JPH07107565B2 - Polarizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a polarizing plate which is preferably used for a liquid crystal display plate and the like.

[Conventional technology]

The polarizing film is formed, for example, by laminating both surfaces of a polyvinyl alcohol film or the like having a polarizing property with iodine, a dichroic dye or the like with a protective film such as a cellulose triacetate film, and a liquid crystal display panel. Is generally manufactured by providing a pressure-sensitive adhesive layer on the polarizing film and press-bonding it to a liquid crystal cell.

As the pressure-sensitive adhesive, various crosslinked acrylic adhesives have been proposed. For example, JP-A-56-95965 discloses a pressure-sensitive adhesive containing a copolymer containing a hydroxyalkyl acrylate as a constituent and a polyfunctional isocyanate compound. The storage stability is poor because the coalesced by the isocyanate compound is crosslinked, and the crosslink density after curing on the polarizing film varies depending on the curing conditions, and the crosslinking progresses over time, so the quality stability was not sufficiently satisfactory. .

As a further big problem, when laminating a polarizing film having the acrylic adhesive layer on a liquid crystal cell or a protective plate glass which is becoming larger in size in recent years, because the positioning often fails, the glass surface of the liquid crystal cell is soiled, Alternatively, since it is difficult to sufficiently degas, when used under conditions of high temperature and high humidity, foaming, interfacial peeling and wrinkles often occur.

[Problems to be solved by the invention]

In view of the above-mentioned drawbacks of the conventional polarizing film, the object of the present invention is to easily laminate to a large liquid crystal cell or a protective glass, in particular, to allow sufficient deaeration, and to prevent bubbles under high temperature and high humidity conditions. It is an object of the present invention to provide a polarizing plate that does not cause peeling or interface peeling.

[Means for solving problems]

The gist of the present invention is that an adhesive thermoplastic resin film is provided on at least one surface of a polarizing film, a large number of coarse irregularities are formed on the outer surface of the adhesive film, and the adjacent concave portions of the coarse irregularities are formed. Or the average interval between adjacent convex portions is about 2 to 10 times the average roughness of 10 points, and further fine unevenness is formed on the surface of the rough unevenness, The present invention resides in a polarizing plate having a surface roughness of 5 to 20 μm.

The polarizing film used in the present invention is not particularly limited and any conventionally known one can be used, for example, polyvinyl alcohol, polyvinyl formal, polyvinyl acetal, saponified product of ethylene / vinyl acetate copolymer, polyvinyl alcohol, etc. Iodine in a film of a resin-based resin, one side or both sides of the polarizing film is imparted with a polarizing property by impregnating a polarizing element such as a dichroic dye and stretching, a cellulose-based film such as cellulose triacetate, a polycarbonate-based film, a poly A laminate of protective films such as an ether sulfone film is often used.

The polarizing plate of the present invention is an adhesive thermoplastic resin film described below on at least one surface of the polarizing film, preferably a polyvinyl butyral film containing a plasticizer is provided, but in some cases, the protective film is It may be one in which a plasticized polyvinyl butyral film or the like is laminated on both surfaces of the above polarizing film without being laminated at all.

Cellulose triacetate used as the polarizing film is preferably a partially saponified product in order to improve the adhesion to plasticized polyvinyl butyral and the like.

Since the adhesive thermoplastic resin film provided on at least one surface of the polarizing film is firmly adhered and laminated to the glass such as liquid crystal cell by heating and pressurization, it is preferably transparent and has appropriate adhesiveness and toughness. The surface which has a polarizing film and is in contact with the polarizing film is formed as a mirror surface.

Examples of the resin used in the adhesive thermoplastic resin film are polyvinyl acetals such as polyvinyl butyral,
Polyurethane, ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-vinyl alcohol copolymer, ethylene-methyl methacrylate copolymer and the like can be mentioned, and polyvinyl butyral containing a plasticizer is particularly preferable.

The reason is that the polarizing plate of the present invention using the plasticized polyvinyl butyral has a high cohesive force, an adhesive force is formed and an adhesive layer of stable quality is formed, and when it is attached to a liquid crystal cell or the like, it has a high temperature. , Not causing bubbles or peeling at the interface under high humidity conditions, and further degrading and degrading the cellulose triacetate film and corroding and degrading the reflective metal foil used for the liquid crystal display panel. This is because it is possible to provide a polarizing plate having no color.

The degree of polymerization of polyvinyl butyral used for plasticized polyvinyl butyral is likely to cause blocking when the film is formed and wound when it is too low, and conversely, when it is too high, high humidity is required when laminating with a polarizing film or glass after film formation. It is generally set to 500 to 2000 because it requires conditions. Further, a butyralization degree of 55 to 80 mol% is preferably used.

As the plasticizer to be added to and mixed with polyvinyl butyral, conventionally known ones can be used, and specific examples thereof include triethylene glycol di2-ethylbutyrate, triethylene glycol di2-ethylhexoate and dibutyl sebacate. Can be mentioned. The amount of these plasticizers used is such that if the polyvinyl butyral layer does not have too much plasticity and there is too much so-called bleeding phenomenon that exudes to the polyvinyl butyral layer surface, it is generally 20 to 60 parts by weight with respect to 100 parts by weight of polyvinyl butyral. , Preferably 30-5
It is 0 parts by weight.

An adhesive film such as a plasticized polyvinyl butyral film may contain an ultraviolet absorber, an antioxidant, a colorant, an adhesive modifier such as a metal salt of carboxylic acid, and the like.

On the outer surface of the adhesive thermoplastic resin film used in the present invention, that is, on the surface which is not in contact with the polarizing film, a large number of rough projections and depressions are formed so as to be sufficiently degassed when laminated on a liquid crystal cell. Has been done. In this unevenness, the average interval between adjacent concave portions or adjacent convex portions is about twice or more than 10-point average roughness in order to enhance deaeration, and the adhesiveness when using a highly adhesive resin Is about 10 times or less to reduce And the average interval of coarse irregularities is generally 100.
~ 500 μm, preferably 200-300 μm, and 10-point average roughness is generally 20-100 μm, preferably 25-70 μm
It is said that

Furthermore, the coarse unevenness formed on the adhesive film is
Since fine irregularities are formed on the surface of the coarse irregularities, it is favorable in terms of degassing and workability in stacking on a liquid crystal cell or the like.

Hereinafter, the adhesive film having the double concave and convex portions will be described with reference to the drawings showing an example of the present invention.

FIG. 1 is a partially cutaway simulated perspective view of a state in which a liquid crystal cell 10 is placed on a polarizing plate 9 of the present invention, and FIG. 2 is a surface roughening at an arbitrary position of an adhesive thermoplastic resin film used in the present invention. It is the figure which simulated represented the curve at the time of measuring the height using the stylus method.

In FIG. 1, a rough unevenness having convex portions 5 and concave portions 6 on the outer surface of an adhesive thermoplastic resin film 4 provided on one surface of a polarizing film 3 composed of a cellulose triacetate layer 1 and a polyvinyl alcohol layer 2 7 are provided in large numbers, and a plurality of fine irregularities 8 are provided on the surface of the coarse irregularities 7, and thus the adhesive film 4 has double irregularities on the surface.

The average interval of the coarse irregularities is obtained, for example, as the average of the intervals between the bottoms of the adjacent coarse concave portions.

As shown in FIG. 2, when considering the part where the surface curve is divided by the reference length L, the distance between the bottoms of the recesses is Wi (i
Is an integer from 1 to n, n + 1 is the number of bottoms of the recesses between the reference lengths L), and the average interval W is It is represented by.

The roughness of the rough unevenness is represented by a 10-point average roughness according to the International Organization for Standardization ISO-R468, which is obtained as follows.

In Figure 2, the average of the heights of the five peaks from the highest mountain 41 to the fifth highest mountain 45 and the height of the five valleys from the deepest valley 51 to the fifth deepest valley 55 The difference from the average value is defined as 10-point average roughness H. Therefore, in FIG. 2, H is
If the height of the peak or valley measured from the base line X is Ha (a is an integer of 1 to 10), it can be calculated by the following formula.

The reference length L is set to a specific length according to the degree of roughness of the surface, but is usually 8 mm in the present invention.

Further, the surface roughness of the fine unevenness on the rough uneven surface and the interval between the adjacent concave portions or convex portions are the roughness degree of the rough unevenness,
It is selected within an appropriate range depending on the material and physical properties of the resin film. The surface roughness of fine irregularities is generally 5 to 20 μm, preferably 5 to 15 μm, expressed as a 10-point average roughness. When the average roughness of the coarse irregularities is relatively small, it is preferable that the surface roughness of the fine irregularities is also relatively small. The ratio of the surface roughness of fine irregularities to the surface roughness of coarse irregularities is preferably in the range of 0.2 to 0.5. Also, the average spacing between adjacent concave portions or adjacent convex portions of fine irregularities is 60 to 130.
μm is preferable, and more preferably 60 to 100 μm
Is.

The 10-point average roughness, which represents the surface roughness of fine irregularities, is measured after removing the rough irregularities (also called swell) from the surface (cross-section) curve illustrated in FIG. To remove coarse irregularities from a cross-section curve, generally, a method using a wave circuit used in an electric surface roughness measuring machine or a locus of the center of a circle when tracing a cross-section curve with a circle having a large radius of curvature is used. Is used, and the former is preferably adopted. At present, most of the stylus type surface roughness measuring devices are of a type that electrically expands the motion of the stylus, and the above wave circuit is usually incorporated in the measuring device in advance. As an example of a roughness measuring device incorporating such a wave circuit, Surfcom 1210, a stylus type surface roughness meter manufactured by Tokyo Seimitsu Co., Ltd.
A type etc. are mentioned.

And in the present invention, the cutoff length (cutting wavelength) in the wave circuit is 0.08 m / in accordance with JIS B0601-1976.
It is preferable to adopt m.

Examples of the method for producing the adhesive film having the double-concavo-convex shape include methods such as an embossing roll method, a calendar roll method, a profile extrusion method, a mechanical etching method, and a method using male and female press plates, among which embossing. The roll method is preferred. In the embossing roll method, an embossing roll having irregularities corresponding to the irregularities to be imparted to the surface of the thermoplastic resin film is used as a molding press roll in the production of the adhesive film.

When forming double unevenness on the embossing roll used for producing the adhesive film, it is preferable to use an engraving method for forming coarse unevenness and a blast method for forming fine unevenness. The engraving method is, for example, a method in which an engraved pattern of a mother roll is coined and transferred onto a roll surface to be manufactured. In the blast method, granular blast material is sprayed onto the roll surface at a high speed.

In the polarizing plate of the present invention, in order to enhance the adhesiveness between the protective film and the film such as plasticized polyvinyl butyral, or the plasticizer in the film such as plasticized polyvinyl butyral when used at high temperature (about 60 ° C. or higher), other In order to prevent the additive from migrating to the polarizing film or the like, a urethane-based adhesive layer, for example, may be provided at the interface between the film such as plasticized polyvinyl butyral and the adjacent layer.

Further, it is convenient for handling that a release film such as a polyethylene film coated with silicon is provided on the surface of the plasticized polyvinyl butyral film.

In order to provide a film such as plasticized polyvinyl butyral on at least one surface of the polarizing film in the present invention, a conventionally known method can be adopted, but a plasticized polyvinyl butyral film formed by extrusion molding or roll molding can be used as the polarizing film. The method of laminating on is preferably adopted.

For example, a plasticized polyvinyl butyral film heated to 50-80 ° C is laminated on the polarizing film of polyvinyl alcohol-based polarizing film / cellulose-based protective film bilayer, or on the surface of protective film / polarizing film / protective film trilayer. After stacking, pressure is applied at about 1 to 4 kg / cm ² to obtain a polarizing plate.

〔Example〕

Example 1 Polyvinyl butyral resin 100 having an average degree of polymerization of 1700, a butyralization degree of 65 mol% and a residual vinyl alcohol of 34.5 mol%
40 parts by weight of triethylene glycol di-2-ethylbutyrate, 0.2 parts by weight of BHT as an antioxidant, and 2- (3-t-butyl-5-methyl-2) as an ultraviolet absorber.
A polyvinyl butyral composition was prepared by adding and mixing 0.2 part by weight of (hydroxyphenyl) 5-chlorobenzotriazole (Tinuvin 326, Ciba Kaigie).

After kneading this composition with a roll at 70 ° C, 150 ° C, 50K
Press with a male and female press plate under the condition of g / cm ² ,
Thickness where one side is a mirror surface and the other side has double unevenness
A 380 μm plasticized polyvinyl butyral film was obtained. The coarse unevenness had a 10-point average roughness of 35 μ, an average interval of 5 times the average roughness, and was a smooth shape, and the surface roughness of the fine unevenness was 8 μ.

This polyvinyl butyral film and a cellulose triacetate / polyvinyl alcohol bilayer separately prepared by a conventional method
The polyvinyl butyral film was laminated under the condition of 70 ° C. and 2 Kg / cm ² so that the mirror surface side of the polyvinyl butyral film was in contact with the polyvinyl alcohol layer to obtain a desired polarizing plate 9 as shown in FIG.

The obtained polarizing plate 9 was cut into a size of 200 × 200 m / m and laminated on a glass plate 11 for liquid crystal cell as follows. In addition, 12 is a liquid crystal enclosed in a liquid crystal cell, and 13 is a spacer.

Place the above polarizing plate so that the polyvinyl butyral layer is in contact with the glass at a predetermined position in the glass, put this in a rubber bag, degassing to 600 mmHg or less under reduced pressure, in an autoclave at 70 ° C., 4 kg / cm ² conditions. Then, the mixture was heated and pressed for about 30 minutes to obtain a liquid crystal display plate in which the above polarizing plate was firmly adhered to a glass plate. At this time, defoaming at the glass interface was sufficient, and there was no residual air bubble on the liquid crystal display panel.

Using the liquid crystal display panel thus obtained as a sample, a humidity resistance test (60 ° C, 90% RH, 500 hours), a heat resistance test (80
(° C, 500 hours).

As a result, the polarizing plate was not peeled off not only in the central part of the sample but also in the peripheral part, and there were no abnormalities such as foaming and wrinkling (see Table 1, repeat number 10).

Further, the polarization performance at this time is the polarization after the moisture resistance / heat resistance test is performed on the liquid crystal display panel obtained by using the conventional polarizing plate in which the acrylic film is provided with the acrylic pressure-sensitive adhesive layer. It was equivalent to performance.

Examples 2 and 3 In the same manner as in Example 1, a polarizing plate having double irregularities formed on the outer surface of plasticized polyvinyl butyral and a liquid crystal display plate were obtained. The irregular shape of polyvinyl butyral and the physical properties of the liquid crystal display panel are shown in Table 1.

Example 4 To 100 parts by weight of a polyvinyl butyral resin having an average degree of polymerization of 850 and a butyralization degree of 72 mol%, the same amount and the same amount of the plasticizer, the antioxidant and the ultraviolet absorber as used in Example 1 were added and mixed. A polyvinyl butyral composition was prepared.

This composition was roll-kneaded at 40 ° C. to form a film, which was then pressed to make one surface a mirror surface and the other surface with rough irregularities of 10 points having an average roughness of 60 μm and an average spacing of 200 μm. As a result, the surface roughness of the fine unevenness provided an emboss of 8 μm. As shown in FIG. 3, these two polyvinyl butyral films 4 and 4 and a polarizing film 3 composed of a trilayer of cellulose triacetate / polyvinyl alcohol / cellulose triacetate prepared by a conventional method are combined with polyvinyl butyral film. The film was laminated under the condition of 50 ° C. and 2 kg / cm ² so that the mirror surface side of the film was in contact with the cellulose triacetate layer to obtain the target polarizing plate 9.

The obtained polarizing plate is cut into a size of 100 mm × 200 mm, placed at a predetermined position on the glass plate 11 of the liquid crystal cell 10 as follows, and a non-reflective protective glass having a metal oxide vapor-deposited on the surface. 14 was put into the assembly. Utilizing the adhesiveness of the plasticized polyvinyl butyral film to the glass, the assembly was lightly pressed to temporarily determine the position, but at this time, the displacement of the liquid crystal cell glass 11 and the protective glass 14 occurred. There wasn't.

This assembly was put in a rubber bag and prepressed for 30 minutes while degassing under reduced pressure at 60 ° C. at 600 mmHg or more.
The degassed state after the preliminary pressing was such that very few residual bubbles remained in the center. 60 in an autoclave
This press was performed by heating and pressurizing for 20 minutes under the condition of ° C and 4 Kg / cm ² . In the state after the main pressing, residual bubbles disappeared, and wrinkles and distortion were not generated, and a liquid crystal display panel with a protective glass having a very good appearance was obtained.

This was subjected to the same moisture resistance test and heat resistance test as in Example 1. As a result, as shown in Table 1, there was no peeling of the polarizing plate, and there was no abnormality such as foaming or wrinkling.

Comparative Example 1 As a polarizing plate, one having a conventional acrylic pressure-sensitive adhesive layer provided on the upper and lower sides of the three-layer polarizing film used in Example 4 was used. After pressure-bonding an acrylic layer on one surface on the same liquid crystal cell glass as used in Example 4 by a conventional method,
Furthermore, protective gatus was laminated on the acrylic layer on the other surface. At the interface between the glass and the acrylic layer, there were residual bubbles immediately after lamination, and after the pressing the bubbles disappeared but wrinkles remained.

When a moisture resistance test was conducted on this liquid crystal display panel, 4 out of 10 foamed, and in a heat resistance test 3 out of 10 foamed.

〔The invention's effect〕

The polarizing plate of the present invention is constituted as described above, and a large number of coarse irregularities are formed on the outer surface of the thermoplastic resin film provided on at least one surface of the polarizing film, and the coarse irregularities are adjacent to each other. The average distance between the concave parts or the adjacent convex parts is
Since it is about 2 to 10 times the 10-point average roughness, and fine irregularities are formed on the surface of the coarse irregularities, and the surface roughness of the fine irregularities is 5 to 20 μm. Stacking on glass for protecting large liquid crystal cells and liquid crystal display plates such as B5 size and A4 size can be done easily compared to conventional polarizing plates provided with an acrylic adhesive layer, The degassing is sufficiently carried out so that no bubbles are generated or no interfacial peeling occurs even under high temperature and high humidity conditions.

[Brief description of drawings]

FIG. 1 is a partially cutaway simulated perspective view of a liquid crystal cell placed on a polarizing plate of the present invention, FIG. 2 is a surface roughness curve of an adhesive thermoplastic resin film used in the present invention, and FIG. It is sectional drawing of the liquid crystal display board with a protective glass obtained using the polarizing plate which shows the other Example of this invention. Polarizing film ... 3, Adhesive thermoplastic resin film ... 4

Claims (2)

[Claims] 1. A polarizing film is provided with an adhesive thermoplastic resin film on at least one surface thereof, and a large number of coarse irregularities are formed on the outer surface of the adhesive film, and the concave portions adjacent to the coarse irregularities are formed. Or the average distance between adjacent protrusions is 10
It is about 2 to 10 times the point average roughness, and further fine irregularities are formed on the surface of the coarse irregularities, and the surface roughness of the fine irregularities is 5 to 20 μm. Polarizing plate. 2. The polarizing plate according to claim 1, wherein the adhesive thermoplastic resin film is a polyvinyl butyral film containing a plasticizer.