JP2020144291A - Phase difference element and manufacturing method of the same - Google Patents

Abstract

To provide a biaxial phase-difference element with a structure capable of designing two plates independently, and a manufacturing method of the same.SOLUTION: A phase difference element for performing corrections so as to reduce a phase difference generated due to the influence of an object comprises: a C plate part 1 where a first layer 11 and a second layer 12 whose refractive index is lower than that of the first layer 11 are laminated in a period shorter than a wavelength of light in a used band; and an A plate part 2 made of a convex-concave structure where a convex part 21 extending in one direction is formed in a period shorter than the wavelength of the light in the used band.SELECTED DRAWING: Figure 1

Description

The present invention relates to a structural biaxial retardation element used in a liquid crystal display or the like and a method for manufacturing the same.

In recent years, liquid crystal display devices have the features of being thin, lightweight, and capable of reducing power consumption, such as calculators, electronic dictionaries, televisions, digital camera displays, car navigation system monitors, mobile phone and computer monitors, and projector displays. It is used as a display for various electronic devices such as elements.

Here, the liquid crystal display can be classified into several types according to the difference in the operation mode of the liquid crystal layer. For example, TN liquid crystal, VA liquid crystal, IPS liquid crystal, OCB liquid crystal and the like are known. Which of these liquid crystal displays is used in an operation mode is selected according to the usage environment of the electronic device and the required performance.

In these liquid crystal displays, the liquid crystal is arranged between a pair of polarizing plates arranged on the cross Nicol, and the orientation of the liquid crystal is controlled by the electric field applied to the transparent electrode. When the liquid crystals are lined up in a direction that does not affect the phase difference, the light is shut off and the display becomes black. Further, when the liquid crystals are arranged in a direction that gives a phase difference, light is transmitted and the display becomes white. However, in an actual system, even when the display is black, the phase of light is actually affected by the anisotropy of the refractive index of the liquid crystal material, and leakage light occurs. In particular, if the viewing angle is tilted at an orientation of 45 ° from the absorption axis of the polarizing plate, the phase change becomes large and the black display cannot be maintained.

In order to correct and improve the phase difference caused by the influence of the birefringence of the liquid crystal, it is possible to compensate for the phase difference of light passing diagonally through the liquid crystal layer by using a phase difference element having birefringence. It has been proposed (see, for example, Patent Document 1). This makes it possible to keep the display black over a wide viewing angle range.

Stretched resin is widely used as a retardation element, but a retardation element using an inorganic material is used in projectors where high-density light is concentrated and in-vehicle head-mounted displays used in harsh environments of high and low temperatures. desirable.

As the inorganic retardation element, a retardation element using a crystal having birefringence, a retardation element using an oriented polycrystalline film formed by oblique vapor deposition of Ta ₂ O ₅ , and a period shorter than the wavelength. There is a processed structural phase difference element.

Among these, the structural phase difference element has optical characteristics determined by the size of the processing pattern, and the desired optical characteristics required for phase difference compensation can be easily designed by simulation. Therefore, it is suitable for a plurality of display models. It has the advantage of being able to respond flexibly.

As a structural retardation element, if the refractive indexes in the X, Y, and Z directions perpendicular to each other are nx, ny, and nz, respectively, a negative C plate (nz <nx = ny) is used, and films having different refractive indexes are formed. A technique for laminating has been reported (see, for example, Patent Document 2).
Further, as the A plate (nx> ny), a retardation element having a one-dimensional lattice structure on a dielectric has been reported (see, for example, Patent Documents 3 and 4).

In these, a retardation element is formed by forming uneven lines and spaces smaller than the wavelength on the dielectric substrate and changing the in-plane refractive index.

Japanese Unexamined Patent Publication No. 2004-145268 U.S. Pat. No. 5,196953 Patent No. 2973254 Patent No. 4125114

Here, in the case of a TN liquid crystal, in the dark, the molecules are vertical at the center of the liquid crystal, and the refractive index is a positive C plate (nz> nx = ny) in which nz in the Z direction is larger than the refractive index nx in the plane direction and ny. Therefore, a negative C plate (nz <nx = ny) is required to correct this. Further, since the liquid crystal molecules near the electrodes are sleeping and exhibit birefringence in the x-direction and the y-direction in the plane, an A plate complementary to this is required to correct this.

Further, in the case of VA liquid crystal, the molecules of the liquid crystal are arranged vertically in the dark and are a positive C plate (nz> nx = ny) having a large refractive index in the Z direction. Therefore, in order to correct this, refraction in the vertical direction is required. A negative C plate with a low rate (nz <nx = ny) is required. Further, in some cases, an A plate that compensates for the deviation of the polarization axis due to the incident angle of the polarizing plate is also required.

Therefore, if the two plates, the C plate and the A plate, can be designed independently, it is possible to realize a phase difference element having a high degree of freedom corresponding to many liquid crystal displays and capable of optimally correcting the phase difference.

Therefore, an object of the present invention is to provide a biaxial retardation element having a structure capable of independently designing two plates and a method for manufacturing the same.

In order to achieve the above object, the phase difference element of the present invention is for correcting the phase difference caused by the influence of the object so as to be small, and has a refractive index higher than that of the first layer and the first layer. It consists of a C-plate portion in which a second layer having a low frequency is laminated at a period shorter than the wavelength of light in the used band, and an uneven structure in which a convex portion extending in one direction is formed at a period shorter than the wavelength of light in the used band. It is characterized by including an A plate portion.

Here, the convex portion may be formed by laminating a third layer and a fourth layer having a refractive index lower than that of the third layer at a period shorter than the wavelength of light in the use band.

Further, the thickness of the outermost surface side of the first layer is preferably 0.4 times or more and 0.7 times or less the thickness of the other layers.

Further, the width D of the convex portion with respect to the pitch P is preferably 0.3 times or more and 0.7 times or less.

Further, a stop layer may be formed between the A plate portion and the C plate portion so that a part of the stop layer is exposed in the concave portion of the uneven structure.

Further, the first layer and the third layer may be made of the same material, and the second layer and the fourth layer may be made of the same material.

Further, the concave portion of the concave-convex structure of the A plate portion may be filled with a material having a refractive index different from that of the convex portion.

Further, the method for manufacturing a phase difference element of the present invention is a method for manufacturing a phase difference element for correcting the phase difference caused by the influence of a target so that the phase difference is reduced, and the C plate portion includes a first layer and the above. A film forming step of laminating a second layer having a refractive index lower than that of the first layer at a period shorter than the wavelength of light in the used band and further forming an A plate layer on the C plate portion extends in one direction. A resist pattern forming step of forming a resist pattern having a concavo-convex structure in which convex portions are arranged in a period shorter than the wavelength of light in the use band on the A plate layer, and the A plate layer being etched using the resist pattern, one It is characterized by having an etching step of forming an A plate portion having a concavo-convex structure in which convex portions extending in a direction are arranged at a period shorter than the wavelength of light in the working band.

In this case, in the film forming step, the third layer and the fourth layer having a refractive index lower than that of the third layer are laminated as the A plate layer at a period shorter than the wavelength of light in the working band. Is also good.

Further, in the film forming step, a stop layer having an etching rate lower than that of the A plate layer may be formed between the A plate layer and the C plate portion.

Further, in the film forming step, it is preferable that the thickness of the outermost surface side of the first layer is formed to be 0.4 times or more and 0.7 times or less the thickness of the other layers. preferable.

Further, in the resist pattern forming step, it is preferable to form the resist pattern so that the width D of the convex portion with respect to the pitch P is 0.3 times or more and 0.7 times or less.

Further, in the film forming step, the first layer and the third layer may be made of the same material, and the second layer and the fourth layer may be made of the same material.

Further, the concave portion of the concave-convex structure of the A plate portion may have a filling step of filling a material having a refractive index different from that of the convex portion.

The two-axis phase difference element of the present invention realizes phase compensation of various liquid crystal displays with high accuracy by forming the two-axis phase difference elements on the same surface, further reduces the number of parts, miniaturizes the device, and reduces the cost. Cost reduction can be realized.

It is a perspective view which shows the phase difference element of this invention. It is sectional drawing which shows the retardation element of this invention. It is sectional drawing which shows the other retardation element of this invention. It is sectional drawing which shows the retardation element of this invention which has a stop layer. It is a perspective view explaining the phase difference element manufacturing method of this invention. It is sectional drawing which shows the retardation element of this invention adhered to a glass substrate. It is sectional drawing which shows the structure of A plate of simulation 1. FIG. It is a graph which shows the relationship between the wavelength of the incident light and the retardation with respect to the fill factor F _Ad of the retardation element of this invention. It is sectional drawing which shows the structure of the phase difference element of simulation 2. It is a graph which shows the relationship between the wavelength of incident light and the diffraction efficiency with respect to the pitch _PCd of the retardation element of this invention. It is sectional drawing which shows the structure of the C plate part of simulation 3. It is a graph which shows the relationship between the wavelength and the transmittance of the incident light when the thickness x of the layer on the outermost surface side of the 1st layer of the retardation element of this invention is changed. It is sectional drawing which shows Example 1 of the retardation element of this invention. It is sectional drawing which shows Example 2 of the phase difference element of this invention. It is a graph which shows the relationship between the azimuth angle of the incident light and the retardation when the incident angle of the light irradiating the retardation element of this invention is changed.

The retardation element of the present invention will be described with reference to FIG. The phase difference element of the present invention is for correcting so that the phase difference caused by the influence of the object becomes small, and is mainly composed of the C plate portion 1 and the A plate portion 2 formed on the C plate portion 1. It is composed. In the present specification, the directions parallel to the boundary surface of the C plate portion 1 and the A plate portion 2 and perpendicular to each other are defined as the X direction and the Y direction, and the direction perpendicular to the boundary surface is defined as the Z direction. Further, the refractive indexes of the C plate portion 1 of the retardation element of the present invention in the X, Y, and Z directions are nx _C , ny _C , nz _C , and the refractive indexes of the A plate portion 2 in the X, Y, and Z directions, respectively. Let it be nx _A , ny _A , and nz _A. Further, the refractive indexes in the X, Y, and Z directions to which the phase difference element of the present invention corrects the phase difference are set to nx _O , ny _O , and nz _O , respectively.

Here, the target refers to an optical element such as a liquid crystal, in which a phase difference occurs due to the influence of birefringence.

The C plate portion 1 is for correcting so that the phase difference in the Z direction with respect to the X direction (or Y direction) caused by the influence of the target becomes small. For example, when the target is a positive C plate (nz _O > nx _O = ny _O ), the C plate portion 1 can be corrected so that the phase difference in the Z direction with respect to the X direction and the Y direction becomes small. A negative C plate (nz _C <nx _C = ny _C ) may be used.

In order to make the C plate portion 1 a negative C plate, the first layer 11 and the second layer 12 having a refractive index lower than that of the first layer 11 may be laminated at a period shorter than the wavelength of light in the band used. ..

The first layer 11 is a layer that is alternately laminated with the second layer 12, and any material may be used as long as it has a higher refractive index than the second layer 12, but for example, titanium oxide (TiO ₂ ), Examples thereof include tantalum pentoxide (Ta ₂ O ₅ ), hafnium oxide (HfO ₂ ), zirconium dioxide (ZrO ₂ ), and silicon nitride (SiN).

The second layer 12 is a layer that is alternately laminated with the first layer 11, and any material may be used as long as it has a lower refractive index than the first layer 11, but for example, silicon dioxide (SiO ₂ ) or Examples thereof include magnesium fluoride (MgF ₂ ).

Of course, any combination of materials for the first layer 11 and the second layer 12 may be used, and it may be determined according to the desired performance of the retardation element.

Further, as shown in FIG. 2, the first layer 11 second layer 12, the cycle (the film thickness d ₁ and a second layer 12 Total thickness d ₂ of the first layer 11) of P _Cd, incident the wavelength of light lambda, when the average refractive index of the C-plate portion 1 and _{n C, P Cd <λ /} n C, preferably _{P Cd} <λ / 2n _C, more preferably _{P Cd} <λ / _{2.8n C} It may be laminated so as to satisfy. For example, when the combination of the first layer 11 and the second layer 12 is TiO ₂ and SiO ₂ and the incident light is visible light, the _PCd is preferably 100 nm or less.

The A plate portion 2 is for correcting so that the phase difference in the X direction (or Y direction) with respect to the Z direction caused by the influence of the target becomes small. For example, when the target is a positive A plate (nx _O > ny _O = nz _O ), the phase difference of the A plate portion 2 in the X direction (or Y direction) with respect to the Z direction is small. A negative A plate that can be corrected (nx _A <ny _A = nz _A ) may be used. Further, when the target for correcting the phase difference is a negative A plate (ny _O <nx _O = nz _O ), the phase difference of the A plate portion 2 in the X direction (or Y direction) with respect to the Z direction is A positive A plate (nx _A > ny _A = nz _A ) that can be corrected so as to be smaller may be used. Since the phase difference becomes 0 at 2nπ (n is an integer), the A plate portion 2 corrects the phase difference in the X direction (or Y direction) with respect to the target Z direction so as to approach 2nπ. Is also good. Therefore, the A plate portion 2 is a positive A plate that corrects the phase difference so that the phase difference in the X direction (or Y direction) with respect to the Z direction approaches 2nπ when the target for correcting the phase difference is the positive A plate. It may be present, or conversely, even if the object is a negative A plate, the phase difference in the X direction (or Y direction) with respect to the Z direction is corrected so as to approach 2nπ. good.

In order to make the A plate portion 2 a negative A plate, as shown in FIG. 1, if the convex portion 21 extending in one direction has a concavo-convex structure formed with a period shorter than the wavelength of light in the used band. good.

Any material may be used for the convex portion 21 of the A plate portion 2 as long as it has a refractive index different from that of the concave portion 22, and examples thereof include SiO ₂ , MgF _2, TiO ₂ , and Ta ₂ O ₅ .

Further, as shown in FIG. 2, the uneven structure of the A plate portion 2 has a period (the sum of the width w ₁ of the convex portion 21 and the width w ₂ of the concave portion 22) of _PAw , the light of the incident light is λ, and the unevenness. When the average refractive index of the structure and _{n Aw, P Aw <λ /} n Aw, may _{preferably, P Aw <λ / 2n Aw} , more preferably be formed so as to satisfy _{P Aw <λ} / _{2.8n Aw} .. For example, when the convex portion 21 is SiO ₂ , the concave portion 22 is air, and the incident light is visible light, the _PAw is preferably 200 nm or less.

Further, in order to increase the retardation, the fill factor F _Ad, which is the ratio of the width w _{1 to} the pitch _PA w, is preferably 0.3 or more and 0.7 or less, preferably 0.4 or more and 0.6 or less.

Further, in order to make the A plate portion 2 a positive A plate, in addition to the same conditions as the negative A plate described above, as shown in FIG. 3, the convex portion 21 is combined with the third layer 23. It is necessary to stack the fourth layer 24, which has a lower refractive index than the third layer 23, at a period shorter than the wavelength of light in the band used.

The third layer 23 is a layer that is alternately laminated with the fourth layer 24, and any material may be used as long as it has a higher refractive index than the fourth layer 24. For example, TiO ₂ and Ta ₂ O ₅ , HfO ₂ , ZrO ₂ , SiN and the like.

The fourth layer 24 is a layer that is alternately laminated with the third layer 23, and any material may be used as long as it has a lower refractive index than the third layer 23. For example, SiO ₂ or MgF ₂ is used. Can be mentioned.

Of course, any combination of materials for the third layer 23 and the fourth layer 24 may be used, and may be determined according to the desired performance of the retardation element.

Further, as shown in FIG. 3, the third layer 23 and fourth layer 24, the cycle (the third layer 23 of the total film thickness d ₃ and the thickness d ₄ of the fourth layer 24) and P _Ad, incident Assuming that the wavelength of light is λ and the average refractive index of the third layer 23 and the fourth layer 24 is n _Ad , P _Ad <λ / n _Ad , preferably P _Ad <λ / 2n _Ad , and more preferably P _Ad <λ. It may be laminated so as to satisfy / 2.8n _Ad . For example, when the combination of the third layer 23 and the fourth layer 24 is TiO ₂ and SiO ₂ and the incident light is visible light, the _PAd is preferably 100 nm or less.

Further, the third layer 23 and fourth layer 24 of the convex portion 21, the cycle (the film thickness d ₁ and the sum of the thickness d ₂ of the second layer 12 of the first layer 11) of P _Cd, the wavelength of the incident light the lambda, when the average refractive index of the C-plate portion 1 and _{n C, P Cd <λ /} n C, as preferably _{P Cd} <λ / 2n _C, more preferably satisfying _{P Cd} <λ / _{2.8n C} It may be laminated on. For example, the combination of the first layer 11 and second layer 12 is TiO ₂ and SiO _2, when the incident light is visible light, _{P C} is preferably 100nm or less.

Further, in order to suppress reflection in the C plate, as shown in FIG. 4, the thickness of the outermost surface side layer 111 (two layers of the uppermost layer and the lowermost layer) of the C plate portion 1 of the first layer 11 is thickened. It is preferable that x is 0.4 times or more and 0.7 times or less the thickness y of the other layers of the first layer 11.

Further, as shown in FIG. 4, a stop layer 3 which is partially exposed to the concave portion 22 having an uneven structure may be formed between the A plate portion 2 and the C plate portion 1. This is to form the A plate portion 2 having a uniform shape of the uneven structure as a dry etching stopper in order to make the height uniform when processing the A plate. The material of the stop layer 3 may be any material as long as the etching rate is lower than that of the A plate portion 2. For example, when the material of the A plate portion 2 is SiO ₂ , Al ₂ O ₃ or the like may be used.

Further, the first layer 11 and the third layer 23 may be made of the same material, and the second layer 12 and the fourth layer 24 may be made of the same material.

Further, in the above description, it is assumed that the concave portion 22 of the concave-convex structure of the A plate portion 2 is a gap and the gap is filled with air, but the concave portion 22 is shown in FIG. 5 (d). As shown in the above, another material 29 having a refractive index different from that of the convex portion 21 may be filled. This has an advantage in that the uneven structure of the A plate portion can be reinforced. Further, as shown in FIG. 5D, the material 29 can be used as a protective film that covers the upper side of the convex portion 21. Further, as shown in FIG. 6, it is also possible to use an optical adhesive as the material 29 and bond the retardation element of the present invention to a glass substrate 9 or the like. In this case, it is necessary to make a difference in the refractive indexes of the convex portion 21 and the material 29. Since the refractive index of the optical adhesive is about 1.5, it is preferable to use a photorefractive index material having a refractive index of 2 or more for the convex portion 21 in order to make a difference from the refractive index.

Next, the method for manufacturing a retardation element of the present invention will be described with reference to FIG. The retardation element manufacturing method of the present invention includes a film forming step, a resist pattern forming step, and an etching step.

In the film forming step, as shown in FIG. 5A, the first layer 11 and the second layer 12 having a lower refractive index than the first layer 11 are used as the C plate portion 1 from the wavelength of light in the band used. It is laminated at a short cycle, and the A plate layer 4 is further formed on the C plate portion 1.

Here, when the A plate portion 2 of the retardation element is a negative A plate, a single material may be formed as the A plate layer 4 in the film forming step. Further, when the A plate portion 2 of the retardation element is a positive A plate, the third layer 23 and the fourth layer having a lower refractive index than the third layer 23 are used as the A plate layer 4 in the film forming process. 24 and 24 may be laminated at a period shorter than the wavelength of light in the band used.

Further, in the film forming step, in order to make the height uniform when processing the A plate portion 2, the stop layer 3 having a lower etching rate than the A plate layer 4 is formed between the A plate layer 4 and the C plate portion 1. May be formed.

Further, in order to reduce the reflectance of the retardation element, in the film forming process, the thickness of the outermost surface side layer 111 (two layers of the uppermost layer and the lowermost layer) of the first layer 11 is set to the other layers. It is preferable to form the thickness at 0.4 times or more and 0.7 times or less.

Further, in the film forming step, the first layer 11 and the third layer 23 may be made of the same material, and the second layer 12 and the fourth layer 24 may be made of the same material.

In the film forming step, the first layer 11, the second layer 12, and the A plate layer 4 of the C plate portion 1 may be formed by any method, and for example, a known film forming technique may be used.

In the resist pattern forming step, as shown in FIG. 5B, a resist pattern 5 having a concavo-convex structure in which convex 51 portions extending in one direction are arranged in a period shorter than the wavelength of light in the used band is formed in the A plate layer 4. It is what forms on top. The resist pattern 5 may be formed by any method. For example, a resist film is formed on the A plate layer 4, and the resist pattern 5 is formed on the resist film by an imprint method or photolithography. Just do it.

Further, in the resist pattern forming step, it is preferable to form the resist pattern 5 so that the width (Fill Factor) of the convex portion 51 with respect to the pitch is 0.3 times or more and 0.7 times or less.

Further, in the etching step, as shown in FIG. 5C, the A plate layer 4 is etched by using the resist pattern 5, and the convex portion 21 extending in one direction has a period shorter than the wavelength of light in the used band. This is a step for forming the A plate portion 2 having the uneven structure arranged in. Etching may be performed by any method as long as it can be etched into a desired shape, and for example, reactive ion etching (RIE) may be used.

Further, the phase difference element manufacturing method of the present invention may include a filling step of filling the concave portion 22 of the concave-convex structure of the A plate portion 2 with a material 29 having a refractive index different from that of the convex portion 21. Any method may be used for the filling, and a known technique such as CVD may be used.

⊚ Simulation Next, the optical characteristics of the retardation element of the present invention were calculated using simulation. The software Diffract MOD manufactured by Synopsys, Inc. was used for the simulation.

[Simulation 1]
The influence of the fill factor F _Ad (ratio of the pitch _PAw and the width w1 of the convex portion 21) of the uneven structure in the A plate portion 2 of the retardation element on the retardation was simulated. As shown in FIG. 7, the A plate portion 2 of the retardation element has a line-and-space-like unevenness in which the convex portion 21 is SiO2 (refractive index: 1.45) and the concave portion 22 is air (refractive index: 1.0). The structure (model 1) was assumed.

The relationship between the wavelength and the retardation of light incident on the fill factor F _Ad shown in Fig. As shown in FIG. 8, it was found that the retardation was large when the fill factor _FAd was 0.3 or more and 0.7 or less, particularly 0.4 or more and 0.6 or less. Further, it was found that when the fill factor F _Ad was between 0.4 and more and 0.6 or less, the fluctuation of retardation was small even if an error occurred in the fill factor F _Ad .

[Simulation 2]
The influence of the pitch _PCd of the first layer 11 and the second layer 12 of the C plate portion 1 on the diffraction was simulated. As the C plate portion 1, as shown in FIG. 9, the first layer 11 was designated as TiO ₂ (refractive index: 2.3), and the second layer 12 was designated as SiO ₂ (refractive index: 1.45). The film thickness ratio of the first layer 11 and the second layer 12 was 1: 1, and the pitch _PCd was (a) 60 nm, (b) 80 nm, and (c) 100 nm. The thickness of the outermost surface side of the first layer 11 was set to 13 nm in both cases. As the A plate portion 2, the width of the convex portion 21 was 56 nm, the height was 60 nm, and the pitch was 140 nm.

The relationship between the wavelength of the incident light and the diffraction efficiency with respect to the pitch _CCD is shown in FIG. As shown in FIG. 10A, the effect of diffraction is small when the pitch _PCd is small, but as shown in FIGS. 10B and 10C, the effect of diffraction is large on the short wavelength side as the pitch _PCd is large. It can be seen that the size increases and the transmission of incident light is hindered.

[Simulation 3]
The effect of the thickness of the layer 111 on the outermost surface side of the first layer 11 of the C plate portion 1 on the transmittance was simulated. As shown in FIG. 11, the C plate portion 1 has a first layer 11 as TiO ₂ (refractive index: 2.3) and a second layer 12 as SiO ₂ (refractive index: 1.45). The film thickness of the first layer 11 excluding the outermost surface side was 27 nm, and the film thickness of the second layer 12 was 27 nm.

FIG. 12 shows the relationship between the wavelength of the incident light and the transmittance when the thickness x of the layer 111 on the outermost surface side of the first layer 11 is changed. Assuming that the ratio of the thickness of the layer other than the outermost surface side of the first layer to the layer on the outermost surface side is TRA, TRA (= x / 27) is 0.40 or more and 0.74 or less as shown in FIG. It can be seen that sometimes the transmittance is high and the reflectance is low.

[Example 1]
Next, an embodiment of the retardation element of the present invention is shown in FIG. The retardation element uses TiO ₂ as the first layer 11 of the C plate portion 1 and SiO ₂ as the second layer 12. The period of the first layer 11 and the second layer 12 was 54 nm, and the film thicknesses of the first layer 11 and the second layer 12 were the same 27 nm. However, as for the layer on the outermost surface side, the first layer 11 was set to 13 nm and the second layer was set to 41 nm. Further, SiO ₂ was used for the A plate portion 2, and the height of the convex portion 21 was 140 nm, the width was 120 nm, and the pitch of the uneven structure was 200 nm. Further, Al ₂ O ₃ was used as the stop layer 3, and the film thickness was set to 10 nm. The retardation element configured in this way had a retardation (Rth) of 50 nm in the Z direction and a retardation (Re) of 10 nm in the x direction.

[Example 2]
Further, an embodiment of another retardation element of the present invention is shown in FIG. As shown in FIG. 6, the retardation element of the present invention has a structure when it is adhered to glass with an optical adhesive. The retardation element uses TiO ₂ as the first layer 11 of the C plate portion 1 and SiO ₂ as the second layer 12. The period of the first layer 11 and the second layer 12 was 54 nm, and the film thicknesses of the first layer 11 and the second layer 12 were the same 27 nm. However, as for the layer on the outermost surface side, the first layer 11 was 21 nm and the second layer was 33 nm. Further, SiO ₂ was used for the A plate portion 2, and the height of the convex portion 21 was 60 nm, the width was 56 nm, and the pitch of the concave-convex structure was 140 nm. Further, as the optical adhesive, one having a refractive index of 1.5 was used.

FIG. 15 shows the relationship between the azimuth angle of the incident light and the retardation when the incident angle of the incident light is changed. In FIG. 15, when the incident angle is 0 degrees, only the retardation of the A plate portion of the retardation element appears. Further, as the incident angle increases, the influence of the C plate portion appears, and the retardation changes depending on the azimuth angle of the incident light. If this phase change is the same as the phase change due to the transmission of the liquid crystal and the positive and negative are opposite, the phase can be corrected and an image with a high viewing angle can be realized.

1 C plate part 2 A plate part 3 Stop layer 4 A plate layer 5 Resist pattern
11 1st layer
12 2nd layer
21 Convex part
22 Recess
23 3rd layer
24 4th layer
29 material
111 The outermost layer of the first layer 11

Claims (14)

A phase difference element for correcting the phase difference caused by the influence of a target so as to be small.
A C plate portion in which a first layer and a second layer having a refractive index lower than that of the first layer are laminated at a period shorter than the wavelength of light in the use band, and
An A plate portion having a concavo-convex structure in which a convex portion extending in one direction is formed with a period shorter than the wavelength of light in the used band,
A phase difference element comprising. The position according to claim 1, wherein the convex portion is formed by laminating a third layer and a fourth layer having a refractive index lower than that of the third layer at a period shorter than the wavelength of light in the use band. Phase difference element. The phase difference according to claim 1 or 2, wherein the thickness of the outermost layer of the first layer is 0.4 times or more and 0.7 times or less the thickness of the other layers. element. The retardation element according to any one of claims 1 to 3, wherein the width D of the convex portion with respect to the pitch P is 0.3 times or more and 0.7 times or less. The retardation element according to any one of claims 1 to 4, wherein a stop layer is formed between the A plate portion and the C plate portion, partly exposed to the concave portion of the concave-convex structure. .. The retardation device according to any one of claims 2 to 5, wherein the first layer and the third layer are made of the same material, and the second layer and the fourth layer are made of the same material. .. The retardation element according to any one of claims 1 to 6, wherein the concave portion of the concave-convex structure of the A plate portion is filled with a material having a refractive index different from that of the convex portion. It is a manufacturing method of a phase difference element for correcting the phase difference caused by the influence of a target so as to be small.
As the C plate portion, the first layer and the second layer having a refractive index lower than that of the first layer are laminated at a period shorter than the wavelength of light in the used band, and an A plate layer is further formed on the C plate portion. The film formation process and
A resist pattern forming step of forming a resist pattern having a concavo-convex structure in which convex portions extending in one direction are arranged in a period shorter than the wavelength of light in the used band on the A plate layer.
An etching step of etching the A plate layer using the resist pattern to form an A plate portion having a concavo-convex structure in which convex portions extending in one direction are arranged at a period shorter than the wavelength of light in the use band.
A method for manufacturing a phase difference element, which comprises. The film forming step is characterized in that, as the A plate layer, a third layer and a fourth layer having a refractive index lower than that of the third layer are laminated at a period shorter than the wavelength of light in the working band. 8. The method for manufacturing a retardation element according to claim 8. The retardation element according to claim 8 or 9, wherein in the film forming step, a stop layer having an etching rate lower than that of the A plate layer is formed between the A plate layer and the C plate portion. Production method. The film forming step is characterized in that the thickness of the outermost surface side of the first layer is formed to be 0.4 times or more and 0.7 times or less the thickness of the other layers. The method for manufacturing a retardation element according to any one of claims 8 to 10. Any of claims 8 to 11, wherein the resist pattern forming step is formed so that the width of the resist pattern with respect to the pitch of the convex portion is 0.3 times or more and 0.7 times or less. The method for manufacturing a retardation element described in Crab. The film forming step according to claim 9 to 12, wherein the first layer and the third layer are made of the same material, and the second layer and the fourth layer are made of the same material. The method for manufacturing a retardation element according to any one. The retardation element according to any one of claims 8 to 13, further comprising a filling step of filling the concave portion of the concave-convex structure of the A plate portion with a material having a refractive index different from that of the convex portion.

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