Method for manufacturing polarizing film

Abstract

To easily manufacture a polarization film.SOLUTION: A method of manufacturing a polarization film is a method of manufacturing the polarization film by drawing a flexible raw material film 11a, and comprises: a first drawing process of drawing a plane part 111 of the raw material film 11a in a first direction X along a plane direction of the plane part 111; and a second drawing process of moving first fixtures 21 and second fixtures 22 arranged alternately at intervals in the first direction X and holding the plane part 111 respectively, in mutually opposite directions in a direction along the plane direction and in a second direction Y crossing the first direction X so as to draw the plane part 111.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a polarizing film. In the law

Background Art

[0002] Patent Document 1 discloses a dimming device. The dimming device disclosed in Patent Document 1 includes two planar members arranged opposite to each other. The planar members have a plurality of unit polarization regions adjacent to each other. The planar member has a transparent substrate and a polarizer attached to the transparent substrate and constituting the unit polarization region. The polarization axes of the unit polarization regions adjacent to each other are different from each other. In the above dimming device, when one planar member is slid with respect to the other planar member, the overlapping state of the unit polarization region of the other planar member with respect to the unit polarization region of one planar member changes from a state where the polarization axes of each other are the same to a state where the polarization axes of each other are different. Thereby, the light transmittance of the dimming device can be changed.

[0003] Further, Patent Document 2 discloses a dimming device. The dimming device disclosed in Patent Document 2 includes two polarizing films arranged opposite to each other. The polarizing film is formed by subjecting a film body having permeability as a raw material of the polarizing film to a stretching treatment in a state where different surfaces of the film body are overlapped with each other. By the above stretching treatment, the direction of one polarization axis and the direction of another polarization axis among the portions adjacent to each other of the polarizing film become different.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the case of the planar material disclosed in Patent Document 1 (hereinafter referred to as polarizing film), the manufacturing process requires a step of attaching polarizers to a transparent substrate such that the polarization axes of adjacent unit polarization regions are different from each other. This makes the manufacturing process of the polarizing film complicated.

[0006] In the case of the polarizing film disclosed in Patent Document 2, the manufacturing process requires overlapping surfaces of different parts of the film. This results in creases at the boundaries between adjacent parts of the polarizing film. In other words, adjacent parts of the polarizing film are not smoothly connected. As a result, the optical properties of the polarizing film may be impaired due to these creases. [Means for solving the problem]

[0007] A method for manufacturing polarizing film to solve the above problems. Law Each aspect is described below. [Aspect 1] A method for manufacturing a polarizing film by stretching a flexible raw material film, comprising: a first stretching step of stretching a planar portion of the raw material film in a first direction along the planar direction of the planar portion; and a second stretching step of stretching the planar portion by holding the planar portion with first and second jigs that are alternately arranged at intervals in the first direction, and moving them in opposite directions in a second direction that is along the planar direction and intersects the first direction.

[0008] According to this configuration, in the first stretching step, the planar portion of the raw film is stretched in a first direction, thereby forming a polarization axis aligned with the first direction on the planar portion. Subsequently, in the second stretching step, the planar portion is stretched by holding it with a first jig and a second jig, which are alternately arranged with a gap between them in the first direction, and moving them in opposite directions in the second direction. As a result, the polarization axes of two adjacent regions in the first direction, sandwiched between the first and second jigs within the planar portion, are tilted to opposite sides. Consequently, a polarizing film can be obtained having a first and second region that are adjacent to each other in the first direction, alternately formed and smoothly connected, with the polarization axes of the first region and the second region tilted to opposite sides. Thus, the above polarizing film can be obtained simply by adding a second stretching step to the conventional first stretching step. Therefore, polarizing films can be easily manufactured.

[0009] [Aspect 2] A method for manufacturing a polarizing film according to embodiment 1, further comprising a supply step of supplying the flat portion by drawing out the raw material film from a roll of the raw material film prior to the first stretching step.

[0010] This configuration allows for the manufacture of polarizing film without cutting the raw material film roll. Therefore, it becomes possible to wind the polarizing film into a roll. Consequently, a roll-wound polarizing film can be obtained.

[0011] [Aspect 3] A method for manufacturing a polarizing film according to embodiment 1 or embodiment 2, wherein the first jig and the second jig are clamping devices that extend in the second direction and clamp the planar portion in the thickness direction, respectively.

[0012] With this configuration, the planar portion of the raw film is held in the thickness direction by the first and second jigs, and the planar portion is stretched by moving the first and second jigs in opposite directions. This makes it easy and precise to tilt the polarization axes of two adjacent regions in the first direction within the area of ​​the planar portion sandwiched between the first and second jigs to opposite sides.

[0013] [Aspect 4] A method for manufacturing a polarizing film according to any one of embodiments 1 to 3, wherein a plurality of the first clamping portions are arranged at equal intervals in the first direction, and a plurality of the second clamping portions are arranged at equal intervals in the first direction, and the second clamping portions are positioned at a distance equal to two adjacent first clamping portions in the first direction.

[0014] According to this configuration, a polarizing film can be obtained in which the lengths of the first region and the second region in the first direction are equal. [Aspect 5] A method for manufacturing a polarizing film according to embodiment 4, wherein in the second stretching step, each of the first jigs and each of the second jigs are moved by an equal distance in the second direction to stretch the planar portion.

[0015] According to this configuration, the inclination of the polarization axis in the first region with respect to the first direction can be made equal to the inclination of the polarization axis in the second region. 。 [Effects of the Invention]

[0017] According to the method for manufacturing a polarizing film according to the present invention, a polarizing film can be easily manufactured. 。 [Brief explanation of the drawing]

[0018] [Figure 1] Figure 1 is a plan view showing a polarizing film according to one embodiment. [Figure 2] Figure 2 is a cross-sectional view of the polarizing film shown in Figure 1. [Figure 3]FIG. 3 is a diagram showing the transmission state of a dimming device according to an embodiment. [Figure 4] FIG. 4 is a diagram showing the blocking state of a dimming device according to an embodiment. [Figure 5] FIG. 5 is a flowchart showing the manufacturing procedure of a polarizing film according to an embodiment. [Figure 6] FIGS. 6(a) and 6(b) are diagrams showing the states before and after the first stretching step of a polarizing film according to an embodiment. [Figure 7] FIGS. 7(a) and 7(b) are diagrams showing the states before and after the second stretching step of a polarizing film according to an embodiment. MODE FOR CARRYING OUT THE INVENTION

[0019] Hereinafter, referring to FIGS. 1 to 7, a polarizing film 10 and a manufacturing method thereof according to an embodiment will be described. First, referring to FIGS. 1 and 2, the configuration of the polarizing film 10 will be described.

[0020] As shown in FIG. 1, the polarizing film 10 of the present embodiment has a rectangular shape in plan view. As shown in FIG. 2, the polarizing film 10 has a film main body 11 made of polyvinyl alcohol dyed with an iodine solution, and a pair of fixing films 12 fixed in a state of sandwiching the film main body 11.

[0021] The fixing film 12 is preferably a film made of, for example, triacetyl cellulose, a so-called TAC film. Hereinafter, the thickness direction of the film main body 11 is simply referred to as the thickness direction Z, the direction orthogonal to the thickness direction Z is referred to as the first direction X, and the direction orthogonal to both the thickness direction Z and the first direction X is referred to as the second direction Y.

[0022] As shown in FIG. 1, in the present embodiment, the long side direction (the left-right direction in FIG. 1) of the polarizing film 10 coincides with the first direction X, and the short side direction (the up-down direction in FIG. 1) of the polarizing film 10 coincides with the second direction Y.

[0023] The film body 11 has a first region A1 and a second region A2 that are adjacent to each other and formed alternately in a first direction X. The first region A1 and the second region A2 are smoothly connected. There are no creases at the boundary between the first region A1 and the second region A2.

[0024] The first region A1 and the second region A2 are formed over the entire polarizing film 10 in the second direction Y. In this embodiment, the length L of the first region A1 in the first direction X is equal to the length L of the second region A2 in the first direction X. Therefore, the first region A1 and the second region A2 are rectangular regions in plan view that have the same shape and size.

[0025] The first region A1 has a first polarization axis pa1 that is inclined with respect to both the first direction X and the second direction Y. The second region A2 has a second polarization axis pa2 that is inclined with respect to both the first direction X and the second direction Y, and is inclined on the opposite side from the first polarization axis pa1.

[0026] The inclination angle α of the first polarization axis pa1 with respect to the virtual axis V extending in the first direction X is 45 degrees. The inclination angle β of the second polarization axis pa2 with respect to the virtual axis V is -45 degrees. Therefore, the first polarization axis pa1 and the second polarization axis pa2 are orthogonal.

[0027] As shown in Figures 3 and 4, the dimming device comprises two polarizing films 10 arranged to overlap each other. In Figures 3 and 4, the polarizing film 10 located in the foreground will be referred to as "polarizing film 10A," and the polarizing film 10 located in the background will be referred to as "polarizing film 10B."

[0028] Figure 3 shows a state in which the first region A1 of polarizing film 10A and the first region A1 of polarizing film 10B overlap, as well as the second region A2 of polarizing film 10A and the second region A2 of polarizing film 10B overlap. In Figure 3, the two polarizing films 10A and 10B are slightly offset in the first direction X to represent the overlapping of the two polarizing films 10A and 10B.

[0029] Light incident on the polarizing film 10A from outside the dimming device becomes linearly polarized light along the first polarization axis pa1 when it passes through the first region A1 of the polarizing film 10A, and becomes linearly polarized light along the second polarization axis pa2 when it passes through the polarizing film 10B.

[0030] In the state shown in Figure 3, all of the light incident on the polarizing film 10A from outside the dimming device that passes through the polarizing film 10A also passes through the polarizing film 10B. Figure 4 shows a state in which the first region A1 of polarizing film 10A and the second region A2 of polarizing film 10B are facing each other, and the second region A2 of polarizing film 10A and the first region A1 of polarizing film 10B are overlapping. In this state, the first polarization axis pa1 and the second polarization axis pa2 are orthogonal, so all the light transmitted through polarizing film 10A is blocked by polarizing film 10B.

[0031] Next, the manufacturing method of the polarizing film 10 will be described with reference to Figures 5 to 7. As shown in Figure 5, the manufacturing process for the polarizing film 10 includes a supply process, a dyeing process, a first stretching process, a second stretching process, a lamination process, and a winding process.

[0032] First, in the supply process, the flat portion 111 is supplied by pulling out the raw material film 11a from the rolled raw material film 11a using the feed roller of the conveying device. The raw material film 11a is a film made of polyvinyl alcohol and is flexible.

[0033] In this embodiment, the conveying direction of the raw material film 11a by the conveying device coincides with the first direction X, and the width direction of the raw material film 11a coincides with the second direction Y. Therefore, the first direction X is the direction along the plane direction of the planar portion 111, and the second direction Y is the direction along the plane direction of the planar portion 111 and is also perpendicular to the first direction X.

[0034] Next, in the dyeing process, the drawn raw material film 11a is dyed by impregnating it with an iodine solution. This causes iodine ions to chemically bond to the chain-like portions of the polyvinyl alcohol molecules that make up the raw material film 11a. It is preferable to perform a water washing process before and after the dyeing process. It is also preferable to perform the dyeing process multiple times. In this case, it is preferable to perform a water washing process between dyeing processes.

[0035] Next, in the first stretching step, the planar portion 111 is stretched in the first direction X, that is, in the transport direction of the raw material film 11a (see Figures 6(a) and 6(b)). In the first stretching step, it is preferable to stretch the planar portion 111 at a magnification m1 of 2 to 6 times. As a result, a polarization axis pa0 along the first direction X is formed in the raw material film 11a.

[0036] Next, in the second stretching step, the first jig 21 and the second jig 22 are arranged alternately with a gap between them in the first direction X. Then, the first jig 21 and the second jig 22 hold the flat portion 111 respectively and move them in opposite directions in the second direction Y, thereby stretching the flat portion 111.

[0037] The first jig 21 and the second jig 22 of this embodiment are clamping devices that extend in the second direction Y and clamp the planar portion 111 in the thickness direction Z, respectively (see Figure 7(a)). Multiple first jigs 21 are arranged at equal intervals in the first direction X. Similarly, multiple second jigs 22 are arranged at equal intervals in the first direction X. The second jigs 22 are positioned at a distance equal to two adjacent first jigs 21 in the first direction X. Each of the first jigs 21 and each of the second jigs 22 are moved by an equal distance in the second direction Y to stretch the raw film 11a (see Figure 7(b)). It is preferable to stretch the planar portion 111 at a magnification ratio obtained by multiplying the magnification ratio m1 in the first stretching step by √2. As a result, in one of the two adjacent regions of the flat portion 111, connected by the jig 21(22), a first polarization axis pa1 is formed, tilted at 45 degrees with respect to the first direction X, and in the other region, a second polarization axis pa2 is formed, tilted at -45 degrees with respect to the first direction X. After the second stretching process, the jigs 21 and 22 are removed from the flat portion 111. Then, the excess portions 112 formed on both sides of the flat portion 111 in the second direction Y are trimmed.

[0038] Next, in the lamination process, fixing films 12 are bonded to both sides of the flat portion 111. By fixing the fixing films 12 to both sides of the flat portion 111, shrinkage deformation of the film body 11, i.e., deformation of the polarization axes pa1 and pa2, is prevented.

[0039] Finally, in the winding process, the flat portion 111 is wound up to obtain a roll-wound polarizing film 10. Next, the operation of this embodiment will be described.

[0040] In the first stretching step, the planar portion 111 of the raw film 11a is stretched in the first direction X, thereby forming a polarization axis pa0 along the first direction X on the planar portion 111. Subsequently, in the second stretching step, the planar portion 111 is stretched by holding it with the first jig 21 and the second jig 22, which are alternately arranged at intervals in the first direction X, and moving them in opposite directions in the second direction Y. As a result, the polarization axes pa1 and pa2 of two adjacent regions A1 and A2 in the first direction X, which are sandwiched between the first jig 21 and the second jig 22, are tilted to opposite sides. Consequently, a polarizing film 10 can be obtained having a first region A1 and a second region A2 that are adjacent to each other and alternately formed in the first direction X, and which are smoothly connected, with the polarization axis pa1 of the first region A1 and the polarization axis pa2 of the second region A2 tilted to opposite sides.

[0041] Next, the operation of this embodiment will be described. (1) The method for manufacturing the polarizing film 10 comprises a first stretching step and a second stretching step. With this configuration, the above-mentioned effects are achieved, and the polarizing film 10 can be obtained simply by adding a second stretching step to the conventional first stretching step in the manufacturing process. Therefore, the polarizing film 10 can be easily manufactured.

[0042] (2) The method for manufacturing the polarizing film 10 further comprises a supply step prior to the first stretching step, in which the raw material film 11a is drawn out from the roll of raw material film 11a to supply the flat portion 111.

[0043] With this configuration, the polarizing film 10 can be manufactured without cutting the rolled raw material film 11a. Therefore, the polarizing film 10 can be wound into a roll. Thus, a rolled polarizing film 10 can be obtained.

[0044] (3) The first jig 21 and the second jig 22 are clamping devices that extend in the second direction Y and clamp the planar portion 111 in the thickness direction Z, respectively. With this configuration, the planar portion 111 of the raw film 11a is held between the first jig 21 and the second jig 22 in the thickness direction Z, and the planar portion 111 is stretched by moving the first jig 21 and the second jig 22 in opposite directions. This makes it easy and precise to tilt the polarization axes pa1 and pa2 of two adjacent regions A1 and A2 in the first direction X within the region of the planar portion 111 that is sandwiched between the first jig 21 and the second jig 22 to opposite sides.

[0045] (4) Multiple first jigs 21 are arranged at equal intervals in the first direction X. Multiple second jigs 22 are arranged at equal intervals in the first direction X. The second jigs 22 are positioned at a distance equal to two adjacent first jigs 21 in the first direction X.

[0046] With this configuration, a polarizing film 10 can be obtained in which the lengths L of the first region A1 and the second region A2 in the first direction X are equal. (5) The second stretching step stretches the planar portion 111 by moving each of the first jigs 21 and each of the second jigs 22 by an equal distance in the second direction Y. This makes it possible to make the inclination of the first polarization axis pa1 with respect to the first direction X equal to the inclination of the second polarization axis pa2.

[0047] (6) The polarizing film 10 comprises a film body 11 and a pair of fixed films 12. The film body 11 has a first region A1 and a second region A2. The first region A1 and the second region A2 are smoothly connected. The first region A1 has a first polarization axis pa1 that is inclined with respect to both the first direction X and the second direction Y. The second region A2 has a second polarization axis pa2 that is inclined with respect to both the first direction X and the second direction Y and is inclined on the opposite side from the first polarization axis pa1.

[0048] With this configuration, the polarizing film 10, formed by a stretching process, does not have creases at the boundary between the first region A1 and the second region A2. Therefore, while having a simple structure, it is possible to avoid the deterioration of optical properties caused by creases.

[0049] <Variation> This embodiment can be implemented with the following modifications. This embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0050] The fixing film 12 is not limited to a film made of triacetylcellulose, so-called TAC film, but can also be a film known as a TAC substitute material. In the second stretching step, the planar portion 111 may be stretched by moving each of the first jigs 21 and each of the second jigs 22 by different distances in the second direction Y. That is, the total value of the inclination angle α of the first polarization axis pa1 and the absolute value of the inclination angle β of the second polarization axis pa2 may be different.

[0051] Multiple first jigs 21 may be arranged at unequal intervals in the first direction X. Similarly, multiple second jigs 22 may be arranged at unequal intervals in the first direction X. That is, the length of the first region A1 in the first direction X and the length of the second region A2 in the first direction X may be different.

[0052] The first jig 21 and the second jig 22 are not limited to the clamping devices exemplified in the above embodiment, and may, for example, have multiple needle portions arranged at intervals in the second direction Y and piercing the flat portion 111.

[0053] The first stretching step and the second stretching step may be performed on the raw material film 11a, which has been cut into individual sheets. The second stretching step involves stretching the planar portion 111 of the raw film 11a by moving it in opposite directions in the second direction Y using the first jig 21 and the second jig 22. The second direction Y is a direction along the plane direction of the planar portion 111 and intersects the first direction X, but does not have to be perpendicular to the first direction X. [Explanation of Symbols]

[0054] 10, 10A, 10B… Polarizing film 11… Film body 11a... Raw material film 111...Plane part 112... Surplus 12…Fixed film 21...First jig 22...Second jig A1…First area A2…Second area pa1…First polarization axis pa2...Second polarization axis X…first direction Y...Second direction Z...Thickness direction

Claims

1. A method for producing a polarizing film by stretching a flexible raw material film, A first stretching step in which the planar portion of the raw material film is stretched in a first direction along the planar direction of the planar portion, The method comprises a second stretching step, in which the planar portion is stretched by holding the planar portion with first and second jigs that are alternately arranged at intervals in the first direction, and moving them in opposite directions in a second direction that is along the planar direction and intersects the first direction. A method for manufacturing polarizing films.

2. Prior to the first stretching step, the system further comprises a supply step of supplying the flat portion by drawing the raw material film from the rolled raw material film. A method for manufacturing a polarizing film according to claim 1.

3. The first and second jigs are clamping devices that extend in the second direction and clamp the planar portion in the thickness direction, respectively. A method for manufacturing a polarizing film according to claim 1.

4. Multiple of the first jigs are arranged at equal intervals in the first direction. Multiple of the second fixtures are arranged at equal intervals in the first direction. The second jig is positioned at a location where it is equal in distance from two adjacent first jigs in the first direction. A method for manufacturing a polarizing film according to any one of claims 1 to 3.

5. In the second stretching step, each of the first jigs and each of the second jigs are moved by an equal distance in the second direction to stretch the planar portion. A method for manufacturing a polarizing film according to claim 4.

Images