JP2005241586A - Inspection device and method for optical film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inspection device and method capable of inspecting an optical film using a simple constitution, and capable of easily detecting defects automatically. <P>SOLUTION: This device is provided with a point light source 1 for emitting a light toward the optical film 2, a screen 3 for projecting the light transmitted through the optical film 2 from the point light source 1, an imaging element 5 capable of imaging a projection image on the screen 3, and a detection means for detecting the illuminance change in a photographed image by the imaging element 5. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an inspection method and an inspection apparatus for an optical film used for a display element using liquid crystal.

  Conventional inspection devices for optical films such as polarizing plates include a light source that emits light, an optical filter, a defect-free polarizing plate that serves as a reference, a polarizing plate to be inspected, a polarizing plate to be inspected for installing a polarizing plate to be inspected, and a projection lens. And a screen that outputs an inspection image, and the like. As a result, the size and degree of the defective part of the dust and the flaw can be identified well, and the inspection can be performed (for example, refer to Patent Document 1).

Japanese Patent Laid-Open No. 10-10322

  However, in the conventional display device described above, a halogen lamp or a metal halide lamp is used as a light source, and a defect-free polarizing plate and a lens for enlarging the inspection image are used in addition to the polarizing plate to be inspected. There has been a problem that the inspection apparatus itself becomes complicated or large. Further, the conventional display device described above has the same optical configuration as that of an existing overhead projector. Normally, when configured in this manner, the polarizing plate is irradiated with light diffused from a halogen lamp or the like, that is, light directed in various directions. In this case, there is a problem that certain types of defects are not projected well, and inspection is missed.

  The present invention has been made in view of such problems, and an object of the present invention is to provide an inspection apparatus and an inspection method capable of inspecting an optical film such as a polarizing plate with a simple configuration.

  An optical film inspection apparatus according to the present invention includes a point light source that irradiates light onto an optical film, a screen that projects light that has passed through the optical film from the point light source, and an imaging device that can capture a projected image on the screen. And detecting means for detecting a change in illuminance of an image captured by the image sensor.

  According to the present invention, an optical film such as a polarizing plate can be inspected with a simple configuration, and automatic defect detection can be easily performed.

Embodiment 1
A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic diagram of an optical film inspection device such as a polarizing film used in, for example, a display device in Embodiment 1 of the present invention, and FIG. 2 is a schematic diagram of an inspection image projected on a screen. A general structure of the polarizing film is that TAC (TriAcetyl Cellulose) is pasted on both sides of a PVA (PolyVinyl Alcohol: Polyvinyl alcohol) layer for reinforcement, and further on the surface of the TAC. A protective film is attached, and an adhesive is attached to the surface of the other TAC. The inspection of the polarizing film is carried out in order to detect foreign matter that has entered each layer inside the film, defects caused by scratches, distortions, etc. in the manufacturing process. This is performed as necessary, for example, at the time of application to the actual product of the polarizing film or after application.

  In FIG. 1, light emitted from a point light source 1 passes through an optical film 2 that is an object to be inspected and is projected onto a screen 3. The point light source 1 is preferably a high-intensity point light source such as a halogen lamp converted into a point light source or an LED (Light Emitting Diode), and further in any direction (in this embodiment, the direction of the object to be inspected). In order to improve the directivity of the outgoing light to the point light source 1, it is preferable to provide a light beam stop means 4 on the outgoing side of the point light source 1. Thereafter, the projected image on the screen 3 is picked up by an image pickup device 5 such as a CCD camera. Note that the distance d1 between the light beam diaphragm means 4 and the optical film 2 and the distance d2 between the optical film 2 and the screen 3 shown in FIG. 1 are the size of the optical film 2 that is an object to be inspected, It is appropriately determined depending on the performance of the point light source 1 or the resolution of the image sensor 5. Furthermore, the focus of the imaging device 5 such as a CCD camera may be adjusted to the center of the inspection image projected on the screen 3.

As shown in the schematic diagram of the projected image 6 on the screen shown in FIG. 2, when there are foreign matters, scratches, distortions, or the like inside or on the surface of the optical film 2, due to changes in the refractive index and transmittance at that portion. Compared with the portion 7 where no defect such as foreign matter, scratch or distortion exists, the shadow 8 is confirmed in the portion where the defect such as foreign matter, scratch or distortion exists. For a certain type of defect, the conventional display device described above is irradiated with light in various directions diffused on the polarizing plate, so that many shadows of the defect cancel each other and become invisible. This defect shadow 8 can only be confirmed using the point light source according to the present invention. The defect shadow 8 may be projected darker than the peripheral portion, may be projected brighter than the peripheral portion, and both light and dark may appear. In any case, such a shadow 8 can be confirmed visually, but automatic detection of a defective product can be easily performed by detecting the difference in illuminance by a detection means (not shown).

  By adopting the above-described configuration, a defect-free change film and a lens for enlarging and projecting are unnecessary, and an extremely simple configuration that displays an inspection image only with a point light source and a change film and a screen to be inspected, Inspection of the optical film can be realized with high accuracy, and automatic detection of defects can be easily performed. In this embodiment, for example, when a polarizing film is used as an optical film, anti-glare treatment (a fine unevenness is created on the surface, and reflection of external light is diffused to suppress reflection) is applied to any surface. It is suitable for application to a film that has not been applied.

Embodiment 2
A second embodiment of the present invention will be described with reference to FIG. FIG. 3 shows a schematic diagram of an optical film inspection apparatus such as a polarizing film in Embodiment 2 of the present invention.

  In FIG. 3, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals, and differences will be described. In FIG. 3, unlike the optical film inspection apparatus or inspection method of FIG. 1, the light emitted from the point light source 1 preferably through the light beam diaphragm means 4 is reflected by the optical film 2 as the inspection object. The reflected image (inspection image) is projected onto the screen 3. The reflection image (inspection image) can be confirmed visually as in the first embodiment, but automatic detection of a defective product is facilitated by detecting the difference in illuminance by a detection means (not shown). be able to. As in the first embodiment, the distance d3 between the light beam diaphragm means 4 and the optical film 2 and the distance d4 between the optical film 2 and the screen 3 shown in FIG. It is appropriately determined depending on the size of the optical film 2 that is an inspection object, the performance of the point light source 1, the resolution of the image sensor 5, and the like. Furthermore, the focus of the image sensor 5 such as a CCD camera may be adjusted to the center of the reflected image (inspection image) projected on the screen 3.

By adopting the above configuration, as in the first embodiment, the optical film can be inspected with high accuracy with a very simple configuration in which an inspection image is displayed only with a point light source, a modified film that is an object to be inspected, and a screen. It is possible to easily detect defects automatically. In addition, this Embodiment is a thing suitable for applying to the film by which the anti-glare process was given to one side, when a polarizing film is used as the optical film 2, for example. At that time, in order to improve the reflection efficiency and detect defects inside the optical film, the surface subjected to the anti-glare treatment is disposed on the side opposite to the surface facing the point light source (distant side). It is preferable. Furthermore, in this embodiment, the position of the image sensor is not limited by the size of the optical film that is a non-inspection object, and the image sensor can capture an inspection image, as compared with the first embodiment. It can be installed at an arbitrary position.

As described above, in the first and second embodiments, the polarizing film used for the display device or the like has been described as the optical film. However, the present invention is also applicable to detection of defective products such as a prism sheet, a diffusion sheet, or a reflective polarizing film. Is possible. Moreover, although the case where a CCD camera is applied as the image sensor has been described in the above embodiment, the same effect can be obtained by using an image sensor such as a line sensor in which CCDs are arranged linearly. In addition, this invention is applicable to the optical film used for all the display apparatuses using a liquid crystal or an electroluminescent (EL) element.

It is the schematic of the inspection apparatus of the optical film in Embodiment 1 of this invention. It is a schematic diagram of the inspection image projected on the screen. It is the schematic of the inspection apparatus of the optical film in Embodiment 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Point light source 2 Optical film 3 Screen 4 Light-beam stop means 5 Image pick-up element 6 Inspection image 7 The part where a defect does not exist 8 The part where a defect exists

Claims (8)

A point light source for irradiating the optical film with light;
A screen for projecting light transmitted through the optical film from the point light source;
An image sensor capable of capturing a projected image on the screen;
Detecting means for detecting a change in illuminance of an image captured by the image sensor;
An optical film inspection apparatus comprising: A point light source for irradiating the optical film with light;
A screen for projecting light reflected by the optical film;
An image sensor capable of capturing a projected image on the screen;
Detecting means for detecting a change in illuminance of an image captured by the image sensor;
An optical film inspection apparatus comprising: The optical film inspection apparatus according to claim 1, wherein the point light source includes a light beam diaphragm. The optical film inspection apparatus according to claim 1, wherein the optical film is a polarizing film. Irradiating the optical film with light from a point light source;
Projecting light transmitted through the optical film from the point light source onto a screen;
Capturing a projected image on the screen;
Detecting an illuminance change in the captured image;
An inspection method for an optical film comprising: Irradiating the optical film with light from a point light source;
Projecting light reflected by the optical film onto a screen;
Capturing a reflected image on the screen;
Detecting an illuminance change in the captured image;
A method for inspecting an optical film, comprising: The optical film inspection method according to claim 5, wherein the point light source includes a light beam stop means. The optical film inspection method according to claim 5, wherein the optical film is a polarizing film.

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