JP2013148448A - Method for inspecting optical film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inspection method which can accurately detect a defect, such as a foreign material on an optical film and a defect due to a small change in film thickness around the foreign matter, can handle an inspected optical film as a product and is performed by efficient visual observation.SOLUTION: An inspection method determines the existence/absence of abnormality of reflected light by irradiating a light source with light from one surface side of an optical film having a transparent optical function layer on the one surface of the film while the other surface of the optical film is brought into close contact with a metal stage member through a transparent liquid layer.

Description

  The present invention relates to a method for inspecting a transparent optical film used for a display device or the like simply and accurately by visual observation.

  In recent years, for display devices such as CRT and liquid crystal, there has been an increasing demand for transparent optical films having various functions in order to improve the quality and function of the display device itself or to provide image quality that is not affected by the environment in which the display device is used. Yes.

  In general, an optical film is a film intended to give various effects by transmitting or reflecting and absorbing light. For example, it has functions such as antireflection, orientation, polarization, phase difference, brightness enhancement, and light shielding.

  The optical film as described above is required to have strict quality with respect to the thickness, dimensional accuracy, exclusion of foreign matters, etc. affecting the optical characteristics in order to efficiently exhibit the optical characteristics, and accordingly the manufacturing environment and method In addition, high accuracy is required for inspection equipment and methods.

  In order to guarantee the quality of such an optical film, various attempts have been made especially for the inspection method for the final form (product) of the optical film. Hereinafter, an antireflection film that reduces the reflection phenomenon caused by the influence of ambient light will be described as an example of an optical film.

  An antireflection film has various configurations, but in general, an optical film in which a high refractive index layer such as a metal oxide and a low refractive index layer made of an organic resin are alternately laminated on one surface of a transparent plastic substrate. A functional layer is formed (Patent Document 1).

  In the quality inspection in the final form of the antireflection film having such a structure, in order to accurately detect defects (foreign matter, thickness unevenness, etc.) occurring in the outermost antireflection layer, the noise of the surface reflection light is detected. Various devices have been devised as a method for suppressing reflected light from the interface of the other surface (surface side in contact with the air layer) of the transparent plastic substrate as a base.

  For example, as shown in FIG. 2 (a), the other surface of the antireflection film 10 (the air layer and the antireflection film 10 in which the hard coat layer 4 and the antireflection layer 5 are sequentially laminated on one surface of the transparent substrate 3). By applying a black paint and providing the black paint layer 6 on the other surface side of the transparent base 3 in contact, reflected light from the interface between the transparent base 3 and the black paint layer 6 is suppressed.

  Further, as shown in FIG. 2B, the other surface (an air layer and the other surface) of the antireflection film 10 in which the hard coat layer 4 and the antireflection layer 5 are sequentially laminated on one surface of the transparent substrate 3. By laminating the black film 8 on the other surface side of the transparent substrate 3 in contact with the adhesive layer 7, the reflected light from the interface between the transparent substrate 3 and the black paint layer 6 is suppressed. (Patent Document 2).

  However, in the inspection method shown in FIG. 2A, the black paint is directly applied to the final form of the antireflection film, so that the damage caused by the application process and the drying process is large, and the antireflection film used after the inspection is utilized as a product. There is a problem that can not be. Further, the inspection method shown in FIG. 2 (b) also has a problem that the antireflection film used after the inspection cannot be used as a product after the inspection in the same manner as the inspection method of FIG. 2 (a) due to the adhesive layer.

JP 2002-341104 A JP 2006-71633 A

  The present invention provides a visual inspection method with no waste, which can accurately detect defects such as foreign matters and defects due to minute changes in the film thickness around the defect, and can be handled as a product even after inspection. .

  As means for solving the above problems, the invention according to claim 1 is characterized in that the other surface of the optical film having a transparent optical functional layer on one surface of the film and the metal stage member are transparent. In an inspection method, a light source is irradiated from one surface side of the optical film in a state of being in close contact with each other through a liquid layer, and the presence or absence of abnormality of the reflected light is visually determined.

  The invention according to claim 2 is the inspection method according to claim 1, wherein the metal stage member has a reflectance of 40% or less.

  The invention according to claim 3 is characterized in that the metal stage member has a chromaticity difference d, 0.005 to 0.010 expressed by the following equation (1). Or it is the inspection method of 2.

ｄ：色度差、ｘ_０：黒塗りフィルムの色度座標ｘ、ｙ_０：黒塗りフィルムの色度座標ｙ
ｘ_ｉ：ステージ部材の色度座標ｘ、 ｙ_ｉ：ステージ部材の色度座標ｙ
但し、ｘ_０＝０．４０３、ｙ_０＝０．３８７

d: chromaticity difference, x ₀ : chromaticity coordinate x of black coating film, y ₀ : chromaticity coordinate y of black coating film
x _i : Stage member chromaticity coordinate x, y _i : Stage member chromaticity coordinate y
_{However, x 0 = 0.403, y 0} = 0.387

The present invention is a state in which the other surface of the optical film having a transparent optical functional layer on one surface of the film according to claim 1 is in close contact with the metal stage member via a transparent liquid layer. By visually inspecting the surface reflected light, the liquid layer can be easily removed even after the inspection, and the optical film used for the inspection is not damaged. Further, the reflectance of the stage member according to claim 2 is 40% or less, and the chromaticity difference d of the stage member according to claim 3 is 0.005 to 0.010. Inspection can be performed easily.
Therefore, according to the inspection method of the present invention, the optical film can be visually inspected for defects with good accuracy, and wasteless quality control that can be handled as a product even after the inspection can be efficiently executed.

It is a schematic sectional drawing which shows one Embodiment of the inspection method of the optical film of this invention. It is a schematic sectional drawing which shows one Embodiment of the inspection method of the conventional optical film. It is a schematic sectional drawing of the reflected light in the base material back surface of an optical film.

  The method for inspecting an optical film of the present invention will be described below in detail with reference to FIG. 1, taking an antireflection film as an example.

FIG. 1 is a schematic cross-sectional view showing an embodiment of the optical film inspection method of the present invention. In the inspection method of the present invention, the other surface of the antireflection film 10 provided with an antireflection function by sequentially laminating the hard coat layer 4 and the antireflection layer 5 on one surface of the transparent substrate 3 (in contact with the air layer). In a state where the stage member 1 is in close contact with the other surface side of the transparent base material 3 via the liquid layer 2, the surface of the antireflection layer 5 is irradiated with light from the light source 20 thereabove, and the reflected light This is a method for visually detecting a change.

  Generally, the transparent substrate 3 used for the antireflection film 10 is a TAC (triacetylcellulose) film, and its refractive index is about 1.51. Therefore, the liquid layer 2 used here plays a role of preventing air from intervening between the TAC film and a stage member described later (see the following formula 2).

  The reflected light of the antireflection film 10 will be described below with reference to FIG. FIG. 3 is a schematic cross-sectional view of a general antireflection film 10, which has a structure in which a hard coat layer 4 and an antireflection layer 5 having substantially the same refractive index as that of the transparent substrate are sequentially formed on the transparent substrate 3. It is configured by stacking. Here, in the antireflection layer 5, incident light becomes reflected light 50 at the interface between the antireflection layer 5 and the hard coat layer 4, and the light interferes with the surface reflected light 40, thereby obtaining an antireflection effect. . At this time, if there is a local defect accompanied by a change in the thickness of the antireflection layer 5, a difference occurs in the antireflection effect due to interference, resulting in poor appearance.

Meanwhile, in the interface between the other transparent substrate 3 which is the surface of the air layer of the antireflection Fiirumu 10, the refractive index n ₀ of the transparent substrate _3, the refractive index n ₁ of the adjacent material (in this case air) As a result, the ratio of the refractive index between the transparent base material 3 and the air layer is increased according to the formula shown in Equation 2, so that the reflectance R is increased, which makes it difficult to detect a defect in the antireflection layer.

  In the present invention, in order to eliminate such a factor that hinders the detection of defects in the antireflection layer, a liquid layer having a refractive index substantially equal to the refractive index of the transparent base material is provided on the other surface of the transparent base material 3. This is a defect inspection in which a metal stage member is closely attached.

  The liquid layer 2 according to the present invention is not particularly limited as long as it has a refractive index near the refractive index of 1.51 of the TAC film. In particular, a liquid having a refractive index of 1.49 to 1.54, more preferably a liquid having low activity and low toxicity that does not damage the TAC film or the stage member.

  Further, the stage member 1 according to the present invention has a function of absorbing incident light and suppressing reflected light at the interface with the TAC film, and a metal member having a reflectance of 40% or less is preferable. If the reflectance exceeds 40%, it is difficult to detect defects in the antireflection layer, which causes a problem in quality control.

  The reflectance at this time is a range of wavelengths of 380 nm to 780 nm in which a projector and a light receiver are installed at an angle of 45 degrees using a reflectance measuring device having a halogen light source and regularly reflected on the metal member surface. This is a value obtained by measuring the maximum value of reflectance. In addition, as a comparative control of reflectance, a white plate was used, and a liquid layer (manufactured by Shinko Sangyo Co., Ltd .: “Petrosafesol AK-EO2” refractive index 1.40 was used between the antireflection film 10 and the stage member 1. ) To select a stage member having a reflectance of 0 to 40%.

For reference, a stainless steel member subjected to a rayent treatment (made by Raydent Kogyo Co., Ltd .: special electroplating treatment) as a metal stage member and a black paint (made by Asahi Pen Co., Ltd .: “CREATIVE COLOR matt, refractive index 1) .51 "), the former has a reflectance of 12% and the latter has a reflectance of 25%, both of which have a reflectance of 40% or less. The reflectance can be made lower than that of the conventional black paint.

  Moreover, the stage member according to the present invention can confirm the change in color by limiting the chromaticity difference in addition to the reflectance, and can detect the defect of the antireflection film visually with higher accuracy. That is, the chromaticity difference of the antireflection film when the stage member is used, the conventional method that is considered to have high visibility (the chromaticity of the antireflection film when the black paint is applied to the back side of the antireflection film) By making it close to (difference), it is possible to visually confirm a change in color due to a defect.

  An XYZ color system (one of the color systems of the International Certification Committee CIE) is used as a system for quantitatively expressing colors such as the above chromaticity difference. In this XYZ color system, numerical values and colors are used. The relationship is difficult to understand. Therefore, when the color tone of the stage member is limited using an xyY color system that expresses an absolute hue from the XYZ color system, the chromaticity difference d expressed by the following equation (3), 0.005 to 0. It is preferable to satisfy 010.

ｄ：色度差、ｘ_０：黒塗りフィルムの色度座標ｘ、ｙ_０：黒塗りフィルムの色度座標ｙ
ｘ_ｉ：ステージ部材の色度座標ｘ、 ｙ_ｉ：ステージ部材の色度座標ｙ

d: chromaticity difference, x ₀ : chromaticity coordinate x of black coating film, y ₀ : chromaticity coordinate y of black coating film
x _i : Stage member chromaticity coordinate x, y _i : Stage member chromaticity coordinate y

  The conversion from the XYZ color system to the xyY color system is obtained from the following equation (4).

  The stage member chromaticity difference d, that is, the specific selection of the stage member, for allowing the defect of the antireflection film to be visually confirmed by the change in color, will be described below.

The high-visibility black paint described above (manufactured by Asahi Pen Co., Ltd .: “CREATIVE COLOR matt, refractive index 1.51”) is applied to the TAC film, and the chromaticity coordinates (x ₀ , seek y _0). Similarly, the chromaticity coordinates (x _i , y _i ) of various stage members are obtained. By substituting these values into the above equation 3, the chromaticity difference d is calculated, and an appropriate stage member is selected.

As an example of implementation, the following results were obtained when a stainless material subjected to a radiant treatment was used as the stage member.
(X ₀ , y ₀ ) = (0.403, 0.387)
(X _i , y _i ) = (0.409, 0.384)
d = 0.068

From the above results, the chromaticity difference d of the stage member is preferably 0.005 to 0.010, and the change in color is visually observed by making the chromaticity difference equivalent to that of a black paint having higher visibility than conventional. Can be confirmed.
That is, by selecting a stage member having a reflectance of 40% or less and a chromaticity difference d of 0.005 to 0.010, a defect inspection of an optical film such as an antireflection film can be accurately and visually performed. it can.

DESCRIPTION OF SYMBOLS 1 Stage member 2 Liquid layer 3 Transparent base material 4 Hard coat layer 5 Antireflection layer 6 Black paint layer 7 Adhesive layer 8 Black film 10 Antireflection film 20 Light source 30 Incident light 40 Surface reflection light 50 Antireflection layer 5 and hard coat Reflected light 60 at the interface of the layer 4 Reflected light at the interface between the transparent substrate 3 and the air layer

Claims (3)

  One surface side of the optical film in a state in which the other surface of the optical film having a transparent optical functional layer on one surface of the film is in close contact with the metal stage member via the transparent liquid layer An inspection method characterized by irradiating a light source from a light source and visually determining whether there is an abnormality in the reflected light.   The inspection method according to claim 1, wherein the metal stage member has a reflectance of 40% or less. The inspection method according to claim 1 or 2, wherein the metal stage member has a chromaticity difference d expressed by the following formula (5), 0.005 to 0.010.

d: chromaticity difference, x ₀ : chromaticity coordinate x of black coating film, y ₀ : chromaticity coordinate y of black coating film
x _i : Stage member chromaticity coordinate x, y _i : Stage member chromaticity coordinate y
_{However, x 0 = 0.403, y 0} = 0.387

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