Light guide film>
Next, the light guide film 51 shown in FIG. 8 is demonstrated as a light guide film of 4th embodiment. In the description of the fourth embodiment, the description of the same configuration as that of the first embodiment may be omitted.

  The light guide film 51 includes a light guide layer 52 and a hard coat layer 53 as in the first embodiment. A diffusion pattern 54 is formed on the back surface of the light guide layer 52. The diffusion pattern 54 is formed of a plurality of light scattering portions that are colored by laser irradiation. Specifically, the diffusion pattern 54 is formed by adding a color former in the material for forming the light guide layer 52 and irradiating the laser after forming the light guide layer 52 so that the color former is colored. .

  The color former dispersed and contained in the material for forming the light guide layer 52 is a pigment whose color is changed by laser irradiation. As this color former, a well-known organic substance or inorganic substance used as a laser marking agent can be used. Specifically, for example, yellow iron oxide, inorganic lead compound, manganese violet, cobalt violet, mercury, cobalt, copper, bismuth, nickel and other metal compounds, pearlescent pigments, silicon compounds, mica, kaolins, silica sand, A diatomaceous earth, a talc, etc. can be mentioned, Among these, 1 type (s) or 2 or more types can be used. However, in the present embodiment, the diffusion pattern 54 is formed as a reflection pattern that reflects light rays, and therefore preferably has a color that reflects light rays. Therefore, in the light guide film 51, it is preferable to use a color former that develops white color by laser irradiation. Conversely, a color former that is carbonized by laser irradiation and changes to black that absorbs light is inappropriate. Examples of such a color former that develops white color include titanium black, cordierite, and mica.

  As the cordierite, in addition to the inorganic compound represented by the composition formula MG2Al3 (AlSi5O18), one in which a part of Mg is substituted with Fe can be used. Moreover, you may use the thing containing a water | moisture content.

  As the mica, natural mica such as mascobite, phlogopite, biotite and sericite, and synthetic mica such as fluorine phlogopite and tetrasilica mica can be used.

  The content of the color former in the light guide layer 51 is not particularly limited, but the lower limit is preferably 0.0001% by mass, and more preferably 0.1% by mass. Further, the upper limit of the content of the color former is preferably 2.5% by mass or less, and more preferably 1% by mass. When the content of the color former is less than the above lower limit, a sufficient color development effect cannot be obtained at the time of laser irradiation, and a desired reflection pattern may not be formed. On the contrary, when the content of the color former exceeds the upper limit, the transparency, mechanical strength, etc. of the light guide layer 52 may be lowered.

  The laser with which the light guide layer 52 is irradiated is not particularly limited, and examples thereof include a carbon dioxide gas laser, a carbon monoxide laser, a semiconductor laser, and a YAG (yttrium / aluminum / garnet) laser. In particular, a carbon dioxide laser having a wavelength of 9.3 μm to 10.6 μm is suitable for forming a fine dot pattern. As the carbon dioxide laser, a lateral atmospheric pressure excitation (TEA) type, a continuous oscillation type, a pulse oscillation type, or the like can be used.

  The shape of the light scattering portion is not particularly limited, but may be a hemispherical shape, a conical shape, a cylindrical shape, a polygonal pyramid shape, a polygonal columnar shape, a hoof shape, or the like. Especially, as a shape of a light-scattering part, a hemispherical shape is preferable. By making the light scattering portion hemispherical, it is possible to improve moldability and prevent an edge from appearing. The arrangement pattern of the diffusion pattern 54 is the same as that of the diffusion pattern 23 in FIG. Further, the average diameter of the light scattering portion is the same as that of the concave portion in FIG.

The light guide film 51 has a diffusion pattern 54 formed by laser irradiation. Therefore, even if the light guide film 51 is formed by a coextrusion molding method, the diffusion pattern 54 does not need to be transferred to the surface of the pressing roll.
<Method for producing light guide film>
Next, although the manufacturing method of the said light guide film 51 is demonstrated below, the manufacturing method of the light guide film 51 of this invention is not limited to the manufacturing method described below.

  As a method for manufacturing the light guide film 51, a step of forming the light guide layer 52 having a wavy fine modulation structure on the surface (STEP 1), and a step of forming the diffusion pattern 54 on the back surface of the light guide layer 52 (STEP 2) And a step (STEP 3) of forming a hard coat layer 53 on the surface of the light guide layer 52. In this embodiment, STEP1 and STEP3 are the same as those described in the first embodiment, and a description thereof is omitted. In the present embodiment, the reverse roll with the diffusion pattern transferred to the surface is not used for the pressing roll.

  STEP 2 forms a light diffusion pattern 54 in the light guide layer 52 by irradiating the light guide layer 52 formed in STEP 1 with laser. The laser with which the light guide layer 52 is irradiated is not particularly limited, and examples thereof include a carbon dioxide gas laser, a carbon monoxide laser, a semiconductor laser, and a YAG (yttrium / aluminum / garnet) laser. In particular, a carbon dioxide laser having a wavelength of 9.3 μm to 10.6 μm is suitable for forming a fine dot pattern. As the carbon dioxide laser, a lateral atmospheric pressure excitation (TEA) type, a continuous oscillation type, a pulse oscillation type, or the like can be used.

<advantage>
In the light guide film 51, since the diffusion pattern 54 includes a plurality of light scattering portions that are colored by laser irradiation, the desired diffusion pattern 54 can be easily and reliably formed. Moreover, when forming the diffusion pattern 54 by such a method, since it is not necessary to provide a convex part etc. in the back surface of the said light guide film 51, thickness reduction can be accelerated | stimulated.

[Other Embodiments]
The light guide film, ultra-thin liquid crystal backlight unit, and portable computer of the present invention can be implemented in variously modified and improved modes in addition to the above-described modes.

  In the said embodiment, although the said light guide film demonstrated the structure where the surface of a light guide layer has a wavy fine modulation structure, it shall be set as the structure where the surface and back surface of a light guide layer have a wavy fine modulation structure. Can do. By having the wavy fine modulation structure on the front and back surfaces of the light guide layer, it is possible to suppress a decrease in luminance and uniformity of the light emitted from the light guide film.

  In the said embodiment, although the surface and back surface of the protective layer of the said light guide film demonstrated the structure which has a fine modulation structure, it can be set as the structure where the surface of a protective layer does not have a fine modulation structure.

  Moreover, the diffusion pattern of the light guide film of the present invention can be formed by various methods such as a printing method such as ink jet printing and screen printing, and a hot pressing method using a flat plate-like inversion mold.

  Further, in the above embodiment, the sheet body forming step (STEP 1) and the diffusion pattern forming step (STEP 2) are described simultaneously. However, as described above, STEP 1 and STEP 2 can be performed in separate steps. Specifically, it is possible to wind the sheet body formed in STEP 1 in a roll shape, and then pull out the sheet body from the roll state to perform STEP 2.

  Moreover, you may perform the process of annealing treatment after STEP2 like the said embodiment. This annealing process is not particularly limited, and a known method can be adopted. For example, a heating method including a heating roll, an infrared heater, hot air, and the like can be employed. Among these methods, it is preferable to perform an annealing treatment with a heating roll. By setting the heating roll to a high temperature, the temperature of the surface of the sheet main body can be increased at a stretch, and the shrinkage rate of the sheet main body can be suppressed.

  In addition to the ultra-thin laptop computer, the portable computer includes a mobile phone terminal such as a mobile phone and a smartphone, and various computers such as a tablet terminal.

As described above, the light guide film and the ultra-thin liquid crystal backlight unit according to the present invention are referred to as, for example, a so-called ultra book because the luminance unevenness of the liquid crystal display surface of the portable computer is suppressed and the thickness is reduced. and ultra thin computer, can be suitably used for such as a portable information terminal such as a mobile phone terminal and a tablet terminal such as a smartphone.

DESCRIPTION OF SYMBOLS 1 Laptop computer, ultra-thin computer 2 Operation part 3 Liquid crystal display part 4 Liquid crystal panel 5 Liquid crystal display part casing 6 Surface support member 7 Hinge part 8 Operation part casing 11 Edge light type backlight unit, backlight unit 12 Light Guide film 13 Reflective sheet 14 Top plate 17 Light source 19 Light guide layer 20 Ridge line 21 Valley line 22 Hard coat layer 23 Diffusion pattern 24 Extrusion device 25 T-die 26 Press roll 33 Light guide film 34 Light guide layer 35 Ridge line 36 Valley line 37 Diffusion pattern 38 Protective layer 39 Co-extruder 40 Extruder 41 Extruder 42 Distribution block 43 Multi-manifold die 44 Press roll 45 Press roll 51 Ride guide film 52 Light guide layer 53 Hard coat layer 54 Diffusion pattern 55 Edge line 56 Valley line 60 Edge Light Backlight unit, backlight unit 61 Ride guide film 62 Reflective sheet 63 Light guide layer 64 Hard coat layer 65 Diffusion pattern 66 Edge line 67 Valley line 68 Light source 111 Edge light type backlight unit 112 Light guide plate 113 Reflective sheet 114 Top plate 115 light source

Claims (12)

A light guide film for an ultra-thin liquid crystal backlight unit that emits light incident from the end face substantially uniformly from the surface,
A light guide layer mainly composed of polycarbonate resin;
A hard coat layer formed on the surface side of the light guide layer,
A light guide film having an average thickness of 600 μm or less. The refractive index (n ₁ ) of the light guide layer is larger than the refractive index (n ₂ ) of the hard coat layer,
2. The light guide film according to claim 1, wherein the light guide layer has a wavy fine modulation structure on a surface thereof. The absolute value (| n ₁ -n ₂ |) of the difference between the refractive index (n ₁ ) of the light guide layer and the refractive index (n ₂ ) of the hard coat layer is 0.1 or less. Item 3. The light guide film according to Item 2. The light guide layer contains an aromatic polycarbonate resin and an antioxidant as main components,
The content of the antioxidant is 0.01 parts by mass or more and 0.1 parts by mass or less with respect to 100 parts by mass of the aromatic polycarbonate resin,
The aromatic polycarbonate-based resin has a weight average molecular weight of 2.0 × 10 ⁴ or more and 5.0 × 10 ⁴ or less,
The ratio (Mw / Mn) of polystyrene-equivalent weight average molecular weight and number average molecular weight of the aromatic polycarbonate resin measured by gel permeation chromatography is 1.0 or more and 2.5 or less. Item 4. The light guide film according to any one of Item 3. Further comprising a protective layer laminated on the surface of the light guide layer,
The protective layer is mainly composed of an acrylic resin,
The light guide film according to any one of claims 1 to 4, wherein the hard coat layer is formed on a surface of the protective layer. The absolute value (| n ₁ −n ₃ |) of the difference between the refractive index (n ₁ ) of the light guide layer and the refractive index (n ₃ ) of the protective layer and the refractive index (n ₂ ) of the hard coat layer 6. The light guide film according to claim 5, wherein an absolute value (| n ₂ −n ₃ |) of a difference from the refractive index (n ₃ ) of the protective layer is 0.1 or less. The refractive index of the light guide layer and the (n _1), the refractive index of the hard coat layer and (n _2), the refractive index of the protective layer and (n _3), but claims 5 or satisfies the following formula (1) The light guide film according to claim 6.
n ₁ > n ₃ > n ₂ (1)   The light guide film according to any one of claims 5 to 7, wherein the light guide layer and the protective layer are formed by a coextrusion molding method.   The light guide film according to claim 1, further comprising a diffusion pattern on a back surface of the light guide layer.   The light guide film according to claim 9, wherein the diffusion pattern is a plurality of light scattering portions that are colored by laser irradiation. Reflective sheet,
The light guide film according to any one of claims 1 to 10, wherein the light guide film is laminated on a surface side of the reflection sheet.
An ultra-thin liquid crystal backlight unit comprising: an optical sheet laminated on a surface of the light guide film; and a light source for irradiating light on an end surface of the light guide film.   A portable computer comprising the ultra-thin liquid crystal backlight unit according to claim 11 in a liquid crystal display unit.

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