KR102536609B1 - High resolution and fast switching electro-optic modulators for tft inspection - Google Patents

Abstract

The present invention provides a method for preparing a nematic curvilinear aligned phase (NCAP) liquid crystal layer comprising elongated liquid crystal droplets using an aqueous solution and an organic solution in which the organic solvent is removed after the water is removed. do. Also provided is a modulator using the NCAP liquid crystal layer of the present invention.

Description

High Resolution and Fast Switching Electro-Optical Modulators for Inspection of Thin Film Transistors

CROSS REFERENCES OF RELATED APPLICATIONS

This application claims priority from US Provisional Patent Application Serial No. 62/181,694, filed on June 18, 2015, the contents of which are incorporated herein by reference.

The present invention relates to a liquid crystal material for use in electro-optical applications. In particular, many embodiments of the present invention relate to liquid crystal/polymer composite materials, and to the manufacture and application of such composite materials.

Voltage imaging technology may be employed to detect and measure defects in flat-panel thin film transistor (“TFT”) arrays. With this measurement technique, the performance of a TFT array is simulated as if the TFT array were assembled into a TFT cell, followed by an electro-optical (hereinafter "EO") light-modulator-based detector. The characteristics of the TFT array are measured by indirectly measuring the voltage distribution on the actual panel using , that is, by so-called voltage imaging technology.

In its most basic form, a voltage imaging optical system ("VIOS") consists of an EO modulator, an imaging objective lens, a charge coupled device (CCD) camera, or other suitable or similar device. It includes a sensor and an image processor. The electro-optical sensor of the EO modulator is a liquid crystal in a polymer matrix (hereafter referred to as a liquid crystal/polymer composite, or “LC/polymer”) film, for example a nematic liquid crystal droplet in a polymer matrix (liquid crystal/polymer composite, or “LC/polymer”) film. , referred to as "LC") based on the light scattering properties of the droplets. In prior operation, the EO modulator was positioned approximately 5-75 microns above the surface of the TFT array, and the indium-tin-oxide (“ITO”) layer on the surface of the EO modulator was A bias voltage is applied across the transparent electrode. As a result, the EO modulator is capacitively coupled to the TFT array so that the electric field associated with the TFT array is sensed by the liquid crystal/polymer composite layer. The intensity of the incident light transmitted through the LC/polymer layer is changed, that is, modulated, by a change in electric field strength across the LC material in the LC/polymer composite material. This light is then reflected by a dielectric mirror and collected by a CCD camera or similar sensor. An incident radiation source, which can be, for example, infrared or visible, is provided to illuminate the LC/polymer film and dielectric mirror.

Because of the proximity of the components to the panels under test (PUT), the LC/polymer modulator structure can be damaged by unwanted particles during normal operation, which can severely shorten its useful life. Therefore, improving the lifetime of modulators may be one of the important goals in research and development of LC/polymer modulators. For example, US Patent No. 7,817,333 discloses an improved LC/polymer modulator structure, and US Patent No. 8,801,964 discloses an encapsulated polymer network liquid crystal modulator with additional improved sensitivity.

Modulator switching rate can be another important characteristic of LC modulator devices. Improved modulator switching speed can lead to improved detection capability, especially for TFT panels with short voltage holding times, such as OLED TFT panels, which is a very important aspect in LC modulator development, especially in LC/polymer matrix research and development. can be

의 부호에 따라 전기장에 평행 또는 수직의 어느 한 방향으로의 액적의 연장(elongation)을 강요한다. 전기장이 주 셀 평면(main cell plane)의 액적을 연장시키기 때문에,

인 LC가 특히 관심의 대상이다. 이 방법으로 획득된 액적의 연장은 필름의 파열 가능성으로 인하여 상대적으로 작다. 이 경우 용제(solvent)가 채용될 수 없으므로, TIPS 또는 PIPS만이 PDLC를 마련하는데 사용될 수 있다. 3) 폴리머 바인더(polymer binder)를 경화(curing)하는 동안 전단 가공(shearing). 이것은 단지 광중합 유도 상 분리(photopolymerization-induced phase separation: PPIPS) PDLC 시스템에서만 사용될 수 있다. LC droplets are generally spherical in polymer dispersed liquid crystal (PDLC) systems due to surface tension. Three methods are known to obtain elongated or flat LC droplets in PDLC [Reference: S.J. K￡OSOWICZ and M. ALEKSANDER, OPTO-ELECTRONICS REVIEW 12(3), 305-312 (2004)]. That is, 1) the PDLC film is stretched on the plastic deformable body, so that the LC droplet is deformed and elongated. Due to the high proportion of liquid crystal, PDLC films are usually supported by a rigid substrate coated with ITO (for electro-optical applications). Therefore, this is not a practical process for making a uniform product. 2) Applying an electric field during phase separation. The electrical contribution to the LC elastic deformation free energy is the LC dielectric anisotropy

Forces an elongation of the droplet in either direction, either parallel or perpendicular to the electric field, depending on the sign of . Since the electric field elongates the droplet in the main cell plane,

Phosphorus LCs are of particular interest. The extension of droplets obtained in this way is relatively small due to the possibility of rupture of the film. Since no solvent can be employed in this case, only TIPS or PIPS can be used to prepare the PDLC. 3) Shearing during curing of the polymer binder. It can only be used in photopolymerization-induced phase separation (PPIPS) PDLC systems.

및 감쇠 시간(decay time)

은 다음과 같이 주어진다: The above three methods may be suitable for small-scale or academic studies. However, for electro-optic devices with stringent uniformity requirements, a practical process for making elongated or planar PDLCs or NCAPs is important. The response time of polymer dispersed liquid crystal films has already been solved by Wu et al. [Reference: B. G. Wu, J. H. Erdmann, and J. W. Doane, Liq. Cryst. 5: 1453 (1989)], rise time

and decay time

is given by:

은 회전 점도(rotational viscosity)이며, E는 인가 전압이고, K는 유효 탄성 계수(effective elastic constant)이며, α는 액적 크기(droplet size)이고, l은 종횡비(aspect ratio)이며,

는 통상 유전 상수(ordinary dielectric constant)이며,

는 유전 이방성(dielectric anisotropy)이다. 액정 액적의 종횡비가 더 클수록 개선된 스위칭 속도를 갖는 PDLC 또는 NCAP으로 귀결될 것이다.here

is the rotational viscosity, E is the applied voltage, K is the effective elastic constant, α is the droplet size, l is the aspect ratio,

is an ordinary dielectric constant,

is dielectric anisotropy. A larger aspect ratio of the liquid crystal droplet will result in a PDLC or NCAP with improved switching speed.

Research related to the present invention suggests that current LC materials and their associated current manufacturing test methods can be improved. Therefore, there is a need in the art for improved electro-optical LC materials, particularly electro-optical LC materials with improved switching speed and resolution, and test equipment. Surprisingly, the present invention meets these and other needs.

In one embodiment, the present invention provides a method of manufacturing a nematic curvilinear aligned phase (NCAP) liquid crystal layer, the method comprising mixing a first solution and a second solution, mixing under conditions suitable to form an emulsion of the dispersed first solution, the first solution comprising a liquid crystal and an organic solvent having a boiling point greater than about 100° C., and the second solution comprising a polymer latex, at least one a surfactant and water, wherein the organic solvent is substantially immiscible with water; laminating the emulsion on a substrate; removing water from the emulsion to form a mixture; and preparing an NCAP liquid crystal layer by removing the organic solvent from the mixture.

In another embodiment, the present invention provides a modulator comprising a nematic curvilinear aligned phase (NCAP) liquid crystal layer comprising a plurality of nematic liquid crystal droplets prepared by the method of the present invention; The modulator has a decay time of less than about 5 milliseconds (ms) and an off-state light transmission of about 5% to about 15%.

In another embodiment, the present invention provides a nematic curvilinear aligned phase (NCAP) liquid crystal layer comprising a plurality of nematic liquid crystal droplets prepared by the method of the present invention, a polymer latex, and at least one surfactant. to provide.

Figure 1 shows the decay times for three different films. Sample 1 is NCAP with a film thickness of 24.0 μm made of liquid crystal 1, sample 2 is NCAP with a film thickness of 13.3 μm made of liquid crystal 2, and sample 3 is an NCAP with a film thickness of 11.8 μm made of liquid crystal 2 of elongated LC droplets. The Y-axis is light transmission, and the X-axis is time, 0.5 ms per unit. A square wave of 0V - 60V - 0V was applied. Transmission in the off state is equivalent for all three films.
2 is a diagram conceptually illustrating a process for manufacturing an NCAP liquid crystal layer according to an embodiment of the present invention. A first solution of liquid crystal and organic solvent is mixed with a second solution of water, surfactant and polymer latex. The mixture of the first and second solutions is emulsified and coated on a substrate where the water is evaporated. The organic solvent is then evaporated to form the NCAP liquid crystal layer of the present invention.
3 is a diagram showing a comparison between a device using an NCAP liquid crystal layer according to the present invention and a device using a conventional NCAP liquid crystal layer, and the NCAP liquid crystal layer according to the present invention has a smaller thickness, which is The distance (d) between the TFT and indium-tin-oxide (ITO) in a typical device_One), the corresponding distance (d₂) to make it shorter.
4 is a diagram conceptually illustrating a voltage imaging system including an electro-optic modulator including an NCAP liquid crystal layer according to the present invention.
FIG. 5 conceptually illustrates an electro-optic modulator assembly including an NCAP layer according to the present invention.

I. General

The present invention provides a nematic curvilinear aligned phase (NCAP) liquid crystal layer comprising an elongated or flattened liquid crystal droplet allowing more liquid crystal droplets in an NCAP liquid crystal layer of a given thickness, compared to a conventional NCAP liquid crystal layer. provides As a result, the thickness of the NCAP liquid crystal layer can be reduced when used in a modulator, which achieves comparable off-state light transmission while exhibiting a shorter decay time. Elongated or flat liquid crystal droplets are prepared using a dual solvent system of water and a high-boiling non-polar organic solvent such as octane. The liquid crystal is first dissolved in a non-polar organic solvent such as octane, and then it is combined with a water solution comprising at least one surfactant and a polymer matrix. The combined solution is emulsified to contain micron-sized liquid crystal (containing an organic solvent) droplets, which are deposited on a substrate, and the water is evaporated. The organic solvent (such as octane) is then evaporated to produce elongated or flat liquid crystal droplets. The thickness of the NCAP liquid crystal layer can be reduced without using a smaller amount of liquid crystal by reducing the number of stacked (light scattering centers) of LC droplets across the thickness direction by the second evaporation step of the high boiling point non-polar organic solvent do.

Several patents assigned to Photon Dynamics disclose modulator assemblies and processes for coating liquid crystal materials using such materials: U.S. Pat. No. 6,151,153 (Modulator Transfer Process and Assembly); U.S. Patent No. 6,211,991 (Modulator Manufacturing Process and Device); U.S. Patent No. 6,866,887 (Method for Manufacturing PDLC-Based Electro-Optic Modulator Using Spin Coating); U.S. Patent Nos. 7,099,067 and 7,916,382 (Scratch and Mar Resistant PDLC Modulator); U.S. Patent No. 7,639,319 to Polymer Dispersed Liquid Crystal Formulations for Modulator Fabrication; U.S. Patent No. 7,817,333 (Modulator with Improved Sensitivity and Lifetime); and U.S. Patent No. 8,801,964 (Encapsulated Polymer Network Liquid Crystal Material, Device and Applications), etc. are those patents, the entire contents of which are incorporated as part of this application by reference.

Conventional methods for preparing NCAP/PDLC liquid crystal layers in the art related to the present invention involve the use of water or organic solvents, but not both. For example, U.S. Patent Nos. 7,639,319 and 7,099,067 disclose a process for preparing a PDLC liquid crystal layer by dissolving a polymer and liquid crystal in a common non-aqueous solvent and then evaporating the non-aqueous solvent to produce a PDLC liquid crystal layer. start the way U.S. Patent No. 7,817,333 uses a latex-based process involving mixing liquid crystal, water and a polymer latex to form an emulsion, the emulsion being mixed and coated on a substrate, and the water being evaporated. The method of the present invention differs from these different water-based and organic solvent-based methods in that they are thinner for a given amount of liquid crystal, take an elongated or flat shape for the liquid crystal particles themselves, and provide improved off-state light Combining transmission and decay times in one way provides an NCAP liquid crystal layer capable of detecting pixels of smaller dimensions.

II. Justice

The term "liquid crystal" refers to a material having properties and behavior of both liquid and solid crystals. For example, liquid crystals can flow like liquids, but can align themselves like crystals, providing various optical properties such as birefringence. Liquid crystals can have thermotropic, lyotropic and metallotropic phases, where the thermotropic and lyotropic phases are mainly organic molecules. Thermotropic liquid crystals are sensitive to temperature and transition to a liquid crystal phase when the temperature changes. Lyotropic liquid crystals are sensitive to temperature and concentration. Metallotropic liquid crystals are a combination of organic and inorganic components, and the liquid crystal phase transition is sensitive to temperature, concentration and ratio of the organic and inorganic components.

The term “organic solvent” refers to a solvent that is substantially immiscible with water and has a boiling point higher than 100°C. The organic solvent of the present invention may be polar or non-polar. Representative non-polar organic solvents include hydrocarbons such as octane, nonane, decane and higher order hydrocarbons, and isomers thereof. Other organic solvents include cyclic hydrocarbons.

“Decay time” is the time required for the light transmission to drop to 10% of the saturation value.

“Off-state light transmission” refers to light transmission in a zero field.

III. nematic Align on the curve ( NCAP ) liquid crystal layer of manufacturing

The method of the present invention involves two solutions being mixed to form an NCAP liquid crystal layer. The first solution contains a liquid crystal and an organic solvent. The second solution is an aqueous solution containing a polymer matrix and a surfactant. The two solutions are mixed to form an emulsion of liquid crystal droplets surrounded by a polymer matrix. The emulsion is laid on a substrate, where first the water is evaporated followed by a second evaporation step to remove the organic solvent. In some embodiments, the present invention provides a method of making a nematic curve-aligned (NCAP) liquid crystal layer, the method comprising mixing a first solution and a second solution, wherein the first dispersed in the second solution. mixing under conditions suitable to form an emulsion of the solution. Here, the first solution includes a liquid crystal and an organic solvent having a boiling point higher than at least about 100°C. The second solution includes a polymer latex, at least one surfactant and water. The organic solvent is substantially immiscible with water. The method also includes placing the emulsion on a substrate, removing water from the emulsion to form a mixture, and removing the organic solvent from the mixture to provide an NCAP liquid crystal layer.

The first solution may include any suitable liquid crystal in the method of the present invention. For example, the liquid crystal (LC) is a nematic LC, a ferroelectric LC, a blue phase LC, a LC/dichroic dye mixture, or a cholesteric LC (ChLC) may include one or more of them. In the dichroic dye + LC system, the dichroic dye can absorb light in the off state and transmit light in the on state, which is dependent on the slope of the s-curve by using a higher light intensity. will improve the corresponding light transmission voltage sensitivity. Also, liquid crystals can scatter light when no voltage is applied. The liquid crystal may be dissolved in the organic solvent used in the method of the present invention. Accordingly, the liquid crystal may be hydrophobic. In some embodiments, the liquid crystal may be a nematic liquid crystal.

The organic solvent of the first solution may be any non-polar organic solvent having a higher boiling point than water. Representative organic solvents include but are not limited to alkanes and cycloalkanes such as octane, nonane, decane, cycloheptane, cyclooctane and isomers thereof. It is not. The non-polar organic solvent may have any suitable boiling point higher than that of water. For example, the boiling point of the nonpolar organic solvent may be higher than about 100°C, higher than about 105°C, 110, 115, 120, 130, 140, or higher than about 150°C. In some embodiments, the organic solvent may have a boiling point greater than about 110°C. In some embodiments, the organic solvent may have a boiling point greater than about 120°C. In some embodiments, the organic solvent may be a non-polar organic solvent. In some embodiments, the organic solvent may be octane, nonane, decane, cycloheptane, cyclooctane or an isomer thereof. In some embodiments, the organic solvent is octane.

The liquid crystal and organic solvent may be present in any suitable ratio. For example, the ratio of liquid crystal to organic solvent is about 1:100 (w/w) to about 10:1 (w/w), or about 1:50 (w/w) to about 5:1 (w/w). w), or about 1:25 (w/w) to about 5:1 (w/w), or about 1:10 (w/w) to about 5:1 (w/w), or about 1:5 (w/w) to about 5:1 (w/w), or about 1:2 (w/w) to about 2:1 (w/w). The ratio of the liquid crystal to the organic solvent is about 1:100 (w/w), 1:50, 1:25, 1:10, 1:9, 1:8, 1:7, 1:6, 1:5 , 1:4, 1:3, 1:2, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or about It may be a ratio of 10:1 (w/w). In some embodiments, the ratio of the liquid crystal to the organic solvent may be about 1:10 (w/w) to about 5:1 (w/w). In some embodiments, the ratio of the liquid crystal to the organic solvent may be about 1:2 (w/w) to about 2:1 (w/w).

The method of the present invention also includes a water based solution comprising a polymer latex and a surfactant. The polymer latex of the second solution may be any suitable water polymer latex. Representative polymer latexes include, but are not limited to, polyurethane, polyacrylate, polyurethane acrylate, or mixtures thereof. A number of emulsification methods can be used. Examples include mechanical stirring, blending, microfludics, homogenizers, and the like. The droplet size of the resulting emulsion can be controlled and may be on the order of 1 to 10 microns. In some embodiments, the polymer latex can be polyurethane, polyacrylate, polyurethane acrylate, or combinations thereof.

The ratio of polymer latex to liquid crystal may be any suitable ratio. For example, the ratio of polymer latex to liquid crystal is about 10:1 (w/w), or about 9:1, 8:1, 7:1, 6:1, 5:1, 5:4, 5 :3, 5:2, 4:1, 4:3, 3:1, 3:2, 2:1, 1:1, 1:2, 2:3, 1:3, 3:4, 1:4 , 2:5, 3:5, 4:5, 1:5, 1:6, 1:7, 1:8, 1:9 or about 1:10 (w/w). The ratio of polymer latex to liquid crystal is also about 10:1 (w/w) to about 1:10 (w/w), about 5:1 (w/w) to about 1:10 (w/w), about 10:1 (w/w) to about 1:5 (w/w), about 5:1 (w/w) to about 1:5 (w/w), or about 3:2 (w/w) to about 1:4 (w/w). In some embodiments, the ratio of polymer latex to liquid crystal is from about 5:1 (w/w) to about 1:10 (w/w). In some embodiments, the ratio of polymer latex to liquid crystal is from about 3:2 (w/w) to about 1:4 (w/w).

The second solution also includes any suitable surfactant or combination of surfactants. The surfactant may include a non-ionic interfacial agent such as a block co-polymer, and/or a surfactant such as a cross-linkable reactive surfactant. It can, but is not limited to these. When the surfactant contains bipartite molecules having suitable chemical properties and the surfactant is present in a sufficient amount, the surfactant can form an interfacial layer. At least a portion of the surfactant may be dissolved in the polymer latex to effectively immobilize the surfactant within the polymer matrix. The anchoring of the interfacial layer to the polymer latex can be physical bonding (block copolymer) or chemical bonding (by cross linking, as in the case of reactive surfactants), or a combination thereof. This fixation of the interfacial layer can improve the stability of the interfacial layer, for example at elevated temperatures. The second portion of the surfactant in the interfacial layer may have a chemical composition that exhibits low surface tension and/or low friction to liquid crystal molecules and/or crystals. Anchoring and/or friction between the liquid crystal molecules and the polymer matrix can be reduced by the interfacial layer, and the alignment orientation and switching speed of the LC molecules when an electric field is applied is greater at lower voltages. can appear quickly.

Examples of surfactants designation explanation manufacturer BYK-022 Blending of defoaming polysiloxane and hydrophobic solids in polyglycol. BYK Chemie Fluorolink D10 A-CF ₂ O(CF ₂ CF ₂ O) _m (CF ₂ O) _n CF ₂ -A, A=CH ₂ OH, MW=1000 Solvay Solexis Fluorolink D A-CF ₂ O(CF ₂ CF ₂ O) _m (CF ₂ O) _n CF ₂ -A, A=CH ₂ OH, MW=500 Solvay Solexis Surfynol DF-58
A silicone-based foam control agent useful in aqueous systems. This product has strong foam control and de-aeration performance. Air Products Surfynol DF-62 An ether-modified polysiloxane based antifoam designed to provide strong defoaming and long-lasting anti-foaming capabilities. air products Surfynol DF-574 It is a self-emulsifying product with organic and organic modified silicone components and effectively removes air absorbed and foam generated during the manufacturing process. air products Surfynol DF-695 It is a silicone emulsion defoamer and provides initial and sustained defoaming performance in water-based formulations. 100% active liquid. air products Flexiwet_ NI-M100 A partially fluorinated alcohol that has been ethoxylated. Innovative Chemical Technologies, Inc. Flexiwet NI-55 Non-ionic (fluorinated) polymeric surfactants without reactive groups. Innovative Chemical Technologies Inc.

Table 1 is part of a list of surfactants that can be combined with LC materials according to embodiments of the present invention. When a nonionic surfactant is used, the driving voltage can be substantially reduced, for example, by adding the nonionic surfactant in a small proportion to the emulsion. The low surface tension portion of the surfactant molecules may include a fluorinated compound such as Fluorolink D or Flexiwet, or a silicone copolymer such as Surfynol DF-62, BYK-022. may include a polymeric or polymer-siloxane. In particular, the reactive fluorinated compound may have the chemical structure shown in Table 1, and the siloxane may have a reactive terminal such as -OH, -NH ₂ , or -COOH. In many embodiments, these materials migrate to the interface of the LC and polymer during LC and polymer phase separation. Other portions of the surfactant molecules may be physically bonded to the polymer through mechanisms such as hydrogen bonding, all or part of van der Waals forces and chemical bonding when reactive groups are present within the polymer matrix. Slight heating can speed up the chemical bonding process.

Surfactants useful in the present invention may also include substrate wetting and leveling agents, such as fluorinated surfactants. Other surfactants useful in the present invention may include emulsifiers such as polysorbates to stabilize the emulsion.

In many embodiments, the use of surfactants with defoaming (ie, defoaming) properties can significantly improve intrinsic switching voltage sensitivity. For example, Surfynol DF-based compounds can substantially reduce the operating voltage of latex-based NCAPs.

Antifoams are a class of surfactants that can be dispersed in an aqueous medium, and the surfactants of the interfacial layer can include one or more antifoams. In many embodiments, the antifoam agent has very low solubility in aqueous media and can have a hydrophile-lipophile balance (HLB) of less than 10. Since the antifoam has very low solubility in water, the antifoam can form small clusters. Each of the clusters may include molecules having a first portion and a second portion. As described above, a first portion of molecules of the cluster may have hydrophilic properties, and a second portion of molecules of the cluster may have hydrophobic properties. In some embodiments, the cluster may have a micelle shape having a first portion facing outward towards the solution and a second portion facing inward toward other molecules of the antifoam cluster. During emulsification, the cluster can prevent the formation of foam by breaking up many air bubbles. After emulsification and degassing, the clusters move freely within a mixture of LC droplets, water-based polymers and water. In many embodiments, the clusters may migrate towards the surface of the LC droplets. When the emulsion dries, the antifoam may form a surfactant layer around the LC droplet such that the interfacial layer is positioned between the LC droplet and the polymer matrix. In some embodiments, the low surface tension end of the antifoam molecule is dispersed near the LC droplet to form a second portion of the interfacial layer, and the orientation-regulating end of the antifoam molecule is connected to the polymer matrix to form the interfacial layer. Forms the first part of the layer.

The substrate is any suitable substrate. For example, the substrate may be a transparent substrate. Other substrates include, but are not limited to, glass, plastic, Mylar, polyester, indium tin oxide (ITO) or mixtures thereof. In some embodiments, the substrate may be glass, plastic, mylar, polyester, or mixtures thereof.

Water and organic solvents can be removed by any means known to those skilled in the art. For example, water and organic solvents can be removed by evaporation at room temperature, then slightly elevated temperature, such as 40°C. A vacuum is not required. For example, water and organic solvents can be evaporated at room temperature, followed by some heating (such as 40° C.) without vacuum. When the emulsion is coated on a substrate, the wet film thickness can be tens of microns. Both water and solvent can evaporate. The formation of air pockets in the film can be avoided by using a lower temperature and vacuum.

The NCAP liquid crystal layer can have any suitable thickness of at least about 1 μm. For example, the NCAP liquid crystal layer may be at least about 1 μm, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 20, 25, 30, 35, 40 , 45, and a thickness of at least about 50 μm. The NCAP liquid crystal layer may also have a thickness of about 1 μm to about 50 μm, about 1 μm to about 25 μm, about 1 μm to about 20 μm, about 1 μm to about 15 μm, about 1 μm to about 10 μm. μm, about 5 μm to about 25 μm, about 5 μm to about 20 μm, or about 5 μm to about 15 μm. In some embodiments, the NCAP liquid crystal layer has a thickness of about 1 μm to about 20 μm. In some embodiments, the NCAP liquid crystal layer has a thickness of about 5 μm to about 15 μm.

The thickness of the NCAP liquid crystal layer may have any suitable level of uniformity across the layer, such as measured by Filmetrics. For example, thickness uniformity can be ±10%.

The dried liquid crystal droplets may take any suitable form. For example, the dried liquid crystal droplets may have an elongated shape such as a three-dimensional ellipse having a major axis and a longitudinal axis. The ratio of the major axis to the longitudinal axis may be from about 100:1 to about 1.5:1, from about 75:1 to about 1.5:1, or from about 50:1 to about 1.5:1. In some embodiments, the NCAP liquid crystal layer includes a plurality of substantially dried liquid crystal droplets having a major axis and a longitudinal axis, wherein the ratio of the major axis to the longitudinal axis is from about 100:1 to about 1.5:1, and the major axis is substantially on the substrate. parallel The dried liquid crystal droplets can also be formed flat, as if pressure is applied to the liquid crystal droplets from above and below to make them flat.

In some embodiments, the present invention provides a method of fabricating a nematic curve-aligned (NCAP) liquid crystal layer, the method comprising mixing a first solution and a second solution to form a liquid crystal droplet - the second solution. One solution includes a nematic liquid crystal and an organic solvent such as octane in a ratio of about 1:2 (w/w) to about 2:1 (w/w), and the second solution includes a polymer latex, at least one interface an active agent and water, wherein the ratio of polymer latex to liquid crystal is from about 3:2 (w/w) to about 1:4 (w/w); depositing the mixture of liquid crystal droplets on a substrate; removing water from the mixture; and removing an organic solvent from the mixture to provide an NCAP liquid crystal layer comprising a plurality of substantially dried liquid crystal droplets having a major axis and a longitudinal axis, wherein the ratio of the major axis to the longitudinal axis is from about 100:1 to about 1.5: 1, wherein the major axis is substantially parallel to the substrate.

In some embodiments, the present invention provides a nematic curve-aligned (NCAP) liquid crystal layer comprising a plurality of liquid crystal droplets prepared by a method of the present invention, a polymer latex, and at least one surfactant. include

IV. Modulator

The present invention also provides a modulator comprising an NCAP liquid crystal layer prepared by the methods of the present invention. In some embodiments, the present invention provides a modulator comprising a nematic curve-aligned (NCAP) liquid crystal layer comprising a plurality of liquid crystal droplets prepared by a method of the present invention. The modulator has a decay time of less than about 5 milliseconds (ms) and an off-state light transmittance of about 5% to about 15%.

The modulator of the present invention may have any suitable decay time. For example, the decay time is less than about 100 milliseconds, or about 90, 80, 75, 70, 60, 50, 45, 40, 35, 30, 25, 20, 15, 10, 9, 8, 7 , 6, 5, 4, 3, 2 or less than 1 millisecond. The decay time may also be between about 1 millisecond and about 100 milliseconds, between about 1 millisecond and about 50 milliseconds, between about 1 millisecond and about 25 milliseconds, between about 1 millisecond and about 10 milliseconds, or about 1 millisecond. to about 5 milliseconds. In some embodiments, the decay time is less than 5 milliseconds.

The modulator of the present invention may have any suitable off-state light transmittance. For example, the off-state light transmittance may be about 1% to about 99%, about 1% to about 75%, about 1% to about 50%, about 1% to about 25%, about 5% to about 25%, or from about 5% to about 15%. The off-state light transmittance of the modulator of the present invention is also about 1%, or 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 , 19, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 95, 96, 97, 98, or 99%. In some embodiments, the off-state light transmittance may range from about 5% to about 15%.

The modulator of the present invention may include various other components suitable for the present invention. For example, the NCAP liquid crystal layer of the modulator may also include a polymer latex and a surfactant, as detailed above.

The modulator of the present invention may also include other layers in addition to the NCAP liquid crystal layer. For example, the modulator may include one or more of a transparent substrate, a pellicle, and indium tin oxide (ITO). The transparent substrate may be any substrate transparent to visible spectrum light, such as glass, plastic, Mylar, polyester, and the like. The pellicle, or dielectric mirror pellicle, can be made from any material known to those skilled in the art. Additionally, the various layers of the modulator may be arranged in any order suitable. For example, the pellicle may be placed on top of the NCAP liquid crystal layer which may be placed on top of the transparent substrate.

4 is a diagram conceptually illustrating components of a voltage imaging system 100 for TFT inspection according to an embodiment of the present invention. Components of the voltage imaging system may include one or more components described in US Patent No. 7,639,319 and/or components of a commercially available voltage imaging system. The voltage imaging system 100 may include an electro-optic modulator assembly 200 , an illuminator 114 , a beam splitter 116 and a camera 118 . The electro-optic modulator assembly 200 comprises a transparent electrode 250 (electrode A), a transparent substrate 220 supporting the transparent electrode 250, an NCAP liquid crystal layer sensor material 260, and a dielectric mirror 270 supported by a thin plastic film such as, for example, a pellicle. can include The transparent electrode 250 may include a thin film made of indium tin oxide (ITO) and is transparent to visible light. The NCAP liquid crystal layer sensor material 260 has an electro-optic response under an electric field. Electrode B may be included in a panel under test (PUT) such as, for example, a TFT plate. By applying a voltage to the transparent electrode 250 (electrode A) and grounding electrode B, a transmission-voltage (T-V) curve can be obtained. In the TFT test, when a constant voltage near the middle of the response curve is applied to the modulator, the voltage applied to each pixel can be detected as a change in the intensity of light from the camera 118. A defective pixel will give an abnormal response.

The voltage applied between electrodes A and B can be expressed by the following equation:

here,

: 전극 A와 B 사이에 인가된 전압,

: Voltage applied between electrodes A and B,

: 센서 물질에 필요한 전압,

: voltage required for the sensor material,

및

: 펠리클과 공기 간극 사이의 전압,

and

: Voltage between the pellicle and the air gap,

: 각 물질의 유전 상수, 및

: dielectric constant of each material, and

d: thickness of each material.

Under a fixed voltage V _Bias , the inter-electrode distance d _air is a function of the intrinsic operating voltage ( V _sensor ) of the liquid crystal sensor material. In many embodiments, the net switching voltage of the liquid crystal sensor material corresponds to a voltage across the sensor material at which light transmission through the sensor material has a maximum sensitivity to changes in voltage across the sensor material. In many embodiments, the operating voltage across the electrodes is related to the net switching voltage of the liquid crystal material by using the equation above. Switching times can be reduced by providing materials with reduced net switching voltages.

5 is a conceptual diagram of an electro-optic modulator assembly 200. Modulator assembly 200 includes sensor material 260 . Sensor material 260 may include a NCAP liquid crystal material as described herein. The modulator assembly may include an anti-reflective coating 210 . The modulator assembly may include an optically transparent support substrate, such as optical glass 220. An antireflective coating 210 may be deposited on the top surface of the optical glass 220 . An optical adhesive 230 may be positioned on a lower surface of the optical glass 220 . A commercially available polyester film 240, such as Mylar, comprising stretched polyethylene terephthalate (PET) may be bonded to the optical glass with an adhesive 230. An optically transparent electrode 250, such as ITO, may be bonded to the polyester film 240. An NCAP liquid crystal layer 260 may be coupled to the optically transparent electrode 250 . A dielectric pellicle mirror 270 comprising a dielectric mirror layer deposited on a thin film of PET, such as Mylar, may be bonded to the lower surface of the liquid crystal sensor material. An organic hard coating 280 may be applied to the dielectric pellicle mirror 250. The organic hard coating 280 may include the hard coating components described in US Pat. No. 7,099,067.

This new fast-switching modulator is suitable for all types of voltage imaging applications, but is particularly useful for testing organic light emitting diode (OLED) displays. OLED displays typically require less holding capacitance due to the fact that OLEDs are current driven devices. This implies that the voltage applied to the pixel electrodes of these displays can decay rapidly, requiring a fast-responsive modulator to ensure optimal voltage image signal strength.

For similar reasons, and because of the short distance between the ITO and the TFT panel under test, as described above with respect to FIG. 3, this modulator can be used with ultra-fine pixels (the smaller the pixel, the smaller the storage capacitance) or the ultra-high speed. It is well suited for panels with high refresh rates (which means the voltage doesn't have to be maintained for a very long time, which makes the storage capacity small). Also, the fast switching modulator may be less susceptible to various signal drifts occurring, for example as a result of depolarizing currents.

V. Cases

Case 1 . nematic Align on the curve ( nematic curvilinear aligned phase: NCAP ) liquid crystal layer

2 grams of nematic liquid crystal (MLC-2156 from EMD Chemicals) was mixed with 1 gram of octane to form a clear solution. This LC/organic solvent mixture was prepared by mixing 2.5 grams of Neorez R-967 (manufactured by DSM) with the following mixtures: 1.5 grams of water, 0.16 grams of Surfynol to form an emulsion. It is emulsified with a mixture of DF-62 (manufactured by Air Products), 0.04 grams of TWEEN 60 and 0.06 grams of FSN (manufactured by DuPont). The emulsion is then coated onto an ITO Mylar film and laminated with another ITO Mylar after complete evaporation of water and octane. For comparison, Sample 2 was prepared in the same manner as described above, except that octane was not used. And, sample 1 was made in the same process as sample 2, but a liquid crystal having a lower optical anisotropy was used.

Figure 1 shows the decay times for three different films: sample 1 is an NCAP made of liquid crystal 1 and has a thickness of 24.0 μm; Sample 2 is an NCAP made of liquid crystal 2 and has a thickness of 13.3 μm; Sample 3 is an NCAP made of liquid crystal 2, which contains elongated liquid crystal droplets and has a thickness of 11.8 μm. The Y axis is light transmission, the X axis is time, 0.5 ms per unit and the total X axis is 25 ms. A square wave of 0V - 60V - 0V was applied. Off-state transmission is equal for all three films. The results are summarized in the table below.

sample source thickness
(μm) rise time
(ms) decay time
(ms) One conventional 24.0 0.80 12.0 2 conventional 13.3 0.91 6.3 3 the present invention 11.8 0.66 3.8

Although the above has been described in detail through examples for the purpose of clarifying understanding, those skilled in the art will understand that changes and modifications can be made within the scope of the following claims. In addition, each reference cited in this specification is incorporated herein by reference in its entirety, which is the same as if each reference was individually incorporated by reference. In case of a conflict between an embodiment of the present invention and a reference provided herein, the embodiment of the present invention takes precedence.

Claims (22)

A method for producing a nematic curvilinear aligned phase (NCAP) liquid crystal layer,
Mixing a first solution and a second solution under conditions for forming an emulsion of the first solution dispersed in the second solution - the first solution is a liquid crystal and an organic solvent having a boiling point higher than 100 ° C. wherein the second solution comprises a polymer latex, at least one surfactant and water, wherein the organic solvent is substantially immiscible with water;
laminating the emulsion on a substrate;
removing water from the emulsion to form a mixture; and
preparing an NCAP liquid crystal layer by removing the organic solvent from the mixture;
NCAP liquid crystal layer manufacturing method comprising a.
According to claim 1,
The liquid crystal,
Nematic liquid crystal, ferroelectric liquid crystal, blue phase liquid crystal, liquid crystal / dichroic dye (Dychroic Dye) mixture, cholesteric (cholesteric) liquid crystal or a mixture thereof
NCAP liquid crystal layer manufacturing method.
According to claim 1,
A method for manufacturing an NCAP liquid crystal layer in which the liquid crystal is a nematic liquid crystal.
According to claim 1,
The organic solvent has a boiling point higher than 110 ℃ NCAP liquid crystal layer manufacturing method.
According to claim 1,
The organic solvent has a boiling point higher than 120 ℃ NCAP liquid crystal layer manufacturing method.
According to claim 1,
NCAP liquid crystal layer manufacturing method in which the organic solvent is a non-polar organic solvent.
According to claim 1,
An NCAP liquid crystal layer manufacturing method in which the organic solvent includes octane.
According to claim 1,
A method for manufacturing an NCAP liquid crystal layer wherein the ratio of liquid crystal to organic solvent is 1:10 (w/w) to 5:1 (w/w).
According to claim 1,
A method for manufacturing an NCAP liquid crystal layer wherein the ratio of liquid crystal to organic solvent is 1:2 (w/w) to 2:1 (w/w).
According to claim 1,
Wherein the polymer latex comprises polyurethane, polyacrylate, polyurethane acrylate or a mixture thereof.
According to claim 1,
A method for manufacturing an NCAP liquid crystal layer wherein the ratio of polymer latex to liquid crystal is 5:1 (w/w) to 1:10 (w/w).
According to claim 1,
A method for manufacturing an NCAP liquid crystal layer wherein the ratio of polymer latex to liquid crystal is 3:2 (w/w) to 1:4 (w/w).
According to claim 1,
A method of manufacturing an NCAP liquid crystal layer in which the substrate includes glass, plastic, Mylar, polyester, or a mixture thereof.
According to claim 1,
A method for preparing an NCAP liquid crystal layer in which water is removed by evaporation.
According to claim 1,
NCAP liquid crystal layer manufacturing method in which organic solvents are removed by evaporation.
According to claim 1,
The NCAP liquid crystal layer has a thickness of 1 μm to 20 μm NCAP liquid crystal layer manufacturing method.
According to claim 1,
NCAP liquid crystal layer manufacturing method of the NCAP liquid crystal layer having a thickness of 5 μm to 15 μm.
According to claim 1,
Mixing the first solution and the second solution under conditions for forming an emulsion of the first solution dispersed in the second solution - the first solution contains nematic liquid crystal and octane in a ratio of 1:2 (w/w) to 2:1 (w/w), wherein the second solution comprises a polymer latex, at least one surfactant and water, wherein the ratio of the polymer latex to the liquid crystal is 3:2 (w/w) to 1:4 (w/w);
laminating the emulsion on a substrate;
removing water from the emulsion to form a mixture; and
preparing the NCAP liquid crystal layer including a plurality of substantially dried liquid crystal droplets by removing the organic solvent from the mixture;
NCAP liquid crystal layer manufacturing method comprising a.
In the modulator,
A nematic curvilinear aligned phase (NCAP) liquid crystal layer prepared by the method of claim 1,
The modulator has a decay time shorter than 5 ms and an off-state light transmission of 5% to 15%.
According to claim 19,
NCAP liquid crystal layer,
polymer latex; and
Further containing a surfactant,
modulator.
According to claim 19,
a transparent substrate supporting the NCAP liquid crystal layer; and
A pellicle stacked on top of the NCAP liquid crystal layer
A modulator further comprising a.
In a nematic curvilinear aligned phase (NCAP) liquid crystal layer,
A plurality of nematic liquid crystal droplets prepared by the method of claim 1;
polymer latex; and
at least one surfactant
NCAP liquid crystal layer comprising a.

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