JP2009091419A - Liquid crystal-containing composition and liquid crystal display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal-containing composition which is inhibited in the deterioration of nominal quality even when stored at high temperatures, a process for producing a liquid crystal-containing composition, and a liquid crystal display element using the same. <P>SOLUTION: For example, a liquid crystal-containing composition 4 appeared in an embodiment of the present invention has a cholesteric crystal 2 and a microcapsule 3 containing the cholesteric crystal 2. The microcapsule 3 comprises a wall material component composed of at least one kind selected from polyurethane and polyurea and a polyol component. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid crystal-containing composition and a liquid crystal display element using the same.

  In recent years, cholesteric liquid crystal display elements have features such as having a memory property of display with no power supply, a bright display because a polarizing plate is not used, and a color display without using a color filter. (See, for example, Patent Document 1).

  In particular, cholesteric liquid crystal is composed of rod-like molecules oriented in a spiral shape, and has the property of interference-reflecting (referred to as selective reflection) light that matches the spiral pitch. Therefore, by setting the spiral pitch to a size corresponding to the wavelengths of red, green, and blue, it is possible to obtain a colorful color display without using a color filter.

  For example, it is known that a cholesteric liquid crystal sealed in a cell composed of a pair of electrodes-attached substrates takes two kinds of alignment states: planar (P) alignment and focal conic (F) alignment. The P orientation is a state in which the helical axis is oriented perpendicular to the substrate surface and causes selective reflection. The F orientation is a state in which the spiral axis is oriented parallel to the substrate surface and transmits light. These two alignment states are changed to each other by applying a voltage between the electrodes.

  Therefore, by arranging a light absorber such as black on the back surface of the cell, a bright display colored in the selective reflection color at the P orientation, and a dark display colored the light absorber at the F orientation. can get. Among the above alignment forms, both the P alignment and the F alignment exist stably with no power supply. Utilizing this property, a memory display that maintains a display without a power source is realized.

On the other hand, for the purpose of preventing the flow of liquid crystal and improving the maintainability of an image against pushing deformation and bending deformation, a technique for dispersing and holding liquid crystal in a polymer such as matrix resin or microcapsule has been proposed (for example, Patent Documents 2 to 4).
Japanese Patent Laid-Open No. 05-080303 JP 2000-147479 A JP 2001-249314 A JP 09-015568 A

  An object of the present invention is to provide a liquid crystal-containing composition that improves CR (contrast) and suppresses an afterimage phenomenon, and a liquid crystal display element using the composition.

The above problem is solved by the following means. That is,
The invention according to claim 1
Cholesteric liquid crystal,
A microcapsule encapsulating the cholesteric liquid crystal and including a wall material component and a polyol component made of at least one selected from polyurethane and polyurea;
It is a liquid crystal containing composition characterized by having.

The invention according to claim 2
2. The liquid crystal-containing composition according to claim 1, wherein the content of the polyol component is 5% by weight or more and 25% by weight or less based on the total amount of the wall material component of the microcapsule.

The invention according to claim 3
The liquid crystal-containing composition according to claim 1, wherein the polyol component has a weight average molecular weight of 20,000 or more and 1,000,000 or less.

The invention according to claim 4
2. The liquid crystal-containing composition according to claim 1, wherein the polyol component is a polyester polyol component.

The invention according to claim 5
A pair of electrodes;
The liquid crystal-containing composition according to any one of claims 1 to 4, which is sandwiched between the pair of electrodes.
It is a liquid crystal display element characterized by having.

  ADVANTAGE OF THE INVENTION According to this invention, while improving CR (contrast), the liquid crystal containing composition which suppressed the afterimage phenomenon, and a liquid crystal display element using the same can be provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that members having substantially the same functions and actions are given the same reference numerals throughout the drawings, and redundant descriptions may be omitted.

  FIG. 1 is a schematic view showing a liquid crystal-containing composition according to an embodiment. FIG. 2 is a schematic view showing a liquid crystal-containing composition according to another embodiment.

  For example, as shown in FIG. 1, the liquid crystal-containing composition 4 according to the embodiment includes a cholesteric liquid crystal 2 and a microcapsule 3 including the cholesteric liquid crystal 2. And the microcapsule 3 is comprised including the wall material component and polyol component which consist of at least 1 type chosen from a polyurethane and a polyurea.

  Moreover, the liquid crystal-containing composition 4 according to the embodiment includes, for example, as shown in FIG. 2, microcapsules 3 containing cholesteric liquid crystals 5 and a resin member 1 in which the microcapsules 3 are dispersed and held. Form may be sufficient.

  The liquid crystal-containing composition 4 according to the embodiment is a slurry-like composition composed of microcapsules 3 enclosing the cholesteric liquid crystal 2 or an ink composition in which the slurry-like composition is mixed with a binder polymer. Is also included.

In the liquid crystal-containing composition 4 according to the embodiment, the microcapsule 3 containing the cholesteric liquid crystal 2 has the above-described configuration, so that the influence of the alignment constraint of the cholesteric liquid crystal 2 by the microcapsule 3 is reduced. Therefore, for example, when white display is performed after black display, the occurrence of an afterimage phenomenon in which the reflectance is reduced is suppressed as compared with the case where white display is performed again after white display. In addition, CR (contrast) is also improved.
In particular, in the form having the resin member 1 that disperses and holds the microcapsules 3, the fluidity of the liquid crystal (the microcapsules that enclose it) is reduced, and the maintainability of the image against pushing deformation and bending deformation is improved. Although the influence of the alignment restraint by the resin member 1 is large, the occurrence of the afterimage phenomenon is suppressed when the microcapsule 3 containing the cholesteric liquid crystal 2 has the above configuration.

  Hereinafter, the liquid crystal-containing composition according to the present embodiment will be described in detail. In the following description, the reference numerals are omitted.

  First, the cholesteric liquid crystal will be described. A cholesteric liquid crystal is a liquid crystal material containing an optically active compound, 1) a method of adding an optically active compound called a chiral agent to nematic liquid crystal, and 2) a method of using an optically active liquid crystal material such as a cholesterol derivative. Etc. In the former case, the nematic liquid crystal material is known as cyanobiphenyl, phenylcyclohexane, phenylbenzoate, cyclohexylbenzoate, azomethine, azobenzene, pyrimidine, dioxane, cyclohexylcyclohexane, stilbene, tolan, etc. A nematic liquid crystal-containing composition is utilized. As the chiral agent, a cholesterol derivative or a compound having an optically active group such as a 2-methylbutyl group is used.

  Additives such as dyes and particles may be added to the cholesteric liquid crystal. Further, it may be gelled using a crosslinkable polymer or a hydrogen bonding gelling agent, or may be any of a polymer liquid crystal, a medium molecular liquid crystal, a low molecular liquid crystal, or a mixture thereof. The helical pitch of the cholesteric liquid crystal may be changed depending on the type and amount of the chiral agent and the material of the liquid crystal. The wavelength of selective reflection may be the ultraviolet wavelength region or the infrared wavelength region in addition to the visible wavelength region. Note that the average particle diameter of cholesteric liquid crystal droplets (including microcapsules) dispersed in a polymer, which will be described later, is desirably at least three times the helical pitch of the cholesteric liquid crystal in order to exhibit memory properties.

The microcapsule will be described.
The microcapsule includes a wall material component made of at least one selected from polyurethane and polyurea and a polyol component. Moreover, you may introduce | transduce vertical alignment components, such as an alkyl group and / or a fluoroalkyl group, into a microcapsule as needed.

  Microcapsules containing a wall material component composed of at least one selected from polyurethane and polyurea can be formed by a known method. Specifically, for example, a polyisocyanate (for example, tolylene diisocyanate, xylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, and the like together with a core material (cholesteric liquid crystal). Isocyanates, adducts such as diisocyanates, triisocyanates, tetraisocyanates, burettes, cyanurates, polyisocyanate prepolymers, etc.) and substances that react with them to form microcapsule walls (eg, polyols, polyamines, two or more amino acids) A prepolymer having a group, piperazine or a derivative thereof) in a water-soluble polymer aqueous solution (aqueous phase) or an oily medium (oil phase) to be encapsulated, and water After emulsified and dispersed in, causing the polymer formation reaction at the interface between the aqueous phase and the oil phase by heating is obtained by forming a microcapsule wall. Of course, it is not limited to these.

  On the other hand, preferred examples of the polyol component include a polyester polyol component and a polyether polyol component, and the polyester polyol component is particularly preferred from the viewpoint of improving CR (contrast) and suppressing the afterimage phenomenon. The polyol component is contained in the microcapsule wall by adding a polyol (for example, polyester polyol or polyether polyol) together with the microcapsule raw material.

  Examples of the polyester polyol include dibasic acids (for example, terephthalic acid, isophthalic acid, adipic acid, azelaic acid, sebacic acid, etc.) or dialkyl esters thereof, or mixtures thereof, and glycols (ethylene glycol, propylene glycol, diethylene glycol). , Butylene glycol, neopentyl glycol, 1,6-hexane glycol, 3-methyl-1,5-pentanediol, 3,3′-dimethylol heptane, polyoxyethylene glycol, polyoxypropylene glycol, polytetramethylene ether glycol Etc.), or mixtures thereof, and polyester polyols obtained by reacting them. Examples of the polyester polyol include polyester polyols obtained by ring-opening polymerization of lactones (polycaprolactone, polyvalerolactone, poly (β-methyl-γ-valerolactone) and the like).

  On the other hand, examples of the polyether polyol include polyethylene glycol, polyoxyethylene glycol, polyoxypropylene glycol, polytetramethylene glycol, and copolymers thereof.

  The weight average molecular weight of the polyol component is desirably 20,000 or more and 1,000,000 or less, more desirably 20,000 or more and 500,000 or less, and further desirably 20,000 or more and 50,000 or less. When the weight average molecular weight is a predetermined value or more, in particular, the afterimage phenomenon is effectively reduced.On the other hand, if the weight average molecular weight is too large, the solubility is reduced, and the compatibility with the solvent is also reduced. In some cases, the microcapsules cannot be produced uniformly.

  Here, the measurement of a weight average molecular weight is performed using gel permeation chromatography (GPC). GPC uses 8020 series (manufactured by Tosoh Corporation), TSKgel, G4000HXL, G2500HXL, G1000HXL (manufactured by Tosoh Corporation, 7.8 mm ID × 30 cm), and THF (tetrahydrofuran) as an eluent. Is used. As experimental conditions, the sample concentration is 0.2% by mass, the flow rate is 1 ml / min, the sample injection amount is 50 μl, the measurement temperature is 40 ° C., and a differential refractometer is used.

  The content of the polyester polyol component is preferably 1% by weight or more and 50% by weight or less, more preferably 5% by weight or more and 25% by weight or less, and still more preferably 10% by weight with respect to the entire capsule wall material component. More than 15% by weight. When the content is in the above range, CR (contrast) is effectively improved and the afterimage phenomenon is reduced.

  The vertical alignment component is introduced into the microcapsule by adding, for example, an alignment material made of a compound having an alkyl group and / or a fluoroalkyl group and a hydroxyl group together with the microcapsule raw material. The alignment property of the polymer (microcapsule) inherently is offset by the vertical alignment property introduced by the vertical alignment component, thereby weakening the alignment regulating force. This results in a straight cholesteric liquid crystal layer with no curvature, improving color purity and display contrast. In addition, since the alignment regulating force is weak, the liquid crystal molecules in contact with the polymer have a small difference in energy regardless of the orientation, and therefore, both the P orientation and the F orientation are stable over time. The details of this vertical alignment component are the same as those described in JP-A-2005-316243.

  Although the afterimage phenomenon tends to occur when the vertical alignment component is introduced into the microcapsule, the afterimage phenomenon is suppressed in this embodiment.

  As described above, the liquid crystal-containing composition according to the present embodiment is used, for example, by dispersing microcapsules encapsulating cholesteric liquid crystals in a binder material and applying them to various surfaces. As a result, the liquid crystal is protected by the microcapsules, so that another functional layer is formed thereon, and it has excellent mechanical strength such as pressure and bending. Further, by using a curable binder material, when the binder material is formed into a layer and then cured, a resin member in which microcapsules containing cholesteric liquid crystal are dispersed and held is formed.

  The liquid crystal-containing composition according to the present embodiment includes screen printing, letterpress printing, intaglio printing, flat plate printing, flexographic printing, and other printing methods, spin coating methods, bar coating methods, dip coating methods, roll coating methods, knife coatings, and the like. A coating method such as a coating method or a die coating method is used by coating on a substrate.

  The liquid crystal-containing composition according to the present embodiment is used for, for example, a display element, an image / information recording element, a spatial light modulator, and the like. In particular, it is preferably used for a display element, that is, a liquid crystal display element. Hereinafter, the liquid crystal display element according to the present embodiment will be described.

  The liquid crystal display element according to the present embodiment has a configuration in which the liquid crystal-containing composition according to the present embodiment is sandwiched between a pair of electrodes. Specifically, for example, as shown in FIG. 3, the liquid crystal-containing composition 4 is sandwiched between substrates 21 and 22 provided with electrodes 11 and 12, respectively, and a voltage pulse is given by a drive circuit 30 to display. It becomes the composition to make. As a display background, a light absorbing member may be provided between the liquid crystal-containing composition 4 and the electrode 12 or on the back surface of the substrate 22. As the substrates 21 and 22, for example, glass or resin (transparent dielectric such as polyethylene terephthalate, polyether sulfone, polycarbonate, polyolefin, etc.) is used. As the electrodes 11 and 12, for example, a transparent conductive film such as an indium tin oxide alloy or zinc oxide is used.

  Here, the liquid crystal display element shown in FIG. 3 shows a form in which microcapsules 3 containing cholesteric liquid crystal 2 are dispersed and held in resin member 1 as liquid crystal-containing composition 4.

  In the liquid crystal display element according to the present embodiment, the liquid crystal-containing composition according to the present embodiment emphasizes the optical difference between the P orientation and the F orientation in the memory state of the cholesteric liquid crystal. In addition to the selective reflection mode described above, a scattering-transmission mode using a difference in light scattering intensity between P and F orientations, an optical rotation mode using a difference in optical rotation, a birefringence mode using a difference in birefringence, etc. May be used. In this case, you may use together with a polarizing plate or a phase difference plate as an auxiliary member. Further, a dichroic dye may be added to the liquid crystal to display in the guest-host mode.

  As a driving method of the liquid crystal display element according to the present embodiment, 1) a segment driving method in which the electrode is sandwiched between electrodes patterned in a display shape, and 2) a liquid crystal between a pair of stripe-shaped electrode substrates that intersect (for example, orthogonal). A simple matrix driving method in which an image is written by scanning line-sequentially across the composition, and 3) active elements such as thin-film transistors, thin-film diodes, and MIM (metal-insulator-metal) elements are provided for each pixel. Active matrix driving method driven through an element 4) Optical driving method in which a photoconductor is stacked and sandwiched between a pair of electrodes, and an image is written by applying a voltage while projecting an optical image. 5) A pair The composition containing the liquid crystal sandwiched between the electrodes is transitioned to the P orientation by applying voltage, and then applied to the phase transition temperature or higher with a laser or thermal head. Thermal driving method for writing an image by, 6) to the electrodes on the substrate by coating a liquid crystal-containing composition, such as an electrostatic driving method for writing an image in the stylus head or an ion head, known drive method is applied.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, these examples do not limit the present invention. Unless otherwise specified, “part” means “part by mass”.

[Example A]
(Example A1)
Nematic liquid crystal E7 (manufactured by Merck & Co., Inc.) 86.25 parts, chiral agent R811 (manufactured by Merck & Co., Ltd.) 11.0 parts, chiral agent R1011 (manufactured by Merck & Co., Ltd.) 2.75 parts, 100 parts of cholesteric liquid crystal selectively reflecting at 650 nm was obtained. 10 parts of this cholesteric liquid crystal, Takenate D-110N (manufactured by Takeda Pharmaceutical Co., Ltd.) as the polyvalent isocyanate, 3 parts of octadecanol (manufactured by Aldrich) as the precursor of the vertical alignment component, and polyester polyol (“Takelac A385”) “Mitsui Takeda Chemical Co., Ltd.) 0.8 parts of ethyl acetate was dissolved in 1000 parts to prepare an oil phase composition. This was put into 10,000 parts of a 1% polyvinyl alcohol aqueous solution, and stirred and dispersed with a mixer to prepare an o / w emulsion having a volume average particle diameter of 7 μm.

  To this, 100 parts of a 10% aqueous solution of polyallylamine (manufactured by Nittobo Co., Ltd.) was added and heated at 70 ° C. for 2 hours to prepare microcapsules having polyurea as a wall material. After the microcapsules were collected by centrifugation, an aqueous polyvinyl alcohol solution was added to obtain a microcapsule liquid crystal paint.

  Next, the microcapsule liquid crystal paint was applied on a commercially available ITO-deposited PET resin film using an applicator so that the dry film thickness was 30 μm. A polyvinyl alcohol aqueous solution in which carbon black was dispersed thereon was applied to a dry film thickness of 3 μm to form a light absorption layer. On the other hand, another ITO-deposited PET resin film is prepared, on which a two-component urethane adhesive is applied to a dry film thickness of 3 μm, and is bonded to the substrate on which the microcapsule liquid crystal paint is applied. Thus, a liquid crystal display element was produced.

  The obtained liquid crystal display element was evaluated for the afterimage index and CR (contrast). The results are shown in Table 1.

-CR (contrast)-
For CR, the voltage (V) -reflectance (Y) characteristic of the liquid crystal display element sample was measured, and the ratio between the maximum reflectance and the minimum reflectance was defined as CR (contrast). A symmetrical rectangular wave pulse (reset voltage) having a size of 600 V, a frequency of 1 kHz, and a length of 1 sec is applied between the upper and lower electrodes of the liquid crystal display element sample to uniformly display the liquid crystal display sample (white display reset). Then, a writing voltage V (a symmetric rectangular wave pulse having a frequency of 1 kHz and a length of 200 msec) was applied, and the luminous reflectance after 3 seconds from the end of the application was measured. This measurement was repeated while changing the magnitude of the writing voltage stepwise to obtain the voltage-reflectance characteristic _{Ywr (} V). Spectral luminance meter CM-2022 (manufactured by Minolta) was used as the reflectance, and luminous reflectance was used as the reflectance.

-Afterimage index-
As an index for evaluating the degree of afterimage, an afterimage index was defined and measured by the following procedure (FIG. 4).
First, as shown in the CR (contrast) evaluation method, the voltage-reflectance characteristic Ywr (V) by white display reset is measured. Further, the magnitude of the reset voltage is set to 200 V, the same measurement is performed, and the current-reflectance characteristic Ykr (V) by the dark (black) display reset is obtained. The voltage at which the reflectance reaches 90% of the maximum value in the voltage-reflectance characteristic by the white display reset is defined as VT4.
Using these values, the afterimage index was defined by the following equation.
Afterimage index = (Ywr (1.2 × VT4) −Ykr (1.2 × VT4)) / Ykr (1.2 × VT4)

(Examples A2 to A6)
Except having changed the addition amount of the polyester polyol according to Table 1, the liquid crystal display element was produced similarly to Example A1, and evaluated. The results are shown in Table 1.

(Comparative Example A1)
A liquid crystal display device was produced and evaluated in the same manner as in Example A1 except that the polyester polyol was not added. The results are shown in Table 1.

  From the results shown in Table 1, it can be seen that the afterimage index is lower in this example than in the comparative example, and the afterimage phenomenon is suppressed. It can also be seen that the present example also improves the CR compared to the comparative example. In particular, it can be seen that the example using a predetermined amount of polyester polyol has a lower afterimage index and a higher CR than the other examples.

[Example B]
(Examples B1 to B4)
Except having changed the kind of polyol according to Table 2, the liquid crystal display element was produced similarly to Example A1, and evaluated. The results are shown in Table 2.

A315: “Takenate A315” manufactured by Mitsui Takeda Chemical Co., Ltd. A385: “Takenate A385” manufactured by Mitsui Takeda Chemical Co., Ltd. A520: “Takenate A520” manufactured by Mitsui Takeda Chemical Co., Ltd. Polyethylene glycol: “Polyethylene glycol 20000” manufactured by Wako Pure Chemical Industries, Ltd. LX732: "Dick Dry LX732" manufactured by Dainippon Ink & Chemicals, Inc.

  From the results in Table 1, it can be seen that in Examples using polyester polyols having a predetermined weight average molecular weight, the afterimage index is low and the CR (contrast) is also high.

It is a schematic block diagram which shows an example of the liquid crystal containing composition which concerns on embodiment. It is a schematic block diagram which shows another example of the liquid crystal containing composition which concerns on embodiment. It is a schematic block diagram which shows an example of the liquid crystal display element which concerns on embodiment. It is a figure for demonstrating an afterimage index.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Resin member 2 Cholesteric liquid crystal 3 Microcapsule 4 Liquid crystal containing composition 11, 12 Electrode 21, 22 Substrate 30 Drive circuit

Claims (5)

Cholesteric liquid crystal,
A liquid crystal-containing composition characterized by having a microcapsule that includes the cholesteric liquid crystal and includes at least one wall material component selected from polyurethane and polyurea and a polyol component.   2. The liquid crystal-containing composition according to claim 1, wherein the content of the polyol component is 5% by weight or more and 25% by weight or less with respect to the total amount of the wall material component of the microcapsule.   2. The liquid crystal-containing composition according to claim 1, wherein the polyol component has a weight average molecular weight of 20,000 or more and 1,000,000 or less.   The liquid crystal-containing composition according to claim 1, wherein the polyol component is a polyester polyol component. A pair of electrodes;
The liquid crystal-containing composition according to any one of claims 1 to 4, which is sandwiched between the pair of electrodes.
A liquid crystal display element comprising:

Images