JP2013057706A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a large liquid crystal display device where display unevenness and light leakage are prevented.SOLUTION: A liquid crystal display device has a backlight light source, a liquid crystal cell, and two polarizers arranged on the visible side of the liquid crystal cell and the backlight light source side thereof. When the elastic modulus of a polarizer (PL1) arranged on the visible side under the environment of 50°C/10%RH in the long-side direction is E1, the elastic modulus of a polarizer (PL2) arranged on the backlight light source side under the environment of 50°C/80%RH in the long-side direction is E2, E2 is within the range of 2-10 GPa, and the absolute value |E1-E2| of a difference between E1 and E2 is within the range of 0-5.0 GPa.

Description

  The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device in which display unevenness does not occur.

  The demand for liquid crystal display devices is expanding in applications such as liquid crystal televisions and personal computer liquid crystal displays. In general, a liquid crystal display device is composed of a liquid crystal cell in which a transparent electrode, a liquid crystal layer, a color filter, etc. are sandwiched between glass plates, and two polarizing plates provided on both sides thereof. A child (also referred to as a polarizing film) is sandwiched between two optical films (also referred to as a polarizing plate protective film).

  However, the recent increase in the size and thickness of LCD TV screens, and the use of LED backlights as the light source, an upper polarizing plate (viewing-side polarizing plate) and a lower polarizing plate (with a liquid crystal cell in between) Depending on the combination of the light source side polarizing plate), the liquid crystal panel, the backlight unit, or both of them are deformed due to the design of the liquid crystal display device, and the members come into contact with each other to locally display unevenness (egg unevenness, hereinafter There is a problem of the occurrence of egg unevenness, and there is a need for improvement. In particular, the contribution of deformation accompanying the increase in the screen size is large, which is a more significant problem in liquid crystal televisions of 30 inches or more.

  Although the generation mechanism of egg unevenness is not yet clearly understood, as a result of analysis, egg unevenness may gradually occur under high-temperature and high-humidity conditions, and the present inventors have developed a liquid crystal panel and a liquid crystal display device accompanying deformation of members. It came to think that it was a contact with the diffusion plate which comprises.

  On the other hand, a technique for improving heat resistance by mixing a general-purpose acrylic resin and a cellulose resin and further improving the brittleness of the acrylic resin has been proposed (see, for example, Patent Documents 1, 2, and 3). Even if this film was used, the display unevenness was not sufficiently effective.

  Patent Document 4 describes that a configuration in which the difference between the dimensional change of the upper polarizing plate (viewing-side polarizing plate) and the dimensional change of the lower polarizing plate (light source-side polarizing plate) with a liquid crystal cell interposed therebetween is preferable. ing. However, even if the upper and lower balances are taken, for example, when the balance can be taken with a large change both in the upper and lower parts, a large residual stress remains in the film, resulting in a deviation from the designed optical value. There has been a problem that display unevenness and light leakage of the liquid crystal display device occur.

International Publication No. 2009/047924 JP 2009-1744 A JP 2009-179731 A JP 2010-032718 A

  The present invention has been made in view of the above-described problems, and a problem to be solved is to provide a liquid crystal display device free from display unevenness and light leakage in a large-sized liquid crystal display device.

As a result of intensive studies to solve the above problems, the present inventors have contributed greatly to the mechanical properties under high-temperature and high-humidity conditions with regard to the occurrence of egg unevenness. The inventors have found that the occurrence of egg unevenness and light leakage can be suppressed by controlling the elastic modulus in a humidity environment in an appropriate region. That is, the said subject of this invention can be solved by the following means.
1. A liquid crystal display device having a backlight light source, a liquid crystal cell, and two polarizing plates disposed on the viewing side of the liquid crystal cell and the backlight light source side, the polarizing plate (PL1) disposed on the viewing side The elastic modulus in the long side direction under the environment of 50 ° C. and 10% RH is E1, and the polarizing plate (PL2) disposed on the backlight source side in the long side direction under the environment of 50 ° C. and 80% RH When the elastic modulus is E2, E2 is in the range of 2 to 10 GPa, and the absolute value | E1-E2 | of the difference between the E1 and E2 is in the range of 0 to 5.0 GPa Liquid crystal display device.
2. In the measurement at a measurement wavelength of 589 nm in a 23 ° C./55% RH environment, the photoelastic coefficient of the film member (F3) disposed on the liquid crystal cell side is a film member constituting the polarizing plate (PL2). The liquid crystal display device according to item 1, wherein the liquid crystal display device is in a range of −6.0 × 10 ^{−12 to} 6.0 × 10 ⁻¹² Pa ⁻¹ .
3. The liquid crystal display according to item 1 or 2, wherein the film member (F3) contains any resin selected from an acrylic resin, a cycloolefin resin, and a cellulose ester resin. apparatus.

  In the present invention, a polarizing plate configuration for a liquid crystal display device free from display unevenness is provided by the above-described configuration, and thus even when used in a liquid crystal display device, particularly a large-sized liquid crystal television, display unevenness and light leakage are prevented. A liquid crystal display device can be provided.

It is the schematic explaining an example of a structure of a liquid crystal display device. It is the figure which showed typically an example of the dope preparation process, casting process, and drying process of a solution casting film forming method.

  The present invention relates to a liquid crystal display device used for a liquid crystal television or a liquid crystal display of a personal computer, and improves display unevenness and light leakage, also called egg unevenness, which occurs under high temperature and high humidity conditions.

  The present invention is a liquid crystal display device having a backlight light source, a liquid crystal cell, and two polarizing plates disposed on the viewing side of the liquid crystal cell and the backlight light source side, and polarized light disposed on the viewing side The elastic modulus in the long side direction under the environment of 50 ° C. and 10% RH of the plate (PL1) is E1, and the polarizing plate (PL2) disposed on the backlight light source side is under the environment of 50 ° C. and 80% RH. When the elastic modulus in the long side direction is E2, E2 is in the range of 2 to 10 GPa, and the absolute value | E1-E2 | of the difference between the E1 and E2 is in the range of 0 to 5.0 GPa. This is a technical feature common to the inventions according to claims 1 to 3.

An embodiment of the present invention is a film member constituting the polarizing plate (PL2) disposed on the backlight side and the film member (F3) disposed on the liquid crystal cell side from the viewpoint of manifesting the effects of the present invention. ) In a measurement wavelength of 589 nm in a 23 ° C./55% RH environment, the photoelastic coefficient is within a range of −6.0 × 10 ^{−12 to} 6.0 × 10 ⁻¹² Pa ^−1. It is preferable because a light leakage reduction effect can be obtained. Furthermore, in this invention, it is preferable from the transparency of a film being obtained that the said film member (F3) contains either resin selected from an acrylic resin, a cycloolefin resin, and a cellulose resin. .

  Thereby, even if it uses for a large sized liquid crystal television, the liquid crystal display device without a display nonuniformity and light leakage can be obtained.

  The configuration of the liquid crystal display device of the present invention will be described in detail. In addition, in this application, "-" is used in the meaning which includes the numerical value described before and behind that as a lower limit and an upper limit.

<Configuration of liquid crystal display device>
As an example of the configuration of a conventional liquid crystal display device, in the direct type, as shown in FIG. 1, [light source 1a / diffuser plate (lower diffusion sheet) 3a / light collecting sheet 4a (prism sheet, etc.) / Upper diffusion sheet 5a / liquid crystal panel 12a (polarizer 10a / optical film (retardation film etc.) 9a, 9b / substrate 8a / liquid crystal cell 7a / optical films 11a, 11b)] This is a configuration used in a liquid crystal display device. On the other hand, a small liquid crystal display device for mobile use has a sidelight type (not shown).

  The diffuser plate (lower diffuser sheet) is an optical sheet having strong light diffusibility for mainly reducing in-plane luminance unevenness of the backlight light source (BLU) 6a, and the condensing sheet transmits diffused light in the front direction of the liquid crystal display device. This is an optical sheet for condensing light in the normal direction of the display device plane, and the upper diffusion sheet is for reducing moire generated by a periodic structure such as a prism sheet as a light condensing sheet or pixels in a liquid crystal cell. And an optical sheet used for further reducing in-plane luminance unevenness that cannot be removed by the lower diffusion sheet.

  Liquid crystal cell display methods include twisted nematic (TN), super twisted nematic (STN), vertical alignment (VA), in-plane switching (IPS), and optically compensated bend cells (OCB). It can be preferably used for a transmissive, reflective, or transflective liquid crystal display device.

  As the light source (illuminant) used for the light source, CCFL (Cold Cathode Fluorescent Lamp, Cold Cathode Tube), HCFL (Hot Cathode Fluorescent Lamp, Hot Cathode Tube), LED (Light Emitting Diode), OLED (Org Diode) Light-emitting diode, organic light emitting diode [organic EL], inorganic EL, and the like can be preferably used.

  As shown in FIG. 1, the liquid crystal display device is generally composed of a liquid crystal cell sandwiched between substrates such as glass plates and two polarizing plates PL1 and PL2 provided on both sides of the liquid crystal cell. Among these polarizing plates, one polarizing plate disposed on the viewing side (upper side) is referred to as viewing side polarizing plate PL1, and the polarizing plate disposed on the light source side (lower side) is referred to as light source side polarizing plate PL2. These polarizing plates are configured by sandwiching a polarizer (also referred to as a polarizing film) with two optical films (polarizing plate protective films). The polarizing plate PL1 is composed of two optical film members 11a (F1) and 9a (F2) with a polarizer interposed therebetween. The polarizing plate PL2 is similarly configured by sandwiching a polarizer with optical film members of 9b (F3) and 11b (F4). Here, the optical film members F2 and F3 are arranged on the liquid crystal cell side.

(Principle of the present invention)
Although the mechanism of manifestation of the effects of the present invention is not clear, the present inventors are responsible for the occurrence of the display unevenness and light leakage due to the contact between the liquid crystal panel and the diffusion plate accompanying the deformation of the members constituting the liquid crystal display device. I came to think that the cause was separation.

  That is, the change in the temperature and humidity environment of the polarizing plate (PL1) and the polarizing plate (PL2) increases the dimensional change in the long side direction of the two polarizing plates, and there is a difference in the environmental difference between the two polarizing plates. Therefore, the dimensional difference becomes large. Therefore, the liquid crystal panel is deformed.

  The reason why display unevenness and light leakage can be solved in the present invention is considered to be as follows. Here, the light leakage means that the design value of the film retardation is shifted due to extra stress applied to the film, and even if it is designed to emit no light in the original black display, part of the light leaks. The phenomenon that ends up.

  In order to suppress the occurrence of display unevenness and light leakage, it is required that the dimensional change of the two upper and lower polarizing plates constituting the liquid crystal cell is small with respect to environmental fluctuations such as temperature and humidity. For this reason, it is preferable that the swelling distortion represented by the difference in the dimensional change rate between the upper and lower polarizing plates is small. However, it is not sufficient that the difference in the dimensional change rate between the upper and lower two sheets is small, and the dimensional change itself between the upper and lower two polarizing plates is small and the difference is also required to be small.

  In the present invention, the environmental variation is suppressed by suppressing the elastic modulus E2 of the polarizing plate on the light source side, particularly in the long side direction, and suppressing the difference | E1-E2 | As a result, it is possible to suppress the occurrence of distortion to a low level, and as a result, it is possible to provide a liquid crystal display device that minimizes deformation and does not cause display unevenness and light leakage.

  Further, by suppressing the photoelastic coefficient of the film member (F3) in contact with the liquid crystal cell in the optical film constituting the light source side polarizing plate (PL2) within a specific range, distortion due to dimensional change of the polarizing plate occurs. In addition, it is possible to suppress the occurrence of an excessive retardation of the film, and an effect of suppressing the occurrence of display unevenness (interference fringes) can be obtained.

Hereinafter, the structure of the liquid crystal cell and the polarizing plate constituting the liquid crystal display device of the present invention will be described. <Liquid crystal cell>
In the liquid crystal panel constituting the liquid crystal display device of the present invention, any liquid crystal cell can be used. As shown in FIG. 1, the liquid crystal cell is sandwiched between a pair of transparent substrates 8a made of glass, plastic or the like, and includes a transparent electrode, a liquid crystal layer, a color filter and the like sandwiched between the transparent substrates. Preferably, it is configured.

<Polarizing plate>
A polarizing plate is comprised from the polarizer and the optical film arrange | positioned at the both sides. This polarizing plate has a function of converting natural light or polarized light into arbitrary polarized light such as linearly polarized light, circularly polarized light, and elliptically polarized light. In the present invention, of these two polarizing plates, the elastic modulus in the long side direction under the environment of 50 ° C. and 10% RH of the polarizing plate (PL1) configured on the viewing side in the liquid crystal display device is E1. When the elastic modulus E2 in the long side direction in the environment of 50 ° C. and 80% RH of the polarizing plate (PL2) configured on the light source side in the liquid crystal display device, E2 is in the range of 2 to 10 GPa. The absolute value | E1-E2 | of the difference between E1 and E2 is in the range of 0 to 5.0 GPa. When E2 is 2 GPa or more and 10 GPa or less and the absolute value of the difference between E1 and E2 is within the above range, the effect of suppressing panel warpage can be obtained. If E2 is less than 2 GPa, the film itself may shrink and the panel may warp. If it exceeds 10 GPa, film processing becomes difficult. On the other hand, if the absolute value of the difference between E1 and E2 exceeds 5.0, the balance between the upper and lower polarizing plates sandwiching the panel becomes worse and the panel is warped.

  Elastic modulus E1 and E2 of a polarizing plate can be adjusted with the film thickness of the optical film to be used, the raw material to comprise, and those combination. By reducing the thickness of the optical film, the elastic modulus of the polarizing plate increases. Conversely, by increasing the thickness of the optical film, the elastic modulus of the polarizing plate can be reduced.

(Polarizer)
A polarizer, which is a main component of a polarizing plate, is an element that allows only light of a polarization plane in a certain direction to pass through. A typical polarizer currently known (also referred to as a polarizing film) is a polyvinyl alcohol type polarized light. There are two types of films: one obtained by dyeing iodine on a polyvinyl alcohol film and the other obtained by dyeing a dichroic dye.

  For the polarizer, a polyvinyl alcohol aqueous solution is formed into a film and dyed by uniaxial stretching or dyed or uniaxially stretched and then preferably subjected to a durability treatment with a boron compound.

(Optical film)
The polarizer has a structure sandwiched between two optical films, and the viewing side polarizing plate (PL1) has an optical film member (F1) disposed on the viewing side and an optical film member (F1) disposed on the liquid crystal cell side ( F2) is sandwiched between the polarizers. The light source side polarizing plate (PL2) is configured by sandwiching a polarizer between an optical film member (F3) disposed on the liquid crystal cell side and an optical film (F4) disposed on the light source side.

Here, it is preferred in the present invention photoelastic coefficient of the optical film member (F3) is in the range of ^{-6.0 × 10 -12 ~6.0 × 10 -12} Pa -1. It is preferable that the photoelastic coefficient of the optical film member F3 is within the above range because an effect of reducing light leakage can be obtained.

  Photoelasticity refers to a phenomenon that exhibits optical anisotropy and exhibits birefringence when an external force is applied to an isotropic substance to cause internal stress. When the stress (force per unit area) acting on the substance is σ and the birefringence is Δn, the stress σ and the birefringence Δn are theoretically proportional and can be expressed as Δn = Cσ. C is the photoelastic coefficient. In other words, taking the stress σ acting on the material on the horizontal axis and the birefringence Δn of the material when the stress is applied on the vertical axis, the relationship between them is theoretically a straight line, and the slope of this straight line Is the photoelastic coefficient C.

  Although it does not specifically limit as a film member used for an optical film, An acrylic resin, a cellulose-ester resin, and a cycloolefin resin are used preferably. These resins are preferable because of their transparency.

<Acrylic resin>
The acrylic resin used in the present invention includes a methacrylic resin. Although it does not restrict | limit especially as resin, What consists of 50-99 mass% of methyl methacrylate units and 1-50 mass% of other monomer units copolymerizable with this is preferable.

  As the acrylic resin and methacrylic resin, a (meth) acrylic monomer alone or a copolymer, or a copolymer of a (meth) acrylic monomer and a copolymerizable monomer can be used. Examples of (meth) acrylic monomers include (meth) acrylic acid; methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, t-butyl (meth) acrylate, ( (Meth) acrylic acid isobutyl, (meth) acrylic acid hexyl, (meth) acrylic acid octyl, (meth) acrylic acid 2-ethylhexyl (meth) acrylic acid C1-10 alkyl; (meth) acrylic acid phenyl etc. ) Aryl acrylate; hydroxyalkyl (meth) acrylates such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate; glycidyl (meth) acrylate; N, N-dialkylaminoalkyl (meth) acrylate; (meth) acrylonitrile; Alicyclic hydrocarbon groups such as tricyclodecane Such as (meth) acrylate can be exemplified. Examples of the copolymerizable monomer include styrene monomers, vinyl ester monomers, maleic anhydride, maleic acid, and fumaric acid. These monomers can be used alone or in combination of two or more.

  Examples of the (meth) acrylic resin include poly (meth) acrylic acid esters such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymer, methyl methacrylate- (meth) acrylic acid ester copolymer Examples thereof include methyl methacrylate, acrylic acid ester- (meth) acrylic acid copolymer, and (meth) acrylic acid ester-styrene copolymer (MS resin and the like). Preferable (meth) acrylic resin is poly (meth) acrylate C1-6 alkyl such as poly (meth) methyl acrylate, particularly methyl methacrylate as a main component (50 to 100% by mass, preferably 70 to 100% by mass). % Methyl) resin.

  Among these, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, and the like are preferable from the viewpoint of thermal decomposition resistance and fluidity of the copolymer. n-Butyl acrylate is particularly preferably used.

  The acrylic resin used for the optical film according to the present invention has a weight average molecular weight (Mw) of 80,000 or more, particularly from the viewpoint of improving brittleness as an optical film and improving transparency when used in combination with a cellulose ester resin. When the weight average molecular weight (Mw) of the acrylic resin is less than 80000, sufficient brittleness improvement cannot be obtained, and compatibility with the cellulose ester resin is deteriorated. The weight average molecular weight (Mw) of the acrylic resin is more preferably in the range of 80,000 to 1,000,000, particularly preferably in the range of 100,000 to 600,000, and most preferably in the range of 150,000 to 400,000. Although the upper limit of the weight average molecular weight (Mw) of an acrylic resin is not specifically limited, It is a preferable form that it shall be 1 million or less from a viewpoint on manufacture.

  A commercially available thing can also be used as an acrylic resin used for the optical film which concerns on this invention. For example, Delpet 60N, 80N (Asahi Kasei Chemicals Co., Ltd.), Dianal BR52, BR80, BR83, BR85, BR88 (Mitsubishi Rayon Co., Ltd.), KT75 (Electrochemical Industry Co., Ltd.) and the like can be mentioned. . Two or more acrylic resins can be used in combination.

<Cellulose ester resin>
The cellulose ester resin used in the optical film according to the present invention is not particularly limited, but the ester group is preferably a linear or branched carboxylic acid ester having about 2 to 22 carbon atoms, and these carboxylic acids are cyclic. Or an ester of an aromatic carboxylic acid. In addition, these carboxylic acids may have a substituent. The cellulose ester is particularly preferably a lower fatty acid ester having 6 or less carbon atoms.

  As a preferred cellulose ester resin, specifically, in addition to cellulose acetate, a propionate group or a butyrate group is bonded in addition to an acetyl group such as cellulose acetate propionate, cellulose acetate butyrate, and cellulose acetate propionate butyrate. And a mixed fatty acid ester of cellulose.

  The cellulose ester resin used in the optical film according to the present invention has an acyl group total substitution degree (T) of 2.0 to 3.3 particularly from the viewpoint of transparency when it is improved in brittleness or compatible with an acrylic resin. 0, the substitution degree of the acyl group having 3 to 7 carbon atoms is 1.2 to 3.0, and the substitution degree of the acyl group having 3 to 7 carbon atoms is preferably 2.0 to 3.0. . That is, the cellulose ester resin according to the present invention is a cellulose ester resin substituted with an acyl group having 3 to 7 carbon atoms. Specifically, propionyl, butyryl and the like are preferably used, but a propionyl group is particularly preferably used. It is done.

  When the total substitution degree of the acyl group of the cellulose ester resin is in the range of 2.0 to 3.0, that is, when the residual degree of the hydroxy group at the 2, 3, 6 position of the cellulose ester molecule is less than 1.0. Is preferred because the compatibility between the cellulose ester resin and the acrylic resin is enhanced, and the transparency is increased when used as an optical film. Further, even when the total substitution degree of the acyl group is less than 2.0, if the substitution degree of the acyl group having 3 to 7 carbon atoms is more than 1.2, the compatibility is improved and the brittleness is increased, which is preferable. . For example, even when the total substitution degree of the acyl group is less than 2.0, the substitution degree of the acyl group having 2 carbon atoms, that is, the acetyl group is low, and the substitution degree of the acyl group having 3 to 7 carbon atoms is 1. When it exceeds 2, compatibility becomes high and transparency improves.

  The acyl group substitution degree of the cellulose ester resin used for the optical film according to the present invention is 2.0 to 3.0 in total substitution degree (T), and 1 substitution degree of the acyl group having 3 to 7 carbon atoms. The total substitution degree of acyl groups other than 3 to 7 carbon atoms, that is, acetyl groups or acyl groups having 8 or more carbon atoms, is preferably 1.3 or less. It is preferable.

  The total substitution degree (T) of the acyl group of the cellulose ester resin is more preferably in the range of 2.5 to 3.0.

  In the present invention, the acyl group may be an aliphatic acyl group or an aromatic acyl group. In the case of an aliphatic acyl group, it may be linear or branched and may further have a substituent. The number of carbon atoms of the acyl group in the present invention includes an acyl group substituent.

  When the said cellulose ester resin has an aromatic acyl group as a substituent, it is preferable that the number of the substituents X substituted to an aromatic ring is 0-5. Also in this case, it is preferable that the substitution degree of the acyl group having 3 to 7 carbon atoms including the substituent is 1.2 to 3.0.

  Further, when the number of substituents substituted on the aromatic ring is 2 or more, they may be the same or different from each other, but they may be linked together to form a condensed polycyclic compound (for example, naphthalene, indene, indane, phenanthrene, quinoline). , Isoquinoline, chromene, chroman, phthalazine, acridine, indole, indoline, etc.).

  In the cellulose ester resin as described above, having a structure having at least one kind of an aliphatic acyl group having 3 to 7 carbon atoms is used as a structure used for the cellulose ester resin of the present invention.

  The substitution degree of the cellulose ester resin used in the optical film according to the present invention is such that the total substitution degree (T) of the acyl group is 2.0 to 3.0, and the substitution degree of the acyl group having 3 to 7 carbon atoms is 1. It is preferable that it is 2-3.0.

  Moreover, it is a preferable structure that the sum total of the substitution degree of other than an acyl group having 3 to 7 carbon atoms, that is, an acetyl group and an acyl group having 8 or more carbon atoms is 1.3 or less.

  The cellulose ester resin used in the optical film according to the present invention is preferably at least one selected from cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate benzoate, cellulose propionate, and cellulose butyrate, That is, those having an acyl group having 3 or 4 carbon atoms as a substituent are preferred.

  Among these, cellulose ester resins that are particularly preferred are cellulose acetate propionate and cellulose propionate.

The portion not substituted with an acyl group is usually present as a hydroxy group. These can be synthesized by known methods.
In addition, the substitution degree of an acetyl group and the substitution degree of other acyl groups are obtained by a method prescribed in ASTM-D817-96.
The weight average molecular weight (Mw) of the cellulose ester resin used for the optical film according to the present invention is 75000 or more, particularly from the viewpoint of improving compatibility with acrylic resin and brittleness, and is preferably in the range of 75,000 to 300,000. More preferably, it is within the range of 100,000 to 240,000, particularly preferably 160000 to 240,000. When the important average molecular weight (Mw) of the cellulose ester resin is less than 75,000, the effect of improving heat resistance and brittleness is not sufficient, and the effect of the present invention cannot be obtained. In the present invention, two or more kinds of cellulose resins can be mixed and used.

<Cycloolefin resin>
The cycloolefin resin used in the optical film according to the present invention is a polymer resin containing an alicyclic structure.

  A preferred cycloolefin resin is a resin obtained by polymerizing or copolymerizing a cyclic olefin. Examples of the cyclic olefin include norbornene, dicyclopentadiene, tetracyclododecene, ethyltetracyclododecene, ethylidenetetracyclododecene, tetracyclo [7.4.0.110, 13.02,7] trideca-2,4. Unsaturated hydrocarbons of polycyclic structures such as 6,11-tetraene and derivatives thereof; cyclobutene, cyclopentene, cyclohexene, 3,4-dimethylcyclopentene, 3-methylcyclohexene, 2- (2-methylbutyl) -1-cyclohexene, cyclo Examples thereof include monocyclic unsaturated hydrocarbons such as octene, 3a, 5,6,7a-tetrahydro-4,7-methano-1H-indene, cycloheptene, cyclopentadiene, cyclohexadiene, and derivatives thereof. These cyclic olefins may have a polar group as a substituent. Examples of the polar group include a hydroxyl group, a carboxyl group, an alkoxyl group, an epoxy group, a glycidyl group, an oxycarbonyl group, a carbonyl group, an amino group, an ester group, and a carboxylic acid anhydride group. Or a carboxylic anhydride group is preferred.

  A preferable cycloolefin resin may be one obtained by addition copolymerization of a monomer other than the cyclic olefin. Addition copolymerizable monomers include ethylene, propylene, 1-butene, 1-pentene, and other ethylene or α-olefins; 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl- Examples include dienes such as 1,4-hexadiene and 1,7-octadiene.

The cyclic olefin is obtained by an addition polymerization reaction or a metathesis ring-opening polymerization reaction. The polymerization is carried out in the presence of a catalyst. Examples of the addition polymerization catalyst include a polymerization catalyst composed of a vanadium compound and an organoaluminum compound. As a catalyst for ring-opening polymerization, a polymerization catalyst comprising a metal halide such as ruthenium, rhodium, palladium, osmium, iridium, platinum, nitrate or acetylacetone compound and a reducing agent; or titanium, vanadium, zirconium, tungsten, molybdenum And a polymerization catalyst composed of a metal halide such as acetylacetone compound and an organoaluminum compound. The polymerization temperature, pressure and the like are not particularly limited, but the polymerization is usually carried out at a polymerization temperature of −50 to 100 ° C. and a polymerization pressure of 0 to 490 N / cm ² .

  The cycloolefin resin used in the optical film according to the present invention is preferably a resin obtained by polymerizing or copolymerizing a cyclic olefin and then hydrogenating it to change the unsaturated bond in the molecule to a saturated bond. The hydrogenation reaction is performed by blowing hydrogen in the presence of a known hydrogenation catalyst. Examples of hydrogenation catalysts include cobalt acetate / triethylaluminum, nickel acetylacetonate / triisobutylaluminum, transition metal compounds such as titanocene dichloride / n-butyllithium, zirconocene dichloride / sec-butyllithium, tetrabutoxytitanate / dimethylmagnesium / alkyl. Homogeneous catalyst comprising a combination of metal compounds; heterogeneous metal catalyst such as nickel, palladium, platinum; nickel / silica, nickel / diatomaceous earth, nickel / alumina, palladium / carbon, palladium / silica, palladium / diatomaceous earth And a heterogeneous solid-supported catalyst in which a metal catalyst such as palladium / alumina is supported on a carrier.

  Or the following norbornene-type polymer is also mentioned as a cycloolefin type resin. The norbornene-based polymer preferably has a norbornene skeleton as a repeating unit. Specific examples thereof include JP-A-62-252406, JP-A-62-2252407, and JP-A-2-133413. JP-A-63-145324, JP-A-63-264626, JP-A-1-240517, JP-B-57-8815, JP-A-5-39403, JP-A-5-43663 JP-A-5-43834, JP-A-5-70655, JP-A-5-279554, JP-A-6-206985, JP-A-7-62028, JP-A-8-176411, Although what was described in the Kaihei 9-241484 gazette etc. can be utilized preferably, it is not limited to these. Moreover, these may be used individually by 1 type and may use 2 or more types together.

  In the present invention, among the norbornene-based polymers, those having a repeating unit represented by any of the following structural formulas (I) to (IV) are preferable.

前記構造式（Ｉ）〜（IV）中、Ａ、Ｂ、Ｃ及びＤは、各々独立して、水素原子又は１価の有機基を表す。

In the structural formulas (I) to (IV), A, B, C and D each independently represent a hydrogen atom or a monovalent organic group.

  Among the norbornene-based polymers, a polymer obtained by metathesis polymerization of at least one compound represented by the following structural formula (V) or (VI) and an unsaturated cyclic compound copolymerizable therewith. A hydrogenated polymer obtained by hydrogenating is also preferred.

前記構造式中、Ａ、Ｂ、Ｃ及びＤは、各々独立して、水素原子又は１価の有機基を表す。ここで、上記Ａ、Ｂ、Ｃ及びＤは特に限定されないが、好ましくは水素原子、ハロゲン原子、一価の有機基、又は、少なくとも２価の連結基を介して有機基が連結されてもよく、これらは同じであっても異なっていてもよい。また、Ａ又はＢとＣ又はＤは単環又は多環構造を形成してもよい。ここで、上記少なくとも２価の連結基とは、酸素原子、イオウ原子、窒素原子に代表されるヘテロ原子を含み、例えばエーテル、エステル、カルボニル、ウレタン、アミド、チオエーテル等が挙げられるが、これらに限定されるものではない。また、上記連結基を介し、上記有機基は更に置換されてもよい。

In the structural formula, A, B, C and D each independently represent a hydrogen atom or a monovalent organic group. Here, A, B, C and D are not particularly limited, but preferably an organic group may be linked through a hydrogen atom, a halogen atom, a monovalent organic group, or at least a divalent linking group. These may be the same or different. A or B and C or D may form a monocyclic or polycyclic structure. Here, the at least divalent linking group includes a hetero atom typified by an oxygen atom, a sulfur atom, and a nitrogen atom, and examples thereof include ether, ester, carbonyl, urethane, amide, thioether, and the like. It is not limited. In addition, the organic group may be further substituted via the linking group.

  Examples of other monomers copolymerizable with the norbornene-based monomer include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, C2-C20 alpha olefins, such as 1-hexadecene, 1-octadecene, 1-eicocene, and derivatives thereof; cyclobutene, cyclopentene, cyclohexene, cyclooctene, 3a, 5,6,7a-tetrahydro-4,7 -Cycloolefins such as methano-1H-indene, and derivatives thereof; 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene, 1,7-octadiene, etc. Conjugated dienes; and the like are used. Among these, an α-olefin, particularly ethylene is preferable.

  These other monomers copolymerizable with the norbornene-based monomer can be used alone or in combination of two or more. In the case of addition copolymerization of a norbornene monomer and another monomer copolymerizable therewith, the ratio of the structural unit derived from the norbornene monomer and the structural unit derived from the other monomer copolymerizable in the addition copolymer However, it is appropriately selected so that the mass ratio is usually 30:70 to 99: 1, preferably 50:50 to 97: 3, more preferably 70:30 to 95: 5.

  When the unsaturated bond remaining in the molecular chain of the synthesized polymer is saturated by a hydrogenation reaction, the hydrogenation rate is 90% or more, preferably 95% or more, particularly from the viewpoint of light resistance deterioration, weather resistance deterioration, etc. Preferably it is 99% or more.

  In addition, examples of the cycloolefin resin used in the present invention include thermoplastic saturated norbornene resins described in paragraph numbers [0014] to [0019] of JP-A-5-2108, and paragraph numbers of JP-A-2001-277430. [0015] to [0031] thermoplastic norbornene polymers, JP 2003-14901 paragraph Nos. [0008] to [0045] thermoplastic norbornene resins, JP 2003-139950 paragraph No. [0014] To [0028] norbornene-based resin composition, Japanese Patent Application Laid-Open No. 2003-161832, paragraph numbers [0029] to [0037], norbornene-based resin, Japanese Patent Application Laid-Open No. 2003-195268, paragraph numbers [0027] to [0036] The norbornene-based resin described in JP 2003-211589 A Paragraph Nos. [0009] to [0023] alicyclic structure-containing polymer resin, norbornene polymer resin or vinyl alicyclic hydrocarbon heavy as described in JP-A-2003-212588, paragraph Nos. [0008] to [0024] Examples include coalesced resins.

  Specifically, ZEONEX manufactured by Nippon Zeon Co., Ltd., ZEONOR (ZEONOR23, ZEONOR40), Arton manufactured by JSR Co., Ltd., Apel manufactured by Mitsui Chemicals Co., Ltd. (APL8008T, APL6509T, APL6013T, APL5014DP, APL6015T) and the like are preferably used. .

  The molecular weight of the cycloolefin resin used in the present invention is appropriately selected according to the purpose of use, but is measured by a gel permeation chromatographic method using a cyclohexane solution (or a toluene solution when the polymer resin is not dissolved). When the polyisoprene or polystyrene-equivalent weight average molecular weight is usually in the range of 5,000 to 500,000, preferably 8,000 to 200,000, more preferably 10,000 to 100,000, the mechanical strength and molding processability of the molded body are high. Balanced and suitable.

  When an acrylic resin and a cellulose ester resin are mixed and used, the acrylic resin and the cellulose ester resin are contained in a compatible state in a mass ratio of 95: 5 to 30:70, preferably 95: 5 50:50, more preferably 90: 10-60: 40.

  When the acrylic resin and the cellulose ester resin have a mass ratio greater than 95: 5, the effect of the cellulose ester resin cannot be sufficiently obtained. When the mass ratio is less than 30:70, the moisture resistance The property becomes insufficient.

  In the optical film according to the present invention, when two or more kinds of resins are mixed and used, the acrylic resin and the cellulose ester resin are preferably contained in a compatible state. The physical properties and quality required for an optical film are achieved by supplementing each other by dissolving different resins.

  In the present invention, the optical film may be used or another polarizing plate protective film may be used. For example, commercially available cellulose ester films (for example, Konica Minoltack KC8UX, KC4UX, KC5UX, KC8UY, KC4UY, KC12UR, KC8UCR-3, KC8UCR-4, KC8UCR-5, KC8UE, KC4UE-4, KC4FR-3, KC4F-4, KC4FR-3, KC4F4 -1, KC8UY-HA, KC8UX-RHA, manufactured by Konica Minolta Opto Co., Ltd.) and the like are preferably used.

  The film member used for the optical film member (F3) is not particularly limited as long as it satisfies the above-described photoelastic coefficient, but in the present invention, it is composed of at least one of acrylic resin, cycloolefin resin, and cellulose ester resin. It is preferable.

  Unless the function as an optical film is impaired, the optical film which concerns on this invention may contain resin and additives other than an acrylic resin and a cellulose-ester resin, and may be comprised. When the resin other than the acrylic resin and the cellulose ester resin is contained, the resin to be added may be mixed without being dissolved even if it is in a compatible state.

  The total mass of the acrylic resin and the cellulose ester resin in the optical film according to the present invention is preferably 55% by mass or more of the optical film, more preferably 60% by mass or more, and particularly preferably 70% by mass or more. is there.

  When using a resin or additive other than the acrylic resin and the cellulose ester resin, it is preferable to adjust the addition amount within a range that does not impair the function of the optical film of the present invention.

<Additives>
(Plasticizer)
In the optical film according to the present invention, a plasticizer can be used in combination in order to improve the fluidity and flexibility of the composition. Examples of the plasticizer include phthalate ester, fatty acid ester, trimellitic ester, phosphate ester, polyester, and epoxy.

  Of these, polyester and phthalate plasticizers are preferably used. Polyester plasticizers are superior in non-migration and extraction resistance compared to phthalate ester plasticizers such as dioctyl phthalate, but are slightly inferior in plasticizing effect and compatibility.

  Therefore, it can be applied to a wide range of uses by selecting or using these plasticizers according to the use.

  The polyester plasticizer is a reaction product of a monovalent or tetravalent carboxylic acid and a monovalent or hexavalent alcohol, and is mainly obtained by reacting a divalent carboxylic acid with a glycol. . Representative divalent carboxylic acids include glutaric acid, itaconic acid, adipic acid, phthalic acid, azelaic acid, sebacic acid and the like.

  In particular, when adipic acid, phthalic acid or the like is used, those having excellent plasticizing properties can be obtained. Examples of the glycol include glycols such as ethylene, propylene, 1,3-butylene, 1,4-butylene, 1,6-hexamethylene, neopentylene, diethylene, triethylene, and dipropylene. These divalent carboxylic acids and glycols may be used alone or in combination.

  The ester plasticizer may be any of ester, oligoester, and polyester types, and the molecular weight is preferably in the range of 100 to 10,000, and preferably in the range of 600 to 3000, which has a large plasticizing effect.

  The viscosity of the plasticizer has a correlation with the molecular structure and molecular weight. In the case of an adipic acid plasticizer, the viscosity is preferably in the range of 200 to 5000 MPa · s (25 ° C.) in view of compatibility and plasticization efficiency. Furthermore, some polyester plasticizers may be used in combination.

  The plasticizer is preferably added in an amount of 0.5 to 30 parts by mass with respect to 100 parts by mass of the optical film according to the present invention. If the added amount of the plasticizer exceeds 30 parts by mass, the surface becomes sticky, which is not preferable for practical use.

(UV absorber)
The optical film according to the present invention preferably contains an ultraviolet absorber, and examples of the ultraviolet absorber used include benzotriazole-based, 2-hydroxybenzophenone-based or salicylic acid phenyl ester-based ones. For example, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (3 Triazoles such as 5-di-t-butyl-2-hydroxyphenyl) benzotriazole, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone And benzophenones.

  Here, among ultraviolet absorbers, ultraviolet absorbers having a molecular weight of 400 or more are less likely to volatilize at a high boiling point and are difficult to disperse even during high-temperature molding, so that the weather resistance is effectively improved with a relatively small amount of addition. be able to.

  Examples of the ultraviolet absorber having a molecular weight of 400 or more include 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole, 2,2-methylenebis [4- (1, 1,3,3-tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol], bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis ( Hindered amines such as 1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and 2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butylmalonic acid Bis (1,2,2,6,6-pentamethyl-4-piperidyl), 1- [2- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] ethyl L] -4- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] -2,2,6,6-tetramethylpiperidine and the like, hindered phenol and hindered amine A hybrid system having both structures can be mentioned, and these can be used alone or in combination of two or more. Among these, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole and 2,2-methylenebis [4- (1,1,3,3- Tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol] is particularly preferred.

(Other additives)
Furthermore, various antioxidants can also be added to the optical film according to the present invention in order to improve the thermal decomposability and thermal colorability during molding. It is also possible to add an antistatic agent to give the optical film antistatic performance.

  For the optical film according to the present invention, a flame retardant acrylic resin composition containing a phosphorus flame retardant may be used.

  Phosphorus flame retardants used here include red phosphorus, triaryl phosphate ester, diaryl phosphate ester, monoaryl phosphate ester, aryl phosphonate compound, aryl phosphine oxide compound, condensed aryl phosphate ester, halogenated alkyl phosphorus. Examples thereof include one or a mixture of two or more selected from acid esters, halogen-containing condensed phosphates, halogen-containing condensed phosphonates, halogen-containing phosphites, and the like.

  Specific examples include triphenyl phosphate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, phenylphosphonic acid, tris (β-chloroethyl) phosphate, tris (dichloropropyl). Examples thereof include phosphate and tris (tribromoneopentyl) phosphate.

<Method for forming optical film>
An example of a method for producing an optical film will be described, but the present invention is not limited to this. As a method for forming an optical film according to the present invention, production methods such as an inflation method, a T-die method, a calendar method, a cutting method, a casting method, an emulsion method, and a hot press method can be used. From the viewpoint of suppression of defects and suppression of optical defects such as die lines, solution casting by casting is preferred.

(Organic solvent)
The organic solvent useful for forming the dope when the optical film according to the present invention is produced by the solution casting method is used without limitation as long as it dissolves acrylic resin, cellulose ester resin, and other additives simultaneously. be able to.

  For example, as a chlorine organic solvent, methylene chloride, as a non-chlorine organic solvent, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro- Examples include 2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, and nitroethane. Methylene chloride, methyl acetate, ethyl acetate and acetone can be preferably used.

  In addition to the organic solvent, the dope preferably contains 1 to 40% by mass of a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. When the proportion of alcohol in the dope increases, the web gels and peeling from the metal support becomes easy, and when the proportion of alcohol is small, the acrylic resin and cellulose ester resin dissolve in a non-chlorine organic solvent system. There is also a role to promote.

  In particular, at least 15 to 45% by mass in total of two kinds of acrylic resin and cellulose ester resin were dissolved in a solvent containing methylene chloride and a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. A dope composition is preferred.

  Examples of the linear or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Ethanol is preferred because of the stability of these dopes, the relatively low boiling point, and good drying properties.

Hereinafter, the preferable film forming method of the optical film according to the present invention will be described.
(1) Dissolution Step In an organic solvent mainly composed of a good solvent for acrylic resin and cellulose ester resin, dissolve the acrylic resin, cellulose ester resin, and, in some cases, other additives in a dissolution vessel to form a dope. Or a step of forming a dope which is a main solution by mixing the acrylic resin and cellulose ester resin solution with other additive solutions as occasion demands.

  For dissolution of acrylic resin and cellulose ester resin, a method performed at normal pressure, a method performed below the boiling point of the main solvent, a method performed under pressure above the boiling point of the main solvent, JP-A-9-95544, JP-A-9- Various dissolution methods such as a method of performing a cooling dissolution method as described in JP-A-95557 or JP-A-9-95538, a method of performing at high pressure as described in JP-A No. 11-21379 can be used, In particular, a method of pressurizing at a temperature equal to or higher than the boiling point of the main solvent is preferable.

  The total amount of the acrylic resin and the cellulose ester resin in the dope is preferably 15 to 45% by mass. An additive is added to the dope during or after dissolution to dissolve and disperse, then filtered through a filter medium, defoamed, and sent to the next step with a liquid feed pump.

  It is preferable to use a filter medium having a collected particle diameter of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml.

  In this method, the aggregate remaining at the time of particle dispersion and the aggregate generated when the main dope is added are aggregated by using a filter medium having a collected particle diameter of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml. Can only be removed. In the main dope, the concentration of particles is sufficiently thinner than that of the additive solution, so that aggregates do not stick together at the time of filtration and the filtration pressure does not increase suddenly.

  FIG. 2 is a diagram schematically showing an example of a dope preparation step, a casting step, and a drying step of a solution casting film forming method preferable for the present invention.

  If necessary, large agglomerates are removed from the acrylic particle charging kettle 41 by the filter 44 and fed to the stock kettle 42. Thereafter, the acrylic particle additive solution is added from the stock kettle 42 to the main dope dissolving kettle 1.

  Thereafter, the main dope solution is filtered by the main filter 3, and an ultraviolet absorbent additive solution is added in-line from 16 to this.

  In many cases, the main dope may contain about 10 to 50% by mass of the recycled material. The return material may contain acrylic particles. In that case, it is preferable to control the addition amount of the acrylic particle addition liquid in accordance with the addition amount of the return material.

  The additive solution containing acrylic particles preferably contains 0.5 to 10% by mass of acrylic particles, more preferably 1 to 10% by mass, and 1 to 5% by mass. Most preferably.

  If it is in the said range, since an addition liquid is low-viscosity, it is easy to handle and it is easy to add to the main dope, it is preferable.

  The return material is a product obtained by finely pulverizing the optical film, which is generated when the optical film is formed, and is obtained by cutting off both sides of the film, or by using an optical film original that has been speculated out due to scratches, etc. .

In addition, an acrylic resin, a cellulose ester resin, and, in some cases, acrylic particles kneaded into pellets can be preferably used.
(2) Casting process An endless metal belt 31, such as a stainless steel belt, or a rotating metal drum, which feeds the dope to a pressure die 30 through a liquid feed pump (for example, a pressurized metering gear pump) and transfers it infinitely. The dope is cast from the pressure die slit to the casting position on the metal support.

A pressure die that can adjust the slit shape of the die base portion and can easily make the film thickness uniform is preferable. The pressure die includes a coat hanger die and a T die, and any of them is preferably used. The surface of the metal support is a mirror surface. In order to increase the film forming speed, two or more pressure dies may be provided on the metal support, and the dope amount may be divided and stacked. Or it is also preferable to obtain the film of a laminated structure by the co-casting method which casts several dope simultaneously.
(3) Solvent evaporation step In this step, the web (the dope is cast on the casting support and the formed dope film is called a web) is heated on the casting support to evaporate the solvent.

  To evaporate the solvent, there are a method of blowing air from the web side and / or a method of transferring heat from the back side of the support by a liquid, a method of transferring heat from the front and back by radiant heat, and the like. High efficiency and preferable. A method of combining them is also preferably used. The web on the support after casting is preferably dried on the support in an atmosphere of 40 to 100 ° C. In order to maintain the atmosphere at 40 to 100 ° C., it is preferable to apply hot air at this temperature to the upper surface of the web or to heat by means such as infrared rays.

From the viewpoint of surface quality, moisture permeability, and peelability, it is preferable to peel the web from the support within 30 to 120 seconds.
(4) Peeling process It is the process of peeling the web which the solvent evaporated on the metal support body in a peeling position. The peeled web is sent to the next process.

  The temperature at the peeling position on the metal support is preferably 10 to 40 ° C, more preferably 11 to 30 ° C. The residual solvent amount at the time of peeling of the web on the metal support at the time of peeling is preferably peeled in the range of 50 to 120% by mass depending on the strength of drying conditions, the length of the metal support, and the like. If the web is peeled off at a time when the amount of residual solvent is larger, if the web is too soft, the flatness at the time of peeling will be lost, and slippage and vertical stripes are likely to occur due to the peeling tension. The amount of solvent is determined.

  The residual solvent amount of the web is defined by the following formula.

Residual solvent amount (%) = (mass before web heat treatment−mass after web heat treatment) / (mass after web heat treatment) × 100
Note that the heat treatment for measuring the residual solvent amount represents performing heat treatment at 115 ° C. for 1 hour.

  The peeling tension at the time of peeling the metal support and the film is usually 196 to 245 N / m. However, when wrinkles easily occur at the time of peeling, it is preferable to peel with a tension of 190 N / m or less. It is preferable to peel at a minimum tension that can be peeled to 166.6 N / m, and then peel at a minimum tension to 137.2 N / m, and particularly preferably peel at a minimum tension to 100 N / m.

In the present invention, the temperature at the peeling position on the metal support is preferably -50 to 40 ° C, more preferably 10 to 40 ° C, and most preferably 15 to 30 ° C.
(5) Drying and stretching step After peeling, a drying device 35 that transports the web alternately through a plurality of rolls arranged in the drying device, and / or a tenter stretching device 34 that clips and transports both ends of the web with clips. Use to dry the web.

  Generally, the drying means blows hot air on both sides of the web, but there is also a means for heating by applying microwaves instead of the wind. Too rapid drying tends to impair the flatness of the finished film. Drying at a high temperature is preferably performed from about 8% by mass or less of the residual solvent. Throughout the drying is generally carried out at 40-250 ° C. It is particularly preferable to dry at 40 to 160 ° C.

  When using a tenter stretching apparatus, it is preferable to use an apparatus that can independently control the film gripping length (distance from the start of gripping to the end of gripping) left and right by the left and right gripping means of the tenter. In the tenter process, it is also preferable to intentionally create sections having different temperatures in order to improve planarity.

  It is also preferable to provide a neutral zone between different temperature zones so that the zones do not interfere with each other.

  The stretching operation may be performed in multiple stages, and it is also preferable to perform biaxial stretching in the casting direction and the width direction. When biaxial stretching is performed, simultaneous biaxial stretching may be performed or may be performed stepwise.

  In this case, stepwise means that, for example, stretching in different stretching directions can be sequentially performed, stretching in the same direction is divided into multiple stages, and stretching in different directions is added to any one of the stages. Is also possible. That is, for example, the following stretching steps are possible.

-Stretch in the casting direction-Stretch in the width direction-Stretch in the casting direction-Stretch in the casting direction-Stretch in the width direction-Stretch in the width direction-Stretch in the casting direction-Stretch in the casting direction Simultaneous biaxial stretching includes stretching in one direction and contracting the other while relaxing the tension. The preferable draw ratio of simultaneous biaxial stretching can be taken in the range of 1.01 to 1.5 times in both the width direction and the longitudinal direction.

  When the tenter is used, the residual solvent amount of the web is preferably 20 to 100% by mass at the start of the tenter, and it is preferable to perform drying while applying the tenter until the residual solvent amount of the web becomes 10% by mass or less. More preferably, it is 5% by mass or less.

  The drying temperature when performing the tenter is preferably 30 to 160 ° C, more preferably 50 to 150 ° C, and most preferably 70 to 140 ° C.

In the tenter process, it is preferable that the temperature distribution in the width direction of the atmosphere is small from the viewpoint of improving the uniformity of the film. The temperature distribution in the width direction in the tenter process is preferably within ± 5 ° C, and within ± 2 ° C. Is more preferable, and within ± 1 ° C. is most preferable.
(6) Winding step This is a step of winding up the optical film by the winder 37 after the residual solvent amount in the web is 2% by mass or less, and the residual solvent amount is 0.4% by mass or less. A film having good stability can be obtained. It is particularly preferable to take up at 0.000 to 0.10% by mass.

  As a winding method, a generally used method may be used. There are a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, and the like.

  The optical film of the present invention is preferably a long film. Specifically, the optical film has a thickness of about 100 m to 5000 m and is usually provided in a roll shape. Moreover, it is preferable that the width | variety of a film is 1.3-4m, and it is more preferable that it is 1.4-2m.

  Although there is no restriction | limiting in particular in the film thickness of the optical film of this invention, When using for the polarizing plate protective film mentioned later, it is preferable that it is 20-200 micrometers, it is more preferable that it is 25-100 micrometers, and it is 30-80 micrometers. It is particularly preferred.

<Preparation method of polarizing plate>
When using the optical film which concerns on this invention as a protective film for polarizing plates, a polarizing plate can be produced by a general method. It is preferable that an adhesive layer is provided on the back side of the optical film of the present invention, and is bonded to at least one surface of a polarizer produced by immersion and stretching in an iodine solution.

  On the other surface, the optical film of the present invention may be used, or another polarizing plate protective film may be used. For example, commercially available cellulose ester films (for example, Konica Minoltack KC8UX, KC4UX, KC5UX, KC8UY, KC4UY, KC12UR, KC8UCR-3, KC8UCR-4, KC8UCR-5, KC8UE, KC4UE-4, KC4FR-3, KC4F-4, KC4FR-3, KC4F4 -1, KC8UY-HA, KC8UX-RHA, manufactured by Konica Minolta Opto Co., Ltd.) and the like are preferably used.

  A polarizer, which is a main component of a polarizing plate, is an element that transmits only light having a plane of polarization in a certain direction. A typical polarizing film known at present is a polyvinyl alcohol polarizing film, which is a polyvinyl alcohol. There are one in which iodine is dyed on a system film and one in which dichroic dye is dyed.

  As described above, the polarizer is formed by forming a polyvinyl alcohol aqueous solution into a film and uniaxially stretching it for dyeing, or after dyeing and uniaxially stretching, and preferably having been subjected to a durability treatment with a boron compound. ing.

(Adhesive layer)
As the pressure-sensitive adhesive used in the pressure-sensitive adhesive layer, a pressure-sensitive adhesive having a storage elastic modulus at 25 ° C. in the range of 1.0 × 10 ⁴ Pa to 1.0 × 10 ⁹ Pa in at least a part of the pressure-sensitive adhesive layer is used. Preferably, a curable pressure-sensitive adhesive that forms a high molecular weight body or a crosslinked structure by various chemical reactions after the pressure-sensitive adhesive is applied and bonded is suitably used.

  Specific examples include, for example, urethane adhesives, epoxy adhesives, aqueous polymer-isocyanate adhesives, curable adhesives such as thermosetting acrylic adhesives, moisture-curing urethane adhesives, polyether methacrylate types, Examples include anaerobic pressure-sensitive adhesives such as ester-based methacrylate type and oxidized polyether methacrylate, cyanoacrylate-based instantaneous pressure-sensitive adhesives, and acrylate-peroxide-based two-component instantaneous pressure-sensitive adhesives.

  The pressure-sensitive adhesive may be a one-component type or a type that is used by mixing two or more components before use.

  The pressure-sensitive adhesive may be a solvent system using an organic solvent as a medium, or an aqueous system such as an emulsion type, a colloidal dispersion liquid type, or an aqueous solution type that is a medium containing water as a main component. It may be a solvent type. The density | concentration of the said adhesive liquid should just be suitably determined with the film thickness after adhesion, the coating method, the coating conditions, etc., and is 0.1-50 mass% normally.

<Measurement method of elastic modulus>
The elastic modulus of the polarizing plate in the present invention is a value measured as follows. That is, using a Tensilon testing machine “RTC-1225A” (manufactured by ORIENTEC), each polarizing plate was cut out at 120 mm (vertical) × 10 mm (width), and sandwiched between 100 mm between chucks (upper and lower 10 mm each). In accordance with JIS-K7127, measurement was performed three times at a pulling rate of 100 mm / min, and the average value was calculated.

<Measuring method of photoelastic coefficient>
The photoelastic modulus of the film member in the present invention is a value measured as follows. That is, each film was cut out by 70 mm (length) × 10 mm (width), and the retardation measurement device “KOBRA31PRW” (manufactured by Oji Scientific Instruments) was used, and the in-plane retardation Ro at a wavelength of 589 nm was in the range of 1 to 10 N. The data obtained by plotting the Ro value against the tensile load was approximated to a straight line, and the photoelastic coefficient was obtained from the slope.

<Liquid crystal display device>
By incorporating the polarizing plate bonded with the optical film according to the present invention into a liquid crystal display device, it is possible to produce various liquid crystal display devices with excellent visibility, but particularly large liquid crystal display devices, digital signage, etc. It is preferably used for a liquid crystal display device for outdoor use. The polarizing plate according to the present invention is bonded to a liquid crystal cell via the adhesive layer or the like.

  The polarizing plate according to the present invention is a reflective type, transmissive type, transflective LCD or TN type, STN type, OCB type, HAN type, VA type (PVA type, MVA type), IPS type (including FFS type), etc. It is preferably used in LCDs of various driving methods. In particular, in a large-screen liquid crystal display device having a screen of 30 or more types, particularly 30 to 54 types, display unevenness does not occur and the effect is maintained for a long time.

Hereinafter, specific embodiments of the present invention will be specifically described with reference to examples, but the embodiments of the present invention are not limited thereto.
<Production of optical film>
<Preparation of optical film 1>
(Preparation of dope solution)
70 parts by mass of Dianal BR85 (acrylic resin manufactured by Mitsubishi Rayon Co., Ltd.) and 30 parts by mass of CAP482-20 (cellulose acetate propionate resin manufactured by Eastman Chemical Co.) are mixed solvent of 252 parts by mass of methylene chloride and 48 parts by mass of ethanol. Dissolved in. (Production of optical film)
The dope solution prepared with the above composition was uniformly cast on a stainless steel band support at a temperature of 22 ° C. and a width of 2 m using a belt casting apparatus. With the stainless steel band support, the solvent was evaporated until the residual solvent amount reached 100% by mass, and the film was peeled from the stainless steel band support with a peeling tension of 162 N / m.

  The solvent was evaporated from the peeled web at 35 ° C., slit to 1.6 m width, and then dried at a drying temperature of 135 ° C. while being stretched 1.1 times in the width direction by a tenter. At this time, the residual solvent amount when starting stretching with a tenter was 10% by mass. After stretching with a tenter and relaxing at 130 ° C for 5 minutes, drying was completed while transporting the drying zone at 110 ° C and 120 ° C with a number of rolls, slitting to a width of 1.5 m, and 10 mm wide at both ends of the film. A knurling process having a thickness of 5 μm was performed, and the film was wound around a 6-inch inner diameter core with an initial tension of 220 N / m and a final tension of 110 N / m, to obtain an optical film 1 (4WA).

  The draw ratio in the MD direction calculated from the rotational speed of the stainless steel band support and the operating speed of the tenter was 1.1 times. The residual solvent amount of this optical film 1 was 0.1% by mass, the film thickness was 40 μm, and the winding number was 4000 m.

<Preparation of optical film 2>
In the production of the optical film 1, the draw ratio and the conveyance tension were controlled so that the finished film thickness was 20 μm, and the optical film 2 (2WA) was produced.

<Other film members used>
4UY: Konica Minolta Tack KC4UY (Konica Minolta Opto Product Co., Ltd. triacetyl cellulose film thickness 40 μm)
4TD: Fujitac 4TD (Fuji Film Co., Ltd. triacetyl cellulose film thickness 40 μm)
6TD: Fujitac 6TD (Fuji Film Co., Ltd. triacetyl cellulose film thickness 60 μm)
ZEONOR 40: ZEONOR film (manufactured by Nippon Zeon Co., Ltd., cycloolefin film thickness 40 μm)
ZEONOR23: ZEONOR film (manufactured by Nippon Zeon Co., Ltd., cycloolefin film thickness 23 μm)
8PET: Commercial PET film, film thickness 80μm
NRT (6TAC): Tack film (Fuji Film Co., Ltd. triacetyl cellulose film: film thickness 60 μm)
1C: Methyl methacrylate / 2- (hydroxymethyl) methyl acrylate copolymer film (prepared in the same manner as 1C described in [Example 6] of JP-A-2006-96960: film thickness 45 μm)
MS2: Methyl methacrylate / styrene copolymer film (produced in the same manner as the optical film 1 using a monomer mass ratio (methyl methacrylate: styrene = 40: 60) (Mw100,000): film thickness 40 μm)
80N: Acrylic resin film (produced in the same manner as the optical film 1 using an acrylic resin (Mw100,000) manufactured by Asahi Kasei Chemicals Corporation: film thickness 40 μm)
4WA: Optical film 1
2WA: Optical film 2
<Preparation of urethane adhesive>
To 100 parts of an aqueous emulsion of polyester-based ionomer type urethane resin “Hydran AP-20” (manufactured by DIC Corporation), 5 parts of a polyisocyanate compound “Hydran Assister C1” (manufactured by DIC Corporation) is added, did.
<Preparation of polarizing plate>
A 120 μm-thick long roll polyvinyl alcohol film was immersed in 100 parts by mass of an aqueous solution containing 1 part by mass of iodine and 4 parts by mass of boric acid, and stretched in the transport direction 5 times at 50 ° C. to produce a polarizer.

（偏光板の弾性率評価）
テンシロン試験機「ＲＴＣ−１２２５Ａ」（ＯＲＩＥＮＴＥＣ社製）を用いて、以下のような評価を行った。 Next, the prepared pressure-sensitive adhesive was applied to both sides of the polarizer with a wire bar so that the thickness after drying was 3 μm, and was bonded to a film as shown in Table 1. Then, after drying at 60 degreeC for 5 minutes, aging was performed at 35 degreeC for 24 hours, and the polarizing plates 1-22 were produced.

(Evaluation of elastic modulus of polarizing plate)
The following evaluation was performed using a Tensilon tester “RTC-1225A” (manufactured by ORIENTEC).

  Each polarizing plate is cut out at 120 mm (vertical) × 10 mm (width), sandwiched between 100 mm between chucks (up and down by 10 mm each), and measured three times at a pulling rate of 100 mm / min according to JIS K7127. The average value was calculated.

(Measurement of photoelastic coefficient of optical film member (F3))
Each film is cut out by 70 mm (length) × 10 mm (width), and using a retardation measuring device “KOBRA31PRW” (manufactured by Oji Scientific Instruments), in-plane retardation at a wavelength of 589 nm in a 23 ° C./55% RH environment. Ro was measured at a tensile load of 10 points in the range of 1 to 10 N, and the data obtained by plotting the Ro value against the tensile load was approximated to a straight line, and the photoelastic coefficient was obtained from the slope.
<Characteristic evaluation as a liquid crystal display device>
The 42-inch television “LEDREGZA42RE1” manufactured by Toshiba, which is an IPS liquid crystal display device, is peeled off in advance, and the polarizing plates 1 to 22 produced above are pasted in advance according to the configuration of Table 1. The liquid crystal display devices 1 to 22 were prepared by bonding so that the absorption axis was in the same direction as the polarizing plate.

  After that, the display device was exposed to an environment of 50 ° C. and 80% RH for 72 hours, and then left in an environment of 23 ° C. and 55% RH for 2 hours, and then the power source (backlight) was turned on, and after 12 hours. The display unevenness and light leakage after 24 hours were observed in black on the screen, and evaluated according to the following criteria.

(Display unevenness)
◎: The image display is uniform ○: The image display is almost uniform △: There is a slight outline at the center and the periphery ×: There is a clear outline at the center and the periphery (light leakage)
A: There is no light leakage. O: There is a slight light leakage. Δ: There is a part of the light leakage and it feels bright. X: There is light leakage and it feels dazzling. The above results are shown in Table 2.

表２に示した結果から明らかなように、本発明の構成で使用した液晶表示装置は、表示ムラ、光漏れがない均一な画質を得ることができる。

As is clear from the results shown in Table 2, the liquid crystal display device used in the configuration of the present invention can obtain uniform image quality without display unevenness and light leakage.

1a light source 2a light emission light source 3a diffusion plate (lower diffusion sheet)
4a Light collecting sheet (prism sheet, lens sheet)
5a Upper diffusion sheet 6a Backlight unit 7a Liquid crystal cell 8a Transparent substrate (glass, plastic)
9a Optical film (F2)
9b Optical film (F3)
10a Polarizer 11a Optical film (F1)
11b Optical film (F4)
12a Liquid crystal panel PL1 Viewing side polarizing plate PL2 Light source side polarizing plate 1 Melting pot 3, 6, 12, 15 Filter 4, 13 Stock tank 5, 14 Liquid feed pump 8, 16 Conduit 10 Ultraviolet absorber charging pot 20 Junction pipe 21 Mixer 30 Pressure die 31 Metal belt 32 Web 33 Peeling position 34 Tenter stretching device 35 Roll drying device 37 Winder 41 Particle charging vessel 42 Stock kettle 43 Pump 44 Filter

Claims (3)

  A liquid crystal display device having a backlight light source, a liquid crystal cell, and two polarizing plates disposed on the viewing side of the liquid crystal cell and the backlight light source side, the polarizing plate (PL1) disposed on the viewing side The elastic modulus in the long side direction under the environment of 50 ° C. and 10% RH is E1, and the polarizing plate (PL2) disposed on the backlight source side in the long side direction under the environment of 50 ° C. and 80% RH When the elastic modulus is E2, E2 is in the range of 2 to 10 GPa, and the absolute value | E1-E2 | of the difference between the E1 and E2 is in the range of 0 to 5.0 GPa Liquid crystal display device. In the measurement at a measurement wavelength of 589 nm in a 23 ° C./55% RH environment, the photoelastic coefficient of the film member (F3) disposed on the liquid crystal cell side is a film member constituting the polarizing plate (PL2). The liquid crystal display device according to claim 1, wherein the liquid crystal display device is in a range of −6.0 × 10 ^{−12 to} 6.0 × 10 ⁻¹² Pa ⁻¹ .   The liquid crystal display device according to claim 1 or 2, wherein the film member (F3) contains any resin selected from an acrylic resin, a cycloolefin resin, and a cellulose ester resin.

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