JP6811553B2 - High resolution, high speed switching electro-optic modulator for TFT inspection - Google Patents

Description

[Cross-reference of related applications]
The present application claims the interests of US Provisional Patent Application No. 62 / 181,694 (Filing Date: June 18, 2015), which is incorporated herein by reference in its entirety.

The present invention relates to liquid crystal materials for use in electro-optic applications. More specifically, many embodiments of the present invention relate to liquid crystal / polymer mixture materials, as well as methods and devices for producing and applying such mixture materials.

Voltage imaging techniques can be used to detect and measure defects in flat panel thin film transistors (“TFTs”). According to this measurement technique, the performance of the TFT array is emulated as if it were concentrated in a TFT cell, and then the characteristics of the TFT array are electro-optic (“EO”) light modulator-based detection. It is measured by indirectly measuring the actual voltage distribution on the panel using a device, that is, by so-called voltage imaging.

A voltage imaging optical system (“VIOS”), in its most basic form, includes an EO modulator, an imaging objective, a charge coupling element (CCD) camera or other suitable or similar sensor, and an image processor. Including. The electro-optical sensor of the EO modulator has a light scattering characteristic of liquid crystal (hereinafter referred to as “LC”) droplets in a polymer matrix, for example, nematic liquid crystal droplets in a polymer matrix (liquid crystal / polymer mixture, that is, LC / polymer) film. based on. In conventional operation, the EO modulator is placed approximately 5 to 75 microns above the surface of the TFT array, and a voltage bias is applied to the transparent electrode of the indium tin oxide (hereinafter, "ITO") layer on the surface of the EO modulator. It is applied. As a result, the EO modulator is capacitively coupled to the TFT array, whereby the electric field associated with the TFT array is detected by the liquid crystal / polymer mixture layer. The intensity of incident light passing through the LC / polymer layer varies, that is, it is modulated by any change in electric field intensity across the liquid crystal (LC) material within the liquid crystal / polymer mixture material. This light is then reflected off the dielectric mirror and collected by a CCD camera or similar sensor. The light source of the incident radiation may be, for example, infrared light or visible light and is provided to illuminate the LC / polymer film and the dielectric mirror.

Due to the close proximity of the components to the test object (PUT), the LC / polymer modulator structure can be susceptible to damage by unwanted particles during normal use. This can significantly reduce the useful life. Therefore, improving the modulator life can be one of the main objectives of research and development of LC / polymer modulators. For example, US Pat. No. 7,817,333 discloses an improved LC / polymer modulator structure, and US Pat. No. 8,801,964 discloses an encapsulated polymer with further improved sensitivity. The network liquid crystal modulator is disclosed.

Modulator switching speed can be another important characteristic of LC modulator devices. Since the improvement of the modulator switching speed can bring about the improvement of the detection ability especially in the TFT panel having a short voltage holding time such as the OLED-TFT panel, it is an important aspect of the development of the LC modulator, especially the research and development of the LC / polymer matrix. Can be.

LC droplets are usually spherical due to surface tension in polymer dispersed liquid crystal (PDLC) systems. In PDLC, three methods have been reported for obtaining stretched or flattened LC droplets. [Reference: S.A. J. KOSOWICZ and M.K. ALEKSANDER, OPTO-ELECTRONICS REVIEW 12 (3), 305-312 (2004)]. 1) The PDLC film is stretched beyond the plastic deformation, and as a result, the LC droplets are deformed and elongated. Due to the high proportion of liquid crystals, PDLC films are usually supported by ITO-coated solid substrates (for electro-optic applications). Therefore, this method is not a practical process for making a uniform product. 2) An electric field is applied during phase separation. By contributing the electric field to the free energy of LC elastic deformation, the droplet is elongated parallel or perpendicular to the electric field according to the sign of LC dielectric anisotropy Δε. LCs with a negative Δε are of particular interest because their droplets are stretched by an electric field in the main cell plane. The elongation of the droplets obtained in this way is somewhat small due to the potential for membrane breakage. In this case, no solvent can be employed, so only TIPS or PIPS can be used to formulate PDLC. 3) Shear deformation occurs during curing of the polymer binder. This approach can only be used in photopolymerization induced phase separation (PPIPS) PDLC systems.

However, the above three methods may be suitable for small-scale academic research. Practical processes for making stretched or flattened PDLCs or NCAPs are important for electro-optic devices with stringent uniformity requirements. The response time of the polymer-dispersed liquid crystal film has been elucidated by Wu et al. (References: BG Wu, JH Erdmann, and JW Doane, Liq. Crystal. 5: 1453 (1989)). The rise time (τ _on ) and decay time (τ _off ) are shown as follows.
Here, γ ₁ is the rotational viscosity, E is the applied voltage, K is the effective elastic modulus, α is the particle size of the droplet, l is the aspect ratio, ε ₀ is the normal permittivity, and Δε is the dielectric anisotropy. Higher aspect ratios of liquid crystal droplets will result in PDLC or NCAP with improved switching rates.

Studies related to the present invention suggest that current LC materials and related current manufacturing test methods may be improved. Therefore, there is a need to improve the electro-optic LC material in the art, and more specifically, to improve the switching speed and resolution of the electro-optic LC material and the test apparatus. Surprisingly, the present invention meets this and other needs.

In one embodiment, the invention provides a method for formulating a Nematic Curve Aligned Phase (NCAP) liquid crystal layer. This method is a step of mixing the first and second solutions, the first solution containing a liquid crystal and an organic solvent having a boiling point of at least about 100 ° C., and the second solution is at least 1 with a polymer latex. The conditions are suitable for forming an emulsion of the first solution dispersed in the second solution, which contains two surfactants and water, and the organic solvent is substantially immiscible with water and is mixed. A step of depositing the emulsion on the substrate, a step of removing water from the emulsion to form a mixture, and a step of removing an organic solvent from the mixture to prepare an NCAP liquid crystal layer. Including.

In another embodiment, the present invention provides a modulator comprising a Nematic Curved Alignment Phase (NCAP) liquid crystal layer having a plurality of nematic liquid crystal droplets formulated by the method of the invention, the modulator being about 5 millisecond. It has an attenuation time of less than a second and an off-state light transmittance of about 5% to about 15%.

In another embodiment, the present invention provides a nematic curve-aligned phase (NCAP) liquid crystal layer comprising a plurality of nematic liquid crystal droplets formulated by the methods of the present invention, a polymer latex, and at least one surfactant. To do.

The decay times for the three different membranes are shown. Sample 1 is an NCAP made of liquid crystal 1 and has a film thickness of 24.0 μm. Sample 2 is an NCAP made of liquid crystal 2 and has a film thickness of 13.3 μm. Sample 3 is an NCAP made of liquid crystal 2 in which a plurality of LC droplets are elongated and has a film thickness of 11.8 μm. The Y-axis is the light transmittance, the X-axis is 0.5 ms per scale, and the entire X-axis is 20 ms. A square wave of 0V-60V-0V was applied. The off-state permeability is comparable for the three membranes.

The structure of the process for producing the NCAP liquid crystal layer according to the present invention is shown. The first solution having the liquid crystal and the organic solvent is mixed with the second solution having water, the surfactant and the polymer latex. The mixture of the first solution and the second solution is emulsified and then coated on the substrate on which the water has evaporated. The organic solvent is subsequently evaporated to give the NCAP liquid crystal layer of the invention.

A comparison between the device using the NCAP liquid crystal layer of the present invention and the device using the NCAP liquid crystal layer of the prior art is shown. The NCAP liquid crystal layer of the present invention has a thinner film thickness, and as a result, the distance d ₂ between the TFT panel and the indium tin oxide (ITO) layer has a corresponding distance d ₁ with the prior art device. It will be shorter than that.

A schematic diagram of a voltage imaging system including an electro-optical modulator having an NCAP liquid crystal layer of the present invention is shown.

The schematic diagram of the electro-optic modulator assembly which has the NCAP liquid crystal layer of this invention is shown.

1. 1. Schematic The present invention provides a New Car Assessment Program (NCAP) liquid crystal layer with elongated or flattened liquid crystal droplets. This makes it possible to impart more liquid crystal droplets to an NCAP liquid crystal layer having a given thickness as compared with the NCAP liquid crystal layer known in the art. As a result, the thickness of the NCAP liquid crystal layer can be reduced when used in modulators, resulting in shorter decay times while having comparable off-state light transmission. The stretched or flattened liquid crystal droplets are prepared using a binary 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 mixed with an aqueous solution having at least one surfactant and a polymer matrix. The mixed solution is emulsified to have micron-sized liquid crystal (containing organic solvent) droplets, deposited on a substrate and water is evaporated. The organic solvent (such as octane) is then evaporated to result in elongated or flattened liquid crystal droplets. Due to the second evaporation step of the high boiling point, non-polar organic solvent, the thickness of the NCAP liquid crystal layer reduces the use of liquid crystal by reducing the number of LC droplets stacked (light scattering center) through the thickness direction. It is possible to reduce the amount.

Photon Dynamics Inc. Several patents assigned to describe modulator assemblies and liquid crystal material coating processes using such materials. These patents include US Patent No. 6,151,153 "Modulator Transfer Process and Assembury", US Patent No. 6,211 and 991 "Modulator Manufacturing Processing Process and Device", and US Patent No. 6,866,887. "Method for Manufacturing PDLC-Based Electro-Optic Modulator Using Spin Coating", US Pat. Nos. 7,099,067 and 7,916,382, "Scratch and Mart. , 319 "Polymer Dispersed Liquid Crystal Formulations for Modular Fabrication", US Pat. No. 7,817,333 "Modulator with Implemented Public "Crystal Materal, Device and Applications", each of which is incorporated herein by reference in its entirety for all of the patents referred to above.

Multiple methods in the art for formulating NCAP / PDLC liquid crystal layers include, but do not use, the use of water or organic solvents. For example, US Pat. Nos. 7,639,319 and 7,099,067 describe a method of formulating a PDLC liquid crystal layer by dissolving a polymer and a liquid crystal in a common non-aqueous solvent. This solvent is then evaporated to form a PDLC liquid crystal layer. U.S. Pat. No. 7,817,333 uses a latex-based process that involves mixing liquid crystal with water and polymer latex to form an emulsion, which is mixed and onto a substrate. It is coated and the water is evaporated. The methods of the present invention combine these different water-based and organic solvent-based methods into a single method that is thinner than a given amount of liquid crystal and is stretched or flattened on the liquid crystal particles themselves. It provides an NCAP liquid crystal layer that adopts the shape of the shape, improves the light transmittance in the off state, reduces the attenuation time, and can detect particles having smaller dimensions.
2. 2. Definition

"Liquid crystal" refers to a substance that has the properties and behavior of both liquid and solid crystals. For example, liquid crystals can flow like liquids, but can be oriented like crystals to provide various optical properties such as birefringence. The liquid crystal may have a thermotropic phase, a liotropic phase, and a metallotropic phase, and the thermotropic phase and the lyotropic phase are mainly organic molecules. Thermotropic liquid crystals are temperature sensitive and transition to the liquid crystal phase when the temperature changes. Riotropic liquid crystals are sensitive to temperature and concentration. Metallotropic liquid crystals are compounds of organic and inorganic components, and the liquid crystal phase transition is sensitive to temperature, concentration, and the ratio of organic and inorganic components.

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

"Attenuation time" refers to the time required for the light transmittance to drop to 10% of the saturation value.

"Light transmittance in the off state" refers to the light transmittance in the absence of an electric field.
3. 3. Formulation of the Nematic Curve Aligned Phase (NCAP) liquid crystal layer.

The method of the present invention comprises two solutions, which are 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 consisting of a plurality of liquid crystal droplets surrounded by a polymer matrix. The emulsion is then deposited on the substrate, first evaporating the water, followed by a second evaporation step to remove the organic solvent. In some embodiments, the present invention provides a method of formulating a Nematic Curve Aligned Phase (NCAP) liquid crystal layer. The method is a step of mixing a first solution and a second solution, the first solution containing a liquid crystal and an organic solvent having a boiling point of at least about 100 ° C., and the second solution is a polymer latex. And at least one surfactant and water, under conditions suitable for forming an emulsion consisting of a first solution dispersed in a second solution, the organic solvent is substantially immiscible with water. , The step of mixing, the step of depositing the emulsion on the substrate, the step of removing water from the emulsion to form a mixture, and the step of removing the organic solvent from the mixture, whereby the NCAP liquid crystal layer is prepared. Including steps.

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

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

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

The method of the present invention also includes an aqueous solution containing a polymer latex and a surfactant. The polymer latex of the second solution can be any suitable aqueous polymer latex. Representative polymer latex includes, but is not limited to, polyurethane, polyacrylate, polyurethane acrylate, and mixtures thereof. Many emulsification methods can be used. Examples include mechanical agitation, mixing, microfluidics, homogenizers and the like. The droplet size of the resulting emulsion can be controlled and can range from about 1 micron to about 10 microns. In some embodiments, the polymer latex can be polyurethane, polyacrylate, polyurethane acrylate, or a mixture thereof.

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

The second solution also contains any suitable surfactant or compound of the plurality of surfactants. The surfactant may include, but is not limited to, a surfactant such as a nonionic surfactant, a block copolyma, and / or a crosslinkable reactive surfactant. The interface layer can form an interface layer if the interface agent contains a plurality of molecules containing two moieties having suitable chemical properties and the interface agent is present in a sufficient amount. At least a portion of the interface can be dissolved in the polymer latex so as to effectively anchor the interface within the polymer matrix. Immobilization of the interface layer to the polymer latex may be a physical bond (in blockcopolyma), a chemical bond (via a cross-linking as in the case of reactive surfactants), or a combination thereof. Immobilization of the interface layer can provide an interface layer with increased stability, for example when the temperature rises. The second portion of the interfacial agent in the interface layer may have a chemical composition that provides low surface tension and / or low friction on liquid crystal molecules and / or crystals. Since the sticking and / or friction between the liquid crystal molecules and the polymer matrix can be reduced by the interfacial layer, the alignment orientation and switching speed of the LC molecules will be faster at lower drive voltages when an electric field is applied. Can occur.

Table 1 is a partial table of interface agents that can be combined with LC materials according to a plurality of embodiments of the present invention. When a nonionic surfactant is used, the drive voltage can be significantly reduced, for example, by adding a small amount of the nonionic surfactant along with the emulsion. The low surface tension portion of the interface agent molecule may contain a fluorine compound such as Fluorolink D or Flexiwet, or may contain a silicone copolyma or siloxane-based polymer such as Surfynol DF-62, BYK-022. In particular, the reactive fluorine compound can have the chemical structure shown in Table 1, and the siloxane can have a reactive end group such as -OH, -NH ₂ , or -COOH. In many embodiments, these materials move to the LC / polymer interface during the LC / polymer phase separation process. The other portion of the interface molecule may be physically attached to the polymer via hydrogen bonds, van der Waals forces, and / or mechanisms such as chemical bonding if reactive groups are present in the polymer matrix. .. With a little heating, the chemical bonding process can be accelerated.

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

In many embodiments, the published improvement in intrinsic switching voltage sensitivity can be achieved using an interface with defoaming properties. For example, compounds in the Surfynol DF series can significantly reduce the operating voltage of latex-based NCAPs.

A defoamer is a class of surfactants that can be dispersed in an aqueous medium, and the surfactant in the interface layer may include one or more defoamers. In many embodiments, the antifoaming agent is very poorly soluble in aqueous media and may have an HLB (hydrophilic lipophilic balance) of less than 10. Since the defoamer can have very low solubility in water, the defoamer can form multiple small clusters. Each cluster may contain a plurality of molecules having a first part and a second part. As mentioned above, the first portion of the cluster molecule may have hydrophilic properties and the second portion of the cluster molecule may have hydrophobic properties. In many embodiments, the cluster has a micellar shape with the first portion oriented outwards towards the solution and the second portion inwardly oriented towards the other molecules of the defoamer cluster. obtain. During emulsification, clusters can block the formation of bubbles by bursting many bubbles. After emulsification and degassing, the clusters are free to move within the mixture of LC droplets, aqueous polymer and water. In many embodiments, the clusters can move towards the surface of the LC droplet. When the emulsion dries, the antifoaming agent can form an interface layer around the LC droplets such that the interface layer is located between the LC droplets and the polymer matrix. In many embodiments, the low surface tension end of the defoaming agent molecule is dispersed adjacent to the LC droplet so as to form a second portion of the interface layer, and the fixed end of the defoaming agent molecule is , Bonded to the polymer matrix to form the first portion of the interface layer.

The substrate can be any suitable substrate. For example, the substrate can 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 can be glass, plastic, mylar, polyester, or a mixture thereof.

Water and organic solvents can be removed by any means known to those of skill in the art. For example, water and organic solvents can be removed by evaporating by slightly raising the temperature to 40 ° C. or the like following room temperature. No vacuum is needed. For example, water and organic solvents can be evaporated by heating slightly (such as 40 ° C.) following room temperature without creating a vacuum. When the emulsion is coated on the substrate, the wet film thickness can be tens of microns. Both water and solvent can be evaporated. The formation of air pockets within the membrane can be avoided by using lower temperatures 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 is 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 can have a thickness of at least about 50 μm. The NCAP liquid crystal layer is 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, about 5 μm to about 25 μm, about 5 μm to about 20 μm, or It can have a thickness of 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, as measured by filmmetry, can also have any suitable level of uniformity across the layer. For example, the thickness uniformity can be +/- 10%.

The dried liquid crystal droplets may adopt any suitable shape. For example, a dry liquid crystal droplet can have an elongated shape with both a primary axis and a secondary axis, such as a three-dimensional ellipse. The ratio of spindle to sub-axis can 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 comprises a plurality of substantially dry liquid crystal droplets having a main axis and a sub-axis, and the ratio of the main axis to the sub-axis is from about 100: 1 to about 1.5: 1. And the spindle is substantially parallel to the substrate. The dried liquid crystal droplets can also be described as being flattened as if pressure was applied to the liquid crystal droplets from above and below to flatten the liquid crystal droplets.

In some embodiments, the present invention provides a method of formulating a Nematic Curve Aligned Phase (NCAP) liquid crystal layer. This method is a step of mixing the first solution and the second solution, in which the first solution mixes a nematic liquid crystal and an organic solvent such as octane from about 1: 2 (w / w) to about 2: 1 (. Containing in a ratio of w / w), the second solution contains a polymer latex, at least one surfactant and water to form liquid crystal droplets, and the ratio of polymer latex to liquid crystal is about 3: 2 (w). From / w) to about 1: 4 (w / w), the mixing step, the step of depositing the liquid crystal droplet mixture on the substrate, the step of removing water from the mixture, and the step of removing the organic solvent from the mixture. Including steps, this formulates an NCAP liquid crystal layer containing a plurality of substantially dry liquid crystal droplets having a principal axis and a sub-axis. The spindle-to-sub-spindle ratio is from about 100: 1 to about 1.5: 1, and the spindle is substantially parallel to the substrate.

In some embodiments, the present invention provides a nematic curve-aligned phase (NCAP) liquid crystal layer comprising a plurality of nematic liquid crystal droplets formulated with the method of the invention, a polymer latex, and at least one surfactant. To do.
4. Modulator.

The present invention also provides a modulator incorporating an NCAP liquid crystal layer formulated by the method of the present invention. In some embodiments, the present invention provides a modulator comprising a Nematic Curve Aligned Phase (NCAP) liquid crystal layer with a plurality of nematic liquid crystal droplets formulated by the methods of the present invention. The modulator has an attenuation time of less than about 5 ms and an off-state light transmission of about 5% to about 15%.

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

The modulators of the present invention may have any suitable off-state light transmittance. For example, the light transmittance in the off state is 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%, and so on. Or it can be from about 5% to about 15%. The light transmittance of the modulator of the present invention in the off state is about 1%, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, and so on. It can be 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 can be 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 contain a polymer latex and a surfactant, both of which have been described in more detail above.

The modulator of the present invention may include a plurality of other layers in addition to the NCAP liquid crystal layer. For example, the modulator may include one or more of transparent substrates, pellicle, indium tin oxide (ITO), and the like. The transparent substrate can be any substrate that is transparent to light in the visible spectrum region, such as glass, plastic, mylar, polyester, and the like. The pellicle or dielectric mirror pellicle can be formulated from any material known to those of skill in the art. In addition, the various layers of the modulator can be arranged in any suitable order. For example, the pellicle can be on the top surface of the NCAP liquid crystal layer, and the NCAP liquid crystal layer can be on the top surface of the transparent substrate.

FIG. 4 schematically shows a plurality of components of a voltage imaging system 100 suitable for a combination for TFT inspection according to a plurality of embodiments. The plurality of components of a voltage imaging system may include one or more components as described in US Pat. No. 7,639,319, and / or a plurality of components of a commercially available voltage imaging system. The voltage imaging system 100 may include an electro-optical modulator assembly 200, a light emitter 114, a beam splitter 116, and a camera 118. The electro-optical modulator assembly 200 includes a transparent electrode 250 (electrode A), a transparent substrate 220 that supports the transparent electrode 250, an NCAP liquid crystal layer sensor material 260, and a thin plastic film, for example, a dielectric mirror 270 supported by a pellicle. Can include. The transparent electrode 250 may include a thin film made of indium tin oxide (ITO) that is transparent to visible light. The NCAP liquid crystal layer sensor material 260 has an electro-optical response under an electric field. Electrode B104 may include a test object (PUT), such as a TFT plate. By applying a voltage to the transparent electrode 250 (electrode A) and grounding the electrode B, a transmittance-voltage (TV) curve can be obtained. In the TFT test, when a constant voltage near the center of the response curve is applied to the modulator, the voltage applied to each pixel can be detected from the camera 118 by the change in light intensity. Defective pixels will provide an unusual response.

The voltage applied between the electrode A and the electrode B can be expressed by the following equation.
V _Bias is a voltage applied between the electrode A and the electrode B. V _sensor is the voltage required for the sensor material. V- _pellicle and V- _air are voltages applied to the pellicle and the air gap. ε is the relative permittivity of each material. d is the thickness of each material.

When V _Bias is fixed, the air gap d _air between the electrodes is a function of the intrinsic operating voltage (V _sensor ) of the liquid crystal sensor material. In many embodiments, the intrinsic switching voltage of the liquid crystal sensor material corresponds to the voltage applied to the sensor material, and the light transmission through the sensor material has the greatest sensitivity to changes in the voltage applied to the sensor material. In many embodiments, the operating voltage across the electrodes is related to the intrinsic switching voltage of the LC material by using the above equation. The switching time can be reduced by providing a material with a reduced intrinsic switching voltage.

FIG. 5 shows a schematic view of the electro-optical modulator assembly 200. The modulator assembly 200 has a sensor material 260. The sensor material 260 may include an NCAP liquid crystal material as described herein. The modulator assembly may have an antireflection coating 210. The modulator assembly may have an optically transparent support substrate such as optical glass 220. The antireflection coating 210 can be deposited on the top surface of the optical glass 220. The optical adhesive 230 may be located on the underside of the optical glass 220. A layer of polyester film 240 containing stretched polyethylene terephthalate (PET), which is commercially available as Mylar®, can be bonded to optical glass with an optical adhesive 230. An optically transparent electrode 250 such as ITO can be bonded to the polyester film 240. The NCAP liquid crystal layer 260 can be coupled to an optically transparent electrode 250. A thin film PET, eg, a dielectric pellicle mirror 270 containing a dielectric mirror layer deposited on Mylar®, can be coupled to the underside of the liquid crystal sensor material. The organic hard coat 280 can be fixed to the dielectric pellicle mirror 250. Organic hard coat 280 may include multiple components of the hard coat described in US Pat. No. 7,099,067.

This new fast switching modulator is suitable for all kinds of voltage imaging applications, but is especially useful for inspection of organic light emitting diode (OLED) displays. Due to the fact that OLEDs are current-driven devices, OLED displays generally require very little holding capacity. This means that the voltage applied to the pixel electrodes of these displays can be quickly attenuated, requiring a fast response modulator to ensure optimum voltage image signal strength.

For similar reasons and due to the shorter distance between the ITO and the TFT under test, as described in connection with FIG. 3, this modulator is well suited for ultra-small pixel panels. (The smaller the pixel, the smaller the storage capacity), or well suited for panels with very high refresh rates (this means that the voltage does not need to be held for a very long time, Therefore, the storage capacity can be small). In addition, fast switching modulators can be less susceptible to various signal drifts resulting from, for example, depolarizing currents.
5. Example.
Example 1. Formulation of the Nematic Curve Aligned Phase (NCAP) liquid crystal layer.

Two grams of nematic liquid crystal (MLC-2156, manufactured by EMD Chemicals) was mixed with 1 gram of octane to form a clear solution. This LC / organic solvent mixture consists of 2.5 grams of Neorez R-967 (manufactured by DSM) and 1.5 grams of water / 0.16 grams of Surfynol DF-62 (manufactured by Air Products) / 0.04 grams. It was emulsified with a mixture of TWEEN 60 / 0.06 grams of FSN (manufactured by DuPont) to form an emulsion. The emulsion was then coated onto an ITO Mylar film, which was then laminated with another ITO Mylar after the water and octane had been completely evaporated. For comparison, Sample 2 was prepared in the same procedure as above, except that octane was not used. Then, sample 1 was prepared by the same procedure as sample 2, but a liquid crystal having a lower optical anisotropy was used.

FIG. 1 shows the decay times for three different membranes. Sample 1 is an NCAP made of liquid crystal 1 and has a film thickness of 24.0 μm. Sample 2 is an NCAP made of liquid crystal 2 and has a film thickness of 13.3 μm. Sample 3 is an NCAP made of liquid crystal 2 in which a plurality of LC droplets are elongated and has a film thickness of 11.8 μm. The Y-axis is the light transmittance, the X-axis is 0.5 ms per scale, and the entire X-axis is 20 ms. A square wave of 0V-60V-0V was applied. The transmittance in the off state is the same for all three membranes. See the table below, which summarizes the results.

Although the above invention has been described in some detail with examples and examples for the purpose of clarifying understanding, those skilled in the art will appreciate that some modifications and modifications can be made within the scope of the appended claims. Will understand. In addition, each reference provided herein is incorporated by reference in its entirety to the same extent that each reference is incorporated individually by reference. In the event of a conflict between the present application and the references provided herein, the present application shall prevail.

Claims (21)

A method for formulating a nematic curve-aligned phase liquid crystal layer (NCAP liquid crystal layer).
A step of mixing the first solution and the second solution, the first solution comprises an organic solvent having a boiling point higher than 100 ° C. at the liquid crystal and the lowest, the second solution, at least a polymer latex A step of mixing, which comprises one surfactant and water, the organic solvent is substantially immiscible with water, and the first solution and the second solution are mixed to form an emulsion .
The stage of depositing the formed emulsion on the substrate and
The step of removing the water from the emulsion to form a mixture, and
The step of removing the organic solvent from the mixture, thereby preparing the NCAP liquid crystal layer, and
To prepare
Method. The liquid crystal includes a nematic liquid crystal, a ferroelectric liquid crystal, a blue phase liquid crystal, a liquid crystal / dichroic dye mixture, a cholesteric liquid crystal, or a mixture thereof.
The method according to claim 1. The liquid crystal is a nematic liquid crystal.
The method according to claim 1. The organic solvent has a boiling point higher than 110 ° C.
The method according to any one of claims 1 to 3. The organic solvent has a boiling point higher than 120 ° C.
The method according to any one of claims 1 to 3. The organic solvent is a non-polar organic solvent,
The method according to any one of claims 1 to 5. The organic solvent contains octane,
The method according to any one of claims 1 to 6. The ratio of liquid crystal to organic solvent is from 1:10 (w / w) to 5: 1 (w / w).
The method according to any one of claims 1 to 7. The ratio of liquid crystal to organic solvent is from 1: 2 (w / w) to 2: 1 (w / w).
The method according to any one of claims 1 to 7. The polymer latex is polyurethane, polyacrylate, polyurethane acrylate, or a mixture thereof.
The method according to any one of claims 1 to 9. The ratio of polymer latex to liquid crystal is from 5: 1 (w / w) to 1:10 (w / w).
The method according to any one of claims 1 to 10. The ratio of polymer latex to liquid crystal is from 3: 2 (w / w) to 1: 4 (w / w).
The method according to any one of claims 1 to 10. The substrate comprises glass, plastic, polyethylene terephthalate , polyester, or a mixture thereof.
The method according to any one of claims 1 to 12. The water is removed by evaporation,
The method according to any one of claims 1 to 13. The organic solvent is removed by evaporation,
The method according to any one of claims 1 to 14. The NCAP liquid crystal layer has a thickness of 20μm from 1 [mu] m,
The method according to any one of claims 1 to 15. The NCAP liquid crystal layer has a thickness of 4 μm to 20 μm.
The method according to any one of claims 1 to 15. Comprising the steps of mixing the first solution and the second solution, the first solution, a nematic liquid crystal and octane 1: wherein a ratio of 1 (w / w): from 2 (w / w) 2 The second solution contains the polymer latex, the at least one surfactant, and the water, and the ratio of the polymer latex to the liquid crystal is 3: 2 (w / w) to 1: 4 (w / w). Ah is, you form an emulsion by mixing the first solution and the second solution, the step of mixing,
The stage of depositing the emulsion on the substrate and
The step of removing the water from the emulsion to form a mixture, and
A step of removing the organic solvent from the mixture, thereby preparing the NCAP liquid crystal layer containing a plurality of substantially dry liquid crystal droplets.
With
The method according to any one of claims 1 to 17. A modulator having a nematic curve-aligned phase liquid crystal layer (NCAP liquid crystal layer) .
And 5 mm less than the second decay time, of 5% to 15% of light transmittance in the off state possess,
The thickness of the nematic curve aligned phase liquid crystal layer (NCAP liquid crystal layer) is 4 μm to 20 μm.
Modulator. The NCAP liquid crystal layer is
With polymer latex,
Surfactant and
Including,
The modulator according to claim 19. A transparent substrate that supports the NCAP liquid crystal layer and
The pellicle laminated on the uppermost surface of the NCAP liquid crystal layer and
Further prepare
The modulator according to claim 19 or 20.