Device for inspecting phase difference film. device for manufacturing phase difference film, method for inspecting phase difference film, and method for manufacturing phase difference film

Abstract

To accurately inspect optical characteristics of a phase difference film.SOLUTION: An inspection device inspects a phase difference film including a liquid crystal layer and a base material in order from a first surface to a second surface facing the first surface. The inspection device includes a light source for emitting linearly polarized monochrome light and projecting the light on the first surface, and an imaging device for receiving the light reflected by the phase difference film and imaging the phase difference film.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to an inspection apparatus for a retardation film, a manufacturing apparatus for a retardation film, an inspection method for a retardation film, and a manufacturing method for a retardation film.

Background Art

[0002] For example, as described in Patent Document 1 and Patent Document 2, retardation films are known. The retardation film disclosed in Patent Document 1 includes a liquid crystal layer having birefringence. The retardation film can be applied to an optical compensation layer or a circular polarizing plate.

[0003] The thickness of the liquid crystal layer affects the optical properties of the liquid crystal layer. Patent Document 1 proposes suppressing local thickness variations of the liquid crystal layer.

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 prior art, inspection apparatuses and inspection methods for inspecting the optical properties of retardation films have not been sufficiently studied. An object of the present disclosure is to accurately inspect the optical properties of a retardation film.

Means for Solving the Problems

[0006] A first inspection apparatus according to an embodiment of the present disclosure is an inspection apparatus for inspecting a retardation film including a liquid crystal layer and a substrate in order from a first surface toward a second surface facing the first surface, A light source that emits linearly polarized monochromatic light and projects the light onto the first surface, An imaging device that receives the light reflected by the retardation film and images the retardation film.

[0007] A second inspection device according to an embodiment of the present disclosure is an inspection device that inspects a retardation film including a liquid crystal layer and a substrate in order from a first surface toward a second surface facing the first surface, a light source that emits monochromatic light and projects the light onto the first surface, an imaging device that receives the light reflected by the retardation film and images the retardation film, and a polarizer located on the optical path of the light from the light source to the imaging device.

[0008] A third inspection device according to an embodiment of the present disclosure is an inspection device that inspects a retardation film including a liquid crystal layer and a substrate in order from a first surface toward a second surface facing the first surface, a light source that emits linearly polarized light and projects the light onto the first surface, an imaging device that receives the light reflected by the retardation film and images the retardation film, and a band-pass filter located on the optical path of the light from the light source to the imaging device.

[0009] A fourth inspection device according to an embodiment of the present disclosure is an inspection device that inspects a retardation film including a liquid crystal layer and a substrate in order from a first surface toward a second surface facing the first surface, a light source that projects light onto the first surface, an imaging device that receives the light reflected by the retardation film and images the retardation film, a band-pass filter located on the optical path of the light from the light source to the imaging device, and a polarizer located on the optical path of the light from the light source to the imaging device.

[0010] An inspection method according to an embodiment of the present disclosure is an inspection method for inspecting a retardation film including a liquid crystal layer and a base material in order from a first surface toward a second surface facing the first surface, the step of projecting light onto the first surface, and the step of receiving reflected light from the retardation film and determining the presence or absence of an abnormality, wherein the presence or absence of the abnormality is determined based on the reception result of linearly polarized monochromatic light.

Advantages of the Invention

[0011] According to the present invention, the optical characteristics of the retardation film can be accurately inspected.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0013] One embodiment of the present disclosure relates to the following <1> to <23>.

[0014] <1> An inspection apparatus for inspecting a retardation film including a liquid crystal layer and a substrate in order from a first surface toward a second surface facing the first surface, a light source that emits linearly polarized monochromatic light and projects the light onto the first surface, and an imaging device that receives the light reflected by the retardation film and images the retardation film.

[0015] <2> An inspection apparatus for inspecting a retardation film including a liquid crystal layer and a substrate in order from a first surface toward a second surface facing the first surface, a light source that emits monochromatic light and projects the light onto the first surface, an imaging device that receives the light reflected by the retardation film and images the retardation film, and a polarizer located on the optical path of the light from the light source to the imaging device.

[0016] <3> An inspection apparatus for inspecting a retardation film including a liquid crystal layer and a substrate in order from a first surface toward a second surface facing the first surface, a light source that emits linearly polarized light and projects the light onto the first surface, an imaging device that receives the light reflected by the retardation film and images the retardation film, and a band-pass filter located on the optical path of the light from the light source to the imaging device.

[0017] <4> An inspection apparatus for inspecting a retardation film including a liquid crystal layer and a substrate in order from a first surface toward a second surface facing the first surface, a light source that projects light onto the first surface, an imaging device that receives the light reflected by the retardation film and images the retardation film, a band-pass filter positioned on the optical path of the light from the light source to the imaging device, a polarizer positioned on the optical path of the light from the light source to the imaging device, the inspection apparatus comprising:

[0018] <5> In the projection onto the first surface, the angle between the vibration direction of the linearly polarized light projected onto the first surface and the optical axis of the liquid crystal layer is 0° or more and 10° or less, the inspection apparatus according to <1> or <3>.

[0019] <6> In the projection onto the first surface, the angle between the vibration direction of the linearly polarized light projected onto the first surface and the slow axis of the liquid crystal layer is 0° or more and 10° or less, the inspection apparatus according to <1>, <3>, or <5>.

[0020] <7> In the projection onto the first surface, the angle between the transmission axis of the polarizer and the optical axis of the liquid crystal layer is 0° or more and 10° or less, the inspection apparatus according to <2> or <4>.

[0021] <8> In the projection onto the first surface, the angle between the transmission axis of the polarizer and the slow axis of the liquid crystal layer is 0° or more and 10° or less, the inspection apparatus according to <2>, <4>, or <7>.

[0022] <9> The polarizer is positioned on the optical path from the retardation film to the imaging device of the reflected light, the inspection apparatus according to <2>, <4>, <7>, or <8>.

[0023] <10> The band-pass filter is the inspection device according to <3> or <4>, which is located on the optical path from the phase difference film to the imaging device for the reflected light.

[0024] <11> The light projected onto the first surface is P-polarized light, and the inspection device according to any one of <1> to <10>.

[0025] <12> The incident angle of the light on the phase difference film is 45° or more and 80° or less, and the inspection device according to any one of <1> to <11>.

[0026] <13> The inspection device further includes a determination device that determines the presence or absence of an abnormality based on the data acquired by the imaging device, and the inspection device according to any one of <1> to <12>.

[0027] <14> The inspection device further includes a display device that displays the image captured by the imaging device, and the inspection device according to any one of <1> to <13>.

[0028] <15> The base material includes a stretched polyester film, and the inspection device according to any one of <1> to <14>.

[0029] <16> A manufacturing device for a phase difference film, comprising a manufacturing device for manufacturing the phase difference film and the inspection device according to any one of <1> to <15>. A manufacturing device for a phase difference film, comprising a manufacturing device for manufacturing the phase difference film and the inspection device according to any one of <1> to <15>.

[0030] <17> An inspection method for inspecting a phase difference film including a liquid crystal layer and a base material in order from a first surface to a second surface facing the first surface, comprising: A step of projecting light onto the first surface; A step of receiving the reflected light from the phase difference film and determining the presence or absence of an abnormality, and the inspection method, wherein the presence or absence of the abnormality is determined based on the light reception result of linearly polarized monochromatic light. The inspection method, wherein the presence or absence of the abnormality is determined based on the light reception result of linearly polarized monochromatic light.

[0031] <18> In the projection onto the first surface, the angle between the vibration direction of the linearly polarized light projected onto the first surface and the optical axis of the liquid crystal layer is 0° or more and 10° or less, the inspection method according to <17>.

[0032] <19> In the projection onto the first surface, the angle between the vibration direction of the linearly polarized light projected onto the first surface and the slow axis of the liquid crystal layer is 0° or more and 10° or less, the inspection method according to <17> or <18>.

[0033] <20> The light projected onto the first surface is P-polarized light, the inspection method according to any one of <17> to <19>.

[0034] <21> The incident angle of the light onto the retardation film is 45° or more and 80° or less, the inspection method according to any one of <17> to <20>.

[0035] <22> The base material includes a stretched polyester film, the inspection method according to any one of <17> to <21>.

[0036] <23> A step of manufacturing the retardation film; A step of inspecting the retardation film manufactured by the inspection method according to any one of <17> to <22>, a method for manufacturing a retardation film.

[0037] Hereinafter, details of an embodiment of the present disclosure will be described. In the drawings attached to this specification, for the convenience of illustration and easy understanding, the scale, the aspect ratio of the vertical and horizontal dimensions, etc. are appropriately changed and exaggerated from those of the actual object.

[0038] In this specification, terms such as "film", "sheet", and "plate" are not distinguished from each other based only on the difference in name. For example, a "retardation film" can only be distinguished from a member called a retardation sheet or a retardation plate based only on the difference in name.

[0039] In this specification, the normal direction of a film-like (sheet-like, plate-like) member refers to a direction parallel to the normal or perpendicular line to the film surface (sheet surface, plate surface) of the target film-like (sheet-like, plate-like) member. The "film surface (sheet surface, plate surface)" refers to the surface that coincides with the target film-like (sheet-like, plate-like) member when the target film-like (sheet-like, plate-like) member is viewed as a whole and globally.

[0040] In this specification, a plurality of upper limit candidates for a numerical range and a plurality of lower limit candidates may be described in separate sentences. In this description, the numerical range may be constituted by combining any one upper limit candidate and any one lower limit candidate. As an example, consider the description "Parameter B may be A1 or more, A2 or more, or A3 or more. Parameter B may be A4 or less, A5 or less, or A6 or less." In this example, the numerical range of Parameter B may be A1 or more and A4 or less, A1 or more and A5 or less, A1 or more and A6 or less, A2 or more and A4 or less, A2 or more and A5 or less, A2 or more and A6 or less, A3 or more and A4 or less, A3 or more and A5 or less, or A3 or more and A6 or less.

[0041] To clarify the relationship of directions between drawings, some drawings show a common first direction D1, second direction D2, and third direction D3 by arrows with common reference signs. The tip side of the arrow is the first side of each direction. The side opposite to the tip of the arrow is the second side of each direction. An arrow pointing into the depth of the drawing paper along the direction perpendicular to the drawing paper is shown by a symbol with a dot in a circle, as shown in FIG. 1 for example.

[0042] <<Retardation Film 10>> The retardation film 10 to be inspected will be described. The retardation film 10 to be inspected may be a long-sized retardation film. The long-sized retardation film 10 can be handled by a roll-to-roll method. The long-sized retardation film 10 is excellent in terms of production efficiency, manufacturing cost, inspection efficiency, and inspection cost.

[0043] "Long-sized" means that an object such as a film has a length of 5 m or more when spread out, and may have a length of 10 m or more, or may have a length of 100 m or more. "Longitudinal direction" means the direction along the longest edge when an object such as a film is spread out. "Transverse direction" means the direction in which the minimum length is obtained when an object such as a film is spread out.

[0044] The retardation film 10 to be inspected may be in sheet form. The sheet retardation film 10 may have a size suitable for final use. The sheet retardation film 10 may be obtained by cutting the long-sized retardation film 10. "Sheet" means that an object such as a film has a maximum length of less than 5 m when spread out, and may have a maximum length of less than 2 m, or may have a maximum length of less than 1 m.

[0045] The retardation film 10 to be inspected includes a first surface 11 and a second surface 12. The first surface 11 and the second surface 12 are a pair of main surfaces of the retardation film 10. The retardation film 10 includes a liquid crystal layer 18 and a base material 16 in this order from the first surface 11 to the second surface 12.

[0046] FIG. 9 shows an example of the retardation film 10 to be inspected. FIG. 9 is a cross-section taken along line A-A of FIG. 3. As shown in FIG. 9, the retardation film 10 may further include an alignment film 17. The alignment film 17 is located between the base material 16 and the liquid crystal layer 18. In the illustrated example, the first surface 11 is constituted by the liquid crystal layer 18. The second surface 12 is constituted by the base material 16.

[0047] As described below, the illustrated inspection apparatus 30 inspects the incoming retardation film 10. That is, this inspection apparatus 30 is an in-line inspection machine. The first direction D1, the second direction D2, and the third direction D3 described in the drawings are based on the inspection apparatus 30. In the region inspected by the inspection apparatus 30, the retardation film 10 has a longitudinal direction in the first direction D1. In the region inspected by the inspection apparatus 30, the retardation film 10 has a short-side direction in the second direction D2. In the region inspected by the inspection apparatus 30, the retardation film 10 has a normal direction in the third direction D3. That is, the third direction D3 is the lamination direction of the base material 16, the alignment film 17, and the liquid crystal layer 18.

[0048] <Liquid crystal layer 18> The liquid crystal layer 18 contains a liquid crystal compound. The liquid crystal layer 18 may contain a cured product of a liquid crystal composition containing a liquid crystal compound. The liquid crystal layer 18 may be a layer in which the alignment of the liquid crystal compound is fixed. The liquid crystal compound may be a polymerizable liquid crystal compound. That is, the liquid crystal layer 18 may contain a cured product of a polymerizable liquid crystal composition containing a polymerizable liquid crystal compound. The liquid crystal layer 18 may be a layer in which the alignment of the polymerizable liquid crystal compound is fixed.

[0049] The liquid crystal layer 18 can be obtained by forming a coating film by applying a liquid crystal composition containing a liquid crystal compound, and then curing the liquid crystal composition. The alignment of the liquid crystal compound in the coating film may be adjusted to horizontal alignment, vertical alignment, inclined alignment, twist alignment, hybrid alignment, etc. By adjusting the alignment of the liquid crystal compound in the coating film, the liquid crystal layer 18 is imparted with birefringence. The liquid crystal layer 18 having birefringence exhibits a phase modulation function. The liquid crystal layer 18 having birefringence functions as a retardation layer.

[0050] The polymerizable liquid crystal compound is not particularly limited. The polymerizable liquid crystal compound may be a polymerizable liquid crystal compound used for forming a layer having birefringence. The polymerizable liquid crystal compound is appropriately selected according to the desired retardation value, wavelength dispersion, alignment, solubility, etc. of the liquid crystal layer 18.

[0051] The liquid crystal layer 18 has an in-plane retardation Re(550) corresponding to its birefringence and thickness. The in-plane retardation Re(550) means the in-plane retardation for light with a wavelength of 550 nm. The in-plane retardation Re(550) of the liquid crystal layer 18 is not particularly limited. In an example where the liquid crystal layer 18 is a λ / 4 retardation layer, the in-plane retardation Re(550) of the liquid crystal layer 18 may be 120 nm or more and 160 nm or less.

[0052] The thickness of the liquid crystal layer 18, that is, the length along the normal direction of the liquid crystal layer 18, may be determined according to the desired optical characteristics. In an example where the liquid crystal layer 18 is a λ / 4 retardation layer, the thickness of the liquid crystal layer 18 may be 0.5 μm or more and 4.0 μm or less.

[0053] <Substrate 16> The substrate 16 supports the liquid crystal layer 18. In the illustrated example, the substrate 16 also supports the alignment film 17. In manufacturing the retardation film 10 by a roll-to-roll method, the substrate 16 may have flexibility to be wound in a roll shape.

[0054] As the material of the substrate 16, resin may be used. The resin-made substrate 16 has flexibility and is suitable for the roll-to-roll manufacturing method. Examples of the material of the substrate 16 include polyethylene terephthalate, polyethylene naphthalate, triacetyl cellulose, polyurethane, polyimide, polyamide, polycarbonate, polymethyl methacrylate, polyacrylate methyl, etc.

[0055] The substrate 16 may include a stretched polyester film. The stretched polyester film has excellent mechanical properties. The polyester film may be uniaxially stretched or biaxially stretched. The biaxial stretching may be sequential biaxial stretching or simultaneous biaxial stretching. The stretched polyester film has birefringence.

[0056] The in-plane retardation Re(550) of the substrate 16 having birefringence may be 3000 nm or more, 5000 nm or more, or 10000 nm or more. The in-plane retardation Re(550) of the substrate 16 may be 50000 nm or less, or 30000 nm or less.

[0057] The thickness of the substrate 16, that is, the length along the normal direction of the substrate, may be 10 μm or more and 1000 μm or less, 25 μm or more and 125 μm or less, or 30 μm or more and 100 μm or less.

[0058] <Alignment film 17> The alignment film 17 has an alignment regulating force. The alignment film 17 adjusts the alignment of the liquid crystal compounds contained in the liquid crystal layer 18. The alignment film 17 arranges the liquid crystal compounds contained in the liquid crystal layer 18 in a certain direction.

[0059] The alignment film 17 may be a photo-alignment film. The photo-alignment film is imparted with an alignment regulating force by exposure. An alignment regulating force is imparted by applying an alignment film-forming composition onto the substrate 16 to form a coating film on the substrate 16 and irradiating the coating film with linearly polarized light.

[0060] The alignment film may be a rubbed alignment film. The rubbed alignment film is imparted with an alignment regulating force by a rubbing treatment. A rubbed alignment film can be obtained by applying an alignment film-forming composition onto the substrate 16 to form a coating film on the substrate 16 and rubbing the coating film using a rubbing roll or the like.

[0061] The material of the alignment film is not particularly limited. As the material of the alignment film, materials used as materials for photo-alignment films or rubbed alignment films may be used. As the material of the photo-alignment film, a photo-alignment material that exhibits an alignment regulating force by irradiating linearly polarized light is used. The material of the photo-alignment film may be either a photo-dimerization type material or a photo-isomerization type material. Examples of the material of the rubbed alignment film include polyvinyl alcohol-based resins, polyimide-based resins, and polyamide-based resins.

[0062] The thickness of the alignment film 17, that is, the length along the normal direction of the alignment film 17, may be 1 nm or more and 3000 or less.

[0063] <Method for Measuring Thickness and In-Plane Phase Difference Re> The thicknesses of the components 16, 17, and 18 constituting the long phase difference film 10 are taken as the average values of the measured values at 20 locations in the observation image by a scanning transmission electron microscope (STEM).

[0064] The in-plane phase difference is taken as the average value of the measured values at 16 locations. The 16 measurement locations are, with a 1 cm region from the outer edge of the measurement sample as a margin, for the region inside the margin, when lines dividing the vertical and horizontal directions into five equal parts are drawn, the 16 intersection points are taken as the centers of measurement. When the measurement sample is rectangular, with a 1 cm region from the outer edge of the rectangle as a margin, measurement is performed with the 16 intersection points of the lines dividing the region inside the margin into five equal parts in the vertical and horizontal directions as the centers, and by calculating the average value, the in-plane phase difference of the measurement sample is specified. When the measurement sample has a shape other than a rectangle such as circular, elliptical, triangular, pentagonal, etc., the square or rectangle with the largest area inscribed in these shapes is specified, and for the square or rectangle, 16 measurements are performed by the above method. The in-plane phase difference is measured using the product name "RETS-100" manufactured by Otsuka Electronics Co., Ltd.

[0065] The measurement of the in-plane phase difference Re using RETS-100 follows the following procedures (A1) to (A4). (A1) First, to stabilize the light source of RETS-100, after turning on the light source, leave it for 60 minutes. Then, select the rotating analyzer method and select the θ mode. By selecting this θ mode, the stage becomes an inclined rotating stage. (A2) Next, input the following measurement conditions into RETS-100. (Measurement Conditions) · Retardation measurement range: Rotating analyzer method · Measurement spot diameter: φ5 mm · Inclination angle range: 0° · Measurement wavelength range: 400 nm to 800 nm · Average refractive index of the layer to be measured (for example, in the case of a PET film, N = 1.617) · Thickness: Thickness measured separately by STEM (A3) Next, without installing the sample in this apparatus, background data is obtained. The apparatus is a closed system, and this is carried out each time the light source is turned on. (A4) Then, the sample is installed on the stage in the apparatus and measured.

[0066] When the measurement target of the in-plane retardation does not have a sufficient size due to reasons such as being narrow in width, a measurement sample having a sufficient size under the same conditions as the measurement target is produced, and the in-plane retardation measured for this measurement sample is used as the in-plane retardation of the measurement target.

[0067] <<Apparatus and Method for Manufacturing a Retardation Film>> The manufacturing apparatus 20 for a retardation film includes a manufacturing apparatus 25 for producing the retardation film 10 and an inspection apparatus 30 for inspecting the produced retardation film 10. The manufacturing method of the retardation film includes a step of producing the retardation film 10 and a step of inspecting the produced retardation film 10.

[0068] FIG. 1 is a schematic diagram showing the manufacturing apparatus 20 and the manufacturing apparatus 25. As shown in FIG. 1, the manufacturing apparatus 25 may include a supply roll 26, a recovery roll 27, an alignment film forming section 28, and a liquid crystal layer forming section 29. The supply roll 26 supplies the wound long base material 16 to the subsequent processing apparatus.

[0069] The alignment film forming section 28 forms the alignment film 17. The alignment film forming section 28 may include a coating apparatus, an exposure apparatus, and a curing apparatus. As an example, the alignment film 17 may be produced as follows. First, using a coating apparatus, an alignment film forming coating liquid is coated on the supplied base material 16. A coating film of the alignment film forming coating liquid is formed on the base material 16. This coating film is exposed to polarized light using an exposure apparatus, and the coating film is further cured using a curing apparatus. Thereby, a long alignment film 17 having an alignment regulating force is formed on the long base material 16.

[0070] The liquid crystal layer forming unit 29 forms the liquid crystal layer 18. The liquid crystal layer forming unit 29 may include a coating device and a curing device. As an example, the liquid crystal layer 18 may be fabricated as follows. First, using a coating device, a coating liquid for forming the liquid crystal layer is applied onto the laminate of the supplied substrate 16 and the alignment film 17. A coating film of the coating liquid for forming the liquid crystal layer is formed on the alignment film 17. The liquid crystal compounds in the coating film are aligned by the alignment film 17. The coating film is cured using a curing device. Thereby, a long liquid crystal layer 18 having birefringence is formed on the long alignment film 17.

[0071] The long retardation film 10 is fabricated as described above. The take-up roll 27 winds up the fabricated retardation film 10. The illustrated manufacturing apparatus 20 is a production line for fabricating the long retardation film 10 in a roll-to-roll manner.

[0072] In the example shown in FIG. 1, the inspection apparatus 30 is located in the conveyance path to the take-up roll 27 of the fabricated retardation film 10. That is, the inspection of the retardation film 10 wound up by the take-up roll 27 has been completed.

[0073] <Inspection Apparatus and Inspection Method for Retardation Film> Next, the inspection apparatus 30 and inspection method for the retardation film will be described with reference to the illustrated specific example. In the inspection apparatus 30 and inspection method, the retardation film 10 including the liquid crystal layer 18 and the substrate 16 is inspected in the order from the first surface 11 toward the second surface 12. First, the inspection apparatus 30 will be described, and then the inspection method will be described.

[0074] In the present embodiment, the inspection apparatus 30 includes a light source 32 and an imaging device 34. The light source 32 projects light onto the first surface 11. The imaging device 34 images the retardation film 10 with the reflected light from the retardation film 10. Based on the imaging data acquired by the imaging device 34, the presence or absence of alignment abnormality of the liquid crystal compounds and the presence or absence of thickness abnormality of the liquid crystal layer 18 are inspected. The manufacturing apparatus 20 may further include a determination device 36 and a display device 38.

[0075] Figures 2 and 3 show the inspection apparatus 30 according to the first aspect of the present embodiment. In the first aspect, the light source 32 emits linearly polarized monochromatic light. The light source 32 projects the linearly polarized monochromatic light onto the first surface 11 of the retardation film 10. The light source is not particularly limited. As the light source, a laser device is exemplified. As the laser device, a semiconductor laser device is exemplified. According to the laser device, linearly polarized light can be generated. According to the laser device, monochromatic light can be generated.

[0076] "Monochromatic light" is light that does not contain light of a plurality of colors. "Monochromatic light" means light having a full width at half maximum (FWHM) of 30 nm or less in spectral radiance. The full width at half maximum is also called FWHM. This full width at half maximum means the width (nm) of the wavelength range in which a radiance of half or more of the maximum radiance is obtained. The radiance is the radiance in the direction from the light source toward the projection area of the retardation film 10, which is the inspection object, on the emission end constituting the light emission surface of the light of the light source.

[0077] The imaging device 34 receives linearly polarized monochromatic light. The imaging device 34 is not particularly limited. The imaging device 34 may be a CMOS camera or a CCD camera. The CMOS camera and the CCD camera include pixels. The image data acquired by the CMOS camera or the CCD camera may include gradation data indicating the brightness of each pixel for each pixel.

[0078] In the projection onto the first surface 11, the optical axis angle between the vibration direction DX of the linearly polarized light projected onto the first surface 11 and the optical axes DA and DB of the liquid crystal layer 18 may be 0° or more and 10° or less, or may be 0° or more and 5° or less. FIG. 2 shows the vibration direction DX of the linearly polarized light projected onto the first surface 11 by projecting it onto the first surface 11.

[0079] The optic axis of the liquid crystal layer 18 refers to the slow axis DA of the liquid crystal layer 18 and the fast axis DB of the liquid crystal layer 18. The slow axis DA is the direction in which the refractive index in the plane is the largest. The fast axis DB is the direction in which the refractive index in the plane is the largest. In FIG. 2, the slow axis DA and the fast axis DB are shown. The optic axis angle means the smaller angle between the vibration direction DX in the projection onto the first surface 11 and the slow axis DA, and the smaller angle between the vibration direction DX in the projection onto the first surface 11 and the fast axis DB.

[0080] The slow axis angle means the angle of the smaller one of the two angles formed by the vibration direction DX and the slow axis DA in the projection onto the first surface 11. The slow axis angle is 0° or more and 90° or less. The fast axis angle means the angle of the smaller one of the two angles formed by the vibration direction DX and the fast axis DB in the projection onto the first surface 11. The fast axis angle is 0° or more and 90° or less. The optic axis angle θ is 0° or more and 45° or less.

[0081] In the projection onto the first surface 11, the slow axis angle between the vibration direction DX of the linearly polarized light projected onto the first surface 11 and the slow axis DA of the liquid crystal layer 18 may be 0° or more and 10° or less, or may be 0° or more and 5° or less. In the example shown in FIG. 2, the optic axis angle coincides with the slow axis angle.

[0082] Also, in the projection onto the first surface 11, the optic axis angle between the vibration direction of the linearly polarized light received by the imaging device 34 and the optic axes DA, DB of the liquid crystal layer 18 may be 0° or more and 10° or less, or may be 0° or more and 5° or less. In the projection onto the first surface 11, the slow axis angle between the vibration direction of the linearly polarized light received by the imaging device 34 and the slow axis DA of the liquid crystal layer 18 may be 0° or more and 10° or less, or may be 0° or more and 5° or less.

[0083] In the illustrated example, the linearly polarized light projected onto the first surface 11 coincides with the linearly polarized light received by the imaging device 34. Therefore, the optical axis angle with respect to the vibration direction of the linearly polarized light projected onto the first surface 11 coincides with the optical axis angle with respect to the vibration direction of the linearly polarized light received by the imaging device 34. The retardation axis angle with respect to the vibration direction of the linearly polarized light projected onto the first surface 11 coincides with the retardation axis angle with respect to the vibration direction of the linearly polarized light received by the imaging device 34.

[0084] The light projected onto the first surface 11 may be P-polarized light. P-polarized light is linearly polarized light that vibrates in a plane parallel to both the direction of light propagation and the normal direction to the plane on which the light is incident.

[0085] The incident angle θt of the light from the light source 32 to the phase difference film 10 may be 45° or more and 80° or less, or may be 50° or more and 75° or less. The incident angle θt is the angle between the direction of light propagation at the time of incidence and the normal direction to the incident surface. The incident angle θt has a value of 0° or more and 90° or less.

[0086] The determination device 36 determines the presence or absence of an abnormality based on the image data acquired by the imaging device 34. The determination device 36 may determine the presence or absence of an abnormality based on the gradation data of the pixels included in the image data. As a specific example, the determination device 36 may compare the difference between the maximum gradation and the minimum gradation with a threshold value. The determination device 36 may compare the difference in gradation between adjacent pixels with a threshold value. The determination device 36 may compare the difference in the average value of gradation in two adjacent regions with a threshold value. The determination device 36 may compare the standard deviation or coefficient of variation of the gradation for all the acquired pixels with a threshold value. The determination device 36 may compare the standard deviation or coefficient of variation of the gradation for a plurality of pixels within a partial region with a threshold value.

[0087] The determination device 36 may be electrically connected to the imaging device 34 wirelessly or by wire. The determination device 36 may obtain the data captured by the imaging device 34 from the imaging device 34. The determination device 36 may include a processing unit such as a processor (CPU: Central Processing Unit) and a storage unit such as a RAM. The data obtained from the imaging device 34 may be recorded in the storage unit. The above-described threshold value may be recorded in the storage unit.

[0088] The display device 38 displays the image captured by the imaging device 34. The display device 38 may be electrically connected to the imaging device 34 wirelessly or by wire. As shown in FIG. 3, the display device 38 may be electrically connected to the imaging device 34 via the determination device 36. The display device 38 may display the image of the retardation film 10 captured by the imaging device 34. The display device 38 may display the determination result of the determination device 36.

[0089] Next, the inspection method will be described. The inspection method of the retardation film according to the present embodiment inspects the retardation film 10 including the liquid crystal layer 18 and the base material 16 in the order from the first surface 11 to the second surface 12. The inspection method includes a first step of projecting light onto the first surface 11 and a second step of receiving the reflected light from the retardation film 10 and determining the presence or absence of an abnormality. The presence or absence of an abnormality is determined based on linearly polarized monochromatic light.

[0090] As shown in FIG. 3, in the first step, light La is emitted from the light source 32. The light La emitted from the light source 32 is projected onto the first surface 11 of the retardation film 10. The light La can be reflected by the retardation film 10.

[0091] As shown in FIG. 4, the retardation film 10 reflects the light from the light source 32 on the first surface 11. This reflection includes specular reflection. The reflection can occur at an interface having a refractive index difference. The retardation film 10 includes a reflecting surface that reflects the light La from the light source 32 in addition to the first surface 11. For example, the retardation film 10 includes a first interface 1S located between the liquid crystal layer 18 and the alignment film 17, and a second interface 2S located between the alignment film 17 and the substrate 16. In the illustrated example, the reflected light reflected by the retardation film 10 includes a first reflected light Lb1 reflected by the first surface 11, a second reflected light Lb2 reflected by the first interface 1S, and a third reflected light Lb3 reflected by the second interface 2S.

[0092] In the second step, the imaging device 34 receives the reflected light Lb from the retardation film 10. The imaging device 34 receives the reflected light Lb from the specular reflection direction of the retardation film 10. The imaging device 34 images the reflecting surface. The imaging device 34 images the retardation film 10. In the second step, the presence or absence of an abnormality is determined based on the reception result of linearly polarized monochromatic light. The abnormality of the liquid crystal layer 18 may be detected based on the brightness variation in the imaged area.

[0093] As an example, the abnormality may be detected as follows. The imaging device 34 includes a plurality of pixels. The imaging device 34 divides the imaging area into small areas assigned to each pixel. The imaging device 34 acquires the brightness of the reflected light from each small area as the gradation data of the pixel corresponding to the small area. Based on the variation of this gradation data, the presence or absence of an abnormality may be determined. Based on the variation of this gradation data, the position where the abnormality occurs may be specified. According to the imaging device 34, by setting the gradation number of each pixel to 256, for example, a slight difference in brightness can be stably detected.

[0094] According to the reception result of linearly polarized monochromatic light acquired by the imaging device 34, the thickness abnormality of the liquid crystal layer 18 can be detected.

[0095] As shown in FIG. 4, the imaging device 34 receives, as the reflected light from the phase difference film 10, a first reflected light Lb1, a second reflected light Lb2, and a third reflected light Lb3. The first reflected light Lb1 is the reflected light at the first surface 11. The second reflected light Lb2 is the reflected light at the first interface 1S. The third reflected light Lb3 is the reflected light at the second interface 2S. The first reflected light Lb1, the second reflected light Lb2, and the third reflected light Lb3 can interfere with each other. If the optical path length difference between two reflected lights Lb1, Lb2, Lb3 reflected at different optical interfaces 11, 1S, 2S becomes an integer multiple of the wavelength, the two reflected lights interfere constructively. If the optical path length difference between two reflected lights Lb1, Lb2, Lb3 reflected at different optical interfaces 11, 1S, 2S becomes the length obtained by adding an integer multiple of the wavelength and a half wavelength, the two reflected lights interfere destructively.

[0096] When the thickness of the liquid crystal layer 18 varies in the plane, the optical path length difference between the first reflected light Lb1 and the third reflected light Lb3 changes. The interference state between the first reflected light Lb1 and the third reflected light Lb3 at the position where the thickness variation occurs is different from the interference state at other positions. As a result, the brightness at the position where the thickness variation occurs is different from the brightness of other regions having the planned thickness without thickness variation.

[0097] Similarly, when the thickness of the liquid crystal layer 18 varies in the plane, the optical path length difference between the first reflected light Lb1 and the second reflected light Lb2 also changes. The interference state between the first reflected light Lb1 and the second reflected light Lb2 at the position where the thickness variation occurs is different from the interference state at other positions. As a result, the brightness at the position where the thickness variation occurs is different from the brightness of other regions having the planned thickness.

[0098] Note that in FIG. 4, the optical path is shown while ignoring the influence of refraction.

[0099] Also, according to the light reception result of linearly polarized monochromatic light acquired by the imaging device 34, the alignment abnormality of the liquid crystal compound can be detected.

[0100] The refractive index of the liquid crystal layer 18 with respect to linearly polarized light vibrating in a certain direction changes according to the alignment of the liquid crystal compound contained in the liquid crystal layer 18. For example, the refractive index of the liquid crystal layer 18 with respect to linearly polarized light vibrating in a certain direction is highest when the vibration direction DX of the linearly polarized light coincides with the slow axis DA of the liquid crystal layer 18.

[0101] When the alignment of the liquid crystal compound changes locally, the refractive index difference at the first surface 11 and the refractive index difference at the first interface 1S change. From this point, the light amount of the first reflected light Lb1 and the light amount of the second reflected light Lb2 change according to the alignment abnormality of the liquid crystal compound. In addition, when the alignment of the liquid crystal compound changes locally, the optical path length of linearly polarized light vibrating in a certain direction in the liquid crystal layer 18 changes. Therefore, the interference state between the second reflected light Lb2 and the first reflected light Lb1, and the interference state between the third reflected light Lb3 and the first reflected light Lb1 also change. Further, when the alignment state changes locally, the incident light to the region can be diffused or absorbed. As a result, the brightness at the position where the alignment abnormality of the liquid crystal compound occurs is different from the brightness of other regions having a predetermined thickness.

[0102] Thus, according to the manufacturing apparatus 20 and the inspection method of the present embodiment, it is possible to detect the thickness abnormality of the liquid crystal layer 18 and the alignment abnormality of the liquid crystal compound in the liquid crystal layer 18. The alignment state of the liquid crystal compound affects the birefringence of the liquid crystal layer 18. By detecting the thickness abnormality of the liquid crystal layer 18 and the alignment abnormality of the liquid crystal compound, it is possible to detect the abnormality of the in-plane retardation Re of the liquid crystal layer 18. Therefore, the liquid crystal layer 18 and the retardation film 10 can be appropriately inspected, and the quality of the liquid crystal layer 18 and the retardation film 10 can be accurately evaluated.

[0103] According to the inspection apparatus and the inspection method of the present embodiment, the presence or absence of an abnormality is determined based on the reflected light Lb in the retardation film 10. The inspection light used for the inspection of the liquid crystal layer 18 and the retardation film 10 does not pass through the base material 16. Therefore, the base material 16 used for the retardation film 10 may have birefringence. The base material 16 may include a stretched polyester film. Regardless of whether the base material 16 has birefringence or not, the optical characteristics of the liquid crystal layer 18 can be evaluated with high accuracy.

[0104] For example, Patent Document 2 (JP2014-170072A) proposes an inspection using transmitted light with an Axeostep manufactured by Axometrics. In this inspection, the in-plane retardation Re and the optical axis are measured by transmitted light. However, when the substrate has birefringence, the measured in-plane retardation Re and the optical axis are also affected by the substrate, and the optical characteristics of the liquid crystal layer cannot be correctly evaluated.

[0105] In addition, the inspection device 30 using reflected light can be miniaturized. As shown in FIG. 1, the inspection device 30 can be used as an in-line inspection device incorporated into the manufacturing device 25 which is the manufacturing line of the retardation film 10. It is excellent not only in the inspection efficiency and inspection cost of the retardation film 10, but also in the production efficiency and manufacturing cost of the retardation film 10.

[0106] As shown in FIG. 3, the inspection device 30 may include a determination device 36. The determination device 36 determines the presence or absence of an abnormality based on the data acquired by the imaging device 34. By using the determination device 36, the data acquired by the imaging device 34 can be automatically calculated, and the presence or absence of an abnormality in the retardation film 10 and the liquid crystal layer 18 can be determined with high precision and easily.

[0107] As an example, the determination device 36 may determine the presence or absence of an abnormality based on the image data acquired by the imaging device 34 as follows. The determination device 36 may determine the presence or absence of an abnormality based on the gradation data of the pixels included in the image data. More specifically, the determination device 36 may determine that there is an abnormality when the difference between the maximum gradation and the minimum gradation is equal to or greater than a threshold value. The determination device 36 may determine that there is an abnormality when the difference in gradation between adjacent pixels is equal to or greater than a threshold value. The determination device 36 may determine that there is an abnormality when the difference between the average gradation values in two adjacent regions is equal to or greater than a threshold value. The determination device 36 may determine that there is an abnormality when the standard deviation or coefficient of variation of the gradation for all the acquired pixels is equal to or greater than a threshold value. The determination device 36 may determine that there is an abnormality when the standard deviation or coefficient of variation of the gradation for a plurality of pixels within a partial region is equal to or greater than a threshold value. An AI technique may be used for the determination by the determination device 36.

[0108] As shown in FIG. 3, the inspection device 30 may include a display device 38. The display device 38 can display an image of the retardation film 10 imaged by the imaging device 34. By using the display device 38, an abnormality can be visually confirmed. The presence or absence of an abnormality can be determined with high precision and easily.

[0109] The present inventors prepared an inspection device according to this embodiment. A quarter-wave retardation film was inspected with the prepared inspection device. The quarter-wave retardation film to be inspected was a long retardation film and included a film thickness abnormal portion extending along its longitudinal direction. An image of the film thickness abnormal portion imaged by the imaging device 34 of the inspection device 20 is shown in FIG. 10.

[0110] By setting the inspection device 30 and the inspection method according to this embodiment as follows, abnormalities in the liquid crystal layer 18 and the retardation film 10 can be detected with higher precision.

[0111] In the projection onto the first surface 11, the optical axis angle between the vibration direction DX of the linearly polarized light projected onto the first surface 11 and the optical axes DA and DB of the liquid crystal layer 18 may be 0° or more and 10° or less, or may be 0° or more and 5° or less. That is, as shown in FIG. 2 as an example, the vibration direction DX of the linearly polarized light incident on the first surface 11 may be parallel or substantially parallel to the slow axis DA or the fast axis DB. According to this example, slight fluctuations in the alignment of the liquid crystal compound can be detected. Therefore, local abnormalities regarding the alignment of the liquid crystal compound can be detected with higher precision.

[0112] Similarly, in the projection onto the first surface 11, the optical axis angle between the vibration direction of the linearly polarized light received by the imaging device 34 and the optical axes DA and DB of the liquid crystal layer 18 may be 0° or more and 10° or less, or may be 0° or more and 5° or less. According to this example, slight fluctuations in the alignment of the liquid crystal compound can be detected. Therefore, local abnormalities regarding the alignment of the liquid crystal compound can be detected with higher precision.

[0113] Also, in the projection onto the first surface 11, the slow axis angle between the vibration direction DX of the linearly polarized light projected onto the first surface 11 and the slow axis DA of the liquid crystal layer 18 may be 0° or more and 10° or less, or may be 0° or more and 5° or less. According to this example, slight fluctuations in the alignment of the liquid crystal compound can be detected. Therefore, local abnormalities regarding the alignment of the liquid crystal compound can be detected with higher precision. In addition, for the linearly polarized light vibrating in the direction parallel to the slow axis, the refractive index of the liquid crystal layer 18 increases. That is, for the linearly polarized light vibrating in the direction parallel to the slow axis, the optical path length when traveling through the liquid crystal layer 18 becomes the longest. According to this example, slight fluctuations in the thickness of the liquid crystal layer 18 can also be detected. Therefore, local abnormalities regarding the thickness of the liquid crystal layer 18 can be detected with higher precision.

[0114] Similarly, in the projection onto the first surface 11, the retardation axis angle between the vibration direction of the linearly polarized light received by the imaging device 34 and the retardation axis DA of the liquid crystal layer 18 may be 0° or more and 10° or less, or may be 0° or more and 5° or less. According to this example, slight variations in the alignment of the liquid crystal compound can be detected. According to this example, slight variations in the thickness of the liquid crystal layer 18 can also be detected. As a result, abnormalities in the liquid crystal layer 18 and the retardation film 10 can be detected with higher precision.

[0115] The light La projected onto the first surface 11 may be P-polarized light. According to this example, abnormalities in the liquid crystal layer 18 and the retardation film 10 can be detected with higher precision.

[0116] As described above, the detection of abnormalities in the liquid crystal layer 18 and the retardation film 10 utilizes the interference of the reflected lights Lb1, Lb2, and Lb3 at the first surface 11, the first interface 1S, and the second interface 2S included in the retardation film 10. The first surface 11 is located on the light-incident side with respect to the first interface 1S and the second interface 2S. In other words, in the optical path that reaches the second interface 2S, the first surface 11 is located upstream of the first interface 1S and the second interface 2S. In addition, the first surface 11 is the interface between the liquid crystal layer 18 and the air layer. Therefore, the refractive index difference at the first surface 11 is usually larger than the refractive index differences at the first interface 1S and the second interface 2S. As a result, the light quantity of the first reflected light Lb1 is significantly larger than the light quantities of the second reflected light Lb2 and the third reflected light Lb3.

[0117] By setting the light La projected onto the first surface 11 as P-polarized light, the reflectance at the first surface 11 can be reduced. As a result, the light quantities of the second reflected light L82 at the first interface 1S and the third reflected light L83 at the second interface 2S can be increased and brought closer to the light quantity of the first reflected light L81 at the first surface 11. As a result, the brightness contrast when an abnormality exists becomes higher, and slight variations in the thickness of the liquid crystal layer 18 and slight variations in the alignment of the liquid crystal compound can be detected. Therefore, abnormalities in the liquid crystal layer 18 and the retardation film 10 can be detected with higher precision.

[0118] The incident angle θt of the light La projected onto the retardation film 10 may be 45° or more and 80° or less, and may also be 50° or more and 75° or less. By setting a lower limit for the incident angle θt, abnormalities in the liquid crystal layer 18 and the retardation film 10 can be detected with higher precision. Although the details of the reason why abnormalities can be detected with high precision are unknown, it is presumed that one factor is that the reflectance at the first interface 1S and the second interface 2S increases as the incident angle increases. However, the present disclosure is not restricted by this presumption. By setting an upper limit for the incident angle θt, a sufficient arrangement space for the imaging device 34 that images the light Lb reflected by the retardation film 10 can be secured.

[0119] In the present embodiment, the presence or absence of an abnormality in the liquid crystal layer 18 is determined based on the light reception result of linearly polarized monochromatic light. And in the inspection device 30 of the first aspect described above, the light source 32 projects linearly polarized monochromatic light onto the first surface. However, the light source 32 does not necessarily emit linearly polarized monochromatic light.

[0120] As a second aspect, the light source 32 may emit monochromatic light and project the monochromatic light onto the first surface 11. The light emitted from the light source 32 may be unpolarized light, circularly polarized light, or elliptically polarized light. In the second aspect, as shown in FIGS. 5 to 8, the inspection device 30 may include a polarizer 40. By using the polarizer 40, the light received by the imaging device 34 becomes linearly polarized monochromatic light. Therefore, based on the light reception result of linearly polarized monochromatic light, the presence or absence of an abnormality in the liquid crystal layer 18 and the retardation film 10 can be determined. Also in the second aspect, for the same reason as described above, the presence or absence of an abnormality in the liquid crystal layer 18 and the retardation film 10 can be determined with high precision.

[0121] As a third aspect, the light source 32 may emit linearly polarized light and project the monochromatic light onto the first surface 11. The light emitted from the light source 32 may include light of a plurality of colors. The wavelength of the light emitted from the light source 32 may spread over the range of 380 nm or more and 780 nm or less, which is the visible light wavelength range.

[0122] In a third aspect, as shown in FIGS. 5 to 8, the inspection apparatus 30 may include a band-pass filter 45. The band-pass filter 45 is an optical filter that mainly transmits monochromatic light. As a specific example, the band-pass filter 45 may be a dielectric multilayer film. The full width at half maximum (FWHM) of the spectral transmittance of the band-pass filter 45 may be 30 nm or less. The full width at half maximum is also referred to as FWHM. This full width at half maximum means the width (nm) of the wavelength range in which a transmittance of half or more of the maximum transmittance is obtained.

[0123] The transmittance shall be the arithmetic mean value of five measured values measured in accordance with JIS Z8722:2009. In the measurement of spectral transmittance, the geometric condition e specified in JIS Z8722:2009 shall be adopted. The five measured values shall be the measured values measured at five measurement positions of a sample of the band-pass filter 45 to be evaluated. The five measurement positions are located at least 5 mm apart from each other. The test environment for measuring the spectral transmittance shall be a temperature of 23°C ± 2°C and a relative humidity of 50% ± 5%. The sample shall be placed in the test environment for 16 hours before the start of the test. Before measuring the spectral transmittance, the light source of the measuring device shall be turned on for 15 minutes to stabilize the output of the light source.

[0124] In the third aspect, by using the band-pass filter 45, the light received by the imaging device 34 becomes monochromatic linearly polarized light. Therefore, based on the light reception result of the monochromatic linearly polarized light, the presence or absence of abnormalities in the liquid crystal layer 18 and the retardation film 10 can be determined. Also in the third aspect, for the same reasons as described above, the presence or absence of abnormalities in the liquid crystal layer 18 and the retardation film 10 can be determined with high accuracy.

[0125] In the fourth aspect, the light emitted from the light source 32 may be unpolarized light, circularly polarized light, or elliptically polarized light. The light emitted from the light source 32 may include light of a plurality of colors. In the fourth aspect, as shown in FIGS. 5 to 8, the inspection device 30 may include a polarizer 40 and a band-pass filter 45. By using the polarizer 40 and the band-pass filter 45, the light received by the imaging device 34 becomes linearly polarized monochromatic light. Therefore, based on the light reception result of the linearly polarized monochromatic light, it is possible to determine the presence or absence of abnormalities in the liquid crystal layer 18 and the retardation film 10. Also in the fourth aspect, for the same reason as described above, it is possible to accurately determine the presence or absence of abnormalities in the liquid crystal layer 18 and the retardation film 10.

[0126] In the second and fourth aspects using the polarizer 40, the transmission axis of the polarizer 40 may be adjusted with respect to the optical axes DA and DB of the liquid crystal layer 18. In the projection onto the first surface 11, the optical axis angle between the transmission axis of the polarizer 40 and the optical axes DA and DB of the liquid crystal layer 18 may be 0° or more and 10° or less, or may be 0° or more and 5° or less. The transmission axis of the polarizer 40 coincides with the vibration direction DX of the linearly polarized light that has passed through the polarizer 40. Therefore, by adjusting the optical axis angle in this way, it is possible to detect a slight variation in the alignment of the liquid crystal compound, similar to the case where the above-described optical axis angle θ1 is adjusted. Therefore, local abnormalities regarding the alignment of the liquid crystal compound can be detected with higher accuracy.

[0127] In the second and fourth aspects using the polarizer 40, the transmission axis of the polarizer 40 may be adjusted with respect to the slow axis DA of the liquid crystal layer 18. In the projection onto the first surface 11, the slow axis angle between the transmission axis of the polarizer 40 and the slow axis DA of the liquid crystal layer 18 may be 0° or more and 10° or less, or may be 0° or more and 5° or less. The transmission axis of the polarizer 40 coincides with the vibration direction DX of the linearly polarized light that has passed through the polarizer 40. Therefore, by adjusting the slow axis angle in this way, it is possible to detect a slight variation in the alignment of the liquid crystal compound and also a slight variation in the thickness of the liquid crystal layer 18, similar to the case where the above-described slow axis angle θ1 is adjusted. As a result, abnormalities in the liquid crystal layer 18 and the retardation film 10 can be detected with higher accuracy.

[0128] In the second and fourth aspects using the polarizer 40, as shown in FIGS. 6 and 7, the polarizer 40 may be disposed on the optical path from the retardation film 10 to the imaging device 34 for the light Lb reflected by the retardation film 10. According to this example, the polarizer 40 can be disposed so as to overlap with the imaging lens (light receiving lens) of the imaging device 34. Therefore, the size of the polarizer 40 can be reduced.

[0129] The polarizer 40 used in the inspection device 30 may have a protective film such as triacetyl cellulose laminated thereon.

[0130] In the third and fourth aspects using the band-pass filter 45, as shown in FIGS. 5 and 7, the polarizer 40 may be disposed on the optical path from the retardation film 10 to the imaging device 34 for the light Lb reflected by the retardation film 10. According to this example, the band-pass filter 45 can be disposed so as to overlap with the imaging lens (light receiving lens) of the imaging device 34. Therefore, the size of the band-pass filter 45 can be reduced.

[0131] In the example shown in FIG. 5, the polarizer 40 is located on the optical path from the light source 32 to the retardation film 10 for the emitted light La. The band-pass filter 45 is located on the optical path from the retardation film 10 to the imaging device 34 for the reflected light Lb.

[0132] In the example shown in FIG. 6, the band-pass filter 45 is located on the optical path from the light source 32 to the retardation film 10 for the emitted light La. The polarizer 40 is located on the optical path from the retardation film 10 to the imaging device 34 for the reflected light Lb.

[0133] In the example shown in FIG. 7, the polarizer 40 is located on the optical path from the retardation film 10 to the imaging device 34 for the reflected light Lb. The band-pass filter 45 is located on the optical path from the retardation film 10 to the imaging device 34 for the reflected light Lb.

[0134] In the example shown in FIG. 8, the polarizer 40 is located on the optical path from the light source 32 to the retardation film 10 of the light La emitted from the light source 32. The band-pass filter 45 is located on the optical path from the light source 32 to the retardation film 10 of the light La emitted from the light source 32.

[0135] According to any of the examples shown in FIGS. 5 to 8, abnormalities in the liquid crystal layer 18 and the retardation film 10 can be detected with high precision.

[0136] In one embodiment described above, the retardation film 10 including the liquid crystal layer 18 and the base material 16 is inspected in the order from the first surface 11 toward the second surface 12 facing the first surface 11. The inspection apparatus 30 according to the first aspect includes a light source 32 that emits linearly polarized monochromatic light and projects the light onto the first surface 11, and an imaging device 34 that receives the light reflected by the retardation film 10 and images the retardation film 10.

[0137] The inspection apparatus 30 according to the second aspect includes a light source 32 that emits monochromatic light and projects the light onto the first surface, an imaging device 34 that receives the light reflected by the retardation film 10 and images the retardation film 10, and a polarizer 40 located on the optical path of the light from the light source 32 to the imaging device 34.

[0138] The inspection apparatus 30 according to the third aspect includes a light source 32 that emits linearly polarized light and projects the light onto the first surface, an imaging device 34 that receives the light reflected by the retardation film 10 and images the retardation film 10, and a band-pass filter 45 located on the optical path of the light from the light source 32 to the imaging device 34.

[0139] The inspection apparatus 30 according to the fourth aspect includes a light source 32 that emits light and projects the light onto the first surface, an imaging device 34 that receives the light reflected by the retardation film 10 and images the retardation film 10, a polarizer 40 located on the optical path of the light from the light source 32 to the imaging device 34, and a band-pass filter 45 located on the optical path of the light from the light source 32 to the imaging device 34.

[0140] In the embodiment described above, the inspection method inspects the retardation film 10 including the liquid crystal layer 18 and the substrate 16 in the order from the first surface 11 toward the second surface 12 facing the first surface 11. The inspection method includes a step of projecting light onto the first surface 11 and a step of receiving the reflected light Lb on the retardation film 10 and determining the presence or absence of an abnormality. The presence or absence of an abnormality is determined based on the reception result of linearly polarized monochromatic light.

[0141] According to the inspection apparatus 30 and the inspection method according to the present embodiment, it is possible to detect local variations in the alignment of the liquid crystal compound and local variations in the thickness of the liquid crystal layer 18 using the reflected light on the retardation film 10. Thereby, the optical characteristics of the liquid crystal layer 18 and the retardation film 10 can be inspected.

[0142] Further, since it is an inspection using reflected light, the influence of the birefringence of the substrate 16 can be eliminated, and the optical characteristics of the liquid crystal layer 18 can be inspected. Therefore, the retardation film 10 including various substrates 16 can be the inspection target.

[0143] Furthermore, it is a non-contact inspection using reflected light, and it is not necessary to cut out an inspection sample from the retardation film 10 to be inspected. Therefore, the inspection apparatus 30 can be incorporated into the manufacturing apparatus 25 for the retardation film 10, for example, the manufacturing line of the retardation film. As a result, the production efficiency of the retardation film 10 can be improved, the manufacturing cost of the retardation film 10 can be reduced, and the quality of the retardation film 10 can be stabilized.

[0144] Although an embodiment has been described with reference to specific examples, the above specific examples do not limit the embodiment. The above-described embodiment can be implemented with various other specific examples, and various omissions, replacements, changes, additions, etc. can be made without departing from the gist thereof.

Explanation of Reference Numerals

[0145] DX: Transmission axis, DA: Slow axis, DB: Fast axis, D1: First direction, D2: Second direction, D3: Third direction, 1S: First interface, 2S: Second interface, 10: Phase difference film, 11: First surface, 12: Second surface, 16: Substrate, 17: Alignment film, 18: Liquid crystal layer, 20: Manufacturing apparatus, 25: Fabrication apparatus, 26: Supply roll, 27: Recovery roll, 28: Alignment film forming section, 29: Liquid crystal layer forming section, 30: Inspection apparatus, 32: Light source, 34: Imaging device, 36: Judgment device, 38: Display device, 40: Polarizer, 45: Bandpass filter

Claims

1. An inspection apparatus for inspecting a retardation film including a liquid crystal layer and a substrate in order from a first surface toward a second surface facing the first surface, the inspection apparatus comprising: a light source that emits linearly polarized monochromatic light and projects the light onto the first surface; an imaging device that receives the light reflected by the retardation film and images the retardation film.

2. An inspection apparatus for inspecting a retardation film including a liquid crystal layer and a substrate in order from a first surface toward a second surface facing the first surface, the inspection apparatus comprising: a light source that emits monochromatic light and projects the light onto the first surface; an imaging device that receives the light reflected by the retardation film and images the retardation film; a polarizer positioned on an optical path of the light from the light source to the imaging device.

3. An inspection apparatus for inspecting a retardation film including a liquid crystal layer and a substrate in order from a first surface toward a second surface facing the first surface, the inspection apparatus comprising: a light source that emits linearly polarized light and projects the light onto the first surface; an imaging device that receives the light reflected by the retardation film and images the retardation film; a band-pass filter positioned on an optical path of the light from the light source to the imaging device.

4. An inspection apparatus for inspecting a retardation film including a liquid crystal layer and a substrate in order from a first surface toward a second surface facing the first surface, the inspection apparatus comprising: a light source that projects light onto the first surface; an imaging device that receives the light reflected by the retardation film and images the retardation film; a band-pass filter positioned on an optical path of the light from the light source to the imaging device; a polarizer positioned on an optical path of the light from the light source to the imaging device.

5. The inspection apparatus according to claim 1 or 3, wherein an angle between a vibration direction of the linearly polarized light projected onto the first surface and an optical axis of the liquid crystal layer in the projection onto the first surface is 0° or more and 10° or less.

6. The inspection apparatus according to claim 1 or 3, wherein an angle between a vibration direction of the linearly polarized light projected onto the first surface and a slow axis of the liquid crystal layer in the projection onto the first surface is 0° or more and 10° or less.

7. The inspection apparatus according to claim 2 or 4, wherein an angle between a transmission axis of the polarizer and an optical axis of the liquid crystal layer in the projection onto the first surface is 0° or more and 10° or less.

8. In the projection onto the first surface, the angle between the transmission axis of the polarizer and the slow axis of the liquid crystal layer is 0° or more and 10° or less. The inspection apparatus according to claim 2 or 4.

9. The polarizer is located on the optical path from the retardation film to the imaging device for the light reflected by the retardation film. The inspection apparatus according to claim 2 or 4.

10. The band-pass filter is located on the optical path from the retardation film to the imaging device for the light reflected by the retardation film. The inspection apparatus according to claim 3 or 4.

11. The light projected onto the first surface is P-polarized light. The inspection apparatus according to any one of claims 1 to 4.

12. The incident angle of the light on the retardation film is 45° or more and 80° or less. The inspection apparatus according to any one of claims 1 to 4.

13. The inspection apparatus according to any one of claims 1 to 4, further comprising a determination device that determines the presence or absence of an abnormality based on the data acquired by the imaging device.

14. The inspection apparatus according to any one of claims 1 to 4, further comprising a display device that displays the image captured by the imaging device.

15. The base material includes a stretched polyester film. The inspection apparatus according to any one of claims 1 to 4.

16. A manufacturing apparatus for a retardation film, comprising: A manufacturing apparatus for a retardation film, comprising a manufacturing apparatus for producing the retardation film and the inspection apparatus according to any one of claims 1 to 4.

17. An inspection method for inspecting a retardation film including a liquid crystal layer and a base material in order from a first surface toward a second surface facing the first surface, A step of projecting light onto the first surface, A step of receiving the reflected light from the retardation film and determining the presence or absence of an abnormality, and The presence or absence of the abnormality is determined based on the light reception result of linearly polarized monochromatic light. The inspection method.

18. In the projection onto the first surface, the angle between the vibration direction of the linearly polarized light projected onto the first surface and the optical axis of the liquid crystal layer is 0° or more and 10° or less. The inspection method according to claim 17.

19. In the projection onto the first surface, the angle between the vibration direction of the linearly polarized light projected onto the first surface and the slow axis of the liquid crystal layer is 0° or more and 10° or less. The inspection method according to claim 17.

20. The light projected onto the first surface is P-polarized light. The inspection method according to claim 17.

21. The inspection method according to claim 17, wherein the incident angle of the light on the retardation film is 45° or more and 80° or less.

22. The inspection method according to claim 17, wherein the substrate includes a stretched polyester film.

23. A step of producing the retardation film; A method for manufacturing a retardation film, comprising: a step of inspecting the produced retardation film by the inspection method according to any one of claims 17 to 22.

Images