KR101039325B1 - Phase retardation plate - Google Patents

Abstract

PURPOSE: A phase retardation device is provided to secure the reliability even in a high temperature and high-humidity environment and to enable the control of thinning and refraction direction of the device. CONSTITUTION: A phase retardation device comprises a base board(100), a liquid crystal polymer layer(200) which is aligned in one direction, an optical adhesive layer(300) interposed between the base board and the liquid crystal polymer layer, and an anti-reflective layer(400) formed on the base board and the outer surface of and the liquid crystal polymer layer. The anti-reflective layer is at least one layer including an inorganic thin film.

Description

Phase delay element {PHASE RETARDATION PLATE}

The present invention relates to a phase delay device, and more particularly, to a phase delay device in which appearance and optical characteristics do not change even in a high temperature and high humidity environment.

In general, an optical pickup apparatus guides laser light generated from a light source to a optical disk through a beam splitter, a collimating lens, and an objective lens, and receives information reflected from the optical disk by receiving the reflected light from the optical disk with a photodetector.

The light emitted from the light source is converted into circularly polarized light whose phase is delayed through the polarizing element and the phase delaying element, and then irradiated onto the optical disk. The circularly polarized light reflected from the optical disk is passed through the phase delaying element and the polarizing element, and the azimuth angle is converted to 90 degrees. After being converted to linearly polarized light, it is transmitted to a photodetector to read information on the optical disk.

The conventional phase delay plate is a method of stretching the polymer film uniaxially to cause a phase delay by causing a difference in the refractive index in the stretching axis direction and a refractive index in the non-stretching direction. However, the stretching method is limited depending on the characteristics of the base film, there is a problem that the thickness can be produced.

When the phase delay device is manufactured by laminating a liquid crystal polymer on a base film, the thickness of the base substrate can be arbitrarily adjusted, so that the phase delay device can be thinned.

However, in order to prevent optical loss, the phase delay element for the optical pickup device is essentially formed with an anti-reflection layer on the outer surface. The anti-reflection layer, the base film, and the linear expansion coefficients of the liquid crystal polymer are different from each other and are exposed to the harsh environment of high temperature and high humidity. If there is a problem that the appearance is deformed or the optical properties change.

Disclosure of Invention The present invention is to solve the above problems, and discloses a phase delay device having no change in appearance and optical properties even in a high temperature and high humidity environment by controlling the physical properties of the optical adhesive.

In order to achieve the above object, a phase delay device according to an aspect of the present invention includes a base substrate, a liquid crystal polymer layer formed on the base substrate and cured by being oriented in one direction, and between the base substrate and the liquid crystal polymer layer. An optical adhesive layer interposed therebetween, and the antireflection layer formed on the outer surface of the base substrate and the liquid crystal polymer layer.

The hygroscopicity and the coefficient of linear expansion of the adhesive layer are adjusted to satisfy the relation (1).

[Relationship 1]

Y ≤-2333X + 7000

(Where X and Y are greater than 0, the unit of X is percent (%), and the unit of Y is μm / (m · ° C.).)

At this time, the range of the hygroscopicity (X) and the linear expansion coefficient (Y) of the adhesive layer may be adjusted to further satisfy the following relational formula (2).

[Relationship 2]

Y ≥-2352X + 4000

(Where X and Y are greater than 0 and the unit of X is percent (%) and the unit of Y is μm / (m · ° C.)).

And the anti-reflection layer is composed of an inorganic thin film and may be formed of at least one layer.

According to the present invention, even if a phase delay device is manufactured by laminating a liquid crystal polymer on a base film, reliability may be secured in poor environmental conditions of high temperature and high humidity.

In addition, there is an advantage that the thickness of the phase delay element and the adjustment of the refractive direction can be adjusted and the thickness of the base film can be arbitrarily selected.

1 is a cross-sectional view of a phase delay device according to an embodiment of the present invention,
2 is a graph showing an example and a comparative example of the optical adhesive layer according to the present invention,
3 is a photograph before and after the reliability test in which the phase delay device using the optical adhesive of Comparative Example 1 was exposed to a high temperature and high humidity environment.
4 is a photograph before and after a reliability test in which a phase delay device including an optical adhesive according to an embodiment of the present invention is exposed to a high temperature and high humidity environment.
5 is a photograph before and after the reliability test in which the phase delay device including the adhesive of Comparative Example 1 is exposed only to a high temperature condition,
6 is a photograph before and after the reliability test in which the phase delay element including the adhesive of Comparative Example 1 is exposed only to high humidity conditions.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description.

However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise.

In the present application, the terms "comprises", "having", and the like are used to specify that a feature, a number, a step, an operation, an element, a component, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

In addition, it is to be understood that the accompanying drawings in this application are shown enlarged or reduced for convenience of description.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the drawings. Like reference numerals designate like elements throughout, and duplicate descriptions thereof will be omitted.

Phase delay device according to an embodiment of the present invention is a base substrate 100, the liquid crystal polymer layer 200 formed on the base substrate 100 and oriented in one direction cured, the base substrate 100 and the The optical adhesive layer 300 interposed between the liquid crystal polymer layer 200, and the anti-reflection layer 400 formed on the outer surface of the base substrate 100 and the liquid crystal polymer layer 200.

The base substrate 100 may maintain a form of the liquid crystal polymer layer 200 from warping deformation and the like by using a general glass substrate, but polycarbonate, polyimide, polyalkylate, polyester sulfone, (alicyclic) polyolefin, poly You may produce with the base film 100 which consists of either (meth) acrylate or polyetherimide.

In this case, the base film 100 may be stretched in one direction or in multiple directions to have a phase delay function. Accordingly, the liquid crystal polymer layer 200 is compensated by the phase delayed by the base film 100 and manufactured. Can be.

For example, if the wavelength of 660nm is to be delayed by 1/4 wavelength, the phase delay value should be 165nm. If the base film has a constant phase delay value of 50 nm in plane, the liquid crystal polymer is manufactured to have a phase delay value of 115 nm to be a quarter wave plate at 660 nm.

The liquid crystal polymer layer 200 is a birefringent polymer, and is prepared by coating a liquid crystal polymer mixed with a predetermined ratio of solvent on a separate substrate rubbed in one direction and irradiating and curing UV light.

Thereafter, the liquid crystal polymer is laminated on the base film 100 using an optical adhesive, and then the substrate is removed.

When the liquid crystal polymer is manufactured as a phase delay layer, it can be manufactured to a thickness of about 1 to 2 μm, thereby making it thinner, and by arranging molecules in one direction by rubbing, the optical axis can be controlled by adjusting the refractive index in a desired direction. There are advantages to it.

The liquid crystal polymer layer 200 may be formed of a plurality of layers so that each liquid crystal polymer layer may produce a wideband phase delay unit for retarding a phase with respect to two or more different wavelengths, and an optical adhesive layer 300 may be formed therebetween. It may be intervened.

The anti-reflection layer 400 is an essential configuration for inserting the phase delay element into the optical pickup device, and is manufactured by forming a plurality of multilayer thin films. The anti-reflection layer 400 is laminated on the bottom surface of the base film 100 and the top surface of the liquid crystal polymer layer 200, respectively.

At this time, the anti-reflection layer 400 is composed of an inorganic thin film of 50 ~ 100nm has a linear expansion coefficient of about 0.0005㎛ / (m · ℃) or less.

However, the base film 100 generally has a linear expansion coefficient of 50 to 100 μm / (m · ° C.), and the liquid crystal polymer layer 200 has a linear expansion coefficient of about 5 to 15 μm / (m · ° C.). The difference in coefficient of linear expansion is large.

Therefore, there is a problem that the appearance and optical characteristics of the phase retarder are changed by the difference in the coefficient of linear expansion at high temperature and high humidity.

However, the optical adhesive according to the embodiment of the present invention discloses an optimal condition in which the above problems do not occur even in an environment of high temperature and high humidity.

That is, the present invention discloses an optimum condition that can ensure the reliability of the product even under the conditions of high temperature (~ 60 °) and high humidity (90 to 95%).

The configuration of the optical adhesive according to an embodiment of the present invention can be applied to all of the general photocurable, thermosetting adhesive composition, the composition ratio of the detailed adhesive can be applied to the general adhesive composition all the more detailed description will be omitted.

Table 1 is a table showing the results of testing the reliability after exposing the optical adhesive according to an embodiment of the present invention and a comparative example at a temperature of 60 ℃ 168 hours at a humidity of 90%.

At this time, the hygroscopicity was measured using AND 70 MS70 equipment, and the coefficient of linear expansion was measured using TA Instrument's Q400 equipment.

Hygroscopicity (%) Coefficient of linear expansion (㎛ / (m · ℃)) High temperature and high humidity reliability results Example 1 0.435 158.43 OK Example 2 0.732 1850.5 OK Example 3 1.156 1058.3 OK Example 4 0.733 2232.6 OK Example 5 1.158 1362.4 OK Example 6 1.164 4272.3 OK Example 7 1.735 2980.1 OK Example 8 2.367 1475.8 OK Example 9 0.734 2731.2 OK Example 10 1.157 1921.3 OK Example 11 1.158 2480.0 OK Example 12 1.158 3994.2 OK Example 13 1.732 2681.2 OK Example 14 1.174 1994.2 OK Comparative Example 1 1.154 4962.7 NG Comparative Example 2 1.736 3489.0 NG Comparative Example 3 1.736 5872.5 NG Comparative Example 4 2.389 4852.9 NG Comparative Example 5 2.372 1937.24 NG Comparative Example 6 2.712 1031.42 NG Comparative Example 7 2.951 2820.3 NG Comparative Example 8 3.298 549.32 NG

Here, the hygroscopicity refers to the degree of absorbing the moisture of the material, which is expressed in terms of weight change rate after exposing the material to moisture (H ₂ O) for a predetermined time.

Generally, moisture absorbed in a polymer is dispersed in a small amount in an orderly manner so that it is free water or aggregates around polar molecules and in fine voids to exist in the form of bonded / clustered H ₂ O. This is the cause of denaturing the inherent physical properties of the polymer.

And coefficient of linear expansion (coefficient of linear expansion) indicates the change in length according to the temperature of the material, expressed in terms of the length change rate according to the change in unit temperature.

Figure 2 is a graph showing the hygroscopicity and the coefficient of linear expansion of the Examples and Comparative Examples of the present invention, in addition to the Examples and Comparative Examples of the present invention, all of the adhesive samples actually tested.

Referring to Table 1, it can be seen that Examples 1 to 3 are located in the first region of FIG. 2, and Examples 4 to 8 are located in the second region of FIG. 2. All showed good values.

In more detail, the hygroscopicity of Examples 3, 5, and 6 was about 1.156%, 1.158%, and 1.164%, respectively, and the coefficients of linear expansion were slightly different, but both showed good optical properties and appearance. .

However, in the case of Comparative Example 1, the hygroscopicity is similar to the hygroscopicity of Examples 3, 5, and 6 (1.1545%), but the linear expansion coefficient is 4962.7 μm / (m · ° C.). And the appearance was confirmed to change.

At this time, the change of optical characteristics is classified as bad (NG) when the phase delay value of the fabricated phase delay element is more than ± 10nm, and the change in appearance is increased by more than 0.005 wavelength at the root mean square. It was classified as bad (NG).

In addition, in Example 7, the hygroscopicity is 1.735% and the coefficient of linear expansion has a value of 2980.1 μm / (m · ° C.), thereby showing excellent optical properties at high temperature and high humidity. Although the coefficient of linear expansion was similar, there was a difference of 3489.0 µm / (m · ° C), which caused a change under high temperature and high humidity.

In the case of Comparative Example 3, the coefficient of linear expansion was larger as 5872.5 μm / (m · ° C.), and more optical changes (defects) were measured than in Comparative Example 2 as a result of the experiment.

As a result, it can be seen experimentally that the hygroscopicity and linear expansion coefficient of the optical adhesive should have values corresponding to the first and second area portions of FIG. 2, and more specifically, the hygroscopicity and linear expansion coefficient range of the adhesive layer is When the hygroscopicity is defined on the X-axis of FIG. 2 and the linear expansion coefficient is defined on the Y-axis, it can be seen that it should be located within a region that satisfies the following Equation 1.

[Relationship 1]

Y ≤-2333X + 7000

(Where X and Y are greater than 0, the unit of X is percent (%), and the unit of Y is μm / (m · ° C.).)

Therefore, the phase retarder having an optical adhesive having a range of the first region and the second region satisfying the relation 1 has excellent appearance and optical characteristics even in a high temperature and high humidity environment.

However, the first region of FIG. 2 satisfies the reliability of high temperature and high humidity, but has low hygroscopicity when the optical adhesive layer 300 is formed, thereby lowering flexibility, and thus, the product has a curved shape in the manufacturing process of the product. When performing a roll-to-roll (roll to roll) process or a punching process for cutting a product to a specification, cracks are generated in the product, thereby lowering productivity.

Therefore, more preferably, the hygroscopicity (X) of the adhesive layer and the range of the linear expansion coefficient (Y) are preferably in the region between the straight line represented by the relational formula (1) and the straight line represented by the following relational formula (2). Equation 2 is a straight line connecting the embodiment in which no crack occurs.

[Relationship 2]

Y ≥-2352X + 4000

(Where X and Y are greater than 0 and the unit of X is percent (%) and the unit of Y is μm / (m · ° C.)).

When the hygroscopicity and the coefficient of linear expansion of the phase delay element have a value between the equation 1 and the equation 2, the reliability is secured even in a harsh environment under high temperature and high humidity, while having sufficient flexibility, thereby reducing the probability of manufacturing defects.

3 is a photograph before and after a reliability test in which a phase delay element using Comparative Example 1 as an optical adhesive is exposed to a high temperature and high humidity environment, and FIG. 4 is a high temperature state of a phase delay element including an optical adhesive according to an embodiment of the present invention. This is a photograph before and after a reliability test exposed to a high humidity environment.

In this case, the test conditions were measured by exposing the phase delay element having an optical adhesive layer having a thickness of 1.5 μm at a temperature of 60 ° C. under a humidity of 90% for 168 hours. Comparative Example 1 is an optical adhesive used in an actual LCD panel.

When the adhesive having the hygroscopicity and linear expansion coefficient of Comparative Example 1 was used, a defect occurred in the appearance of the phase delay device. This phenomenon is a difference between the thermal expansion coefficient of the anti-reflection layer 400 and the linear expansion coefficient of the polymer layers below the phase delay layer. Because it represents.

In addition, when the optical adhesive layer 300 has a high hygroscopicity, it is determined that the hygroscopicity of the adhesive also affects the above results because the expansion ratio rapidly increases under high temperature and high humidity conditions.

On the contrary, as shown in FIG. 4, the phase delay device including the adhesive having the hygroscopicity and the linear expansion coefficient of Example 1 of the present invention was tested under the same conditions, and it was confirmed that there was no change in appearance and optical properties.

5 and 6 are photographs experimented by exposing the phase delay element including the adhesive of Comparative Example 1 to a high temperature and high humidity environment, respectively. Referring to FIGS. 5 and 6, it can be seen that the appearance defects and the optical characteristics do not change when the test results are performed only at high temperature or high humidity environmental conditions.

This is because the adhesive force of the adhesive is lowered under the conditions of high humidity, but the difference in expansion coefficient between the layers does not occur, it is judged to be because the original shape well maintained even with the lower adhesive force.

In addition, in the case of a high temperature, the expansion rate difference between the layers occurs, but the adhesive force of the adhesive layer does not occur, so that the original state can be maintained.

However, in the case of high temperature and high humidity conditions, the decrease in adhesive force and mismatching of the expansion rate between the layers may occur at the same time, thereby confirming that a defect occurs as described above.

Therefore, when the hygroscopicity and the linear expansion coefficient of the optical adhesive layer 300 is in the second region of FIG. 2 as described in the present invention, the expansion rate mismatching between the layers may be covered.

The phase delay device according to the embodiment of the present invention may be used in an optical pickup device, but is not necessarily limited thereto, and may be used in an overall optical product.

The optical pickup apparatus may be a general optical pickup apparatus such as a BD, CD or DVD optical pickup apparatus. Since the configuration of the optical pickup device is the same as in the related art, a detailed description thereof will be omitted.

As described above, the present invention has been described in detail through the preferred embodiments, but the present invention is not limited to the contents of these embodiments. Those skilled in the art to which the present invention pertains, although not disclosed in the embodiments, various modifications, changes or additions are possible within the scope of the appended claims, all of which fall within the technical scope of the present invention. You will have to look.

100: base substrate 200: liquid crystal polymer layer
300: optical adhesive layer 400: antireflection layer

Claims (9)

A base substrate;
A liquid crystal polymer layer formed on the base substrate and aligned in one direction and cured;
An optical adhesive layer interposed between the base substrate and the liquid crystal polymer layer; And
It includes; the anti-reflection layer formed on the outer surface of the base substrate and the liquid crystal polymer layer,
The anti-reflection layer is formed of at least one layer composed of an inorganic thin film, the linear expansion coefficient of the base substrate, the liquid crystal polymer layer and the anti-reflection layer satisfies the relationship of the base substrate> liquid crystal polymer layer> anti-reflection layer,
A hygroscopicity (X) and a linear expansion coefficient (Y) of the optical adhesive layer satisfy the following relational expressions 1 and 2.
[Relationship 1]
Y ≤-2333X + 7000
[Relationship 2]
Y ≥-2352X + 4000
(Where X and Y are greater than 0, the unit of X is percent (%), and the unit of Y is μm / (m · ° C.).) The phase delay device of claim 1, wherein the liquid crystal polymer layer is formed of a plurality of layers to delay phases of light in different wavelength bands, and an optical adhesive layer is interposed between the liquid crystal polymer layers. The phase delay device of claim 1, wherein the base substrate is a base film. An optical pickup apparatus comprising a phase delay device manufactured by claim 1. delete delete delete delete delete

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