KR20240000604A - display device - Google Patents

Abstract

A display device capable of preventing condensation on the back of a front panel is provided.
The display device 1 includes a display panel 2 having an image display surface 2a for displaying an image, an air gap layer 7 provided in front of the image display surface 2a, and a front surface of the air gap layer 7. It is provided with a front plate (4) provided in and an anti-fog layer (10) provided between the front plate (4) and the void layer (7). The anti-fog layer 10 has a film base 11 that is a cellulose acylate layer, and a saponification layer 12 that contains cellulose and is provided on the back of the film base 11. The saponification layer 12 is formed by saponifying the first base surface 11a of the film base 11.

Description

display device

The present invention relates to a display device.

BACKGROUND ART [0002] Display devices having a display panel for displaying images are widely used as electronic signboards. When a display device is used as an electronic sign, a front plate is provided in front of the display panel to protect the display panel. For example, Patent Document 1 below describes a configuration in which a front plate is disposed in front of a display panel with an air gap layer interposed therebetween.

Japanese Patent Publication No. 2017-016024

However, in Patent Document 1, there was a problem in that condensation occurred on the back of the front panel due to a temperature difference between the inside and outside of the display device (the front side and the back side of the front panel), making the display difficult to see. In particular, when the thickness of the void layer becomes thinner due to thinning of the display device, the above-mentioned problems become more noticeable. In addition, a method such as abolishing the void layer and attaching a front plate to the front of the display panel using, for example, a transparent adhesive, is also conceivable, but in this case, the cost increases.

The present invention has been made in view of the above background, and its purpose is to provide a display device that can prevent condensation on the back of the front panel while suppressing an increase in cost.

In order to achieve the above object, the display device of the present invention includes a display panel having an image display surface for displaying an image, an air gap layer provided in front of the image display surface, a front plate provided in front of the air gap layer, and a front plate. and an anti-fog layer provided between the void layers, and the anti-fog layer has a cellulose acylate layer and a saponification layer containing cellulose provided on the back of the cellulose acylate layer.

The display panel may be a liquid crystal display panel, and a polarizing plate may be provided on the image display surface.

An optical functional layer may be provided between the front plate and the anti-fog layer to convert incident light into circularly polarized light and emit it.

The optical function layer may contain a polarizing plate.

The optical functional layer may include a polarizing plate and a quarter wave plate disposed on both surfaces of the polarizing plate.

The absolute value of the thickness direction retardation Rth of the anti-fog layer may be 100 nm or less.

The absolute value of the in-plane phase difference Re of the anti-fogging layer may be 20 nm or less.

The thickness of the saponification layer may be within the range of 1 μm or more and 3 μm or less.

According to the present invention, it is possible to provide a display device that can prevent condensation on the back of the front panel while suppressing an increase in cost.

1 is an external view of a display device.
Figure 2 is an exploded view of the display device.
Figure 3 is a cross-sectional view of the display device.
Figure 4 is a cross-sectional view of the display device.
Figure 5 is a graph showing the relationship between water absorption and acyl group ratio.
Figure 6 is a graph showing the relationship between the acyl group ratio and the thickness of the saponification layer.
7 is a cross-sectional view of the display device.
8 is a cross-sectional view of the display device.

As shown in FIGS. 1 and 2, the display device 1 includes a display panel 2 for displaying an image consisting of a front frame 3, a front plate 4, and a back cover 5. It is stored in the case 6, and is installed outdoors, such as inside a station, for example, and is used as an electronic signboard that displays advertisements, etc. The display panel 2 is a well-known image display panel using, for example, liquid crystal, organic EL (Electro Luminescence), etc., and displays images on the image display surface 2a provided on the front. In addition, in this embodiment, the display panel 2 is an image display panel (liquid crystal panel) using liquid crystal, and a polarizing plate is provided on the image display surface 2a (the image display surface 2a is composed of a polarizing plate), as an example. Give an explanation.

As shown in FIG. 3, the front plate 4 is formed of a transparent member such as glass, for example. And the front plate 4 is disposed in front of the image display surface 2a and spaced apart from the image display surface 2a. As a result, the gap layer 7 is formed between the back of the front plate 4 and the image display surface 2a (the front of the display panel 2). By providing the void layer 7 in this way, manufacturing costs can be suppressed compared to the case where the front plate 4 is adhered to the image display surface 2a using a transparent adhesive or the like. Additionally, it also contributes to improving the heat dissipation properties of the display panel 2. In addition, in FIG. 3 and FIGS. 4, 7, and 8 described later, the front frame 3 and the rear cover 5 are omitted from illustration in order to avoid complicating the drawings.

On the other hand, there is a problem that providing the void layer 7 causes condensation to form on the back of the front plate 4, making it difficult to see the display. This causes the display panel 2 to generate heat as the image is displayed (lighted up), and as a result, moisture is released from the polarizing plate provided on the image display surface 2a, increasing the humidity of the air in the void layer 7. For this reason, when the display device 1 is used in an external environment with a low temperature, the front panel 4 is cooled from the front, and fine water droplets are likely to be formed on the back surface of the front panel 4. At this time, when fine water droplets are formed on the back surface of the front plate 4, the pixels of the display device 1 are enlarged by the water droplets, making the display look dazzling, or the water droplets gather further to form a water film, causing damage caused by the water film. The display becomes uneven and may be recognized.

In particular, when the thickness of the void layer 7 becomes thinner due to thinning of the display device 1, moisture released from the polarizing plate provided on the image display surface 2a, etc., in a state in which the volume of the void layer 7 is reduced, enters the void layer. By being included in the air of (7), the degree of increase in the humidity of the void layer (7) increases, condensation becomes more likely to occur, and the above-mentioned problems become more noticeable. Problems caused by condensation like this are likely to occur when the display device 1 is used in winter when the outside temperature is low, and also, after the display panel 2 has been turned on for a long time, the light is turned off and the display is displayed again. In this case, moisture released as heat from the display panel 2 when turned on cools and condenses on the back of the front panel 4 when the light is turned off, causing glare or unevenness when the display is displayed again, due to a mechanism such as this. easy to do.

For this reason, in the display device 1, an anti-fog layer 10 is provided between the front plate 4 and the air gap layer 7. By doing this, condensation on the back of the front plate 4 is prevented. In addition, in this embodiment, since the anti-fog layer is formed by sticking an anti-fog film on the back of the front plate 4, in the following description, the anti-fog layer is called an anti-fog film, and the anti-fog layer and the anti-fog film have common features. Add symbols to explain.

The anti-fog film 10 (anti-fog layer 10) includes a film base 11 (cellulose acylate layer) and a saponification layer 12. The thickness of the anti-fog film 10 is not particularly limited, and is, for example, within the range of 10 μm or more and 500 μm or less. Additionally, in this embodiment, the thickness is set to 130 μm, for example.

The saponification layer 12 serves the function of preventing the formation of fine water droplets. The saponification layer 12 is provided on one surface of the film base 11 (in this embodiment, the surface on the display panel 2 side, hereinafter referred to as the first base surface 11a). The saponification layer 12 is a saponified cellulose layer, and the cellulose layer contains saponified TAC.

The film base 11 is the film main body of the anti-fog film 10, and also functions as a support for supporting the saponification layer 12. The film base 11 is a cellulose acylate layer of the present invention formed of cellulose acylate. Cellulose acylate is cellulose triacetate (triacetylcellulose, hereinafter referred to as TAC) in this embodiment, but is not limited to TAC and may be another cellulose acylate different from TAC. Additionally, the film base 11 does not contain saponified cellulose acylate.

Cellulose acylate is explained in detail below. Cellulose acylate is a product in which the ratio of esterification of the hydroxy group of cellulose to carboxylic acid, that is, the degree of substitution of the acyl group (hereinafter referred to as the degree of acyl group substitution) satisfies all the conditions of the following formulas (1) to (3). This is particularly desirable. In addition, in (1) to (3), both A and B are acyl group substitution degrees, the acyl group in A is an acetyl group, and the acyl group in B has 3 to 22 carbon atoms.

2.4≤A+B≤3.0… (One)

0≤A≤3.0… (2)

0≤B≤2.9… (3)

The glucose unit that makes up cellulose and is bonded to β-1,4 has hydroxyl groups at the 2nd, 3rd, and 6th positions. Cellulose acylate is a polymer in which some or all of the hydroxy groups of cellulose are esterified and the hydrogen of the hydroxy group is replaced with an acyl group having 2 or more carbon atoms. In addition, if one hydroxy group in the glucose unit is 100% esterified, the degree of substitution is 1, so in the case of cellulose acylate, if the hydroxy groups at positions 2, 3, and 6 are each 100% esterified, the degree of substitution is 1. The degree becomes 3.

Here, in glucose units, the degree of substitution of the acyl group at the 2nd position is DS2, the degree of substitution of the acyl group at the 3rd position is DS3, and the degree of substitution of the acyl group at the 6th position is DS6, so that the total acyl group is calculated as "DS2+DS3+DS6". The degree of substitution is preferably 2.00 to 3.00, and in this embodiment, it is 2.86.

There may be only one type of acyl group, or two or more types may be used. When there are two or more types of acyl groups, it is preferable that one of them is an acetyl group. The total degree of substitution of the hydrogens of the hydroxyl groups at the 2nd, 3rd, and 6th positions by acetyl groups is DSA, and the total degree of substitution by acyl groups other than acetyl groups at the 2nd, 3rd, and 6th positions. When is set to DSB, the value of "DSA+DSB" is preferably 2.2 to 2.86, and particularly preferably 2.40 to 2.80. It is preferable that the DSB is 1.50 or more, and it is especially preferable that it is 1.7 or more. Preferably, at least 28% of the DSB is a substitution of the hydroxyl group at the 6th position, but more preferably at least 30%, more preferably at least 31%, and especially preferably at least 32% of the hydroxyl group at the 6th position. It is preferable that it is a substitution of time. Moreover, the value of "DSA+DSB" at the 6th position of cellulose acylate is preferably 0.75 or more, more preferably 0.80 or more, and especially preferably 0.85 or more.

The acyl group having 2 or more carbon atoms may be an aliphatic group or an aryl group, and is not particularly limited. For example, there are alkyl carbonyl esters, alkenyl carbonyl esters, aromatic carbonyl esters, and aromatic alkyl carbonyl esters of cellulose, and each of them may further have a substituted group. Propionyl group, butane oil group, pentane oil group, hexane oil group, octane oil group, decane oil group, dodecane oil group, tridecane oil group, tetradecane oil group, hexadecane oil group, octadecanoyl group, iso-view Examples include tannoyl group, t-butanoyl group, cyclohexanecarbonyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, and cinnamoyl group. Among these, propionyl group, butanoyl group, dodecane oil group, octadecanoyl group, t-butane oil group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group, etc. are more preferable, and propionyl group and butane group. Oily groups are particularly preferred.

In addition to cellulose acylate, the film base 11 may contain various additives such as plasticizers, ultraviolet absorbers, and anti-deterioration agents, and/or, for example, fine particles to prevent the anti-fog films 10 from sticking together.

Examples of plasticizers include phosphate esters, ester oligomers, and sugar ester derivatives. By using these plasticizers, physical properties such as hardness of the film are appropriately adjusted, water absorption is provided to suppress the generation of fine water droplets in the saponification layer 12 of cellulose acylate, and the saponification layer is made easier to form. In addition, it is possible to design an anti-fog film with optical properties suitable for use as a display device. As the plasticizer, ester oligomers and sugar ester derivatives are preferable, and ester oligomers are particularly preferable.

The film base 11 preferably contains as a plasticizer an ester oligomer that has a repeating unit containing an ester bond of dicarboxylic acid and diol and has a molecular weight in the range of 500 to 10,000, and the film base of this embodiment ( 11) also includes this. This molecular weight is determined by measuring the weight average molecular weight, number average molecular weight, and terminal functional group weight by GPC (Gel Permeation Chromatography) because the ester oligomer has a molecular weight distribution unlike the plasticizer with a molecular weight of less than 500. And the number average molecular weight can be obtained by measuring the osmotic pressure, the viscosity average molecular weight can be obtained by measuring the viscosity, etc. In this embodiment, the number average molecular weight is determined by measuring terminal functional groups. By using an ester oligomer with a molecular weight in the range of 500 to 10,000 as a plasticizer, the anti-fog film 10 can form a thick saponification layer 12 through saponification treatment, and the cellulose formed in the saponification layer 12 can be used as a plasticizer. By increasing water absorption, an anti-fog film 10 in which the formation of fine water droplets is suppressed can be obtained. In addition, by using the above-mentioned ester oligomer as a plasticizer, the saponification layer 12 on the first film surface 10a can be formed more reliably thick compared to the case of using a general plasticizer monomer with a molecular weight of less than 500. As the molecular weight of the ester oligomer increases, precipitation is suppressed and water absorption as cellulose can be improved. From the viewpoint of compatibility with cellulose acylate and the formability of the saponification layer 12, the molecular weight of the ester oligomer is more preferably in the range of 700 to 5,000, and more preferably in the range of 900 to 3,000.

The above dicarboxylic acid is more preferably an aliphatic dicarboxylic acid having a carbon number of 2 to 10. The above diol is more preferably an aliphatic diol having a carbon number of 2 to 10. This means that by using aliphatic dicarboxylic acid and aliphatic diol, the saponification layer 12 of the anti-fog film 10 is easily formed, and also has birefringence (in-plane retardation Re and thickness direction) when used in the display device 1. This is because the anti-fog film 10 with a small phase difference (Rth) is obtained. Examples of aliphatic carboxylic acids include malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, azelaic acid, cyclohexanedicarboxylic acid, maleic acid, and fumaric acid. As aliphatic diol, ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2-methyl-1 ,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 1 , 4-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, etc. In this embodiment, an ester oligomer of adipic acid and ethanediol (the number average molecular weight according to the terminal hydroxyl group determination method is about 1000) is used as the ester.

Additionally, sugar ester derivatives can also be preferably used as plasticizers. This is because it is difficult to deposit on the surface after forming the saponification layer 12, and even if it does precipitate, the formation of a fine water film is suppressed. The sugar ester derivative may be either a monosaccharide ester derivative or a polysaccharide ester derivative, or both. Sugars include monosaccharides such as glucose, galactose, mannose, fructose, xylose, and arabinose, lactose, sucrose, nystose, 1F-fructosylnistose, stachyose, maltitol, lactitol, lactulose, cellobiose, Examples include polysaccharides such as maltose, cellotriose, maltotriose, raffinose or kestose, gentiobiose, gentiotriose, gentiotetraose, xylotriose, and galactosyl sucrose. Preferred are glucose, fructose, sucrose, kestose, nistose, 1F-fructosylnistose, stachyose, etc., and more preferably sucrose and glucose. In addition, oligosaccharides can be used as polysaccharides, and as oligosaccharides, they are produced by causing enzymes such as amylase to act on starch, sucrose, etc., and examples of oligosaccharides include maltooligosaccharides, isomaltooligosaccharides, fructooligosaccharides, and galacto-oligosaccharides. , xylooligosaccharide.

The monocarboxylic acid used to esterify all or part of the OH groups in the monosaccharide or polysaccharide structure is not particularly limited, and known aliphatic monocarboxylic acids, alicyclic monocarboxylic acids, and aromatic monocarboxylic acids can be used. There may be one type of carboxylic acid used, and two or more types may be used.

Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelagonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, and lauric acid. Acids, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecanoic acid, stearic acid, nonadecanoic acid, arachic acid, behenic acid, lignoceric acid, cerotic acid, heptacosanoic acid, montanic acid, Saturated fatty acids such as melisic acid and lacseric acid, unsaturated fatty acids such as undecylenic acid, oleic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid, and octenoic acid, cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, and alicyclic monocarboxylic acids.

Examples of preferable aromatic monocarboxylic acids include aromatic monocarboxylic acids obtained by introducing an alkyl group or an alkoxy group into the benzene ring of benzoic acid such as benzoic acid or toluic acid, and benzene rings such as cinnamic acid, benzilic acid, biphenylcarboxylic acid, naphthaline carboxylic acid, or tetraline carboxylic acid. Aromatic monocarboxylic acids having two or more or their derivatives may be mentioned, and benzoic acid and naphthylic acid are particularly preferred.

In addition, specific examples of the sugar ester include ester derivatives of sucrose, and more specifically, benzoic acid ester (Monopet (registered trademark) SB, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.).

The amount of plasticizer in the film base 11 is preferably 0% or more and 50% or less with respect to the mass of cellulose acylate in the film base 11. That is, when the mass of cellulose acylate in the film base 11 is MA and the mass of the plasticizer in the film base 11 is MB, the film base 11 is (MB/MA) × The mass ratio (unit; %) calculated as 100 is between 0% and 50%. This mass ratio is preferably 2% or more and 30% or less, and more preferably 4% or more and 20% or less.

The anti-fog film 10 is manufactured by saponifying a cellulose acylate film. Cellulose acylate can be saponified by contacting it with an aqueous solution such as sodium hydroxide and/or potassium hydroxide. In addition to alkali and water, the saponification liquid preferably contains one or two or more organic solvents selected from the group consisting of alcohols, ethers, amides, and sulfoxides. This is because by including an organic solvent, the saponification layer 12 can be formed thickly on the cellulose acylate, the water absorption of the saponification layer 12 is increased, and an anti-fogging film with good fine water droplet prevention performance is obtained. As alcohols, alcohols having 2 to 8 carbon atoms are preferable. Alcohols having 2 to 8 carbon atoms include, for example, ethanol, isopropyl alcohol, 1-propanol, 1-butanol, hexanol, ethylene glycol, glycerin, propylene glycol, butylene glycol, and pentaerythine. Litol, etc. can be mentioned. Among them, ethanol and isopropyl alcohol are particularly preferable. As ethers, ethers having a carbon number of 2 to 10 and containing at least one hydroxyl group are preferable. For example, diethylene glycol, dipropylene glycol, triethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol Ethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, ethylene glycol monoethyl ether acetate, propylene glycol Lycol monomethyl ether acetate, diethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, etc. are mentioned. Among them, diethylene glycol monoethyl ether and propylene glycol monomethyl ether are particularly preferable. Examples of amides include N,N-dimethylformamide and dimethylacetamide. Examples of sulfoxides include dimethyl sulfoxide.

The saponification layer 12 can be formed by a coating method by coating or an immersion method by dipping. The saponification treatment by the immersion method may be under any conditions, but includes, for example, a saponification process, a first washing process, a neutralization process, a second washing process, and a drying process. In the saponification process, the film is immersed in an aqueous alkali solution to saponify the film surface. As an alkali, for example, sodium hydroxide (NaOH) or potassium hydroxide (KOH) is used. The saponification liquid contains propylene glycol monomethyl ether. In the first cleaning process, the film that has undergone the saponification process is cleaned. Washing is performed, for example, with pure water. In the neutralization process, an acid or an aqueous acid solution is used as a neutralizing liquid, and the film that has undergone the first cleaning process is neutralized with this neutralizing liquid. In the second cleaning process, the film that has undergone the neutralization process is washed with, for example, pure water. In the drying process, the film that has undergone the second cleaning process is dried. On the side where the saponification layer 12 is not needed, the saponification layer 12 may be formed on one side by a method such as laminating a protective film.

In addition, in the method by application, an alkaline solution as a saponification liquid is applied to one film surface of a long cellulose acylate film using TAC as cellulose acylate, and the applied cellulose acylate film is heated, The saponification layer 12 (anti-fogging film 10) can be produced by washing with water. The saponification liquid contains isopropyl alcohol. The saponification layer 12 is a layered region where cellulose acylate is saponified through saponification treatment by application and heating. The film base 11 is the non-saponified portion of the cellulose acylate film that has not been saponified, that is, the remainder excluding the saponification layer 12.

In addition, regarding the method of manufacturing the cellulose acylate film (film base 11) that serves as the base of the anti-fog film 10, and the method of saponifying the film base 11 to form the saponification layer 12, Japanese It is described in Unexamined Patent Publication 2017-57242 (in particular, saponification is described in detail in paragraphs [0040] to [0048]), and the anti-fog film 10 of the present invention can be manufactured using this method.

In addition, in the example shown in FIG. 3, the saponification liquid is applied to one side of the cellulose acylate film (film base 11) to form the saponification layer 12, but the film base 11 is immersed in the saponification liquid. Thus, the saponification layer 12 may be formed on both sides of the film base 11. In this case, as in the display device 50 shown in FIG. 4, an anti-fog film ( 51) is formed, and this anti-fog film 51 is attached to the back of the front plate 4. In addition, in the description using the drawings after FIG. 4, the same members as those in the above-described embodiment are given the same reference numerals and description is omitted. In addition, the method of forming the saponification layer 12 by immersing in the saponification liquid is described in detail in paragraphs [0074] and [0075] of International Publication Publication 2020/004331, and this method can be used.

The thickness of the saponification layer 12 is preferably within the range of 0.3 μm to 20 μm, more preferably within the range of 0.5 μm to 15 μm, and particularly preferably within the range of 2 μm to 12 μm.

The thickness of the saponification layer 12 of the anti-fog film 10 can be determined by the ATR method of FT-IR or a method of dissolving the anti-fog film 10 in methylene chloride and/or chloroform. In addition, the thickness of the saponification layer 12 is obtained by the following method in this embodiment. A sample sampled from the anti-fog film 10 in which the film base 11 was saponified was immersed in dichloromethane for 24 hours. The sample remaining undissolved in this immersion is dried, and the thickness of the dried sample is measured three times. The average of the three measured values is taken as the thickness of the saponification layer 12.

The water absorption of the saponification layer 12 can be reliably increased by forming the saponification layer 12 as a layer containing cellulose. When the saponification layer 12 is detected as a layer by the dichloromethane immersion method described above, it can be seen that the saponification layer 12 is formed as a layer containing cellulose. Also, when, for example, only the surface is in a cellulose state due to saponification, the saponified portion is not observed as a layer by dichloromethane immersion, and it is assumed that the cellulose portion and the cellulose acylate portion are mixed. .

The ATR method of FT-IR can be measured as follows. Let the amount of acyl groups on the side of the saponification layer 12 (i.e., the first film side 10a) of the anti-fog film 10 be X, and the first base side of the anti-fog film 10 (film base 11) When the amount of acyl groups on the surface opposite to (11a) (hereinafter referred to as the second base surface 11b) is Y, the acyl group ratio obtained by X/Y is 0.7 or less. In this embodiment, for example For example, it is set to 0.3. The smaller the acyl group ratio, the fewer acyl groups the first film surface 10a has with respect to the second base surface 11b, which means that more acyl groups are saponified to become hydrophilic groups in the saponification treatment of the cellulose acylate film. . The thickness of the saponification layer can be determined by the same method as comparing the measurement by the FT-IR ATR method with the thickness of the saponification layer by immersion in dichloromethane.

The acyl group amount It is obtained as the spectral intensity of the acyl group obtained by . Specifically, the spectral intensity of the signal of the acyl group of cellulose acylate is corrected (normalized) to the spectral intensity of the common signal of the cellulose polymer. In this embodiment, since TAC is used as cellulose acylate, the acyl group is an acetyl group, and the signal of the acetyl group is 1210 cm ^-1 . The common signal of cellulose-based polymer is preferably set to 1030 cm ^-1 . Then, the spectral intensity of the signal of the acyl group of cellulose acylate obtained through correction is determined as the acyl group amount X and the acyl group amount Y. In this way, the acyl group amount X and the acyl group amount Y are indices that are replaced by the number of acyl groups.

As is well known, the ATR method of FT-IR is a method of obtaining spectral intensity by injecting light into a measurement sample, and the obtained spectral intensity is not that of the surface of the measurement sample in the strict sense. When the measurement angle is set to 45 degrees using a diamond prism, which is a method of the general FT-IR ATR method, the penetration depth of light from the surface of the measurement sample is about 2 to 3 μm. Since the saponification layer 12 of this embodiment is very thin as will be described later, as the penetration depth of light becomes deeper than 2 μm, the reliability of the acyl group amount obtained for the saponification layer 12 weakens. Therefore, it is desirable to obtain the spectral intensity in the range of 2 μm depth from the first film surface 10a as the acyl group amount The spectral intensity in the following range is referred to as the acyl group amount

Likewise, it is desirable to obtain the spectral intensity in a range of 2 μm in depth from the second base surface 11b as the acyl group amount Y, and this is also done in this embodiment. In addition, as in the example of FIG. 4, when the saponification layer 12 is also provided on the second base surface 11b, the acyl group amount is determined at the center of the thickness direction of the film base 11, and this is used as the acyl group amount Y. It is preferable to use it from the viewpoint of simplicity and reliability as an acyl group amount determined for the film base 11. When it is difficult to determine the acyl group amount Y on the second base surface 11b by the above method, the anti-fog film 10 is dissolved in methylene chloride and/or chloroform, and a film is formed from this solution. The amount of acyl groups on the film surface may be determined by other methods, such as by IR.

The anti-fog film 10 of the present invention has water absorbing properties. The water absorption in the present invention is such that when the surface temperature of the anti-fog film 10 is lower than the temperature (dew point) at which moisture in the air in contact with the anti-fog film 10 condenses, moisture is removed from the surface of the anti-fog film 10. The anti-fog film 10 exhibits the ability to quickly absorb moisture before forming fine water droplets. Absorbency can be measured by exposing the surface of the anti-fog film 10 to air with a dew point higher than the surface temperature of the anti-fog film 10 and measuring the time until clouding is recognized. In the present invention, the water absorption is measured by exposing the anti-fog film 10 to a water bath set at 45°C, observing cloudiness at room temperature (23°C), and measuring the time until it starts to become cloudy due to fine water droplets. Time was measured (see Table 1). In the present invention, the absorbency is the absorbency in the above-mentioned measurement, and is preferably 10 seconds or longer. This is because the high water absorption of the anti-fog film 10 makes it difficult for fine water droplets to form on the back of the front panel 4, and good display performance without glare or display unevenness is obtained. Moreover, from the viewpoint of compatibility with the optical properties described later, 600 seconds or less is preferable for water absorption. As for water absorption, it is preferably 15 seconds or more and 300 seconds or less, and more preferably 20 seconds or more and 150 seconds or less.

Additionally, by keeping the thickness of the saponification layer 12 within a predetermined range, water absorption can be more reliably improved. Specifically, it is as follows. The acyl group ratio is related to water absorption. Specifically, as shown in Figure 5, the smaller the acyl group ratio, the better the water absorption. As shown in Figure 5, in a graph where the vertical axis is water absorption and the horizontal axis is the acyl group ratio, the relationship between water absorption and acyl group is approximately a straight line. There is a correlation between the acyl group ratio and the thickness of the saponification layer 12, and as shown in FIG. 6, the thickness of the saponification layer 12 increases as the acyl group ratio decreases. Since the water absorption improves as the acyl group ratio decreases as described above, it can be seen from FIGS. 5 and 6 that the water absorption improves as the thickness of the saponification layer 12 increases.

The thickness, water absorption, and optical properties of the saponification layer 12 depend on the increase or decrease in the amount of solvent and/or alkali in the saponification liquid, the treatment temperature, the method of saponification treatment by immersion or application, and the cellulose acylate of the saponification liquid. It can be adjusted by the penetration of or the reaction of the infiltrated alkali by heat treatment after penetration. In addition, through the saponification treatment, the saponification liquid penetrates into the cellulose acylate, the alkali and the cellulose acylate react depending on the treatment temperature or heat treatment, and the saponification layer 12 is formed as a layer containing cellulose, resulting in high water absorption and An anti-fog film with good optical properties can be prepared. In addition, in this example, the cellulose acylate film is formed by casting a polymer solution (hereinafter referred to as dope) containing cellulose acylate on a support to form a cast film, peeling the cast film from the support, and drying it. making. The type and amount of plasticizer of the film base 11 can be adjusted by the prescription of the dope.

In addition, the thickness of the saponification layer 12 is related to the display unevenness performance of the display panel 2, as shown in the examples described later (comparison of Example 1 and Example 2-11 (see Table 1)). From the viewpoint, it is preferable to be 1 μm or more. In addition, the thickness of the saponification layer 12 is determined by the performance related to the viewing angle of the display panel 2, as shown in the examples described later (comparison of Examples 1-4 and Examples 5-11 (see Table 1)). From the viewpoint, it is preferable that it is 3 μm or less. Taking these into consideration, the thickness of the saponification layer 12 is preferably within the range of 1 μm or more and 3 μm or less. By keeping the thickness of the saponification layer 12 within this range, it is possible to achieve both performance regarding display unevenness and viewing angle performance of the display panel 2.

The anti-fog film 10 is manufactured in a long length in this embodiment, for example, an adhesive layer is provided on the second base surface 11b, and it is cut into a sheet of a desired size and provided for use. The adhesive layer is for attaching the anti-fog film 10 to the attachment object, and as described above, in this embodiment, the anti-fog film 10 is attached to the back of the front plate 4 (see Fig. 3). ).

In addition, as in the display device 60 shown in FIG. 7, an optical function layer 61 may be provided between the anti-fog film 10 and the front plate 4 to convert incident light into circularly polarized light and emit it. . By doing this, visibility can be improved when the display device 60 is observed through polarized sunglasses. Furthermore, in the example of FIG. 7 , the optical function layer 61 is comprised of the polarizing plate 62 and the transparent protective layer 63 provided on both surfaces of the polarizing plate 62, but the optical function layer 61 of the display device 70 shown in FIG. 8 Like the functional layer 71, the polarizing plate 72 and the quarter wave plate 73 provided on both surfaces of the polarizing plate 72 may be used as an optical functional layer. In the configuration of FIG. 8 , visibility (visibility when observing the display device 70 through polarized sunglasses) can be further improved compared to the configuration of FIG. 7 .

In addition, it is preferable that the absolute value of the thickness direction retardation Rth of the anti-fog film 10 is 400 nm or less. Moreover, it is preferable that the absolute value of the in-plane phase difference Re is 80 nm or less. When the thickness direction phase difference Rth and the in-plane phase difference Re are within the above range, rainbow unevenness that occurs when observed through polarizing sunglasses can be prevented. In addition, when the above-described optical functional layer 61 (see FIG. 9) or the optical functional layer 71 (see FIG. 10) is provided, the luminance of the display panel 2 observed from the front, and the display panel In order to obtain the viewing angle performance of (2), the absolute value of the thickness direction retardation Rth of the anti-fog film 10 is preferably 100 nm or less. Moreover, it is preferable that the absolute value of the in-plane phase difference Re is 20 nm or less. In order to keep the thickness direction retardation Rth and the in-plane retardation Re within the above range, in the step of manufacturing the film base 11, the degree of acyl group substitution is increased, and/or the thickness direction retardation Rth and/or the in-plane retardation Re are within the above range. Examples include adding an additive to adjust the phase difference Re.

[Table 1]

<Verification of effectiveness>

Hereinafter, using Table 1, with respect to the effect of the present invention, the display device of Example 1-11 and the anti-fog film provided with the anti-fog film having the saponification layer (saponification layer containing cellulose) of the present invention are provided. , Explanation while comparing the display device of Comparative Example 1-3, in which the anti-fog film does not have (or cannot detect) the saponification layer of the present invention, and the display device of Comparative Example 4, in which the anti-fog film is not provided. Do.

The materials, degree of substitution (degree of acyl group substitution), additives, and thickness of the base material (film base) of the anti-fog films of Examples and Comparative Examples are as shown in Table 1. In addition, the formation method, composition, and thickness of the surface layer of the anti-fog film of Examples and Comparative Examples are as shown in Table 1.

Regarding the materials described in Table 1, material A is "TAC", a cellulose acylate in which all acyl groups are acetyl groups, the degree of acyl group substitution of the cellulose acylate is 2.86, and the viscosity average degree of polymerization is 320. Material B is "DAC (cellulose diacetate, diacetylcellulose)", which is a cellulose acylate in which all acyl groups are acetyl groups, the acyl group substitution degree of cellulose acylate is 2.40, and the viscosity average degree of polymerization is 300. Material C is “PET (polyethylene terephthalate).” In addition, additive A is "an oligomer containing ester of adipic acid and ethylene glycol as a repeating unit (molecular weight according to terminal functional group determination method is 1000)", and additive B is "1,2,3-triacetoxypropane. ", additive C is "TPP (triphenyl phosphate)", and additive D is benzoic acid ester of sucrose (Monopet (registered trademark) SB, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.).

Regarding the formation method and processing method of the surface layer in Table 1, for Examples 1-11 and Comparative Examples 1 and 2, the surface layer was formed by saponifying the substrate. There are three methods (processing methods) for forming the surface layer by saponification: Conditions A-C below.

Condition A

A surface layer was formed by saponifying both sides of the substrate by the immersion method (a method of saponification by immersing the substrate in a saponification liquid). Specifically, it was immersed in a saponification solution of 8:2 propylene glycol monomethyl ether and water in a NaOH solution with a concentration of 1.5 mol/L, adjusting the liquid temperature and immersion time. Afterwards, as the first cleaning step, the water is immersed in pure water at a temperature of 25°C for 15 seconds to clean, and as a neutralization step, the water is immersed in an aqueous solution of sulfuric acid (H2SO4aq) at a temperature of 25°C and a concentration of 0.3 mol/L for 15 seconds to neutralize. As a cleaning step, immersion cleaning was performed in pure water at a temperature of 25°C for 15 seconds, and the surface of the substrate was dehydrated with an air knife. Then, as a drying step, it was dried in an environment of a temperature of 100°C for 60 seconds to form a surface layer.

Condition B

A surface layer was formed by saponifying one side of the substrate by a coating method (a method of applying saponification liquid to a substrate to perform saponification). Specifically, the base material wound into a roll was unwound and transported, and the saponification liquid was applied to one film side of the base material using a coating device provided in the transport path. The prescription for saponification liquid is as follows. In addition, in the following prescriptions, % is a percentage of the mass.

Potassium hydroxide (KOH) 3.3%

isopropyl alcohol 88%

water 3%

propylene glycol 5%

Surfactants 0.04%

The cellulose acylate film coated with the saponification liquid was guided to a heating chamber provided in the conveyance path, heated while conveyed, and then sent to a water tank containing water and washed with water to form a surface layer.

Condition C

A surface layer was formed by saponification using the dipping method in the same manner as in Condition A described above. On the other hand, differently from condition A, after immersion in a NaOH aqueous solution at a temperature of 50°C and a concentration of 1.5 mol/L for 180 seconds, immersion cleaning was performed with pure water at a temperature of 25°C for 15 seconds as a first cleaning step, and as a neutralization step, the temperature was 25°C. , neutralized by immersing in an aqueous solution of sulfuric acid (H2SO4aq) with a concentration of 0.3 mol/L for 15 seconds, and as a second cleaning step, immersing and cleaning in pure water at a temperature of 25°C for 15 seconds, and dehydrating the surface of the film with an air knife. As a drying process, it was dried for 60 seconds in an environment with a temperature of 140°C to form a surface layer.

In each of Examples 1-11 and Comparative Examples 1 and 2, the conditions for forming the surface layer (immersion time, etc.) were different. In addition, regarding the thickness of the surface layer, a sample sampled from an anti-fog film was immersed in dichloromethane for 24 hours, the sample remaining undissolved in this immersion was dried, and the thickness of the dried sample was measured three times. It was taken as the average of the measured values. In Example 1, a sufficient amount of cellulose to function as a saponification layer of the present invention could be detected as a thick layer on the surface, but in Comparative Examples 1 and 2, a sufficient amount of cellulose to function as a saponification layer was detected. It was not possible to detect anything contained in the surface layer. For this reason, for Examples 1-11, the composition of the surface layer was set to "cellulose", and for Comparative Examples 1 and 2, the composition of the surface layer was set to "acetylcellulose". In addition, for Examples 1-11, the thickness of the saponification layer, which is the surface layer, could be measured, so the measured thickness is described. However, for Comparative Examples 1 and 2, since the thickness of the surface layer could not be measured, the thickness was written as " -" was used.

In addition, since Comparative Example 3 used a ready-made anti-fog film (Scotch Tint (registered trademark) SH2CLHF, manufactured by 3M), the degree of substitution, additives, and thickness of the base material were set to "-". In addition, since the hydrophilic coating applied to the substrate functions as a surface layer, the forming method of the surface layer was set to "application", the processing method was set to "-", and the composition of the surface layer was set to "hydrophilic coat". In addition, since the thickness of the hydrophilic coating layer, which is the surface layer, was not measured, the thickness was set to "-". In addition, for Comparative Example 4, since the anti-fog film was not provided as described above, the items related to the anti-fog film and the items related to the properties (optical properties, water absorption) described later are set to "-".

For the anti-fog films of the examples and comparative examples, the in-plane retardation Re and the thickness direction retardation Rth were measured as optical properties using an automatic birefringent meter (KOBRA-HB, Oji Keisoku Co., Ltd.). Additionally, the water absorbency of the anti-fog films of Examples and Comparative Examples was investigated. The results are as shown in Table 1. In addition, for Comparative Example 4, since the anti-fogging film was not provided as described above, the results of optical properties and water absorption were all set to "-". In addition, regarding the water absorption of the anti-fog film, the anti-fog film is bonded to a 2 mm glass plate with an adhesive, a water bath set at 45°C is prepared, and a glass plate is placed 10 cm above the water bath so that the anti-fog film faces the water surface of the water bath and absorbs the vapor from the water bath. When the sheet is exposed to prevent leakage and brought to room temperature (23°C) to observe fogging on the surface of the anti-fog film, the time (seconds) until fogging begins after the sheet is exposed to the above-described environment is shown.

Subsequently, the display devices of the examples and comparative examples were evaluated for display unevenness, polarization sunglasses (SG) suitability, panel brightness, and viewing angle. The results are as shown in Table 1.

Evaluation of display unevenness was performed based on the following evaluation criteria.

In addition, this evaluation was conducted under the following conditions without providing the above-described optical functional layer, that is, a layer that converts incident light into circularly polarized light and emits it.

A signage display device was prepared with 32-inch (72cm x 40cm) IPS liquid crystal display cells arranged horizontally. The front plate was a 6mm glass plate, and the distance between the liquid crystal cell and the front plate was 8mm. Various films of the present invention were bonded to the inside through an acrylic adhesive.

The display device was installed in a room at 5°C, the display device was turned on and off for 2 hours each, and when turned on again, the display state was observed from a distance of about 1 m and evaluated based on the following criteria.

A: The display area looks good overall.

B: Some glare is visible on the display.

C: Glare is visible on the display.

D: Glare and display unevenness are seen in the display area.

The suitability of polarized sunglasses was evaluated based on the following evaluation standards.

In addition, this evaluation was performed under the following conditions without providing the optical function layer mentioned above.

Wearing polarized sunglasses, the signage display device was observed while changing the viewing position in the display state, and evaluated based on the following criteria.

A: No occurrence of rainbow unevenness.

B: When the viewing position is changed, a slight rainbow unevenness may be seen.

C: When the viewing position is changed, rainbow unevenness may be clearly visible.

The panel brightness was evaluated based on the measured brightness value.

In addition, this evaluation was performed under the following conditions by providing the above-mentioned optical function layer 71 (see FIG. 8).

We prepared a signage display device with VA panels of 55 inches (1220 mm x 685 mm) arranged vertically.

A COP of Re 140 nm is used as a λ/4 plate, and circular polarizers are placed on the front and back of the polarizer with the Re axis at +45 degrees and -45 degrees with respect to the absorption axis of the polarizer, and the long side direction of the display device is aligned with the absorption axis of the polarizer. It was bonded to the inside of the front plate glass so that it was parallel.

Additionally, the anti-fog films of Example 1-11 and Comparative Example 1-3 were bonded together through an acrylic adhesive. And for each of these, the luminance when the display device was observed from the front was measured, and it was expressed as a ratio when the luminance before bonding the anti-fog film (in the case of only a polarizing plate) was 100. In addition, in Comparative Example 4, since the anti-fog film was not originally provided and the anti-fog film was not present either before or after the anti-fog film was bonded, the evaluation value of the brightness was set to "100".

The viewing angle was evaluated based on the following evaluation criteria.

The above-described VA panel (a circularly polarizing plate and an anti-fog film bonded to the back of the front plate glass) was placed in a white display state, observed with the naked eye from left and right angles, and the display state was evaluated based on the following criteria.

A: Equivalent to polarizer only.

B: The change in white and black when the angle is changed is slightly larger than when using only the polarizer.

C: The change in white and black when the angle is changed is greater than when using only the polarizer, and it appears colored when the inclination angle is large. D: It is colored and appears rainbow uneven.

As shown in Table 1, through comparison of Examples and Comparative Examples, it was confirmed that display unevenness of the display panel could be prevented by providing an anti-fog film having a saponification layer of the present invention. In addition, it was confirmed that the thickness of the saponification layer (surface layer) is preferably 1 μm or more from the viewpoint of display unevenness and water absorption, and is preferably 3 μm or less from the viewpoint of panel brightness, viewing angle, and polarization sunglasses suitability. In addition, it was confirmed that suppressing the thickness direction phase difference Rth and the in-plane phase difference Re low is desirable from the viewpoint of polarization sunglasses suitability and viewing angle.

1, 50, 60, 70 indicators
2 display panel
2a Image display surface
3 frames ago
4 Front panel
5 Back cover
6 cases
7 void layer
10, 51 Anti-fog layer, anti-fog film
10a first film plane
11 Film base (cellulose acylate layer)
11a first base surface
11b second base surface
12 Saponification layer
61, 71 Optical functional layer
62, 72 polarizer
63 protective layer
73 1/4 wave plate

Claims (8)

a display panel having an image display surface for displaying images;
a void layer provided in front of the image display surface;
A front plate provided in front of the void layer,
An anti-fog layer provided between the front plate and the void layer,
The display device wherein the anti-fog layer has a cellulose acylate layer and a saponification layer containing cellulose provided on the back of the cellulose acylate layer. In claim 1,
The display panel is a liquid crystal display panel, and a polarizing plate is provided on the image display surface. In claim 2,
A display device comprising an optical functional layer that converts incident light into circularly polarized light and emits it, between the front plate and the anti-fogging layer. In claim 3,
A display device in which the optical functional layer includes a polarizing plate. In claim 4,
The display device wherein the optical functional layer includes a polarizing plate and a quarter wave plate disposed on both sides of the polarizing plate. The method according to any one of claims 1 to 5,
A display device in which the absolute value of the thickness direction retardation Rth of the anti-fog layer is 100 nm or less. The method according to any one of claims 1 to 6,
A display device in which the absolute value of the in-plane phase difference Re of the anti-fog layer is 20 nm or less. The method according to any one of claims 1 to 7,
A display device wherein the saponification layer has a thickness of 1 μm or more and 3 μm or less.