JP2007094207A - Optical functional layer forming composition and method of manufacturing optical functional film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical functional layer forming composition capable of forming an optical functional layer excellent in transparency. <P>SOLUTION: The optical functional layer forming composition comprises rod-shaped compounds and a solvent mixture of alcohol solvent and other organic solvent, wherein the amount of alcohol solvent in the solvent mixture falls into the range of 5 to 20 mass%. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a composition for forming an optical functional layer used for forming an optical functional layer constituting an optical functional film mainly used in a liquid crystal display device, and more specifically, a rod-shaped compound having a random homogeneous orientation formed therein. It is related with the composition for optical function layer formation used suitably in order to form the optical function layer excellent in transparency including.

Since the liquid crystal display device has features such as power saving, light weight, thinness, etc., the conventional C
Instead of RT display, it has been rapidly spreading in recent years. As a general liquid crystal display device, as shown in FIG. 3, a liquid crystal display device having an incident-side polarizing plate 102 </ b> A, an emitting-side polarizing plate 102 </ b> B, and a liquid crystal cell 104 can be exemplified. The polarizing plates 102A and 102B are configured to selectively transmit only linearly polarized light (schematically illustrated by arrows in the figure) having a vibration surface in a predetermined vibration direction. They are arranged to face each other in a crossed Nicol state so as to have a right angle relationship with each other. The liquid crystal cell 104 includes a large number of cells corresponding to the pixels, and is disposed between the polarizing plates 102A and 102B.

Here, in such a liquid crystal display device 100, the liquid crystal cell 104 has a VA (Vertical Alignment) method in which nematic liquid crystal having negative dielectric anisotropy is sealed (in the drawing, a liquid crystal director is schematically shown by a dotted line). As an example, the linearly polarized light transmitted through the incident-side polarizing plate 102A is phase-shifted when passing through the non-driven cell portion of the liquid crystal cell 104. And is blocked by the output-side polarizing plate 102B. On the other hand, when the liquid crystal cell 104 is transmitted through the portion of the driven cell, the linearly polarized light is phase-shifted, and an amount of light corresponding to the amount of the phase shift is transmitted through the polarizing plate 102B on the emission side. Emitted. Thus, a desired image can be displayed on the exit side polarizing plate 102B side by appropriately controlling the driving voltage of the liquid crystal cell 104 for each cell. The liquid crystal display device 100 is not limited to the above-described light transmission and blocking modes, and light emitted from the non-driven cell portion of the liquid crystal cell 104 is emitted from the polarizing plate on the emission side. There has also been devised a liquid crystal display device configured so that light emitted from the portion of the cell in the driving state is blocked by the polarizing plate 102B on the emission side while being emitted through 102B.

  By the way, considering the case where linearly polarized light is transmitted through the non-driven cell portion of the VA liquid crystal cell 104 as described above, the liquid crystal cell 104 has birefringence and is refracted in the thickness direction. Since the refractive index and the refractive index in the plane direction are different, the light incident along the normal line of the liquid crystal cell 104 out of the linearly polarized light transmitted through the polarizing plate 102A on the incident side is transmitted without being phase-shifted. Of the linearly polarized light transmitted through the polarizing plate 102 </ b> A, light incident in a direction tilted from the normal line of the liquid crystal cell 104 has a phase difference when passing through the liquid crystal cell 104 and becomes elliptically polarized light. This phenomenon is caused by the fact that the liquid crystal molecules aligned in the vertical direction in the liquid crystal cell 104 act as a positive C plate. Note that the magnitude of the phase difference generated with respect to light transmitted through the liquid crystal cell 104 (transmitted light) depends on the birefringence value of the liquid crystal molecules sealed in the liquid crystal cell 104, the thickness of the liquid crystal cell 104, and the transmitted light. It is also affected by the wavelength.

  Due to the above phenomenon, even when a certain cell in the liquid crystal cell 104 is in a non-driven state, the linearly polarized light is essentially transmitted as it is and should be blocked by the polarizing plate 102B on the output side. A part of the light emitted in the direction inclined from the normal line leaks from the polarizing plate 102B on the emission side. For this reason, in the conventional liquid crystal display device 100 as described above, the display quality of the image observed from the direction inclined from the normal line of the liquid crystal cell 104 is mainly lower than the image observed from the front. There was a problem (problem of viewing angle dependency) that deteriorated due to

  Various techniques have been developed so far in order to improve the problem of viewing angle dependency in the conventional liquid crystal display device 100 as described above, and a representative method is a method using an optical function film. The method using the optical function film improves the viewing angle problem by disposing the optical function film 40 having predetermined optical characteristics between the liquid crystal cell 104 and the polarizing plate 102B as shown in FIG. Is the method. The optical function film used to improve the viewing angle problem uses a retardation film exhibiting refractive index anisotropy, which improves the viewing angle dependency of the liquid crystal display device. Widely used as a means.

  Conventionally, as the retardation film, as shown in FIG. 2, an alignment film 22 is provided on an arbitrary transparent substrate 21, and an optical functional layer 23 having liquid crystal molecules is formed on the alignment film 22. In general, the liquid crystal molecules are oriented by the orientation regulating force of the film so as to develop a desired refractive index anisotropy. As such a retardation film, for example, as disclosed in Patent Document 1 or Patent Document 2, an optical functional layer having a cholesteric regular molecular structure (an optical functional layer exhibiting birefringence) is used as an alignment film. A retardation film formed on a substrate having the same is disclosed. Patent Document 3 discloses a retardation film in which an optical functional layer made of a discotic compound (an optical functional layer exhibiting birefringence) is formed on a substrate having an alignment film.

  The retardation film significantly reduces the problem of viewing angle dependency of the liquid crystal display device by appropriately designing the refractive index anisotropy of the optical functional layer so as to cancel the phase difference generated in the liquid crystal cell of the liquid crystal display device. This is useful in that it can be improved. However, since the conventional retardation film has an essential structure for aligning the liquid crystal molecules, there is a problem in the adhesion between the alignment film and the retardation.

  In order to solve such problems, the present inventors, as a retardation film capable of expressing desired optical characteristics without using an alignment film, are formed on a substrate and a rod-like compound that is directly formed on the substrate and randomly oriented. A retardation film having an optical functional layer having Such a retardation film having no alignment film is excellent in adhesion between the optical functional layer and the substrate, and the optical functional layer having the rod-like compound with the randomly homogeneous alignment is an optical characteristic as a negative C plate. It is useful in that it is excellent in the expression of the film, and has attracted attention as having a quality that surpasses the conventional phase difference film in terms of durability and stability of optical characteristics.

  However, a retardation film having no alignment film as described above is usually obtained by applying the composition for forming an optical functional layer containing the rod-shaped compound on a substrate having a property as a negative C plate. However, the conventional composition for forming an optical functional layer may have difficulty in forming a homogeneous random homogeneous orientation, and the optical functional layer may become cloudy. was there.

JP-A-3-67219 JP-A-4-322223 Japanese Patent Laid-Open No. 10-312166

  This invention is made | formed in view of the said problem, and it aims at providing the composition for optical function layer formation which can form the optical function layer excellent in transparency.

  In order to solve the above problems, the present invention provides an optical functional layer forming composition comprising a rod-shaped compound and a mixed solvent comprising an alcohol solvent and another organic solvent, the amount of the alcohol solvent in the mixed solvent Is within the range of 5% by mass to 20% by mass, providing a composition for forming an optical functional layer.

  According to the present invention, when the optical functional layer is formed using the composition for forming an optical functional layer of the present invention by including an alcohol solvent within the above range in the mixed solvent, the mixture is not cloudy and transparent. An optical functional layer having excellent properties can be formed.

  In the said invention, it is preferable that the said composition for optical function layer formation is used in order to form the optical function layer in which the said rod-shaped compound formed random homogeneous orientation. Since the optical functional layer in which the rod-like compound has formed a random homogeneous orientation can exhibit optical characteristics as a negative C plate without the presence of an orientation film, for example, the composition for forming an optical functional layer of the present invention on a substrate is used. This is because it is possible to form an optical functional layer by directly applying an object, whereby an optical functional layer having excellent adhesion to the substrate can be formed.

  In the said invention, it is preferable that the said rod-shaped compound is what has a polymeric functional group. Since the rod-shaped compound has a polymerizable functional group, it becomes possible to polymerize and fix the rod-shaped compound. Therefore, using the composition for forming an optical functional layer of the present invention, alignment stability and optical characteristics This is because an excellent optical functional layer can be formed.

  Moreover, in the said invention, it is preferable that the said rod-shaped compound is a liquid crystalline material. This is because when the rod-shaped compound is a liquid crystalline material, an optical functional layer having excellent optical characteristics per unit thickness can be formed using the composition for forming an optical functional layer of the present invention.

  Furthermore, in the said invention, it is preferable that the said liquid crystalline material is a material which shows a nematic phase. When the liquid crystalline material is a material exhibiting a nematic phase, an optical functional layer in which a rod-like compound has formed a more homogeneous random homogeneous alignment can be formed using the optical functional layer forming composition of the present invention. Because.

  The present invention uses a substrate having properties as a negative C plate and the composition for forming an optical functional layer, and applies the composition for forming an optical functional layer on the substrate. And an optical functional film comprising a rod-like compound directly formed on the substrate and having a random homogeneous orientation, and a method for producing the optical functional film.

According to the present invention, an optical functional film having an optical functional layer having excellent transparency can be produced by forming an optical functional layer using the composition for forming an optical functional layer.
Moreover, by forming the optical functional layer directly on the substrate, an optical functional film having excellent adhesion between the optical functional layer and the substrate can be produced.
Furthermore, in the optical functional layer of the optical functional film produced according to the present invention, the rod-shaped compound forms a random homogeneous orientation. It can be made excellent in the expression of optical properties that act as a C plate.

  According to the composition for forming an optical functional layer of the present invention, there is an effect that an optical functional layer excellent in transparency can be formed.

  Hereinafter, the composition for forming an optical functional layer of the present invention and the method for producing an optical functional film will be described in detail.

A. First, the composition for forming an optical functional layer of the present invention will be described. The composition for forming an optical functional layer of the present invention contains a rod-shaped compound and a mixed solvent composed of an alcohol solvent and another organic solvent, and the amount of the alcohol solvent in the mixed solvent is from 5% by mass to It is within the range of 20% by mass.

  According to the present invention, when the optical functional layer is formed using the composition for forming an optical functional layer of the present invention by including an alcohol solvent within the above range in the mixed solvent, the mixture is not cloudy and transparent. An optical functional layer having excellent properties can be obtained.

  In the composition for forming an optical functional layer of the present invention, the mechanism by which white turbidity is suppressed due to the alcohol solvent being contained in the above-mentioned mixed solvent within the above range is not clear, but by the following mechanism It is thought to be a thing. That is, since the rod-shaped compound contained in the composition for forming an optical functional layer of the present invention is insoluble in an alcohol solvent, the composition for forming an optical functional layer of the present invention is present when the alcohol solvent is present in the mixed solvent. When an optical functional layer is formed using a product, in-plane orientation of the rod-shaped compound can be promoted. From such a thing, it is thought that the white turbidity of an optical function layer can be prevented as a result of suppressing the arrangement | sequence defect of a rod-shaped compound.

  In the present invention, the content of the alcohol-based solvent in the mixed solvent is determined to be within the range of 5% by mass to 20% by mass, and the range is determined based on the following reason. That is, if the amount of the alcohol solvent is less than the above range, the optical functional layer may become cloudy when the optical functional layer is formed using the optical functional layer forming composition of the present invention. is there. On the other hand, if the amount of the alcohol solvent is larger than the above range, the rod-shaped compound described later may not be dissolved at a desired concentration in the composition for forming an optical functional layer of the present invention.

In addition, the amount of the alcohol solvent in the mixed solvent in the present invention can be measured by gas chromatography. Examples of such gas chromatography measurement conditions include the following conditions.
(1) Measuring equipment Shimadzu Corporation (2) Detector FID
(3) Column SBS-200 3m
(4) Column temperature 100 ° C
(5) Injection temperature 150 ° C
(6) Carrier gas He 150 kPa
(7) Hydrogen pressure 60kPa
(8) Air pressure 50kPa

  Further, the composition for forming an optical functional layer of the present invention is preferably used for forming an optical functional layer in which the rod-like compound has formed a random homogeneous orientation. The optical functional layer in which the rod-like compound has formed a random homogeneous orientation has excellent optical characteristics that act as a negative C plate, so an optical functional layer with excellent optical characteristics can be formed without using an alignment film. Because it can. In addition, since an alignment film is not required, for example, by using the composition for forming an optical functional layer according to the present invention, the optical functional layer is directly formed on the base, thereby allowing the base and the optical functional layer to adhere to each other. This is because an optical functional film having excellent properties can be obtained.

  The random homogeneous orientation is one of the arrangement forms of rod-like compounds that impart optical characteristics as a negative C plate to an optical functional layer formed using the optical functional layer forming composition of the present invention. Conventionally, as an arrangement form of rod-like compounds that exhibit optical characteristics as a negative C plate, an arrangement form having a cholesteric structure was generally used, but the above random homogeneous orientation has a feature that does not have a cholesteric structure It is.

The random homogeneous orientation has at least the following three characteristics. That is, the random homogeneous orientation is
First, when the optical functional layer is viewed from the direction perpendicular to the surface of the optical functional layer, the arrangement direction of the rod-shaped compounds is random (hereinafter, simply referred to as “irregularity”).
Second, the size of the domain formed by the rod-shaped compound in the optical functional layer is smaller than the wavelength in the visible light region (hereinafter, sometimes simply referred to as “dispersibility”),
Third, the rod-like compound is in-plane oriented in the optical functional layer (hereinafter, sometimes simply referred to as “in-plane orientation”),
At least.

  Next, the random homogeneous orientation will be described with reference to the drawings. FIG. 1 is a schematic view showing an example of an optical functional film having an optical functional layer prepared using the composition for forming an optical functional layer of the present invention. Hereinafter, in order to explain the random homogeneous alignment, an optical functional layer formed using the optical functional layer forming composition of the present invention on a substrate 1 as illustrated in FIGS. 1 (a) and 1 (b). Reference is made to an optical function film 10 having 2. FIG. 1C is a schematic view when viewed from the direction A which is perpendicular to the surface of the optical function layer 2 of the optical function film 10 shown in FIGS. 1A and 1B. .

First, the “irregularity” will be described with reference to FIG. The “irregularity” indicates that the rod-like compounds 3 are randomly arranged in the optical functional layer 2 as shown in FIG.
Here, in the present invention, in order to explain the arrangement direction of the rod-shaped compound 3, the molecular major axis direction (hereinafter referred to as a molecular axis) represented by a in FIG. . Therefore, the arrangement direction of the rod-shaped compounds 3 being random means that the molecular axes a of the rod-shaped compounds 3 included in the optical functional layer 2 are randomly oriented.

  In addition to the arrangement state illustrated in FIG. 1C, even when the rod-like compound has a cholesteric structure, the direction of the molecular axis a is random as a whole, and therefore, formally, the Although it corresponds to “regularity”, as described above, the “irregularity” does not include a form caused by a cholesteric structure.

  Next, the “dispersibility” will be described with reference to FIG. As shown in FIG. 1A, the above “dispersibility” means that when the rod-shaped compound 3 forms the domain b in the optical functional layer 2, the size of the domain b is smaller than the wavelength in the visible light region. It shows that. In the random homogeneous orientation, the smaller the size of the domain b is, the more preferable, and the state where the rod-like compound is dispersed in a single molecule is the most preferable.

  Next, the “in-plane orientation” will be described with reference to FIG. As shown in FIG. 1A, the “in-plane orientation” is such that the rod-shaped compound 3 in the optical functional layer 2 has the molecular axis a substantially perpendicular to the normal direction A of the optical functional layer 3. It means that it is oriented. As the “in-plane orientation”, as shown in FIG. 1A, the molecular axes a of all rod-like compounds 3 in the optical functional layer 2 are substantially perpendicular to the normal direction A. For example, as shown in FIG. 1B, even if the rod-like compound 3 whose molecular axis a ′ is not perpendicular to the normal direction A is present in the optical functional layer 2, as shown in FIG. This includes the case where the average direction of the molecular axis a of the rod-shaped compound 3 existing in the optical functional layer 3 is substantially perpendicular to the normal direction A.

  The random homogeneous orientation is characterized by exhibiting at least “irregularity”, “dispersibility” and “in-plane orientation” as described above. It can be confirmed by the following method that the optical functional layer produced by the method has these characteristics.

First, a method for confirming the “irregularity” will be described. The “irregularity” is an evaluation of in-plane retardation (Re) of an optical functional layer formed from the composition for forming an optical functional layer of the present invention, and the presence or absence of a selective reflection wavelength due to a cholesteric structure. This can be confirmed.
That is, the in-plane retardation (Re) evaluation of the optical functional layer formed from the composition for forming an optical functional layer of the present invention can confirm that the rod-like compound is randomly oriented, depending on the presence or absence of the selective reflection wavelength. It can be confirmed that the rod-shaped compound does not form a cholesteric structure.

  The rod-like compound is randomly oriented because the in-plane retardation (Re) value of the optical functional layer formed from the composition for forming an optical functional layer of the present invention is random and the orientation state of the rod-like compound is random. It can be confirmed by being within the range indicating that In particular, in the present invention, the in-plane retardation (Re) of the optical functional layer is preferably in the range of 0 nm to 5 nm. Here, the in-plane retardation (Re) is the refractive index Nx in the fast axis direction (the direction in which the refractive index is the smallest) in the plane of the optical functional layer formed from the optical functional layer forming composition of the present invention. , And the refractive index Ny in the slow axis direction (direction in which the refractive index is the largest) and the thickness d (nm) of the optical function layer, a value represented by the equation Re = (Nx−Ny) × d It is.

  Here, the reason why the rod-like compounds can be confirmed to be randomly arranged by in-plane retardation (Re) is based on the following reason. That is, the in-plane retardation (Re) is a parameter indicating the refractive index difference in the in-plane direction, as is clear from the above definition formula. In the optical functional layer formed from the optical functional layer forming composition of the present invention, when the rod-shaped compounds are arranged with regularity in one direction, the refractive index in a specific direction increases, The refractive index difference tends to increase. On the other hand, when the rod-shaped compounds are arranged randomly, the refractive index in a specific direction does not increase in the plane of the optical functional layer, and thus the refractive index difference tends to decrease. Therefore, the “irregularity” can be evaluated by evaluating the in-plane retardation (Re) showing such a refractive index difference.

  The Re of the optical function layer can be obtained, for example, by subtracting Re indicated by a layer other than the optical function layer from Re of the optical function film. That is, the Re of the optical function layer can be obtained by measuring Re of the entire optical function film and the optical function film obtained by cutting the optical function layer and subtracting the latter Re from the former Re. Re can be measured, for example, by the parallel Nicol rotation method using KOBRA-WR manufactured by Oji Scientific Instruments.

  The fact that the rod-shaped compound does not have a cholesteric structure means that, for example, an ultraviolet-visible near-infrared spectrophotometer (UV-3100, etc.) manufactured by Shimadzu Corporation is used, and the optical functional layer in the present invention has a selective reflection wavelength. It can be evaluated by confirming that it is not. This is because the cholesteric structure has a selective reflection wavelength that depends on the helical pitch of the cholesteric structure.

  Next, a method for confirming the “dispersibility” will be described. The “dispersibility” is a range in which the haze value of the optical functional layer formed from the composition for forming an optical functional layer of the present invention indicates that the domain size of the rod-shaped compound is not more than the wavelength in the visible light region. It can be confirmed by being within. Especially in this invention, it is preferable that the haze value of the said optical function layer exists in the range of 0%-5%. Here, as the haze value, a value measured in accordance with JIS K7105 is used.

  Here, the haze value of the optical function layer can be obtained, for example, by subtracting the haze value of a layer other than the optical function layer from the haze value of the optical function film. That is, the haze value of the optical function layer can be determined by measuring the haze value of the entire optical function film and the optical function film obtained by cutting the optical function layer and subtracting the latter haze value from the former haze value. it can. As the haze value, a value measured according to JIS K7105 is used.

  Here, it can be confirmed that haze has the above-mentioned “dispersibility”, that is, the size of the domain formed by the rod-shaped compound is smaller than the wavelength in the visible light region, based on the following reason. Is. That is, when the rod-shaped compound forms a domain and the size of the domain is larger than the wavelength of visible light, visible light is scattered in the optical functional layer. Tend to. Therefore, the “dispersibility” can be evaluated by measuring the haze of the optical functional layer in the visible light region.

  The specific size of the domain is preferably not more than the wavelength of visible light, that is, not more than 380 nm, more preferably not more than 350 nm, and particularly preferably not more than 200 nm. In the present invention, since the rod-shaped compound is preferably monomolecularly dispersed, the lower limit value of the domain size is the size of a single molecule of the rod-shaped compound. The size of such a domain can be evaluated by observing the optical functional layer with a polarizing microscope, AFM, SEM, or TEM.

  Next, a method for confirming the “in-plane orientation” will be described. The above-mentioned “in-plane orientation” means that the value of the in-plane retardation (Re) of the optical functional layer formed from the composition for forming an optical functional layer of the present invention is in the above-mentioned range and is optically negative. It can be confirmed by having a retardation (Rth) value in the thickness direction showing the properties of the C plate. Especially, it is preferable that the said thickness direction retardation (Rth) exists in the range of 50 nm-400 nm. Here, the retardation in the thickness direction (Rth) is the refractive index in the fast axis direction (the direction in which the refractive index is the smallest) in the plane of the optical functional layer formed from the composition for forming an optical functional layer of the present invention. Nth, the refractive index Ny in the slow axis direction (direction in which the refractive index is the largest), the refractive index Nz in the thickness direction, and the thickness d (nm) of the optical function layer, Rth = {(Nx + Ny) / 2−Nz} × d. Here, the Rth value in the present invention indicates the absolute value of the value represented by the above formula.

  Here, the in-plane retardation (Re) and the retardation in the thickness direction (Rth), the optical functional layer formed from the composition for forming an optical functional layer of the present invention has the above-mentioned “in-plane orientation”. It is based on the reason that we can confirm that That is, the retardation in the thickness direction (Rth) is a parameter resulting from the difference between the average value of the refractive index in the in-plane direction and the refractive index in the thickness direction, as is apparent from the above definition. As described above, since the value of the in-plane retardation (Re) of the optical functional layer is a value within a certain range from the “irregularity”, the value of the retardation (Rth) in the thickness direction. Depends on the refractive index (Nz) in the thickness direction. Here, the refractive index (Nz) in the thickness direction tends to increase due to the in-plane orientation of the rod-shaped compound. In this case, the value of retardation (Rth) in the thickness direction tends to decrease. Therefore, when the value of retardation (Rth) in the thickness direction of the optical functional layer is within the above range, the “in-plane orientation” can be evaluated.

  The retardation (Rth) in the thickness direction of the optical functional layer can be obtained, for example, by subtracting Rth indicated by a layer other than the optical functional layer from Rth of the optical functional film. That is, the Rth of the optical functional layer can be obtained by measuring Rth of the entire optical functional film and the optical functional film obtained by cutting the optical functional layer and subtracting the latter Rth from the former Rth. Rth can be measured by, for example, the parallel Nicol rotation method using KOBRA-WR manufactured by Oji Scientific Instruments.

  The composition for forming an optical functional layer of the present invention is suitably used for forming an optical functional layer having a random homogeneous orientation having the above characteristics. In addition, since the optical functional layer forming composition of the present invention contains an alcohol-based solvent, when the optical functional layer containing the rod-shaped compound having the above-mentioned random homogeneous orientation is formed, the optical functional layer having better transparency Can be formed.

  The composition for forming an optical functional layer of the present invention comprises a rod-shaped compound and a mixed solvent composed of an alcohol solvent and another organic solvent. Hereinafter, each structure of the composition for optical function layer formation of this invention is demonstrated in detail.

1. Mixed solvent First, the mixed solvent which comprises the composition for optical function layer formation of this invention is demonstrated. The mixed solvent used in the present invention consists of an alcohol solvent and another organic solvent.

(1) Alcohol solvent The alcohol solvent used for the mixed solvent will be described. The alcohol solvent used in the present invention has a function of preventing the optical functional layer from becoming clouded when the optical functional layer is formed using the optical functional layer forming composition of the present invention.

  The amount of the alcohol solvent in the mixed solvent in the present invention is not particularly limited as long as it is in the range of 5% by mass to 20% by mass. Especially in this invention, it is preferable to exist in the range of 10 mass%-20 mass%. Here, the method for quantifying the amount of the alcohol solvent is the same as described above, and therefore the description thereof is omitted here.

  The alcohol solvent used in the present invention is not particularly limited as long as it does not erode a substrate described later. Such an alcohol solvent is not limited to one type, and two or more types may be mixed and used.

  The alcohol solvent used in the present invention may be a monohydric alcohol having one OH group contained in the molecule or a polyhydric alcohol having two or more OH groups. However, it is preferable to use a monohydric alcohol.

  In addition, the alcohol solvent used in the present invention may be any of primary alcohol, secondary alcohol, and tertiary alcohol, but it is preferable to use primary alcohol.

Furthermore, examples of the alcohol solvent used in the present invention include aliphatic saturated alcohols, aliphatic unsaturated alcohols, alicyclic alcohols, aromatic alcohols, and heterocyclic alcohols. It is preferable to use an aliphatic saturated alcohol.
As the aliphatic saturated alcohol, it is preferable to use a lower aliphatic saturated alcohol. More specifically, the number of carbon atoms constituting the hydrocarbon chain is preferably in the range of 1 to 6, particularly 3 to 3. It is preferable to be within the range of 5. Examples of the lower aliphatic saturated alcohol having carbon number include straight chain hydrocarbon chains and those having side chains. In the present invention, any of the lower aliphatic saturated alcohols Can also be suitably used.

  Among the above alcohol solvents, specific examples of alcohol solvents that are preferably used in the present invention include methanol, ethanol, N-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, and the like. be able to. Of these, isopropyl alcohol and N-propyl alcohol are more preferably used in the present invention.

(2) Organic solvent Next, the organic solvent which comprises the mixed solvent in this invention is demonstrated. The organic solvent in this invention has a function which melt | dissolves the rod-shaped compound mentioned later to a desired density | concentration. The organic solvent used in the present invention may be a single solvent or a mixed solvent of a plurality of solvents.

  The organic solvent used in the present invention is not particularly limited as long as it can dissolve a rod-shaped compound described later at a desired concentration. Examples of the organic solvent used in the present invention include hydrocarbon solvents such as benzene and hexane; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and methylcyclohexanone; ether solvents such as tetrahydrofuran and 1,2-dimethoxyethane. Solvents: Halogenated alkyl solvents such as chloroform and dichloromethane; Ester solvents such as methyl acetate, butyl acetate and propylene glycol monomethyl ether acetate; Amide solvents such as N, N-dimethylformamide, and Sulphoxide solvents such as dimethyl sulfoxide Can be illustrated. Of these, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and methyl cyclohexanone can be preferably used in the present invention.

2. Next, the rod-shaped compound constituting the composition for forming an optical functional layer of the present invention will be described. The rod-shaped compound used for this invention will not be specifically limited if a desired optical characteristic can be provided to the optical function layer formed using the composition for optical function layer formation of this invention. Especially in this invention, it is preferable that the said rod-shaped compound can form a random homogeneous orientation. Here, the “rod-shaped compound” in the present invention refers to a compound in which the main skeleton of the molecular structure is rod-shaped.

  Examples of the rod-shaped compound used in the present invention include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, and cyano-substituted phenylpyrimidines. And alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles. Moreover, not only the above low molecular liquid crystalline compound but a high molecular liquid crystalline compound can also be used.

As the rod-shaped compound used in the present invention, a compound having a relatively small molecular weight is preferably used. Specifically, a compound having a molecular weight in the range of 200 to 1200, particularly in the range of 400 to 800 is preferably used. When the molecular weight is within the above range, for example, when the optical functional layer is formed on the substrate using the optical functional layer forming composition of the present invention, the rod-shaped compound is likely to penetrate into the substrate. This is because the adhesion between the substrate and the optical functional layer can be improved.
In addition, regarding the molecular weight, the rod-shaped compound that is a material having a polymerizable functional group to be described later and is polymerized when the optical functional layer is formed using the optical functional layer forming composition of the present invention, The molecular weight of

  In addition, the rod-like compound used in the present invention is preferably a liquid crystalline material exhibiting liquid crystallinity. This is because when the rod-shaped compound is a liquid crystalline material, an optical functional layer having excellent optical properties per unit thickness can be formed using the composition for forming an optical functional layer of the present invention.

  The rod-like compound in the present invention is preferably a liquid crystalline material exhibiting a nematic phase among the above liquid crystalline materials. When the liquid crystalline material is a material exhibiting a nematic phase, an optical functional layer in which the rod-shaped compound has formed a more homogeneous random homogeneous alignment can be formed using the composition for forming an optical functional layer of the present invention. Because it can.

  Further, the liquid crystalline material exhibiting the nematic phase is preferably a molecule having spacers at both mesogenic ends. This is because the liquid crystalline material having spacers at both ends of the mesogen is excellent in flexibility and can effectively prevent the optical functional layer in the present invention from becoming clouded.

  As the rod-like compound 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. Since the rod-shaped compound has a polymerizable functional group, the rod-shaped compound can be polymerized and fixed. For example, by fixing the rod-shaped compound in a state of forming a random homogeneous orientation. This is because it is possible to obtain an optical functional layer that is excellent in array stability and hardly changes in optical characteristics. In the present invention, the rod-shaped compound having the polymerizable functional group may be mixed with the rod-shaped compound having no polymerizable functional group.

The “three-dimensional crosslinking” means that liquid crystal molecules are polymerized three-dimensionally to form a network (network) structure.

  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.

  The rod-like compound in the present invention is a liquid crystalline material exhibiting liquid crystallinity and particularly preferably has a polymerizable functional group at the terminal. For example, if a nematic liquid crystalline material having a polymerizable functional group at both ends is used, the composition can be polymerized three-dimensionally to form a network structure. This is because it is possible to form an optical functional layer having alignment stability and excellent optical characteristics. Moreover, even if it has a polymerizable functional group at one end, it can be cross-linked with other molecules to stabilize the sequence.

  Examples of such rod-shaped compounds used in the present invention include compounds represented by the following formulas (1) to (6).

  Here, the liquid crystalline materials represented by the chemical formulas (1), (2), (5) and (6) are disclosed in DJ Broer et al., Makromol. Chem. 190, 3201-3215 (1989), or DJ Broer et al., Makromol. Chem. 190, 2250 (1989), or can be prepared similarly. The preparation of liquid crystalline materials represented by the chemical formulas (3) and (4) is disclosed in DE 195,04,224.

Specific examples of the nematic liquid crystalline material having an acrylate group at the terminal include those represented by the following chemical formulas (7) to (17).

  In the present invention, the rod-shaped compound may be used alone or in combination of two or more. For example, when the rod-shaped compound is used by mixing a liquid crystalline material having one or more polymerizable functional groups at both ends and a liquid crystalline material having one or more polymerizable functional groups at one end, The polymerization density (crosslink density) and the optical characteristics can be arbitrarily adjusted by adjusting the ratio, which is preferable.

As the content of the rod-shaped compound in the composition for forming an optical functional layer of the present invention, according to the forming method when forming the optical functional layer using the composition for forming an optical functional layer of the present invention, etc. The composition for forming an optical functional layer of the present invention is not particularly limited as long as it is within a range where a desired viscosity can be obtained. Especially in this invention, it is preferable that content of the said rod-shaped compound exists in the range of 5 mass%-50 mass% in the composition for optical function layer formation, Especially in the range of 5 mass%-20 mass%. It is preferable that
The content of the rod-shaped compound can be determined by measuring 2 g of the composition for forming an optical functional layer of the present invention in an aluminum cup, drying it in an oven at 150 ° C. for 1 hour, and calculating from the volatile loss.

3. Optical Functional Layer Forming Composition The optical functional layer forming composition of the present invention may have a constitution other than the mixed solvent and the rod-like compound. Examples of such other configurations include silicon leveling agents such as polydimethylsiloxane, methylphenylsiloxane, and organically modified siloxane; linear polymers such as polyalkyl acrylate and polyalkyl vinyl ether; fluorine-based surfactants, Surfactants such as hydrocarbon surfactants; fluorine leveling agents such as tetrafluoroethylene; photopolymerization initiators and the like can be mentioned. Especially in this invention, when using the rod-shaped compound which has a polymerizable functional group polymerized by light irradiation as said rod-shaped compound, it is preferable that a photoinitiator is included.

  Examples of the photopolymerization initiator include benzophenone, methyl o-benzoylbenzoate, 4,4-bis (dimethylamine) benzophenone, 4,4-bis (diethylamine) benzophenone, α-amino acetophenone, 4,4-dichlorobenzophenone. 4-benzoyl-4-methyldiphenyl ketone, dibenzyl ketone, fluorenone, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methylpropiophenone, p-tert -Butyldichloroacetophenone, thioxanthone, 2-methylthioxanthone, 2-chlorothioxanthone, 2-isopropylthioxanthone, diethylthioxanthone, benzyldimethyl ketal, benzylmethoxyethyl acetal, benzoin Ether, benzoin butyl ether, anthraquinone, 2-tert-butylanthraquinone, 2-amylanthraquinone, β-chloroanthraquinone, anthrone, benzanthrone, dibenzsuberone, methyleneanthrone, 4-azidobenzylacetophenone, 2,6-bis (p-azidobenzylidene) ) Cyclohexane, 2,6-bis (p-azidobenzylidene) -4-methylcyclohexanone, 2-phenyl-1,2-butadion-2- (o-methoxycarbonyl) oxime, 1-phenyl-propanedione-2- ( o-ethoxycarbonyl) oxime, 1,3-diphenyl-propanetrione-2- (o-ethoxycarbonyl) oxime, 1-phenyl-3-ethoxy-propanetrione-2- (o-benzoyl) oxime, Hiller ketone, 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone, naphthalenesulfonyl chloride Quinolinesulfonyl chloride, n-phenylthioacridone, 4,4-azobisisobutyronitrile, diphenyl disulfide, benzthiazole disulfide, triphenylphosphine, camphorquinone, N1717 manufactured by Adeka, carbon tetrabromide, tribromophenyl Examples include a combination of a photoreductive dye such as sulfone, benzoin peroxide, eosin, and methylene blue with a reducing agent such as ascorbic acid or triethanolamine. In this invention, these photoinitiators can be used 1 type or in combination of 2 or more types.

  The content of the photopolymerization initiator is not particularly limited as long as the rod-shaped compound can be polymerized in a desired time, but usually 1 to 10 parts by weight with respect to 100 parts by weight of the rod-shaped compound. Is preferably within the range of 3 parts by weight to 6 parts by weight. If the content of the photopolymerization initiator is more than the above range, the arrangement of the rod-shaped compounds may be disturbed in the optical functional layer formed using the composition for forming an optical functional layer of the present invention. is there. Moreover, it is because there exists a possibility that it cannot superpose | polymerize within desired time depending on the kind of rod-shaped compound when content is less than the said range.

  When the photopolymerization initiator is used, a photopolymerization initiation assistant can be used in combination. Examples of such photopolymerization initiation assistants include tertiary amines such as triethanolamine and methyldiethanolamine, and benzoic acid derivatives such as ethyl 2-dimethylaminoethylbenzoate and ethyl 4-dimethylamidebenzoate. Yes, but not limited to these.

  Furthermore, the compound as shown below can be added to the composition for forming an optical functional layer of the present invention within a range not impairing the object of the present invention. Examples of compounds that can be added include polyester (meth) acrylate obtained by reacting (meth) acrylic acid with a polyester prepolymer obtained by condensing polyhydric alcohol and monobasic acid or polybasic acid; A polyurethane (meth) acrylate obtained by reacting a compound having two isocyanate groups with each other and then reacting the reaction product with (meth) acrylic acid; bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolak Type epoxy resins, polycarboxylic acid polyglycidyl esters, polyol polyglycidyl ethers, aliphatic or cycloaliphatic epoxy resins, amino group epoxy resins, triphenolmethane type epoxy resins, dihydroxybenzene type epoxy resins and the like (meta Acu Photopolymerizable compounds such as epoxy (meth) acrylate obtained by reacting Le acid; photopolymerizable liquid crystal compound having an acryl group or methacryl group and the like. The amount of these compounds added to the composition for forming an optical functional layer can be determined within a range that does not impair the object of the present invention. By adding the compound as described above, the mechanical strength of the optical functional layer formed using the composition for forming an optical functional layer of the present invention is improved, and the stability may be improved.

  The viscosity of the composition for forming an optical functional layer of the present invention may be arbitrarily adjusted according to the method for forming the optical functional layer using the composition for forming an optical functional layer of the present invention, and is usually 25. Within the range of 0.5 mPa · s to 10 mPa · s at ° C., preferably within the range of 1 Pa · s to 5 Pa · s, particularly preferably within the range of 1 Pa · s to 3 Pa · s.

  The use of the composition for forming an optical functional layer of the present invention is not particularly limited, but it is preferably used for forming an optical functional layer constituting an optical functional film used in a liquid crystal display device. The rod-shaped compound contained in the composition for forming an optical functional layer is most preferably used for forming an optical functional layer having a random homogeneous orientation. The details of such random homogeneous orientation are as described above, and the description thereof is omitted here.

  The method for producing the composition for forming an optical functional layer of the present invention is not particularly limited as long as it is a method capable of producing the composition for forming an optical functional layer having the above-described configuration, and a method for producing a general organic solvent-based composition The method used as can be applied. As such a method, for example, a method of dissolving the rod-like compound or the like at a predetermined concentration in a mixed solvent containing an alcohol solvent within the above range can be mentioned.

B. Next, a method for producing an optical function film of the present invention will be described. The method for producing an optical functional film of the present invention uses a base material having properties as a negative C plate and the optical functional layer forming composition, and the optical functional layer forming composition is formed on the base material. Is applied to produce an optical functional film having a base material and an optical functional layer containing a rod-like compound that is formed directly on the base material and has a random homogeneous orientation.

  According to the present invention, an optical functional film having an optical functional layer excellent in transparency can be produced by forming an optical functional layer using the composition for forming an optical functional layer containing an alcohol solvent.

Moreover, according to this invention, the optical function film excellent in the adhesiveness of an optical function layer and a base material can be manufactured by forming the said optical function layer directly on a base material. Thus, it is understood that the adhesion mechanism between the two is improved by directly forming the optical functional layer on the substrate due to the following mechanism. That is, since the optical functional layer is directly formed on the base material, the rod-shaped compound contained in the optical functional layer can penetrate into the base material from the surface of the base material. There is no clear interface at the bonded portion, and both are “mixed”. For this reason, it is considered that the adhesion is remarkably improved as compared with the adhesion by the conventional interface interaction.
In addition, in the conventional optical functional film having a configuration having an alignment film, light is multiply reflected at the interface between the alignment film and the optical function layer or at the interface between the alignment film and the substrate, resulting in interference unevenness. there were. However, the optical functional film produced according to the present invention does not have an alignment film as described above, and the adhesive portion between the base material and the optical functional layer is in a “mixed” state. There is no interface. Therefore, there is an advantage that the multiple reflection does not occur and the quality is not deteriorated due to the interference unevenness.

  Furthermore, according to the present invention, since the rod-like compound forms a random homogeneous alignment in the optical functional layer, the optical properties, particularly the optical properties acting as a negative C plate, can be obtained without using an alignment film. An optical functional film having excellent properties can be produced.

The method for producing an optical functional film of the present invention uses a substrate and a composition for forming an optical functional layer. Hereafter, the manufacturing method of the optical function film of this invention is demonstrated in detail.
The composition for forming an optical functional layer used in the present invention is the same as that described in the above section “A. Composition for forming an optical functional layer”, and the description thereof is omitted here.

1. Base material First, the base material used for this invention is demonstrated. The base material used in the present invention has a function as a negative C plate. Further, as will be described later, the optical functional film obtained by the method for producing an optical functional film of the present invention is such that the optical functional layer is directly formed on the substrate, whereby the rod-like compound contained in the optical functional layer is randomly homogeneous. Since it forms an alignment, the substrate used in the present invention also has a function as a so-called alignment film for the rod-shaped compound to form a random homogeneous alignment. Hereinafter, the base material used in the present invention will be described.

  The base material used in the present invention is not particularly limited as long as it has properties as an optically negative C plate. Here, in the present invention, “having properties as an optically negative C plate” means that the refractive index in the X direction and Y direction in the surface of the base sheet is Nx, Ny, and the refractive index in the thickness direction. Is Nz, it means that the relationship Nx = Ny> Nz is established.

  The base material used in the present invention has a property as a negative C plate for the following reason. That is, as described above, the base material used in the present invention functions as a so-called alignment film for the rod-shaped compound to form a random homogeneous orientation, but the base material has a property as a negative C plate. This is because the rod-like compound cannot form a random homogeneous orientation if it does not exist.

In the present invention, a mechanism in which the rod-shaped compound forms a random homogeneous orientation by forming an optical functional layer using the optical functional layer forming composition on a substrate having properties as a negative C plate. Is not clear, but is thought to be based on the following mechanism.
That is, for example, considering the case where the base material is formed of a polymer material, when the base material has a property as a negative C plate, the polymer material constituting the base material has a specific regularity in the in-plane direction. It is thought that they are arranged randomly without having. When the rod-shaped compound is applied onto a substrate having a polymer material randomly arranged in the in-plane direction on the surface, the rod-shaped compound partially penetrates into the substrate and the molecular axes are randomly arranged. It is thought to be arranged along the molecular axis of the polymer material. By such a mechanism, it is considered that the base material having the negative C plate exhibits a function as an alignment film that forms random homogeneous alignment.

Due to the mechanism described above, the base material is considered to have a function as an alignment film for forming a random homogeneous orientation of the rod-shaped compound. Therefore, the base material used in the present invention has an alignment regulating force with respect to the rod-shaped compound. In addition, the base material must have a configuration in which the constituent material of the base material exhibiting the properties as a negative C plate is present on the base material surface. Therefore, even when the substrate has properties as a negative C plate, when the optical functional layer is formed on the substrate, the rod-shaped compound has an alignment regulating force with respect to the rod-shaped compound. Those having a structure that cannot be in contact with the constituent material cannot be used as a base material in the present invention.
As such a substrate that cannot be used in the present invention, for example, a support made of only a polymer material and having a function as a negative C plate, and an optical element having refractive index anisotropy on the support are described. A substrate having a configuration in which a retardation layer containing an anisotropic material is laminated can be given. In the base material having such a configuration, the polymer material that constitutes the support is a constituent material of the base material that has an orientation regulating force for the rod-shaped compound, but an optical functional layer is formed on the base material. Due to the presence of the retardation layer, the rod-shaped compound cannot contact the polymer material. Therefore, even if the base material which has such a structure has the property as a negative C plate, it is not included in the base material in this invention.

The properties of the substrate used in the present invention as a negative C plate are appropriately determined according to the type of rod-shaped compound used in the composition for forming an optical functional layer, the optical characteristics required for the optical functional film produced according to the present invention, and the like. Select and use. In particular, in the present invention, the thickness direction retardation (Rth) of the substrate is preferably in the range of 20 nm to 100 nm, particularly preferably in the range of 25 nm to 80 nm, and in particular, 30 nm to 60 nm. It is preferable to be within the range. When the retardation (Rth) in the thickness direction of the base material is within the above range, the rod-shaped compound is random in the optical functional layer of the optical functional film produced according to the present invention regardless of the type of the rod-shaped compound. This is because it becomes easy to form a homogeneous alignment. Moreover, it is because the said rod-shaped compound can form homogeneous random homogeneous orientation because the retardation (Rth) of the thickness direction of the said base material exists in the said range.
Here, the retardation in the thickness direction (Rth) is the refractive index Nx in the fast axis direction (the direction in which the refractive index is smallest) and the slow axis direction (refractive in the plane of the substrate used in the present invention. The refractive index Ny in the direction in which the rate is the largest), the refractive index Nz in the thickness direction, and the thickness d (nm) of the base material are expressed by the formula Rth = {(Nx + Ny) / 2−Nz} × d. Value. As the value of retardation (Rth) in the thickness direction in the present invention, a value measured by KOBRA-WR manufactured by Oji Scientific Instruments is used at room temperature.

In addition, in the present invention, from the viewpoint of forming an optical functional layer having a more homogeneous random homogeneously oriented rod-shaped compound on the base material, the thickness direction retardation (Rth) is in the above range, The in-plane retardation (Re) is preferably in the range of 0 nm to 300 nm, particularly preferably in the range of 0 nm to 150 nm, and more preferably in the range of 0 nm to 125 nm.
Here, the in-plane retardation (Re) is the refractive index Nx in the fast axis direction (direction in which the refractive index is smallest) and the slow axis direction (refractive index) in the plane of the substrate used in the present invention. Is the value represented by the equation Re = (Nx−Ny) × d, based on the refractive index Ny in the largest direction) and the thickness d (nm) of the substrate. As the value of the in-plane retardation (Re) in the present invention, a value measured by KOBRA-WR manufactured by Oji Scientific Instruments is used at room temperature.

  The transparency of the substrate used in the present invention may be arbitrarily determined according to the transparency required for the optical functional film produced according to the present invention, but usually the transmittance in the visible light region is 80% or more. Is preferable, and 90% or more is more preferable. This is because if the transmittance is low, the selection range of the rod-like compound or the like may be narrowed. Here, the transmittance | permeability of a base material can be measured by JISK7361-1 (the test method of the total light transmittance of a plastic transparent material).

  The thickness of the base material used in the present invention is not particularly limited as long as it has the necessary self-supporting properties depending on the use of the optical functional film produced according to the present invention, but is usually in the range of 10 μm to 188 μm. The inside is preferable, in particular within the range of 20 μm to 125 μm, particularly preferably within the range of 30 μm to 80 μm. This is because if the thickness of the substrate is thinner than the above range, the self-supporting property required for the optical functional film produced according to the present invention may not be obtained. Further, if the thickness is thicker than the above range, for example, when cutting the optical function film produced according to the present invention, the processing waste may increase or the cutting blade may be worn quickly. It is.

  In addition, as long as the base material used in the present invention has the above optical characteristics, a flexible material having flexibility or a rigid material having no flexibility can be used, but a flexible material should be used. Is preferred. This is because by using a flexible material, the production process of the optical functional film of the present invention can be a roll-to-roll process, and an optical functional film excellent in productivity can be obtained.

  Examples of the flexible material include cellulose derivatives, norbornene polymers, cycloolefin polymers, polymethyl methacrylate, polyvinyl alcohol, polyimide, polyarylate, polyethylene terephthalate, polysulfone, polyethersulfone, amorphous polyolefin, modified acrylic polymer, polystyrene, epoxy Resins, polycarbonates, polyesters and the like can be exemplified, and among them, cellulose derivatives and norbornene-based polymers are preferably used.

  As the cellulose derivative, it is preferable to use a cellulose ester, and among the cellulose esters, it is preferable to use cellulose acylates. This is because cellulose acylates are advantageous in terms of availability because they are widely used industrially.

  As said cellulose acylates, C2-C4 lower fatty acid ester is preferable. The lower fatty acid ester may include only a single lower fatty acid ester such as cellulose acetate, and may include a plurality of fatty acid esters such as cellulose acetate butyrate and cellulose acetate propionate. There may be.

  In the present invention, among the above lower fatty acid esters, cellulose acetate can be particularly preferably used. As the cellulose acetate, it is most preferable to use triacetyl cellulose having an average acetylation degree of 57.5 to 62.5% (substitution degree: 2.6 to 3.0). Since triacetyl cellulose has a molecular structure with relatively bulky side chains, the rod-shaped compound contained in the composition for forming an optical functional layer penetrates into the substrate by constituting the substrate from triacetyl cellulose. This is because the adhesion between the substrate and the optical functional layer can be further improved in the optical functional film produced according to the present invention. Moreover, since triacetylcellulose is easy to express the property as a negative C plate, it becomes easy to form the random homogeneous orientation of the said rod-shaped compound. 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). In addition, the acetylation degree of the triacetyl cellulose constituting the triacetyl cellulose film can be determined by the above method after removing impurities such as a plasticizer contained in the film.

  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. Since the cycloolefin polymer has low moisture absorption and permeability, the base material used in the present invention is composed of the cycloolefin polymer, so that the optical functional film obtained by the present invention can be stable over time. This is because it can be made excellent.

  Specific examples of the cycloolefin polymer used in the present invention include trade name Arton manufactured by JSR Corporation and trade name ZEONOR manufactured by Nippon Zeon Co., Ltd.

  The base material used in the present invention is preferably subjected to a stretching treatment. By performing the stretching treatment, the rod-shaped compound easily penetrates into the substrate, and due to this, the adhesion between the substrate and the optical functional layer is excellent, and the rod-shaped compound is more homogeneous. This is because an optical functional layer having a random homogeneous orientation can be formed.

  The stretching treatment is not particularly limited and may be arbitrarily determined according to the material constituting the substrate. Examples of such a stretching process include a uniaxial stretching process and a biaxial stretching process. Of these, the stretching treatment in the present invention is preferably a biaxial stretching treatment.

  The stretching method of the biaxial stretching treatment is not particularly limited as long as it can impart desired negative C plate properties to the base material. In the present invention, for example, a roll stretching method is used. It can be appropriately carried out by any stretching method such as long gap stretching method, tenter stretching method, tubular stretching method and the like. In the stretching treatment, the polymer film is preferably heated to, for example, a glass transition temperature or higher and a melting point temperature or lower.

The structure of the base material in the present invention is not limited to a structure composed of a single layer, and may have a structure in which a plurality of layers are laminated. When it has the structure by which the several layer was laminated | stacked, the layer of the same composition may be laminated | stacked, and the several layer which has a different composition may be laminated | stacked.
As the structure of the base material in which a plurality of layers having different compositions are laminated, for example, a film made of a material for randomly orienting the rod-like compound such as triacetyl cellulose and a cycloolefin polymer having excellent water permeability are used. A mode of laminating with the support can be exemplified.

2. Next, a method for producing an optical functional film by forming an optical functional layer on the substrate using the composition for forming an optical functional layer in the present invention will be described. In the method for producing an optical functional film of the present invention, the optical functional layer is formed by directly coating the optical functional layer forming composition on the substrate.

  The coating method for applying the optical functional layer forming composition on the substrate is not particularly limited as long as the method has a uniform thickness and can achieve desired flatness. Specifically, gravure coating method, reverse coating method, knife coating method, dip coating method, spray coating method, air knife coating method, spin coating method, roll coating method, printing method, dip pulling method, curtain coating method, die coating Examples thereof include, but are not limited to, a method, a casting method, a bar coating method, an extrusion coating method, and an E-type coating method.

  The thickness of the coating film of the composition for forming an optical functional layer is not particularly limited as long as the desired flatness can be achieved, but is preferably in the range of 0.1 μm to 50 μm, In particular, the range of 0.5 μm to 30 μm is preferable, and the range of 0.5 μm to 10 μm is particularly preferable. If the thickness of the coating film of the composition for forming an optical functional layer is thinner than the above range, the planarity of the optical functional layer may be impaired. If the thickness is thicker than the above range, the drying load of the solvent increases and production This is because the performance may deteriorate.

  As a method for drying the coating film of the optical functional layer forming composition, a commonly used drying method such as a heat drying method, a reduced pressure drying method, a gap drying method, or the like can be used. In addition, the drying method in the present invention is not limited to a single method, and a plurality of drying methods may be employed, for example, by changing the drying method sequentially according to the amount of solvent remaining.

  When a polymerizable material is used as the rod-shaped compound, a method for polymerizing the polymerizable material is not particularly limited, and may be arbitrarily determined according to the type of polymerizable functional group of the polymerizable material. . In particular, in the present invention, a method of curing by irradiation with actinic radiation is preferable. The actinic radiation is not particularly limited as long as it is a radiation capable of polymerizing a polymerizable material, but it is usually preferable to use ultraviolet light or visible light from the viewpoint of the ease of the device, etc. Among them, it is preferable to use irradiation light having a wavelength of 150 to 500 nm, preferably 250 to 450 nm, and more preferably 300 to 400 nm.

  As the light source of this irradiation light, low pressure mercury lamp (sterilization lamp, fluorescent chemical lamp, black light), high pressure discharge lamp (high pressure mercury lamp, metal halide lamp), short arc discharge lamp (super high pressure mercury lamp, xenon lamp, mercury xenon) Lamp). Among these, use of a metal halide lamp, a xenon lamp, a high-pressure mercury lamp, etc. is recommended. The irradiation intensity can be appropriately adjusted according to the content of the photopolymerization initiator.

3. Optical Function Film Finally, the optical function film manufactured by the method for manufacturing an optical function film of the present invention will be described. The optical functional film produced by the present invention has a base material and an optical functional layer directly formed on the base material. In the optical functional layer, the rod-shaped compound forms a random homogeneous alignment.

The optical functional film produced by the present invention is characterized by excellent transparency due to the optical functional layer being formed using the optical functional layer forming composition.
The optical functional film produced by the present invention has the advantage that, when used for an optical compensation film for a liquid crystal display device, for example, unevenness and white turbidity are less likely to occur and high display quality can be achieved. Have.
In addition, the optical functional film produced according to the present invention allows the substrate and the optical functional layer to be firmly adhered to each other by forming the optical functional layer directly on the substrate. It has the advantage that it does not produce etc.
Furthermore, the optical functional film produced according to the present invention is excellent in the expression of optical characteristics that act as a negative C plate because the rod-like compound forms a random homogeneous orientation in the optical functional layer.

  Hereinafter, the optical function film manufactured by the method for manufacturing an optical function film of the present invention will be described in detail. In addition, about the random homogeneous orientation in this invention, since it is the same as that of what was demonstrated in the above-mentioned item of "A. Composition for optical function layer formation", description here is abbreviate | omitted.

  The thickness of the optical functional film produced according to the present invention is not particularly limited as long as it is within a range in which desired optical characteristics can be expressed, but usually within a range of 30 μm to 200 μm, particularly 30 μm to 150 μm. Within the range, it is preferable to be within the range of 30 μm to 100 μm.

  The optical functional film produced according to the present invention preferably has a haze value measured in accordance with JIS K7105 in the range of 0.1% to 5%, particularly in the range of 0.1% to 1%. It is preferable that it is in a range of 0.1% to 0.5%.

  The retardation (Rth) in the thickness direction of the optical functional film produced according to the present invention may be appropriately selected according to the use of the optical functional film, and is not particularly limited. In particular, in the present invention, the thickness direction retardation (Rth) is preferably in the range of 50 nm to 500 nm, more preferably in the range of 100 nm to 400 nm, and particularly preferably in the range of 100 nm to 400 nm. When the retardation (Rth) in the thickness direction is within the above range, the optical function film produced according to the present invention is suitable for improving the viewing angle characteristics of a VA (Vertical Alignment) liquid crystal display device. Because it can. Here, since the definition of the retardation in the thickness direction (Rth) and the measurement method are the same as those described in the section “1. Substrate”, the description thereof is omitted here.

Further, the in-plane retardation (Re) of the optical functional film produced according to the present invention may be appropriately selected according to the use of the optical functional film, and is not particularly limited. In particular, in the present invention, the in-plane retardation (Re) is preferably in the range of 0 nm to 5 nm, more preferably in the range of 0 nm to 3 nm, and particularly in the range of 0 nm to 1 nm. More preferred. When the in-plane retardation (Re) is within the above range, the optical functional film produced according to the present invention is suitable for improving the viewing angle characteristics of a VA (Vertical Alignment) liquid crystal display device. This is because it can be used as a film.
Here, the definition of the in-plane retardation (Re) and the measurement method are the same as the contents described in the section “1. Substrate”, and thus the description thereof is omitted here.

  The in-plane retardation (Re) value may have wavelength dependency. For example, the long wavelength side may have a larger value than the short wavelength side, and the short wavelength side may have a larger value than the long wavelength side.

  The application of the optical functional film produced by the present invention is not particularly limited, and can be used for various applications as an optical functional film. Specific applications of the optical function film of the present invention include, for example, an optical compensator (for example, a viewing angle compensator), an elliptically polarizing plate, and a luminance improving plate used in a liquid crystal display device. Especially in this invention, it can use suitably for the use as a negative C plate. Thus, when 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.

  The optical function film of the present invention can be used for a polarizing plate by being bonded to a polarizer. A polarizing plate is usually formed by forming a polarizing plate and a polarizing plate protective film on both surfaces thereof. In the present invention, for example, an optical functional film in which the polarizing plate protective film on one side is produced according to the present invention. Thus, for example, a polarizing plate having an optical compensation function for improving the viewing angle characteristics of a liquid crystal display device can be obtained.

  Although it does not specifically limit as said polarizer, For example, a dye type polarizer using a dichroic dye, a dichroic dye, a polyene type polarizer, etc. can be used. In general, iodine-based polarizers and dye-based polarizers are manufactured using polyvinyl alcohol.

  Furthermore, the optical function film of the present invention may be used after being subjected to a stretching treatment. A mode for performing such a stretching treatment is not particularly limited, and examples thereof include a mode in which the optical functional film obtained by the present invention is stretched and used as a biaxial film.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the technical idea described in the claims of the present invention has substantially the same configuration and exhibits the same function and effect regardless of the case. It is included in the technical scope of the invention.

  Hereinafter, the present invention will be described more specifically with reference to examples.

Example 1
As a nematic liquid crystal, a compound represented by the following formula (I) was used and dissolved in a mixed solvent of anone: isopropyl alcohol = 9: 1 in a mass ratio of 20% by mass. A photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy Japan, Inc.) was prepared so as to be 1% by mass with respect to the mass of the nematic liquid crystal, and a composition for forming an optical functional layer was produced.

The ink composition was applied onto a 80 μm thick triacetylcellulose (TAC) film substrate by a bar coating method, dried in a 50 ° C. oven for 2 minutes, and then 100 mJ / cm ² under a nitrogen atmosphere. Were cured by irradiating with ultraviolet rays to form an optical functional layer, thereby producing an optical (compensation) film.

(Example 2)
An optical (compensation) film was produced in the same manner as in Example 1 except that a mixed solvent of anone: n-propyl alcohol = 9: 1 was used in a mass ratio.

(Example 3)
An optical (compensation) film was produced in the same manner as in Example 1 except that a mixed solvent of anone: n-propyl alcohol = 8: 2 was used in terms of mass ratio.

(Comparative Example 1)
An optical (compensation) film was produced in the same manner as in Example 1 except that a mixed solvent of anone: isopropyl alcohol = 7: 3 was used in a mass ratio.

(Comparative Example 2)
An optical (compensation) film was produced in the same manner as in Example 1 except that a mixed solvent of anone: n-propyl alcohol = 7: 3 was used in a mass ratio.

(Comparative Example 3)
A nematic liquid crystal similar to that used in Example 1 was dissolved in 20% by mass in a solvent composed only of anone. A photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy Japan, Inc.) was adjusted to 1% by mass with respect to the mass of the nematic liquid crystal to prepare a composition for forming an optical functional layer. Thereafter, an optical (compensation) film was produced in the same manner as in Example 1.

(Evaluation)
(1) Haze and total light transmittance (%)
The haze and total light transmittance of the optical (compensation) films prepared in the above examples and comparative examples were measured according to the method specified in JIS K 7361.

(2) Unevenness and cloudiness under crossed Nicols For the optical (compensation) films produced in the above examples and comparative examples, commercially available polarizing plates (HCL2-5618HCS, manufactured by Sanlitz Co., Ltd.) are arranged on both sides in a crossed Nicol arrangement. Then, they were installed on a liquid crystal backlight, and the degree of unevenness and cloudiness on the front surface was visually observed and evaluated under a dark room. The criteria for judging the degree of cloudiness are as follows.
○: No cloudiness is observed, transparency is high and good.
X: White turbidity was observed, transparency was lowered, and it was poor.

  The evaluation results are shown in Table 1. As shown in Table 1, the optical (compensation) film in the examples had good unevenness and cloudiness under haze and crossed Nicols. On the other hand, none of the optical (compensation) films in the comparative examples had good haze and unevenness and white turbidity under crossed Nicols.

It is the schematic which shows an example of the optical function film which has an optical function layer formed using the composition for optical function layer formation of this invention. It is a schematic sectional drawing which shows an example of the conventional phase difference film. It is a schematic sectional drawing which shows an example of the conventional phase difference film.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Base material 2 ... Optical functional layer 3 ... Rod-shaped compound 10 ... Optical functional film 21 ... Base material 22 ... Orientation film 23 ... Optical functional layer 40 ... Phase difference film 100 ... Liquid crystal display device 102A, 102B ... Polarizing plate 104 ... Liquid crystal cell

Claims (6)

An optical functional layer forming composition comprising a rod-shaped compound and a mixed solvent comprising an alcohol solvent and another organic solvent,
The composition for forming an optical functional layer is characterized in that the amount of the alcohol solvent in the mixed solvent is in the range of 5% by mass to 20% by mass.   2. The optical functional layer forming composition according to claim 1, wherein the optical functional layer forming composition is used for forming an optical functional layer in which the rod-like compound has formed a random homogeneous orientation. Composition.   The composition for forming an optical functional layer according to claim 1, wherein the rod-shaped compound has a polymerizable functional group.   The composition for forming an optical functional layer according to any one of claims 1 to 3, wherein the rod-like compound is a liquid crystalline material.   The composition for forming an optical functional layer according to claim 4, wherein the liquid crystalline material is a material exhibiting a nematic phase. Using a substrate having properties as a negative C plate and the composition for forming an optical functional layer according to any one of claims 1 to 5,
Optical having a base material and an optical functional layer containing a rod-like compound that is directly formed on the base material and has formed a random homogeneous orientation by applying the optical functional layer forming composition on the base material. A method for producing an optical functional film, comprising producing a functional film.

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