Abstract:
A method of manufacturing a laminate includes: a step of deriving, by the processor, an in-plane positional relationship between the retardation film and the object from an image of each of the retardation film and the object captured by the camera while the retardation film and the object are disposed in this order from a side of the camera within the imaging area of the camera at positions on a side opposite to the camera with respect to the (2n+1)λ/4 retardation film; and a step of performing alignment of the retardation film to the object based on the positional relationship derived by the processor, and then attaching the retardation film to the object.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
       [0001]    The present application claims priority to Japanese Priority Patent Application JP 2010-169555 filed in the Japan Patent Office on Jul. 28, 2010, the entire content of which is hereby incorporated by reference. 
       BACKGROUND 
       [0002]    The present application relates to a method of manufacturing a laminate with high alignment accuracy, and to a method of manufacturing a retardation film. In addition, the disclosure relates to a retardation film allowing improvement in alignment accuracy. 
         [0003]    Recently, a display capable of three-dimensional display has been increasingly developed. A three-dimensional display method includes, for example, a method where a right-eye image and a left-eye image are displayed on a display screen, and the images are viewed by a viewer wearing polarized glasses (for example, see Japanese Unexamined Patent Application Publication No. 2000-221461). The method is achieved by disposing a patterned retardation film on a front surface of a display capable of two-dimensional display, for example, a cathode-ray tube, a liquid crystal display, or a plasma display. The retardation film is patterned to have retardation or an optical axis at a display pixel level in order to control a polarization state of light incident to respective two eyes. It is therefore necessary to attach the retardation film to a display in correspondence to pixels of the display. 
         [0004]    When the retardation film is attached to a display panel or to a black stripe film, accurate alignment is necessary. Moreover, when the retardation film is manufactured of a roll base, the roll base needs to be accurately aligned to a punching machine. In the former case, for example, it is therefore conceivable that both the retardation film and the film are put with alignment marks, an image of each alignment mark be captured by a detection camera, and a relative positional relationship between the both be derived from the image. In the latter case, for example, it is conceivable that the roll base is put with an alignment mark, a plurality of detection cameras be fixed to the punching machine, an image of the alignment mark on the roll base be captured by a detection camera, and a relative positional relationship between the base and the punching machine be derived from the image. 
       SUMMARY 
       [0005]    A method of forming the alignment mark on an object conceivably includes, for example, a method where an alignment mark is added on a produced object by evaporation or printing, or a method where an object is produced using a marked member. However, when such a method is used for attaching the retardation film to the display panel, a retardation region of the retardation film is formed in a separate step from formation of the alignment mark. It is therefore necessary to perform accurate positioning of one while recognizing a position of the other in order to improve alignment accuracy. This disadvantageously results in a complicated manufacturing process or increase in number of steps. 
         [0006]    Thus, for example, both a patterned retardation region and an alignment mark region of a retardation film are conceivably collectively formed by transfer using a metal master having an irregular pattern so that the patterned retardation region and the alignment mark region of the retardation film are formed in one step. In such a case, alignment accuracy may be improved with a simple method and in a small number of steps. However, in such a case, a λ/4 retardation film and a polarizing plate need to be provided between a detection camera and the alignment mark region for image recognition of the alignment mark region. 
         [0007]    However, for example, when the retardation film is attached to the display panel, a protective film is beforehand attached to a surface of the retardation film to protect the surface from being damaged or stained. Similarly, when the retardation film is attached to a black stripe film, a protective film is beforehand attached to a surface of the retardation film. In addition, when the retardation film is manufactured of a roll base, a protective film is also beforehand attached to a surface of the roll base in the case of cutting the retardation film into a desired size. 
         [0008]    A PET film having high retardation is typically used for a base of the protective film. Polarization is therefore disturbed by the protective film, and therefore the detection camera hardly captures a clear image of the alignment mark. This disadvantageously leads to reduction in accuracy of position detection of the alignment mark, resulting in reduction in alignment accuracy. 
         [0009]    It is desirable to provide a method of manufacturing a laminate with high alignment accuracy, and a method of manufacturing a retardation film. In addition, it is desirable to provide a retardation film allowing improvement of alignment accuracy. 
         [0010]    A method of manufacturing a laminate according to an embodiment includes the following four steps. In the following, λ denotes, for example, a wavelength in a green range of about 500 to 560 nm. 
         [0011]    (A1) A first step of preparing equipment having one or more cameras and a processor processing an image captured by each of the cameras, and having a polarizing plate and a (2n+1)λ/4 retardation film (n is an integer of 0 or more) in this order from a camera side within an imaging area of the camera. 
         [0012]    (A2) A second step of preparing a retardation film having a retardation layer with a patterned retardation region including two or more kinds of retardation regions different in slow-axis direction from each other and having a protective film with a retardation of (n/2−0.14)λ or more and (n/2+0.14)λ or less, and preparing an object to be attached with the retardation film. 
         [0013]    (A3) A third step of deriving, by the processor, an in-plane positional relationship between the retardation film and the object from an image of each of the retardation film and the object captured by the camera while the retardation film and the object are disposed in this order from a camera side within an imaging area of the camera at positions on a side opposite to the camera with respect to the (2n+1)λ/4 retardation film. 
         [0014]    (A4) A fourth step of performing alignment of the retardation film to the object based on the positional relationship derived by the processor, and then attaching the retardation film to the object. 
         [0015]    In the method of manufacturing the laminate according to the embodiment, a film having a retardation of (n/2−0.14)λ or more and (n/2+0.14)λ or less is used as the protective film for protecting the retardation layer. This allows a sufficiently high contrast to be obtained when the retardation film and the object are imaged by the camera through the protective film. 
         [0016]    A method of manufacturing a retardation film according to an embodiment includes the following four steps. In the following, λ denotes, for example, a wavelength in a green range of about 500 to 560 nm. 
         [0017]    (B1) A first step of preparing equipment having a punching machine, one or more cameras fixed to the punching machine, and a processor processing an image captured by each of the cameras, and having a polarizing plate and a (2n+1)λ/4 retardation film (n is an integer of 0 or more) in this order from a camera side within an imaging area of the camera. 
         [0018]    (B2) A second step of preparing a retardation roll sheet having a retardation layer with a patterned retardation region including two or more kinds of retardation regions different in slow-axis direction from each other and having a protective film with a retardation of (n/2−0.14)λ or more and (n/2+0.14)λ or less. 
         [0019]    (B3) A third step of deriving, by the processor, an in-plane positional relationship between the retardation roll sheet and the punching machine from an image of the retardation roll sheet captured by the camera. 
         [0020]    (B4) A fourth step of performing alignment of the retardation roll sheet to the punching machine based on the positional relationship derived by the processor, and then producing a retardation film by punching the retardation roll sheet by the punching machine. 
         [0021]    In the method of manufacturing the retardation film according to the embodiment, a film having a retardation of (n/2−0.14)λ or more and (n/2+0.14)λ or less is used as the protective film for protecting the retardation layer. This allows a sufficiently high contrast to be obtained when the retardation roll sheet is imaged by the camera through the protective film. 
         [0022]    A retardation film according to an embodiment includes a retardation layer and a protective film. The retardation layer has a patterned retardation region including two or more kinds of retardation regions different in slow-axis direction from each other. The protective film has a retardation of (n/2−0.14)λ or more and (n/2+0.14)λ or less (n is an integer of 0 or more). In the above, λ denotes, for example, a wavelength in a green range of about 500 to 560 nm. 
         [0023]    In the retardation film according to the embodiment, a film having a retardation of (n/2−0.14)λ or more and (n/2+0.14)λ or less is used as the protective film for protecting the retardation layer. Consequently, for example, in the case of attaching the retardation film to an object such as a display panel or a black stripe film, when the retardation film and the object are imaged by the camera through the protective film, a sufficiently high contrast may be obtained. In addition, for example, in the case of punching the retardation film from a roll, when the roll is imaged by the camera through the protective film, a sufficiently high contrast may be obtained. 
         [0024]    According to the method of manufacturing the laminate of the embodiment, when the retardation film and the object are imaged by the camera through the protective film, a sufficiently high contrast may be obtained, leading to improvement in alignment accuracy. 
         [0025]    According to the method of manufacturing the retardation film of the embodiment, when the retardation roll sheet is imaged by the camera through the protective film, a sufficiently high contrast may be obtained, leading to improvement in alignment accuracy. 
         [0026]    According to the retardation film of the embodiment, when the retardation film and the object are imaged by the camera through the protective film, or when the roll is imaged by the camera through the protective film, a sufficiently high contrast may be obtained, leading to improvement in alignment accuracy. 
         [0027]    Additional features and advantages are described herein, and will be apparent from the following Detailed Description and the figures. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0028]    The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments and, together with the specification, serve to explain the principles of the application. 
           [0029]      FIGS. 1A and 1B  are a perspective diagram of a retardation film according to an embodiment, and a top diagram of a retardation layer in the retardation film, respectively. 
           [0030]      FIG. 2  is a diagram illustrating an example of a sectional configuration in an A-A arrow direction of the retardation film of  FIG. 1B . 
           [0031]      FIG. 3  is a diagram illustrating another example of the retardation film of  FIG. 2 . 
           [0032]      FIG. 4  is a diagram illustrating another example of the retardation film of  FIG. 1B . 
           [0033]      FIG. 5  is a diagram explaining punching of the retardation film of  FIG. 1A  in a manufacturing process. 
           [0034]      FIG. 6  is a diagram explaining an example of a position detection system used in punching as shown in  FIG. 5 . 
           [0035]      FIG. 7  is a diagram explaining another example of the position detection system used in punching as shown in  FIG. 5 . 
           [0036]      FIGS. 8A and 8B  are diagrams illustrating an example of a relationship between retardation and a contrast of a protective film. 
           [0037]      FIG. 9  is a table illustrating an example of a relationship between various films used as the protective film and punching accuracy. 
           [0038]      FIG. 10  is a diagram illustrating an example of a method of attaching the retardation film of  FIG. 1A  to a black stripe film. 
           [0039]      FIG. 11  is a diagram illustrating an example of a position detection system used in attaching as shown in  FIG. 10 . 
           [0040]      FIG. 12  is a diagram illustrating another example of the position detection system used in attaching as shown in  FIG. 10 . 
           [0041]      FIG. 13  is a diagram illustrating an example of a method of attaching the retardation film of  FIG. 1A  to a display panel. 
           [0042]      FIG. 14  is a diagram illustrating an example of a position detection system used in attaching as shown in  FIG. 13 . 
           [0043]      FIG. 15  is a diagram illustrating another example of the position detection system used in attaching as shown in  FIG. 13 . 
       
    
    
     DETAILED DESCRIPTION 
       [0044]    Embodiments of the present application will be described below in detail with reference to the drawings. 
         [0045]    1. Embodiment ( FIGS. 1 to 9 ) 
         [0046]    Example of punching a retardation film from a retardation roll sheet 
         [0047]    2. Application Examples ( FIGS. 10 to 15 ) 
         [0048]    Example of attaching a retardation film to a black stripe film 
         [0049]    Example of attaching a retardation film to a display panel 
       1. Embodiment 
       [0050]    Configuration of Retardation Film  10   
         [0051]      FIG. 1A  schematically illustrates a retardation film  10  according to a first embodiment.  FIG. 1B  illustrates an example of a top configuration of a retardation layer  12  (described later) of the retardation film  10  of  FIG. 1A .  FIG. 2  illustrates an example of a sectional configuration in an A-A arrow direction of the retardation film  10  of  FIG. 1A . 
         [0052]    The retardation film  10  has a patterned retardation region  10 A disposed in a place to be opposed to a display pixel region when the retardation film  10  is used for 3D display, and alignment mark regions  10 B disposed along borders of the patterned retardation region  10 A. Each alignment mark region  10 B may have a single-straight-line pattern, for example, as shown in  FIG. 1B . Alternatively, while not shown, the alignment mark region  10 B may have a multiple-straight-line pattern, a dot-line pattern, a broken-line pattern, a dashed-line pattern, a dot pattern, a circle pattern, or a combination thereof. 
         [0053]    The retardation film  10  includes, for example, a retardation layer  12  and a protective film  13  on a substrate  11  as shown in  FIG. 2 . An optical function layer  14  such as an anti-glare layer or an anti-reflection layer may be provided between the retardation layer  12  and the protective film  13  as shown in  FIG. 3 . When no layer is provided between the retardation layer  12  and the protective film  13 , the protective film  13  is separably attached to the retardation layer  12 . In contrast, when the optical function layer  14  is provided between the retardation layer  12  and the protective film  13 , the protective film  13  is separably attached to the optical function layer  14 . 
         [0054]    The retardation layer  12  has a flat region (non-orientation region  12 E) in which the patterned retardation region  10 A and the alignment mark region  10 B are not formed. For example, the flat region is formed between the patterned retardation region  10 A and the alignment mark region  10 B as shown in  FIG. 1B . 
         [0055]    The substrate  11  is a sheet-like film supporting the retardation layer  12 , and is configured of, for example, a transparent resin film. For example, the substrate  11  is preferably small in optical anisotropy, namely, small in birefringence. A transparent resin film having such a property includes, for example, TAC (triacetylcellulose), COP (cycloolefin polymer), COC (cycloolefin copolymer), or PMMA (polymethylmethacrylate). COP includes, for example, ZEONOR or ZEONEX (registered trademark of ZEON CORPORATION) or ARTON (registered trademark of JSR Corporation). Thickness of the substrate  11  is, for example, 30 to 500 μm. For example, the substrate  11  may have a single-layer structure or a multi-layer structure. When the substrate  11  has a multi-layer structure, the substrate  11  has, for example, a two-layer structure including, while not shown, a resin layer formed on a surface of a base. 
         [0056]    The retardation layer  12  has retardation regions  12 A and  12 B in the patterned retardation region  10 A, and has a mark region  12 C and mark surrounding regions  12 D in the alignment mark region  10 B. The retardation layer  12  further has, for example, a flat region (non-orientation region  12 E) in which the patterned retardation region  10 A and the alignment mark region  10 B are not formed. The non-orientation region  12 E is substantially free from retardation, and, for example, formed between the patterned retardation region  10 A and the alignment mark region  10 B as shown in  FIG. 2 . The non-orientation region  12 E may be eliminated as necessary. 
         [0057]    For example, the retardation regions  12 A and  12 B have a stripe pattern each, and are alternately arranged in the patterned retardation region  10 A. For example, stripe width in each retardation region is the same as a pixel pitch of a display device. The retardation regions  12 A and  12 B have different retardation characteristics from each other. Specifically, the retardation region  12 A has a slow axis AX 1  in a predetermined direction, and the retardation region  12 B has a slow axis AX 2  in a direction different from the direction of the slow axis AX 1 . For example, the slow axes AX 1  and AX 2  are perpendicular to each other. For example, retardation of the retardation region  12 A is −λ/4, and retardation of the retardation region  12 B is +λ/4. The retardation regions  12 A and  12 B preferably have the same absolute value of retardation. In this specification, λ denotes, for example, a major wavelength (for example, 550 nm) of a light source  420  in a detector  400  described later. 
         [0058]    Retardation may be measured by several kinds of ellipsometry, for example, the rotating analyzer method and the Senarmont Method. In the specification, a value obtained using the rotating analyzer method is shown as a retardation value. In the above, the different signs of retardation show that directions of the respective slow axes are different by 90 degrees from each other. 
         [0059]    Retardation need not have a value specified in the specification for any of wavelengths (over the whole visible range). For example, retardation preferably has the value specified in the specification in a green range corresponding to λ of about 500 to 560 nm. This is because a human retina has high sensitivity to light in a green wavelength band, and besides, when retardation is appropriately adjusted in the green region, retardation may be relatively appropriately adjusted even in a blue or red region. 
         [0060]    For example, the mark region  12 C and the mark surrounding region  12 D have a stripe pattern each. The mark region  12 C is surrounded by the mark surrounding regions  12 D along all or part of borders of the mark region  12 C. For example, the mark region  12 C is formed (in a gap) between a pair of mark surrounding regions  12 D as shown in  FIG. 2 . For example, respective stripe widths in the mark region  12 C and the mark surrounding region  12 D are the same as respective stripe widths in the retardation regions  12 A and  12 B. The mark region  12 C and the mark surrounding region  12 D have different retardation characteristics from each other. Specifically, the mark region  12 C has a slow axis AX 3  in a predetermined direction, and the mark surrounding region  12 D has a slow axis AX 4  in a direction different from the direction of the slow axis AX 3 . For example, the slow axes AX 3  and AX 4  are perpendicular to each other. 
         [0061]    For example, the slow axes AX 3  and AX 4  are in directions different from those of the slow axes AX 1  and AX 2  in the patterned retardation region  10 A, respectively, as shown in  FIG. 1B . For example, retardation of the mark region  12 C is different from retardation of the retardation region  12 A or  12 B, and retardation of the mark surrounding region  12 D is different from retardation of the retardation region  12 A or  12 B. Here, the mark region  12 C and the mark surrounding region  12 D preferably have the same absolute value of retardation. 
         [0062]    For example, the slow axes AX 3  and AX 4  may be in the same directions as those of the slow axes AX 1  and AX 2  in the patterned retardation region  10 A, respectively, as shown in  FIG. 4 . For example, retardation of the mark region  12 C is equal to retardation of the retardation region  12 B (for example, +λ/4), and retardation of the mark surrounding region  12 D is equal to retardation of the retardation region  12 A (for example, −λ/4). Here, the mark region  12 C and the mark surrounding region  12 D preferably have the same absolute value of retardation. 
         [0063]    The protective film  13 , a transparent resin film, is separably attached to a surface of the retardation layer  12  (or the optical function layer  14 ) via an adhesion layer (not shown) or by static electricity. The protective film  13  has a retardation of (n/2−0.14)λ or more and (n/2+0.14)λ or less (n is an integer of 0 or more, and λ is the same as above). 
         [0064]    Method of Manufacturing Retardation Film  10   
         [0065]    Next, an example of a method of manufacturing the retardation film  10  is described. While a case that the retardation film  10  is manufactured using a roll sheet is described below, the retardation film  10  may be manufactured in a sheet-feeding manner. 
         [0066]    First, while not shown, an optical orientation film, a rubbing orientation film, or a pattern-transfer orientation film is formed on a roll-sheet-like substrate including a thermoplastic material such as plastic. Here, portions of the optical orientation film, the rubbing orientation film, or the pattern-transfer orientation film are simultaneously collectively formed in correspondence to the retardation regions  12 A and  12 B, the mark region  12 C, and the mark surrounding regions  12 D, which are formed later. In this way, a roll-sheet-like substrate  11 ′ (not shown) is formed. The substrate  11 ′ refers to a windable roll sheet including the same layer structure and the same material as those of the substrate  11 . 
         [0067]    Next, a liquid crystal layer (not shown) containing a liquid-crystalline monomer is formed on a surface of the substrate  11 ′, followed by orientation treatment (heating treatment) of the liquid-crystalline monomer in the liquid crystal layer on the substrate  11 ′. Shearing stress may be produced at a boundary between the liquid-crystalline monomer and the substrate due to coating of the liquid-crystalline monomer in a previous step, causing orientation caused by flow (flow-induced orientation) or orientation caused by external force (external-force-induced orientation), and consequently liquid crystal molecules may be oriented in an unintentional direction. The heating treatment is performed to temporarily cancel an orientation state of the liquid-crystalline monomer oriented in such an unintentional direction. This allows solvent to be dried from the liquid crystal layer, and consequently only the liquid-crystalline monomer in a state of an isotropic phase is left in the liquid crystal layer. 
         [0068]    Then, the liquid crystal layer is gradually cooled to a temperature slightly lower than the phase transition temperature of the monomer. The liquid crystal layer is cooled to a temperature lower than the phase transition temperature in this way, which allows the liquid-crystalline monomer to be oriented in accordance with respective patterns of the orientation film formed in the surface of the substrate  11 ′. After the orientation treatment, the liquid crystal layer is irradiated with UV light to polymerize the liquid-crystalline monomer. While such irradiation treatment is typically performed at approximately room temperature, the treatment temperature may be raised up to the phase transition temperature in order to adjust a retardation value. In addition, the liquid-crystalline monomer may be polymerized not only by UV light but also by heat or electron beams. However, use of UV light is advantageous in simplifying a process. Consequently, an orientation state of liquid crystal molecules is fixed, leading to formation of a retardation layer  12 ′ (not shown) including retardation regions  12 A and  12 B, mark regions  12 C, and mark surrounding regions  12 D. This is the end of manufacturing of a retardation roll sheet  10 ′ (not shown) having the retardation layer  12 ′ on the substrate  11 ′. The retardation layer  12 ′ refers to a layer in a shape of a windable roll sheet including the same layer structure and the same material as those of the retardation layer  12 . Similarly, the retardation roll sheet  10 ′ refers to a windable roll sheet including the same layer structure and the same material as those of the retardation film  10 . 
         [0069]    Finally, the protective film  13  is attached to a surface of the retardation roll sheet  10 ′, and then the retardation roll sheet  10 ′ is wound on a winding roll (not shown). In this way, a retardation roll sheet  10 D (not shown) having the protective film  13  on a surface thereof is manufactured. 
         [0070]    Next, description is made on a method of manufacturing the retardation film  10  using the retardation roll sheet  10 D manufactured by the above method. In the following, manufacturing equipment of the retardation film  10  is first described, and a manufacturing process of the retardation film  10  is then described. 
         [0071]      FIG. 5  illustrates an example of a configuration of the manufacturing equipment of the retardation film  10 . The manufacturing equipment includes an unwinding roll  310  that unwinds and supplies the retardation roll sheet  10 D and a punching machine  320  that punches the retardation film  10  from the retardation roll sheet  10 D. For example, the punching machine  320  includes a blade (not shown) for punching a portion (punched portion  10 C) of the retardation roll sheet  10 D just below the punching machine  320  and a support stage (not shown) for supporting the blade. 
         [0072]    The manufacturing equipment further includes a stage (not shown) that adjusts a position of the punching machine  320 , a processor  330  that controls a position of the stage and controls cameras  410  described later, and a detector  400  that detects a position of the punching machine  320  with respect to the retardation roll sheet  10 D. 
         [0073]    For example, in the case of detecting an optimum position of the punching machine  320 , the stage allows the punching machine  320  to scan (move) in a direction perpendicular to an extending direction (moving direction) of the retardation roll sheet  10 D according to a control signal from the processor. For example, in the case of alignment, the stage disposes the punching machine  320  at a desired position according to a control signal from the processor  330 . 
         [0074]    For example, in the case of detecting the optimum position, the processor  330  outputs the control signal to the stage to allow the punching machine  320  to scan, and concurrently outputs a control signal, to a plurality of (four) cameras  410  (described later) fixed to the punching machine  320 , instructing the cameras to perform imaging. In the case of detecting the optimum position, the processor  330  acquires an image captured by the camera  410 , and derives the optimum position of the punching machine  320  from the image. Furthermore, for example, in the case of punching, the processor  330  outputs a control signal to the stage to set the punching machine  320  to the optimum position, and then outputs a control signal to the stage to press the punching machine  320  to the retardation roll sheet  10 D. 
         [0075]    The detector  400  includes, for example, the plurality of (four) cameras  410  fixed to the punching machine  320  as shown in  FIG. 5 . The detector  400  includes, for example, a light source  420 , a polarizing plate  430 , a retardation film  440 , and a polarizing plate  450  for each of the cameras  410 , as shown in  FIG. 6 . The light source  420 , the polarizing plate  430 , the retardation film  440 , and the polarizing plate  450  are disposed in at least an imaging area of the camera  410 , and disposed in this order toward the punching machine  320 . 
         [0076]    The retardation roll sheet  10 D is disposed between the polarizing plate  430  and the retardation film  440  in such a manner that the protective film  13  faces the retardation film  440 . For example, the light source  420  and the polarizing plate  430  are fixed just below the retardation roll sheet  10 D, for example, just below an alignment mark region  10 B of the retardation roll sheet  10 D as shown in  FIG. 6 . For example, the light source  420  and the polarizing plate  430  may be fixed just below a patterned retardation region  10 A of the retardation roll sheet  10 D as shown in  FIG. 7 . 
         [0077]    For example, the retardation film  440  and the polarizing plate  450  move together with the camera  410  and the punching machine  320  in the direction perpendicular to the extending direction (moving direction) of the retardation roll sheet  10 D. For example, the retardation film  440  and the polarizing plate  450  are fixed on a lens (not shown) of the camera  410 . 
         [0078]    For example, the camera  410  is configured of a CMOS (Complementary Metal Oxide Semiconductor) image sensor or a CCD (Charge Coupled Device) image sensor. For example, the light source  420  outputs non-polarized white light. The polarizing plate  430  transmits a polarization component in a predetermined direction (for example, 45-degree direction). The retardation film  440  is configured of a (2n+1)λ/4 retardation film (n is an integer of 0 or more). The polarizing plate  450  transmits a polarization component in a predetermined direction (for example, 135-degree direction). 
         [0079]    The manufacturing equipment having such a configuration is used to form the retardation film  10 . Specifically, first, the retardation roll sheet  10 D is unwound and supplied from the unwinding roll  310  and moves in the extending direction of the retardation roll sheet  10 D. Concurrently, each camera  410  is allowed to scan in the direction perpendicular to the extending direction of the retardation roll sheet  10 D. For example, when the light source  420  and the polarizing plate  430  are fixed just below the alignment mark region  10 B of the retardation roll sheet  10 D, an imaging area of each camera  410  traverses a region including the alignment mark region  10 B of the retardation roll sheet  10 D and borders of the patterned retardation region  10 A of the sheet  10 D. On the other hand, when the light source  420  and the polarizing plate  430  are fixed just below the patterned retardation region  10 A of the retardation roll sheet  10 D, an imaging area of each camera  410  traverses a region including borders of the patterned retardation region  10 A of the sheet  10 D. 
         [0080]    When the light source  420  and the polarizing plate  430  are fixed just below the alignment mark region  10 B of the retardation roll sheet  10 D, each camera  410  may detect an image of the retardation roll sheet  10 D, for example, an image as shown in upper right of  FIG. 6 . For example, the mark region  12 C in the alignment mark region  10 B is black, and the mark surrounding region  12 D therein is white. Accordingly, (two) boundaries B 1  between the mark region  12 C and the mark surrounding regions  12 D are detected from an image captured during scan of each camera  410  in the direction perpendicular to the extending direction of the retardation roll sheet  10 D, and furthermore a relative positional relationship of each camera  410  to the alignment mark region  10 B is derived from the image. 
         [0081]    In contrast, when the light source  420  and the polarizing plate  430  are fixed just below the patterned retardation region  10 A of the retardation roll sheet  10 D, each camera  410  may detect an image of the retardation roll sheet  10 D, for example, an image as shown in upper right of  FIG. 7 . For example, the retardation region  12 B in the patterned retardation region  10 A is black, and the retardation region  12 A therein is white. Accordingly, (two) boundaries B 2  between the retardation regions  12 A and  12 B are detected from an image captured during scan of each camera  410  in the direction perpendicular to the extending direction of the retardation roll sheet  10 D, and furthermore a relative positional relationship of each camera  410  to the patterned retardation region  10 A is derived from the image. 
         [0082]    The optimum position of the punching machine  320  is derived from the positional relationship obtained in this way, and the punching machine  320  is disposed at the optimum position. Then, the punching machine  320  is pressed to the retardation roll sheet  10 D to punch the sheet  10 D. In this way, the retardation film  10  is formed of the retardation roll sheet  10 D. 
         [0083]    Effects 
         [0084]    Next, advantages of the method of manufacturing the retardation film  10  are described in contrast to a method of manufacturing a retardation film according to a comparative example. 
         [0085]    When the retardation film is manufactured of a roll base, in the case that the retardation film is cut into a desired size, a protective film is beforehand attached to a surface of the roll base to protect the surface from being damaged or stained. 
         [0086]    A PET film having high retardation is typically used for a base of the protective film. Since polarization is therefore disturbed by the protective film, the detection camera hardly captures a clear image of the alignment mark, which has led to a disadvantage of reduction in accuracy of position detection of the alignment mark, resulting in reduction in alignment accuracy. 
         [0087]    In contrast, in the embodiment, a film having a retardation of (n/2−0.14)λ or more and (n/2+0.14)λ or less is used as the protective film  13  for protecting the retardation layer  12 . Furthermore, when the retardation film  10  is punched from the retardation roll sheet  10 D in a manufacturing process, the retardation film  440  including the (2n+1)λ/4 retardation film and the polarizing plate  450  are disposed between the camera  410  and the retardation roll sheet  10 D. This allows a sufficiently high contrast to be obtained when the retardation layer  12  is imaged by the camera  410  through the protective film  13 . 
         [0088]      FIG. 8A  illustrates a relationship between an R/L contrast (a ratio of luminance of the retardation region  12 A to luminance of the retardation region  12 B) and retardation of the protective film  13 .  FIG. 8B  illustrates a relationship between an L/R contrast (a ratio of luminance of the retardation region  12 B to luminance of the retardation region  12 A) and retardation of the protective film  13 . The R/L contrast means a degree of brightness of the retardation region  12 A with respect to the retardation region  12 B, and the L/R contrast means a degree of brightness of the retardation region  12 B with respect to the retardation region  12 A. 
         [0089]      FIG. 9  illustrates a result of an experiment on punching accuracy when various commercially-available films are used as the protective film  13  in the manufacturing equipment of  FIG. 5 . A remark “black and white negative” in  FIG. 9  means a black-and-white negative image of an image obtained by using another film. Results of five of the films in  FIG. 9  are plotted in  FIGS. 8A and 8B . 
         [0090]      FIGS. 8A and 8B  and  FIG. 9  reveal that when retardation of the protective film  13  is (n/2−0.14)λ or more and (n/2+0.14)λ or less, both the R/L contrast and the L/R contrast are 5 or more. Moreover,  FIGS. 8A and 8B  and  FIG. 9  reveal that when each contrast is 5 or more, the retardation film  10  may be accurately punched from the retardation roll sheet  10 D. In other words, when each contrast is 5 or more, the boundaries B 1  and B 2  may be recognized from an image captured by the camera  410 , and thus the retardation film  10  may be accurately punched from the retardation roll sheet  10 D. 
         [0091]    In this way, in the embodiment, when the retardation roll sheet  10 D is imaged by the camera  410  through the protective film  13 , a sufficiently high contrast may be obtained. As a result, alignment accuracy may be improved. 
         [0092]    In the past, since the alignment mark is formed by printing or the like on a retardation film before punching, or a retardation region is formed in a film with the mark, the retardation region is formed in a separate step from formation of the alignment mark. It is therefore necessary to perform accurate positioning of one while recognizing a position of the other in order to improve alignment accuracy. This has disadvantageously resulted in a complicated manufacturing process or increase in number of steps. 
         [0093]    On the other hand, in the embodiment, portions of the optical orientation film, the rubbing orientation film, or the pattern-transfer orientation film are simultaneously collectively formed in correspondence to the retardation regions  12 A and  12 B, the mark regions  12 C, and the mark surrounding regions  12 D on a roll-sheet-like substrate including a thermoplastic material such as plastic. This eliminates need of accurate positioning of the alignment mark region  10 B while recognizing a position of the patterned retardation region  10 A. As a result, alignment accuracy may be improved with a simple method and in a small number of steps. 
       2. Application Examples 
     Application Example 1 
       [0094]    For example, the detector  400  in the embodiment may be applied to attaching the retardation film  10  to a black stripe film  600  as shown in  FIGS. 10 ,  11  and  12 . 
         [0095]      FIG. 10  schematically illustrates an aspect of attaching the retardation film  10  to the black stripe film  600 .  FIGS. 11 and 12  illustrate an example of a configuration necessary for using the detector  400  for attaching the retardation film  10  to the black stripe film  600 . 
         [0096]    The black stripe film  600  reduces crosstalk that may occur when the retardation film  10  is used for 3D display, and, for example, has a black stripe region  600 A and alignment mark regions  600 B as shown in  FIG. 10 . The black stripe region  600 A is disposed at a position to be opposed to a display pixel region when the black stripe film  600  is used for 3D display. 
         [0097]    The black stripe region  600 A has black stripes  610  (see  FIG. 12 ) in regions opposed to boundaries between the retardation regions  12 A and  12 B when the retardation film  10  is used for 3D display. The alignment mark region  600 B has a mark surrounding region  620  having width wider than width of the mark region  12 C of the retardation film and a pair of mark regions  630  provided on both sides of the mark surrounding region  620  (see  FIG. 11 ). The black stripe  610  and the mark region  630  have light-blocking properties, and the mark surrounding region  620  and any region other than the black stripes  610  in the black stripe region  600 A have light-transmitting properties. In the alignment mark region  600 B, at least the mark surrounding region  620  is configured of a material substantially free from retardation. 
         [0098]    The detector  400  having the above configuration is used to attach the retardation film  10  to the black stripe film  600 . Specifically, first, the retardation film  10  and the black stripe film  600  are disposed at predetermined positions. Next, for example, each camera  410  is allowed to scan together with the retardation film  10  in a direction perpendicular to an extending direction of the alignment mark region  10 B of the retardation film  10 . 
         [0099]    Next, for example, when the light source  420  and the polarizing plate  430  are fixed just below the alignment mark region  10 B, an imaging area of each camera  410  traverses, for example, a region including the alignment mark region  10 B and borders of the patterned retardation region  10 A. On the other hand, when the light source  420  and the polarizing plate  430  are fixed just below the patterned retardation region  10 A, an imaging area of each camera  410  traverses, for example, a region including borders of the patterned retardation region  10 A. 
         [0100]    When the light source  420  and the polarizing plate  430  are fixed just below the alignment mark region  10 B, each camera  410  may detect an image of the retardation film  10 , for example, an image as shown in upper right of  FIG. 11 . For example, the mark region  12 C in the alignment mark region  10 B is black, and the mark surrounding region  12 D therein is white. Accordingly, (two) boundaries B 1  between the mark region  12 C and the mark surrounding regions  12 D, (two) boundaries B 3  between the mark regions  630  and the mark surrounding region  620 , and distances D 1  and D 2  between the boundaries B 1  and B 3  are detected from an image captured during scan of each camera  410  in the direction perpendicular to the extending direction of the alignment mark region  10 B (see an upper right figure of  FIG. 11 ). Here, for example, a position of the retardation film  10 , at which the distances D 1  and D 2  derived from the image captured by each camera  410  are equal or approximately equal to each other, is derived. The position obtained in this way is set as an optimum position of the retardation film  10 , and the retardation film  10  is disposed at the derived optimum position. Then, the retardation film  10  is pressed to the black stripe film  600  so that the retardation film  10  is attached to the black stripe film  600 . In this way, the retardation film  10  is attached to the black stripe film  600 . 
         [0101]    On the other hand, when the light source  420  and the polarizing plate  430  are fixed just below the patterned retardation region  10 A, each camera  410  may detect an image of the retardation film  10 , for example, an image as shown in upper right of  FIG. 12 . For example, the retardation region  12 B in the patterned retardation region  10 A is black, and the retardation region  12 A therein is white. Accordingly, (two) boundaries B 2  between the retardation regions  12 A and  12 B, (two) borders B 4  of the black stripe  610 , and distances D 3  and D 4  between the boundaries B 2  and B 4  are detected from an image captured during scan of each camera  410  in the direction perpendicular to the extending direction of the patterned retardation region  10 A (see an upper right figure of  FIG. 12 ). Here, for example, a position of the retardation film  10 , at which the distances D 3  and D 4  derived from the image captured by each camera  410  are equal or approximately equal to each other, is derived. The position obtained in this way is set as an optimum position of the retardation film  10 , and the retardation film  10  is disposed at the derived optimum position. Then, the retardation film  10  is pressed to the black stripe film  600  so that the retardation film  10  is attached to the black stripe film  600 . In this way, the retardation film  10  is attached to the black stripe film  600 . 
         [0102]    In the application example, a film having a retardation of (n/2−0.14)λ or more and (n/2+0.14)λ or less is used as the protective film  13  for protecting the retardation layer  12  in the same way as the embodiment. Furthermore, when the retardation film  10  is attached to the black stripe film  600  in a manufacturing process, a retardation film  440  including a (2n+1)λ/4 retardation film and a polarizing plate  450  are disposed between the camera  410  and the retardation film  10 . This allows a sufficiently high contrast to be obtained when the retardation layer  12  is imaged by the camera  410  through the protective film  13 . As a result, alignment accuracy may be improved. 
       Application Example 2 
       [0103]    For example, the detector  400  in the embodiment may be further applied to attaching the retardation film  10  to a display panel  700  as shown in  FIGS. 13 ,  14  and  15 . 
         [0104]      FIG. 13  schematically illustrates an aspect of attaching the retardation film  10  to the display panel  700 .  FIGS. 14 and 15  illustrate an example of a configuration necessary for using the detector  400  for attaching the retardation film  10  to the display panel  700 . 
         [0105]    While not shown, the display panel  700  includes, for example, a panel section and a deflector provided on a light emission side of the panel section. The panel section includes, for example, a liquid crystal panel, a plasma display panel, an organic EL display panel, and a cathode ray tube. The display panel  700  has, for example, a display pixel region  700 A and alignment mark regions  700 B as shown in  FIG. 13 . The display pixel region  700 A is to output image light. 
         [0106]    The display pixel region  700 A has boundaries  710  (see  FIG. 15 ) in regions opposed to boundaries between pixels adjacent to each other. The alignment mark region  700 B has a mark surrounding region  720  having width wider than width of the mark region  12 C of the retardation film and a pair of mark regions  730  provided on both sides of the mark surrounding region  720  (see  FIG. 14 ). The boundary  710  and the mark region  730  have light-blocking properties, and the mark surrounding region  720  and any region other than the boundaries  710  in the display pixel region  700 A have light-transmitting properties. In the alignment mark region  700 B, at least the mark surrounding region  720  is configured of a material substantially free from retardation. 
         [0107]    The detector  400  having the above configuration is used to attach the retardation film  10  to the display panel  700 . Specifically, first, the retardation film  10  and the display panel  700  are disposed at predetermined positions. Next, for example, each camera  410  is allowed to scan together with the retardation film  10  in a direction perpendicular to the extending direction of the alignment mark region  10 B of the retardation film  10 . 
         [0108]    Next, for example, when the light source  420  and the polarizing plate  430  are fixed just below the alignment mark region  10 B, an imaging area of each camera  410  traverses, for example, a region including the alignment mark region  10 B and borders of the patterned retardation region  10 A. On the other hand, when the light source  420  and the polarizing plate  430  are fixed just below the patterned retardation region  10 A, an imaging area of each camera  410  traverses, for example, a region including borders of the patterned retardation region  10 A. 
         [0109]    When the light source  420  and the polarizing plate  430  are fixed just below the alignment mark region  10 B, each camera  410  may detect an image of the retardation film  10 , for example, an image as shown in upper right of  FIG. 14 . For example, the mark region  12 C in the alignment mark region  10 B is black, and the mark surrounding region  12 D therein is white. Accordingly, (two) boundaries B 1  between the mark region  12 C and the mark surrounding regions  12 D, (two) boundaries B 5  between the mark regions  730  and the mark surrounding region  720 , and distances D 5  and D 6  between the boundaries B 1  and B 5  are detected from an image captured during scan of each camera  410  in the direction perpendicular to the extending direction of the alignment mark region  10 B (see an upper right figure of  FIG. 14 ). Here, for example, a position of the retardation film  10 , at which the distances D 5  and D 6  derived from the image captured by each camera  410  are equal or approximately equal to each other, is derived. The position obtained in this way is set as an optimum position of the retardation film  10 , and the retardation film  10  is disposed at the derived optimum position. Then, the retardation film  10  is pressed to the display panel  700  so that the retardation film  10  is attached to the display panel  700 . In this way, the retardation film  10  is attached to the display panel  700 . 
         [0110]    On the other hand, when the light source  420  and the polarizing plate  430  are fixed just below the patterned retardation region  10 A, each camera  410  may detect an image of the retardation film  10 , for example, an image as shown in upper right of  FIG. 15 . For example, the retardation region  12 B in the patterned retardation region  10 A is black, and the retardation region  12 A therein is white. Accordingly, (two) boundaries B 2  between the retardation regions  12 A and  12 B, (two) borders B 6  of the respective boundaries  710 , and distances D 7  and D 8  between the boundaries B 2  and the borders B 6  are detected from an image captured during scan of each camera  410  in the direction perpendicular to the extending direction of the patterned retardation region  10 A (see an upper right figure of  FIG. 15 ). Here, for example, a position of the retardation film  10 , at which the distances D 7  and D 8  derived from the image captured by each camera  410  are equal or approximately equal to each other, is derived. The position obtained in this way is set as an optimum position of the retardation film  10 , and the retardation film  10  is disposed at the derived optimum position. Then, the retardation film  10  is pressed to the display panel  700  so that the retardation film  10  is attached to the display panel  700 . In this way, the retardation film  10  is attached to the display panel  700 . 
         [0111]    In the application example, a film having a retardation of (n/2−0.14)λ or more and (n/2+0.14)λ or less is used as the protective film  13  for protecting the retardation layer  12  in the same way as the embodiment. Furthermore, when the retardation film  10  is attached to the display panel  700  in a manufacturing process, a retardation film  440  including a (2n+1)λ/4 retardation film and a polarizing plate  450  are disposed between the camera  410  and the retardation film  10 . This allows a sufficiently high contrast to be obtained when the retardation layer  12  is imaged by the camera  410  through the protective film  13 . As a result, alignment accuracy may be improved. 
         [0112]    While the disclosure has been described with the embodiments and the application examples hereinbefore, the embodiments and the like are not limitative, and various modifications or alterations may be made. 
         [0113]    For example, while the pair of mark surrounding regions  12 D have been provided in the alignment mark region  10 B in the embodiments and the like, one or both of the mark surrounding regions  12 D may be omitted. 
         [0114]    For example, while the plurality of cameras  410  have been used for the detector  400  in the embodiments and the like, only one camera  410  may be used. 
         [0115]    It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.