Patent Application
20180079959
The present invention relates to a liquid crystal element using a liquid crystal with negative dielectric anisotropy which is useful as an electrooptical liquid crystal display material.
From a viewpoint of excellent display quality, an active matrix-type liquid crystal display device is used in the markets of portable terminals, liquid crystal televisions, projectors, computers, and the like. In an active matrix display system, a thin film transistor (TFT) or a metal insulator metal (MIM) is used for each pixel, and it is important that a high voltage holding ratio is maintained in this system. In addition, in order to obtain wider visual angle properties, a TFT display in combination with VA, IPS, or OCB mode is proposed, and in order to realize brighter display, a reflective type of an ECB mode is proposed. In order to deal with such display elements, new liquid crystal compounds or liquid crystal compositions are currently proposed.
A vertical alignment (VA) display, in which a liquid crystal medium having negative dielectric anisotropy which has particularly been demanded increasingly in recent years is used, shows a higher response speed than other types of displays, but a halftone response speed is slightly slow, and thus, it is necessary that further improvement is performed. In the liquid crystal medium, the improvement can be performed by decreasing a rotational viscosity (γ1). In addition, in the VA display, it is necessary to control a tilt direction of liquid crystal molecules at the time of applying a voltage. As a control method, a method of performing rubbing with respect to an alignment film, adding protrusions into a cell, slightly shifting the positions of upper and lower transparent electrodes, or providing a slit in a transparent electrode is disclosed (PTL 2). A technology of adding a small amount of a polymerizable liquid crystal compound into a liquid crystal medium and causing polymerization in a cell, to set an arbitrary pre-tilt angle is disclosed as a new technology (PTL 3).
However, it is not yet possible to sufficiently optimize the electrooptical properties of the VA display, even when a liquid crystal medium which has been available until now is used. There are continuous demands for a display that has a wide operating temperature range, a high-speed responsiveness at a low temperature, a halftone response speed, a high contrast, a wide viewing angle, a low threshold voltage, and a high resistance value, and includes a small amount of residual monomers and shows a high voltage holding ratio, even after polymerization of a polymerizable liquid crystal compound is performed.
A liquid crystal medium showing a high VHR value and a low rotational viscosity is disclosed in (PTL 1), but in a case where a liquid crystal medium including a compound of Formula (1), the content of which is greater than 10%, is used, a percentage of residual monomers is significantly increased, this causes a decrease in a VHR value and an increase in an ID value, and thus, the display quality is not sufficient. In addition, the rotational viscosity is not sufficient, either.
A method of using gas chromatography (GC) is disclosed in Page 12 of (PTL 4) as a simple measurement method of the amount of a polymerizable compound remaining in a liquid crystal phase after polymerization, but it is difficult to quantitatively measure the amount of the polymerizable compounds after the polymerization reaction which may have various molecular weights by the GC, and thus, reliability of a measurement result is low.
[PTL 1] JP-A-2004-131704
[PTL 2] JP-A-11-242225
[PTL 3] JP-A-2002-357830
[PTL 4] JP-A-2006-078968
An object of the present invention is to provide a liquid crystal element which sufficiently optimizes mainly the electrooptical properties of a VA display, has a wide operating temperature range, a high-speed responsiveness at a low temperature, a halftone response speed, a high contrast, a wide viewing angle, a low threshold voltage, and a high resistance value, and includes a small amount of residual monomers and shows a high voltage holding ratio, even after polymerization of a polymerizable liquid crystal compound is performed.
As a result of intensive studies to solve the aforementioned problems, the inventors found the optimal configuration of a liquid crystal element and completed the present invention.
A liquid crystal element of the present invention uses a liquid crystal composition including a liquid crystal compound which has three or four ring structures and a negative dielectric anisotropy (Δ∈) whose absolute value is 1 or more, a liquid crystal compound which has two, three, or four ring structures and a dielectric anisotropy (Δ∈) whose absolute value is 1 or less, and a polymerizable compound, wherein the total content of these compounds is 95% or more, and one or more of compounds represented by General Formula (1) is used as the liquid crystal compound having a dielectric anisotropy (Δ∈) whose absolute value 1 or more, thereby obtaining a high voltage holding ratio, a low ion density, and a high resistance value. In addition, it is possible to decrease the amount of residual monomers, and thus, excellent long team stability is obtained and display quality is improved.
According to the present invention, there is provided a liquid crystal element, in which a liquid crystal composition is disposed between a pair of substrates on which a transparent electrode and an alignment film are formed, the liquid crystal composition includes a liquid crystal compound which has three or four ring structures and a negative dielectric anisotropy (Δ∈) whose absolute value is 1 or more; a liquid crystal compound which has two, three, or four ring structures and a dielectric anisotropy (Δ∈) whose absolute value is 1 or less; and a polymer of a polymerizable compound, the total content of the liquid crystal compound which has three or four ring structures and a negative dielectric anisotropy (Δ∈) whose absolute value is 1 or more, the liquid crystal compound which has two, three, or four ring structures and a dielectric anisotropy (Δ∈) whose absolute value is 1 or less, and the polymerizable compound before polymerization in the liquid crystal composition used in the liquid crystal element is 95% or more of the total content of the liquid crystal composition and the polymerizable compound before polymerization, and the liquid crystal compound which has three or four ring structures and a negative dielectric anisotropy (Δ∈) whose absolute value is 1 or more includes one or more of compounds represented by General Formula (1):
wherein R1 and R2 each independently represent an alkyl group having 1 to 15 carbon atoms, at least one CH2 group in the alkyl group may be substituted with —O—, —CH═CH—, —CO—, —OCO—, —COO—, —C≡C—, CF2O—, and —OCF2—, provided that O atoms are not directly adjacent to each other, at least one H atom in the alkyl group may be arbitrarily substituted with a halogen atom, a ring A1 represents any one of:
at least one CH2 group in the ring A1 may be substituted with an O atom, at least one CH group in the ring A1 may be substituted with a N atom, and at least one H atom in the ring A1 may be substituted with Cl, CF3, or OCF3.
In the liquid crystal element, an active element using a transparent electrode may be provided on one or both of the pair of substrates configuring the liquid crystal element, and a driving display of a VA mode may be performed.
In the liquid crystal element, a polymerizable compound is cured in a state where a liquid crystal composition including the polymerizable compound is interposed between a pair of substrates, and the liquid crystal composition and a polymer of the polymerizable compound are formed between the pair of substrates.
The compound of General Formula (1) is selected from the following formulae.
The compound of General Formula (1) is preferably selected from the following formulae, and
is more preferably a compound in which —R2 is —O—R21 and the number of carbon atoms of R1 is 1 to 8 (R21 is the same as R2). More suitable examples thereof are as follows.
In addition, one or more of compounds represented by General Formulae (2) to (4):
(in the formulae, R1, R2, and the ring A1 are each independently the same as the components described in claim 1, the rings A2 are each independently the same as the rings A1, Z1 to Z4 each independently represent a single bond, —CH═CH—, —C≡C—, —CH2CH2—, —(CH2)4—, —COO—, —OCH2—, —CH2O—, —OCF2—, or —CF2O—, at least one of Z1 and Z2 is not a single bond, Z5 represents a CH2 group or an O atom, m1 and m2 each independently represent 0 to 3, and the sum of m1+m2 are each independently 1, 2, or 3) can be included in the liquid crystal composition in the liquid crystal element.
Preferable examples of General Formula (2) include compounds represented by the following formulae.
More preferable examples thereof include compounds represented by:
(in the formulae, Alkyl's each independently represent an alkyl group having 1 to 8 carbon atoms, Alkoxy's each independently represent an alkoxy group having 1 to 8 carbon atoms, Alkenyl's each independently represent an alkenyl group having 2 to 9 carbon atoms, and Alkenyloxy's each independently represent an alkenyloxy group having 2 to 9 carbon atoms).
Preferable examples of General Formula (3) include compounds represented by the following formulae.
More preferable examples thereof include compounds represented by:
(in the formulae, Alkyl's each independently represent an alkyl group having 1 to 8 carbon atoms, Alkoxy's each independently represent an alkoxy group having 1 to 8 carbon atoms, Alkenyl's each independently represent an alkenyl group having 2 to 9 carbon atoms, and Alkenyloxy's each independently represent an alkenyloxy group having 2 to 9 carbon atoms).
Preferable examples of General Formula (4) include compounds represented by the following formulae.
More preferable examples thereof include compounds represented by:
(in the formulae, Alkyl's each independently represent an alkyl group having 1 to 8 carbon atoms, and Alkenyl's each independently represent an alkenyl group having 2 to 9 carbon atoms).
In addition, one or more of compounds represented by General Formula (5):
(in the formula, R1, R2, Z3, Z4, and m1 are each independently the same as the components described in claims described above, rings B1 to B3 each independently represent any one of:
at least one CH2 group in each of the rings B1 to B3 may be substituted with an O atom, and one at least one CH group in each of the rings B1 to B3 may be substituted with a N atom) can be included in the liquid crystal composition in the liquid crystal element.
Preferable examples of General Formula (5) include compounds represented by the following formulae.
More preferable examples thereof include compounds represented by the following formulae.
In the formulae, Alkyl's each independently represent an alkyl group having 1 to 8 carbon atoms, Alkenyl's each independently represent an alkenyl group having 2 to 9 carbon atoms, and Alkenyloxy's each independently represent an alkenyloxy group having 2 to 9 carbon atoms.
The polymerizable compound in the liquid crystal element can include at least one of a disc-like liquid crystal compound having a structure containing a benzene derivative, a triphenylene derivative, a truxene derivative, a phthalocyanine derivative, or a cyclohexane derivative as a core of the center of a molecule, and a linear alkyl group, a linear alkoxy group, or a substituted benzoyloxy group as substituents being present radially on side chains thereof.
Specifically, the polymerizable compound can be a polymerizable compound represented by General Formula (6).
In the formula, P1 represents a polymerizable functional group, Sp1 represents a spacer group having 0 to 20 carbon atoms, Q1 represents a single bond, —O—, —NH—, —NHCOO—, —OCONH—, —CH═CH—, —CO—, —COO—, —OCO—, —OCOO—, —OOCO—, —CH═CH—, —CH═CH—COO—, —OCO—CH═CH—, or —C≡C—, n1 and n2 represent 1, 2, or 3, MG represents a mesogen group or a mesogen support group, and R3 represents a halogen atom, a cyano group, or an alkyl group having 1 to 25 carbon atoms, at least one CH2 group in the alkyl group may be substituted with —O—, —S—, —NH—, —N(CH3)—, —CO—, —COO—, —OCO—, —OCOO—, —SCO—, —COS—, or —C≡C—, provided that 0 atoms are not directly adjacent to each other, or R3 represents P2—Sp2-Q2, and P2, Sp2, and Q2 are each independently the same as P1, Sp1, and Q1.
The polymerizable compounds represented by General Formula (6) may be polymerizable compounds represented by (6)-1 or (6)-2.
MG of General Formula (6) is one represented by the following formula:
(in the formula, C1 to C3 each independently represent a 1,4-phenylene group, a 1,4-cyclohexylene group, a 1,4-cyclohexenyl group, a tetrahydropyran-2,5-diyl group, a 1,3-dioxane-2,5-diyl group, a tetrahydrothiopyran-2,5-diyl group, a 1,4-bicyclo(2,2,2) octylene group, a decahydronaphthalene-2,6-diyl group, a pyridine-2,5-diyl group, a pyrimidine-2,5-diyl group, a pyrazine-2,5-diyl group, a 1,2,3,4-tetrahydronaphthalene-2,6-diyl group, a 2,6-naphthylene group, a phenanthrene-2,7-diyl group, a 9,10-dihydrophenanthrene-2,7-diyl group, a 1,2,3,4,4a,9,10a-octahydrophenanthrene 2,7-diyl group, or a fluorene 2,7-diyl group, the 1,4-phenylene group, the 1,2,3,4-tetrahydronaphthalene-2,6-diyl group, the 2,6-naphthylene group, the phenanthrene-2,7-diyl group, the 9,10-dihydrophenanthrene-2,7-diyl group, the 1,2,3,4,4a,9,10a-octahydrophenanthrene 2,7-diyl group, and the fluorene 2,7-diyl group may include one or more of F, Cl, CF3, OCF3, a cyano group, an alkyl group having 1 to 8 carbon atoms, an alkoxy group, an alkanoyl group, an alkanoyloxy group, an alkenyl group having 2 to 8 carbon atoms, an alkenyloxy group, an alkenoyl group, or an alkenoyloxy group as a substituent, Y1 and Y2 each independently represent a —COO—, —OCO—, —CH2CH2—, —OCH2—, —CH2O—, —CH═CH—, —C≡C—, —CH═CHCOO—, —OCOCH═CH—, —CH2CH2COO—, —CH2CH2OCO—, —COOCH2CH2—, —OCOCH2CH2—, —CONH—, —NHCO—, or a single bond, and n5 represents 0, 1, or 2), or a disc-like liquid crystal compound represented by General Formula (6)-13:
(in the formula, R7's each independently represent P1-Sp1-Q1 or a substituent of Formula (6-e), R81 and R82 each independently represent a hydrogen atom, a halogen atom, or a methyl group, R83 represents an alkoxy group having 1 to 20 carbon atoms, and at least one hydrogen atom in the alkoxy group includes a substituent represented by Formulae (6-a) to (6-d) described in claim 18).
In addition, Sp1 and Sp2 of General Formula (6) each independently represent an alkylene group, the alkylene group may be substituted with one or more of halogen atoms or CN, and one or more of CH2 groups present in this group may be substituted with —O—, —S—, —NH—, —N(CH3)—, —CO—, —COO—, —OCO—, —OCOO—, —SCO—, —COS—, or —C≡C—, provided that O atoms are not directly adjacent to each other.
In addition, P1 and P2 of General Formula (6) may each independently represent any one of:
(in the formulae, R41 to R43, R51 to R53, and R61 to R63 each independently represent a hydrogen atom, a halogen atom, or an alkyl group having 1 to 5 carbon atoms).
Preferable examples of General Formula (6) include:
(in the formulae, W1's each independently represent F, CF3, OCF3, CH3, OCH3, an alkyl group having 2 to 5 carbon atoms, an alkoxy group, an alkenyl group, COOW2, OCOW2, or OCOOW2, here, W2 represents a linear or branched alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 5 carbon atoms, and n6 represents 0, 1, 2, 3, or 4), or a polymerizable compound in which at least one of Sp1, Sp2, Q1, and Q2 of General Formula (6) is a single bond or n3+n4 is 3 to 6.
More preferable examples thereof include a polymerizable compound in which P1 and P2 of General Formula (6) is Formula (6-b) described in claim 17, a polymerizable compound in which W1 of General Formulae (6)-5 to (6)-8 or (6)-10 to (6)-12 is F, CF3, OCF3, CH3, or OCH3, and n6 is equal to or greater than 1, or a polymerizable compound selected from the group consisting of the compounds represented by General Formulae (6)-5 to (6)-12.
The liquid crystal composition in the liquid crystal element may include or substantially may not include an initiator, and the liquid crystal composition preferably does not substantially include an initiator.
In addition, the liquid crystal composition in the liquid crystal element preferably includes 0.1% to 10.0% by weight of the polymerizable compound and more preferably includes 0.1% to 2.0% by weight of the polymerizable compound.
In this specification, the inventors used a new analysis method which is developed for performing an accurate measurement of the amount of the residual monomer. A base on a side of a cell which is an analysis target is peeled off, and a liquid crystal attached to the inner surface of the base is collected by blowing inert gas, and is set as a sample. A solvent is added to the sample, the resultant material is filtered through a filter, the amount of residual monomer is measured by a high performance liquid chromatography (HPLC) device, and a percentage of the residual monomer is calculated. Accordingly, the detection of the percentage of the residual monomer which is equal to or smaller than approximately 0.3% was not possible in the related art, but it is currently possible to perform a detection of the percentage of the residual monomer in such a range with excellent accuracy.
A compound represented by General Formula (7) can be further included as other compounds.
One or more of compounds represented by:
(in the formula, R1, R2, and the ring A1 are each independently the same as the components described in claim 1) can be included. An upper limit value of the preferable content of these compounds in the liquid crystal composition is 5%, 4%, 3%, 2%, or 1%, and it is preferable that these compounds are not substantially included. Not substantially including a component means intentionally not including a component.
Hereinafter, the present invention will be further described with reference to examples, but the present invention is not limited thereto. In addition, “%” means “% by mass”.
TN-I: A nematic phase-isotropic liquid phase transition temperature (° C.) is set as a liquid crystal phase upper limit temperature.
T-N: A solid phase or a smectic phase-nematic phase transition temperature (° C.) is set as a liquid crystal phase lower limit temperature.
Δ∈: dielectric anisotropy at 25° C.
Δn: refractive index anisotropy at 25° C.
η: viscosity at 20° C.
V0: threshold value voltage at 20° C.
γ1: rotational viscosity coefficient at 20° C.
These values of physical properties are values regarding a liquid crystal mixture before adding a monomer.
VHR (after polymerization process): voltage holding ratio (%) at 25° C. after a polymerization process
VHR (after polymerization process, heated at 150° C. for 1 hour): voltage holding ratio (%) at 25° C. after a polymerization process, remaining in an oven at 150° C. for 1 hour, and natural cooling
VHR (after polymerization process, suntest, 30 min): voltage holding ratio (%) at 25° C. after a polymerization process, and remaining in a suntest for 30 minutes
ID (after polymerization process): ion density at 25° C. after a polymerization process
ID (after polymerization process, heated at 150° C. for 1 hour): ion density at 25° C. after a polymerization process, remaining in an oven at 150° C. for 1 hour, and natural cooling
ID (after polymerization process, suntest, 30 min): ion density at 25° C. after a polymerization process, and remaining in a suntest for 30 minutes
(In the measurement conditions of the voltage holding ratio, an applied voltage was 5 V, a frame time was 16.5 msec, and a pulse width was 62 μsec. In the measurement conditions of the ion density, an applied voltage was 20 V, a triangular wave was 0.05 Hz, R Sense was 5×106Ω, and a gain was 100. For the suntest, SUNTEST CPS+, manufactured by Toyo Seiki Seisaku-sho, Ltd., was used. For measuring all of the values, a VA mode cell (cell thickness of 3.5 μm, alignment film RN-1517), which the liquid crystal composition was injected thereinto followed by being irradiated with ultraviolet light for 600 seconds (3.0 J/cm2) to perform the polymerization process, was used.
The following abbreviations are used for describing the compounds.
n—CnH2n+1—
-2— —CH2CH2—
-1O— —CH2O—
—O1— —OCH2—
-On— —OCnH2n+1
ndm—CnH2n+1—CH═CH—(CH2)m-1—
As a base material 20-113, a mixture of the following compounds was used.
The values of the physical properties of the liquid crystal compositions and elements of Example 1 which is the liquid crystal element of the present invention and Comparative Example 1 are shown in Table 2. 2% of the polymerizable compound (Ph-3H) was added with respect to 98% of the liquid crystal composition. 2% of the polymerization initiator (Irg651) was added with respect to the polymerizable compound.
In Example 1, the values of the physical properties required for a liquid crystal television were satisfied and values of VHR (after polymerization process) and ID (after polymerization process) were excellent. On the other hand, regarding the liquid crystal composition of Comparative Example 1, γ1 was large and therefore, the response time appears to be long. The percentage of the residual monomer after polymerization process was large, and the values of VHR (after polymerization process) and ID (after polymerization process) were not good, as compared with those in Example 1. From the above results, it is found that, in Example 1 which is the liquid crystal element of the present invention, the properties required for a liquid crystal television are satisfied, the percentage of the residual monomer is sufficiently decreased, reliability is excellent, and thus, the liquid crystal element is significantly useful as a long-life active matrix-type liquid crystal display element.
In addition, the values of the physical properties of the liquid crystal compositions and elements of Example 2 and Comparative Example 2 are shown in Table 3. 2% of the polymerizable compound (Ph-3H) was added with respect to 98% of the liquid crystal composition. 2% of the polymerization initiator (Irg651) was added with respect to the polymerizable compound.
In Example 2, the values of the physical properties required for a liquid crystal television were satisfied and values of VHR (after polymerization process) and ID (after polymerization process) were excellent. On the other hand, regarding the liquid crystal composition of Comparative Example 1, γ1 was large and therefore, the response time appears to be long. The percentage of the residual monomer after polymerization process was large, and the values of VHR (after polymerization process) and ID (after polymerization process) were not good, as compared with those in Example 2. From the above results, it is found that, in Example 2 which is the liquid crystal element of the present invention, the properties required for a liquid crystal television are satisfied, the percentage of the residual monomer is sufficiently decreased, reliability is excellent, and thus, the liquid crystal element is significantly useful as a long-life active matrix-type liquid crystal display element.
Further, in order to confirm a relationship between the liquid crystal composition and the percentage of the residual monomer, the VHR, and the ID, results obtained by performing experiments of changing the additive amounts of the liquid crystal base 20-113 and the liquid crystal compounds are shown in Table 3, Table 4,
As shown in Table 2, when the additive amount of 5-Cy-Ph5-O2 or 3-Ph-Ph5-O2 which is the liquid crystal compound corresponding to Formula (1) is equal to or smaller than 5%, the percentage of the residual monomer shows a sufficiently small value, but when the additive amount thereof is equal to or greater than 10%, the percentage of the residual monomer is increased. In addition, the VHR (after polymerization process) which is related to the display properties or reliability is decreased, and the ID (after polymerization process) is increased. However, as shown in Table 3, even when the additive amount of 3-Cy-Cy-Ph-O2 or 3-Cy-Ph-Ph5-O2 which is the liquid crystal compound corresponding to Formula (2) is increased, the percentage of the residual monomer is sufficiently small, the VHR (after polymerization process) which is related to the display properties or reliability or the ID (after polymerization process) is also excellent.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-048324 | Mar 2015 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2016/056215 | 3/1/2016 | WO | 00 |
