JP5543083B2 - Laminated film - Google Patents

Description

  The present invention relates to a laminated film. The present invention also relates to light diffusion films and displays having anisotropic diffusivity used for lighting covers, glazings, light guide plates, signboards, displays, screens, and the like, and more particularly, backlights and liquid crystal displays for liquid crystal displays and rear projections. Light diffusing film excellent in light diffusibility, suitably used for a flat screen and a rear projection display, etc., and a backlight and a liquid crystal display for a liquid crystal display using the light diffusion sheet, a rear projection screen and a rear projection type Regarding display.

  In recent years, displays using various principles have been used in various applications such as portable devices, notebook computers, monitors, and televisions. Among them, liquid crystal displays (LCDs) are widely used from small screen products for portable devices to large screen products such as monitors and televisions. In the LCD, an image is displayed by providing a backlight, which is a surface light source, on the back side of the screen in order to irradiate the liquid crystal element sandwiched between the polarizing plates uniformly from the back side of the screen.

  Backlights used in LCDs are roughly classified into two types: (1) A light guide plate processed with a transparent acrylic plate or the like is used, and light is incident on the light guide plate from a fluorescent tube arranged on its side surface. A sidelight type that takes out light in the observation direction while spreading the light rays into a plane using the action of the engraved scattering dots, and (2) one or more fluorescent tubes directly under the screen without using a light guide plate There is a direct type that arranges. Taking advantage of each feature, the sidelight type is easy to cope with small size and thin, and the direct type is easy to cope with large size.

  These backlights are required not only to have a function of entering light from the back side of the screen, but also to have the ability to shine the entire screen uniformly and brightly. In order to satisfy such requirements, an optical functional sheet such as a light diffusion sheet, a prism sheet, or a brightness enhancement sheet (polarization separation sheet) is incorporated in the backlight.

  Among these optical functional sheets, the light diffusion sheet functions as follows. That is, in the case of a sidelight type backlight, light from the side faces the screen, so that the light from the light guide plate has a distribution that is biased in the horizontal direction of the screen, and is also carved into the light guide plate in order to take out in the screen direction. Luminance unevenness due to scattered dots is also observed. Therefore, the light diffusion sheet is overlaid on the light guide plate in order to equalize the light emission distribution and conceal the shadows of the dots engraved on the light guide plate. The light diffusing sheet for the sidelight type backlight has a structure in which a light diffusing layer containing a diffusing component composed of a transparent resin, a crosslinked particle, an inorganic particle, and the like is formed on a transparent substrate such as a polyester resin. A light diffusing sheet or the like is used (see Patent Document 1).

  Further, in the case of a direct type backlight, since the fluorescent tube is installed directly under the screen, uneven brightness appears corresponding to the shape of the fluorescent tube. Therefore, in order to conceal the fluorescent tube image and equalize the light emission distribution, here, a light diffusing plate (light diffusing sheet) having a thickness of 2 to 3 mm having a strong light scattering property (concealing property) is used as the fluorescent tube. Place on the upper side. The light diffusing sheet for direct type backlight is, for example, a light diffusing sheet formed by kneading a transparent resin such as methacrylic resin and a diffusing component such as silicone resin particles using an injection molding method or an extrusion molding method. Etc. are used (see Patent Document 2).

  In addition, liquid crystal displays that use direct type backlights are used for applications that require a wide viewing angle, such as large televisions. Therefore, one or more light diffusing sheets with directivity are stacked on the above light diffusing sheet. Used. This light diffusing sheet has the same structure as the light diffusing layer containing a diffusing component such as particles as described in Patent Document 1, but the average particle diameter of the particles is increased to about 20 μm, and the particle size relative to the binder is further increased. By setting the mass ratio to be high, particles having the role of a convex lens are densely formed in the light diffusion layer, thereby providing directivity and improving luminance (see Patent Document 3).

  Regardless of which type of backlight is used, since a fluorescent tube that occupies a large number of linear or linear portions is installed as a light source, the light source is originally emitted in a direction parallel to the longitudinal direction of the fluorescent tube. The brightness distribution of the light rays differs. Also, depending on the application of the display, it may be designed to have a different luminance distribution in the vertical and horizontal directions of the screen. For this reason, it is required to control the diffusibility in the vertical and horizontal directions of the screen. In this regard, in the case of the light diffusing sheet cited as an example in Patent Documents 1 to 3, such diffusibility cannot be controlled because the diffusion performance is uniform in all directions.

  In order to control such diffusibility, an anisotropic light diffusing sheet having different diffusing performances in the vertical and horizontal directions of the screen is required. As such an anisotropic diffusion sheet, for example, (1) a sheet in which a micro linear substance having a refractive index different from that of the matrix is dispersed in a transparent matrix (see Patent Document 4), (2) on the surface A sheet (see Patent Document 5) provided with vertically-divided spindle-shaped convex portions (see Patent Document 5), (3) A sheet in which a woven fabric made of fibers having different refractive indexes in the vertical and horizontal directions and a transparent substrate are bonded together (see Patent Document 6) Etc.

  In recent years, there has been an increasing demand for a large screen mainly for TVs, and a rear projection display has been attracting attention as a device suitable for large screen display. Although the CRT was generally used as the image source for rear projection displays, devices using liquid crystal panels and micromirror arrays have been developed, and these have become lighter, thinner, more compact and have higher brightness. Expected to be realized.

  The rear projection display is a display that displays an image by enlarging and projecting an image generated by a CRT, a liquid crystal panel, or the like onto a rear projection screen using a projection lens. The screen used here plays a role of appropriately distributing projection light and enabling good image recognition. As the screen, for example, it is possible to use a diffuser plate with isotropic diffusivity mixed with diffusing particles. However, since the incident light is divergently incident, the periphery of the screen is directed outward. When observed from the front side of the screen, the brightness unevenness on the screen becomes noticeable, such as bright and dark at the center and dark when viewed from an oblique direction and darker near and brighter.

  In order to eliminate such luminance unevenness, a Fresnel lens sheet is generally arranged on the projection lens side. The Fresnel lens sheet functions to convert the projection light divergingly incident on the screen from the projection lens into parallel light substantially perpendicular to the screen surface. In this way, if the direction of light at each part of the screen is changed to a direction perpendicular to the screen surface and then diffused, almost uniform brightness can be realized over the entire screen regardless of the direction of observation. I can do it. Further, a lenticular lens sheet is generally used as means for diffusing the light that has become parallel light through the Fresnel lens sheet. The lenticular lens sheet is a sheet on which a lenticular lens having a vertical direction as a longitudinal direction on a surface on which image light is incident is formed, and has an anisotropic diffusibility for diffusing incident parallel light in a horizontal direction and expanding a viewing angle. It is a sheet.

  When the CRT is used as the image source, the exit surface of the lenticular lens sheet is generally formed in a convex lens shape with a condensing part for condensing light from the lens formed on the entrance surface for color adjustment. It is. In addition, the non-condensing part where the light from the lenticular lens formed on the incident surface is not condensed is convex with a top parallel to the sheet surface, and black paint or the like is formed on the top of the convex part to improve contrast. An external light absorbing layer (black stripe) is provided.

Further, in the screen using the lenticular lens as described above, a wide viewing angle is obtained because light is diffused widely in the horizontal direction, but the viewing angle in the vertical direction remains narrow. Although it is not necessary to widen as much as the horizontal direction, it is desirable to slightly widen the viewing angle also in the vertical direction. In recent years, as means for widening the viewing angle in the vertical direction, a lenticular lens extending in the horizontal direction is combined with a lenticular lens extending in the vertical direction (see Patent Document 7), and a front plate having a light diffusion property is provided (Patent Document). 8), a lenticular lens sheet or a Fresnel lens sheet with diffusing particles inserted therein, or a surface provided with a diffusing layer (see Patent Document 9), or containing elliptical particles (Patent Document 10). For example).
JP-A-6-59107 JP-A-6-73296 JP 2002-357703 A JP-A-4-314522 JP 2002-107510 A JP-A-8-160205 JP 2000-338607 A JP 2002-277966 A JP 2001-228547 A JP 2001-31806 A

However, first, the anisotropic light diffusion sheet proposed for LCD applications has the following problems.
In the case of the sheet of (1), there are two types of composition combinations. One is a phase-separated resin composition in which resins that are incompatible with each other are combined. This is because the resin composition is supplied to a T-die extruder, extruded at a predetermined melting temperature, and then the extruded plate is stretched to change the shape of the dispersed resin from spherical to linear (dispersed substantially in parallel). It is changed to obtain an anisotropic diffusion sheet. In this case, there is a problem that if the resin does not have an appropriate affinity, it is peeled off at the interface during stretching, and the resin shape cannot be deformed. Another combination is one in which inorganic particles having a rod-like shape are dispersed. Similarly to the above, an anisotropic light diffusion sheet can be obtained by extrusion and stretching. However, in this case, there is a problem that it is difficult to align the orientation of the inorganic particles having a rod shape. Further, as in both of these types, in the case of diffusion inside the film, it is difficult to obtain high anisotropic diffusibility. In the case of the sheet (2), it is processed using a technique such as mold molding in order to transfer a regular pattern to the surface. When a shape that cannot completely cover the surface, such as a vertically split spindle shape, is transferred, gaps between individual protrusions remain as flat portions. Since the light incident on the flat portion is emitted as it is, the diffusion efficiency is inferior, and the luminance distribution of the emitted light is uneven. In addition, when adjusting the diffusion performance, it is necessary to design and manufacture a new mold, and there is a problem that it takes cost and time.
In the case of the sheet of (3), the difference in the refractive index of the fibers in the vertical and horizontal directions is mainly used, but the anisotropy is insufficient only with the refractive index difference. Furthermore, although there is almost no description of the gaps in the weave of the fabric in Patent Document 6, the diffusion efficiency is lowered unless the light rays passing through this portion are reduced. In addition, this method has a problem that it is costly because it involves a plurality of steps.

  In addition, the following problems can be raised regarding the rear projection display. That is, when combining a lenticular lens sheet in which lenses extending in the vertical direction and a lenticular lens extending in the horizontal direction are combined, or when a front plate having light diffusibility is provided, the number of parts increases, so the part cost and manufacturing cost. Becomes higher. In addition, since the number of stacked screens increases, the screen becomes thicker and heavier, and the influence of multiple scattering between the layers also increases.

  In addition, when a diffusion layer is formed inside or on the surface of a component, it is necessary to mix a large amount of a diffusing agent in order to obtain a sufficient effect of widening the viewing angle in the vertical direction. Becomes darker.

Furthermore, as described above, the lenticular lens sheet needs to have a complicated shape on the front and back surfaces, and there is a problem that the yield is low and the manufacturing cost is high.
Moreover, the thing containing the elliptical particle | grains like patent document 10 cannot obtain high anisotropic diffusibility easily.

  Accordingly, an object of the present invention is to overcome the problems of the prior art, achieve low light cost, high light utilization efficiency, and light diffusion having anisotropic diffusivity that can easily control the diffusivity in the vertical and horizontal directions. It is an object of the present invention to provide a film, a backlight for a liquid crystal display and a liquid crystal display, a rear projection screen and a rear projection display using the film.

Copolymer of polyethylene terephthalate, isophthalic acid copolymerized ethylene terephthalate, polymethyl methacrylate, cyclohexanedimethanol copolymerized PET (layer A) and polybutylene terephthalate, polyethylene terephthalate, tetrafluoroethylene and vinylidene fluoride It is a film having at least a structure in which layers (B layer) composed of any one of a polymerized polymer and a modified polypropylene are alternately laminated in the width direction, satisfying the following formula (1), and having at least one surface unevenness, The molten fluid in which the unevenness is alternately laminated in the width direction with the A layer and the B layer is spontaneously generated by the difference between the density of each resin in the molten state and the density after cooling in the cooling process when discharging and casting from the die. manner has been formed on the film surface, the depth of the irregularities 5μm And the upper 3mm or less, the laminated film, wherein the width direction thickness of the A layer and B layer is 100μm or more 1000μm or less, respectively.

0.001 ≦ | X−Y | ≦ 0.1 Formula (1)
Here, ρA (M) is the density (g / cm ³ ) in the molten state of the thermoplastic resin A,
ρA (F) is the density (g / cm ³ ) in the film state of the thermoplastic resin A,
ρB (M) is the density (g / cm ³ ) in the molten state of the thermoplastic resin B,
ρB (F) is the density (g / cm ³ ) of the thermoplastic resin B in the film state,
X is (ρA (F) −ρA (M)) / ρA (F),

Y is (ρB (F) −ρB (M)) / ρB (F)

  The laminated film of the present invention can be obtained by a process having a small number of steps, has a small number of parts, has high light utilization efficiency, and has anisotropic diffusivity that can easily control the diffusivity in the vertical and horizontal directions. It becomes a diffusion film.

  In order to achieve the above object, the laminated film of the present invention is a film having at least a structure in which layers composed of a resin A (A layer) and layers composed of a resin B (B layer) are alternately laminated in the width direction. Equation (1) must be satisfied.

0.001 ≦ | X−Y | ≦ 0.1 Formula (1)
Here, ρA (M) is the density (g / cm ³ ) in the molten state of the thermoplastic resin A,
ρA (F) is the density (g / cm ³ ) in the film state of the thermoplastic resin A,
ρB (M) is the density (g / cm ³ ) in the molten state of the thermoplastic resin B,
ρB (F) is the density (g / cm ³ ) of the thermoplastic resin B in the film state,
X is (ρA (F) −ρA (M)) / ρA (F),

Y is (ρB (F) −ρB (M)) / ρB (F)
The laminated film having such characteristics can produce an anisotropic diffusion film at a low cost because irregularities are spontaneously formed on the film surface only in the film casting process without going through a process such as stretching. Is possible. Moreover, the diffusibility of the vertical / horizontal direction can be easily controlled by adjusting the kind of resin to be combined and the width ratio of each layer.

  This is a casting method in which a molten fluid in which layers made of resin A (layer A) and layers made of resin B (layer B) are alternately stacked in the width direction is discharged from a die in the manufacturing method of the present invention described later. In the cooling process, unevenness is spontaneously formed on the film surface due to the difference between the density of each resin in the molten state and the density after cooling.

  FIG. 1 shows an example of a structure in which layers (A layer) made of resin A and layers (B layer) made of resin B of the present invention are alternately laminated in the width direction. In FIG. 1, the Y direction is the longitudinal direction, the X direction is the width direction, and the Z direction is the thickness direction. The width direction refers to a direction substantially orthogonal to the longitudinal direction (winding direction). Also, the exposed surface substantially parallel to the XY plane of the film is clearly wider than the other XZ and YZ planes of the film under normal use.

  In the laminated film of the present invention, it is preferable that a total of 30 or more layers in the width direction are laminated alternately in the width direction. More preferably, it is 100 layers or more, More preferably, it is 10,000 layers or more. As the number of layers increases, a wider film can be obtained, so that productivity is improved, and since the pitch becomes finer, the uniformity of diffusivity is excellent. The upper limit of the number of layers is not particularly limited, but is expected to be about 1000000 layers.

  In the present invention, it is particularly limited that a layer using a resin other than the resin A and the resin B is provided and that a layer is formed using a plurality of types of resins as the resin A or the resin B. These layers (a layer using a resin other than the resin A and the resin B, and a plurality of types of resins for the resin A or the resin B are used, and the first type of the resin A or The arrangement of the A layer and the B layer other than the layer using the resin B is also not particularly limited. In the case of having such a C layer, it is more preferable to stack them in a regular permutation such as A (BCA) n, A (BCBA) n, A (BABCBA) n. Here, n is the number of repeating units. For example, in the case of A (BCA) n where n = 3, this indicates that the layers are stacked in a permutation of ABCABCABCA in the thickness direction.

Resin used as the resin A, resin B in the present invention, Ru using thermoplastic resin. Examples of such thermoplastic resins include polyolefin resins such as polyethylene, polypropylene, polystyrene, and polymethylpentene, alicyclic polyolefin resins, polyamide resins such as nylon 6 and nylon 66, aramid resins, polyethylene terephthalate, and polybutylene terephthalate.・ Polypropylene terephthalate ・ Polybutyl succinate ・ Polyester resin such as polyethylene-2,6-naphthalate, polycarbonate resin, polyarylate resin, polyacetal resin, polyphenylene sulfide resin, tetrafluoroethylene resin, trifluoroethylene resin, trifluoride Fluorine resin such as ethylene chloride resin, ethylene tetrafluoride-6-fluoropropylene copolymer, vinylidene fluoride resin, acrylic resin, methacrylic resin, poly Acetal resin, polyglycolic acid resin, polylactic acid resin, and the like, and mixtures of these resins. These resins may be those obtained by copolymerizing other components. However, the resin A and the resin B are selected so as to satisfy the above formula (1). Various additives such as antioxidants, antistatic agents, crystal nucleating agents, inorganic particles, organic particles, thinning agents, thermal stabilizers, lubricants, infrared absorbers, ultraviolet absorbers, for refractive index adjustment A dopant or the like may be added.

  In the present invention, since the anisotropic diffusibility can be further increased, it is preferable to add a diffusion element to the thermoplastic resin. Examples of the diffusing element include inorganic particles such as silica particles, alumina particles, calcium carbonate particles, barium sulfate particles, and titanium oxide particles, and organic particles such as crosslinked polystyrene and crosslinked styrene-acrylic particles. Use is a preferred embodiment. Moreover, it is also a preferable aspect that a resin that is incompatible with the thermoplastic resin serving as a matrix instead of the particles is dispersed in the matrix.

  Resin A and resin B used for the laminated film of the present invention must satisfy the following formula (1). This is because irregularities are spontaneously formed on the surface due to the difference in shrinkage from the molten state of the resin A and the resin B to the cooled and solidified state. If | X−Y | is less than 0.001, there is no difference in the amount of shrinkage, so that irregularities are not formed on the surface and anisotropic diffusibility cannot be obtained. On the other hand, when | X−Y | is larger than 0.1, the flatness of the film is extremely deteriorated, so that the image is distorted when fixed to a display or the like.

0.001 ≦ | X−Y | ≦ 0.1 Formula (1)
Here, .rho.A (M) is the density in the molten state of the thermoplastic resin A (g / ^cm 3),
ρA (F) is the density (g / cm ³ ) in the film state of the thermoplastic resin A,
ρB (M) is the density (g / cm ³ ) in the molten state of the thermoplastic resin B,
ρB (F) is the density (g / cm ³ ) of the thermoplastic resin B in the film state,
X is (ρA (F) −ρA (M)) / ρA (F),

Y is more preferably (ρB (F) −ρB (M)) / ρB (F), and | X−Y | is 0.03 or more and 0.08 or less. When this range is satisfied, a better anisotropic diffusibility is obtained and the flatness is excellent.

The density (g / cm ³ ) of the resin in the molten state is generally called the melt density, and a measurement method is described in JIS K7210 (1999) and the like. The melt density can be determined by dividing MFR by MVR if the melt mass flow rate (MFR) and melt volume rate (MVR) are known. The temperature at which the density in the molten state is measured is measured at a temperature in the range of 180 ° C. or higher and 350 ° C. or lower where the resin A and the resin B melt and flow and do not decompose and deteriorate. It shall be measured. When the measurable temperature range is wide, measure at a temperature between the upper limit temperature of -20 ° C and the upper limit temperature of -10 ° C.

  Moreover, the density in a film state is defined as each density of the A layer and the B layer in the film at 25 ° C. The density in the film state can be variously adjusted by controlling the crystallinity of the resin even if it is the same resin.

  The difference in refractive index between the resin A and the resin B used in the present invention is preferably 0.01 or more and 0.6 or less. When the difference in refractive index between the resin A and the resin B is 0.01 or more and 0.6 or less, the effect of condensing the emitted light in one direction is also exhibited, and the anisotropic diffusibility can be further improved. Become. More preferably, the difference in refractive index between the resin A and the resin B is 0.03 or more and 0.3 or less. In this case, the adhesion between the layers is excellent while maintaining high anisotropic diffusibility.

At least one side surface has unevenness, a depth of the irregularities is Ru der than 3mm less 1 [mu] m. In the present invention, even if the unevenness depth is less than 1 μm, the anisotropic diffusion property is expressed by the refractive index difference between the A layer and the B layer laminated in the width direction, but the unevenness depth is 1 μm. As described above, the difference in the degree of diffusion in the diffusion direction and the non-diffusion direction can be further increased. On the other hand, if it exceeds 3 mm, it is not preferable because the flatness is greatly lowered and the strength is lowered, for example, curling is likely to occur. Further, the uneven shape may be any of a rectangular wave shape, a triangular wave shape, a sine wave shape, a pulse wave shape, a lens shape, and the like. Moreover, what combined these may be sufficient and the space | interval of an unevenness | corrugation may be regular or irregular.
In the present invention, the depth of the unevenness is defined by RzJIS described in JIS B0601 (2001) Annex 1. More preferably, the depth of the unevenness is 5 μm or more and 300 μm or less. It is preferable that the unevenness depth is 5 μm or more and 300 μm or less because the degree of diffusion becomes sharper. Further, in the present invention, X and Y in Formula 1 satisfy the relationship X <Y, and at least concave and convex portions present on the surface of one side are portions where A layers and B layers are alternately stacked in the width direction. It is preferable to exist on the A layer. That is, it is preferable that there are uneven projections on the surface of the layer whose volume change during the cooling process is smaller. At first glance, this aspect can also be understood as a basic form of the present invention, but in reality, it depends on the thickness ratio of the A layer and B layer in the width direction, the surface tension of each resin, the adhesive force between each resin, etc. However, the position of the uneven portion is affected. If the structure of this aspect is satisfied by precisely controlling this, it is preferable that a more controlled dense anisotropic diffusibility is expressed.

  In the laminated film of the present invention, it is preferable to have a layer made of resin A or a layer made of resin B on at least one surface. That is, it is preferable that there is a layer made of the resin A or a layer made of the resin B so that the A layer and the B layer laminated in the width direction are covered with at least one surface. This layer is called a surface layer in the present invention. FIG. 2 shows an example of the surface layer. In FIG. 2, the surface layer which consists of resin A exists in the surface (lower side) of one side. With such a structure, delamination between the A layer and the B layer laminated in the width direction is difficult to occur, and the strength increases, so that the shape stability is excellent. It is more preferable to have a layer made of resin A or a layer made of resin B on both surfaces. At this time, it is also possible to maintain surface irregularities. Further, at least two surface layers may be laminated on one side.

  The thickness of the surface layer is preferably 0.5 μm or more and 3 mm or less. If it is less than 0.5 μm, the effect of suppressing delamination is poor. On the other hand, if it is larger than 3 mm, flexibility is greatly reduced, and handling becomes difficult.

It is preferable that the melt specific resistance of the resin A and / or the resin B is 5 × 10 ⁶ Ω · cm or more and 5 × 10 ¹⁰ Ω · cm or less. When the melt specific resistance of the resin A or / and the resin B is 5 × 10 ⁶ Ω · cm or more and 5 × 10 ¹¹ Ω · cm or less, it is brought into close contact with the casting drum and cooled by applying a high voltage during the casting process. Therefore, it is preferable because it is easy to maintain the uneven shape of the surface that occurs spontaneously. On the other hand, when the melt specific resistance does not satisfy 5 × 10 ⁶ Ω · cm or more and 5 × 10 ¹⁰ Ω · cm or less, it is necessary to press against the cooling rotator by an external force such as a touch roll or an air knife, so it is formed spontaneously. Since the uneven shape on the surface is deformed, the anisotropic diffusion performance is likely to be lowered. In the present invention, even if only one of the resin A and the resin B is used, if the melt specific resistance is 5 × 10 ⁶ Ω · cm or more and 5 × 10 ¹¹ Ω · cm or less, the entire film can be uniformly cooled. The present inventors have found that high anisotropic diffusivity can be expressed. The melt specific resistance of the present invention is measured at a temperature within a range of 180 ° C. or higher and 350 ° C. or lower where the resin A and the resin B melt and flow and do not decompose and deteriorate, although the temperature to be measured differs depending on the resin to be combined. A and resin B are measured at the same temperature. When the measurable temperature range is wide, measure at a temperature between the upper limit temperature of -20 ° C and the upper limit temperature of -10 ° C.

  The laminated film of the present invention is preferably used as an anisotropic diffusion film. In the case of the laminated film of the present invention, for example, when spot-like light is incident perpendicularly to the film surface, the transmitted light spreads in the width direction but hardly spreads in the longitudinal direction. It will be.

  Next, preferred configurations of a backlight for a liquid crystal display using the light diffusion sheet of the present invention are illustrated in FIGS. 3 and 4, but the present invention is not limited to these configurations. FIG. 3 is a diagram schematically showing a configuration of a backlight when incorporated in a sidelight type backlight of a liquid crystal display. In FIG. 3, the sidelight type backlight is arranged on the light guide plate 6 processed with a transparent acrylic plate, one or a plurality of linear fluorescent tubes 8 arranged on the side surface, and the bottom surface side of the light guide plate 6. Brightness improvement of the reflection sheet 7 made, the anisotropic diffusion film 5 of the present invention arranged on the surface side of the light guide plate 6, and a prism sheet or a polarization separation sheet installed further above the anisotropic diffusion film 5 It is composed of a sheet 4. One or more anisotropic diffusion films 5 of the present invention in a sidelight type backlight are used at least on the surface side of the light guide plate 6 and combined with a brightness enhancement sheet 4 such as a prism sheet or a polarization separation sheet as shown in FIG. It is preferable. Moreover, the position of the anisotropic diffusion film 5 of the present invention when combined with the brightness enhancement sheet 4 is not particularly limited. Moreover, since the anisotropic diffusion film of this invention can also have a condensing function by adjusting the uneven | corrugated shape of a surface, it is also possible to abbreviate | omit a prism sheet.

  In the case of a sidelight type backlight, since light rays are incident from the side surface of the light guide plate 6, the light rays emitted from the surface of the light guide plate 6 have different orientation characteristics in the vertical and horizontal directions of the screen. Therefore, by using the anisotropic diffusion film 5 of the present invention in which the vertical and horizontal diffusibility is controlled according to the light distribution characteristics from the light guide plate 6, the alignment characteristics in both directions can be adjusted and uniformized.

  FIG. 4 is a diagram schematically showing a configuration of a backlight when the anisotropic diffusion film of the present invention is incorporated in a direct type backlight of a liquid crystal display. In FIG. 4, in the direct type backlight, a plurality of linear fluorescent tubes 8 are arranged on the bottom surface of a casing 10 on which a reflection sheet 7 is spread, a diffusion plate 9 is arranged on the upper portion of the fluorescent tubes 8, and the present invention is further formed thereon. The anisotropic diffusion film 5 is arranged. It is preferable that one or more anisotropic diffusion films 5 of the present invention in a direct type backlight are used at least on the fluorescent tube 8 and combined with the brightness enhancement sheet 4 as shown in FIG. Moreover, the position of the anisotropic diffusion film 5 of the present invention when combined is not particularly limited. In the case of the direct type backlight, since the linear fluorescent tubes 8 are arranged in parallel at the back of the screen, the alignment characteristics are significantly different in the vertical and horizontal directions of the screen than the above-described sidelight type backlight. Therefore, by utilizing the anisotropic diffusibility by the anisotropic diffusion film 5 of the present invention, it becomes possible to adjust and uniform the alignment characteristics in both directions.

In any case of the backlight, the uneven surface on the surface of the anisotropic diffusion film 5 of the present invention may be used in any direction of the incident type or the emitting side of the light from the fluorescent tube 11.
By using the anisotropic diffusion film 5 having such a configuration, it becomes easy to control the light distribution characteristics in the horizontal direction and the vertical direction, and it becomes possible to obtain a liquid crystal display with high light use efficiency and a controlled luminance distribution. . Moreover, the anisotropic diffusion film 5 of this invention can be preferably used also for a rear projection type display use.

The rear projection screen using the anisotropic diffusion film 5 of the present invention is more preferably combined with a Fresnel lens sheet. As the Fresnel lens sheet, a Fresnel lens sheet that can be manufactured by a known method can be used. For example, there is a method of molding a lens surface by pressing a thermoplastic resin with a heated stamper, a method of molding a lens sheet using a resin that is cured by irradiation with active energy rays such as ultraviolet rays and electron beams, etc. Although it mentions, it is not limited to the material and the manufacturing method in particular.
The two members can be combined in such a way that the lens surface of the Fresnel lens sheet and the uneven surface of the anisotropic diffusion film face each other, and the lens surface of the Fresnel lens sheet and the flat surface of the anisotropic diffusion film face each other. The combination which installs so that the flat surface of both sheets may face each other, etc. are used preferably.
In addition to these two members, an anisotropic diffusion film having the same or different surface shape, a light diffusing sheet exhibiting isotropic diffusivity, a lenticular lens sheet, etc. It is also a preferable aspect to install outside.
By using the rear projection screen having such a configuration, it is easy to control the viewing angle in the horizontal direction and the vertical direction, and it is possible to provide a bright rear projection display with high light utilization efficiency.

Next, the preferable manufacturing method of the laminated | multilayer film of this invention is demonstrated below.
Two types of resins A and B are prepared in the form of pellets. In this case, it is not always necessary to be a pellet.
The pellets are supplied to the extruder after pre-drying in hot air or under vacuum as necessary. In the extruder, the heat-melted resin is made uniform in the amount of resin extruded by a gear pump or the like, and foreign matter or denatured resin is removed through a filter or the like.

The resin sent from different flow paths using these two or more extruders is then sent to the feed block. An example of a preferred feed block of the present invention is shown in FIG.
FIG. 5 is a plan view of the feed block. The feed block 16 includes a side plate 11, a resin A supply unit 12, a slit portion 13, a resin B supply unit 14, and a side plate 15, which are used by being integrated. The feed block of FIG. 5 has two resin introduction ports 17 derived from the resin A supply unit 12 and the resin B supply unit 14. Here, the types of resin introduced into the plurality of slits existing in the slit portion are the bottom surfaces of the liquid reservoir portions 18 of the resin A supply portion 12 and the resin B supply portion 14 and the end portions of the slits in the slit members. And is determined by the positional relationship. The mechanism will be described below.

  FIG. 6A is an enlarged view of the slit portion 13. A p-p ′ section showing the shape of the slit 20 a is (b) in the figure, and a q-q ′ section showing the shape of the slit 20 b is (c) in the figure. As shown in (b) and (c), the ridgeline 22 of each slit is inclined with respect to the thickness direction of the slit member.

  In FIG. 7, the resin A supply part 12, the slit part 13, and the resin B supply part 14 are shown among the feed blocks. And the height of the bottom face 27 and 29 of the liquid reservoir part in each of the resin A supply part 12 and the resin B supply part 14 is the height between the upper end part 25 and the lower end part 24 of the ridge line 26 existing in the slit part. To position. Accordingly, the resin is introduced from the liquid reservoir 18 from the side where the ridge line 26 is high (arrow 28 in FIG. 7), but the slit is sealed from the side where the ridge line 26 is low and the resin is introduced. Not.

  Although not shown, in the slit adjacent to the slit noted in FIG. 7, the ridge line of the slit is disposed at an angle opposite to that in FIG. 7, and is introduced from the resin A supply unit 12 to the slit unit 13. Thus, since the resin A or the resin B is selectively introduced for each slit, the resin A and the resin B are formed in the slit portion 13 and flow out from the lower outlet 19. That is, the base of the structure in which the layer made of the resin A and the layer made of the resin B in FIG. 1 are arranged is formed.

  When such a feed block is used, the number of layers can be easily adjusted by the number of slits. The thickness of each layer can be easily adjusted by the shape of the slit (length, gap), the flow rate of the fluid, and the degree of compression in the width direction. On the other hand, the shape of each layer is basically a square shape, but by adjusting the viscosity difference or density difference between the resin A and the resin B, the square shape is deformed in the flow process, and the lens It can be shaped like an ellipse, an ellipse, or a circle. A preferable number of slits is 5 or more and 30000 or less in one slit portion. When the number is less than 5, the number of layers is too small, and the efficiency is poor. On the other hand, when the number is more than 30000, it becomes difficult to control the flow rate unevenness, and the accuracy of the layer thickness is insufficient, so that uneven diffusivity is likely to occur. In addition, when it has 200 or more cores, it is preferable to use the feed block which has 2 or more slit parts separately. This is because if there are 400 or more (200 or more cores) slits in one slit part, it is difficult to make the flow rate of each slit uniform.

  The fluid having the arrangement structure of the resin A and the resin B obtained in this way may form a resin layer on one side or both sides according to necessity with the die shown in FIG. FIG. 8 is a cross-sectional view showing an example of a die used in the present invention. In the die of FIG. 8, there are three inlets, and the third resin flows from the inlet 30. The third resin is preferably supplied to the feed block by means different from the supply means. Further, the resin flow in which the resin A and the resin B formed by the feed block are laminated flows from the inlet 31. These are merged and laminated at the junction 33, and a third resin layer is formed on the surface of the resin flow in which the resin A and the resin B are laminated in the width direction, and the resin is discharged from the die discharge port 26. The Rukoto. Note that the third resin may be the same as or different from the resin A or the resin B. The die used in the present invention may be a multi-manifold die as shown in FIG. 8 or a single manifold die.

  By using the feed block and the die, the sheet discharged from the die has a laminated film structure which is a preferred embodiment of the present application as shown in FIGS.

  The discharge sheet thus obtained is cooled and solidified by a casting drum, a calendering roll or the like. When discharging from the die, the core interval may fluctuate due to a neck-down phenomenon, so it is preferable to provide an edge guide at the end of the die lip. The edge guide is provided between the die lip and the cooling body in order to constrain the end of the resin film discharged from the die. Down can be suppressed. By doing so, the laminated film discharged from the die is thinned in the thickness direction depending on the relationship between the discharge amount and the take-off speed, but the width-direction dimension does not change, so the accuracy in the width direction of each layer is improved.

  Also, when solidifying by cooling, using a wire-like, tape-like, needle-like or knife-like electrode, it is possible to adhere to a cooling body such as a casting drum by electrostatic force, a slit-like, spot-like, or planar-like It is preferable to use a method in which air is blown out from the apparatus and brought into close contact with a cooling body such as a casting drum, or a method in which the roll is brought into close contact with the cooling body. In particular, in the present invention, a method of closely contacting the casting drum by electrostatic force is preferable. The obtained laminated film is stretched as necessary and wound with a winder.

An evaluation method of physical property values used in the present invention will be described.
(Method for evaluating physical properties)
(1) Internal shape As for the internal shape of the film, an electron microscope JSM-6700F (manufactured by JEOL Ltd.) or optical microscope Leica DMLB HC was used for a sample obtained by cutting a cross section (width direction-thickness direction cross section) using a microtome. Was used to enlarge and observe the cross-section in the thickness direction-width direction of the film, photographed cross-sections, and measured the thickness and shape of each layer. The photographing magnification was appropriately adjusted in the range of 100 to 2000 times so that it could be accurately measured according to the thickness of each layer.

(2) Density in the Melted State The density (melting density) of each resin in the molten state was measured according to JIS K7210 (1999) B method. For the measurement, a Toyo Seiki melt indexer F-F01 was used. The preheating time for the resin was 3 minutes. The resin used in Example 1 was measured at 240 ° C., and the others were measured at 270 ° C.

(3) Density in Film State The density of each resin in the film state was measured according to JIS K7112 (1999) D method. In addition, each resin layer was isolate | separated from the film and it measured at 25 degreeC.

(4) Unevenness depth The unevenness depth of the film surface was measured according to JIS B0601 (2001), and RzJIS described in Appendix 1 was obtained. The measurement was performed using a high-precision thin film level difference measuring device ET-10 manufactured by Kosaka Laboratory. The conditions are as follows.

Stylus tip radius: 0.5 μm
Stylus load: 5mg
Measurement length: 2mm
Cut-off: 0.08mm
Stylus speed: 4μm / sec
Measurement surface: Surface (5) Melting specific resistance Two electrode plates are placed in the molten resin, the voltage (V ') when a voltage of 500 V is applied is measured, and the melting specific resistance (ρ) is expressed by the following equation: Asked. The resin used in Example 1 was measured at 240 ° C., and the others were measured at 270 ° C.
ρ (Ω · cm) = V · S · R / I · V '
V: Applied voltage (V)
S: Electrode area (cm 2)
R: Resistor resistance I: Distance between electrodes (cm)
V ′: Measurement voltage (V)
(6) Anisotropic diffusion In a dark room, with the laminated film 10 cm away from the wall, the laminated film is fixed so that the laminated film is parallel and the uneven surface is opposite to the wall, and the laser pointer is perpendicular to the uneven surface. (Green laser pointer GLP-FB (manufactured by Kochi Hoyonaka Giken Co., Ltd.): A laser beam output from a beam diameter of 1 mm, a wavelength of 532 nm, and an output of less than 1 mW) was irradiated, and the shape of the beam image displayed on the wall was observed. Here, the image projected on the wall is preferably a case where the laser beam is selectively diffused in one direction. The determination was made by measuring the length (L) in the maximum longitudinal direction of the beam image and the length (W) in the direction perpendicular to the maximum longitudinal direction, and obtaining this ratio (L / W). When L / W is 30 or more, ◎, when L / W is 20 or more and less than 30, ◯, when L / W is 10 or more and less than 20, Δ, and when L / W is less than 10, ×.

(7) Intrinsic viscosity Calculated from the solution viscosity measured at 25 ° C in orthochlorophenol. The solution viscosity was measured using an Ostwald viscometer. The unit is [dl / g]. The n number was 3, and the average value was adopted.

(8) Refractive index The refractive index (n) of the resin was measured according to JIS K7142 (1996) A method.

Example 1
As the resin A and the resin B, the following resins were used.

Resin A: Polymethylmethacrylate (PMMA) n = 1.49
Sumipex MGSS made by Sumitomo Chemical
Resin B: Copolymer (TFE / VDF) of 18 mol% tetrafluoroethylene and 82 mol% vinylidene fluoride n = 1.38
NEOFRON RP-4020 made by Daikin
Next, the resin A is supplied to the extruder 1 and the resin B is supplied to the extruder 2. Each resin is melted at 240 ° C., passed through a gear pump and a filter, and then put into the feed block as shown in FIG. A and resin B were allowed to flow. In the feed block, the resin A and the resin B were alternately laminated in the width direction so that the resin A was on both outer sides, and the laminated flow was guided to the die. Further, the resin A was supplied to the extruder 3 to be in a molten state at 240 ° C., and after passing through a gear pump and a filter, the resin A was laminated on one surface of the laminated flow with a die.
The sheet discharged from the die was extruded onto a casting drum while the end portion was restrained by an edge guide, and rapidly cooled and solidified with a drum held at a temperature of 40 ° C. by a wire electrode applied with electrostatic force. The average thickness of the obtained film was 310 μm, and the resin A was laminated on the surface of one side with an average thickness of 10 μm. Table 1 shows the structure and performance of the obtained laminated film.

(Example 2)
Films were formed in the same manner as in Example 1 except that the following resins were used as the resin A and the resin B, and the respective resins were melted at 270 ° C. with an extruder. The average thickness of the obtained film was 310 μm, and the resin A was laminated on the surface of one side with an average thickness of 10 μm. Table 1 shows the structure and performance of the obtained laminated film.

Resin A: Polyethylene terephthalate (PET) with intrinsic viscosity of 0.65 n = 1.58
Resin B: Polybutylene terephthalate (PBT) n = 1.57
Toraycon 1200S made by Toray
(Example 3)
A film was formed in the same manner as in Example 2 except that the following resins were used as the resin A and the resin B. The average thickness of the obtained film was 310 μm, and the resin A was laminated on the surface of one side with an average thickness of 10 μm. Table 1 shows the structure and performance of the obtained laminated film.

Resin A: Polyethylene terephthalate (PET) with intrinsic viscosity of 0.65 n = 1.58
Resin B: Modified polypropylene (modified PP) n = 1.51
836DG3 made by Sumitomo Chemical
Example 4
A film was formed in the same manner as in Example 2 except that the following resins were used as the resin A and the resin B. The average thickness of the obtained film was 310 μm, and the resin A was laminated on the surface of one side with an average thickness of 10 μm. Table 1 shows the structure and performance of the obtained laminated film.

Resin A: Ethylene terephthalate copolymer (PET / I) copolymerized with 25 mol% of isophthalic acid having an intrinsic viscosity of 0.68 n = 1.58
Resin B: Polyethylene terephthalate (PET) with an intrinsic viscosity of 0.65 n = 1.58
(Example 5)
A film was formed in the same manner as in Example 2 except that a feed block having three slit portions was used. The average thickness of the obtained film was 310 μm, and the resin A was laminated on the surface of one side with an average thickness of 10 μm. Table 1 shows the structure and performance of the obtained laminated film.
(Examples 6 to 7)
A film was formed in the same manner as in Example 2 except that the discharge amount was adjusted and the lamination ratio was changed. The average thickness of the obtained film was 310 μm, and the resin A was laminated on the surface of one side with an average thickness of 10 μm. Table 1 shows the structure and performance of the obtained laminated film.

(Example 8)
A film was formed in the same manner as in Example 2 except that dies having different die widths were used. The average thickness of the obtained film was 310 μm, and the resin A was laminated on the surface of one side with an average thickness of 10 μm. Table 1 shows the structure and performance of the obtained laminated film.
Example 9
A film was formed in the same manner as in Example 2 except that the resin A was laminated on both surfaces with a die. The average thickness of the obtained film was 310 μm, and the resin A was laminated on the surface of one side with an average thickness of 10 μm. Table 1 shows the structure and performance of the obtained laminated film.
(Example 10)
A film was formed in the same manner as in Example 2 except that the film forming speed and the discharge amount were adjusted and the thickness was changed. The average thickness of the obtained film was 1200 μm, and the resin A was laminated on the surface of one side with an average thickness of 20 μm. Table 1 shows the structure and performance of the obtained laminated film.
(Example 11)
A film was formed in the same manner as in Example 6 except that layers were not formed on both surface layers. The average thickness of the obtained film was 300 μm. Table 1 shows the structure and performance of the obtained laminated film. This film tended to cause slight peeling between layers due to bending or the like.
(Comparative Example 1)
A film was formed in the same manner as in Example 1 except that the following resins were used as the resin A and the resin B. The average thickness of the obtained film was 310 μm, and the resin A was laminated on the surface of one side with an average thickness of 10 μm. Table 1 shows the structure and performance of the obtained laminated film.

Resin A: Polyethylene terephthalate (PET) with an intrinsic viscosity of 0.65
Resin B: Polyethylene terephthalate (PET) with an intrinsic viscosity of 0.65
(Example 12)
The following resins were used as the resin A and the resin B, and a film was formed in the same manner as in Example 2 except that the resin A was laminated with a die so that the resin A was disposed on one surface. However, the resin A corresponding to the A layer contained 1% by weight of polymethylpentene particles (DX820) manufactured by Mitsui Chemicals as a diffusion element with respect to the total amount of the resin A. The average thickness of the obtained film was 310 μm, and the resin A was laminated on the surface of one side with an average thickness of 10 μm. Table 1 shows the structure and performance of the obtained laminated film. Since the film of this example contains a diffusing element in the resin A constituting the A layer, it was superior in anisotropic diffusibility as compared with a film not containing the diffusing element.

Resin A: Eastman PETG6763 (cyclohexanedimethanol copolymerized PET) n = 1.57
Resin B: Polybutylene terephthalate (PBT)
TORAYCON 1200S n = 1.57

  The present invention relates to a laminated film. The present invention also relates to light diffusion films and displays having anisotropic diffusivity used for lighting covers, glazings, light guide plates, signboards, displays, screens, and the like, and more particularly, backlights and liquid crystal displays for liquid crystal displays and rear projections. Light diffusing film excellent in light diffusibility, suitably used for a flat screen and a rear projection display, etc., and a backlight and a liquid crystal display for a liquid crystal display using the light diffusion sheet, a rear projection screen and a rear projection type It relates to the display.

Cross section of laminated film Cross section of laminated film Sidelight LCD backlight Direct type LCD backlight Feed block Slit part Sectional view of the state where the slit part and the resin supply part are connected Cross section of die

Explanation of symbols

1: Resin B
2: Resin A
3: Resin A
4: Prism sheet or polarized light separation sheet 5: anisotropic diffusion film 6: light guide plate 7: reflector 8: fluorescent tube 11: side plate 12: resin supply unit 13: slit unit 14: resin supply unit 15: side plate 16: feed Block 34: Die

Claims (7)

Copolymer of polyethylene terephthalate, isophthalic acid copolymerized ethylene terephthalate, polymethyl methacrylate, cyclohexanedimethanol copolymerized PET (layer A) and polybutylene terephthalate, polyethylene terephthalate, tetrafluoroethylene and vinylidene fluoride It is a film having at least a structure in which layers (B layer) composed of any one of a polymerized polymer and a modified polypropylene are alternately laminated in the width direction, satisfying the following formula (1), and having at least one surface unevenness, The molten fluid in which the unevenness is alternately laminated in the width direction with the A layer and the B layer is spontaneously generated by the difference between the density of each resin in the molten state and the density after cooling in the cooling process when discharging and casting from the die. manner has been formed on the film surface, the depth of the irregularities 5μm And the upper 3mm or less, the laminated film, wherein the width direction thickness of the A layer and B layer is 100μm or more 1000μm or less, respectively.
0.001 ≦ | X−Y | ≦ 0.1 Formula (1)
Here, ρA (M) is the density (g / cm ³ ) in the molten state of the thermoplastic resin A,
ρA (F) is the density (g / cm ³ ) in the film state of the thermoplastic resin A,
ρB (M) is the density (g / cm ³ ) in the molten state of the thermoplastic resin B,
ρB (F) is the density (g / cm ³ ) of the thermoplastic resin B in the film state,
X is (ρA (F) −ρA (M)) / ρA (F),
Y is (ρB (F) −ρB (M)) / ρB (F). The laminated film according to claim 1, which has a layer made of thermoplastic resin A or a layer made of thermoplastic resin B on at least one surface. 3. The laminated film according to claim 1, wherein the thermoplastic resin A and / or the thermoplastic resin B has a melt specific resistance of 5 × 10 ⁶ or more and 5 × 10 ¹⁰ Ω · cm or less. X <a Y, and at least the convex portion of the irregularities present on one side of the surface, of the claims 1-3 present on the A layer at a site A layer and the B layer are alternately laminated in the width direction The laminated film according to any one of the above. An anisotropic diffusion film comprising the laminated film according to claim 1. A liquid crystal display backlight system comprising the anisotropic diffusion film according to claim 5. A rear projection type screen and a rear projection type display comprising the anisotropic diffusion film according to claim 5.

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