JP2011118190A - Polarizing reflector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing reflector which is one multilayer laminated film, that is hardly broken in a film manufacturing method, to improve productivity and is produced without using a tacky adhesive, and which improves the luminance of a LCD backlight. <P>SOLUTION: The polarizing reflector is obtained by alternately layering a layer (A layer) comprising a thermoplastic resin and another layer (B layer) comprising another thermoplastic resin having the composition different from that of the resin constituting the A layer on each other to form 50 or more layers, satisfies inequality (1): Rmin≤40%, inequality (2): Rmax≥60% and inequality (3): Λmd≥7% (wherein Rmin and Rmax are the minimum value (Rmin) and the maximum value (Rmax) of the reflectance (%) when the polarized light having 550 nm wavelength is made incident on the surface of the polarizing reflector at 0° incident angle and the polarizing reflector is rotated by 180° around the optical axis of the incident light; Λmd is the breaking elongation in such a direction that the reflectance shows Rmax) and has ≤5 saturation C* of the transmitted light. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a polarizing reflector in which two types of thermoplastic resins are alternately laminated.

In recent years, liquid crystal displays (Liquid Crystal Display) having the advantages of thin and light weight, low power consumption, and high image quality are rapidly spreading to applications such as televisions, personal computers and mobile phones. A liquid crystal display is generally composed of a backlight unit, a liquid crystal unit, and a front plate unit. A backlight unit is a member that requires a function to uniformly and efficiently guide light from LEDs and fluorescent lamps to a liquid crystal unit, and is composed of a light guide plate, a reflector plate, a diffuser plate, a prism sheet, and the like. ing. The liquid crystal unit is a liquid crystal cell member that controls the orientation of liquid crystal molecules by applying a transparent electrode to a liquid crystal sandwiched between transparent substrates such as glass, a color filter that adds hue and contrast to the transmitted light of the LCD, a retardation plate, It is comprised from a polarizing plate. The front panel unit consists of a hard coat layer that protects the front panel from scratches, an anti-glare layer that prevents glare on the surface, an antireflection layer that prevents liquid crystal contrast deterioration due to external light, and other films that expand the viewing angle. Yes. Various LCD display methods such as the conventional STN (Super Twisted Nematic) method, TFT (Thin Film Transistor) method, DSTN (Dual Super Twisted Nematic) method, FSTN (Film-compensated STN) method are adopted. Yes.

  In recent years, where a low carbon dioxide society is required, a brighter display screen with lower power consumption than before is required. However, a polarizer having a polarization function of a polarizing plate used in a conventional LCD is obtained by adsorbing and orienting a polarizing element such as iodine or a dichroic dye on a hydrophilic film such as a polyvinyl alcohol film. Therefore, nearly half of the light from the fluorescent lamp was absorbed wastefully. The polarizing plate has a structure in which a polarizer is covered with a triacetyl cellulose film from above and below, or a structure in which both upper and lower surfaces are coated with an acrylic resin.

  However, in recent years, a reflective multilayer polarizer, which is a polymer multilayer film, has appeared, and by disposing it between a fluorescent lamp and a polarizing plate, a material that drastically reduces light absorption at the polarizing plate and brings about high brightness has been proposed. Yes. (Patent Document 1) This principle will be described. The light from the fluorescent lamp is reflected by the reflective polarizer, and the light in the direction transmitted by the polarizing plate is transmitted, and the light in one absorbed direction is reflected. The reflected light reflected by the reflective polarizer is now diffusely reflected by the reflecting plate to cancel the polarization, and is guided again to the reflective polarizer. Similarly, with respect to the light retroreflected by the reflecting plate, only the light in the transmission direction of the polarizing plate is guided to the liquid crystal cell, thereby suppressing the light absorption by the polarizing plate and efficiently bringing the light to the display unit. Therefore, the luminance is improved. (Patent Document 2) That is, the reflective polarizer is a birefringent body having a transmission axis and a reflection axis in a plane, and may be referred to as a polarized light separation reflection film.

  Since the biaxially stretched film of the reflective polarizer cannot provide a high degree of polarization, the performance of improving the luminance of the LCD backlight is insufficient. Therefore, the uniaxially stretched film manufactured by extending | stretching only in one direction was used. However, stretching in only one direction can provide high polarization properties, while mechanical properties of the film are easy to tear in the stretching direction (here, the reflection axis direction), and film tearing frequently occurs during the manufacturing process. There is a problem that the production yield is low and the cost is increased. This film breakage occurs particularly between the winder and the tenter, and it has been desired to improve performance such as elongation at break and tear strength that can withstand the tension therebetween. On the other hand, the appropriately adjusted biaxially stretched reflective polarizer did not break the film, but had insufficient performance for improving the brightness of the LCD backlight. (Patent Document 3) Further, since the color and polarization performance of one multilayer laminated film was insufficient, it was necessary to bond a plurality of multilayer laminated films having different thicknesses with an adhesive material interposed therebetween. Furthermore, since the handleability is insufficient, it was necessary to use a multilayer laminated film sandwiched between two thick diffusion films having a self-supporting thickness of 150 μm with an adhesive.

Japanese National Publication No. 9-506837 (2nd page) Japanese Patent No. 3704523 (2nd page) JP2009-037235 (2nd page)

  The object of the present invention is to increase the elongation in the direction of the transmission axis as compared with conventional polymer reflective polarizers, thereby reducing the number of process breaks during film production and improving the productivity. Further, the present invention provides a polarizing reflector that improves the brightness of an LCD backlight with a single multilayer laminated film that does not use an adhesive.

In order to solve the problem, the present invention has the following configuration and various preferred modes. That is, the present invention is formed by alternately stacking 50 or more layers each consisting of a thermoplastic resin layer (A layer) and a thermoplastic resin layer (B layer) having a composition different from the resin constituting the A layer, A polarizing reflector satisfying the following formulas (1) to (3) and having a saturation C * of transmitted light of 5 or less.

Rmin ≦ 40% (1) Equation Rmax ≧ 60% (2) Equation Λmd ≧ 7% (3) Equation (where Rmin and Rmax are polarized light reflected at a wavelength of 550 nm) The minimum value (Rmin) and maximum value (Rmax) of the reflectance (%) when the surface of the body is irradiated at an incident angle of 0 ° and the polarizing reflector is rotated halfway around the incident optical axis. , Λmd is the elongation at break in the direction showing Rmin.)

Compared to conventional polarizing reflectors, the elongation in the transmission axis direction and the tearing strength in the reflection axis direction are increased, and the process is not broken at the time of film production, thereby improving productivity. In addition, the mechanical properties in the in-plane direction of the film are balanced, and the handleability when used in an LCD backlight unit is excellent.

(A) Film cross section of reflective polarizer (b) Film cross section of polarizing reflector It is explanatory drawing explaining an example of the manufacturing method of the reflecting material used for this invention, (a) is a schematic front view of an apparatus, (b), (c), (d) is LL ', MM, respectively. It is sectional drawing of the resin flow path cut | disconnected by ', NN'. Example of relationship between layer order and layer thickness (layer thickness distribution) of polarizing reflector used in the present invention

In the polarizing reflector of the present invention, 50 layers or more of layers made of a thermoplastic resin (layer A) and layers made of a thermoplastic resin having a composition different from the resin constituting the layer A (layer B) are alternately laminated. Therefore, it is necessary that the following expressions (1) to (3) are satisfied and the saturation C * of the transmitted light is 5 or less.
Rmin ≦ 40% (1) Equation Rmax ≧ 60% (2) Equation Λmd ≧ 7% (3) Equation (where Rmin and Rmax are polarized light reflected at a wavelength of 550 nm) The minimum value (Rmin) and maximum value (Rmax) of the reflectance (%) when the surface of the body is irradiated at an incident angle of 0 ° and the polarizing reflector is rotated halfway around the incident optical axis. , Λmd is the elongation at break in the orientation indicating Rmin).

  The thermoplastic resins used in the present invention are chain polyolefins such as polyethylene, polypropylene, poly (4-methylpentene-1), polyacetal, and ring-opening metathesis polymerization of norbornenes, addition polymerization, and addition copolymerization with other olefins. Biodegradable polymers such as alicyclic polyolefin, polylactic acid, polybutyl succinate, etc., polyamides such as nylon 6, nylon 11, nylon 12, nylon 66, aramid, polymethyl methacrylate, polyvinyl chloride, polyvinylidene chloride , Polyvinyl alcohol, polyvinyl butyral, ethylene vinyl acetate copolymer, polyacetal, polyglycolic acid, polystyrene, styrene copolymer polymethyl methacrylate, polycarbonate, polypropylene terephthalate, polyethylene terephthalate Polyester, polybutylene terephthalate, polyethylene-2,6-naphthalate, etc., polyethersulfone, polyetheretherketone, modified polyphenylene ether, polyphenylene sulfide, polyetherimide, polyimide, polyarylate, tetrafluoroethylene resin, A trifluorinated ethylene resin, a trifluorinated ethylene resin, a tetrafluoroethylene-6 fluoropropylene copolymer, polyvinylidene fluoride, or the like can be used. Of these, polyester is particularly preferred from the viewpoint of strength, heat resistance, transparency and versatility. These may be a homopolymer, a copolymer, or a mixture.

  The polyester is preferably a polyester obtained by polymerization from a monomer mainly composed of an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid and a diol. Here, as the aromatic dicarboxylic acid, for example, terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-diphenyl Examples include dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, 4,4'-diphenylsulfone dicarboxylic acid, and the like. Examples of the aliphatic dicarboxylic acid include adipic acid, suberic acid, sebacic acid, dimer acid, dodecanedioic acid, cyclohexanedicarboxylic acid and ester derivatives thereof. Of these, terephthalic acid and 2,6 naphthalenedicarboxylic acid exhibiting a high refractive index are preferable. These acid components may be used alone or in combination of two or more thereof, and further may be partially copolymerized with oxyacids such as hydroxybenzoic acid.

  Examples of the diol component include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, and 1,5-pentanediol. 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2-bis (4- Hydroxyethoxyphenyl) propane, isosorbate, spiroglycol and the like. Of these, ethylene glycol is preferably used. These diol components may be used alone or in combination of two or more.

The thermoplastic resin of the present invention is, for example, among the above polyesters, polyethylene terephthalate and its polymer, polyethylene naphthalate and its copolymer, polybutylene terephthalate and its copolymer, polybutylene naphthalate and its copolymer, Furthermore, it is preferable to use polyhexamethylene terephthalate and its copolymer, polyhexamethylene naphthalate and its copolymer, and the like.
Furthermore, for example, when the thermoplastic resin B of the present invention is a copolyester, it is preferable that the same basic skeleton as that of polyethylene terephthalate is included from the viewpoint of easily realizing a highly accurate laminated structure. Here, the basic skeleton is a repeating unit constituting the resin. For example, in the case of polyethylene terephthalate, ethylene terephthalate is the basic skeleton. If the A layer and the B layer, which are thermoplastic resins, are resins containing the same basic skeleton, the lamination accuracy is high and delamination at the lamination interface is less likely to occur.
Alternating in the present invention means that a thermoplastic resin A layer and a B layer are laminated in a regular direction such as A (BA) _n (n is a natural number) in the thickness direction.
As for the number of laminated layers of the polarizing reflector of the present invention, it is necessary that the A layer and the B layer are alternately 50 layers or more. This is because when the number of layers is less than 50, high reflectance cannot be obtained over a wavelength range of 400 nm to 700 nm in the reflection axis direction of the polarizing reflector. Preferably, it is 400 layers or more, More preferably, it is 800 layers or more. The laminated structure of 50 layers or more in the polarizing reflector of the present invention can be produced by the following method.
The laminated structure of the polarizing reflector used in the present invention can be easily realized by the same method as described in the paragraphs [0053] to [0063] of JP-A-2007-307893. However, the gap and length of the slit plate are different because of design values that determine the layer thickness.
In the polarizing reflector of the present invention, a polarizing reflector 4 having an achromatic color and excellent polarization characteristics is composed of only one multilayer laminated portion 1 as shown in FIG. On the other hand, in the conventional polymer reflective polarizer 3 shown in FIG. 1A, 3 to 4 multilayer laminated portions 1 having different thicknesses are bonded via an adhesive material 2. Here, the multilayer laminated portion refers to a portion where the resin A and the resin B are alternately laminated and does not contain a third component such as an adhesive material. Hereinafter, a process of making a laminated structure will be described with reference to FIG.
The laminating apparatus 7 shown in FIG. 2 has the same three slit plates as the apparatus described in Japanese Patent Application Laid-Open No. 2007-307893. An example of the layer thickness distribution of the laminated structure obtained by the laminating apparatus 7 is shown in FIG. When the horizontal order is the layer arrangement order 18 and the vertical axis is the thickness (nm) 19 of each layer, the laminated structure is formed by the inclined structure 11 and the slit plate 72 of the layer thickness by the resin laminate flow formed by the slit plate 71. The inclined structure 12 of the layer thickness by the laminated flow of the formed resin and the inclined structure 13 of the layer thickness by the laminated flow of the resin formed by the slit plate 73 are provided. Moreover, as shown in FIG. 3, it is preferable that one inclined structure is opposite in direction to any other inclined structure. Furthermore, from the viewpoint of suppressing a flow mark due to an unstable phenomenon of the resin flow, a thick film layer 20 having a thickness of 1 μm or more is provided on the outermost layer. In addition, the inclined structure formed by one slit plate is composed of a layer thickness distribution 21 of resin A and a layer thickness distribution 22 of resin B, and the lamination ratio is the extrusion of resin A and resin B of two extruders. It can be easily adjusted by the ratio of the amounts. The lamination ratio is determined by the ratio of the total thickness of the resin A layer and the total thickness of the resin B layer excluding the thick film layer. Each layer thickness is calculated | required by observing a lamination | stacking cross section with a transmission electron microscope. From the viewpoint of exhibiting high reflection performance in the reflection axis, the lamination ratio is preferably 0.7 to 1.4. In the present invention, from the viewpoint of achieving high elongation, the lamination ratio is more preferably 0.7 to 0.9 so that the volume ratio of the amorphous thermoplastic resin B layer is high. The range of the layer thickness formed from each slit plate is a flow rate that flows through each slit of the slit plate so that the average layer thickness is in the range of 50 nm to 170 nm in order to strongly reflect light in the entire visible light range. Is adjusted by its length and gap. Moreover, since the thickness of each layer also changes proportionally by adjusting the overall thickness, the absolute value of the layer thickness can be adjusted. More preferably, it is 50 nm-150 nm. In addition, the average layer thickness here is an average of the layer thicknesses of the adjacent A layer and B layer. For example, in the layer thickness distribution of 903 layers, B1, A1, B2, A2, B3,..., A450, B451 and the respective layers in the remaining 901 thin film layers excluding the outermost two thick film layers. Are arranged, the average layer thickness distribution is the layer thickness distribution obtained by sequentially plotting the average of Bm and Am (m is an integer), such as the average of B1 and A1, and the average of B2 and A2. Become.
As shown in FIG. 2B, the resin flow having a laminated structure that flows out from each slit plate constituting the laminating apparatus 7 flows out from the outlets 11L, 12L, and 13L of the laminating apparatus, and then the merger 8 Then, rearrangement is performed in the cross-sectional shapes of 11M, 12M, and 13M shown in FIG. Next, the length in the film width direction of the cross section of the flow path is widened inside the connecting pipe 9 and flows into the base 10, and further widened by the manifold and extruded from the lip of the base 10 into a sheet in a molten state. Then, it is cooled and solidified on the casting drum to obtain an unstretched film. Here, the value obtained by dividing the film width direction length 17 of the base lip, which is the widening ratio inside the base, by the length 15 in the film width direction at the inlet of the base is set to 5 or less, so that lamination by widening is performed. A polarizing reflector, which is a multilayer laminated film that suppresses disturbance and has a uniform reflectance and reflection band in the film width direction, is obtained. More preferably, the widening ratio is 3 or less.
Subsequently, the method of extending | stretching at the temperature more than the glass transition point temperature (Tg) of resin which comprises an unstretched film is employ | adopted. The stretching method at this time is preferably adopted from a known uniaxial stretching method, sequential biaxial stretching method, or simultaneous biaxial stretching method from the viewpoint of realizing high polarization characteristics and thermal dimensional stability. The known uniaxial stretching method is a method of stretching in the longitudinal direction, the method of stretching in the width direction, and the known biaxial stretching method is a method of stretching in the longitudinal direction and then stretching in the width direction, and stretching in the width direction. A method of stretching in the longitudinal direction may be performed later, and stretching in the longitudinal direction and stretching in the width direction may be combined multiple times. For example, in the case of a stretched film composed of polyester, the stretching temperature and the stretching ratio can be appropriately selected. In the case of a normal polyester film, the stretching temperature is 80 ° C. or higher and 130 ° C. or lower, and the stretching ratio is 1 time. It is preferably 7 times or more. The stretching method in the longitudinal direction is performed using a change in the peripheral speed between the rolls. Moreover, the well-known tenter method is utilized for the extending | stretching method of the width direction. That is, the film is conveyed while being held at both ends by a clip and stretched in the width direction. In the simultaneous biaxial stretching method, the film is conveyed while being gripped at both ends by a simultaneous biaxial tenter and stretched simultaneously and / or stepwise in the longitudinal direction and the width direction. Stretching in the longitudinal direction is achieved by increasing the distance between the clips of the tenter and in the width direction by increasing the distance between the rails on which the clips run. The tenter clip subjected to stretching and heat treatment in the present invention is preferably driven by a linear motor system. In addition, there are a pantograph method, a screw method, etc. Among them, the linear motor method is excellent in that the stretching ratio can be freely changed because the degree of freedom of each clip is high.
From the viewpoint of imparting polarization characteristics, the polarizing reflector of the present invention preferably employs film forming conditions for a stretched film having strong uniaxial anisotropy for the stretching ratio, stretching temperature, and heat treatment temperature. For example, in the case of a uniaxially oriented polyester film, the film is stretched at a stretching temperature of 90 ° C. to 100 ° C. and a stretching ratio of 4 to 7 times in the film longitudinal direction or the width direction, and the stretched film is heat treated at 170 to 250 ° C. in a tenter. Preferably it is done. Furthermore, it is also preferable to perform a relaxation heat treatment of about 2 to 10% in the width direction or the longitudinal direction in order to impart thermal dimensional stability of the film. On the other hand, in the case of a biaxially oriented polyester film, from the viewpoint of improving the elongation at break while maintaining the polarization characteristics, the stretching temperature is 100 ° C. to 130 ° C. and the stretching ratio is 3.2 times in order to suppress the orientation in the film longitudinal direction as much as possible. It is preferable that the stretching temperature is 90 ° C to 100 ° C, the stretching ratio is 4 times or more and less than 6 times, and the heat treatment temperature is 210 ° C to 240 ° C. In order to make the orientation angle of the film width as uniform as possible, it is also preferable to provide an intermediate cooling zone of 70 ° C. or less after the stretching in the width direction.
The thickness of the polarizing reflector of the present invention is determined from the balance between the thickness of each layer and the total number of laminated layers, and is preferably 50 μm to 200 μm from the viewpoint of realizing moldability, appropriate supportability, and high polarization characteristics. The polarizing reflector of the present invention must satisfy the following formulas (1) to (3).

Rmin ≦ 40% (1) Formula Rmax ≧ 60% (2) Formula Λmd ≧ 7% (3) where Rmin and Rmax are polarized reflectors having a wavelength of 550 nm. Are the minimum value (Rmin) and maximum value (Rmax) of the reflectance (%) when the polarizing reflector is irradiated with an incident angle of 0 ° and the polarizing reflector is rotated about the incident optical axis halfway. The direction indicating the minimum value (Rmin) of the reflectance is referred to as the transmission axis, and the direction indicating the maximum value (Rmax) is referred to as the reflection axis. The reflectance can be measured with a spectrophotometer or a spectrocolorimeter. Light polarized by using a polarizer is incident perpendicularly to the surface of the polarizing reflector, and the reflectance is measured. At this time, by rotating the polarizer by 180 degrees by 5 degrees, the reflectance of the light whose polarization direction is rotated by 5 degrees with respect to the fixed polarizing reflector is measured. The minimum reflectance Rmin is preferably 30% or less from the viewpoint of improving the brightness of the LCD. More preferably, it is 20% or less. The refractive index difference between the resin A layer and the B layer in the direction showing the minimum value of the polarizing reflector is adjusted to 0.02 or less, more preferably 0.01 or less, and further preferably 0.005 or less. it can. This is achieved by appropriately selecting the optimum resin for the A layer and the B layer, the stretching temperature, the stretching speed, and the heat treatment temperature. Specifically, a resin in which the refractive index of the non-oriented state of the A layer and the B layer is the same or the refractive index of the B layer is higher than the A layer by 0.001 or more and 0.01 or less is selected. Preferably, it is 0.003 or more and 0.006 or less. On the other hand, the maximum reflectance (Rmax) is preferably 80% or more from the viewpoint of improving the brightness of the LCD. More preferably, it is 90% or more. Selection of a resin combination in which the difference in refractive index between the resin A layer and the B layer in the direction showing the maximum value of the polarizing reflector is 0.08 or more, more preferably 0.1 or more, and further preferably 0.12 or more. And can be adjusted by the film forming conditions. As film forming conditions for imparting these refractive index differences, when the A layer is polyethylene terephthalate and the B layer is a copolymer thereof, the stretching temperature is 90 ° C. or more, and the stretching ratio is 5 times or more and less than 7 times. Preferably, the heat treatment temperature can be achieved by performing a heat treatment at 230 ° C. to 240 ° C. The polarizing reflector of the present invention satisfies the formula (3). Since the conventional reflective polarizer has few entanglement nodes in the transmission axis direction (direction orthogonal to the stretching direction) in both the A layer and the B layer, the formula (3) cannot be satisfied. The reason for this is that by setting a high draw ratio in only one direction and a low heat treatment temperature below 200 ° C., the orientation of molecular chains in the reflection axis direction (stretching direction) proceeds extremely, and the molecular chains in the transmission axis direction are entangled. I think that the node is gone. An entangled knot can be a knot of polymer chains by pulling randomly entangled polymer chains. This knot is entangled and called a knot, and the elasticity of the polymer chain is born between the knots. The polarizing reflector of the present application is designed based on the technical idea of inducing this entangled node point in the transmission axis direction. Specifically, in the present invention, in the uniaxially stretched film, a high heat treatment temperature has been impossible due to thermal crystallization with a low surface magnification. By increasing the volume fraction of the layer and setting the heat treatment temperature to 230 ° C. or higher, the B layer is completely melted, and the orientation of the reflection axis is completely lost, so that this entangled node can be induced in the transmission axis direction. . The A layer maintains a high alignment state in order to impart polarization characteristics, but the non-orientation of the B layer leads to an increase in elongation. Another means is to induce entangled nodes in the transmission axis direction without sacrificing polarization properties as much as possible. In other words, the idea is to increase the entanglement nodes without increasing the orientation of the molecular chain of the transmission axis. Specifically, the stretching is performed at a stretching temperature at which the molecular chain is relaxed, and the fine stretching is performed in several steps. That is. This high-temperature multiple times of micro-stretching entangles the joints without raising the orientation. However, since the refractive index of the crystalline A layer side in the transmission axis direction slightly increases after heat treatment, the non-crystalline B layer should be selected in advance with a resin B that matches the increasing refractive index of the A layer side. Thus, an increase in the elongation in the transmission axis direction is achieved without sacrificing the polarization characteristics as much as possible. Furthermore, as another means, this entanglement node is artificially induced by crosslinking with an additive. The network structure of molecular chains is formed by cross-linking, and entangled nodes are formed in the direction of the transmission axis, so that the elongation is improved. Furthermore, as another means, an amorphous resin is administered to the crystalline A layer side, so that the amorphous resin is dispersed in the orientation crystallized state of the A layer, and an entangled nodal point is induced. However, it is somewhat effective in improving elongation. The present invention aims at a more specific achievement means based on the above technical idea. The polarizing reflector of the present invention has a breaking elongation in an orientation showing a minimum value (Rmin) of reflectivity from the viewpoint of film breakage in the manufacturing process and handling property when used as an LCD backlight member. Satisfies 15% or more. More preferably, it is 30% or more. As a method for achieving the above, low magnification and high-temperature multistage stretching in the film longitudinal direction (transmission axis direction) in the sequential biaxial stretching method is optimal from the viewpoint of improving the elongation by imparting molecular chain entanglement. The total draw ratio is 3 times or less, more preferably 2.4 times or less, and even more preferably 2 times or less. The number of stretching is preferably 2 times or 3 times from the viewpoint of improving elongation and uneven thickness. From the viewpoint of imparting a little orientation in order to improve the elongation in the transmission axis direction while maintaining the polarization characteristics, the stretching temperature is preferably a glass transition point + 30 ° C. or higher and a crystallization temperature −10 ° C. or lower. In the case of a polyester film, it is preferably 100 ° C. or higher and lower than 120 ° C. On the other hand, from the viewpoint of improving elongation by relaxing the orientation of molecular chains, an amorphous material containing at least one component selected from a cyclohexanedimethanol component, a dimer acid component, and an isophthalic acid component that accelerates the orientation relaxation. This is achieved by adding a copolyester having a hydrophilic property to the A layer or the B layer. It can also be achieved by incorporating a pseudo-crosslinked structure by adding an additive containing an acrylic / styrene component having an epoxy group.

  The saturation C * of the transmitted light of the polarizing reflector of the present invention needs to be 5 or less. If it exceeds 5, the white color of the fluorescent tube is discolored when used for the backlight of the LCD, and the color rendering property of the display unit is deteriorated. More preferably, it is an achromatic color of 3.5 or less. The achievement method uses a laminated apparatus having a refractive index difference between the resin A layer and the B layer on the reflection axis and having three slit plates similar to the apparatus described in Japanese Patent Application Laid-Open No. 2007-307893. However, this can be achieved by setting the layer thickness distribution of the polarizing reflector having the three inclined structures shown in FIG.

The polarizing reflector of the present invention has a microwave refractive index of 1.74 to 1.84 in an orientation showing the minimum reflectance (Rmin), and a microwave in an orientation showing the maximum reflectance (Rmax). The refractive index is preferably 1.84 to 1.9. If the microwave refractive index in the orientation showing the minimum reflectance (Rmin) is less than 1.74, the self-supporting property becomes weak, and if it exceeds 1.84, 1. 76-1.8 is more preferable. On the other hand, if the microwave refractive index in the orientation showing the maximum value (Rmax) of the reflectance is less than 1.84, the polarization characteristics are deteriorated, and if it exceeds 1.9, the orientation is strong and easily broken. 1.845 to 1.885 are more preferable. The method for achieving this is, for example, by using a crystalline polymer mainly composed of polyethylene terephthalate in the A layer and an amorphous polymer that is a copolyester mainly composed of ethylene terephthalate in the B layer, and stretching in the longitudinal direction of the film. The temperature is 100 ° C. to 120 ° C., the draw ratio is 1 to 3 times multi-stage stretch, the film width direction stretch temperature is 90 ° C. to 100 ° C., the stretch ratio is 4.5 to 6 times, and the heat treatment temperature is 210 ° C. or higher. It shall be 240 degrees C or less. Moreover, it is also preferable to provide a cooling zone of less than 70 ° C. in the film forming step from the viewpoint of suppressing bowing after the end of stretching.
The polarization degree of the polarizing reflector of the present invention is preferably 60% or more and 85% or less. Here, the degree of polarization P is represented by an average value of the degree of polarization ρ (λ) of each wavelength at wavelengths of 380 nm to 730 nm obtained according to the following equations (4) and (5).
P = Σρ (λ) / Δλ (4) Formula ρ (λ) = (Tmax−Tmin) / (Tmax + Tmin) × 100 (5) where Δλ is a wavelength section of a wavelength of 380 nm to 730 nm. Ρ (λ) is obtained over a wavelength interval for each wavelength of 1 nm. Tmax and Tmin are a maximum value (Tmax) and a minimum value (Tmin), respectively, of the transmittance (%) when the polarizing reflector is half-rotated about the incident optical axis.

If the degree of polarization is less than 60%, the luminance of the LCD backlight is slightly improved. On the other hand, if it exceeds 85%, it is preferably 65% or more and 80% or less from the viewpoint of decreasing the breaking elongation in the transmission axis direction.
The refractive index difference between the resin A layer and the B layer on the reflection axis of the polarizing reflector is 0.1 or more, more preferably 0.12 or more, and the refractive index difference between the resin A layer and the B layer on the transmission axis is 0.015. The ratio can be adjusted by selecting a combination of resins that is less than 0.005, more preferably less than 0.005, and film forming conditions. In order to achieve a high degree of polarization, it is preferable that the resin A layer is crystalline and the resin B is amorphous.

  The polarizing reflector of the present invention has a wavelength section of 400 nm to 400 nm from the viewpoint that it is necessary to guide the light to the display unit of the liquid crystal cell without changing the color even when receiving light from the LED or the fluorescent tube as the backlight member. A spectral reflection curve that is flat over 700 nm is preferred. From the viewpoint of preventing color change even with respect to the viewing angle, it is more preferable that the spectral reflection curve is flat over a wavelength range of 400 nm to 900 nm.

  In order to obtain a flat spectral reflection curve, the layer thickness distribution as shown in FIG. 3, that is, the layer thickness distribution of the resin A layer or the resin B layer has three or more inclined structures, and It is preferable that all the inclined structures are not inclined in the same direction and have a laminated structure. More preferably, it has six or more inclined structures.

  It is preferable that a plurality of slits having the same slit length and slit gap exist over at least 200 slits between the three slit plates of the laminating apparatus 7. More preferably, it is 300 or more. The slit length is the length of a comb tooth portion that forms a flow path for allowing resin to flow alternately through the resin A layer and the resin B layer within the slit plate. It is the distance from the resin inflow port to the slit gap to the tip of the comb tooth portion opened from the flow path of each layer.

  The layer thickness distribution indicating the inclined structure is composed of thin film layers. Here, the thin film layer refers to a layer having a layer thickness of 200 nm or less, and the thick film layer refers to a layer having a thickness of 1 μm or more. Moreover, as a method of obtaining an inclined structure, it is achieved by inclining the gaps and lengths of the slits inside the laminating apparatus. This can be achieved by monotonically increasing or decreasing the slit length and gap. In the present invention, it is preferable to obtain an inclined structure by adjusting the gap of the slit. Further, the inclination of the designed inclined structure is called the design inclination, and when the slit gap is the same, it can be expressed by the value of the longest slit length / the shortest slit length of the slit length of the slit plate. This value is preferably in the range of 2.6 to 1.7. More preferably, it is 2.4-2.

  Inclined structure means that the thickness difference between the adjacent resin layers is 50 nm or less in the distribution of the layer thickness of the thin film layer of the resin A layer or the resin B layer. It is a layer thickness group of A layer or B layer having a layer thickness distribution having a positive or negative slope in which the square of R is 0.5 or more.

  This will be described below with reference to FIG. In the layer thickness distribution 21 of the resin A layer shown in FIG. 3, only one of the inclined structures formed by the three slit plates has the inclination of the inclined structure opposite to the inclination of the other inclined structures. I understand that. In this way, by optimizing the inclination of the inclined structure and increasing the overlapping part of the layer thickness, the low reflection area is reduced over a long wavelength section, and the saturation C * of the transmitted light is also reduced from the viewpoint of flattening the spectral reflection curve. Can be small. The chroma C * is preferably 5 or less from the viewpoint of color rendering properties of the LCD display unit. More preferably, it is 3.5 or less.

  Therefore, the layer thickness distribution of FIG. 3 can obtain an achromatic polarizing reflector as compared with the conventional simple gradient in which the layer thickness changes monotonically over the entire thickness direction. The number of layer thicknesses of the overlapping portions is preferably 200 layers or more. More preferably, it is 300 layers or more.

  From the viewpoint of improving the breaking elongation in the transmission axis direction and the tearing strength in the reflection axis direction while maintaining a high degree of polarization, the polarizing reflector of the present invention has a diphenyldicarboxylic acid component, naphthalene dicarboxylic acid in the resin B layer. A copolyester containing at least one component selected from an acid component, a polyetherimide component, or a bisphenoxyethanol fluorene component is preferable. The copolymerization amount is preferably 5 mol% or more and 40 mol% or less. If it is less than 5 mol% or exceeds 40 mol%, the polarization characteristics are deteriorated, so that the improvement of the brightness of the LCD is suppressed. Therefore, it is preferable that it is 10 mol% or more and 30 mol% or less.

  For example, when the resin A layer is polyethylene terephthalate or polybutylene terephthalate, the resin B is preferably a copolymer thereof. Compared to these main skeleton components, diphenyldicarboxylic acid component, naphthalenedicarboxylic acid component, polyetherimide component, or bisphenoxyethanol fluorene component has a high electron density, so it is unstretched by copolymerization or alloying. Then, the resin B layer has a higher refractive index than the resin A layer. Further, since the glass transition point is high, film formation is possible even at a stretching temperature at which the orientation of the polyethylene terephthalate is easy to relax during co-stretching. In order to suppress reflection of polarized light of a component parallel to the transmission axis, the refractive index difference between the resin A layer and the B layer on the transmission axis is adjusted to less than 0.005 by providing orientation only on the resin A layer side. Can do. More preferably, it is 0.003 or less. Further, by imparting the orientation, the breaking elongation of the transmission axis and the tear resistance of the reflection axis are improved. A specific aspect is that the stretching temperature in the longitudinal direction of the film is 100 ° C. to 120 ° C. and the stretching ratio is 1 to 3 times to give a slight orientation to the transmission axes of the resin A layer and the B layer, Next, the orientation of the reflection axes of the A layer and the B layer is imparted by setting the stretching temperature in the film width direction to 90 ° C. to 110 ° C. and the stretching ratio to 4.5 to 6 times. When the stretching temperature in the machine direction is low and the stretching is performed once, the thickness becomes uneven, and the refractive index increases because the orientation is too strong, and the degree of polarization decreases. As a result, the luminance improvement rate of the LCD backlight decreases. Furthermore, when the resin B layer is crystalline, the resin B layer is melted and orientation relaxation occurs by setting the heat treatment temperature corresponding to the melting point or higher to 220 ° C. or higher and lower than 240 ° C. Therefore, the transmission axis can match the refractive indexes of the resin A layer and the B layer, and the reflection axis can take a large difference in refractive index. When the copolymerization amount is less than 5 mol%, the refractive index of the resin A layer and the refractive index of the resin B layer on the transmission axis cannot be matched. On the other hand, when the copolymerization amount is 40 mol% or more, the refractive index of the B layer becomes too high, so that the polarization degree of the polarizing reflector of the present invention becomes low and the effect on improving the luminance of the LCD backlight becomes small. Therefore, 10 mol% or more and 30 mol% or less are preferable.

  In the polarizing reflector of the present invention, the resin A layer preferably contains at least one component selected from a cyclohexanedimethanol component, a dimer acid component, and an isophthalic acid component. The copolymerization amount is preferably a copolyester contained in an amount of 1 mol% to 8 mol%. If it is less than 1 mol%, the elongation at break and tear resistance are not improved, and if it exceeds 8 mol%, the difference in refractive index between the resin A layer and the B layer on the reflection axis does not increase, so that a high degree of polarization is achieved. I can't do that. More preferably, they are 2 mol% or more and 5 mol% or less. Further, among these, a two-component copolymer polyester is more preferable.

The polarizing reflector of the present invention preferably has a thermal shrinkage rate of −0.5% or more and 1.5% or less when left for 30 minutes in an atmosphere of 150 ° C. From the viewpoint of thermal dimensional stability when used for a backlight member, −0.3 or more and 1% or less is preferable. The accomplishment method is that polyethylene terephthalate is used for the A layer and copolymer polyester is used for the B layer. Further, the stretching ratio of the reflection axis is 5 times or more by the tenter method, followed by intermediate cooling at 70 ° C., and further the heat treatment temperature is 230 ° C. This is achieved by applying a relaxation treatment in the film width direction of 2% to 5% at 240 ° C. or lower. The relaxation treatment is preferably performed at a temperature of 160 ° C to 70 ° C. In the intermediate cooling step, it is more preferable to perform a humidification treatment with a humidity of 50% or more for 1 second or more from the viewpoint of imparting dimensional stability.
The temperature of the tenter clip used in the tenter method here is circulated and cooled with a cooling fan and cooling water so as to be less than 75 ° C. even at a heat treatment temperature of 230 ° C. or higher. Since the film edge of the uniaxially stretched film was unstretched in the conventional film forming method, it was difficult to form a film at a high heat treatment temperature exceeding 180 ° C. because it thermally crystallized in the heat treatment step.

  The polarizing reflector of the present invention preferably contains an acrylic / styrene polymer having an epoxy group. Since the epoxy group reacts with the carboxyl group and the hydroxyl group at the molecular end of the copolymer polyester of the present invention to form a crosslinked structure, the elongation at break of the transmission axis and the tear resistance of the reflection axis are improved. The addition amount is preferably 0.1% by weight to 3% by weight. If it is too small, there is no effect, and if it is too large, the cross-linking reaction is severely caused to bleed out. 0.5 to 2% by weight is preferred.

  The tear strength of the polarizing reflector of the present invention is preferably 2 N / mm or more. When it is 2 N / m or more, film tearing in the film width direction (TD direction) between the tenter and the winder during the film forming process is reduced. More preferably, it is 3 N / mm or more. More preferably, it is 5 N / mm or more.

A display backlight unit comprising the polarizing reflector, backlight, diffuser and polarizer of the present invention is preferred. Here, the backlight is a fluorescent tube or LED, and the diffuser is a diffusion film or a diffusion plate. Moreover, a polarizer is a polarizing plate.
In particular, the polarizing reflector of the present invention is preferably used for an LCD backlight unit. Examples of the configuration of the backlight member include a reflector / fluorescent tube / diffusion plate and a direct-type backlight unit having a prism / polarized reflector / polarizer configuration, and the polarized reflector of the present invention has a viewpoint of improving luminance. From the viewpoint of improving the luminance of the fluorescent tube, the fluorescent tube is preferably disposed between the fluorescent tube and the polarizing plate.

  A film insert molded product obtained by integrally molding the polarizing reflector of the present invention and the resin molded body using the polarizing reflector of the present invention is preferable. Film insert moldings are generally manufactured by inserting a special film that has undergone design printing into a plastic mold, and then pouring the heat-fluidized molding material (injection resin) into the mold. It is an injection-molded product with integrated design film. The polarizing reflector of the present invention preferably has a film thickness of 70 μm or more and 200 μm or less from the viewpoint of easy insert molding. The film thickness of the present invention can be easily adjusted by adjusting the thickness of the thick film layer and the number of laminated layers, or by bonding with a transparent film having a different thickness. Furthermore, in order to improve the adhesiveness with the insert resin or the printed layer applied to the polarizing reflector of the present invention, acrylic, urethane, polyester, polyvinyl chloride on the surface of the polarizing reflector of the present invention in advance. An easy-adhesion layer such as a vinyl acetate copolymer resin may be formed.

Hereinafter, it demonstrates using the Example of the polarizing reflector of this invention.
[Methods for measuring physical properties and methods for evaluating effects]
The characteristic value evaluation method and the effect evaluation method are as follows.

(1) Layer thickness, number of layers, layered structure The layer structure of the film was determined by observation with a transmission electron microscope (TEM) for a sample obtained by cutting a cross section using a microtome. That is, using a transmission electron microscope H-7100FA type (manufactured by Hitachi, Ltd.), the cross section of the film was magnified 10000 to 40000 times under the condition of an acceleration voltage of 75 kV, a cross-sectional photograph was taken, the layer configuration and the thickness of each layer Was measured. In some cases, in order to obtain high contrast, a staining technique using a known RuO ₄ or OsO ₄ was used.

(2) Layer Thickness Calculation Method The TEM photographic image of about 40,000 times obtained in the item (1) was captured at an image size of 720 dpi using CanonScanD123U. Save the image to a personal computer as a bitmap file (BMP) or compressed image file (JPEG), and then use the image processing software Image-Pro Plus ver.4 (distributor Planetron Co., Ltd.) Was opened and image analysis was performed. In the image analysis process, the relationship between the thickness in the thickness direction and the average brightness of the area sandwiched between the two lines in the width direction was read as numerical data in the vertical thick profile mode. Using the spreadsheet software (Excel2000), the data of the position (nm) and the brightness was adopted in the sampling step 6 (decimation 6), and then numerical processing of a three-point moving average was performed. Furthermore, the obtained data whose brightness changes periodically is differentiated, and the maximum and minimum values of the differential curve are read by a VBA (Visual Basic for Applications) program. The layer thickness was calculated as the layer thickness. This operation was performed for each photograph, and the layer thicknesses of all layers were calculated. Of the obtained layer thickness, a layer having a thickness of 1 μm or more was defined as a thick film layer. The thin film layer was a layer having a thickness of 500 nm or less.

(3) A reflectance / transmittance measurement sample for incident light having a polarization component was cut out at 5 cm × 5 cm from the center in the film width direction. The reflectance and transmittance were measured with a basic configuration using an integrating sphere attached to a spectrophotometer (U-4100 Spectrophotometer) manufactured by Hitachi, Ltd. In the reflectance measurement, the measurement was performed using the sub-white plate of aluminum oxide attached to the apparatus as a reference. In the reflectance measurement and the transmittance measurement, the MD (Machine Direction) direction of the sample was set to the vertical direction, the former was placed behind the integrating sphere, and the latter was placed on the holder in front of the integrating sphere. In addition, a polarizer manufactured by the attached Grande Terra Co., Ltd. is installed, and linearly polarized light is incident on the sample perpendicularly at an azimuth angle in which the polarization component is rotated in 5 degree increments at 0 to 180 °, and reflection at a wavelength of 250 to 1500 nm. The rate was measured. Measurement conditions: slit is 2 nm (visible) / automatic control (infrared), gain is set to 2, and scanning speed is 600 nm / min. The reflectance R and transmittance T at an azimuth angle of 0 to 180 degrees were obtained. When measuring the reflection of the sample, it was painted black with Magic Ink (registered trademark) in order to eliminate interference caused by reflection from the back surface. From these measurement results, the minimum value (Rmin) and maximum value (Rmax) of the reflectance at a wavelength of 550 nm and the minimum value (Tmin) and maximum value (Tmax) of the transmittance were measured. In addition, the attached aluminum oxide was used for the sub white board.

(4) Elongation at break The elongation at break was measured at 25 ° C. and 65% RH using an Instron type tensile tester (Orientec Co., Ltd. film tensile strength automatic measuring device “Tensilon AMF / RTA-100”). The measurement was carried out in accordance with JIS-K7127. For each of the film width direction (MD direction: Machine Direction) and the film width direction (TD direction: Transverses Direction) from the central portion in the film width direction, a sample film having a width of 10 mm is subjected to a test length of 100 mm and a pulling speed of 200 mm / min. Tensile strength, elongation at break in the film longitudinal direction and width direction were determined. It was confirmed that the longitudinal direction and the direction of the minimum value (Rmin) of the reflectance coincided, and Λmd was obtained. The number of n was 5 times, and the average value was adopted.

(5) Color tone measurement sample was cut out from the central part in the film width direction at 5 cm × 5 cm, and a *, b * value in transmitted light was measured using CM-3600d manufactured by Konica Minolta Co., Ltd. The value was determined. CMA-103 attached to the apparatus was used for the white calibration plate. The saturation C ^* was calculated using the following formula (6). The chromaticness index a *, b * was calculated based on JIS Z8722 (2000) with F10 as the light source and 10 ° field of view.
Saturation C = √ (a * ^ 2 + b * ^ 2) Equation (6).

(6) The heat shrinkage rate sample was cut out from the central part in the film width direction in the longitudinal direction 150 mm × width direction 10 mm. This sample piece was left in an atmosphere of 23 ° C. and 60% RH for 30 minutes, and in that atmosphere, two marks were made at an interval of about 100 mm in the longitudinal direction of the film, and a Nikon universal projector (Model V-16A) was used. ) Was used to measure the interval between the marks, and the value was taken as A. Next, the sample is allowed to stand in an atmosphere of 150 ° C. under a load of 3 g for 30 minutes, and then cooled for 1 hour in an atmosphere of 23 ° C. and 60% RH. This was measured and designated as B. At this time, the thermal contraction rate was calculated from the following formula (7). For each of the film longitudinal direction (MD) and the width direction (TD), the n number was 3, and the average value was adopted.

       Thermal contraction rate (%) = 100 × (A−B) / A (7)

(7) Polarization degree Using the transmittance obtained by the measurement in the item (3), the polarization degree P was determined according to the following formulas (4) and (5). That is, it calculated | required as an average value of polarization degree (rho) ((lambda)) of each wavelength in wavelength 380nm -730nm.
P = Σρ (λ) / Δλ (4) Formula ρ (λ) = (T _max −T _min ) / (T _max + T _min ) × 100 (5) where Δλ is a wavelength of 380 nm. The wavelength section of ˜730 nm, and ρ (λ) is obtained over the wavelength section for each wavelength of 1 nm.

(8) Microwave refractive index The microwave refractive index was measured using a microwave molecular orientation meter with a sample cut out at a size of 10 × 10 cm from the center in the width direction of the film. The molecular orientation meter MOA-2001 (frequency: 4 GHz) manufactured by KS Systems (currently Oji Scientific Instruments) was used as the microwave molecular orientation meter. The microwave refractive index was measured in increments of 3 ° from 0 ° to 90 °, and the microwave refractive index having the highest and lowest values of the refractive index was obtained. The value having the highest refractive index is the reflection axis and TD direction, and the value having the lowest refractive index is the transmission axis and MD direction. The number of measurements was 5 and the average value was adopted.

(9) Luminance improvement rate The polarizing reflector used as a sample was cut out from the position of the center part of the film width direction by the size of 700 mm of longitudinal direction x 400 mm of width direction. Next, a 50% diffuser plate, a microlens sheet, a polarizing reflector, and a polarizing plate are placed in this order on a 32-inch direct backlight unit for evaluation (fluorescent tube diameter 3 mm, fluorescent tube pitch 20.5 mm, 19 lamps). And measured. Here, it arrange | positioned so that the longitudinal direction of a fluorescent tube and MD direction of the polarizing reflector of this invention may become a parallel relationship. After the fluorescent tube is turned on for 60 minutes to stabilize the light source, CA-2000 (Konica Minolta Co., Ltd.) is used, and the attached CCD camera is positioned 90 cm from the backlight surface in front of the backlight surface. The front luminance (cd / m ² ) was measured. First, the average front luminance was measured in a state where no polarizing reflector was installed (blank state). Then, the average front luminance was measured by installing a polarizing reflector between the microlens sheet and the polarizing plate. Under the present circumstances, it arrange | positioned in the state which made the longitudinal direction (MD) which is the transmission axis of a polarizing reflector correspond with the transmission axis of a polarizing plate. The luminance improvement rate was obtained by dividing the measured average front luminance by the front luminance in the blank state and multiplying by 100.

(10) Tear strength in the TD direction Measured using a heavy load tear tester (manufactured by Toyo Seiki). The sample has a rectangular size with A side length of 75 mm and B side length of 63 mm, and a 20 mm depth cut is made at the center of the A side and the remaining 43 mm is torn. The indicated value was read. The tear strength was a value obtained by dividing the tear force (N) obtained from the indicated value by the film thickness (mm). The measurement was performed using 10 samples, and the average value was adopted.

(11) Refractive index of thermoplastic resins A and B Measured according to JIS K7142 (1996) A method.

(12) Evaluate the crystallinity of Resin A and Resin B by weighing 5 mg with an electronic balance, sandwiching them with aluminum packing, and measuring with a Seiko Instruments Inc. The analysis was performed according to JIS-K-7122 (1987) using a disk session SSC / 5200 manufactured by the same company. From 25 ° C to 300 ° C, 20 ° C / min. The temperature was raised at 25 ° C. and kept in the molten state for 5 minutes, then rapidly cooled and again from 25 ° C. to 300 ° C. at 20 ° C./min. The temperature was raised. At this time, the crystallinity was determined based on the presence or absence of a crystallization peak. That is, if the crystallization enthalpy (ΔHcc) was 6 J / g or less, it was judged to be amorphous, and if it was 6 J / g or more, it was judged to be crystalline.

(13) Film-forming stability The film breakage between the tenter and the winder was evaluated according to the following criteria. The process of winding the product through the film through the biaxial turret type winder, winding the winder, and performing edge trimming with a cutter was performed five times. The winding conditions around the winder were the same each time.

  ○: No film tearing occurred.

  Δ: Film breakage occurred once or twice.

  X: Film tear occurred 3 times or more.

(Thermoplastic resin)
The following were prepared as the thermoplastic resin A.
(Resin A-1) To a mixture of 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol, 0.09 part by weight of magnesium acetate and 0.03 part by weight of antimony trioxide are added with respect to the amount of dimethyl terephthalate. Transesterification is performed by heating and raising the temperature by a conventional method. Subsequently, 0.020 part by weight of 85% aqueous phosphoric acid solution is added to the transesterification product with respect to the amount of dimethyl terephthalate, and then the polycondensation reaction layer is transferred. Further, the reaction system was gradually depressurized while being heated and heated, and a polycondensation reaction was performed at 290 ° C. under a reduced pressure of 1 mmHg by a conventional method to obtain polyethylene terephthalate having IV = 0.63. Refractive index 1.58.
(Resin A-2) Polyethylene terephthalate obtained by adding 3% by weight of ARUFON XGM-4042 to the polyethylene terephthalate of resin A-1. Refractive index 1.58.
(Resin A-3) Polyethylene naphthalate having IV = 0.43 obtained by polycondensation of naphthalene 2,6-dicarboxylic acid dimethyl ester (NDC) and ethylene glycol (EG) by a conventional method.
Refractive index 1.65.
(Resin A-4) A polymer alloy obtained by blending 80 parts by weight of polyethylene terephthalate of resin A-1 and 20 parts by weight of resin B-1. Refractive index 1.58.
(Resin A-5) A polymer alloy obtained by blending 90 parts by weight of polyethylene terephthalate of resin A-1 and 10 parts by weight of resin B-5. Refractive index 1.58.
(Resin A-6) Polybutylene terephthalate Refractive index 1.57.

On the other hand, as the thermoplastic resin B, the following were prepared.
(Resin B-1) Polyethylene terephthalate copolymerized with IV = 0.75 (cyclohexanedimethanol (CHDM) 30 mol%). Refractive index 1.575.
(Resin B-2) Polyethylene terephthalate copolymerized with IV = 0.73 (4,4′-diphenyldicarboxylic acid (DfDC) 20 mol%). Refractive index 1.595.
(Resin B-3) Polyethylene terephthalate copolymerized with IV = 0.72 (10 mol% of bisphenoxyethanol fluorene component). Refractive index 1.6.
(Resin B-4) A polymer alloy obtained by blending 30 parts by weight of polyetherimide and 70 parts by weight of resin B-1. Refractive index 1.6
(Resin B-5) Polyethylene terephthalate copolymerized with dimer acid 10 mol% and isophthalic acid 7 mol%. Refractive index 1.57
(Resin B-6) Polyethylene terephthalate copolymerized with (naphthalene 2,6-dicarboxylic acid 30 mol%). Refractive index 1.605
(Resin B-7) A polymer alloy obtained by blending 80 parts by weight of polyethylene terephthalate copolymerized with 30 mol% of naphthalene 2,6-dicarboxylic acid and 20 parts by weight of resin B-5. Refractive index 1.595
(Resin B-8) A polymer alloy obtained by blending 90 parts by weight of resin B-1 and 10 parts by weight of resin B-5. Refractive index 1.575
(Resin B-9) Copolymerized polyethylene terephthalate obtained by adding 3% by weight of ARUFON XGM-4042 (manufactured by Toagosei) to the resin B-1. Refractive index 1.58
(Resin B-10) Polyethylene naphthalate copolymerized with 30 mol% of terephthalic acid. Refractive index 1.65.
In addition, 0.02 parts by weight of colloidal silica particles having an average particle diameter of 1.2 μm are added to the thermoplastic resin A with respect to 100 parts by weight of the thermoplastic resin A, while the thermoplastic resin B contains no particles. It was. The resins used in the examples and comparative examples were combined as shown in Table 2. In addition, the thermal measurement of the polymer was performed in advance using a thermal differential scanning meter, and it was confirmed that the thermoplastic resin A was crystalline and the thermoplastic resin B was amorphous.

[Example 1]
Resins A-1 and B-3 were respectively charged into two single-screw extruders, melted at 280 ° C., and kneaded. Next, after passing through 5 sheets of FSS type leaf disk filters, the lamination ratio excluding the thick film layer of the film becomes thermoplastic resin A / thermoplastic resin B = 0.8 / 1 by a gear pump. 903 layers are laminated in a thickness direction by combining them in a 903 layer laminating apparatus that uses a total of 3 slit plates with 301 slit plates and 3 303 slit plates. It was set as the laminated body made. The method for forming a laminate was carried out according to the description in paragraphs [0053] to [0056] of JP-A-2007-307893. Since there is a confluence layer of the A layers, the number of gaps in the slit plate is 905. Here, all the slit lengths are constant, and only the slit gap is changed to make the layer thickness distribution an inclined structure. The resulting laminate had 452 layers of thermoplastic resin A and 451 layers of thermoplastic resin B, and had an inclined structure that was alternately laminated in the thickness direction. The target layer thickness distribution pattern calculated from the gap between the slit plates of the laminating apparatus is shown in FIG. The inclination at the time of design was designed so that each inclination structure 11, 12, 13 described in FIG. The slit gap was adjusted so that the thick film layer had a thickness 20 times that of the adjacent layer. Moreover, the value obtained by dividing the film width direction length 17 of the base lip, which is the widening ratio inside the base, by the length 15 in the film width direction at the inlet of the base was set to 2.5.

  Next, the laminate is supplied to a T-die and formed into a sheet, and then rapidly cooled and solidified on a casting drum whose surface temperature is maintained at 25 ° C. while applying an electrostatic applied voltage of 8 kV with a wire, and unstretched A film was obtained. This unstretched film was stretched at 115 ° C. by a longitudinal stretching machine at a first stage stretching ratio of 1.1 times, then stretched by 1.05 times, then 2.1 times, and slightly stretched in the longitudinal direction. Orientation was imparted to. Next, after guiding both ends to a tenter gripped by clips, 105 ° C, 5.5 times transverse stretching, 70 ° C intermediate cooling, 240 ° C heat treatment, about 3% TD relaxation at 150 ° C Thus, a laminated film having a thickness of 93 μm was obtained. In the intermediate cooling process, a humidification process with a humidity of 60% or more is performed for 1 second or longer, and the cooling temperature of the tenter is circulated with a cooling fan and cooling water so that the clip temperature of the tenter is less than 75 ° C. even at the heat treatment temperature. Yes. The results of measuring the physical properties of this film are shown in Table 1.

The layer thickness distribution at the center in the width direction of the obtained laminated film is such that the layer thickness of the thin film layer is 55 nm to 150 nm in 300 layers counted from the outermost layer side on both the front and back surfaces except for the outermost layer which is a thick film layer. All layers A and B had a sloped structure in which the layer thickness monotonously increased as shown in FIG.
These inclined structures have continuity in the layer thickness distribution of the thin film layer formed from each slit in the range where the thickness difference between adjacent resin layers is 50 nm or less, and the square of R by the least square approximation. Four layer thickness distributions having a thickness of 0.7 or more were formed.
The remaining 301 layers at the central portion in the film thickness direction also had an inclined structure in which the layer thickness of the thin film layer was entirely within the range of 60 nm to 155 nm and the layer thickness monotonously increased. Also for this inclined structure, the layer thickness distribution in which the difference in thickness between adjacent adjacent resin layer thicknesses is 50 nm or less and the square of R by the least square approximation is 0.7 or more is 2 One was formed.

  Each of them had a structure in which 903 layers of the thermoplastic resin A layer and the thermoplastic resin B layer were alternately laminated. It was confirmed that the layer thickness of the thin film layer belonged to the range of 50 nm to 155 nm over 901 of the 903 layers. The two thick film layers serving as the outermost layers were 1.5 μm. As a result of evaluating the laminated film, it was a polarizing reflector having the appearance of a half mirror. The physical property results are shown in Table 1. Table 2 shows various conditions.

  The obtained polarizing reflector was achromatic from the front. It was a film having polarization characteristics suitable for a display member. Moreover, the stable film formation was confirmed without the trouble of the film tearing between a tenter and a winder on manufacturing process management.

[Examples 2 to 4]
A polarizing reflector was obtained in the same manner as in Example 1 except that the content of the film forming conditions described in Table 2 was changed. The results are shown in Table 1. The obtained polarizing reflector was achromatic from the front. It was a film having polarization characteristics suitable for a display member. Moreover, the stable film formation was confirmed without the trouble of the film tearing between a tenter and a winder on manufacturing process management.

[Example 5]
The stretching for 3 times in the longitudinal stretching process of Example 1 was stopped and changed to 2 longitudinal stretching processes. Table 2 shows the changes in the film forming conditions. Example 1 was the same as in Example 2 except for the contents described in Table 2. The results are shown in Table 1. The obtained polarizing reflector is shown in Table 1. The obtained polarizing reflector was achromatic from the front. It was a film having polarization characteristics suitable for a display member. Moreover, the stable film formation was confirmed without the trouble of the film tearing between a tenter and a winder on manufacturing process management.

[Examples 6 to 12]
A polarizing reflector was formed only by lateral uniaxial stretching without performing longitudinal stretching. The film forming conditions were the same as in Example 1 except for the contents described in Table 2. The results are shown in Table 1. The obtained polarizing reflector was achromatic from the front. It was a film having polarization characteristics suitable for a display member. Moreover, the stable film formation was confirmed without the trouble of the film tearing between a tenter and a winder on manufacturing process management.

[Comparative Example 1]
A polarizing reflector was formed only by lateral uniaxial stretching without performing longitudinal stretching. The film forming conditions are shown in Table 2. Example 1 was the same as in Example 2 except for the contents described in Table 2. The results are shown in Table 1. In production process management, film breakage frequently occurred between the tenter and the winder, and stable film formation could not be performed.

[Comparative Example 2]
The extrusion temperature of Example 1 was changed to 300 ° C., and the same procedure as in Example 1 was performed except for the change in the film forming conditions described in Table 1. Table 1 shows the physical property results of the obtained polarizing reflector. Although the luminance improvement of the LCD backlight was good, film tearing frequently occurred between the tenter and the winder in terms of manufacturing process management, and stable film formation could not be performed.

[Comparative Example 3]
Using the same resin as in Comparative Example 1, the laminating apparatus 7 was changed, and an 801-layer feed block having a configuration in which two slit plates with 267 slits and two 269 slit plates in total were used. Using. The layer thickness pattern was a monotonous inclined structure in the thickness direction from the front surface to the back surface. Specifically, the design is such that the layer thickness distribution of FIG. 7 described in JP-A-2009-037235 is obtained. By using this laminating apparatus, a laminated body in which 801 layers were alternately laminated in the thickness direction was obtained. The design gradient for forming the thin film layer was 2.5 designs. The slit length is the same over the number of 100 slits between the slit plate that forms the thinnest thin film layer and the slit plate that forms the intermediate thin film layer. Between the slit plate forming the thickest thin film layer and the slit plate forming the intermediate thin film layer, the slit length is the same over the number of 30 slits. Here, the slit width (gap) was all constant, and only the length was changed. Further, the breakdown of the laminated structure is a laminated body having an inclined structure in which the thermoplastic resin A is composed of 400 layers and the thermoplastic resin B is composed of 401 layers alternately laminated in the thickness direction.

Next, in the merger 8, the laminated flow of 801 layers obtained by joining the laminated flows from the respective slit plates is widened, and the laminated body is supplied to a T-die and formed into a sheet shape. While applying an electrostatic applied voltage, it was rapidly cooled and solidified on a casting drum maintained at a surface temperature of 25 ° C. to obtain an unstretched film.

  This unstretched film is stretched by 2.8 times at 92 ° C. with a longitudinal stretching machine, guided to a tenter holding both ends with clips, and then stretched at 95 ° C. and 5.0 times, followed by an intermediate cooling zone at 70 ° C. Then, heat treatment was performed at 240 ° C., and about 3% TD relaxation was performed at 100 ° C. to obtain a polarizing reflector having a thickness of 80 μm. The layer thickness of layer number 1 which is the outermost layer was 1.7 μm, and the layer thickness of layer number 801 was 1.5 μm.

  In manufacturing process management, film breakage between the tenter and the winder did not occur frequently, and stable film formation was possible, but the coloration was severe, and the LCD backlight brightness improvement performance was insufficient. It was.

  The present invention relates to a polarizing reflector having both azimuth axes having different reflectivities in the same plane. More specifically, the present invention relates to a polarizing reflector suitable as a backlight member, a polarizing sunglasses, a polarizing filter, and an optical sensor member using polarized light for improving the luminance of the LCD. The polarizing reflector is a polarizing reflector suitable for display members, automobile members, anti-counterfeiting preparation members such as holograms, optical printing equipment, cameras, solar cell members, building materials, and the like, and molded articles thereof.

1: Multilayer laminated part 2: Adhesive material part 3: Reflective polarizer 4: Polarizing reflector 5: Film thickness direction 6: Film width direction 7: Laminating apparatus 71: Slit plate 72: Slit plate 73: Slit plate 8: Merger 9: Connecting pipe 10: Base 11: Layer thickness gradient structure formed by slit plate 71 12: Layer thickness gradient structure formed by slit plate 72 13: Layer thickness gradient structure 11L formed by slit plate 73 : Resin flow path 12L from the outlet of the slit plate 71: resin flow path 13L from the outlet of the slit plate 72: resin flow path 11M from the outlet of the slit plate 73: communicating with the outlet of the slit plate 71, Resin flow path 12M arranged by the recombiner: communicates with the outlet of the slit plate 72, and resin flow path 13M arranged by the merger: communicates with the outlet of the slit plate 73 to join Resin flow path 14 arranged in the width direction length of the resin flow path 15: length in the film width direction at the inlet of the base 16: cross section of the flow path at the inlet of the base 17: film of the base lip Width direction length 18: Layer arrangement order 19: Layer thickness 20: Point indicating thickness of thick film layer 21: Layer thickness distribution of resin A 22: Layer thickness distribution of resin B

Claims (9)

A layer made of a thermoplastic resin (A layer) and a layer made of a thermoplastic resin having a composition different from the resin constituting the A layer (B layer) are alternately laminated by 50 layers or more, and the following (1) to ( 3) A polarizing reflector satisfying the equation and having a transmitted light saturation C * of 5 or less.
Rmin ≦ 40% (1) Equation Rmax ≧ 60% (2) Equation Λmd ≧ 7% (3) Equation (where Rmin and Rmax are polarized light reflected at a wavelength of 550 nm) The minimum value (Rmin) and maximum value (Rmax) of the reflectance (%) when the surface of the body is irradiated at an incident angle of 0 ° and the polarizing reflector is rotated halfway around the incident optical axis. , Λmd is the elongation at break in the orientation showing Rmax.) The microwave refractive index in the direction showing the maximum reflectance (Rmax) is 1.84 to 1.9, and the microwave refractive index in the direction showing the minimum reflectance (Rmin) is 1.74 to 1. The polarizing reflector according to claim 1, which is .84. The polarizing reflector according to claim 1, wherein the polarization degree is 60% or more and 85% or less. The B layer is a copolyester containing at least one component selected from a diphenyldicarboxylic acid component, a naphthalene dicarboxylic acid component, a polyetherimide component, or a bisphenoxyethanol fluorene component. Polarized reflector. The polarizing reflector according to claim 1, wherein the A layer is a copolyester containing at least one component selected from a cyclohexanedimethanol component, a dimer acid component, and an isophthalic acid component. The polarizing reflector according to claim 1, which has a thermal shrinkage rate of −0.3% or more and 1% or less when left in a 150 ° C. atmosphere for 30 minutes. The polarizing reflector according to claim 1, comprising an acrylic / styrene component having an epoxy group. A backlight unit for display comprising the polarizing reflector according to any one of claims 1 to 7, a backlight, a diffuser, and a polarizer. The molded object using the polarizing reflector in any one of Claims 1-7.

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