Patent Application
20210301206
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2020-056410, filed Mar. 26, 2020, the entire contents of which are incorporated herein by reference.
Embodiments described herein relate generally to a liquid crystal material composition and display device.
Recently, various types of illumination devices employing polymer dispersed liquid crystal (which may be referred to as “PDLC” hereinafter) capable of switching a diffusing state of diffusing incident light and a transmitting state of causing the incident light to be transmitted have been proposed.
On the other hand, there is a demand of improving the display quality in the display devices which employ PDLC.
The present disclosure relates generally to a liquid crystal material composition and a display device.
According to an embodiment, a liquid crystal material composition includes a liquid crystal mixture containing at least one kind of each of a first liquid crystalline compound, a second liquid crystalline compound and a third liquid crystalline compound, a polymerization initiator and a monomer compound including acryloyl groups at respective terminals.
In general, according to one embodiment, a liquid crystal material composition comprises a liquid crystal mixture containing at least one kind of a first liquid crystalline compound, at least one kind of a second liquid crystalline compound and at least one kind of a third liquid crystalline compound, a polymerization initiator and a monomer compound including acryloyl groups at respective terminals, and the at least one kind of the first liquid crystalline compound contains a first aromatic ring including a halogens group, a second aromatic ring including a halogens group and bonded to the first aromatic ring through a first bond, and a third aromatic ring including an aliphatic group and bonded to the second aromatic ring through a second bond, the at least one kind of the second liquid crystalline compound contains a first aromatic ring including a halogens group, a second aromatic ring including a halogens group and bonded to the first aromatic ring through the first bond and a first alicyclic group including an aliphatic group and bonded to the second aromatic ring through a third bond, and the at least one kind of the third liquid crystalline compound contains a fourth aromatic ring, a fifth aromatic ring bonded to the fourth aromatic ring through a fourth bond, a second alicyclic group including an aliphatic group and bonded to the fourth aromatic ring through a fifth bond, and a third alicyclic group including an aliphatic group and bonded to the fifth aromatic ring through a sixth bond.
According to another embodiment, a display device comprises a first substrate, a second substrate opposing the first substrate, a liquid crystal layer located between the first substrate and the second substrate and containing a liquid crystal mixture containing at least one kind of a first liquid crystal compound, at least one kind of a second liquid crystalline compound and at least one kind of a third liquid crystalline compound, and a polymer originated from a monomer compound including acryloyl groups at respective terminals and an alignment film located on the first substrate and in contact with the liquid crystal layer, and the at least one kind of the first liquid crystalline compound contains a first aromatic ring including a halogens group, a second aromatic ring including a halogens group and bonded to the first aromatic ring through a first bond, and a third aromatic ring including an aliphatic group and bonded to the second aromatic ring through a second bond, the at least one kind of the second liquid crystalline compound contains a first aromatic ring including a halogens group, a second aromatic ring including a halogens group and bonded to the first aromatic ring through the first bond and a first alicyclic group including an aliphatic group and bonded to the second aromatic ring through a third bond, and the at least one kind of the third liquid crystalline compound contains a fourth aromatic ring, a fifth aromatic ring bonded to the fourth aromatic ring through a fourth bond, a second alicyclic group including an aliphatic group and bonded to the fourth aromatic ring through a fifth bond, and a third alicyclic group including an aliphatic group and bonded to the fifth aromatic ring through a sixth bond.
Embodiments will be described hereinafter with reference to the accompanying drawings. The disclosure is a mere example, and arbitrary change of gist which can be easily conceived by a person of ordinary skill in the art naturally falls within the inventive scope. To more clarify the explanations, the drawings may pictorially show width, thickness, shape and the like, of each portion as compared with an actual aspect, but they are mere examples and do not restrict the interpretation of the invention. In the present specification and drawings, elements like or similar to those in the already described drawings may be denoted by similar reference numbers and their detailed descriptions may be arbitrarily omitted.
<Display Device>
In the embodiment, a display device employing polymer dispersed liquid crystal will be explained as an example of the display device DSP. The display device DSP comprises a display panel PNL and wiring substrates F1 to F3. In addition, the display device DSP also comprises a light source unit (not shown).
The display panel PNL includes a first substrate SUB1 and a second substrate SUB2. The first substrate SUB1 and the second substrate SUB2 are each formed into a flat plate shape parallel to the X-Y plane. The first substrate SUB1 and the second substrate SUB2 overlap in a planer view. The display panel PNL includes a display area DA which displays images and a frame-shaped non-display area NDA surrounding the display area DA. The display area DA is located in a region where the first substrate SUB1 and the second substrate SUB2 overlap. The display panel PNL includes n scanning lines G (G1 to Gn) and m signal lines S (S1 to Sm), in the display area DA. Note that each of n and m is a positive integer, and n may be equal to or different from m. The scanning lines G extend along the first direction X and are arranged to be spaced apart from each other along the second direction Y. The signal lines S extend along the second direction Y and are arranged to be spaced apart from each other along the first direction X.
The first substrate SUB1 includes end portions E11 and E12 extending along the first direction X and end portions E13 and E14 extending along the second direction Y. The second substrate SUB2 includes end portions E21 and E22 extending along the first direction X and end portions E23 and E24 extending along the second direction Y. In the example illustrated, the end portions E11 and E21, the end portions E13 and E23, and the end portions E14 and E24 overlap in planar view, but may not overlap. The end portion E22 is located between the end portion E12 and the display area DA in planar view. The first substrate SUB1 includes an extension portion Ex between the end portions E12 and E22.
The wiring substrates F1 to F3 are each bonded to the extension portion Ex and arranged in this order along the first direction X. The wiring substrate F1 comprises a gate driver GD1. The wiring substrate F2 comprises a source driver SD. The wiring substrate F3 comprises a gate driver GD2. Note that the wiring substrates F1 to F3 may be replaced with a single wiring substrate.
The signal lines S are drawn to the non-display area NDA and bonded to the source driver SD. The scanning lines G are drawn to the non-display area NDA and bonded to the gate drivers GD1 and GD2. In the example illustrated, odd-numbered scanning lines G are drawn between the end portion E14 and the display area DA and bonded to the gate driver GD2. Meanwhile, even-numbered scanning lines G are drawn between the end portion E13 and the display area DA and bonded to the gate driver GD1. Note that the connection between the gate drivers GD1 and GD2 and the scanning lines G in relation to each other is not limited to that of the example illustrated.
In the example illustrated, the light-emitting elements LS are located between the extension portion Ex and the wiring substrate F4. Further, the light-emitting element LS is located between the wiring substrate F1 to F3 and the second substrate SUB2. The light-emitting elements LS emit light from the light-emitting portions EM to the end portion E22. The light entering from the end portion E22 propagates in the display panel PNL in an opposite direction to the arrow indicating the second direction Y, as will be described later. Note that the light-emitting elements LS may be opposed to the end portions of both the first substrate SUB1 and the second substrate SUB2, that is, for example, the end portions E11 and E21.
The liquid crystal layer 30 is located between the alignment films 14 and 22. The liquid crystal layer 30 is formed of a liquid crystal material composition, which will be described in detail later and comprises polymer dispersed liquid crystal containing polymers 31 and liquid crystal compound 32. The polymers are those originated from a monomer compound containing acryloyl groups respectively at both terminals, as will be described in detail later. The polymers can be obtained by, for example, polymerizing monomer compounds in a state of being aligned in a predetermined direction by the alignment restriction force of the alignment films 14 and 22. For example, the alignment treatment direction of the alignment films 14 and 22 agrees with the first direction X, and the alignment films 14 and 22 have the alignment restriction force along the first direction X. Therefore, the polymers 31 are formed into a strip shape extending along the first direction X. The liquid crystal compounds 32 are dispersed in gaps of the polymers 31, and the liquid crystal compounds of the liquid crystal compounds 32 are aligned such that their longitudinal axes extend along the first direction X.
The polymers 31 and the liquid crystal compounds 32 each have optical anisotropy or refractive anisotropy. The liquid crystal compounds 32 may be of a positive liquid crystal compound having a positive dielectric anisotropy or a negative liquid crystal compound having a negative dielectric anisotropy. The polymers 31 and the liquid crystal compounds 32 have different response performances to an electric field. The response performance of the polymers 31 to the electric field is lower than the response performance of the liquid crystal compounds 32 to the electric field. In the enlarged portion in the drawing, the polymers 31 are represented by upward-sloping hatch lines, and the liquid crystal compounds 32 are represented by downward-sloping hatch lines.
An external natural light beam L12 entering the display panel PNL is transmitted through the liquid crystal layer 30 without being scattered. That is, the external natural light entering the display panel PNL from the lower surface 10B is transmitted through the upper surface 20T, and the external natural light entering the display panel PNL from the upper surface 20T is transmitted through the lower surface 10B. Therefore, when the user observes the display panel PNL from an upper surface 20T side, the background on a lower surface 10B side can be visually recognized through the display panel PNL. Similarly, when the user observes the display panel PNL from the lower surface 10B side, the background on the upper surface 20T side through the display panel PNL can be visually recognized.
In the region overlapping the pixel electrode 13A, an external natural light beam L22 entering the display panel PNL is transmitted without being substantially scattered by the liquid crystal layer 30, as in the case of the external natural light beam L12 shown in
<Liquid Crystal Material Composition>
The liquid crystal layer 30 is formed of a liquid crystal material composition. The liquid crystal material composition contains a liquid crystal mixture containing at least one kind of a first liquid crystalline compound, at least one kind of a second liquid crystalline compound and at least one kind of a third liquid crystalline compound, a polymerization initiator, and a monomer compound including acryloyl groups at respective terminals.
[First Liquid Crystalline Compound]
The first liquid crystalline compound contains a first aromatic ring containing a halogen group, a second aromatic ring including a halogens group and bonded to the first aromatic ring through a first bond and a third aromatic ring including an aliphatic group and bonded to the second aromatic ring through a second bond. The first liquid crystalline compound can be represented in following formula (1).
In the in chemical formula (1), X and X independently represent fluorine atoms, chlorine atoms, bromine atoms or iodine atoms respectively, Ar1, Ar2 and Ar3 independently represent benzene rings or naphthalene rings, respectively, R represents an aliphatic group having one to ten carbon atoms, Z1 and Z2 independently represent a single bond, —CH2CH2—, —CH2O—, —OCH2—, —CH2CH2O—, —OCH2CH2—, —CH2CH2CH2O—, —OCH2CH2CH2—, —CH═CH—, —C═C—, —CF2O—, —OCF2—, —COO— or —OCO—, and c and d independently represent 1, 2 or 3, respectively.
In the formula (1), X1 and X2 are each equivalent to a halogen group. It is preferable that the halogen group be, for example, a fluorine atom or chlorine atom.
R is equivalent to an aliphatic group. The aliphatic group is, for example, an alkyl group having one to ten carbon atoms, an alkenyl group having two to ten carbon atoms or an alkynyl groups having two to ten carbon atoms.
Ar1 is equivalent to the first aromatic ring. To the first aromatic ring, one to three X1 corresponding to the halogen group are bonded. When two or more halogen groups are bonded the first aromatic ring, the halogen groups may be the same as or different from each other.
Ar2 is equivalent to the second aromatic ring. To the second aromatic ring, one to three X2 corresponding to the halogen group are bonded. When two or more halogen groups are bonded to the second aromatic ring, the halogen groups may be the same as or different from each other.
Ar3 is equivalent to the third aromatic ring. To the third aromatic ring, one R corresponding to the aliphatic group is bonded. To the third aromatic ring, two or more Rs may be bonded or some other organic group than the aliphatic group may be bonded.
Z1 corresponds to the first bond, and Z2 corresponds to the second bond.
In a structure of the first liquid crystalline compound as above, the first aromatic ring including a halogen group can be represented by one of the following formulas (2-1) to (2-8).
Further, in a structure of the first liquid crystalline compound, the second aromatic ring including a halogen group can be represented by one of the following formulas (3-1) to (3-11).
Further, in a structure of the first liquid crystalline compound, the third aromatic ring including an aliphatic group can be represented in the following formula (4-1) or (4-2).
In the above-provided formulas (4-1) and (4-2), Ra is an alkyl group having one to ten carbon atoms.
[Second Liquid Crystalline Compound]
The second liquid crystalline compound contains a first aromatic ring including a halogen group, a second aromatic ring including a halogens group and bonded to the first aromatic ring through the first bond, and a first alicyclic group including an aliphatic group and bonded to the second aromatic ring through the third bond. The second liquid crystalline compound having such a structure as above can be represented by the following formula (5).
In the formula (5), X1 and X2 are each as defined in the above-provided formula (1), Ar1 and Ar2 are each as defined in the above-provided formula (1), C1 is 1,4-cyclohexyl group, Z1 is as defined in the above-provided formula (1), Z3 represents a single bond, —CH2CH2—, —CH2O—, —OCH2—, —CH2CH2O—, —OCH2CH2—, —CH2CH2CH2O—, —OCH2CH2CH2—, —CH═CH—, —C═C—, —CF2O—, —OCF2—, —COO—, —OCO— or 1,4-cyclohexyl group, and c and d are each as defined in the above-provided formula (1), and R is as defined in the above-provided formula (1).
In the above formula (5), C1 corresponds to the first alicyclic group and Z3 corresponds to the third bond.
In a structure of the second liquid crystalline compound as above, the first aromatic ring including a halogen group can be represented by one of the above formulas (2-1) to (2-8).
Further, in a structure of the second liquid crystalline compound, the second aromatic ring including a halogen group can be represented by one of the above formulas (3-1) to (3-11). Note that, in a structure of the second liquid crystalline compound as above, Z3 corresponding to the third bond is bonded to the second aromatic ring including a halogen group in place of Z2 corresponding to the second bond.
Further, in a structure of the second liquid crystalline compound, the first alicyclic group having an aliphatic group can be represented in following formula (6).
In the above formula (6), Ra is as defined by the above formulas (4-1) and (4-2).
[Third Liquid Crystalline Compound]
The third liquid crystalline compound contains a fourth aromatic ring, a fifth aromatic ring bonded to the fourth aromatic ring through the fourth bond, a second alicyclic group including an aliphatic group and bonded to the fourth aromatic ring through the fifth bond and a third alicyclic group including an aliphatic group and bonded to the fifth aromatic ring through the sixth bond. The third liquid crystalline compound having such a structure can be represented by the following formula (7).
R—C2—Z5—Ar4—Z4—Ar5—Z6—C3—R (7)
In the formula (7), Ar4 and Ar5 independently represent benzene rings or naphthalene rings, respectively, R is as defined in the formula (1), Z4, Z5 and Z6 independently represent a single bond, —CH2CH2—, —CH2O—, —OCH2—, —CH2CH2O—, —OCH2CH2—, —CH2CH2CH2O—, —OCH2CH2CH2—, —CH═CH—, —C═C—, —CF2O—, —OCF2—, —COO— or —OCO—, and C2 and C3 are each independently a 1,4-cyclohexyl group.
In the above formula (7), Ar4 is equivalent to the fourth aromatic ring, and Ar5 is equivalent to the fifth aromatic ring. To each of the fourth aromatic ring and the fifth aromatic ring, a halogen atom may be independently bonded.
Z4 is equivalent to the fourth bond, Z5 is equivalent to the fifth bond, and Z6 is equivalent to the sixth bond.
C2 is equivalent to the second alicyclic group, and C3 is equivalent to the third alicyclic group.
In the structure of the third liquid crystalline compound as above, the fourth aromatic ring can be represented by the following formula (8-1) or (8-2).
Further, in the structure of the third liquid crystalline compound, the fifth aromatic ring can be represented by one of the following formulas (9-1) to (9-6).
Further, in the structure of the third liquid crystalline compound, the second alicyclic group including an aliphatic group can be represented by the following formulas (10).
In the above formula (10), Ra is as defined by the above formulas (4-1) and (4-2).
Further, in the structure of the third liquid crystalline compound, the third alicyclic group including an aliphatic group can be represented by the following formula (11).
In the above formula (11), Ra is as defined by the above formulas (4-1) and (4-2).
The liquid crystal mixture contains at least one kind of each of the first liquid crystalline compound, the second liquid crystalline compound and the third liquid crystalline compound can contain, for example, within a range of 5 to 50 parts by weight when a total weight of the first liquid crystal compound, the second liquid crystalline compound and the third liquid crystalline compound is set to 100 parts by weight. The liquid crystal mixture contains, for example, one to ten kinds of the first liquid crystalline compounds, one to five kinds of the second liquid crystalline compounds, and one to five kinds of the third liquid crystalline compounds.
[Monomer Compound]
The liquid crystal material composition contains a monomer compound including acryloyl groups at respective terminals. Such a monomer compound can be represented in the following formula (12).
In the formula (12), Z7 and Z9 independently represent alkylene groups having one to ten carbon atoms, respectively, and Z8 represents a single bond, —CH2CH2—, —CH2O—, —OCH2—, —CH2CH2O—, —OCH2CH2—, —CH2CH2CH2O—, —OCH2CH2CH2—, —CH2CH2OCO—, —COOCH2CH2—, —CH2CH2COO—, —OCOH2CH2—, —CH═CH—, —C═C—, —CF2O—, —OCF2—, —COO— or —OCO—, Ar6 represents a benzene ring, j is 1, 2 or 3, and k is 1 or 2.
In the above formulas (12), Ar6 may be substituted by a phenyl group an alkoxy group, or an alkyl group having one to five carbon atoms.
In the above formula (12), when j is 2 or 3, plurality of Ar6 and Z8 may be the same as or different from each other. Further, when k is 2, a plurality of Z9 may be the same as or different from each other.
Such a monomer compound can be represented specifically by the following formulas (13-1) to (13-14).
In the above formulas (13-1) to (13-14), g and h independently represent integers of 1 to 10, respectively.
The polymer originated from the monomer compound including acryloyl groups at respective terminals has, for example, a repetitious structural unit represented by the following formula (14).
In the formula (14), Z7, Z8, Z9, Ar6 and j are each as defined by the above formula (12).
[Polymerization Initiator]
The polymerization initiator is a compound which produces active species such as radicals, cations or anions in a chain polymerization such as radical polymerization, cationic polymerization or anionic polymerization, and initiates the chain polymerization of monomer compounds. The polymerization initiator polymerizes, for example, the monomer compounds in chain polymerization and forms the polymers 31 originated from the monomer compounds.
The polymerization initiator is, for example, a heat polymerization initiator, which produces active species by heating. The heat polymerization initiator is, for example, a heat radical polymerization initiator or a heat cation polymerization initiator.
The heat radical polymerization initiator contains, for example, an azo-based compound or a peroxide-based compound.
The azo-based compound is, for example, 2,2′-azobis(isobutyronitrile), 2,2′-azobis(2-methylbutyronitrile), 2,2′-azobis(2,4-dimethylvaleronitrile), 4,4′-azobis (4-cyanovaleric acid), 2,2′-azobis(2-methylpropionate)dimethyl, 2,2′-azobis(2-methylpropionamidine)dihydrochloride or 2,2′-azobis[2-(2-imidazoline-2-yl)propane]dihydrochloride.
The peroxide-based compound is, for example, tert-butyl hydroperoxide, cumene hydroperoxide, di-tert-butylperoxide, dicumyl peroxide or benzoyl peroxide.
The heat-cationic polymerization initiator is, for example, dicyandiamide, cyclohexyl p-toluenesulfonate, diphenyl(methyl)sulfonium tetrafluoroborate, benzyl(4-hydroxyphenyl) methylsulfonium hexafluoroantimonate, or (4-hydroxyphenyl)methyl(2-methyl benzyl) sulfonium hexafluoroantimonate.
Such a heat polymerization initiator produces active species, for example, when heated to 80° C. or higher, and then polymerizes the monomer compounds contained in the liquid crystal material composition to form the polymers 31. Note that in some embodiments, it is preferable to heat the heat polymerization initiator to 90° C. or higher, or more preferably 100° C. or higher.
Further, the polymerization initiator may be, for example, a photopolymerization initiator, which produces active species by irradiation of ultraviolet radiation, electron beam or the like. The photopolymerization initiator is, for example, a photo-radical polymerization initiator, a photo-cation polymerization initiator or a photo-anion polymerization initiator.
The photo-radical polymerization initiator contains, for example, a benzophenone-based compound, an acetophenone-based compound, a benzoin-based compound, a thioxanthone-based compound or a phosphine oxide-based compound.
The benzophenone-based compound is, for example, benzophenone, 4-benzoylbenzoic acid, 2-benzoylbenzoic acid, methyl 2-benzoylbenzoate, 4,4′-bis (dimethylamino)benzophenone, 4,4′-bis (diethylamino)benzophenone, 4,4′-dichlorobenzophenone, 1,4′-dibenzoyl benzene, 4-methyl benzophenone, hydroxy benzophenone, 2,4,6-trimethyl benzophenone, 4-phenyl benzophenone, 4-methoxy-3,3′-dimethyl benzophenone, 4-benzoyl 4′-methyl diphenyl sulfide or 4,4′-carbonylbis(diperoxyphthalic acid di-tert-butyl).
The acetophenone-based compound is, for example, acetophenone, 2-hydroxy-2-methyl propiophenone, 2-hydroxy-4′-(2-hydroxyethoxy)-2-methyl propiophenone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-4′-(methylthio)-2-morpholino propiophenone, 2-benzyl-2-dimethylamino)-4′-morpholino butyrophenone, 2-isonitroso propiophenone, or 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropane-1-one.
The benzoin-based compound is, for example, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2-phenyl-2-(p-toluene sulfonyloxy)acetophenone, 2,2-diethoxy acetophenone or 2,2-dimethoxy-2-phenyl acetophenone.
The thioxanthone-based compound is, for example, 2-chlorothioxanthone, 2,4-dichlorothioxanthone, 2-isopropyl thioxanthone or 2,4-diethyl thioxanthene-9-one.
The phosphine oxide-based compound is, for example, diphenyl(2,4,6-trimethyl benzoyl)phosphine oxide, phenyl bis(2,4,6-trimethyl benzoyl)phosphine oxide, or lithium phenyl(2,4,6-trimethyl benzoyl)phosphinate.
The photo-radical polymerization initiator may be, besides the compounds listed above, (±)-camphorquinone, benzil, benzoyl methyl formate, p-anisil, 2-ethyl anthraquinone, 2,2′-bis(2-chlorophenyl)-4,4′,5,5′-tetraphenyl-1,2′-biimidazole, or 1-(9-ethyl-9H-carbazol-3-yl)ethanone O-acetyl oxime.
The photo-cation polymerization initiator contains, for example, an iodonium salt-based compound, a sulfonium salt-based compound, or an triazine-based compound.
The iodonium salt-based compound is, for example, diphenyliodonium trifluoromethanesulfonate, diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroarsenate, bis (4-tert-butylphenyl)iodonium triflate, bis(4-tert-butylphenyl)iodonium hexafluorophosphate or 4-isopropyl-4′-methyldiphenyliodonium tetrakis (pentafluorophenyl)borate.
The sulfonium salt-based compound is, for example, cyclopropyldiphenylsulfonium tetrafluoroborate, triphenyl sulfonium bromide, triphenyl sulfonium tetrafluoroborate, tri-p-tolyl sulfonium trifluoromethanesulfonate, or tri-p-tolyl sulfonium hexafluorophosphate.
The triazine-based compound is, for example, 2-(4-methoxyphenyl)-4,6-bis(trichloromethyl)-1,3,5-triazine, 2-(1,3-benzodioxole-5-yl)-4,6-bis(trichloromethyl)-1,3,5-triazine, 2-(4-methoxystyryl)-4,6-bis(trichloromethyl)-1,3,5-triazine, 2-(3,4-dimethoxy styryl)-4,6-bis(trichloromethyl)-1,3,5-triazine, 2-[2-(furan-2-yl)vinyl]-4,6-bis(trichloromethyl)-1,3,5-triazine or 2-[2-(5-methylfuran-2-yl)vinyl]-4,6-bis(trichloromethyl)-1,3,5-triazine.
The photo-cation polymerization initiator may be 4-nitrobenzenediazonium tetrafluoroborate in addition to the compounds provided above.
The photo-anion polymerization initiator is, for example, 2-(9-oxoxanthene-2-yl)propionate 1,5,7-triazabicyclo[4.4.0]dec-5-ene, 2-(9-oxoxanthene-2-yl)propionate 1,5-diazabicyclo[4.3.0]non-5-ene, 2-(9-oxoxanthene-2-yl)propionate 1,8-diazabicyclo[5.4.0]undec-7-ene, acetophenone O-benzoyl oxime, cyclohexylcarbamate 2-nitrobenzyl, cyclohexylcarbamate 1, 2-bis(4-methoxyphenyl)-2-oxoethyl, or nifedipine.
Such a photo-polymerization initiator produces active species, for example, by irradiation of ultraviolet rays, and thus polymerizes the monomer compounds contained in the liquid crystal material composition. The photo-polymerization initiator has a sensitivity wavelength region to the ultraviolet radiation in a range of approximately, for example, 350 to 380 nm.
Usable examples of the light source which generates ultraviolet rays for irradiation are a metal halide lamp, a high-pressure mercury lamp and a super-high-pressure mercury lamp.
It is preferable that the wavelength of ultraviolet radiation may be in an absorption wavelength range of the photo-polymerization initiators listed above, and the ultraviolet rays of an absorption wavelength range which is not the absorption wavelength range of the liquid crystal mixture contained in the liquid crystal material composition. More specifically, it is preferable to use a metal halide lamp, a high-pressure mercury lamp or a super-high-pressure mercury lamp, by cutting ultraviolet rays of 330 nm or less, or more preferably, 350 nm or less. It is also preferable to use a UV-LED lamp which can irradiate a single wavelength.
The exposure amount of the ultraviolet radiation should preferably be 10 to 10000 mJ/cm2, and more preferably, 50 to 5000 mJ/cm2.
The illuminance of the ultraviolet radiation should preferably be 1 to 200 mW/cm2, and more preferably 2 to 100 mW/cm2.
The time period for irradiating the ultraviolet rays should be selected appropriately according to the intensity of the ultraviolet radiation, but it should preferably be 10 to 600 seconds. More preferably, the UV-exposure should be carried out to achieve 1200 mJ/cm2 to 2400 mJ/cm2.
Further, the amount of the polymerization initiators is, for example, 0.1 to 30% by weight to the monomer compound, should preferably be 1 to 20% by weight, and more preferably 5 to 15% by weight.
According to the present embodiment, with use of such a liquid crystal material composition, a display device with an improved display quality can be provided.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions, and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-056410 | Mar 2020 | JP | national |
