JP2008033242A - Retardation member and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a retardation member in which an arbitrary retardation value can be set easily and clearly, and which substantially avoids occurrence of retardation unevenness and surface irregularity of the appearance. <P>SOLUTION: The retardation member is obtained by incorporating an anisotropic refractive index material into a transparent polymeric base material. A mixed state of the anisotropic refractive index material and the transparent polymeric base material is made proper by regulating the magnetic relaxation time (T<SB>2</SB>) of the<SP>1</SP>H nucleus of the transparent polymeric base material to a solvent used in a coating solution prepared by dissolving the anisotropic refractive index material, accordingly the retardation member comprises a layered area in which the anisotropic refractive index material and the transparent polymeric base material are substantially uniformly mixed and a layered area of the transparent polymeric base material. A method for manufacturing the retardation member is also provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a retardation member used in a liquid crystal display device and a method for manufacturing the same.

  Although liquid crystal display devices are widely used for various displays, the display quality of images observed mainly from the direction inclined from the normal line of the liquid crystal cell, mainly the contrast, is generally lower than images observed from the front. There is a problem of doing.

Various techniques have been developed to improve the problem of dependence on the viewing angle. As one of the techniques, a retardation layer having a cholesteric regular molecular structure (a retardation layer exhibiting birefringence) is used. There has been known a liquid crystal display device in which optical compensation is performed by disposing such a retardation layer between a liquid crystal cell and a polarizing plate (Patent Documents 1 and 2).
Also known is a liquid crystal display device in which optical compensation is performed by disposing a retardation layer made of a discotic compound (retardation layer exhibiting birefringence) between a liquid crystal cell and a polarizing plate ( Patent Document 3).

  If the phase difference layer as described above is used, the phase difference generated in the VA liquid crystal cell acting as a positive C plate and the phase difference caused in the phase difference layer acting as a negative C plate are offset. By doing so, it is possible to improve the problem of viewing angle dependency of the liquid crystal display device. However, the retardation layer has a problem in adhesion between the retardation layer and a substrate (for example, a TAC (cellulose triacetate) film which is a protective film of a polarizing layer).

  In order to solve this problem, it has been proposed to improve the adhesion by heat-treating the liquid crystal and the alignment film (Patent Document 4). However, in this method, when the base material is a base material having low heat and humidity resistance (for example, TAC), the base material may expand and contract due to the influence of moisture, and the liquid crystal layer may peel off due to the influence.

  As a method that does not cause the above-mentioned adhesion problem, a method of forming a cellulose acetate film after mixing a retardation increasing agent in a cellulose acetate solution may be applied when producing a cellulose acetate film. Known (Patent Documents 5 and 6). However, this method requires the addition of a retardation increasing agent during the film formation of the cellulose acetate film, which inevitably increases the quantity of one lot, and an arbitrary retardation can be obtained for a small quantity. There wasn't. In addition, since the retardation increasing agent is usually hydrophobic, there is a problem that the adhesiveness is lowered when the retardation layer is laminated with a polarizing plate made of a hydrophilic resin such as polyvinyl alcohol.

  In order to solve the above-mentioned problems, the present inventors have previously described a retardation film in which a refractive index anisotropic material is contained in a polymer film, wherein the refractive index anisotropic material is A retardation film characterized by having a concentration gradient in the thickness direction of the polymer film was provided (Patent Document 7).

  This retardation film can change the retardation value as the retardation film by changing the amount and concentration of the coating solution. Therefore, a retardation film having an arbitrary retardation value can be easily obtained even in a small lot. It has the advantage that it can be obtained. In addition, since a retardation layer, which is a separate layer, is not laminated and formed on the substrate, there is no problem such as peeling of the retardation layer from the substrate film. Reliability, alkali resistance (saponification resistance) and reworkability (repetitive work suitability is increased).

However, since the refractive index anisotropic material in the polymer film has a concentration gradient in the thickness direction, setting the retardation value as a retardation film requires trial and error, and clear to the target value. It was difficult to set. Moreover, the refractive index anisotropy material is reduced at a lower concentration between the layer region where the concentration of the refractive index anisotropic material in the polymer film is high and has a gentle concentration gradient and the layer region only of the polymer substrate. An intermediate layer region was present, which caused retardation retardation of the retardation film and unevenness of the appearance of the retardation film.
JP-A-3-67219 JP-A-4-322223 Japanese Patent Laid-Open No. 10-312166 JP 2003-207644 A JP 2000-1111914 A JP 2001-249223 A International Publication WO2006-016641 Pamphlet

  As described above, in the retardation film in which the refractive index anisotropic material is contained in the polymer film described in the pamphlet of International Publication WO2006-016641, the refractive index anisotropic material in the polymer film has a thickness. Since it is unavoidable to have a concentration gradient in the direction, it is difficult to change the retardation value as a phase difference film, and to set the target value clearly, and to the retardation film, the retardation unevenness and appearance There was a problem of unevenness.

  The present invention has been made in consideration of such problems, and in addition to causing no problems such as peeling of the retardation layer from the substrate that occurs when the retardation layer is formed, any retardation value can be obtained. It is possible to provide a retardation member that can be easily set to be clear, and that does not substantially cause retardation unevenness and uneven appearance.

  The inventors of the present invention have intensively studied to solve the above-mentioned problems, and are used to dissolve the refractive index anisotropic material and apply it to the surface of the transparent polymer substrate when producing the retardation member. When a transparent polymer base material that exhibits certain properties is selected with respect to the solvent to be used, the refractive index anisotropic material is almost uniformly mixed in the transparent polymer base material, and there is substantially no concentration gradient. The layer region in which the transparent polymer base material and the refractive index anisotropic material are uniformly present and the layer region only of the transparent polymer base material can be clearly distinguished and have such a structure. The present invention has been completed by finding that the above-mentioned problems can be solved by the retardation member.

That is, the present invention is a phase difference member in which a refractive index anisotropic material is contained in a transparent polymer base material, and a layer region in which the refractive index anisotropic material and the transparent polymer base material are mixed almost uniformly. And a layer region of a transparent polymer substrate, and a method for producing the same, and a method for producing the retardation member, which is transparent to a solvent used in a coating solution in which a refractive index anisotropic material is dissolved. By adjusting the magnetic relaxation time (T ₂ ) of the ¹ H nucleus of the molecular substrate, the mixed state of the refractive index anisotropic material and the transparent polymer substrate is optimized, which is an important characteristic of the retardation member. The present invention has succeeded in significantly improving retardation unevenness and uneven appearance, and provides a retardation member having excellent characteristics.

The characteristics of the transparent polymer substrate used in the present invention will be described more specifically. The value of the magnetic relaxation time (T ₂ ) of ¹ H nuclei with respect to the solvent used in the coating solution at 40 ° C. is less than 28 μSec. When a transparent polymer substrate having a value at 80 ° C. of 40 μSec or more is selected, the refractive index anisotropic material is mixed almost uniformly in the transparent polymer substrate, as described above, and the concentration gradient is substantially increased. In the cross-sectional observation by TEM, there is a structure in which the layer region where the transparent polymer base material and the refractive index anisotropic material exist uniformly can be clearly distinguished from the layer region only of the transparent polymer base material. It turns out that it is obtained.

On the other hand, even when a transparent polymer substrate made of the same type of polymer is used, the magnetic relaxation time (T ₂ ) of ¹ H nuclei with respect to the solvent used in the coating solution is not within the above range. In the transparent polymer base material, since the refractive index anisotropic material has a concentration gradient in the thickness direction, in the cross-sectional observation by TEM, the intermediate layer region containing the refractive index anisotropic material at a lower concentration Therefore, the layer region where the transparent polymer substrate and the refractive index anisotropic material exist uniformly cannot be clearly distinguished from the layer region including only the transparent polymer substrate.

  The reason why such a phenomenon occurs is not yet clear, but when a transparent polymer substrate having the above characteristics is used, the coating solution in which the refractive index anisotropic material is dissolved penetrates the transparent polymer substrate. Instead, it is presumed that it is eluted from the transparent polymer base material side into the coating liquid in which the refractive index anisotropic material is dissolved.

  In order to obtain the retardation member of the present invention having the above-described structure, the transparent polymer base material is coated with a coating liquid in which the refractive index anisotropic material is dissolved in a solvent. Near the surface, the refractive index anisotropic material and the transparent polymer base material are mixed, and this causes the refractive index anisotropic material to be mixed almost uniformly in the transparent polymer base material and has a substantially concentration gradient. In addition, it is possible to obtain a retardation member having a structure in which a layer region where the transparent polymer substrate and the refractive index anisotropic material are uniformly present and a layer region including only the transparent polymer substrate can be clearly distinguished. And the retardation value as a phase difference film can be easily set clearly by setting the quantity and density | concentration of the said coating liquid suitably.

  In the present invention, a material having a liquid crystallinity (liquid crystal material) is preferably used as the refractive index anisotropic material. Since the liquid crystal material has a liquid crystal structure when filled in the transparent polymer substrate, it can effectively exert an effect on the transparent polymer substrate. The liquid crystal material preferably has a rod-like molecular structure, and can further strengthen the regularity of the refractive index of the transparent polymer substrate. The liquid crystal material preferably contains a polymerizable functional group. After the liquid crystal material is filled in a transparent polymer substrate, the liquid crystal material is polymerized by this polymerizable functional group to form a polymer. After the phase difference member is formed, the liquid crystal material can be prevented from oozing out, and a stable phase difference member can be obtained.

In the present invention, a layer region in which the refractive index anisotropic material and the transparent polymer base material are mixed almost uniformly is on the surface side of the transparent polymer base material, and then there is substantially no refractive index anisotropic material. There is a layer region of only a transparent polymer substrate.
That is, when the cross section of the retardation member of the present invention is observed with a TEM, the layer region in which the transparent polymer base material and the refractive index anisotropic material are uniformly mixed (the transparent polymer base material of the refractive index anisotropic material) A clear boundary can be confirmed between the layer region in which there is substantially no concentration gradient in the thickness direction) and the layer region in which only the transparent polymer substrate exists, and no intermediate region (transition region) is observed. .

The retardation member of the present invention preferably has a thickness direction retardation of 70 to 300 nm. The retardation Rth in the thickness direction of the retardation member is represented by the following formula.
Rth [nm] = {(nx + ny) / 2−nz} × d
nx: refractive index in the slow axis direction in the in-plane direction of the base material ny: refractive index in the fast axis direction in the in-plane direction of the base material nz: refractive index in the thickness direction of the base material d: thickness of the base material

  That Rth according to the above definition takes a positive value means that nx ≧ ny> nz, that is, the refractive index nz in the thickness direction of the substrate is smaller than the refractive index in the substrate surface. This is of a kind called a so-called negative C plate. If the electric dipole moment vector (polarization vector) of the refractive index anisotropic material is oriented in the surface of the substrate, a negative C plate with Rth> 0 can be obtained. On the other hand, when the electric dipole moment is oriented perpendicularly (thickness direction) to the substrate surface, a so-called positive C plate in which Rth <0 (nz> nx ≧ ny) is obtained. In the present invention, both positive and negative C plates can be manufactured by selecting the materials used and the manufacturing conditions.

  In the transparent polymer substrate of the retardation member of the present invention, a layer region in which refractive index anisotropic materials are mixed in a state where there is substantially no concentration gradient in the thickness direction and a layer region of only the transparent polymer substrate The structure with a clear boundary is formed without depending on the amount and concentration of the coating liquid if the transparent polymer substrate having the appropriate characteristics described above is selected, and the amount and concentration of the coating liquid. Because the layer region where the refractive index anisotropic material is mixed is formed with the thickness and concentration corresponding to, it is easy not only to change the retardation value as a phase difference member, but also clear to the required value It becomes possible to set to. Therefore, since the range of the retardation value substantially obtained is expanded and clear, the viewing angle improvement effect can be greatly improved.

  The retardation member of the present invention preferably has a haze value of 1% or less when measured according to JIS-K7105, and the film surface direction of the thickness direction retardation (Rth) measured at a wavelength of 550 nm of the retardation member. Is preferably in the range of ± 5 nm with reference to the average value of Rth.

  In addition, the shape of the retardation member of the present invention is not particularly limited, and may be a film, a sheet, a plate, or the like depending on the shape of the transparent polymer substrate used. In the case of a film, the film thickness is preferably about 10 to 200 μm, particularly about 20 to 100 μm.

  Two or more retardation members of the present invention can be bonded to each other, and a film having other functions can also be bonded to an optical functional layer (for example, an antireflection layer) other than the retardation member. Alternatively, it can also be directly bonded to the polarizing layer to serve as a protective film. Since the retardation member of the present invention and the display device using the optical functional film or the polarization film using the retardation member can be set to have an appropriate retardation, the display device has high reliability and excellent display quality. be able to.

  Furthermore, the present invention was applied to at least one surface of the transparent polymer base material by a coating process in which a refractive index anisotropic material is dissolved or dispersed in a solvent, and the coating process. It has a mixing step of mixing the refractive index anisotropic material in the coating liquid with the transparent polymer base material, and a drying step of drying the solvent of the coating liquid applied by the coating step. A method for producing a phase difference member is provided.

  In the present invention, the mixing step may be performed during the drying step. This is because by adjusting the drying temperature or the like, it may be possible to advance the mixture of the refractive index anisotropic material and the transparent polymer substrate even during drying. Further, the degree of mixing of refractive index anisotropic materials and the refractive index anisotropy (retardation value) may be controlled by controlling the drying conditions.

  Furthermore, in this invention, it is preferable to have the fixing process which fixes the refractive index anisotropic material mixed in the transparent polymer base material after the said drying process. For example, in the case where the liquid crystal material used as the refractive index anisotropic material has a polymerizable functional group, the liquid crystal material is mixed in the transparent polymer base material and then polymerized to polymerize. This is because it is possible to prevent the liquid crystal material from seeping out from the surface after production, and the stability of the retardation member can be improved.

  The retardation member of the present invention is a retardation member in which a refractive index anisotropic material is contained in a transparent polymer base material, and the refractive index anisotropic material and the transparent polymer base material are mixed almost uniformly. Therefore, it has a structure that can be clearly distinguished from a layer in which the transparent polymer base material and the refractive index anisotropic material are uniformly present and a layer of the transparent polymer base material only, without a concentration gradient. In addition to not causing problems such as peeling of the retardation layer from the base material that occurs when the retardation layer is formed, any retardation value can be easily set to clear, and there is also uneven retardation and uneven appearance. It is a retardation member that does not substantially occur. Furthermore, the refractive index anisotropic material is mixed almost uniformly with the transparent polymer base material, and the concentration of the transparent polymer base material and the refractive index anisotropic material is constant and in equilibrium. There is no change in phase guarantee characteristics even with respect to changes in temperature and temperature, and a stable product can be obtained.

The retardation member of the present invention and the manufacturing method thereof will be described in more detail below.
A. Hereinafter, the phase difference member of the present invention will be described in detail for each configuration.
1. Transparent polymer substrate The transparent polymer substrate used in the present invention has a magnetic relaxation time (T ₂ ) of ¹ H nucleus with respect to the solvent used in the coating solution at 40 ° C. of less than 28 μSec, and The value at 80 ° C. needs to be 40 μSec or more. When such a transparent polymer base material is used, the refractive index anisotropic material is almost uniformly mixed in the transparent polymer base material and does not substantially have a concentration gradient. A layer having a structure in which the layer region where the molecular substrate and the refractive index anisotropic material are uniformly present and the layer region including only the transparent polymer substrate can be clearly distinguished is obtained.

In the present invention, the transparent polymer substrate can be used as long as the properties with respect to the solvent used in the coating liquid exhibit the above-described properties, while the transparent polymer substrate composed of the same kind of polymer is used. Even if it is used, if the magnetic relaxation time (T ₂ ) of ¹ H nuclei with respect to the solvent used in the coating solution is not within the above range, the refractive index is anisotropic in the transparent polymer substrate. The concentration material causes a concentration gradient in the thickness direction, and the retardation member of the present invention cannot be obtained.

  The transparent polymer substrate used in the present invention preferably has regularity in refractive index in addition to the above-described characteristics. The regularity of the refractive index in the present invention refers to, for example, (1) the transparent polymer substrate acts as a negative C plate, (2) the stretched transparent polymer substrate is a negative C plate, and a positive C plate. , A plate, or having a characteristic of a biaxial plate. In particular, it is preferable to use a transparent polymer substrate having a thickness direction retardation (Rth) of 20 to 100 nm and an in-plane retardation (Re) of 0 to 300 nm.

  The transparent polymer substrate used in the present invention may be a rigid material having no flexibility, but it is preferable to use a flexible material having flexibility. The materials that make up the flexible material include cellulose resin, norbornene polymer, cycloolefin polymer, polymethyl methacrylate, polyvinyl alcohol, polyimide, polyarylate, polyethylene terephthalate, polysulfone, polyethersulfone, amorphous polyolefin, and modified acrylic polymer. , Polystyrene, epoxy resin, polycarbonate, polyester, and the like can be exemplified, but in the present invention, a cellulose-based resin and a norbornene-based polymer can be suitably used.

  Examples of the norbornene-based polymer include cycloolefin polymer (COP) and cycloolefin copolymer (COC). In the present invention, it is preferable to use a cycloolefin polymer. Specific examples of the cycloolefin polymer used in the present invention include, for example, trade name: ARTON manufactured by JSR Corporation.

  As said cellulose resin, it is preferable to use a cellulose ester, and also among cellulose esters, it is preferable to use a cellulose acylate. As the cellulose acylates, lower fatty acid esters having 2 to 4 carbon atoms are preferable.

  In the present invention, cellulose acetate can be particularly preferably used among the above lower fatty acid esters. As cellulose acetate, it is most preferable to use triacetyl cellulose (TAC) having an average acetylation degree of 57.5 to 62.5% (substitution degree: 2.6 to 3.0). Here, the degree of acetylation means the amount of bound acetic acid per unit mass of cellulose. The degree of acetylation can be determined by measurement and calculation of the degree of acetylation in ASTM: D-817-91 (test method for cellulose acetate and the like). Specific examples of the triacetyl cellulose used in the present invention include, for example, a triacetyl cellulose film (trade name: KC4UYW) manufactured by Konica Minolta.

  The transparent polymer substrate used in the present invention may be uniaxially or biaxially stretched. By performing the stretching treatment, the liquid crystal may be easily mixed in the transparent polymer substrate. In addition to a single layer, a plurality of layers having the same or different compositions may be stacked.

  The shape of the transparent polymer substrate is not particularly limited and may be selected as appropriate, such as a film, a sheet, and a plate shape. In the case of a film, the film thickness is preferably in the range of usually 10 to 200 μm, particularly 20 to 100 μm.

  Further, in order to reduce the variation in retardation in the thickness direction, the variation in the thickness direction retardation (Rth) measured at a wavelength of 550 nm of the transparent polymer substrate used is ± 5 nm on the basis of the average value of Rth. It is preferable to be within the range.

2. Next, the refractive index anisotropic material used in the present invention will be described. The refractive index anisotropic material used in the present invention is not particularly limited as long as it can be filled in a transparent polymer base material and has birefringence.

  In the present invention, a liquid crystal material having a relatively small molecular weight is preferably used because of easy filling into the transparent polymer substrate. Specifically, a liquid crystal material having a molecular weight in the range of 200 to 1200, particularly in the range of 400 to 800 is preferably used. In addition, molecular weight here has the polymeric functional group mentioned later, and shows the molecular weight before superposition | polymerization about the liquid crystal material superposed | polymerized within a transparent polymer base material.

  In the present invention, the liquid crystal material is preferably a nematic liquid crystalline molecular material. If it is a nematic liquid crystalline molecular material, several to several hundreds of nematic liquid crystalline molecules that have entered the gaps in the transparent polymer base material are aligned in the transparent polymer base material, so that the refractive index anisotropy is more sure. It is because it can express to. In particular, the nematic liquid crystalline molecule is preferably a molecule having spacers at both ends of the mesogen. This is because nematic liquid crystal molecules having spacers at both ends of the mesogen are flexible, so that they can be prevented from becoming clouded when entering a gap in the transparent polymer substrate.

  As the liquid crystal material used in the present invention, those having a polymerizable functional group in the molecule are suitably used, and among them, those having a polymerizable functional group capable of three-dimensional crosslinking are preferable. As long as it has a polymerizable functional group, it can be polymerized (cross-linked) after being filled in the transparent polymer base material. This is because it is possible to prevent a problem and to obtain a phase difference member that can be used stably.

  Such a polymerizable functional group is not particularly limited, and various polymerizable functional groups that are polymerized by the action of ionizing radiation such as ultraviolet rays and electron beams, or heat are used. Representative examples of these polymerizable functional groups include radically polymerizable functional groups or cationic polymerizable functional groups. Further, representative examples of radically polymerizable functional groups include functional groups having at least one addition-polymerizable ethylenically unsaturated double bond, and specific examples include vinyl groups having or not having substituents, An acrylate group (generic name including an acryloyl group, a methacryloyl group, an acryloyloxy group, and a methacryloyloxy group) and the like can be given. Specific examples of the cationic polymerizable functional group include an epoxy group. In addition, examples of the polymerizable functional group include an isocyanate group and an unsaturated triple bond. Among these, from the viewpoint of the process, a functional group having an ethylenically unsaturated double bond is preferably used.

  In the present invention, a liquid crystal molecule having a rod-like molecular structure and having the polymerizable functional group at the terminal is particularly preferably used. For example, if nematic liquid crystalline molecules having polymerizable functional groups at both ends are used, they can be polymerized three-dimensionally to form a network (network) structure, making a stronger transparent polymer substrate Because you can. Specifically, a liquid crystalline molecule having an acrylate group at the terminal is preferably used. Specific examples of nematic liquid crystalline molecules having an acrylate group at the terminal are shown in the following chemical formulas (1) to (6).

  Here, the liquid crystalline molecules represented by the chemical formulas (1), (2), (5) and (6) are DJ Broer et al., Makromol Chem. 190, 3201-3215 (1989) or Makromol Chem. 190, 2250 ( 1989), or analogously thereto. The preparation of liquid crystalline molecules represented by the chemical formulas (3) and (4) is disclosed in DE195,04,224.

  Specific examples of the nematic liquid crystalline molecule having an acrylate group at the terminal include those represented by the following chemical formulas (7) to (17) (wherein a and b are integers of 3 to 6).

  In the present invention, two or more kinds of refractive index anisotropic materials, for example, liquid crystal materials may be used. For example, the liquid crystal material is a liquid crystal molecule having a rod-like molecular structure and having one or more polymerizable functional groups at both ends, and a liquid crystal molecule having a rod-like molecular structure and polymerizable at one end In the case of including one having one or more functional groups, the polymerization density (crosslinking density) and the retardation function can be suitably adjusted by adjusting the blending ratio of both.

  Retardation function is further enhanced because rod-like liquid crystalline molecules having one or more polymerizable functional groups at one end are more likely to be mixed in a transparent polymer substrate and oriented in the transparent polymer substrate. This is because it tends to be easy to do. On the other hand, rod-like liquid crystalline molecules having one or more polymerizable functional groups at both ends can increase the polymerization density, so that the molecules can be prevented from seeping out and have durability such as solvent resistance and heat resistance. It is because sex can be imparted.

  In addition, the liquid crystal material used in the present invention is a liquid crystalline molecule having a rod-like molecular structure and having the polymerizable functional group from the viewpoint of further enhancing the retardation function and improving the reliability of the film. It is preferable to use a liquid crystal molecule having a rod-like molecular structure and having no polymerizable functional group. In particular, a liquid crystalline molecule having a rod-like molecular structure having the above-mentioned polymerizable functional group at both ends, and a liquid crystal molecule having a rod-like molecular structure having the above-mentioned polymerizable functional group at one end In addition, it is preferable to use a liquid crystal molecule having a rod-like molecular structure and having no polymerizable functional group at both ends. This is because a rod-like liquid crystalline molecule having no polymerizable functional group is more likely to be mixed in a transparent polymer substrate, and is more easily aligned in the transparent polymer substrate, so that the retardation function is more easily enhanced. . On the other hand, by mixing rod-like liquid crystalline molecules having a polymerizable functional group to enable intermolecular polymerization, it is possible to impart durability such as prevention of molecular exudation, solvent resistance and heat resistance. Because it can.

3. Retardation member In the retardation member of the present invention, the refractive index anisotropic material and the transparent polymer base material are almost uniformly mixed, and only the layer region and the transparent polymer base material which do not have a concentration gradient substantially. The layer region has a feature that can be clearly distinguished. Here, having no concentration gradient means that the concentration does not differ substantially at any two points in the thickness direction, and is not limited to the magnitude of the concentration.

  In the retardation member of the present invention, in the observation of secondary ions derived from a refractive index anisotropic material by time-of-flight secondary ion mass spectrometry (TOF-SIMS) described below, the refractive index anisotropic material is a transparent polymer. There is substantially no concentration gradient in the thickness direction of the refractive index anisotropy material in the region mixed in the base material. Therefore, when the cross section of the retardation member of the present invention is observed with a TEM, the refractive index and the transparent polymer base material are refracted. A layer region in which refractive index anisotropic materials are mixed almost uniformly (a layer region in which the refractive index anisotropic material has substantially no concentration gradient in the thickness direction in the transparent polymer base material), and a transparent polymer group A clear boundary can be confirmed with the layer region where only the material exists, and it is considered that the intermediate region (transition region) is not observed.

  In the following, the layer region in which the transparent polymer substrate of the present invention and the refractive index anisotropic material are mixed almost uniformly (the concentration gradient in the thickness direction of the refractive index anisotropic material in the transparent polymer substrate is A substantially non-existing layer region) may be referred to as a retardation enhancement region, and a layer region including only a transparent polymer substrate may be referred to as a substrate region.

  As a method of composition analysis, the phase difference member is cut by GSP (precision oblique cutting method) so that a cross section in the thickness direction appears, and time-of-flight secondary ion mass spectrometry (TOF-SIMS) of the cross section is performed. Can be used to measure the concentration distribution of the material in the thickness direction.

As time-of-flight secondary ion mass spectrometry (TOF-SIMS), for example, TFS-2000 manufactured by Physical Electronics is used as a time-of-flight secondary ion mass spectrometer. For example, the primary ion species is Ga ⁺ , and the primary ion energy is The measurement can be carried out by measuring positive and / or negative secondary ions in the cross section in the thickness direction of the phase difference member at 25 kV and subsequent acceleration of 5 kV. In this case, the concentration distribution in the thickness direction of the refractive index anisotropic material can be obtained by plotting the secondary ion intensity derived from the liquid crystal against the thickness direction. Similarly, when the secondary ion intensity derived from the base material is plotted with respect to the thickness direction, the relative concentration change between the refractive index anisotropic material and the base material can be seen. The secondary ions derived from the refractive index anisotropic material are, for example, the sum of the secondary ions observed relatively strongly on the surface or at the place where the liquid crystal can be estimated by another analysis method such as cross-sectional TEM observation. Can be used. As the secondary ions derived from the base material, for example, the sum of secondary ions observed relatively strongly at the surface or at a location where it can be estimated that the liquid crystal is not filled by another analysis method such as cross-sectional TEM observation can be used. .

  The shape of the retardation member of the present invention is not particularly limited, and may be a film, a sheet, a plate shape or the like depending on the shape of the transparent polymer substrate used. As the film thickness, it is obtained as a thickness approximately equivalent to the thickness of the transparent polymer substrate used plus the coating thickness of the coating liquid. In the case of a film shape, as the substrate film, Usually, those in the range of 10 to 200 μm, particularly in the range of 20 to 100 μm are preferably used.

  In the present invention, since the retardation enhancement region where the liquid crystal exists is formed in the retardation member as described above, various optical functions based on birefringence can be achieved. For example, as will be described later, when TAC (cellulose triacetate) acting as a negative C plate is used as a transparent polymer substrate and a rod-shaped refractive index anisotropic material having a molecular structure is used as a liquid crystal, negative C The function as a plate will be further strengthened. In addition, the retardation member of the present invention has high peel strength and high reliability such as heat resistance and water resistance (repeated cold heat in the use environment or durability against interfacial peeling upon contact with water). .

As the retardation member of the present invention, a retardation enhancement region is formed on one surface side of a transparent polymer substrate, or a retardation enhancement region is formed on both surface sides of a transparent polymer substrate. There is something.
In FIG. 1, a retardation enhancement region 2 containing liquid crystal is formed on one surface side 3 of a transparent polymer substrate 1, and a retardation enhancement region 2 is formed on the opposite surface side 4. The substrate region 5 is not formed. On the other hand, what is shown in FIG. 2 is one in which a retardation enhancement region 2 is formed on both surface sides of a transparent polymer substrate.

  The thickness of the retardation enhancement region in the present invention is usually in the range of 0.5 to 20 μm, preferably 1 to 15 μm, more preferably 2 to 10 μm. If it is smaller than the above range, a sufficient retardation value cannot be obtained, and it is difficult to increase the thickness beyond the above range. The absence of a concentration gradient in the refractive index anisotropic material-containing layer region can be determined by composition analysis of the retardation enhancement region and the substrate region (for example, the TOF-SIMS method described above).

  In the present invention, the concentration of the refractive index anisotropic material in the retardation enhancement region is preferably in the range of 20 to 80% by mass. If it is less than 20% by mass, it becomes difficult to obtain a sufficient retardation value depending on the required retardation value. On the other hand, when it exceeds 80 mass%, adhesiveness with a transparent polymer base material may be insufficient. In addition, when the refractive index anisotropic material is not subjected to cross-linking polymerization, the refractive index anisotropic material easily oozes to the surface.

  In the retardation member of the present invention, it is preferable that the variation in thickness direction retardation (Rth) measured at a wavelength of 550 nm of the retardation member in the film surface direction is within a range of ± 5 nm on the basis of the average value of Rth. In the retardation member of the present invention, the concentration of the refractive index anisotropic material is substantially uniform in the retardation enhancement region, and the concentration (distribution) of the refractive index anisotropic material in the retardation member is substantially thermodynamically. The equilibrium state has been reached, and it is considered that the state is highly stable. For this reason, it is considered that variations in the in-plane direction (and thickness direction) of the retardation value can be minimized. The retardation member of the present invention has a small variation in retardation. For example, when the retardation member is applied to a display device as an optical compensation film, the display screen is uniformly optically compensated to display a viewing angle or the like. A display device with excellent quality can be obtained.

  The retardation member of the present invention preferably has a thickness direction retardation of 70 to 300 nm. This is because, in such a case, for example, the viewing angle improvement effect can be improved. In addition, the value of the said thickness direction and in-plane direction retardation is 23 degreeC and 55% RH environment, for example using an automatic birefringence measuring apparatus (For example, Oji Scientific Instruments company make, brand name: KOBRA-21ADH). Thus, a three-dimensional refractive index measurement can be performed at a wavelength of 589 nm, and the refractive indexes nx, ny, and nz can be obtained. Moreover, in the phase difference member of this invention, the haze value at the time of measuring based on JIS-K7105 can achieve 1% or less, Furthermore, 0.8% or less can be achieved.

  The retardation member of the present invention is one in which at least the refractive index anisotropic material is contained in a transparent polymer substrate, but contains other components as long as the effects of the present invention are not impaired. May be. For example, a residual solvent, a photopolymerization initiator, a polymerization inhibitor, a leveling agent, a chiral agent, a silane coupling agent and the like may be contained. In addition, the retardation member of the present invention may be one in which another layer is directly laminated. For example, when the retardation value is insufficient as the retardation member, another retardation layer may be directly laminated. It is also possible to directly laminate other optical functional layers such as a polarizing layer, a light reflection preventing layer, and an ultraviolet absorbing layer.

4). Applications The retardation member of the present invention can be used for various applications as an optical functional film. Specifically, an optical compensator (for example, a viewing angle compensator), an elliptically polarizing plate, a brightness improving plate, and the like can be given. In particular, the use as an optical compensator is suitable. Typically, a cellulosic resin, cycloolefin polymer (COP) or cycloolefin copolymer (COC) is used as a transparent polymer substrate, and a liquid crystal compound having a rod-like molecular structure is used as a liquid crystal material. It can be used for applications.
When the retardation member of the present invention is used as an optical compensator which is a negative C plate, it is suitably used for a liquid crystal display device having a liquid crystal layer such as a VA mode or an OCB mode.

B. Method for producing retardation member In the method for producing a retardation member of the present invention, a coating liquid in which a refractive index anisotropic material is dissolved or dispersed in a solvent is applied to at least one surface of a transparent polymer substrate. A coating step, a mixing step of mixing the refractive index anisotropic material in the coating liquid applied by the coating step, for example, a liquid crystal material, with the transparent polymer substrate, and a coating applied by the coating step And a drying step of drying the solvent in the liquid.

The method for producing the retardation member of the present invention will be specifically described with reference to the drawings.
FIG. 3 is a process diagram showing an example of a method for producing a retardation member of the present invention. As shown in FIG. 3 (a), first, an application step of applying a coating liquid 6 in which a refractive index anisotropic material is dissolved or dispersed in a solvent is performed on the transparent polymer substrate 1. Next, as shown in FIG. 3B, in the coating liquid applied by the mixing step of mixing the refractive index anisotropic material in the coating liquid with the transparent polymer substrate, and the coating step. A drying step of drying the solvent is performed. Thereby, from the transparent polymer substrate surface, the refractive index anisotropic material in the coating liquid is mixed, and the retardation enhancement region containing the refractive index anisotropic material on the surface side of the transparent polymer substrate 2 is formed. As a result, a retardation enhancement region 2 containing a refractive index anisotropic material and a substrate region 5 containing no refractive index anisotropic material are formed in the transparent polymer substrate. Finally, as shown in FIG. 3 (c), by fixing the refractive index anisotropic material contained in the transparent polymer base material by irradiating the ultraviolet rays 7 from the retardation enhancement region 2 side, By performing the conversion step, the phase difference member 8 is formed.

  According to such a method for producing a retardation member of the present invention, it is possible to easily form a retardation member by applying the coating liquid, and the coating amount of the coating liquid, etc. It is possible to change the retardation value of the obtained phase difference film only by changing. Each step may be performed twice or more.

Hereafter, the manufacturing method of the phase difference member of this invention is demonstrated for every process.
1. Application Step The application step in the present invention is a step of applying a coating liquid in which a refractive index anisotropic material is dissolved or dispersed in a solvent on at least one surface of a transparent polymer substrate. In this invention, the retardation value of the phase difference member obtained can be changed with the application quantity of the coating liquid in an application | coating process.

  The coating liquid used in the present invention contains at least a solvent and a refractive index anisotropic material dissolved or dispersed in the solvent, and other additives are added as necessary. The Specific examples of such an additive include a photopolymerization initiator when the refractive index anisotropic material used is a photocurable material. In addition, a polymerization inhibitor, a leveling agent, a chiral agent, a silane coupling agent, etc. can be mentioned.

  The refractive index anisotropic material used in the coating liquid is the same as that described in the column “A. Retardation member”, and thus the description thereof is omitted here. Note that a refractive index anisotropic material, for example, a liquid crystal material has a polymerizable functional group, and a fixing step (a step of polymerizing liquid crystal to polymerize) described later is performed in the manufacturing process of the retardation member. Strictly different from the one used for the coating liquid because the refractive index anisotropic material contained in the retardation member is polymerized at a predetermined degree of polymerization. It is.

The solvent used in the coating solution is a solvent that can sufficiently swell the transparent polymer substrate and can dissolve or disperse the liquid crystal, and is used as a transparent polymer. As long as the magnetic relaxation time (T ₂ ) of ¹ H nuclei with respect to the solvent of the substrate is less than 28 μSec at 40 ° C. and the value at 80 ° C. can be set to 40 μSec or more, it is not particularly limited. Absent.

  Examples of the solvent include aromatic hydrocarbon solvents such as benzene, toluene and xylene, aliphatic hydrocarbon solvents such as hexane, ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, tetrahydrofuran, and 1,2. -Ether solvents such as dimethoxyethane, alkyl halide solvents such as chloroform and dichloromethane, ester solvents such as methyl acetate, ethyl acetate, butyl acetate, propylene glycol monomethyl ether acetate, and amides such as N, N-dimethylformamide Examples of the solvent include sulfoxide solvents such as dimethyl sulfoxide, but are not limited thereto.

  Further, the solvent used in the present invention may be one kind of single solvent or two or more kinds of mixed solvents. Specifically, when the transparent polymer substrate is TAC and the liquid crystal is a nematic liquid crystal having an acrylate at the terminal, cyclic ketones, especially cyclohexanone, are preferably used.

Although it does not specifically limit as a density | concentration of the refractive index anisotropic material in the solvent in the coating liquid of this invention, Usually in the range of 5-40 mass%, Especially in the range of 15-30 mass%. Preferably there is. The coating amount on the transparent polymer substrate varies depending on the required retardation value of the obtained retardation member, but the coating amount after drying of the liquid crystal is 0.8 to 8 g / m. within ² range is preferably within a range especially of 1.6~5g / m ^2.

  The coating method in this step is not particularly limited as long as the coating liquid can be uniformly coated on the surface of the transparent polymer substrate. Bar coating, blade coating, spin coating, die coating, slit Methods such as reverse, roll coating, dip coating, ink jet method, and microgravure method can be used. In the present invention, it is particularly preferable to use blade coating, die coating, slit reverse, and roll coating.

2. Mixing step and drying step In the present invention, after the coating step, the mixing step of mixing the refractive index anisotropic material in the coating liquid applied by the coating step and the transparent polymer substrate, and the coating A drying step of drying the solvent in the coating liquid applied in the step is performed.

  The mixing step is a step of leaving the transparent polymer base material after coating so that the transparent polymer base material is sufficiently mixed and taken in the coated refractive index anisotropic material layer. Depending on the type and the like, it may be performed simultaneously with the drying step.

  In the mixing step, 90% by weight or more, preferably 95% by weight or more, particularly preferably 100% by weight of the refractive index anisotropic material in the coating liquid is mixed and taken into the transparent polymer substrate. It is preferable. When the refractive index anisotropic material, for example, a liquid crystal material is not mixed in the transparent polymer substrate but remains on the surface of the transparent polymer substrate, the surface becomes cloudy and the light transmittance of the film is lowered. Because there are cases. The transparent polymer substrate after the mixing and drying step preferably has a haze value of 10% or less when the surface on the mixed side is measured in accordance with JIS-K7105, and in particular, 2% Hereinafter, it is particularly preferably 1% or less.

  Moreover, the said drying process is a process of drying the solvent in a coating liquid, and temperature and time differ greatly by the kind of solvent to be used, and whether it performs simultaneously with a mixing process. For example, when cyclohexanone is used as a solvent and it is carried out simultaneously with the mixing step, it is usually performed at a temperature in the range of room temperature to 120 ° C., preferably 70 to 100 ° C., for 30 seconds to 10 minutes, preferably about 1 to 5 minutes. A drying process is performed.

3. Immobilization step Further, when the refractive index anisotropic material used, for example, the liquid crystal material has a polymerizable functional group, the fixation step is performed in order to polymerize the refractive index anisotropic material into a polymer. . By performing such an immobilization process, it becomes possible to prevent the refractive index anisotropic material once taken into the transparent polymer base material from oozing out and improve the stability of the obtained retardation member. It is something to be made.

  Various methods are used for the fixing step in the present invention depending on the refractive index anisotropic material used. For example, when the liquid crystal is a crosslinkable compound, a photopolymerization initiator is contained and irradiated with ultraviolet rays or an electron beam, and if it is a thermosetting compound, it is heated.

  The retardation member of the present invention can be used in various display devices such as liquid crystal display devices and organic EL display devices.

  FIG. 4 shows an example of a liquid crystal display device using the retardation member of the present invention. The liquid crystal display device 20 of FIG. 4 includes an incident-side polarizing plate 102A, an outgoing-side polarizing plate 102B, and a liquid crystal cell 104. As the liquid crystal cell 104, for example, a VA (Vertical Alignment) method in which nematic liquid crystal having negative dielectric anisotropy is sealed can be employed.

Hereinafter, the present invention will be specifically described with reference to examples.
[Example 1]
15% by mass of a photopolymerizable liquid crystal compound as a refractive index anisotropic material is dissolved in cyclohexanone, and dried by bar coating on TAC film (manufactured by Konica Minolta, trade name: KC4UYW, thickness 42 μm) as a transparent polymer substrate. The coating amount was 4.3 g / m ² (corresponding to 4 μm in terms of film thickness). Subsequently, the solvent was dried and removed by heating at 40 ° C. for 1 minute and at 80 ° C. for 1 minute, and the liquid crystal compound was mixed with the polymer on the substrate surface. Furthermore, the photopolymerizable liquid crystal compound was fixed by irradiating the coated surface with ultraviolet rays to produce a retardation film. The concentration of the refractive index anisotropic material in the retardation enhancement region of the obtained retardation film was 39.8% by mass. The concentration is such that the layer of the retardation enhancement region (thickness 9 μm) is composed only of the refractive index anisotropic material and the transparent polymer substrate material, and the substrate before coating and after completion of the retardation film. The thickness reduction (5 μm) was calculated from the density of the transparent polymer substrate and the refractive index anisotropic material, assuming that it was mixed in the retardation enhancement layer. The obtained retardation film was used as a sample and evaluated according to the following items.
The liquid crystal compound used in this example is a liquid crystal mixture containing the following compounds in which a and b are 4 in the above formula (17).

1. Optical characteristics The phase difference of the sample was measured by an automatic birefringence measuring apparatus (manufactured by Oji Scientific Instruments, trade name: KOBRA-WR). Anisotropy that increases the phase difference of the substrate film was confirmed from the chart of the optical phase difference and the incident angle of the measurement light when the measurement light was made incident on the sample surface vertically or obliquely. Moreover, the three-dimensional refractive index was measured with the same measuring apparatus. The results are shown in Table 1 below.

2. In order to investigate the transparency of the haze sample, the haze value was measured with a turbidimeter (manufactured by Nippon Denshoku Industries Co., Ltd., trade name: NDH2000). As a result, the coating amount was 4.3 g / m ² and it was as good as 0.3% or less.

3. Adhesion test A peel test was conducted to examine the adhesion. As a peel test, a 1 mm square cut is put in a grid pattern in the obtained sample, an adhesive tape (manufactured by Nichiban Co., Ltd., cello tape (registered trademark)) is applied to the liquid crystal surface, and then the tape is peeled off by visual inspection. Observed. As a result, the degree of adhesion was 100%.
Adhesion degree (%) = (part that was not peeled / area where tape was applied) × 100

4). Moisture and heat resistance test The sample was left in an environment of 60 ° C. and 90% Rh for 1000 hours, and the adhesion was measured by the method described above. As a result, there was no change in adhesion before and after the test.

5. Water resistance test The sample was immersed in pure water for 1 day at room temperature (23.5 ° C), and the adhesion was measured by the method described above. As a result, there was no change in adhesion before and after the test.

6). Cross-sectional observation by TEM A phase difference film sample was cut out and embedded in a resin. It was then adhered to a microtome support. Surfaces were obtained with an ultramicrotome equipped with a diamond knife, and after ultrathin sections were prepared, vapor staining with metal oxide (osmium tetroxide) was performed, and TEM observation was performed. The results are shown in FIG. As is clear from FIG. 5, it was found that the material was divided into two layers of a refractive index anisotropic material layer (thickness direction: 9 μm thickness) and a substrate TAC (depth direction: 37 μm thickness).

7). Material distribution measurement in the thickness direction The phase difference film is cut by GSP (precision oblique cutting method) so that a cross section in the thickness direction appears, and a time-of-flight secondary ion mass spectrometer (TOF-SIMS) (apparatus: ULVAC-PHI) Using TRIFT-II), the concentration distribution of the material in the thickness direction on the cut surface was measured. Measurement conditions are: positive and negative secondary ion polarity, 3 to 1850 in mass range (M / Z), no energy filter, contrast diaphragm 0 #, subsequent acceleration 5 kV, sample potential +3.2 kV, pulse frequency 8 0.5 kHz, pulse width 9 ns, with bunching, and with charge neutralization.

  As a measurement result, in the positive secondary ion spectrum, 121 amu, which is strongly confirmed in the refractive index anisotropic material, is a peak derived from the refractive index anisotropic material, and 43 amu, which is strongly confirmed in the TAC base material, is a peak derived from the TAC base material. FIG. 6 shows a profile in which these peak intensities are taken on the vertical axis and the depth direction is taken on the horizontal axis.

In any peak, a peak of almost the same level is observed up to the interface between the refractive index anisotropy material and the base material, which is observed from the outermost surface and observed by TEM. The peak derived from the property material was not observed at all, and the peak intensity derived from the TAC increased.

8). Measurement of Raman spectrum 8-1. Cross-sectional observation by micro-Raman spectroscopy The phase difference film was cut out, and the cross-section was cut out after embedding with resin. The results of Raman spectrum measurement of the sample cross section are shown in FIGS. 7 and 8 (Sekitechnotron Micro Laser Raman Spectrometer (Raman One), no base correction, excitation wavelength, etc. are the same as 8-2).
The base material and the refractive index anisotropic material layer have clearly different peaks, but no difference was observed in the peak at 4 points in the depth direction of the refractive index anisotropic material layer.

8-2. Observation of Liquid Crystal Alignment State by Raman Scattering Spectroscopy The spectrum of the same sample as the above 8-1 by Raman scattering spectroscopy was measured with a laser Raman spectrophotometer (JASCO NRS-3000). The exposure time was 15 seconds, the number of integrations was 8, and the excitation wavelength was 532.11 nm.
(1) First, a cross-section of TAC (manufactured by Konica Minolta), which is a base material, is cut out and incident on the cross-section so that the electric field vibration plane of linearly polarized light is parallel or perpendicular to the film plane, and a Raman spectrum is obtained (FIG. 11-). 1, FIG. 11-2).
(2) Next, the cross section of the one manufactured in Example 1 is taken out, and similarly, the light is incident on the cross section which is a mixed layer of liquid crystal and TAC so that the electric field vibration plane of linearly polarized light is parallel or perpendicular to the film plane. Spectra were obtained (FIGS. 12-1 and 12-2).
(3) Next, from the film surface of what was produced in Example 1, a linearly polarized electric field vibration surface was incident from the coated surface side so as to be parallel or perpendicular to the film width direction, and a Raman spectrum was obtained (FIG. 13-1). FIG. 13-2).

Table 2 shows each peak intensity and calculated peak intensity ratio obtained from the obtained Raman spectrum.

  Normally, in Raman spectroscopy, when monochromatic light (ν0) such as laser light hits a substance, strong light having the same wavelength as the incident light (Rayleigh scattered light ν0) and weak light having a wavelength different from the incident light (Raman scattered light ν0 ± ν) is scattered, and the Raman scattered light appears to deviate from the incident light by a certain wave number based on the vibration and rotation of the molecules constituting the substance, and this wave value is called a Raman shift. This measurement is for confirming the alignment state of the liquid crystal. That is, from the phase difference value of each sample, it is considered that the liquid crystals in this sample are randomly homogeneously oriented and further stretched so that molecules are oriented to some extent in the stretching direction. In this measurement, the linearly polarized light whose electric field vibration plane was changed was incident on the sample, and the alignment state of the liquid crystal was observed mainly by comparing the peak intensity ratio considered to be the benzene ring-derived peak and the CH-derived peak of the liquid crystal. .

(1) Even when linearly polarized light is incident from the coating surface and the electric field vibration surface is changed, the difference in the peak intensity ratio is small (FIGS. 13-1 and 13-2). This result indicates that the liquid crystal molecules are oriented in a random direction.
(Vibration plane parallel: 0.775, vertical: 0.756)
(2) When linearly polarized light is incident from the cross section and the electric field vibration plane is changed to be perpendicular (peak intensity ratio 0.467) and parallel (peak intensity ratio 1.033) to the film plane, It became larger (FIGS. 12-1 and 12-2).
From this result and the result of (1), it is shown that the liquid crystal molecules are randomly oriented in the plane, but the liquid crystal molecules are oriented horizontally with respect to the film surface, that is, the random homogeneous orientation. ing.

  That is, in the retardation member of the present invention, a material in which the refractive index anisotropic material is randomly homogeneously oriented can be obtained in the layer region where the refractive index anisotropic material and the transparent polymer base material are mixed almost uniformly.

The degree of homogeneous orientation and random orientation in the layer region where the transparent polymer base material of the retardation member of the present invention is mixed almost uniformly can be measured by Raman scattering spectroscopy.
In Raman scattering spectroscopy, a layer region where refractive index anisotropic materials such as liquid crystal and transparent polymer base material are mixed almost uniformly. Obtained when the electric field vibration plane of linearly polarized light incident on the cross section is parallel to the surface. The Raman peak intensity ratio between the benzene ring-derived peak and the CH-derived peak of the liquid crystal is 1.1 of the peak intensity ratio when the electric field vibration plane of linearly polarized light incident on the cross section cut perpendicular to the stretching direction is parallel to the surface. When it is more than double, it can be said that the orientation is substantially homogeneous.
On the other hand, in Raman scattering spectroscopy, when linearly polarized light is incident from the surface of a layer region in which a refractive index anisotropic material such as liquid crystal and a transparent polymer substrate are mixed almost uniformly, the electric field vibration plane is The Raman peak intensity ratio between the benzene ring-derived peak and the CH-derived peak of the liquid crystal when parallel is within 1.1 times the peak intensity obtained when the electric field vibration plane of linearly polarized light is aligned in the vertical direction. In some cases, it can be said that the orientation is substantially random.

9. Cross-sectional observation by FT-IR A phase difference film was cut out, and the cross-section was cut out after embedding with a resin. FT-IR imaging measurement of the sample cross section was performed. In FT-IR spectra were output on 1160 cm ^-1 and 1604cm ^-1 derived from the refractive index anisotropic material. As a result, the refractive index anisotropic material-derived peak was observed unevenly distributed in the depth direction of about 9 μm from the surface.

  From the above, it is considered that the refractive index anisotropic material-containing layer is present at 9 μm in the depth direction from the film surface and is present at a substantially uniform concentration in the depth direction.

10. To evaluate the solubility ¹ H nuclear magnetic relaxation time (T ₂₎ measurement substrate film of cyclohexanone, it was measured and evaluated by Pulse NMR method ^(first magnetic relaxation time measurement of H nuclei).

<Pretreatment>
The sample was cut to a width of about 2 mm and a length of 30 mm, put into a Durham tube having an outer diameter of 7 mm and a length of 30 mm, cyclohexanone was added, and the Durham tube was put into a Pulse NMR sample tube to obtain a measurement sample.

<Measurement conditions>
In the measurement, the temperature was started within 1 minute after the sample was inserted into the apparatus, and after reaching the set temperature, the sample was left for about 5 minutes and measured. The measurement was performed under the following conditions, and a standing time of 5 minutes was similarly secured at each temperature.
Measurement temperature: 40 ° C, 60 ° C, 80 ° C, 100 ° C
Pulse sequence: Solid Echo method (T ₂ measurement)
Signal measurement time (X axis): 2 msec (100 points measurement)

<Evaluation method>
Analyzing the obtained results, the value of T ₂ of _{2 to} 3 and the ratio thereof are determined. Among these, those having T ₂ exceeding 1 msec are excluded as liquid phase components, and the remaining 1 to 2 components are used as a percentage. Recalculation and the result.
In addition, when the obtained T ₂ value was plural, the following calculation was performed as an evaluation method for the purpose of comparison between samples, and a combined value was obtained.

<Calculation method>
When the obtained T ₂ is two components of Ta and Tb (unit: μsec) and the percentages are Ta A% and Tb B%, the total value T-Total is as follows.
T-Total = 1 / [{(1 / Ta) × A} + {(1 / Tb) × B}]
Similarly, in the case of three components,
T-Total = 1 / [{(1 / Ta) × A} + {(1 / Tb) × B} + {(1 / Tc) × C}]
It was.

The results are shown in Table 3. The value of T ₂ in the measurement represents the molecular mobility of the ¹ H nuclei near the sample, the smaller the value of T ₂ is small, a rigid molecular mobility is low, the value of T ₂ is large in the reverse This shows that the molecular mobility is high and flexible.

  Compared to Comparative Example 1 (base material: TF80UL), the value of the base material used in Example 1 (base material: KC4UYW) is low at the initial temperature of 40 ° C. during production and drying, and conversely at 80 ° C. Thus, the base material of Example 1 was higher. As described above, this value corresponds to the flexibility of the substrate with respect to the solvent. In this result, the flexibility of Comparative Example 1 is high at 40 ° C. and that of Example 1 is high at 80 ° C. This is presumed that, at the initial drying temperature, in Comparative Example 1, the base material and the solvent were mixed faster, so that the liquid crystal did not catch up with the solvent as it entered the depth direction, and a concentration gradient was generated.

11. Appearance observation result This retardation film was sandwiched under polarizing plate crossed Nicols and confirmed with transmitted light. In this phase difference film, no difference in refractive index is observed in the plane in the direction perpendicular to the light source (perpendicular to the phase difference film surface), but no unevenness is observed. Although light leaks due to the phase difference and is observed as white, unevenness was not particularly observed.

[Example 2]
As a refractive index anisotropic material, the same photopolymerizable liquid crystal compound as in Example 1 was dissolved in 18% by mass in cyclohexanone, and the coating amount after drying by bar coating on TAC film (trade name: KC4UYW, manufactured by Konica Minolta) The coating was performed so as to be 5.0 g / m ² . Subsequently, the solvent was dried and removed by heating at 40 ° C. for 1 minute and at 80 ° C. for 1 minute, and the liquid crystal compound was mixed with the polymer on the substrate surface. Furthermore, the photopolymerizable liquid crystal compound was fixed by irradiating the coated surface with ultraviolet rays to produce a retardation film.
When the cross section was observed by TEM in the same manner as in Example 1, the thickness of the refractive index anisotropic material-containing layer was 10 μm, and the substrate TAC was 36 μm.

Example 3
As a refractive index anisotropic material, the same photopolymerizable liquid crystal compound as in Example 1 was dissolved in 18% by mass in cyclohexanone, and the coating amount after drying by bar coating on TAC film (trade name: KC4UYW, manufactured by Konica Minolta) The coating was carried out to 3.2 g / m ² . Subsequently, the solvent was dried and removed by heating at 40 ° C. for 1 minute and at 80 ° C. for 1 minute, and the liquid crystal compound was mixed with the polymer on the substrate surface. Furthermore, the photopolymerizable liquid crystal compound was fixed by irradiating the coated surface with ultraviolet rays to produce a retardation film.
When the cross section was observed with TEM in the same manner as in Example 1, the thickness of the refractive index anisotropic material-containing layer was 7 μm, and the substrate TAC was 39 μm.

Example 4
As a refractive index anisotropic material, the same photopolymerizable liquid crystal compound as in Example 1 was dissolved in 18% by mass in cyclohexanone, and the coating amount after drying by bar coating on TAC film (trade name: KC4UYW, manufactured by Konica Minolta) The coating was performed so as to be 2.6 g / m ² . Subsequently, the solvent was dried and removed by heating at 40 ° C. for 1 minute and at 80 ° C. for 1 minute, and the liquid crystal compound was mixed with the polymer on the substrate surface. Furthermore, the photopolymerizable liquid crystal compound was fixed by irradiating the coated surface with ultraviolet rays to produce a retardation film.
When the cross section was observed with TEM in the same manner as in Example 1, the thickness of the refractive index anisotropic material-containing layer was 5 μm, and the substrate TAC was 40 μm.

[Comparative Example 1]
As a refractive index anisotropic material, the same photopolymerizable liquid crystal compound as in Example 1 was dissolved in cyclohexanone in an amount of 20% by mass, and bar coating was applied to the surface of the base film made of TAC film (Fuji Photo Film Co., Ltd., trade name: TF80UL). Thus, the coating amount after drying was 2.5 g / m ² . Subsequently, the solvent was dried and removed by heating at 40 ° C. for 1 minute and 80 ° C. for 1 minute, and the photopolymerizable liquid crystal compound was mixed in the TAC film. Furthermore, the photopolymerizable liquid crystal compound was fixed by irradiating the coated surface with ultraviolet rays to produce a retardation film.
When the cross section was observed by TEM in the same manner as in Example 1, the sample mixed with the refractive index anisotropic material had three layers (a high concentration region in the retardation enhancement region, an intermediate region in the retardation enhancement region, and a substrate). It was found that it was divided into areas)). (Fig. 9)
The material concentration distribution measurement in the thickness direction was performed.

  The phase difference film is cut by GSP (precision oblique cutting method) so that a cross section in the thickness direction appears, and in accordance with the case of Example 1, a time-of-flight secondary ion mass spectrometer (TOF-SIMS) is used. The concentration distribution of the material in the thickness direction on the cut surface was measured.

  As a measurement result, in the positive secondary ion spectrum, 27, 55, 104, 121, and 275 amu, which were strongly measured on the coated surface of the refractive index anisotropic material, were used as peaks derived from the refractive index anisotropic material, and the coating was not performed. The 15, 43, 327 amu measured strongly on the back surface were taken as TAC film-derived peaks, and the value obtained by normalizing the sum of these peak intensities with the total secondary ion intensity was plotted on the vertical axis. FIG. 10 shows a profile in which the construction surface is zero and the thickness direction is on the horizontal axis. However, since 27 and 55 amu were also observed from the TAC film, the positive secondary ions as the peaks derived from the refractive index anisotropic material partially include the contribution of the TAC film.

  In the result of the profile in the thickness direction of the positive secondary ion spectrum, the concentration of the refractive index anisotropic material is relatively high and the concentration gradient is gentle up to about 1.5 μm from the coated surface. It is clear that there is a region where the concentration of refractive index anisotropy material is attenuated and the concentration gradient is steep around 3 μm, and there is a base material region containing almost no refractive index anisotropy material from about 3 μm. Became. This is a cross section obtained by TEM in which the refractive index anisotropic material mixed side is observed to be divided into three layers (a high concentration region in the retardation enhancement region, an intermediate region in the retardation enhancement region, and a substrate region). Consistent with observation results.

Further, for the measurement of magnetic relaxation time (T ₂ ) of ¹ H nuclei in solid-state NMR measured in Example 1, the same measurement was performed on the base material (TF80UL). As a result, the magnetic relaxation time (T ₂ ) of ¹ H nuclei at 80 ° C., which is the same as the drying temperature, was the value shown in Table 2. The difference by the base material was clearly confirmed.

  Further, the appearance was observed in the same manner as in Example 1. As a result, when observed from an oblique direction of 40 °, unevenness considered to be due to retardation unevenness of the retardation film was observed.

It is a typical sectional view showing an example of a phase contrast member. It is a typical sectional view showing other examples of a phase contrast member. It is process drawing which shows an example of the manufacturing method of a phase difference member. It is a general | schematic disassembled perspective view which shows an example of the liquid crystal display device provided with the phase difference member. 3 is a TEM photograph showing a cross section of the retardation member of Example 1. FIG. It is a figure which shows the density | concentration distribution by the positive secondary ion spectrum measurement of TOF-SIMS measurement of the phase difference member of Example 1. FIG. 3 is a graph showing Raman spectra of points 1 to 3 of the retardation member of Example 1. FIG. 6 is a graph showing a Raman spectrum of points 4 to 6 of the retardation member of Example 1. FIG. 4 is a TEM photograph showing a cross section of a retardation film of Comparative Example 1. It is a figure which shows the density | concentration distribution by the positive secondary ion spectrum measurement of the TOF-SIMS measurement of the phase difference film of the comparative example 1. It is a Raman scattering spectroscopic spectrum incident from the TAC cross section of the retardation member of Example 1 (the electric field vibration plane of linearly polarized light is horizontal to the film plane). FIG. 2 is a Raman scattering spectroscopic spectrum (a linearly polarized electric field vibration plane is perpendicular to a film plane) incident from a TAC cross section of the retardation member of Example 1. FIG. It is a Raman scattering spectroscopic spectrum (the electric field vibration surface of linearly polarized light is horizontal to the film surface) incident from the TAC-liquid crystal mixed layer section of the retardation member of Example 1. It is a Raman scattering spectroscopy spectrum (the electric field vibration plane of linearly polarized light is perpendicular to the film plane) incident from the TAC-liquid crystal mixed layer section of the retardation member of Example 1. It is a Raman scattering spectroscopic spectrum (the linearly polarized electric field vibration surface is horizontal to the film surface) incident from the film surface of the retardation member of Example 1. It is a Raman scattering spectroscopy spectrum (the linearly polarized electric field vibration plane is perpendicular to the film plane) incident from the film surface of the retardation member of Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Transparent polymer base material 2 ... Retardation reinforcement | strengthening area | region 3 ... Surface side 4 ... Opposite surface side 5 ... Base material area | region 6 ... Coating liquid 7 ... Ultraviolet ray 8 ... Phase difference member 10 ... Phase difference member 20 ... Liquid crystal Display device

Claims (24)

  A phase difference member comprising a transparent polymer base material containing a refractive index anisotropic material, wherein the layer region in which the refractive index anisotropic material and the transparent polymer base material are almost uniformly mixed, and the transparent polymer base material A phase difference member comprising: a layer region.   The phase difference member according to claim 1, wherein the refractive index anisotropic material is mixed almost uniformly within a depth of 15 μm near the surface of the transparent polymer substrate.   By applying a solution in which the refractive index anisotropic material is dissolved in a solvent to the transparent polymer base material, the transparent polymer base material and the refractive index anisotropic material are substantially uniform in the vicinity of the transparent polymer base material surface. The phase difference member according to claim 1, wherein the phase difference member is mixed. The value of the magnetic relaxation time (T ₂ ) of ¹ H nuclei with respect to the solvent of the transparent polymer substrate at 40 ° C. is less than 28 μSec, and the value at 80 ° C. is 40 μSec or more. The phase difference member according to any one of the above.   The retardation member according to any one of claims 1 to 4, wherein the transparent polymer substrate is a cellulose resin, a cycloolefin polymer (COP), or a cycloolefin copolymer (COC).   The retardation member according to any one of claims 1 to 5, wherein the transparent polymer substrate is a cellulose ester.   The retardation member according to claim 5, wherein the transparent polymer substrate is a cycloolefin polymer (COP) or a cycloolefin copolymer (COC) using norbornene as a raw material monomer.   The retardation member according to claim 6, wherein the transparent polymer substrate is cellulose acetate.   The retardation member according to claim 8, wherein the transparent polymer substrate is triacetylcellulose.   The retardation member according to any one of claims 1 to 9, wherein the refractive index anisotropic material is a liquid crystal material.   The retardation member according to claim 10, wherein the refractive index anisotropic material is a nematic liquid crystalline molecular material.   The retardation member according to claim 10 or 11, wherein the refractive index anisotropic material contains a liquid crystalline compound having a molecular structure having a polymerizable functional group at least at one end.   11. The refractive index anisotropic material contains a mixture of a liquid crystal compound having a molecular structure having a polymerizable functional group at one terminal and a liquid crystal compound having a molecular structure having no polymerizable functional group at one terminal. The phase difference member of any one of thru | or 12. The retardation member according to claim 10, wherein the refractive index anisotropic material contains a liquid crystal compound represented by the following chemical formula (wherein a and b are integers of 3 to 6).
  The phase difference member according to claim 3, wherein the solvent is a cyclic ketone.   The retardation member according to claim 15, wherein the solvent is cyclohexanone.   The retardation member according to claim 1, wherein the retardation in the thickness direction is 70 to 300 nm.   The phase difference member according to claim 1, wherein the phase difference member is a phase difference film.   The rank according to any one of claims 1 to 18, wherein the refractive index anisotropic material is randomly homogeneously oriented in a layer region in which the refractive index anisotropic material and the transparent polymer base material are mixed almost uniformly. Phase difference member.   In Raman scattering spectroscopy, a liquid crystal obtained when the linearly polarized electric field vibration plane incident on the cross section of the layer region where the refractive index anisotropic material, which is a liquid crystal, and the transparent polymer base material are mixed almost uniformly is parallel to the surface The Raman peak intensity ratio between the benzene ring-derived peak and the CH-derived peak is 1.1 times the peak intensity ratio when the plane of electric field vibration of linearly polarized light incident on the section cut perpendicular to the stretching direction is parallel to the surface. The phase difference member according to claim 19, which is as described above.   In Raman scattering spectroscopy, when linearly polarized light is incident from the surface of a layer region in which a liquid crystal refractive index anisotropic material and a transparent polymer base material are mixed almost uniformly, the electric field vibration plane is parallel to the width direction. The Raman peak intensity ratio between the benzene ring-derived peak and the CH-derived peak of the liquid crystal in this case is within 1.1 times the peak intensity obtained when the electric field vibration plane of linearly polarized light is aligned in the vertical direction. Item 21. The retardation member according to Item 19 or 20.   An application step of applying a coating liquid in which a refractive index anisotropic material that is liquid crystal is dissolved or dispersed in a solvent is applied to at least one surface of the transparent polymer substrate, and the refraction in the applied coating liquid 22. The method according to claim 1, further comprising a mixing step of mixing the rate anisotropic material and the transparent polymer base material, and a drying step of drying the solvent in the coating liquid. Manufacturing method of the phase difference member.   The method for producing a retardation member according to claim 22, wherein the mixing step is performed during the drying step.   The retardation member according to any one of claims 1 to 21, wherein the retardation member is produced by the method according to claim 22 or 23.