JP2004341294A - Optical sheet, backlight unit using the same, and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical sheet having an emission line prevention layer having improved visibility from the surface side, a backlight unit using the optical sheet, and a method for manufacturing the optical sheet. <P>SOLUTION: The optical sheet, where the emission line prevention layer for absorbing rays is laminated, is not equipped with the emission line prevention layer at a fixed distance toward the inside from nearly the entire periphery of the edge. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical sheet, a backlight unit of a liquid crystal display device using the same, and a method for manufacturing an optical sheet.
[0002]
[Prior art]
2. Description of the Related Art As a liquid crystal display device, a backlight system in which a liquid crystal screen is illuminated from the back surface to emit light has become widespread, and a backlight unit is provided on the back surface side of the liquid crystal screen. Here, a conventional backlight unit will be described with reference to FIGS. FIG. 6 is a perspective view of a conventional backlight unit, and FIG. 7 is a plan view of the back surface of the optical sheet of FIG.
[0003]
As shown in FIG. 6, the backlight unit 20 includes a rod-shaped lamp 21 as a light source, a rectangular plate-shaped light guide plate 22 arranged so that an end thereof is along the lamp 21, and a light guide plate 22 on the front surface side. The light diffusion sheet 23 includes a light diffusion sheet 23, a prism sheet 24 disposed on the front side of the light diffusion sheet 23, and a reflection sheet 28 laminated on the back side of the light guide plate 22. At this time, the light diffusion sheet 23 becomes the optical sheet 26 having the bright line prevention layer 25.
[0004]
The function of the backlight unit 20 will be described. First, a light beam incident on the light guide plate 22 from the lamp 21 is reflected by a reflection dot or a reflection layer (not shown) on the back surface of the light guide plate 22 and each side surface, and the surface of the light guide plate 22 is exposed. Is emitted from. Light emitted from the light guide plate 22 enters the light diffusion sheet 23, is diffused, and is emitted from the surface of the light diffusion sheet 23. Thereafter, the light beam emitted from the light diffusion sheet 23 enters the prism sheet 24, and is emitted by the prism portion 24a formed on the surface of the prism sheet 24 as a light beam having a distribution having a peak almost directly above. As described above, the light beam emitted from the lamp 21 is diffused by the light diffusion sheet 23, is refracted by the prism sheet 24 so as to show a peak almost directly above, and furthermore, the liquid crystal screen (not shown) It illuminates the entire surface. In addition, since a certain light beam is also emitted to the back surface side of the light guide plate 22, on the back surface side of the light guide plate 22, the radiation of the light beam to the back surface side is reduced, and the brightness of the backlight unit 20 is improved. A reflection sheet 28 is provided.
[0005]
There is also a backlight unit in which a light diffusion sheet or a prism sheet is further provided on the front surface side of the prism sheet 24 in consideration of the light-condensing characteristics of the prism sheet 24.
[0006]
At this time, when viewed from the front side, the backlight unit 20 has a structure in which the luminance on the lamp 21 side is inevitably too large, so that a bright line (luminance) is applied to the band such as the outer edge along the lamp 21 and the outer edge opposite thereto. Is formed in a band (bright line generation band) of the optical sheet 26 where a bright line appears, by screen printing using a printing ink containing a pigment such as white, black, or gray. The bright line preventing layer 25 is laminated so as to prevent the occurrence of bright lines.
[0007]
Note that the backlight unit 20 is a so-called edge light type, but a bright line may be generated due to factors such as the position of a lamp even in other types, for example, a direct type backlight unit. The bright line preventing layer may be applied to a prism sheet, a reflection sheet, or the like, in addition to the light diffusion sheet.
[0008]
The present invention has been completed based on an idea unique to the inventor, and there is nothing to be described as a prior art document.
[0009]
[Problems to be solved by the invention]
However, the optical sheet 26 includes the bright line preventing layer 25 from substantially the entire periphery of the end toward the inside. Since the bright line preventing layer 25 is located at the edge of the optical sheet 26, it may have a crack or other damage. For example, when cutting out the optical sheet 26 as shown in FIG. 8C in order to exclude FIG. 8B from the original sheet 27 having the printed portion 27a as shown in FIG. Since a metal blade (Thomson blade, Pinnacle blade or the like) or the like is pushed into the portion 27a, the bright line preventing layer 25 is liable to be damaged such as a crack.
[0010]
Therefore, when the optical sheet 26 having the crack such as a crack in the bright line preventing layer 25 is used for a backlight unit of a liquid crystal display device, a part of the bright line preventing layer 25 is peeled off and looks black from the surface side. Was.
[0011]
The present invention has been made in view of these inconveniences, and an object of the present invention is to provide an optical sheet having a bright line preventing layer having good visibility from the surface side, and to provide a backlight unit and an optical sheet manufacturing method using the same. It is assumed that.
[0012]
[Means for Solving the Problems]
That is, the present invention is an optical sheet in which a bright line preventing layer that absorbs light rays is laminated, and does not include the bright line preventing layer within a certain distance from substantially the entire periphery of the end toward the inside. Features.
[0013]
Here, the “optical sheet” refers to a sheet having various optical functions such as diffusion, light collection, refraction, and reflection, and specifically includes a light diffusion sheet, a prism sheet, a reflection sheet, and the like. Further, the “bright line generation band” means a band in which a bright line is generated and / or a band which causes a bright line to be generated when the bright line preventing layer according to the present invention is not laminated in the backlight unit. I do. Further, the “bright line” means a linear portion having a luminance higher than the surroundings.
[0014]
According to the present invention, the bright line preventing layer formed on the optical sheet absorbs the light in the bright line generation band, so that only the light in the necessary area reaches on the front side, and the visibility from the front side is good. Become.
[0015]
Further, since the bright line preventing layer is not provided within a predetermined distance inward from substantially the entire periphery of the end of the optical sheet, the bright line preventing layer is hardly damaged. Therefore, a part of the bright line preventing layer does not peel off and does not appear black from the surface side, and does not impair the visibility from the surface side.
[0016]
In the present invention, it is preferable that the bright line preventing layer is a printing layer.
[0017]
By using the printed layer as the bright line preventing layer, the bright line preventing layer can be easily formed.
[0018]
In the present invention, it is preferable that the substantially entire circumference is 90% or more of the entire circumference.
[0019]
Since the bright line preventing layer is not provided from 90% or more of the entire circumference of the end of the optical sheet to a certain distance toward the inside, most of the bright line preventing layer is hardly damaged.
[0020]
Furthermore, it is particularly preferable that no bright line preventing layer is provided within a predetermined distance from the entire periphery of the end of the optical sheet toward the inside.
[0021]
Since the bright line preventing layer is not provided within a predetermined distance from the entire circumference of the end of the optical sheet toward the inside, the bright line preventing layer is not damaged.
[0022]
In the present invention, it is preferable that the certain distance is 0.05 mm or more.
[0023]
Since the bright line preventing layer is not provided in an area of less than 0.05 mm inward from substantially the entire periphery of the end of the optical sheet, the bright line preventing layer is further hardly damaged.
[0024]
Further, in the present invention, it is preferable that the predetermined distance is within 5.0 mm.
[0025]
If it exceeds 5.0 mm, the light rays at the edges of the optical sheet cannot be blocked by the window frame of the liquid crystal display device or the like, and there is a possibility that light rays in an unnecessary area may reach on the front surface side.
[0026]
In the present invention, it is preferable that the thickness of the printing layer is 3 μm or more and 14 μm or less.
[0027]
When the thickness of the printing layer is less than 3 μm, the absorbency is insufficient. On the other hand, when the thickness of the printing layer exceeds 14 μm, the drying property of the printing layer is reduced, and the printing layer may cause poor adhesion.
[0028]
In the present invention, it is preferable that the printing layer is formed by gradation printing and / or solid printing.
[0029]
By forming the printing layer by gradation printing and / or solid printing, it is possible to easily form various shapes of the printing layer.
[0030]
Further, in the present invention, the printing layer is formed from at least one kind of ink selected from the group consisting of an evaporative drying type ink, an oxidation polymerization type ink, a heat curing type ink, a two-component reaction type ink, and an ultraviolet curing type ink. It is preferred that
[0031]
Further, the present invention includes a transparent base material layer, an optical functional layer laminated on the front surface side of the base material layer, and a sticking prevention layer laminated on the back surface side of the base material layer. It is preferable to have a bright line prevention layer laminated on the back side of the sticking prevention layer or on the front side of the optical functional layer.
[0032]
Further, the present invention preferably includes a reflection sheet that reflects light rays, and a bright line preventing layer laminated on the surface side of the reflection sheet.
[0033]
With this configuration, since the bright line preventing layer is formed on the reflective sheet, it is possible to prevent light rays from being reflected in the bright line generation band, and as a result, it is possible to prevent luminance unevenness and to improve visibility from the front side. It becomes.
[0034]
In addition, the present invention includes a lamp, a light guide plate that guides light emitted from the lamp to the front surface side, and the above-described optical sheet that is arranged on the front surface side of the light guide plate and uniformly guides the light beam in the surface direction. Is preferred.
[0035]
By doing so, it is possible to prevent the generation of bright lines in a band (bright line generation band) such as the outer edge portion along the lamp and the outer edge portion facing the outer edge portion. As a result, it is possible to prevent luminance unevenness and to visually recognize from the surface side. The property becomes good.
[0036]
The present invention also includes a lamp, a light guide plate that guides light emitted from the lamp to the front side, and the above-described optical sheet that is disposed on the back side of the light guide plate and uniformly guides light in the surface direction. Is also preferred.
[0037]
With this configuration, since the bright line preventing layer is formed on the reflection sheet, it is possible to prevent light rays from being reflected in a band (bright line generating band) such as an outer edge portion along the lamp and an outer edge portion opposed thereto, and as a result, the brightness unevenness is reduced. Can be prevented, and visibility from the front surface side is improved.
[0038]
Further, the present invention comprises a forming step of forming absorbing means on the raw sheet, and a molding step of cutting out an optical sheet from the raw sheet on which the absorbing means is formed. It is characterized in that a bright line preventing layer for absorbing light rays is not provided at a certain distance from substantially the entire circumference toward the inside.
[0039]
In the molding process, a predetermined distance inward from substantially the entire periphery of the edge of the optical sheet, so as not to have a bright line prevention layer, for example, when cutting out the optical sheet, most of the bright line prevention layer Since a metal blade or the like is not pushed into the bright line preventing layer, scars such as cracks can be hardly generated in the bright line preventing layer.
[0040]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1A is a schematic cross-sectional view illustrating an optical sheet according to an embodiment of the present invention, and FIG. 1B is a schematic rear view of the optical sheet of FIG.
[0041]
The optical sheet 1 includes a base layer 2, a light diffusion layer 3 stacked on the front side of the base layer 2, a sticking prevention layer 4 stacked on the back side of the base layer 2, and a sticking prevention layer 4. And a bright line preventing layer 5 laminated on the back side.
[0042]
The base material layer 2 is transparent because it is necessary to transmit light, and is preferably colorless and transparent.
[0043]
The light diffusion layer 3 includes a binder 6 and beads 7 dispersed in the binder 6. By dispersing the beads 7 in this manner, the light beam transmitted through the light diffusion layer 3 from the back surface to the front surface can be uniformly diffused. By providing the beads 7 whose upper end protrudes from the binder 6, light can be diffused better.
[0044]
The anti-sticking layer 4 includes a binder 8 and beads 9 dispersed in the binder 8, and prevents sticking by the beads 9 protruding from the binder 8.
[0045]
The bright line prevention layer 5 includes a printing layer 5 formed on the sticking prevention layer 4. That is, the optical sheet 1 has an absorption area and a transmission area by forming the printing layer 5 that absorbs light on the anti-sticking layer 4 that transmits light.
[0046]
At this time, the printing layer 5 is not formed within a certain distance from substantially the entire periphery of the end of the optical sheet 1 toward the inside.
[0047]
As shown in FIG. 1B, the print layer 5 is laminated so as to cover the bright line generation band on the back surface of the optical sheet 1.
[0048]
Although the printing layer 5 is not formed within a certain distance from substantially the entire periphery of the edge of the optical sheet 1 toward the inside, the light is blocked by a window frame or the like of the liquid crystal display device. On the side, only the rays of the required area reach.
[0049]
Further, since the printing layer 5 is laminated on the relatively flat outer surface of the sticking prevention layer 4, the adhesiveness is high.
[0050]
According to the optical sheet 1, since the light in the emission line generation band is not absorbed by the printing layer 5 formed on the optical sheet 1 and is not incident, only the light in the necessary area reaches the front side, and the front side does not. The visibility from is improved.
[0051]
Furthermore, since the printing layer 5 is not provided within a certain distance from substantially the entire periphery of the end of the optical sheet 1 toward the inside, the printing layer 5 is hardly damaged. Therefore, a part of the print layer 5 does not peel off and does not look black from the front side, and does not cause a problem in visibility from the front side.
[0052]
Further, by using the printed layer 5 as the bright line preventing layer, the bright line preventing layer can be easily formed.
[0053]
Further, in the backlight unit of the liquid crystal display device, a lamp, a light guide plate for guiding light rays emitted from the lamp to the surface side, and an optical sheet 1 disposed on the surface side of the light guide plate for uniformly guiding light rays in the surface direction. With this configuration, it is possible to prevent the occurrence of a bright line in a band such as an outer edge portion along the lamp and an outer edge portion facing the outer edge portion. Visibility is good.
[0054]
Further, the shape of the bright line preventing layer in the present invention may be as follows.
[0055]
FIG. 2 is a schematic rear view showing another example of the optical sheet of the present invention.
[0056]
In FIG. 2A, the bright line preventing layer 15a is not formed in a predetermined distance inward from the entire periphery of the end of the optical sheet 15 and is formed in a square shape.
[0057]
In FIG. 2B, the bright line preventing layer 35a is not formed within a certain distance inward from substantially the entire periphery of the end of the optical sheet 35, and the start and end points are formed at the end of the optical sheet 35. Are formed in a single line to contact.
[0058]
In FIG. 2C, the bright line preventing layer 45a is not formed from a substantially entire circumference of the end of the optical sheet 45 to a predetermined distance toward the inside, and one side of the end of the optical sheet 45 is removed. Thus, it is formed along the edge of the optical sheet 45.
[0059]
Further, another example of the optical sheet of the present invention will be described. FIG. 3A is a schematic sectional view showing an optical sheet according to an embodiment of the present invention, and FIG. 3B is a schematic surface view of the optical sheet shown in FIG.
[0060]
The optical sheet 51 includes a base layer 52, a light diffusion layer 53 stacked on the front side of the base layer 52, a sticking prevention layer 54 stacked on the back side of the base layer 52, and a light diffusion layer 53. And a bright line prevention layer 55 laminated on the front surface side.
[0061]
The light diffusion layer 53 includes a binder 56 and beads 57 dispersed in the binder 56. By dispersing the beads 57 in this manner, the light that passes through the light diffusion layer 53 from the back surface to the front surface can be uniformly diffused. Further, the beads 57 are embedded in the binder 56, but the upper ends thereof may be projected from the binder.
[0062]
The bright line preventing layer 50 includes a printing layer 50 formed on the light diffusion layer 53. That is, the optical sheet 51 has an absorption area and a diffusion area by forming the printing layer 50 that absorbs light on the light diffusion layer 53 that diffuses light.
[0063]
At this time, the printing layer 50 is not formed within a certain distance from substantially the entire periphery of the end of the optical sheet 51 toward the inside.
[0064]
Then, as shown in FIG. 3B, the print layer 50 is laminated so as to cover the bright line generation band on the surface of the optical sheet 51.
[0065]
Note that the printing layer 50 is not formed within a certain distance inward from substantially the entire periphery of the edge of the optical sheet 51 but is shielded from light by a window frame of a liquid crystal display device. On the side, only the rays of the required area reach.
[0066]
The base layer 52 and the anti-sticking layer 54 may be the same as those shown in FIG.
[0067]
According to the optical sheet 51, the print layer 50 formed on the optical sheet 51 does not absorb and emit the light in the emission line generation band. The visibility from is improved.
[0068]
Further, since the print layer 50 is not provided within a predetermined distance from substantially the entire periphery of the end of the optical sheet 51 toward the inside, the print layer 50 is hardly damaged. Therefore, a part of the print layer 50 does not peel off and does not appear black from the front side, and does not cause a problem in visibility from the front side.
[0069]
Further, by using the printing layer 50 as the bright line preventing layer, the bright line preventing layer can be easily formed.
[0070]
Further, another example of the optical sheet of the present invention will be described. FIG. 4A is a schematic cross-sectional view illustrating an optical sheet according to an embodiment of the present invention, and FIG. 4B is a schematic rear view of the optical sheet illustrated in FIG.
[0071]
The optical sheet 11 includes a reflection sheet 13 and a bright line preventing layer 12 laminated on the surface side of the reflection sheet 13.
[0072]
The reflection sheet 13 reflects light rays.
[0073]
The bright line prevention layer 12 is composed of a print layer 12 formed on a reflection sheet 13. That is, the optical sheet 11 has an absorption area and a reflection area by forming the printing layer 12 that absorbs light on the reflection sheet 13 that reflects light.
[0074]
At this time, the printing layer 12 is not formed within a predetermined distance from substantially the entire periphery of the end of the optical sheet 11 toward the inside.
[0075]
Then, as shown in FIG. 4B, the print layer 12 is laminated so as to cover the bright line generation band on the back surface of the optical sheet 11.
[0076]
Although the printing layer 12 is not formed within a certain distance from substantially the entire periphery of the edge of the optical sheet 11 toward the inside, the light is blocked by a window frame or the like of the liquid crystal display device. On the side, only the rays of the required area reach.
[0077]
According to the optical sheet 11, the light in the emission line generation band is absorbed by the print layer 12 formed on the optical sheet 11, so that only the light in the required area reaches the front side, and the visibility from the front side is reduced. It will be good.
[0078]
Furthermore, since the printing layer 12 is not provided within a predetermined distance from substantially the entire circumference of the end of the optical sheet 11 toward the inside, the printing layer 12 is hardly damaged. Therefore, a part of the print layer 12 does not peel off and does not look black from the front side, and does not cause a problem in visibility from the front side.
[0079]
Further, by using the printed layer 12 as the bright line preventing layer, the bright line preventing layer can be easily formed.
[0080]
Further, in the backlight unit of the liquid crystal display device, a lamp, a light guide plate for guiding light rays emitted from the lamp to the front side, and an optical sheet 11 arranged on the back side of the light guide plate to uniformly guide light rays in the surface direction. With this configuration, it is possible to prevent light rays from being reflected in a band (emission line generation band) such as an outer edge portion along the lamp and an outer edge portion opposed thereto, and as a result, luminance unevenness can be prevented. The visibility from the surface side is improved.
[0081]
The fixed distance is preferably 0.05 mm or more, more preferably 0.1 mm or more, and particularly preferably 0.2 mm or more. If the thickness is less than 0.05 mm, a metal blade or the like may be brought into contact with the bright line preventing layer when the optical sheet is cut out from the raw sheet, which may cause cracks or the like in the bright line preventing layer. .
[0082]
Further, the above-mentioned fixed distance is preferably within 5.0 mm, particularly preferably within 1.0 mm. If the distance exceeds 5.0 mm, light rays at the edge of the optical sheet cannot be blocked by the window frame of the liquid crystal display device or the like, and light rays in an unnecessary area on the front surface side are allowed to reach.
[0083]
The substantially entire circumference is preferably 90% or more of the entire circumference, and particularly preferably the entire circumference.
[0084]
Since the bright line preventing layer is not provided within a predetermined distance inward from substantially the entire periphery of the end of the optical sheet, most of the bright line preventing layer is hardly damaged.
[0085]
The material of the base layer is not particularly limited, and examples thereof include synthetic resins such as polyethylene terephthalate, polyethylene naphthalate, acrylic resin, polycarbonate, polystyrene, polyolefin, cellulose acetate, and weather-resistant vinyl chloride.
[0086]
It is preferable that the thickness of the base layer be 50 μm or more and 250 μm or less. If the thickness of the base material layer is less than 50 μm, curling is likely to occur when a resin composition for forming a light diffusion layer or the like is applied. On the other hand, if the thickness of the base material layer exceeds 250 μm, the brightness of the liquid crystal display device or the like may be reduced, and further, the thickness of the backlight unit or the like may be increased to meet the demand for a thinner liquid crystal display device or the like. It also goes against it.
[0087]
The polymer used for the binder is not particularly limited, and examples thereof include an acrylic resin, a polyurethane, a polyester, a fluororesin, a silicone resin, a polyamideimide, and an epoxy resin. Further, in addition to the polymer, for example, a plasticizer, a stabilizer, a deterioration inhibitor, a dispersant, and the like may be blended in the binder.
[0088]
The beads are substantially spherical, and the material thereof is not particularly limited, and examples thereof include acrylic resin, polyurethane, polyvinyl chloride, polystyrene, polyacrylonitrile, and polyamide.
[0089]
The particle size of the beads is preferably from 0.1 μm to 100 μm, particularly preferably from 1 μm to 50 μm. When the particle diameter is less than 0.1 μm, the light diffusion effect becomes insufficient. On the other hand, when the particle diameter exceeds 100 μm, it becomes difficult to apply the resin composition forming the light diffusion layer. That is because. The particle diameter of the beads is derived by measuring the diameter of the particles by arbitrarily extracting 100 beads with a microscope, and averaging the diameters. Further, when the beads are not spherical, the value of the size of the beads in an arbitrary direction and the size of the beads in a direction orthogonal thereto are averaged.
[0090]
The thickness of the light diffusion layer (meaning the thickness of the binder portion excluding the beads) is not particularly limited, but is preferably, for example, 1 μm or more and 30 μm or less.
[0091]
The compounding amount of the beads in the light diffusion layer is preferably from 0.1 to 500 parts by weight, particularly preferably from 10 to 300 parts by weight, based on 100 parts by weight of the polymer in the binder. When the amount is less than 0.1 part by weight, the light diffusion effect becomes insufficient. On the other hand, when the amount exceeds 500 parts by weight, it is difficult to apply the resin composition forming the light diffusion layer. It is because it becomes.
[0092]
The thickness of the anti-sticking layer (meaning the thickness of the binder portion excluding the beads) is not particularly limited, but is, for example, 1 μm or more and 10 μm or less.
[0093]
The amount of the beads in the anti-sticking layer is preferably from 0.01 to 100 parts by weight based on 100 parts by weight of the polymer in the binder. With such a relatively small amount, the beads can be separated from each other and dispersed in the binder.
[0094]
Note that, instead of the light diffusion layer, an optical function layer that performs a predetermined optical function such as diffusion, collection, refraction to the normal direction side, and reflection of transmitted light may be provided. A bead coating type in which beads are dispersed in a binder, a prism type in which prism portions are formed in multiple stripes, an emboss type, or the like may be provided. Further, the base layer and the optical function layer may be separate layers, and these two layers may be integrally formed.
[0095]
The material of the reflection sheet is not particularly limited, and examples thereof include synthetic resins such as polyethylene terephthalate, polyethylene naphthalate, acrylic resin, polycarbonate, polystyrene, polyolefin, cellulose acetate, and weather-resistant vinyl chloride.
[0096]
Further, the reflection sheet may have a white pigment and / or air bubbles dispersed in the synthetic resin.
[0097]
In addition, the surface of the reflection sheet may be formed in a mat shape and / or a slender strip-shaped inclined surface in a stripe shape (a large number of adjacent slopes are parallel).
[0098]
The material of the white pigment is not particularly limited. Examples include pigments and organic fine powders such as polystyrene and styrene-divinylbenzene copolymer. Among these, titanium dioxide is particularly preferred.
[0099]
The printing layer is preferably formed by screen printing using a printing ink.
[0100]
The material of the printing ink is not particularly limited as long as it can be used for screen printing. For example, evaporative drying ink, oxidation polymerization ink, heat curing ink, two-component reaction ink, ultraviolet light At least one ink selected from the group consisting of curable inks is included. Among these, an ultraviolet curable ink suitable for gradation printing is preferable.
[0101]
As the printing ink, (a) an opaque ink such as black or gray, which prevents generation of bright lines by absorption, and (b) a transparent (including colored transparent, translucent, etc.) ink mixed with a pigment And a type in which the generation of bright lines is prevented by controlling the transmittance of light rays by diffusion, absorption and the like by a pigment. Among these, it is preferable that the visibility of the bright line preventing layer from the surface side of the liquid crystal display device or the like is low (b).
[0102]
As the pigment to be mixed with the printing ink used in the above (b), a blue pigment is preferable. The bright line preventing layer due to the light diffusion effect tends to look yellow on the backlight, but the yellow tint can be eliminated by mixing a blue pigment.
[0103]
The content of the blue pigment is preferably from 0.05 to 1.0 part by weight based on 100 parts by weight of the printing ink. If the content of the blue pigment is less than 0.05 part by weight, the effect of eliminating the appearance of yellow is small, while if it exceeds 1.0 part by weight, the blue color is too dark, and the bright line preventing layer has a blue line. It is because it is expressed in a state.
[0104]
It is preferable that the printing layer is formed by gradation printing and / or solid printing.
[0105]
Therefore, the print layer may be composed of a solid area and a gradation area in which the dot pattern is gradually changed so as to blur the boundary between the print layer and the transmission area. The gradation area is composed of a plurality of dots of substantially square and the same size, and the arrangement pattern of the dots is configured such that the arrangement density is gradually reduced from the edge side toward the inside to form gradation. It is preferred that By doing so, the boundary of the print layer can be blurred. The dot pattern at the boundary between the solid-painted area and the gradation area may be formed in a random pattern, and the effect of blurring the boundary of the print layer is greater than in the case of a regular dot pattern.
[0106]
The thickness of the printing layer is preferably 3 μm or more and 14 μm or less.
[0107]
When the thickness of the printing layer is less than 3 μm, the absorbency is insufficient. On the other hand, when the thickness of the printing layer exceeds 14 μm, the drying property of the printing layer is reduced, and the printing layer may cause poor adhesion.
[0108]
Next, an example of a method for manufacturing the optical sheet 1 will be described. FIG. 5 is a schematic view illustrating an example of a method for manufacturing the optical sheet 1 suitable for carrying out the present invention.
[0109]
The method of manufacturing the optical sheet 1 includes a forming step of forming a printed portion 17 on the back surface of the raw sheet 18 and a molding step of cutting out the optical sheet 1 from the raw sheet 18 having the printed portion 17 formed thereon. In the molding step, the printing layer 5 is not provided at a fixed distance from substantially the entire periphery of the end of the optical sheet 1 toward the inside.
[0110]
(1) Production of raw sheet 18
A resin composition obtained by mixing beads in a binder is applied to the surface of the base material layer 2, and a resin composition obtained by mixing beads in a binder is applied to the back surface of the base material layer 2. The raw sheet 18 includes the light diffusion layer 3 stacked on the front side of the base layer 2 and the anti-sticking layer 4 stacked on the back side of the base layer 2.
[0111]
(2) Forming process (see FIG. 4A)
The screen plate is attached to the printing press, and the raw sheet 18 is set on a printing table of the printing press. Thereafter, the printing portion 17 is formed in a U-shape by screen-printing the printing ink on the sticking prevention layer 4.
[0112]
(3) Molding process (see FIGS. 4B and 4C)
The optical sheet 1 as shown in FIG. 4C is cut out by pressing a metal blade into the optical sheet 1 as shown in FIG. . At this time, the printed layer 5 is not formed within a predetermined distance from substantially the entire periphery of the end of the optical sheet 1 toward the inside. Therefore, since the metal blade is not pushed into most of the printed portion, scars such as cracks can be hardly generated in the printed layer 5.
[0113]
Note that the optical sheet of the present invention, the backlight unit of the liquid crystal display device using the same, and the method of manufacturing the same are not limited to the above-described embodiment. Screen printing, which can perform basic printing and precise gradation printing, is preferable. However, if the position and shape can be precisely controlled as described above, a method other than screen printing is also possible.
[0114]
【The invention's effect】
As described above, according to the present invention, the bright line preventing layer formed on the optical sheet absorbs the light in the bright line generation band. Has good visibility.
[0115]
Further, since the bright line preventing layer is not provided within a predetermined distance inward from substantially the entire periphery of the end of the optical sheet, the bright line preventing layer is hardly damaged. Therefore, a part of the bright line preventing layer does not peel off and does not appear black from the surface side, and does not impair the visibility from the surface side.
[Brief description of the drawings]
FIG. 1A is a schematic sectional view showing an optical sheet according to an embodiment of the present invention, and FIG. 1B is a schematic rear view of the optical sheet shown in FIG.
FIG. 2 is a schematic rear view showing another example of the optical sheet of the present invention.
FIG. 3A is a schematic cross-sectional view showing another example of the optical sheet according to one embodiment of the present invention, and FIG. 3B is a schematic surface view of the optical sheet of FIG.
FIG. 4A is a schematic cross-sectional view showing another example of the optical sheet of one embodiment of the present invention, and FIG. 4B is a schematic surface view of the optical sheet of FIG.
FIG. 5 is a schematic view showing an example of a method for producing an optical sheet suitable for carrying out the present invention.
FIG. 6 is a perspective view of a conventional backlight unit.
FIG. 7 is a plan view of the back surface of the optical sheet of FIG. 6;
FIG. 8 is a schematic view showing an example of a conventional method for manufacturing an optical sheet.
[Explanation of symbols]
1, 11, 15, 25, 26, 35, 45, 51 Optical sheet
2,52 Base layer
3, 23, 53 Light diffusion layer
4,54 Anti-sticking layer
5, 12, 15a, 25a, 35a, 45a, 50 Bright line prevention layer
6, 8, 56, 58 binder
7, 9, 57, 59 beads
13,28 Reflective sheet
17 Printed part
18, 27 raw sheet
20 backlight unit
21 lamp
22 Light guide plate
24 prism sheet

Claims (13)

An optical sheet laminated with a bright line preventing layer that absorbs light rays,
An optical sheet, wherein the bright line preventing layer is not provided within a predetermined distance from substantially the entire periphery of the end toward the inside. The optical sheet according to claim 1, wherein the bright line prevention layer is a printing layer. The optical sheet according to claim 1, wherein the substantially entire circumference is 90% or more of the entire circumference. The optical sheet according to any one of claims 1 to 3, wherein the fixed distance is 0.05 mm or more. The optical sheet according to claim 1, wherein the predetermined distance is within 5.0 mm. The optical sheet according to any one of claims 2 to 5, wherein the thickness of the printing layer is 3 µm or more and 14 µm or less. The optical sheet according to claim 2, wherein the printing layer is formed by gradation printing and / or solid printing. 3. The printing layer is formed of at least one kind of ink selected from the group consisting of evaporative drying type ink, oxidation polymerization type ink, heat curing type ink, two-component reaction type ink, and ultraviolet curing type ink. 8. The optical sheet according to any one of items 1 to 7, A transparent base layer, an optical functional layer laminated on the front side of the base layer, and a sticking prevention layer laminated on the back side of the base layer,
The optical sheet according to any one of claims 1 to 8, further comprising a bright line prevention layer laminated on the back side of the sticking prevention layer or on the front side of the optical functional layer. The optical sheet according to any one of claims 1 to 8, further comprising: a reflection sheet that reflects light rays; and a bright line preventing layer laminated on a surface side of the reflection sheet. The light sheet according to any one of claims 1 to 9, wherein the lamp, a light guide plate that guides a light beam emitted from the lamp to the surface side, and a light guide that is arranged on the surface side of the light guide plate and guides the light beam uniformly in the surface direction. A backlight unit of a liquid crystal display device comprising: A liquid crystal comprising: a lamp; a light guide plate that guides light emitted from the lamp to the front side; and an optical sheet according to claim 10 that is disposed on the back side of the light guide plate and guides the light uniformly in the surface direction. Backlight unit for display device. A forming step of forming absorbing means on the raw sheet, and a molding step of cutting out an optical sheet from the raw sheet formed with the absorbing means,
The method of manufacturing an optical sheet, wherein in the molding step, a bright line preventing layer that absorbs light is not provided at a predetermined distance inward from substantially the entire periphery of the edge of the optical sheet.

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