WO2007123357A1

WO2007123357A1 - Dry film photoresist resin composition for ldi

Info

Publication number: WO2007123357A1
Application number: PCT/KR2007/001993
Authority: WO
Inventors: Kook Hyeon Han; Jeong Kun Kim; Chang Pyo Hong; Byeong Il Lee
Original assignee: Kolon Industries Inc.
Priority date: 2006-04-24
Filing date: 2007-04-24
Publication date: 2007-11-01

Abstract

The present invention comprising the new DFR resin composition for LDI (optimal exposure energy 2~15mJ/cm2 below) comprising thioxanthone derivatives as photopolymerizable initiator keeps the basic physical properties of the conventional DFR and significantly improves the sensitivity in spite of a little amount of the light exposure, thereby maximizing the productivity with regard to the formation of the image on the PCB, lead frame, PDP and other displays.

Description

DRY FILM PHOTORESIST RESIN COMPOSITION FOR LDI

Technical Field

The present invention relates to a dry film photoresist (hereinafter, DFR) resin

composition and more particularly, to a dry film photoresist resin composition for high

sensitive DFR, especially Laser Direct Image(hereinafter, LDI) among dry films

applicable to image preparing process of Printed Circuit Board(hereinafter, PCB), lead

frame, etc for the image formation.

Background Art

DFR or liquid photoresist (hereinafter, LPR) is generally used for forming circuit

in PCB. DFR is widely used for not only preparation for PCB and lead frame but also for

manufacturing for Rib barrier of PDP(Plasma Display Panel) and ITO (Indium Tin Oxide)

electrode of display, electrode of Bus Address, and Black Matrix.

In the preparation for PCB and lead frame, the most important one is the process

for forming circuit on the copper foil, i.e. the Copper Clad Lamination Sheet(hereinafter,

CCLS). The image transcription method employed in this process is called the

Photolithography for which the original image substrate is called the artwork (the term

used usually in the field of manufacturing of PCB and lead frame) or the photomask (the

term in the filed of semiconductor). And the artwork image comprises both the areas through which the light does and

does not pass, in which manner the image is transcribed. The above-referred image

transcription process is called the light exposure process.

In the light exposure process, UV (ultra violet) is used in the field of the PCB and

lead frame and the short wave Visible Rays (about 400-450 nm, violet-blue color region)

has been used a little.

Transmittance and non-transmittance of the light make the image of the artwork

transcription on CCLS and Copper foil, respectively. The material for forming image on

exposed area is the photoresist (hereinafter, PR). Therefore PR should be laminated or

coated before the transcription of the artwork image. There are two kinds of PR according

to PR shape and liquid PR is called the LPR and solidified PR in form of the film is called

the DFR.

According to reaction pattern, when the exposed area is photopolymerized, it's

called the negative PR, when the exposed area is photodecomposed, the positive PR. The

PR for PCB or lead frame is employed by almost negative PR.

After the image is transcribed on PR, the developing process is followed (the

developing process is described in the case of the negative PR). The unexposed area is

washed off and eliminated by the developing solution, and the final image is transcribed

on the PR. The developer used is weak alkali solution. The organic solvent was used for

the developer but does not used any more because of the environmental problems. Na₂CO₃ or K₂CO₃ about 1 weight percent (wt %) solution is generally used for

the developer, and a few companies employ the commercially exclusive developers.

After the developing process, through "etching-stripping" or "plating-stripping-

etching" process, the circuit made of substantial copper is made. If it takes more time for

the light exposure process than for the any other processes, that is, if the light exposure

process is the rate control step, the total productivity depends on the light exposure time.

Accordingly, when the manufacturer has the high yield it needs higher sensitive PR which

has less amount of the optimal exposure energy.

The PR for LDI requires much lower optimal exposure energy than the

conventional high sensitive PR. In the general exposure process using the artwork, the

exposure equipment uses the collimated light or scattering light and the exposure

equipment transmits the light on all the sides of the artwork and the PR below the artwork

is exposed by the light at the same time although there is a little deviation of location.

Meanwhile, the light source of LDI is not general lamp but laser dot so the

exposure process for LDI is characterized by drawing directly image on PR without the

artwork. Because the total sides of PR can not be exposed by the light at the same time

and the only area passed by laser is exposed, the exposure equipment for LDI requires

much longer time than the exposure equipment using general lamp.

Nevertheless the reason that the LDI method is favorable is as follows;

When the artwork is used, the original image stored in the computer is transcribed into the raw material of the artwork by laser, and developed and made into the image in

manufacturing the artwork. But there is the problem that the image deviation among the

products can be generated according to the condition of the developing process.

Although the artwork is made within the optimal condition the space between the

artwork and the PR may exist in the image transcription. The resolution gets much worse,

resulting in the fault of the final circuit on account of the space.

To overcome the faults LDI exposure method that direct laser makes the original

image stored in the computer transcribed on PR without the artwork has been developed.

Because it takes long exposure time for LDI exposure method the DFR with high

sensitivity is urgently needed.

Disclosure of Invention

The present invention relates to the new DFR resin composition for high sensitive

(optimal exposure light energy 20mJ/cm² below), especially for LDI(optimal exposure

energy 2~ 15m J/cm² below) .

The inventors of this invention found out that the use of thioxanthone derivatives

as photopolymerizable initiator in DFR resin composition help to react a little amount of

the light much sensitively so as to form circuit, thereby the DFR prepared by the

composition comprising thioxanthone derivatives keeping the basic physical properties of

the conventional DFR and significantly improving the sensitivity in spite of a little amount of the light exposure.

It is therefore an object of the present invention to provide a DFR resin

composition suitable for the high sensitive LDI (optimal exposure light energy 2~15

mJ/cm² below) with keeping the basic physical properties.

Specially, the present invention provides a DFR resin composition comprising the

thioxanthone derivatives represented by the following Formula (I) as photopolymerizable

initiator.

Formula (I)

Wherein R1-R4 are a hydrogen atom, halogen atom, C1-C5 alkyl and C1-C5

alkyl oxide, respectively.

Hereinafter, the present invention will be described in further detail as follows.

The present invention is directed to a high sensitive DFR resin composition with

the optimal exposure energy 20mJ/cm² below, especially, 2~15mJ/cm² for LDI, which

relates to a DFR composition keeping resolution and thin film adherence of the

conventional DFR product despite less exposure energy.

In the present description, the term "photoresist resin composition" may be

referred to as "photoresist layer interposed between a polyethylene terephthalate(PET) film and a polyethylene(PE) film. The PR layer comprises (a) photopolymerizable initiator,

(b) an alkali developable binder polymer, (c) a photopolymerzable monomer, and (d) other

additives ".

The individual components of the DFR resin composition are follows.

(a) Photopolymerizable initiator

The term "photopolymerizable initiator" is referred to as "a material initiating the

chain reaction of the photopolymerizable oligomer by UV and other radiation and a

compound playing an important role in curing the dry film resist.

This invention especially comprises the thioxanthone derivatives represented by

the following formula I and further comprises the usually used other additives.

Formula (I)

Wherein R1~R4 are a hydrogen atom, halogen atom, C1-C5 alkyl and C1-C5

alkyl oxide, respectively.

The use of thioxanthone derivatives as photopolymerizable initiator react a little

amount of the light much sensitively so as to form circuit.

The DFR prepared by the composition comprising thioxanthone derivatives keeps the basic physical properties of the conventional DFR and dramatically improves the

sensitivity in spite of a little amount of the light exposure.

The content of the photopolymerizable initiator is preferably 0.3 ~4 wt% in order

to achieve the circuit width after the reactivity of initiation, light exposure and etching

process. If the content is 0.3 wt % below it is such a weak reactivity that the initiator can

not be used in condition of less exposure energy (about 20mJ/cm below). The

photopolymerizable initiator of 4 wt% above may prevent from achieving the preferable

circuit width after etching process because of the inverted trapezoid form of circuit.

In addition, the photopolymerizable initiators generally used excepting the

initiator represented by the above formula I are anthraquinone derivatives such as 2-

methyl anthraquinone, 2-ethyl anthraquinone; benzoin derivatives such as bezoin methyl

ether, benzophenone, phenanthrene quinine and 4,4'-bis-(dimethylamino)benzophenone,

etc.

Besides, the photopolymerizable initiator can be any one compound selected from

1 -hydroxycyclohexylphenyl ketone, 2,2-dimethoxy- 1 ,2-diphenylethane- 1 -one, 2,-mthyl- 1 -

[4-(methylthio)phenyl] -2-morpolynopropane- 1 -one, 2-benzyl-2-dimethylamino- 1 - [4-

morpolynophenyl]butane- 1 -one, 2-hydroxy-2-methyl- 1 -phenylpropane- 1 -one, 2,4,6-

trimethylbenzoyldiphenylphosphine oxide, l-[4(2-hydroxymethoxy)phenyl]-2-hydroxy-2-

methylpropane-1-one, 2,4-diethylthioxanetone, 2-chlorothioxanetone, 2,4-

dimethylthioxanetone, 3,3-dimethyl-4-methoxybenzophenone, benzophenone, l-chloro-4- propoxythioxanetone, 1 -(4-isopropylphenyl)2-hydroxy-2-methylpropane- 1 -one, 1 -(4-

dodecylphenyl)-2-hydroxy-2-methylpropane- 1 -one, 4-benzoyl-4 '-methyldimethylsulfide,

4-dimethylaminobenzoic acid, methyl 4-dimethylaminobenzoate, ethyl A-

dimethylaminobenzoate, butyl 4-dimethylaminobenzoate, 2-ethylhexyl A-

dimethylaminobenzoate, 2-isoamyl 4-dimethylaminobenzoate, 2,2-diethoxyacetophenone,

benzylketone dimethylacetal, benzylketone β-methoxy diethylacetal, 1 -phenyl- 1,2-

propyldioxime-o,o'-(2-carbonyl)ethoxyether, methyl o-benzoylbenzoate, bis[4-

dimethylaminophenyl]ketone, 4,4 '-bis(diethylamino)benzophenone, 4,4 '-

dichlorobenzophenone, benzyl, benzoin, methoxybenzoin, ethoxybenzoin,

isopropoxybenzoin, n-butoxybenzoin, isobutoxybenzoin, tert-butoxybenzoin, p-

dimethylaminoacetophenone, p-tert-butyltrichloroacetophenone, p-tert-

butyldichloroacetophenone, thioxanetone, 2-methylthioxanetone, 2-isopropylthioxanetone,

dibenzosuberone, α,α-dichloro-4-phenoxyacetophenone,_ and pentyl A-

dimethylaminobenzoate.

The content of the photopolymerizable initiator is preferably 2 to 10 wt % based

on the total weight of the DFR resin composition comprising the thioxanthone derivatives

represented by the formula I.

(b) Alkali developable binder polymer

Alkali developable binder polymer of the present invention is a copolymer of

(meth)acrylate and (meth)acrylate ester. More specifically, the copolymer of (meth)acrylate and (meth)acrylate ester is a

copolymerized acrylate polymer obtained by copolymerization of at least two monomers

selected from the group consisting of methyl acrylate, methyl methacrylate, ethylacrylate,

methyl methacrylate, butyl acrylate, butyl methacrylate, acrylic acid, methacrylic acid, 2-

hydroxy ethyl acrylate, 2-hydroxy ethyl methacrylate, 2-hydroxy propyl acrylate, 2-

hydroxy propyl methacrylate, acrylamide, methacrylamide, styrene, and α-methyl styrene.

Alkali developable binder polymer of the present invention has the number

average molecular weight of 30,000 to 150,000 and a glass transition temperature of 20 to

150 ⁰C in consideration of the coating ability, the conformability of the dry film resist, and

the mechanical strength of the resist itself after circuit formation. Preferably, the content of

the binder polymer is 20 to 80 wt. % with respect to the total weight of the DFR resin

composition.

(c) photopolymerizable monomer

The photopolymerizable monomer of the present invention comprises the

compound having at least two terminal ethylene functional groups. More particularly, the

photopolymerizable monomer is selected from the group consisting of 1,6-hexane-

diol(meth)acrylate, l,4-cyclohexanediol-(meth)acrylate, propylene glycol(meth)acrylate,

polyethylene glycol-(meth)acrylate, 2-di-(p-hydroxyphenyl)-propane-di-(meth)acrylate,

glycerol tri(meth)acrylate, trimethyllol propane tri-(meth)acrylate, polyoxy propyl

trimethylrol tri-(meth)acrylate, polyethylene(propylene)-di(meth)acrylate having bisphenol-A and multifunctional (meth)acrylate having urethane functional group.

Preferably, the content of photopolymerizable monomer is 5 to 70 wt. % with

respect to the total weight of the DFR resin composition.

(d) Other additives

The additives as used herein may include a plasticizer, a color stabilizer, a

coloring agent, a labeling agent, etc. The detailed component and the content are not

specifically limited.

The DFR resin composition was prepared according to the aforementioned

component combination and coated with thickness of 5 -150 μm on the conventional

substrate film by using the conventional coating method and subsequently dried and

laminated on the dried photosensitive resin layer by employing the conventional protective

film such as polyethylene. The dried film was exposed and developed and finally

measured for the physical properties. The exposure process can be performed by UV,

visible ray, Laser Direct exposure equipment such as laser or the conventional lamp

exposure equipment including the collimated light, scattering light, etc.

The DFR resin composition applicable to image preparing process of PCB, lead

frame, PDP and other displays can be manufactured by the above-mentioned process in

the condition of the exposure light energy 3-15 mJ/cm² below, when the Laser Direct

exposure equipment is used. Meanwhile, when the general lamp exposure equipment is employed the DFR resin composition needs the exposure light energy 20 mJ/cm² below.

Best Mode for Carrying out the Invention

The following examples are intended to describe the invention further and in no

way serve to limit the scope of the present invention.

Examples 1 to 4 and Comparative Example 1

The Examples of the present invention exemplify the DFR resin composition

suggested in the present invention. The specified compositions are presented in Tables 1.

With methylethylketone (MEK) and methanol (MeOH) were dissolved the

photopolymerizable initiators to which photopolymerzable monomers and alkali

developable binder polymers were added and mixed with mechanical stirrer during 1 hour

and the resulting photosensitive resin composition was coated on the PET film of 19μm by

the coating bar.

The coated photosensitive resin composition was dried at 80 "C in a hot air oven

for 5 minutes. Then, the dried film was laminated on the photosensitive resin layer by

using protective film (PE).

The dried film was laminated on CCL by the lamination apparatus (Hakuto

MachόlOi), in condition of 110^°C, lamination roll pressure 4kg_f/cm², velocity 2.0 m/min

on the surface of which Stouffer Step Tablet was placed and was exposed by Perkin-Elmer ™ OB712, and developed with Na₂CO₃ 1 wt % solution, spray pressure 1.5kgf/cm .

The circuit physical properties were measured by using KOLON Test Artwork in

the condition of the specific sensitivity and the results are presented in the following Table

2 and 3.

Table 1

The physical properties of the dry film photoresist measured by the conventional

exposure equipment are presented in table 2.

Table 2

The physical properties of the dry film photoresist measured by the 355 run Laser

Direct exposure equipment (Orbotech Paragon-8000m) are presented in table 3. The

evaluation of the properties is achieved by the same method as the evaluation in the table

2.

Table 3

The physical properties of the dry film photoresist measured by the 405 nm Laser

Direct exposure equipment (Pentax Dl-μ) are presented in table 4. The evaluation of the

properties is achieved by the same method as the evaluation in the table 2.

Table 4

As the above table 2 to 4 are presented, the DFR resin composition of the present

invention keep the basic physical properties the same as or not less, and has much less

substantial optimal exposure energy than the conventional comparative example 1. Industrial Applicability

The present invention comprising the new DFR resin composition for LDI

(optimal exposure energy 2~15mJ/cm² below) comprising thioxanthone derivatives as

photopolymerizable initiator keeps the basic physical properties of the conventional DFR

and significanly improves the sensitivity in spite of a little amount of the light exposure,

thereby maximizing the productivity with regard to the formation of the image on the PCB,

lead frame, PDP and other displays.

Claims

What is claimed is:

1. A dry film photoresist resin composition for LDI (Laser Direct Image)

comprising the thioxanthone derivatives represented by the following formula I as a

photopolymerizable initiator.

Formula I

wherein, R1-R4 is a hydrogen atom, a halogen atom, C1-C5 alkyl, and Cl-C 5

alkyl oxide, respectively.

2. The dry film photoresist resin composition according to claim 1, wherein the

thioxanthone derivative represented by the following formula I include 0.3 to 4.0

weight % with respect to the total weight of the dry film photoresist resin composition.

3. A process for preparing a dry film photoresist resin composition for LDI (Laser

Direct Image) comprising the thioxanthone derivatives represented by the following

formula I as a photopolymerizable initiator, comprising the step of formation of the image

on PCB, lead frame, PDP and other displays by using laser direct exposure equipment with 3-15 mJ/cm

Formula I

wherein, R.1-R4 is a hydrogen atom, a halogen atom, C1-C5 alkyl, and C1-C5

alkyl oxide, respectively.