JP5945131B2 - Method for producing optical multilayer film - Google Patents

Description

  The present invention relates to a method for producing an optical multilayer film in which a plurality of types of optical material layers are alternately laminated.

  As a conventional method for producing an optical multilayer film, for example, as described in Patent Document 1, a method for producing an optical multilayer film using a co-extrusion feed block and an ISG (boundary surface forming) apparatus is known. ing.

JP-A-4-278324

  By the way, in order to manufacture an optical multilayer film having a multilayer structure, it is necessary to set a long resin flow path in the film manufacturing apparatus. However, if the resin flow path becomes too long, the interface between the molten resin layers becomes wavy. It will be disturbed. As a result, the uniformity of the thickness of each optical material layer of the obtained optical multilayer film is lowered, so that the quality of the optical multilayer film becomes unstable. However, the above prior art does not consider such a problem at all.

  The objective of this invention is providing the manufacturing method of the optical multilayer film which can improve the layer thickness precision of each optical material layer of an optical multilayer film.

  The present invention is a method for producing an optical multilayer film in which a plurality of types of optical material layers are alternately laminated, and a plurality of types of melting are performed using a feed block having a plurality of manifolds for processing a molten resin into a sheet shape. Forming a resin laminate composed of 10 to 400 molten resin layers by forming a resin in a sheet shape by each manifold and laminating a plurality of types of molten resins alternately in that state; The step of forming an unstretched multilayer film in which the thickness of each molten resin layer is 300 nm to 2000 nm by thinning the resin laminate using a T-die, and heating and stretching the unstretched multilayer film, A step of forming an optical multilayer film in which the total number of optical material layers is 10 to 400, and the thickness of each optical material layer is 200 nm or less. It is an feature.

  In such a method for producing an optical multilayer film according to the present invention, a film is produced by forming a resin laminate composed of 10 to 400 molten resin layers using only a feed block having a plurality of manifolds. Since the resin flow path in the apparatus is prevented from becoming unnecessarily long, wavy disturbance at the interface between the molten resin layers is reduced. Thereby, the layer thickness precision of each optical material layer of an optical multilayer film can be improved.

  Preferably, the width and thickness of the manifold are set for each type of molten resin. In this case, the manifolds that process the same type of molten resin into a sheet form have the same width and thickness. For this reason, the thickness of the optical material layer of the same kind can be made uniform in the optical multilayer film.

  Preferably, the method further includes a step of forming a skin layer laminated on the resin laminate before supplying the resin laminate to the T-die. In this case, an optical multilayer film having a structure in which a skin layer is formed between each stack in which a plurality of types of optical material layers are alternately laminated, and an optical multilayer in which skin layers are formed on the lowermost layer and the uppermost layer The film can be easily manufactured by a series of flows.

  According to the present invention, the layer thickness accuracy of each optical material layer of the optical multilayer film can be improved. This makes it possible to produce an optical multilayer film with stable quality.

It is a side view which shows the optical multilayer film manufactured by one Embodiment of the manufacturing method of the optical multilayer film which concerns on this invention. It is a flowchart which shows the manufacturing process of the optical multilayer film shown in FIG. It is a perspective view which shows the feed block used in the manufacturing process shown in FIG. It is a schematic diagram which shows a mode that molten resin is multilayered in the feed block shown in FIG. FIG. 4 is a schematic diagram showing how molten resin that has come out of a resin introduction path flows through a manifold in the feed block shown in FIG. 3. It is a perspective view which shows simply the T die used in the manufacturing process shown in FIG. It is the schematic which shows a mode that a film is extended | stretched with a horizontal stretcher in the manufacturing process shown in FIG.

  Hereinafter, the manufacturing method of the optical multilayer film concerning this invention is demonstrated in detail with reference to drawings.

  FIG. 1 is a side view showing an optical multilayer film produced by an embodiment of the method for producing an optical multilayer film according to the present invention. In the figure, the optical multilayer film 1 can be applied to, for example, a liquid crystal display device.

  The optical multilayer film 1 is designed to have a reflection spectrum that matches the target reflection spectrum. The target reflection spectrum mainly reflects the first polarized light polarized in a specific direction in a predetermined wavelength range in the wavelength range of 400 nm to 700 nm, and depends on the wavelength in the wavelength range of 400 nm to 700 nm. Instead, the second polarized light polarized in the direction orthogonal to the specific direction is mainly transmitted. That is, the optical multilayer film 1 is a wavelength selective polarization separation film having a polarization separation function and a wavelength selection function. The predetermined wavelength band is, for example, a red wavelength band (430 nm ≦ λ ≦ 480 nm), a green wavelength band (510 nm ≦ λ ≦ 560), and a blue wavelength band (600 nm ≦ λ ≦ 660 nm).

  The optical multilayer film 1 has three stacks 2. A protective layer (skin layer) 3 is formed on the lower part of the lowermost stack 2 and on the upper part of the uppermost stack 2. A spacer layer (skin layer) 4 is interposed between each stack 2. Here, the stacking direction of the stack 2 is the z direction, and the directions orthogonal to the z direction are the x direction and the y direction.

  The stack 2 includes a plurality of basic blocks (basic pairs) 5 in which two types of optical material layers 5a and 5b are stacked in the z direction. The stack 2 is a stacked body in which a plurality of basic blocks 5 are stacked in the z direction, and has a structure in which optical material layers 5a and 5b are alternately stacked. The total number of optical material layers 5a and 5b in each stack 2 is 10 to 400 layers. The thickness of each of the three stacks 2 can be adjusted as appropriate according to the optical characteristics of the target optical multilayer film, and may be the same or different.

  FIG. 2 is a flowchart showing manufacturing steps of the optical multilayer film 1 described above. In FIG. 2, first, two types of resins are prepared, and these resins are melted and extruded by separate extruders (not shown) to transfer the two types of molten resins to the feed block 10 (see FIG. 3). (Step S101).

Here, a transparent thermoplastic resin is used as the resin. Examples of transparent thermoplastic resins include methacrylic resins (PMMA, etc.), polycarbonate resins (PC), ABS resins (acrylonitrile-styrene-butadiene copolymer resins), MS resins (methyl methacrylate-styrene copolymer resins), Polystyrene resin (PS), AS resin (acrylonitrile-styrene copolymer resin), polyolefin resin (polyethylene, polypropylene, etc.), cyclic polyolefin resin, polyester resin (polyethylene terephthalate, polyethylene naphthalate, etc.), polyethersulfone resin (PES) ), Polysulfone resin and the like.
Two types of resins are selected from these resins.

  At this time, it is preferable to combine resins that are compatible with each other (good compatibility) when the resins are formed in multiple layers from the viewpoint that an interface with less turbulence and less disturbance is obtained. For example, combinations such as PMMA and PC, MS and PC, PMMA and AS, and the like can be given.

  Furthermore, the combination of the same kind of resin from which a composition differs is preferable. For example, PEN and PET, PEN and PETG, coPEN and PET, coPEN and PETG, or MS which is a combination of two or more resins having different copolymer composition ratios (for example, methyl methacrylate / styrene = 6/4 and methyl methacrylate / Styrene = 8/2), combinations of PEN and coPEN, PET and PETG, PET and PCTG, and the like. Here, PETG and PCTG are both CHDM (cyclohexanedimethanol) -modified PET and have different CHDM ratios. coPEN is, for example, a copolymer of 2,6 naphthalene dicarboxylate methyl ester and dimethyl isophthalate and dimethyl terephthalate and ethylene glycol.

  In order to provide sufficient optical characteristics, a combination is selected such that the difference in refractive index is 0.01 or more, preferably 0.05 or more, more preferably 0.08 or more.

  In addition, when adding refractive index anisotropy to a specific layer, a combination of resins with a large absolute value of intrinsic birefringence, a combination of a resin with a large absolute value of intrinsic birefringence and a resin with a small absolute value, or intrinsic birefringence Select resin combinations that have different signs (positive and negative). Examples of the resin having a large intrinsic birefringence absolute value include PS, PC, and PET, and examples of the resin having a small intrinsic birefringence absolute value include PMMA.

  In order to provide sufficient refractive index anisotropy, a combination of resins having crystallinity, or a combination of a resin having crystallinity and a resin having almost no crystallinity is selected. Examples of the resin having crystallinity include SPS (syndiotactic polystyrene), PEN, and PET. Examples of the resin having almost no crystallinity include PMMA, PS, PC, PCTG, and PETG.

  As the extruder, a general one is used. Specifically, although not particularly illustrated, the extruder is provided to cover the screw, a screw for kneading the solid granular or molten resin by rotation, a hopper for supplying the resin to the screw, And a cylindrical cylinder having a heater portion for heating the resin. When it is necessary to knead the resin sufficiently, a twin screw extruder in which two screws are arranged in one cylinder is used.

  Next, two types of molten resin layers supplied alternately from different extruders are processed into a sheet shape by the feed block 10 (see FIG. 3) and stacked, whereby two or more molten resin layers are alternately stacked. A resin laminate is formed (step S102).

  As shown in FIG. 3, the feed block 10 has a plurality of manifolds 11 connected to the extruder. The manifold 11 is connected to the main manifold 12 via an extruder and a resin introduction path (not shown), and connected to the extruder via a resin introduction path 13 and is integrated with the main manifold 12. And a confluence manifold 14. The merge manifold 14 has a substantially bent shape. The manifolds 11 adjacent to each other are connected to different extruders. That is, different types of molten resins are supplied to the manifolds 11 adjacent to each other.

  The width and thickness of the manifold 11 are set for each type of molten resin that passes through the manifold 11. Accordingly, the manifold 11 through which the same type of molten resin passes has the same width and thickness, that is, the shape. In addition, you may make the width and thickness of all the manifolds 11 equal regardless of the kind of molten resin.

As shown in FIG. 4, the molten resin J ₁ supplied to the main manifold 12 is formed into a flat sheet shape in the main manifold 12. As shown in FIGS. 4 and 5, the molten resin J ₂ supplied to the merging manifold 14 located on the most upstream side among the merging manifolds 14 is formed into a flat sheet in the merging manifold 14. in, it joins the sheet-shaped molten resin J _1. Further, the merging manifold 14 molten resin J ₁ supplied to the merging manifold 14 located one downstream from the a state of being formed into flat sheet shape in the the merging manifold 14, the sheet-shaped molten resin J Merge to ₂ . Furthermore, the merging manifold melt resin J ₂ supplied to the merging manifold 14 located one downstream from 14, in a state of being formed into a flat sheet shape in the the merging manifold 14, the sheet-shaped molten resin J Merge to ₁ . Hereinafter, the sheet-like molten resin layers J ₁ and J ₂ are sequentially joined and laminated.

As a result, a resin laminate in which a plurality of molten resin layers J ₁ and J ₂ are alternately laminated is formed. At this time, a resin laminate is formed by the feed block 10 so that the total number of the molten resin layers J ₁ and J ₂ is 10 to 400 layers. Note that the ratio of the thicknesses of the molten resin layers J ₁ and J ₂ can be controlled by changing the ratio of the discharge amounts of the molten resins supplied from the two extruders.

  Next, by passing the resin laminate sent from the feed block 10 through the T-die 20 (see FIG. 6), the resin laminate is widened so that the width and thickness of each molten resin layer become desired values. Thinned to form an unstretched multilayer film (step S103). At this time, an unstretched multilayer film is formed such that the thickness of each molten resin layer is 300 nm to 2000 nm.

  As shown in FIG. 6, the T-die 20 has a resin introduction part 21 for introducing the resin laminate supplied from the feed block 10, and widens the width of the resin laminate introduced into the resin introduction part 21 and is a resin laminate. A manifold / preland portion 22 that reduces the thickness of the body and a die lip portion 23 that is provided downstream of the manifold / preland portion 22 and adjusts the thickness of the unstretched multilayer film extruded from the T die 20. .

  Here, in order to ensure the thickness accuracy of the obtained film, the dimensional accuracy of the manifold / preland portion 22 and the die lip portion 23 is important. The thickness fluctuation width is preferably suppressed to 50 nm or less with respect to the design thickness of one layer, and the dimensional accuracy of the manifold / preland portion 22 and the die lip portion 23 at that time is approximately 1/10 of the thickness fluctuation width. It is preferable to set to about １ ／. That is, it is preferable that the dimensional accuracy of the manifold / preland portion 22 and the die lip portion 23 is suppressed to a swing width of 5 nm to 10 nm or less. When there is a fluctuation width larger than this, the color unevenness of the transmitted light appears remarkably in the film plane.

  Furthermore, temperature control of the T-die 20 is important in order to stably maintain the film thickness accuracy. In this case, for example, the temperature variation (film width direction and change with time) of the die lip portion 23 is set to 10 ° C. or less, preferably 5 ° C. or less.

  Next, the unstretched multilayer film formed by the T die 20 is heated and stretched to form the stack 2 in which the thickness of each of the optical material layers 5a and 5b is 200 nm or less (step S104). Examples of the heat stretching method include longitudinal stretching, lateral stretching, and simultaneous biaxial stretching.

  In the longitudinal stretching, the film is stretched in the flow direction between a low-speed stretching roll and a high-speed stretching roll while the film is controlled to a predetermined temperature with a heating roll. At this time, a desired draw ratio can be obtained mainly by adjusting the rotation speed (ratio) of each draw roll. Moreover, the multistage extending | stretching method used as a desired magnification can also be used by using a some extending | stretching roll and raising a draw ratio gradually. Furthermore, the cooling rate between each extending roll can be adjusted with the distance between each extending roll. Further, in order to control the cooling temperature more precisely, the temperature can be kept using an external heat source such as an infrared heater.

  In the transverse stretching, for example, a transverse stretching machine 24 as shown in FIG. 7 is used. The transverse stretching machine 24 has a plurality of clips 25 that hold both ends of the film F, and a hot-air circulating heating furnace (not shown) that heats the film F. The film F is sent to the hot air circulation heating furnace in a state where both ends of the film F are held by the plurality of clips 25. And the film F comes to be extended | stretched in the width direction when the clip 25 drive | works on the rail 26 installed so that the width | variety may spread toward the advancing direction of the film F. FIG. At this time, a desired draw ratio can be obtained by adjusting the width between the rails 26.

  Biaxial stretching can be performed sequentially by performing transverse stretching after longitudinal stretching, but simultaneous biaxial stretching in the longitudinal and transverse directions is possible by using a pantograph method or the like for the clip used for transverse stretching. . When performing simultaneous biaxial stretching, a pantograph-type clip is used, and the clip traveling speed at the outlet of the hot air circulating furnace is further increased than the clip traveling speed at the inlet of the hot air circulating furnace in transverse stretching. At this time, by adjusting the width between the rails and the difference in clip traveling speed, desired stretching ratios can be obtained in the vertical and horizontal directions.

  As described above, the stack 2 in which the total number of the optical material layers 5a and 5b is 10 to 400 and the thickness of each optical material layer 5a and 5b is 200 nm or less is manufactured.

  At this time, before the resin laminate is guided to the T die 20, the molten resin forming the skin layer laminated on the resin laminate is supplied to the T die 20 through the dedicated resin flow path. The optical multilayer film 1 in which a plurality of stacks 2 and skin layers 3 and 4 are laminated may be manufactured in a lump. As the molten resin for forming the skin layer, a transparent thermoplastic resin (described above) is used in the same manner as the molten resin for forming the molten resin layer. In this case, unlike the case where the plurality of stacks 2 are separately manufactured and then the skin layers 3 and 4 are laminated on the stack 2, the optical multilayer film 1 can be easily manufactured in a series of flows.

  As described above, in this embodiment, only the feed block 10 is used to form a resin laminate having a relatively small number of molten resin layers of 10 to 400 layers. It is not necessary to set the resin flow path longer than necessary. For this reason, the interface between the molten resin layers is less likely to be disturbed in a wavy manner, and the uniformity of the layer film of each molten resin layer is prevented from being lowered. Thereby, the layer thickness precision of each optical material layer 5a, 5b of the optical multilayer film 1 can be improved. Thus, according to this embodiment, the optical multilayer film 1 with stable quality can be manufactured by a simple process. In addition, since the molten resin layer is multi-layered only by the feed block 10, the configuration of the film manufacturing apparatus can be simplified and the cost can be reduced.

  The present invention is not limited to the above embodiment. For example, in the above embodiment, the optical multilayer film 1 is manufactured by alternately laminating two different types of optical material layers 5a and 5b. However, the present invention is not limited to this, and three or more different types of optical material layers are alternately laminated. An optical multilayer film may be manufactured.

DESCRIPTION OF SYMBOLS 1 ... Optical multilayer film, 2 ... Stack, 3 ... Protective layer (skin layer), 4 ... Spacer layer (skin layer), 5a, 5b ... Optical material layer, 10 ... Feed block, 11 ... Manifold, 12 ... Main manifold, 14 ... Merge manifold, 20 ... T die, J ₁ , J ₂ ... Molten resin layer.

Claims (2)

A method for producing an optical multilayer film in which a plurality of types of optical material layers are alternately laminated,
Using a feed block having a plurality of manifolds that process the molten resin into a sheet shape, a plurality of types of molten resin are formed into a sheet shape by the respective manifolds, and in that state, the plurality of types of molten resins are alternately joined together. Forming a resin laminate composed of 10 to 400 molten resin layers,
The step of forming an unstretched multilayer film in which the thickness of each molten resin layer is 300 nm to 2000 nm by thinning the resin laminate using a T die,
Forming the optical multilayer film in which the total number of the optical material layers is 10 to 400 and the thickness of each optical material layer is 200 nm or less by heating and stretching the unstretched multilayer film; only including,
The number of laminated molten resin layers in the resin laminate corresponds to the number of manifolds,
The manufacturing method of an optical multilayer film, wherein the manifold has a width and a thickness set for each type of the molten resin . Wherein the resin laminate prior to being fed to the T-die method of optical multilayer film according to claim 1, further comprising a step of forming a skin layer is laminated to the resin laminate.

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