JP2012242565A - Optical sheet, backlight unit using the same, and manufacturing method of optical sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical sheet capable of preventing damages to another member on which it is superposedly disposed.SOLUTION: An optical sheet comprises a sheet body having an optical function and a plurality of fibers which are protrusively provided on the back side of the sheet body. It is effectively that the sheet body and the plurality of fibers are bonded via an adhesive part. It is effectively that the adhesive part is layered on the back side of the sheet body. It is effectively that the plurality of fibers are protrusively provided on the back side of the sheet by an electrostatic flocking process.

Description

  The present invention relates to an optical sheet, a backlight unit using the optical sheet, and a method for manufacturing the optical sheet.

  Liquid crystal display devices are widely used as display devices for screens of televisions, personal computers, and the like, and are broadly classified into direct-view types for directly viewing the display screen and projection types for viewing images projected on the screen. Direct-view liquid crystal display devices include a transmissive type that transmits light from the backlight, a reflective type that does not have a backlight and uses reflected light such as natural light and room light, and a reflective type in bright places and a transmissive type in dark places. There is a transflective type. On the other hand, projection-type liquid crystal display devices include a front type that projects an image on the front surface of a screen and a rear type that projects an image on the back surface of the screen.

  In the transmissive liquid crystal display device, a backlight system that illuminates a liquid crystal layer from the back is widespread, and backlight units such as an edge light type (side light type) and a direct type are provided on the lower surface side of the liquid crystal layer. As shown in FIG. 7, the edge light type backlight unit 40 generally includes a lamp 41 as a light source, and a rectangular plate-shaped light guide plate 42 that is disposed so that an end thereof is along the lamp 41. A plurality of optical sheets 43 disposed on the surface side of the light guide plate 42 are provided. As the lamp 41 as the light source, an LED (light emitting diode), a cold cathode tube, or the like is used. However, LEDs are currently spreading from the viewpoint of miniaturization and energy saving. The optical sheet 43 has optical functions such as diffusion and refraction with respect to transmitted light. (1) A light diffusion sheet 44 disposed on the surface side of the light guide plate 42 and mainly having a light diffusion function. (2) A prism sheet 45 disposed on the surface side of the light diffusion sheet 44 and having a function of refraction in the normal direction is used.

  Although not shown, a backlight unit in which more optical sheets 43 such as a light diffusion sheet and a prism sheet are disposed in consideration of the light guide characteristics of the light guide plate 42 and the optical functions of the optical sheet 43 described above. There is also.

  The function of the backlight unit 40 will be described. First, a light beam incident on the light guide plate 42 from the lamp 41 is reflected by a reflective dot or a reflection sheet (not shown) on the back surface of the light guide plate 42 and each side surface. Emitted from the surface. The light beam emitted from the light guide plate 42 enters the light diffusion sheet 44, is diffused, and is emitted from the surface. Thereafter, the light beam emitted from the surface of the light diffusion sheet 44 enters the prism sheet 45, is refracted toward the normal direction by the prism portions of the plurality of protrusions formed on the surface, is emitted from the surface, and further upwards. Illuminates the entire liquid crystal layer (not shown).

  As shown in FIG. 7 (b), the light diffusion sheet 44 disposed on the surface of the light guide plate 42 is generally made of a transparent synthetic resin base layer 46 and the base layer 46. And an anti-sticking layer 48 laminated on the back surface of the base material layer 46. The optical layer 47 generally has a structure in which resin beads 50 are dispersed in a binder 49, and is configured to exhibit a light diffusion function or the like with respect to transmitted light. The anti-sticking layer 48 has a structure in which a small amount of beads 52 are dispersed and dispersed in the binder 51, and the lower part of the beads 52 protrudes from the back surface of the binder 51. The anti-sticking layer 48 has the back surface of the light diffusing sheet 44 in close contact with the surface of another optical sheet or the like (light guide plate 42), that is, sticking to generate interference fringes, or wound and stored in a roll shape in the manufacturing process. This prevents the inconvenience that blocking (adhesion) occurs.

  As the beads 52 dispersed in the anti-sticking layer 48 of the light diffusion sheet 44, acrylic beads or the like are generally used. Since these acrylic beads are relatively hard, the light is projected by the beads 52 protruding on the back surface. The surface of the light guide plate 42 and the like disposed on the back surface side of the diffusion sheet 44 may be damaged. The scratches on the light diffusion sheet cause uneven brightness in the liquid crystal display device.

  Therefore, in order to prevent damage to other members such as a light guide plate and a prism sheet disposed on the back surface side, an optical sheet (see Japanese Patent Application Laid-Open No. 2004-85626, etc.) provided with a damage prevention layer on the back surface. ) Has been developed.

  However, even in the optical sheet provided with the scratch-preventing layer, there is a fine bead for preventing sticking, so that it is not possible to sufficiently prevent damage to other optical sheets.

JP 2004-85626 A

  The present invention has been made in view of these inconveniences, and an optical sheet capable of preventing damage and sticking to other members disposed in a stacked manner, and using this optical sheet, brightness unevenness and interference fringes can be prevented. An object of the present invention is to provide a high-quality backlight unit that prevents generation and the like.

The invention made to solve the above problems is
A sheet body having an optical function;
An optical sheet including a plurality of fibers protruding from the back side of the sheet body.

  Since the optical sheet has a plurality of fibers projecting from the back side of the sheet body, the optical sheet is projected to other members such as a light guide plate, a prism sheet, and the like disposed on the back side. Contact with fiber. Since the plurality of fibers in contact with each other are relatively soft, there is a low possibility of scratching even if they are in contact with other members.

  In addition, the optical sheet has a high anti-sticking property because it makes contact with other members such as a light guide plate placed on the back side with multiple fibers, preventing the occurrence of interference fringes due to sticking. can do.

  The sheet main body and the plurality of fibers may be bonded via an adhesive portion. With such an adhesive part, a plurality of fibers can be bonded more firmly to the sheet body, and the fibers can be prevented from falling off.

  The adhesive part is preferably laminated on the entire back surface of the sheet body. Thus, by laminating the adhesive portion on the entire back surface of the sheet main body, a plurality of fibers can be projected over the entire back surface of the sheet main body. Can be improved.

  It is preferable that the adhesive part is attached to the back surface of the sheet body in a scattered manner. By attaching the adhesive portion to the back surface of the sheet main body in a scattered manner in this way, it is possible to reduce the amount of adhesive to be applied and the number of layers laminated on the back surface of the sheet main body. The light transmittance can be improved while maintaining the anti-scratching property and anti-sticking property.

  The adhesive part may be formed from an acrylic emulsion adhesive. The acrylic emulsion adhesive is easy to apply to the sheet body and has a low ignition risk. Therefore, the workability of the optical sheet can be improved.

  It is preferable that the plurality of fibers protrude from the back side of the sheet body by an electrostatic flocking method. With this electrostatic flocking method, it is possible to plant a plurality of fibers at a desired angle with respect to the back side of the sheet main body, and to easily adjust the density of the fibers to be planted. Therefore, according to the electrostatic machining method, it is possible to improve the above-described scratch resistance, sticking resistance, and the like.

  The said fiber is good in it being a transparent chemical fiber. Thus, by setting it as a transparent chemical fiber, the light transmittance of a sheet | seat main body is maintained, and the reduction of the light transmittance of the said optical sheet can be prevented.

The density of the fibers per unit area of the sheet body rear surface 40 present / cm ² or more 5000 / cm ² or less. Thus, by setting the density of the fibers per unit area on the back surface of the sheet main body within the above range, it is possible to prevent the light transmittance from being reduced while improving the above-described scratch resistance and anti-sticking properties.

  The average diameter of the fibers is preferably 5 μm or more and 50 μm or less. The average length is preferably 20 μm or more and 2 mm or less. By making the average diameter and the average length of the fibers within the above ranges, it is possible to improve the thin film properties of the optical sheet while effectively exhibiting the above-mentioned scratch prevention properties, sticking prevention properties, and the like.

  The said sheet | seat main body can be equipped with a base material layer and the optical layer formed in the surface of this base material layer. Thus, by separating the sheet body into the base material layer and the optical layer, it is possible to easily and reliably project a plurality of fibers on the base material layer while reducing the influence on the optical function. it can.

The invention made to solve the above problems is
In a backlight unit for a liquid crystal display device that guides light emitted from a lamp to the surface side by dispersing it,
A backlight unit for a liquid crystal display device comprising the optical sheet.

  The backlight unit can prevent the occurrence of uneven brightness due to scratches on other members due to the high scratch resistance to the other members of the optical sheet, and can improve the quality of the liquid crystal display screen. Handling during transportation, storage, etc. can be facilitated. In addition, the backlight unit can prevent sticking with other members disposed on the back surface side by preventing sticking of the optical sheet, thereby preventing occurrence of interference fringes due to close contact.

The invention made to solve the above problems is
An optical layer forming step of laminating an optical layer on the surface of the base material layer;
An adhesive application process for applying an adhesive to the back surface of the base material layer;
A fiber implantation process in which a plurality of fibers are implanted on the surface coated with the adhesive;
An optical sheet manufacturing method comprising an adhesive curing step of curing an adhesive after flocking, and an excess fiber removing step of removing excess fibers from the sheet body after the adhesive is cured.

  According to the method for producing an optical sheet, by having the above-described steps, a plurality of fibers can be implanted on a desired surface of the optical sheet, and the plurality of fibers can be firmly fixed with an adhesive. it can. Therefore, the optical sheet obtained by the manufacturing method can exhibit high scratch resistance and anti-sticking properties to other members.

  Here, the “adhesive part” means a cured product of the adhesive applied to the sheet body. The “optical layer” means a layer that exhibits a predetermined optical function with respect to transmitted light.

  As described above, the optical sheet of the present invention is excellent in scratch resistance, sticking prevention, and the like on the surface of an optical sheet or the like disposed on the back side. Moreover, the backlight unit of the present invention can prevent generation of luminance unevenness and interference fringes due to scratches on the optical sheet, the light guide plate, and the like. Furthermore, the backlight unit of the present invention is easy to handle during manufacture, transportation, storage and the like.

It is a typical sectional view showing the optical sheet concerning one embodiment of the present invention. It is typical explanatory drawing which shows the optical sheet which concerns on the form different from the optical sheet of FIG. 1, Comprising: (a) is typical sectional drawing, (b) is typical for showing the coating state of an adhesive part. It is a top view. It is typical explanatory drawing which shows the optical sheet which concerns on the form different from the optical sheet of FIG.1 and FIG.2. It is typical explanatory drawing which shows the optical sheet which concerns on the form different from the optical sheet of FIG.1, FIG2 and FIG.3. It is typical explanatory drawing which shows the optical sheet which concerns on the form different from the optical sheet of FIGS. 1-4. (A) is a flowchart which shows the manufacturing method of the optical sheet of FIG. 1, (b) is typical explanatory drawing which shows a process (D). (A) is a typical perspective view which shows a general edge light type | mold backlight unit, (b) is typical sectional drawing which shows a general light-diffusion sheet.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.
The optical sheet 1 in FIG. 1 is a so-called light diffusion sheet, and includes a sheet body 2 and a plurality of fibers 3 protruding from the back side of the sheet body 2. The sheet main body 2 includes a base layer 4 and an optical layer 5 laminated on the surface of the base layer 4.

  Since the base material layer 4 needs to transmit light, it is made of a transparent synthetic resin or glass. The term “transparency” as used herein includes colored transparency and translucency in addition to colorless transparency, and colorless transparency is particularly preferred. The synthetic resin used for the base material layer 4 is not particularly limited, and examples thereof include polyethylene terephthalate, polyethylene naphthalate, acrylic resin, polycarbonate, polystyrene, polyolefin, cellulose acetate, and weather resistant vinyl chloride. Can do. Among them, polyethylene terephthalate having excellent transparency and high strength is preferable, and polyethylene terephthalate having improved bending performance is particularly preferable.

  The base material layer 4 may contain an antistatic agent. By containing the antistatic agent, it is possible to prevent the optical sheet 1 from being charged by static electricity generated in the plurality of fibers 3 protruding from the sheet main body 2. The antistatic agent is not particularly limited, and known ones can be used, for example, anionic antistatic agents such as alkyl sulfates and alkyl phosphates, and cationic systems such as quaternary ammonium salts and imidazoline compounds. Antistatic agents, non-ionic antistatic agents such as polyethylene glycol-based, polyoxyethylene sorbitan monostearic acid ester and ethanolamides, and high-molecular antistatic agents such as polyacrylic acid are used. Among these, a cationic antistatic agent having a relatively large antistatic effect is preferable, and an antistatic effect is exhibited by addition of a small amount. In addition, the antistatic agent is dispersed and contained in an appropriate amount uniformly in the base material layer 4 so that the fibers 3 protrude without unevenness in an electrostatic flocking process of the fibers 3 described later.

  The average thickness of the base material layer 4 is not particularly limited, but is, for example, 10 μm or more and 500 μm or less, preferably 35 μm or more and 250 μm or less, and particularly preferably 50 μm or more and 188 μm or less. When the thickness of the base material layer 4 is smaller than the above range, inconveniences such as curling and handling become difficult when the resin composition for forming the optical layer 5 is applied. On the other hand, if the thickness of the base material layer 4 is larger than the above range, the luminance of the liquid crystal display device may decrease, and the thickness of the backlight unit becomes large, which is contrary to the demand for thinning of the liquid crystal display device. It will also be a thing.

  The optical layer 5 has a binder 7 and a plurality of light diffusing agents 8 disposed substantially uniformly in the binder 7. The plurality of light diffusing agents 8 can uniformly diffuse the light beam that passes through the optical layer 5 from the back side to the front side. Further, the light diffusing agent 8 forms fine irregularities on the surface of the optical layer 5 substantially uniformly, and the concave and convex portions of the fine irregularities are formed in a lens shape. The optical sheet 1 exhibits an excellent light diffusing function due to the lens action of the fine unevenness, and the refracting function that refracts the transmitted light toward the normal direction due to the light diffusing function and the transmitted light as the normal line. It also has a light condensing function that condenses macroscopically in the direction.

  The light diffusing agent 8 is a particle having a property of diffusing light, and is roughly classified into an inorganic filler and an organic filler. Specifically, for example, silica, aluminum hydroxide, aluminum oxide, zinc oxide, barium sulfide, magnesium silicate, or a mixture thereof can be used as the inorganic filler. Specific examples of the organic filler include acrylic resin, acrylonitrile resin, polyurethane, polyvinyl chloride, polystyrene, polyamide, polyacrylonitrile, and the like. Among them, an acrylic resin having high transparency is preferable, and polymethyl methacrylate (PMMA) is particularly preferable.

  The binder 7 is formed by curing (crosslinking or the like) a polymer composition containing a base polymer. By this binder 7, the light diffusing agent 8 is disposed and fixed at substantially equal density on the entire surface of the base material layer 4. In addition, the polymer composition for forming this binder 7 includes, for example, a fine inorganic filler, a curing agent, a plasticizer, a dispersant, various leveling agents, an antistatic agent, an ultraviolet absorber, an antioxidant, and a viscosity. A modifier, a lubricant, a light stabilizer and the like may be appropriately blended.

  The plurality of fibers 3 are provided so as to protrude through an adhesive portion 6 laminated on the back surface of the sheet body 2. Specifically, the plurality of fibers 3 are implanted substantially uniformly in the adhesive portion 6 laminated on the back surface of the sheet body 2 and project substantially vertically.

  The adhesive portion 6 is formed of an adhesive that is applied to the entire back surface of the sheet body 2. With this adhesive portion 6, a plurality of fibers 3 can be projected over the entire back surface of the sheet body 2. Moreover, the base part of the fiber 3 can be joined more firmly, and the dropping of the fiber 3 can be prevented.

  The adhesive forming the adhesive portion 6 is not particularly limited, and a water-soluble adhesive, a solvent-type adhesive, an ultraviolet curable adhesive, or the like can be used. Among them, it is preferable to use a water-soluble adhesive that is easy to apply to a sheet and has a low ignition risk. Specific examples of water-soluble adhesives include adhesives such as acrylic emulsions, urethane emulsions, epoxy emulsions, and vinyl acetate emulsions, and acrylic emulsion adhesives are particularly preferred from the standpoint of sprayability and wear. . Specific examples of solvent-type adhesives include adhesives such as epoxy resins, acrylic resins, urethane resins, polyester resins, vinyl acetate resins, vinyl chloride resins, and phenol resins. Therefore, an epoxy resin is particularly preferable. Furthermore, a transparent thing is preferable from a viewpoint of improving the light transmittance, and colorless and transparent are especially preferable. In consideration of the environment, an adhesive (low VOC adhesive) that hardly releases volatile organic compounds (VOC) is preferable. The thickness of the adhesive portion 6 is not particularly limited, but is set to, for example, 0.1 μm or more and 10 μm or less after curing.

  The method for flocking the plurality of fibers 3 is not particularly limited as long as the plurality of fibers 3 can project from the back side of the sheet main body 2, but it is preferable to use an electrostatic flocking method. If the electrostatic flocking method is used, a plurality of fibers 3 can be flocked and fixed at a desired angle with respect to the back surface of the sheet body 2, and the density of the fibers 3 to be flocked can be easily adjusted. Can do. In particular, it is preferable to plant and fix a plurality of fibers 3 substantially perpendicularly to the back surface of the sheet body 2. By flocking the plurality of fibers 3 substantially vertically, the fibers 3 can be prevented from falling before the adhesive that joins the bases of the fibers 3 is cured. In addition, as an electrostatic flocking processing method, for example, a sheet having an uncured adhesive portion with respect to one electrode is set to be a counter electrode, and a DC high voltage is applied to the sheet and supplied between the electrodes. The processing method etc. which flock along the electric force line by the Coulomb force, and plant the hair by piercing the base of the fiber into the surface of the sheet. Such an electrostatic flocking method is not particularly limited as long as it is a known electrostatic flocking method.

  The fiber 3 is not particularly limited, and natural fiber and chemical fiber can be used. Examples of natural fibers include cotton fibers and hemp fibers. Examples of chemical fibers include rayon fibers, polyester fibers, polyolefin fibers (polyethylene fibers, polypropylene fibers, etc.), polyamide fibers (aliphatic polyamide fibers, aromatic polyamide fibers, etc.), acrylic fibers, polyacrylonitrile. Fiber, polyvinyl alcohol fiber, polyimide fiber, carbon fiber, silicone fiber, fluorine fiber and the like. Especially, a chemical fiber can be shape | molded in the shape which does not have curl, and can be used suitably for an electrostatic flocking method. In particular, a transparent chemical fiber is preferable from the viewpoint of increasing light transmittance, and a colorless and transparent chemical fiber is more preferable.

The lower limit of the density of the fibers 3 per unit area of the back surface of the seat body 2 is preferably 40 present / cm ^2, more preferably 60 present / cm ^2, particularly preferably 80 present / cm ^2. On the other hand, the upper limit of the density of the fibers 3, preferably 5000 / cm ^2, more preferably 4,000 / cm ^2, particularly preferably 3000 / cm ^2. If the density of the fibers 3 on the back surface of the sheet body 2 is smaller than the lower limit, it may not be possible to sufficiently exert the function of preventing damage to other members and the function of preventing sticking. Further, when the density of the fibers 3 is equal to or higher than a certain level, extraneous foreign matters mixed on the back surface side of the sheet body 2 can be captured by the fiber layer formed by the plurality of fibers 3 and confined in the fiber layer. . For this reason, it becomes difficult for the other member arrange | positioned on this surface to contact an external foreign material, and, thereby, the damage of another member can further be reduced. On the contrary, if this density is larger than the above upper limit, the light transmittance may be lowered.

  The lower limit of the average diameter of the fibers 3 is preferably 5 μm, more preferably 10 μm, and particularly preferably 20 μm. On the other hand, the upper limit of the average diameter of the fibers 3 is preferably 50 μm, more preferably 40 μm, and particularly preferably 30 μm. If the average diameter of the fibers 3 is smaller than the lower limit, the above-mentioned scratch preventing function and sticking preventing function may not be sufficiently exhibited. On the contrary, if the average diameter is larger than the above upper limit, the light transmittance may be lowered.

  The lower limit of the average length of the fibers 3 is preferably 20 μm, more preferably 40 μm, and particularly preferably 80 μm. The upper limit of the average length of the fibers 3 is preferably 2 mm, more preferably 1 mm, and particularly preferably 0.5 mm. If the average length of the fibers 3 is smaller than the above lower limit, the above-described scratch preventing function and sticking preventing function may not be sufficiently exhibited. On the other hand, if the average length is larger than the above upper limit, the thickness of the backlight unit using the optical sheet increases due to the material, average diameter, and the like of the fiber 3, which is contrary to the demand for thinning the liquid crystal display device. There is a risk that the fiber 3 is bent and the anti-sticking function cannot be obtained and the light transmittance is lowered.

  The aspect ratio of the fiber 3 is preferably 2 or more and 40 or less. When the aspect ratio of the fiber 3 is smaller than the lower limit, the above-described electrostatic flocking method may not be suitably performed. On the other hand, if the aspect ratio of the fiber 3 is larger than the above upper limit, the fiber 3 may be bent and the sticking prevention function may not be obtained, and the light transmittance may be reduced. The aspect ratio is the ratio of the average length to the average fiber diameter.

  The total light transmittance of the optical sheet 1 is preferably 20% or more. If the total light transmittance is smaller than the above range, the luminance may be lowered.

  The haze value of the optical sheet 1 is preferably 50% or more. When the haze value is smaller than the above range, the diffusion performance is insufficient, and there is a risk of uneven brightness.

  The “total light transmittance” is a value measured according to JIS K7361. The “haze value” is a value measured according to JIS K7105.

  Since the optical sheet 1 has a plurality of fibers 3 protruding from the back surface of the sheet body 2, the plurality of fibers 3 come into contact with other members when storing and transporting the sheets and assembling a liquid crystal display device. To do. Since the plurality of fibers 3 are relatively soft and have a predetermined stiffness, even if a force acts in the direction of the back surface of the optical sheet 1, the plurality of fibers 3 cause deformation such as bending and absorb the force. In addition, it is possible to prevent the other members disposed on the back surface side from being damaged. In addition, even when the fiber 3 comes off the adhesive portion 6 and comes into contact with another member, the possibility that the other member is damaged is low. As a result, the cause of damage to other members can be significantly reduced. In addition, sticking between the optical sheet 1 and another member is prevented by the plurality of fibers 3 coming into contact with each other, and uneven brightness on the screen of the liquid crystal display device is suppressed.

  The optical sheet 1 is substantially uniform on the surface of the base material layer 4 by embossing instead of the sheet body 2 in which the optical layer 5 in which the light diffusing agent 8 is dispersed in the binder 7 is laminated on the base material layer 4. It is also possible to use a sheet body having a light diffusing function by forming fine irregularities on it.

<Optical sheet manufacturing method>
Although the manufacturing method of the said optical sheet 1 is not specifically limited, For example, as shown to Fig.6 (a), (A) The base material sheet which shape | molds the sheet | seat (henceforth the base material sheet 40) which comprises a base material layer. A molding step, (B) an optical layer forming step of laminating the optical layer 5 on the surface of the substrate sheet 40, (C) an adhesive coating step of coating an adhesive on the back surface of the substrate sheet 40, ( D) a fiber flocking step of flocking a plurality of fibers 3 on the back surface of the base material sheet 40 coated with an adhesive; (E) an adhesive curing step of curing the adhesive after flocking to form the adhesive portion 6; (F) The method which has a surplus fiber removal process of removing a surplus fiber from the base material sheet 40 after adhesive hardening can be mentioned.

  In the step (A), the molten thermoplastic resin is extruded from a T die, and then the extruded body is stretched in the layer longitudinal direction and the layer width direction to form the base sheet 40 into a long sheet. It is a process. As a known extrusion method using a T die, for example, a polishing roll method and a chill roll method can be exemplified. In addition, the base material sheet 40 can also be stretched, and examples of known film stretching methods include methods such as a tubular film biaxial stretching method and a flat film biaxial stretching method.

  In the step (B), an optical layer coating liquid is produced by mixing the light diffusing agent 8 with the polymer composition constituting the binder 7, and this optical layer coating liquid is applied to the surface of the substrate sheet 40. This is a step of laminating the optical layer 5 by processing. As a well-known method for laminating the optical layer, for example, a coating method using a roll coater, a bar coater, a blade coater, a spin coater, a gravure coater, a flow coater, spraying, screen printing or the like can be mentioned.

  Step (C) is a step of applying an adhesive to the back surface of the base sheet 40. The adhesive in this step is in an uncured state. As a means for applying the adhesive, a known method can be used, and examples thereof include a spraying method using a spray gun and a coating method using a roll coater.

  In the step (D), as shown in FIG. 6B, the electrode 32 is disposed on the back surface (surface coated with the adhesive) side of the substrate sheet 40 in a flat state so as to face the substrate sheet 40. A DC high voltage is applied between the base sheet 40 and the electrode 32, and a plurality of fibers 3 are dropped from the fiber supply device 31 toward the base sheet 40 by the Coulomb force generated during this time, and uncured adhesion In this step, the base of the fiber 3 is pierced into the agent, and the plurality of fibers 3 are implanted in a shape protruding from the base sheet 40. The flocking method used in this step is not particularly limited as long as it is a known electrostatic flocking processing method, in addition to the down method of dropping the plurality of fibers 3 shown in FIG. Any of an up method in which a plurality of fibers are raised from below and a side method in which a plurality of fibers fly from the lateral direction may be used. Further, in the electrostatic flocking processing method, the flocking direction of a plurality of fibers can be adjusted by manipulating the direction of the electric lines of force, so that the flocked base sheet 40 may be flocked, for example, You may plant the hair in the state in which the base material sheet 40 was mounted on the roll.

  The step (E) is a step of forming the adhesive portion 6 by curing the adhesive in which the base portions of the plurality of fibers 3 are pierced. When a water-soluble adhesive or a solvent-type adhesive is used, it is cured by a drying process. A well-known method can be used as the means for the drying treatment, and examples thereof include a method using a hot air dryer. In the case of using an ultraviolet curable adhesive, it is cured by ultraviolet irradiation. As a means for ultraviolet irradiation, a known method can be used, and examples thereof include an ultraviolet irradiation method using a low pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a metal halide lamp, an ultraviolet laser and the like as a light source.

  A process (F) is a process of removing the excess fiber adhering to this surface, without adhering to the back surface of the base material sheet 40. FIG. As a means for removing excess fibers, a known method can be used, and examples thereof include air blowing, vibration, brushing, and the like. An optical sheet is formed by cutting the long base sheet 40 after performing this step (F).

  According to this manufacturing method, the plurality of fibers 3 can be planted on the back surface of the base sheet 40, and the plurality of fibers 3 can be firmly fixed by the adhesive portion 6. Therefore, the optical sheet obtained by the manufacturing method can exhibit high scratch resistance and anti-sticking properties to other members. Note that the optical layer 5 may be laminated on the surface of the base sheet 40 after the plurality of fibers 3 protrude from the back surface of the base sheet 40. That is, after performing the step (A), the steps (C) to (F) may be performed, and then the step (B) may be performed. Moreover, it is good also as a manufacturing method which makes the base material sheet 40 itself contain an optical function instead of implementing a process (B). Specifically, for example, a method of forming an optical function by forming fine irregularities on the substrate sheet 40 by embossing in the step (A) can be mentioned.

  A backlight unit for a liquid crystal display device according to the present invention includes a rectangular light guide plate, a lamp provided along the long side edge of the light guide plate, and a light diffusion sheet provided to overlap the light guide plate surface. A rectangular optical sheet such as a prism sheet or a microlens sheet, and the optical sheet is used as the light guide plate, the light diffusion sheet, the prism sheet, the microlens sheet, or the like. As described above, since the optical sheet has high scratch resistance to other members, anti-sticking, total light transmittance, uniformity such as luminance, economy and thin film properties, the backlight unit is The use efficiency of the emitted light can be remarkably increased, and the high luminance, high quality, energy saving and thin and light weight demanded by society today can be promoted.

<Other embodiments>
The optical sheet of the present invention is not limited to the above-described embodiment, and may be the following embodiment.

  The optical sheet 11 in FIG. 2 is a so-called light diffusion sheet, and includes a sheet body 2 and a plurality of fibers 3 protruding from the back surface of the sheet body 2. The sheet body 2 includes a base layer 4 and an optical layer 5 laminated on the surface of the base layer 4. The base material layer 4, the optical layer 5, the binder 7, the light diffusing agent 8, the manufacturing method, the adhesive, and the material of the fiber 3 are the same as those of the optical sheet 1 in FIG. Is omitted.

  The plurality of fibers 3 are provided so as to protrude through a plurality of adhesive portions 16 attached to the back surface of the sheet body 2 in a scattered manner. The adhesive portion 16 is obtained by attaching the adhesive to the back surface of the base material layer 4 in a scattered manner (island shape).

  As shown in FIG. 2 (b), since the adhesive part 16 is applied to the back surface of the base material layer 4 in a scattered manner, the adhesive part 16 is applied to the entire back surface of the base material layer 4 as in the adhesive part 6 of FIG. The amount of adhesive to be applied can be made small compared to the case of applying. As a result, the transparency of the optical sheet 11 can be increased as compared with the optical sheet 1 of the above-described embodiment. The plurality of adhesive portions 16 are formed substantially uniformly on the back surface of the base material layer 4. The number and area of the plurality of adhesive portions 16 and the number of the plurality of fibers 3 for each adhesive portion are determined so that the density of the fibers 3 per unit area on the back surface of the base material layer 4 is in the above-described range. It is preferable. Thereby, the damage prevention function and sticking prevention function to the other member mentioned above are exhibited. 2 (a) and 2 (b), a plurality of fibers 3 fixed to one adhesive portion 16 are shown, but a single fiber 3 may be used. Moreover, the hair transplantation method of the some fiber 3 can use the electrostatic hair transplant processing method similarly to the optical sheet 1 of FIG.

  The optical sheet 12 in FIG. 3 is a so-called light diffusion sheet, and includes a sheet body 2 and a plurality of fibers 3 protruding from the back surface of the sheet body 2. The sheet body 2 includes a base material layer 4, an antistatic agent layer 17 laminated on the surface of the base material layer 4, and an optical layer 5. Since the fiber 3, the base material layer 4, the optical layer 5, the adhesive agent part 6, the binder 7, the light diffusing agent 8, and the manufacturing method are the same as those of the optical sheet 1 in FIG. Is omitted.

  The antistatic agent layer 17 is formed from a synthetic resin containing an antistatic agent. The antistatic agent is not particularly limited as described above, and a known one can be used.

  The antistatic agent layer 17 better prevents the optical sheet 12 from being charged by static electricity generated in the plurality of fibers 3 protruding from the sheet body 2 than when the base material layer 2 contains an antistatic agent. be able to.

  The optical sheet 13 in FIG. 4 is a so-called prism sheet, and includes a sheet body 2 and a plurality of fibers 3 protruding from the back surface of the sheet body 2. The sheet body 2 includes a base material layer 4 and a prism layer 18 laminated on the surface of the base material layer 4. Since the fiber 3, the base material layer 4, the adhesive agent part 6, the manufacturing method, etc. are the same as that of the optical sheet 1 of the said FIG. 1, the same number is attached | subjected and description is abbreviate | omitted.

  The prism layer 18 includes a sheet-like portion 19 laminated on the surface of the base material layer 4 and a prism portion 20 formed of a large number of triangular prisms. The triangular prisms of the prism portion 20 are parallel, equally spaced, and dense. It is arranged. A synthetic resin is used as a material for forming the prism layer 18. The manufacturing method is not particularly limited, and the base material layer 4 and the prism layer 18 may be integrally formed, or may be separately formed and bonded via an adhesive layer laminated between the base material layer 4 and the prism layer 18. The prism layer 18 may be laminated on the base material layer 4.

  The optical sheet 13 has a strong front luminance improvement effect due to the prism layer 18 and can enhance the light recycling effect in the backlight unit and suppress the luminance unevenness of the emitted light. Further, the optical sheet 13 has high scratch resistance and sticking resistance to other members due to the plurality of fibers 3.

  The optical sheet 13 may have a form in which the ridge line of the prism part 20 meanders, a form in which the arrangement of the triangular prisms of the prism part 20 is not equally spaced, a form in which the ridge line of the prism part 20 curves in the height direction, and the like. It is.

  The optical sheet 14 in FIG. 5 is a so-called microlens sheet, and includes a sheet body 2 and a plurality of fibers 3 protruding from the back surface of the sheet body 2. The sheet body 2 includes a base material layer 4 and a microlens surface 21 laminated on the surface of the base material layer 4. Since the fiber 3, the base material layer 4, the adhesive agent part 6, the manufacturing method, etc. are the same as that of the optical sheet 1 of the said FIG. 1, the same number is attached | subjected and description is abbreviate | omitted.

  The microlens surface 21 includes a sheet-like portion 22 laminated on the surface of the base material layer 4 and a microlens array 23 formed on the surface of the sheet-like portion 22. The microlens surface 21 may be configured only by the microlens array 23 without the sheet-like portion 22. In this case, the microlens array 23 is formed directly on the surface of the base material layer 4. Also good. Further, the microlens surface 21 and the base material layer 4 may be integrally formed.

  The optical sheet 14 has optical functions such as high condensing, refraction in the normal direction side, and diffusion by the microlens array 23, and the optical functions can be easily and reliably controlled. Therefore, for example, the optical sheet 14 can control the peak direction of the incident light beam to the prism sheet of the backlight unit to an optimum tilt angle for refraction in the normal direction side. Furthermore, the optical sheet 14 has high scratch resistance and sticking resistance to other members due to the plurality of fibers 3.

  The “microlens” means a microlens having a partially spherical interface, and corresponds to a hemispherical convex lens, a hemispherical concave lens, or the like.

  The optical sheet and the backlight unit of the present invention are not limited to the above embodiment. The optical sheet is not limited to the light diffusion sheet, the light condensing sheet (prism sheet, microlens sheet, etc.), for example, other light guide plate, polarizing sheet, retardation sheet, field expansion sheet, lenticular lens sheet, Fresnel The present invention can also be applied to an optical sheet such as a lens sheet. In particular, it is suitably used as an optical sheet for a backlight unit disposed between a light guide plate and a liquid crystal display element. The optical sheet disposed at such a position is required to prevent generation of interference fringes due to scratching and sticking to other members. Therefore, the optical sheet capable of exhibiting a high function of preventing damage to other members and a function of preventing sticking can be suitably used.

  In addition to the base material layer, the optical layer, and the antistatic agent layer, the optical sheet may have other layers such as an ultraviolet absorber layer, a topcoat layer, and an easy adhesion layer in the sheet body.

  Further, as a method for fixing the plurality of fibers 3, the base of the fibers 3 may be directly bonded to the base material layer 4 without using an adhesive. For example, after shaping | molding the base material layer 4, before the base material layer 4 hardens | cures completely, the method of planting the some fiber 3 in the base material layer 4 etc. can be used.

  As described above, the optical sheet of the present invention is useful as a component of a backlight unit of a liquid crystal display device, and can be suitably used particularly for a transmissive liquid crystal display device.

DESCRIPTION OF SYMBOLS 1 Optical sheet 2 Sheet | seat main body 3 Fiber 4 Base material layer 5 Optical layer 6 Adhesive part 7 Binder 8 Light diffusing agent 11, 12, 13, 14 Optical sheet 16 Adhesive part 17 Antistatic agent layer 18 Prism layer 19 Sheet-like part DESCRIPTION OF SYMBOLS 20 Prism part 21 Micro lens surface 22 Sheet-like part 23 Micro lens array 31 Fiber supply apparatus 32 Electrode 40 Base material sheet

Claims (12)

A sheet body having an optical function;
An optical sheet comprising: a plurality of fibers protruding from the back side of the sheet body.   The optical sheet according to claim 1, wherein the sheet main body and the plurality of fibers are bonded via an adhesive portion.   The optical sheet according to claim 2, wherein the adhesive portion is entirely laminated on the back surface of the sheet main body.   The optical sheet according to claim 2, wherein the adhesive portion is attached to the back surface of the sheet body in a scattered manner.   The optical sheet according to claim 2, 3 or 4, wherein the adhesive part is formed of an acrylic emulsion adhesive.   The optical sheet according to any one of claims 1 to 5, wherein the fiber is protruded from the back side of the sheet body by an electrostatic flocking method.   The optical sheet according to any one of claims 1 to 6, wherein the fiber is a transparent chemical fiber. The optical sheet according to any one of claims 1 to 7, wherein a density of fibers per unit area of the back surface of the sheet body is 40 / cm ² or more and 5000 / cm ² or less.   9. The optical sheet according to claim 1, wherein the fiber has an average diameter of 5 μm to 50 μm and an average length of 20 μm to 2 mm.   The optical sheet according to any one of claims 1 to 9, wherein the sheet body includes a base material layer and an optical layer formed on a surface of the base material layer. A backlight unit for a liquid crystal display device that guides light emitted from a lamp to the surface side by dispersing,
A backlight unit for a liquid crystal display device, comprising the optical sheet according to any one of claims 1 to 10. An optical layer forming step of laminating an optical layer on the surface of the base material layer;
An adhesive application process for applying an adhesive to the back surface of the base material layer;
A fiber implantation process in which a plurality of fibers are implanted on the surface coated with the adhesive;
An optical sheet manufacturing method comprising: an adhesive curing step of curing an adhesive after flocking; and an excess fiber removing step of removing excess fibers from the sheet body after the adhesive is cured.

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