KR101167231B1 - Optical sheet for direct type liquid crystal display device and backlight unit - Google Patents

Abstract

It is an object of the present invention to provide an optical sheet for a direct type liquid crystal display device which can be manufactured with high productivity while suppressing costs, and which is provided with a high sticking resistance and an optical function.
This invention is equipped with the transparent base material layer and the optical layer laminated | stacked on the surface side of this base material layer, The biaxially stretched polyester film containing a filler is used as said base material layer, The average particle diameter of this filler is 70 nm or more and 200 nm. The following is an optical sheet for direct type liquid crystal display devices. It is preferable that content of a filler is 0.01 mass% or more and 1 mass% or less. As the filler, inorganic fine particles such as silica or organic fine particles such as acrylic resin can be used. It is preferable to make the draw ratio of the biaxially stretched polyester film in the longitudinal direction 2.5 to 4.5 times, and to make the draw ratio of the width direction 3 to 5 times.

Description

Optical sheet and backlight unit for direct type liquid crystal display device {OPTICAL SHEET FOR DIRECT TYPE LIQUID CRYSTAL DISPLAY DEVICE AND BACKLIGHT UNIT}

The present invention relates to an optical sheet for a direct type liquid crystal display device and a backlight unit for a direct type liquid crystal display device having the same.

Background Art [0002] A liquid crystal display device has a back light system that emits light by illuminating the liquid crystal layer from the back side, and a backlight unit such as an edge light type or a direct type is provided on the lower surface side of the liquid crystal layer. In particular, as a backlight unit for a large screen display device, a direct type backlight unit is suitably used in view of maintaining uniformity of luminance on the entire surface. The direct type backlight unit 50 basically includes a backlight 52 having a plurality of lamps 51 as a light source as shown in FIG. 6 (a), and various types of optics disposed on the surface side of the backlight 52. A sheet is provided. Examples of such an optical sheet include a light diffusion sheet 53 disposed on the surface side of the backlight 52, a prism sheet 54 disposed on the surface side of the light diffusion sheet 53, and the like.

The function of the direct type backlight unit 50 will be described. First, the light rays emitted from the backlight 52 enter the light diffusion sheet 53, are diffused from the light diffusion sheet 53, and the light diffusion sheet 53. Emitted from the surface. Thereafter, the light rays emitted from the light diffusion sheet 53 enter the prism sheet 54 and are emitted as light rays of a distribution showing peaks in a substantially normal direction by the prism portion 54a formed on the surface of the prism sheet 54. do.

In this manner, the light rays emitted from the backlight 52 are diffused by the light diffusion sheet 53 and refracted by the prism sheet 54 to show a peak in a substantially normal direction, and the liquid crystal layer on the surface side (not shown). Not to illuminate the entire surface. Although not shown, the prism sheet is for the purpose of alleviating the condensing characteristics of the prism sheet 54 described above, protecting the prism portion 54a, or preventing sticking of the liquid crystal panel such as a polarizing plate and the prism sheet 54. An optical sheet is further disposed on the surface side of 54.

Generally as the light-diffusion sheet 53 with which the said backlight unit 50 is equipped, the light-diffusion agent 59 is disperse | distributed in the transparent base material layer 55 and the binder 58, as shown to FIG. 6 (b). Light-diffusion sheet of the bead coating type which has the light-diffusion layer 56 and the sticking prevention layer 57 in which the beads 61 were disperse | distributed in the binder 60 (for example, Unexamined-Japanese-Patent No. 7-5305, Japan Patent publication 2000-89007). In addition, instead of coating the beads, an embossed light diffusion sheet which transfers the irregularities onto the surface of the transparent base material layer by using a metal mold having an irregular shape (for example, Japanese Patent Laid-Open No. 2006-47608, Japanese Patent) See also Publication No. 2006-335028). These types of light diffusing sheets exhibit light diffusing functions due to minute irregularities on the surface.

Generally, the light-diffusion sheet 53 performs the process of extrusion molding a molten thermoplastic resin from a T die, and the process of extending | stretching this extrusion molded body in a film longitudinal direction and a film width direction, and forming a base film, And then laminating the anti-sticking composition in which the beads are dispersed in the binder to the back surface of the base film, and laminating the light diffusing layer composition in which the light diffusing agent is dispersed in the binder to the surface of the base film. Is being manufactured. In this method, the composition for sticking prevention layer and the composition for light-diffusion layer are prepared beforehand, and these compositions are laminated | stacked one by one on the base film in a production line separate from the production line of base film formation (base film formation containing an extending process). It is called offline lamination method because production line of lamination and production line of lamination are separate). However, in the manufacturing method of the light-diffusion sheet which requires such a several production line, manufacturing cost becomes large and a manufacturing process becomes complicated, and a problem also arises in the point of productivity and work efficiency.

Japanese Patent Laid-Open No. 7-5305 Japanese Patent Laid-Open No. 2000-89007 Japanese Patent Publication No. 2006-47608 Japanese Patent Laid-Open No. 2006-335028

SUMMARY OF THE INVENTION The present invention has been made in view of these problems, and can be manufactured with high productivity while suppressing costs, and an optical sheet for a direct type liquid crystal display device provided with a high sticking resistance and an optical function, and comprising the same An object of the present invention is to provide a backlight unit.

The invention made to solve the above problems,

As an optical sheet for direct type liquid crystal display devices which has a transparent base material layer and the optical layer laminated | stacked on the surface side of this base material layer,

As the base material layer, a biaxially stretched polyester film containing a filler is used,

The average particle diameter of this filler is 70 nm or more and 200 nm or less, The optical sheet for direct type liquid crystal display devices characterized by the above-mentioned.

According to the said optical sheet for direct type liquid crystal display devices, the biaxially stretched polyester film containing a filler is used as a base material layer of an optical sheet, and the filler particle and the polyester-based resin which exists in the periphery are on the surface of a base material layer. It protrudes and this sticking part exhibits the high sticking prevention function with respect to the other layer laminated | stacked on the back surface side of a base material layer. Therefore, since this direct type liquid crystal display optical sheet has a sticking prevention function without separately stacking an anti-sticking layer, there is no need to perform a conventional off-line lamination process, thereby reducing manufacturing costs and manufacturing processes. Efficiency can be achieved. Moreover, especially with respect to the optical sheet of the optical area used for the big screen of a direct type | mold liquid crystal display device, the big manufacturing cost reduction and the simplification of a manufacturing process can be achieved.

By using an average particle diameter of 70 nm or more and 200 nm or less as a filler contained in the base material layer of the said direct type liquid crystal display device optical sheet, it is possible to obtain a high anti-sticking function and excellent transparency. That is, by containing the filler whose average particle diameter is 70 nm or more in a base material layer, it becomes possible to form the protrusion part of predetermined height on the surface of a base material layer, and another layer laminated | stacked on the back surface side of a base material layer without providing a sticking prevention layer. It can effectively express the anti-sticking function. On the other hand, by containing the filler whose average particle diameter is 200 nm or less in a base material layer, it becomes possible to provide the optical sheet which has the outstanding transparency, exhibiting such a sticking prevention function. Moreover, by using the filler whose average particle diameter is 200 nm or less in this way, the fall of mechanical strength, such as the tensile strength of an optical sheet, can be prevented.

It is preferable that content of the said filler in a base material layer is 0.01 mass% or more and 1 mass% or less. By using the filler in such a content, it becomes possible to obtain a high sticking prevention function and to obtain mechanical strength such as excellent transparency and tensile strength. That is, since many protrusion parts can be formed on the surface of a base material layer by making content of the filler in a base material layer 0.01 mass% or more, a sticking prevention function can fully be expressed. On the other hand, by making content of the filler in a base material layer into 1 mass% or less, while exhibiting a high sticking prevention function, it becomes possible to hold | maintain transparency at an excellent level, and to suppress the fall of the mechanical strength of an optical sheet effectively.

The filler may be selected from the group consisting of silica, alumina, titanium dioxide, calcium carbonate, kaolin, barium sulfate, acrylic resin, melamine resin, silicone resin and crosslinked polystyrene. By using these inorganic fine particles or organic fine particles as the filler contained in the base material layer, it is possible to give a certain strength to the protruding portion formed on the surface of the base material layer, and therefore, sticking to another layer laminated on the back side of the base material layer. The prevention function can be expressed effectively. Moreover, high transparency of a base material layer can be maintained by using these filler components which have said average particle diameter. In addition, by using an inorganic component of silica, alumina, titanium dioxide, calcium carbonate, kaolin or barium sulfate as the filler component contained in the substrate layer, it becomes possible to enhance the heat resistance and water resistance of the substrate layer.

It is preferable that the draw ratio of the biaxially stretched polyester film used as a base material layer is 2.5 times or more and 4.5 times or less, and the draw ratio of the width direction is 3 times or more and 5 times or less. By setting the draw ratio in the longitudinal direction of the biaxially stretched polyester film to 2.5 times or more and the draw ratio in the width direction to 3 times or more, the filler-based particles and the polyester-based resin component present therein are sufficiently formed on the surface of the base layer. It protrudes. And since this protrusion part contacts the surface of the other layer laminated | stacked on the back surface side of an optical sheet, sticking of a base material layer and another layer is prevented effectively. Moreover, by setting the draw ratio in the longitudinal direction of the biaxially stretched polyester film to 4.5 times or less and the draw ratio in the width direction to 5 times or less, a high sticking prevention function is obtained and the suppression of excessive thinning of the film and The mechanical strength can be maintained.

It is preferable that the F5 value of the longitudinal direction and the width direction of the biaxially stretched polyester film used as a base material layer is 80 MPa or more and 120 MPa or less. By setting the F5 values in the longitudinal direction and the width direction of the biaxially stretched polyester film within the ranges of the predetermined values, the strain caused by the tension when the film is processed can be suppressed, and the occurrence of wave-like wrinkles can be prevented. The surface of the base material layers other than the protrusions of the filler particles and the polyester resin present around them can be kept in a smooth state, and the anti-sticking function exhibited by the protrusions can be optimized. In addition, "F5 value" in this application means the stress of the direction at the time of giving 5% of tensile distortion to the film made into object in 25 degreeC.

It is preferable that the static friction coefficients of the biaxially stretched polyester film used as a base material layer are 0.3 or more and 0.6 or less, and the dynamic friction coefficient is 0.3 or more and 0.5 or less. By setting the static friction coefficient of the biaxially stretched polyester film to 0.3 or more and the dynamic friction coefficient to 0.3 or more, the friction between the base layer and the other layer due to the protrusion formed on the surface of the base layer by the filler particles or the like becomes sufficiently large, and Thereby, the sticking prevention function of the other layer with respect to a base material layer is exhibited effectively. Moreover, when the static friction coefficient of a biaxially-stretched polyester film is 0.6 or less and the dynamic friction coefficient is 0.5 or less, while exhibiting a high sticking prevention function, the surface of base layers other than the said protrusion part and the other layer laminated | stacked thereon The surfaces are sufficiently in contact with each other to obtain a stable laminated structure.

It is preferable that arithmetic mean roughness Ra of the biaxially stretched polyester film used as a base material layer is 0.04 micrometer or more and 0.25 micrometer or less. By setting the arithmetic mean roughness Ra of the biaxially stretched polyester film to 0.04 µm or more, the filler particles and the polyester-based resin components present around them are sufficiently protruded on the surface of the base material layer, and an excellent sticking prevention function appears. . Moreover, by making arithmetic mean roughness Ra of a biaxially stretched polyester film into 0.25 micrometer or less, adhesiveness of a base material layer and the other layer laminated | stacked thereon can be suitably maintained, exhibiting a high sticking prevention function.

Moreover, it is preferable that the maximum roughness Ry of the biaxially stretched polyester film used as a base material layer is 0.4 micrometer or more and 0.8 micrometer or less, and 10-point average roughness Rz is 0.3 micrometer or more and 0.6 micrometer or less. By setting the maximum roughness Ry or the 10-point average roughness Rz of the biaxially stretched polyester film to a value within the above range, an excellent sticking prevention function is obtained and the adhesion between the base layer and the other layer can be properly maintained. have.

The optical layer of the said direct type liquid crystal display optical sheet may have a light-diffusion agent and its binder. According to the optical sheet provided with the optical layer containing this light-diffusion agent and its binder, optical functions, such as light condensation, refraction to a normal direction side, and diffusion, can be improved. In addition, the optical layer may have a fine concavo-convex shape having refractive properties. The optical sheet having the optical layer having such a fine concavo-convex shape can improve light diffusivity and facilitate control of light diffusivity. Moreover, since it is not necessary to form an optical layer separately, it becomes possible to thin an optical sheet more.

Therefore, in the backlight unit for direct type liquid crystal display devices which disperse | distribute the light beam emitted from a lamp and lead it to the surface side, when this optical sheet is provided, the biaxially stretched polyester film containing the filler which has a predetermined average particle diameter will be made. By using this, sticking between the back side of the base material layer and the other layer can be effectively suppressed while maintaining transparency, and the manufacturing cost can be reduced and the manufacturing process can be made more efficient. Moreover, when this optical sheet is equipped with the optical layer containing a light-diffusion agent and its binder, the outstanding optical functions, such as light condensation, refraction to a normal line direction, and diffusion, are exhibited.

As described above, according to the optical sheet for direct type liquid crystal display device of this invention, filler particle | grains and polyester-based resin which exist in the periphery protrude on the surface of a base material layer, and this protrusion part is located in the back surface side of an optical sheet. Since the high sticking prevention function is exhibited with respect to the other layers to be laminated, there is no need to perform the stacking layer of the sticking prevention layer which is conventionally performed offline, so that the manufacturing cost can be reduced and the manufacturing process can be made more efficient. Moreover, by using the thing whose average particle diameter is 70 nm or more and 200 nm or less as a filler contained in a base material layer, high transparency can be obtained simultaneously with the outstanding anti-sticking function, and the fall of a mechanical strength can be prevented.

1 is a schematic cross-sectional view of an optical sheet for direct type liquid crystal display device according to an embodiment of the present invention.
FIG. 2 is a flowchart illustrating a manufacturing method of an optical sheet for a direct type liquid crystal display of FIG. 1.
It is a schematic diagram which shows the manufacture of each step of the manufacturing method of FIG.
4 is a schematic diagram showing an apparatus for carrying out the manufacturing method of FIG.
FIG. 5 is a schematic cross-sectional view of an optical sheet for direct type liquid crystal display device according to an embodiment different from FIG. 1.
6 (a) is a schematic perspective view of a general direct type backlight unit, and (b) is a schematic cross-sectional view showing a conventional general light diffusion sheet.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described in detail, referring drawings suitably.

The optical sheet 1 for the direct type liquid crystal display device shown in FIG. 1 mainly has a transparent base material layer 2, and the optical layer 3 laminated | stacked on the surface side of this base material layer.

The transparent base material layer 2 is a biaxially stretched polyester film comprised from the polyester resin 4 containing the filler 5 whose average particle diameter is 70 nm or more and 200 nm or less. On the surface of the base material layer 2, many particle | grains of the filler 5 and the protrusion part of the polyester-type resin 4 around it are formed.

Since the polyester-based resin 4 constituting the base material layer 2 needs to transmit light, transparency is required. Although it does not specifically limit as such polyester-type resin 4 as long as it has transparency, For example, terephthalic acid, isophthalic acid, orthophthalic acid, 2, 5- naphthalenedicarboxylic acid, 2, 6- naphthalenedicarboxylic acid Acids, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, diphenylcarboxylic acid, diphenoxyethanedicarboxylic acid, diphenylsulfoncarboxylic acid, anthracenedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, malonic acid, dimethylmalonic acid, succinic acid , 3,3-diethylsuccinic acid, glutaric acid, 2,2-dimethylglutamic acid, adipic acid, 2-methyladipic acid, trimethyladipic acid, pimelic acid, azelaic acid, dimer acid, sebacic acid, subvertic acid At least one of dicarboxylic acids such as acid and dodecadicarboxylic acid, ethylene glycol and propylene Recall, hexamethylene glycol, neopentyl glycol, 1,2-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, decamethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentane Homopolymers or copolymers obtained by polycondensing at least one kind of diols such as diol, 1,6-hexadiol, 2,2-bis (4-hydroxyphenyl) propane, bis (4-hydroxyphenyl) sulfone, or these The thing which blended 2 or more types of homopolymers and copolymers is mentioned. Among these, polyethylene terephthalate excellent in transparency and high in strength, polybutylene terephthalate, polyethylene-2,6-naphthalate is preferable, and polyethylene terephthalate is particularly preferable. Polyethylene terephthalate can be produced, for example, by placing dimethyl terephthalate and ethylene glycol in a reactor, performing a transesterification reaction while gradually increasing the internal temperature, and then transferring the reaction product to a polymerization reactor and performing a polymerization reaction under high temperature vacuum. .

The filler 5 contained in the base material layer 2 is not particularly limited as long as the average particle diameter is 70 nm or more and 200 nm or less, and known inorganic fine particles and organic fine particles can be used. Preferred examples of the filler 5 include silica, alumina, titanium dioxide, calcium carbonate, kaolin, barium sulfate, acrylic resin, melamine resin, silicone resin, and crosslinked polystyrene. By using these specific fillers 5, the protrusions formed on the surface of the base material layer 2 can be provided with the strength necessary to exhibit a sufficient anti-sticking function. The sticking of another layer can be suppressed effectively. Moreover, by using these fillers 5 which have a predetermined average particle diameter, the high transparency required as an optical sheet can be maintained. In addition, by using inorganic fine particles of silica, alumina, titanium dioxide, calcium carbonate, kaolin or barium sulfate as the filler 5, it becomes possible to enhance the heat resistance, water resistance, impact resistance, tensile strength, and the like of the base layer.

The average particle diameter of the filler 5 is 70 nm or more and 200 nm or less. By biaxially stretching the polyester-based resin 4 including the filler 5 having a particle size in such a range to form the base material layer 2, the particles of the filler 5 are present in the surroundings thereof. It protrudes on the surface of the base material layer 2 with the system resin 4, and many protrusion parts are formed. Such a large number of such protruding portions effectively exert a function of preventing sticking (attaching) to other layers stacked on the back surface side of the base layer 2. That is, by making the average particle diameter of the filler 5 contained in the base material layer 2 into 70 nm or more, the protrusion part of moderate height will be formed, the sticking with another layer will be prevented effectively, and the sticking prevention function will become high. Moreover, by making the average particle diameter of the filler 5 contained in the base material layer 2 into 200 nm or less, the outstanding transparency of the base material layer 2 is formed, forming the protrusion part of a magnitude | size sufficient to show a sticking prevention function. At the same time, the degradation of the matrix function caused by the polyester-based resin 4 can be prevented, and mechanical strength such as tensile strength of the entire optical sheet can be maintained highly. In addition, when the average particle diameter of the filler 5 contained in the base material layer 2 is below the said upper limit, the generation | occurrence | production of the wound with respect to the other layer laminated | stacked on the back surface side of the base material layer 2 is suppressed. The average particle diameter of the filler 5 is more preferably 100 nm or more and 150 nm or less.

Although content of the filler 5 in the base material layer 2 is not specifically limited as long as transparency of the base material layer 2 is ensured and the desired sticking prevention effect is shown, Preferably it is 0.01 mass% or more and 1 mass%. Hereinafter, More preferably, they are 0.05 mass% or more and 0.8 mass% or less, Most preferably, they are 0.08 mass% or more and 0.4 mass% or less. By making content of the filler 5 in the base material layer 2 into 0.01 mass% or more, the particle | grains of the filler 5 and the protrusion part by the polyester-based resin 4 around it are made of the base material layer 2 Since many can be formed on surface, expression of sufficient sticking prevention function is attained. Moreover, by making content of the filler 5 in the base material layer 2 into 1 mass% or less, the high sticking prevention function, the maintenance of transparency required as an optical sheet, and the maintenance of high mechanical strength are achieved at the balance. It becomes possible.

It is preferable that the draw ratio of the biaxially stretched polyester film used as the base material layer 2 is 2.5 times or more and 4.5 times or less, and the draw ratio of the width direction is 3 times or more and 5 times or less. By setting the draw ratio in the longitudinal direction of the biaxially stretched polyester film to 2.5 times or more and the draw ratio in the width direction to 3 times or more, the filler 5 and the polyester-based resin 4 present therein after stretching It protrudes in sufficient size in many places on the surface of the base material layer 2. By contacting the surface of the other layer laminated | stacked on the back surface side of an optical sheet by these many protrusion parts, excessive close_contact | adherence with a base material layer and another layer is prevented, and the sticking prevention effect appears. In addition, by setting the draw ratio in the longitudinal direction of the biaxially stretched polyester film to 4.5 times or less and the draw ratio in the width direction to 5 times or less, the excessive protruding portion due to the thinning of the film is exhibited while exhibiting a high anti-sticking function. It is possible to prevent the formation and the deterioration of mechanical strength accordingly.

The F5 value in the longitudinal direction and the width direction of the biaxially stretched polyester film used as the base material layer 2 is preferably 80 MPa or more and 120 MPa or less, more preferably 90 MPa or more and 110 MPa or less. The F5 value in the longitudinal direction and the width direction was 23 ° C. and 65% using a tensile force tester according to the method specified in JIS-Z1702, for a sample cut out from the center of the substrate layer 2 (biaxially stretched polyester film). When extended | stretched to the longitudinal direction or the width direction at the speed | rate of 300 mm / min of tensile velocity at room temperature of RH, the stress applied to the sample with respect to elongation 5% is measured, and it is calculated | required as the value divided by the cross-sectional area of a sample. When the value of F5 in the longitudinal direction of the biaxially stretched polyester film is smaller than 80 MPa, it is easy to deform when tension is loaded in the traveling direction at the time of release processing of the film. Moreover, when the F5 value of the width direction of a biaxially-stretched polyester film is smaller than 80 Mpa, the elasticity of a film will reduce and it will become easy to produce the wave-like wrinkles continuous in a running direction. These problems can be prevented by setting the F5 value in the longitudinal direction and the width direction of the biaxially stretched polyester film to 80 MPa or more. In addition, by preventing deformation and wrinkles of the film in this way, the surface of the base material layer 2 other than the protruding portion of the filler 5 and the polyester resin 4 present around it is kept in a smooth state. In addition, the sticking prevention function exhibited by the protruding portion can be optimized. On the other hand, by setting the F5 value in the longitudinal direction and the width direction of the biaxially stretched polyester film to 120 MPa or less or 110 MPa or less, the flexibility, processability and durability of the film can be properly maintained.

It is preferable that the static friction coefficients of the biaxially stretched polyester film used as the base material layer 2 are 0.3 or more and 0.6 or less, and the dynamic friction coefficient is 0.3 or more and 0.5 or less. The static friction coefficient and the dynamic friction coefficient of a biaxially stretched polyester film are measured according to the method prescribed | regulated to JIS-K7125. By setting the static friction coefficient of the biaxially stretched polyester film to 0.3 or more and the dynamic friction coefficient to 0.3 or more, the filler 5 formed on the surface of the base material layer 2 and the polyester resin 4 present therein Due to the large number of protrusions, the friction between the substrate layer and the other layer laminated thereon becomes large enough. As a result, sticking of the other layer with respect to a base material layer is exhibited effectively. Moreover, when the static friction coefficient of a biaxially-stretched polyester film is 0.6 or less and the dynamic friction coefficient is 0.5 or less, the sticking prevention effect by the said protrusion part is fully exhibited, and the surface of base layers other than those protrusion parts The surface of the other layer laminated | stacked thereon reliably contacts and the stable laminated structure is obtained. Moreover, by making the dynamic friction coefficient of a biaxially-stretched polyester film into 0.5 or less, generation | occurrence | production of a wrinkle and a wound at the time of film processing can be prevented, and it can suppress that an uneven optical characteristic expresses.

Arithmetic mean roughness Ra of the biaxially stretched polyester film used as the base material layer 2 is preferably 0.04 µm or more and 0.25 µm or less, and more preferably 0.05 µm or more and 0.15 µm or less. By making the arithmetic mean roughness Ra of a biaxially stretched polyester film into 0.04 micrometer or more, the filler 5 and the polyester-based resin 4 which exist in the periphery protrude at sufficient height on the surface of the base material layer 2 Thus, sticking to the other layer laminated on the back surface side of the base material layer 2 can be effectively prevented. Moreover, when the arithmetic mean roughness Ra of a biaxially stretched polyester film is 0.25 micrometer or less, the sticking prevention effect by protrusion parts, such as the filler 5, is fully exhibited, and the base material layers other than those protrusion parts It becomes possible to maintain the adhesiveness between the surface and the surface of the other layer laminated thereon at an appropriate level.

Moreover, it is preferable that the largest roughness Ry of the biaxially stretched polyester film used as the base material layer 2 is 0.4 micrometer or more and 0.8 micrometer or less. Moreover, it is preferable that the 10-point average roughness Rz of the biaxially stretched polyester film used as the base material layer 2 is 0.3 micrometer or more and 0.6 micrometer or less. By setting the maximum roughness Ry and the 10-point average roughness Rz of the biaxially stretched polyester film to the values within the above ranges, the filler 5 and the polyester resin 4 present in the vicinity thereof are the base layer 2 The scattering area is also projected to a sufficient height on the surface of) to obtain a high anti-sticking effect and to maintain an appropriate level of adhesion between the base layer and the other layer.

Although the thickness (average thickness) of the base material layer 2 is not specifically limited, For example, 10 micrometers or more and 500 micrometers or less, Preferably they are 35 micrometers or more and 250 micrometers or less, Especially preferably, they are 50 micrometers or more and 188 micrometers or less. When the thickness of the base material layer 2 is less than the said range, when coating the resin composition for forming the optical layer 3, it will become easy to generate | occur | produce a problem, or becomes difficult to handle. On the contrary, when the thickness of the base material layer 2 exceeds the said range, the brightness | luminance of a liquid crystal display device may fall, and also the thickness of a backlight unit may become large and it may go against the request of thickness reduction of a liquid crystal display device.

The optical layer 3 laminated on the surface side of the base material layer includes a plurality of light diffusing agents 6 that are substantially uniformly disposed on the surface of the base material layer 2, and a binder 7 of the plurality of light diffusing agents 6. ). These light diffusing agents 6 are covered with a binder 7. In this way, the plurality of light diffusing agents 6 contained in the optical layer 3 uniformly diffuses the light passing through the optical layer 2 from the back side to the front side, and condenses the light in the normal direction. Optical function can be improved. Moreover, fine unevenness | corrugation is formed in the surface of the optical layer 3 by the some light-diffusion agent 6 substantially uniformly. In this way, the light beam can be more diffused by the lenticular refraction of the fine unevenness formed on the surface of the optical sheet 1. In addition, although the average thickness of the optical layer 3 is not specifically limited, For example, it is about 1 micrometer or more and about 30 micrometers or less.

The light diffusing agent 6 is a particle having a property of diffusing light rays, and largely classified into an inorganic filler and an organic filler. As the inorganic filler, for example, silica, aluminum hydroxide, aluminum oxide, zinc oxide, barium sulfide, magnesium silicate, or a mixture thereof can be used. As the material of the organic filler, for example, acrylic resin, acrylonitrile resin, polyurethane, polyvinyl chloride, polystyrene, polyacrylonitrile, polyamide and the like can be used. Especially, acrylic resin with high transparency is preferable, and polymethylmethacrylate (PMMA) is especially preferable.

The shape of the light diffusing agent 6 is not particularly limited, and examples thereof include spherical shape, spindle shape, needle shape, rod shape, cubic shape, plate shape, scaly shape, fiber shape, and the like. Spherical beads excellent in light diffusivity are preferable.

As a minimum of the average particle diameter of the light-diffusion agent 6, 1 micrometer, especially 2 micrometers, and 5 micrometers are preferable. On the other hand, as an upper limit of the average particle diameter of the light-diffusion agent 6, 50 micrometers, especially 20 micrometers, and 15 micrometers are preferable. If the average particle diameter of the light diffusing agent 6 is less than the above range, the unevenness of the surface of the optical layer 3 formed by the light diffusing agent 6 becomes small, and the light diffusivity required as the light diffusing sheet may not be satisfied. There is. On the contrary, when the average particle diameter of the light-diffusion agent 6 exceeds the said range, the thickness of the optical sheet 1 will increase and it will become difficult to spread uniformly.

As a minimum of the compounding quantity of the light-diffusion agent 6 (the compounding quantity conversion of solid content conversion with respect to 100 parts of base polymers in the polymer composition which is the formation material of the binder 7), 10 parts, especially 20 parts, and 50 parts are preferable, and As an upper limit, 500 parts, especially 300 parts and 200 parts are preferable. If the compounding quantity of the light diffusing agent 6 is less than the above range, the light diffusivity becomes insufficient. On the other hand, if the compounding quantity of the light diffusing agent 6 exceeds the above range, the effect of fixing the light diffusing agent 6 is reduced. Because it becomes. In addition, since the so-called commercial light-diffusion sheet arrange | positioned at the surface side of a prism sheet does not require a high light diffusivity, as a compounding quantity of the light-diffusion agent 6, 10 parts or more and 40 parts or less, especially 10 parts More than 30 parts are preferable.

The binder 7 is formed by crosslinking and curing the polymer composition containing the base polymer. The light diffusing agent 6 is arranged and fixed to the surface of the base material layer 2 by substantially equal density by this binder 7. In addition, the polymer composition for forming the binder 7 may be suitably blended with a base inorganic polymer, for example, a micro inorganic filler, a curing agent, a plasticizer, a dispersant, various leveling agents, an ultraviolet absorber, an antioxidant, a viscosity modifier, a lubricant, a light stabilizer, and the like. You may be.

The base polymer is not particularly limited, and examples thereof include acrylic resins, polyurethanes, polyesters, fluorine resins, silicone resins, polyamideimide, epoxy resins, ultraviolet curable resins, and the like. Or it can mix and use 2 or more types. In particular, as the base polymer, a polyol having high processability and capable of easily forming the optical layer 3 by means such as coating is preferable. In addition, the base polymer itself used for the binder 7 is preferably transparent from the viewpoint of improving light transmittance, and colorless transparent is particularly preferable.

As said polyol, the polyol obtained by superposing | polymerizing the monomer component containing a hydroxyl group containing unsaturated monomer, the polyester polyol obtained by hydroxyl group excess conditions, etc. are mentioned, for example, These can be used individually or in mixture of 2 or more types.

As the hydroxyl group-containing unsaturated monomer (a), for example, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, allyl alcohol, homoallyl alcohol, Hydroxyl-containing unsaturated monomers such as cinnamic alcohol and crotonyl alcohol, (b) ethylene glycol, ethylene oxide, propylene glycol, propylene oxide, butylene glycol, butylene oxide, 1,4-bis (hydroxymethyl) Dihydric alcohols or epoxy compounds such as cyclohexane, phenylglycidyl ether, glycidyl decanoate, and proxel FM-1 (manufactured by Daicel Kagaku Co., Ltd.); for example, acrylic acid, methacrylic acid, and maleic acid. And hydroxyl group-containing unsaturated monomers obtained by reaction with unsaturated carboxylic acids such as fumaric acid, crotonic acid and itaconic acid. A polyol can be manufactured by superposing | polymerizing 1 type (s) or 2 or more types chosen from these hydroxyl-containing unsaturated monomers.

In addition, the polyol is ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, tert-butyl acrylate, ethylhexyl acrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, methacrylate. N-butyl acid, tert-butyl methacrylate, ethylhexyl methacrylate, glycidyl methacrylate, cyclohexyl methacrylate, styrene, vinyltoluene, 1-methylstyrene, acrylic acid, methacrylic acid, acrylonitrile , Vinyl acetate, vinyl propionate, vinyl stearate, allyl acetate, diallyl adipic acid, diallyl itacate, diethyl maleate, vinyl chloride, vinylidene chloride, acrylamide, N-methylol acrylamide, N-butoxymethyl 1 or 2 or more types of ethylenically unsaturated monomers chosen from acrylamide, diacetone acrylamide, ethylene, propylene, isoprene, etc., and hydroxyl-containing containing selected from said (a) and (b) It may be prepared by polymerizing a monomer.

The number average molecular weight of the polyol obtained by superposing | polymerizing the monomer component containing a hydroxyl-containing unsaturated monomer is 1000 or more and 500000 or less, Preferably it is 5000 or more and 100000 or less. Moreover, the hydroxyl value is 5 or more and 300 or less, Preferably it is 10 or more and 200 or less, More preferably, it is 20 or more and 150 or less.

Polyester polyol obtained on the condition of hydroxyl excess is (c) ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1, 3- butanediol, 1, 4- butanediol, 1, 5- pentanediol, neo Pentyl glycol, hexamethylene glycol, decamethylene glycol, 2,2,4-trimethyl-1,3-pentanediol, trimethylolpropane, hexanetriol, glycerin, pentaerythritol, cyclohexanediol, hydrogenated bisphenol A, bis ( Polyhydric alcohols such as hydroxymethyl) cyclohexane, hydroquinone bis (hydroxyethyl ether), tris (hydroxyethyl) isocinurate, xylylene glycol, and (d) maleic acid, fumaric acid, succinic acid Polybasic acids such as adipic acid, sebacic acid, azelaic acid, trimethic acid, terephthalic acid, phthalic acid, isophthalic acid, and the like It can manufacture by making it react on conditions more than the number of carboxyl groups of a base acid.

The number average molecular weight of the polyester polyol obtained under such hydroxyl group excess conditions is 500 or more and 300000 or less, Preferably it is 2000 or more and 100000 or less. Moreover, the hydroxyl value is 5 or more and 300 or less, Preferably it is 10 or more and 200 or less, More preferably, it is 20 or more and 150 or less.

As a polyol used as a base polymer of the said polymer composition, the acryl polyol obtained by superposing | polymerizing the monomer component containing the said polyester polyol and the said hydroxyl-containing unsaturated monomer, and having a (meth) acryl unit etc. is preferable. The binder 7 which uses such polyester polyol or acryl polyol as a base polymer has high weather resistance, and can suppress yellowing of the optical layer 3, etc. Either one of the polyester polyol and the acrylic polyol may be used, or both of them may be used.

The number of hydroxyl groups in the polyester polyol and acryl polyol is not particularly limited as long as it is two or more per molecule, but when the hydroxyl value in the solid content is 10 or less, the crosslinking score decreases, and solvent resistance, water resistance, heat resistance, surface hardness, and the like. There exists a tendency for the film physical property of to fall.

What is necessary is just to contain a micro inorganic filler in the polymer composition which forms the binder 7. Thus, by containing a micro inorganic filler in the binder 7, the heat resistance of the optical layer 3 and the optical sheet 1 improves. Although it does not specifically limit as an inorganic substance which comprises this micro inorganic filler, An inorganic oxide is preferable. This inorganic oxide is defined as various oxygen-containing metal compounds in which metal elements mainly form a three-dimensional network through bonding with oxygen atoms. As the metal element constituting the inorganic oxide, for example, an element selected from Groups 2 to 6 of the Periodic Table of the Elements is preferable, and an element selected from Groups 3 to 5 of the Periodic Table of the Elements is more preferable. In particular, an element selected from Si, Al, Ti, and Zr is preferable, and colloidal silica having a metal element of Si is most preferred as a micro inorganic filler in terms of heat resistance improving effect and uniform dispersibility. Moreover, the shape of a micro inorganic filler should just be arbitrary particle shapes, such as spherical shape, needle shape, plate shape, scale shape, crushing shape, and is not specifically limited.

As a minimum of the average particle diameter of a micro inorganic filler, 5 nm is preferable and 10 nm is especially preferable. On the other hand, as an upper limit of the average particle diameter of a micro inorganic filler, 50 nm is preferable and 25 nm is especially preferable. This is because when the average particle diameter of the micro inorganic filler is less than the above range, the surface energy of the micro inorganic filler becomes high, and aggregation and the like tends to occur. This is because transparency cannot be maintained completely.

As a minimum of compounding quantity (the compounding quantity only of an inorganic component) with respect to 100 parts of base polymers of a micro inorganic filler, 5 parts are preferable in conversion of solid content, and 50 parts are especially preferable. On the other hand, as an upper limit of the said compounding quantity of a micro inorganic filler, 500 parts are preferable, 200 parts are more preferable, 100 parts are especially preferable. If the blending amount of the micro inorganic filler is less than the above range, the heat resistance of the optical sheet 1 may not be sufficiently expressed. On the contrary, if the blending amount exceeds the above range, blending into the polymer composition becomes difficult and the optical layer 3 It is because there exists a possibility that the light transmittance of () may fall.

What is necessary is just to use the said micro inorganic filler in which the organic polymer was fixed to the surface. Thus, by using an organic polymer fixed micro inorganic filler, the dispersibility in the binder 7 and the affinity with the binder 7 are aimed at. The organic polymer is not particularly limited in terms of its molecular weight, shape, composition, presence or absence of a functional group, and any organic polymer can be used. Moreover, about the shape of an organic polymer, the thing of arbitrary shapes, such as linear form, a branch form, a crosslinked structure, can be used.

As specific resin which comprises the said organic polymer, For example, (meth) acrylic resin, polystyrene, polyvinyl acetate, polyolefin, such as polyethylene and a polypropylene, polyester, such as polyvinyl chloride, polyvinylidene chloride, polyethylene terephthalate, and these The resin etc. which modified partly by functional groups, such as a copolymer, an amino group, an epoxy group, a hydroxyl group, and a carboxyl group, are mentioned. Especially, it is preferable to have an organic polymer containing (meth) acryl units, such as (meth) acrylic-type resin, (meth) acryl- styrene-type resin, and (meth) acryl-polyester-type resin, as an essential component, having film forming ability. . On the other hand, a resin having compatibility with the base polymer of the polymer composition is preferable, and therefore it is most preferable that it is the same composition as the base polymer included in the polymer composition.

In addition, a micro inorganic filler may contain the organic polymer in microparticles | fine-particles. This makes it possible to impart appropriate flue and toughness to the inorganic material that is the core of the micro inorganic filler.

What is necessary is just to use the thing containing an alkoxyl group for the said organic polymer, As the content, 0.01 mmol or more and 50 mmol or less per 1 g of micro inorganic fillers which fixed the organic polymer are preferable. By such an alkoxy group, the affinity with the matrix resin which comprises the binder 7 and the dispersibility in the binder 7 can be improved.

The said alkoxyl group represents the RO group couple | bonded with the metal element which forms a particulate skeleton. This R is an alkyl group which may be substituted, and the RO group in microparticles | fine-particles may be same or different. Specific examples of R include methyl, ethyl, n-propyl, isopropyl, n-butyl and the like. It is preferable to use the same metal alkoxyl group as the metal which comprises a micro inorganic filler, and, when a micro inorganic filler is colloidal silica, it is preferable to use the alkoxyl group which makes silicon a metal.

Although it does not restrict | limit especially about the content rate of the organic polymer in the micro inorganic filler which fixed the organic polymer, 0.5 mass% or more and 50 mass% or less are preferable based on a micro inorganic filler.

A polyfunctional isocyanate compound, a melamine compound and an aminoplast having two or more functional groups which react with hydroxyl groups in the polymer composition constituting the binder 7 using the organic polymer fixed to the micro inorganic filler, and having a hydroxyl group What is necessary is just to contain at least 1 sort (s) of thing chosen from resin. Thereby, the micro inorganic filler and the matrix resin of the binder 7 are combined by a crosslinked structure, and storage stability, pollution resistance, flexibility, weather resistance, storage stability, etc. become favorable, and the film obtained has glossiness.

As said base polymer, the polyol which has a cycloalkyl group is preferable. Thus, by introducing a cycloalkyl group into the polyol as the base polymer constituting the binder 7, the hydrophobicity such as water repellency and water resistance of the binder 7 is increased, and the warpage resistance, dimensional stability and the like of the optical sheet 1 under high temperature and high humidity conditions. This is improved. In addition, the basic performance of the coating layer such as weather resistance, hardness, dryness, solvent resistance, etc. of the optical layer 3 is improved. In addition, the affinity with the micro inorganic filler having the organic polymer fixed on the surface thereof and the uniform dispersibility of the micro inorganic filler are further improved.

It does not specifically limit as said cycloalkyl group, For example, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, a cyclodecyl group, a cyclo undecyl group, a cyclododecyl group, a cyclotree A decyl group, a cyclo tetradecyl group, a cyclopentadecyl group, a cyclohexadecyl group, a cycloheptadecyl group, a cyclooctadecyl group, etc. are mentioned.

The polyol which has the said cycloalkyl group is obtained by copolymerizing the polymerizable unsaturated monomer which has a cycloalkyl group. The polymerizable unsaturated monomer which has this cycloalkyl group is a polymerizable unsaturated monomer which has at least 1 cycloalkyl group in a molecule | numerator. It does not specifically limit as this polymerizable unsaturated monomer, For example, cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, tert- butylcyclohexyl (meth) acrylate, cyclododecyl (meth) acrylate Etc. can be mentioned.

Moreover, what is necessary is just to contain isocyanate as a hardening | curing agent in a polymer composition. Thus, by containing an isocyanate hardening | curing agent in a polymer composition, it becomes a stronger crosslinked structure and the film physical property of the optical layer 3 further improves. As this isocyanate, the substance similar to the said polyfunctional isocyanate compound is used. Especially, aliphatic isocyanate which prevents yellowing of a film is preferable.

In particular, when a polyol is used as the base polymer, any one or two or more kinds of hexamethylene diisocyanate, isopron diisocyanate and xylene diisocyanate may be used as a curing agent to be blended in the polymer composition. When these curing agents are used, the curing reaction rate of the polymer composition increases, and even if a cationic group that contributes to the dispersion stability of the micro inorganic filler is used as the antistatic agent, the decrease in the curing reaction rate by the cationic antistatic agent can be sufficiently compensated. . Moreover, the improvement of the curing reaction rate of such a polymer composition contributes to the uniform dispersibility of the micro inorganic filler in a binder. As a result, the optical sheet 1 can suppress curvature and yellowing by heat, ultraviolet rays, etc. especially.

Moreover, what is necessary is just to knead the antistatic agent in a polymer composition. By forming the binder 7 from the polymer composition in which the antistatic agent is kneaded in this way, the antistatic effect is expressed on the optical sheet 1, and thus, static electricity is charged, such as sucking dust or making it difficult to overlap with a prism sheet. This can prevent problems caused by. In addition, when the antistatic agent is coated on the surface, stickiness and fouling of the surface are caused. Such a hazard is reduced by kneading in the polymer composition. The antistatic agent is not particularly limited, and for example, anionic antistatic agents such as alkyl sulfates and alkyl phosphates, cationic antistatic agents such as quaternary ammonium salts and imidazoline compounds, polyethylene glycol series, and polyoxyethylene sorbitan mono Nonionic antistatic agents, such as stearic acid ester and ethanol amide, polymeric antistatic agents, such as polyacrylic acid, etc. are used. Among them, cationic antistatic agents having a relatively high antistatic effect are preferable, and the addition of a small amount results in an antistatic effect.

An adhesive layer (primer layer) may be provided between the base material layer 2 and the optical layer 3 (not shown). Although the average thickness in the case of providing an easily bonding layer is not specifically limited, For example, it can be about 1 micrometer or more and about 30 micrometers or less. By providing such an easily bonding layer, bonding of the base material layer 2 and the optical layer 3 through an easily bonding layer can be made sure, and a more stable laminated structure can be obtained. As resin which comprises an easily bonding layer, acrylic resin, polyurethane resin, polyester resin, rubber resin, etc. are used preferably.

As an example of the acrylic resin which comprises an easily bonding layer, resin which has acrylic acid, methacrylic acid, and these derivatives as a component is mentioned. Specifically, acrylic acid, methacrylic acid, methyl methacrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, acrylamide, acrylonitrile, hydroxyl acrylate and the like, and monomers copolymerizable with these (e.g. For example, a copolymer with styrene, divinylbenzene, etc. can be mentioned.

The polyurethane resin which comprises an easily bonding layer is resin which has a urethane bond in a principal chain, and is usually obtained by reaction of a polyisocyanate and a polyol. Examples of the polyisocyanate include TDI, MDI, NDI, TODI, HDI, IPDI, and the like. Moreover, ethylene glycol, propylene glycol, glycerin, hexane triol etc. are mentioned as an example of a polyol. Moreover, the resin which increased the molecular weight can also be used by making a chain extender react with the polyurethane polymer obtained from polyisocyanate and a polyol.

Polyester resin which comprises an easily bonding layer is resin which has an ester bond in a principal chain, and is usually obtained by reaction of a polycarboxylic acid and a polyol. Examples of the polycarboxylic acid include fumaric acid, itaconic acid, adipic acid, sebacic acid, terephthalic acid, isophthalic acid, and the like. As an example of a polyol, what was illustrated about the said polyurethane-type resin is mentioned.

Representative examples of the rubber resin constituting the easily adhesive layer are diene synthetic rubber. Examples of the diene synthetic rubber include polybutadiene, styrene-butadiene copolymer, styrene-butadiene-acrylonitrile copolymer, styrene-butadiene-divinylbenzene copolymer, butadiene-acrylonitrile copolymer, polychloroprene and the like. .

As shown in FIG. 2, the optical sheet 1 for direct type liquid crystal display devices of FIG. 1 can be manufactured by a base film formation process (STP1), an extending process (STP2), and an optical layer formation process (STP3).

The base film formation process (STP1) in the manufacturing method of the optical sheet 1 of FIG. 2 contains the filler 5 substantially uniformly as shown in FIG. 3 by the well-known extrusion molding method using T die | dye. It is a process of forming the base film extruded body 9 which is an elongate strip formed from polyester-type resin 4. As a well-known extrusion molding method using a T die, the polishing roll method and the chill roll method are mentioned, for example.

The base film formation process (STP1) is performed by the extrusion molding apparatus which occupies a part of the schematic diagram shown in FIG. This extrusion apparatus mainly comprises an extruder, a T-die 20, a pair of pressing rolls 21, a winding machine, and the like. As an extruder, a single screw extruder or a twin screw extruder can be used. As the T die 20, known ones such as fishtail dies, manifold dies and coat hanger dies can be used. The pair of pressing rolls 21 are disposed adjacent to and parallel to each other, and the extruder and the T die 20 are in the molten state of the polyester resin 4 and the filler 5 in the nip of the pair of pressing rolls 21. Of the mixture 8 is configured to be extrudable in sheet form. This pair of press rolls 21 are provided with a temperature control means, and are comprised so that control of surface temperature to the temperature which is optimal for extrusion molding is possible. As the press roll 21, it is preferable to use the metal elastic roll which consists of a metal roll and the flexible roll which coat | covered an elastic body on the surface. Using the extrusion apparatus having such a structure, first, the mixture 8 of the polyester resin 4 and the filler 5 in the molten state is supplied to the T die 20, and is extruded by the extruder and the T die 20. The mixture 8 is extruded, and the base film extruded body 9 is formed by pressing with a pair of pressing rolls 21. In addition, the melting temperature of the polyester resin 4 extruded from the T die 20 is appropriately selected in consideration of the melting point of the polyester resin to be used.

Although the filler 5 is disperse | distributed substantially uniformly in the polyester resin 4 which comprises the base film extruded body 9, the surface of the base film extruded body 9 is mostly polyester-based resin 4 or a filler. (5) does not protrude, and forms the substantially flat surface. Although the thickness of the base film extruded body 9 is not specifically limited, According to the structure of the T die to be used, and the ratio of extending | stretching performed later, it can set suitably and can be 40 micrometers or more and 2000 micrometers or less.

As for the extending process (STP2) in the manufacturing method of the optical sheet 1 of FIG. 2, the base film extruded body 9 formed in the above-mentioned base film formation process as shown in FIG. It is a process of forming the base material layer 2 which is a stretched film, ie, a biaxially stretched polyester film, by extending | stretching to a direction.

This stretching process (STP2) can be performed at a suitable temperature between the softening temperature and melting temperature of the polyester-based resin 4 constituting the base film extruded body 9. Although the draw ratio in an extending process can be adjusted according to the thickness of the desired base material layer 2 (biaxially stretched polyester film), the draw ratio of the longitudinal direction is 2.5 times or more and 4.5 times or less, and the draw ratio of the width direction is 3 It is preferable that it is more than 5 times. The thickness of the stretched base material layer 2 becomes thinner by the reciprocal of this draw ratio (red) than the thickness of the base film extruded body 9. The preferable thickness of the base material layer 2 is as above-mentioned. By setting the draw ratio in the longitudinal direction of the biaxially stretched polyester film to 2.5 times or more and the draw ratio in the width direction to 3 times or more, the filler 5 contained in the inside of the base film extruded body 9 is surrounded by the surroundings. It protrudes in many places on the surface of a base material layer along polyester resin 4 which exists in. And since many protrusion parts formed with the filler 5 etc. contact scatteredly on the surface of the other layer laminated | stacked on the back surface side of an optical sheet, sticking of a base material layer and another layer is prevented effectively. Moreover, by setting the draw ratio of the biaxially stretched polyester film in the longitudinal direction to 4.5 times or less and the draw ratio in the width direction to 5 times or less, A high sticking prevention function is obtained by the protrusion part, and the fall of the mechanical strength by excessive protrusion of the filler 5, or excessive thinning of a film can be prevented.

The stretching step STP2 is performed by a biaxial stretching apparatus 22 having a well-known structure occupying a part of the schematic diagram shown in FIG. 4. This biaxial stretching apparatus 22 is mainly equipped with the heat extending part, a heat processing part, etc. As a biaxial stretching method, well-known methods, such as a tubular film biaxial stretching method and the flat film biaxial stretching method, can be employ | adopted. In addition, the biaxial stretching method may be a sequential biaxial stretching method in which stretching in the film longitudinal direction and stretching in the film width direction are performed, or a simultaneous biaxial stretching method in which stretching in the film longitudinal direction and stretching in the film width direction may be performed simultaneously. . According to sequential biaxial stretching, the stretched film with favorable planarity and dimensional stability and few thickness nonuniformity can be obtained. On the other hand, according to simultaneous biaxial stretching, the stretched film with favorable in-plane balance can be obtained.

As a method of sequential biaxial stretching, for example, the base film extruded body 9 is led to a roll group heated and stretched in the film length direction, and then the film is led to a heated tenter while holding both ends of the film with a clip. It can extend in the width direction. As a method of simultaneous biaxial stretching, for example, the both ends of the base film extruded body 9 are gripped with a clip, led to a heated tenter, and stretched in the film width direction. Orientation can be performed. In general, heat treatment is performed on these stretched articles in order to provide planar stability and dimensional stability.

The optical layer formation process (STP3) in the manufacturing method of the optical sheet 1 of FIG. 2 is the surface of the base material layer 2 which is a biaxially stretched polyester film formed in the above-mentioned extending process as shown in FIG. The optical layer composition 10 including the plurality of light diffusing agents 6 and the binder 7 of the light diffusing agent 6 is laminated using a known roll coat technique, and then dried. It is a process of forming the optical layer 3 and completing the optical sheet 1.

The roll coat of the lamination step (STP3) is performed by a roll coater having a known structure occupying a part of the schematic diagram shown in FIG. This roll coater is mainly equipped with the coater pan 23, the pickup roll 24a, the adjustment roll 24b, the application roll 24c, and the backup roll 24d. A direct roll coater having the same rotation direction of the application roll and the advancing direction of the coating may be used, or a reverse roll coater in which the rotation direction of the application roll and the advancing direction of the coating are opposite. The coater pan 23 is filled with the optical layer composition 10 including the plurality of light diffusing agents 6 and the binder 7 of the light diffusing agents 6, and the rotation of the pickup roll 24a. The composition 10 for an optical layer is spread out from the coater pan 23. In this way, the composition 10 for optical layers containing the light diffusing agent 6 and the binder 7 is attached to the outer circumferential surface of the pickup roll 24a and transferred to the application roll 24c. In the meantime, the adjustment roll 24b adjusts the quantity of the composition 10 for optical layers adhering to the outer peripheral surface of the pickup roll 24a. The base material supported between the application | coating roll 24c and the backup roll 24d by rotating the application | coating roll 24c with the composition 10 for optical layers in the same direction as the delivery direction of the base material layer 2, or a reverse direction. The composition 10 for an optical layer is laminated | stacked on the layer 2, and then dried and the optical sheet 1 which is a laminated body of the base material layer 2 and the optical layer 3 is formed.

Lamination of the composition for an optical layer 10 in the optical layer forming step (STP3) was performed using a bar coater, a blade coater, a spin coater, a gravure coater, a flow coater, a spray, screen printing, or the like instead of the method using the roll coater described above. You may employ | adopt a well-known coating method.

After the stretching step (STP2), before the optical layer forming step (STP3), a step of forming the above-mentioned easily adhesive layer (primer layer) on the surface of the base material layer 2 may be provided. As a method and an apparatus in the case of forming an easily bonding layer, the thing similar to formation of the optical layer 2 can be used. In the coating liquid for forming an easily bonding layer, the hardening | curing agent (for example, polyisocyanate resin, carbodiimide resin, etc.) of the quantity of about 1 mass part or more and 5 mass parts or less is mix | blended with respect to 100 mass parts of resin components, for example. You may also

What is necessary is just to perform the cutting process which cut | disconnects the obtained base material layer 2 or the optical sheet 1 to predetermined size between extending | stretching process (STP2) and optical layer formation process (STP3), or after optical layer formation process (STP3). By performing a cutting process after an optical layer formation process (STP3), a desired optical sheet can be manufactured efficiently, and generation | occurrence | production of the curl, the peeling of an optical layer, etc. resulting from the winding of an optical sheet can be suppressed.

As explained so far, according to the optical sheet for direct type liquid crystal display device of this embodiment, the particle | grains of a filler protrude on the surface of a base material layer with the polyester resin which exists in the circumference | surroundings, and many protruding parts are formed. Thus, the function of preventing sticking (sticking) to the other layer laminated on the back surface side of the base material layer is effectively exhibited. In addition, according to the optical sheet, it is possible to achieve a high level of anti-sticking function, maintenance of transparency required as the optical sheet, and maintenance of high mechanical strength in a balanced manner. In addition, since it is not necessary to separately perform the step of forming an anti-sticking layer with respect to the optical sheet, it is possible to achieve a reduction in the manufacturing cost and an efficiency in the manufacturing process, particularly with respect to the optical sheet used for the direct type liquid crystal display device having a large display area. Can be. In addition, as shown in Figs. 2 to 4, by manufacturing the optical sheet for direct type liquid crystal display in one continuous production line, the manufacturing process can be simplified and speeded up.

The optical sheet 11 for direct type liquid crystal display device of FIG. 5 is an optical sheet according to an embodiment different from that of FIG. 1, and the fine uneven | corrugated shape 12 which has refractive property is formed in the surface. In this optical sheet 11, the part which has the fine uneven | corrugated shape 12 functions as an optical layer. The component and the structure of the base material layer 2 of the optical sheet 11 are similar to the optical sheet 1 of the said embodiment.

The fine concave-convex shape 12 is not particularly limited as long as it exhibits light diffusivity equivalent to that of the optical layer 3 in the above-described embodiment, but for example, the height of each convex portion (more than both concave portions adjacent to each other). The height from the high bottom position) can be made into 0.05 micrometer or more and 1 micrometer or less.

Although it does not specifically limit as a manufacturing method of the optical sheet 11, For example, the following method is employable. That is, prior to the above stretching process (sequential biaxial stretching or simultaneous biaxial stretching in the film longitudinal direction and the film width direction), (a) the sheet-like sheet having a reverse shape of the surface of the optical sheet A method of laminating a mixture and peeling off the sheet form, and (b) performing an injection molding step of injecting and injecting a molten mixture of a polyester resin and a filler into a mold having an inverted shape on the surface of the optical sheet. Method (c) A method of reheating a mixture of sheeted polyester resin and filler and sandwiching it between a metal mold and a metal plate as described above to perform a step of transferring a shape, and (d) Inverting the surface of the optical sheet A method of performing a step of transferring the melted mixture of a polyester-based resin and a filler through a nip of a roll type having a shape on a main surface and another roll, and transferring the shape. Can.

According to the optical sheet for direct type liquid crystal display device of this embodiment, like the optical sheet of the said embodiment, sticking of a base material layer and another layer by the particle | grains of a filler and the protrusion part of the polyester-based resin which exists in the periphery of it In addition to effective prevention, high transparency and mechanical strength can be maintained. Moreover, since it is not necessary to perform the process of separately forming a sticking prevention layer with respect to an optical sheet, reduction of a manufacturing cost, efficiency of a manufacturing process, etc. can be achieved. In addition, the optical sheet provided with the optical layer which has such a fine concavo-convex shape can improve light diffusivity and ease control.

The optical sheet for direct type liquid crystal display devices of this invention is not limited to these embodiment. For example, you may separately form the optical layer which has a fine uneven | corrugated shape on the surface of a base material layer. Thus, as a material of the optical layer which has a fine uneven shape formed separately, the synthetic resin which has a light transmittance can be used. As such a synthetic resin, For example, polyester-based resin, such as polyethylene terephthalate and polyethylene naphthalate; Cellulose resins such as diacetyl cellulose and triacetyl cellulose; Polycarbonate resin; Acrylic resins such as polymethyl methacrylate; Styrene resins such as polystyrene and acrylonitrile-styrene copolymers; Olefin resins such as polyethylene, polypropylene, polyolefins having a cyclic to norbornene structure, and ethylene-propylene copolymers; Vinyl chloride resins; Amide resins such as nylon and aromatic polyamides; Imide resin; Sulfone resin; Polyether sulfone resin; Polyether ether ketone resins; Polyphenylene sulfide resin; Vinyl alcohol-based resins; Vinylidene chloride-based resins; Vinyl butyral resin; Arylate resins; Polyoxymethylene resin; Epoxy resin etc. are mentioned.

Moreover, as an optical layer laminated | stacked on the surface of a base material layer, it is a microlens sheet which has a microlens array which consists of several hemispherical microlenses on the surface (i) besides what was mentioned above, for example, (ii) a plurality of triangular on the surface A prism sheet having a columnar prism portion in a stripe shape, (iii) a lenticular lens sheet having a plurality of semi-cylindrical cylindrical lens portions in a stripe shape on a surface thereof, and (iv) a fresnel with the curvature of the lens arranged on the surface thereof Lens sheets or the like can also be used. These optical layers can also be laminated on the base layer according to well-known coating methods.

The manufacturing method of the optical sheet for direct type liquid crystal display devices is not limited to the method by one continuous production line. In consideration of the flexibility of the production process, the sharing of a manufacturing apparatus and manpower resources, etc., it is also possible to perform a base film formation process, an extending process, and an optical layer formation process as another production line.

The optical sheet for direct type liquid crystal display device of this invention is provided not only as a downward diffusion sheet provided in proximity to a backlight, but also above other optical sheets, such as a prism sheet, in a backlight unit for liquid crystal display devices, such as a television monitor. It can be used also as an upward diffusion sheet. That is, since the optical sheet for direct type liquid crystal display devices of this invention has the outstanding sticking prevention function, it is used suitably as a downward diffusion sheet provided on the smooth surface near to a backlight. And since such sticking prevention function does not prevent application to applications other than the downward diffusion sheet, the transparency of the direct type liquid crystal display device is not only used as the downward diffusion sheet but also as the upward diffusion sheet, thereby providing excellent transparency. And reduction in manufacturing cost and efficiency of manufacturing efficiency of the entire backlight unit can be achieved while maintaining mechanical strength.

(Example)

Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not interpreted limitedly based on description of this Example.

The measuring method of the physical property value in a following example is as follows.

(1) anti-sticking

What superposed | superposed the acrylic plate completely through water through each polyester film was left to stand on environmental test conditions (70 degreeC x H95%) for 24 hours. After standing, peeling of the polyester film and the acrylic plate was tested, and the ease of peeling was judged based on the following criteria.

Peeled off very easily… ◎ (very good)

It peeled easily. ○ (good)

There was some resistance, but was peeled off… △ (somewhat bad)

The resistance was large and did not peel easily. X (bad)

(2) static friction coefficient and dynamic friction coefficient

A slip tester was used for each polyester film, and the static friction coefficient and the dynamic friction coefficient were measured according to the ASTM-D1894-08 standard.

(3) arithmetic mean roughness (Ra)

Arithmetic mean roughness Ra was calculated | required based on JISB0601-2001 about each polyester film.

(4) Maximum Roughness (Ry)

About each polyester film, maximum roughness Ry was calculated | required based on JISB0601-2001.

(5) 10-point average roughness (Rz)

About each polyester film, 10-point average roughness (Rz) was calculated | required based on JISB0601-2001.

(6) total light transmittance

About the optical sheet which laminated | stacked the optical layer, the total light transmittance was measured with the haze meter by Sugashi Kenki Co., Ltd. according to JISK7105-1981.

Example 1

A molten mixture of 99.9% by mass of polyethylene terephthalate (hereinafter referred to as 'PET') and 0.1% by mass of colloidal silica having an average particle diameter of 120 nm was supplied to a T-die, followed by extrusion molding to form a PET film extruded body, and the PET film A base material layer (biaxially stretched polyester film) having an average thickness of 188 µm was obtained by sequentially stretching the extruded body at a magnification of 3 times in the film length direction and 4 times in the film width direction. About this biaxially stretched polyester film, the sticking prevention property, the static friction coefficient, the dynamic friction coefficient, the arithmetic mean roughness Ra, the maximum roughness Ry, and the 10-point average roughness Rz were measured. On the surface of this biaxially stretched polyester film, 100 parts by mass of a polyurethane-based resin ('Byron 3900' of Toyobo Seki Co., Ltd.) and a modified polyisocyanate resin (Coronate of Nippon Polyurethane Co., Ltd.) L ') 5 mass parts containing the blending solution was apply | coated and dried, and the easily bonding layer (primer layer) of thickness 10micrometer was formed. Subsequently, 100 parts by mass of a binder resin compound ('Byron 200' of Toyobo Seki Co., Ltd.) using polyester polyol as a base polymer, 50 parts by mass of colloidal silica having an average particle diameter of 20 nm, and a curing agent (Nippon Polyurethane) Acrylic resin beads (SEKISUICA) having an average particle diameter of 15 µm in a polymer composition containing 5 parts by mass of `` coronate HX '' manufactured by Co., Ltd. and 5 parts by mass of a light stabilizer (`` PUVA-1033 '' of Otsuka Chemical Co., Ltd.) A coating solution was prepared by mixing 50 parts of 'MBX-15' of Seihinko KK. The coating liquid was coated on the surface of the easily adhesive layer and cured to form an optical layer having a thickness of 20 µm to obtain an optical sheet. About this optical sheet, the total light F5 value was measured in accordance with the said method. Table 1 shows the measurement results of these physical properties.

[Example 2]

A substrate layer (biaxially stretched polyester film) and an optical sheet were formed in the same manner as in Example 1 except that the average particle diameter of the colloidal silica used as a raw material component for forming the PET film extruded body was changed to 80 nm. Physical properties were measured. A measurement result is combined with Table 1 and shown.

[Example 3]

A substrate layer (biaxially stretched polyester film) and an optical sheet were formed in the same manner as in Example 1 except that the average particle diameter of the colloidal silica used as a raw material for forming the PET film extruded body was changed to 170 nm. Physical properties were measured. A measurement result is combined with Table 1 and shown.

Example 4

A substrate layer (biaxially stretched polyester film) and an optical sheet were formed in the same manner as in Example 1 except that the amount of colloidal silica used as a raw material component for forming the PET film extruded body was changed to 0.005% by mass. Physical properties were measured. A measurement result is combined with Table 1 and shown.

[Example 5]

A substrate layer (biaxially stretched polyester film) and an optical sheet were formed in the same manner as in Example 1 except that the amount of colloidal silica used as a raw material component for forming the PET film extruded body was changed to 2.0 mass%. Physical properties were measured. A measurement result is combined with Table 1 and shown.

Comparative Example 1

A polyester film having an average thickness of 188 μm was obtained without stretching in the film longitudinal direction and the film width direction, and a base layer and an optical sheet were formed in the same manner as in Example 1 to measure various properties described above. did. A measurement result is combined with Table 1 and shown.

Comparative Example 2

The substrate layer (biaxially stretched polyester film) and the optical sheet were formed in the same manner as in Example 1 except that the average particle diameter of the colloidal silica used as a raw material component for forming the PET film extruded body was changed to 40 nm. Physical properties were measured. A measurement result is combined with Table 1 and shown.

[Comparative Example 3]

A substrate layer (biaxially stretched polyester film) and an optical sheet were formed in the same manner as in Example 1 except that the average particle diameter of the colloidal silica used as a raw material for forming the PET film extruded body was changed to 300 nm. Physical properties were measured. A measurement result is combined with Table 1 and shown.

[Example 6]

Except for using a melt mixture of 99.9% by mass of polyethylene terephthalate and 0.1% by mass of polymethyl methacrylate (hereinafter referred to as 'PMMA') particles as a raw material for forming a PET film extruded body. Similarly, the base material layer (biaxially stretched polyester film) and the optical sheet were formed, and the above-mentioned various physical properties were measured. A measurement result is combined with Table 1 and shown.

[Example 7]

As described in Example 6, except that the average particle diameter of PMMA particles used as a raw material for forming a PET film extruded body was changed, a base layer (biaxially stretched polyester film) and an optical sheet were formed to form various properties described above. Was measured. A measurement result is combined with Table 1 and shown.

[Example 8]

As described in Example 6, except that the average particle diameter of PMMA particles used as a raw material for forming a PET film extruded body was changed to 170 nm, a base layer (biaxially stretched polyester film) and an optical sheet were formed to form various properties described above. Was measured. A measurement result is combined with Table 1 and shown.

[Example 9]

Except for changing the amount of PMMA particles used as a raw material component for forming the PET film extruded to 0.005% by mass, similar to Example 6 to form a base material layer (biaxially stretched polyester film) and an optical sheet to the various physical properties Was measured. A measurement result is combined with Table 1 and shown.

[Example 10]

As described in Example 6, except that the amount of PMMA particles used as a raw material component for forming the PET film extruded body was changed to form a base layer (biaxially stretched polyester film) and an optical sheet, Was measured. A measurement result is combined with Table 1 and shown.

[Comparative Example 4]

A polyester film having an average thickness of 188 μm was obtained without stretching in the film longitudinal direction and the film width direction, and a base layer and an optical sheet were formed in the same manner as in Example 6 to measure various properties described above. did. A measurement result is combined with Table 1 and shown.

[Comparative Example 5]

As described in Example 1, except that the average particle diameter of PMMA particles used as a raw material component for forming the PET film extruded body was changed, a base layer (biaxially stretched polyester film) and an optical sheet were formed to form various properties described above. Was measured. A measurement result is combined with Table 1 and shown.

[Comparative Example 6]

As described in Example 1, except that the average particle diameter of PMMA particles used as a raw material for forming a PET film extruded body was changed to 300 nm, a base layer (biaxially stretched polyester film) and an optical sheet were formed to form various properties described above. Was measured. A measurement result is combined with Table 1 and shown.

Notes 1 and 2: In these comparative examples, the sticking resistance was good, but when observed with an electron microscope, fine scratches were observed on the surface of the acrylic plate used for the test.

As can be seen from the results in Table 1, the biaxially stretched polyester films of Examples 1 to 10 containing an inorganic filler or an organic filler having an average particle diameter value in a range of 70 nm or more and 200 nm or less are subjected to biaxial stretching. Significantly superior anti-sticking properties compared to the biaxially stretched polyester films of Comparative Examples 2 and 5, which contain the polyester films of Comparative Examples 1 and 4 which have not been carried out, and fillers having values of average particle diameters outside the above ranges. It could be seen that. Moreover, although the polyester films of the comparative examples 3 and 6 showed the high sticking prevention property by the large particle diameter of a filler, when observed with the electron microscope, the minute wound is observed in many places of the surface of the acryl plate laminated | stacked in the test. It became.

Further, Examples 2 and 3 using inorganic fillers or organic fillers having an average particle diameter of 120 nm in a range of 100 nm or more and 150 nm or less include Examples 2 and 3, which include a filler having a value of an average particle diameter outside this range. Or it turned out that it exhibits the better sticking prevention effect compared with Example 7 and 8. In addition, Examples 1 and 6 using the inorganic filler or the organic filler whose amount is 0.1 mass% in the range of 0.01 mass% or more and 1 mass% or less are Example 4 and 5 or Example 9 containing the filler which is an amount outside this range. And compared with 10, it turned out that it shows a more favorable sticking prevention effect similarly to the above.

According to the optical sheet for direct type liquid crystal display device, while sticking with the other layer laminated | stacked on the back surface side is prevented effectively, manufacturing cost can be reduced and efficiency of a manufacturing process becomes possible. Therefore, in particular, the optical sheet of the large area used for the large screen of the direct type liquid crystal display device is industrially useful because a large reduction in the manufacturing cost and a simplified manufacturing process can be achieved.

One… Optical sheet 2... Substrate layer
3 ... Optical layer 4.. Polyester resin
5 ... Filler 6.. Light diffusing agent
7 ... bookbinder
8… Mixture of polyester resin (4) and filler (5)
9 ... Base Film Extruded Body
10... An optical layer composition comprising a light diffusing agent 6 and a binder 7
11 ... Optical sheet 12... Fine irregularities
20... T die 21... 1 pair rolling roll
22... Stretching apparatus 23. Coater fan
24a... Pickup roll 24b... Adjustable roll
24c... Application roll 24d... Backup roll
50... Backlight unit 51... lamp
52 ... Backlight 53.. Light diffusion sheet
54 ... Prism sheet 54a... Prism part
55... Substrate layer 56. Light diffusion layer
57... Sticking prevention layer 58... bookbinder
59... Light diffusing agent 60... bookbinder
61... Biz

Claims (12)

An optical sheet for direct type liquid crystal display device comprising a transparent base material layer and an optical layer laminated on the surface side of the base material layer,
As the base material layer, a biaxially stretched polyester film containing a filler is used,
The average particle diameter of the filler is 70 nm or more and 200 nm or less,
Content of the said filler is 0.01 mass% or more and 1 mass% or less,
The F5 value of the longitudinal direction and the width direction of the said biaxially-stretched polyester film is 80 Mpa or more and 120 Mpa or less, The optical sheet for direct type liquid crystal display devices characterized by the above-mentioned. The method of claim 1,
And said filler is selected from the group consisting of silica, alumina, titanium dioxide, calcium carbonate, kaolin, barium sulfate, acrylic resin, melamine resin, silicone resin and crosslinked polystyrene. The method of claim 1,
The draw ratio in the longitudinal direction of the biaxially stretched polyester film is 2.5 times or more and 4.5 times or less, and the draw ratio in the width direction is 3 times or more and 5 times or less, the optical sheet for a direct type liquid crystal display device. The method of claim 1,
The static friction coefficient of the said biaxially-stretched polyester film is 0.3 or more and 0.6 or less, and the dynamic friction coefficient is 0.3 or more and 0.5 or less, The optical sheet for direct type liquid crystal display devices characterized by the above-mentioned. The method of claim 1,
Arithmetic mean roughness Ra of the said biaxially stretched polyester film is 0.04 micrometer or more and 0.25 micrometer or less, The optical sheet for direct type liquid crystal display devices characterized by the above-mentioned. The method of claim 1,
The maximum roughness Ry of the said biaxially stretched polyester film is 0.4 micrometer or more and 0.8 micrometer or less, The optical sheet for direct type liquid crystal display devices characterized by the above-mentioned. The method of claim 1,
The 10-point average roughness (Rz) of the said biaxially stretched polyester film is 0.3 micrometer or more and 0.6 micrometer or less, The optical sheet for direct type liquid crystal display devices characterized by the above-mentioned. The method of claim 1,
The optical sheet for a direct type liquid crystal display device, wherein the optical layer has a light diffusing agent and a binder thereof. The method of claim 1,
An optical sheet for a direct type liquid crystal display device, wherein the optical layer has a fine concavo-convex shape having refractive properties. A backlight unit for a direct type liquid crystal display device which disperses light rays emitted from a lamp and leads it to a surface side.
A backlight unit for a direct type liquid crystal display device, comprising the optical sheet for direct type liquid crystal display device according to claim 1. delete delete

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