KR20090129631A - Apparatus and method for inspecting surface of liquid crystal alignment layer - Google Patents

Abstract

PURPOSE: A liquid crystal alignment film surface testing apparatus and a method thereof are provided to test a defect of a minute groove on a substrate with a minute groove like a rubbing groove formed on an alignment film of a liquid crystal display device. CONSTITUTION: A polarizer(12) is located between a light source part(10) and a to-be-tested object. The polarizer polarizes emitting light. The polarizer emits the polarized light on the surface of the to be tested object. A phase-contrast microscope detects and controls light incident on the surface of the to-be- tested object at a dead angle and reflected. A light source(11) of the light source unit is singular light and parallel light which does not have a coherent characteristic.

Description

Apparatus and method for inspecting surface of Liquid Crystal Alignment Layer

The present invention relates to an apparatus and a method for inspecting the surface state of a liquid crystal alignment film, and more particularly, to an apparatus and a method for inspecting a state and a defect of rubbing grooves in an alignment film for controlling the alignment of liquid crystal molecules in a liquid crystal display device.

A liquid crystal device widely used as an image display device is a display device using a polarization characteristic of light that a liquid crystal has. In the liquid crystal element, a liquid crystal is injected between a pair of substrates, and a voltage is applied to the liquid crystal layer between the substrates to control the transmitted light and the reflected light. Transparent electrodes are formed on each substrate, and an alignment film for determining the initial arrangement of the liquid crystal layer is formed thereon. The orientation of liquid crystal molecules on the alignment film is determined by the surface interaction between the alignment film and the liquid crystal molecules, and the alignment state of the liquid crystal molecules is a very important factor that determines the performance of the liquid crystal device. For this reason, the process of inspecting and evaluating the surface of the alignment layer is one of the important factors that can reduce the defective rate in the production of the liquid crystal display.

However, in the fabrication of a conventional liquid crystal display device, the defect of the alignment film was inevitably inspected after the injection of the liquid crystal, and thus, the liquid crystal display device had to suffer huge losses such as discarding the injected liquid crystal.

Therefore, in order to inspect and evaluate the alignment film, the above-described defects of the microgrooves on the sample surface by aerobic method (method of adding moisture to the sample surface and then reflecting the reflected light by eye inspection or optical light receiving means). Inspected. However, in the aerobic phase method, since there is almost no difference in intensity between the reflected light from the defect and the reflected light from the normal portion, a minute defect could not be detected.

In addition, methods for observing molecular states from molecular vibration, such as infrared absorption spectroscopy and Raman scattering spectroscopy, which are used as methods for evaluating and inspecting conventional liquid crystal alignment films, have been mainly limited to research purposes but have not been applied to actual production.

On the other hand, the surface defect inspection apparatus which irradiates the linearly polarized light of a laser beam on the surface of an inspection object at the incidence angle corresponding to Brewster's angle, selects the polarization direction of a laser beam, and detects the defect on the surface of an inspection object by the reflected light of a laser beam (Japan Japanese Patent Laid-Open No. 3-291552) has been proposed.

The surface defect inspection apparatus and similar methods use a method of inspecting a surface defect with a Hee-Ne laser or a laser light as a light source, but in a flying image method using a CCD (Charge Couple Device) camera, In the case of imaging such coherent light with a CCD camera, since the laser light is reflected from the surface or the back of the protective film of the CCD tip, the transparent electrode or the glass filter, etc., there is a problem of causing interference with the incident light. . That is, since there are numerous optical surfaces in the path of light, there is a problem in that a very complicated image is created due to interference from each surface.

In addition to the above-mentioned vibration spectroscopy by infrared absorption or the like, a method of evaluating the birefringent phase difference of light transmitted through a sample by a method of evaluating the alignment film, or the polarization direction is horizontal or parallel to the film surface. Method to observe the in-plane anisotropy of the film caused by molecular orientation from the difference in the reflected light intensity or the polarization degree of the reflected light by entering orthogonal linearly polarized light (Japanese Patent Laid-Open Nos. 4-95845, 9-90368, 9-60368) ) Has been proposed.

However, the method by vibration spectroscopy using light such as infrared absorption spectroscopy is suitable for the analysis of the alignment film formed on the silicon substrate, but the transparent liquid crystal film is prepared on the glass substrate to measure the liquid crystal element in which the liquid crystal alignment film is provided thereon. When the glass substrate and the transparent electrode film absorb infrared rays, there is a problem that is not appropriate for evaluation of the liquid crystal element.

In addition, the polarization state of the reflected light is widely used by the rotational analyzer method required by the analyzer angle dependence of the intensity of light passing through the analyzer. In this method, the intensity of light in the 360 degree rotation of the analyzer is measured. In order to solve this problem, a measurement time of one point of the sample surface is long, and there is a problem in that enormous time is required for evaluating one shape of molecular orientation of a large area.

In addition, even when the polarization modulation method is used, when the alignment film is evaluated by the above-described method, it is necessary to rotate the alignment film 360 degrees while keeping the angle of incidence constant. There is a problem that is required.

Recently, atomic scale equipment such as Scanning Electron Microscope (SEM) or Atomic Force Microscope (AFM) has been used as an attempt to observe the rubbing state of the alignment layer. The results of observation of the microgrooves by AFM have been reported.

However, the inspection and evaluation method of the alignment film using the SEM or AFM is difficult to prepare for observing a sample, and only a small range can be observed, which takes a long time to observe a wide range. For example, SEM requires a sample to be placed in a vacuum chamber, and AFM measures a very weak force called atomic force, so the range that can be observed at once is as small as several nm to several μm. Therefore, it takes a lot of time to observe a wide range to some extent, even if the installation of the equipment is very expensive and difficult to install conditions there is a problem as a device for measuring the rubbing groove is not efficient.

Accordingly, an object of the present invention is to provide a liquid crystal alignment film surface inspection apparatus and method capable of inspecting defects of the fine grooves in a substrate having fine grooves on the same surface as the rubbing grooves formed in the alignment layer of the liquid crystal display device.

In addition, another object of the present invention is to solve the above-mentioned problems of the prior art, and it is possible to significantly reduce the defect of the liquid crystal display device due to the alignment film by evaluating the surface state of the alignment film fabricated on the glass substrate and detecting the defect. It is providing the liquid crystal aligning film surface inspection apparatus and method.

The liquid crystal aligning film surface inspection apparatus according to the present invention for achieving the above objects, the light source unit for emitting light for irradiating the surface state of the inspection object, and the emitted light is incident to inspect the surface state of the inspection object A liquid crystal alignment layer surface inspection apparatus having a support for an object and a light receiving unit comprising a camera and a monitor for detecting and converting the reflected light of the incident light, wherein the light is disposed between the light source and the object to be polarized, and then A polarizer for emitting polarized light to the surface to be irradiated; And image forming control means for detecting and controlling the light reflected by the polarized light incident on the surface of the irradiated object in a rectangular shape, wherein the light source of the light source unit is monochromatic light and has no coherent characteristics. It is done.

In addition, the liquid crystal alignment film surface inspection method according to the present invention for achieving the above objects, the light source unit for emitting light for irradiating the surface state of the inspection object, and the surface state of the inspection object by the incident light is incident A liquid crystal aligning film surface inspection method using a liquid crystal alignment film surface inspection apparatus having a light-receiving portion comprising a camera and a monitor for detecting and converting reflected light of the incident light for inspecting the light. ) Emitting a parallel light source having no characteristics; Polarizing the emitted light through a polarizer positioned between the light source unit and the inspected object and then emitting polarized light onto a surface to be irradiated; Injecting the polarized light into a square on the surface of the irradiated object; And detecting and controlling the light reflected by the incident light from the surface of the irradiated object.

In this case, the angle emitted from the light source unit and reflected on the inspected object and incident on the imaging control means is a Brewster angle according to the refractive index of the inspected object.

In this case, RC LED may be used as the light source of the light source unit, and the test object may be an interface between the alignment layer of the liquid crystal, the alignment of the domain, and the composite monolayer. In addition, it is preferable that a phase difference microscope is used for the said imaging control means.

As described above, the present invention provides a phase difference of 1/4 wavelength in the low frequency region of the conjugated surface at a position where defects (foreign materials, scratches, scratches, irregularities in density, etc.) are present on the surface of the alignment film of the liquid crystal, or where microgrooves are caused by rubbing. By applying, it is very effective in detecting foreign matter with little difference in refractive index between the background and observing geometric defects (or intentional microstructure) on the same background material.

In addition, the present invention has the advantage that can remove the optical noise other than the reflected light by the P-polarized input light.

In addition, the present invention has the effect of inspecting the rubbing state and impurities of the alignment layer surface and the spacer position of the empty cell.

In addition, the present invention has the advantage of not having to consider the dispersion effect of the refractive index of the sample by using a monochromatic light beam as a light source.

DETAILED DESCRIPTION Hereinafter, detailed descriptions of preferred embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the same components in the figures represent the same numerals wherever possible. Specific details are set forth in the following description, which is provided to aid a more general understanding of the present invention. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

The present invention is composed of a light source unit for emitting light, an object support for entering the emitted light to inspect the surface state of the inspected object, and a light receiving unit including a camera and a monitor for detecting and converting the reflected light.

In order to solve the above-mentioned problems of the prior art, the present invention proposes an apparatus and method for solving the above problems by using a method different from the conventional methods in the light source unit and the light receiving unit, respectively.

The light source unit of the present invention basically proposes a light source and an incident optical system designed to satisfy the Brewster condition without interference noise.

In general, laser light has excellent monochromaticity and parallelism, but interference noise is inevitable due to coherence characteristics. Therefore, in the present invention, a light source having no coherent characteristics is adopted as the input light source. If the light source is not a single color, the Brewster angle varies depending on the wavelength due to the refractive index dispersion of the alignment layer, so that a single light source is used as an input light source. In addition, a parallel light source is a condition of an incident light source so that light is incident on Brewster conditions at any position on the surface of the alignment film having a flat surface. When these three interphases are satisfied, the light source is later provided with a polarizer so that the polarization of light becomes P-polarized light parallel to the incident surface to satisfy the Brewster condition. Liver-> cases

In such a light source and an incident optical system, light having a monochromatic, parallel, non-coherence of P-polarized light can be incident in parallel to the irradiation surface of the alignment film.

The intensity of reflected light due to the P-polarized light may be represented by Equation 1 below.

Where n is the relative refractive index of the medium and θ is the incident angle.

However, when the incident angle is the Brewster angle, the reflection coefficient according to Equation 1 becomes 0.

Therefore, the P-polarized parallel light incident on the surface at the Brewster's angle is incident on each part of the surface and there is no reflection at the position where Brewster's condition is met, but the position or rubbing where there is a defect (foreign material, flaw, scratch, density irregularity, etc.) The location of the micro grooves due to the Brewster condition is broken and reflection occurs.

In the present invention, by adopting an optical system for inspecting the surface shape through a CCD device by expanding the reflected light from the surface in the light receiving unit, the focus of the microscope objective lens to obtain an image that is significantly improved in performance compared to the measurement using a conventional microscope optical system. The Phase Contrast Microscope (PCM) system is used to position the optical low frequency filter in the vicinity. This method provides a special advantage in detecting foreign matter with little difference in refractive index between the background and observing geometric defects (or intentional microstructures) on the same background material by applying a phase difference of 1/4 wavelength in the low frequency region of the conjugate surface. Have

In principle, no reflection from the surface of the flat alignment film can occur for P-polarized incident light. In practice, however, very slight reflections can occur due to slight S polarization due to the extinction ratio of the polarizer, thermal fluctuations in the surface, or phase changes caused by surface reflection.

These reflections are background reflections and do not produce special patterns. However, rubbing, surface defects, impurities, and the like on the surface of the alignment film disturb the Brewster conditions and cause reflection according to their shape on the surface. Therefore, in the present invention, the light reflected from the surface is enlarged using a microscope objective lens. Behind the objective lens, a CCD camera is mounted so that the light reflected from the surface is captured by the CCD camera and displayed on the monitor. According to circumstances, an analyzer may be installed on the light receiving unit to remove optical noise other than the reflected light caused by the P-polarized input light.

The apparatus and method described above can inspect the rubbing state, impurities, and spacer positions of empty cells on the surface of the alignment layer.

Hereinafter, a liquid crystal alignment film surface inspection apparatus and a method according to the present invention will be described in detail with reference to FIG. 1.

1 shows an alignment film inspection apparatus according to a preferred embodiment of the present invention. First, the light source unit 10 uses a RC-LED (Resonant Cavity Light Emitting Diode), which is a monochromatic light and has no coherent characteristics. Create The polarizer 12 which polarizes the light from the light source 11 of the light source unit 10 is effective to use a polarizing plate having a high extinction ratio. In this embodiment, a Glan-Thompson polarizer is used. The polarizer 12 is installed on a rotation stage (not shown) to adjust the polarization direction of the laser beam. There must be a device (not shown) capable of adjusting the angle of incidence 51 to match the Brewster angle of incidence, which is determined by Equation 2 below according to the refractive index of the object 20.

Where n1 is the refractive index of the air and n2 is the refractive index of the medium.

The x-y stage 21 may be used as a fine moving means for inspecting the entire surface of the object to be installed thereon, and may be used by adding an electric moving means such as a step motor in some cases.

The reflected surface shape is imaged by the CCD camera or the C-MOS imaging camera 34 via the objective lens 31 of the light receiving portion 30, the quarter-wave retardation filter 32, and optionally the polarizer 33. Is measured.

Although the magnification of the objective lens 31 is determined according to the field of view setting, the magnification of the objective lens 31 is determined so that a working distance can be sufficiently secured in consideration of being installed in a rectangular shape. The quarter-wave retardation filter 32 is installed at the focal point of the objective lens 31, but the quarter-wave retardation filter 32 is disposed so that the spatial low frequency portion has a quarter wavelength retardation with respect to the other portions. ) And the center of the objective lens 32 is exactly matched. In addition, in some cases, the 1/4 wavelength retardation filter 32 may be installed in the fine x-y stage to match the focal point. In some cases, another polarizer 33 may be provided to increase the contrast or to detect the polarization dependent property of the surface. The reflected surface shape is measured by an image camera such as a CCD camera and the like and is image-processed by the image signal processor 40.

As described above, the light source unit of the present invention basically proposes a light source and an incident optical system designed to satisfy the Brewster condition without interference noise, and by using this to optically observe the shape of the rubbing formed on the alignment layer, Inspection of defects present on the surface of the alignment film.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by the equivalents of the claims.

1 is a view showing an alignment film inspection apparatus according to a preferred embodiment of the present invention.

Claims (8)

A light source unit emitting light for irradiating the surface state of the inspected object, an object support for inspecting the surface state of the inspected object, and a camera and monitor for detecting and converting the reflected light of the incident light; In the liquid crystal aligning film surface inspection apparatus provided with the light receiving part comprised, A polarizer positioned between the light source unit and the inspected object to polarize the emitted light and to emit polarized light on a surface to be irradiated; And And image forming control means for detecting and controlling the light reflected by the polarized light incident on the surface of the irradiated object in a rectangular shape. And a light source of the light source unit is a monochromatic light and parallel light without coherent characteristics. The method of claim 1, And an angle emitted from the light source unit and reflected by the inspected object to be incident on the image forming control means is a Brewster angle according to the refractive index of the inspected object. The light source of claim 1, wherein the light source of the light source unit is Liquid crystal aligning film surface inspection apparatus characterized by being RC LED. According to claim 1, The test object, The liquid crystal aligning film surface inspection apparatus characterized by the boundary surface of the alignment film of a liquid crystal, the orientation of a domain, and a composite monomolecular film. The image forming control means according to claim 1 or 2, It is a phase difference microscope, The liquid crystal aligning film surface inspection apparatus. A light source unit emitting light for irradiating the surface state of the inspected object, an object support for inspecting the surface state of the inspected object, and a camera and monitor for detecting and converting the reflected light of the incident light; In the liquid crystal aligning film surface inspection method using the liquid crystal aligning film surface inspection apparatus provided with the light receiving part comprised, Emitting a parallel light source from the light source unit and having no coherent property; Polarizing the emitted light through a polarizer positioned between the light source unit and the inspected object and then emitting polarized light onto a surface to be irradiated; Injecting the polarized light into a square on the surface of the irradiated object; And And detecting and controlling the light reflected by the incident light from the surface of the object to be irradiated. The method of claim 6, And an angle emitted from the light source unit and reflected by the inspected object to be incident on the image forming control means is a Brewster's angle according to the refractive index of the inspected object. 8. The image forming control means according to claim 6 or 7, It is a phase difference microscope, The liquid crystal aligning film surface inspection method characterized by the above-mentioned.

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