JP3746797B2 - Polarizer - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a polarizing plate.
[0002]
[Prior art]
Currently, an iodine-based film in which iodine is adsorbed and oriented in polyvinyl alcohol (hereinafter referred to as PVA), or a dye-based film in which dichroic dye is adsorbed and oriented in PVA is used as a polarizer, and at least one side of the film is a PVA-based film. A polarizing plate having a configuration in which a protective film such as triacetyl cellulose (TAC) is bonded through an adhesive layer formed using an aqueous resin solution (PVA adhesive) is used. This polarizing plate has a problem that the end surfaces of the protective film and the polarizer are easily peeled off when used for a long time under wet heat.
[0003]
In order to solve this, a polarizing plate with improved wet heat resistance has been proposed by bonding a polarizing film and a protective film using a PVA adhesive and then drying by heating at a temperature of 90 to 110 ° C. .
[0004]
[Problems to be solved by the invention]
However, even when heat-dried at such a high temperature, it is difficult to say that the heat-and-moisture resistance is still sufficient.
[0005]
[Means for Solving the Problems]
As a result of intensive studies, the present inventors have found that such a problem can be solved by using a PVA adhesive containing a specific amount of glyoxal, and have reached the present invention.
[0006]
That is, the present invention relates to a polarizing plate in which a protective film is bonded to at least one surface of a polyvinyl alcohol polarizing film via a polyvinyl alcohol adhesive layer. This adhesive layer is composed of glyoxal and a polyvinyl alcohol resin that is an adhesive component. It is related with the polarizing plate currently formed using the polyvinyl alcohol-type adhesive agent containing the glyoxal whose ratio is (1-65) / 100 (weight ratio).
[0007]
Hereinafter, the present invention will be described in detail. As the PVA polarizing film, a conventionally known PVA polarizing film can be used. For example, an iodine polarizing film in which iodine is adsorbed and oriented on the PVA film, and a dichroic dye is adsorbed and oriented on the PVA film. Examples thereof include dye-based polarizing films and polyene-based polarizing films obtained by partially dehydrating these films. The thickness is, for example, about 10 to 50 μm.
[0008]
Examples of the PVA film include a PVA film, a polyvinyl butyral film, a polyvinyl acetal film, a polyvinyl formal film, and a poly (ethylene-vinyl acetate) copolymer saponified film.
[0009]
Examples of the protective film include acetylcellulose-based films excellent in optical transparency such as triacetylcellulose (TAC) and diacetylcellulose (DAC) whose surface is saponified. The thickness is, for example, about 10 to 200 μm.
[0010]
The ratio of glyoxal and PVA resin in the PVA adhesive is (1 to 65) / 100 (weight ratio), preferably (2 to 50) / 100 (weight ratio). If the amount of glioxal is less than this range, the effect of preventing peeling of the protective film is reduced, and if it is increased, the adhesive becomes brittle, which is not preferable. The ratio of the PVA-based resin to water is not particularly limited, but is, for example, about (1-10) / 100 (weight ratio), preferably (1-5) / 100 (weight ratio).
[0011]
Examples of the PVA resin include fully saponified PVA having a polymerization degree of 1500 to 3500, partially saponified PVA, polyvinyl butyral, partially acetalized PVA, partially formalized PVA, and a saponified poly (ethylene-vinyl acetate) copolymer. Is mentioned. These may contain a small amount of other copolymer components, and may have a functional group such as a carboxyl group or an ester thereof, an amino group, a silyl group, or a methylol group.
[0012]
The PVA adhesive can be easily prepared by, for example, dissolving glyoxal and PVA resin in water at the above-described ratio. The PVA adhesive is usually applied after being stored at a temperature of 15 ° C. to 30 ° C. after preparation. When this temperature range is deviated, there is a tendency that the appearance quality of the polarizing plate is deteriorated.
[0013]
Then, zinc chloride is added to the PVA adhesive containing glyoxal to accelerate the curing of the adhesive. The ratio of zinc chloride in the PVA adhesive to the PVA resin in the adhesive is (12 or less) / 100 (weight ratio), preferably (2-6) / 100 (weight ratio). If the amount of zinc chloride exceeds this range, the PVA adhesive containing glyoxal will gel, making it difficult to uniformly apply the adhesive. When zinc chloride is added, the adhesive is applied immediately without being stored after preparation. Moreover, cobalt chloride, magnesium chloride, ammonium chloride, boron trifluoride-etherate, barium oxide, alkyl iodide, etc. can be added to the PVA adhesive containing glyoxal instead of zinc chloride.
[0014]
As a method of laminating the PVA polarizing film and the protective film, for example, a PVA adhesive is uniformly applied on the surface of the PVA polarizing film or the protective film, and the protective film or the PVA polarizing film is overlaid on the coated surface and rolled. The method of pasting and drying by etc. is mentioned.
[0015]
The bonding temperature is usually in the range of 15 to 30 ° C. The drying temperature is usually in the range of 30 to 85 ° C., preferably in the range of 40 to 80 ° C. The thickness of the adhesive layer after drying is usually about 5 μm or less.
[0016]
Thus, through the adhesive layer formed using the polyvinyl alcohol-based adhesive containing glyoxal and having a ratio of glyoxal to the polyvinyl alcohol-based resin as the adhesive component of (1 to 65) / 100 (weight ratio). The polarizing plate of the present invention in which a protective film is bonded to at least one surface of the polarizing film is obtained.
[0017]
【The invention's effect】
Since the polarizing film and the protective film are bonded through the adhesive layer formed using the PVA adhesive containing a specific amount of glyoxal in the polarizing plate of the present invention, the polarizing film under wet heat conditions There is no problem of end face peeling of the protective film, and it is excellent in durability. For this reason, it can be used even under wet heat conditions that could not be used with conventional polarizing plates.
[0018]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to this.
[0019]
Example 1 (reference)
A 75 μm-thick PVA film (average polymerization degree of about 1700, saponification degree of 99.9% or more) is subjected to uniaxial stretching (stretching ratio 5 times), and an aqueous solution containing iodine and potassium iodide while being kept in tension [ Iodine / potassium iodide / water = 0.05 / 5/100 (weight ratio)] for 60 seconds. Next, it was immersed for 300 seconds in a 65 ° C. aqueous solution containing potassium iodide and boric acid [potassium iodide / boric acid / water = 6 / 7.5 / 100 (weight ratio)]. After washing with pure water at 25 ° C. for 20 seconds, it was dried at 50 ° C. to obtain a PVA polarizing film.
[0020]
Glyoxal was added to an aqueous solution of PVA (average polymerization degree of about 1700, saponification degree of 99.6% or more) to obtain an adhesive [PVA / water / glyoxal = 4/100 / 0.6 (weight ratio)]. Stored at ° C. Under an atmosphere of 28 ° C., this adhesive was applied to both sides of the polarizing film, and a protective film (a triacetyl cellulose film (Fujitac UV-80, thickness 80 μm) whose surface was saponified) was applied to both sides. Pasted. And it dried at 80 degreeC for 6 minutes, and obtained the polarizing plate (thickness of an adhesive layer is about 0.1 micrometer). Table 1 shows changes in the single transmittance immediately after drying (difference between the transmittance of the polarizing plate and the single transmittance of the polarizing film) and the end face peeling state of the polarizing plate after 500 hours at 60 ° C. × 90% RH.
[0021]
Example 2 (reference)
A polarizing plate was obtained in the same manner as in Example 1 except that the ratio of PVA / glyoxal was changed to 4 / 0.08 (weight ratio). The results are shown in Table 1.
[0022]
Example 3 (reference)
A polarizing plate was obtained in the same manner as in Example 1 except that the drying temperature after bonding the polarizing film and the protective film was 50 ° C. The results are shown in Table 1.
[0023]
Example 4 (reference)
Instead of an aqueous solution containing iodine and potassium iodide, it is immersed for 5 minutes in a 60 ° C. aqueous solution containing dichroic dye and sodium nitrate (dichroic dye / phosphoric acid / water = 0.5 / 40/2000 (weight ratio)). A polarizing plate was obtained in the same manner as in Example 1 except that an aqueous boric acid solution [boric acid / water = 150/2000 (weight ratio)] was used instead of the aqueous solution containing potassium iodide and boric acid. . The results are shown in Table 1.
[0024]
Example 5
Adhesive with a small amount of zinc chloride added [PVA / water / glyoxal / zinc chloride = 4/100 / 0.4 / 0.14 (weight ratio)] was used as an adhesive and applied immediately after preparing the adhesive. A polarizing plate was obtained in the same manner as in Example 4 except that drying after bonding was performed at 55 ° C. The results are shown in Table 1.
[0025]
Example 6
A polarizing plate was obtained in the same manner as in Example 5 except that the ratio of [PVA / water / glyoxal / zinc chloride] was [4/100 / 1.0 / 0.17 (weight ratio)]. The results are shown in Table 1.
[0026]
Example 7
A polarizing plate was obtained in the same manner as in Example 5 except that the ratio of [PVA / water / glyoxal / zinc chloride] was [4/100 / 1.4 / 0.23 (weight ratio)]. The results are shown in Table 1.
[0027]
Example 8
A polarizing plate was obtained in the same manner as in Example 5 except that the ratio of [PVA / water / glyoxal / zinc chloride] was [4/100 / 1.9 / 0.23 (weight ratio)]. The results are shown in Table 1.
[0028]
Comparative Example 1
A polarizing plate was obtained in the same manner as in Example 1 except that glioxal was not used. The results are shown in Table 1.
[0029]
Comparative Example 2
A polarizing plate was obtained in the same manner as in Example 4 except that no glioxal was used. The results are shown in Table 1.
[0030]
Comparative Example 3
A polarizing plate was obtained in the same manner as in Example 4 except that the glyoxal was not used and the drying condition after bonding was 100 ° C. × 5 minutes. The results are shown in Table 1.
[0031]
Comparative Example 4
A polarizing plate was obtained in the same manner as in Example 4 except that an aqueous solution containing PVA and methylol melamine [PVA / methylol melamine / water = 4 / 0.5 / 100 (weight ratio)] was used as an adhesive. The results are shown in Table 1.
[0032]
Comparative Example 5
A polarizing plate was obtained in the same manner as in Example 4 except that an aqueous solution containing PVA and boric acid [PVA / boric acid / water = 4 / 0.04 / 100 (weight ratio)] was used as an adhesive. The results are shown in Table 1.
[0033]
[Table 1]
━━━━━━━━━━━━━━━━━━━━━━
Experiment number Single transmittance Contact under wet heat
Change (%) Detachment of wearing interface ━━━━━━━━━━━━━━━━━━━━━━
Example 1 (reference) 0 None Example 2 (reference) 0 None Example 3 (reference) 0 None Example 4 (reference) 0 None ────────────────── ────
Example 5 0 None Example 6 0 None Example 7 0 None Example 8 0 None ──────────────────────
Comparative Example 1 0 Yes Comparative Example 2 0 Yes Comparative Example 3 1 Yes Comparative Example 4 0 Yes Comparative Example 5 0 Yes ━━━━━━━━━━━━━━━━━━━━━━

Claims (3)

A protective film is bonded to at least one surface of the polyvinyl alcohol polarizing film via a polyvinyl alcohol adhesive layer, and a polyvinyl alcohol adhesive is applied to the surface of the polarizing film or the protective film. In the polarizing plate obtained by stacking and laminating films and drying , the adhesive layer has a ratio of glyoxal and the polyvinyl alcohol resin as an adhesive component of (1 to 65) / 100 (weight ratio). containing glyoxal, further containing zinc chloride, and characterized by being formed by using the ratio of zinc chloride and polyvinyl alcohol resins are the (12 or less) / 100 polyvinyl alcohol-based adhesives are (by weight) Polarizing plate.   The polarizing plate according to claim 1, wherein the amount of glyoxal in the polyvinyl alcohol-based adhesive is 50 parts by weight or less with respect to 100 parts by weight of the polyvinyl alcohol-based resin. In the method of bonding a protective film to at least one surface of a polyvinyl alcohol polarizing film via a polyvinyl alcohol adhesive layer to produce a polarizing plate , the adhesive layer is a ratio of glyoxal and a polyvinyl alcohol resin that is an adhesive component. Containing 1 to 65/100 (weight ratio) of glyoxal, further containing zinc chloride, and the ratio of zinc chloride to polyvinyl alcohol resin is (12 or less) / 100 (weight ratio) method for producing a polarizing plate and forming with the system adhesive.