JP4873164B2 - Antireflection film and polarizing plate - Google Patents

Description

  The present invention relates to a highly durable antireflection film having high density and high mechanical strength and less degradation such as hydrolysis of a polarizing plate protective film, and a polarizing plate using the same.

  In an optical display device such as an LCD, CRT, or plasma display panel, an antireflection film that prevents reflection of external light such as sunlight or a fluorescent lamp is often used. Recently, not only indoor use but also outdoor use is increasing due to the spread of mobile devices such as digital cameras, mobile phones, digital video cameras, and car navigation.

  For outdoor use, reflection of outside light is larger, and an antireflection film, that is, an AR film, having a reflectance close to zero is required. In general, the AR film uses a dry coating technique capable of forming a thin film having a thickness of several nanometers. Among these, the sputtering method is a thin film with higher visibility than other dry coating methods such as vapor deposition, ion plating, and CVD because it has higher film thickness uniformity and fewer defects such as pinholes. Can be formed. In addition, since a dense film can be formed, it is possible to form a thin film with extremely excellent mechanical properties.

  On the other hand, in LCD applications, an antireflection film layer having a structure laminated on a protective film of a polarizing plate is often used. In recent years, a polarizing plate or an antireflection film has been required to have higher required durability performance with an increase in use in a vehicle or an outdoor environment. Generally, a triacetyl cellulose (TAC) film is used as a protective film for a polarizing plate because of its high hygroscopicity. However, under severe conditions of high temperature or high temperature and high humidity, the TAC film is hydrolyzed, so that it lacks durability.

Accordingly, antireflection film layers having various water vapor barrier properties have been developed. According to Japanese Patent Application Laid-Open No. 2004-53797 of Patent Document 1, an antireflection film layer having a barrier property that is less than half that of a substrate. Is forming. According to JP-A-10-10317 JP-Patent Document 2, a light-transmissive inorganic thin film layer 300~1000g ^/ m 2 ^/ day to one side of a plastic film, on the other side of 0 to 10 g ^/ m 2 / day barrier The thin film layer is formed.

On the other hand, due to an increase in the frequency of use in the current outdoor environment, durability at an extremely high temperature close to 100 ° C. is required particularly for in-vehicle applications. At this time, if the water vapor barrier property is too high, there is almost no ingress of moisture from the outside, but in particular, in a high temperature environment, moisture generated from the polarizing plate and the TAC film itself stagnate in the film, so it is rather durable. I have found the problem of lack of sex. Therefore, development of an antireflection film having a reasonably high permeability to the outside of water vapor generated inside is desired.
JP 2004-53797 A Japanese Patent Laid-Open No. 10-10317

  As described above, the sputtering method has the advantages of excellent uniformity in film thickness control and few defects such as pinholes, and thus has high visibility and high yield in the production stage. Further, since a very dense film can be formed, there is a great advantage that an antireflection film layer having excellent mechanical properties such as scratch resistance can be formed.

  On the other hand, a thin film formed by this sputtering film formation has a feature that the barrier performance of water vapor is higher than other film formation methods because of the high density of the film. Accordingly, an object of the present invention is to provide an antireflection film having high density and strong scratch-resistant mechanical properties, high moisture permeability, and high high-humidity heat durability, and a polarizing plate having the antireflection film.

The invention according to claim 1 is an antireflection film in which a hard coat layer, two or more primer layers, and an antireflection layer are sequentially laminated on a transparent base film, and the two or more primer layers are wherein a a first primer layer in contact with the hard coat layer and a second primer layer in contact with the antireflection layer, said first primer layer and said second primer layer is made of a metal or metal compound alone or mixtures, the It is first primer layer and said second primer layer, Ri different compositions der, and the thickness of the second primer layer has a 10nm or less and the film thickness of the first primer layer is the second primer layer It is an antireflection film characterized by being thinner than the film thickness .
The invention according to claim 2 is the antireflection film according to claim 1, wherein the antireflection layer is formed by laminating a plurality of optical thin film layers having different refractive indexes.
The invention according to claim 3 is the antireflection film according to claim 1 or 2, wherein the antireflection layer is formed by a sputtering method.
According to a fourth aspect of the present invention, the first primer layer in contact with the hard coat layer has fine irregularities on the surface, and the composition of the second primer layer and the first primer layer in contact with the antireflection layer The antireflection film according to claim 1, wherein the antireflection films are different from each other.
The invention according to claim 5 is the antireflection film according to any one of claims 1 to 4, wherein the transparent substrate film is a triacetyl cellulose film.
The invention described in claim 6 is characterized in that an alkali saponification treatment is performed on the transparent substrate film provided with the hard coat layer before forming the two or more primer layers. The antireflection film according to any one of the above.
The invention according to claim 7 is the antireflection film according to claim 6, wherein the surface of the hard coat layer is subjected to a low-temperature plasma surface treatment after the alkali saponification treatment.
The invention according to claim 8 is the antireflection film according to any one of claims 1 to 7 , wherein an antifouling layer is laminated on the antireflection layer.
The invention according to claim 9, temperature 40 ° C., water vapor permeability at a relative humidity of 90% RH is reflected according to claim 1, characterized in that at ^20g / m 2 / day or more It is a prevention film.
A tenth aspect of the present invention is a polarizing plate having the antireflection film according to any one of the first to ninth aspects.

  According to the present invention, an antireflection film having excellent mechanical properties such as scratch resistance and high high-humidity heat durability and a polarizing plate having the same are provided.

Embodiments of the present invention will be described below. FIG. 1 is a cross-sectional view of an embodiment of the antireflection film of the present invention.
In FIG. 1, an antireflection film 100 of the present invention has a hard coat layer 2, a first primer layer 3, a second primer layer 4, and an antireflection layer 5 sequentially laminated on a transparent substrate film 1. Further, an antifouling layer 6 is laminated on the antireflection layer 5.
As the transparent base film 1, a base material that is a surface protective layer of a polyvinyl alcohol film on which a polarizer is adsorbed is applied. The transparent substrate film 1 is not limited to any material as long as the effects of the present invention are achieved, and generally includes cellulose acetate resins such as triacetyl cellulose. Furthermore, when using these, the acetylation degree is not ask | required. What is necessary is just to select the thickness of the transparent base film 1 suitably according to the intended use, and a thing about 25-300 micrometers is used normally. Further, the transparent substrate film 1 may contain additives such as a plasticizer, an ultraviolet absorber, and a deterioration inhibitor.

  A hard coat layer 2 for sufficiently exhibiting the mechanical strength of the antireflection layer 5 may be provided on the transparent substrate film 1. As the hard coat layer 2, ionizing rays, ultraviolet curable resins, or thermosetting resins are used, and acrylic resins such as ultraviolet curable acrylic esters, acrylamides, methacrylic esters, and methacrylamide are used. And organosilicon resins and polysiloxane resins are most suitable. A polymerization initiator may be added to these materials in order to improve curability. The hard coat layer 2 has a physical thickness of 0.5 μm or more, preferably 3 to 20 μm. Further, the hard coat layer 2 may be subjected to an antiglare treatment by dispersing transparent fine particles having an average particle size of 0.01 to 3 μm.

  It is preferable that after the hard coat layer 2 is provided on the transparent base film 1, an alkali saponification treatment is performed. In particular, in a triacetyl cellulose base material, an alkali saponification treatment in which an ester group is hydrolyzed and a hydroxyl group is imparted is preferable, thereby significantly improving the adhesion of the subsequent bonding to the polyvinyl alcohol layer 10. . Further, since the saponification treatment is a treatment in the liquid, the erosion / penetration property is high, and the hard coat layer 2 also has high adhesion to the subsequent layers.

  Further, after the saponification step, surface treatment may be further performed on the hard coat layer 2 side. At this time, examples of the surface treatment method include corona discharge treatment, electron beam treatment, flame treatment, glow discharge treatment, and atmospheric pressure plasma treatment. In the present invention, it is particularly preferable to perform a low temperature plasma surface treatment.

  Thereafter, the first primer layer 3 and the second primer layer 4 are sequentially provided on the hard coat layer 2. Examples of the material for the primer layer include metals such as silicon, nickel, chromium, tin, gold, silver, platinum, zinc, titanium, tungsten, zirconium, and palladium, or alloys composed of two or more of these metals, Examples include metal compounds such as oxides, fluorides, sulfides, and nitrides, which may be a mixture. At this time, it is desirable that the first primer layer 3 and the second primer layer 4 form films having different compositions.

The 1st primer layer 3 is a layer for forming the growth direction laminated | stacked after that in an irregular direction by forming a minute uneven surface. It is sufficient that a very small amount of particles are attached to the substrate surface, and the film may be in the form of particles or islands. The thickness is a physical film thickness of about 5 nm or less, and more preferably 2 nm or less. In addition, in order to form the subsequent film irregularly, a thin film may be formed in a zigzag structure or a wave structure, but it is necessary to select a film thickness and material that do not affect the transparency. There is. As a film forming condition of such a layer, for example, sputtering with a very short film forming time can be cited, and irradiation for several seconds can be cited depending on apparatus conditions.
The first primer layer 3 is preferably formed from alumina, silica, niobium oxide, titanium oxide or the like.

The second primer layer 4 is used for improving adhesion. The thickness may be as long as the transparency of the base material is not impaired, and is preferably a physical film thickness of 10 nm or less, for example, about 1 to 10 nm, and is preferably thicker than the first primer layer 3.
For the second primer layer 4, for example, a layer having a single bond such as SiO, or a commercially available silane coupling agent may be used.

  These primer layers are preferably formed by a dry coating method such as a sputtering method, a reactive sputtering method, a vapor deposition method, an ion plating method, or a chemical vapor deposition (CVD) method. Sputtering is particularly preferred.

  The antireflection layer 5 includes a low refractive index transparent thin film layer having a light refractive index of less than 1.6 at a wavelength of 550 nm and a light extinction coefficient of 0.5 or less at a wavelength of 550 nm, or light at a wavelength of 550 nm. High refractive index transparent thin film layer having a refractive index of 1.9 or more, low refractive index transparent thin film layer having a light refractive index of less than 1.6, medium refractive index transparent thin film having a light refractive index of about 1.6 to 1.9 Examples thereof include a laminate of a plurality of optical thin films having different refractive indexes such as layers. For example, a high-refractive-index transparent thin film layer and a low-refractive-index transparent thin-film layer are alternately laminated, and in order from the substrate side, a high-refractive-index transparent thin-film layer, a low-refractive-index transparent thin-film layer, and a high-refractive-index transparent thin-film layer And a low refractive index transparent thin film layer.

  High refractive index transparent thin film layer materials include indium, tin, titanium, silicon, zinc, zirconium, niobium, magnesium, bismuth, cerium, tantalum, aluminum, germanium, potassium, antimony, neodymium, lanthanum, thorium, hafnium, etc. Or an alloy composed of two or more of these metals, oxides thereof, fluorides, sulfides, nitrides, and the like. Specific examples include titanium oxide, niobium oxide, zirconium oxide, tantalum oxide, zinc oxide, indium oxide, and cerium oxide, but are not limited thereto. Moreover, when laminating | stacking two or more, it is not necessary to select the same material necessarily, According to the objective, it should just select suitably.

  Examples of the material for the low refractive index transparent thin film layer include, but are not limited to, materials such as silicon oxide, titanium nitride, magnesium fluoride, barium fluoride, calcium fluoride, hafnium fluoride, and lanthanum fluoride. In addition, when a plurality of layers are stacked, it is not always necessary to select the same material, and it may be appropriately selected according to the purpose.

  Examples of the medium refractive index transparent thin film layer include aluminum oxide and cerium fluoride.

  The antireflection layer 5 made of these optical thin film layers can be formed by a dry coating method such as a sputtering method, a reactive sputtering method, a vapor deposition method, an ion plating method, or a chemical vapor deposition (CVD) method. High film thickness uniformity and few defects such as pinholes, so it is possible to form thin films with better visibility, and dense films can be formed, resulting in mechanical properties such as scratch resistance. It is preferable to use a sputtering method because an excellent thin film can be formed. Among them, the dual magnetron sputtering (DMS) method, in which film formation is performed by applying a voltage in the middle frequency region, is optimal because higher productivity can be obtained by higher film formation speed and higher discharge stability.

  If necessary, an antifouling layer 6 may be provided on the outermost surface layer on the antireflection layer 5. The antifouling layer 6 is a layer obtained from a fluorine-containing silicon compound having two or more silicon atoms bonded to a reactive functional group. The reactive functional group in the present invention means a group that can react with and bind to the uppermost layer of the antireflection layer. Moreover, it is a layer formed by making the reactive functional groups of a fluorine-containing silicon compound react. Thereby, it is hard to get dirt on the surface, and even if it gets dirty, the wiping performance can be improved.

By the way, when measuring the water vapor transmission rate of these antireflection films, it changes under the influence of the material and thickness of the base material and the functional layer, and further the temperature and humidity. The temperature dependence of moisture permeability is expressed by the Arrhenius equation.
P = P0e-E / RT
P: moisture permeability (water vapor permeability per unit thickness, unit water vapor pressure difference)
P0: Moisture permeability of absolute zero E: Activation energy of moisture permeability
R: Gas constant
T: Absolute temperature

In the case of a triacetyl cellulose film that is widely used as a surface protective film for polarizing plates, the water vapor permeability with a thickness of 100 μm is 120 to 160 g / m ² / day at a temperature of 25 ° C. and a relative humidity of 90%, and a temperature of 40 ° C. and a relative humidity of 90%. 380 g / m ² / day. By laminating various layers on this substrate, water vapor hardly penetrates the film. In particular, the water vapor permeability of the antireflection layer formed of a dense film having excellent mechanical properties is almost zero, and exhibits excellent water vapor barrier performance.

  The antireflection layer 5 is formed by laminating a plurality of inorganic compounds. If at least one of the layers has an excellent water vapor barrier property, the water vapor barrier performance of the entire film becomes high. Since any further escape of moisture from the inside of the film is reduced, it is necessary to improve the performance so as to increase the overall water vapor permeability.

  That is, in the present invention, the water vapor permeability of the antireflection layer 5 is adjusted, and the first primer layer 3 that makes the thin film growth direction irregular between the hard coat layer 2 and the antireflection layer 5, adhesion By sandwiching the second primer layer 4 for imparting, for example, the low moisture permeability, which is a feature of the dense film, is improved while maintaining the feature that enables the formation of the dense film, which is a great advantage of the sputtering method. Therefore, it is possible to form an antireflection film having moderate durability and high durability with good adhesion.

The antireflection film of the present invention, the temperature 40 ° C., water vapor permeability at a relative humidity of 90% RH is preferably at least ^20g / m 2 / day, more preferably 40~250g ^/ m 2 ^/ day.

  Next, the polarizing plate 101 having the antireflection film 100 will be described with reference to FIG. The polarizing plate 101 is prepared by laminating the antireflection film 100, the polyvinyl alcohol film 10 dyed with iodine, and the film 1 made of the same material as the transparent substrate film 1 on the opposite surface in this order and bonding them together. Can do. In addition, about layer structure other than an antireflection film, not only this but a well-known technique is employable.

  EXAMPLES Hereinafter, although an Example and a comparative example further demonstrate this invention, this invention is not limited to the following example.

[Example 1]
The transparent base film 1 is made of 80 μm thick triacetyl cellulose, coated with an ultraviolet curable acrylic resin, dried and UV cured to provide a 5 μm hard coat layer 2, and then a 1.5 N- at 40 ° C. The film was immersed in a NaOH solution for 2 minutes, washed with water and dried.

A glow plasma treatment was performed on the saponified hard coat layer 2, and an Al ₂ O ₃ film was formed as a first primer layer 3 by a sputtering method. The film was formed for 2 seconds under the conditions of an electric power of 7 kW and an argon gas flow rate of 1300 sccm. As the second primer layer 4, an SiO layer was deposited with an optical film thickness of 6 nm under the conditions of power 2.0 kW and argon gas flow rate 300 sccm. Thereafter, four layers of TiO ₂ / SiO ₂ / TiO ₂ / SiO ₂ were provided as the antireflection layer 5 in the order of film formation. The film formation of TiO ₂ has an electric power of 2.5 kW, an argon gas flow rate of 300 sccm, an oxygen gas flow rate of 40 sccm, and the film formation of SiO ₂ has an electric power of 2.0 kW, an argon gas flow rate of 300 sccm, and an oxygen gas flow rate of 20 sccm. The pressure in the layer was 0.5 Pa.

The optical film thickness of each antireflection layer is monitored by an optical film thickness monitor, and the optical film thickness of the antireflection layer is a high refractive index transparent thin film layer (TiO ₂ ) or a low refractive index transparent thin film layer. The film formation time was set to 60 nm / 44 nm / 105 nm / 145 nm for (SiO ₂ ), high refractive index transparent thin film layer (TiO ₂ ), and low refractive index transparent thin film layer (SiO ₂ ), respectively.

  Thus, as shown in FIG. 2, the 25 μm-thick polyvinyl alcohol film 10 and 80 μm-thick triacetylcellulose 1 bonded to the back surface of the prepared antireflection film 100 are bonded to each other. The attached polarizing plate 101 was produced.

[Example 2]
A polarizing plate with an antireflection function was formed under the same conditions as in Example 1 except that an SiO ₂ film was used as the first primer layer 3.

[Comparative Example 1]
A polarizing plate with an antireflection function was prepared under the same conditions as in Example 1 except that the hard coat layer was saponified and then directly provided with an antireflection layer.

[Comparative Example 2]
After the plasma treatment, a polarizing plate having an antireflection layer was prepared under the same conditions as in Example 1 except that only the first primer layer was provided without providing the second primer layer.

[Comparative Example 3]
After performing the plasma treatment, a polarizing plate having an antireflection layer was prepared under the same conditions as in Example 1 except that only the second primer layer was provided without providing the first primer layer.

[Comparative Example 4]
After providing the hard coat layer on the triacetyl cellulose film, it was bonded to the polarizing plate without providing the antireflection layer.

[Evaluation]
Samples obtained in Examples and Comparative Examples were evaluated by the following methods. The results are shown in Table 1.

(1) Steel Wool Abrasion Test Steel wool # 0000 is fixed to an abrasion tester, a load of 500 gf is applied, and a 10-reciprocal abrasion test is performed on the antireflection layer of each sample. ) Was observed visually.

(2) Heat resistance test The polarizing plate created in the Examples and Comparative Examples was attached to glass via an adhesive film, and held in a constant temperature and humidity chamber set at a dry environment temperature of 95 ° C. Durability was evaluated. The presence or absence of degradation such as hydrolysis of the cellulose film was judged by visual observation, confirmation of acetic acid odor, and change in absorption spectrum of carbonyl group in infrared spectroscopic measurement.

(3) Moisture and heat resistance test The polarizing plate created in the examples and comparative examples was attached to glass via an adhesive film, and the temperature and humidity chamber was set under conditions of a dry environment at a temperature of 60 ° C and a relative humidity of 95%. The durability was evaluated. The presence or absence of degradation such as hydrolysis of the cellulose film was judged by visual observation, confirmation of acetic acid odor, and change in absorption spectrum of carbonyl group in infrared spectroscopic measurement.

(4) Water vapor transmission rate Each of the water vapor transmission rates in an environment of a temperature of 40 ° C. and a relative humidity of 90% Rh was measured in the antireflection film before the polarizing plate was attached. The water vapor permeability was measured using a method according to JIS Z0208.

  In the polarizing plate provided with the antireflection film prepared in Examples 1 and 2, since the scratch resistance performance is good, the adhesiveness is good. Further, in the heat resistance and moist heat resistance, the polarizing plate and the polarization are not less than 1000 hours. It can be confirmed that the protective film of the plate has excellent durability without deterioration. On the other hand, the adhesion of the first primer layer of Comparative Example 1 is weak, but the adhesion of the second primer layer of Comparative Example 2 is good. It was confirmed that hydrolysis reaction occurred in about time.

  The antireflection film and polarizing plate of the present invention are useful for optical display devices such as LCDs, CRTs, and plasma display panels.

It is sectional drawing of one Embodiment of the antireflection film of this invention. It is sectional drawing of one Embodiment of the polarizing plate of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transparent base film 2 Hard-coat layer 3 1st primer layer 4 2nd primer layer 5 Antireflection layer 6 Antifouling layer 10 Polarizing film (polyvinyl alcohol)
100 Antireflective film 101 made by the present invention 101 Polarizing plate having an antireflective film made by the present invention

Claims (10)

An antireflection film in which a hard coat layer, two or more primer layers, and an antireflection layer are sequentially laminated on a transparent substrate film,
The two or more primer layers have a first primer layer in contact with the hard coat layer and a second primer layer in contact with the antireflection layer, and the first primer layer and the second primer layer are made of metal or It consists of a single metal compound or a mixture,
It said first primer layer and said second primer layer, Ri different composition der,
An antireflection film, wherein the second primer layer has a thickness of 10 nm or less, and the first primer layer has a thickness smaller than that of the second primer layer. .   The antireflection film according to claim 1, wherein the antireflection layer is formed by laminating a plurality of optical thin film layers having different refractive indexes.   The antireflection film according to claim 1, wherein the antireflection layer is formed using a sputtering method. The first primer layer in contact with the hard coat layer has fine irregularities on the surface,
The composition of the second primer layer in contact with the antireflection layer and the first primer layer are different.
The antireflection film according to any one of claims 1 to 3.   The said transparent base film is a triacetyl cellulose film, The antireflection film in any one of Claims 1-4 characterized by the above-mentioned.   6. The antireflection film according to claim 1, wherein the transparent substrate film provided with the hard coat layer is subjected to an alkali saponification treatment before forming the two or more primer layers. .   The antireflection film according to claim 6, wherein the surface of the hard coat layer is subjected to a low temperature plasma surface treatment after the alkali saponification treatment. The antireflection film according to any one of claims 1 to 7 , wherein an antifouling layer is laminated on the antireflection layer. The antireflection film according to any one of claims 1 to 8 , wherein the water vapor permeability at a temperature of 40 ° C and a relative humidity of 90% RH is 20 g / m ² / day or more. A polarizing plate characterized by having an antireflection film according to any of claims 1 to 9.

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