CN104007579A - Ultrathin liquid crystal backlight guide light film, ultrathin liquid crystal backlight unit and portable computer - Google Patents

Abstract

The invention provides a light guide film for an ultra-thin liquid crystal backlight, an ultra-thin liquid crystal backlight unit and a portable computer, which can achieve thinning and can suppress the decrease in brightness and its uniformity. The light guide film for ultra-thin liquid crystal backlight of the present invention is a light guide film for ultra-thin liquid crystal backlight with an average thickness of 600 μm or less, which emits light incident from the end surface substantially uniformly from the surface, and is characterized in that the surface or surface And the back has a wavy micro-modulation structure. In addition, it is preferable that the interval between the ridgelines of the fine modulation structure is preferably not less than 1 mm and not more than 500 mm. Furthermore, it is preferable that the average height of the ridgelines based on the approximate imaginary plane through which the plurality of valley lines of the finely modulated structure pass is preferably not less than 5 μm and not more than 40 μm.

Description

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

technical field

The invention relates to a light guide film for ultrathin liquid crystal backlight, an ultrathin liquid crystal backlight unit and a portable computer.

Background technique

In liquid crystal display devices, a backlight method in which a liquid crystal layer is irradiated from the back to emit light is widespread, and backlight units such as side light type and direct type are mounted on the lower surface of the liquid crystal layer. Generally, as shown in FIG. 6 , the side-light type backlight unit 111 is placed on the inner surface side of the top plate 114 as the backmost casing of the liquid crystal display unit, and includes a reflector 113 disposed on the surface of the top plate 114 and disposed on the top plate 114. The light guide plate 112 on the surface of the reflection plate 113 described above and the light source 115 that irradiates light to the end surface of the light guide plate 112 (refer to Japanese Patent Laid-Open Publication No. 2010-177130). In the side-light type backlight unit 111, the light irradiated from the light source 115 is incident on the end surface of the light guide plate 112, and the light incident on the light guide plate 112 propagates in the light guide plate 112 and exits from the surface of the light guide plate 112. In addition, the light emitted from the back surface of the light guide plate 112 is reflected by the reflector 113 and enters the light guide plate 112 again, so that the loss of light can be reduced.

A portable computer including the above-mentioned liquid crystal display unit is required to be thinner and lighter in order to improve its portability and convenience, and therefore the liquid crystal display unit is also required to be thinner. In particular, in ultra-thin notebook computers called ultrabooks (registered trademarks), where the thickest part of the casing is 21 mm or less, it is desirable that the thickness of the liquid crystal display part be from 4 mm to 5 mm. Edge-lit backlight units in display units are required to be further thinned.

Therefore, for the light guide film used in the ultra-thin portable computer, the thinning of the light guide film is also required while the liquid crystal display portion is required to be thinned. Specifically, as the thickness of the light guide film It is desirable to be about 600 μm or less.

However, according to the above-mentioned ultra-thin light guide film, there is a disadvantage in that the light guide from the incident end to the opposite end and the diffusivity of light rays in the left and right directions of the incident direction are reduced. As a result, there is a problem that the brightness and uniformity of the screen of the ultra-thin portable computer decrease.

prior art literature

Patent Document 1: Japanese Patent Laid-Open Publication No. 2010-177130

Contents of the invention

In view of the above-mentioned problems, an object of the present invention is to provide a light guide film, an ultra-thin liquid crystal backlight unit, and a portable computer capable of reducing the thickness and suppressing reductions in brightness and uniformity thereof.

In order to solve the above problems, the present invention provides a light guide film, which is a light guide film for ultra-thin liquid crystal backlights with an average thickness of 600 μm or less, which emits light incident from the end surface substantially uniformly from the surface. A wavy fine modulation structure (modulation structure), or a wavy fine modulation structure on the front and back.

Since the light guide film has a wavy fine modulation structure on the surface, or the surface and the back, it can improve the light guide performance, diffusion performance, or light extraction performance, and can suppress the brightness and brightness of the light emitted from the surface even if it is ultra-thin below 600 μm. decrease in its uniformity. Specifically, when the ridgeline direction of the finely modulated structure of the light guide film is set approximately parallel to the incident direction of the light, since the wavelike finely modulated structure is used to easily condense the transmitted light toward the ridgeline direction side, The light guide property of the incident light can be improved, and since the light emitted from the surface is slightly diffused in the direction perpendicular to the ridge line due to the refraction at the wavy finely modulated structure, the diffusivity of the emitted light can be improved. On the other hand, when the direction of the ridge line of the fine modulation structure of the light guide film is substantially perpendicular to the incident direction of the light, the incident angle of the light to the front and/or rear surface changes due to the wave-shaped fine modulation structure. , so it is possible to improve the light extraction performance from the surface.

Preferably, the interval between the ridge lines of the fine modulation structure is not less than 1 mm and not more than 500 mm. Preferably, the average height of the ridgelines based on the approximate imaginary plane through which the plurality of valley lines pass is 5 μm or more and 40 μm or less. By making the interval between the ridge lines and the height of the ridge lines within the above range, the light guiding performance, diffusion performance, or light extraction performance can be effectively improved.

Preferably, the light guide film is formed by extrusion molding. According to the extruded sheet molding method, by making the extrusion die have the inverse shape of the cross-sectional shape perpendicular to the ridge line of the finely modulated structure, it is possible to easily and reliably form the surface or the surface and the back surface with wavy fine grains. Light-guiding film with modulation structure.

Preferably, the light guide film has a retardation value of 50 nm or less, and a residual stress of 8×10 ⁵ Pa or less. By setting the retardation value and residual stress of the light guide film within the above-mentioned ranges, problems such as deformation over time and increase in retardation value can be reduced, and as a result, the above-mentioned improvement can be maintained for a long time. The effect of light guide performance and diffusion performance, or light extraction performance.

Preferably, the back of the light guide film has a diffusion pattern. Thereby, light introduced from the light source can be efficiently diffused by the diffusion pattern and emitted from the surface side.

Preferably, the diffusion pattern of the light guide film is composed of a plurality of hemispherical recesses. Accordingly, reduction in thickness of the light guide film can be promoted.

In addition, it is preferable that the light diffusion pattern is composed of a plurality of light scattering parts, and the light scattering parts are colored by laser irradiation. Thereby, a desired diffusion pattern can be easily and reliably formed. In addition, when the diffusion pattern is formed by such a method, since it is not necessary to provide convex portions or the like on the back surface of the light guide film, it is possible to promote thinning of the light guide film.

In addition, in order to solve the above problems, the present invention provides an ultra-thin liquid crystal backlight unit, which includes a reflector; the light guide film is laminated on the surface side of the reflector; and a light source is directed toward the guide. The end surface of the optical film is irradiated with light. In addition, the present invention provides a portable computer including the above-mentioned ultra-thin liquid crystal backlight unit in a liquid crystal display portion. Since the light guide film has light guide performance and diffusion performance, or light extraction performance as described above, the ultra-thin liquid crystal backlight unit and the portable computer can promote luminance and surface uniformity of luminance.

In addition, "surface" means the display surface side of a liquid crystal display part. The term "rear surface" refers to the top plate side, that is, the side opposite to the display surface of the liquid crystal display unit. The so-called "residual stress" refers to the stress generated inside even if no external stress is applied, and is calculated by the formula "retardation value (Re) (nm) / (photoelastic coefficient (10 ¹² /Pa) × thickness (cm) )” calculated value.

As described above, the light guide film for ultra-thin liquid crystal backlight, ultra-thin liquid crystal backlight unit, and portable computer of the present invention can achieve thinning, and can suppress the decrease in brightness and its uniformity.

Description of drawings

1 is a schematic perspective view of a notebook computer according to an embodiment of the present invention. FIG. 1(A) shows a state where a liquid crystal display unit is opened, and FIG. 1(B) shows a state where a liquid crystal display unit is closed.

FIG. 2 is a perspective view schematically showing an ultra-thin liquid crystal backlight unit of the portable computer of FIG. 1 .

3 is a cross-sectional view A1 - A2 (schematic cross-sectional view) of the light guide film of the ultra-thin liquid crystal backlight unit of the portable computer shown in FIG. 2 .

FIG. 4 is a partially enlarged view schematically showing a manufacturing apparatus for a light guide film of the ultra-thin liquid crystal backlight unit in FIG. 2 .

5 is a cross-sectional view schematically showing an ultra-thin liquid crystal backlight unit in a different form from the ultra-thin liquid crystal backlight unit of FIG. 2 .

FIG. 6 is a cross-sectional view schematically showing a conventional side-light type backlight unit.

Explanation of reference signs

1 portable computer, ultra-thin computer

2 operation department

3LCD display part

4LCD panel

5 Housing for liquid crystal display

6 surface support components

7Hinge part (ヒンジ part)

8 Case for operation part

11 ultra-thin LCD backlight unit, backlight unit

12 light guide film

13 reflector

14 top plate

15 light sources

16 main bodies

17 Diffusion Patterns

18 Ridgeline

19 Valley Line

21 extrusion molding device

22T shape die

23 pressing roller

23a Press roller

23b Press roller

31 backlight units

32 light guide film

36 main bodies

37 Diffusion Patterns

38 Ridgeline

39 Valley Line

Detailed ways

[first embodiment]

＜Portable computer＞

The portable computer 1 of FIG. 1 is a notebook computer, and has an operation part 2 and a liquid crystal display part 3 connected to the operation part 2 in a rotatable (openable and closable) manner. The thickness (the thickest part (when the liquid crystal display unit 3 is closed)) of the casing of the portable computer 1 (the casing that accommodates the entire constituent parts of the portable computer 1) is 21 mm or less, and is called a so-called ultrabook (registered trademark ) portable computer (hereafter sometimes referred to as "slim computer 1").

The liquid crystal display unit 3 of the ultra-thin computer 1 has a liquid crystal panel 4 and an edge-light type ultra-thin liquid crystal backlight unit 11 (hereinafter sometimes referred to as "backlight unit 11") that irradiates light to the liquid crystal panel 4 from the back side. "). The casing 5 for the liquid crystal display unit passing through the casing holds the surface, side surfaces, and sides of the liquid crystal panel 4 . Here, the liquid crystal display case 5 has a top plate 14 arranged on the front (and back) of the liquid crystal panel 4 , and a surface support member 6 arranged on the front side around the front of the liquid crystal panel 4 . In addition, the casing of the ultra-thin computer 1 has a case 5 for a liquid crystal display unit and a case 8 for an operation unit. On the casing 5, a central processing unit (ultra-low voltage CPU) and the like are built in.

Although the thickness of the liquid crystal display part 3 is not particularly limited as long as the thickness of the casing can be within the desired range, the upper limit of the thickness of the liquid crystal display part 3 is preferably 7 mm, more preferably 6 mm, and even more preferably It is 5mm. On the other hand, the lower limit of the thickness of the liquid crystal display portion 3 is preferably 2 mm, more preferably 3 mm, and still more preferably 4 mm. If the thickness of the liquid crystal display unit 3 exceeds the above-mentioned upper limit, there is a problem that it is difficult to comply with the thinning request of the ultrathin computer 1 . Moreover, if the thickness of the liquid crystal display part 3 is less than the said lower limit, there exists a problem that the intensity|strength and brightness of the liquid crystal display part 3 will fall.

＜Backlight unit＞

The backlight unit 11 of FIG. 2 has a light guide film 12 , a reflection plate 13 laminated on the back surface of the light guide film 12 , and a light source 15 that irradiates light to the light guide film 12 . The light source 15 is disposed on the end surface side of the light guide film 12 described later that is substantially perpendicular to the ridgeline direction of the fine modulation structure.

(light guide film)

The light guide film 12 in FIG. 3 efficiently guides the light incident from the end surface and emits the light substantially uniformly from the surface side. The average thickness of the light guide film is 600 μm or less. The light guide film 12 has a sheet main body 16 . A diffusion pattern 17 is formed on the back surface of the sheet main body 16 .

The sheet main body 16 is formed in a substantially rectangular parallelepiped shape. The average thickness of the sheet main 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 still more 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 still more preferably 200 μm. When the average thickness of the sheet main body 16 exceeds the above-mentioned upper limit, it may not meet the demand for thinning the backlight unit 11 desired in the ultrathin computer 1 . In addition, when the average thickness of the sheet body 16 is less than the lower limit, there is a problem that the strength of the light guide film 12 is insufficient, and there is a problem that the light from the light source 15 cannot be sufficiently incident.

Since the sheet main body 16 is required to have translucency, it is formed to be transparent, especially colorless and transparent. The main component of the sheet body 16 is not particularly limited, and examples thereof include synthetic resins such as polycarbonate-based resins excellent in transparency and strength, and acrylic resins excellent in transparency and scratch resistance. Among them, a polycarbonate-based resin is preferable as the main component of the sheet body 16 . Polycarbonate-based resin has excellent transparency and high refractive index, so it is easy to form a layer with an air layer (a layer formed in the gap between the optical sheet 16 disposed on the surface side of the light guide film 12 and disposed on the guide film 12). The interface of the layer formed by the gap between the reflectors 13 on the back side of the optical film 12 causes total reflection and can efficiently transmit light. In addition, since the polycarbonate-based resin has heat resistance, deterioration due to heat generation of the light source 15 and the like are less likely to occur. In addition, polycarbonate-based resins have lower water absorption than acrylic-based resins, and thus have high dimensional stability.

There is no particular limitation on the polycarbonate resin as described, it can be only any one of linear polycarbonate resin or branched polycarbonate resin, and it can also include linear polycarbonate resin and Polycarbonate-based resin with both branched polycarbonate-based resins.

The linear polycarbonate-based resin is a linear aromatic polycarbonate-based resin produced by a known phosgene method or a melting method, and is composed of a carbonate component and a bisphenol component. As the precursor substance for introducing the carbonate component, phosgene, diphenyl carbonate, and the like may, for example, be mentioned. In addition, examples of bisphenols include 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane, 1,1-bis (4-hydroxyphenyl)cyclohexane, 1,1-bis(3,5-dimethylsulfonyl-4-hydroxyphenyl)cyclohexane, 1,1-bis(4-hydroxyphenyl)decane , 1,1-bis(4-hydroxyphenyl)propane, 1,1-bis(4-hydroxyphenyl)cyclodecane, 1,1-bis(3,5-dimethyl-4-hydroxyphenyl) ) cyclododecane, 4,4'-dihydroxydiphenyl ether, 4,4'-thiobisphenol, 4,4'-dihydroxy-3,3-dichlorodiphenyl ether, etc. These may be used alone or in combination of two or more. The linear polycarbonate-based resin is produced, for example, by the method described in US Pat. No. 3,989,672.

The branched polycarbonate-based resin is a polycarbonate-based resin produced using a branching agent, and examples of the branching agent include phloroglucinol, 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, 1,1,1-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, 1,1,1-tris(3,5-dichloro-4-hydroxyphenyl)ethane, 1,1,1 - Tris(3-bromo-4-hydroxyphenyl)methane, 1,1,1-tris(3-bromo-4-hydroxyphenyl)ethane, 1,1,1-tris(3,5-dibromo -4-hydroxyphenyl)methane, 1,1,1-tris(3,5-dibromo-4-hydroxyphenyl)ethane, 4,4'-dihydroxy-2,5-dihydroxydiphenyl ether wait.

The branched polycarbonate-based resin is produced, for example, by the following method described in Japanese Patent Laid-Open Publication No. 03-182524: making polycarbonate derived from aromatic bisphenols, the branching agent, and phosgene The reaction mixed solution of polycarbonate oligomer, aromatic bisphenols and end-capping agent becomes the mode of turbulent flow, the reaction mixed solution is reacted while stirring the described reaction mixed solution, the viscosity of the reaction mixed solution When the temperature rises, an alkaline aqueous solution is added and the reaction mixture is reacted so that the reaction mixture becomes a laminar flow.

The sheet main body 16 preferably contains the branched polycarbonate resin in an amount ranging from 5% by weight to 80% by weight in the polycarbonate-based resin, more preferably in a range from 10% by weight to 60% by weight. The branched polycarbonate resin. This is because: if the branched polycarbonate resin is less than 5% by weight, the extensional viscosity decreases, making it difficult to form by extrusion molding, and if the branched polycarbonate resin exceeds 80% by weight, the shear viscosity of the resin will decrease. increase, the formability decreases.

Although the sheet main body 16 may contain other arbitrary components within the range that does not impair transparency, it is preferable to contain 90% by mass or more of the linear polycarbonate-based resin and/or branched-chain polycarbonate-based resin, It is more preferable to contain 98% by mass or more of the linear polycarbonate resin and/or branched polycarbonate resin. Among them, as the optional components mentioned above, ultraviolet absorbers, stabilizers, lubricants, processing aids, plasticizers, impact resistance additives, phase difference reducers, matting agents, antibacterial agents, antifungal agents, etc. .

The surface of the sheet main body 16 has a wave-like fine modulation structure. In addition, the direction of the ridge line 18 of the wave-like finely modulated structure is substantially perpendicular to the end face where the light is incident. Therefore, when the light propagating in the light guide film 12 is reflected on the surface, since a part of the traveling direction of the light is deviated to the side of the ridge line 18, the light is easily focused toward the side of the ridge line. In addition, since the light emitted from the surface is slightly diffused in the direction perpendicular to the ridgeline direction due to the refraction at the wavy fine modulation structure, the diffusibility of the emitted light can be improved.

The ridgeline pitch p of the fine modulation structure is not particularly limited, but is preferably not less than 1 mm and not more than 500 mm. The upper limit of the interval p between ridge lines is more preferably 100 mm, still more preferably 60 mm. On the other hand, the lower limit of the ridge line interval p is more preferably 10 mm, and still more preferably 20 mm. When the ridgeline interval p is out of the above-mentioned range, it is difficult for the light rays propagating in the light guide film 12 to converge toward the ridgeline direction side. In addition, although it is preferable that all of the ridgeline intervals p of the finely modulated structure are within the above-mentioned range, some of the plurality of ridgeline intervals p of the finely modulated structure may be outside the above-mentioned range. In this case, As long as 50% or more of the multiple ridgeline intervals are within the above-mentioned range, it is preferable that 70% of the ridgeline intervals are within the above-mentioned range.

Also, the average height h of the ridgelines 18 based on the approximate imaginary plane through which the plurality of valley lines 19 of the modulation structure pass is not particularly limited, but is preferably not less than 5 μm and not more than 40 μm. The upper limit of the average height h is more preferably 20 μm, still more preferably 15 μm. On the other hand, the lower limit of the average height h is more preferably 7 μm, still more preferably 9 μm. When the average height h is out of the range, it is difficult for the light rays propagating in the light guide film 12 to converge toward the ridgeline direction.

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 still more preferably 30 nm or less. When the retardation value (Re) exceeds the above-mentioned upper limit, the optical characteristics of the light rays change, so there is a problem that the diffusivity of the light rays emitted from the sheet body 16 cannot be improved.

In addition, the residual stress of the sheet body 16 is not particularly limited, but is preferably 8×10 ⁵ Pa or less, more preferably 5×10 ⁵ Pa or less, and still more preferably 3×10 ⁵ Pa or less. When the residual stress exceeds the above-mentioned upper limit, there is a problem that the sheet body 16 is likely to be deformed with time, and the surface of the deformed sheet body 16 is curved. In addition, there are problems such as an increase in retardation value (Re), which is a property of photoelasticity. As a result, the effect of improving the brightness and uniformity of light emitted from the sheet body 16 cannot be maintained for a long period of time.

The required light guiding distance of the sheet body 16 from the end surface on the light source 15 side is not particularly limited, but the lower limit of the required light guiding distance is preferably 7 cm, more preferably 9 cm, and even more preferably 11 cm. On the other hand, the upper limit of the necessary light guiding distance is preferably 25 cm, more preferably 23 cm, and even more preferably 21 cm. If the required light guiding distance is less than the lower limit, there is a problem that it cannot be used for a relatively large terminal. On the contrary, when the necessary light guiding distance exceeds the above upper limit, there are problems that, as described above, since the sheet main body 16 is thin, the sheet main body 16 is easily bent, and the light guiding property is deteriorated. Insufficient. In addition, the required light guide distance of the sheet main body 16 from the end surface on the light source 13 side refers to the required distance for the light emitted from the light source 15 and incident on the end surface of the sheet main body 16 to travel from the end surface toward the end surface opposite to the end surface. distance. Specifically, for example, for a single-sided edge-light type backlight unit, the so-called necessary light guiding distance from the end surface of the sheet main body 16 on the light source 15 side refers to the end surface of the sheet main body on the light source side and the end surface opposite to the end surface. For the side-light type backlight unit, the so-called necessary light guide distance from the end surface of the light source 15 side of the so-called sheet main body 16 refers to the distance between the end surfaces of the opposite sheet main bodies where the light sources are respectively arranged. 1/2 of the distance.

The surface area of the sheet body 16 is not particularly limited, but the lower limit of the surface area is preferably 150 cm ² , more preferably 180 cm ² , and still more preferably 200 cm ² . On the other hand, the upper limit of the surface area is preferably 760 cm ² , more preferably 740 cm ² , and still more preferably 720 cm ² . If the surface area of the sheet body 16 is smaller than the lower limit, there is a problem that it cannot be used for a relatively large terminal. Conversely, if the surface area of the sheet body 16 exceeds the upper limit, there is a problem that, as described above, since the sheet body 16 is thin, the sheet body 16 tends to warp, and sufficient light guiding properties cannot be obtained.

The diffusion pattern 17 is composed of a plurality of recesses and is formed on the back surface of the sheet main body 16 . The plurality of recesses are formed in scattered spots on the back surface of the sheet main body 16 and arranged so that uniform light can be emitted from the front side of the light guide film 12 . Specifically, the plurality of recesses are formed such that their presence ratio is small near the light source 15 , and their presence ratio increases as the distance from the light source 15 increases. The ratio of existence of the plurality of recesses may be adjusted by adjusting the arrangement position while keeping the size of each recess the same, or the ratio of existence of the plurality of recesses may be adjusted by changing the size of each recess. However, from the viewpoint of promoting thinning of the light guide film 12 and improving light guide performance, it is preferable to adjust the arrangement position while making the sizes of the respective recesses the same.

The average diameter of the recesses is not particularly limited, but is preferably 50 μm or less. The upper limit of the average diameter of the recesses is more preferably 40 μm, still more preferably 30 μm. On the other hand, the lower limit of the average diameter of the concave portion is preferably 0.5 μm, more preferably 1 μm, and still more preferably 5 μm. When the average diameter of the concave portion exceeds the above upper limit, there are problems in that brightness unevenness occurs and the height of the concave portion becomes large, making it difficult to promote thinning of the light guide film 12 . On the contrary, when the average diameter of the recesses is smaller than the lower limit, there is a problem that the light scattering effect cannot be sufficiently obtained. In addition, the term "diameter" refers to an intermediate value between the maximum width of the outer shape and the width of the outer shape in a direction perpendicular to the direction of the largest width. In addition, "average diameter" means the average value of the diameter of a some recessed part.

The shape of the recess is not particularly limited, and hemispherical, conical, cylindrical, polygonal pyramid, polygonal prism, hoof shape, etc. can be used. Among them, it is preferable that the recessed portion is formed as a hemispherical recessed portion. By forming the recessed portion as a hemispherical recessed portion, formability can be improved, edge protruding can be prevented, and thinning can be promoted.

(Reflective plate)

The reflection plate 13 reflects the light emitted from the back side of the light guide film 12 from the front side. Examples of the reflector 13 include white sheets obtained by dispersing fillers in base resins such as polyester resins, and specular reflections improved by depositing metals such as aluminum or silver on the surface of a film made of polyester resins or the like. Sexual mirror film, etc.

(roof)

The top plate 14 is formed of a metal or resin plate. As the metal top plate 14, for example, an aluminum plate can be used. Here, the thickness of the plate is preferably not less than 500 μm and not more than 1200 μm, more preferably not less than 700 μm and not more than 900 μm. In addition, the periphery of the plate material of the top plate 14 is formed to be bent toward the surface side, and the bent portion functions as a rib so that the top plate 14 has sufficient strength as the top plate 14 . In addition, the portion (central portion) other than the curved portion of the rib is a flat surface, but it may be embossed (embossed) with a pattern such as a geometric pattern.

(light source)

The light source 15 is built in the housing 5 for the liquid crystal display unit, and the irradiating surface is disposed so as to face (or abut against) the end surface of the light guide film 12 substantially perpendicular to the ridgeline direction of the fine modulation structure. Various light sources can be used as the light source 15 , for example light emitting diodes (LEDs). Specifically, a light source in which a plurality of light emitting diodes are arranged along the end surface of the light guide film 12 can be used as the light source 15 .

In the backlight unit 11, a single-sided side light mode in which the light source 15 is arranged only on the side of one side edge of the light guide film 12 may be adopted, or it may be respectively arranged on the sides of the opposite side edges of the light guide film 12. The side light mode of the light source 15 and the like.

<Manufacturing method of light guide film>

A method of manufacturing the light guide film 12 will be described below.

The manufacturing method of the light guide film 12 includes a step of molding the sheet main body 16 having a wave-shaped fine modulation structure (step 1 ), and a step of forming the diffusion pattern 17 on the sheet main body 16 (step 2 ). In addition, although step 1 and step 2 can be performed separately through separate processes, in this embodiment, by using the extrusion sheet molding method in step 1 and making the pressing roller into a roller on which a diffusion pattern is transferred in step 2 Shaped transfer mold (reverse type), so that step 1 and step 2 can be performed at the same time.

Step 1 is implemented using the extrusion molding device 21 of FIG. 4 . The extrusion molding device 21 has an extruder, a T-die 22, a pair of pressing rolls 23, a take-up device (not shown in the figure), and the like. As the T-shaped die 22, known dies such as a fishtail die, a branch pipe die, and a coat hanger die can be used, for example. In addition, the cross-sectional shape of the T-shaped die 22 is an inverse shape of the cross-sectional shape perpendicular to the ridge line of the finely modulated structure. Thereby, a light guide film having a wave-like fine modulation structure on the surface can be formed.

A pair of pressing rollers 23 are arranged in parallel adjacent to each other. The extruder and the T-die 22 can extrude the molten resin in a sheet form into the gap between the pair of pressing rollers 23 . A pair of pressing rollers 23 is provided with a temperature control device, which can control the surface temperature of the pressing rollers to the most suitable temperature for extrusion molding. As the pressing roller 23, it is preferable to use a metal elastic roller composed of a metal roller and a flexible roller whose surface is covered with an elastic body.

The pair of pressing rollers 23 is composed of a pressing roller 23a and a pressing roller 23b. Among them, the pressing roller 23a serves as a transfer mold on which the diffusion pattern is transferred on the surface.

Step 1 is carried out by extruding a sheet forming method, which provides the forming material of the sheet main body 16 in a molten state to the T-shaped die 22, and extrudes the forming material from the extruder and the T-shaped die 22. After coming out, it is pressed by a pair of pressing rollers 23 . In addition, 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 and the like. The average thickness of the sheet main body 16 formed in step 1 is 600 μm or less. The average thickness of the sheet main body 16 is adjusted by adjusting the arrangement interval of the pair of pressing rollers 23 or the like.

In addition, the arrangement interval and rotation speed of the pair of pressing rollers 23 are adjusted in consideration of the supply amount and molten state of the forming material of the sheet body 16 extruded from the T-die 22 .

Step 2 is performed by transferring the diffusion pattern transferred on the surface of the pressing roller 23 a before the forming material of the sheet body 16 in a molten state is solidified. In step 2, the diffusion pattern transferred on the surface of the pressing roller 23 a is transferred to the back surface of the sheet main body 16 by pressing the forming material of the sheet main body 16 in a molten state with a pair of pressing rollers 23 . In step 2, a plurality of recesses are formed on the back surface of the sheet main body 16 by the transfer.

＜Advantages＞

The surface of the sheet body 16 of the light guide film 12 has a wave-shaped fine modulation structure, and the direction of the ridge line of the wave-shaped fine modulation structure is substantially perpendicular to the end face where the light is incident, so when the light propagating in the light guide film 12 is reflected on the surface, a part The traveling direction of the light is deviated toward the ridgeline 18 side, so the light is easily focused toward the ridgeline direction. Therefore, the light guide property of the incident light can be improved. In addition, since the light emitted from the surface of the light guide film 12 is slightly diffused in the direction perpendicular to the ridge line due to the refraction at the wavy finely modulated structure, the diffusivity of the emitted light can be improved. Therefore, even if the light guide film 12 is an ultra-thin type with an average thickness of 600 μm or less, it is possible to suppress a decrease in the brightness and uniformity of light rays emitted from the light guide film.

In addition, 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 side.

In this light guide film 12, according to the extrusion sheet molding method, by making the extrusion die have an inverse shape of the cross-sectional shape of the fine modulation structure perpendicular to the ridge line, the sheet main body 16 can be easily and reliably formed. A light guide film with a wavy fine modulation structure on the surface.

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 difficult to deform over time, and the stress due to photoelasticity can be reduced. The properties cause problems such as an increase in the retardation value, and as a result, the effect of improving the light guiding properties and diffusivity of the light guiding film can be maintained for a long time.

In addition, since the backlight unit 11 has the light guide film 12, it can be thinned. In addition, the backlight unit 11 can suppress the reduction of brightness and its uniformity through the light guide film 12 .

In addition, since the portable computer 1 has the backlight unit 11 , the thickness can be reduced, and the decrease in luminance and its uniformity can be suppressed.

[Second Embodiment]

＜Backlight unit＞

The backlight unit 31 in FIG. 5 has a light guide film 32 , a reflection plate 13 laminated on the back surface of the light guide film 32 , and a light source 15 that irradiates light to the light guide film 32 . The light source 15 is arranged on the end surface side of the light guide film 32 described later, which is substantially parallel to the direction of the ridgeline of the fine modulation structure.

＜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 unit of a notebook computer whose case thickness is 21 mm or less.

The light guide film 32 efficiently emits the light incident from the end surface substantially uniformly from the surface side. The light guide film 32 has a sheet main body 36 . In addition, the light guide film 32 is disposed so that the end surface substantially parallel to the ridgeline direction of the fine modulation structure faces (or abuts against) the light source.

The surface of the sheet main body 36 has a wave-like fine modulation structure. In addition, the direction of the ridge line 38 of the wave-like finely modulated structure is substantially parallel to the end face where the light is incident. Therefore, the direction of the ridge line 38 of the finely modulated structure is substantially perpendicular to the traveling direction of the light propagating in the light guide film 32, so the incident angle of the light to the surface changes due to the wavy finely modulated structure. , so it is possible to improve the light-extraction property of light-exited from the surface of the light guide film 32 .

The ridgeline pitch p of the finely modulated structure is not particularly limited, but is preferably not less than 1 mm and not more than 500 mm. The upper limit of the interval p between ridge lines is more preferably 100 mm, still more preferably 60 mm. On the other hand, the lower limit of the ridge line interval p is more preferably 10 mm, and still more preferably 20 mm. When the distance between the ridge lines is smaller than the lower limit, there is a problem that excessive emission of light from the surface of the light guide film 32 may occur. On the other hand, when the distance between the ridge lines exceeds the upper limit, the effect of improving the light extraction performance of the light guide film 32 may be low. In addition, although it is preferable that all the ridgeline intervals of the finely modulated structure are within the above range, some of the plurality of ridgeline intervals p of the finely modulated structure may be outside the above range. In this case, as long as the multiple More than 50% of the ridgeline intervals are within the above-mentioned range, and preferably 70% of the ridgeline intervals are within the above-mentioned range.

Also, the average height of the ridgelines 38 based on the approximate imaginary plane through which the plurality of valley lines 39 of the modulation structure pass is not particularly limited, but is preferably not less than 5 μm and not more than 40 μm. The upper limit of the average height h is more preferably 20 μm, still more preferably 15 μm. On the other hand, the lower limit of the average height is more preferably 7 μm, still more preferably 9 μm. When the average height is smaller than the lower limit, the effect of improving the light extraction performance of the light guide film 32 may be low. On the other hand, when the average height exceeds the upper limit, there is a problem that light rays are excessively emitted from the surface of the light guide film 32 .

In addition, other shapes, main components, additives, etc. 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. 2 , and thus their descriptions are omitted.

A diffusion pattern 37 is formed on the back surface of the sheet main 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 preliminarily containing a color developer in the forming material of the sheet body 36 , and irradiating the color developer with laser light after molding the sheet body 36 .

The color developer dispersed and contained in the forming material of the sheet main body 36 is a pigment capable of changing color by laser irradiation. As the color developer, known organic or inorganic substances used as laser marking agents can be used. Specifically, metal compounds such as yellow iron oxide, inorganic lead compounds, manganese violet, cobalt violet, mercury, cobalt, copper, bismuth, nickel, pearlescent pigments, silicon compounds, micas, kaolins, silica sand, silicon One kind of algae, talc, etc. may be used, or two or more kinds thereof may be used. However, in this embodiment, since the diffusion pattern 37 is formed as a reflective pattern that reflects light, it is preferable to have a color that reflects light. Therefore, in the light guide film 32 , it is preferable to use a color developer that appears white when irradiated with laser light, whereas a color developer that becomes black and absorbs light due to carbonization by laser irradiation is not suitable. Examples of the above-mentioned color-developing agent for displaying white include titanium black, cordierite, mica, and the like.

As the cordierite, besides an inorganic compound represented by the composition formula Mg2Al3 (AlSi5O18), a substance in which a part of Mg is replaced by Fe can also be used. In addition, a substance containing moisture can also be used.

As the mica, natural micas such as muscovite, phlogopite, biotite, and sericite, and synthetic micas such as fluorophlogopite and fluorotetrasilicon mica, can be used.

The content of the developer in the sheet body 36 is preferably 0.0001% by mass to 2.5% by mass, more preferably 0.1% by mass to 1% by mass. When the content of the color developer is less than the above lower limit, a sufficient color development effect cannot be obtained during laser irradiation, and there is a problem that a desired reflective pattern cannot be formed. On the contrary, when the content of the color developer exceeds the upper limit, there is a problem that the transparency, mechanical strength, and the like of the sheet main body 36 decrease.

The laser beam irradiated to the sheet main body 36 is not particularly limited, and examples thereof include carbon dioxide laser, carbon monoxide laser, semiconductor laser, YAG (yttrium aluminum garnet) laser, and the like. Among them, CO2 lasers with wavelengths from 9.3 μm to 10.6 μm are suitable for forming fine diffusion patterns. As the carbon dioxide laser, a transverse atmospheric excitation type (TEA), 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, and hemispherical, conical, cylindrical, polygonal pyramid, polygonal prism, hoof shape, etc. can be used. Among them, the shape of the light scattering portion is preferably hemispherical. By making the light-scattering portion hemispherical, formability can be improved and edge protrusion can be prevented. In addition, the arrangement pattern of the diffusion pattern 37 is the same as that of the diffusion pattern 17 in FIG. 2 . In addition, the average diameter of the light scattering portion is the same as that of the concave portion of the diffusion pattern 17 of FIG. 2 .

The light guide film 32 can easily and reliably form a desired diffusion pattern 37 by irradiating laser light. In addition, when the diffusion pattern 37 is formed by such a method, since it is not necessary to provide protrusions or the like on the back surface of the light guide film 32 , thickness reduction can be promoted.

In addition, since the light guide film 32 is irradiated with laser light to form the diffusion pattern 37, even when it is molded by melt extrusion molding, it is not necessary to transfer the diffusion pattern to the surface of the pressing roller.

[Other implementations]

In addition, the light guide film for ultra-thin liquid crystal backlight, ultra-thin liquid crystal backlight unit, and portable computer of the present invention may be implemented in various modified and improved forms other than the above-described forms.

In the above-mentioned embodiments, the structure in which the surface of the sheet main body of the light guide film has a wave-shaped fine modulation structure has been described, but the light guide film may have a structure in which the surface and back surface of the sheet main body have a wave-like fine modulation structure. By providing the surface and the back surface of the sheet main body with a wavy finely modulated structure, it is possible to further suppress reductions in the luminance and uniformity of light emitted from the light guide film.

In addition, the diffusion pattern can also be formed as a convex portion by a printing method. In this case, when the sheet main body is formed by the above-mentioned extrusion sheet molding method, as a pair of pressing rolls, a pair of pressing rolls having no diffusion pattern transferred on the surface is used. As a printing method for forming the convex portion, an inkjet printing method or a screen printing method using white or transparent ink can be used. By forming the diffusion pattern as a convex portion by a printing method, the diffusion pattern can be easily and reliably formed.

The ultra-thin liquid crystal backlight unit equipped with the light guide film can use the top plate as a reflection plate. By forming the surface of the top plate as a reflective surface, the light emitted from the back side of the light guide film can be reflected toward the front side by the reflective surface.

Furthermore, in the embodiment, the light guide having the wavy fine modulation structure is produced using a T-shaped die whose cross-sectional shape is an inversion of the cross-sectional shape of the fine modulation structure perpendicular to the ridge line. The method of the film has been described, but it is not limited thereto. For example, the light guide film having the wavy fine modulation structure can also be produced by adjusting the arrangement interval and the rotation speed of the pair of pressing rollers 23 . In addition, in this case, a well-known shape can be used for the cross-sectional shape of an extrusion die.

In addition, in the above-mentioned embodiment, the forming process of the sheet main body (step 1) and the diffusion pattern forming process (step 2) have been described simultaneously, but as described above, step 1 and step 2 may be performed separately, Specifically, the sheet main body formed in step 1 may be rolled into a roll, and then the sheet main body may be pulled out from the roll to perform step 2.

In addition, a heat treatment (anilling treatment) step may be performed after step 2 as in the above-mentioned embodiment. The heat treatment is not particularly limited, and a known method can be used. For example, a heating method including a heating roller, an infrared heater, hot air, or the like can be used. Among these methods, it is preferable to perform heat treatment with a heating roll. By raising the temperature of the heating roller, the temperature of the surface of the sheet main body can be raised at once, and the shrinkage of the sheet main body can be suppressed.

Industrial Applicability

As mentioned above, the portable computer having the light guide film for ultra-thin liquid crystal backlight of the present invention and the ultra-thin liquid crystal backlight unit can suppress the reduction of the brightness and uniformity of the liquid crystal display surface, and can realize thinning, so For example, it is suitable for ultra-thin computers called ultrabooks, mobile terminals such as smartphones, portable information terminals such as tablet terminals, and the like.

Claims (10)

1. A light guide film, characterized in that, The light guide film is a light guide film for ultra-thin liquid crystal backlight with an average thickness of 600 μm or less, which emits the light incident from the end surface substantially uniformly from the surface, The surface has a wavy fine modulation structure, or the surface and the back have a wavy fine modulation structure. 2. The light guide film according to claim 1, characterized in that, The interval between the ridgelines of the fine modulation structure is not less than 1 mm and not more than 500 mm. 3. The light guide film according to claim 1, characterized in that, The average height of the ridgelines based on the approximate imaginary plane through which the plurality of valley lines of the finely modulated structure pass is not less than 5 μm and not more than 40 μm. 4. The light guide film according to claim 1, characterized in that, The light guide film is formed by extrusion sheet molding. 5. The light guide film according to claim 1, characterized in that, The retardation value (Re) is 50 nm or less, and the residual stress is 8×10 ⁵ Pa or less. 6. The light guide film according to claim 1, characterized in that, Features a diffused pattern on the back. 7. The light guide film according to claim 6, characterized in that, The diffusion pattern is composed of a plurality of hemispherical recesses. 8. The light guide film according to claim 6, characterized in that, The diffusion pattern is composed of a plurality of light-scattering parts, and the light-scattering parts are colored by laser irradiation. 9. An ultra-thin liquid crystal backlight unit, characterized in that it comprises: Reflective plate; The light guide film according to any one of claims 1 to 8, laminated on the surface side of the reflective plate; and The light source irradiates light to the end surface of the light guide film. 10. A portable computer comprising the ultra-thin liquid crystal backlight unit according to claim 9 in a liquid crystal display portion.