JP6148495B2 - Light guide film for ultra-thin liquid crystal backlight, ultra-thin liquid crystal backlight unit, and portable computer - Google Patents

Description

  The present invention relates to a light guide film for an ultra-thin liquid crystal backlight, 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. 6, the edge light type backlight unit 111 is generally placed on the inner surface side of the top plate 114 that is the casing on the backmost surface of the liquid crystal display unit, and is arranged on the surface of the top plate 114. A reflecting plate 113, a light guide plate 112 disposed on the surface of the reflecting plate 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). reference). 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 plate 113 and is incident on the light guide plate 112 again to reduce the light beam loss.

  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 an ultra-thin laptop computer in which the thickest part of the casing called Ultrabook (registered trademark) is 21 mm or less, the thickness of the liquid crystal display part is desired to be about 4 mm to 5 mm. The edge light type backlight unit incorporated in the 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 conjunction 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.

  However, according to the ultra-thin light guide film, there is an inconvenience that the light guide property from the incident end to the opposite end and the diffusibility of the incident direction of the light beam to the left and right are lowered. As a result, the ultra-thin portable computer may reduce screen brightness and uniformity.

JP 2010-177130 A

  The present invention has been made in view of such circumstances, and a light guide film, an ultra-thin liquid crystal backlight unit, and a mobile phone that can be reduced in thickness and can suppress reduction in luminance and uniformity thereof. Is to provide type computers.

The invention made to solve the above problems is
A light guide film for an ultra-thin liquid crystal backlight having an average thickness of 600 μm or less that emits light incident from the end face substantially uniformly from the surface,
The front surface or the front and back surfaces have a wavy fine modulation structure.

  Since the light guide film has a wavy fine modulation structure on the front surface or the front surface and the back surface, the light guide property, the diffusibility, or the light output property is promoted, and the light guide film emits from the surface even if it is ultra-thin 600 μm or less. It is possible to suppress a decrease in the brightness of the light beam and its uniformity. Specifically, when the ridge line direction and the incident direction of the light beam in the fine modulation structure of the light guide film are installed substantially parallel, the transmitted light beam is likely to be condensed on the ridge line side due to the wavy fine modulation structure. In addition, the light beam emitted from the surface is slightly diffused in the direction perpendicular to the ridge line by refraction at the wavy fine modulation structure, so that the diffusibility of the emitted light beam can be improved. Can do. 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 film are set substantially perpendicular to each other, the incident angle of the light beam on the front surface or the back surface varies due to the wavy fine modulation structure. , Light emission from the surface can be improved.

  The ridge line interval in the fine modulation structure is preferably 1 mm or more and 500 mm or less, and the average height of the ridge line based on the approximate virtual plane through which a plurality of valley lines passes is preferably 5 μm or more and 40 μm or less. Thus, by making the said ridgeline space | interval and ridgeline height into the said range, the above-mentioned light guide property, diffusibility, or light emission property can be promoted effectively.

  The light guide film may be formed by an extrusion sheet forming method. According to such an extrusion sheet forming method, a light guide film having a fine modulation structure with a wavy surface or front and back surfaces can be easily and reliably formed by giving the extrusion die an inverted shape perpendicular to the ridgeline of the fine modulation structure. Can be formed.

The retardation value of the light guide film is preferably 50 nm or less, and the residual stress is preferably 8 × 10 ⁵ Pa or less. In this way, by setting the retardation value and residual stress of the light guide film within the above ranges, the risk of distortion due to change with time, an increase in retardation value, etc. is reduced. The effect of improving the property can be maintained for a long time.

  The light guide film preferably has a diffusion pattern on the back surface. 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 have a configuration in which the diffusion pattern includes a plurality of hemispherical concave portions. Thereby, thinning of the light guide film can be promoted.

  Further, the light diffusion pattern may be composed of a plurality of light scattering portions 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, since it is not necessary to provide a convex part etc. in the back surface of the said light guide film, thickness reduction of the said light guide film can be accelerated | stimulated.

  Another invention for solving the above-mentioned problems is an ultra-thin liquid crystal comprising a reflector, the light guide film laminated on the surface side of the reflector, and a light source for irradiating light on the end face of the light guide film. The portable computer includes a backlight unit and the ultra-thin liquid crystal backlight unit in a liquid crystal display unit. The ultra-thin liquid crystal backlight unit and the portable computer can promote luminance and surface uniformity of the luminance because the light guide film has light guiding property, diffusing property, or light emitting property as described above. it can.

The “surface” means the display surface side of the liquid crystal display unit. The “back surface” means the top plate side and the opposite side of the display surface of the liquid crystal display unit. “Residual stress” is the stress generated inside without applying external stress, and the calculation formula “retardation (Re) (nm) / (photoelastic coefficient (10 ¹² / Pa) × thickness (cm )) ”.

  As described above, the light guide film for an ultra-thin liquid crystal backlight, the ultra-thin liquid crystal backlight unit, and the portable computer of the present invention can be reduced in thickness and reduced in luminance and uniformity thereof. The

It is a schematic perspective view of the laptop computer which concerns on one Embodiment of this invention, (A) shows the state which opened the liquid crystal display part, (B) shows the state which closed the liquid crystal display part. It is a typical perspective view which shows the ultra-thin liquid crystal backlight unit of the portable 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 the portable computer 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 ultra-thin liquid crystal backlight unit which concerns on a different form from the ultra-thin liquid crystal backlight unit of FIG. It is typical sectional drawing which shows the conventional edge light type backlight unit.

[First embodiment]
<Portable computer>
A portable computer 1 shown in FIG. 1 is a laptop computer, and 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 portable computer 1 has a casing (a casing that entirely accommodates the components of the portable computer 1) having a thickness (the thickest part (when the liquid crystal display unit 3 is closed)) of 21 mm or less. Registered trademark) (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 liquid crystal backlight unit 11 (hereinafter referred to as “backlight unit”) that emits light toward the liquid crystal panel 4 from the back side. 11 ”). The liquid crystal panel 4 is held by the casing 5 for the liquid crystal display section of the housing around the front surface, side surfaces, and direction. Here, the casing 5 for the liquid crystal display unit includes a top plate 14 disposed on the 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 a liquid crystal display casing 5 and the liquid crystal display casing 5 so as to be rotatable via a hinge portion 7. CPU) etc. are built in.

  The thickness of the liquid crystal display unit 3 is not particularly limited as long as the thickness of the housing is within a desired range, but the upper limit of the thickness of the liquid crystal display unit 3 is preferably 7 mm, more preferably 6 mm, and even more preferably 5 mm. On the other hand, the lower limit of the thickness of the liquid crystal display unit 3 is preferably 2 mm, more preferably 3 mm, and even more preferably 4 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>
The backlight unit 11 of FIG. 2 includes a light guide film 12, a reflector 13 laminated on the back surface of the light guide film 12, and a light source 15 that irradiates the light guide film 12. The light source 15 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 in FIG. 3 efficiently guides light incident from the end face and emits the light from the surface side substantially uniformly. The light guide film has an average thickness of 600 μm or less. The light guide film 12 has a sheet body 16. A diffusion pattern 17 is formed on the back surface of the sheet body 16.

  The sheet body 16 is formed in a substantially rectangular parallelepiped shape. The average thickness of the sheet body 16 is 600 μm or less. The upper limit of the average thickness of the sheet body 16 is more preferably 580 μm, and further preferably 550 μm. On the other hand, the lower limit of the average thickness of the sheet body 16 is preferably 100 μm, more preferably 150 μm, and even more preferably 200 μm. When the average thickness of the sheet main body 16 exceeds the above 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 average thickness of the sheet body 16 is less than the lower limit, the light guide film 12 may have insufficient strength, and the light from the light source 15 may not be sufficiently incident.

  Since the sheet main body 16 needs to have translucency, it is formed transparent, particularly colorless and transparent. Although it does not specifically limit as a main component of the sheet | seat main body 16, Synthetic resins, such as a polycarbonate-type resin excellent in transparency, intensity | strength, etc., and an acrylic resin excellent in transparency, scratch resistance, etc., are mentioned. Especially, as a main component of the sheet | seat main body 16, polycarbonate-type resin is preferable. Since the polycarbonate-based resin is excellent in transparency and has a high refractive index, the air layer (the layer formed in the gap with the optical sheet 16 disposed on the surface side of the light guide film 12 and the back side of the light guide film 12). Total reflection is likely to occur at the interface with the reflection plate 13 disposed in the gap between the reflecting plate 13 and the light beam can be propagated efficiently. Further, since the polycarbonate-based resin has heat resistance, it is difficult for the light source 15 to deteriorate due to heat generation. In addition, since the polycarbonate resin has less water absorption than the acrylic resin, the dimensional stability is high.

  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.

  The linear polycarbonate-based resin is a linear aromatic polycarbonate-based resin produced by a known phosgene method or 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-hydroxy). Phenyl) cyclohexane, 1,1-bis (3,5-dimesyl-4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) decane, 1,1-bis (4-hydroxyphenyl) propane, , 1-bis (4-hydroxyphenyl) cyclodecane, 1,1-bis (3,5-dimethyl-4-hydroxyphenyl) cyclododecane, 4,4′-dihydroxydiphenyl ether, 4,4′-thiodiphenol, 4 , 4'-dihydroxy-3,3-dichlorodiphenyl ether and the like. These can be used alone or in combination of two or more. Such a linear polycarbonate resin is produced by, for example, the method described in US Pat. No. 3,998,672.

  The branched polycarbonate resin is a polycarbonate resin produced 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) Tan, 4,4'-dihydroxy-2,5-dihydroxydiphenyl ether, and the like.

  Such branched polycarbonate resins include, for example, aromatic diphenols, polycarbonate oligomers derived from the above branching agents and phosgene, aromatic diphenols, and the like, as described in JP-A No. 03-182524. A method in which an end stop agent is reacted while stirring so that the reaction mixture containing these becomes a turbulent flow, and when the viscosity of the reaction mixture rises, an aqueous alkali solution is added and the reaction mixture is reacted as a laminar flow. Can be manufactured.

  The sheet body 16 preferably contains the branched polycarbonate resin in the polycarbonate resin in the range of 5 wt% to 80 wt%, and more preferably in the range of 10 wt% to 60 wt%. . This is because if the branched polycarbonate-based resin is less than 5% by weight, the elongational viscosity decreases and molding by extrusion molding becomes difficult. If the branched polycarbonate resin exceeds 80% by weight, the shear viscosity of the resin increases and the moldability becomes low. It is because it falls.

  The sheet body 16 may contain other optional components as long as the transparency is not impaired, but preferably contains 90% by mass or more, more preferably 98% by mass of the linear polycarbonate resin and / or branched polycarbonate resin. It is good to include the above. Examples of the optional component include an ultraviolet absorber, a stabilizer, a lubricant, a processing aid, a plasticizer, an impact resistance aid, a phase difference reducing agent, a matting agent, an antibacterial agent, and an antifungal agent.

  The surface of the sheet body 16 has a wavy fine modulation structure. Further, the direction of the ridge line 18 in the wavy fine modulation structure is substantially orthogonal to the end face on which the light beam is incident. Thereby, when the light rays propagating through the light guide film 12 are reflected on the surface, the traveling direction of some of the light rays approaches the ridge line 18 side, so that the light rays are easily condensed 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 through the light guide film 12 is not easily condensed on the ridge line direction side. In addition, although it is preferable that all the ridge line intervals p in the fine modulation structure are within the above range, some of the plurality of ridge line intervals p in the fine modulation structure may be outside the above range. Of the plurality of ridge line intervals, 50% or more, preferably 70% ridge line intervals may be within the above range.

  In addition, the average height h of the ridge line 18 based on the approximate virtual plane through which the plurality of valley lines 19 in the modulation structure passes is not particularly limited, but is preferably 5 μm or more and 40 μm or less. The upper limit of the average height h is more preferably 20 μm and even more preferably 15 μm. On the other hand, the lower limit of the average height h is more preferably 7 μm and even more preferably 9 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 retardation value (Re) of the sheet body 16 is not particularly limited, but is preferably 50 nm or less, more preferably 40 nm or less, and further preferably 30 nm or less. When the retardation value (Re) exceeds the above upper limit, the optical characteristics of the light beam change, so that the diffusibility of the light beam emitted from the sheet body 16 may not be improved.

As the residual stress of the seat body 16, although not particularly limited, and is preferably 8 × ¹⁰ 5 Pa or less, more preferably 5 × ¹⁰ 5 Pa or less, more preferably 3 × ¹⁰ 5 Pa or less. When the residual stress exceeds the above upper limit, the sheet body 16 is likely to be distorted due to a change with time, and the distorted surface of the sheet body 16 may be curved. Further, the retardation value (Re) generated as a photoelastic property may increase. As a result, there is a possibility that the effect of improving the luminance and uniformity of the light beam emitted from the sheet body 16 cannot be maintained for a long time.

  The diffusion pattern 17 includes a plurality of concave portions and is formed on the back surface of the sheet main body 16. The plurality of recesses are formed in a dotted shape on the back surface of the sheet body 16 and are arranged so that uniform light can be emitted from the light guide film 12 from the front surface side. Specifically, the plurality of recesses are formed so that the existence ratio at a position close to the light source 15 is small, and the existence ratio increases as the distance from the light source 15 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 is preferably 50 μm or less. As an upper limit of the average diameter of the said recessed part, 40 micrometers is more preferable and 30 micrometers is further more preferable. On the other hand, the lower limit of the average diameter of the recesses is preferably 0.5 μm, more preferably 1 μm, and even more preferably 5 μm. When the average diameter of the recess exceeds the upper limit, luminance unevenness may occur, and the height of the recess increases, which may make it difficult to promote thinning of the light guide film 12. Conversely, when the average diameter of the recesses is less than the lower limit, the light scattering effect may not be sufficiently obtained. 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.

(reflector)
The reflection plate 13 reflects the light beam emitted from the back surface side of the light guide film 12 from the front surface side. The reflector 13 is a regular reflection 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 having improved properties.

(Top board)
The top plate 14 is formed from a metal or resin plate. As this metal top plate 14, for example, an aluminum plate can be used. Here, the thickness of the plate material is preferably 500 μm or more and 1200 μm or less, and more preferably 700 μm or more and 900 μm or less. The top plate 14 is formed with the periphery of the plate material curved toward the surface side, and the curved portion functions as a rib and has sufficient strength as the top plate 14. In addition, although parts (center part) other than the curved part of this rib are made into the flat surface, patterns, such as a geometric pattern, can also be embossed.

(light source)
The light source 15 is incorporated in the casing 5 for the liquid crystal display unit, and is disposed so that the irradiation surface faces (or abuts) an end surface that is substantially perpendicular to the ridge line direction in the fine modulation structure of the light guide film 12. Various light sources 15 can be used. For example, a light emitting diode (LED) can be used. Specifically, a light source 15 in which a plurality of light emitting diodes are arranged along the end face of the light guide film 12 can be used.

  In the backlight unit 11, the one-side edge light system in which the light source 15 is disposed on the side of only one side edge of the light guide film 12, or the light source 15 is disposed on the side of the opposite side edge of the light guide film 12. It is possible to employ a double-sided edge light system or the like that is disposed respectively.

<Method for producing light guide film>
Next, a method for manufacturing the light guide film 12 will be described.

  The manufacturing method of the light guide film 12 includes a step (STEP 1) of forming a sheet body 16 having a wavy fine modulation structure and a step (STEP 2) of forming a diffusion pattern 17 on the sheet body 16. 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 21 of FIG. The extrusion molding device 21 includes an extruder and a T-die 22, a pair of pressing rolls 23, a winding device (not shown), and the like. As the T die 22, 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 22 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 23 are disposed adjacent and in parallel. The extruder and the T-die 22 are configured to be able to extrude molten resin into a sheet shape at the nip between a pair of pressing rolls 23. The pair of pressing rolls 23 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 23, 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 23 includes a pressing roll 23a and a pressing roll 23b. Among these, the press roll 23a is formed as an inverted type in which the diffusion pattern is transferred to the surface.

  STEP 1 is performed by an extrusion sheet forming method in which the forming material of the molten sheet body 16 is supplied to the T die 22, the forming material is extruded from the extruder and the T die 22, and then pressed by a pair of pressing rolls 23. . The melting temperature of the forming material of the sheet body 16 extruded from the T die 22 is appropriately selected in consideration of the melting point of the resin used. The average thickness of the sheet body 16 formed in STEP 1 is 600 μm or less. The average thickness of the sheet body 16 is adjusted by adjusting the arrangement interval of the pair of pressing rolls 23.

  Further, the arrangement interval, the rotation speed, and the like of the pair of pressing rolls 23 are adjusted in consideration of the supply amount of the forming material of the sheet main body 16 extruded from the T die 22, the molten state, and the like.

  STEP2 is performed by transferring the diffusion pattern transferred to the surface of the pressing roll 23a before the forming material of the molten sheet body 16 is cured. In STEP 2, the material for forming the molten sheet main body 16 is pressed by the pair of pressing rolls 23, whereby the diffusion pattern transferred to the surface of the pressing roll 23 a is transferred to the back surface of the sheet main body 16. In STEP 2, a plurality of recesses are formed on the back surface of the sheet body 16 by this transfer.

<Advantages>
In the light guide film 12, the surface of the sheet main body 16 has a wavy fine modulation structure, and the ridge line direction in the wavy fine modulation structure is substantially orthogonal to the end face on which the light beam is incident. When the light rays propagating in the film 12 are reflected on the surface, the traveling direction of some of the light rays approaches the ridge line 18 side, so that the light rays are easily collected on the ridge line direction side. For this reason, the light guide property of the incident light beam can be improved. In addition to this, the light emitted from the surface of the light guide film 12 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 is improved. For this reason, even if the light guide film 12 is ultra-thin with an average thickness of 600 μm or less, the luminance of the light emitted from the light guide film and a decrease in the uniformity thereof are suppressed.

  Furthermore, since the light guide film 12 has the diffusion pattern 17 on the back surface, the light can be efficiently scattered by the diffusion pattern 17 and emitted from the front surface side.

  In the light guide film 12, according to the extrusion sheet molding method, the surface of the sheet main body 16 has a wavy fine modulation structure by attaching an inverted shape of the vertical cross-sectional shape to the ridgeline of the fine modulation structure to the extrusion die. A light guide film can be formed easily and reliably.

In addition, since the retardation value (Re) of the light guide film 12 is 50 nm or less and the residual stress is 8 × 10 ⁵ Pa or less, the light guide film 12 is less likely to be distorted due to aging, and the retardation due to the photoelastic property. Since the risk of increasing the value is reduced, as a result, it is possible to maintain the light guide property and diffusibility improving effect of the light guide film for a long period of time.

  Further, since the backlight unit 11 includes the light guide film 12, the thickness can be reduced. Further, the backlight unit 11 is prevented from being reduced in luminance and uniformity by the light guide film 12.

  In addition, since the portable computer 1 includes the backlight unit 11, the portable computer 1 can be reduced in thickness and can be prevented from being deteriorated in luminance and uniformity.

[Second Embodiment]
<Backlight unit>
The backlight unit 31 in FIG. 5 includes a light guide film 32, the reflector 13 laminated on the back surface of the light guide film 32, and the light source 15 that irradiates the light guide film 32 with light. The light source 15 is disposed on the end face side substantially parallel to the ridge line direction in the fine modulation structure of the light guide film 32 described later.

<Light guide film>
The light guide film 32 is used as a light guide film of an edge light type ultra-thin liquid crystal backlight unit in a liquid crystal display part of a laptop computer having a casing thickness of 21 mm or less.

  The light guide film 32 efficiently and uniformly emits light incident from the end surface from the surface side. The light guide film 32 has a sheet body 36. The light guide film 32 is disposed such that an end surface substantially parallel to the ridge line direction in the fine modulation structure and the light source face (or abut).

  The surface of the sheet body 36 has a wavy fine modulation structure. In addition, the direction of the ridge line 38 in the wavy fine modulation structure and the end face on which the light beam enters are positioned substantially in parallel. As a result, the direction of the ridgeline 38 of the fine modulation structure is positioned substantially perpendicular to the traveling direction of the light beam propagating through the light guide film 32, so that the incident angle of the light beam on the surface varies due to the wavy fine modulation structure. As a result, the light output from the surface of the light guide film 32 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 is less than the lower limit, the light guide film 32 may be excessively emitted from the surface. On the other hand, when the ridge line interval exceeds the above upper limit, the light output improvement effect of the light guide film 32 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 p in the fine modulation structure may be outside the above range. Of these ridge line intervals, 50% or more, preferably 70% of the ridge line intervals may be within the above range.

  Further, the average height of the ridge line 38 based on the approximate virtual plane through which the plurality of valley lines 39 in the modulation structure passes is not particularly limited, but is preferably 5 μm or more and 40 μm or less. The upper limit of the average height h is more preferably 20 μm and even more preferably 15 μm. On the other hand, the lower limit of the average height is more preferably 7 μm, and even more preferably 9 μm. When the average height is less than the lower limit, there is a possibility that the effect of improving the light output property of the light guide film 32 is low. On the other hand, when the average height exceeds the upper limit, the light guide film 32 may be excessively emitted from the surface of the light guide film 32.

  The other shapes, main components, additives, and the like of the sheet main body 36 are the same as those of the sheet main body 16 of the light guide film 12 in FIG.

  A diffusion pattern 37 is formed on the back surface of the sheet body 36. The diffusion pattern 37 is composed of a plurality of light scattering portions that are colored by laser irradiation. Specifically, the light scattering portion is formed by allowing the color former to be contained in the forming material of the sheet main body 36, and irradiating the laser after forming the sheet main body 36 to develop the color.

  The color former dispersed and contained in the forming material of the sheet main body 36 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 37 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 32, it is preferable to use a color former that develops white color by laser irradiation, and on the contrary, 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 sheet main body 36 is preferably 0.0001% by mass to 2.5% by mass, and more preferably 0.1% by mass to 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 above upper limit, the transparency and mechanical strength of the sheet main body 36 may be lowered.

  The laser for irradiating the sheet body 36 is not particularly limited, and examples thereof include a carbon dioxide 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 diffusion 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 hemispherical, conical, cylindrical, polygonal pyramid, polygonal column, hoof, or the like. Especially, as a shape of the said light-scattering part, a hemisphere is preferable. By making the said light-scattering part hemispherical, while improving a moldability, it can prevent that an edge comes out. The arrangement pattern of the diffusion pattern 37 is the same as that of the diffusion pattern 17 in FIG. Further, the average diameter of the light scattering portion is the same as the concave portion of the diffusion pattern 17 in FIG.

  The light guide film 32 can easily and reliably form a desired diffusion pattern 37 by laser irradiation. Moreover, when forming the diffusion pattern 37 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 32, thickness reduction can be accelerated | stimulated.

  In addition, since the light guide film 32 has the diffusion pattern 37 formed by laser irradiation, the diffusion pattern does not need to be transferred to the surface of the pressing roll even when the light guide film 32 is formed by a melt extrusion molding method. .

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

  In the said embodiment, although the said light guide film demonstrated the structure where the surface of a sheet | seat main body has a wavy fine modulation structure, it can be set as the structure where the surface and back surface of a sheet | seat main body have a wavy fine modulation structure. . By having the wavy fine modulation structure on the front and back surfaces of the sheet main body, it is possible to further suppress a decrease in luminance and uniformity of light emitted from the light guide film.

  Further, the diffusion pattern may be formed as a convex portion by a printing method. In this case, when a sheet body is formed by the above-described extrusion sheet forming method, a pair of pressing rolls having no diffusion pattern transferred to the surface is used. As a printing method for forming the convex shape, it can be performed by an ink jet printing method or a screen printing method using a white or transparent ink. By forming the diffusion pattern on the concave portion by a printing method, the diffusion pattern can be easily and reliably formed.

  The ultra-thin liquid crystal backlight unit in which the light guide film is disposed can use a top plate as a reflecting plate. By forming the surface of the top plate as a reflection surface, the light beam emitted from the back surface side of the light guide film can be reflected on the surface side by this reflection surface.

  Moreover, in the said embodiment, although the cross-sectional shape demonstrated the method of manufacturing the said light guide film which has the said wavy fine modulation structure using the T die which is a reverse shape of a perpendicular cross-sectional shape with the ridgeline of the said fine modulation structure. For example, the light guide film having the wavy fine modulation structure may be manufactured by adjusting the interval between the pair of pressing rolls 23 and the rotation speed. In this case, a known cross-sectional shape of the extrusion die can be used.

  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 an annealing process 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.

  As described above, the portable computer provided with the light guide film for an ultra-thin liquid crystal backlight and the ultra-thin liquid crystal backlight unit according to the present invention has a reduced thickness and uniformity of the liquid crystal display surface and is thin. Therefore, it can be suitably used for, for example, an ultra-thin computer called a so-called Ultrabook, a mobile information terminal such as a smartphone, and a portable information terminal such as a tablet terminal.

DESCRIPTION OF SYMBOLS 1 Portable computer, ultrathin 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 Ultrathin liquid crystal backlight unit, backlight unit 12 Light guide film 13 Reflector 14 Top plate 15 Light source 16 Sheet body 17 Diffusion pattern 18 Ridge line 19 Valley line 21 Extrusion device 22 T-die 23 Press roll 23a Press roll 23b Press roll 31 Backlight unit 32 Light guide film 36 Sheet main body 37 Diffusion pattern 38 Edge line 39 Valley line

Claims (8)

A light guide film for an ultra-thin liquid crystal backlight having an average thickness of 600 μm or less that emits light incident from the end face substantially uniformly from the surface,
A light guide film surface or the surface and back surface have a wavy microstructure modulation structure, characterized in that the ridge line interval in the fine modulation structure is 1mm or less than 500mm. 2. The light guide film according to claim 1 , wherein the average height of the ridge lines based on the approximate virtual plane through which the plurality of valley lines in the fine modulation structure passes is 5 μm or more and 40 μm or less. The light guide film according to claim 1, wherein the retardation value (Re) is 50 nm or less, and the residual stress is 8 × 10 ⁵ Pa or less. The light guide film according to claim 1 , wherein the back surface has a diffusion pattern. The light guide film according to claim 4 , wherein the diffusion pattern includes a plurality of hemispherical concave portions. The light guide film according to claim 4 , wherein the diffusion pattern includes a light scattering portion including a plurality of color formers that are colored by laser irradiation. reflector,
An ultra-thin liquid crystal backlight comprising: the light guide film according to any one of claims 1 to 6 ; and a light source that irradiates light to an end surface of the light guide film. unit. A portable computer comprising the ultra-thin liquid crystal backlight unit according to claim 7 in a liquid crystal display unit.

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