KR20110093253A - Apparatus for measuring of aligning state of alignment layer and method for measuring tht same - Google Patents

Abstract

PURPOSE: An alignment state measuring device of alignment layer and measuring method thereof are provided to exclude interference by a layer neighboring to an alignment layer. CONSTITUTION: An alignment state measuring device of the alignment layer includes as follows. A illuminating unit(10) illuminates light to a vertical direction. A polarizer(20) is located on a rear end of the illuminating unit and linearly polarizes the entered light from the illuminating unit. A beam splitter(30) reflects and transmits one part of the light emitted form the polarizer and is located on rear end of the polarizer. A compensator(40) is located on rear end of the beam splitter and circle-polarizes the transmitted light which passed through the beam splitter. A sample plate is formed on rear end of the compensator and has an alignment layer on a surface. An analyzer(60) penetrates the polarized light to a specific direction among linearly polarized light from the compensator at the alignment layer of the sample substrate and is located on a path of the light reflected from the beam splitter. An optical detector(70) detects the intensity of the light transmitted the analyzer. A control unit controls the rotation of the analyzer and the sample substrate by calculating alignment state information of the alignment layer form the intensity of the light detected from the optical detector.

Description

Apparatus for measuring alignment state of alignment film and measuring method {APPARATUS FOR MEASURING OF ALIGNING STATE OF ALIGNMENT LAYER AND METHOD FOR MEASURING THT SAME}

The present invention relates to a state information measuring apparatus and a measuring method of the alignment film, in particular by measuring the alignment state information of the alignment film by using light reflected perpendicularly to the alignment film, by excluding interference by a layer adjacent to the boundary surface of the alignment film The present invention relates to an alignment state measuring apparatus and a measuring method of an alignment film that can improve measurement accuracy.

The liquid crystal display device is largely divided into a liquid crystal display panel for displaying an image and a circuit portion for driving the liquid crystal display panel.

The liquid crystal display panel includes a TFT substrate having a pixel electrode and a TFT array, which is a switching element, a CF substrate having a color filter array, and a liquid crystal layer formed between the two substrates.

The liquid crystal layer should have a uniform initial arrangement, and the initial alignment of the liquid crystal layer is determined through an alignment layer formed on one or both sides of the TFT substrate and the CF substrate. The alignment layer is composed of a polymer material layer such as polyimide, and the surface is treated to have a constant direction and intensity by physical rubbing or a patterning process using polarized ultraviolet rays.

Since the alignment direction and the alignment intensity of the alignment film are the main factors that determine the direction in which the liquid crystals are aligned at the interface and the degree to which the liquid crystals are fixed, defects in the alignment process step are a direct cause of deterioration of image quality.

Therefore, before the liquid crystal is filled between the TFT substrate and the CF substrate, the alignment state of the alignment layer, that is, the optical anisotropy measurement, must be performed. Ellipsometry is used as one of the methods for measuring the optical anisotropy of the alignment layer.

The elliptic method is an analysis method that investigates the optical properties of a material by using the property that the polarization state of the light changes according to the refractive index or thickness of the medium after the light incident on the material is reflected or transmitted on the surface of the medium. This method measures the phase difference of the reflected or transmitted light generated by birefringence when linearly polarized light is incident on the sample as a function of the rotation angle of the sample.

The optical anisotropy measuring method of the alignment film using the elliptic method has been disclosed in Korean Patent Laid-Open Publication No. 2008-0061196 entitled "Rubber angle measuring device of liquid crystal alignment film and its measuring method".

According to this technique, angularly polarized light allows the analyzer to rotate at a constant angle. In this case, the analyzer may transmit only the light polarized in a specific direction among the light transmitted through the sample. And the orientation angle of an oriented film, ie, the optically anisotropic state, is detected from the intensity of the specific polarization which transmitted the analyzer.

However, in the conventional transmissive alignment film measuring apparatus, since a thin film transistor array or a color filter array such as an ITO electrode is formed under the alignment film, incident light is interfered by the thin film transistor array or the color filter array to cause a measurement error. There is a disadvantage in that the optical anisotropy measurement accuracy of the alignment film is lowered.

On the other hand, the optical anisotropy measuring method of the alignment film using the elliptical polarization method has been disclosed in the title of "Optical anisotropy parameter measuring apparatus and measurement method" in Korea Patent Publication No. 2006-0085574.

According to this technique, the polarized light inclined at a predetermined angle with respect to the axial direction of the alignment film is incident on the sample substrate, and the polarization component orthogonal to the polarization direction of the incident light is detected among the light reflected from the surface of the sample substrate, and the detection is performed. Based on the result, the optical anisotropy parameter of the alignment film is measured.

However, according to the conventional reflective measurement method, the anisotropy formed by the light reflected from the sample substrate after being incident in the oblique direction is greater than the anisotropy formed by the alignment film formed on the sample substrate, and the light incident on the sample is linearly polarized. Because of this, the anisotropy of the alignment film is not reflected well in the measurement, there is a disadvantage in that the accuracy of the measurement is poor.

SUMMARY OF THE INVENTION An object of the present invention for solving the disadvantages of the background art is to provide an apparatus for measuring an alignment state of an alignment film and a method for measuring interference by a layer adjacent to the alignment film.

In addition, an object of the present invention is to provide an alignment state measuring device and a measuring method of the alignment film to reflect the anisotropy of the surface of the alignment film by irradiating circularly polarized light proceeding in the normal direction to the surface of the alignment film.

According to one aspect of the present invention, an alignment state measuring apparatus for an alignment layer includes a light irradiator for irradiating light in a vertical direction, a polarizer positioned at a rear end of the light irradiator and linearly polarizing light incident from the light irradiator, and a rear end of the polarizer. An optical splitter positioned at the rear end of the optical splitter and reflecting and transmitting a part of the light incident from the polarizer; a compensator configured to circularly polarize the light transmitted through the optical splitter; a sample substrate having an alignment film formed at the rear end of the compensator; A detector positioned in the path of the light reflected by the light beam and reflected by the alignment layer of the sample substrate and transmitting the polarized light in a specific direction among the linearly polarized light in the compensator, a photodetector for detecting the intensity of the light transmitted through the detector From the intensity of light detected by the detector, the alignment state information of the alignment layer is calculated and the analyzer and the sample A controller for controlling the rotation of the plate.

Here, it is preferable that the compensator delays the incident light by 90 °, and the optical axis of the polarizer and the optical axis of the compensator are shifted by 45 °.

In addition, the light irradiation unit irradiates light of a wavelength band of 320 nm or less, in particular ultraviolet rays of 135 nm to 310 nm.

In addition, a narrow band pass filter may be disposed in front of the analyzer to transmit only light of a specific wavelength band among the light reflected from the alignment layer surface.

In addition, the control unit measures the apparent retardation of the alignment film while changing the rotation angle of the analyzer with respect to all azimuth angles of the sample substrate, and calculates the alignment state information of the alignment film based on the measured apparent retardation value.

Here, the maximum amplitude of the apparent retardation is analyzed to the extent of rubbing of the alignment film, and the azimuth angle at which the amplitude of the apparent retardation is maximum is analyzed in the alignment axial direction of the alignment film.

In addition, the alignment state measurement method of the alignment film according to an aspect of the present invention comprises the steps of arranging the sample substrate on which the polarizer, the beam splitter, the compensator and the alignment film are formed to be in a straight line with respect to the traveling direction of the light, Setting the optical axis of the compensator to be turned by 45 °, rotating the sample substrate to have a first azimuth angle, fixing the sample substrate, allowing light to be emitted through the light irradiation unit, and the analyzer at a predetermined speed Receiving the light reflected from the sample substrate while being rotated and passing through the analyzer to the detector, measuring the Fourier coefficient from the intensity of the received light, and calculating the apparent retardation value using the Fourier coefficient; Rotate the sample substrate with the azimuth angle by a predetermined angle and calculate the apparent retardation value while rotating the analyzer continuously Repeating the process.

According to the present invention, only the light incident on the surface of the alignment layer is reflected and the light reflected from the layer adjacent to the alignment layer is not reflected, thereby eliminating the influence of interference by the layer adjacent to the alignment layer, thereby improving the reflecting property of the surface of the alignment layer and measuring the measurement. This has the advantage of improving accuracy.

1 is a block diagram of an alignment film alignment state measurement apparatus according to an embodiment of the present invention.
2 and 3 are graphs showing the interference characteristics of the alignment layer according to the light energy of the light irradiation part according to the embodiment of the present invention.
4 is a graph illustrating a method of calculating alignment state information of an alignment layer according to an exemplary embodiment of the present invention.

1 is a configuration diagram of an alignment film alignment state measuring device according to an embodiment of the present invention, and the present invention relates to a device for measuring the alignment direction and the alignment intensity of the liquid crystal alignment film.

Referring to FIG. 1, an embodiment of the present invention includes a light irradiator 10, a polarizer 20, a light splitter 30, a compensator 40, a sample substrate 50, an analyzer 60, and a photodetector 70. ) And the controller 80.

The light irradiator 10 irradiates the sample substrate 50 with light in a normal direction, that is, light in a vertical direction, and the light irradiator 10 transmits light emitted from the light source 11 and the light source 11. It includes an optical fiber 12 and a beam receiver 13 for irradiating light transmitted through the optical fiber 12 in the vertical direction. Here, since the light anisotropy measurement accuracy increases only when there is no light reflected from the interface between the alignment layer 90 and the glass base layer among the light incident on the alignment layer 90, the wavelength band reflected from the surface of the light incident on the alignment layer 90 is reflected. Light must be used, and the wavelength band can be derived from an elliptic constant graph shown for each light energy band shown in FIGS. 2 and 3.

2 shows alpha (α) values of light energy bands irradiated onto the sample substrate, and FIG. 3 shows beta (β) values of light energy bands irradiated onto the sample substrate and shows light energy smaller than 4.0 eV. It can be seen that the interference phenomenon (vibration) caused by the alignment layer appears in the wavelength band, and the vibration caused by the interference disappears in the portion where the light energy is 4.0 eV or more. The disappearance of the vibration due to the interference of the alignment layer means that the light reflected from the interface between the alignment layer and the lower thin film transistor array or the color filter array is not detected, only the light reflected from the surface of the alignment layer is detected. At this time, since the wavelength of light having a light energy of 4.0 eV is 310 nm, the light irradiator 10 irradiates light having a wavelength shorter than 320 nm, particularly ultraviolet light in a band of 135 nm to 310 nm, and reflects the anisotropy of light reflected from the surface of the alignment layer. It is preferable to measure.

In order to irradiate ultraviolet rays in the wavelength range of 135 nm to 320 nm, the light irradiator 10 may generate ultraviolet rays or oscillate using a xenon arc lamp and a narrow band pass filter. Ultraviolet rays are generated by multiplying 4ω or 3ω frequencies using a Q-switching Nd: YAG laser having a wavelength of 1064 nm or a titanium sapphire laser (Ti: sapphire Laser) having an oscillation wavelength of 834 nm.

The polarizer 20 is positioned in the traveling direction of the light emitted from the light irradiator 10, that is, the lower end of the light irradiator 10, and linearly polarizes the light incident from the light irradiator 10. At this time, the polarizer 20 is mounted on the rotating stage 21 to rotate at a constant speed or angle.

The light splitter 30 transmits a part of the light incident from the polarizer 20, that is, the light incident from the polarizer 20, that is, at the lower end of the polarizer 20 and is incident from the polarizer 20 in the sample direction, and a part of the analyzer ( 60).

The compensator 40 is a λ / 4 (90 °) phase of the linearly polarized light transmitted through the optical splitter 30 and positioned at the lower end of the optical splitter 30, that is, at the lower end of the optical splitter 30. By delaying, circularly polarized light is made incident on the alignment film 90. In this case, since the light delayed in phase by the compensator 40 is incident on the alignment layer 90 while circularly vibrating, the information on the alignment state of the alignment layer 90 is better reflected than when the linearly polarized light is incident. In addition, the compensator 40 is mounted on the rotating stage 41 to have a predetermined position angle and to rotate at a constant speed or angle. Here, the optical axis of the polarizer 20 and the optical axis of the compensator 40 is preferably shifted by 45 °. For this purpose, the polarizer 20 and the compensator 40 are initially rotated by the rotation of the rotating stages 21 and 41. 45 ° to each other is set to be twisted.

Meanwhile, a sample substrate 50 having an alignment layer 90 having a predetermined direction and intensity is positioned below the compensator 40, and the light traveling in the direction toward the sample substrate 50 is formed in the alignment layer 90. All are reflected off the surface.

The analyzer 60 is located on one side of the optical splitter 30, which is a path of light reflected by the optical splitter 30, and is rotated at a constant speed and angle to be polarized in a specific direction among the light reflected from the alignment layer 90. Only transmit light. That is, the light reflected by the alignment layer 90 is linearly polarized while passing through the compensator 40 and then reflected by the reflecting surface of the light splitter 30 to be incident on the analyzer 60. In addition, only light polarized in a specific direction is transmitted to the light incident on the analyzer 60, and the rest is reflected. In this case, a narrow band pass filter 62 may be disposed in front of the analyzer 60 to pass only light having a specific wavelength band.

The photo detector 70 outputs an electrical signal according to the intensity of the light when the light passing through the analyzer 60 is incident.

The controller 80 calculates optical anisotropy state information of the alignment layer 90 from the intensity of the detected light of the photodetector 70, and controls the rotation of the analyzer 60 and the sample substrate 50. That is, the controller 80 controls the rotation of the rotating stage 51 on which the sample substrate 50 is fixed so as to have a specific azimuth angle, and continuously rotates the analyzer 60 to have a predetermined angle difference. In doing so, the brightness waveform at the corresponding azimuth angle is detected and the Fourier coefficients are measured from the brightness waveform. Then, the apparent retardation of the alignment layer 90 is measured using the measured Fourier coefficients.

In this way, the controller 80 sequentially changes the azimuth angle of the sample substrate 50, and continuously rotates the analyzer 60 each time the azimuth angle changes, while the apparent liter at all azimuth angles of the sample substrate 50 is changed. Measure the value of the date.

Thus, when the apparent retardation values at all azimuth angles of the sample substrate 50 are measured, the orientation axial direction and the degree of orientation of the alignment film are calculated from the apparent retardation values. At this time, the amplitude maximum value of the apparent retardation is analyzed as the degree of rubbing of the alignment film, and the azimuth angle of the sample substrate 50 at which the amplitude of the apparent retardation is maximum is analyzed in the alignment axial direction of the alignment film.

Hereinafter, an alignment state measuring method of an alignment layer according to an embodiment of the present invention will be described.

First, the polarizer 20, the optical splitter 30, the compensator 40, and the sample substrate 50 are disposed so as to be located in a straight line. At this time, the controller 80 rotates the polarizer 20 and the compensator 40 fixed on the rotating stages 21 and 41 by a predetermined angle, so that the optical axis of the polarizer 20 and the optical axis of the compensator 40 are turned by 45 °. To lose.

In addition, the controller 80 rotates the rotary stage 51 so that the sample substrate 50 has a first azimuth angle, and then fixes the sample substrate 50, and an optical signal is transmitted through the light source 11 of the light irradiation unit 10. To be created. Then, the light generated from the light source 11 is linearly polarized through the polarizer 20 and then passes through the light splitter 30 to be incident to the compensator 40. The light incident on the compensator 40 is delayed in λ / 4 (90 °) phase. Accordingly, the phase delayed light is circularly polarized and proceeds toward the sample substrate 50.

The light propagated toward the sample substrate 50 is all reflected on the surface of the alignment layer 90, and the reflected light is linearly polarized while passing through the compensator 40 and proceeds toward the analyzer 60. At this time, since the narrow band pass filter 62 is mounted in front of the analyzer 60, only the light of a specific wavelength band of the light which advanced to the analyzer 60 side enters into the analyzer 60 side.

In addition, the controller 80 continuously rotates the analyzer 60 at a constant speed so that only light polarized in a specific direction among the light incident on the analyzer 60 passes through the analyzer 60 to allow the photodetector 70 to pass through. To be incident on.

When light is incident on the photodetector 70, the photodetector 70 outputs an electrical signal according to the intensity of the incident light.

Thereafter, the controller 80 measures a Fourier coefficient from the electrical signal waveform output from the photodetector 70 and calculates an apparent retardation value using the Fourier coefficient.

In addition, when the calculation of the apparent retardation value is completed, the controller 80 rotates the sample substrate 50 having the first azimuth angle by a predetermined angle and calculates the apparent retardation value while continuously rotating the analyzer 60. Repeat.

Here, retardation can be computed by the process mentioned later.

For example, the light intensity measured when the sample substrate has a specific azimuth angle and the analyzer is rotated is equal to the absolute value square of the electric field defined by Equation 1 below, including the azimuth angle A of the analyzer.

는 각각 출사광과 입사광의 전기장 존스벡터를 가리키며

는 각각 검광자와 편광자의 존스행렬으로

와 같으며,

는 보상기의 존스행렬으로

와 같다.

은 θ각 만큼 좌표축을 회전시키는 회전행렬으로

와 같고

는 시료의 반사를 나타내는 존스행렬로

와 같이 쓸 수 있다. 괄호속의 A, C, S, P 등은 각각 검광자, 보상기, 시료, 그리고 편광자의 방위각을 말하며 δ _c 는 보상기의 위상지연각도를 말한다. 이상적인 λ/4 보상기의 위상지연각도는 90°이다. 빛의 세기를 회전하는 검광자의 방위각 A의 함수로 나타내면 아래의 수학식 2와 같이 정의된다.From here

Are the electric field Jones vectors of the outgoing light and the incident light, respectively.

Is the Jones matrix of the analyzer and the polarizer, respectively.

Is the same as

Is the Jones matrix of the compensator

Same as

Is a rotation matrix that rotates the axes by θ.

Like

Is the Jones matrix representing the reflection of the sample

Can be written as: A, C, S, and P in parentheses refer to the azimuth angles of the analyzer, compensator, sample, and polarizer, respectively, and δ _c is the phase delay angle of the compensator. The phase delay angle of an ideal λ / 4 compensator is 90 °. When the intensity of light is expressed as a function of the azimuth A of the rotating analyzer, it is defined as in Equation 2 below.

In the above Equation 2, the Fourier coefficient may be defined as an elliptic constant of the alignment layer. If the optical axis of the compensator coincides with the azimuth angle of the sample substrate on which the alignment layer is formed, the elliptic constants α and β are represented by Equation 3 and Equation 3 below. Is defined as 4.

In this case, t _e and t ₀ indicate the transmission coefficients of the slow axis and the fast axis, respectively.

Where P is the azimuth angle of the polarizer and δ _c is the optical axis of the compensator, in which an embodiment of the present invention fixes the optical axis of the polarizer at 45 ° and delays λ / 4 (90 °) phase with the compensator. Therefore, when tanP = 1, δ _c = 90 is substituted and Equations 3 and 4 are summarized, the elliptic constants ψ, Δ are defined as Equations 5 and 6 below.

와 같이 정의되며, 투과계수들은 각각

와 같이 나타낼 수 있으므로, 타원상수는 아래의 수학식 7 및 수학식 8과 같이 정의된다.Here, in the x, y Cartesian coordinate system in which the direction of the coordinate axis is aligned with the direction of the main axis of the alignment film, the light propagation direction is set as the z axis, and the transmission coefficients of the electric field components in each axial direction are t _x and t _y . Is

Are defined as

Since it can be expressed as, an elliptic constant is defined as in Equations 7 and 8 below.

Here, d is the thickness of the alignment layer, λ is the wavelength of light and retardation is defined as the difference between the normal refractive index and the abnormal refractive index multiplied by the thickness of the film, the retardation using the elliptic constant and It can be defined together.

즉 Δ도 매우 작아지며

이므로

이 되어

가 만족되어, 수학식 6은 Δ=β와 같이 근사할 수 있다. 따라서 매우 작은 이방성은 아래의 수학식 10과 같이 푸리에 계수인 β로 그 리타데이션을 간단하게 표현할 수 있다. At this time, when the anisotropy of the alignment film is very small

Δ is also very small

Because of

This

Is satisfied, and Equation 6 can be approximated as Δ = β. Therefore, very small anisotropy can be simply expressed by the Fourier coefficient β as shown in Equation 10 below.

The method of measuring the orientation axial direction and the degree of orientation of the alignment film using the retardation value calculated as described above will be described with reference to FIG. 4.

Referring to FIG. 4, the X axis represents the azimuth angle of the sample substrate on which the alignment layer is formed, and the Y axis represents the apparent retardation value. The brightness of the light is detected by continuously rotating the analyzer while the sample substrate is fixed to have a specific azimuth angle. Subsequently, the apparent retardation value according to the brightness of the detected light is substituted into Equation (9). Then, the sample substrate is rotated by a predetermined angle to change the azimuth angle, and then the analyzer is continuously rotated to calculate the apparent retardation value at the azimuth angle. The calculation for the apparent retardation value for each azimuth angle is repeated. When completed, as shown in FIG. 4, the apparent retardation of the azimuth angle of the sample substrate is represented by a fitting function, and then the function graph is analyzed to measure the rubbing degree of the alignment layer and the orientation axial direction.

At this time, the amplitude maximum value A of the apparent retardation is the degree of rubbing of the alignment film, and the azimuth angle B of the sample substrate at which the amplitude of the apparent retardation is the maximum, that is, 100 °, becomes the alignment axial direction of the alignment film.

10: light irradiation unit 11: light source
12 fiber optic 13 beam receptor
20: polarizer 30: light splitter
40: compensator 50: sample substrate
60: analyzer 70: photo detector
80 control unit 90 alignment layer
21,41,51,61: Rotation Stage

Claims (7)

Light irradiation unit for irradiating light in the vertical direction;
A polarizer positioned at a rear end of the light irradiator and linearly polarizing light incident from the light irradiator;
A light splitter positioned at a rear end of the polarizer and reflecting and transmitting a part of light incident from the polarizer;
A compensator positioned at a rear end of the light splitter and circularly polarizing the light transmitted through the light splitter;
A sample substrate positioned at a rear end of the compensator and having an alignment layer formed on a surface thereof;
An analyzer positioned in a path of light reflected by the light splitter and transmitting light polarized in a specific direction among linearly polarized light in the compensator after being reflected by the alignment layer of the sample substrate;
A photo detector for detecting the intensity of light transmitted through the analyzer; And
And a control unit for calculating alignment state information of the alignment layer from the intensity of light detected by the photodetector and controlling rotation of the analyzer and the sample substrate. The method of claim 1,
And the compensator retards incident light by 90 degrees, and the optical axis of the polarizer and the optical axis of the compensator are shifted by 45 degrees. The method of claim 1,
The light irradiation unit is a device for measuring the alignment state of the alignment film, characterized in that for irradiating light in the wavelength band of 135nm ~ 320nm. The method of claim 1,
An apparatus for measuring an alignment state of an alignment layer, wherein a narrow band pass filter is disposed in front of the analyzer. The method of claim 1,
Measuring the apparent retardation of the alignment layer while varying the rotation angle of the analyzer with respect to all azimuth angles of the sample substrate, and calculating the alignment state information of the alignment layer based on the measured apparent retardation value. Orientation State Measuring Device. 6. The method of claim 5,
The maximum amplitude of the apparent retardation is the degree of rubbing of the alignment film,
The azimuth angle at which the amplitude of the apparent retardation is maximum is the orientation axis direction of the alignment film. Arranging the sample substrate on which the polarizer, the beam splitter, the compensator, and the alignment layer are formed so as to be in a straight line with respect to the traveling direction of the light;
Setting the optical axis of the polarizer and the optical axis of the compensator to be offset by 45 °;
Fixing the sample substrate after the sample substrate is rotated to have a first azimuth angle;
Allowing light to be emitted through the light irradiator;
Rotating the analyzer at a predetermined speed and receiving light reflected from the sample substrate and transmitted through the analyzer to the detector;
Measuring a Fourier coefficient from the received light intensity and calculating an apparent retardation value using the Fourier coefficient; And
And rotating the sample substrate having the first azimuth angle by a predetermined angle, and repeating the process of calculating an apparent retardation value while continuously rotating the analyzer.

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