WO2003060573A2

WO2003060573A2 - Antiglare optical film, polarizing plate and display unit using the same

Info

Publication number: WO2003060573A2
Application number: PCT/JP2003/000130
Authority: WO
Inventors: Tsutomu Arai; Keiichi Miyazaki; Isao Ikuhara; Hirohisa Hokazono
Original assignee: Fuji Photo Film Co., Ltd.
Priority date: 2002-01-11
Filing date: 2003-01-09
Publication date: 2003-07-24
Also published as: AU2003208003A1; WO2003060573A3; KR20040071306A; AU2003208003A8; TWI265307B; TW200302923A

Abstract

An antiglare optical film comprising : a transparent film substrate (1) having a fine uneven surface structure (4) provided on at least one side of the transparent film substrate (1), wherein a proportion of reflected scattered light with an oblique angle θ of 10 ° or above is not greater than 2 % and an average interval of peaks in the fine uneven surface is from 1 µm to 50 µm.

Description

DESCRIPTION ANTIGLARE OPTICAL FILM, POLARIZING PLATE AND DISPLAY UNIT USING THE SAME

Technical Field

The present invention relates to an optical film having antiglare properties, an antireflective film having antiglare properties , a polarizing plate having antiglare properties and a display unit comprising same.

Background Art

In display units such as cathode ray tubes (CRT) , plasma display panels (PDP) , electroluminescence displays (ELD) and liquid crystal displays (LCD) , it has been a practice to provide an antiglare (glare-reducing) film or an antiglare antireflection film as the outermost layer of a display to thereby prevent reduction in contrast or reflection caused by reflex of outside light.

However, apicture in black on such a display looks whitish black or gray when observed diagonally. This phenomenon is expressed as "poor recession in black color", "poor lifting in black color", "loose black color", "whitish black color", or "poor whiteness". The contrary case of presenting a black picture in theblack color as such is expressedas "goodrecession in black color", "good lifting in black color", "no lifting in black color", "tight black color", "clearly black color", or "good whiteness". The above phenomenon is caused by the fact that the light scattering is enhanced due to the unevenness (peak/valley) structure on the film surface for imparting antiglare properties and thus scattering light enters into a part which originally has a black color. This is unfavorable because of lowering the contrast, damaging the high-grade picture and display and worsening the display qualities. As a σountermeasure to this problem, it is suggested to lessen the peas and roughens on the film surface. Although a black picture can look black by this method, there arises another problem of worsening in antiglare properties. Namely, it is difficulttomakeablackpicturelookingblackwithoutworsening antiglare properties .

In image display units, on the other hand, it has been required to minimize the pixel size so as to improve display qualities (high definition) . In case where a high-definition display is observed through an antiglare antireflection film, however, the display qualities are extremely worsened due to serious glareness . Although ithas been known that this problem can be effectively solved by changing the refraction indexes of a binder and a filler to give inner haze, this method is accompanied by some troubles such as worsening tightness in black color, lowering front contrast and lowering front luminance. On the other hand, it has been qualitatively known that glareness can be relieved by potentiating antiglare properties . In case where the antiglare properties are excessively potentiated, however, a picture becomes vague and is extended onto the whole display surface thereby largely worsening the visibility, when the display surface is exposed to light (this phenomenon is called "white blur") . That is to say, there has been known neither an antiglare film nor an antiglare antireflection filmwhereby antiglare properties can be imparted to a high-definition display while making a black picture to look black as such without causing white blur or lowering front contrast or front luminance.

Further, in order to provide an antiglare optical film, a method involving the application of an antireflective film to a support having an unevenness surface, a method involving the addition of mat particles for forming an unevenness surface to a coating solution for forming an antireflective layer, etc. have been studied. However, the former method is disadvantageous in that when the antireflective layer coating solution flows from the peak to the valley, an in-plane unevenness in film thickness occurs, causing remarkable deterioration of antireflective properties as compared with the coat layer on a smooth surface. The latter method is disadvantageous in thatmatparticles having aparticlediameter of about 1 μm or more required to realize sufficient antiglare properties must be embedded in a thin film having a thickness of from 0.1 to 0.3 μm, causing exfoliation of mat particles. As a method for overcoming these problems, JP-A-12-329905 discloses a method involving the provision of antiglare properties after the formation of an antireflective film. In some detail , there is proposed amethodwhich comprises pressing an antireflective film having an antireflective layer applied thereto under an embossing roll to form an unevenness on the antireflective layer without impairing the antireflective properties thereof. However, such an antireflective film is disadvantageous in that it exhibits gradually decreasing antiglare properties during prolonged use. For the aforementioned reasons, no practical coated antireflective films which can satisfy the desired antire lective properties and film strength at the same time over an extended period of time have been present.

Disclosure of the Invention

An object of the present invention is to provide an antiglare optical film which allows black to be viewed as black and exhibits a high front contrast. Another object of the present invention is to provide an antiglare optical film which can be mounted on a high definition display while maintaining these properties. A further object of the present invention is to provide an antiglare optical film which can be fairly blurred white. A still further object of the present invention is to provide an antiglare optical film which exhibits little or no change of antiglare properties even after prolonged use, particularly in a severe atmosphere of high temperature and humidity, i.e., no deterioration of initial properties. A further object of the present invention is to provide a polarizing plate and a displayunit comprising such an antiglare optical film.

The objects of the present invention were accomplished as ollows .

(1) An antiglare optical film comprising a fine unevenness sur ace structure provided on at least one side of a transparent film substrate, characterized in that the proportion of oblique angle of not smaller than 10° is not greater than 2% and the average interval of peaks in the fine unevenness surface is from 1 μm to 50 μm.

(2) The antiglare optical film as described in Clause (1) , wherein the average interval of peaks is from 1 μm to 20 μm.

(3) The antiglare optical film as described in Clauses (1) and (2) , wherein the average of oblique angles with respect to regular reflection face measured on the surface of the film in from 1 to 2 square microns (μm²) is from not smaller than 1° to less than 5°. (4) The antiglare optical film as described in Clauses (1) to (3) , comprising an antireflective layer on the uppermost surface thereof.

(5) The antiglare optical film as described in Clauses (1) to (3) , wherein it is subjected to embossing to roughen the surface of the film, rendering itself antiglare.

(6) The antiglare optical film as described in Clause (5) , wherein the percent retention R of arithmetic mean of roughness defined by the equation (I) is not smaller than 30%:

wherein R_A represents the arithmetic mean roughness of the sur ace of the antireflective layer after 1 , 000 hours of storage in an atmosphere of 65°C and 95%RH (relative humidity) ; and R_B represents the arithmetic mean roughness of the surface of the antireflective layer before storage in an atmosphere of 65°C and 95%RH (relative humidity) .

(7) The antiglare optical film as described in Clauses (4) to (6) , wherein the antireflective layer is made of a low refraction layer having a lower refractive index than that of the supporting substrate, a high refraction layer is provided interposed between said supporting substrate and said antireflective layer, the refractive index of said high refraction layer is higher than that of the supporting substrate and the thickness of the high refraction layer is substantially uniform. (8) The antiglare optical film as described in Clause (7) , wherein amiddle refraction layer is provided interposedbetween the supporting substrate and the high refraction layer, the refractive index of the middle refraction layer is higher than that of the supporting substrate, the refractive index of the middle re raction layer is lower than that of the high re raction layer and the thickness of the middle refraction layer is substantially uniform.

(9) The antiglare optical film as described in Clauses (4) to (8) , wherein the average value of specular reflectance of light having a wavelength of from 450 to 650 nm incident at an angle of 5° is not greater than 0.5%.

(10) The antiglare optical film as described in Clauses (4) to (8) , wherein the average value of specular reflectance of light having a wavelength of from 450 to 650 nm incident at an angle of 5° is not greater than 0.3%.

(11) The antiglare optical film as described in Clauses (4) to (10) , wherein the various layers are formed by coating a coating composition containing a film-forming solute and at least one solvent, removing the solvents by drying, and then curing the coating composition thermally and/or by an ionizing radiation.

(12) The antiglare optical film as described in Clauses (8) to (11) , wherein themiddle refraction layer, thehigh refraction layer and the low refraction layer satisfy the following relationships (I) , (II) and (III) , respectively, with respect to designed wavelength λ (= 500 nm) : λ/4 x 0.80 < nidi <λ/4 x 1.00 (I) λ/2 x 0.75 < n2d2 <λ/2 x 0.95 (II) λ/4 x 0.95 < n3d3 <λ/4 x 1.05 (III) wherein nl represents the refractive index of the middle refraction layer; dl represents the thickness (nm) of themiddle refraction layer; n2 represents the refractive index of the high refraction layer; d2 represents the thickness (nm) of the high refraction layer; n3 represents the refractive index of the low refraction layer; and d3 represents the thickness (nm) of the low refraction layer.

(13) The antiglare optical film as described in Clauses (7) to (12) , wherein the lowrefraction layer ismade of aheat-curing or ionizing radiation-curing fluorine-containing resin.

(14) The antiglare optical film as described in Clauses (7) to (13) , wherein the high refraction layer is formed by coating a coating composition containing an ultrafine material containing at least one metal oxide selected from the group consisting of Ti, Zr, In, Zn, Sn and Sb oxides, an anionic dispersant, a curable resin having a trifunctional or higher polymerizable group and a polymerization initiator, removing the solvent by drying, and then curing the coating composition thermally and/or by an ionizing radiation. (15) The antiglare optical film as described in Clauses (7) to (14) , wherein the low refraction layer has a contact angle of not smaller than 100° with respect to pure water.

(16) The antiglare optical film as described in Clauses (1) to (15) , having at least one hard coat layer interposed between the low refraction layer and the transparent film substrate.

(17) The antiglare optical film as described in Clauses (1) to (16) , having at least one forward scattering layer interposed between the antiglare layer and the transparent support.

(18) A process for the preparation of an antiglare optical film comprising a fine unevenness surface structure provided on at least one side of a transparent film substrate, characterized in that the surface of the film is subjected to embossing so that the proportion of oblique angle of not smaller than 10° is not greater than 2% and the average interval of peaks in the fine unevenness surface is from 1 μm to 50 μm.

(19) The process for the preparation of an antiglare optical film as described in Clause (8) , wherein the average interval of peaks is from 1 μm to 20 μm.

(20) The process for the preparation of an antiglare optical film as described in Clauses (18) and (19) , wherein the average of oblique angles with respect to regular reflection face measured on the surface of the film in rom 1 to 2 square microns is from not smaller than 1° to less than 5°.

(21) The process for the preparation of an antiglare optical film as described in Clauses (18) to (20) , wherein there is provided an antireflective layer on the uppermost surface layer and the surface of the antireflective layer is subjected to embossing.

(22) The process for the preparation of an antiglare optical film as described in Clause (21) , wherein the percent retention R of arithmetic mean of roughness defined by the equation (I) is not smaller than 30%:

(I) R = R_A/R_B wherein R_A represents the arithmetic mean roughness of the surface of the antireflective layer after 1 , 000 hours of storage in an atmosphere of 65°C and 95%RH (relative humidity) ; and R_B represents the arithmetic mean roughness of the surface of the antireflective layer before storage in an atmosphere of 65°C and 95%RH (relative humidity) . (23) The process for the preparation of an antiglare optical film as described in Clause (22) , wherein the antireflective layer which has been subjected to embossing is then subjected to treatment in a solution comprising water in an amount of not smaller than 10% by mass (weight) or in a vapor of said solution at a temperature of from 60°C to 200°C for 10,000 to 100,000 seconds.

(24) A process for the preparation of an antiglare optical ilm comprising an antiglare layer and a fine unevenness surface structure provided on at least one side of a transparent film substrate, characterizedin that the antiglare layer is adjusted such that the proportion of oblique angle of not smaller than 10° is not greater than 2% and the average interval of peaks in the fine unevenness surface is from 1 μm to 50 μm.

(25) A polarizing plate comprising two sheets of surface protective films laminated on both surfaces of a polarizer, respectively, characterized in that an antiglare optical film described in Clauses (1) to (17) is used as at least one of the surface protective films .

(26) A polarizing plate comprising as at least one surface protective film an antiglare optical film which is subjected to saponification on the side thereof opposite the side provided with said antiglare layer by coating the transparent support with an alkaline solution before the formation of an antiglare optical film as described in Clauses (1) to (17) or coating said antiglare optical film with an alkaline solution after the formation thereof.

(27) The polarizing plate as described in Clauses (25) and (26) , wherein the film other than the antiglare optical film among said surface protective films is an optical compensation film having an optical compensation layer containing an optically anisotropic layer on the side of said surface protective film opposite the polarizer, said optically anisotropic layer is a layer having a negative birefringence made of a compound having a discotic structure unit, the surface of the disc having a discotic structure unit is oblique to the surface of said surface protective film and the angle made by the surface of the disc having a discotic structure unit and the surface of said surface protective film varies with the depth of the optically anisotropic layer. (28) A display unit having at least one sheet of antiglare optical film described in Clauses (1) to (17) or polarizing plate described in Clauses (25) to (27) .

(29) The display unit as described in Clause (28) , which is a TN, STN, VA, IPS or OCB mode transmission type, reflection type or semi-transmission type liquid crystal display unit.

(29) A transmission type or semi-transmission type liquid crystal display unit having at least one sheet of a polarizing plate described in Clauses (25) to (27) , characterized in that a polarization separation film having a polarization selection layer is disposed interposed between the polarizing plate disposed on the side opposite the viewing side and the back light.

(30) A surface protective plate for organic EL display having a λ/4 plate disposed on the transparentprotective filmdisposed on the side of a polarizing plate described in Clauses (25) and (27) opposite the antiglare optical film.

BRIEF DESCRIPTION OF THE DRAWINGS Fig.1 is a sectional model view showing the constitution of the layers of the antiglare optical film according to the invention .

Fig.2 is amodel view showing themeasurement of an oblique angle in the invention.

Fig.3 illustrates an example of the method for providing a coated type antireflective film with antiglare properties.

Fig. 4 is a schematic sectional view illustrating the basic layer structure of the antireflective film to be embossed.

Fig. 5 illustrates a two-dimensional network structure as viewed from above the layer.

Fig. 6 illustrates a two-dimensional network structure as viewed from above the layer.

1 : transparent support

2 : hard coat layer

3: low-refractive layer

4 : grains

21: antireflective film

22 : transparent support

23: antireflective layer

24 : emboss roll

25 : backup roll

211: transparent support

212: hard coat layer

213: middle refraction layer 214: high refraction layer

215: low refraction layer

7 : void

8 : inorganic material

The fundamental constitution of the antiglare optical filmof the inventionwill be illustratedby reference to figures . The mode shown in Fig. 1 is an example of the antiglare optical film of the invention consisting of a transparent support 1, a hard coat layer 2 and a low-refractive layer in this order. 4 stands for grains. The hard coat layer 2 may be composed of two or more layers .

The antiglare optical film of the invention, which has a fine unevenness surface structure on at lease one face of a transparent film substrate, exhibit antiglare properties by scattering a reflection image due to light scattering.

In the invention, an oblique angle and the ratio thereof are determined by the following method. Namely, three apexes of a triangle of 0.5 to 2 μm² in area are tentatively determined at a face of a transparent film substrate. Then three points at which three perpendiculars extendedupward from these apexes respectively intersect the film surface are determined. Then the angle between a normal line of a triangle having the three points as apexes and a perpendicular extended from the support upward vertically is referred to as the oblique angle. Measuring an area of 0.25 mm² or more on the substrate is divided into the triangles and measurements are performed. Then the ratio of points showing oblique angles of 10° or above to all of the points measured is determined.

Now, the method of determining the oblique angle will be described in greaterdetail . AsFig.2 shows, perpendiculars are extended upward vertically from three points A, B and C on a support. The points at which these perpendiculars intersect the surface are referred to as A' , B' and C respectively. The angle θ between the normal line D' of the triangle A' , B' and C and the perpendicular O' extended upward vertically from the support is referred to as the oblique angle. The measurement area on the support is preferably 0.25 mm² or more. Dividing this area into triangles on the support, the measurement is carried out. The average of the oblique angles thus determined is calculatedand thus the average oblique angle of the surface is obtained. Although several systems areusable for this measurement, an example thereof will be illustrated. In this case, use is made of Model SXM520-AS150 manufactured by Micromap (USA) . When an objective lens with the magnification (xlO) is used, for example, the oblique angle is measured in the unit of 0.85 μm and the measurement area is 0.48 mm². With an increase in the magnification of the objective lens, the measurement unit and the measurement area are lessened. The measurement data can be analyzed by using a software such as MAT-LAB and thus the oblique angle distribution can be calculated. Thus, the ratio of oblique angle of 10° or above can be easily determined. In the invention, the ratio of oblique angle of 10° or above is 2% or less, still preferably 1% or less. Thus, both of the antiglare properties and the effect of allowing a black picture to look black as such can be established.

In the antiglare optical film of the invention, it is preferable that the average oblique angle is 1° or more but less than 5° . The oblique angle may attain a peak at a certain degree and it may show two or more peaks. For example, the oblique angle may have a peak at 1°, show a ratio of 10° or above of 2% or less and have an average oblique angle of 4°. Alternatively, it may have peaks at 1.5° and 5 °, show a ratio of 10° or above of 2% or less and have an average oblique angle of 6°.

Concerning the surface peaks and valleys, the cycle and height of the unevenness surface can be measured by using a surface roughnessmeter . Twoparallelpeak count levels±0.0125 μm apart from the average line of the sectional curve of the film surface are drawn. A peak is defined when the curve intersects the lower peak count level once or more. Then the average interval among the peaks is calculated by dividing the measurement distance by the peak count. In the invention, the average intervals among peaks (Sm) range from 1 μm to 50 μm, still preferably from 1 μm to 20 μm and the most preferably from 1 μm to 15 μm. More specifically speaking, measurement may be made by using a surface roughness meter Model SE-3C (manufactured by Kosaka Kenkyusho) at a V. magnification of 20,000 or 10,000, cut-off value of 0.25, measuring length of 2.5 and recorder H. magnification of 50. Sm can be decreased by, for example, adding a large amount of grains having the same average grain diameter as the film thickness order. However, this known method results in worsening in whiteness.

To provide an antiglare film showing no glare in a high-definition monitor merely by appropriately designing the fine unevenness surface structure, it is unavoidable to accept loose black color. Although both of antiglare properties and tight black color can be established to a certain extent by using inner scattering or inner haze as described above, it is unavoidable that the contrast is lowered in this case. In the invention, it has been found out that glare can be prevented in a high-definition monitor and the worsening in the effect of allowingablackpicture to look black as such canbeprevented withoutdamagingthe contrastbycontrolling the ratioofoblique angle of 10° or above to 2% or less and controlling Sm to from 1 μm to 50 μm or from 1 μm to 20 μm.

The surface oblique angle distribution and Sm can be arbitrarily controlledby appropriately selecting the diameter and count of grains in the antiglare layer, the ratio of the grains to the binder in the antiglare layer and the dry film thickness . The surface form can be controlled by appropriately selecting the physical properties of coating solution (s), coating conditions and drying conditions. To more accurately design the surface, it is the most desirable to employ embossing as described above. Embossing is illustrated in detail in JPA 2000-329905. Namely, a desired surface form can be obtained by setting an emboss roll to a desired surface oblique angle distribution and Sm. However , the surface formof the invention can be obtained by an arbitrary method without restricted thereto .

In the invention, the refraction index of the hard coat layer is not mentioned in a single value. Namely, it is preferable that the hard coat layer is a non-uniform refraction index layer having particles dispersed in a material constituting the hard coat layer. It is preferable that the refraction index of the material constituting the hard coat layer ranges from 1.57 to 2.00. It is reported by, for example , JPA 8-110401, that in case where the material having a high refraction index is selected from among fine grains of 100 nm or less in grain diameter made of at least one member selected from among monomers having ethylenically unsaturated group and oxides of titanium, aluminum, indium, zinc, tin, antimony and zirconium, the grain diameter of the grains is sufficiently less than the wavelength of light and thus no scattering arises . Therefore, such a material behaves just like as a uniform substance from an optical viewpoint. The hard coat layer may serve as an antiglare layer too. Alternatively, an antiglare layer may be further formed on the hard coat layer.

It is preferable that the compound to be used in the hard coat layer is a polymer having a saturated hydrocarbon or polyether as the main chain, still preferably a polymer having a saturated hydrocarbon as the main chain. It is preferable that a binder polymer has been crosslinked. It is preferable that the polymer having a saturated hydrocarbon as the main chain is obtained by polymerization of an ethylenically unsaturated monomer. To obtain the crosslinkable binder polymer, it is preferable to use a monomer having two or more ethylenicallyunsaturatedgroups . To achieve ahigh refraction index, it is preferable that the monomer contains in its structureatleastonemember selectedfromamongaromaticcycles , halogen atoms other than fluorine, sulfur, phosphorus and nitrogen atoms. Examples of the monomer having two or more ethylenically unsaturated groups include esters of polyhydric alcohol with (meth) acrylic acid (for example, ethylene glycol di (meth) acrylate, 1,4-dicyclohexane diacrylate, pentaerythritol tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) crylate, tri ethylolethane tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, pentaerythritol hexa (meth) acrylate, 1,2 ,3-cyclohexane tetramethacryalte, polyurethane polyacrylate, polyester polyacrylate) , vinylbenzene and its derivatives (for example, 1 ,4-divinylbenzene, 2-acryloylethyl-4-vinylbenzoate, 1 ,4-divinylcyclohexanone) , vinylsulfone (for example, divinylsulfone) , acrylamdies (for example, methylenebisacrylamide) and methacrylamides . Examples of the high-refraction index monomer include bis (4-methacryloylthiophenyl) sulfide, vinylnaphthalene, vinylphenyl sulfide and 4-methacryloxyphenyl-4 ' -methoxyphenyl thioether .

It is preferable that the polymer having polyether as the main chain is synthesized by ring-opening polymerization of a polyfunctional epoxy compound.

After the application, it is necessary to cure such a monomer having ethylenically unsaturated groups by polymerization using ionized radiation or heating. Such a monomer having ethylenically unsaturated groups can be polymerized by irradiating ionized radiation or heating in the presence of a photoradical initiator or a heat radical initiator.

Accordingly, an antireflection film can be formed by preparing a coating solution containing the monomer having ethylenically unsaturated groups and the photoradical initiator or the heat radical initiator preferably together with mat grains and an inorganic filler, applying the coating solution on the transparent support and then polymerizing by using ionized radiation or heating.

Examples of the photoradical initiator include acetophenones , benzophenones , Michler' s benzoyl benzoate, amidoxime esters, tetramethyl thiuram monosulfide and thioxanthones . It is particularly preferable to use a photoradical initiator of the photocleavage type. Photoradical initiators of the photocleavage type are described in Saishin UV Koka G±jutsu (p.159, published by Kazuhiro Kobo, Gijutsu Joho Kyokai K.K. , 1991) . As examples of marketed photoradical polymerization initiators of the photocleavage type, Irgacures (651, 184, 907) manufactured by Ciba Geigy Japan.

Per 100 parts by mass of the polyfunctional monomer, the photopolymerization initiator is used preferably in an amount of from 0.1 to 15 parts by mass, still preferably from 1 to 10 parts by mass.

In addition to the photopolymerization initiator, use may be made of a photosensitizer . Specific examples of the photosynthesizer include N-butylamine, triethylamine, tri-n-butylphosphine, Michler' s ketone and thioxanthone. As a substitute for the monomer having two or more ethylenically unsaturated groups or in addition thereto, a crosslinkage structuremaybe introduced into thebinderpolymer by reaction with a crosslinkable group. Examples of the crosslinkable group include isocyanate group, epoxy group, aziridine group, oxazolidine group, aldehyde group, carbonyl group, hydrazine group, carboxyl group, methylol group and active methylene group. Moreover, use may be made, as the monomer for introducing the crosslinkage structure, of vinylsulfoniσacid, acidanhydrides , cyanoacrylatederivatives , melamine, etherified methylol, esters and urethane and metal alkoxides such as tetramethoxysilane. It is also possible to use a functional group showing crosslinkability as the result of a decomposition reaction, for example, a block isocyanate group. In the invention, the crosslinkable group is not restricted to the compounds as cited above but use can be made of compounds showing reactivity as the result of the decomposition of functional groups.

After the application, such a compound having a crosslinkable group should be crosslinked by, for example, heating.

To elevate the refraction index of the material constituting the hard coat layer, it is preferable that the hard coat layer contains fine grains having a grain diameter of 100 nm or less, preferably 50 nm or less, made of at least one member selected from oxides of titanium, aluminum, indium, zinc, tin, antimony and zirconium. Examples of the fine grains include Ti0₂, A1₂0₃, ln₂0₃, ZnO, Zn0₂, Sb₂0₃, ITO and Zr0₂.

It is preferable that the content of the inorganic fine grains amounts 10 to 90% by mass, still preferably 20 to 80% by mass and particularly preferably 30 to 60% by mass, based on the total mass of the hard coat layer.

To impart antiglare properties, prevent a decrease in the reflectivity due to interference by the hard coat layer and prevent irregular color, use is made in the hard coat layer mat grains of an inorganic compound or an organic polymer . For example, it is preferable to use silica grains, Ti0₂ grains, AI₂O3 grains, crosslinkable acryl grains, styrene grains, crosslinkable styrene grains, melamine resin grains, benzoguanamine resin grains or crosslinkable siloxane grains. Considering favorable dispersion stability (high affinity with thebinder) ofthegrains in the antiglarehardcoatlayer coating solution during the production and favorable sedimentation stability (low specific gravity) , it is further preferable to use grains of an organic polymer. The average grain diameter of the mat grains in the invention ranges from 0.3 μm to 10.0 μm, still preferably from 0.5 μm to 7.0 μm and still preferably form 1 μm to 6 μm. Concerning the shape of the mat grains, use canbemadeofeither spherical or irregularones . Toachieve stable antiglare properties, it is preferable to use spherical grains. It is also possible to use grains of two or more types different from each other.

It is preferable to use mat grains having a grain diameter exceeding 1/3 of the film thickness of the hard coat layer. The grain diameter distribution can be measured by the Coulter counter method or the centrifugation method. The distribution is determined in terms of grain count distribution. The dry film thickness of the hard coat layer preferably ranges from 2 μm to 10 μm, still preferably from 3 to 6 μm. As a method of achieving antiglare properties, JP

2000-329905 discloses a method wherein an antireflection layer is formed and then antiglare properties are imparted to the antiglare antireflection film. More specifically, the antireflection layer is applied and then the antireflective film is pressed with an emboss roll in this method. This method is also applicable to the antiglare optical filmof the invention . In this step, it is preferable to apply pressure of from 1 kgf/cm to 1000 kgf/cm, and control the temperature to from 25°C to 300°. The roll may be made of various materials, for example, metals such as iron and aluminum and plastics.

To impart an antireflection function, a low-refractive layer may be applied on the antiglare layer to give an antiglare antireflection film. The refractive index of the low-refractive layer ranges from 1.38 to 1.49, preferably from 1.38 to 1.44. In the antireflection film, it is preferable that the low-refractive layer fulfills the following relationships (I) .

mλ/4x0.7<nldl<mλ/4xl.3 (I)

In the above formula, m is a positive odd number (being 1 in general) ; nl stands for the refraction index of the low-refractive layer; and dl stands for the film thickness (nm) of the low-refractive layer. It is preferable that the low-refractive layer contains a fluorine-containing compound crosslinkable due to ionized radiation and inorganic fine fillers so that it has a coefficient of dynamic friction of from 0.03 to 0.15 and a contact angle towater of from 90° to 120° . Examples of the fluorine-containing crosslinkable polymer usable in the low-refractive layer include perfluoroalkyl-containing silane compounds (for example,

(heptadecafloro-1 , 1 ,2 ,2-tetradecyl) triethoxysilane) and fluorine-containing copolymers having a fluorine-containing monomer and another monomer for imparting a crosslinkable group as constituting monomers .

Specific examples of the fluorine-containing monomer include fluoroole ins (for example, fluoroethylene, vinylidene fluoride, tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluorol-2,2-dimethyl-l,3-dioxol) , partly or completely fluorinated (meth) acrylic acid alkyl ester derivatives (for example, Viscoat 6FM manufactured by Osaka Organic Chemical Industry, M-2020 manufactured by Daikin Industries) and completely or partly fluorinated vinyl ethers . Examples of the monomer for imparting a crosslinkable group include (meth) acrylate monomers preliminarily having a crosslinkable functional group in the molecule such as glycidyl methacrylate and (meth) acrylate monomers having, for example, carboxyl group, hydroxyl group, amino group or sulfonate group (for example, (meth) acrylic acid, methylol (meth) acrylate, hydroxyalkyl (meth) acrylate, allyl acrylate) . Itis known that the lattermonomers make itpossible to introduce a crosslinkage structure after the completion of the copolymerization, as reported by JPA 10-25388 and JPA 10-147739. It is also possible to use not only such a polymer having a fluorine monomer as its constituting unit as described above but also a copolymer with a fluorine-free monomer. The monomer usable together is not particularly restricted. For example, it is possible to use olefins (for example, ethylene, propylene, isoprene, vinyl chloride, vinylidene chloride) , acrylic acid esters (for example, methyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate) , methacrylic acid esters (for example, methyl methacrylate, ethyl methacrylate, butyl methacrylate, ethylene glycol dimethacrylate) , styrene derivatives (for example, styrene, di inylbenzene, vinyltoluene, α-methylstyrene) , vinyl ethers (for example, methyl vinyl ether) , vinyl esters (for example, vinyl acetate, vinyl propionate, vinyl cinnamate) , acrylamides (for example, N-tertbutγl acrylamide, N-cyclohexyl acrylamide) , methacrylamides and acrylonitrile derivatives.

As the inorganic grains to be used in the low-refractive layer, it is preferable to use amorphous ones. Preferable examples thereof include those made of metal oxides, nitrides, sulfides and halides and metal oxides are particularly preferable. Examples of the metal atom include Na, K, Mg, Ca, Ba, Al, Zn, Fe, Cu, Ti , Sn, In, W, Y, Sb, Mn, Ga, V, Nb, Ta, Ag, Si, B, BI, MO, Ce, Cd, Be, Pb and Ni . Among all, Mg, Ca, B and Si are still preferable. It is also possible to use an inorganic compound containing two types of metals. It is particularly preferable to use silicon dioxide, i.e., silica as the inorganic compound.

The average grain diameter of the inorganic grains preferably ranges from 0.001 to 0.2 μm, still preferably from 0.005 to 0.05 μm. It is also preferable that the grain diameter of the fine grains is as uniform as possible (homogeneous dispersion) .

It is preferable that the content of the inorganic fine grains ranges from 5% by mass to 90% by mass, still preferably from 10% by mass to 70% by mass and still preferably from 20% by mass to 50% by mass, based on the mass of the whole low-refractive layer.

It is also preferable to use the inorganic fine grains after a surface-treatment . Examples of the surface treatment include physical surface treatment such as plasma discharge and corona discharge and chemical surface treatments with the use of a coupling agent. It is preferable to use a coupling agent. As the coupling agent, it is preferable to use an organoalkoxymetal compound (for example, titanium coupling agent, silane coupling agent) . In case where the inorganic fine grains are silica, it is particularly effective to employ a silane coupling treatment.

Each of the layers of the antiglare film and the antiglare antireflection film, i.e. , the antiglare optical film, can be formed by a coating method such as dip coat method, air knife coat method, curtain coat method, roller coat method, wire bar coat method, gravure coat method or extrusion coat method (USP 2 , 681 ,294) . Two or more layers may be coated at the same time. Methods for the simultaneous coating are described in USP 2,761,791, ibid.2,941898, ibid.3,508, 947 and ibid.3,526,528 andYuji Harasaki, CotinguKogaku , p.253, AsakuraShoten (1973) .

In case where the grain-containing layer is free from any inner scattering, the haze of the antiglare film and the antiglare antireflection film preferably ranges from 0% to 18% , still preferably from 0% to 15%. In case where the grain-containing layer has inner scattering, it preferably ranges from 15% to 80%, still preferably from 20% to 65%.

As the transparent film substrate, it is preferable to use a plastic film having a light permeability of 80% or above. Examples of the polymer constituting the plastic film include cellulose esters (for example, triacetyl cellulose, diacetyl cellulose, acetate butyrate cellulose, propionyl cellulose, butyryl cellulose, acetyl propionyl cellulose, nitrocellulose) , polyamides, polycarbonates, polyesters (for example, polyethylene terephthalate , polyethylene naphthalate, polγ-1 , 4-cyclohexanedimethylene terephthalate, polyethylene-1 ,2-diphenoxyethane-4 ,4' -dicarboxylate, polybutylene terephthalate) , polystyrenes (for example, syndiotactic polystyrene) , polyolefins (for example, polypropylene, polyethylene, polymethylpentene) and norbornene polymer films (for example, Arton manufactured by JSR, Zeonor manufactured by Nippon Zenon, Zeonex manufactured by Nippon Zenon) , polyacrylic resin films such as polymethyl methacrylate, polyurethane resin films, polyether sulfone ilms , polyester films , polycarbonate films , polysulfone films , polyether films, polymethylpentene films and polyether ketone films. Among all, cellulose esters, polyethylene terephthalate and polyethylene naphthalate are preferable, celluloseesters are stillpreferableandlower fattyacidesters of cellulose are still preferable. The term "lower fatty acid" means a fatty acid having 6 or less carbon atoms. It is preferable that the carbon atomnumber is 2 (cellulose acetate) , 3 (cellulose propionate) or 4 (cellulose butyrate) . As the cellulose ester, cellulose acetates such as diacetyl cellulose and triacetyl cellulose are preferable. Use may be also made of mixed fatty acid esters such as cellulose acetate propionate or cellulose acetate butyrate.

In particular, in the case where the antireflective film of the present invention is used as one of surface protective films or polarizing plate to be used in a liquid crystal display unit, organic EL display unit or the like, triacetyl cellulose is preferably used. Alternatively, in the case where the antireflective film of the present invention is laminated with a glass substrate or the like for planar CRT, PDP or the like, polyethylene terephthalate or polyethylene naphthalate is desirable.

The light transmittance of the transparent support is preferably not smaller than 80%, more preferably not smaller than 86%. The haze of the transparent support is preferably not greater than 2.0%, more preferably not greater than 1.0%. The refractive index of the transparent support is preferably from 1.4 to 1.7.

In general, the degrees of substitution of cellulose acetate are not uniformly distributed at the 2-, 3- and 6-hydroxγl groups in 1/3 portions but there is observed a tendency that the degree of substitution at the hydroxyl group at the 6-position becomes lower. It is preferable in the invention that the degree of substitution of the hydroxyl group at the 6-position is higher than those of the hydroxyl groups at the 2- and 3-positions.

It is preferable that the hydroxyl group at the 6-position is substituted by acyl group at a ratio of from 30% to 40%, still preferably 31% or more and particularly preferably 32% or more. It is also preferable that the degree of substitution of the acyl group at the 6-position of cellulose acetate is 0.88 or abov .

As the cellulose acetate, use can be made of the cellulose acetates obtained by Synthesis Example 1 (paragraphs 0043 to

0044) , Synthesis Example 2 (paragraphs 0048 to 0049) and Synthesis Example 3 (paragraphs 0051 to 0052) in JPA 11-5851.

Next, a case of using a cellulose acetate film will be described in detail .

In general, a cellulose acetate film is produced by the solvent cast method. In the solvent cast method, a film is produced by using a solution (dope) of cellulose acetate in an organic solvent. As the organic solvent, use is generally made of a halogenated hydrocarbon such as methylene chloride. Use can be made therefor of organic solvents cited in Kokai Giho (Journal of technical disclosure) published by Japan Institute of Invention and Innovation (Kogi No. 2001-1745, published on March 15, 2001, hereinafter abbreviated as Kokai Giho 2001-1745) . Although halogenated hydrocarbons such as methylene chloride canbe employedwithoutany technical problem, it is preferable from the viewpoints of the global environment and working environment to use an organic solvent substantially free from any halogenated hydrocarbon. The expression "being substantially free from" means containing less than 5% by mass (preferably 2% by mass) of a halogenated hydrocarbon n the organic solvent. The cellulose acetate film of the invention can contain various additives (for example, plasticizer, anti-UV agent, antioxidant, fine grains , optical property-controlling agent) described in, for example, Kokai Giho 2001-1745, pp. 15 to 22. As the optical property-controlling agent, it is preferable to use an aromatic compound having at least two aromatic rings as a retardation-elevating agent to thereby control the retardation of the polymer film. Specific examples of the retardation-elevating agent are described in, for example, Kokai Giho 2001-1745, JPA 2000-111914, JPA 2000-275434 and PCT/JP00/02619.

It is preferable that the cellulose acetate film to be used as the transparent film substrate in the invention is preliminarily surface-treated. As the surface treatment, use canbemade of corona discharge, glowdischarge, flame treatment, acid treatment, alkali treatment or UV irradiation. To enhance the adhesiveness to the orientation film as will be described hereinafter, it is particularly preferable to treat with an acid or an alkali, i.e., saponification to the transparent support. As such surface treatment, use can be made of the methods described in Kokai Giho 2001-1745, pp. 29 to 30. It is also possible that, after the formation of an antiglare optical film, an alkali solution is applied to the optical film. It is also preferable to use, as a surface protective film, an antiglare optical film having been saponified on the face opposite to the face on which the antiglare layer is formed. The cellulose acetate film may be preliminarily undercoated. For theundercoating, usemaybemadeof themethod described in Kokai Giho 2001-1745, pp. 30 to 31.

In the present invention, the desired antiglare properties may be attained by effecting embossing involving pressing over an embossing roll as previously mentioned. The unevenness developed by embossing can easily be gradually reduced with time over an extended period of time. Further studies have been made of this phenomenon. As a result, the following discovery was given, a plastic material having a relatively high water absorption such as cellulose ester (e.g. , triacetyl cellulose, diacetyl cellulose, propionyl cellulose, butyryl cellulose, acetyl propionyl cellulose, nitrocellulose) which is a material desirable as transparent plastic support for antiglare optical film of the present invention is subject to remarkable acceleration of reduction of unevenness due to synergistic effect of water content in the atmosphere and heat. However, when subjected to embossing involving the roughening of the antireflective layer side, followed by treatment with hot water or water vapor, the antireflective film shows a temporary reduction of unevenness surface but then shows a drastically lessened change of unevenness even after prolonged use or in severe atmosphere of high temperature and humidity. Referring to a desirable method for obtaining an antireflective film having a desired unevenness surface, i.e., desired antiglarepropertiesas finalproduct, thismethodis adesirable method which comprises designing the unevenness surface before treatment with hot water or water vapor to be slightly great in expectation of reduction of unevenness due to the treatment so that the unevenness surface after treatment with hot water or water vapor is optimum.

The basic constitution of the antireflective film having antiglare properties of the present invention will be described in connection with the attached drawings.

[Provision of antiglare properties]

Fig.3 illustrates an example of the method for providing a coated type antireflective film with antiglare properties . in Fig. 3, an antireflective film (21) is pressed on the antireflective layer (23) side thereof over an emboss roll (24) and a backup roll (25) so that it is provided with unevenness surface on at least one side thereof to exhibit antiglare properties without impairing its antireflective properties.The uniformity in film thickness necessary for maintaining antireflective properties depends on the number and design of light interference layers. For example, in the case of a three-layer design having a low refraction layer, a high refraction layer and a middle refraction layer laminated to a thickness of λ/4n for each layer in this order from an air interface layer, the upper limit of uniformity in thickness is ± 3% for each layer. When the upper limit of uniformity in thickness exceeds the above defined range, the resulting antireflective film exhibits remarkably deteriorated antireflective properties. The degree of antiglare properties can be controlled by the process conditions in embossing step such as film surface temperature, pressure and processing speed and the dynamic physical properties of the transparent support havingan antireflective film. However, embossingundermilder conditions is desirable from the standpoint of planeness of film, stability of process, cost, etc.

[Treatment with hot water]

The treatment of the antiglare antireflective film thus embossed with hot water for the purpose of preventing the reduction ofunevenness on the embossed surface due to prolonged use is preferably effected at a continuous process after embossing from the standpoint of both maintenance of properties of embossed surface and economy. The treatment with hot water can be accomplished most simply and effectively by passing the embossed antireflective film through a hot water bath the temperature of which has been kept within a predetermined range. The same effect can be exerted also by passing the embossed antireflective film through a solution containing water or its vapor. Examples of the solution containing water include a mixture ofwater anda solventmisciblewithwater atanarbitrary ratio such as lowermonovalent alcohol (methanol , ethanol , etc. ) , lower divalent alcohol (ethylene glycol, etc.) and lower trivalentalcohol (glycerin) . Thewatercontentofthesolution is preferably not lower than 10% by mass, more preferably not lower than 20% by mass, even more preferably not lower than 50% by mass. Taking into account the economy, environmental pollution, toxicity, etc. , however, purewater ismostdesirable . The temperature of hot water treatment is preferably from not lower than 60°C to not higher than 200°C, more preferably from not lower than 70°C to not higher than 190°C, most preferably from not lower than 80°C to not higher than 180°C. The temperature of hot water treatment is preferably not higher than the temperature of embossing. When the temperature of hot water treatment exceeds the temperature of embossing, the unevenness on the embossed surface can be easily reduced, making it difficult to control the processing time. The hot water treatment time is closely related to the hot water treatment temperature and is preferably from not smaller than 1 second to not greater than 100,000 seconds. Taking into account the productivity, etc. , however, it is more preferably from not smaller than 2 seconds to not greater than 100,000 seconds, most preferably from not smaller than 4 seconds to not greater than 1,000 seconds. The antiglare antireflective film of the present invention preferably exhibits a percent retention R of arithmetic mean roughness of not smaller than 30% as defined by the equation (I) : (I) R = R_A/R_B wherein R_A represents the arithmetic mean roughness of the surface of the antireflective layer after 1 , 000 hours of storage in an atmosphere of 65°C and 95%RH (relative humidity) ; and R_B represents the arithmetic mean roughness of the surface of the antireflective layer before storage in an atmosphere of 65°C and 95%RH (relative humidity) .

The percent retention R of the antiglare antireflective film of the present invention is preferably not smaller than

40%, more preferably not smaller than 50%, even more preferably not smaller than 80%, particularly not smaller than 90%. [Surface roughness]

The surface roughness of the antiglare antireflective film can be evaluated by analyzing data obtained by observing theuneven surfaceofa sampleprovided ithantiglareproperties under a scanning microscope. The arithmetic mean roughness (Ra) is evaluated according to JIS-B-0601. In the present invention, the arithmetic mean roughness (Ra) of the surface of the antireflective film is predetermined to fall within the range of from 0.05 to 2 μm. Ra is preferably from 0.07 to 1.5 μm, more preferably from 0.09 to 1.2 μm, most preferably from 0.1 to 1 μm. When Ra falls below 0.05 μm, a sufficient antiglare function cannotbe obtained. When Raexceeds 2 μm, the resulting antireflective film is subject to reduction of resolution and white glittering of image upon irradiation with external light. Further, in the present invention, the proportion of unevenness intensity having a period of from 1 to 10 μm in all the unevenness surface intensities is preferably not smaller than 15%, more preferably not smaller than 20%, even more preferably not smaller than 25%, most preferably not smaller than30%. As thisproportionincreases, theresultingantiglare properties give finer and higher texture. The proportion of unevenness intensity having a period of from 1 to 10 μm is determined by power spectral density analysis. Power spectral density (PSD) is defined by the following equation (2) . PSD = 1/A |π/2jdxjdy-exp{i(px + qy)}z(x, y)|² (2) wherein A represents the scanning region; p and q each represent frequency in the horizontal direction; and x(x, y) represents image data. The root mean square (RMS) of unevenness intensity having a period of from 1 to 10 μm and all the unevenness surface intensities are then determined. The root mean square (RMS) of unevenness intensity is defined by the following equation (3) . (3) RMS = ^PSDdpdq

The proportion of unevenness intensity having a period of from 1 to 10 μm corresponds to the ratio (RMSi-io/RMStotai) of root mean square of unevenness intensity having a period offrom1 to 10 μm (RMSi-io) to rootmean squareofall theunevenness surface intensities (RMStotai) •

The average pitch between adjacent peaks on the surface of the antireflective film is preferably from 10 to 60 μm, more preferably from 15 to 40 μm, most preferably from 15 to 20 μm. The average depth from the top of peak to the bottom of valley is preferably from 0.05 to 2 μm, more preferably from 0.1 to

1 μm. The haze of the entire antiglare antireflective film is preferably not greater than 15%. The reflectance of the entire antiglare antireflective ilm is preferably not greater than 2.5%. [Formation of antireflective film]

Fig. 4 is a schematic sectional view illustrating the basic layer structure of the antireflective film to be embossed. The antireflective film comprises a transparent support (211) , a hard coat layer (212) , a middle refraction layer (213) , a high refraction layer (214) and a low refraction layer (215) laminated in this order. It is described in JP-A-59-50501 that the optical thickness, i.e., product of multiplication of refractive index and thickness of middle refraction layer, high refraction layer and low refraction layer in such a three-layer antireflective film is preferably around one fourth of the total wavelength λ or an integral multiple thereof.

However, in order to realize the reflectance properties of the present invention involving low reflectance and lessened tint of reflected light, it is necessary that the middle refraction layer, the high refraction layer and the low refraction layer satisfy the following relationships (I) , (II) and (III) , respectively, with respect to designed wavelength λ (= 500 nm) :

λ/4 x 0.80 < nidi <λ/4 x 1.00 (I) λ/2 x 0.75 < n2d2 <λ/2 x 0.95 (II) λ/4 x 0.95 < n3d3 <λ/4 x 1.05 (III)

wherein nl represents the refractive index of the middle refraction layer; dl represents the thickness (nm) of themiddle refraction layer; n2 represents the refractive index of the high refraction layer; d2 represents the thickness (nm) of the high refraction layer; n3 represents the refractive index of the low refraction layer; and d3 represents the thickness (nm) of the low refraction layer. Further, it is necessary that for a transparent support made of a triacetyl cellulose (refractive index: 1.49) , nl be from 1.60 to 1.65, n2 be from 1.85 to 1.95 and n3 be from 1.45 to 1.45. It is also necessary that for a transparent support made of a polyethylene terephthalate (refractive index: 1.66) , nl be from 1.65 to 1.75 , n2 be from 1.85 to 2.05 and n3 be from 1.35 to 1.45. It is known thatwhen theaforementionedmaterial ofmiddle refraction layer or high refraction layer having such a refractive index cannot be selected, the principle of equivalent film having in combination a layer having a refractive index higher than the predetermined refractive index and a layer having a re ractive index lower than the predetermined refractive index can be employed to form a layer substantially optically equivalent to the middle refraction layer or high refraction layer having the predetermined refractive index. This principle can be employed to realize the reflectance properties of the present invention . The term "substantially three layer" as used herein is meant to indicate a four- or five-layer antireflective layer comprising such an equivalent film. The reflectance properties of the present invention attained by the aforementioned layer constitution can satisfy both low reflectance and reduction of tint in reflected light. Therefore, when applied to the uppermost surface of a liquid crystal display unit for example, the antiglare optical film of the present invention can provide a display unit having an unprecedentedly high visibility. Since the specular reflectance at an incidence angle of 5° and an emission angle of -5° average over a wavelength range of from 450 nm to 650 nm is not greater than 0.5%, preferably not greater than 0.3%, thedeteriorationofvisibilitydue to the reflectionofexternal light by the surface of the display unit can be prevented to a sufficient level. Further, when the antiglare optical film of the present invention is applied to a liquid crystal display unit, the tint developed when an external light having a high luminescence such as indoor fluorescent lamp is slightly reflected thereupon is neutral and inoffensive.

The middle refraction layer and the high refraction layer are formed by coating a coating composition containing an inorganic particulate material having a high refractive index, a heat- or ionizing radiation-curing monomer, an initiator and a solvent, removing the solvent by drying, and then curing the coated material thermally and/or by ionizing radiation. As the inorganic particulate material there is preferably used one comprising at least one metal oxide selected from the group consisting of Ti, Zr, In, Zn, Sn and Sb oxides. The middle refraction layer and high refraction layer thus formed exhibit an excellent scratch resistance and adhesivity as compared with those obtained by coating a polymer solution having a high refractive index and drying the coated material . In order to secure dispersion stability, film strength after curing, etc. , it is preferred that a polyfunctional (meth) acrylate monomer and anionic group-containing (meth) acrylate dispersant as described in JP-A-11-153703 and US Patent 6,210,858 Bl be incorporated in the coating composition.

In particular , the high refraction layer is preferably formed by coating a coating composition containing an inorganic particulate material containing at least one metal oxide selected from the group consisting of Ti , Zr, In, Zn, Sn and Sb oxides, a heat- or ionizing radiation-curing monomer, an initiator and a solvent, removing the solvent by drying, and then curing the coated material thermally and/or by ionizing radiation .

The average particle diameter of the inorganic particulate material is preferably from 1 to 100 nm as measured by Coulter counter method. When the average particle diameter of the inorganic particulate material is not greater than 1 nm, the resulting inorganic particulate material has too great a specific surface area and thus has an insufficient stability in dispersion to disadvantage. On the contrary, when the average particle diameter of the inorganicparticulatematerial is not smaller than 100 nm, the resulting inorganic particulate material causes scattering of visible light due to difference in refractive index from binder to disadvantage. The haze of the high refraction layer and the middle refraction layer is preferably not greater than 3%, more preferably not greater than 1%.

The low refraction layer is preferably made of a fluorine-containing compound which cures thermally or when irradiated with ionizing radiation. The dynamic friction coefficient of said curable material is preferably from 0.03 to 0.15. The contact angle of the curable material with respect to pure water is preferably not smaller than 100 degrees, more preferably from 100 to 120 degrees. When the dynamic friction coefficient of the curable material is higher than 0.15, the resulting curable material is subject to scratching when rubbed on the surface thereof to disadvantage. When the contact angle of the curable material with respect to pure water falls below 100 degrees, the resulting curable material is subject to attachment of fingerprints, oil stain, etc. to disadvantage from the standpoint of stainproofness .

Examples of said curable fluorine-containing polymer compound include perfluoroalkyl group-containing silane compounds (e.g. , (heptadeσafluoro-1 , 1 ,2 ,2-tetradecyl) triethoxysilane) . Other examples of the curable fluorine-containing polymer compound include fluorine-containing copolymer comprising as structural units a fluorine-containing monomer and a monomer for providing a crosslinkable group. Specific examples of the fluorine-containingmonomerunit include fluoroolefines (e.g., fluoroethylene, vinylidene fluoride, tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoro-2 ,2-dimethyl-l ,3-dioxol) , partly or fully fluorinated alkylester derivatives of (meth) acrylic acid (e.g. , PiscoatδFM (producedbyOSAKAORGANIC CHEMICAL INDUSTRY LTD . ) , M-2020 (producedbyDAIKIN INDUSTRIES , LTD. ) , fullyorpartlyfluorinatedvinyl ethers, etc. Preferred among these fluorine-containing monomer units is hexafluoropropylene because it has a low refractive index and can be easily handled.

Examples of the monomer for providing a crosslinkable group include (meth) acrylate monomers having a crosslinkable functional group in its molecule such as glycicyl methacrylate . Other examples of the monomer for providing a crosslinkable group include (meth) acrylate monomers having carboxyl group, hydroxyl group, amino group, sulfonic acid group, etc. (e.g., (meth) acrylic acid, methylol (meth) acrylate, hydroxyalkyl (meth) acrylate, allyl acrylate). It is disclosed in JP-A-10-25388 and JP-A-10-147739 that the latter monomers can have a crosslinked structure incorporated therein after 130

copolymerization. Thus, the latter monomers are particularly preferred.

As the fluorine compound to be incorporated in the low refraction layer there is more preferably used a fluorine-containing polymer having a crosslinkable functional group which undergoes crosslinking after coating. The crosslinking of the polymer is preferably effected thermally or by ionizing radiation. Specific examples of the heat-crosslinkable fluorine-containingpolymer include Opstar JN7228 (trade name of heat-crosslinkable fluorine-containing polymer having a refractive index of 1. 2 and a fluorine content of 36% by mass produced by JSR Corporation) .

As the ionizing radiation-crosslinkable luorine-containing polymer there is preferably used a polymer having an ethylenically unsaturated group in its side chains. The crosslinking of these polymers having an ethylenically unsaturated group can be accomplished by irradiation with ionizing radiation. It is more desirable that photo-radical polymerization initiator be added during this process. Examples of the photo-radical polymerization initiator include acetophenones , benzophenones , Michler' s benzoyl benzoate, amyloxim ester, tetramethyl thiuraum monosulfide, thioxanthones , etc.

In particular, photo-cleavable photo-radical polymerization initiators are preferred. For the details of photo-cleavable photo-radical polymerization initiators, reference can be made to Kazuhiro Takabo, "Saishin UV Kouka Gijutsu (Modern Technique of UV Curing) " , Gijutsu Joho Kyokai , page 159, 1991. Examples of commercially available photo-cleavable photo-radical polymerization initiators include IRGACURE 651 , 184 and 907 (produced by Ciba-Geigy Japan Limited) .

The photo-polymerization initiator is preferably used in an amount of from 0.1 to 15 parts by weight, more preferably from 1 to 10 parts by weight based on 100 parts by weight of the fluorine-containing polymer.

In addition to the photo-polymerization initiator, a photosensitizer may be used. Specific examples of the photosensitizer include n-butylamine, triethylamine, tri-n-butylphosphine, and Michler' s ketone and thioxanthone.

Other examples of the ionizing radiation-crosslinkable fluorine-containing polymer include a combination of a polymer having an acid catalyst-crosslinkable functional group in its side chains and an ionizing radiation acid generator, and a combination of a polymer having a basic catalyst reactive functional group in its side chains and an ionizing radiation base generator. The former is preferred. As the acid catalyst-crosslinkable functional group there is preferably used an epoxy group. As the ionizing radiation acid generator there is preferably used a photo-acid generator. Specific examples of the photo-acid generator include triarylsulfonium salts, and diaryl iodonium salts.

The photo-acid generator is preferably used in an amount of from 0.1 to 15 parts by weight, more preferably from 1 to 10 parts by weight based on 100 parts by weight of the fluorine-containing polymer.

As the ionizing radiation there may be used UV, light, electron ray, radiation or the like, preferably light. Preferred among light is UV. Preferred examples of UV source include metal halide lamp, high voltage mercury vapor lamp, etc. , preferably metal halide lamp. The illuminance and dose of UV are preferably as great as possible so far as they have no adverse effects on the base and are preferably from 50 to 1,000 mW/cm² and from 200 to 1,000 mj/cm², more preferably from 150 to 600 mW/cm² and from 250 to 900 mJ/cm², respectively.

More preferably, an inorganic particulate compound is dispersed in the fluorine-containing polymer to enhance the film strength.

Referring to the physical properties of the fluorine-containing polymer, the fluorine-containing polymer exhibits a dynamic friction coefficient of from 0.03 to 0.15 and a contact angle of from 90 to 120° with respect to water.

There may be used not only the aforementioned polymer having a fluorine-containing monomer as a structural unit but also a copolymer thereof with a monomer free of fluorine atom. The monomer unit which can be used in combination with the aforementioned polymer is not specifically limited. Examples of themonomer unit employable herein include olefins (ethylene , propylene, isoprene, vinyl chloride, vinylidene chloride, etc.), acrylic acid esters (methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexγl acrylate, etc. ) , methacrylic acid esters (methyl methacrylate, ethyl methacrylate, butyl methacrylate, ethylene glycol dimethacrylate, etc.), styrene derivatives (styrene, divinyl benzene, vinyl toluene, α-methylstyrene, etc. ) , vinyl ethers (methyl vinyl ether, etc. ) , vinyl esters (vinyl acetate, vinyl propionate , vinyl cinnamate, etc.), acrylamides (N-tert-butylacrylamide, N-cyclohexylacrylamide , etc.), methacrylamides , acrylonitrile derivatives, etc. These monomer units are disclosed in JP-A-10-25388 and JP-A-10-147739.

As a means for lowering the dynamic friction coe ficient to provide scratch resistance, a copolymer unit for improving slipperiness can be introduced. A method for introducing a polydimethyl siloxane segment into side chains is disclosed in JP-A-11-228631. This method is particularly preferred. The fluorine-containing resin to be used in the formation of the low refraction layer preferably comprises a particulate Si oxide incorporated therein before use to render itself resistant to scratch. From the standpoint of antireflective properties, the refractive index of the fluorine-containing resin is preferably as low as possible. However, as the refractive index of the fluorine-containing resin lowers, the scratch resistance of the fluorine-containing resin worsens. Therefore, by optimizing the refractive index of the fluorine-containing resin and the added amount of particulate Si oxide, the point at which scratch resistance and low refractive index are best balanced.

As the particulate Si oxide, silica sol dispersed in a commercially available organic solvent may be incorporated in the coating composition. Alternatively, various commercially available silicapowders maybe dispersed in an organic solvent. In order to lower the reflectance of the antiglare optical film, it is necessary that the refractive index of the low refraction layer be sufficiently lowered. Examples of the material having a refractive index of not smaller than 1.40 include inorganic materials such as magnesium fluoride and calcium fluoride and organic materials such as fluorine-containing compound having a great fluorine content. However, these fluorine-containing compounds have an insufficient scratch resistance as a film to be disposed on the outermost surface of a display unit due to its insufficient coercive force and insufficient adhesion to substrate . In this case, the lowrefraction layerpreferablycomprises an inorganic particulate material and a coupling agent incorporated therein from the standpoint of scratch resistance. As the inorganic particulate material to be incorporated in the low refraction layer there is preferably used one having a low refractive index. The refractive index of the inorganic particulatematerial ispreferablyfrom1.30 to 1.49. Preferred examples of the inorganic particulate material include silica, and magnesium fluoride, particularly silica.

The average particle diameter of said inorganic particulate material is preferably from 0.001 to 0.2 μm, more preferably from 0.001 to 0.05 μm. The particle diameter of particles is preferably as uniform (monodisperse) as possible.

The added amount of said inorganic particulate material is preferably from 5 to 90% by mass, more preferably from 10 to 70% by mass, particularly from 10 to 50% by mass based on the total weight of the low refraction layer. In the present invention, it is particularly preferred that saidinorganicparticulatematerial be subjected to surface treatment before use. As the surface treatment method there may be used a physical surface treatment method such as plasma discharge treatmentand coronadischarge treatmentor achemical surface treatment method such as treatment using a coupling agent. Preferred among these treatment methods is treatment method using a coupling agent. As such a coupling agent there is preferably used an organoalkoxy metal compound (e.g. , titanium coupling agent, silane coupling agent) , including a compound of the general formula (1-1) . In the case where said inorganic particulate material is silica, silane coupling treatment is particularly effective. The compound of the general formula (1-1) is preferably preferred.

(R^x)m - Si (OR₂)_n (1-1) wherein R¹ represents a substitutedor unsubstitutedalkyl group or aryl group; R² represents a substituted or unsubstituted alkyl group or acyl group; m represents an integer of from 0 to 3 ; and n represents an integer of from 1 to 4 , with the proviso that the sum of m and n is 4.

The compound represented by the formula (1-1) will be described hereinafter.

In the general formula (1-1) , R¹ represents a substituted or unsubstituted alkyl group or aryl group. Examples of the alkyl group include methyl, ethyl, propyl, isopropyl, hexyl, t-butyl, sec-butyl, hexyl, decyl , hexadecyl, etc. The alkyl group is preferably a Cι-C₃₀, more preferably Cι-Cι₆, particularly Ci-Cβ alkyl group. Examples of the aryl group include phenyl group, naphthyl group, etc. Particularly preferred among these aryl groups is phenyl group.

The substituent is not specifically limited. Preferred examples of the substituent employable herein include halogen (fluorine, chlorine, bromine, etc.) , hydroxyl group, mercapto group, carboxyl group, epoxy group, alkyl group (methyl, ethyl, i-propyl , propyl , t-butyl , etc. ) , aryl group (phenyl , naphthyl , etc.) , aromatic heterocyclic group (furyl, pyrazolyl, pyridyl , etc.), alkoxy group (methoxy, ethoxy, i-propoxy, hexyloxy, etc.), aryoxy (phenoxy, etc.), alkylthio group (methylthio, ethylthio, etc.), arylthio group (phenylthio, etc.), alkenyl group (vinyl, 1-propenyl, etc.), alkoxysilyl group

(trimethoxysilyl, triethoxysilyl , etc.), acyloxy group (acetoxy, acryloyloxy, methacryloyloxy, etc. ) , alkoxycarbonyl group (methoxycarbonyl , ethoxycarbonyl , etc.), aryloxycarbonyl group (phenoxycarbonyl , etc. ) , carbamoyl group (carbamoyl, N-methylcarbamoyl , N,N-dimethylcarbamoγl, N-methγl-N-octylcarbamoyl, etc.), acylamino group (acetylamino, benzoylamino, acrylamino, methacrylamino, methacrylamino, etc.), etc.

More desirable among these substituents are hydroxyl group, mercaptogroup, carboxyl group, epoxygroup, alkyl group, alkoxysilyl group, acyloxy group, and acylamino group. Particularlypreferredamong these substituents are epoxygroup, polymerizable acyloxy group (acryloyloxy, methacryloyloxy) , andpolymerizable acylamino group (acrylamino, methacrylamino) . These substituents may be further substituted.

R² represents a substituted or unsubstituted alkyl group or acyl group. The description of alkyl group, acyl group and substituents thereon are same as for R¹. R² is preferably an unsubstituted alkyl group or unsubstituted acyl group, particularly an unsubstituted alkyl group. The suffix m represents an integer of from 0 to 3. The suffix n represents an integer of from 1 to 4. The sum of m and n is 4. When there are a plurality of R¹ or R², the plurality ofR¹ orR²maybethesameordifferent. The suffixmis preferably 0 , 1 or 2 , particularly 1.

Specific examples of the compound represented by the formula (1-1) will be given below, but the present invention is not limited thereto.

(1) (C₂H_B0)4-Si

(4) (CH₃COz)4-Si

( 5 ) (CH₃CO₂)2 - Si - (OC₂HE)2

(9)

(10)

(11) v t CH₂0CH-CH Si-(OCH₃)₃

0

(12) — 7— CH₂GH₂CH₂-Si-(OCH₃)₃

0

(14)

(15)

(16) C₃F₇CH2CH2-Si-(OC2H5)₃

(17) C_sF₁3CH2CH2-Si-(OC₂H5)₃

(18)

=\

COCH CH,CH₉-Si-(OCH

(19)

Λ

C0 H-CH,CH--Si-(0CH 3,)'3

(20)

C0,CH,CH--Si-(0CH 3'3

(21)

C0₂CH₂CH₂CH₂CH₂-Si-(OC₂H₅)₃

(22)

=\

CH₂CH Sι-(0CH₃)₃ (23)

-CHysHocH 3'3

(24)

(25)

H0-C-CH, Z^uCH"2₅-S ^Ui¹-(0^uC^uH"3'3

0

(26)

NH2CH2CH2CH2 - Si - (0 CHs)₃

(27)

HS- CH2CH₂CH₂-Si- (OCH₃)₃

(28)

(29)

(30)

(CH₃0)₃-Si-CH2CH2CH2CH2-Si-(OCH₃)₃ (31)

(CH3O)8-Si-CHsCH₂CH2CHaCH2CH2-Si-(OCHa)8

(32)

(CH₃0)₂ - Si - CH₂CH₂CH2CH₂ - Si - (OCH₃)₃

I I

CHs CH₃

(33)

CONHCH₂CH₂CH₂-Si-(OCH₃)₃

(34)

-CH,

CONHCH₂CH₂CH₂-Si-(OCH₃)₃

(35)

=\

CO-N- -CH,CH,CH,-Si-(OCH i 3'3

CH,

(36)

CO-NHCH₂CH₂CH₂CH₂- -Si-(OCH 3)'3

(37)

CO-NHCH₂CH₂CH₂-Si-(0CH₃)₂

CH₃

(38)

( ^- CH,0CH_?CH_? )_? — Si-(0CH₃)₂ (39)

Y7 ^■C υHi i,n0vGwHii-oCwHi l--Si-( V.0UCWHM3/2

CH '',3

(40)

HO-C-CH₂ 2C^VH"2₇C^VH Si-

CH,

(41)

(42)

\

C0₂CH₂CH₂CH₂ ) — Si-(0CH₃ z)

(43)

CHs=CH-Si-(OCHa)a

(44)

CHs

(45)

C0₂CH₂CH₂CH_z-Si-(OCH₃)₂

CH, (46)

(47)

(48)

HS- CH₂CH₂CH2-Si - (OCH₃)₂

CH₃

Particularlypreferred among these specific examples are compounds (1) , (12) , (18) and (19) .

The compound of the formula (1-1) maybe used as a surface treatment for inorganicparticulatematerial tobe incorporated in the low refraction layer to effect surface treatment previously before the preparation of the low refraction layer coating solution. In the present invention, however, it is particularly preferred that the compound of the general (1-1) be added to the coating solution during the preparation of the low refraction layer coating solution. The amount of the compound of the formula (1-1) to be added is from 0.5 to 1,000% by mass, preferably from 5 to 900% by mass, more preferably from 50 to 700% by mass based on the inorganic particulate material . During this procedure, excess silane coupling agent is preferably evaporated at the step of coating and drying.

In the low refraction layer containing such an inorganic particulate material , the inorganic particulate material preferably has a two-dimensional network structure. Fig. 5 illustrates the two-dimensional network structure as viewed from above the layer. The two-dimensional network structure indicates a structure having voids 7 as shown in Fig.5 developed when primary particles of inorganic material 8 are maldistributed during the process of drying the coat layer. The term voids 7" as used herein is meant to indicate that no inorganic particulate material 8 is present in the low refraction layeror, ifany, thedensityof inorganicparticulate material is 50 times or more smaller than that of the network portion. The network in the two-dimensional structure may be discontinuous . An example of such a network structure is shown in Fig. 6. This structure can be confirmed under optical microscope, SEM or the like.

In a preferred embodiment, the two-dimensional network structure has an average void area of from 0.3 to 1,000 μm², more preferably from 1 to 100 μm². The % void area (proportion ofvoid in all the area) of the two-dimensional network structure is^" from 40 to 90%, more preferably from 50 to 80%. The average void area and % void area can be determined by analyzing optical microphotograph or SEM photograph. In the case where the network structure is discontinuous as shown in Fig. 6, approximate average pore area can be determined by supposing an imaginary network on the extension of the discontinuous network .

It is thought that the two-dimensional network structure of the inorganic particulate material formed plays a role of finemattingagenttoprovidea remarkableimprovementofscratch resistance. However, its mechanism is unknown. Further, the mechanismof formation of the two-dimensional network structure of inorganic particulate material of the present invention is unknown. It needs only to form such a structure consequently. The antiglare optical film may further comprise a hard coat layer, a forward scattering layer, an antistatic layer, an undercoat layer and a protective layer provided therein .

The hard coat layer is preferably provided to provide the transparent film substrate with scratch resistance. The hard coat layer also acts to enhance the adhesion of the transparent film substrate to the upper layer. The hard coat layer is preferably formed by optionally adding an inorganic filler such as silica and alumina to a composition having an oligomer such as polyfunctional acryl monomer, urethane acrylate and epoxy acrylate and various polymerization initiators dissolved in a solvent, applying the coating composition thus obtained to the transparent film substrate, drying the coatedmaterial to remove the solvent, and then curing the coated material thermally and/or by ionizing radiation. In the antiglare optical film of the present invention, the forward scattering layer is preferably provided to exert the effect of improving the viewing angle when it is tilted vertically and horizontally in the case where the antiglare optical film is applied to a liquid crystal display unit. By dispersing particles having different refractive indexes in the aforementioned hard coat layer, the hard coat layer acts also as a forward scattering layer.

The various layers in the antiglare optical film can be formed by dip coating method, air knife coating method, curtain coating method, roller coating method, wire bar coating method, gravure coating method, microgravure coating method or extrusion coating method (US Patent 2 ,681 ,294) . Microgravure coating method and gravure coating method are preferredbecause they can minimize the wet coated amount to eliminate drying unevenness . Gravure coating method is particularly preferred from the standpoint of crosswise uniformity in thickness . Two or more layers may be simultaneously applied. For the details of simultaneous coating method, reference can be made to US Patents 2, 761, 791, 2,941,898, 3,508 , 947 and3, 526, 528, andYuji Harasaki, ^λλKotingu Kougaku (Coating Engineering) " , page 253, Asakura Shoten, 1973.

In the case where the antiglare optical film is used as one of surface protective films for polarizer, it is necessary that the transparent film substrate be subjected to saponification with an alkali on the side thereof opposite the antireflective layer. A specific means for alkaline saponification can be selected from the following two methods . The method (1) is preferred because it can be effected at the same step as for general-purpose triacetyl cellulose film. However, the method (1) may be disadvantageous in that the alkaline saponification extends up to the antireflective film side of the transparent film substrate, causing the alkaline hydrolysis of the surface of the transparent film substrate resulting in deterioration thereof and staining on the surface thereof with the saponifying solution left behind. In this case, the method (2) is preferred although it involves a special step.

(1) Methodwhichcomprisesdippinga t ansparentfilmsubstrate having an antireflective layer formed thereon in an alkaline solution at least once to saponify the back surface thereof.

(2) Method which comprises applying an alkaline solution to an antiglare optical film on the side thereof opposite the antireflective film before or after the formation of an antireflective film on the transparent film substrate, and then subjecting the coated material to heating, washing with water and/or neutralization so that only the back side of the film is saponified.

In case of using in a display unit, it is preferable that the antiglare optical film of the invention is located as the outermost face of the display by, for example, providing an pressure-sensitive adhesive layer. In case where triacetyl cellulose is used as the transparent film substrate, triacetyl cellulose is employed as a protective film for protecting the polarization layer of the polarizing plate. It is therefore preferable from the viewpoint of cost to use the antiglare optical film of the invention as the protective film as such. It is preferable that the antiglare optical film of the invention is employed in the visible side of the surface protective film of the polarizing plate. The film other than the antiglare optical film is an optical compensation film containing an optically anisotropic layer in the side of the sur ace protective film opposite to the polarizingplate. This optically anisotropic layer is a layer made up of a compound having a discotic structural unit and having a negative double refraction. It is preferable that the disc face of the discotic structural unit inclines to the surface protective film face and the angle between the disc face of the discotic structural unit and the surface protective film face changes in the depth direction of the optically anisotropic layer.

It is preferable that this optically anisotropic layer is made up of a discotic liquid crystal compound. Examples of the discotic liquid crystal compound include benzene derivatives reported in a study by C. Destrade et al . , Mol. Cryst., vol. 71, p. Ill (1981), truxene derivatives reported in studies by C. Destrade et al . , Mol. Cryst., vol. 122, p. 141 (1985) and Physics Lett, A., vol. 78, p. 82 (1990), cyclohexane derivatives reported in a study by B. Kohne et al . , Angew. Chem., vol. 96, p. 70 (1984) and aza-crown and phenylacetylene macrocycles reported in a study by J. M. Lehn et al., J. Chem. Commun., p. 1974 (1985), and a study by J. Zhang et al . , J. Am. Chem. Soc, vol. 116, p. 2655 (1994). In general, a discotic liquid crystal compound has a structure in which such a compound serving as the mother nucleus at the center of its molecule is radially surrounded by linear substituents such as linear alkyl, alkoxy or substituted benzoyloxy groups, thereby showing liquid crystalunity. However, the invention is not restricted to this illustration, so long as the molecule per se has monoaxial properties and can impart a definite orientation.

In the invention, it is not necessary that the "liquid crystal compound" in the optically anisotropic layer made up of the liquid crystal compound has liquid crystallinity in the optically anisotropic layer constituting the elliptical polarizing plate of the invention. Namely, the low-molecular weight discotic liquid crystal compound may have, for example, a group reacting due to heat or light and undergo polymerization or crosslinkage due to the heat or light to give a polymer having no liquid crystallinity, thereby forming an optically anisotropic layer.

Preferable examples of the discotic liquid crystal compound are cited in JPA 8-50206.

In the optically anisotropic layer constituting the elliptical polarizing plate of the invention, it is preferable that the disc face of the discotic liquid crystal compound inclines to the transparent support face and the angle between the disc thereof and the transparent support face changes in the depth direction of the optically anisotropic layer.

The angle (oblique angle) of the disc face of the discotic liquid crystal compound generally increases or decreases with an increase in the distance in the depth direction of the optically anisotropic layer from the bottom of the optically anisotropic . Itispreferable thatthis obliqueangleincreases with an increase in the distance. Examples of the change in the oblique angle include continuous increase, continuous decrease, intermittent increase, intermittent decrease, changes involving continuous increase and continuous decrease, and intermittent changes involving decrease and increase . The intermittent changes include a region in the depth direction where the oblique angle shows no change. It is preferable that the oblique angle increases or decreases as a whole, though a change-free region is included. It is still preferable that the oblique angle increases as a whole and a continuous change is further preferable. The optically anisotropic layer can be generallyobtained by applying a solution of the discotic liquid crystal compound and other compounds in a solvent on an orientation film, drying, then heating to the discotic nematicphase-forming temperature, and then cooling while maintaining the orientated state (i.e. , the discotic nematic phase) . Alternatively, the antiglare optical film layer can be obtained by applying a solution of the discotic liquid crystal compound and other compounds (together with, for example, polymerizable monomer, photopolymerization initiator) in a solvent on an orientation film, drying, thenheating to thediscoticnematicphase-forming 03 00130

temperature, and then polymerizing (by, for example, UV-irradiation) . The discotic nematic phase transfer temperature of the discotic liquid crystal compound to be used in the invention preferably ranges from 70 to 300°C, still preferably from 70 to 170°C.

The oblique angle of the optically anisotropic layer in the side of the transparent support can be controlled generally by selecting an appropriate discotic liquid crystal compound or an orientation film material, or selecting an appropriate rubbing method. The oblique angle in the opposite side (the atmosphere side) can be controlled generally by selecting an appropriate discotic liquid crystal compound or the compounds

(for example, plasticizer, surfactant, polymerizable monomer , polymer) to be used together with the discotic liquid crystals . Moreover, the extent of the change in the oblique angle can be controlled by the selection.

As theplasticizer, surfactantandpolymerizablemonomer, use can be made of arbitrary compounds , so long as being compatible with the discotic liquid crystal compound and not inhibiting the orientation of the discotic liquid crystal compound. Among all, it is preferable to use polymerizable monomers (for example, compounds having vinyl group, vinyloxy group, aσryloyl group andmethacryloyl group) . These compounds may be used generally in an amount of from 1 to 50% by mass (preferably from 5 to 30% by mass) based on the discotic liquid crystals .

As the polymer to be used together with the discotic liquid crystal compound, use can be made of arbitrary polymers, so long as being compatible with the discotic liquid crystal compound and not inhibiting the orientation of the discotic liquid crystal compound. Examples of the polymer include cellulose esters. Preferable examples of the cellulose esters include cellulose acetate, cellulose acetate propionate, hydroxypropyl cellulose and cellulose acetate butyrate. Such a polymer may be used generally in an amount of from 0.1 to

50% by mass (preferably from 0.1 to 8% by mass , still preferably from 0.1 to 5% by mass) based on the discotic liquid crystals.

The optically anisotropic layer made up of the liquid crystal compound to be used in the invention is provided on theorient tion filmlocatedon a celluloseac tate filmemployed as the transparent support. The orientation film is a rubbed film made of a crosslinkable polymer.

Preferable examples of the orientation film to be used in the invention include the orientation films described in JPA 9-152509.

The antiglare optical film of the invention is employed in display units such as liquid crystal displays (LCD) , plasma display panels (PDP) , electroluminescence displays (ELD) and cathode ray tubes (CRT) . In case where the antireflection film has a transparent support, it is preferable that the transparent support side of the antiglare optical film is adhered to the image display face of a display unit.

There are various liquid crystal cell modes in LCD. In a liquidcrystal cell of the STNmode, column-type liquidcrystal molecules are substantially horizontally orientated and twisted by 180° to 270°, when no voltage is applied. In a liquid crystal cell of the TNmode, column-typeliquidcrystalmolecules are substantially horizontally orientated and twisted by 60° to 120°, when no voltage is applied. These liquid crystal cells of the STN mode and the TN mode have been most frequently employed in monochrome and color liquid crystal display units and reported in a great number of documents .

In a liquidcrystal cell of theVAmode, column-type liquid crystal molecules are substantially vertically orientated, when no voltage is applied. Liquid crystal cells of the VA modeinclude: (1) liquidcrystal cells oftheVAmode inanarrower sense wherein column-type liquid crystal molecules are substantiallyverticallyorient tedwhen novoltage is applied, while these molecules are substantially horizontally orientated upon the application of voltage (described in JPA 2-176625) / as well as (2) liquid crystal cells of the multi-domain vertical alignment (MVA) mode with an enlarged view (described in SID97, Digest of tech. Papers (proceedings) 28 (1997) 845) ; (3) liquid crystal cells of the n-axially symmetric microcell (n-ASM) mode wherein column-type liquid crystal molecules are substantiallyvertically orientated when no voltage is applied, while these molecules are orientated in the twistedmulti-domain type upon the application ofvoltage (described in Proceedings of Nihon Ekisho Toronkai, 58-59, (1998)); and (4) liquid crystal cells of the SURVAIVAL mode (published on LCD International 98) .

Liquid crystal cells of the OCB mode, which are liquid crystal display units with the use of a liquid crystal cell wherein column-type liquid crystal molecules are orientated in substantially opposite directions (symmetrically) at the upper andlowerparts of the cells , aredisclosedbyUSP ,583, 825 and USP 5,410,422. Since the column-type liquid crystal molecules are orientated symmetrically at the upper and lower parts of the cells, these liquid crystal cells of the bend orientation mode have an optical self-compensation f nction . Thus, this liquid crystal mode is called the optically compensatory bend (OCB) liquid crystal mode. Liquid crystal display units of this OCB mode are advantageous in having a high response speed.

Inliquidcrystal cells oftheECBmode, column-type liquid crystal molecules are orientated in substantially horizontally when no voltage is applied. These cells have been most frequently employed as color TFT liquid crystal display units and reported in a great number of documents . For example, these 130

cells are described in EL, PDP , LCD Displays, publishedby Toray Research Center (2001) .

Now, the invention will be described in greater detail by reference to the following examples. However, it is to be understood that the invention is not construed as being restricted thereto.

In the case where the antiglare optical filmof thepresent invention is used in a transmission type or semi-transmission type liquid crystal display unit, an illuminance enhancement film (polarization separation film having a polarization selection layer, e.g. , D-BEF, producedby Sumitomo 3MCo. , Ltd. ) canbeprovidedinterposedbetween thepolarizingplatedisposed on the side thereof opposite the viewing side and the backlight to obtain a display unit having a higher viewability. Further, when combined with a λ/4 plate, the antiglare optical film of the present invention can be used as a surface protective plate for organicELdisplay to lessen reflectedlight from the surface thereof and the interior thereof.

EXAMPLES

EXAMPLE 1

(Preparation of a coating solution for hard coat layer) 250 g of a mixture of dipentaerythritol pentaacrylate with dipentaerythritol hexaacrylate (DPHA® manufactured by Nippon Kayaku) was dissolved in 439 g of a solvent mixture of methyl ethyl ketone with cyclohexanone (50/50 % by mass) . To the obtained solution was added a solution of 7.5 g of a photopolymerization initiator (Irgacure® 907 manufactured by Ciba Geigy) and 5.0 g of a photosensitizer (Kayacure® DETX manufactured by Nippon Kayaku) in 49 g of methyl ethyl ketone. The resultant solution was filtered through a polypropylene filter of 3 μm in pore size, then applied and UV-cured. The coating film thus obtained had a refraction index of 1.53 and a film thickness of 4 μm.

(PreparationofcoatingsolutionAforantiglarehardcoatlayer) 4165 parts by mass of a mixture of dipentaerythritol pentaacrylate with dipentaerythritol hexaacrylate (DPHA® manufactured by Nippon Kayaku) , 9941 parts by mass of a coating solution for hard coat containing a zirconium oxide dispersion (Z-7401® manufactured by JSR) , 1029 parts by mass of methyl ethyl ketone, 3099 parts by mass of cyclohexanone and 452 parts by mass of a photopolymerization initiator (Irgacure® 907 manufactured by Ciba Geigy) were mixed together.

To the resultant solution was further added 1314 parts by mass of a dispersion of crosslinkable polystyrene grains having an average grain diameter of 2 μm (grains being SX-200H® manufactured by Soken Kagaku; grain/methyl ethyl ketone/cyclohexanone=20/ 0/40 (% by mass) ) and the mixture was thoroughly stirred and mixed in an air disperser and filtered through a filter to give a coating solution for antiglare high-refractive layer . The coating filmobtainedbyapplying this solution and UV-curing the same had a refraction index of 1.61 and a film thickness of 1.4 μm.

To variously change the oblique angle distribution and surface roughness, the grain diameter of the crosslinkable polystyrene grains was varied from 2 to 5 μm.

(Preparation of coating solution B for antiglare hard coat layer)

To 1000 parts by mass of the coating solution A for hard coat layer (refraction index after evaporating the solvent and UV-curing: 1.51), 150 parts by mass of grains for imparting forward scattering properties made of crosslinkable polystyrene and having an average grain diameter of 1.3 μm (SX-130H, refraction index: 1.61 , manufacturedby SokenKagaku) . The resultant mixture was stirred for 10 minutes in an air disperser and filtered through a polypropylene filter (PPE-03) having a pore size of 3 μm to give a coating solution B for ahard coat layer having forward-scatteringproperties imparted thereto. (Preparation of coating solution for low-refractive layer)

200 parts by mass of a heat-crosslinkable fluorinated polymer having a refraction index of 1.43 (JN-7228®, solid content: 6%bymass , solvent: methyl ethyl ketone, manufactured by JSR) , 17 parts bymass of silica sol (MEK-ST®, average grain diameter: 10 to 20 nm, solid content: 30% by mass, solvent: methyl ethyl ketone, manufactured by Nissan Chemical Industries) , and the remainder 135 parts bymass of methyl ethyl ketone/cyclohexanone (giving amass composition ratio ofmethyl ethyl ketone/cyclohexanone of the whole solvent in the coating solution=90/10) were mixed and stirred together and then filtered through a polypropylene filter having a pore size of 1 μm to give a coating solution for low-refractive layer.

[Preparation of sample 1]

The coating solution for hard coat layer as described above was applied onto a triacetyl cellulose support (TD-80UF manufactured by Fuji Photofilm) with a bar coater and dried at 120°C. Then the coating layer was cured by UV-irradiation (luminance: 400 mW/cm², irradiation dose: 300 mJ/cm²) with the use of an air cooled metal halide lamp (manufactured by Eye Graphics) of 160 W/cm to thereby form a hard coat layer of 4 μm in thickness.

Subsequently, the coating solution for antiglare hard coat layer as described above was applied thereon with the use of a bar coater and dried and UV-cured under the same conditions as in the hard coat layer as described above . Thus an antiglare hard coat layer was formed. Samples of from 0.5 μm to 7 μm in antiglare hard coat layer thickness werepreparedby changing the application dose. As listed in Table 1, desired samples differing in surface oblique angle distribution and surface roughness from each other were prepared by appropriately combining the grain diameter of the crosslinkable polystyrene grains in the antiglare hard coat layer and the film thickness . Then the coating solution A for low-refractive layer as described above was further applied thereon with the use of a bar coater, dried at 80°C and crosslinked by heating to 120°C for 10 minutes to give a low-refractive layer of 0.096 μm in thickness . This sample corresponds to the case shown in Fig.1 having, between the support 1 and the antiglare high-refractive layer 2 , another hard coat layer formed by using the coating solution for hard coat layer as described above.

[Process for preparing sample 2]

A sample having no crosslinkable polystyrene grains in the antiglare hard coat layer was prepared as in the process for preparing the sample 1. A low-refractive layer having no unevenness on the surfacewas formedbyapplyingas in theprocess forpreparing the sample 1. Using a one-f ce embossing calender machine (manufactured by Yuri Roll) and setting an emboss roll made of steel and a backup roll surface-covered with a polyamide material, embossing was carried out with the use of the emboss roll having a desired surface shape at a press pressure of 600 kg/cm, a preheat roll temperature of 120°C, an emboss roll temperature of 120°C and a treatment speed of 2 m/min. Thus antiglareantireflection filmsamples havingeach fineas listed in Table 2 were obtained.

The antiglare antireflection films produced in the examples were each immersed in a 2.0 N aqueous NaOH solution at 55°C for 2 minutes to thereby saponify the triacetyl cellulose face on the back of the film. Using the thus treated film together with a triacetyl cellulose film (TAC-TD80U, manufactured by Fuji Photofilm) of 80 μm in thickness having been saponified under the same conditions, the both faces of a polarizer, which had been prepared by adsorbing iodine by polyvinyl alcohol and drawn, were adhered and protected to give a polarizing plate. Then a polarizing plate in the visible side of a liquid crystal display unit (provided with a polarization separation film having a polarization selective layer D-BEF manifested by Sumitomo 3M between a backlight and a liquid crystal cell) of a note personal computer on which a transmission TN liquid display unit was loaded was replaced by the polarizing plate prepared above in such a manner that the antiglare antireflection film serves as the outermost face, followed by evaluation.

(Evaluation of antiglare antireflection film)

The antiglare antireflection films thus produced were evaluated in the following items.

Because of being an antiglare antireflection film, it is ideal that the thus produced optical film has a low reflectivity, sufficient antiglare properties, no glare and little white blur and allows a black picture in the black color to look as such.

(1) Evaluation of antiglare properties

The antiglare antireflection film thus produced was bonded to a display as described above and an uncovered fluorescent lamp (8000 cd/cm²) having no louver was reflected. Then the extent of blur in the reflected image was evaluated in accordance with the following criteria. "X" means the NG level.

Outline of lamp no or little distinguishable: ^λO" Outline of lamp somewhat vague but distinguishable:

_"Δ_" Lamp being little vague: ^λλX"

(2) Evaluation of applicability to high definition monitor (glareness) To evaluate the applicability of the antiglare antireflection film to a high definition monitor, the antiglare antireflection film produced above was bonded to the UXGA 15 inch TFT-TN liquid crystal display (providedwith apolarization 'separation film having a polarization selective layer D-BEF manufactured by Sumitomo 3M between a backlight and a liquid crystal cell) as described above and then sensorily evaluated with the naked eye in accordance with the following criteria. λX" means the NG level. No glareness: ©"

A little but not disturbing glareness: O" Disturbing glareness: "X"

(3) 5° specular average reflectivity Using the antiglare antireflection film produced above, the spectral reflectivity at an angle of incidence of 5° was measured within a wavelength region of 450 to 650 nm with the use of a spectrophotometer (manufactured byNippon Bunko) . The result was expressed in the average reflectivity of 450 to 650 nm. A lower reflectivity means the better performance.

(4) Extent of allowing black picture to look black as such

The effect of the obtained film of allowing ablack picture to lookblack as such wasmeasuredwith theuseof a goniphotometer manufacturedbyMurakami Color ResearchLaboratory. The sample was irradiated with light in the direction of 5° and the scattering light in the direction shifting 40° from the regular reflection 5° (i.e., 45°). The results were logarithimcally indicated. A value lower by 1 or 2 respectively means the invasion of scatteringlight 10-foldor 100-fold, therebymaking the black picture looking less black. The absolute value has nomeaning. Namely, thevalue ofa certain samplewas determined and the difference form it in scattering light dose was logarithmically calculated. As the results of comparison with sensory evaluation data, it was found out that samples showing a value of 6.0 or higher had an excellent effect of allowing a black picture to look black as such. Samples of 5.3 or lower were unusable because of giving whitish images. Samples of from 5.3 to 6.0 showed somewhat whitish images. Samples different from each other by 0.2 or more were distinguishable from each other.

(5) White blur

A black picture was presented on a display under the standardmeasurementconditions as in (4) . Thenanincandescent lamp (500W) 2 m apart was reflected on the upper 1/3 of the display and the white blur in the whole display was evaluated.

When the white blur spread over 1/2 or more of the display, the visibilitywas seriouslyworsened. ^λX"means theNG level. White blur spreading over less than 1/2: "O" White blur spreading over 1/2 or more: "X"

(6) Average oblique angle and ratio of oblique angle of 10° or above Using an apparatus Model SXM520-AS150 (mama Microchip, USA) , anobjective lens with themagnification (xlO) , theoblique angle was measured in the unit of 0.85 μm and the measurement area was 0. 8 mm².

The measurement data were analyzed by using a software MAT-LAB and thus the oblique angle distribution was calculated, thereby giving the desired data.

Table 1 shows the results of the examples on the samples prepared in the production of preparing sample 1.

[Table 1]

The samples 6, 7 and 8 according to the invention made it possible to achieve a black display of the effect of allowing a black picture to look black as such of 6.0 or above while sustaining favorable (O) antiglare properties . In contrast, the comparative samples of the existing methods (Nos. 1, 2, 3, 4 and 5) failed to achieve the effect of 6.0 or above while sustaining favorable antiglare properties.

Moreover, it can be understood that the samples 7 and 8 according to the invention, which could improve glareness, are antiglare antireflection films applicable to high definition monitors.

EXAMPLE 2

Table 2 shows the results of the samples prepared in the production of preparing sample 2. Each of the samples of the invention could achieve a black display without any whiteness and suffered from no trouble in antiglare properties. Also, the glareness could be improved too. Thus, it is found out that these samples are antiglare antireflection films applicable to high definition monitors. It can be also understood that these samples can sustain favorable white blur . [Table 2]

00

EXAMPLE 3

As the protective film of the in the liquid crystal cell side of the polarizing plate in the liquid crystal visible side of the transmission TN liquid crystal cell having the antiglare optical films of EXAMPLES 1 and 2 bonded thereto and the protective filmin the liquid crystal cell side of thepolarizing plate of the backlight side, use was made of a wide view film

(Wide View Film SA-12B manufactured by Fuji Photofilm) having an optical compensation layer wherein thedisc face of adiscotic structural unit inclines to the surface protective film face, and the angle between the disc face of the discotic structural unit and the surface protective film face changes in the depth direction of the optically anisotropic layer. Thus a liquid crystal display unit showing an excellent contrast in a light room, having an extremelywideview angles both in thehorizontal and vertical directions, having an extremely high visibility and being excellent in display qualities could be obtained.

EXAMPLE 4 Using a coating solution for antiglare hard coat as a substitute for the coating solution A for antiglare hard coat layer of EXAMPLES 1 and 2, a layer having a forward scattering function was provided. Then a transmission TN liquid crystal displayunitprovidedwithapolarizingplatehavingthis forward scattering antiglare optical film as in the outermost face and the wide view film (Wide View Film SA-12B manufactured by Fuji Photofilm) in the liquid crystal cell side was constructed.

Compared with EXAMPLE 4, the limit angle at which gradation is inverseddue to the siftof thevision angle downward was improved from 40° to 60°. Thus, it was highly excellent in visibility and display qualities.

EXAMPLE 5

When the antiglare optical film produced in EXAMPLES 1 and 2 were bonded to a glass plate on the surface of an organic EL display unit with the use of a pressure-sensitive adhesive, the reflection and reflectivity on the glass surface could be regulated and thus a display unit having a high visibility could be obtained.

EXAMPLE 6

A λ/4 plate was bonded to the face opposite to the side having the antiglare layer of the polarizing plate provided with the antiglare optical film on one face produced in EXAMPLES 1 and 2. Then the polarizing plate was bonded to a glass plate on the surface of ah organic EL display unit . Thus , the surface reflection and the reflection from the inside of the surface glass could be cut and a highly visible picture was obtained. 130

EXAMPLES 1A - 10A

(Preparation of hard coat layer coating solution A)

306 parts by mass of a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (DPHA, producedbyNIPPON KAYAKU CO. , LTD . ) were dissolved in a mixture of 16 parts by mass of methyl ethyl ketone and 220 parts by mass of cyclohexanone. To the solution thus obtained were then added 7.5 parts by mass of a photopolymerization initiator (IRGACURE 907, produced by Ciba-Geigy Japan Limited) . The mixture was then stirred until dissolution was made. To the mixture were then added 450 parts by mass of MEK-ST (methyl ethyl ketone dispersion of Si0₂ sol having an average particle diameter of from 10 to 20 nm and a solid content concentration of 30% by mass, produced by NISSAN CHEMICAL INDUSTRIES, LTD. ) . The mixture was stirred, and then filtered through a polypropylene filter (PPE-03) having a pore diameter of 3 μm to prepare a hard coat layer coating solution A.

(Preparation of titanium dioxide dispersion) 30 parts by mass of ultrafine powder of titanium dioxide (TTO-55B, produced by ISHIHARA TECHNO CORP.) , 1 part by mass of dimethylaminoethy1 acrylate (DMAEA, produced by KOHJIN Co. ,Ltd. ) , 6 parts bymass of a phosphoric acid group-containing anionic dispersant (KAYARAD PM-21, produced by NIPPON KAYAKU CO. , LTD . ) and 63 parts by mass of cyclohexanone were subjected to dispersion in a sand grinder until the average particle diameter of the mixture reached 42 nm as measured by Coulter counter method to prepare a titanium dioxide dispersion.

(Preparation of middle refraction layer coating solution A)

0.11 parts by mass of a photopolymerization initiator

(IRGACURE 907, produced by Ciba-Geigy Japan Limited) and 0.04 parts by mass of a photosensitizer (KAYACURE DETX, produced by NIPPON KAYAKU CO. , LTD.) were dissolved in a mixture of 75 parts by mass of cyclohexanone and 19 parts by mass of methyl ethyl ketone. To the solution thus obtained were then added 3.1 parts bymass of a titanium dioxide dispersion and 2.1 parts by mass of a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (DPHA, produced by NIPPON KAYAKU CO. , LTD . ) . The mixture was stirred at room temperature for 30 minutes , and then filtered through a polypropylene ilter having a pore diameter of 3 μm (PPE-03) to prepare a middle refraction layer coating solution.

(Preparation of middle refraction layer coating solution B)

1.2 parts by mass of a photopolymerization initiator

(IRGACURE 907, produced by Ciba-Geigy Japan Limited) and 0.4 parts by mass of a photosensitizer (KAYACURE DETX, produced by NIPPON KAYAKU CO. , LTD . ) were dissolved in a mixture of 750 parts by mass of cyclohexanone and 190 parts by mass of methyl ethyl ketone. To the solution thus obtained were then added 105 parts by mass of a titanium dioxide dispersion and 21 parts by mass of a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (DPHA, produced by NIPPON KAYAKU CO. , LTD . ) . The mixture was stirred at room temperature for 30 minutes , and then filtered through a polypropylene filter having a pore diameter of 3 μm (PPE-03) to prepare a middle refraction layer coating solution B.

(Preparation of high refraction layer coating solution)

0.13 parts by mass of a photopolymerization initiator

(IRGACURE 907, produced by Ciba-Geigy Japan Limited) and 0.04 parts by mass of a photosensitizer (KAYACURE DETX, produced by NIPPON KAYAKU CO. , LTD.) were dissolved in a mixture of 54 parts by mass of cyclohexanone and 18 parts by mass of methyl ethyl ketone. To the solution thus obtained were then added 26.4 parts by mass of a titanium dioxide dispersion and 1.6 parts by mass of a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (DPHA, produced by NIPPON KAYAKU CO. , LTD . ) . The mixture was stirred at room temperature for 30 minutes , and then filtered through a polypropylene filter having a pore diameter of 3 μm (PPE-03) to prepare a high refraction layer coating solution.

(Preparation of low refraction layer coating solution) A 6 mass-% methyl ethyl ketone solution of a heat-crosslinkable fluorine-containing polymer having a refractive index of 1.42 (JN-7228 , produced by JSR Corporation) was subjected to solvent substitution to obtain a polymer solution having 10% by mass of a solid content incorporated in a mixed solvent comprising 85% by mass of methyl isobutyl ketone and 15% by mass of 2-butanol. To 70 parts by mass of the polymer solution thus obtained were then added 10 parts by mass of MEK-ST (methyl ethyl ketone dispersion of Si0₂ sol having an average particle diameter of from 10 to 20 nm and a solid content concentration of 30% bymass , producedbyNISSAN CHEMICAL INDUSTRIES, LTD.) , 42 parts bymass of methyl isobutyl ketone and 28 parts by mass of cyclohexanone. The mixture was stirred, andthen filtered through apolypropylene filterhaving a pore diameter of 3 μm (PPE-03) to prepare a low refraction layer coating solution.

(Preparation of antireflective film)

The aforementioned hard coat layer coating solution A was applied to a triacetyl cellulose film having a thickness of 80 μm (TAC-TD80U, produced by Fuji Photo Film Co., Ltd.) using a gravure coater, and then dried at a temperature of 100°C for2minutes. Subsequently, thecoatedmaterial was irradiated with ultraviolet rays so that the coat layer was cured to form a hard coat layer (refractive index: 1.51; thickness: 6 μm) . Subsequently, the aforementionedmiddle refraction layer coating solution A was applied to the hard coat layer using a gravure coater, dried at a temperature of 100°C, and then irradiated with ultraviolet rays so that the coat layer was cured to form amiddle refraction layer (refractive index: 1.63 ; thickness: 67 nm) .

Theaforementionedhigh refraction layer coating solution was applied to themiddle refraction layer using a gravure coate , dried at a temperature of 100°C, and then irradiated with ultraviolet rays so that the coat layer was cured to form a high refraction layer (refractive index: 1.90; thickness: 107 nm) .

Further, the aforementioned low refraction layer coating solution was applied to the high refraction layerusing a gravure coater. The coat layer was then cured at a temperature of 120°C for 8 minutes to form a low refraction layer (refractive index:

1.43; thickness: 86 nm) . Thus, an antireflective film was prepared.

(Provision of antiglare properties)

The antireflective film thus obtained was then subjected to embossing using a one-side embossing calendering machine (produced by YURI ROLL CO. ,LTD . ) having a steel embossing roll with a desired surface shape and a backup roll coated with a polyamide material on the surface thereof mounted thereon at a pressure of 1,000 Kg/cm, a preheat roll temperature of 100°C, an embossing roll temperature of 160°C and a processing rate of 2 m/min so that the proportion of an oblique angle of not smaller than 10° is 1%, the average oblique angle is 4.5° and the average interval Sm between peaks is 10 μm.

(Evaluation of antireflective film)

The filmthus obtainedwas thenevaluatedfor the following properties . (1) Specular reflectance

Using a Type V-550 spectrophotometer (produced by JASCO Corporation) with a Type ARV-474 adapter mounted thereon, the filmwas measured for specular reflectance at an incidence angle of 5° and an emission angle of -5° within a wavelength range of from 380 to 780 nm. The measurements were then averaged over a wavelength range of from 450 to 650 nm to give an average reflectance by which the antireflective properties of the film were then evaluated.

(2) Evaluation of pencil hardness

In order to give an index of scratch resistance, the film was evaluated for pencil hardness according to JIS K 5400. The antireflective film was conditioned at a temperature of 25°C and a humidity of 60%RH for 2 hours, and then evaluated for hardness with 2H to 5H testing pencils defined in JIS S 6006 at a load of 500 g according to the following criterion. The highest allowable hardness was used for evaluation. Number of scratches found when samples (n = 5) are evaluated is from zero to 2: OK Number of scratches found when samples (n = 5) are evaluated is 3 or more: NG

(3) Measurement of contact angle

In order to give an index of surface stain resistance, the optical material was conditioned at a temperature of 25°C anda humidity of 60%RH for 2 hours , and thenmeasured for contact angle with respect to pure water. Thus , an index of fingerprint adherability was given.

The results were as follows: Specular reflectance: 0.27%

Pencil hardness evaluated: 3H

Contact angle measured: 103°

(Hot water treatment) The filmthus obtainedwas dippedinhotwaterundervarious conditions set forth in Table 3 to undergo hot water treatment. The film which had thus been subjected to hot water treatment was then exposed to high temperature and humidity conditions of 65°C and 95%RH so that it was subjected to accelerated test against leveling of unevenness on the embossed surface thereof during prolonged use. Comparison was then made among various conditions and with unprocessed product. The results are set forth in Table 3.

Table 3

The antireflective films of Examples 1A to 10A initially exhibit not only very desirable reflecting properties but also an excellent scratch resistance and a high contact angle with respect to pure water and hence an excellent water repellency and oil repellency resulting in excellent stainproofness and high pencil hardness that makes themselves difficultly scratchable. The antireflective films of Examples 1A to 10A, which had been subjected to hot water treatment according to the invention, exhibited a percent retention of surface arithmetic average roughness of not smaller than 30% even after 1,000 hours of exposure to high temperature and humidity conditions of 65° and 95%RH and hence an excellent durability.

Example 11A

The antireflective film of Example 7A which had been subjected to hot water treatment was dipped in a 2.0 N aqueous solution of NaOH having a temperature of 55°C for 2 minutes to saponify the triacetyl cellulose on the back side thereof. Atriacetyl cellulose filmhaving a thickness of 80 μm (TAC-TD80U, produced by Fuji Photo Film Co., Ltd.) was subjected to saponification in the same manner as mentioned above. A polarizer prepared by allowing a polyvinyl alcohol to absorb iodine, and then stretching the film was then laminated with and protected by the two films on the respective side thereof to prepare a polarizing plate. The polarizing plate thus preparedwas thenusedwith its antireflective filmsidedisposed on the uppermost surface to replace the viewing side polarizing plate in the liquid crystal display of a note type personal computer comprising a transmission type TN liquid crystal display unit (having D-BEF, which is a polarization separation filmhaving a polarization selection layer producedby Sumitomo 3M Co. , Ltd. , interposed between the back light and the liquid crystal cell) . As a result, a display unit having extremely little reflection of background and a very high display quality was obtained.

Example 12A

The saponification procedure of Example 11A was followed except that the antireflective film was coated with a 1.0 N aqueous solution of KOH on the back side thereof using a #3 bar, processed at a temperature of 60°C for 10 seconds, washed with water , and then dried. The polarizing plate thus prepared was thenmountedon the liquidcrystal displayunit. As a result, a display unit having a high display quality as in Example 11A was obtained.

Example 13A

As each of the protective film on the liquid crystal cell side and the protective film on the back light side of the polarizing plate on the viewing side of the transmission type TN liquid crystal cell having the antireflective film of Example 12A mounted thereon there was used a viewing angle expansion film (Type SA-12B wide view film, produced by Fuji Photo Film Co. , Ltd.) comprising an optical compensation layer arranged such that a discotic structural unit having its disc surface oblique to the surface of the transparent support and the angle formed by the disc surface of the discotic structural unit and the surface of the transparent support varies in the depth direction of the optically anisotropic layer. As a result, a liquid crystal displayunithaving an excellent contrastunder daylight, a very wide horizontal and vertical viewing angle, an extremely excellent viewability and a high display quality was obtained.

Example 14A The polarizingplateprovidedwith an antireflective film on one side thereof prepared in Example 12A was laminated with a λ/4 plate on the side thereof opposite the antireflective film. The laminate thus prepared was then stuck to the surface glass plate in an organicELdisplayunit. As a result, a display unit having an extremely high viewability free from reflection on the surface thereof and the interior of the surface glass was obtained.

Example 15A (Preparation of antiglare hard coat layer coating solution A) To 245 g of a commercially available silica-containing UV-curing hard coat solution (product obtained by modifying the solvent composition of Desolite Z7526, produced by JSR Corporation; solvent composition: 57/43 mixture of methyl isobutyl ketone and methyl ethyl ketone; solid content concentration: approx. 72%; Siθ2 content in solid content: approx. 38%; polymerizable monomer and polymerization initiator contained) was added 19.6 g of Y-acryloxypropyl trimethoxy silane (KBM-5103, produced by Shin-Etsu Chemical Co . , Ltd. ) . The mixture was then diluted with 33.6 g of methyl isobutyl ketone. A coat layer obtained by applying this solution and curing the coat by ultraviolet rays exhibited a refractive index of 1.51.

To this solution was then added 44 g of a dispersion obtained by dispersing a 25% methyl isobutyl ketone dispersion of a particulate crosslinkable polystyrene having an average particle diameter of 3.5 μm (trade name: SX-350H, produced by Soken Chemical & Engineering Co., Ltd.) at 10,000 rpm in a Polytrondisperser for30minutes . Subsequently, tothemixture was added 57.8 g of a dispersion obtained by dispersing a 25% methyl isobutyl ketone dispersion of a particulate crosslinkable polystyrene having an average particle diameter of 5 μm (trade name: SX-500H, produced by Soken Chemical & Engineering Co., Ltd.) at 10,000 rpm in a Polytron disperser for 30 minutes.

The aforementioned mixture was filtered through a polypropylene filter having a pore diameter of 30 μm to prepare a antiglare hard coat layer coating solution A.

(Preparation of low refraction layer coating solution A) To 177 g of a heat-crosslinkable fluorine-containing polymer having a refractive index of 1.42 (JN-7228, produced by JSR Corporation; solid content concentration: 6%) were added 15.2 g of a silica sol (MEK-ST; average particle diameter: 10 to 20 nm; solid content concentration: 30%, produced by NISSAN CHEMICAL INDUSTRIES, LTD.), 95 g of methyl ethyl ketone and 9.0 g of cyclohexanone. The mixture was stirred, and then filtered through a polypropylene filter having a pore diameter of 1 μm to prepare a low refraction layer coating solution A.

(Sample 15A)

(1) Coating of antiglare hard coat layer

The aforementioned antiglare hard coat layer coating solution Al was applied to a roll of a triacetyl cellulose film having a thickness of 80 μm (TAC-TD80U, produced by Fuji Photo Film Co. , Ltd. ) while being uncoiled using a microgravure roll with a diameter of 50 mm having a gravure pattern having 180 lines per inch and a depth of 40 μm and doctor blade at a gravure roll rotary speed of 30 rpm and a conveyance speed of 5 m/sec, and then dried at a temperature of 120°C for 4 minutes. The coat layer was then irradiated with ultraviolet ray from an air-cooled metal halide lamp having an output of 160 W/cm

(produced by EYEGRAPHICS Co. , Ltd. ) at an illuminance of 400 mW/cm² and a dose of 300 mJ/cm² in a nitrogen atmosphere so that it was cured to a thickness such an arrangement that the proportion of oblique angle of not smaller than 10° is 2%, the average oblique angle is 4.5° and the average interval Smbetween peaks is 10 μm, thereby forming an antiglare hard coat layer. The film was then wound. (2) Coating of low refraction layer

The aforementioned low refraction layer coating solution was applied to the roll of a triacetyl cellulose film having the antiglare hard coat layer provided thereon while being uncoiled using a microgravure roll with a diameter of 50 mm having a gravure pattern having 180 lines per inch and a depth of 40 μm and doctor blade at a gravure roll rotary speed of 30 rpm and a conveyance speed of 10 m/sec, and then dried at a temperature of 80°C for 2 minutes. The coat layer was then irradiatedwith ultraviolet ray from an air-cooledmetal halide lamp having an output of 240 W/cm (produced by EYEGRAPHICS Co . , Ltd.) at an illuminance of 400 mW/cm², a dose of 300 mJ/cm² and a temperature of 140°C in a nitrogen atmosphere for 10 minutes so that it was thermally crosslinked to form a low refraction layer to a thickness of 0.096 μm. The film was then wound. The surface of the sample was vacuum-metallized with gold, and then photographed under SEM. The presence of two-dimensional network structure was then confirmed on the photograph.

Sample 15A was similar to Sample 8 in respect to white blur, degree of viewability of black as black, antiglare properties and glittering and was excellent in scratch resistance such as resistance to rubbing with steel wool and resistance to rubbing with wet cotton rod.

This application is based on Japanese Patent application JP 2002-23870, filed January 31, 2002, and Japanese Patent application JP 2002-4565, filed January 11, 2002, the entire contents of those are hereby incorporated by reference, the same as if set forth at length.

Claims

1. An antiglare optical film comprising: a transparent film substrate having a fine unevenness surface structure provided on at least one side of the transparent film substrate, wherein a proportion of an oblique angle of not smaller than 10° is not greater than 2% and an average interval of peaks in the fine unevenness surface is from 1 μm to 50 μm.

2. The antiglare optical film according to claim 1 , wherein the average interval of peaks is from 1 μm to 20 μm.

3. The antiglare optical film according to claim 1 or 2, wherein an average of oblique angles with respect to regular reflection face measured on the surface of the film in from 1 to 2 μm² is from not smaller than 1° to less than 5°.

4. The antiglare optical film according to any one of claims 1 to 3, comprising an antireflective layer on the uppermost surface thereof.

5. The antiglare optical film according to any one of claims 1 to 3, wherein the fine unevenness surface structure is formed by embossing in order to roughen a surface of the film, to render the antiglare optical film antiglare.

6. The antiglare optical film according to claim 5, further comprising an antireflective layer, wherein a percent retention R of arithmetic mean of roughness defined by the following equation (I) is not smaller than 30%:

wherein R_A represents an arithmetic mean roughness of a surface of the antiglare optical film after 1,000 hours of storage in an atmosphere of 65°C and 95%RH (relative humidity) ; and R_B represents an arithmetic mean roughness of a surface of the antiglare optical film before the storage in an atmosphere of 65°C and 95%RH (relative humidity) .

7. The antiglare optical film according to any one of claims 1 to 4 , comprising at least one forward scattering layer interposed between the antiglare layer and the substrate.

8. A process for preparing of an antiglare optical film comprising a fine unevenness surface structure provided on at least one side of a transparent film substrate, the process comprising: embossing of a surface of the film so that a proportion of obliqueangleofnot smaller than 10° is notgreater than 2% and an average interval of peaks in the fine unevenness surface is from 1 μm to 50 μm.

9. The process according to claim 8, wherein the average interval of peaks is from 1 μm to 20 μm.

10. The process according to claim 8 or 9 , wherein an average of oblique angles with respect to regular reflection face measured on a surface of the film in from 1 to 2 μm² is from not smaller than 1° to less than 5°.

11. The process according to any one of claims 8 to 10, wherein the antiglare optical film comprises an antireflective layer on an uppermost surface layer and a surface of the antireflective layer is subjected to the embossing.

12. The process according to claim 11 , wherein a percent retention R of arithmetic mean of roughness defined by the following equation (I) is not smaller than 30%:

wherein R_A represents an arithmetic mean roughness of a surface of the antireflective layer after 1,000 hours of storage in an atmosphere of 65°C and 95%RH (relative humidity) ; and R_B represents an arithmetic mean roughness of a surface of the antireflective layer before storage in the atmosphere of 65°C and 95%RH (relative humidity) .

13. The process according to claim 12, further comprising: subjecting the antiglare optical film in a solution comprising water in an amount of not smaller than 10% by weight or in a vapor of the solution at a temperature of from 60°C to 200°C for 10,000 to 100,000 seconds, after the embossing.

14. Aprocess for preparing of an antiglare optical film comprising a transparent film substrate and an antiglare layer provided on at least one side of the substrate, the antiglare layer having a fine unevenness surface structure, the process comprising: adjusting the antiglare layer such that a proportion of oblique angle of not smaller than 10° is not greater than 2% and an average interval of peaks in the fine unevenness surface is from 1 μm to 50 μm.

15. A polarizing plate comprising a polarizer and two surface protective films laminated on both surfaces of the polarizer, respectively, wherein at least one of the surface protective films is the antiglare optical film according to any one of claims 1 to 7.

16. A display unit comprising the antiglare optical film according to any one of claims 1 to 7 or the polarizing plate according to claim 15.