KR102314448B1 - Optical resin material, method for preparing said optical resin material, optical resin member formed of said material and polarizing plate comprising said member - Google Patents

Abstract

The present invention is a resin material useful for optical applications in which orientation birefringence is very small or a desired value, and a resin product such as an optical film having reduced temperature dependence of intrinsic birefringence that affects optical properties can be stably and reliably obtained. to provide technology. The present invention also relates to an optical resin material comprising a composite component system in which the number of components z defined under the condition of counting the raw number of (co)polymer x (x≥1) in the number of components is 2 or more. , using the uniaxially stretched film composed of the composite component system, in a state in which the temperature of the film is controlled stepwise in the range of 15 to 70 ° C., the intrinsic birefringence Δn ⁰ at each temperature is measured, respectively, from the obtained measurement results An optical resin material in which the absolute value of the intrinsic birefringence temperature coefficient at 15° C. to 70° C. calculated as the amount of change in intrinsic birefringence per 1° C. is ^{within the range of 1.0×10 -5} (° C. ^-1 ) or less, and the temperature dependence of intrinsic birefringence is reduced , a method for producing the optical resin material, a film-shaped optical resin member and a polarizing plate made of the material.

Description

An optical resin material, a method of manufacturing the optical resin material, an optical resin member made of the material, and a polarizing plate comprising the member MEMBER}

In particular, the present invention relates to an optical resin material in which temperature dependence of intrinsic birefringence of a polymer is suppressed (that is, intrinsic birefringence does not change with measurement temperature), and intrinsic birefringence is adjusted to almost zero or a desired value, the optical resin material It relates to a manufacturing method, an optical resin member made of these materials, and a polarizing plate made of the member.

In recent years, the spread and development of liquid crystal displays are dazzling, and it is not an exaggeration to say that they are used for all products of electronic devices. And in the monitor of a desktop PC, the liquid crystal TV, etc., the enlargement is also advancing, and the product of 40 inches or more has come out a lot. A liquid crystal panel generally used for a liquid crystal display has a structure in which a liquid crystal component is sandwiched between two glass substrates, a cell for liquid crystal display, and a polarizing plate, and a polarizing film is generally applied to the surface of each substrate. , a retardation film, an antireflection film, and the like have a structure in which optical members such as an optical film capable of exhibiting various functions are laminated. A light-transmitting resin called "optical resin" or "optical polymer" is widely used for the material of such an optical member. In addition, the optical member which consists of these resin materials is not limited for the object for the liquid crystal display mentioned above, It is used for various optical-related apparatuses. For example, in addition to the above, a lens in a lens system for signal reading of an optical disk, a plastic lens such as a Fresnel lens for a projection screen, or a lenticular lens, etc., has more excellent optical properties. It is also used as a requested|required functional member.

Here, from the viewpoint of the productivity, the resin film is produced by, for example, melt extrusion molding and stretching. In various optical films or plastic lenses made of optical polymers manufactured in this way, the polymer molecules are oriented in one direction for various reasons and are not in an ideal amorphous state, and the refractive index is different depending on the polarization direction of the incident light. , that is, it is known that birefringence occurs. There are several known types of birefringence of polymers, but what is important for transparent polymers used in optical films for liquid crystal displays and plastic lenses used in the above-mentioned various optical devices is " orientation birefringence" and "photoelastic birefringence".

On the other hand, there is known a method of substantially eliminating one of orientation birefringence and photoelastic birefringence by selection of an additive to the light-transmitting polymer and its concentration, or a combination of copolymerization and selection of a composition ratio. In the method, the attenuation of the other side was insufficient. Under these circumstances, the inventors of the present application propose a method of simultaneously attenuating and substantially eliminating orientation birefringence and photoelastic birefringence of an optical resin material, and an optical resin (optical polymer) in which both orientation birefringence and photoelastic birefringence are very small, and The proposal regarding the application of the said resin to the optical member (optical element, an optical component, etc.) is made (refer patent document 1).

Specifically, for an optical material having a complex component system of three or more components including a binary system or more copolymer system, the combination and component ratio (composition ratio) of the components of the composite component system, the optical material has both orientation birefringence and photoelastic birefringence. A method of selecting so as to be canceled at the same time has been proposed, whereby an optical resin having very small both orientation birefringence and photoelastic birefringence is obtained. As a result, the problem of light leakage due to birefringence can be improved, and by using the obtained optical resin, "color unevenness phenomenon", "light leakage", "color change dependent on observation angle", etc. occurring in the screen can be eliminated. making it possible to suppress

Japanese Patent Publication No. 4624845

However, as a result of intensive studies by the present inventors, in the prior art, an optical resin having very small both orientation birefringence and photoelastic birefringence was obtained in a three-component or more complex component system including a binary or higher copolymer system. The optical properties in the film are at room temperature, and it has been newly recognized that there are the following technical problems in an actual use environment. Specifically, in the prior art described above, the composite component system is determined using the intrinsic birefringence of each homopolymer corresponding to each monomer constituting each component of the copolymer, and in this case, the intrinsic birefringence is set at room temperature (room temperature). , but it was newly discovered that intrinsic birefringence has a temperature dependence and, in particular, the tendency increases with temperature increase, the present inventors have come to recognize that it is necessary to consider this point. That is, as described above, optical films are used in various optical-related devices. For example, mobile phones and PCs are not necessarily used at so-called normal temperature, and even in a very cold or sweltering temperature environment. In particular, since these devices generate heat during operation, various heat dissipation and cooling means are considered, but the temperature of the optical film locally increases. On the other hand, if a product that takes into account the temperature dependence of intrinsic birefringence newly discovered by the present inventors, which affects the optical properties, is obtained, it is practically extremely useful.

Therefore, it is an object of the present invention to stably and reliably obtain a resin product such as an optical film in consideration of the temperature dependence of intrinsic birefringence (i.e., orientation birefringence intrinsic to polymer) that affects the optical properties newly discovered by the present inventors. It is an object to provide a technique that can stably and reliably obtain a resin material useful for optical applications having very small intrinsic birefringence and reduced temperature dependence. If such a technology is provided, "color spot phenomenon", "light leakage" or "color change depending on observation angle" occurring in the screen due to the optical film used in various optical devices used in various temperature ranges It becomes possible to suppress the etc. reliably, and it becomes possible to design stable, high-performance liquid crystal displays etc. Another object of the present invention is to appropriately use the above technique, to set the intrinsic birefringence to a desired value after considering the temperature dependence, and to stably and reliably adjust a resin material useful for optical applications in which the temperature dependence is reduced. It is an object of providing a technique that makes it possible to synthesize a polymer that easily exhibits orientation birefringence, for example. If such a technique is provided, for example, in the case of a retardation film for a liquid crystal display, in the manufacturing process, it is necessary to adjust the orientation birefringence and thickness so as to obtain a desired retardation by stretching the film, but stretching is easy to manufacture. With the magnification, it becomes possible to obtain a film having a desired orientation birefringence, and thus a great advantage in manufacturing is obtained.

Regarding the problems of the prior art described above, the present inventors have intensively studied, and as a result, for example, in an optical resin material having a binary or more complex component system including a binary or more copolymerized system or a unimodal or more (co)polymerized system. In contrast, when designing the combination of the types of monomer components constituting the composite component system and the component ratio (composition ratio), the inventors newly discovered intrinsic birefringence affecting optical properties (that is, intrinsic orientation birefringence) The method of reducing the temperature dependence in was discovered, and led to this invention.

The above object is achieved by the following present invention. That is, the present invention relates to an optical resin comprising a composite component system in which the number of components z defined under the conditions of counting the raw number x (x≥1) of the (co)polymer in the number of components is 2 or more. As a material, the composite component system consists only of a copolymer having an element number x of 2 or more, or a polymer having an element number x of 1 or a copolymer having an element number x of 2 or more, and an anisotropy of polarizability and at least capable of being oriented in the polymer Composed of one low molecular weight organic compound, the combination of components constituting the composite component system is the intrinsic birefringence temperature coefficient of each homopolymer corresponding to each monomer component forming the copolymer or polymer, and the low molecular weight At least one of the intrinsic birefringence temperature coefficients that the organic compound exhibits in common among the respective homopolymers is selected to have a different sign from the others, and the component ratio of each component constituting the composite component system is a different sign regarding the intrinsic birefringence temperature coefficient By using the relationship, the optical resin material is selected such that the intrinsic birefringence temperature dependence is canceled out.

^{As a preferred form of the optical resin material, intrinsic birefringence Δn 0} at each temperature is obtained using a uniaxially oriented film composed of the composite component system, in a state in which the temperature of the film is controlled stepwise in the range of 15 to 70 ° C. ^{The absolute value of the intrinsic birefringence temperature coefficient dΔn 0} /dT at 15° C. to 70° C. obtained as the amount of change in intrinsic birefringence per 1° C. from the measurement results obtained by each measurement is 1.0 × 10 ^-5 (° C. ^-1 ) or less within the range , in which the temperature dependence of intrinsic birefringence is reduced.

In addition, the present invention is an optical resin material comprising a composite component system in which the number of components z defined on the condition that the number of components x (x≥2) of the copolymer is counted by including the number of components in the number of components, the composite component system is Consists of only a copolymer in which x is 3 or more, or a copolymer in which x is 2 or more, and at least one low molecular weight organic compound that has anisotropy of polarization and can be oriented in a polymer, constituting the composite component system The combination of components is each sign of intrinsic birefringence of each homopolymer corresponding to each monomer component forming the copolymer, and a sign of orientation birefringence that the low molecular weight organic compound has in common among the homopolymers. At least one of at least one has a different sign from the other, and at least one of the intrinsic birefringence temperature coefficient of each homopolymer and the intrinsic birefringence temperature coefficient common among the homopolymers of the low molecular weight organic compound is different from the other It is selected to have a different sign, and the component ratio of each component constituting the composite component system is the intrinsic birefringence and An optical resin material is provided, characterized in that the intrinsic birefringence temperature dependence is selected such that it cancels out at the same time.

The following are mentioned as a preferable aspect of the said optical resin material. Using the uniaxially oriented film composed of the composite component system, in a state in which the temperature of the film is controlled stepwise in the range of 15 to 70° C., the intrinsic birefringence Δn ⁰ at each temperature is measured, respectively, and 1 from the obtained measurement result The absolute value ^{of the intrinsic birefringence temperature coefficient dΔn 0} /dT at 15 ° C to 70 ° C, calculated as the amount of change in intrinsic birefringence per ° C, is ^{within the range of 1.0 × 10 -5} (℃ ^-1 ) or less, and the temperature dependence of intrinsic birefringence is reduced. being; An optical resin material composed of a copolymer made by copolymerizing three or more types of monomer components, wherein the combination of the above three types of monomer components and the composition ratio of these monomer components are each homopolymer corresponding to each monomer component. ^{The intrinsic birefringence Δn 0} at 25° C. of the uniaxially oriented film made ^{of the film and the intrinsic birefringence Δn 0} at each temperature were measured in a state where the temperature of the film was controlled stepwise in the range of 15 to 70° C., and the measurement results obtained from is determined by using the intrinsic birefringence Temperature dΔn ⁰ / dT calculated as the amount of change of 1 ℃ per intrinsic birefringence, the intrinsic birefringence Δn ⁰ in unconfined 25 ℃ as measured with the stretched film made of the copolymer, its absolute value is 3.0×10 ⁻³ or less, adjusted to be almost zero, or adjusted so that the absolute value of intrinsic birefringence at 25°C becomes a desired value of 0.01 or more, and in any case, at 15°C to 70°C The temperature dependence of the intrinsic birefringence is reduced, adjusted so that the absolute value of the intrinsic birefringence temperature coefficient dΔn ⁰ /dT is 1.0×10 ^-5 (° C. ^{-1 ) or less.}

In addition, the present invention, as another embodiment, as a method for producing any one of the above optical resin materials, determining the type of the monomer component of the composite component system selected as a raw material, and determining the composition ratio of two or more selected monomer components Having a raw material adjusting process, in the raw material adjusting process, with respect to the uniaxially oriented film made of each homopolymer corresponding to each monomer component, in a state in which the temperature of the film is controlled stepwise in the range of 15 to 70 ° C. ^{The intrinsic birefringence temperature coefficient dΔn 0} /dT, which is the amount of change in intrinsic birefringence per 1 ° C., is calculated from the obtained measurement results, and the intrinsic birefringence temperature coefficient dΔn ⁰ /dT and measured at 25 ° C. Create a relationship graph with the intrinsic birefringence Δn ⁰ , and from the relationship graph, a composition in which the intrinsic birefringence Δn ⁰ measured at 25° C. and the intrinsic birefringence temperature coefficient dΔn ⁰ /dT together becomes zero A combination in which a composition may exist, or By selecting a combination in which a composition in which the intrinsic birefringence temperature coefficient dΔn ⁰ /dT is zero and the absolute value of intrinsic birefringence at 25°C becomes a desired value of 0.01 or more is selected, the type of monomer component is determined, and ^{, the intrinsic birefringence Δn 0} measured at 25 ° C inherent to the copolymer made by copolymerizing the selected monomer component is zero, or the absolute value of the intrinsic birefringence measured at 25 ° C. becomes a desired value of 0.01 or more, and the intrinsic Assuming that the birefringence temperature coefficient dΔn ⁰ /dT becomes zero, by calculating the mass ratio of each monomer component, the composition ratio of the monomer components to be combined is determined, the monomer component of the selected and determined type is used, and the monomer component It provides a method for producing an optical resin material, characterized in that the copolymer is synthesized by copolymerizing the monomers blended so as to have the determined composition ratio.

When determining the composition ratio of the monomer components to be combined as a preferred form of the method for producing the optical resin material, the monomer components are N types (where N is an integer of 3 or more), and unique to a copolymer made by copolymerizing these monomer components. Assuming that the intrinsic birefringence and intrinsic birefringence temperature coefficient together become 0 (zero) or the desired value, calculate the mass fraction of each monomer using the following simultaneous equations, and determine the composition ratio of monomers constituting the copolymer thing can be heard

[In the formula (i), Δn ⁰ ₁ represents the intrinsic birefringence of the first homopolymer, Δn ⁰ ₂ represents the intrinsic birefringence of the second homopolymer, and Δn ⁰ _N is the N-th homopolymer shows the intrinsic birefringence of . In the above formula (ii), dΔn ⁰ ₁ /dT represents the intrinsic birefringence temperature coefficient of the first homopolymer, dΔn ⁰ ₂ /dT represents the intrinsic birefringence temperature coefficient of the second homopolymer, and dΔn ⁰ _N /dT represents the intrinsic birefringence temperature coefficient of the N-th homopolymer. In the above formula (iii), W ₁ , W ₂ , and W _N represent the mass fraction (%) of the first, second, and Nth monomers, respectively.]

Further, the present invention provides a film-shaped optical resin member, wherein any one of the above optical resin materials is formed into a film and adjusted so that the temperature dependence indicated by the intrinsic birefringence does not occur. As the preferable aspect, the film-shaped optical resin member formed by forming an adhesive layer in at least one surface of the said film further is mentioned. Furthermore, this invention provides the polarizing plate which consists of these film-shaped optical resin members, The polarizing plate characterized by the above-mentioned.

Here, in the present specification, ^{"nearly zero" intrinsic birefringence Δn 0} means that it is zero or close to zero and can be regarded as almost zero, and if expressed numerically, its absolute value is 3.0 × 10 ^{- It} means that it is 3 or less, Furthermore, it is more preferable in it being ^{1.0x10 -3 or less.} In addition, when expressed numerically, "the temperature dependence of intrinsic birefringence is reduced" means that the intrinsic birefringence at each temperature is measured in a state in which the temperature of the uniaxially oriented film is controlled stepwisely in the range of 15 to 70 ° C. ^{And, when the intrinsic birefringence temperature coefficient "dΔn 0} /dT", which is the amount of change in intrinsic birefringence per 1 ° C., is calculated from these measurement results, the absolute value is within the range of ^{1.0 × 10 -5} (° C. ^{-1 ) or less.} it means that

According to the present invention, for example, as a resin useful for optical applications with very small orientation birefringence, a resin product such as an optical film in consideration of the temperature dependence of intrinsic birefringence that affects optical properties can be stably and reliably obtained. technology is provided. As a result, "staining phenomenon", "light leakage" or "color dependent on the observation angle" that occurs in the screen due to the optical film used in various temperature ranges and used in various optical-related devices that generate heat by operation in particular. change", etc. can be suppressed reliably, and it becomes possible to design stable, high-performance liquid crystal displays, etc. Further, according to the present invention, there is provided a technique that makes it possible to adjust the orientation birefringence to a desired value after taking the temperature dependence into account, and to synthesize a polymer that tends to exhibit orientation birefringence. For example, in the case of a retardation film for a liquid crystal display, in the manufacturing process, it is necessary to adjust the orientation birefringence and thickness so that the desired retardation is obtained by stretching the film. can be obtained, and further, extremely useful effects on the industry are obtained, such as being able to stably and reliably prepare a resin material useful for optical applications with reduced temperature dependence. In addition, in a liquid crystal display, an optical resin member formed by forming a pressure-sensitive adhesive layer on at least one surface of a film in which the film-shaped optical resin material provided by the present invention is further processed using an adhesive is used for a liquid crystal display, conventionally A very useful effect in practical use is obtained in that it is possible to control the problems of "color unevenness", "light leakage", "color change depending on the viewing angle", etc.

^{1 shows the intrinsic birefringence Δn 0} at 25° C. measured using films each formed with each homopolymer corresponding to the four monomers, and the intrinsic birefringence amount of change per 1° C. obtained for these homopolymers. A copolymer (copolymer) composed of a combination of a birefringence coefficient dΔn ⁰ /dT and, in that case, monomers thereof, three kinds of monomers in which ^{Δn 0} and dΔn ^{0 /dT of the copolymer are both 0 (zero)} It is a diagram showing that there are two types of combinations.
2 shows the orientation of a film formed of a polymer having almost zero intrinsic birefringence at 25° C. formed with a ternary copolymer P (MMA/TFEMA/BzMA = 52.0/42.0/6.0) made by copolymerizing three types of monomers. A diagram showing the temperature dependence of birefringence Δn _{or .} MMA is an abbreviation for methyl methacrylate, TFEMA is an abbreviation for 2,2,2-trifluoroethyl methacrylate, and BzMA is an abbreviation for benzyl methacrylate.
3 is a diagram showing the temperature dependence ^{of the intrinsic birefringence Δn 0} of a film formed of a polymer having almost zero intrinsic birefringence at 25° C. made by copolymerizing the three monomers shown in FIG. 2 .
4 is a diagram showing the temperature dependence ^{of the intrinsic birefringence Δn 0} of a film formed of a two-component copolymer P (MMA/MeMI = 82/18) formed by copolymerizing two types of monomers. MeMI is an abbreviation for methyl maleimide.
Fig. 5 shows (a) orientation birefringence Δn in each of the three-component copolymer P (MMA/PhMA/BzMA = 39/23/38) prepared in Example 1 and the homopolymer PMMA of MMA, which is one of the monomers used. _{A graph showing the relationship between or} and the degree of orientation, and (b) a diagram showing the temperature dependence of the ^{intrinsic birefringence Δn 0 .}
6 shows the intrinsic birefringence Δn in each of the three-component copolymer P (MMA/PhMA/EMI = 29/54/17) prepared in Example 3 and the homopolymer of MMA, which is one of the monomers used (abbreviated as PMMA). ^It is a diagram showing the temperature dependence of 0. PhMA is an abbreviation for phenyl methacrylate, and EMI is an abbreviation for ethyl maleimide.
7 is a conceptual diagram of a temperature control device for a sample film used when examining the temperature dependence of intrinsic birefringence.
^{8 is a graph showing the intrinsic birefringence Δn 0} at 25° C. measured using a film formed from each homopolymer corresponding to the three monomers and the photoelastic coefficient C obtained from the photoelastic birefringence measured using the film. It is a graph showing the relationship, and as a combination of these monomers, it is a diagram showing that the composition of a copolymer (copolymer) in which ^{Δn 0 and C are both 0 (zero).}

Next, the present invention will be described in more detail by giving preferred modes for carrying out the invention.

First, each term used in the present invention will be described. "Orientation birefringence" is generally birefringence expressed when the main chain of a chain polymer (polymer chain) is oriented, for example, a manufacturing process by extrusion molding and stretching of a polymer film, and injection molding It arises in the manufacturing process of various polymer optical elements and components. That is, the polymer chains oriented by stress in the molding process are generally not relaxed during cooling and solidification , and the main chains are oriented in the film and optical element, which causes orientation birefringence.

The "orientation birefringence" is generally performed by heating the polymer film to be measured above its glass transition temperature, uniaxially stretching in a softened state, and then cooling and solidifying, and then measuring at room temperature with a commercially available birefringence measuring device. can At that time, as shown in Formula (1), a polymer main chain of linearly polarized light having a polarization plane (a plane including the propagation direction of light and the vibration direction of the electric field) in the direction parallel to and perpendicular to the uniaxial stretching direction. The difference (n _p -n _{d ) between the refractive index n p in} the parallel direction and the refractive index n _{d in} the orthogonal direction is defined as orientation birefringence Δn _{or .}

In addition, the case where this Δn _or is not zero is said to be "birefringence is occurring", and the value is called "oriented birefringence". In addition, when Δn _or is a positive (+) value, that is, when the refractive index in the parallel direction is large, "positive orientation birefringence" is called, and when Δn _or is a negative (-) value, that is, orthogonal direction The case where the refractive index of is large is called "negative orientation birefringence". Further, it is known that zero birefringence can be achieved at the molecular level by random copolymerizing a positive orientation birefringence monomer and a negative orientation birefringence monomer in an appropriate ratio, and it has also been put to practical use as a polymer for pickup lenses of optical discs.

In the above, when linearly polarized light enters the stretched film, when the passing light is decomposed into two orthogonal linearly polarized light, retardation (retardation) occurs due to birefringence. The retardation Re has the same relationship with the orientation birefringence and thickness d of the film as shown in the following formula (2).

In a general measuring apparatus, there are many things which can measure said retardation. _{This means that orientation birefringence (DELTA)n or} can be calculated|required by calculation by dividing the result of retardation obtained by measurement by the film thickness d.

Here, the orientation birefringence Δn _or can be related to the above-described orientation degree f, the intrinsic birefringence Δn ⁰ , and the expression (3). That is, the degree to which the polymer main chain is oriented is referred to as the degree of orientation and is expressed as "f", and "f" takes a value between 0 and 1.

f = 1 means that all polymer molecules are constant (completely stretched state), and f = 0 means that the polymer molecules are completely random. "Intrinsic birefringence" (DELTA)n ⁰ corresponds to orientation birefringence at the time of orientation degree f = 1, and is an intrinsic property according to the kind of polymer. This degree of orientation f can be measured by an infrared dichroism method or the like. Therefore, by measuring the orientation degree f and orientation birefringence (DELTA)n _or , respectively, "intrinsic birefringence (DELTA)n ⁰ " in the polymer film to be measured can be calculated|required. As described above, orientation birefringence is a value resulting from the fact that the polymer is not fully relieved during cooling and solidification after melting, and the main chain exists in an oriented state in the film and optical element. By examining in detail the value of intrinsic "intrinsic birefringence", various studies are being conducted from the viewpoint of enabling selection of an ideal material in which orientation birefringence does not occur in optical applications using polarized light.

In addition, in an optical element/part formed of a polymer, in addition to the orientation birefringence described above, volume shrinkage that occurs when generally cooled to a temperature near the glass transition temperature (Tg) to a temperature lower than that, or applied at a temperature below Tg There is photoelastic birefringence caused by external stress. This photoelastic coefficient is an intrinsic property according to the kind of polymer. As described above, the present inventors have so far produced the above-mentioned "oriented birefringence" and "photoelastic birefringence" at the same time even if the optical film is manufactured by a conventional optical film manufacturing method such as melt extrusion, which is prone to birefringence. A design method capable of obtaining an optical film without light leakage is proposed.

Industrially manufactured optical elements and parts made of polymers are generally "a method of heating a polymer to a glass transition temperature or higher, molding it in a molten state, and cooling it to solidify", such as extrusion molding, stretching, and injection molding. Many are manufactured by Therefore, orientation birefringence tends to occur as described above, and photoelastic birefringence tends to occur when stress is applied to the obtained optical element at a glass transition temperature or lower. Such birefringence becomes a factor for reducing the performance of the optical film of a liquid crystal display, various lenses, etc. which are calculated|required to maintain the polarization state of incident polarized light. On the other hand, the present inventors have already paid attention to the above-described intrinsic birefringence and photoelastic coefficient, and selected three or more monomer components (repeating unit structures) having different combinations of signs in each of them, any of which is approximately zero. By adjusting the copolymer composition ratio as much as possible, a polymer that essentially does not cause orientation birefringence or photoelastic birefringence is obtained. By using the polymer synthesized in this way, it is possible to obtain optical films, optical elements, and parts having almost zero birefringence, which is an extremely important technique for applications requiring such low birefringence.

Moreover, if this technique is applied, it will become possible to adjust an intrinsic birefringence to a certain suitable value, and to synthesize|combine the polymer which is easy to express orientation birefringence. For example, in the case of a retardation film for a liquid crystal display, in the manufacturing process, orientation birefringence and thickness are adjusted so that the desired retardation is obtained by stretching the film. The range of stretching conditions, such as etc., is also limited in reality. That is, in order to obtain a desired orientation birefringence with a draw ratio which is easy to manufacture, it is preferable that intrinsic birefringence is a certain range.

Various types of retardation film are manufactured and marketed industrially, and according to the mode and structure of a liquid crystal display, it is suitably selected and used. Hereinafter, a preferable range of intrinsic birefringence will be described in terms of design, taking as an example a quarter wave plate used in many liquid crystal displays. In a quarter wave plate, in principle, retardation of a quarter of a wavelength is given, but the polymer has a wavelength dependence of birefringence, and visible light is not a single wavelength, but a wavelength of about 400 nm to 800 nm. In general, design is often based on the wavelength vicinity of green light having high visibility (eg, around 550 nm). Here too, if the design is based on a wavelength of 550 nm, first, a quarter wavelength is 137.5 nm. Although the commercial item of retardation film is about 100 micrometers in thickness or less normally, research and development are advancing aiming at the further thinning of about 20 micrometers in recent years. Here, for a film having a thickness of 100 μm, the orientation birefringence Δn _or is about 1.4×10 ^{−3 according to the} above formula (2). The intrinsic birefringence Δn ⁰ calculated by is about 0.014. The absolute value of the intrinsic birefringence required for a film material is low since it became also possible to obtain a higher orientation degree by the improvement of the recent extending|stretching technique. When these are considered, the preferable absolute value of intrinsic birefringence in the case of manufacturing retardation film is 0.01 or more, More preferably, it is 0.05 or more, More preferably, it is 0.1 or more. The said orientation degree f can be measured by the infrared absorption dichroism method mentioned later, etc. In addition, when it is difficult to measure the degree of orientation, in a polymer with low crystallinity, if _{the absolute value of orientation birefringence Δn or} in a film with a thickness of about 100 μm or less is about 1.4 × 10 ^-3 or more, the absolute value of intrinsic birefringence is estimated to be 0.01 or more can do. The reason for this presumption is that, except for crystalline polymers, most of the polymers that do not satisfy this condition are not reported. As described above, in some applications, such as optical films for liquid crystal displays, it is particularly important to adjust the intrinsic birefringence of the polymer to substantially zero or a suitable desired value, and material design taking this point into consideration is being done

The present inventors discovered the following important facts in the process of developing an optical film, such as a retardation film, designed by the method as described above as a product suitable for the above request, and at the same time, the environment in which the product using the optical film is used In view of the fact that there is a possibility that the temperature of the optical film may also rise due to heat generated during operation of the mounted product, which spans a wide variety of fields, it has been recognized that it is necessary to add improvement to the previously proposed method. That is, the present inventors measured the temperature dependence of the intrinsic birefringence of a polymer in the process of conducting detailed examinations, and the value of intrinsic birefringence is not constant with respect to temperature, it changes, and in particular, the tendency increases with temperature rise. It made a new discovery that was not previously recognized at all. Until now, the intrinsic birefringence of a polymer is usually measured at room temperature (room temperature), and various discussions have been made with this as an intrinsic value according to the polymer. This means that various developments have been made on the premise of the quality of the product under the conditions of room temperature (room temperature). On the other hand, for example, the usage environment of the liquid crystal display to which the optical film is applied spans a wide range, under extremely cold conditions, in a vehicle in midsummer, under a work environment accompanied by heat generation, etc., in extreme heat exceeding 60 ° C. Many are used under the conditions of In addition, it is known that electronic equipment itself generates heat during operation, and also in this respect, the optical film is affected by temperature. The present inventors, in light of this situation, in the development of an optical film, considering the temperature dependence in the intrinsic birefringence of the polymer discovered by the present inventors provides an optical film product that can stably express more excellent performance I felt it was necessary to do it. According to the studies of the present inventors, for example, it is known that there is a temperature dependence on the intrinsic birefringence of the stretch haze (TAC) of a retardation plate used for a polarizing plate for a VA liquid crystal used in a liquid crystal TV, and furthermore, there is a large tendency of the temperature dependence. could This is, at least, in order to make a polarizing plate mounted on a product that generates heat during operation higher quality than that of the conventional one, the reduction of the temperature dependence of the intrinsic birefringence discovered by the present inventors is the required performance, and the material of the product considering the temperature dependence It means doing development becomes important.

Here, when the present inventors studied in detail about the temperature dependence of the intrinsic birefringence of a polymer so far, when they discovered the following. First, it was confirmed that the temperature dependence of the intrinsic birefringence resulting from the orientation of the main chain of the polymer chain is similarly temperature dependent even in a polymer species having almost zero intrinsic birefringence (that is, almost no orientation). In addition, as a result of measuring the rate of change of intrinsic birefringence with respect to temperature (intrinsic birefringence temperature coefficient) for various polymers, these are also properties inherent to the polymer, and that there are those with positive (+) and negative (-) signs. Confirmed.

As described above, the present inventors, using the conventional measurement results for intrinsic birefringence and photoelastic coefficient, select three or more types of monomer components (repeating unit structures) having different combinations of signs in each of them, It is also proposed to adjust the copolymer composition ratio so that it may become substantially zero, and the polymer which does not raise|generate orientation birefringence and photoelastic birefringence essentially is obtained. However, the above new discovery is that there is a temperature dependence on the measurement result of the intrinsic birefringence of each homopolymer, which was conventionally considered to exhibit an intrinsic value regardless of temperature, used in determining the monomer composition, the inventors of the present invention In order to provide an optical film with excellent performance stably maintained even under a wide range of operating temperature environments or when the mounted device generates heat due to operation, it is recognized that new technology development is necessary in consideration of this point. came to do The present inventors, as a result of detailed examination under the above recognition, have also obtained a new discovery that the rate of change of intrinsic birefringence with respect to temperature (intrinsic birefringence temperature coefficient) is also an inherent property of a polymer, and using this, the temperature in intrinsic birefringence In consideration of dependence, it has been found that a polymer design in which the effect of temperature change is suppressed can be realized, and the present invention has been achieved.

More specifically, in the present invention, focusing on the fact that the temperature dependence (intrinsic temperature coefficient of intrinsic birefringence) of the intrinsic birefringence of the homopolymer shows positive (+) or negative (-), respectively, a repeat composed of their monomer composition Provided is a technique for obtaining a copolymer (polymer) or the like having a desired intrinsic birefringence temperature dependence by appropriately selecting a unit structure and adjusting it to an appropriate copolymer composition ratio. A polymer having almost zero intrinsic birefringence and having an intrinsic birefringence temperature coefficient of zero (always zero, birefringence does not change with temperature) realized by the technique provided in the present invention, or a suitable suitable intrinsic birefringence desired A polymer having a size and an intrinsic birefringence temperature coefficient of zero is considered to be particularly promising when it is used as a retardation film for a liquid crystal display as described below. The retardation film is used to compensate for the birefringence of the liquid crystal layer of a liquid crystal panel and other optical films (three-dimensionally canceling the birefringence and eliminating the effect of birefringence), If it can be compensated, it is extremely useful. In addition, according to the technology provided by the present invention, for example, when the birefringence of a liquid crystal layer or other optical film changes depending on the temperature, the opposite intrinsic birefringence temperature coefficient is set to cancel it. It is also possible to provide suitably, and the practically remarkable effect that the compensation method can be made into various is also acquired.

In addition, as described above, a material exhibiting a desired value of intrinsic birefringence can be stably and reliably obtained, furthermore, the temperature dependence is reduced, and a resin material in which intrinsic birefringence is suppressed from changing with temperature can be reliably and stably obtained. If it can be obtained, since intrinsic birefringence is stably maintained with respect to temperature change, optical films, such as retardation film obtained using this material, the performance is maintained stably. For this reason, a liquid crystal display constructed using such a retardation film or the like is an excellent product that can stably maintain high performance even when used in various temperature environments or when the mounted device generates heat during operation. .

The optical resin material with reduced temperature dependence of intrinsic birefringence of the present invention can be carried out in the same way as the design method in the case of obtaining a polymer having substantially zero intrinsic birefringence and zero photoelastic coefficient, which the present inventors proposed earlier. As a result, as will be described later, a resin material useful for optical applications having very small intrinsic birefringence, which has a reduced temperature dependence, and intrinsic birefringence, which is the object of the present invention, is a desired value, and the temperature For a resin material useful for optical applications with reduced dependence, an optical film with stable performance can be easily and reliably obtained by designing a monomer composition according to the following formula and determining the synthesis conditions of the resin so as to match the obtained monomer composition.

Here, first, about the design method in the case of obtaining a copolymer with almost zero intrinsic birefringence and zero photoelastic coefficient, previously proposed by the present inventors, methyl methacrylate (MMA) and 2,2,2-trifluoro A ternary copolymer consisting of roethyl methacrylate (TFEMA) and benzyl methacrylate (BzMA) will be described in detail as an example.

^{The intrinsic birefringence Δn 0} of the ternary copolymer synthesized so as to have a mass ratio of _{W PMMA} , W _PTFEMA , and W _PBzMA of the three monomer components, respectively, is obtained by using each intrinsic birefringence of the homopolymer synthesized from each monomer. , can be obtained by the following formula (4). In addition, the photoelastic coefficient C of the terpolymer synthesized such that _{the monomer component has a mass ratio of W PMMA} , W _PTFEMA , and W _{PBzMA is obtained by using the following formula (} 5) can be obtained. The following formula (6) is a formula showing the monomer composition of the ternary copolymer, and shows that three kinds of monomer components are copolymerized at a mass ratio (%) of _{W PMMA} , W _PTFEMA , and W _{PBzMA .}

In the above formula (4), Δn ⁰ _PMMA represents the intrinsic birefringence of the homopolymer of MMA (PMMA), Δn ⁰ _PTFEMA represents the intrinsic birefringence of the homopolymer of TFEMA (PTFEMA), and Δn ⁰ _{PBzMA represents the intrinsic birefringence of the BzMA} It shows the intrinsic birefringence of the homopolymer (PBzMA). In the formula (5), C _PMMA represents the photoelastic coefficient of the homopolymer of MMA, C _{PTFEMA represents the photoelastic coefficient of the homopolymer of TFEMA} , and C PBzMA represents the photoelastic coefficient of the BzMA homopolymer .

In the above formula (4), ^{the value of the intrinsic birefringence Δn 0} of the ternary copolymer on the left side is zero (Δn ⁰ = 0), and in the above equation (5), the value of the photoelastic coefficient C of the ternary copolymer on the left side is zero (C = 0), and by solving the equation by simultaneous with equation (6), both intrinsic birefringence Δn ⁰ and photoelastic coefficient C become zero (hereinafter also referred to as zero-zero birefringence polymer). ), a monomer composition of MMA, TFEMA, and BzMA that enables the synthesis of W _PMMA /W _PTFEMA /W _PBzMA = 52.0/42.0/6.0 is obtained. Then, when a ternary copolymer having such a monomer composition is actually synthesized and its intrinsic birefringence and photoelastic coefficient are measured, it becomes almost zero under a temperature condition of 25°C.

The design method of the ternary copolymer according to the simultaneous equations described above is easier to understand when considered with reference to FIG. 8 . 8 : is a graph which took the photoelastic coefficient as a vertical axis, and intrinsic birefringence as a horizontal axis, but the present inventors call the "birefringence map". Although the values in PMMA, PTFEMA and PBzMA of the homopolymer composed of each monomer are plotted in FIG. 8, it can be seen that the triangle connecting these includes the origin. As is mathematically clear, in this case, a solution is obtained when the left sides of the above-described equations (4) and (5) are set to zero and sequencing. In addition, by measuring the intrinsic birefringence and photoelastic coefficient for various homopolymers as described above, and plotting these values in the birefringence map, when a copolymer of any kind of monomer combination is obtained, a zero-zero birefringence polymer will be obtained. It is possible to visually judge whether or not Then, for a combination in which a solution including the origin (zero) is obtained, by solving the formulas (4) to (6) to obtain the monomer composition, it is possible to easily and reliably prepare a birefringent polymer having both intrinsic birefringence and photoelastic coefficient of zero.

(Measuring method of birefringence)

"Intrinsic birefringence of a polymer" in this specification is measured by the following method. First, a suitable organic solvent is used, the polymer solution to be measured is adjusted, a film is prepared from the solution, and the orientation birefringence and the orientation degree are measured using the obtained film as follows, and from these measured values obtained The intrinsic birefringence of the polymer was determined. To explain the three-component polymer composed of the above monomers as an example, first, the obtained polymer was put in a glass sample tube together with tetrahydrofuran in a mass ratio of 4 times, stirred, and sufficiently dissolved. Then, the polymer solution was developed in a glass plate shape to a thickness of about 0.3 mm using a knife coater, left to stand at room temperature for one day, and dried. Next, the obtained film was removed from the glass plate, and further dried for 48 hours in a reduced pressure dryer at 60° C., the obtained polymer film having a thickness of about 40 μm was processed into a dumbbell shape, and a Tensilon general-purpose testing machine (Orien Co., Ltd.) Tech (manufactured by ORIENTEC Co., Ltd.) was uniaxially stretched. At this time, the extending|stretching temperature was adjusted to 120-140 degreeC, the extending|stretching speed|rate was adjusted to the range of 2-30 mm/min., a draw ratio 1.1-3.0, etc., and the film of several orientation degrees f was produced. And the orientation birefringence of the film after extending|stretching was measured using the automatic birefringence measuring apparatus ABR-10A (Uniopt Co., Ltd. product). In addition, the orientation degree of the film after extending|stretching was measured by the infrared absorption dichroism method. And the value of orientation birefringence measured as mentioned above was divided by the orientation degree of the film after extending|stretching (or extrapolated), and the intrinsic birefringence of the said polymer was calculated|required. In addition, the intrinsic birefringence of the film made of the polymer measured by the above method was 0.16×10 ⁻³ at 25° C., and at room temperature, it was a size that could be regarded as almost zero.

(Temperature dependence of intrinsic birefringence)

Using a polymer having almost zero intrinsic birefringence composed of the ternary copolymer (MMA/TFEMA/BzMA = 52.0/42.0/6.0) obtained as described above, hot stretching for 40 mm at 102°C, 40 mm/min, and stretching Then, the temperature dependence of the intrinsic birefringence was investigated for the sample stored at room temperature for 24 hours, controlling the temperature to 16 degreeC - 70 degreeC. Specifically, the retardation (Re) when the temperature was raised by the temperature control device was measured. 2, the measurement result of orientation birefringence was shown. This was calculated|required by dividing the measured retardation by the film thickness of 28 micrometers. In addition, what divided this by the orientation degree f=0.107 of the polymer molecular chain in a polymer film is intrinsic birefringence shown in FIG. As can be seen from these figures, the birefringence was zero in the vicinity of room temperature at 25°C, but the birefringence increased as the temperature increased. As can be seen from these figures, this temperature dependence had a relatively linear relationship with the temperature. Moreover, when the value of orientation birefringence 0.10*10 ^-3 is multiplied by 80 micrometers in thickness of a general polarizing plate protective film, it turns out that it corresponds to 8 nm by retardation. Generally, 1 nm retardation can be visually recognized when it arrange|positions between orthogonal nicols (polarizing plates made orthogonal), Thus, it turns out that the influence of the birefringence change by this temperature change is large.

(Examination of temperature dependence of intrinsic birefringence of polymer)

From the above results, the present inventors conducted the same tests on optical films of various monomer compositions, investigated the temperature dependence of intrinsic birefringence, and showed an example of the results in FIG. 4 .

The example shown in FIG. 4 is a two-component copolymer composed of MMA/MeMI (methylmaleimide), and the copolymer composition is MMA/MeMI=80/20. As shown in FIG. 4 , it was confirmed that the intrinsic birefringence of the polymer exhibits temperature dependence, similarly to the three-component copolymer illustrated in FIG. 3 shown earlier. The intrinsic birefringence temperature coefficient dΔn ⁰ /dT was 2.9×10 ⁻⁵ ° C. ⁻¹ . Although not shown, it was confirmed that both the polymer exhibiting positive (+) intrinsic birefringence at room temperature and the polymer having negative (-) intrinsic birefringence at room temperature had temperature dependence.

(Temperature dependence of intrinsic birefringence of each homopolymer)

All of the polymers showing the results in Figs. 3 and 4 showed a positive (+) correlation with respect to temperature, but it was found that the degree was not uniform and varied depending on the monomer composition. Here, in order to examine the difference in degree, the degree of correlation was compared with the amount of change in Δn per 1°C for homopolymers corresponding to various monomers. ^{In Table 1, the value of the intrinsic birefringence Δn 0} at 25° C. (room temperature) of each polymer and the intrinsic birefringence ^{temperature coefficient dΔn 0} /dT, which is the amount of change in Δn per 1° C. obtained by measuring while controlling the temperature at 15° C. to 70° C. showed the results of As a result, it was recognized that the degree of correlation with temperature tends to depend on the side chain structure of each polymer. For example, it was suggested that it is low in a polymer having a rigid structure, and is high in a polymer having a structure that is not rigid and has a large polarization anisotropy. In addition, in Table 1, PPhMA is an abbreviation of a homopolymer of phenyl methacrylate, PMI is an abbreviation of a homopolymer corresponding to polymaleimide, PMeMI is an abbreviation of a homopolymer corresponding to polymethylmaleimide, and PEMI is , is an abbreviation for homopolymer corresponding to polyethylmaleimide, PCHMI is an abbreviation for homopolymer corresponding to polycyclohexylmaleimide, and the others are the same abbreviations for homopolymer as described above.

[Table 1]

Temperature dependence of intrinsic birefringence of each homopolymer

The monomer forming the copolymer or polymer constituting the optical resin material of the present invention is not limited to the above-described monomers, and for example, aromatic monomers, acrylic monomers, vinyl monomers, and maleimide monomers exemplified below. , polar monomers, etc. can be appropriately used.

Examples of the aromatic monomer include styrene, alpha-methylstyrene, benzyl (meth)acrylate, alkylphenoxypolyalkylene glycol (meth)acrylate, and 6-(4,6-dibromo-2-isopropyl). Phenoxy)-1-hexyl acrylate, 6-(4,6-dibromo-2-s-butylphenoxy)-1-hexyl acrylate, 2,6-dibromo-4-nonylphenyl acrylate , 2,6-dibromo-4-dodecylphenyl acrylate, 2- (1-naphthyloxy) -1-ethyl acrylate, 2- (2-naphthyloxy) -1-ethyl acrylate, 6 -(1-naphthyloxy)-1-hexyl acrylate, 6-(2-naphthyloxy)-1-hexyl acrylate, 8-(1-naphthyloxy)-1-octyl acrylate, 8-( 2-naphthyloxy)-1-octyl acrylate, 2-phenylthio-1-ethyl acrylate and phenoxyethyl (meth)acrylate can be exemplified, but are not limited thereto.

As an acryl-type monomer, the (meth)acrylate etc. which have an alkyl (meth)acrylate and an alkyl cyclic or a heterocyclic ring in a side chain are mentioned, for example. Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, isobutyl (meth) acrylate, n-hexyl (meth) Acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl ( meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-dodecyl (meth) acrylate, n-tridecyl (meth) acrylate, and n-tetradecyl (meth) Acrylates etc. are mentioned. These may be used individually by 1 type, and may use 2 or more types together. In addition, alkyl (meth)acrylate means an alkyl acrylate and/or an alkyl methacrylate.

Examples of the vinyl-based monomer include vinyl acetate, vinyl chloride, vinyl toluene, and various vinyl ethers.

Examples of the maleimide-based monomer include N-phenylmaleimide, N-(2-methylphenyl)maleimide, N-(2-ethyl)phenylmaleimide, N-(2-isopropyl)phenylmaleimide, N -(3-methylphenyl)maleimide, N-(3-ethylphenyl)maleimide, N-(4-methylphenyl)maleimide, N-(4-ethylphenyl)maleimide, N-(2,6-dimethylphenyl) ) Maleimide, N- (2,6-diethylphenyl) maleimide, N- (2,6-diisopropylphenyl) maleimide, N- (2,4,6-trimethylphenyl) maleimide, N- Carboxyphenylmaleimide, N-(2-chlorophenyl)maleimide, N-(2,6-dichlorophenyl)maleimide, N-(2-bromophenyl)maleimide, N-(perbromophenyl)maleimide , N-(2,4-dimethylphenyl)maleimide, para-tolyl maleimide, and the like. Examples of N-alkyl-substituted maleimides other than the above phenylmaleimides include N-methylmaleimide, N-ethylmaleimide, Nn-propylmaleimide, Ni-propylmaleimide, Nn-butylmaleimide, Ni-butylmaleimide, Ns-butylmaleimide, Nt-butylmaleimide, Nn-pentylmaleimide, Nn-hexylmaleimide, Nn-heptylmaleimide, Nn-octylmaleimide, N-laurylmaleimide, N -N-alkyl-substituted maleimides, such as stearyl maleimide, N-cyclopropyl maleimide, N-cyclobutyl maleimide, N-cyclohexyl maleimide, and N-methylcitraconimide, etc. are mentioned.

As a polar monomer, an ethylenically unsaturated carboxylic acid, an ethylenically unsaturated sulfonic acid, an ethylenically unsaturated phosphoric acid, a hydroxyl-containing monomer, a nitrogen-containing monomer, etc. are mentioned, for example.

Examples of the ethylenically unsaturated carboxylic acid include acrylic acid, methacrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. have.

As another polar monomer, Hydroxyl group containing monomers, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate; (meth)acrylamide, N Amide group-containing monomers, such as N-dimethyl (meth)acrylamide, N-methylol (meth)acrylamide, N-methoxymethyl (meth)acrylamide, and N-butoxymethyl (meth)acrylamide; amino group-containing monomers such as 2-(N,N-dimethylamino)ethyl (meth)acrylate; glycidyl group-containing monomers such as glycidyl (meth)acrylate; Alkoxysilyl group-containing monomers such as propyltrimethoxysilane (meth)acrylate, propyldimethoxysilane (meth)acrylate, and propyltriethoxysilane (meth)acrylate; (meth)acrylonitrile, N- (meth) ) acryloylmorpholine, N-vinyl-2-pyrrolidone, and the like.

Moreover, as another monomer, acrylonitrile, methacrylonitrile, etc. are mentioned, for example. In addition, neopentyl glycol di (meth) acrylate, hexanediol di (meth) acrylate, propylene glycol di (meth) acrylate, trimethylol propane tri (meth) acrylate, tetramethylolmethane tetra (meth) acrylic What has two or more polymerizable functional groups, such as a rate and dipentaerythritol hexa (meth)acrylate, is mentioned.

Said (co)polymer can be manufactured by normal solution polymerization, block polymerization, emulsion polymerization or suspension polymerization, actinic radiation polymerization, etc.

The optical resin material of the present invention is composed of a copolymer or polymer formed with the above monomers and a low molecular weight organic compound that can be oriented in these polymers, and is a resin material with reduced temperature dependence of intrinsic birefringence. may be Various plasticizers as illustrated below are mentioned as a low molecular weight organic compound which has the anisotropy of polarizability and can be orientated in a polymer which can be used in that case, for example. Representative plasticizers include, for example, polyoxyethylene aryl ether, dialkyl adipate, 2-ethylhexyldiphenyl phosphate, t-butylphenyldiphenyl phosphate, di(2-ethylhexyl)adipate, toluenesulfonamide, di Propylene glycol dibenzoate, polyethylene glycol dibenzoate, polyoxypropylene aryl ether, dibutoxyethoxyethyl formal, and dibutoxyethoxyethyl adipate are mentioned. In the present invention, compounds containing two aromatic groups are particularly effective, for example, 1,2-diphenylethene (alias: trans-stilbene) or diphenylsulfide, diethyleneglycoldiol as a benzoic acid ester type. Benzoate, dipropylene glycol dibenzoate, benzyl benzoate, 1, 4- cyclohexane dimethanol dibenzoate, etc. are mentioned. In addition, the method of counting the number of "aromatic groups" counts condensed rings, such as a naphthalene ring, to one.

According to the study of the present inventors, by adding the low molecular weight organic compound as exemplified above to the (co)polymer described above, the intrinsic birefringence (Δn ⁰ ) and the intrinsic birefringence temperature coefficient (Δn ⁰ / dT) can be changed. The results of examination on this point are shown below. Specifically, trans-stilbene and diphenyl sulfide are each taken as examples of low molecular weight organic compounds, and an optical resin material obtained by adding these low molecular weight organic compounds to PMMA is filmed, and for each film, the intrinsic birefringence (Δn ⁰ ) and the intrinsic birefringence temperature coefficient (Δn ⁰ /dT) were measured, respectively. In Table 2 below, the result was put together and shown. At this time, the addition amount of the low molecular weight compound to PMMA was made into 2 types, 3 mass % and 10 mass %, and each film was produced. ^{In addition, for comparison, the intrinsic birefringence (Δn 0} ) and the intrinsic birefringence temperature coefficient (Δn ⁰ /dT) inherent to PMMA without addition of a low molecular weight compound are shown together in Table 2. As shown in Table 2, by adding a low molecular weight organic compound to the (co)polymer PMMA, the intrinsic birefringence (Δn ⁰ ) and intrinsic birefringence temperature coefficient (Δn ⁰ /dT) of the (co)polymer correspond to the amount added. ) was confirmed to change. This means that the (co)polymer can be designed to reduce the intrinsic birefringence temperature dependence of the obtained film by a simple method of adding an appropriate amount of a low molecular weight organic compound as exemplified above.

[Table 2]

Intrinsic birefringence and intrinsic birefringence temperature coefficient when a low molecular weight organic compound is added to PMMA

The optical resin material in which the temperature dependence of intrinsic birefringence prescribed|regulated by this invention is reduced can be obtained easily and reliably by the following method. For example, intrinsic birefringence and intrinsic birefringence temperature coefficient of a copolymer made by copolymerizing the monomer components as described above are both 0 (zero), or intrinsic birefringence at 25° C. suitable for the production of retardation films, etc. Assuming that the absolute value of is a desired value of 0.01 or more, and assuming that the intrinsic birefringence temperature coefficient becomes 0 (zero), the mass fraction of each monomer can be calculated by solving the following simultaneous equations, and the above-described target performance It is possible to determine the composition ratio of the monomers constituting the copolymer showing Therefore, the copolymer exhibiting the desired performance can be easily obtained by blending and polymerizing the monomers in consideration of the reactivity and reaction conditions of the respective monomers so that the desired monomer composition ratio obtained above may be obtained.

[In the formula (i), Δn ⁰ ₁ represents the intrinsic birefringence of the first homopolymer, Δn ⁰ ₂ represents the intrinsic birefringence of the second homopolymer, and Δn ⁰ _N is the N-th homopolymer shows the intrinsic birefringence of . In the above formula (ii), dΔn ⁰ ₁ /dT represents the intrinsic birefringence temperature coefficient of the first homopolymer, dΔn ⁰ ₂ /dT represents the intrinsic birefringence temperature coefficient of the second homopolymer, and dΔn ⁰ _N /dT represents the intrinsic birefringence temperature coefficient of the N-th homopolymer. In the above formula (iii), W ₁ , W ₂ , and W _N represent the mass fraction (%) of the first, second, and Nth monomers, respectively.]

More specifically, for example, a resin material useful for an optical film in which the intrinsic birefringence targeted by the present invention is a polymer having substantially zero or a desired value, and the temperature dependence of these intrinsic birefringence is reduced, is three types. In the case of a copolymer consisting of a monomer of, it can be obtained by the following method. First, by the method shown in Fig. 8 described above, the kind of monomer component capable of forming a polymer having substantially zero intrinsic birefringence is selected. Here, it is assumed that three types of monomers from the first to the third are selected. Next, for each film made of a homopolymer corresponding to each of these three types of monomers, the temperature dependence of intrinsic birefringence is investigated in the same manner as described above, respectively, and each intrinsic birefringence temperature coefficient dΔn ⁰ /dT is obtained save And it is assumed that the mass fractions (%) of the three types of monomers from the first to the third are W ₁ , W ₂ , and W ₃ , respectively, and the following simultaneous equations (iv) to (vi) are established. And, for example, the left side of the equation (iv) is zero (Δn ⁰ = 0), and the left side of the equation (v) is zero (dΔn ⁰ /dT = 0), and the solution of _{W 1} , W _{2 , W 3 is} By obtaining , it is possible to obtain a polymer having almost zero intrinsic birefringence, and furthermore, a polymer having zero intrinsic birefringence temperature coefficient and no temperature dependence on orientation birefringence. Further, at this time, when the value of the left side of the expression (iv) and the value of the left side of the expression (v) are set to desired values, the orientation birefringence is adjusted to the desired value, and furthermore, the temperature dependence of the liquid crystal display is reduced. It is possible to obtain an optical film useful for the retardation film of

What made the above-mentioned formulas (i)-(iii) into a formula of three components (N=3) is the following formula.

According to the simultaneous equations of (iv) to (vi), for example, a polymer having almost zero intrinsic birefringence, and furthermore, the design method of a ternary copolymer for obtaining a polymer having zero intrinsic birefringence temperature coefficient is described above. Similar to Fig. 8, it is easier to understand when we think about Fig. 1 . 1 is also used for designing the monomer composition ratio for synthesizing an optical resin material in Examples to be described later. In the above formula, the first monomer is MMA and the corresponding homopolymer is PMMA, and the first monomer in the formula is PMMA. The second monomer is PhMA, the corresponding homopolymer is PPhMA, the third monomer in the above formula is EMI or BzMA, and the corresponding homopolymer is PEMI or PBzMA. In FIG. 1 , the intrinsic birefringence Δn ⁰ at 25° C. (room temperature) is taken on the abscissa axis, the intrinsic birefringence temperature coefficient dΔn ⁰ /dT is taken on the ordinate axis, and homopolymers corresponding to the respective monomers PMMA, PPhMA, PBzMA and PEMI are taken. , respectively, the intrinsic birefringence Δn ⁰ and the intrinsic birefringence temperature coefficient dΔn ⁰ /dT are plotted.

From Figure 1, it can be seen that the triangle connecting each plot of PMMA, PPhMA, and PEMI and the triangle connecting each plot of PMMA, PPhMA and PBzMA include the origin (Δn ⁰ = dΔn ⁰ /dT = 0). have. As is mathematically clear, in these cases, when all the left sides of the above-described formulas (iv) and (v) are set to zero, a solution is obtained. In this way, for various homopolymers, the intrinsic birefringence Δn ⁰ and temperature dependence at 25° C. (room temperature) are measured and the intrinsic birefringence temperature coefficient dΔn ⁰ /dT obtained by examining the temperature dependence is measured, and these values are plotted in the map. By doing so, it is possible to visually judge whether a polymer having a combination of monomers of any kind can be obtained, for example, as a polymer having substantially zero intrinsic birefringence and zero intrinsic birefringence temperature coefficient. And, for a combination in which a solution including the origin is obtained, if the monomer composition is obtained by solving the formulas (iv) to (vi), easily and reliably, the orientation birefringence is almost zero, and the orientation birefringence is an optical film having no temperature dependence. The composition ratio of the polymer that can obtain Therefore, by using the optical resin material of the present invention prepared by copolymerizing a plurality of monomers under the above design, the temperature dependence of the intrinsic birefringence of the resin is reduced, and even when used under various temperatures, stable optical properties are shown. It becomes possible to provide a more useful optical film product. In addition, without limiting to the description herein, by solving the equation of any N component in the above formulas (i) to (iii) under Δn ⁰ = dΔn ⁰ /dT = 0, the intrinsic birefringence is almost zero, Further, it is possible to design a polymer having an intrinsic birefringence temperature coefficient of almost zero and reduced temperature dependence of intrinsic birefringence. Usually, when it becomes the number of components more than 4 components, the monomer composition of the copolymer which can become a solution of an equation is obtained two or more.

[Example]

Next, an Example and a comparative example are illustrated and this invention is demonstrated more concretely. In addition, "part" or "%] in the text is based on mass unless otherwise specified.

(Design of monomer composition ratio)

In this example, the three types of monomers shown in FIG. 1, PhMA (first monomer), BzMA (second monomer) and EMI (third monomer) are selected, and a copolymer of these monomers is combined. When obtained, the optical film manufactured with the obtained copolymer was designed so that both intrinsic birefringence and intrinsic birefringence temperature coefficient became zero. Specifically, the composition ratio of the three types of monomers was calculated as described above using the following formulas (iv) to (vi).

Specifically, in this Example, in order to design a copolymer capable of obtaining an optical film in which both intrinsic birefringence and intrinsic birefringence temperature coefficient become zero, using the above simultaneous equations (iv) to (vi), Similarly, the mixing|blending of a monomer was computed. Substituting the intrinsic birefringence and intrinsic birefringence temperature coefficients for each of the homopolymers used above into the formulas (iv) to (vi), respectively, the following formulas (vii), (viii), and (ix) are obtained.

And, when the simultaneous equations are calculated by setting the left side of the formulas (vii) and (viii) to 0 (zero), as a mass fraction (%), MMA/PhMA/BzMA = 33/34/33 as a monomer composition ratio In the case of a synthesized copolymer, the intrinsic birefringence and intrinsic birefringence temperature coefficient of the optical film made of the copolymer are expected to be zero together.

(Synthesis of Polymer)

Hereinafter, the procedure for synthesizing the polymer will be described so that the mass fractions of the three monomers calculated in the above example have a monomer composition of MMA/PhMA/BzMA = 33/34/33. Aiming for a copolymer satisfying the above composition ratio obtained by calculation, taking into consideration the reactivity of each monomer used for polymerization, etc., in a glass sample tube, methyl methacrylate (MMA) and phenyl methacrylate (PhMA) ) and benzyl methacrylate (BzMA) were mix|blended so that it might become 41/22/37 by mass ratio. In addition, perbutyl O (trade name, manufactured by NOF CORPORATION) was added as a polymerization initiator in an amount set to 0.2 mass % with respect to the total amount of these monomers. After mixing and stirring these raw materials and making them uniform enough, it filtered through a membrane filter, and transferred to the test tube. These test tubes were placed in a hot water bath at 70°C, and polymerization was performed for 24 hours. Subsequently, heat treatment was performed in a dryer at 90°C for 24 hours.

The polymer thus obtained was dissolved in 10-fold amount of methylene chloride, and the obtained polymer solution was added dropwise to methanol to precipitate the polymer. The polymer was filtered and the remaining monomer was removed by sufficiently drying to obtain a ternary copolymer. As ^{a result of measuring the copolymerization ratio of this copolymer using 13} CNMR, the desired mass fraction and favorable agreement were obtained.

In the measured monomer ratio of the copolymer, the intrinsic birefringence at 25° C. calculated from the above formulas (iv) and (v) is Δn ⁰ =0.11×10 ^-3 , and the intrinsic birefringence temperature coefficient is dΔn ⁰ /dT = 0.32×10 ^-5 °C ^-1 .

(Measurement of optical properties of films produced from polymers)

A film was produced from the polymer obtained above as follows, and the optical properties of the obtained film were further investigated. First, the obtained polymer was put into a glass sample tube together with a 5-fold amount of methylene chloride by mass ratio, stirred, and was fully dissolved. Next, the obtained polymer solution was developed in a glass plate shape to a thickness of about 0.3 mm using a knife coater, left to stand at room temperature for one day, and dried. And the obtained film was peeled off from a glass plate, and it was further dried for 24 hours within a 90 degreeC vacuum dryer. The polymer film having a thickness of about 40 µm obtained as described above was processed into a dumbbell shape, and uniaxially stretched with a Tenshiron general-purpose testing machine (manufactured by Orientec, Ltd.). At this time, the stretching temperature was set to 114°C, and the stretching speed was set to 50 mm/min. , the stretching ratio was adjusted in the range of 1.5 to 2.5 and the like, and several films having an orientation degree f were produced. And the birefringence of the film after extending|stretching was measured using the automatic birefringence measuring apparatus ABR-10A (made by Uniopt Co., Ltd.), respectively. In addition, the orientation degree of the film after extending|stretching was measured by the infrared absorption dichroism method. As a result, the intrinsic birefringence of the film produced above was -0.16×10 ^-3 at 25° C., which was a size that could be regarded as almost zero.

(Temperature dependence of the film's intrinsic birefringence)

The temperature dependence of orientation birefringence and intrinsic birefringence was investigated while controlling the temperature at 12° C. to 70° C. for a sample of the hot-stretched film obtained as described above, which was stored at room temperature for 24 hours after stretching. Specifically, the retardation (Re) when the temperature was raised by a temperature control device was measured. The orientation birefringence was calculated|required by dividing this by the film thickness, and the result plotted with respect to the orientation degree f of a polymer was shown to Fig.5 (A). Moreover, the intrinsic birefringence was calculated|required from the orientation birefringence and the orientation degree f, and what measured the temperature change was shown in FIG.5(B). Here, the orientation degree f was considered to be constant in the measurement temperature range. As can be seen from these figures, in the film made of the copolymer prepared in the present Example, the birefringence hardly changed even if the temperature increased, and the temperature dependence was reduced. The intrinsic birefringence temperature coefficient of the prepared film was dΔn ⁰ /dT = 0.15×10 ⁻⁵ ° C. ⁻¹ . In addition, calculation of the intrinsic birefringence temperature coefficient was calculated|required from the data of 15 degreeC - 70 degreeC. In any case of this specification, the intrinsic birefringence temperature coefficient was computed from the data of 15 degreeC - 70 degreeC. In addition, for comparison, in FIG. 5, the measurement result of PMMA was also plotted similarly.

In the same manner as in Example 1, except that a copolymer having a monomer mass ratio of MMA/PhMA/BzMA = 40/27/33 of the copolymer was prepared, in the same manner as in Example 1, for the film obtained from the copolymer, intrinsic birefringence at 25°C and the intrinsic birefringence temperature coefficient were obtained. As a result, the intrinsic birefringence at 25 ° C. is Δn ⁰ = -0.22 × 10 ^-3 , and the intrinsic birefringence temperature coefficient is dΔn ⁰ /dT = 0.38 × 10 ^-5 ° C ^-1 , the copolymer prepared in this example. Also in the film made of , the birefringence hardly changed even when the temperature increased, and the temperature dependence was reduced.

In the same manner as in Example 1, except that a three-component copolymer was prepared in which the mass ratio of the monomer of the copolymer was MMA/PhMA/EMI = 29/54/17, the monomer composition was designed, and the copolymer so that the obtained monomer composition was obtained. was synthesized And about the film obtained from this copolymer, the intrinsic birefringence in 25 degreeC and the intrinsic birefringence temperature coefficient were calculated|required. 6 shows the results. As a result, the intrinsic birefringence at 25 ° C. is Δn ⁰ = -0.47 × 10 ^-3 , and the intrinsic birefringence temperature coefficient is ^{dΔn 0} /dT = -0.12 × 10 ^-5 ° C ^-1 , with the copolymer prepared in this example. In the film made, even when the temperature increased, the birefringence hardly changed, and the temperature dependence was reduced.

(Measurement of temperature dependence of intrinsic birefringence of polymer)

In the present invention, when the temperature dependence of intrinsic birefringence is investigated, the film sample having the configuration shown in FIG. 7 is used as a temperature control device for the film sample, so that the film sample at the time of birefringence measurement is reliably at the desired temperature. 1 in FIG. 7 is a sample holder whose center is a hollow, and by arranging a film sample in this hollow part, it has a structure which can ensure a sample at a desired temperature. This sample holder has two thermocouples shown by 2 and 3 in FIG. 7, and measures the temperature of a sample with these thermocouples. By properly operating the circulation type handy cooler TRL·108H·LM (manufactured by THOMAS KAGAKU Co., Ltd.) for a closed system shown at 4 in Fig. 7, the temperature of these thermocouples Let the temperature become the desired temperature, the sample is brought to the desired temperature, and the birefringence is measured in that state. Reference numeral 5 denotes a recorder for recording information from a thermocouple. In the present invention, a touch-type paperless recorder TR·V550 (trade name, manufactured by KEYENCE CORPORATION) was used. Intrinsic birefringence was measured using such an apparatus using a film sample with strict temperature control.

1: sample holder
2, 3: thermocouple
4: Circulation type handy cooler for closed systems
5: Recorder

Claims (10)

A method for producing an optical resin material comprising a composite component system of three or more components and having reduced temperature dependence of intrinsic birefringence, the method comprising:
having an adjustment step for adjusting each component constituting the copolymer, which is a composite component system of three or more components,
^{The intrinsic birefringence Δn 0} at each temperature of the uniaxially oriented film made of the copolymer adjusted in the adjustment step is controlled in stages in the range of 15° C. to 70° C. ^{The absolute value of the intrinsic birefringence temperature coefficient dΔn 0} /dT at 15° C. to 70° C. calculated as the amount of change in intrinsic birefringence per 1° C. from the measurement result obtained by measuring in the same manner is 1.0 × 10 ^-5 (° C. ^-1 ) or less The method for producing an optical resin material characterized in that ^{the intrinsic birefringence Δn 0} at 25° C. is within the range and its absolute value is 3.0×10 ^{−3 or less.}
(1) Measurement of retardation Re of the uniaxially oriented film
_{(2) The orientation birefringence Δn or} is obtained by dividing the measured value of retardation Re of the film by the thickness d of the film
(3) The orientation degree of the uniaxially oriented film is measured, and the orientation birefringence Δn _or when the orientation degree f=1 obtained using the measured orientation degree is taken as the measured value of the intrinsic birefringence Δn ⁰ at the individual temperature. A method for producing an optical resin material comprising a composite component system of three or more components and having reduced temperature dependence of intrinsic birefringence, the method comprising:
having an adjustment step for adjusting each component constituting the copolymer, which is a composite component system of three or more components,
^{The intrinsic birefringence Δn 0} at each temperature of the uniaxially oriented film made of the copolymer adjusted in the adjustment step is controlled in stages in the range of 15° C. to 70° C. ^{The absolute value of the intrinsic birefringence temperature coefficient dΔn 0} /dT at 15° C. to 70° C. calculated as the amount of change in intrinsic birefringence per 1° C. from the measurement result obtained by measuring in the same manner is 1.0 × 10 ^-5 (° C. ^-1 ) or less The method for producing an optical resin material characterized in that the ^{measured intrinsic birefringence Δn 0} at 25° C. is within the range and its absolute value is 0.01 or more.
(1) Measurement of retardation Re of the uniaxially oriented film
_{(2) The orientation birefringence Δn or} is obtained by dividing the measured value of retardation Re of the film by the thickness d of the film
(3) The orientation degree of the uniaxially oriented film is measured, and the orientation birefringence Δn _or when the orientation degree f=1 obtained using the measured orientation degree is taken as the measured value of the intrinsic birefringence Δn ⁰ at the individual temperature. The optical resin material obtained by the manufacturing method of the optical resin material of Claim 1 or 2 is adjusted so that the temperature dependence shown by the intrinsic birefringence formed by forming into a film shape, The film-form optics characterized by the above-mentioned. absence of resin. 4. The method of claim 3,
Moreover, the film-shaped optical resin member formed by forming an adhesive layer on at least one surface of the said film. A polarizing plate characterized in that the film-shaped optical resin member according to claim 3 is used as a forming material. A polarizing plate characterized in that the film-shaped optical resin member according to claim 4 is used as a forming material. delete delete delete delete

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